Hard mask removing method and hard mask removing device

Abstract

[Problem] To prevent a silicon carbonitride film from being damaged when a hard mask is removed. [Solution] The present invention includes performing a hydrogen ashing treatment and, subsequently, etching by a ClF3 gas, on a wafer in which the upper surface of an SiCN film, on which a pattern is formed, of an insulating layer 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, wherein the hard mask is formed of at least one of tungsten silicide (WSi) and tungsten silicide nitride (WSiN).

Description

Hard mask removal method and hard mask removal apparatus

[0001] The present disclosure relates to a hard mask removal method and a hard mask removal apparatus.

[0002] In recent years, the use of tungsten (W), a low-resistance material, for wiring in semiconductor devices has been considered. When W is used as the wiring material, a tungsten silicide (WSi) film is sometimes used as a hard mask to form a pattern such as a trench by etching in an insulating layer formed on a wiring layer made of W on a substrate. The WSi film is formed by etching a chlorine (Cl ２ ) gas, oxygen (O ２ The metal is removed by etching with plasma generated from hydrogen bromide (HBr) gas (see, for example, Patent Document 1).

[0003] Patent No. 6557588

[0004] The technique according to the present disclosure suppresses damage to the silicon carbonitride film when the hard mask is removed.

[0005] One aspect of the technology disclosed herein is a hard mask removal method for removing a hard mask covering an upper surface of a silicon carbonitride film on a substrate, the hard mask being formed of at least one of tungsten silicide and tungsten nitride silicide, the hard mask having a surface of the pattern and a surface of the hard mask covered with a fluorocarbon by-product, the hard mask being formed of at least one of tungsten silicide and tungsten nitride silicide, the method comprising: a first step of removing the by-product by reacting it with hydrogen plasma; and a second step of removing the hard mask by reacting it with a fluorochlorine-based gas and transforming it into various gases.

[0006] According to the technique of the present disclosure, it is possible to suppress damage to the silicon carbonitride film when removing the hard mask.

[0007] Fig. 2 is a flowchart showing an example of a hard mask removal method according to an embodiment of the technology disclosed herein. Fig. 3 is a diagram showing an example of steps of the hard mask removal method of Fig. 1 in sequence. Fig. 4 is a diagram showing an example of steps of the hard mask removal method of Fig. 1 in sequence. Fig. 5 is a diagram showing an example of steps of the hard mask removal method of Fig. 1 in sequence. Fig. 6 is a plan view schematically showing an example of the configuration of a substrate processing apparatus used when performing the hard mask removal method according to the present embodiment.

[0008] When W is used for wiring, the use of not only a WSi film but also a tungsten silicide nitride (WSiN) film or a mixed film of WSi and WSiN as a hard mask for forming a pattern on an insulating layer is also being considered. Furthermore, in order to remove the WSi film or WSiN film, chemical treatment using a gas is being considered for the substrate. Chemical treatment using such a gas involves the use of a chlorine fluoride-based gas, for example, chlorine trifluoride (ClF ３ ) gas non-plasma etching process, in which ClF ３ The WSi film or WSiN film is removed by reacting the gas with the WSi or WSiN and transforming it into various gases.

[0009] Incidentally, a silicon carbonitride (SiCN) film is sometimes used as an insulating layer that is an underlying layer for the WSi film and the WSiN film. ３ When the WSi film or WSiN film is removed by etching with gas, the exposed SiCN film is ３ It may react with the gas, resulting in etching and damage to the SiCN film.

[0010] In contrast, the technique according to the present disclosure uses ClF to form a WSi film or a WSiN film. ３ When the SiCN film is removed by etching using a gas, the SiCN film is covered with residue, thereby preventing the SiCN film from being damaged.

[0011] An embodiment of the technology according to the present disclosure will be described below with reference to the drawings. Fig. 1 is a flowchart showing an example of a hard mask removal method according to this embodiment, and Figs. 2A to 2D are diagrams sequentially showing an example of steps of the hard mask removal method of Fig. 1. Figs. 2A to 2D show enlarged partial cross sections near the surface of a wafer W.

[0012] In the hard mask removal method according to the present embodiment, first, a wafer W (substrate) is received, which has an insulating layer previously formed with patterns such as trenches and via holes in another substrate processing apparatus. As shown in Fig. 2A, the 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, W is formed on the base 10.

[0013] On the wiring layer 11, for example, three layers of SiCN films 12a to 12c (silicon carbonitride films) and two layers of silicon dioxide (SiO ２ The insulating layer 14 is formed of, for example, a SiCN film 12a and a SiO ２ Film 13a, SiCN film 12b, SiO ２ The film 13b and the SiCN film 12c are stacked in this order from below.

[0014] Furthermore, a hard mask 15 made of a mixed film of WSi and WSiN is formed on the insulating layer 14 so as to cover the upper surface of the SiCN film 12c. The hard mask 15 may be made of only WSi or only WSiN.

[0015] Furthermore, a plurality of patterns 16, such as trenches exposing the wiring layer 11 at the bottom, are formed in the insulating layer 14 and the hard mask 15. These patterns 16 are formed by subjecting the wafer W to an etching process using a carbon fluoride (CF)-based gas in another substrate processing apparatus. CF-based by-products (deposits) 17, which are generated when the insulating layer 14 is etched, cover the surface of the hard mask 15 and the surface of the insulating layer 14 inside the patterns 16 ( FIG. 2A ).

[0016] By the way, the CF-based depot 17 is ClF ３It is difficult to remove by etching with ClF ３ In the etching process using gas, ClF ３ This may prevent the gas from coming into contact with the hard mask 15, which may hinder the removal of the hard mask 15. 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, the CF-based deposit 17 is applied to the wafer W by hydrogen (H ２ A hydrogen ashing process is performed using hydrogen plasma generated from the SiO 2 gas (first step) (step S11).

[0017] In the hydrogen ashing process, the CF-based deposits 17 are removed by reacting them with hydrogen plasma. Hydrogen plasma contains many hydrogen ions, which are highly 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 deposits 17 covering the upper surface of the hard mask 15. Therefore, in the hydrogen ashing process, the CF-based deposits 17 covering the upper surface of the hard mask 15 are selectively removed. On the other hand, the CF-based deposits 17 that cover the surface of the insulating layer 14 on the side surfaces of the hard mask 15 and inside the pattern 16 are hardly contacted by the hydrogen ions that are incident almost perpendicularly toward the wafer W, and are therefore hardly removed.

[0018] The hydrogen ashing process is completed before the CF-based deposits 17 covering the upper surface of the hard mask 15 are completely removed. The execution time of the hydrogen ashing process is determined by confirming in advance, through experiments or the like, the processing time at which the CF-based deposits 17 covering the upper surface of the hard mask 15 are not completely removed by the hydrogen ashing process, and then by taking this processing time into consideration. After the hydrogen ashing process is completed, uncut portions 17a of the CF-based deposits 17 remain on the upper surface of the hard mask 15 ( FIG. 2B ).

[0019] Next, as shown in FIG. ３ An etching process using a gas is performed (second step) (step S12). ３ The gas contacts the top surface of the hard mask 15 and removes the hard mask 15. For example, ClF ３The gas reacts with WSi contained in the hard mask 15 as shown in the following formula (1), to produce tungsten fluoride (VI) (WF ６ ) gas, silicon tetrafluoride (SiF ４ ) gas, chlorine gas, and chlorine fluoride (ClF) gas are produced.

[0020] WSi ２ +5ClF ３ → WF ６ +2SiF ４ + 2Cl ２ +ClF ... (1)

[0021] Also, ClF ３ The gas reacts with WSiN contained in the hard mask 15 as shown in the following formula (2), resulting in WF ６ Gas, SiF ４ Gas, Cl ２ gas, ClF gas and nitrogen (N ２ ) gas is produced.

[0022] 2WSiN+10ClF ３ → 2WF ６ +4SiF ４ + 4Cl ２ + 2ClF + N ２ … (2)

[0023] Thus, ClF ３ In the gas etching process, ClF ３ The hard mask 15 is removed by converting the gas and the hard mask 15 into various gases. When the hard mask 15 is removed, the SiCN film 12c is exposed and the ClF ３ There is a risk that the SiCN film 12c may react with the gas and be etched.

[0024] However, in this embodiment, ClF ３ During the etching process using the gas, the remaining 17a of the CF-based deposit 17, as well as the CF-based deposit 17 covering the surface of the insulating layer 14 on the side of the hard mask 15 and inside the pattern 16, are removed by ClF ３The CF-based deposit 17 reacts with the gas to produce residue 18. This residue 18 spreads around 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 unpolished portion 17a of the CF-based deposit 17 remains on the upper surface of the hard mask 15, the residue 18 generated from the unpolished portion 17a is likely to remain on the upper surface of the hard mask 15, and this allows the residue 18 to reliably cover the upper surface of the SiCN film 12c. The residue 18 covering the upper surface of the SiCN film 12c is formed by the ClF ３ This prevents the gas from coming into contact with the SiCN film 12c. ３ This can prevent damage caused by etching with gas.

[0025] Next, as shown in FIG. 1 , the wafer W is subjected to an ashing process (fourth step) (step S13) and a wet etching process using a chemical solution (third step) (step S14). The ashing process in step S13 is, for example, a hydrogen ashing process, but may also be an oxygen ashing process. These ashing and wet etching processes remove the residue 18 and the CF-based deposits 17 covering the surface of the insulating layer 14 on the side surfaces of the hard mask 15 and inside the pattern 16 ( FIG. 2D ). Thereafter, the method ends. Note that if the residue 18 and the remaining CF-based deposits 17 can be removed by wet etching alone, the ashing process in step S13 may be skipped.

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

[0027] In FIG. 3, a substrate processing apparatus 21 (hard mask removal apparatus) ３ The system has a plurality of, for example, three gas etching chambers 22 (gas etching processing units) for performing etching processing using gas, and a plurality of, for example, three ashing chambers 23 (ashing processing units) for performing hydrogen ashing processing.

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

[0029] In the substrate processing apparatus 21, a transfer robot (not shown) is built into each of the loader module 26 and the transfer module 24. Each transfer robot transfers wafers W between the gas etching chamber 22, the ashing chamber 23, and each load port 27.

[0030] The loader module 26 is an atmospheric transfer system or a nitrogen transfer system, and its interior is maintained at atmospheric pressure. The transfer module 24 is a vacuum transfer system, and its interior is depressurized to an almost vacuum. The load lock module 25 is configured so that its interior can be switched between atmospheric pressure and an almost vacuum. When a wafer W is transferred between the transfer module 24 and the loader module 26, the load lock module 25 switches its internal pressure. This allows the transfer of the wafer W without changing the internal pressure of the transfer module 24 or the loader module 26. The gas etching chamber 22 and the ashing chamber 23 are connected to the transfer module 24 via a gate valve 28.

[0031] When performing the hard mask removal method according to the present embodiment, in the substrate processing apparatus 21, the wafer W transferred from the load port 27 is first loaded 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.

[0032] At this time, the pressure inside the ashing chamber 23 is set to, for example, 10 mTorr to 30 mTorr, and H ２A mixed gas of hydrogen gas and argon (Ar) gas is supplied to the ashing chamber 23. Furthermore, a high-frequency power for plasma generation, e.g., 200 W to 400 W, is supplied to the upper electrode (not shown) of the ashing chamber 23, and a high-frequency power for bias, e.g., 50 W to 200 W, is supplied to the lower electrode (not shown) of the ashing chamber 23. The execution time of the hydrogen ashing process in the ashing chamber 23 is set to, e.g., 20 to 40 seconds. As described above, the execution time of this hydrogen ashing process is a processing time that does not completely remove the CF-based deposit 17 covering the upper surface of the hard mask 15. Therefore, on the wafer W unloaded from the ashing chamber 23 after the hydrogen ashing process, unpolished portions 17a of the CF-based deposit 17 remain on the upper surface of the hard mask 15.

[0033] Next, the wafer W is transferred from the ashing chamber 23 to the gas etching chamber 22. In the gas etching chamber 22, ClF ３ The hard mask 15 is removed by the etching process using the gas, but at the same time, residues 18 are generated from the CF-based deposits 17 that remain unetched 17a and from the CF-based deposits 17 that cover the surface of the insulating layer 14 on the side surfaces of the hard mask 15 and inside the pattern 16. The residues 18 reach the upper surface of the SiCN film 12c, cover the upper surface of the SiCN film 12c, and are then removed by ClF ３ This prevents the gas from coming into contact with the SiCN film 12c.

[0034] At this time, the pressure inside the gas etching chamber 22 is set to, for example, 100 mTorr to 300 mTorr, and the gas etching chamber 22 is filled with ClF ３ Gas and N ２ A mixture of gases is supplied: ClF ３ The gas flow rate is, for example, 10 sccm to 30 sccm, and N ２ The flow rate of the gas is, for example, 350 sccm to 400 sccm. The wafer W is heated by a stage (not shown) on which the wafer W is placed, and the temperature of the wafer W is set to 90° C. or higher. ３ The duration of the gas etching process is set to, for example, 200 to 280 seconds.

[0035] In the gas etching chamber 22, the hard mask 15 is removed, and the residue 18 covering the upper surface of the SiCN film 12c is etched with ClF ３ The contact between the gas and the SiCN film 12c is prevented, and the SiCN film 12c is ３ To suppress damage caused by etching with gas.

[0036] Thereafter, the wafer W is again loaded into the ashing chamber 23 and subjected to hydrogen ashing processing. The wafer W is then transferred to the load port 27, removed from the substrate processing apparatus 21, and further transferred to another substrate processing apparatus, where the wafer W is subjected to wet etching processing.

[0037] According to this embodiment, the wafer W is etched with ClF 3 in a state where the unetched portion 17a of the CF-based deposit 17 remains on the upper surface of the hard mask 15 and the CF-based deposit 17 covering the surface of the insulating layer 14 on the side surface of the hard mask 15 and inside the pattern 16 remains. ３ At this time, residues 18 resulting from the unetched portions 17a and the CF-based deposits 17 cover the upper surface of the SiCN film 12c exposed after the hard mask 15 is removed. ３ The residue 18 prevents the gas from coming into contact with the SiCN film 12c. ３ To suppress damage caused by etching with gas.

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

[0039] For example, the substrate processing apparatus 21 performs hydrogen ashing and ClF ３ The gas etching processes were carried out in the ashing chamber 23 and the gas etching chamber 22, respectively. However, the ashing chamber 23 was not provided with ClF ３ In this case, the ashing chamber 23 may be configured to supply hydrogen ashing and ClF ３This allows for both gas-based etching and etching processes, thereby improving throughput.

[0040] In the above-described embodiment, in order to remove the hard mask 15 made of a mixed film of WSi and WSiN, ClF is used as a chlorine fluoride gas. ３ Although a gas is used, other chlorine fluoride gases may also be used.

[0041] This application claims priority based on Japanese Patent Application No. 2024-002493, filed on January 11, 2024, the entire contents of which are incorporated herein by reference.

[0042] W wafer 12a to 12c SiCN film 14 insulating layer 15 hard mask 16 pattern 17 CF-based deposit 18 residue 21 substrate processing apparatus 22 gas etching chamber 23 ashing chamber

Claims

1. A hard mask removal method for removing a hard mask covering the upper surface of a silicon carbonitride film having a pattern formed thereon, wherein the surface of the pattern and the surface of the hard mask are covered by a fluorocarbon-based by-product, the hard mask is formed of at least one of tungsten silicide and tungsten silicide nitride, a first step of reacting the by-product with hydrogen plasma to remove it, and a second step of reacting the hard mask with a chlorine fluoride-based gas to transform it into various gases to remove the hard mask.

2. The hard mask removal method according to claim 1, wherein in the first step, the by-product covering the upper surface of the hard mask is selectively removed.

3. The hard mask removal method according to claim 2, wherein in the first step, the by-product covering the upper surface of the hard mask is not completely removed.

4. The hard mask removal method according to claim 1, wherein in the second step, the hard mask is removed, and 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 fluoride-based gas covers the silicon carbonitride film.

5. The hard mask removal method according to claim 1, further comprising a third step of subjecting the substrate to a wet etching treatment after the second step.

6. The hard mask removal method according to claim 5, having a fourth step of further subjecting the substrate to an ashing treatment between the second step and the third step.

7. A hard mask removal apparatus for removing a hard mask covering the upper surface of a silicon carbonitride film having a pattern formed thereon, wherein the surface of the pattern and the surface of the hard mask are covered by a fluorocarbon-based by-product, the hard mask is formed of at least one of tungsten silicide and tungsten silicide nitride, an ashing treatment unit for reacting the by-product with hydrogen plasma to remove it, and a gas etching treatment unit for reacting the hard mask with a chlorine fluoride-based gas to transform it into various gases to remove the hard mask after the removal of the by-product by the hydrogen plasma.

8. The hard mask removing device according to claim 7, wherein in the ashing processing unit, the by-products covering the upper surface of the hard mask are selectively removed.

9. The hard mask removing device according to claim 8, wherein in the ashing processing unit, the by-products covering the upper surface of the hard mask are not completely removed.

10. The hard mask removing device according to claim 7, wherein in the gas etching processing unit, while the hard mask is removed, residues generated by the reaction of the by-products that could not be completely removed by the reaction with the hydrogen plasma and the chlorine fluoride-based gas cover the silicon carbonitride film.

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