TWI612579B - High aspect ratio shallow trench isolation etching method - Google Patents

Abstract

The invention provides a shallow trench isolation etching method with a high aspect ratio, which includes an etching step, the etching step includes a plurality of deep etching sub-steps, and the plurality of deep etching sub-steps is used to etch a depth of the trench, wherein The value of the process parameter used in each deep etching sub-step to change the deposition amount of the reaction by-product changes according to a first rule that can reduce the deposition amount of the reaction by-product; or, The value of the process parameter that can change the deposition amount of the reaction by-product is changed according to a second rule that can alternately increase and decrease the deposition amount of the reaction by-product. The shallow trench isolation etching method with high aspect ratio provided by the present invention can not only simplify the etching step, but also does not need to make any modification to the etching device under the premise of obtaining an ideal trench etching morphology, thereby saving process time and Reduce etching costs.

Description

Shallow trench isolation etching method with high aspect ratio

The invention relates to the field of microelectronics technology, in particular to a shallow trench isolation etching method with a high aspect ratio.

In recent years, with the increase in the integration of semiconductor devices, the size of individual components has gradually become smaller. For process nodes of 32nm and below 32nm, shallow trench isolation etching has a higher aspect ratio (depth of trench / groove Trench diameter), which places higher requirements on the etching process for etching shallow trenches on a wafer to obtain a trench etching morphology with an ideal aspect ratio.

At present, people usually use a continuous etching method to etch the wafer, that is, the total etching depth of the wafer is completed in one step, and the sidewalls of the trench are improved by adjusting parameters such as the excitation power and the flow rate of the etching gas (such as HeO). Topography of smoothness. However, during the wafer etching process, especially during the etching process of wafers with a process node of 32nm or less, the reaction byproducts generated by the reaction will quickly accumulate on the sidewalls of the hard cover layer of the trench, resulting in wafer trenches. The opening size of the trench becomes smaller, which results in a reduction in the amount of plasma entering the trench. As a result, the critical dimensions of the wafer trench (such as the trench width) decrease sharply with the increase of the etching depth, so that the desired depth cannot be obtained. Aspect ratio of trench etch morphology. In addition, the accumulation of reaction by-products on the side walls of the hard cover layer increases accumulation The electric charge on the hard mask layer and the electric field generated by the electric charge will cause the etching direction of the plasma to deviate from the original vertical direction toward the side wall of the trench, thereby causing a recessed etched shape on the side wall of the trench. , As shown in Figure 1.

In order to obtain the ideal trench etching morphology, people also use another etching method, as shown in Figure 2, the etching method mainly includes the following steps:

(a) An etching step using a hydrogen halide-containing gas. The wafer 102 exposing the mask 101 is etched to a predetermined depth, as shown in FIG. 2 (a).

(b) An etching step using a fluorine-containing gas. That is, the etching gas is replaced with a fluorine-containing gas, and the wafer 102 is further etched, as shown in FIG. 2 (b).

(c) a protective film forming step. A sputtering method is used to form a protective film 103 on the wafer 102, and the protective film 103 is deposited on the top of the mask 101 and the sidewall and bottom of the trench 104, as shown in FIG. 2 (c).

(d) a protective film removing step. Only the protective film 103 on the sidewall 104a of the trench 104 is retained, and the remaining protective film 103 is removed, as shown in FIG. 2 (d).

(e) Repeat steps (b), (c), and (d) until the trench 104 of the wafer 102 reaches the etching depth required by the process, as shown in FIG. 2 (e).

Although the above etching method can obtain a trench etching morphology with an ideal aspect ratio to a certain extent, it inevitably has the following problems in practical applications:

First, because the above-mentioned etching method requires the addition of a step of forming a protective film by sputtering in the etching process, and this step is accompanied by the loops of steps (b), (c), and (d) during the entire etching process. Repeated execution, resulting in a longer etching process.

Second, because the protective film forming step in the above-mentioned etching method is completed by sputtering, the conventional etching device usually does not have a sputtering function, so it is necessary to The conventional etching device is specially designed, which results in an increase in the manufacturing cost of the device.

The present invention aims to solve at least one of the technical problems in the prior art, and proposes a shallow trench isolation etching method with a high aspect ratio, which can not only simplify the etching step on the premise of obtaining an ideal trench etching morphology, Moreover, there is no need to make any modification to the etching device, so that the process time can be saved and the manufacturing cost of the device can be reduced.

In order to achieve the object of the present invention, a shallow trench isolation etching method with a high aspect ratio is provided. The etching step includes a plurality of deep etching sub-steps, and the plurality of deep etching sub-steps is used for the depth of the trench. Etching is performed, wherein the value of the process parameter used in each deep etching sub-step that can change the deposition amount of the reaction by-product is changed according to a first rule that can reduce the deposition amount of the reaction by-product; or The value of the process parameter used in the deep etching sub-step to change the deposition amount of the reaction by-product is changed according to a second rule that can alternately increase and decrease the deposition amount of the reaction by-product.

Wherein, the etching step further includes a groove ruling formation sub-step. The groove ruling forming sub-step is used to form a groove ruling on the wafer before the plurality of deep etching sub-steps.

The first rule is that among the plurality of deep etching sub-steps, a value of the process parameter used in each deep etching sub-step is relative to a value of the process parameter used in an adjacent previous deep etching sub-step. Numeric gradation A unit gradation.

The first rule is that among the multiple deep etching sub-steps, the value of the process parameter used at the beginning of each deep etching sub-step is relative to the same depth. The value of the process parameter used at the end of the etching substep is changed by a unit. The value of the process parameter used at the beginning of each deep etching substep is different from the value of the process parameter at the end of the next previous deep etching substep. The values of the process parameters used are the same.

Wherein, the first rule is: in the plurality of deep etching sub-steps, the value of the process parameter used in each deep etching sub-step is first changed by a unit gradation relative to the initial value of the same deep etching sub-step. , And then maintain the value of a unit gradual change until the end of the deep etch substep, the value of the process parameter used at the beginning of each deep etch substep and the value used at the end of the next previous deep etch substep The values of the process parameters are the same.

The process parameters include at least one of a flow rate of a regulating gas, a base temperature, and a chamber pressure, which can change a deposition amount of a reaction by-product.

Preferably, the number of units that are changed between each two adjacent deep etching sub-steps is the same.

Preferably, the process time of each deep etching sub-step is the same.

Preferably, the value of the process time used in each deep etching sub-step ranges from 5 to 10 seconds.

Preferably, the regulating gas includes a regulating gas that can increase the amount of deposits of the reaction byproducts. The flow rate of the regulating gas used in the first deep etching sub-step ranges from 5 to 30 sccm.

Preferably, the value of the temperature of the pedestal used in the first deep etching sub-step ranges from 50 to 60 ° C.

Preferably, the value of the chamber pressure used in the first deep etching sub-step ranges from 10 to 45 mT.

Wherein, the second rule is that in the plurality of deep etching sub-steps, the values of the process parameters used by the two adjacent deep etching sub-steps alternate between two different fixed amounts.

Preferably, the process parameter includes a flow rate of a regulating gas that can change a deposition amount of the reaction by-product; and, for a regulating gas that can increase a deposition amount of the deposition on the reaction by-product, a first deep etching sub-step The flow rate of the adjustment gas used is the larger one of the two fixed amounts; for the adjustment gas that can reduce the deposit accumulation of the reaction by-products, the adjustment gas used in the first deep etching sub-step The flow rate is the smaller of the two fixed amounts.

Preferably, the values of the process parameters used in two adjacent two deep etching sub-steps are alternately fixed by the same amount.

Wherein, the second rule is that in the plurality of deep etching sub-steps, the value of the process parameter used at the beginning of each deep etching sub-step is relative to the process parameter used at the end of the same deep etching sub-step. The value of is gradually changed by a unit. The value of the process parameter used at the beginning of each deep etching sub-step is the same, and the value of the process parameter used at the end of each deep etching sub-step is the same.

Preferably, from the beginning to the end of the etching step, the plasma is always in an enlightened state.

Preferably, the regulating gas includes any one of nitrogen, helium, argon, fluorine-containing gas and oxygen, or a combination of at least two gases.

Wherein, the second rule is that among the multiple deep etching sub-steps, the value of the process parameter used in each deep etching sub-step is relative to the same deep etching first. The initial value of the substep is changed by one unit, and the value after the unit is changed is maintained until the end of the deep etching substep. The value of the process parameter used at the beginning of each deep etching substep is the same. The values of the process parameters used at the end of the deep etching sub-step are the same.

Preferably, from the beginning to the end of the etching step, the plasma is always in an enlightened state. Preferably, the regulating gas includes any one of nitrogen, helium, argon, fluorine-containing gas and oxygen, or a combination of at least two gases.

The present invention has the following beneficial effects: The shallow trench isolation etching method with high aspect ratio provided by the present invention divides the etching step into a trench prototype forming sub-step for forming a trench prototype on a wafer and a plurality of deep etching A sub-step, the multiple deep-etching sub-steps are used to etch the depth of the trench, and the values of the process parameters used in each deep-etching sub-step that can change the deposition amount of the reaction by-products are The first rule change that the deposition amount of the product gradually decreases can make the reaction by-product deposition layer on the sidewall of the trench stop the etching reaction gradually with the increase of the etching time; or, used in each deep etching sub-step The value of the process parameter that can change the deposition amount of the reaction by-products is changed according to the second rule that can alternately increase and decrease the deposition amount of the reaction by-products, which can make the entire etching process The procedure mainly based on etching and the procedure mainly based on deposition are performed alternately. By using each of the deep etching sub-steps following one of the above rules, rapid accumulation of reaction byproducts on the top wall of the mask and the side wall of the trench can be avoided, and an ideal etched shape with a smooth side wall and no inflection points can be obtained. At the same time, the shallow trench isolation etching method with high aspect ratio provided by the present invention only needs to adjust specific process parameters without adding additional steps. Compared with the prior art, the etching step is not only simple, but also does not require any etching device. Changes that can reduce Manufacturing cost of the device.

1,102‧‧‧chips

2‧‧‧ Overlay

3‧‧‧ oxide layer

4‧‧‧ reaction byproduct sedimentary layer

101‧‧‧ curtain

103‧‧‧ protective film

104‧‧‧Groove

104a‧‧‧ sidewall

FIG. 1 is an electron microscope scan image of a trench etching morphology obtained by using a conventional wafer etching process; and FIG. 2 (a) is a trench obtained after an etching process using a hydrogen halide gas using another conventional etching method. Schematic diagram of trench etched morphology; Figure 2 (b) is a schematic diagram of trench etched morphology obtained after an etching process using a fluorine-containing gas using another conventional etching method; Figure 2 (c) is a diagram of an existing etched morphology A schematic view of a trench etching morphology obtained after a protective film formation process of another etching method; FIG. 2 (d) is a schematic view of a trench etch morphology obtained after a protective film removal process using another existing etching method; FIG. 2 (e) is a schematic diagram of a trench etching morphology finally obtained by using another existing etching method; FIG. 3A is a flowchart of a shallow trench isolation etching method with a high aspect ratio according to the first embodiment of the present invention FIG. 3B is a schematic diagram of a trench etching morphology obtained by completing each of the deep etching sub-steps in FIG. 3A; FIG. 4 is a schematic diagram of a shallow trench isolation etching method with a high aspect ratio according to a second embodiment of the present invention Process box FIG. 5 is a schematic diagram of a shallow trench isolation etching method with a high aspect ratio according to a third embodiment of the present invention Process block diagram; FIG. 6A is a flowchart of a high-aspect-ratio shallow trench isolation etching method provided by a fourth embodiment of the present invention; FIG. 6B is a trench obtained by completing each deep etching sub-step in FIG. 6A Schematic diagram of etching morphology; FIG. 7 is a flowchart of a high-aspect-ratio shallow trench isolation etching method according to a fifth embodiment of the present invention; FIG. 8 is a high-aspect-ratio shallow Flow chart of trench isolation etching method. .

In order to enable those skilled in the art to better understand the technical solutions of the present invention, the method for shallow trench isolation etching with high aspect ratio provided by the present invention is described in detail below with reference to the accompanying drawings.

The shallow trench isolation etching method with high aspect ratio provided by the present invention includes an etching step for etching a trench on a surface to be etched of a wafer. In this etching step, the wafer is etched using the following procedure: the etching gas and the regulating gas are passed into the reaction chamber, and the upper electrode power source (such as a radio frequency power source) is turned on, and the upper electrode power source applies the upper electrode power to the reaction chamber. The etching gas in the reaction chamber is excited to form a plasma; the lower electrode power is turned on, and the lower electrode power applies a lower electrode power to the wafer, so that the plasma etches the wafer until a groove having a predetermined etching depth is etched on the surface to be etched of the wafer. groove. It should be noted that the etching gas refers to a gas capable of performing an etching function alone, and its flow rate is generally large. In contrast, the etch effect of the regulating gas is limited, it mainly plays an auxiliary role, and the flow rate is generally small.

The above-mentioned etching step includes multiple deep-etching sub-steps, and the multiple deep-etching sub-steps are used to etch the depth of the trench. Among them, the values of the process parameters used in each deep etching sub-step that can change the deposition amount of the reaction by-products are changed according to a first rule that can reduce the deposition amount of the reaction by-products, which can make the With the increase, the effect of the reaction byproduct deposition layer on the sidewall of the trench to stop the etching reaction gradually weakens; or, the value of the process parameter used in each deep etching substep that can change the deposition amount of the reaction byproduct is set to make the reaction byproduct The second regular change in which the deposition amount of the product is increased and decreased alternately between the two procedures can make the procedure based on etching and the procedure based on deposition alternately performed throughout the etching process. The so-called reaction by-product deposits refer to macromolecular substances that are easily deposited in the reaction by-products, which will accumulate and settle on the surface of the etching trench during the etching process.

Wherein, the above-mentioned etching step further includes a groove ruling formation sub-step, the groove ruling forming sub-step is preceded by a plurality of deep etching sub-steps, and the groove ruling forming sub-step is used to form a groove ruling on the wafer. The so-called groove prototype refers to a shallow groove formed in advance at a corresponding position on a wafer in order to facilitate etching to form a groove on the wafer.

By using each of the deep etching sub-steps following one of the above rules, rapid accumulation of reaction byproducts on the top wall of the mask and the side wall of the trench can be avoided, and an ideal etched shape with a smooth side wall and no inflection points can be obtained. At the same time, the shallow trench isolation etching method with high aspect ratio provided by the present invention only needs to adjust specific process parameters without adding additional steps. Compared with the prior art, the etching step is not only simple, but also does not require any etching device. The modification can reduce the manufacturing cost of the device.

The following is a description of the high-aspect-ratio shallow trench isolation etching method provided by the present invention. Six specific embodiments are described in detail.

Specifically, FIG. 3A is a flow block diagram of a shallow trench isolation etching method with a high aspect ratio according to the first embodiment of the present invention, and FIG. 3B is a trench etch obtained by completing each deep etching sub-step in FIG. 3A Schematic illustration. Please refer to FIG. 3A and FIG. 3B together. In the high-aspect-ratio shallow trench isolation etching method provided in this embodiment, a trench prototype forming sub-step is used to form a trench prototype on a wafer, and multiple deep etchings are performed. The sub-step is used to etch the depth of the trench. The value of the process parameter used in each depth etching sub-step that can change the deposition amount of the reaction by-product is the first to reduce the deposition amount of the reaction by-product. The rule is changed. The first rule is: among a plurality of deep etching sub-steps, the value of the process parameter used in the next deep etching sub-step is relative to the value of the process parameter used in the next previous deep etching sub-step. To change a unit recursively.

As shown in FIG. 3A, the etching step includes a groove ruling formation sub-step S0 and n deep etching sub-steps for forming a groove ruling on the wafer 1, respectively S1, S2, S3, ..... ., Sn, n are positive integers, and n depth etching sub-steps are used to etch the depth of the trench formed on the wafer 1. The value of the process parameter used in the deep etching sub-step S1 to change the deposition amount of the reaction by-product is equal to M; the value of the process parameter used in the deep etching sub-step S2 to change the deposition amount of the reaction by-product is The value is equal to M + x or Mx, that is, the value of the process parameter used in the deep etching sub-step S2 is changed by the value x (increased or decreased by one unit variable) relative to the value of the process parameter used in the deep etching sub-step S1; The value of the process parameter used in the deep etching sub-step S3 to change the deposition amount of the reaction byproducts is equal to M + 2x or M-2x, that is, the value of the process parameter used in the deep etching sub-step S3 is relative to the deep etching. The value of the process parameter used in sub-step S2 is changed gradually. x; and so on, the value of the process parameter used in the deep etching sub-step Sn that can change the deposit accumulation amount of the reaction by-product is equal to M + (n-1) x or M- (n-1) x, that is, the depth The value of the process parameter used in the etching sub-step Sn is gradually changed by x relative to the value of the process parameter used in the deep etching sub-step S (n-1).

As shown in FIG. 3B, an oxide layer 3 and a mask layer 2 having a pattern are sequentially arranged on the surface to be etched of the wafer 1 from bottom to top. Before performing the deep etching sub-steps S1 to Sn, the shallow trench isolation etching method with a high aspect ratio further includes a sub-step S0 for forming a trench prototype on the wafer 1, and is used to first etch a certain amount on the surface to be etched of the wafer 1. depth. Then, the deep etching sub-steps S1 to Sn are sequentially performed. In the deep etching sub-step S1, the value of the process parameter that can change the deposition amount of the reaction byproducts is equal to M. Under this condition, the deposition amount of the reaction byproducts is the largest, so that the deposition effect is greater than the etching effect. After the deep-etching sub-step S1 is completed, a reaction by-product deposition layer 4 is formed on the sidewall of the trench, which is used to block the lateral progress of the etching reaction and achieve anisotropic etching. In the deep-etching sub-step S2, the value of the process parameter is gradually changed from the value of the process parameter used in the deep-etching sub-step S1 by x, that is, the deposition amount of the reaction by-product is reduced, thereby reducing the deposition effect. Furthermore, after the deep-etching sub-step S2 is completed, the thickness of the reaction by-product deposition layer 4 is reduced due to consumption. By analogy, as the etching depth increases, the deposition gradually weakens, and the thickness of the reaction by-product deposition layer 4 is gradually consumed until it is completely consumed after the deep etching sub-step Sn is completed. Preferably, the number of units that are changed between each two adjacent deep etching sub-steps is the same, that is, the above-mentioned x is a fixed value, which can be automatically controlled by a compiler to implement the use of each deep etching sub-step. The value of process parameters is changed gradually, so that automatic control can be realized. Similarly, the same process time can be used for each deep etching sub-step, so that It is convenient to realize automatic control, and preferably, the value of the process time used in each deep etching sub-step ranges from 5 to 10 seconds.

It can be known from the above that by making the values of the process parameters used in each deep etching sub-step that can change the deposition amount of the reaction by-products change according to the above-mentioned first rule of this embodiment, it is possible to avoid the deposition of reaction by-products. The amount rapidly increased at the top of the side wall, while ensuring that the reaction by-products were not accumulated enough to prevent the plasma from entering the bottom of the trench, and to prevent the plasma from deviating from the original vertical direction, leading to corners in the side wall of the trench. The ideal etched topography of the inflection point.

FIG. 4 is a flow block diagram of a high-aspect-ratio shallow trench isolation etching method according to a second embodiment of the present invention. The schematic view of the trench etching morphology obtained in each deep etching sub-step is similar to FIG. 3B. Please refer to FIG. 4 and FIG. 3B together. In the shallow trench isolation etching method with a high aspect ratio provided in this embodiment, a trench prototype forming sub-step is used to form a trench prototype on a wafer, and multiple deep etchings are performed. The sub-step is used to etch the depth of the trench. The value of the process parameter used in each depth etching sub-step that can change the deposition amount of the reaction by-product is the first to reduce the deposition amount of the reaction by-product. The rule is changed. The first rule is: in a plurality of deep etching sub-steps, the value of the process parameter used at the beginning of each deep etching sub-step is relative to the value of the process parameter used at the end of the same deep etching sub-step. A unit is gradually changed. The value of the process parameter used at the beginning of each deep etching substep is the same as the value of the process parameter used at the end of the next previous deep etching substep.

As shown in FIG. 4, the etching step includes a groove ruling formation sub-step S0 and n deep etching sub-steps for forming a groove ruling on the wafer 1, which are S1 and S2, respectively. S3,..., Sn, n are positive integers, and n depth etching sub-steps are used to etch the depth of the trench formed on the wafer 1. The initial value of the process parameter used in the deep etching sub-step S1 to change the deposition amount of the reaction by-products is equal to M, and the end value is equal to M + x or Mx, that is, the value of the process parameter used is in deep etching. The sub-step S1 is linearly increased or decreased; the initial value of the process parameter used in the deep etching sub-step S2 to change the deposition amount of the reaction byproduct is equal to M + x or Mx, and the end value is equal to M + 2x Or M-2x, that is, the value of the process parameter used in the deep etching sub-step S2 is linearly increased or decreased in the deep etching sub-step S2, and the deep etching sub-step S2 and the deep etching sub-step S1 are linearly changed. The slope is the same. The initial values of the process parameters used in the deep etch sub-step S2 are the same as the values of the process parameters used at the end of the deep etch sub-step S1; the deposits used in the deep etch sub-step S3 can change the reaction by-product deposits The initial value of the process parameter is equal to M + 2x or M-2x, and the end value is equal to M + 3x or M-3x, that is, the value of the process parameter used in the deep etching sub-step S3 The depth etch sub-step S3 is linearly increased or decreased. The slope of the linear change of the depth etch sub-step S3 and the depth etch sub-step S2 are the same. The initial values of the process parameters used in the depth etch sub-step S3 and the depth etch sub-step The value of the process parameter used at the end of step S2 is the same; and so on, the initial value of the process parameter used in the deep etching sub-step Sn that can change the deposition amount of the reaction byproduct is equal to M + (n-1) x or M- (n-1) x, the ending value is equal to M + nx or M-nx, that is, the value of the process parameter used in the deep etching substep Sn is linearly increased or decreased in the deep etching substep Sn, The slope of the linear change of the deep etching sub-step Sn is the same as that of the deep etching sub-step S (n-1). The initial values of the process parameters used in the deep etching sub-step Sn are the same as those at the end of the deep etching sub-step S (n-1). The values of the process parameters used are the same.

As shown in FIG. 3B, an oxide layer 3 and a mask layer 2 having a pattern are sequentially arranged on the surface to be etched of the wafer 1 from bottom to top. Before performing the deep etching sub-steps S1 to Sn, the shallow trench isolation etching method with a high aspect ratio further includes a sub-step S0 for forming a trench prototype on the wafer 1, and is used to first etch a certain amount on the surface to be etched of the wafer 1. depth. Then, the deep etching sub-steps S1 to Sn are sequentially performed. In the deep etching sub-step S1, the initial value of the process parameter that can change the deposition amount of the reaction byproduct is equal to M, and the ending value is equal to M + x or Mx. Under this condition, the deposition amount of the reaction byproduct is the largest. Therefore, the deposition effect is greater than the etching effect. After the deep etching sub-step S1 is completed, a reaction byproduct deposition layer 4 is formed on the sidewall of the trench, which is used to prevent the etching reaction from proceeding in the lateral direction to achieve anisotropic etching. In the deep etching sub-step S2, the initial value of the process parameter is the same as the end value of the process parameter used in the deep etching sub-step S1, and the end value of the process parameter in the deep etching sub-step S2 is relative to the process in the deep etching sub-step S2 The initial value of the parameter changes by x, that is, the deposition amount of the reaction byproduct is reduced, thereby reducing the deposition effect. After the deep etching substep S2 is completed, the thickness of the reaction byproduct deposition layer 4 is consumed due to the consumption. Thinning. By analogy, as the etching depth increases, the deposition gradually weakens, and the thickness of the reaction by-product deposition layer 4 is gradually consumed until it is completely consumed after the deep etching sub-step Sn is completed. Preferably, the number of units that are changed between each two adjacent deep etching sub-steps is the same, that is, the above x is a fixed value, which can be automatically controlled by a compiler to be used in each deep etching sub-step. The initial value and the end value of the process parameters change linearly, so that automatic control can be realized. Similarly, the process time used in each deep etching sub-step can also be made the same to facilitate automatic control, and preferably, the process time used in each deep etching sub-step ranges from 5 to 10 seconds.

It can be known from the above that by making the initial value and the end value of the process parameter of each depth etching sub-step that can change the deposition accumulation amount of the reaction by-product according to the above-mentioned first rule of this embodiment, the reaction by-product can be avoided The amount of deposited deposits rapidly increased on the top of the sidewall, and at the same time, the accumulation of by-products of the reaction was not enough to prevent the plasma from entering the bottom of the trench, and to prevent the plasma from deviating from the original vertical direction, resulting in corners of the trench sidewall. Ideal etched morphology with smooth sidewalls and no inflection points.

FIG. 5 is a flow block diagram of a shallow trench isolation etching method with a high aspect ratio according to a third embodiment of the present invention. The schematic view of the trench etch morphology obtained by each deep etching sub-step is similar to FIG. 3B. Please refer to FIG. 5 and FIG. 3B together. In the shallow trench isolation etching method with a high aspect ratio provided in this embodiment, a trench prototype forming sub-step is used to form a trench prototype on a wafer, and multiple deep etchings are performed. The sub-step is used to etch the depth of the trench. The value of the process parameter used in each depth etching sub-step that can change the deposition amount of the reaction by-product is the first to reduce the deposition amount of the reaction by-product. The rule is changed. The first rule is: in a plurality of deep etching sub-steps, the value of a process parameter used in each deep etching sub-step is first changed by a unit variable relative to the initial value of the same deep etching sub-step. The value of the unit variable is maintained until the end of the deep etching substep. The value of the process parameter used at the beginning of each deep etching substep is the same as the process parameter used at the end of the next previous deep etching substep. The values are the same.

As shown in FIG. 5, the etching step includes a groove ruling formation sub-step S0 and n deep etching sub-steps for forming a groove ruling on the wafer 1, which are S1, S2, S3, ..... ., Sn, n are positive integers, and n depth etching sub-steps are used to etch the depth of the trench formed on the wafer 1. Among them, the variable reaction pair used in the deep etching sub-step S1 can be changed. The initial value of the process parameter of the product deposition amount of the product is equal to M. For a period of time, the value of the process parameter linearly changes a unit variable with respect to the initial value of the process parameter to obtain an intermediate value M + x or Mx, and then maintain the The intermediate value is up to the end of the deep etching sub-step S1, and the end value is equal to M + x or Mx, that is, the value of the process parameter used is increased or decreased linearly in the deep etching sub-step S1, and then the linear change is maintained. The value of the process parameter (that is, the intermediate value) is until the end of the deep etching sub-step S1; the initial value of the process parameter used in the deep etching sub-step S2 which can change the deposition amount of the reaction byproduct is equal to M + x or Mx. During the time, the value of the process parameter linearly changes a unit variable with respect to the initial value of the process parameter to obtain an intermediate value M + 2x or M-2x, and then maintain the intermediate value until the end of the deep etching substep S1, and the end value is equal to M + 2x or M-2x, that is, the value of the process parameter used is linearly increased or decreased in the deep etching sub-step S2, and then Keep the linearly changed process parameter value (ie, the middle value) until the end of the deep etching sub-step S2; the initial value of the process parameter used in the deep etching sub-step S3 that can change the deposition amount of the reaction byproduct is equal to M + 2x Or M-2x, for a period of time, the value of the process parameter linearly changes a unit recursive value relative to the initial value of the process parameter to obtain the intermediate value M + 3x or M-3x, and then maintain the intermediate value until the deep etching sub-step S3 At the end, the end value is equal to M + 3x or M-3x, that is, the value of the process parameter used is linearly increased or decreased in the deep etching sub-step S3, and then the value of the process parameter after the linear change is maintained (that is, (The middle value) until the end of the deep etching sub-step S3; and so on, the initial value of the process parameter used in the deep etching sub-step Sn to change the deposition amount of the reaction byproduct is equal to M + (n-1) x or M- (n-1) x, in a period of time, the value of the process parameter linearly changes a unit variable with respect to the initial value of the process parameter. To the intermediate value M + nx or M-nx, and then maintain the intermediate value until the end of the deep etching sub-step Sn, and obtain the end value equal to M + nx or M-nx, that is, the value of the process parameter used is in the deep etching sub-step The linear increase or decrease in Sn is maintained first, and then the value of the process parameter (that is, the intermediate value) after the linear change is maintained until the end of the deep etching sub-step Sn.

As shown in FIG. 3B, an oxide layer 3 and a mask layer 2 having a pattern are sequentially arranged on the surface to be etched of the wafer 1 from bottom to top. Before performing the deep etching sub-steps S1 to Sn, the shallow trench isolation etching method with a high aspect ratio further includes a sub-step S0 for forming a trench prototype on the wafer 1, and is used to first etch a certain amount on the surface to be etched of the wafer 1. depth. Then, the deep etching sub-steps S1 to Sn are sequentially performed. In the deep etching sub-step S1, the initial value of the process parameter that can change the deposition amount of the reaction by-product deposits is equal to M, the intermediate value is equal to M + x or Mx, and the ending value is equal to M + x or Mx. Under this condition, The deposition amount of the reaction byproducts is the largest, so that the deposition effect is greater than the etching effect. After the deep etching substep S1 is completed, a reaction byproduct deposition layer 4 is formed on the sidewall of the trench, which is used to prevent the etching reaction from proceeding in the lateral direction. To achieve anisotropic etching. In the deep etching sub-step S2, the initial value of the process parameter is the same as the end value of the process parameter used in the deep etching sub-step S1, and the end value of the process parameter in the deep etching sub-step S2 is relative to the process in the deep etching sub-step S2 The initial value of the parameter is changed by x, that is, the deposition amount of the reaction byproduct is reduced, thereby reducing the deposition effect. After the deep etching substep S2 is completed, the thickness of the reaction byproduct deposition layer 4 is reduced due to consumption. thin. By analogy, as the etching depth increases, the deposition gradually weakens, and the thickness of the reaction by-product deposition layer 4 is gradually consumed until it is completely consumed after the deep etching sub-step Sn is completed. Preferably, the unit recursive number changed between two adjacent two deep etching sub-steps is the same, that is, the above-mentioned x is a fixed value, which can be compiled by The device can automatically control the change of the initial value, the intermediate value and the end value of the process parameters used in each deep etching sub-step, so as to realize automatic control. Similarly, the process time used in each deep etching sub-step can also be made the same to facilitate automatic control, and preferably, the process time used in each deep etching sub-step ranges from 5 to 10 seconds.

It can be known from the above that by changing the initial value, the intermediate value, and the end value of the process parameters used in each deep etching sub-step that can change the deposition amount of the reaction by-product deposits according to the above-mentioned first rule of this embodiment, the reaction can be avoided The accumulation of by-product deposits rapidly increased at the top of the side wall, and at the same time, the accumulation of by-products of the reaction was not enough to prevent the plasma from entering the bottom of the trench, and to prevent the plasma from deviating from the original vertical direction, causing corners of the trench sidewall Finally, the ideal etched morphology with smooth sidewalls and no inflection points is obtained.

Of course, this embodiment is not limited to this, and other changes can also be made. For example, each deep etching sub-step can be divided into two deep etching sub-steps. Taking the deep etching sub-step S1 as an example, The middle value of the process parameter is linearly changed to obtain a deep etching sub-step S11, and the middle value of the process parameter is maintained until the deep etching sub-step S1 ends as another deep etching sub-step S12.

Of course, in the above-mentioned first to third embodiments, in the above-mentioned etching step, the groove ruling formation sub-step S0 for forming the groove ruling on the wafer 1 may not be performed, and the wafer may be directly passed through the deep etching sub-step on the wafer. A trench prototype is formed first, and then the depth of the trench formed on the wafer 1 is etched.

Regarding the adjustment of the gas flow, because of the different gases, some gases can play a role in increasing the accumulation of the sediment, such as N2, and some gases can play a role in reducing The effect of this deposit build-up, such as NF3. Therefore, by simultaneously passing the adjusting gas and the etching gas mainly serving as an etching gas into the reaction chamber, and in a plurality of deep etching sub-steps, by making the flow rate of the adjusting gas used in the next deep etching sub-step relative to the adjacent The adjustment of the flow rate of the adjusting gas used in the previous deep etching sub-step changes a unit variable, which can reduce the deposition amount of reaction by-products. Further, for a regulating gas that can increase the amount of deposits deposited, the variation rule may be: the flow rate of the regulating gas used in each deep etching sub-step is relative to that of the regulating gas used in the next previous deep etching sub-step. The flow rate is reduced by a unit taper to reduce the amount of deposits of reaction byproducts. For a regulating gas that can reduce the amount of deposits deposited, the variation rule can be: the flow rate of the regulating gas used in each deep etching sub-step is increased by one compared to the flow rate of the regulating gas used in the next previous deep etching sub-step. Units are tapered to reduce the amount of deposits of reaction byproducts. Of course, in practical applications, only a regulating gas that can reduce or increase the amount of sediment accumulation can be passed in, or a combination of a regulating gas that can reduce and increase the amount of sediment accumulation can be passed at the same time, and each To the role of the development of their own rules of change.

The regulating gas includes any one of nitrogen, helium, argon, oxygen, and fluorine-containing gas, or a combination of at least two gases. Preferably, the value of the unit variable is in the range of 1 to 2 sccm; for the adjustment gas that can increase the deposition amount of the sediment, the value of the flow rate of the adjustment gas used in the first deep etching sub-step is in the range of 5 to 30 sccm.

In the following, the adjusting gas is N2 as an example to further explain the shallow trench isolation etching method with a high aspect ratio provided in this embodiment. Specifically, since N2 can increase the deposition amount during the trench etching process, if the flow of N2 is gradually reduced, the deposition of reaction by-products on the trench upper and sidewalls will gradually weaken, so that Stop Shen The amount of deposits accumulates too quickly on the trench openings and sidewalls.

Based on the above principles, when performing each of the deep etching sub-steps described above, the flow rate of N2 used in each deep etching sub-step can be reduced by one unit of the variable relative to the flow rate of N2 used in the next previous deep etching sub-step. . Specifically, taking the value of the process time used for each deep etching sub-step as 5s as an example, during the first 5s etching time, the flow of N2 is the largest, so that after the etching is completed, the trench A certain amount of deposits of reaction by-products will be deposited on the upper openings and sidewalls of the grooves, preventing the etching reaction from proceeding laterally. During the second 5s etching time, the flow rate of N2 is reduced relative to the flow used in the first 5s etching time, so that the deposition amount of the reaction byproducts is reduced, and the accumulation of the reaction byproducts is further reduced. The effect is weakened, and physical bombardment and chemical effects cause more and more consumption of the deposits, so that after the second 5s etching time is completed, the thickness of the reaction byproduct deposition layer 4 is reduced due to consumption. By continuing to reduce the flow of N2 following the above rules, the accumulation of reaction by-products can be made weaker and weaker, so that the accumulation of deposits at the mouth of the trench will not rapidly increase, and the accumulation will not be sufficient to hinder the plasma Entering the bottom of the trench or changing the direction of the plasma causes the phenomenon that the etched shape is bent to both sides, and finally an ideal etched shape with smooth sidewalls and no inflection points can be obtained.

Preferably, the unit variable number ranges from 1 to 2 parameter units, but in practical applications, for different regulating gases, the unit variable number can be set according to the specific conditions, as long as it can play a groove on the wafer 1. The primary and secondary relationships of the etching and deposition processes may be adjusted. For example, for Ar, the unit taper number is preferably 10 sccm; for NF3, for example, the unit taper number is preferably 2 sccm.

For the pedestal temperature, the relationship between the pedestal temperature and the deposition amount of the by-products of the reaction is: pedestal temperature The higher the reaction byproducts are more easily volatilized, so that the deposition amount of the reaction byproducts is less; on the other hand, the lower the base temperature is, the more the reaction byproducts are deposited. Therefore, in a plurality of deep etching sub-steps, by changing the temperature of the susceptor used in the deep etching sub-steps according to the first rule provided in the first to third embodiments, it is possible to reduce the deposition amount of reaction by-products. . In practical applications, wafers are usually heated using a pedestal for carrying wafers, so that the temperature of the pedestal can be adjusted by adjusting the heating power of the pedestal. Preferably, the range of the pedestal temperature used in the first deep etching sub-step is in the range of 50 to 60 ° C; the range of the unit taper number is in the range of 1 to 2 ° C.

As for the pressure of the chamber, its relationship with the deposition amount of the reaction byproducts is: the higher the chamber pressure, the longer the reaction byproducts stay in the reaction chamber, and the more the deposition amount of the reaction byproducts is On the contrary, the lower the chamber pressure, the shorter the residence time of the reaction by-products in the reaction chamber, and the less the accumulation of reaction by-product deposits. Therefore, in a plurality of deep etching sub-steps, by changing the chamber pressure used in the deep etching sub-steps according to the first rule provided by the first to third embodiments, it is possible to reduce the deposition amount of the reaction by-products. . Preferably, the value of the chamber pressure used in the first deep etching sub-step is in the range of 10 to 45 mT; the value of the unit variable is in the range of 1 to 2 mT.

FIG. 6A is a flowchart of a high-aspect-ratio shallow trench isolation etching method according to a fourth embodiment of the present invention, and FIG. 6B is a schematic view of a trench etching morphology obtained in each deep etching sub-step in FIG. 6A . Please refer to FIG. 6A and FIG. 6B together. In the high-aspect-ratio shallow trench isolation etching method provided in this embodiment, a trench prototype forming sub-step is used to form a trench prototype on a wafer, and multiple deep etchings are performed. The sub-step is used to etch the depth of the trench, and the process used in each deep-etching sub-step can change the deposition amount of the reaction by-products. The value of the parameter is changed according to a second rule that alternates between the increase and decrease of the deposition amount of the reaction by-products. The second rule is: in a plurality of deep etching sub-steps, each adjacent two The values of the process parameters used in each of the deep etching sub-steps alternate between two different fixed amounts.

As shown in FIG. 6A, the etching step includes a groove ruling formation sub-step S0 and n deep etching sub-steps for forming a groove ruling on the wafer 1, which are S1, S2, S3, S4, ... ..., Sn, n are positive integers, and n depth etching sub-steps are used to etch the depth of the trench formed on the wafer 1. The value of the process parameter used in the deep etching sub-step S1 to change the deposition amount of the reaction by-product is equal to A (a fixed value); the deep etching sub-step S2 is used to change the deposition of the reaction by-product. The value of the process parameter of the deposition amount is equal to B (another fixed value); the value of the process parameter of the depth etching sub-step S3 that can change the deposition amount of the reaction byproduct is equal to A; the value of the process parameter used by the deep etching sub-step S4 The value of the process parameter that can change the deposition amount of the reaction by-product is equal to B; and so on, the process parameter used in the deep etching sub-step S (n-1) that can change the deposition amount of the reaction by-product is The value is equal to A; the value of the process parameter used in the deep etching sub-step Sn to change the deposition accumulation amount of the reaction by-product is equal to B.

As shown in FIG. 6B, an oxide layer 3 and a mask layer 2 having a pattern are sequentially provided on the surface to be etched of the wafer 1 from bottom to top. Before performing the deep etching sub-steps S1 to Sn, the shallow trench isolation etching method with a high aspect ratio further includes a sub-step S0 for forming a trench prototype on the wafer 1, and is used to first etch a certain amount on the surface to be etched of the wafer 1. depth. Then, the deep etching sub-steps S1 to Sn are sequentially performed. In the deep-etching sub-step S1, the value of the process parameter that can change the deposition accumulation amount of the reaction by-product is equal to A. Under this condition, the reaction by-product The deposition amount of the deposit is an increasing process, that is, the deposition effect is greater than the etching effect, so that after the deep etching sub-step S1 is completed, a reaction byproduct deposition layer 4 is formed on the sidewall of the trench for blocking the etching reaction. It is carried out laterally to achieve anisotropic etching. In the deep etching sub-step S2, the value of the process parameter is changed from the value A of the process parameter used in the deep etching sub-step S1 to the value B. Under this condition, the deposition amount of the reaction byproduct is reduced. That is, the deposition effect is smaller than the etching effect, so that after the deep-etching sub-step S2 is completed, the thickness of the reaction by-product deposition layer 4 is reduced as it is consumed. By analogy, the reaction by-products are alternately looped multiple times between the increase and decrease procedures, and are finally completely consumed after the deep etching sub-step Sn is completed. Preferably, the values of the process parameters used by the two adjacent deep etching sub-steps are alternately fixed, that is, the two adjacent deep etching sub-steps are between two fixed values of A and B. Alternately, this can also be achieved by using a compiler to automatically control the alternation of the process parameter values used in each of the two adjacent deep etching sub-steps, thereby achieving automatic control. Similarly, the process time used in each deep etching sub-step can also be made the same to facilitate automatic control, and preferably, the process time used in each deep etching sub-step ranges from 5 to 10 seconds.

It can be known from the above that by making the value of the process parameter of each deep etching sub-step that can change the deposition amount of the reaction by-product deposit change according to the above-mentioned second rule of this embodiment, the reaction by-product deposition can also be avoided. The accumulation volume rapidly increased at the top of the side wall, and at the same time, the accumulation of the reaction byproducts was not enough to prevent the plasma from entering the bottom of the trench, and to prevent the plasma from deviating from the original vertical direction, resulting in corners of the trench sidewall. Ideal etched topography without inflection points.

Preferably, the process parameters include sediment accumulation that can change the reaction byproducts The volume of the regulating gas is different. Due to different gases, some gases can play a role in increasing the accumulation of the sediment, such as N2, and some gases can play a role in reducing the accumulation of the sediment, such as NF3. Therefore, for a regulating gas that can increase the amount of deposits of reaction byproducts, the flow rate of the regulating gas used in the first deep etching sub-step is a larger one of the two fixed amounts, and for reducing the reaction, Regulated gas for the accumulation of by-product deposits. The flow rate of the regulated gas used in the first deep etching sub-step is the smaller of the two fixed amounts, so that it can be applied to the upper opening of the trench and the sidewall first. A certain amount of deposits of reaction byproducts are deposited to prevent the etching reaction from proceeding laterally.

The regulating gas may include any one of nitrogen, helium, argon, oxygen, and fluorine-containing gas, or a combination of at least two gases. Preferably, the two fixed amounts are both in the range of 5-30 sccm. It should be noted that, because the response speed of the flow rate of the adjustment gas is faster than the temperature of the base or the pressure of the chamber, it is more suitable for the case where the two fixed quantities are frequently alternated. In addition, when following the second rule to gradually adjust the flow of the gas, the difference between the two fixed amounts should be appropriately increased compared to the unit taper number in the first rule to ensure that the reaction by-products increase and decrease by two. The effect of alternating programs is obvious.

In the following, the adjusting gas is N2 as an example to further explain the shallow trench isolation etching method with a high aspect ratio provided in this embodiment. Specifically, since N2 can increase the deposition amount during the trench etching process, if the flow of N2 is gradually reduced, the deposition of reaction by-products on the trench upper and sidewalls will gradually weaken, so that Prevents deposit buildup from growing too fast on the trench openings and sidewalls.

Based on the above principle, when performing each of the deep etching sub-steps described above, the flow rate of N2 used in each of the two adjacent deep etching sub-steps can be different between two The fixed amounts alternate between 15 sccm and 8 sccm, and the flow rate of N2 used in the first deep etching sub-step is 15 sccm. Specifically, taking the value of the process time used for each deep etching sub-step as 5s as an example, during the first 5s etching time, the flow of N2 is 15 sccm, so after the etching is completed, A certain amount of deposits of reaction by-products will be deposited on the upper openings and sidewalls of the trenches, preventing the etching reaction from proceeding laterally. During the second 5s etching time, the flow rate of N2 was replaced from the original 15sccm to 8sccm, that is, compared with the first 5s etching time, the flow rate used was reduced, so that the deposition amount of reaction byproducts was deposited. Decreasing, and thus reducing the accumulation of reaction by-products, and physical bombardment and chemical effects cause more and more consumption of the deposits, so that after completing the second 5s etching time, the thickness of the reaction by-product deposition layer 4 Thinned by being consumed. During the third 5s etching time, the flow rate of N2 was restored to 15sccm again, so that a thicker deposit of reaction byproducts was re-stacked on the sidewall of the trench. By making the flow of N2 alternate between two different fixed amounts in accordance with the above rules, an ideal etched shape with smooth sidewalls and no inflection points can be finally obtained.

In practical applications, for different regulating gases, the above two fixed amounts can be set according to specific conditions. For example, for Ar, the flow rate is preferably alternated between 50 sccm and 80 sccm; for NF3, the flow rate is preferably 5 sccm and 10 sccm. .

FIG. 7 is a flow block diagram of a shallow trench isolation etching method with a high aspect ratio according to a fifth embodiment of the present invention. The schematic view of the trench etch morphology obtained by each deep etching sub-step is similar to FIG. 6B. Please refer to FIG. 7 and FIG. 6B together. In the high-aspect-ratio shallow trench isolation etching method provided in this embodiment, a trench prototype formation sub-step is used to form a trench prototype on a wafer, and multiple deep etchings are performed. The sub-step is used to etch the depth of the trench, and the process parameters used in each deep-etching sub-step can change the deposition amount of the reaction by-products. The value of is changed according to a second rule that alternates between the increase and decrease of the deposition amount of the reaction by-products. The second rule is: among multiple deep etching sub-steps, each deep etching sub-step The value of the process parameter used at the beginning is gradually changed by a unit variable relative to the value of the process parameter used at the end of the same deep etching substep. The value of the process parameter used at the beginning of each deep etching substep is the same. The values of the process parameters used at the end of the deep etch substep are the same.

As shown in FIG. 7, the etching step includes a groove ruling formation sub-step S0 and n deep etching sub-steps for forming a groove ruling on the wafer 1, which are S1, S2, S3, S4, ... ..., Sn, n are positive integers, and n depth etching sub-steps are used to etch the depth of the trench formed on the wafer 1. The initial value of the process parameter used in the deep etching sub-step S1 to change the deposition amount of the by-products of the reaction is equal to A, and the end value is equal to Ax or A + x, that is, the value of the used process parameter is in deep etching. The sub-step S1 is linearly reduced; the initial value of the process parameter used in the deep etching sub-step S2 to change the deposition amount of the by-products of the reaction is equal to A, and the end value is equal to Ax or A + x, that is, deep etching The values of the process parameters used in the sub-step S2 are linearly reduced in the deep-etching sub-step S2. The slope of the linear change of the deep-etching sub-step S2 and the deep-etching sub-step S1 is the same. The process used in the deep-etching sub-step S2 is the same. The initial value of the parameter is the same as the initial value of the process parameter used in the deep etch sub-step S1; the initial value of the process parameter used in the deep etch sub-step S3 that can change the deposition amount of the reaction byproduct is equal to A, and the end value is equal to Ax or A + x, that is, the value of the process parameter used in the deep etching sub-step S3 decreases linearly in the deep etching sub-step S3, Etching sub-step of S3 and the slope of the etching depth varies linearly sub-step S2 is the same as the initial depth of etching process parameters employed sub-step S3 The value is the same as the initial value of the process parameter used in the deep etching sub-step S2; and so on, the initial value of the process parameter used in the deep etching sub-step Sn that can change the deposition amount of the reaction by-product is equal to A, and the end value Equal to Ax or A + x, that is, the value of the process parameter used in the deep etching sub-step Sn decreases linearly within the deep etching sub-step Sn, and the deep etching sub-step Sn and the deep etching sub-step S (n-1) The slope of the linear change is the same, and the initial values of the process parameters used in the deep etching sub-step Sn are the same as the initial values of the process parameters used in the deep etching sub-step S (n-1).

As shown in FIG. 6B, an oxide layer 3 and a mask layer 2 having a pattern are sequentially provided on the surface to be etched of the wafer 1 from bottom to top. Before performing the deep etching sub-steps S1 to Sn, the shallow trench isolation etching method with a high aspect ratio further includes a sub-step S0 for forming a trench prototype on the wafer 1, and is used to first etch a certain amount on the surface to be etched of the wafer 1. And then perform the deep etching sub-steps S1 to Sn in order. In the deep etching sub-step S1, an initial value of a process parameter that can change a deposition amount of a reaction by-product deposit is equal to A, and the initial value is linearly changed to obtain an end value, and the end value is equal to Ax or A + x. Under this condition, The deposition amount of reaction byproducts is a reduced procedure, that is, the deposition effect is greater than the etching effect at the beginning of the deep etching sub-step 1, and the deposition effect is smaller than the etching effect at the end, so that during the completion of the deep etching sub-step S1, A reaction byproduct deposition layer 4 is first formed on the sidewall of the trench to prevent the etching reaction from proceeding laterally to achieve anisotropic etching, and then, as the etching effect increases and the deposition effect weakens, the thickness of the reaction byproduct deposition layer 4 Thinned by being consumed. In the deep etching sub-step S2, the initial value of the process parameter that can change the deposition amount of the by-products of the reaction by-product is equal to A, and the initial value is linearly changed to obtain the end value, and the end value is equal to Ax or A + x, that is, the deep etchant The initial values of the process parameters of step S2 and the manufacturing of the deep etching sub-step S1 The initial values of the process parameters are equal, and the end values of the process parameters of the deep etch sub-step S2 are equal to the end values of the process parameters of the deep etch sub-step S1. Under this condition, the amount of deposits of reaction byproducts increases from The procedure is the same as the deep etching sub-step S1. Preferably, the initial values of the process parameters of each depth etching sub-step are equal, and the ending values of the process parameters of each depth etching sub-step are equal, that is, the initial values of the process parameters of each depth etching sub-step are equal to A, and the initial values are linear The end value is obtained by the change. The end value is equal to Ax or A + x. Similarly, the compiler can be used to automatically control the change of the process parameter values used in each deep etching sub-step to achieve automatic control. Similarly, the process time used in each deep etching sub-step can also be made the same to facilitate automatic control, and preferably, the process time used in each deep etching sub-step ranges from 5 to 10 seconds.

It can be known from the above that by making the value of the process parameter of each depth etching sub-step that can change the deposition amount of the reaction by-products change according to the above-mentioned second rule of the present embodiment, the reaction by-products deposits can also be avoided. The accumulation volume rapidly increased at the top of the side wall, and at the same time, the accumulation of the reaction byproducts was not enough to prevent the plasma from entering the bottom of the trench, and to prevent the plasma from deviating from the original vertical direction, resulting in corners of the trench sidewall. Ideal etched topography without inflection points.

In the following, the adjusting gas is N2 as an example to further explain the shallow trench isolation etching method with a high aspect ratio provided in this embodiment. Specifically, since N2 can increase the deposition amount during the trench etching process, if the flow of N2 is gradually reduced, the deposition of reaction by-products on the trench upper and sidewalls will gradually weaken, so that Prevents deposit buildup from growing too fast on the trench openings and sidewalls.

Based on the above principle, when performing each of the deep etching sub-steps described above, the flow rate of N2 used in each deep etching sub-step can be linearly changed from the initial value to the ending value, preferably the initial flow rate of N2 in each deep etching sub-step. The value is 15 sccm and the ending value is 8 sccm. Specifically, taking the process time of each depth etching sub-step as 5s as an example, during the first 5s etching duration, the initial flow of N2 is 15sccm, so that a certain amount of reaction by-product deposits will be deposited on the upper opening and the sidewall of the trench to prevent the etching reaction from proceeding in the lateral direction, and then linearly change the flow rate of N2 to 8 sccm, that is, the flow rate is reduced, so that the reaction by-products The deposition amount of the sediment is reduced, which further weakens the accumulation of reaction byproducts, while physical bombardment and chemical effects cause more and more consumption of the deposits, making the thickness of the reaction byproduct deposition layer 4 thinner due to consumption, That is to say, in this deep etching sub-step (that is, the first 5s etching time program), a deposition-based process is performed first, and then Processes based on etching are gradually carried out. During the second 5s etching time, the initial flow of N2 was restored to 15sccm again, so that a thicker deposit of reaction by-products was re-stacked on the sidewall of the trench. By making the flow of N2 linearly change to the ending value in accordance with the above rule, an ideal etched shape with smooth sidewalls and no inflection points can be obtained in the end.

In practical applications, for different regulating gases, the above initial and ending values can be set according to specific conditions. For example, for Ar, the flow rate is preferably linearly changed between 50 sccm and 80 sccm; for NF3, the flow rate is preferably 5 sccm. And 10 sccm.

FIG. 8 is a flow block diagram of a shallow trench isolation etching method with a high aspect ratio according to a sixth embodiment of the present invention. The schematic view of the trench etching morphology obtained in each deep etching sub-step is similar to FIG. 6B. Please refer to FIG. 8 and FIG. 6B together. In a shallow trench isolation etching method with a high aspect ratio, a trench ruling sub-step is used to form a trench ruling on a wafer, and multiple deep etch sub-steps are used to etch the depth of the trench. The value of the process parameter used to change the deposition amount of the reaction by-products is changed according to a second rule that can alternately increase and decrease the deposition amount of the reaction by-products. The second rule is: In multiple deep etching sub-steps, the value of the process parameter used in each deep etching sub-step is changed by a unit gradation relative to the initial value of the same deep etch sub-step, and then maintained by a unit gradation. Values until the end of the deep etching sub-step, the values of the process parameters used at the beginning of each deep etching sub-step are the same, and the values of the process parameters used at the end of each deep-etching sub-step are the same.

As shown in FIG. 6B, the etching step includes a groove ruling formation sub-step S0 and n deep etching sub-steps for forming a groove ruling on the wafer 1, which are S1, S2, S3, S4, ... ..., Sn, n are positive integers, and n depth etching sub-steps are used to etch the depth of the trench formed on the wafer 1. The initial value of the process parameter used in the deep etching sub-step S1 to change the deposition amount of the reaction by-products is equal to A. Within a period of time, the value of the process parameter linearly changes by one unit relative to the initial value of the process parameter. Variable to obtain the intermediate value A + x or Ax, and then maintain the intermediate value until the end of the deep etching substep S1, and obtain the end value equal to A + x or Ax, that is, the value of the process parameter used is within the deep etching substep S1 First increase or decrease linearly, and then maintain the linearly changed process parameter value (that is, the middle value) until the end of the deep etching sub-step S1; the deep etching sub-step S2 can be used to change the deposition amount of the reaction by-products. The initial value of the process parameter is equal to A. For a period of time, the value of the process parameter linearly changes a unit variable with respect to the initial value of the process parameter to obtain the intermediate value A + x or Ax, and then maintain the intermediate value. Value until the end of the deep etching sub-step S2, and the end value is equal to A + x or Ax, that is, the value of the process parameter used is linearly increased or decreased in the deep etching sub-step S2, and then the process after the linear change is maintained The value of the parameter (that is, the middle value) is until the end of the deep etching sub-step S2; the initial value of the process parameter used in the deep etching sub-step S3 to change the deposition amount of the reaction by-product is equal to A, and within a period of time, the process parameter The value of is linearly changed by a unit variable with respect to the initial value of the process parameter to obtain the intermediate value A + x or Ax, and then maintains the intermediate value until the end of the deep etching sub-step S3, and the end value is equal to A + x or Ax, that is, The value of the process parameter used is linearly increased or decreased in the deep etching sub-step S3, and then the value of the process parameter (that is, the middle value) after the linear change is maintained until the end of the deep etching sub-step S3; and so on, the depth The initial value of the process parameter used in the etching sub-step Sn to change the deposit accumulation amount of the reaction by-product is equal to A, within a period of time The value of the process parameter changes linearly with respect to the initial value of the process parameter. A unit variable value is obtained to obtain an intermediate value A + x or Ax, and then the intermediate value is maintained until the end of the deep etching sub-step Sn, and the end value is equal to A + x or Ax. That is, the value of the adopted process parameter is linearly increased or decreased in the deep etching sub-step Sn, and then the value of the process parameter (ie, the intermediate value) after the linear change is maintained until the end of the deep etching sub-step Sn.

As shown in FIG. 6B, an oxide layer 3 and a mask layer 2 having a pattern are sequentially provided on the surface to be etched of the wafer 1 from bottom to top. Before performing the deep etching sub-steps S1 to Sn, the shallow trench isolation etching method with a high aspect ratio further includes a sub-step S0 for forming a trench prototype on the wafer 1, and is used to first etch a certain amount on the surface to be etched of the wafer 1. And then perform the deep etching sub-steps S1 to Sn in order. In the deep etching sub-step S1, an initial value of a process parameter that can change a deposition amount of a reaction by-product deposit is equal to A, and the initial value is linearly changed. To obtain the intermediate value A + x or Ax, and then maintain the intermediate value until the end of the deep etching sub-step S1, and obtain the ending value equal to Ax or A + x. Under this condition, the deposition amount of the reaction byproducts is reduced. In the process of deep etching substep 1, the deposition effect is greater than the etching effect at the beginning, and the deposition effect is less than the etching effect at the end, so that in the process of completing the deep etching substep S1, a reaction by-product will be formed on the sidewall of the trench. The laminated layer 4 is used to prevent the etching reaction from proceeding laterally to achieve anisotropic etching. Then, as the etching effect is enhanced and the deposition effect is weakened, the thickness of the reaction by-product deposition layer 4 is reduced due to consumption. In the deep etching sub-step S2, the initial value of the process parameter that can change the deposition amount of the reaction by-product deposits is equal to A, and the initial value is linearly changed to obtain an intermediate value A + x or Ax, and then the intermediate value is maintained until the deep etching Step S2 ends, and the end value is obtained. The end value is equal to Ax or A + x, that is, the initial value of the process parameter of the deep etching sub-step S2 is equal to the initial value of the process parameter of the deep etching sub-step S1. The end value of the process parameter is equal to the end value of the process parameter of the deep etching sub-step S1. Under this condition, the procedure for increasing the deposition amount of the by-products from reaction to decrease is the same as that of the deep etching sub-step S1. By analogy, the initial values of the process parameters of each depth etching sub-step are equal, and the ending values of the process parameters of each depth etching sub-step are equal, that is, the initial values of the process parameters of each depth etching sub-step are equal to A, and the initial values are linear Change to get the intermediate value A + x or Ax, and then keep the intermediate value until the depth etch substep ends, get the end value, the end value is equal to Ax or A + x, which can also be achieved by the compiler to automatically control each depth etcher Changes in the values of the process parameters used in the steps to achieve automatic control. Similarly, the process time used for each deep etching sub-step can also be made the same to facilitate automatic control, and preferably, the process time used for each deep-etching sub-step is the same. The value ranges from 5 to 10s.

It can be known from the above that by making the value of the process parameter of each depth etching sub-step that can change the deposition amount of the reaction by-products change according to the above-mentioned second rule of the present embodiment, the reaction by-products deposits can also be avoided. The accumulation volume rapidly increased at the top of the side wall, and at the same time, the accumulation of the reaction byproducts was not enough to prevent the plasma from entering the bottom of the trench, and to prevent the plasma from deviating from the original vertical direction, resulting in corners of the trench sidewall. Ideal etched topography without inflection points.

In the following, the adjusting gas is N2 as an example to further explain the shallow trench isolation etching method with a high aspect ratio provided in this embodiment. Specifically, since N2 can increase the deposition amount during the trench etching process, if the flow of N2 is gradually reduced, the deposition of reaction by-products on the trench upper and sidewalls will gradually weaken, so that Prevents deposit buildup from growing too fast on the trench openings and sidewalls.

Based on the above principle, when performing each of the deep etching sub-steps described above, the flow rate of N2 used in each deep etching sub-step can be linearly changed from the initial value to the ending value, preferably the initial flow rate of N2 in each deep etching sub-step. The value is 15 sccm and the ending value is 8 sccm. Specifically, taking the process time of each depth etching sub-step as 5s as an example, during the first 5s etching duration, the initial flow of N2 is 15sccm, so that a certain amount of reaction by-product deposits will be deposited on the upper opening and the sidewall of the trench to prevent the etching reaction from proceeding in the lateral direction, and then linearly change the flow rate of N2 to 8 sccm, that is, the flow rate is reduced, so that the reaction by-products The deposition amount of the sediment is reduced, which further weakens the accumulation of reaction byproducts, while physical bombardment and chemical effects cause more and more consumption of the deposits, making the thickness of the reaction byproduct deposition layer 4 thinner due to consumption, That is, in this deep In the degree-etching sub-step (that is, the first 5s etching time program), a deposition-based process is performed first, and then. Processes based on etching are gradually carried out. During the second 5s etching time, the initial flow of N2 was restored to 15sccm again, so that a thicker deposit of reaction by-products was re-stacked on the sidewall of the trench. By making the flow of N2 linearly change to the ending value in accordance with the above rule, an ideal etched shape with smooth sidewalls and no inflection points can be obtained in the end.

Of course, this embodiment is not limited to this, and other changes can also be made. For example, each deep etching sub-step can be divided into two deep etching sub-steps. Taking the deep etching sub-step S1 as an example, the initial value of the process parameters will be determined by The middle value of the process parameter is linearly changed to obtain a deep etching sub-step S11, and the middle value of the process parameter is maintained until the deep etching sub-step S1 ends as another deep etching sub-step S12.

In practical applications, for different regulating gases, the above initial and ending values can be set according to specific conditions. For example, for Ar, the flow rate is preferably linearly changed between 50 sccm and 80 sccm; for NF3, the flow rate is preferably 5 sccm. And 10 sccm.

In the fifth embodiment and the sixth embodiment, preferably, the process parameters include a flow rate of a regulating gas that can change a deposition amount of a deposit of a reaction by-product. Because of different gases, some gases may play a role in increasing the deposit. The amount of accumulation, such as N2, and some gases can reduce the accumulation of this sediment, such as NF3. Therefore, for a regulating gas that can increase the deposition amount of the reaction byproduct, the initial value of the flow rate of the regulating gas used in each deep etching sub-step should be greater than the ending value of the flow rate of the regulating gas, and for reducing the reaction gas, Regulated gas for product deposit build-up. The initial value of the regulated gas flow used in each deep etching sub-step should be less than the end of the regulated gas flow. Value in order to be able to deposit a certain amount of reaction by-product deposits on the trench opening and the sidewall first to prevent the etching reaction from proceeding laterally.

In the fifth embodiment and the sixth embodiment, the adjustment gas may include any one of nitrogen, helium, argon, fluorine-containing gas, and oxygen, or a combination of at least two gases. It should be noted that, because the response speed of the flow rate of the adjustment gas is faster than the base temperature or the chamber pressure, it is more suitable for the case where the initial value and the end value frequently change linearly. In addition, when following the second rule to gradually adjust the flow of the gas, the difference between the initial value and the end value should be appropriately increased compared to the unit taper number in the first rule to ensure that the reaction by-products increase and decrease by two. The effect of alternating between programs is obvious.

Of course, in the above-mentioned fourth to sixth embodiments, in the above-mentioned etching step, the groove ruling formation sub-step S0 for forming the groove ruling on the wafer 1 may not be performed, and the wafer may be directly passed through the deep etching sub-step on the wafer. A trench prototype is formed first, and then the depth of the trench formed on the wafer 1 is etched.

In the above first to sixth embodiments, preferably, the value of the upper electrode power used in the etching step ranges from 600 to 1200W. The value of the lower electrode power used in the etching step ranges from 100 to 300W. The etching gas used in the etching step includes chlorine gas and hydrogen bromide gas. The flow rate of the etching gas ranges from 50 to 350 sccm.

In addition, it is preferable that the plasma is always in an enlightened state from the beginning to the end of the etching step. In other words, in the process of performing multiple deep etching sub-steps, after completing the current deep etching sub-step and before proceeding to the next deep etching sub-step, the upper electrode power and the lower electrode power are always kept on to ensure that The plasma continues to glow, making the entire etching step continuous.

The reason why this is set is because the frequent switching of the enlightenment and extinction in the prior art, the charged particles suspended in the chamber after the extinction are easy to fall, and the plasma is also in a relatively unstable state during the enlightenment and extinction. (The initial reflection power is easy to be too high), which results in unstable deposition or desorption of reaction byproducts on the side walls of the chamber, which in turn makes it easy for particles to fall, which leads to the fall of contaminated particles during the entire etching process, causing the wafer to be damaged. Pollution further reduces the yield of the product. In the above-mentioned first to sixth embodiments, the plasma is always in an enlightened state, which can effectively avoid the above problems, thereby improving the yield of the product.

In the above embodiments, only the numerical values of the process parameters are changed as each depth etching sub-step is performed in sequence, without any transition steps or additional steps, and the etching gas and the conditioning gas are simultaneously etched to make the total etching time phase Compared with single-step etching, the total etching time is shortened. Therefore, the shallow trench isolation etching method with high aspect ratio provided by the foregoing embodiments of the present invention not only has simple etching steps and flexible adjustment methods, but also does not require any modification to the etching device, thereby reducing the manufacturing cost of the device.

Of course, in practical applications, after completing each deep etching sub-step, the power of the upper electrode and the lower electrode may also be turned off, and then turned on again when the next deep etching sub-step is performed.

It can be understood that the above embodiments are merely exemplary embodiments used to explain the principle of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various variations and improvements can be made without departing from the spirit and essence of the present invention, and these variations and improvements are also considered as the protection scope of the present invention.

Claims (18)

A shallow trench isolation etching method with a high aspect ratio is characterized in that it includes an etching step, the etching step includes a plurality of deep etching sub-steps, and the plurality of deep etching sub-steps is used to etch the depth of the trench. The multiple deep etching sub-steps include a tendency to reduce the deposition amount of the reaction by-products on the sidewalls of the trenches. The process parameters used in each deep etching sub-step can change the deposition amount of the reaction by-products. The value of is changed according to a first rule that can reduce the deposition amount of the by-products of the reaction by-product, wherein the first rule is: among the plurality of deep etching sub-steps, the process used in each deep etching sub-step The value of the parameter is changed by a unit variable relative to the value of the process parameter used in the next previous deep etching substep; or, in the multiple deep etching substeps, each of the deep etching substeps is initially The value of the process parameter used is the same as the value of the process parameter used at the end of the next previous deep etching substep; or, The value of the process parameter used in the three deep etching sub-steps that can change the deposition amount of the reaction by-products is changed according to a second rule that can alternate the increase and decrease of the deposition amount of the reaction by-products. , Wherein the second rule is: in the plurality of deep etching sub-steps, the values of the process parameters used by two adjacent deep etching sub-steps alternate between two different fixed amounts; or, In the plurality of deep etching sub-steps, the values of the process parameters used at the beginning of each deep etching sub-step are the same, and the process parameters used at the end of each deep etching sub-step are the same. The numbers have the same value. The high-aspect-ratio shallow trench isolation etching method according to item 1 of the patent application scope, wherein the etching step further includes a trench ruling formation sub-step, and the trench ruling forming sub-step precedes the plurality of deep etching sub-steps. The sub-step of forming the groove prototype is used to form a groove prototype on the wafer. The high-aspect-ratio shallow trench isolation etching method according to item 1 of the patent application scope, wherein the first rule is: among the plurality of deep etching sub-steps, each of the deep etching sub-steps is used at the beginning The value of the process parameter is relative to the value of the process parameter used at the end of the same deep etching substep. The value of the process parameter is gradually changed by a unit. The value of the process parameter used at the beginning of each deep etching substep is adjacent to the value of the neighboring process. The values of the process parameters used at the end of the last deep etching sub-step are the same. The high-aspect-ratio shallow trench isolation etching method according to item 1 of the patent application scope, wherein the first rule is: among the plurality of deep etching sub-steps, the process parameter used in each deep etching sub-step The value of is gradually changed from the initial value of the same deep etch substep by a unit gradation, and then the value after the gradual change of a unit gradation is maintained until the deep etch substep ends, which is used at the beginning of each deep etch substep. The value of the process parameter is the same as the value of the process parameter used at the end of the next previous deep etching substep. The shallow trench isolation etching method with high aspect ratio as described in any one of claims 1, 3, and 4, wherein the process parameters include a flow rate of a regulating gas that can change a deposition amount of deposits of reaction by-products, At least one of a base temperature and a chamber pressure. According to the high-aspect-ratio shallow trench isolation etching method described in item 5 of the scope of the patent application, wherein the number of units that are tapered between each adjacent two deep-etch substeps is the same. The shallow trench isolation etching method with high aspect ratio as described in item 1 of the scope of patent application, wherein the process time of each deep etching sub-step is the same. The shallow trench isolation etching method with high aspect ratio as described in item 7 of the scope of the patent application, wherein the process time used in each deep etching sub-step ranges from 5 to 10 s. The high-aspect-ratio shallow trench isolation etching method according to item 5 of the scope of patent application, wherein the adjusting gas includes a adjusting gas that can increase the amount of deposits of the reaction by-products; The value of the flow rate of the regulating gas ranges from 5 to 30 sccm. According to the high-aspect-ratio shallow trench isolation etching method described in item 5 of the patent application scope, the value of the pedestal temperature used in the first deep etching sub-step ranges from 50 to 60 ° C. According to the high-aspect-ratio shallow trench isolation etching method described in item 5 of the patent application scope, the value of the chamber pressure used in the first deep etching sub-step ranges from 10 to 45 mT. The high-aspect-ratio shallow trench isolation etching method according to item 1 of the patent application scope, wherein the process parameters include a flow rate of a regulating gas that can change a deposition amount of the reaction by-product deposit; and, for increasing the reaction Regulatory gas for deposit accumulation of by-products, first deep The flow rate of the adjustment gas used in the degree etching sub-step is the larger one of the two fixed amounts; for the adjustment gas that can reduce the deposition accumulation amount of the reaction byproduct, the first deep etching sub-step is used. The flow rate of the regulating gas is a smaller one of the two fixed amounts. The shallow trench isolation etching method with high aspect ratio according to item 1 or item 12 of the patent application scope, wherein the values of the process parameters used in each of the two adjacent deep etching sub-steps are alternately fixed by the same amount. The high-aspect-ratio shallow trench isolation etching method according to item 1 of the patent application scope, wherein the second rule is: among the plurality of deep etching sub-steps, each of the deep etching sub-steps is used at the beginning. The value of the process parameter is relative to the value of the process parameter used at the end of the same depth etching substep. It is a unit gradient. The value of the process parameter used at the beginning of each depth etching substep is the same. The values of the process parameters used at the end of the etching sub-step are the same. The high-aspect-ratio shallow trench isolation etching method according to item 1 of the patent application scope, wherein the second rule is: among the plurality of deep etching sub-steps, the process parameter used in each deep etching sub-step The value of is gradually changed from the initial value of the same deep etch substep by a unit gradation, and then the value after a unit gradual change is maintained until the deep etch substep ends. The values of the process parameters are the same, and the values of the process parameters used at the end of each deep etching sub-step are the same. The high-aspect-ratio shallow trench isolation etching method according to item 1 of the patent application scope, wherein the plasma is always in an enlightened state from the beginning to the end of the etching step. state. The high-aspect-ratio shallow trench isolation etching method according to item 5 of the application, wherein the adjusting gas includes any one of nitrogen, helium, argon, fluorine-containing gas, and oxygen, or a combination of at least two gases . The high-aspect-ratio shallow trench isolation etching method according to item 12 of the application, wherein the adjusting gas includes any one of nitrogen, helium, argon, fluorine-containing gas, and oxygen, or a combination of at least two gases .