Hard mask removal method and hard mask removal device

Abstract

To prevent a silicon carbonitride film from being damaged when a hard mask is removed.SOLUTION: A hard mask removal method includes applying a hydrogen ashing treatment and then applying etching treatment with ClF3 gas on a wafer in which an upper surface of an SiCN film of an insulating layer on which a pattern is formed is covered with a hard mask, a surface of the pattern and a surface of the hard mask are covered with a CF-based deposit, and the hard mask is formed of at least one of tungsten silicide (WSi) and tungsten silicide nitride (WSiN).SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

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

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The technology according to the present disclosure suppresses damage to a silicon carbonitride film when removing a hard mask.

Means for Solving the Problems

[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 with 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 a chlorine fluoride-based gas with the hard mask to alter it into various gases to remove the hard mask.

Advantages of the Invention

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

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0008] When forming a pattern on an insulating layer when using W for wiring, not only a WSi film but also a tungsten silicide nitride (WSiN) film and a mixed film of WSi and WSiN are being considered as hard masks. And, in order to remove the WSi film and the WSiN film, chemical treatment using a gas is being considered for the substrate. Such chemical treatment using a gas corresponds to non-plasma etching treatment with a chlorine fluoride-based gas, for example, chlorine trifluoride (ClF3) gas. In this etching treatment, the WSi film and the WSiN film are removed by reacting the ClF3 gas with WSi or WSiN and altering them into various gases.

[0009] By the way, a silicon carbonitride (SiCN) film may be used as the insulating layer that is the underlying layer of the WSi film and the WSiN film. And, when the WSi film and the WSiN film are removed by etching treatment with ClF3 gas, the exposed SiCN film may react with the 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 a residue when removing the WSi film and the 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 a hard mask removal method according to the present embodiment, and FIG. 2 is a process diagram of the hard mask removal method of FIG. 1. In FIG. 2, an enlarged partial cross section near the surface of the wafer W is shown.

[0012] In the hard mask removal method according to the present embodiment, first, a wafer W (substrate) on which patterns such as trenches and via holes are formed in an insulating layer in advance by another substrate processing apparatus is received. This wafer W has, for example, a base portion 10 made of silicon (Si) or silicon germanium (SiGe), and on the base portion 10, for example, a wiring layer 11 made of W is formed.

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

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

[0015] Furthermore, a plurality of patterns 16 such as trenches for 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. Then, a CF-based by-product (depo) 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 and inside the pattern 16 (FIG. 2(A)).

[0016] By the way, the CF-based depo 17 is difficult to be removed by an etching process using ClF3 gas, and the ClF3 gas inhibits the removal of the hard mask 15 by preventing the ClF3 gas from touching the hard mask 15 in the etching process using the ClF3 gas. Therefore, in the present embodiment, the CF-based depo 17 covering the surface of the hard mask 15 is removed prior to the removal of the hard mask 15. Specifically, a hydrogen ashing process using hydrogen plasma generated from hydrogen (H2) gas is performed on the wafer W (the first step) (step S11).

[0017] In the hydrogen ashing process, the CF-based deposit 17 is removed by reacting it with hydrogen plasma. Although hydrogen plasma contains a large amount of hydrogen ions, hydrogen ions are highly anisotropic and have many components that are incident almost vertically toward the wafer W. Therefore, hydrogen ions actively contact the CF-based deposit 17 covering the upper surface of the hard mask 15. Accordingly, 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 surface of the hard mask 15 and inside the pattern 16 hardly contacts the hydrogen ions incident almost vertically toward the wafer W and is thus hardly removed.

[0018] In addition, the hydrogen ashing process ends before the CF-based deposit 17 covering the upper surface of the hard mask 15 is completely removed. The execution time of the hydrogen ashing process at this time is determined with reference to the processing time confirmed in advance by experiments or the like, which is the processing time 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 ends, the remaining deposit 17a of the CF-based deposit 17 remains on the upper surface of the hard mask 15 (Fig. 2(B)).

[0019] Next, the wafer W is subjected to an etching process with ClF3 gas (the second step) (step S12). At this time, the ClF3 gas contacts 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) to generate tungsten(VI) fluoride (WF6) gas, silicon tetrafluoride (SiF4) gas, chlorine gas, and chlorine fluoride (ClF) gas.

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

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

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

[0023] Thus, in the etching process using ClF3 gas, the hard mask 15 is removed by transforming the ClF3 gas and the hard mask 15 into various gases. By the way, when the hard mask 15 is removed, the SiCN film 12c is exposed and may react with the ClF3 gas, resulting in etching of the SiCN film 12c.

[0024] However, in this embodiment, during the execution of the etching process using ClF3 gas, the remaining portion 17a of the CF-based deposit 17, 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 react with the ClF3 gas to generate a residue 18. This residue 18 wraps around to the upper surface of the SiCN film 12c and covers the upper surface of the SiCN film 12c (FIG. 2(C)). In particular, since the remaining portion 17a of the CF-based deposit 17 remains on the upper surface of the hard mask 15, the residue 18 generated from the remaining portion 17a is likely to stay on the upper surface of the hard mask 15, thereby reliably covering the upper surface of the SiCN film 12c with the residue 18. And the residue 18 covering the upper surface of the SiCN film 12c prevents the ClF3 gas from contacting the SiCN film 12c. As a result, it is possible to suppress the SiCN film 12c from being etched and damaged by the ClF3 gas.

[0025] Next, the wafer W is subjected to an ashing process (the fourth step) (step S13) and a wet etching process using a chemical solution (the third step) (step S14). The ashing process in step S13 is, for example, a hydrogen ashing process, but it may also be an oxygen ashing process. These ashing processes and wet etching processes remove the residue 18 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 (FIG. 2(D)). Then, this method is terminated. Note that when the residue 18 and the remaining CF-based deposit 17 can be removed only by the wet etching process, the ashing process in step S13 may be skipped.

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

[0027] In FIG. 3, a substrate processing apparatus 21 (hard mask removal apparatus) includes a plurality of, for example, three gas etching chambers 22 (gas etching processing units) that execute etching processing using ClF3 gas, and a plurality of, for example, three ashing chambers 23 (ashing processing units) that execute 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 a container, for example, a FOUP (not shown) that houses a plurality of wafers W is attached to each load port 27.

[0029] In the substrate processing apparatus 21, the loader module 26 and the transfer module 24 each incorporate a transfer robot (not shown). Each transfer robot transfers the 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 transfer system or a nitrogen transfer system, and the inside is maintained at atmospheric pressure. The transfer module 24 is a vacuum transfer system, and the inside is depressurized to almost vacuum. The load lock module 25 is configured to be able to switch the inside between atmospheric pressure and almost vacuum. When the wafer W is transferred between the transfer module 24 and the loader module 26, the load lock module 25 switches the internal pressure. Thereby, the transfer of the wafer W is realized without changing the internal pressure of the transfer module 24 and the loader module 26. Note that the gas etching chamber 22 and the ashing chamber 23 are connected to the transfer module 24 via a gate valve 28.

[0031] When executing the hard mask removal method according to this embodiment, in the substrate processing apparatus 21, the wafer W transported from the load port 27 is first carried 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 pressure inside 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 into the ashing chamber 23. Further, 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 treatment in the ashing chamber 23 is set to, for example, 20 seconds to 40 seconds. The execution time of this hydrogen ashing treatment is the treatment time when the CF-based deposit 17 covering the upper surface of the hard mask 15 is not completely removed. Therefore, in the wafer W carried out from the ashing chamber 23 after the hydrogen ashing treatment, the remaining part 17a of the CF-based deposit 17 remains on the upper surface of the hard mask 15.

[0033] Next, the wafer W is carried 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 with ClF3 gas. At the same time, residues 18 are generated from the remaining part 17a of the CF-based deposit 17, the side surface of the hard mask 15, and the CF-based deposit 17 covering the surface of the insulating layer 14 inside the pattern 16. This residue 18 wraps around to the upper surface of the SiCN film 12c, covers the upper surface of the SiCN film 12c, and prevents the ClF3 gas from contacting 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 a mixed gas of ClF3 gas and N2 gas is supplied into the gas etching chamber 22. The flow rate of the ClF3 gas is, for example, 10 sccm to 30 sccm, and the flow rate of the N2 gas is, for example, 350 sccm to 400 sccm. Further, the wafer W is heated by a mounting table (not shown) on which the wafer W is placed, and the temperature of the wafer W is set to 90°C or higher. The execution time of the etching process using the ClF3 gas in the gas etching chamber 22 is set to, for example, 200 seconds to 280 seconds.

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

[0036] Thereafter, the wafer W is again carried into the ashing chamber 23 and subjected to a hydrogen ashing process. Then, after the wafer W is transported to the load port 27, it is taken out from the substrate processing apparatus 21 and further transported to another substrate processing apparatus. In this another substrate processing apparatus, a wet etching process is performed on the wafer W.

[0037] According to the present embodiment, the remaining 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 remains on the side surface of the hard mask 15 and inside the pattern 16. In this state, the wafer W is subjected to an etching process using the ClF3 gas. At this time, the residue 18 generated from the remaining portion 17a and the CF-based deposit 17 covers the upper surface of the SiCN film 12c exposed when the hard mask 15 is removed. The residue 18 prevents the ClF3 gas from contacting the SiCN film 12c. That is, the residue 18 suppresses the SiCN film 12c from being etched by the ClF3 gas and damaged.

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

[0039] For example, in the substrate processing apparatus 21, the hydrogen annealing process and the etching process using ClF3 gas were performed in the annealing chamber 23 and the gas etching chamber 22, respectively. However, the annealing chamber 23 may be configured to be able to supply ClF3 gas therein. In this case, in the annealing chamber 23, both the hydrogen annealing process and the etching process using ClF3 gas can be performed, and the throughput can be improved.

[0040] Also, in the above-described embodiment, ClF3 gas was used as the chlorine fluoride-based gas to remove the hard mask 15 made of a mixed film of WSi and WSiN, but other chlorine fluoride-based gases may be used.

Description of Reference Numerals

[0041] W wafer 12a to 12c SiCN films 14 Insulating layer 15 Hard mask 16 Pattern 17 CF-based depo 18 Residue 21 Substrate processing apparatus 22 Gas etching chamber 23 Annealing chamber

Claims

1. A hard mask removing method for removing a hard mask covering the upper surface of a silicon carbonitride film having a pattern formed thereon on a substrate, wherein the surface of the pattern and the surface of the hard mask are covered with 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 a chlorine fluoride-based gas with the hard mask to alter it into various gases to remove the hard mask.

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

7. A hard mask removing apparatus for removing a hard mask covering the upper surface of a silicon carbonitride film having a pattern formed thereon on a substrate, wherein the surface of the pattern and the surface of the hard mask are covered with 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 a chlorine fluoride-based gas with the hard mask to alter 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 apparatus 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 apparatus 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 apparatus 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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