Hard mask removal method and hard mask removal device

Abstract

When removing the hard mask, damage to the silicon carbonitride film is suppressed. The upper surface of the SiCN film of the insulating layer on which the pattern is formed is covered with a hard mask, and the surface of the pattern and the surface of the hard mask are covered with a CF-based deposit. After performing a hydrogen ashing treatment on a wafer in which the hard mask is formed by at least one of tungsten silicide (WSi) and tungsten silicide (WSiN), an etching treatment with ClF3 gas is performed.

Description

Technology Field

[0001] The present disclosure relates to a hard mask removal method and a hard mask removal device. Background Technology

[0002] In recent years, the use of tungsten (W), a low-resistance material, for wiring in semiconductor devices has been considered. When tungsten is used as a wiring material, a tungsten silicide (WSi) film is sometimes used as a hard mask to form patterns, such as trenches, by etching on an insulating layer formed on top of a wiring layer made of tungsten on a substrate. The WSi film is then removed by etching using plasma generated from chlorine (Cl2) gas, oxygen (O2) gas, or hydrogen bromide (HBr) gas (see, for example, Patent Document 1). Prior art literature

[0003] Patent Publication No. 6557588 The problem to be solved

[0004] The technology according to the present disclosure prevents the silicon carbide film from being damaged when removing the hard mask. means of solving the problem

[0005] One aspect of the technology according to the present disclosure is a hard mask removal method for removing a hard mask covering the upper surface of a silicon carbonitride film having a pattern formed on a substrate, wherein the surface of the pattern and the surface of the hard mask are covered by a fluorocarbon-based byproduct, and the hard mask is formed by at least one of tungsten silicide and tungsten nitride silicide, and the method comprises a first step of removing the byproduct by reacting it with hydrogen plasma, and a second step of removing the hard mask by reacting the hard mask with a chlorine-based gas to transform it into various gases. Effects of the invention

[0006] According to the technology of the present disclosure, damage to the silicon carbide film can be suppressed when removing the hard mask. Brief explanation of the drawing

[0007] FIG. 1 is a flowchart illustrating an example of a hard mask removal method according to one embodiment of the technology according to the present disclosure. FIG. 2a is a diagram showing an example of the process of the hard mask removal method of FIG. 1 in sequence. FIG. 2b is a diagram showing an example of the process of the hard mask removal method of FIG. 1 in sequence. FIG. 2c is a diagram showing an example of the process of the hard mask removal method of FIG. 1 in sequence. FIG. 2d is a diagram showing an example of the process of the hard mask removal method of FIG. 1 in sequence. FIG. 3 is a schematic plan view showing an example of the configuration of a substrate processing device used when executing the hard mask removal method according to the present embodiment. Specific details for implementing the invention

[0008] When tungsten is used for wiring, it is being considered that not only WSi films but also tungsten silicide (WSiN) films or mixed films of WSi and WSiN may be used as hard masks for forming patterns on the insulating layer. Additionally, it is being considered that chemical treatment using gas may be performed on the substrate to remove WSi films or WSiN films. Such chemical treatment using gas corresponds to non-plasma etching treatment using chlorine-based gases, such as chlorine trifluoride (ClF3) gas, and in this etching treatment, WSi films or WSiN films are removed by reacting ClF3 gas with WSi or WSiN to transform them into various gases.

[0009] However, silicon carbonitride (SiCN) films are sometimes used as insulating layers that serve as the underlying layers of WSi films and WSiN films. When WSi films or WSiN films are removed by etching treatment with ClF3 gas, the exposed SiCN film may react with ClF3 gas, and as a result, the SiCN film may be etched and damaged.

[0010] In contrast, the technology according to the present disclosure suppresses damage to the SiCN film by covering the SiCN film with residue when removing the WSi film or WSiN film by etching treatment with ClF3 gas.

[0011] Hereinafter, an embodiment of the technology according to the present disclosure will be described with reference to the drawings. FIG. 1 is a flowchart showing an example of a hard mask removal method according to the present embodiment, and FIGS. 2a to 2d are drawings showing an example of a process of the hard mask removal method of FIG. 1 in sequence. In FIGS. 2a to 2d, an enlarged cross-sectional view of the area near the surface of a wafer (W) is shown.

[0012] In the hard mask removal method according to the present embodiment, first, a wafer (W) (substrate) having a pattern such as a trench or via hole formed in the insulating layer is received in another substrate processing device. As shown in FIG. 2a, this wafer (W) has a base (10) made of, for example, silicon (Si) or silicon germanium (SiGe), and a wiring layer (11) made of, for example, tungsten is formed on the base (10).

[0013] On top of the wiring layer (11), an insulating layer (14) is formed, for example, consisting of three layers of SiCN films (12a to 12c) (silicon carbonitride films) and two layers of silicon dioxide (SiO2) films (13a, 13b). In the insulating layer (14), for example, SiCN films (12a), SiO2 films (13a), SiCN films (12b), SiO2 films (13b), and SiCN films (12c) are stacked in this order from the bottom.

[0014] Additionally, a hard mask (15) made of a mixture of WSi and WSiN is formed on the insulating layer (14) to cover the upper surface of the SiCN film (12c). Additionally, the hard mask (15) may be composed of only WSi or only WSiN.

[0015] Additionally, a plurality of patterns (16), such as trenches that expose a wiring layer (11) at the bottom, are formed on the insulating layer (14) or the hard mask (15). These patterns (16) are formed by performing an etching treatment on the wafer (W) using a fluorocarbon (CF)-based gas in a different substrate processing device. Then, a CF-based byproduct (deposit) (17) generated when the insulating layer (14) is etched covers the surface of the insulating layer (14) on the surface of the hard mask (15) or inside the patterns (16) (Fig. 2a).

[0016] However, the CF-based deposit (17) is difficult to remove by etching treatment with ClF3 gas, and there is a risk that the removal of the hard mask (15) may be hindered by preventing the ClF3 gas from coming into contact with the hard mask (15) during etching treatment with ClF3 gas. Therefore, in this embodiment, the CF-based deposit (17) covering the surface of the hard mask (15) is removed prior to the removal of the hard mask (15). Specifically, as shown in FIG. 1, a hydrogen ashing treatment is performed on the wafer (W) using hydrogen plasma generated from hydrogen (H2) gas (first step) (step S11).

[0017] In the hydrogen ashing process, the CF-based deposit (17) is removed by reacting it with hydrogen plasma. Although the hydrogen plasma contains many hydrogen ions, the hydrogen ions are strongly anisotropic and have many components that are incident almost perpendicularly toward the wafer (W). Therefore, the hydrogen ions actively come into contact with the CF-based deposit (17) covering the upper surface of the hard mask (15). Thus, in the hydrogen ashing process, the CF-based deposit (17) covering the upper surface of the hard mask (15) is selectively removed. On the other hand, the CF-based deposit (17) covering the surface of the insulating layer (14) on the side of the hard mask (15) or inside the pattern (16) is hardly removed because it is difficult for it to come into contact with the hydrogen ions incident almost perpendicularly toward the wafer (W).

[0018] Additionally, the hydrogen ashing process is terminated while the CF-based deposit (17) covering the upper surface of the hard mask (15) is not completely removed. The execution time of the hydrogen ashing process at this time is determined by reference to the processing time, which is confirmed in advance through experiments or the like, when the CF-based deposit (17) covering the upper surface of the hard mask (15) is not completely removed by the hydrogen ashing process. After the hydrogen ashing process is terminated, the residue (17a) of the CF-based deposit (17) remains on the upper surface of the hard mask (15) (Fig. 2b).

[0019] Next, as illustrated in FIG. 1, an etching treatment with ClF3 gas is performed on the wafer (W) (second step) (step S12). At this time, the ClF3 gas comes into contact with the upper surface of the hard mask (15) and removes the hard mask (15). For example, the ClF3 gas reacts with WSi contained in the hard mask (15) as shown in the following formula (1), and generates tungsten fluoride (VI) (WF6) gas, silicon tetrafluoride (SiF4) gas, chlorine gas, and chlorine fluoride (ClF) gas.

[0020] WSi2+5ClF3→ WF6+2SiF4+2Cl2+ClF... (1)

[0021] In addition, ClF3 gas reacts with WSiN contained in the hard mask (15) as shown in the following formula (2) and generates WF6 gas, SiF4 gas, Cl2 gas, ClF gas and nitrogen (N2) gas.

[0022] 2WSiN+10ClF3→ 2WF6+4SiF4+4Cl2+2ClF+N2… (2)

[0023] In this way, in the etching process using ClF3 gas, the hard mask (15) is removed by changing the ClF3 gas and the hard mask (15) into various gases. However, when the hard mask (15) is removed, the SiCN film (12c) is exposed and reacts with the ClF3 gas, and there is a risk that the SiCN film (12c) will be etched.

[0024] However, in the present embodiment, during the execution of the etching process with ClF3 gas, the residual (17a) of the CF-based deposit (17) and the CF-based deposit (17) covering the surface of the insulating layer (14) on the side of the hard mask (15) or inside the pattern (16) react with the ClF3 gas to generate residue (18). This residue (18) returns to the upper surface of the SiCN film (12c) and covers the upper surface of the SiCN film (12c) (Fig. 2c). In particular, since the residual (17a) of the CF-based deposit (17) remains on the upper surface of the hard mask (15), the residue (18) generated from the residual (17a) tends to stay on the upper surface of the hard mask (15), and thereby, the upper surface of the SiCN film (12c) can be reliably covered by the residue (18). Also, the residue (18) covering the upper surface of the SiCN film (12c) prevents ClF3 gas from coming into contact with the SiCN film (12c). As a result, the SiCN film (12c) can be prevented from being etched and damaged by ClF3 gas.

[0025] Next, as illustrated in FIG. 1, an ashing treatment (step 4) (step S13) and a wet etching treatment using a chemical solution are performed on the wafer (W) (step 3) (step S14). The ashing treatment in step S13 is, for example, a hydrogen ashing treatment, but may also be an oxygen ashing treatment. Through these ashing treatments or wet etching treatments, residues (18) and CF-based deposits (17) covering the surface of the insulating layer (14) on the side of the hard mask (15) or inside the pattern (16) are removed (Fig. 2d). After that, the method is terminated. In addition, if residues (18) or remaining CF-based deposits (17) can be removed by wet etching treatment alone, the ashing treatment in step S13 may be skipped.

[0026] FIG. 3 is a schematic plan view showing an example of the configuration of a substrate processing device used when executing the hard mask removal method according to the present embodiment.

[0027] In FIG. 3, the substrate processing device (21) (hard mask removal device) has a plurality of, for example, three gas etching chambers (22) (gas etching processing unit) that perform etching treatment with ClF3 gas, and a plurality of, for example, three ashing chambers (23) (ashing processing unit) that perform hydrogen ashing treatment.

[0028] The gas etching chamber (22) and the ashing chamber (23) are connected to the transfer module (24). The transfer module (24) is connected to the loader module (26) through the load lock module (25). The loader module (26) is provided with a plurality of load ports (27), and each load port (27) is equipped with a container for accommodating a plurality of wafers (W), such as a FOUP (not shown).

[0029] In the substrate processing device (21), the loader module (26) or the transfer module (24) each incorporates a transport robot (not shown). Each transport robot transports a wafer (W) between the gas etching chamber (22), the ashing chamber (23), and each load port (27).

[0030] The loader module (26) is an atmospheric transport system or a nitrogen transport system, and its interior is maintained at atmospheric pressure. The transfer module (24) is a vacuum transport system, and its interior is depressurized to near vacuum. The load lock module (25) is configured to switch its interior to atmospheric pressure or near vacuum. When a wafer (W) is transported between the transfer module (24) and the loader module (26), the load lock module (25) switches the internal pressure. This enables the transport of the wafer (W) without changing the internal pressure of the transfer module (24) or the loader module (26). Additionally, the gas etching chamber (22) or the ashing chamber (23) is connected to the transfer module (24) through the gate valve (28).

[0031] When executing the hard mask removal method according to the present embodiment, in the substrate processing device (21), the wafer (W) being transported from the load port (27) is first brought into the ashing chamber (23). In the ashing chamber (23), the CF-based deposit (17) covering the upper surface of the hard mask (15) is selectively removed by hydrogen ashing treatment.

[0032] At this time, the internal pressure of the ashing chamber (23) is set to, for example, 10 mTorr to 30 mTorr, and a mixed gas of H2 gas and argon (Ar) gas is supplied to the inside of the ashing chamber (23). In addition, high-frequency power for plasma generation is supplied to the upper electrode (not shown) of the ashing chamber (23) at, for example, 200 W to 400 W, and high-frequency power for bias is supplied to the lower electrode (not shown) of the ashing chamber (23) at, for example, 50 W to 200 W. The execution time of the hydrogen ashing process in the ashing chamber (23) is set to, for example, 20 seconds to 40 seconds. This execution time of the hydrogen ashing process is a processing time during which the CF-based deposit (17) covering the upper surface of the hard mask (15) is not completely removed, as described above. Therefore, in the wafer (W) removed from the ashing chamber (23) after hydrogen ashing treatment, the residue (17a) of the CF-based deposit (17) remains on the upper surface of the hard mask (15).

[0033] Next, the wafer (W) is introduced from the ashing chamber (23) into the gas etching chamber (22). In the gas etching chamber (22), the hard mask (15) is removed by etching treatment with ClF3 gas, but at the same time, residue (17a) of the CF-based deposit (17) and residue (18) from the CF-based deposit (17) covering the surface of the insulating layer (14) on the side of the hard mask (15) or inside the pattern (16) are generated. This residue (18) goes into the upper surface of the SiCN film (12c), covers the upper surface of the SiCN film (12c), and prevents the ClF3 gas from coming into contact with the SiCN film (12c).

[0034] At this time, the internal pressure of the gas etching chamber (22) is set to, for example, 100 mTorr to 300 mTorr, and a mixed gas of ClF3 gas and N2 gas is supplied to the inside of the gas etching chamber (22). The flow rate of ClF3 gas is, for example, 10 sccm to 30 sccm, and the flow rate of N2 gas is, for example, 350 sccm to 400 sccm. In addition, the wafer (W) is heated by a loading platform (not shown) for loading the wafer (W), and the temperature of the wafer (W) is set to 90°C or higher. The execution time of the etching process with ClF3 gas in the gas etching chamber (22) is, for example, set to 200 seconds to 280 seconds.

[0035] In the gas etching chamber (22), while the hard mask (15) is removed, the residue (18) covering the upper surface of the SiCN film (12c) prevents contact between the ClF3 gas and the SiCN film (12c) and prevents the SiCN film (12c) from being etched and damaged by the ClF3 gas.

[0036] After that, the wafer (W) is brought back into the ashing chamber (23) and hydrogen ashing treatment is performed. Then, the wafer (W) is returned to the load port (27), then removed from the substrate processing device (21), and returned to another substrate processing device. In this other substrate processing device, wet etching treatment is performed on the wafer (W).

[0037] According to the present embodiment, etching treatment with ClF3 gas is performed on a wafer (W) while residual (17a) of the CF-based deposit (17) remains on the upper surface of the hard mask (15) and CF-based deposit (17) covering the surface of the insulating layer (14) remains on the side of the hard mask (15) or inside the pattern (16). At this time, residue (18) generated from the residual (17a) or the CF-based deposit (17) covers the upper surface of the SiCN film (12c) exposed after the hard mask (15) is removed. The residue (18) prevents the ClF3 gas from coming into contact with the SiCN film (12c). That is, the residue (18) prevents the SiCN film (12c) from being etched and damaged by the ClF3 gas.

[0038] Although preferred embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above, and various modifications and changes are possible within the scope of the gist thereof.

[0039] For example, in the substrate processing device (21), hydrogen ashing treatment and etching treatment with ClF3 gas are performed in the ashing chamber (23) and the gas etching chamber (22), respectively. However, the ashing chamber (23) may be configured to supply ClF3 gas into it. In this case, both hydrogen ashing treatment and etching treatment with ClF3 gas can be performed in the ashing chamber (23), thereby improving throughput.

[0040] In addition, in the above-described embodiment, ClF3 gas was used as the fluorine-based gas to remove the hard mask (15) made of a mixture of WSi and WSiN, but other fluorine-based gases may be used.

[0041] The present application claims priority based on Japanese patent application No. 2024-002493 filed on January 11, 2024, and incorporates the entire contents of the application herein by reference. Explanation of the symbols

[0042] W: Wafer 12a to 12c: SiCN film 14: Insulating layer 15: Hard Mask 16: Pattern 17: CF-based deposits 18: Remnants 21: Substrate processing device 22: Gas etching chamber 23: Ashing Chamber

Claims

Claim 1 A hard mask removal method for removing a hard mask covering the upper surface of a silicon carbonitride film having a pattern formed on a substrate, wherein the surface of the pattern and the surface of the hard mask are covered by a fluorocarbon-based byproduct, and the hard mask is formed by at least one of tungsten silicide and tungsten nitride silicide, and the hard mask removal method comprises a first step of removing the byproduct by reacting it with hydrogen plasma, and a second step of removing the hard mask by reacting the hard mask with a chlorine-based gas to transform it into various gases. Claim 2 A hard mask removal method according to claim 1, wherein in the first step, the byproduct covering the upper surface of the hard mask is selectively removed. Claim 3 A hard mask removal method according to paragraph 2, wherein in the first step, the by-product covering the upper surface of the hard mask is not completely removed. Claim 4 A hard mask removal method according to claim 1, wherein in the second step, the hard mask is removed and the residue generated by the reaction of the by-product that could not be completely removed by the reaction with the hydrogen plasma and the chlorine-based fluoride gas covers the silicon carbonitride film. Claim 5 A hard mask removal method according to claim 1, further comprising a third step of performing a wet etching treatment on the substrate after the second step. Claim 6 A hard mask removal method according to claim 5, having a fourth step of additionally performing an ashing treatment on the substrate between the second step and the third step. Claim 7 A hard mask removal device for removing a hard mask covering the upper surface of a silicon carbonitride film having a pattern formed on a substrate, wherein the surface of the pattern and the surface of the hard mask are covered by a fluorocarbon-based byproduct, and the hard mask is formed by at least one of tungsten silicide and tungsten silicide, and the hard mask removal device comprises an ashing treatment unit for removing the byproduct by reacting it with hydrogen plasma, and a gas etching treatment unit for removing the hard mask by reacting the hard mask with a chlorine-based gas to transform it into various gases after removing the byproduct by the hydrogen plasma. Claim 8 A hard mask removal device according to claim 7, wherein in the ashing processing unit, the by-product covering the upper surface of the hard mask is selectively removed. Claim 9 A hard mask removal device according to claim 8, wherein the ashing processing unit does not completely remove the by-product covering the upper surface of the hard mask. Claim 10 A hard mask removal device according to claim 7, wherein in the gas etching treatment unit, as the hard mask is removed, a residue generated by the reaction of the by-product that could not be completely removed by the reaction with the hydrogen plasma and the chlorine-based fluoride gas covers the silicon carbonitride film.

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