Highly selective silicon oxide / silicon nitride etch by selective boron nitride or aluminum nitride deposition

Abstract

A method for selectively etching silicon oxide relative to silicon nitride includes: exposing a substrate to a first gas that forms a first layer on a silicon oxide film and a second layer on a silicon nitride film, wherein the first gas contains boron, aluminum, or both boron and aluminum; exposing the substrate to a nitrogen-containing gas that reacts with the first layer on the silicon oxide film to form a first nitride layer and reacts with the second layer on the silicon nitride film to form a second nitride layer, wherein the thickness of the second nitride layer is greater than the thickness of the first nitride layer. The method further includes exposing the substrate to an etching gas that etches the first nitride layer and the silicon oxide film, wherein the second nitride layer protects the silicon nitride film from being etched by the etching gas.

Description

[0001] Cross-references to related applications

[0002] This application relates to and claims priority to U.S. Provisional Patent Application Serial No. 62 / 864,378, filed June 20, 2019, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to the field of semiconductor manufacturing and semiconductor devices, and more particularly to a method for selectively etching silicon oxide relative to silicon nitride. Background Technology

[0004] The development of advanced semiconductor technology presents significant challenges due to the need for selective dry etching to remove one material relative to others. Selective silicon oxide etching relative to silicon nitride has numerous applications in semiconductor manufacturing, and preferred passivations (mostly carbon-based) have been extensively explored for high etch selectivity when using plasmas containing fluorocarbon (FC) or hydrofluorocarbon (HFC) gases. The need for high etch selectivity is particularly important for devices with small silicon nitride loss tolerances, such as self-aligned contacts (SAC). Summary of the Invention

[0005] Several embodiments disclose a method for selectively etching silicon oxide relative to silicon nitride. According to one embodiment, the method includes: providing a substrate containing a silicon oxide film and a silicon nitride film; a1) exposing the substrate to a first gas, the first gas forming a first layer on the silicon oxide film and a second layer on the silicon nitride film, wherein the first gas contains boron, aluminum, or both; and a2) exposing the substrate to a nitrogen-containing gas, the nitrogen-containing gas reacting with the first layer on the silicon oxide film to form a first nitride layer and reacting with the second layer on the silicon nitride film to form a second nitride layer, wherein the thickness of the second nitride layer is greater than the thickness of the first nitride layer. The method further includes a3) exposing the substrate to an etching gas, the etching gas etching the first nitride layer and the silicon oxide film, wherein the second nitride layer protects the silicon nitride film from etching by the etching gas. According to one embodiment, the method further includes a0) exposing the substrate to a gas containing H2, the gas terminating the silicon oxide film with -OH surface species and with -NH... x Surface species terminate the silicon nitride film.

[0006] According to one embodiment, the method includes: providing a substrate containing a silicon oxide film and a silicon nitride film; a1) exposing the substrate to a BCl3 gas, the gas forming a first BCl3 layer on the silicon oxide film and a second BCl3 layer on the silicon nitride film; and a2) exposing the substrate to an NH3 gas, the gas reacting with the first BCl3 layer on the silicon oxide film to form a first boron nitride layer and reacting with the second BCl3 layer on the silicon nitride film to form a second boron nitride layer, wherein the thickness of the second boron nitride layer is greater than the thickness of the first boron nitride layer. The method further includes a3) exposing the substrate to a plasma-excited CF4 gas, the gas etching the first boron nitride layer and the silicon oxide film, wherein the second boron nitride layer protects the silicon nitride film from etching by the etching gas. According to one embodiment, the method further includes a0) exposing the substrate to an H2-containing gas, the gas terminating the silicon oxide film with -OH surface species and with -NH... x Surface species terminate the silicon nitride film. Attached Figure Description

[0007] In the attached diagram:

[0008] Figure 1 This is a process flow diagram for selectively etching a silicon oxide film relative to a silicon nitride film according to an embodiment of the present invention;

[0009] Figures 2A-2D A method for selectively etching a silicon oxide film relative to a silicon nitride film according to an embodiment of the present invention is schematically illustrated by cross-sectional views.

[0010] Figure 3 This is a process flow diagram for selectively etching a silicon oxide film relative to a silicon nitride film according to an embodiment of the present invention; and

[0011] Figures 4A-4E A method for selectively etching a silicon oxide film relative to a silicon nitride film according to an embodiment of the present invention is illustrated schematically by means of a cross-sectional view. Detailed Implementation

[0012] Figure 1 This is a process flow diagram for selectively etching a silicon oxide film relative to a silicon nitride film according to an embodiment of the present invention, and Figures 2A-2D A method for selectively etching a silicon oxide film relative to a silicon nitride film according to an embodiment of the present invention is illustrated schematically by means of a cross-sectional view.

[0013] Now for reference Figure 1 and Figure 2A The processing method in process flow diagram 10 includes, in step 12, providing a substrate 2 containing a SiO2 film 200 and a Si3N4 film 220. Figure 2AIn the example shown, the SiO2 film 200 and the Si3N4 film 220 are on the same horizontal plane, but embodiments of the invention can also be applied to films that are not on the same horizontal plane but are vertically offset. Si3N4 is the most thermodynamically stable silicon nitride and therefore the most commercially important silicon nitride. However, embodiments of the invention can be applied to other silicon nitrides containing Si and N as main components, wherein the silicon nitride can have a wide range of Si and N compositions (Si... x N y Similarly, SiO2 is the most thermodynamically stable of silicon oxides and is therefore the most commercially important. However, embodiments of the invention can be applied to other silicon oxides containing Si and O as major components, wherein the silicon oxide can have a wide range of Si and O compositions (SiO2). x O y ).

[0014] The method further includes exposing the substrate 2 to a first gas 201 in step 14. The first gas 201 may contain boron, aluminum, or both boron and aluminum. The first gas 201 may include boron hydride, boron halide, organoaluminum compounds, aluminum hydride, aluminum chloride, or combinations thereof. According to one embodiment, the first gas 201 may be selected from the group consisting of BH3, BCl3, BF3, Al(CH3)3, AlH3, AlCl3, and combinations thereof. Exposure can be performed with or without plasma excitation of the first gas 201. Exposure to the first gas 201 forms a first layer 202 (e.g., BCl3) on the SiO2 film 200 and a second layer 222 (e.g., BCl3) on the Si3N4 film 220. Figure 2B As schematically shown, the first layer 202 is thinner than the second layer 222, and the first layer may be incomplete, having pores that expose the underlying SiO2 film 200. This preferential adsorption of the first gas 201 on the Si3N4 film 220 is attributed to the higher adsorption energy of the first gas 201 on the Si3N4 film 220 compared to its adsorption energy on the SiO2 film 200, and this effect is highly preferred in the absence of plasma excitation or when remote plasma excitation is used with the first gas 201.

[0015] The method further includes exposing the substrate 2 to a nitrogen-containing gas 203 in step 16. According to one embodiment, the nitrogen-containing gas 203 may be selected from the group consisting of nitrogen hydrides, nitrogen halides, N2, and combinations thereof. For example, nitrogen hydrides may include NH3, N2H4, or combinations thereof. For example, nitrogen halides may include NCl3. In one example, the nitrogen-containing gas 203 may be selected from the group consisting of NH3, N2H4, NCl3, N2, and combinations thereof.

[0016] Exposure can be performed with or without plasma excitation containing nitrogen gas 203. The nitrogen gas 203 reacts with the first layer 202 and the second layer 222 to form a first nitride layer 204 and a second nitride layer 224, respectively. The first nitride layer 204 and the second nitride layer 224 may contain boron nitride, aluminum nitride, or both. Figure 2C As schematically shown, the first nitride layer 204 may be incomplete, having pores that expose the underlying SiO2 film 200. However, this is not necessary, and the first nitride layer may be continuous. The second nitride layer 224 has a greater thickness than the first nitride layer 204 and is substantially continuous, at least over the underlying Si3N4 film 220.

[0017] In one example, the first gas 201 contains BCl3 and the nitrogen-containing gas contains NH3. The basic reaction for forming boron nitride (BN) and volatile HCl byproducts can be represented as:

[0018] BCl3 + NH3 → BN + 3HCl

[0019] The formation of boron nitride is thermodynamically favorable, and boron nitride provides strong etch protection against a variety of commonly used etch gases.

[0020] According to one embodiment, exposure steps 14 and 16 can be performed alternately and sequentially. According to another embodiment, exposure steps 14 and 16 can at least partially overlap in time. As indicated by process arrow 18, exposure steps 14 and 16 can be repeated at least once until the thickness of the second nitride layer 224 is sufficient to act as an etch stop layer, while the thickness of the first nitride layer 204 is insufficient to protect the SiO2 film 200 in subsequent etching processes.

[0021] The method further includes exposing the substrate 2 to etching gas 205 in step 20. This in Figure 2DThe diagram is schematically shown. Typically, the etching gas 205 can be selected from any gas used for etching silicon oxide, boron nitride, and aluminum nitride. The etching gas 205 can be plasma-excited and may contain fluorocarbon gases, hydrofluorocarbon gases, hydrochlorofluorocarbon gases, hydrochlorofluorocarbon gases, or combinations thereof. In some instances, the etching gas 205 may contain CF4, CF2Cl2, CH2F2, CH4, CH3F, CHF3, C4H6, C2H4, C3H6, CH2Cl2, CH3Cl, CH2ClF, CHCl2F, or combinations thereof. The etching gas 205 may optionally further include Ar, He, or combinations thereof. Exposure to the etching gas 205 etches the first nitride layer 204 and the SiO2 film 200. Although the second nitride layer 224 is partially etched, the Si3N4 film 220 is not etched as long as the second nitride layer 224 provides sufficient protection against the etching gas 205. In one instance, exposure to the etching gas 205 can be stopped before the second nitride layer 224 stops providing sufficient protection to the Si3N4 film 220 from etching.

[0022] Plasma excitation of etching gas 205 can be performed in conventional commercial plasma processing systems, including inductively coupled plasma (ICP) systems, capacitively coupled plasma (CCP) systems, microwave plasma systems, remote plasma systems that generate plasma excitation of material from upstream of the substrate, electron cyclotron resonance (ECR) systems, and other systems.

[0023] As indicated by process arrow 22, exposure steps 14, 16, and 20 can be repeated at least once to redeposit the first nitride layer 204 and the second nitride layer 224 and further etch the SiO2 film 202. According to Figure 2D In the schematic embodiment shown, exposure to etching gas 205 completely removes the first nitride layer 204 from the substrate 2 and etches the SiO2 film 202. According to another embodiment, exposure to etching gas 205 may only partially remove the first nitride layer 204 and etch the SiO2 film 202 before repeating exposure steps 14 and 16. Once the SiO2 film 202 has been sufficiently etched, a second nitride layer 224 can be removed using a dry or wet etching process (using a strong oxidizing agent).

[0024] Figure 3 This is a process flow diagram for selectively etching a silicon oxide film relative to a silicon nitride film according to an embodiment of the present invention, and Figures 4A-4E A method for selectively etching a silicon oxide film relative to a silicon nitride film according to an embodiment of the present invention is schematically illustrated by a cross-sectional view. The processing method in process flow diagram 30 is similar to... Figure 1The process flow diagram 10 is shown, but the former further includes a pretreatment step of exposing the substrate to a gas containing H2, which enhances the preferential formation of the first layer on the silicon nitride film relative to the silicon oxide film, and thus enhances the formation of the subsequent nitride layer on the silicon nitride film.

[0025] Process flow diagram 30 includes a substrate 4 containing a SiO2 film 400 and a Si3N4 film 420, provided in 32. This is in Figure 4A This is schematically illustrated. Subsequently, in step 34, the method includes exposing the substrate 4 to an H2-containing gas 401. This is in... Figure 4B The diagram is schematically shown. Exposure to H2-containing gas 401 results in the termination of the SiO2 film 400 with the -OH surface 402 and the -NH... x Surface 422 terminates Si3N4 film 420.

[0026] The method further includes exposing the substrate 4 to a first gas 403 at step 36. Exposure to the first gas 403 forms a first layer 404 (e.g., BCl3) on the SiO2 film 400 and a second layer 424 (e.g., BCl3) on the Si3N4 film 420. This... Figure 4C It is shown schematically in the diagram.

[0027] The method further includes exposing the substrate 4 to a nitrogen-containing gas 405 in step 38. The nitrogen-containing gas 405 reacts with the first layer 404 and the second layer 424 to form a first nitride layer 406 and a second nitride layer 426, respectively. According to one embodiment, exposure steps 34, 36, and 38 may be performed alternately and sequentially. According to another embodiment, exposure steps 34, 36, and 38 may overlap at least partially in time. As indicated by process arrow 40, exposure steps 34, 36, and 38, or exposure steps 36 and 38, may be repeated at least once until the thickness of the second nitride layer 426 is sufficient to act as an etch stop layer, while the thickness of the first nitride layer 406 is insufficient to protect the SiO2 film 400 during subsequent etching processes.

[0028] The method further includes exposing the substrate 4 to etching gas 407 in step 42. This in Figure 4E The diagram schematically illustrates the process of exposing the first nitride layer 406 and the SiO2 film 400 to etching gas 407. Although the second nitride layer 426 is partially etched, the Si3N4 film 420 remains unetched as long as the second nitride layer 426 provides sufficient protection against the etching gas 407. In one example, exposure to the etching gas 407 can be stopped before the second nitride layer 426 ceases to adequately protect the Si3N4 film 420 from etching.

[0029] As indicated by process arrow 44, exposure steps 34, 36, 38, and 42 can be repeated at least once to redeposit the first nitride layer 406 and the second nitride layer 426 and further etch the SiO2 film 402. According to Figure 4E In the schematic embodiment shown, exposure to etching gas 407 completely removes the first nitride layer 406 from the substrate 4 and etches the SiO2 film 402. According to another embodiment, exposure to etching gas 407 may only partially remove the first nitride layer 406 and etch the SiO2 film 402 before repeating exposure steps 36, 38, and 42, or before repeating exposure steps 34, 36, 38, and 42.

[0030] Several embodiments of selective etching of silicon oxide relative to silicon nitride have been described. For illustrative and descriptive purposes, the foregoing description of embodiments of the invention has been presented. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. This specification and the appended claims include terms used for descriptive purposes only and should not be construed as limiting. Those skilled in the art will understand that many modifications and variations are possible in light of the above teachings. Those skilled in the art will recognize various equivalent combinations and substitutions of the various components shown in the drawings. Therefore, it is intended that the scope of the invention is not limited by this specific embodiment, but rather by the claims appended thereto.

Claims

1. A substrate processing method, comprising: A substrate containing a silicon oxide film and a silicon nitride film is provided; a1) Expose the substrate to a first gas, which forms a first layer on the silicon oxide film and a second layer on the silicon nitride film, wherein the first gas contains boron, aluminum, or both boron and aluminum; a2) Expose the substrate to a nitrogen-containing gas, which reacts with the first layer on the silicon oxide film to form a first nitride layer, and reacts with the second layer on the silicon nitride film to form a second nitride layer, wherein the thickness of the second nitride layer is greater than the thickness of the first nitride layer; as well as a3) Expose the substrate to an etching gas that etches the first nitride layer and the silicon oxide film, wherein the second nitride layer protects the silicon nitride film from being etched by the etching gas.

2. The method of claim 1, further comprising: Repeat steps a1) and a2) at least once before proceeding to step a3).

3. The method of claim 1, further comprising: Repeat steps a1), a2), and a3) at least once to further etch the silicon oxide film.

4. The method of claim 1, further comprising: a0) Expose the substrate to a gas containing H2, which terminates the silicon oxide film with -OH surface species and with -NH x Surface species terminate the silicon nitride film.

5. The method of claim 4, further comprising: Repeat a0), a1), a2), and a3) at least once to further etch the silicon oxide film.

6. The method of claim 4, further comprising: Repeat a1), a2), and a3) at least once to further etch the silicon oxide film.

7. The method of claim 1, wherein, The first gas contains boron hydride, boron halide, organoaluminum compounds, aluminum hydride, aluminum chloride, or combinations thereof.

8. The method of claim 1, wherein, The first gas is selected from the following groups: BH3, BCl3, BF3, Al(CH3)3, AlH3, AlCl3, and combinations thereof.

9. The method of claim 1, wherein, The nitrogen-containing gas is selected from the following group: nitrogen hydrides, nitrogen halides, N2, and combinations thereof.

10. The method of claim 1, wherein, The nitrogen-containing gas is selected from the following groups: NH3, N2H4, NCl3, N2, and combinations thereof.

11. The method of claim 1, wherein, The etching gas contains fluorocarbon gas, hydrofluorocarbon gas, hydrochlorofluorocarbon gas, hydrochlorofluorocarbon gas, or a combination thereof.

12. The method of claim 1, wherein, The etching gas is selected from the group consisting of: CF4, CF2Cl2, CH2F2, CH4, CH3F, CHF3, C4H6, C2H4, C3H6, CH2Cl2, CH3Cl, CH2ClF, CHCl2F, and combinations thereof.

13. A substrate processing method, comprising: A substrate containing a silicon oxide film and a silicon nitride film is provided; a1) Expose the substrate to BCl3 gas, which forms a first BCl3 layer on the silicon oxide film and a second BCl3 layer on the silicon nitride film; a2) The substrate is exposed to NH3 gas, which reacts with the first BCl3 layer on the silicon oxide film to form a first boron nitride layer, and reacts with the second BCl3 layer on the silicon nitride film to form a second boron nitride layer, wherein the thickness of the second boron nitride layer is greater than the thickness of the first boron nitride layer. as well as a3) Expose the substrate to plasma-excited CF4 gas, which etches the first boron nitride layer and the silicon oxide film, wherein the second boron nitride layer protects the silicon nitride film from being etched by the plasma-excited CF4 gas.

14. The method of claim 13, further comprising: Repeat steps a1) and a2) at least once before proceeding to step a3).

15. The method of claim 13, further comprising: Repeat a1), a2), and a3) at least once to further etch the silicon oxide film.

16. The method of claim 13, further comprising: a0) Expose the substrate to a gas containing H2, which terminates the silicon oxide film with -OH surface species and with -NH x Surface species terminate the silicon nitride film.

17. The method of claim 16, further comprising: Repeat a0), a1), a2), and a3) at least once to further etch the silicon oxide film.

18. The method of claim 16, further comprising: Repeat a1), a2), and a3) at least once to further etch the silicon oxide film.

19. A substrate processing method, comprising: A substrate containing a silicon oxide film and a silicon nitride film is provided; a1) Expose the substrate to a boron-containing gas, which forms a first boron-containing layer on the silicon oxide film and a second boron-containing layer on the silicon nitride film; a2) Expose the substrate to a nitrogen-containing gas, which reacts with the first boron-containing layer on the silicon oxide film to form a first boron nitride layer, and reacts with the second boron-containing layer on the silicon nitride film to form a second boron nitride layer, wherein the thickness of the second boron nitride layer is greater than the thickness of the first boron nitride layer; as well as a3) Expose the substrate to an etching gas that etches the first boron nitride layer and the silicon oxide film, wherein the second boron nitride layer protects the silicon nitride film from being etched by the etching gas.

20. The method of claim 19, wherein, The boron-containing gas is selected from the group consisting of BH3, BCl3, BF3, and combinations thereof; the nitrogen-containing gas is selected from the group consisting of NH3, N2H4, NCl3, N2, and combinations thereof; and the etching gas is selected from the group consisting of CF4, CF2Cl2, CH2F2, CH4, CH3F, CHF3, C4H6, C2H4, C3H6, CH2Cl2, CH3Cl, CH2ClF, CHCl2F, and combinations thereof.

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