TWI462180B - Method of etching a multi-layer - Google Patents

Description

Way of etching composite film

The present invention discloses a method of etching a composite film, particularly a method capable of reducing sidewall polymerization residue generation and avoiding collapse of an aluminum layer in a composite film.

In the modern information society, microprocessor systems consisting of integrated circuits (ICs) have long been used in all aspects of life, such as home appliances, mobile devices, and personal computers. There is a trace of the integrated circuit.

In order to connect various active or passive components on a semiconductor substrate, aluminum or an alloy thereof is often used as a wire, and a complicated interconnecting system is gradually formed by a patterning process. Generally, a method for forming a patterned aluminum layer is to first deposit a photoresist layer on the aluminum layer, and perform a photo-etching-process (PEP) by using a mask of different patterns to The pattern on the photoresist is transferred to the aluminum layer.

Please refer to FIG. 1 , which is a schematic cross-sectional view of a conventional process for forming a patterned aluminum layer. As shown in FIG. 1, a dielectric layer 10, a barrier 12, an aluminum layer 14, and an anti-reflection coating (ARC) 16 are sequentially disposed on a semiconductor substrate (not shown). And a photoresist layer 22. The barrier layer 12 is a selective structure, which may be a material such as titanium, titanium nitride or tantalum nitride. Most of them are conventionally used as a via plug for forming a via plug. The adhesion is increased, and the anti-reflection layer 16 reduces the reflection of light during exposure.

Due to the difference in material between the composite layers, recipes of different etching gases must be used to accurately remove the anti-reflective layer 16 or the aluminum layer 14. These formulations typically comprise chlorine gas (Cl ₂ ), bromine trichloride (BCl ₃ ), nitrogen (N ₂ ), trifluoromethane (CHF ₃ ) or hydrocarbons. Among them, chlorine gas and bromine trichloride are used as etching gases, and are excited as radicals by plasma generated in the etching chamber to perform anisotropic etching against the reflective layer 16 and the aluminum layer 14. In order to maintain good directionality, a passivation gas such as a hydrocarbon is used to generate a polymer on the sidewall and obtain good sidewall protection.

The conventional bromine trichloride has a passivation property in addition to an etching function, and thus is widely used for anisotropic etching. However, the use of bromine trichloride also tends to cause excessive loose polymer residue on the side walls to easily cause disadvantages such as corrosion of the aluminum layer. As shown in Fig. 1, since bromine trichloride also has a passivation function, if bromine trichloride and other passivating species are used at the same time, excessive polymerization residue 24 is generated on the side wall and is not dense enough. And because too much loose polymer residue 24 is formed on the sidewalls, many of the chlorine radicals (Cl _plasma ) generated by the plasma excitation are easily adsorbed in the polymerization residue 24 and react with the aluminum layer 14 in the sidewall. Please refer to Figure 2, which is a schematic diagram of the reaction of the aluminum layer to initiate corrosion of the aluminum layer. As shown in Fig. 2, after the aluminum metal (Al _(s) ) in the aluminum layer 14 reacts with the chlorine radical (Cl _plasma ), a gaseous and liquid intermediate AlCl _{x is} produced, and the liquid AlCl _{x is} contacted. Water (H ₂ O) produces aluminum hydroxide (Al(OH) _x ) and gaseous and liquid hydrochloric acid (HCl _{(g) + (aq)} ). The liquid hydrochloric acid (HCl _(aq) ) then reacts with the aluminum layer to regenerate AlCl _x , and then enters the aforementioned cycle, and continues to go back and forth, causing the aluminum layer to be severely eroded, thereby causing the aluminum layer to collapse. phenomenon. Although this situation can be avoided by the barrier of moisture H ₂ O, this will additionally increase the factors required for control in the etching process, which will complicate the process.

Therefore, a simple dry etching process is required to etch the aluminum layer and the anti-reflection layer, and to reduce the polymerization residue and the aluminum layer collapse.

The present invention provides a method of etching a composite film, particularly a method of reducing the generation of etching polymerization residues and increasing the density of the polymerization residue to avoid collapse of the aluminum layer in the composite film.

In accordance with the scope of the patent application, the present invention provides a method of etching a composite film comprising an aluminum layer disposed on a semiconductor substrate and an anti-reflective layer disposed on the aluminum layer. The method first performs a first etching step of etching the anti-reflective layer by providing a first etching gas, wherein the first etching gas contains a chlorine-containing substance. A second etching step is then performed to etch the aluminum layer by providing a second etching gas, wherein the second etching gas does not contain a chlorine-containing compound.

According to the scope of the patent application, the present invention further provides a method of anisotropically etching an aluminum layer. The method includes providing an etch gas to etch the aluminum layer, wherein the etch gas comprises a chlorine-containing species but does not comprise a chlorine-containing compound.

The method for etching a composite film proposed by the present invention excludes a chlorine-containing compound as an etching gas, which not only makes the etching process simpler, but also reduces the phenomenon of polymerization residue and aluminum layer collapse, and can obtain a better etching effect.

Please refer to FIG. 3, which is a flow chart of etching a composite film in the present invention. As shown in FIG. 3, the method for etching a composite film of the present invention comprises the following steps: Step 100: providing a composite film on a semiconductor substrate, the composite film comprising at least one aluminum layer, and one of the anti-resistances disposed on the aluminum layer Reflective layer.

Step 102: performing a first etching step on the composite film by using a patterned mask, providing a first etching gas and a first passivation gas to etch the anti-reflective layer, wherein the first etching gas comprises a chlorine-containing substance (chlorine-containing substance).

Step 104: After step 102 is performed, a second etching step is performed to provide a second etching gas and a second passivation gas to etch the aluminum layer, wherein the second etching gas does not contain a chlorine-containing compound (chlorine- Containing compound).

Step 106: After etching the aluminum layer, an over-etching step is performed to etch a barrier layer under the aluminum layer.

For a detailed description of each step, please refer to FIG. 4 to FIG. 7 , and FIG. 4 to FIG. 7 are structural schematic views of the steps of the method for etching the composite film of the present invention. As shown in FIG. 4 and step 100, a composite film is first provided on the semiconductor substrate 108. The composite film sequentially includes a dielectric layer 110, a barrier layer 112, an aluminum layer 114, an anti-reflection layer 116, and a film. Mask layer 122. The dielectric layer 110 may be yttrium oxide (SiO ₂ ), tantalum nitride, tantalum carbide, tetraethoxy decane (TEOS), undoped bismuth glass (USG), phosphorous silicate glass (PSG), borophosphorus bismuth glass. (BPSG), or other low-k dielectric material or any combination of the above, and the barrier layer 112 may be made of titanium or titanium nitride, tantalum nitride or combinations thereof. The aluminum layer 114 may be an aluminum alloy such as a copper-aluminum alloy in addition to a general aluminum metal. The anti-reflective layer 116 comprises titanium or titanium nitride, etc., which may be a single layer or a double layer structure, for example, comprising a bottom anti-reflection layer and a top anti-reflection layer. The bottom anti-reflection layer comprises titanium nitride and the top anti-reflection layer. The material of the reflective layer may be the same as or different from the bottom anti-reflective layer, for example, an organic anti-reflective material, or other inorganic anti-reflective materials such as silicon oxynitride (SiON). The mask layer 122 has a patterned structure, such as a photoresist, the pattern of which can be transferred to the anti-reflective layer 116 and the aluminum layer 114 underneath the subsequent etching step.

Next, referring to FIG. 5 and step 102, a first etching step is performed to provide a first etching gas 126 and a first passivation gas to etch the anti-reflective layer 116 but less etch the aluminum layer 114, so that step 102 ends. The anti-reflective layer 116 in most of the wafer is etched or even slightly damaged by the underlying aluminum layer 114, but a small amount of anti-reflective layer 116 may remain in some areas. The first etching gas 126 may be any other chlorine-containing substance that does not contain various chlorine-containing compounds, for example, only chlorine gas is used but bromine trichloride is not used. In another embodiment of the present invention, the first etching gas 126 dedicated to etching the anti-reflective layer 116 but not etching the aluminum layer 114 may also contain all chlorine-containing substances. Simultaneous use of chlorine or various chlorine-containing compounds, such as the simultaneous use of chlorine and bromine trichloride. The first passivation gas may comprise a hydrocarbon or the like. In a preferred embodiment of the invention, the first passivation gas is preferably ethylene (C ₂ H ₄ ).

The first etching step is performed in a plasma etch reaction chamber. Table 1 provides a preferred etching recipe and operating environment for the first etching gas 126 to be chlorine. As shown in Table 1, the first etching step can be performed in the following state: the pressure range in the plasma etching reaction chamber is controlled to be between 12 and 18 mTorr, and the pressure-coupled plasma power is in the range of 1200 to 1600 watts. The range of bias power is 250 to 350 watts, the time range is 120 to 180 seconds, the flow rate of chlorine gas is 150 to 210 standard cubic centimeter per minute (sccm), and the flow rate of ethylene is 120 to 180 sccm. . The time of the first etching step can be adjusted according to the material and thickness of the anti-reflection layer 116 to be etched, and is not limited to the number of seconds shown in Table 1, which can be longer or shorter.

Next, referring to FIG. 6 and step 104, after etching the pattern of the anti-reflective layer 116, a second etching step is performed to etch the aluminum layer 114, which uses a second etching gas 128 and a second passivation gas. . In order to avoid the conventional use of bromine trichloride, which tends to cause excessive polymerization residue, thereby causing aluminum corrosion and collapse of the aluminum layer, the second etching gas 128 of the present invention is a chlorine-containing substance that does not contain a chlorine-containing compound, for example, only used. Chlorine-containing substances such as chlorine, but it is necessary to exclude various conventional chlorine-containing compounds such as bromine trichloride. The second passivation gas contains hydrocarbons and the like. In a preferred embodiment of the invention, the second passivation gas is ethylene (C ₂ H ₄ ). The second etching step can also be performed in-situ in the plasma etching reaction chamber. Please refer to Table 1. The second etching step can be performed in the following state: the pressure range in the plasma etching reaction chamber is controlled in Between 8 and 12 mTorr, the transformer-coupled plasma power range is between 1300 and 1700 watts, the bias power range is 250 to 350 watts, the chlorine gas flow rate ranges from 120 to 180 sccm, and the ethylene flow rate ranges from 120 to 180 sccm. . It should be noted that the time used for the second etching step is determined by the end point detection. If the thickness of the aluminum or other metal to be etched is increased or decreased, the time of the second etching step will also change, so The number of seconds listed in 1 is for reference only and is not intended to be a limitation of the invention.

When steps 102 and 104 are completed, the layout pattern on mask layer 122 has been transferred to aluminum layer 114 to form patterned aluminum layer 114. Next, referring to FIG. 7, as shown in step 106, an over-etching step is performed in-situ to etch the barrier layer 112 and the aluminum layer 114 remaining in a portion of the upper portion of the wafer by the third etching gas 130. This step may cause the thickness loss of the dielectric layer 110 to ensure that the aluminum layer 114 and the barrier layer 112 to be removed are etched out. For the operating parameters, please refer to Table 1, which will not be repeated here. After the end of step 106, the process of completely patterning the aluminum layer 114 can be completed by finally cleaning the polymer residue with argon gas or the like and removing the mask layer 122.

As described in the prior art, it is conventional to use bromine trichloride as an etching gas and a passivation gas, so that it is easy to generate excessive polymerization residue on the sidewall of the patterned aluminum layer, causing corrosion of aluminum and causing collapse of the aluminum layer. . Therefore, the etching method proposed by the present invention avoids the use of a chlorine-containing compound such as molybdenum trichloride as an etching gas and a passivation gas such as a hydrocarbon as an etching gas when etching the aluminum layer. Conventional bromine trichloride produces sidewall polymers primarily by bombardment of the mask layer, but these polymers are generally relatively loose, while hydrocarbons have longer polymer chains and The denser structure (such as [CH]x polymer) can completely replace the passivation function of bromine trichloride, and does not reduce the protective ability of the sidewall due to the removal of bromine trichloride. On the contrary, it can avoid excessive polymerization. The generation of the residue can effectively prevent the residue from adsorbing excessive chlorine radicals and causing the aluminum layer to collapse. Therefore, the method for etching a composite film proposed by the present invention can reduce the polymerization residue and the collapse of the aluminum layer by eliminating the chlorine-containing compound and making the aluminum etching process simpler, and can obtain better etching. effect. The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be within the scope of the present invention.

108‧‧‧Semiconductor substrate

10,110‧‧‧ dielectric layer

12,112‧‧‧Block

14,114‧‧‧Aluminum layer

16,116‧‧‧Anti-reflective layer

22,122‧‧‧mask layer

24‧‧‧ Polymer residue

100,102 104,106‧‧‧Steps

126‧‧‧First etching gas

128‧‧‧Second etching gas

130‧‧‧ Third etching gas

Fig. 1 is a schematic cross-sectional view showing a process of forming a patterned aluminum layer.

Figure 2 is a schematic representation of the generation of polymeric residues on conventional sidewalls.

Figure 3 is a flow chart of etching a composite layer in the present invention.

4 to 7 are schematic views showing the structure of each step of the method for etching a composite film of the present invention.

100,102 104,106. . . step

Claims (20)

A method of etching a composite film, the composite film comprising a barrier layer disposed on a semiconductor substrate, an aluminum layer disposed on the dielectric layer, and an anti-reflection layer disposed on the aluminum layer, the method comprising: Performing a first etching step to provide a first etching gas to etch the anti-reflective layer, wherein the first etching gas comprises a chlorine-containing substance; performing a second etching step to provide a second etching Gas etching the aluminum layer, wherein the second etching gas does not comprise a chlorine-containing compound; and performing a third etching step to provide a third etching gas to etch the barrier layer, wherein the third layer The etching gas contains a chlorine-containing substance. The method of claim 1, wherein the chlorine-containing compound comprises boron trichloride (BCl ₃ ). The method of claim 1, wherein the second etching gas comprises chlorine. The method of claim 1, wherein the first etching gas comprises chlorine (Cl ₂ ) and boron trichloride (BCl ₃ ). The method of claim 1, wherein the first etching gas comprises chlorine. The method of claim 1, wherein the first etching step further comprises providing a first passivation gas. The method of claim 6, wherein the first passivation gas comprises a hydrocarbon. The method of claim 6, wherein the first passivation gas comprises ethylene (C ₂ H ₄ ). The method of claim 1, wherein the second etching step further comprises providing a second passivation gas. The method of claim 9, wherein the second passivation gas comprises a hydrocarbon. The method of claim 9, wherein the second passivation gas comprises ethylene. The method of claim 6, wherein the first etching step is performed according to the following state: a pressure range of 12 to 18 mTorr, and a transformer-coupled plasma power range of 1200 to 1600 watts, a bias voltage The power range is 250 to 350 watts, the time range is 120 to 180 seconds, the flow rate of the first etching gas ranges from 150 to 210 sccm, and the flow rate of the first passivation gas ranges from 120 to 180 sccm. The method of claim 9, wherein the second etching step is as follows State: a pressure range of 8 to 12 mTorr, a transformer-coupled plasma power range of 1300 to 1700 watts, a bias power range of 250 to 350 watts, and a flow rate range of 120 to 180 sccm for the first etch gas The flow rate of the first passivation gas ranges from 120 to 180 sccm. A method for anisotropically etching an aluminum layer, comprising: etching the aluminum layer, wherein the etching step comprises using only one etching gas and a hydrocarbon, the etching gas containing a chlorine-containing substance, but Does not contain a chlorine-containing compound. The method of claim 14, wherein the chlorine-containing compound comprises boron trichloride. The method of claim 14, wherein the etching gas comprises chlorine. The method of claim 14, further comprising providing a passivation gas. The method of claim 17, wherein the passivation gas comprises a hydrocarbon. The method of claim 17, wherein the passivating gas comprises ethylene. The method of claim 17, wherein the etching step is performed according to the following state: a pressure range of 8 to 12 mTorr, and a transformer-coupled plasma power range is 1300 to 1700 watts, a bias power range of 250 to 350 watts, a flow rate of the etching gas of 120 to 180 sccm, and a flow rate of the passivation gas of 120 to 180 Sccm.