Substrate processing method and substrate processing apparatus

Abstract

The present disclosure relates to a substrate processing method and a substrate processing apparatus that suppress surface roughness of a silicon film after etching. The following processes are implemented: a first process of supplying a processing gas containing a halogen-containing gas and an alkaline gas to a substrate on which a silicon film is formed on a surface and which is set to a first temperature, modifying the surface of the silicon film to generate a reaction product; and a second process of removing the reaction product by setting the substrate to a second temperature after the first process.

Description

Technical Field

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

[0002] When manufacturing semiconductor devices, the Si film, among Si and SiGe films formed on the surface of a semiconductor wafer (hereinafter referred to as a wafer) serving as a substrate, is sometimes selectively etched. For example, Patent Document 1 describes the use of F2 gas and NH3 gas as etching gases, with the ratio of NH3 gas to the etching gas set to a predetermined value, to perform such selective etching.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 6426489 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] The present disclosure provides a technology capable of suppressing the surface roughness of a silicon film after etching.

[0008] Solutions for solving problems

[0009] The substrate processing method disclosed herein includes: a first step of supplying a processing gas containing a halogen-containing gas and an alkaline gas to a substrate having a silicon film formed on its surface and set to a first temperature, so as to modify the surface of the silicon film and generate a reaction product; and a second step of, after the first step, setting the substrate to a second temperature to remove the reaction product.

[0010] Effects of the Invention

[0011] According to the present disclosure, the surface roughness of the silicon film after etching can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1A It is a longitudinal sectional side view of a wafer to be processed according to the first embodiment of the present disclosure.

[0013] Figure 1B is a longitudinal sectional side view of the wafer.

[0014] Figure 1C is a longitudinal sectional side view of the wafer.

[0015] Figure 2A is a longitudinal sectional side view of the wafer.

[0016] Figure 2B is a longitudinal sectional side view of the wafer.

[0017] Figure 2C is a longitudinal sectional side view of the wafer.

[0018] Figure 3A It is a longitudinal sectional side view showing the surface of the wafer.

[0019] Figure 3B It is a longitudinal sectional side view showing the surface of the wafer.

[0020] Figure 4 It is a plan view showing one embodiment of a substrate processing apparatus for performing the above-mentioned processing.

[0021] Figure 5 It is a longitudinal sectional side view showing an example of a process module provided in the substrate processing apparatus.

[0022] Figure 6 It is a longitudinal sectional side view of a wafer to be processed according to the second embodiment of the present invention.

[0023] Figure 7 It is a longitudinal sectional side view of a recess formed in the wafer.

[0024] Figure 8 It is an explanatory diagram showing the change of the concave portion.

[0025] Figure 9 It is an explanatory diagram showing the change of the concave portion.

[0026] Figure 10 It is an explanatory diagram showing the change of the concave portion.

[0027] Figure 11 It is an explanatory diagram showing the change of the concave portion.

[0028] Figure 12 It is a top view showing the results of the evaluation test.

[0029] Figure 13 It is a top view showing the results of the evaluation test.

[0030] Figure 14 Schematic diagram of a concave portion of a wafer showing the results of an evaluation test.

[0031] Figure 15 It is a graph showing the results of the evaluation test. DETAILED DESCRIPTION

[0032] [First embodiment]

[0033] An outline of a process according to a first embodiment of the substrate processing method of the present disclosure will be described. Figure 1AThis is a longitudinal sectional side view of the surface of a wafer W, which is a substrate before processing. A Si (silicon) film 11 and a SiGe (silicon germanium) film 12, which is a silicon-containing film, are exposed on the surface of the wafer W. Of the Si film 11 and the SiGe film 12, only the Si film 11 is selectively etched partially. In other words, etching is performed so that the Si film 11 remains on the wafer W after processing.

[0034] In order to perform the above-mentioned selective etching, step S1 is performed as the etching. In this step S1, a halogen-containing gas and an alkaline gas are supplied to the wafer W as process gases to selectively modify the surface of the Si film 11 and the surface of the SiGe film 12 to generate a reaction product. In this embodiment, the halogen-containing gas is F2 (fluorine) gas, and the alkaline gas is NH3 (ammonia) gas. After performing this step S1 (first process), step S2 (second process) is performed to sublime the reaction product by heat treatment, thereby selectively etching the surface of the Si film 11. The above-mentioned reaction product is ammonium fluorosilicate (AFS).

[0035] The formation and sublimation of the reaction product described above are repeated. That is, a repetitive process of sequentially repeating the first and second steps is performed to control the etching amount of the Si film 11. At the end of this repetitive process (i.e., at the end of etching), the Si film 11 remains on the surface of the wafer W. However, as shown in evaluation tests later, depending on the processing conditions when supplying the processing gas, the surface of the remaining Si film 11 after the treatment forms irregularities, resulting in a relatively large surface roughness (surface roughness). The process of this embodiment is performed to suppress this surface roughness.

[0036] Next, the processing performed on wafer W will be described in sequence with reference to Figures 1 to 3. The arrows in each figure indicate processing gases, and the processing shown in each figure is performed after wafer W is loaded into a processing container and the container is evacuated to a vacuum atmosphere at a predetermined pressure. The wafer W being processed is adjusted to a desired temperature. In this embodiment, steps S1 and S2 are performed in different processing containers.

[0037] First, the processing container is evacuated to, for example, 100 mTorr (13.3 Pa) to 10 Torr (1333 Pa), and the temperature of the wafer W is adjusted to, for example, -20°C to 60°C as a first temperature. This temperature range is set to allow the reaction of generating the AFS by the above-mentioned processing gas to occur without sublimating the AFS. The reason for not sublimating the AFS will be described later. Performing the process at or near room temperature is advantageous in terms of suppressing the amount of energy used in the process, so the temperature of the wafer W is more preferably set to, for example, 20°C to 30°C.

[0038] While the temperature of the wafer W is being adjusted in this manner, F2 gas and NH3 gas are supplied as process gases into the processing container. As described above, the surface of the Si film 11 is modified, and an AFS layer 13 is formed on the surface of the Si film 11. For example, variations in the concentration distribution and flow of the gas in the processing container may cause variations in the thickness of the AFS layer 13 ( Figure 1B However, since the temperature of the wafer W is adjusted so that the AFS layer 13 does not sublime but remains, the processing gas is further supplied to the wafer W while the AFS layer S13 covers the Si film 11 .

[0039] In the thinner portion of the AFS layer 13, the processing gas penetrates the AFS layer 13 and reaches the Si film 11 below, modifying the Si film 11. However, in the thicker portion of the AFS layer 13, the processing gas is prevented from penetrating downward, and modification of the Si film is difficult to occur below the thicker portion. Therefore, the thickness of the AFS layer 13 is made uniform ( Figure 1C When the thickness of the AFS layer 13 is made uniform in this manner, the supply of the process gas is stopped, and step S1 is terminated.

[0040] Next, step S2 (second step) is performed to heat the wafer W to a second temperature higher than the temperature in step S1 (first step), for example, 80°C to 300°C. By this heating, the AFS layer 13 is sublimated and removed, and the Si film 11 covered by the AFS layer 13 is exposed ( Figure 2A ). The surface of the Si film 11 is etched through a series of steps S1 and S2. However, since the thickness of the AFS layer 13 is made uniform in step S1 as described above, each portion of the Si film 11 is etched with high uniformity. Consequently, the formation of unevenness on the surface of the Si film 11 after etching is suppressed.

[0041] Then, step S1 is performed again. Thus, the processing gas is supplied to the wafer W adjusted to the above-mentioned temperature, and the surface of the Si film 11 is selectively formed into the AFS layer 13 ( Figure 2B Then, by further continuing the supply of the processing gas while the AFS layer 13 remains, the thickness of each portion of the AFS layer 13 is made uniform ( Figure 2C Then, step S2 is performed again. Thus, the AFS layer 13 formed in the second step S1 is sublimated ( Figure 3A By progressing the process in this manner, the formation of irregularities on the surface of the Si film 11 is suppressed even after the second etching (after the second execution of step S1 and step S2).

[0042] Thereafter, the cycle consisting of step S1 and step S2 is repeated to advance the selective etching of the Si film 11. Then, when the remaining Si film 11 reaches the desired thickness, the repeated processing of step S1 and step S2 is stopped. That is, the etching process is stopped so that the Si film 11 ( Figure 3B Since the formation of unevenness on the surface of the Si film 11 is suppressed in the third and subsequent cycles, as in the first and second cycles, the formation of unevenness on the surface of the Si film 11 is also suppressed after the treatment is stopped. In other words, the treatment is terminated with the surface roughness of the Si film 11 suppressed.

[0043] Next, refer to Figure 4 1 to 3 , a substrate processing apparatus 2 is described as one embodiment of a substrate processing apparatus that performs the series of processes described in FIG1 to FIG3 . The substrate processing apparatus 2 includes a loading / unloading unit 21 for loading and unloading wafers W, two load lock chambers 31 disposed adjacent to the loading / unloading unit 21, two thermal processing modules 30 disposed adjacent to each of the two load lock chambers 31, and two processing modules 4 disposed adjacent to each of the two thermal processing modules 30.

[0044] The loading and unloading section 21 includes an atmospheric transfer chamber 23, which houses a first substrate transfer mechanism 22 and is maintained at atmospheric pressure. A carrier mounting table 25, located to the side of the atmospheric transfer chamber 23, is used to mount a carrier 24 for storing wafers W. Reference numeral 26 in the figure denotes a positioning chamber adjacent to the atmospheric transfer chamber 23. This chamber is used to rotate the wafer W and optically determine its eccentricity to position it relative to the first substrate transfer mechanism 22. The first substrate transfer mechanism 22 transfers wafers W between the carrier 24 on the carrier mounting table 25, the positioning chamber 26, and the load lock chamber 31.

[0045] A second substrate transfer mechanism 32 having, for example, a multi-jointed arm structure is provided in each load lock chamber 31. The second substrate transfer mechanism 32 transfers wafers W between the load lock chamber 31, the thermal treatment module 30, and the process module 4. The interiors of the process containers constituting the thermal treatment module 30 and the process modules 4 are set to a vacuum atmosphere, and the interior of the load lock chamber 31 is switched between a normal pressure atmosphere and a vacuum atmosphere, so that wafers W can be transferred between the process containers in these vacuum atmospheres and the normal pressure transfer chamber 23.

[0046] Reference numeral 33 in the figure denotes a freely openable and closable gate valve, which is respectively provided between the atmospheric transfer chamber 23 and the load lock chamber 31, between the load lock chamber 31 and the thermal treatment module 30, and between the thermal treatment module 30 and the treatment module 4. The thermal treatment module 30 includes the aforementioned processing vessel, an exhaust mechanism for exhausting the processing vessel to form a vacuum atmosphere, and a worktable provided in the processing vessel and capable of heating the wafer W placed therein. The thermal treatment module 30 is configured to perform the aforementioned step S2.

[0047] Reference Figure 5 The processing module 4 is described with reference to a longitudinal sectional side view of FIG. The processing module 4 executes the aforementioned step S1. Reference numeral 41 in the figure denotes a processing container constituting the processing module 4. Reference numeral 42 in the figure denotes a transfer port for wafers W, which is opened in the side wall of the processing container 41 and is opened and closed by the gate valve 33 described above. A worktable 51 for placing wafers W is provided within the processing container 41, and lift pins (not shown) are provided on the worktable 51. The lift pins are used to transfer wafers W between the second substrate transfer mechanism 32 and the worktable 51.

[0048] A temperature adjustment unit 52 is embedded in the worktable 51 to maintain the temperature of the wafer W placed on the worktable 51. The temperature adjustment unit 52 is configured as, for example, a flow path forming part of a circulation path for a temperature adjustment fluid, such as water, and adjusts the temperature of the wafer W through heat exchange with the fluid. However, the temperature adjustment unit 52 is not limited to a flow path for such a fluid and may also be configured as a heater for resistive heating, for example.

[0049] One end of an exhaust pipe 53 opens into the processing chamber 41, and the other end of the exhaust pipe 53 is connected to an exhaust mechanism 55, such as a vacuum pump, via a valve 54 serving as a pressure changing mechanism. The pressure in the processing chamber 41 is adjusted to within the aforementioned range by adjusting the opening of the valve 54, and then processing is performed.

[0050] A gas showerhead 56, serving as a process gas supply mechanism, is installed above the processing chamber 41, facing the workbench 51. The gas showerhead 56 is connected to the downstream side of gas supply lines 61-64. The upstream sides of these lines are connected to gas supply sources 66-69 via flow control units 65, respectively. Each flow control unit 65 includes a valve and a mass flow controller. The gases supplied from the gas supply sources 66-69 are supplied to or blocked downstream by opening and closing the valves included in the flow control units 65.

[0051] F2 gas, NH3 gas, Ar (argon) gas, and N2 (nitrogen) gas are supplied from gas supply sources 66, 67, 68, and 69, respectively. Thus, these HF gas, NH3 gas, Ar gas, and N2 gas can be supplied from the gas showerhead 56 into the processing container 41. Ar gas and N2 gas are supplied into the processing container 41 as carrier gases along with the F2 gas and NH3 gas. The flow rates of the F2 gas and NH3 gas supplied into the processing container 41 are, for example, 100 sccm to 1000 sccm for the F2 gas and 4 sccm to 80 sccm for the NH3 gas.

[0052] In addition, if Figure 4 As shown, the substrate processing apparatus 2 includes a control unit 20 as a computer, and the control unit 20 includes a program, a memory, and a CPU. The program includes commands (various steps) for performing the aforementioned processing and transport of the wafer W. The program is stored in a storage medium such as an optical disc, a hard disk, a magneto-optical disc, a DVD, etc., and is installed in the control unit 20. The control unit 20 outputs control signals to various parts of the substrate processing apparatus 2 through the program to control the operation of each part. Specifically, the control signals are used to control the operation of the processing module 4, the operation of the heat treatment module 30, the operation of the first substrate transport mechanism 22, the operation of the second substrate transport mechanism 32, and the operation of the positioning chamber 26. The operation of the processing module 4 includes, for example, the temperature of the fluid supplied to the workbench 51, the supply and shutoff of each gas from the gas shower head 56, and the adjustment of the exhaust flow rate by the valve 54.

[0053] The transport path of the wafer W in the substrate processing apparatus 2 will be described. Figure 1A The carrier 24 of the wafer W on which the various films are formed as described above is placed on the carrier mounting table 25. The wafer W is then transported in the order of the atmospheric pressure transfer chamber 23, the positioning chamber 26, the atmospheric pressure transfer chamber 23, and the load lock chamber 31, and is then transferred to the processing module 4 via the thermal treatment module 30. The process described in step S1 is then performed as described above to form the AFS layer 13. Subsequently, the wafer W is transferred to the thermal treatment module 30 to undergo sublimation of the AFS layer 13 in step S2.

[0054] Steps S1 and S2 are then repeated a predetermined number of times by reciprocating the wafer W between the processing module 4 and the thermal treatment module 30. The wafer W is then transferred from the thermal treatment module 30 to the load lock chamber 31 and then to the atmospheric transfer chamber 23, and returned to the carrier 24.

[0055] According to the processing method described in this embodiment, as described above, the Si film 11 can be selectively etched between the Si film 11 and the SiGe film 12, and the roughness of the surface of the Si film 11 after the etching process can be suppressed. Therefore, the yield of semiconductor products manufactured from the wafer W after the etching process can be improved.

[0056] In the above-mentioned processing example, steps S1 and S2 are repeated three or more times when etching the Si film 11. However, the number of repetitions is not limited to the above-mentioned example, and may be two times, for example. Furthermore, steps S1 to S2 may be performed only once without repetition. In addition, in the above-mentioned substrate processing apparatus 2, the wafer W is transported between the processing module 4 and the heat treatment module 30, and steps S1 and S2 are performed in different processing containers. The processing is not limited to this. For example, steps S1 and S2 may be performed by changing the temperature of the workbench 51 of the processing module 4. In other words, steps S1 and S2 may be performed in the same processing container. However, in this case, when steps S1 and S2 are repeated, time is required to cool the workbench 51 in order to perform step S1 again after executing step S2. Therefore, in order to obtain high throughput when repeating steps S1 and S2, it is preferable to place the wafer on a workbench in a different processing container for processing as described above.

[0057] Furthermore, in the example described as a silicon-containing film, the SiGe film 12 is exposed on the surface of the wafer W. However, for example, a SiN film or a SiO2 film may be exposed on the surface of the wafer W instead of the SiGe film 12. Compared to a Si film, these SiN and SiO2 films have a lower Si content. Therefore, compared to the Si film 11, it is difficult for NH3 gas and F2 gas to generate an AFS. Therefore, even if a SiN film or a SiO2 film is exposed on the surface of the wafer W instead of the SiGe film 12, the Si film 11 can be selectively etched. Furthermore, the halogen gas is not limited to F2 gas; for example, even if IF7 gas, IF5 gas, ClF3 gas, or SF6 gas is used, the AFS layer 13 can be generated and similar processing can be performed.

[0058] Furthermore, in the above example, F2 gas and NH3 gas are simultaneously supplied to the wafer W for processing. That is, the period during which the F2 gas is supplied coincides with the period during which the NH3 gas is supplied. However, this is not the only way to supply each gas. For example, F2 gas and NH3 gas may be alternately and repeatedly supplied, causing one of the F2 gas and NH3 gas adsorbed on the Si film 11 to react with the other gas, thereby generating AFS. In other words, these gases may be supplied so that the period during which the F2 gas is supplied and the period during which the NH3 gas is supplied do not overlap. Alternatively, the period during which the F2 gas is supplied and the period during which the NH3 gas is supplied may only partially overlap. However, by supplying F2 gas and NH3 gas simultaneously as in the process shown in Figures 1 to 3, the aforementioned AFS layer 13 can be rapidly formed and the thickness of the AFS layer 13 can be made uniform, thereby improving throughput, and is therefore preferred.

[0059] In the above example, the AFS layer 13 is sublimated by increasing the temperature of the wafer W in step S2 compared to the temperature of the wafer W in step S1. However, this is not limited to changing the temperature of the wafer W in this manner. For example, step S2, like step S1, can be performed by the processing module 4. Furthermore, during step S2, the opening of the valve 54 in the exhaust pipe 53 is increased compared to that during step S1. This reduces the pressure within the processing chamber 41 during step S2 compared to that during step S1. This pressure change can also be used to sublime the AFS layer 13.

[0060] [Second embodiment]

[0061] In the second embodiment, as the Figure 6 The following description will be given of a case where a wafer W having the structure 71 shown is processed. Figure 6 : is a longitudinal sectional side view of the structure 71. The structure 71 includes a Si film, and the structure 71 includes a recess 72 formed by punching the Si film in the longitudinal direction (the thickness direction of the wafer W), and a recess 73 punched in the Si film so as to extend from the left side wall and the right side wall of the recess 72 to the left and right respectively. The recess 72 is open on the surface of the wafer W, and the various gases supplied to the wafer W are introduced into the recess 73 through the recess 72. A large number of recesses 73 are formed at different heights in the longitudinal direction on the left and right sides of the recess 72, so that the recesses 73 and the Si film are alternately arranged in the longitudinal direction on the left and right sides of the recess 72.

[0062] Referring to a schematically shown enlarged recess 73 Figure 7The structure 71 will be further described with reference to a longitudinal cross-sectional side view. Due to the structure already described, the upper and lower walls forming the recess 73 are formed of a Si film, shown as Si film 74 in the figure. Furthermore, the sidewalls forming the recess 73 are formed of a SiGe film 75. In this second embodiment, the Si film 74 forming the upper and lower walls of the recess 73 is selectively etched relative to the SiGe film 75 to reduce the longitudinal thickness of the Si film 74. In other words, the opening width of the recess 73 is increased. This etching is performed to suppress the surface roughness of the Si film 74 after etching.

[0063] Below, refer to Figures 8 to 11 The etching process of the second embodiment will be described focusing on the differences from the etching process of the first embodiment. Figures 8 to 11 This is a schematic diagram showing changes in Si film 74 estimated to occur during processing. In this process, in addition to NH3 gas, F2 gas and HF (hydrogen fluoride) gas are used as fluorine-containing gases. In the figure, F2 gas is indicated by 81, NH3 gas is indicated by 82, and HF gas is indicated by 83.

[0064] First, while the pressure in the processing container 41 accommodating the wafers W and the temperature of the wafers W in the processing container 41 are adjusted to, for example, the same pressure and temperature as in step S1 of the first embodiment, the F2 gas 81 and the NH3 gas 82 are simultaneously supplied as in step S1 ( Figure 8 , step T1). Thus, the surface layer of the Si film 74 forming the concave portion 73 is modified to produce the AFS layer 13. When forming the AFS layer 13, fine concave and convex portions are formed on the surface layer of the Si film 74 due to the action of each gas, and the AFS layer 13 is formed so as to cover the Si film 74 having the concave and convex portions formed thereon ( Figure 9 ).

[0065] After the supply of F2 gas 81 and NH3 gas 82 into the processing container 41 is stopped, N2 gas is supplied into the processing container 41 and the exhaust is performed, and the remaining F2 gas 81 and NH3 gas 82 are purged and removed from the processing container 41 (step T2). Thereafter, HF gas 83 is supplied into the processing container 41 ( Figure 10 : Step T3), it is believed that a reaction represented by the following formula 1 occurs between the HF gas 83, the AFS layer 13, and the Si film 74 in contact with the AFS ((NH4)2SiF6) layer 13.

[0066] 2Si((NH4)2SiF6) + 4HF → SiF6 + SiH4 + (NH4)2SiF6 ... Equation 1. If the above reaction is described in detail, the AFS layer 13 formed in step T1 contains a relatively high amount of fluorine. By supplying HF gas 83, which also contains fluorine, in step T3, the fluorine in the AFS layer 13 becomes even more excessive, fluorinating the extreme surface of the Si film 74 in contact with the AFS layer 13, forming a modified layer 75. It has been found that by using the fluorine-containing gas supply as a trigger, the fluorine contained in the AFS layer 13 is utilized to transform the extreme surface of the Si film 74 into the modified layer 75.

[0067] After that, the supply of HF gas 83 into the processing container 41 is stopped, and N2 gas is supplied into the processing container 41 and the exhaust is performed, and the residual HF is purged and removed from the processing container 41 (step T4). Then, similarly to step S2 of the first embodiment, the wafer W is heated to a temperature higher than the temperature in steps T1 to T4, for example, 80°C to 300°C. By this heating, the AFS layer 13 and the modified layer 75 are sublimated and removed, and the Si film 74 covered by these layers is exposed ( Figure 11 : Step T5).

[0068] As described above, by removing the extreme surface of the Si film 74 where the unevenness was formed after step T1, the surface roughness of the Si film 74 exposed in step T5 is suppressed. Furthermore, as in the first embodiment, the above process selectively etches the Si film 74 between the Si film 74 and the SiGe film 75. Furthermore, the cycle including steps T1 to T5 is repeated thereafter, and the selective etching of the Si film 11 progresses, and the thinning of the Si film 74 progresses. When the Si film 74 reaches the desired thickness, the repetition of steps T1 to T5 is stopped.

[0069] According to the etching process of the second embodiment described above, as also shown in the evaluation test below, the roughness of the Si film after etching can be more reliably suppressed. Figure 4 In the substrate processing apparatus 2 described in the embodiment, steps T1 to T4 are performed in the processing module 4, and step T5 is performed in the heat treatment module 30. Furthermore, steps T1 to T4 performed in the processing module 4 correspond to the first step of modifying the Si film 74 to generate a reaction product. Furthermore, step T1 corresponds to the first supply step, in which F2 gas, which is a first fluorine-containing gas, and NH3 gas, which is an alkaline gas, are supplied to the wafer W in parallel. Furthermore, step T3 corresponds to the second supply step. As described above, in this example, step T3 is performed to supply HF gas, which is a second fluorine-containing gas of a different type from the first fluorine-containing gas, to the wafer W.

[0070] The processing module 4 that performs steps T1 to T4 is configured, for example, as follows: in addition to the aforementioned gas supply sources 66 to 69, a HF gas supply source is also provided, which is connected to the gas showerhead 56 via a flow path. Furthermore, similar to the flow paths for the other gases, a flow rate regulator 65 is provided in the HF gas flow path, and HF gas is supplied at a desired flow rate into the processing container 41 via the gas showerhead 56. Furthermore, when supplying the HF gas into the processing container 41, for example, Ar gas and N₂ gas are also supplied as carrier gases.

[0071] In step T3, a gas that reacts with the AFS layer 13 to cause the fluorine contained in the AFS layer 13 to react with the Si film 74 may be used. It is conceivable to use other fluorine-containing gases, such as F2 gas or NF3 (nitrogen trifluoride) gas, instead of HF gas. When F2 gas is used, the same type of fluorine-containing gas is used in steps T1 and T3. In the above-described process example, to prevent the process in step T3 from being affected by the gas used in step T1, a purge using N2 gas, an inert gas, is performed in step T2. However, in cases where F2 gas is used in both steps T1 and T3, step T2 can be omitted. Specifically, in step T1, F2 gas and NH3 gas are first supplied to the process container 41 together, and then the supply of NH3 gas, which is one of the F2 and NH3 gases, is stopped, resulting in a state where only F2 gas is supplied to the process container 41. This allows the process in step T3 to be performed while omitting step T2.

[0072] Alternatively, in step T3, NH3 gas may be supplied instead of a fluorine-containing gas. As described above, the AFS layer 13 contains a large amount of fluorine. However, the supply of NH3 gas causes a reaction between the fluorine in the AFS layer 13, the NH3, and the extreme surface of the Si film 74. This modifies the extreme surface of the Si film 74, resulting in a reaction product that sublimates along with the AFS layer 13 and is removed in step T5. This reduces the surface roughness of the Si film 74 after step T5. When NH3 gas is supplied in step T3, step T2 can be omitted, similar to the case of using F2 gas in step T3.

[0073] As described above, the gas supplied to the wafer W in the second supply process after the first supply process is performed is not limited to the second fluorine-containing gas of a different type from the first fluorine-containing gas. The first supply process is a process in which the supply of F2 gas (the first fluorine-containing gas) to the wafer W and the supply of NH3 gas to the wafer W are performed in parallel. In addition, in the first embodiment, the supply periods of F2 gas and NH3 gas are consistent (the timing of the start of supply of each gas is the same and the timing of the end of supply of each gas is the same) and are described as simultaneous supply in this specification. In the second embodiment, when the supply of F2 gas and the supply of NH3 gas are performed in parallel, the timing of the start of supply of these gases is not limited to being the same. In other words, the supply of F2 gas and NH3 gas is not limited to being simultaneous as described in this specification.

[0074] Furthermore, steps T1 to T5 are not limited to being repeated multiple times, but may be performed only once. Furthermore, an example is shown in which the wall surface of the recess 73 formed laterally toward the structure 71 is etched, but the etching location is arbitrary and is not limited to etching the wall surface.

[0075] The embodiments disclosed herein are to be considered in all respects as illustrative and non-restrictive. The embodiments described above may be omitted, replaced, modified, or combined in various ways without departing from the scope of the appended claims and their spirit.

[0076] 〔Evaluation Test〕

[0077] Evaluation test 1

[0078] An evaluation test conducted in association with the technology disclosed herein is described. As evaluation test 1, as described in the embodiment, the etching process of steps S1 and S2 is repeated multiple times on wafer W. With respect to wafer W used in this process, as shown in the embodiment, Si film 11 and SiGe film 12 are exposed on the surface of wafer W. In step S1 of this evaluation test 1, the flow rate of F2 gas and the flow rate of NH3 gas supplied to the processing container for accommodating wafer W are respectively set to values ​​within the ranges described. In addition, as described in the embodiment, together with these F2 gas and NH3 gas, Ar gas and N2 gas are also supplied to the processing container. In addition, the pressure in the processing container and the temperature of wafer W in step S1 are also set to values ​​within the ranges described in the embodiment.

[0079] In this evaluation test 1, the supply time of the processing gas (F2 gas and NH3 gas) in step S1 and the number of repetitions of steps S1 and S2 were changed once for each wafer W. In addition, an image of the surface of the Si film 11 was obtained for each wafer W after processing, and the etching selectivity (= etching amount of Si film 11 / etching amount of SiGe film 12) was calculated. As evaluation test 1-1, the supply time of the processing gas was set to 30 seconds, and the above-mentioned number of repetitions was set to 6 times. As evaluation test 1-2, the supply time of the processing gas was set to 45 seconds, and the above-mentioned number of repetitions was set to 4 times. As evaluation test 1-3, the supply time of the processing gas was set to 60 seconds, and the above-mentioned number of repetitions was set to 3 times. Therefore, in each evaluation test of evaluation tests 1-1 to 1-3, the total supply time of the processing gas to the wafer W was 180 seconds.

[0080] In the evaluation tests 1-1 to 1-3, the etching selectivity ratio was 30 or more, and thus the Si film 11 was selectively etched with respect to the SiGe film 12. Figure 12 The images obtained in the evaluation tests 1-1 to 1-3 and the images obtained from the Si film 11 before being processed are schematically shown. In the obtained images, the concavities and convexities on the surface of the Si film 11 are shown as black and white contrast. Figure 12 The image shown is an image that surrounds the concave portion of the concave-convex portion and is shown with dots. For the convenience of illustration, the dense convex portions are shown as one convex portion by surrounding them together. Figure 12 As shown, the formation of irregularities was confirmed in the image of Evaluation Test 1-1, but only minute irregularities were formed in Evaluation Tests 1-2 and 1-3.

[0081] In Evaluation Tests 1-2 and 1-3, where the process gas supply time in step S1 was long, the surface roughness of Si film 11 was suppressed. This is because in Evaluation Test 1-1, the reaction between the process gas and the surface layer of Si film 11 was insufficient, resulting in sublimation in step S2 with low thickness uniformity of AFS layer 13. On the other hand, in Evaluation Tests 1-2 and 1-3, it is believed that the surface layer of Si film 11 reacted sufficiently with the process gas, forming AFS layer 13 with a highly uniform thickness, as described in the embodiments.

[0082] Furthermore, it is believed that in evaluation test 1-2, in which the supply time was 45 seconds, the surface roughness was sufficiently suppressed, and even with a supply time slightly shorter than 45 seconds, the roughness was suppressed. However, in evaluation test 1-1, in which the supply time of the process gas was 30 seconds, some roughness was observed. Based on the above, it is believed that the supply time of the process gas is preferably 40 seconds or longer. However, when the supply time of the process gas is too long, the process gas is blocked by the formed AFS layer 13 and cannot act on the Si film 11, thereby wasting the process gas. Considering that the roughness of the Si film 11 is appropriately suppressed when the supply time of the process gas is 60 seconds, it is believed that it is preferably set to a supply time longer than this, for example, less than 120 seconds.

[0083] Evaluation test 2

[0084] Next, evaluation test 2 will be described. In this evaluation test 2, as in evaluation test 1, the Si film 11 was etched by repeating steps S1 and S2 on a plurality of wafers W. Furthermore, the image of the surface of the Si film 11 was acquired and the etching selectivity was calculated. In this evaluation test 2, the supply time of the processing gas in one step S1 was set to 30 seconds uniformly between each wafer W, and the number of repetitions of steps S1 and S2 was set to 6 uniformly between each wafer W for processing. Therefore, the supply time of the processing gas and the number of repetitions of S1 and S2 were the same as those in the above-mentioned evaluation test 1-1. However, the flow rate of NH3 gas was different from that in evaluation test 1-1. Regarding the flow rate of NH3 gas in this evaluation test 2 (2-1, 2-2), the relationship was evaluation test 2-1 < evaluation test 1-1 < evaluation test 2-2. In addition, in evaluation test 2, the processing conditions other than the flow rate of NH3 gas were set in the same way as the processing conditions of evaluation test 1.

[0085] The etching selectivity ratios in the evaluation tests 2-1 and 2-2 were 30 or greater, and thus the Si film 11 was selectively etched with respect to the SiGe film 12 . Figure 13 This figure schematically shows the images acquired in the evaluation tests 2-1 and 2-2, similarly to the evaluation test 1. Figure 13 It is also shown in Figure 12 Schematic diagram of the image of the evaluation test 1-1 is shown in FIG. Figure 13As shown, in Evaluation Test 2-1, the roughness was greater than in Evaluation Test 1-1, while in Evaluation Test 2-2, the roughness was suppressed. Therefore, the greater the flow rate of NH3 gas, the more the roughness was suppressed. This is believed to be because the F2 gas was supplied at a relatively high flow rate. Therefore, a higher flow rate of NH3 gas increased the amount of the surface layer of the Si film 11 that was converted into the AFS layer 13, resulting in a higher thickness uniformity of the AFS layer 13, as already mentioned.

[0086] Furthermore, in Evaluation Test 1-1, the ratio of the NH3 gas flow rate to the F2 gas flow rate (NH3 gas flow rate / F2 gas flow rate) was 0.026. As described above, some irregularities were observed in Evaluation Test 1-1, confirming that this ratio is preferably greater than 0.026. Furthermore, in Evaluation Test 2-2, the NH3 gas flow rate was set within the range described in the embodiment, and the NH3 gas flow rate / F2 gas flow rate was 0.036. Therefore, it was confirmed that this ratio is more preferably set to 0.036 or greater.

[0087] Evaluation test 3

[0088] Next, the evaluation test 3 will be described. Figure 6 、 Figure 7 Multiple wafers W having the structure 71 described in FIG. 1 were processed by repeating the cycle consisting of steps T1 to T5 described in the second embodiment 10 times. The flow rate of HF gas supplied into the processing chamber 41 in step T3 was varied for each wafer W processed. Furthermore, SEM images were captured of the processed wafers W to observe the surface condition of the Si film 74 in the structure 71. Tests conducted with HF gas flow rates of 100 sccm, 200 sccm, and 450 sccm are designated Evaluation Tests 3-1, 3-2, and 3-3, respectively.

[0089] Furthermore, the pressure within the processing container 41 was set to a value within the range described in the embodiment, and the supply time of the HF gas was set to 30 seconds. Furthermore, the flow rates of the Ar gas and the N2 gas supplied into the processing container 41 along with the HF gas were each set to 275 sccm. Furthermore, as evaluation test 3-4, the same conditions as those of evaluation tests 3-1 to 3-3 were used, except that step T3 and step T4 (the purge with N2 gas after the supply of HF gas) were not performed, and images were acquired using an SEM. Therefore, the processing in this evaluation test 3-4 is the same as the processing described in the first embodiment, which repeats steps S1 and S2.

[0090] exist Figure 14The upper, middle, and lower sections show schematic diagrams of images obtained in evaluation tests 3-1, 3-2, and 3-4, respectively. When compared with evaluation test 3-4, the roughness of the surface of Si film 74 was suppressed in evaluation tests 3-1 to 3-3. Therefore, as described in the second embodiment, it is shown that HF ​​gas is preferably supplied. In evaluation tests 3-1 to 3-3, one of evaluation tests 3-2 and 3-3 suppressed the above-mentioned roughness more than evaluation test 3-1, reaching a practically desirable level. In addition, in evaluation tests 3-2 and 3-3, the state of roughness was the same, so in Figure 14 Only the schematic diagram of 3-2 among these evaluation tests 3-2 and 3-3 is shown.

[0091] Based on the above results, it is confirmed that the flow rate of HF gas supplied to wafer W in step T3 is preferably greater than 100 sccm, and more preferably greater than 200 sccm. As described above, during the supply of HF gas, 250 sccm of each of Ar gas and N2 gas, which serve as inert gases, is supplied. Therefore, the ratio of the flow rate of HF gas to the flow rate of all gases supplied into processing container 41 is expressed by the following equation 2. Note that X in equation 2 is the flow rate of HF gas.

[0092] Xsccm / (X+250+250)sccm…Equation 2

[0093] When X = 100 sccm, according to Equation 2, the ratio is 0.1667, and when X = 200 sccm, according to Equation 2, the ratio is 0.2857. Therefore, this Evaluation Test 3 shows that the ratio of the HF gas flow rate to the total gas flow rate supplied to the processing container 41 is preferably greater than 0.1667, and more preferably greater than 0.2857. Furthermore, it is believed that the roughness conditions between Evaluation Tests 3-2 and 3-3 are similarly due to the fact that, as described above, the Si film 74 is modified by the fluorine in the AFS layer 13 to improve roughness, but even if the HF gas flow rate is increased, the amount of fluorine that can contribute to the modification of the Si film 74 in the AFS layer 13 is limited.

[0094] Evaluation test 4

[0095] Next, evaluation test 4 is described. In evaluation test 4, the wafer W having structure 71 formed thereon was treated by repeating the cycle consisting of steps T1, T2, and T5 in the second embodiment 9 times. Then, after the treatment as described above, an SEM image of the structure 71 was obtained, and the etching amount near the opening portion in the recess 73 and the etching amount near the deep portion (near the end portion on the opposite side of the opening portion) were measured. In addition, the smaller the difference in their etching amount, the better. Regarding the flow rate of NH3 gas supplied to the processing container 41 in step S1, it is set variably for each wafer W and is set to any one of 5sccm, 8sccm, 10sccm, 12sccm, and 14sccm.

[0096] Regarding other processing conditions in step S1, the flow rates of F2 gas and Ar gas supplied into processing vessel 41 were set to 500 sccm and 200 sccm, respectively. The flow rate of N2 gas was modified based on the flow rate of NH3 gas, with the total flow rate of N2 gas and NH3 gas set to 700 sccm. Furthermore, the supply time of F2 gas and NH3 gas in one cycle was set to 15 seconds. Furthermore, the temperature of wafer W was set to a value within the range described in the embodiment.

[0097] Figure 15 This is a graph summarizing the results of Evaluation Test 4. The vertical axis represents the etching amount (unit: nm) and the horizontal axis represents the NH3 gas flow rate (unit: sccm). The vertical axis is scaled for every 2nm increase in A, where A is a real number. As shown in the graph, when the NH3 gas flow rate is 5 sccm, the etching amount near the depth is smaller than the etching amount near the opening, and the difference in etching amount is relatively large. When the NH3 gas flow rate is 8 sccm, the etching amount near the depth is smaller than the etching amount near the opening. When compared with the case of 5 sccm, the difference in etching amount is small, but in practical terms, it is desirable to make this etching amount difference even smaller.

[0098] Furthermore, when the flow rate of the NH3 gas is 10 sccm or greater, the difference in etching amount is sufficiently small. This is believed to be because, when the flow rate of the NH3 gas is 10 sccm or greater, the NH3 gas is sufficiently supplied from the opening to the deep portion of the recess 73, and the AFS layer 13 is sufficiently formed on the surfaces of the upper and lower walls of the Si film 74 constituting the recess 73.

[0099] As described above, the results of Evaluation Test 4 indicate that when uniformly etching each portion of recess 73 by supplying F2 gas and NH3 gas into processing container 41 in parallel, the NH3 gas flow rate is preferably set to greater than 8 sccm, and more preferably to 10 sccm or greater. As described above, F2 gas was supplied at 500 sccm. Therefore, in Evaluation Test 4, the results indicate that the ratio of the NH3 gas flow rate to the F2 gas flow rate is preferably greater than 8 sccm / 500 sccm = 0.016, and more preferably 10 sccm / 500 sccm = 0.02 or greater.

[0100] Description of Reference Numerals

[0101] W: wafer; 11: Si film; 13: AFS layer.

Claims

1. A substrate processing method, comprising: In a first step, a process gas containing a halogen-containing gas and an alkaline gas is supplied to a substrate having a silicon film formed on a surface thereof and set to a first temperature, thereby modifying the surface of the silicon film to generate a reaction product. as well as In the second step, after the first step, the substrate is set to a second temperature to remove the reaction product. Here, in the first step, the processing gas is supplied to the substrate for a predetermined time or longer while the reaction product remains on the silicon film, so that the thickness of the reaction product becomes uniform.

2. The substrate processing method according to claim 1, wherein: The method includes a repeated process in which the first process and the second process are repeated in sequence.

3. The substrate processing method according to claim 2, wherein: At the end of the repeated steps, the silicon film remains on the substrate.

4. The substrate processing method according to any one of claims 1 to 3, wherein: The second temperature is a temperature higher than the first temperature.

5. The substrate processing method according to any one of claims 1 to 3, wherein: The substrate has a silicon-containing film different from the silicon film formed on the surface thereof, The first step and the second step are steps of selectively modifying the silicon film with respect to the silicon-containing film to remove the silicon film.

6. The substrate processing method according to claim 5, wherein: The silicon-containing film is a SiGe film.

7. The substrate processing method according to any one of claims 1 to 3, wherein: The first temperature is -20°C to 60°C.

8. The substrate processing method according to any one of claims 1 to 3, wherein: In the first step, the halogen-containing gas and the alkaline gas are simultaneously supplied to the substrate.

9. The substrate processing method according to claim 8, wherein: In the first step, the halogen-containing gas and the alkaline gas are simultaneously supplied to the substrate for 40 seconds or more.

10. The substrate processing method according to any one of claims 1 to 3, wherein: The halogen-containing gas is fluorine gas, and the alkaline gas is ammonia gas.

11. The substrate processing method according to claim 10, wherein: In the first step, the fluorine gas is supplied into a processing container accommodating the substrate and the ammonia gas is supplied into the processing container in parallel. A ratio of a flow rate of the ammonia gas supplied into the processing container to a flow rate of the fluorine gas supplied into the processing container is greater than 0.

16.

12. The substrate processing method according to any one of claims 1 to 3, wherein: The first step includes: a first supplying step of supplying the halogen-containing gas to the substrate and supplying the alkaline gas to the substrate in parallel; and The second supply step is performed after the first supply step, and includes supplying only one of the halogen-containing gas and the alkaline gas to the substrate.

13. The substrate processing method according to claim 12, wherein: The halogen-containing gas includes a first fluorine-containing gas supplied to the substrate in the first supply step and a second fluorine-containing gas supplied to the substrate in the second supply step. The first fluorine-containing gas and the second fluorine-containing gas are of different types.

14. The substrate processing method according to claim 13, wherein: The first fluorine-containing gas is fluorine gas, The second fluorine-containing gas is hydrogen fluoride gas.

15. A substrate processing method comprising the following steps: supplying a process gas containing a halogen-containing gas and an alkaline gas to a substrate having a silicon film formed on a surface thereof, thereby modifying the surface of the silicon film to generate a reaction product; Next, the processing gas is supplied to the substrate for a predetermined time or longer while the reaction product remains on the silicon film, so that the thickness of the reaction product becomes uniform. Next, the reaction product is removed.

16. A substrate processing apparatus comprising: a processing container for housing a substrate having a silicon film formed on a surface thereof; a processing gas supply mechanism for supplying a processing gas containing a halogen-containing gas and an alkaline gas into the processing container; and A control unit outputs a control signal to implement a first step and a second step, wherein in the first step, the surface of the silicon film is modified by the processing gas to generate a reaction product, the processing gas is supplied for a predetermined time or longer while the reaction product remains on the silicon film, so that the thickness of the reaction product becomes uniform, and in the second step, after the first step, the reaction product is removed.

Images