Substrate processing method and substrate processing apparatus

Abstract

To provide technology capable of removing titanium oxide films.SOLUTION: A substrate processing method according to one embodiment of the present disclosure has a process for preparing a substrate on which titanium nitride film and titanium oxide film are stacked in this order, and a process for supplying an etching gas containing hydrogen fluoride gas to the substrate and etching the titanium oxide film.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a substrate processing method and a substrate processing apparatus. [Background technology]

[0002] A technology has been disclosed in which a portion of titanium formed on a layer to be etched is irradiated with light to form a titanium oxide film, and then a pattern is formed on the layer to be etched by utilizing the difference in etching rate (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-311936 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique capable of removing titanium oxide films. [Means for solving the problem]

[0005] A substrate processing method according to one aspect of the present disclosure includes the steps of preparing a substrate having a titanium nitride film and a titanium oxide film stacked in this order, and supplying an etching gas containing hydrogen fluoride gas to the substrate to etch the titanium oxide film. [Effects of the Invention]

[0006] According to the present disclosure, the titanium oxide film can be removed. [Brief explanation of the drawings]

[0007] [Figure 1] 3 is a flowchart illustrating a substrate processing method according to an embodiment. [Figure 2] 1A to 1C are cross-sectional views illustrating an example of a substrate processing method according to an embodiment. [Figure 3] FIG. 10 is a cross-sectional view showing an example of an etching step. [Figure 4] FIG. 10 is a cross-sectional view showing another example of an etching step. [Figure 5] 1 is a cross-sectional view showing a substrate processing apparatus according to an embodiment. [Figure 6] FIG. 10 is a diagram showing an example of the results of measuring oxygen concentration. [Figure 7] FIG. 10 is a diagram showing an example of the results of measuring fluorine concentration. [Figure 8] FIG. 1 shows the results of measuring the etching amount of each film. [Figure 9] FIG. 2 shows the results of measuring the etching amount of each film. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, non-limiting exemplary embodiments of the present disclosure will be described with reference to the accompanying drawings. In all the accompanying drawings, the same or corresponding reference numerals are used to designate the same or corresponding members or components, and redundant descriptions will be omitted.

[0009] [Substrate Processing Method] A substrate processing method according to an embodiment will be described with reference to Fig. 1 to Fig. 4. Fig. 1 is a flowchart showing the substrate processing method according to an embodiment. Fig. 2 is a cross-sectional view showing an example of the substrate processing method according to an embodiment.

[0010] As shown in FIG. 1, the substrate processing method according to the embodiment includes a preparation step S1 and an etching step S2.

[0011] In the preparation step S1, first, as shown in FIG. 2(a), a substrate 101 is prepared. The substrate 101 is, for example, a silicon substrate. Next, as shown in FIG. 2(b), a titanium nitride film 102 is formed on the substrate 101. The titanium nitride film 102 can be formed, for example, by chemical vapor deposition (CVD) or physical vapor deposition (PVD). Next, the titanium nitride film 102 formed on the substrate 101 is exposed to an oxidizing atmosphere. As a result, as shown in FIG. 2(c), the surface of the titanium nitride film 102 is oxidized, and a titanium oxide film 103, which is a natural oxide film, is formed. As a result, a substrate 101 is formed in which the titanium nitride film 102 and the titanium oxide film 103 are laminated in this order. The oxidizing atmosphere is, for example, air. In the preparation step S1, instead of exposing the titanium nitride film 102 to an oxidizing atmosphere, a titanium oxide film 103 may be formed on the substrate 101 by, for example, a CVD method or a PVD method.

[0012] The etching step S2 is performed after the preparation step S1. In the etching step S2, as shown in Fig. 2(d), an etching gas containing hydrogen fluoride (HF) gas is supplied to the substrate 101 to etch and remove the titanium oxide film 103.

[0013] 3 is a cross-sectional view showing an example of the etching step S2. The etching step S2 may include an HF treatment. The HF treatment may include supplying hydrogen fluoride gas to the substrate 101 while maintaining the substrate 101 at a first treatment temperature. The first treatment temperature is, for example, 200°C or higher and 300°C or lower. When the hydrogen fluoride gas is supplied to the substrate 101, a reaction shown in formula (1) occurs.

[0014] TiO2+4HF→TiF4+2H2O (1)

[0015] 3, when hydrogen fluoride gas is supplied to the substrate 101, the titanium oxide film 103 reacts with the hydrogen fluoride gas to generate volatile titanium fluoride (TiF4) 103a, which etches the titanium oxide film 103. In this case, there is no need to change the temperature during the etching step S2. This allows for a reduction in the time required to etch the titanium oxide film 103.

[0016] 4 is a cross-sectional view showing another example of the etching step S2. The etching step S2 may include a COR (Chemical Oxide Removal) treatment and a PHT (Post Heat Treatment) treatment. In the etching step S2, the COR treatment and the PHT treatment may be performed once in this order, or may be repeated multiple times in this order. When the COR treatment and the PHT treatment are repeated multiple times in this order, purging using an inert gas such as nitrogen (N2) gas may be performed after the PHT treatment and before the COR treatment.

[0017] The COR process is a chemical etching process that does not generate plasma. The COR process may include supplying a mixed gas of hydrogen fluoride gas and ammonia (NH3) gas (hereinafter simply referred to as "mixed gas") to the substrate 101 while maintaining the substrate 101 at a second process temperature. The second process temperature is, for example, 50°C or higher and 70°C or lower. When the mixed gas is supplied to the substrate 101, the reactions shown in formulas (2) and (3) occur.

[0018] TiO2+4HF+4NH3→TiF4+2H2O+4NH3(2) TiF4+2HF+4NH3→(NH4)2TiF6(3)

[0019] 4(a), when the mixed gas is supplied to the substrate 101, the titanium oxide film 103 reacts with the hydrogen fluoride gas and ammonia gas to produce nonvolatile ammonium hexafluorotitanate [(NH4)2TiF6] 103b. Ammonia gas is an example of a basic gas. The basic gas may also be hydrazine (NH4) gas.

[0020] The PHT process may include heat-treating the substrate 101 while maintaining it at a third process temperature higher than the second process temperature. The third process temperature is a temperature at which the ammonium hexafluorotitanate 103b sublimes, and is, for example, 200° C. or higher and 300° C. or lower. When the substrate 101 is heat-treated at the third process temperature, the reaction shown in formula (4) occurs.

[0021] (NH4)2TiF6 → TiF4 + 2HF + 2NH3 (4)

[0022] That is, as shown in FIG. 4(b), when the substrate 101 is heat-treated at the third treatment temperature, the ammonium hexafluorotitanate 103b sublimes and the titanium oxide film 103 is etched.

[0023] As described above, according to the substrate processing method of the embodiment, an etching gas containing hydrogen fluoride gas is supplied to the substrate 101 on which the titanium nitride film 102 and the titanium oxide film 103 are stacked in this order, and the titanium oxide film 103 is etched. In this case, the titanium oxide film 103 can be removed.

[0024] [Substrate Processing Apparatus] The substrate processing apparatus 1 according to the embodiment will be described with reference to Fig. 5. As shown in Fig. 5, the substrate processing apparatus 1 is a batch type apparatus that processes a plurality of substrates W at once.

[0025] The substrate processing apparatus 1 includes a processing chamber 10, a gas supply unit 30, an exhaust unit 40, a heating unit 50, and a control unit 90.

[0026] The processing vessel 10 is capable of reducing the pressure inside. The processing vessel 10 accommodates a substrate W inside. The processing vessel 10 has an inner tube 11 and an outer tube 12. The inner tube 11 and the outer tube 12 have a cylindrical shape with a ceiling and an open lower end. The outer tube 12 covers the outside of the inner tube 11. The inner tube 11 and the outer tube 12 have a double-tube structure arranged coaxially. The inner tube 11 and the outer tube 12 are formed from a heat-resistant material such as quartz.

[0027] The ceiling of the inner pipe 11 may be flat, for example. A storage section 13 for storing a gas nozzle is formed on one side of the inner pipe 11 along its longitudinal direction (vertical direction). For example, a part of the side wall of the inner pipe 11 protrudes outward to form a convex section 14, and the inside of the convex section 14 is formed as the storage section 13.

[0028] A rectangular opening 15 is formed in the side wall of the inner tube 11 opposite the housing portion 13 along its longitudinal direction (vertical direction).

[0029] The opening 15 is a gas exhaust port formed so as to be able to exhaust gas from the inner tube 11. The length of the opening 15 is the same as the length of the boat 16, or is formed so as to extend in the vertical direction and be longer than the length of the boat 16.

[0030] The lower end of the processing vessel 10 is supported by a cylindrical manifold 17. The manifold 17 is made of, for example, stainless steel. A flange 18 is formed at the upper end of the manifold 17. The flange 18 supports the lower end of the outer tube 12. A seal member 19, such as an O-ring, is provided between the flange 18 and the lower end of the outer tube 12. This keeps the inside of the outer tube 12 airtight.

[0031] An annular support member 20 is provided on the inner wall of the upper portion of the manifold 17. The support member 20 supports the lower end of the inner tube 11. A lid member 21 is airtightly attached to the opening at the lower end of the manifold 17 via a sealing member 22 such as an O-ring. This airtightly closes the opening at the lower end of the processing vessel 10, i.e., the opening of the manifold 17. The lid member 21 is made of, for example, stainless steel.

[0032] A rotating shaft 24 is provided through the center of the lid 21 via a magnetic fluid seal 23. The lower part of the rotating shaft 24 is rotatably supported by an arm 25A of an elevation mechanism 25 made up of a boat elevator.

[0033] A rotating plate 26 is provided at the upper end of the rotating shaft 24. A boat 16 that holds substrates W is placed on the rotating plate 26 via a quartz heat retention stand 27. The boat 16 rotates by rotating the rotating shaft 24. The boat 16 moves up and down integrally with the lid 21 by raising and lowering the lifting mechanism 25. This allows the boat 16 to be inserted into and removed from the processing vessel 10. The boat 16 can be accommodated within the processing vessel 10. The boat 16 holds a plurality of substrates W (e.g., 50 to 150 substrates) approximately horizontally with spacing between them in the vertical direction.

[0034] The gas supply unit 30 is configured to be able to introduce various process gases used in the above-described substrate processing method into the inner tube 11. The gas supply unit 30 includes a hydrogen fluoride supply unit 31 and an ammonia supply unit 32.

[0035] The hydrogen fluoride supply unit 31 includes a supply pipe 31a inside the processing vessel 10 and a supply path 31b outside the processing vessel 10. A hydrogen fluoride gas supply source 31c, a mass flow controller 31d, and a valve 31e are installed on the supply path 31b, in this order from upstream to downstream in the gas flow direction. Thus, the supply timing of the hydrogen fluoride gas from the supply source 31c is controlled by the valve 31e, and the mass flow controller 31d adjusts the flow rate to a predetermined value. The hydrogen fluoride gas flows from the supply path 31b into the supply pipe 31a and is discharged from the supply pipe 31a into the processing vessel 10.

[0036] The ammonia supply unit 32 includes a supply pipe 32a inside the processing vessel 10 and a supply path 32b outside the processing vessel 10. An ammonia gas supply source 32c, a mass flow controller 32d, and a valve 32e are installed on the supply path 32b, in this order from upstream to downstream in the gas flow direction. The supply timing of the ammonia gas from the supply source 32c is controlled by the valve 32e, and the flow rate is adjusted to a predetermined value by the mass flow controller 32d. The ammonia gas flows from the supply path 32b into the supply pipe 32a and is then discharged from the supply pipe 32a into the processing vessel 10.

[0037] Each of the supply pipes 31a, 32a is fixed to the manifold 17. Each of the supply pipes 31a, 32a is made of, for example, quartz. Each of the supply pipes 31a, 32a extends linearly in the vertical direction near the inner pipe 11, and then bends in an L-shape within the manifold 17 and extends horizontally, thereby penetrating the manifold 17. Each of the supply pipes 31a, 32a is arranged side by side along the circumferential direction of the inner pipe 11 and is formed at the same height as each other.

[0038] A plurality of discharge ports 31f, 32f are provided in the supply pipes 31a, 32a at portions thereof located within the inner pipe 11. The discharge ports 31f, 32f are formed at predetermined intervals along the extension direction of the respective supply pipes 31a, 32a. Each discharge port 31f, 32f discharges gas in the horizontal direction. The interval between each discharge port 31f, 32f is set to be the same as the interval between the substrates W held in the boat 16, for example. The height direction position of each discharge port 31f, 32f is set at the midpoint between vertically adjacent substrates W. This allows each discharge port 31f, 32f to efficiently supply gas to the opposing surfaces between adjacent substrates W.

[0039] The gas supply unit 30 may mix multiple types of gases and discharge the mixed gas from a single supply pipe. The supply pipes 31a, 32a may have different shapes and arrangements. The gas supply unit 30 may further include a supply pipe for supplying another gas in addition to hydrogen fluoride gas and ammonia gas.

[0040] The exhaust unit 40 exhausts gas that is discharged from the inner tube 11 through the opening 15 and then discharged from a gas outlet 41 via a space P1 between the inner tube 11 and the outer tube 12. The gas outlet 41 is formed on the side wall of the upper part of the manifold 17, above the support unit 20. An exhaust passage 42 is connected to the gas outlet 41. A pressure adjustment valve 43 and a vacuum pump 44 are sequentially disposed in the exhaust passage 42, so that the inside of the processing chamber 10 can be exhausted.

[0041] The heating unit 50 is provided around the outer tube 12. The heating unit 50 is provided, for example, on the base plate 28. The heating unit 50 has a cylindrical shape so as to cover the outer tube 12. The heating unit 50 includes, for example, a heater, and heats each substrate W in the processing chamber 10.

[0042] The control unit 90 is an electronic circuit such as a CPU (Central Processing Unit), FPGA (Field Programmable Gate Array), ASIC (Application Specific Integrated Circuit), etc. The control unit 90 executes various control operations described in this specification by executing instruction codes stored in a memory or by being a circuit designed for a specific application.

[0043] [Operation of the Substrate Processing Apparatus] An example of the operation of the substrate processing apparatus 1 when carrying out the substrate processing method according to the embodiment will be described.

[0044] First, the control unit 90 controls the lifting mechanism 25 to load the boat 16 holding the substrates W into the processing vessel 10, and then airtightly closes the opening at the bottom of the processing vessel 10 with the lid 21. Next, the control unit 90 controls the exhaust unit 40 to reduce the pressure inside the processing vessel 10, and controls the heating unit 50 to adjust the temperature of the substrates W to a predetermined temperature. Each substrate W may be the substrate 101 described above.

[0045] Next, the control unit 90 controls the gas supply unit 30, the exhaust unit 40, and the heating unit 50 to perform the etching step S2. Specifically, first, the control unit 90 controls the heating unit 50 to maintain the temperature of the substrate W at the first processing temperature, controls the gas supply unit 30 to supply hydrogen fluoride gas into the processing vessel 10, and controls the exhaust unit 40 to maintain the inside of the processing vessel 10 at the processing pressure. As a result, the titanium oxide film 103 reacts with the hydrogen fluoride gas to generate volatile titanium fluoride 103a, and the titanium oxide film 103 is etched.

[0046] Next, the control unit 90 increases the pressure inside the processing vessel 10 to atmospheric pressure and decreases the temperature inside the processing vessel 10 to the unloading temperature, and then controls the lifting mechanism 25 to unload the boat 16 from the processing vessel 10. This completes the processing of the plurality of substrates W.

[0047] [Experimental results] (Experiment 1) In Experiment 1, substrates W11 to W15 were prepared, each having a laminate film formed on its surface, in which a titanium nitride film and a titanium oxide film were laminated in this order.

[0048] For the substrate W11, the oxygen concentration and fluorine concentration contained in the laminated film were measured by secondary ion mass spectrometry (SIMS) without performing the etching step S2 described above.

[0049] For the substrates W12 to W15, the oxygen concentration and fluorine concentration in the laminated film were measured by SIMS after the above-mentioned etching step S2 was performed. The conditions for the etching step S2 performed on the substrates W12 to W15 were as follows.

[0050] (Board W12) COR treatment + PHT treatment Substrate temperature during COR processing: 65°C COR processing time: 1 minute

[0051] (Board W13) COR treatment + PHT treatment Substrate temperature during COR processing: 65°C COR processing time: 10 minutes

[0052] (Board W14) HF treatment Substrate temperature during HF treatment: 200°C HF treatment time: 5 minutes

[0053] (Board W15) HF treatment Substrate temperature during HF treatment: 250°C HF treatment time: 3 minutes

[0054] Fig. 6 is a diagram showing an example of the results of measuring oxygen concentration. Fig. 6 shows the oxygen concentration [atoms / cc] contained in the laminated films on the substrates W11 to W15 on a logarithmic scale. Fig. 7 is a diagram showing an example of the results of measuring fluorine concentration. Fig. 7 shows the fluorine concentration [atoms / cc] contained in the laminated films on the substrates W11 to W15 on a logarithmic scale.

[0055] 6, it can be seen that the oxygen concentration is lower in the substrates W12 to W15 than in the substrate W11. From this result, it is considered that oxygen can be removed from the stacked film in both the case where the COR treatment and the PHT treatment are performed as the etching step S2 and the case where the HF treatment is performed.

[0056] 7, it can be seen that the fluorine concentration is higher in the substrates W12 to W15 than in the substrate W11. From this result, it is considered that fluorine can be introduced into the stacked film in both the case where the COR treatment and the PHT treatment are performed as the etching step S2 and the case where the HF treatment is performed.

[0057] From the above results, it is considered that the substrate processing method according to the embodiment can simultaneously remove the titanium oxide film from the laminated film and introduce fluorine into the titanium nitride film.

[0058] (Experiment 2) In Experiment 2, a substrate having a titanium oxide (TiO) film formed on its surface, a substrate having a titanium nitride (TiN) film formed on its surface, and a substrate having a silicon nitride (SiN) film formed on its surface were prepared. Subsequently, each substrate was subjected to the HF treatment as the etching step S2 described above. During the HF treatment, the substrate temperature was maintained at 200°C. The etching amount of each film was calculated by subtracting the film thickness of each film (silicon nitride film, titanium nitride film, and titanium oxide film) after etching step S2 from the film thickness of each film before etching step S2.

[0059] Figure 8 shows the results of measuring the etching amount of each film. In Figure 8, the horizontal axis represents the HF treatment time [minutes], and the vertical axis represents the etching amount [nm]. In Figure 8, the solid line represents the etching amount of the titanium oxide film, the dashed line represents the etching amount of the titanium nitride film, and the dashed line represents the etching amount of the silicon nitride film.

[0060] 8, the amount of etching of the titanium oxide film increases as the HF treatment time is increased, whereas the amount of etching of the titanium nitride film remains almost unchanged even when the HF treatment time is increased. From this result, it is believed that by performing HF treatment in the etching step S2, it is possible to selectively etch and remove the titanium oxide film while leaving the titanium nitride film in place in a stacked film in which a titanium nitride film and a titanium oxide film are stacked in this order.

[0061] 8, it can be seen that, like the titanium nitride film, the etching amount of the silicon nitride film remains almost unchanged even if the HF treatment time is extended. From this result, it is believed that the titanium oxide film can be selectively etched away from the silicon nitride film.

[0062] (Experiment 3) In Experiment 3, the HF treatment was carried out on each film under the same conditions as in Experiment 2, except that the substrate temperature during the HF treatment was set to 250° C., and the etching amount of each film was calculated.

[0063] Figure 9 shows the results of measuring the etching amount of each film. In Figure 9, the horizontal axis represents the HF treatment time [minutes], and the vertical axis represents the etching amount [nm]. In Figure 9, the solid line represents the etching amount of the titanium oxide film, the dashed line represents the etching amount of the titanium nitride film, and the dashed line represents the etching amount of the silicon nitride film.

[0064] 9, the amount of etching of the titanium oxide film increases as the HF treatment time is increased, whereas the amount of etching of the titanium nitride film remains almost unchanged even when the HF treatment time is increased. From this result, it is considered that by performing the HF treatment in the etching step S2, it is possible to selectively etch and remove the titanium oxide film while leaving the titanium nitride film in place in a stacked film in which a titanium nitride film and a titanium oxide film are stacked in this order.

[0065] 9, it can be seen that, like the titanium nitride film, the etching amount of the silicon nitride film remains almost unchanged even if the HF treatment time is extended. This result suggests that the titanium oxide film can be selectively etched away from the silicon nitride film.

[0066] Furthermore, hafnium oxide (HfO2), zirconium oxide (ZrO2), and aluminum oxide (AlO3) films are also hardly etched by HF treatment. This is thought to be because when hafnium oxide, zirconium oxide, and aluminum oxide films react with hydrogen fluoride gas, stable, non-volatile aluminum fluoride (AlF3), hafnium fluoride (HfF4), and zirconium fluoride (ZrF4) are produced, respectively. As a result, it is thought that titanium oxide films can be selectively etched and removed relative to hafnium oxide, zirconium oxide, and aluminum oxide films.

[0067] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive, and the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

[0068] In the above embodiment, the substrate processing apparatus is described as a batch-type apparatus that processes multiple substrates at once, but the present disclosure is not limited to this. For example, the substrate processing apparatus may be a single-wafer-type apparatus that processes substrates one by one. For example, the substrate processing apparatus may be a semi-batch-type apparatus that processes multiple substrates placed on a turntable in a processing chamber by rotating the turntable and passing the substrates sequentially through multiple processing regions arranged along the rotation direction of the turntable. [Explanation of symbols]

[0069] 101 Substrate 102 Titanium nitride film 103 Titanium oxide film S1 Preparation process S2 Etching process

Claims

1. preparing a substrate on which a titanium nitride film and a titanium oxide film are laminated in this order; supplying an etching gas containing hydrogen fluoride gas to the substrate to etch the titanium oxide film; A substrate processing method comprising:

2. The titanium oxide film is a natural oxide film formed on the surface of the titanium nitride film. The substrate processing method according to claim 1 .

3. The preparing step includes: forming a titanium nitride film on the substrate; exposing the titanium nitride film to an oxidizing atmosphere; Including, The substrate processing method according to claim 1 .

4. the etching gas is hydrogen fluoride gas, the etching step includes reacting the titanium oxide film with the hydrogen fluoride gas to generate titanium fluoride; The substrate processing method according to claim 1 .

5. The etching step includes maintaining the temperature of the substrate at 200° C. or higher and 300° C. or lower. The substrate processing method according to claim 4 .

6. the etching gas is a mixed gas of hydrogen fluoride gas and a basic gas, the etching step includes reacting the titanium oxide film with the mixed gas to produce ammonium hexafluorotitanate; The substrate processing method according to claim 1 .

7. the etching step includes sublimating the ammonium hexafluorotitanate after supplying the mixed gas to the substrate; The substrate processing method according to claim 6 .

8. a processing vessel for accommodating a substrate; a gas supply unit that supplies an etching gas containing hydrogen fluoride gas into the processing chamber; A control unit; Equipped with The control unit a step of placing a substrate having a titanium nitride film and a titanium oxide film stacked in this order in the processing vessel; supplying the etching gas to the substrate accommodated in the processing vessel to etch the titanium oxide film; configured to perform Substrate processing equipment.

Images