TWI899920B - Plasma etching method and etching apparatus - Google Patents

Abstract

The present invention provides a plasma etching method, comprising the steps of: providing a device to be etched, which includes a base layer, an etching material layer sequentially located on the base layer, and a mask layer, wherein the mask layer has a first pattern exposing the etching material layer; applying a first low-frequency bias radio frequency signal to perform a first etching process, forming a second pattern on the etching material layer, wherein the etching depth of the second pattern is the etching material layer. The invention also provides a plasma etching apparatus.

Description

Plasma etching method and etching apparatus

The present invention relates to the field of semiconductors, and in particular to a plasma etching method and an etching device.

NAND flash memory is a superior storage device to hard drives. As people pursue low-power, lightweight, and high-performance non-volatile storage products, it has gained widespread application in electronic products. Currently, planar NAND flash memory has reached its practical scalability limit. To further increase storage capacity and reduce the storage cost per bit, 3D NAND memory has been proposed.

The existing 3D NAND memory manufacturing process requires alternating deposition of different materials on a substrate to form an interleaved base layer, and etching through-holes into the base layer. As storage capacity increases, the number of interleaved layers gradually increases, and the depth of the through-holes in the base layer also increases. Because the hard mask layer and the base layer have relatively high etch selectivity, when etching the base layer using a plasma etching process, a hard mask layer is typically formed on the base layer. The etched pattern of the hard mask layer exposes the base layer area to be etched.

Etching the hard mask layer involves high aspect ratio etching, and the topography of the resulting hard mask pattern is crucial for subsequent etching of the base layer. We aim for: 1) consistent and vertical sidewalls in the hard mask pattern to avoid pattern deformation during etching, which could prevent the hard mask pattern from transferring properly to the base layer; and 2) the critical dimensions at the bottom of the hard mask pattern must meet the preset critical dimensions, as this would directly impact the size of the vias in the base layer.

Because low-frequency RF bias power can increase the impact of plasma, it is typically used during hard mask etching to increase the etch rate in previous technologies. To ensure complete etching of the hard mask layer, the etch depth inevitably reaches the base layer. Byproducts generated during the plasma attack on the base layer easily sputter onto the sidewalls of the hard mask pattern and are difficult to remove. This makes it impossible to control the critical bottom dimension of the hard mask pattern and may even cause the etch to stop. Ultimately, this leads to defects in 3D NAND memory and reduces the processing yield.

The present invention provides a plasma etching method and apparatus that sequentially perform first, second, and third etching processes during the etching of an etched material layer (a hard mask layer serving as a base layer). The first etching process primarily utilizes anisotropic etching to form a second pattern whose etching depth does not reach the base layer. The second etching process primarily utilizes isotropic etching to completely etch the etched material layer and produce a third pattern whose bottom critical dimension reaches a preset critical dimension. The third etching process modifies the sidewall morphology of the third etched pattern, generating a fourth pattern with consistent top and bottom profiles and a bottom critical dimension that meets a preset critical dimension. This provides a hard mask pattern with excellent etched morphology for the base layer. This invention solves the problem of the bottom critical dimension of the pattern failing to meet the preset critical dimension and the difficulty in controlling the bottom morphology during high-aspect-ratio etching of the material layer being etched, while ensuring etching quality and etching speed. The present invention ensures that the second etching process can completely etch the etched material layer by precisely controlling the etching depth of the first etching process. After the third etching process is completed, the base layer has a smaller etching depth, which greatly reduces the impact on the next etching process (which mainly etches the base layer).

To achieve the above objectives, the present invention provides a plasma etching method, which is performed in a plasma processing chamber and comprises the following steps: Providing a device to be etched, wherein the device to be etched comprises a base layer, an etching material layer sequentially disposed on the base layer, and a mask layer, wherein the mask layer has a first pattern, wherein the first pattern exposes the area of the etching material layer to be etched; Applying a first low-frequency biased radio frequency signal to the processing chamber to perform a first etching process, forming a second pattern in the etching material layer, wherein the etching depth of the second pattern is 70% to 98% of the thickness of the etching material layer; A high-frequency bias RF signal is applied to the processing chamber to perform a second etching process, forming a third pattern; the etching depth of the third pattern is greater than or equal to the thickness of the etched material layer; and the critical dimension at the bottom of the third pattern reaches a preset critical dimension. A second low-frequency bias RF signal is applied to the processing chamber to perform a third etching process, forming a fourth pattern that penetrates the etched material layer and a portion of the thickness of the base layer; the critical dimension at the bottom of the fourth pattern reaches a preset critical dimension.

Optionally, the frequencies of the first low-frequency offset RF signal and the second low-frequency offset RF signal are 10 kHz to 2 MHz, and the frequency of the high-frequency offset RF signal is 4 MHz to 15 MHz.

Optionally, the frequencies of the first low-frequency offset RF signal and the second low-frequency offset RF signal are the same or different.

Optionally, the aspect ratio of the fourth graphic is in the range of 10:1 to 150:1.

Optionally, the material of the mask layer is an intermediate phase of silicon oxide and silicon nitride (SiON).

Optionally, the material of the etching material layer includes any one or more of amorphous carbon (ACL), silicon carbide, polysilicon, and silicon nitride.

Optionally, the material of the base layer includes any one or more of silicon dioxide and silicon nitride.

Optionally, the etching depth is controlled by an etching endpoint detection method or process time.

Optionally, the first pattern includes grooves and/or holes.

Optionally, after the third etching process is completed, a fourth etching process is performed to remove the mask layer. Optionally, a first process gas is injected into the processing chamber to perform the first etching process, wherein the flow ratio of the sulfur-containing gas to the oxygen-containing gas in the first process gas is a first flow ratio, and the first flow ratio is less than or equal to 1:5.

Optionally, a second process gas is injected into the processing chamber to perform a second etching process, and the flow ratio of the sulfur-containing gas to the oxygen-containing gas in the second process gas is a second flow ratio, which is less than the first flow ratio; a third process gas is injected into the processing chamber to perform a third etching process, and the flow ratio of the sulfur-containing gas to the oxygen-containing gas in the third process gas is recorded as a third flow ratio, which is less than the first flow ratio.

The present invention also provides a plasma etching apparatus for implementing the plasma etching method described herein. The apparatus comprises: a processing chamber having a susceptor disposed therein, on which the device to be etched is placed; a plurality of bias RF power supplies for generating a plurality of bias RF signals and applying them to the susceptor; the plurality of bias RF signals being used to control plasma energy during a plurality of etching processes; a controller for switching the corresponding bias RF power supply based on the etching process. Optionally, the plurality of bias RF signals include at least one low-frequency bias RF signal and at least one high-frequency bias RF signal.

Optionally, the controller internally stores a plurality of process durations corresponding to the plurality of etching processes and an execution sequence of the plurality of etching processes; the controller switches the corresponding biased RF power supply based on the process durations and the execution sequence to operate.

Optionally, the plasma etching device further includes a plurality of air inlet pipes, which can be respectively connected to a plurality of process gas sources, and the plurality of process gas sources are respectively used to provide corresponding process gases to the processing chamber in the plurality of etching processes; the controller opens the corresponding air inlet pipes based on the etching process.

Compared with the prior art, the beneficial effects of the present invention are:

1) The plasma etching method of the present invention sequentially performs first, second, and third etching processes during the etching process, using low-frequency, high-frequency, and low-frequency biased RF signals, respectively. The first etching process primarily utilizes anisotropic etching, forming a second pattern whose etching depth does not reach the base layer. The second etching process primarily utilizes isotropic etching, completely etching the material layer and generating a third pattern whose bottom critical dimension reaches a preset critical dimension. The third etching process modifies the sidewall morphology of the third etched pattern, generating a fourth pattern with consistent top and bottom contours and a bottom critical dimension that reaches a preset critical dimension. This invention solves the problem of failing to achieve the preset critical dimension at the bottom of the etched pattern and the difficulty in controlling the morphology of the bottom etched pattern during high-aspect-ratio etching of an etched material layer. The resulting fourth pattern maintains excellent verticality of its sidewalls despite a relatively high aspect ratio. The etched material layer serves as a hard mask for the base layer, and the excellent etched morphology of the fourth pattern significantly improves the etch quality of the base layer in the subsequent process.

The present invention precisely controls the etching depth of the second pattern to 70% to 98% of the thickness of the material layer being etched, ensuring that the second etching process can completely etch the material layer. Furthermore, when the bottom dimension of the third pattern reaches a preset critical dimension, the etching depth of the third pattern just reaches the upper surface of the base layer or penetrates a small thickness of the base layer. Furthermore, the sidewalls of the third pattern have minimal irregularities, thereby reducing the difficulty of modifying the third pattern during the third etching process. As a result, after the third etching process is completed, the base layer has a relatively small etching depth, reducing the impact on the next process (which uses the base layer as the primary etching target layer).

2) The plasma etching apparatus of the present invention can switch the corresponding biased RF signal and process gas based on the etching process in the processing chamber, and can accurately control the duration and execution sequence of each etching process, ensuring the etching effect of the device to be etched and significantly improving the device performance.

To more clearly illustrate the technical solution of the present invention, the following briefly introduces the figures required for the description. Obviously, the figures described below are an embodiment of the present invention. For those with ordinary knowledge in this field, other figures can be obtained based on these figures without further effort:

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any further progress are also within the scope of protection of the present invention.

It should be understood that when used in this specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and/or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or combinations thereof.

It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used in this specification and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It should be further understood that the term "and/or" used in this specification and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

As used in this specification and the appended claims, the term "if" may be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" may be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

In addition, in the description of the present invention, the terms "first", "second", "third", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

FIG1 is a schematic diagram of an inductively coupled plasma processing apparatus 1. The inductively coupled plasma processing apparatus 1 includes a processing chamber 10, a liner 102, an insulating window 108, an inductively coupled coil 112, and a base 105.

The processing chamber 10 includes a generally cylindrical sidewall 101 with an opening 109 for accommodating the entry and exit of the device W to be etched. An inner liner 102 is disposed within the processing chamber 10 to protect the inner wall of the processing chamber 10 from plasma corrosion. An insulating window 108 is located at the top of the processing chamber. A process gas inlet 103 is provided at one end of the sidewall 101, near the insulating window 108. A susceptor 105 is located at the bottom of the processing chamber 10 to support the device W to be etched.

The inductively coupled coil 112 is located outside the processing chamber 10 (above the insulating window 108). RF power from the RF power supply 116 drives the inductively coupled coil 112 to generate a strong high-frequency alternating magnetic field. This magnetic field generates an eddy electric field within the processing chamber 10. This electric field accelerates the small number of electrons present within the processing chamber 10, causing them to collide with gas molecules of the input process gas. These collisions lead to the ionization of the process gas and the excitation of plasma, thereby generating plasma within the processing chamber 10. The plasma contains a large number of active particles such as electrons, cations, excited atoms, molecules and electrically neutral free radicals. These particles can undergo various physical and chemical reactions with the surface of the device to be etched, causing the morphology of the surface to be etched to change, thus completing the etching process.

The etching process primarily utilizes cations and free radicals in the plasma. Since cations are charged, they can move in a specific direction under the influence of the electric field, exhibiting anisotropy (suitable for etching in a certain direction). Free radicals, being uncharged, can diffuse in all directions, exhibiting isotropy (suitable for etching in all directions). A biased RF signal applied to the susceptor 105 by the biased RF power source 207 accelerates the cations downward, impacting the area to be etched on the device W, thereby weakening the bonding forces between molecules in the area to be etched. The area to be etched where the molecular bonding force is weakened is captured by free radicals, converted into volatile gas compounds and released, thereby forming an etched pattern in the area to be etched.

Compared to high-frequency bias RF signals, low-frequency bias RF signals are more effective in enhancing the impact energy and directionality of cations, facilitating their arrival at the bottom of the etched pattern. Therefore, low-frequency bias RF signals are often used in high-aspect-ratio etching processes to increase the etch rate of the device W being etched. Under the bombardment of high-energy cations, molecules at the bottom of the etched pattern (where intermolecular bonds are weakened by cation attack) are more likely to be captured by free radicals and converted into volatile gaseous compounds than molecules on the sidewalls of the etched pattern. Although free radicals have isotropic characteristics, anisotropic physical etching has become the mainstream etching method under low-frequency bias radio frequency conditions.

The device W to be etched typically includes a base layer and an etch material layer located above the base layer. The process involved in the present invention etches the etch material layer, which is the primary etching target layer in the subsequent process. Therefore, the present invention requires that the etch material layer be completely etched while minimizing the etching of the base layer. When using a low-frequency biased RF signal for etching, the etching rate is high. To ensure complete etching of the etch material layer, the etching depth inevitably reaches the base layer. Byproducts generated during the plasma bombardment of the base layer easily sputter onto the sidewalls of the etched material layer pattern, making them difficult to remove. This results in a decrease in the lateral etching rate at the bottom of the etched material layer pattern, and the critical dimension at the bottom of the etched material layer pattern cannot reach the preset critical dimension, resulting in deformation.

With the advancement of semiconductor process nodes and the continuous reduction of feature sizes, plasma etching using only low-frequency bias RF signals can no longer meet the processing requirements for high aspect ratio etched patterns.

The present invention sequentially performs first, second, and third etching processes during the etching of an etched material layer, using low-frequency, high-frequency, and low-frequency biased radio frequency power sources, respectively. The first etching process primarily utilizes physical attack in the vertical direction (the depth direction of the etched pattern) to complete the primary etching task, and its etching depth does not reach the base layer. The second etching process primarily utilizes chemical etching in the lateral direction (the width direction of the etched pattern) to completely etch the etched material layer and achieve a preset critical dimension at the bottom of the etched material layer pattern. The third etching process, still primarily based on vertical physical impact, is used to modify the morphology of the sidewalls of the etched material layer pattern. This method achieves high-quality, high-aspect-ratio etched patterns in the material layer of the device W to be etched, while also achieving a high etching speed. Furthermore, by precisely controlling the etching depth of the first etching process, the present invention achieves complete etching of the etched material layer while maintaining a relatively low etching depth in the base layer, minimizing the impact on the subsequent process (which primarily etches the base layer).

Example 1

The present invention provides a plasma etching method, which is performed in a plasma processing chamber, as shown in FIG2 , and includes the following steps:

In step S100, a device W to be etched is provided. As shown in FIG3 , the device W to be etched includes a base layer 150, an etching material layer 140 and a mask layer 130 sequentially located on the base layer 150. In this embodiment, the etching material layer 140 serves as a hard mask layer for the base layer 150, and the mask layer 130 serves as a mask layer for the etching material layer 140. Before the process of the present invention begins, the mask layer 130 has a first pattern 161, which exposes the area of the etching material layer 140 to be etched.

In this embodiment, the mask layer 130 is made of an interphase of silicon oxide and silicon nitride (SiON). The first pattern 161 includes trenches and/or holes. The first pattern 161 can be obtained by conventional photolithography and etching, which will not be described in detail here.

In this embodiment, the material of the etching material layer 140 includes one or more of amorphous carbon (ACL), silicon carbide, polycrystalline silicon, and silicon nitride. The etching material layer 140 can be a single layer structure or a multi-layer stacked structure. The present invention does not limit the number of layers in the stacked structure.

In this embodiment, the material of the base layer 150 includes one or more of silicon dioxide and silicon nitride. In a preferred embodiment, the base layer 150 is an overlapping layer of silicon oxide and silicon nitride.

In step S200, a first low-frequency biased RF signal is applied to the processing chamber to perform a first etching process, forming a second pattern 162 (as shown in FIG. 4 ) in the etching material layer 140. The etching depth of the second pattern 162 is 70% to 98% of the thickness of the etching material layer. Optionally, the etching depth of the second pattern 162 is 90% to 98% of the thickness of the etching material layer to improve the efficiency of the etching process.

In this embodiment, a first process gas is injected into the processing chamber to perform a first etching process. Under the action of an RF electric field, the first process gas generates a corresponding first plasma. The first process gas primarily consists of a sulfur-containing gas (e.g., hydroxysulfide COS) and an oxygen-containing gas (e.g., oxygen _O2 ). The flow ratio of the sulfur-containing gas to the oxygen-containing gas in the first process gas is referred to as a first flow ratio. In this embodiment, the first flow ratio is less than or equal to 1:5. Experimental results have shown that this first flow ratio facilitates the ionization of the sulfur-containing gas, generating a high number of cations. In this embodiment, the frequency of the first low-frequency bias RF signal is 10kHz to 2MHz, which can provide greater energy to the positive ions in the first plasma, so that the first etching process is mainly anisotropic physical etching.

As the etching depth increases, the energy and number of cations reaching the bottom of the second feature gradually decrease, resulting in a weakening of the cation impact force and a deterioration of the ion collimation. As shown in Figure 4, the sidewalls at the bottom of the second feature exhibit an inward-converging morphology. The critical dimension at the bottom of the second feature does not reach the preset critical dimension.

In this embodiment, the etching depth can be controlled through an etching endpoint detection method or process time. By precisely controlling the etching depth of the first etching process to 70% to 98% of the thickness of the etched material layer, it is possible to prevent byproducts generated by cations bombarding the base layer 150 from splattering onto the sidewalls of the second pattern 162 and adversely affecting the critical dimensions at the bottom of the second pattern. On the other hand, an appropriate unetched thickness (2% to 30% of the thickness of the etched material layer) can be reserved in the etched material layer 140 for the subsequent etching process, so as to form a high-quality, high-aspect-ratio etched pattern on the device W to be etched through the subsequent etching process, and the etching depth of the base layer 150 will not exceed a preset depth threshold (described in detail later).

In step S300, a high-frequency bias RF signal is applied to the processing chamber to perform a second etching process, forming a third pattern 163. As shown in FIG5 , the etching depth of the third pattern 163 is greater than or equal to the thickness of the etched material layer 140. During the second etching process, the bottom of the third pattern is laterally etched, so that the critical dimension at the bottom of the third pattern reaches a predetermined critical dimension.

In this embodiment, a second process gas is injected into the processing chamber to perform a second etching process. Under the influence of an RF electric field, the second process gas generates a corresponding second plasma. The second process gas primarily comprises a sulfur-containing gas (e.g., hydroxysulfide COS) and an oxygen-containing gas (e.g., oxygen _O2 ). The flow ratio of the sulfur-containing gas to the oxygen-containing gas in the second process gas is referred to as a second flow ratio, which is less than the first flow ratio. In this embodiment, the second flow ratio is 1:10. This is for illustrative purposes only and is not intended to be limiting of the present invention.

In this embodiment, the frequency of the high-frequency bias RF signal is 4 MHz to 15 MHz. Since the impact force of the positive ions in the second plasma is relatively low, the second etching process is mainly isotropic chemical etching.

Under the bombardment of cations, the bonding between molecules in the bombarded layer weakens, breaking the molecular bonds. Oxygen, impacted by electrons in the radiofrequency electric field, dissociates into oxygen free radicals (O) (O₂+e → O+O+e, where e represents an electron). Increasing the volume of oxygen in the second process gas allows for more oxygen free radicals (O), increasing the probability of oxygen free radicals combining with the molecules whose bonds have been broken, thereby increasing the chemical etching rate.

In the second etching process, the ion impact energy is relatively low, so the etching depth of the etched material layer 140 is limited. By precisely controlling the etching depth of the first etching process, the present invention ensures that the etching depth of the etched material layer 140 in the second etching process does not exceed 30% of the thickness of the etched material layer, ensuring that the etched material layer 140 is completely etched.

When the etching depth of the first etching process is 70% to 98% of the thickness of the etched material layer, the bottom dimension of the third pattern 163 can be guaranteed to reach the preset critical dimension. The etching depth of the third pattern 163 just reaches the upper surface of the base layer or penetrates the minimum thickness of the base layer 150, preventing excessive etching of the base layer 150 and reducing the generation of reaction byproducts that attack the base layer 150. In addition, the sidewalls of the third pattern 163 have minimal irregularities, which can reduce the difficulty of subsequent modification of the third pattern sidewalls.

In step S400, a second low-frequency bias RF signal is applied to the processing chamber to perform a third etching process, forming a fourth feature 164 that penetrates the etched material layer 140 and a portion of the base layer 150. The aspect ratio of the fourth feature 164 ranges from 10:1 to 150:1. As shown in Figure 6, the critical dimension at the bottom of the fourth feature meets the preset critical dimension, and the sidewalls of the fourth feature have good verticality.

In this embodiment, a third process gas is injected into the processing chamber to perform a third etching process. Under the influence of an RF electric field, the third process gas generates a corresponding third plasma. The third process gas primarily comprises a sulfur-containing gas (e.g., hydroxysulfide COS) and an oxygen-containing gas (e.g., oxygen _O2 ). The flow ratio of the sulfur-containing gas to the oxygen-containing gas in the third process gas is referred to as a third flow ratio, which is less than the first flow ratio.

The frequency of the second low-frequency bias RF signal is 10 kHz to 2 MHz. The frequencies of the first and second low-frequency bias RF signals can be the same or different. The third etching process still primarily utilizes anisotropic physical etching, primarily used to modify the sidewalls of the 163 layer after the second etching process. Compared to the first process gas, the third process gas contains less sulfur-containing gas, and the number of cations in the third plasma is less than that in the first plasma. This reduction in the number of cations can reduce the generation of reaction byproducts that bombard the base layer 150. Because the sidewalls of the third pattern 163 have relatively minor irregularities, the difficulty of modifying them is low. Even if the number of positive ions in the third plasma is reduced, it is sufficient to produce a fourth pattern 164 with a good sidewall morphology. Furthermore, due to the low difficulty of modifying the sidewalls of the third pattern, after the third etching process is completed, the etching depth of the base layer 150 is relatively small (less than the preset depth threshold), reducing the impact on the next process (which primarily etches the base layer).

S500: Perform a fourth etching process to remove the mask layer 130.

A fourth process gas is injected into the processing chamber to perform a fourth etching process. The fourth process gas generates a corresponding fourth plasma under the action of the radio frequency electric field. The fourth plasma etches and removes the mask layer 130, resulting in the device W to be etched as shown in FIG. 7 , completing the high aspect ratio etching of the material layer 140 of the device W to be etched.

The fourth process gas in this embodiment is a mixed gas of oxygen and fluorine-containing gas, which is used to remove the SiON-based mask layer 130, which will not be described in detail here.

As shown in FIG8 , the present invention further provides a plasma etching device 2 for implementing the plasma etching method of the present invention.

The plasma etching apparatus 2 includes a processing chamber 20, a plurality of biased RF power supplies 207, a controller 230, and a plurality of gas inlet pipes 220.

A susceptor 205 is provided inside the processing chamber 20 , and the device W to be etched is placed on the susceptor 205 .

Multiple RF bias power supplies 207 are used to generate multiple RF bias signals and apply them to the susceptor 205. The multiple RF bias signals are used to control the energy of the plasma during multiple etching processes. In the present invention, the multiple RF bias power supplies include at least one low-frequency RF bias power supply 207a and one high-frequency RF bias power supply 207b.

The controller 230 stores a plurality of process times corresponding to the plurality of etching processes and the execution sequence of the plurality of etching processes. The controller 230 switches the corresponding bias RF power supply 207 to operate based on the process time and execution sequence of the etching process.

Multiple inlet lines 220 are connected to multiple process gas sources 204 via multiple flow control valves 221. The multiple process gas sources 204 are used to provide corresponding process gases to the processing chamber 20 during various etching processes. A controller 230 opens corresponding inlet lines 220 and adjusts the valve opening of the corresponding flow control valve 221 based on the etching process.

It should be understood that the order of execution of each step in the above embodiment does not imply the order of execution. The execution order of each process should be determined based on its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art will readily conceive of various equivalent modifications or substitutions within the technical scope disclosed herein, and such modifications or substitutions should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the patent application.

1: Plasma Etching Apparatus 10: Processing Chamber 101: Processing Chamber Wall 102: Liner 103: Process Gas Inlet 105: Base 108: Insulation Window 109: Opening 112: Inductively Coupled Coil 116: RF Power Supply 130: Mask Layer 140: Etching Material Layer 150: Base Layer 161: First Pattern 162: Second Pattern 163: Third Pattern 164: Fourth Pattern 2: Plasma Etching Apparatus 20: Processing Chamber 204: Process Gas Source 205: Base 207: Bias RF Power Supply 207a: Low-frequency bias RF power supply 207b: High-frequency bias RF power supply 220: Inlet pipe 221: Flow regulating valve 230: Controller W: Device to be etched S100-S400: Steps

Figure 1 is a schematic diagram of a plasma etching apparatus; Figure 2 is a flow chart of a plasma etching method according to a first embodiment of the present invention; Figure 3 is a schematic diagram of a device to be etched before etching according to the first embodiment of the present invention; Figure 4 is a schematic diagram of the device to be etched after the first etching process according to the first embodiment of the present invention; Figure 5 is a schematic diagram of the device to be etched after the second etching process according to the first embodiment of the present invention; Figure 6 is a schematic diagram of the device to be etched after the third etching process according to the first embodiment of the present invention; Figure 7 is a schematic diagram of the device to be etched after the fourth etching process according to the first embodiment of the present invention; Figure 8 is a schematic diagram of the plasma etching apparatus according to the present invention.

S100~S400: Steps

Claims (16)

A plasma etching method is performed in a plasma processing chamber and comprises the following steps: Providing a device to be etched, the device comprising a base layer, an etching material layer sequentially disposed on the base layer, and a mask layer, the mask layer having a first pattern that exposes the area of the etching material layer to be etched; Applying a first low-frequency biased radio frequency signal to the processing chamber to perform a first etching process, forming a second pattern in the etching material layer, wherein the etching depth of the second pattern is 70% to 98% of the thickness of the etching material layer; A high-frequency bias RF signal is applied to the processing chamber to perform a second etching process, forming a third pattern having an etching depth greater than or equal to the thickness of the etched material layer; a critical dimension at the bottom of the third pattern reaches a preset critical dimension; the critical dimension includes at least one of the width and diameter of the pattern; A second low-frequency bias RF signal is applied to the processing chamber to perform a third etching process, forming a fourth pattern penetrating the etched material layer and a portion of the thickness of the base layer; the critical dimension at the bottom of the fourth pattern reaches a preset critical dimension; the etching depth of the base layer is less than a preset depth threshold. The plasma etching method of claim 1, wherein the frequencies of the first low-frequency offset RF signal and the second low-frequency offset RF signal are 10 kHz to 2 MHz, and the frequency of the high-frequency offset RF signal is 4 MHz to 15 MHz. The plasma etching method of claim 1, wherein the frequencies of the first low-frequency bias RF signal and the second low-frequency bias RF signal are the same or different. The plasma etching method of claim 1, wherein the aspect ratio of the fourth pattern is in the range of 10:1 to 150:1. The plasma etching method as described in claim 1, wherein the material of the mask layer is silicon oxynitride. The plasma etching method as described in claim 1, wherein the material of the etching material layer includes any one or more of amorphous carbon, silicon carbide, polycrystalline silicon, and silicon nitride. The plasma etching method as described in claim 1, wherein the material of the base layer includes any one or more of silicon dioxide and silicon nitride. The plasma etching method of claim 1, wherein the etching depth is controlled by an etching endpoint detection method or process time. The plasma etching method of claim 1, wherein the first pattern comprises trenches and/or holes. The plasma etching method as described in claim 1, wherein after the third etching process is completed, a fourth etching process is performed to remove the mask layer. The plasma etching method as described in claim 1, wherein a first process gas is injected into the processing chamber to perform the first etching process, and the flow ratio of the sulfur-containing gas to the oxygen-containing gas in the first process gas is a first flow ratio, and the first flow ratio is less than or equal to 1:5. A plasma etching method as described in claim 11, wherein a second process gas is injected into the processing chamber to perform the second etching process, the flow ratio of the sulfur-containing gas to the oxygen-containing gas in the second process gas is a second flow ratio, and the second flow ratio is less than the first flow ratio; a third process gas is injected into the processing chamber to perform the third etching process, the flow ratio of the sulfur-containing gas to the oxygen-containing gas in the third process gas is a third flow ratio, and the third flow ratio is less than the first flow ratio. A plasma etching apparatus for implementing the plasma etching method according to any one of claims 1 to 12, comprising: a processing chamber having a susceptor disposed therein, on which a device to be etched is placed; a plurality of bias RF power supplies for generating a plurality of bias RF signals and applying them to the susceptor; the plurality of bias RF signals being used to control plasma energy in a plurality of etching processes; a controller for switching the corresponding bias RF power supply based on the etching process. The plasma etching apparatus of claim 13, wherein the plurality of bias RF signals include at least one low-frequency bias RF signal and at least one high-frequency bias RF signal. The plasma etching device as described in claim 13, wherein the controller internally stores multiple process durations corresponding to the multiple etching processes and the execution sequence of the multiple etching processes; the controller switches the corresponding biased RF power supply based on the process durations and the execution sequence to operate. The plasma etching device as described in claim 13 further includes multiple air inlet pipes, which can be respectively connected to multiple process gas sources, and the multiple process gas sources are respectively used to provide corresponding process gases to the processing chamber in the multiple etching processes; the controller opens the corresponding air inlet pipes based on the etching process.