Substrate processing method and substrate processing apparatus

Abstract

To suppress roughness on the surface of an etched silicon film.SOLUTION: A first step for supplying processing gas containing halogen-containing gas and basic gas to a substrate in which a silicon film is formed on the surface and the substrate itself is set to a first temperature and generating a reaction product by altering the surface of the silicon film and a second step for removing the reaction product by setting the substrate to the second temperature after the first step.SELECTED DRAWING: Figure 1C

Description

[Technical Field]

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

[0002] In manufacturing a semiconductor device, there are cases where the Si film of the Si film and the SiGe film formed on the surface of a semiconductor wafer (hereinafter referred to as a wafer) serving as a substrate is selectively etched. For example, Patent Document 1 describes that the selective etching is performed by using F gas and NH gas as etching gases and setting the ratio of NH gas to the etching gas to a predetermined value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6426489 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique capable of suppressing the roughness of the surface of a silicon film after etching. [Means for solving the problem]

[0005] The substrate processing method of the present disclosure includes a first step of supplying a processing gas containing a halogen-containing gas and a basic gas to a substrate having a silicon film formed on its surface and having a first temperature, thereby modifying the surface of the silicon film and generating a reaction product; a second step of heating the substrate to a second temperature after the first step and removing the reaction product; Including fruit, The second temperature is higher than the first temperature. Another substrate processing method of the present disclosure includes a first step of supplying a processing gas containing a halogen-containing gas and a basic gas to a substrate having a silicon film formed on a surface thereof and having a first temperature, thereby modifying the surface of the silicon film and generating a reaction product; a second step of heating the substrate to a second temperature after the first step and removing the reaction product; Including, the substrate has a silicon-containing film different from the silicon film formed on a surface thereof; the first step and the second step are steps of selectively modifying and removing the silicon film relative to the silicon-containing film, The silicon-containing film is a SiGe film. Another substrate processing method of the present disclosure includes a first step of supplying a processing gas containing a halogen-containing gas and a basic gas to a substrate having a silicon film formed on a surface thereof and having a first temperature, thereby modifying the surface of the silicon film and generating a reaction product; a second step of heating the substrate to a second temperature after the first step and removing the reaction product; Including, The first temperature is between -20°C and 60°C. Another substrate processing method of the present disclosure includes a first step of supplying a processing gas containing a halogen-containing gas and a basic gas to a substrate having a silicon film formed on a surface thereof and having a first temperature, thereby modifying the surface of the silicon film and generating a reaction product; a second step of heating the substrate to a second temperature after the first step and removing the reaction product; Including, the halogen-containing gas is fluorine gas, the basic gas is ammonia gas, In the first step, the supply of the fluorine gas into a processing vessel storing the substrate and the supply of the ammonia gas into the processing vessel are performed in parallel; The ratio of the flow rate of the ammonia gas supplied into the processing vessel to the flow rate of the fluorine gas supplied into the processing vessel is greater than 0.016. Another substrate processing method of the present disclosure includes a first step of supplying a processing gas containing a halogen-containing gas and a basic gas to a substrate having a silicon film formed on a surface thereof and having a first temperature, thereby modifying the surface of the silicon film and generating a reaction product; a second step of heating the substrate to a second temperature after the first step and removing the reaction product; Including, The first step comprises: a first supply step in which the halogen-containing gas and the basic gas are supplied to the substrate in parallel; a second supply step of supplying only one of the halogen-containing gas and the basic gas to the substrate after the first supply step; Includes: [Effects of the Invention]

[0006] According to the present disclosure, it is possible to suppress the roughness of the surface of the silicon film after etching. [Brief explanation of the drawings]

[0007] [Figure 1A] 1 is a longitudinal sectional side view of a wafer undergoing processing according to a first embodiment of the present disclosure. [Figure 1B] FIG. 2 is a vertical cross-sectional side view of the wafer. [Figure 1C] FIG. 2 is a vertical cross-sectional side view of the wafer. [Figure 2A] FIG. 2 is a vertical cross-sectional side view of the wafer. [Figure 2B] FIG. 2 is a vertical cross-sectional side view of the wafer. [Figure 2C] FIG. 2 is a vertical cross-sectional side view of the wafer. [Figure 3A] FIG. 2 is a vertical cross-sectional side view showing the surface of the wafer. [Figure 3B] FIG. 2 is a vertical cross-sectional side view showing the surface of the wafer. [Figure 4] FIG. 2 is a plan view showing an embodiment of a substrate processing apparatus for performing the above-described processing. [Figure 5] FIG. 2 is a vertical sectional side view showing an example of a processing module provided in the substrate processing apparatus. [Figure 6] FIG. 10 is a longitudinal sectional side view of a wafer undergoing processing according to a second embodiment of the present disclosure. [Figure 7] FIG. 3 is a vertical cross-sectional side view of a recess formed in the wafer. [Figure 8] 5A and 5B are explanatory views showing changes in the recessed portion. [Figure 9] 5A and 5B are explanatory views showing changes in the recessed portion. [Figure 10] 5A and 5B are explanatory views showing changes in the recessed portion. [Figure 11] 5A and 5B are explanatory views showing changes in the recessed portion. [Figure 12] FIG. 10 is a plan view showing the results of an evaluation test. [Figure 13] FIG. 10 is a plan view showing the results of an evaluation test. [Figure 14] 10A and 10B are schematic diagrams of recesses on a wafer showing the results of an evaluation test. [Figure 15] FIG. 10 is a graph showing the results of an evaluation test. DETAILED DESCRIPTION OF THE INVENTION

[0008] [First embodiment] An outline of a process according to a first embodiment of the substrate processing method of the present disclosure will be described. Fig. 1A is a longitudinal cross-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 a portion of the Si film 11 is selectively etched. That is, etching is performed so that the Si film 11 remains on the wafer W after processing.

[0009] To achieve the selective etching, a halogen-containing gas and a basic gas are supplied to the wafer W as processing gases, and the surface of the Si film 11 is selectively altered to generate a reaction product in step S1. In this embodiment, the halogen-containing gas is F2 (fluorine) gas, and the basic gas is NH3 (ammonia) gas. After performing step S1 (first step), the reaction product is sublimated by heat treatment in step S2 (second step), thereby selectively etching the surface of the Si film 11. The reaction product is ammonia fluorosilicate (AFS).

[0010] The generation and sublimation of the reaction product are repeated. That is, a repeating process in which the first and second processes are repeated in order is performed, and the etching amount of the Si film 11 is controlled. At the end of this repeating process (i.e., at the end of etching), the Si film 11 is left on the surface of the wafer W. However, as will be shown later in an evaluation test, depending on the processing conditions when supplying the processing gas, unevenness is formed on the surface of the Si film 11 remaining after processing, and the surface roughness (surface roughness) of the remaining Si film 11 becomes relatively large. The processing of this embodiment is performed so as to suppress this surface roughness.

[0011] Next, with reference to Figures 1 to 3, the processing performed on the wafer W will be explained in order. The arrows in each figure indicate processing gases, and the processing shown in each figure is performed in a state where the wafer W is loaded into a processing chamber and the processing chamber is evacuated to a vacuum atmosphere at a predetermined pressure. During processing, the wafer W is adjusted to a desired temperature. Note that, in this embodiment, steps S1 and S2 are performed in different processing chambers.

[0012] First, for example, the processing chamber 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 a first temperature, for example, -20°C to 60°C. The reason for setting the temperature in this range is to prevent the AFS from sublimating, even though a reaction that generates the AFS occurs due to the processing gas described above. The reason for not allowing the AFS to sublime will be described later. Processing at room temperature or a temperature close to room temperature is advantageous in reducing the amount of energy used in processing, so it is more preferable that the temperature of the wafer W be, for example, 20°C to 30°C.

[0013] With the wafer W temperature adjusted in this way, F2 gas and NH3 gas, which are process gases, are supplied into the processing chamber, and as described above, the surface of the Si film 11 is altered, and an AFS layer 13 is formed on the surface of the Si film 11. For example, suppose that variations in the concentration distribution and flow of gas within the processing chamber cause variations in the thickness of the AFS layer 13 (FIG. 1B). However, because the temperature of the wafer W is adjusted so that the AFS layer 13 remains without sublimating, further process gas is supplied to the wafer W in a state in which the AFS 13 covers the Si film 11.

[0014] The process gas penetrates the AFS layer 13 in areas where the AFS layer 13 is relatively thin, reaching the underlying Si film 11 and altering the Si film 11. However, in areas where the AFS layer 13 is relatively thick, the process gas is prevented from penetrating downward, making it difficult for the Si film to be altered below the relatively thick areas. Therefore, the thickness of the AFS layer 13 is made uniform (FIG. 1C). Once the thickness of the AFS layer 13 is made uniform, the supply of the process gas is stopped, and step S1 is completed.

[0015] Next, step S2 (second step) is performed, in which the wafer W is heated to a second temperature, for example, 80°C to 300°C, which is higher than the temperature in step S1 (first step). This heating sublimes and removes the AFS layer 13, exposing the Si film 11 that was covered by the AFS layer 13 (FIG. 2A). In this way, the surface of the Si film 11 is etched in a series of steps S1 and S2. However, because the thickness of the AFS layer 13 is made uniform in step S1 as described above, each part of the Si film 11 is etched with high uniformity. Therefore, the formation of irregularities on the surface of the Si film 11 after etching is suppressed.

[0016] Thereafter, step S1 is performed again. Accordingly, processing gas is supplied to the wafer W adjusted to the temperature described above, and the surface of the Si film 11 selectively becomes an AFS layer 13 (FIG. 2B). Then, by continuing to supply processing gas while the AFS layer 13 remains, the thickness of each portion of the AFS layer 13 is made uniform (FIG. 2C). Subsequently, step S2 is performed again. Accordingly, the AFS layer 13 formed in the second step S1 is sublimated (FIG. 3A). By proceeding in this manner, the formation of irregularities is suppressed on the surface of the Si film 11 after the second etching (after the second steps S1 and S2 are performed).

[0017] Thereafter, the cycle consisting of step S1 and step S2 is repeated, and selective etching of the Si film 11 progresses. Then, when the remaining Si film 11 reaches a desired thickness, the repeated processing of step S1 and step S2 is stopped. That is, the etching processing is stopped so that the Si film 11 remains on the wafer W (FIG. 3B). In the third and subsequent cycles, the formation of irregularities on the surface of the Si film 11 is suppressed as in the first and second cycles, so the formation of irregularities on the surface of the Si film 11 after the processing is stopped is also suppressed. That is, the processing is completed with the surface roughness of the Si film 11 suppressed.

[0018] Next, a substrate processing apparatus 2, which is one embodiment of the substrate processing apparatus that performs the series of processes described with reference to Figures 1 to 3, will be described with reference to the plan view of Figure 4. The substrate processing apparatus 2 includes a load / unload section 21 for loading and unloading wafers W, two load lock chambers 31 provided adjacent to the load lock section 21, two heat treatment modules 30 provided adjacent to the two load lock chambers 31, and two process modules 4 provided adjacent to the two heat treatment modules 30, respectively.

[0019] The load / unload section 21 includes an atmospheric pressure transfer chamber 23 in which a first substrate transfer mechanism 22 is installed and which is kept under atmospheric pressure, and a carrier mounting table 25 provided on the side of the atmospheric pressure transfer chamber 23 and on which a carrier 24 for accommodating a wafer W is mounted. In the drawing, reference numeral 26 denotes an orienter chamber adjacent to the atmospheric pressure transfer chamber 23, which is provided to rotate the wafer W to optically determine the amount of eccentricity and to align the wafer W with the first substrate transfer mechanism 22. The first substrate transfer mechanism 22 transfers the wafer W between the carrier 24 on the carrier mounting table 25, the orienter chamber 26, and the load lock chamber 31.

[0020] A second substrate transfer mechanism 32 having, for example, an articulated arm structure is provided within each load lock chamber 31, and the second substrate transfer mechanism 32 transfers wafers W between the load lock chamber 31, the heat treatment module 30, and the treatment module 4. The treatment vessels constituting the heat treatment module 40 and the treatment vessels constituting the treatment module 4 are in a vacuum atmosphere, and the load lock chamber 31 can be switched between a normal pressure atmosphere and a vacuum atmosphere so that wafers W can be transferred between these vacuum atmosphere treatment vessels and the normal pressure transfer chamber 23.

[0021] In the drawing, reference numeral 33 denotes a gate valve that can be opened and closed, and is provided between the atmospheric pressure transfer chamber 23 and the load lock chamber 31, between the load lock chamber 31 and the heat treatment module 30, and between the heat treatment module 30 and the treatment module 4. The heat treatment module 30 includes the above-mentioned treatment vessel, an exhaust mechanism for exhausting the inside of the treatment vessel to form a vacuum atmosphere, and a stage that is provided in the treatment vessel and is capable of heating the wafer W placed thereon, and is configured to be able to perform the above-mentioned step S2.

[0022] The processing module 4 will be described with reference to the longitudinal side view of FIG. 5. This processing module 4 executes the above-mentioned step S1. In the figure, 41 denotes a processing vessel constituting the processing module 4. In the figure, 42 denotes a transfer port for the wafer W that opens in the side wall of the processing vessel 41 and is opened and closed by the gate valve 33 described above. A stage 51 on which the wafer W is placed is provided within the processing vessel 41, and the stage 51 is provided with lift pins (not shown). The wafer W is transferred between the second substrate transfer mechanism 32 and the stage 51 via the lift pins.

[0023] A temperature adjustment unit 52 is embedded in the stage 51, and the wafer W placed on the stage 51 is set to the aforementioned temperature. This temperature adjustment unit 52 is configured as a flow path that forms part of a circulation path through which a temperature adjustment fluid such as water flows, and adjusts the temperature of the wafer W by heat exchange with the fluid. However, the temperature adjustment unit 52 is not limited to being a flow path for such a fluid, and may be configured as, for example, a heater for performing resistance heating.

[0024] One end of an exhaust pipe 53 opens into the processing vessel 41, and the other end of the exhaust pipe 53 is connected to an exhaust mechanism 55, which is constituted by, for example, a vacuum pump, via a valve 54, which is a pressure change mechanism. By adjusting the opening of the valve 54, the pressure inside the processing vessel 41 is set to the pressure range described above, and processing is performed.

[0025] A gas shower head 56, which is a processing gas supply mechanism, is provided at the upper side of the processing vessel 41, facing the stage 51. The downstream sides of gas supply paths 61 to 64 are connected to the gas shower head 56, and the upstream sides of the gas supply paths 61 to 64 are connected to gas supply sources 66 to 69 via flow rate adjusters 65, respectively. Each flow rate adjuster 65 includes a valve and a mass flow controller. The gas supplied from the gas supply sources 66 to 69 is supplied downstream and cut off by opening and closing the valves included in the flow rate adjuster 65.

[0026] Gas supply sources 66, 67, 68, and 69 supply F2 gas, NH3 gas, Ar (argon) gas, and N2 (nitrogen) gas, respectively. Therefore, HF gas, NH3 gas, Ar gas, and N2 gas can be supplied into processing vessel 41 from gas shower head 56. Ar gas and N2 gas are supplied as carrier gases into processing vessel 41 together with F2 gas and NH3 gas. The flow rates of F2 gas and NH3 gas supplied into processing vessel 41 are, for example, 100 sccm to 1000 sccm for F2 gas and 4 sccm to 80 sccm for NH3 gas.

[0027] As shown in FIG. 4 , the substrate processing apparatus 2 includes a control unit 20, which is a computer. The control unit 20 includes a program, a memory, and a CPU. The program contains instructions (steps) for performing the aforementioned wafer W processing and wafer W transport. The program is stored on a storage medium, such as a compact disc, a hard disk, a magneto-optical disc, or a DVD, and is then installed in the control unit 20. The control unit 20 outputs control signals to each component of the substrate processing apparatus 2 based on the program, thereby controlling the operation of each component. Specifically, the control signals control the operation of the processing module 4, the heat treatment module 30, the first substrate transport mechanism 22, the second substrate transport mechanism 32, and the orienter chamber 26. The operation of the processing module 4 includes, for example, adjusting the temperature of the fluid supplied to the stage 51, supplying and shutting off gases from the gas shower head 56, and adjusting the exhaust flow rate using the valve 54.

[0028] The transfer path of the wafer W in the substrate processing apparatus 2 will now be described. As described with reference to FIG. 1A, the carrier 24 storing the wafer W on which each film has been formed is placed on the carrier mounting table 25. The wafer W is then transferred in the order of the atmospheric pressure transfer chamber 23 → the orienter chamber 26 → the atmospheric pressure transfer chamber 23 → the load lock chamber 31, and then transferred to the processing module 4 via the heat treatment module 30. Then, as described above, the processing described as step S1 is performed, and the AFS layer 13 is formed. Next, the wafer W is transferred to the heat treatment module 40, where the AFS layer 13 is sublimated in step S2.

[0029] Thereafter, steps S1 and S2 are repeated a predetermined number of times by transporting the wafer W back and forth between the processing module 4 and the heat treatment module 40. Thereafter, the wafer W is transported from the heat treatment module 40 to the load lock chamber 31, then to the atmospheric pressure transfer chamber 23, and then returned to the carrier 24.

[0030] According to the processing method of this embodiment, as described above, it is possible to selectively etch the Si film 11 out of the Si film 11 and the SiGe film 12, and also to suppress roughness on the surface of the Si film 11 after the etching process, thereby increasing the yield of semiconductor products manufactured from the wafers W after the etching process.

[0031] In the above processing example, steps S1 and S2 are repeated three or more times to etch the Si film 11. However, the number of repetitions is not limited to the above example and may be, for example, two. Furthermore, steps S1 and S2 may be performed only once without repetition. In the above-described substrate processing apparatus 2, the wafer W is transferred between the processing module 4 and the heat treatment module 40, and steps S1 and S2 are performed in different processing chambers. This processing is not limited to this. For example, steps S1 and S2 may be performed by changing the temperature of the stage 51 of the processing module 4. That is, steps S1 and S2 may be performed in the same processing chamber. However, in this case, when steps S1 and S2 are repeated, time is required to cool the stage 51 so that step S1 can be performed again after step S2. Therefore, to achieve high throughput when steps S1 and S2 are repeated, it is preferable to perform steps S1 and S2 on stages in different processing chambers, as described above.

[0032] In the above-described example of the silicon-containing film, the SiGe film 12 is exposed on the surface of the wafer W. However, instead of the SiGe film 12, for example, a SiN film or a SiO2 film may be exposed on the surface of the wafer W. These SiN and SiO2 films have a lower Si content than Si films. Therefore, compared to the Si film 11, they are less likely to cause AFS with NH3 gas and F2 gas. 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, an AFS layer 13 can be generated using IF7 gas, IF5 gas, ClF3 gas, or SF6 gas, and similar processing can be performed.

[0033] In the above example, F2 gas and NH3 gas are simultaneously supplied to the wafer W for processing, i.e., the period during which F2 gas is supplied and the period during which NH3 gas is supplied coincide. However, this is not a limitation. For example, F2 gas and NH3 gas may be alternately supplied, and the AFS may be generated by reacting one of the F2 gas and NH3 gas adsorbed on the Si film 11 with the other gas. That is, these gases may be supplied so that the period during which F2 gas is supplied and the period during which NH3 gas is supplied do not overlap. Alternatively, the period during which F2 gas is supplied and the period during which NH3 gas is supplied may be supplied so that they only partially overlap. However, simultaneous supply of F2 gas and NH3 gas, as in the process shown in FIGS. 1 to 3, is preferable because it allows for the rapid formation of the AFS layer 13 and the uniform thickness of the AFS layer 13, as described above, and therefore increases throughput.

[0034] In the above example, the AFS layer 13 is sublimated by increasing the temperature of the wafer W in step S2 compared to step S1, but this is not limited to changing the temperature of the wafer W. For example, step S2 is also performed in the same process module 4 as step S1. When step S2 is performed, the opening of the valve 54 of the exhaust pipe 53 is increased compared to when step S1 is performed. This reduces the pressure inside the process vessel 41 when step S2 is performed compared to when step S1 is performed. The AFS layer 13 may be sublimated by this pressure change.

[0035] Second Embodiment The second embodiment will be described assuming that processing is performed on a wafer W having a structure 71 shown in FIG. 6 formed on its surface. FIG. 6 is a vertical cross-sectional side view of the structure 71. The structure 71 has a Si film and includes a recess 72 formed in the Si film in the vertical direction (thickness direction of the wafer W) and recesses 73 formed in the Si film from the left and right side walls of the recess 72 to the left and right, respectively. The recess 72 opens to the surface of the wafer W, and gases supplied to the wafer W are introduced into the recess 73 through the recess 72. A large number of recesses 73 are formed on the left and right sides of the recess 72 at different heights in the vertical direction, so that the recesses 73 and the Si film are arranged alternately in the vertical direction on the left and right sides of the recess 72.

[0036] The structure 71 will be further described with reference to the longitudinal cross-sectional side view of FIG. 7 , which shows an enlarged schematic view of one of the recesses 73. Because of the configuration described above, the upper and lower walls of the recess 73 are formed of a Si film, and are shown as Si films 74 in the figure. The side walls of the recess 73 are also 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, thereby reducing the vertical thickness of the Si film 74. In other words, the opening width of the recess 73 is widened. This etching is performed so as to suppress the roughness of the surface of the Si film 74 after etching.

[0037] The etching process of the second embodiment will be described below with reference to FIGS. 8 to 11, focusing on the differences from the etching process of the first embodiment. FIGS. 8 to 11 are schematic diagrams showing changes in the Si film 74 that are presumed to occur during the process. In this process, in addition to NH gas, F gas and HF (hydrogen fluoride) gas are used as fluorine-containing gases. In the figures, F gas is represented as 81, NH gas as 82, and HF gas as 83.

[0038] First, the pressure inside the processing vessel 41 storing the wafer W and the temperature of the wafer W inside the processing vessel 41 are adjusted to, for example, the same pressure and temperature as in step S1 of the first embodiment, and F2 gas 81 and NH3 gas 82 are simultaneously supplied as in step S1 (FIG. 8, step T1). This alters the surface layer of the Si film 74 forming the recess 73, resulting in the formation of an AFS layer 13. When this AFS layer 13 is formed, fine irregularities 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 with the irregularities formed in this way (FIG. 9).

[0039] After the flow of F2 gas 81 and NH3 gas 82 into the processing vessel 41 is stopped, N2 gas is supplied into the processing vessel 41 and exhaust is performed, and the remaining F2 gas 81 and NH3 gas 82 are purged and removed from the processing vessel 41 (step T2). Thereafter, HF gas 83 is supplied into the processing vessel 41 (FIG. 10: step T3), and a reaction represented by the following formula 1 is considered to occur between the HF gas 83, the AFS layer 13, and the Si film 74 in contact with the AFS ((NH4)2SiF6) layer 13. 2Si+((NH4)2SiF6)+4HF→SiF6+SiH4+(NH4)2SiF6...Formula 1

[0040] To explain the above reaction in more detail, the AFS layer 13 formed in step T1 contains a relatively large amount of fluorine. When HF gas 83, which also contains fluorine, is supplied in step T3, the fluorine in this AFS layer 13 becomes even more excessive, and the very surface of the Si film 74 in contact with the AFS layer 13 is fluorinated, forming an altered layer 75. In this way, it is thought that the supply of the fluorine-containing gas acts as a trigger to utilize the fluorine contained in the AFS layer 13, causing the very surface of the Si film 74 to change into the altered layer 75.

[0041] Thereafter, the supply of HF gas 83 into the processing vessel 41 is stopped, and N2 gas is supplied into the processing vessel 41 while exhausting the gas, thereby purging the remaining HF from the processing vessel 41 (step T4). Thereafter, similar to step S2 in the first embodiment, the wafer W is heated to a temperature higher than the temperature in steps T1 to T4, for example, to 80°C to 300°C. This heating sublimes and removes the AFS layer 13 and the altered layer 75, exposing the Si film 74 that was covered by these layers (FIG. 11: step T5).

[0042] As described above, by removing the extreme surface of the Si film 74 on which irregularities were formed after step T1, the roughness of the surface of the Si film 74 exposed in step T5 is suppressed. As in the first embodiment, the above process selectively etches the Si film 74 out of the Si film 74 and the SiGe film 75. Then, a cycle consisting of steps T1 to T5 is repeated thereafter, the selective etching of the Si film 74 progresses, and the Si film 74 is thinned. When the Si film 74 reaches a desired thickness, the repeated process of steps T1 to T5 is stopped.

[0043] According to the etching process of the second embodiment described above, the roughness of the Si film after etching can be more reliably suppressed, as shown in the evaluation test described later. The etching process of the second embodiment can also be performed using the substrate processing apparatus 2 described in FIG. 4, for example. Steps T1 to T4 are performed in the processing module 4, and step T5 is performed in the heat treatment module 40. Steps T1 to T4 performed in the processing module 4 correspond to a first step of modifying the Si film 74 to generate a reaction product. Step T1 corresponds to a first supply step in which a first fluorine-containing gas, F gas, and a basic gas, NH gas, are supplied to the wafer W in parallel. Step T3 corresponds to a second supply step, which, as described above, in this example, supplies HF gas, a second fluorine-containing gas different from the first fluorine-containing gas, to the wafer W.

[0044] The process module 4 performing steps T1 to T4 is configured such that, in addition to the gas supply sources 66 to 69 described above, a HF gas supply source is provided, and the HF gas supply source is connected to the gas shower head 56 via a flow path. A flow rate adjuster 65 is provided in the HF gas flow path, similar to the flow paths of the other gases, and HF gas is supplied into the process vessel 41 via the gas shower head 56 at a desired flow rate. When the HF gas is supplied into the process vessel 41, for example, Ar gas and N2 gas are also supplied into the process vessel 41 as carrier gases.

[0045] In step T3, any gas that can react with the AFS layer 13 to cause a reaction between the fluorine contained in the AFS layer 13 and the Si film 74 may be used. Therefore, instead of HF gas, other fluorine-containing gases, such as F2 gas or NF3 (nitrogen trifluoride) gas, may be used. When F2 gas is used, the same type of fluorine-containing gas is used in steps T1 and T3. In the above-described processing example, purging with N2 gas, an inert gas, is performed in step T2 to prevent the processing in step T3 from being affected by the gas used in step T1. However, if F2 gas is used in both steps T1 and T3, step T2 may be omitted. Specifically, first, F2 gas and NH3 gas are both supplied into the processing vessel 41 in step T1. Then, the supply of NH3 gas is stopped, leaving only F2 gas supplied into the processing vessel 41. This allows the processing in step T3 to be performed without performing step T2.

[0046] Alternatively, NH3 gas may be supplied in place of a fluorine-containing gas in step T3. As described above, the AFS layer 13 contains a large amount of fluorine. By supplying NH3 gas, the fluorine in the AFS layer 13 reacts with the NH3 and the very surface of the Si film 74, causing the very surface of the Si film 74 to change in quality to become a reaction product. This product is then sublimated and removed together with the AFS layer 13 in step T5. This suppresses the roughness of the surface of the Si film 74 after step T5 is performed. When NH3 gas is supplied in step T3 in this way, step T2 may be omitted, as in the case of using F2 gas in step T3.

[0047] As described above, the gas supplied to the wafer W in the second supply step after the first supply step in which F gas (first fluorine-containing gas) and NH gas are supplied to the wafer W in parallel is not limited to a second fluorine-containing gas different from the first fluorine-containing gas. In the first embodiment, the simultaneous supply of F gas and NH gas was described herein as meaning that the supply periods of the F gas and NH gas are the same (the supply start timing and the supply end timing are the same for each gas). In the second embodiment, the simultaneous supply of F gas and NH gas does not necessarily mean that the supply start timing of each gas is the same. That is, the simultaneous supply of F gas and NH gas is not limited to the simultaneous supply described herein.

[0048] Furthermore, steps T1 to T5 do not necessarily have to be repeated multiple times, but may be performed only once. Furthermore, although an example has been given in which the wall surface of recess 73 formed in the lateral direction of structure 71 is etched, any location may be etched, and the etching is not limited to etching the wall surface.

[0049] It should be noted that the embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive, and various omissions, substitutions, modifications, and combinations may be made to the above-described embodiments without departing from the scope and spirit of the appended claims.

[0050] [Evaluation test] Evaluation Test 1 Evaluation tests performed in connection with the technology of the present disclosure will be described. In Evaluation Test 1, a wafer W was subjected to an etching process in which steps S1 and S2 were repeated multiple times, as described in the embodiment. The wafer W used in this process had an exposed Si film 11 and an exposed SiGe film 12 on its surface, as described in the embodiment. In Step S1 of Evaluation Test 1, the flow rates of F2 gas and NH3 gas supplied into a processing chamber containing the wafer W were set within the respective ranges described above. As described in the embodiment, Ar gas and N2 gas were also supplied into the processing chamber along with the flow rates of F2 gas and NH3 gas. The pressure in the processing chamber and the temperature of the wafer W in Step S1 were also set within the ranges described in the embodiment.

[0051] In this evaluation test 1, the supply time of the process gas (F2 gas and NH3 gas) in one step S1 and the number of repetitions of steps S1 and S2 were changed for each wafer W. Then, for each processed wafer W, an image of the surface of the Si film 11 was acquired, and the etching selectivity ratio (=etching amount of Si film 11 / etching amount of SiGe film 12) was calculated. In evaluation test 1-1, the supply time of the process gas was 30 seconds, and the number of repetitions was 6. In evaluation test 1-2, the supply time of the process gas was 45 seconds, and the number of repetitions was 4. In evaluation test 1-3, the supply time of the process gas was 60 seconds, and the number of repetitions was 3. Therefore, in each of evaluation tests 1-1 to 1-3, the total time for supplying the process gas to the wafer W was 180 seconds.

[0052] In Evaluation Tests 1-1 to 1-3, the etching selectivity was 30 or more, and therefore, the Si film 11 was selectively etched relative to the SiGe film 12. FIG. 12 shows images acquired in Evaluation Tests 1-1 to 1-3 and an image obtained from the Si film 11 before processing. The acquired images show the surface irregularities of the Si film 11 as a black-and-white contrast. In the image shown in FIG. 12, the concave portions of the irregularities are circled and dotted, and for convenience of illustration, closely spaced convex portions are shown as a single convex portion by circumscribing them together. As shown in FIG. 12, the formation of concaves and convex portions was confirmed in the image of Evaluation Test 1-1. However, in Evaluation Tests 1-2 and 1-3, only slight concaves and convex portions were formed.

[0053] Thus, in evaluation tests 1-2 and 1-3, in which the processing gas was supplied for a relatively long time in one step S1, the surface roughness of the Si film 11 was suppressed. This is thought to be because, in evaluation test 1-1, the reaction between the processing gas and the surface layer of the Si film 11 was insufficient, and sublimation in step S2 was performed in a state in which the thickness of the AFS layer 13 was not uniform. On the other hand, in evaluation tests 1-2 and 1-3, the surface layer of the Si film 11 reacted sufficiently with the processing gas, and the AFS layer 13 was formed with a highly uniform thickness, as described in the embodiment.

[0054] In Evaluation Test 1-2, where the supply time was 45 seconds, the surface roughness was sufficiently suppressed, and it is believed that this roughness could be suppressed even with a supply time slightly shorter than 45 seconds. However, some roughness was observed in Evaluation Test 1-1, where the processing gas was supplied for 30 seconds. From the above, it is believed that a processing gas supply time of 40 seconds or more is preferable. However, if the processing gas supply time is too long, the processing gas will be blocked by the formed AFS layer 13 and will not be able to act on the Si film 11, resulting in unnecessary consumption of the processing gas. Considering that the roughness of the Si film 11 was appropriately suppressed with a processing gas supply time of 60 seconds, it is believed that a supply time longer than that, for example, 120 seconds or less, is preferable.

[0055] Evaluation Test 2 Next, Evaluation Test 2 will be described. In Evaluation Test 2, similar to Evaluation Test 1, steps S1 and S2 were repeatedly performed on multiple wafers W to etch the Si film 11. Images of the surface of the Si film 11 were then acquired, and the etching selectivity ratio was calculated. In Evaluation Test 2, the processing gas supply time in step S1 was the same for each wafer W, 30 seconds, and steps S1 and S2 were repeated the same number of times, six times, for each wafer W. Therefore, the processing gas supply time and the number of repetitions of S1 and S2 were the same as in Evaluation Test 1-1. However, the flow rate of NH3 gas differed from Evaluation Test 1-1. The relationship of the flow rates of NH3 gas in Evaluation Test 2 (2-1, 2-2) was Evaluation Test 2-1 < Evaluation Test 1-1 < Evaluation Test 2-2. In Evaluation Test 2, the processing conditions other than the flow rate of NH3 gas were the same as those in Evaluation Test 1.

[0056] The etching selectivity ratios in Evaluation Tests 2-1 and 2-2 were 30 or higher, and therefore, the Si film 11 was selectively etched relative to the SiGe film 12. Figure 13 shows the images acquired in Evaluation Tests 2-1 and 2-2, shown in the same format as in Evaluation Test 1. To facilitate understanding of the test results, a schematic diagram of the image of Evaluation Test 1-1 shown in Figure 12 is also shown in Figure 13. As shown in Figure 13, the roughness in Evaluation Test 2-1 was greater than that in Evaluation Test 1-1, and the roughness was suppressed in Evaluation Test 2-2. Therefore, the larger the flow rate of NH3 gas, the more the roughness was suppressed. This is thought to be because, since F2 gas was supplied at a relatively high flow rate, the larger the flow rate of NH3 gas, the more the surface layer of the Si film 11 was transformed into the AFS layer 13, and as described above, the thickness uniformity of the AFS layer 13 was improved.

[0057] In Evaluation Test 1-1, the ratio of the flow rate of NH3 gas to the flow rate of F2 gas (NH3 gas flow rate / F2 gas flow rate) was 0.026. As described above, slight unevenness was observed in Evaluation Test 1-1, and it was confirmed that it is preferable to set the ratio to be greater than 0.026. In Evaluation Test 2-2, the NH3 gas was set to a value 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 it is more preferable to set the ratio to 0.036 or more.

[0058] Evaluation Test 3 Next, evaluation test 3 will be described. A cycle consisting of steps T1 to T5 described in the second embodiment was repeated 10 times for a plurality of wafers W on which the structures 71 described in FIGS. 6 and 7 were formed. The flow rate of the HF gas supplied into the processing chamber 41 in step T3 was changed for each wafer W to be processed. Images of the processed wafers W were then obtained by SEM, and the surface state of the Si film 74 on the structures 71 was observed. Tests conducted with the HF gas flow rates set to 100 sccm, 200 sccm, and 450 sccm are designated evaluation tests 3-1, 3-2, and 3-3, respectively.

[0059] The pressure inside the processing vessel 41 was set to a value within the range described in the embodiment, and the HF gas supply time was set to 30 seconds. The flow rates of Ar gas and N2 gas supplied into the processing vessel 41 together with the HF gas were each set to 275 sccm. Evaluation test 3-4 was performed under the same conditions as evaluation tests 3-1 to 3-3, except that steps T3 and T4 (purging with N2 gas after supplying HF gas) were not performed, and images were obtained using an SEM. Therefore, the process in evaluation test 3-4 is a process in which steps S1 and S2 described in the first embodiment are repeated.

[0060] The upper, middle, and lower rows of Figure 14 show schematic diagrams of images acquired in Evaluation Tests 3-1, 3-2, and 3-4, respectively. Compared to Evaluation Test 3-4, the surface roughness of the Si film 74 was suppressed in Evaluation Tests 3-1 to 3-3. This demonstrates the desirability of supplying HF gas, as described in the second embodiment. Among Evaluation Tests 3-1 to 3-3, the roughness was suppressed more in Evaluation Tests 3-2 and 3-3 than in Evaluation Test 3-1, reaching a practically desirable level. Because the roughness was similar in Evaluation Tests 3-2 and 3-3, Figure 14 shows only the schematic diagram of Evaluation Test 3-2.

[0061] From the above results, it was confirmed that the flow rate of HF gas supplied to wafer W in step T3 is preferably greater than 100 sccm, and more preferably 200 sccm or greater. As described above, during the supply of HF gas, inert gases Ar gas and N2 gas are supplied at 250 sccm each. Therefore, the ratio of the flow rate of HF gas to the flow rate of all gases supplied into processing vessel 41 is expressed by the following equation 2. Note that X in equation 2 is the flow rate of HF gas. Xsccm / (X+250+250)sccm...Formula 2

[0062] When X = 100 sccm, Equation 2 gives the value of 0.1667, and when X = 200 sccm, Equation 2 gives the value of 0.2857. Therefore, it can be seen from Evaluation Test 3 that the ratio of the flow rate of HF gas to the flow rate of all gases supplied into processing vessel 41 is preferably greater than 0.1667, and more preferably 0.2857 or greater. The reason why the roughness states were similar between Evaluation Tests 3-2 and 3-3 is thought to be that, as mentioned above, the roughness is improved by the action of fluorine in AFS layer 13 altering Si film 74, but even if the flow rate of HF gas is increased, the amount of fluorine that can contribute to the alteration of Si film 74 in AFS layer 13 is limited.

[0063] Evaluation Test 4 Next, evaluation test 4 will be described. In evaluation test 4, a wafer W having structure 71 formed thereon was subjected to nine cycles of processing consisting of steps T1, T2, and T5 in the second embodiment. After the processing described above, an SEM image of structure 71 was acquired, and the etching amount near the opening of recess 73 and the etching amount near the back (near the end opposite the opening) were measured. Note that the smaller the difference between these etching amounts, the better. In step S1, the flow rate of NH3 gas supplied into processing chamber 41 was set differently for each wafer W, and was set to one of 5 sccm, 8 sccm, 10 sccm, 12 sccm, and 14 sccm.

[0064] Other processing conditions for step S1 are as follows: the flow rates of F2 gas and Ar gas supplied into the processing vessel 41 were 500 sccm and 200 sccm, respectively. The flow rate of N2 gas was changed according to the flow rate of NH3 gas, and the flow rate of N2 gas was set so that the total flow rate of N2 gas and NH3 gas was 700 sccm. The supply time of F2 gas and NH3 gas in one cycle was 15 seconds. The temperature of the wafer W was set to a value within the range described in the embodiment.

[0065] FIG. 15 is a graph summarizing the results of Evaluation Test 4, with the vertical and horizontal axes showing the etching amount (unit: nm) and the NH3 gas flow rate (unit: sccm), respectively. The vertical axis is scaled in increments of 2 nm relative to A, which is a real number. As shown in the graph, when the NH3 gas flow rate is 5 sccm, the etching amount near the back is smaller than the etching amount near the opening, and these etching amounts are relatively large. When the NH3 gas flow rate is 8 sccm, the etching amount near the back is smaller than the etching amount near the opening, and although the difference in these etching amounts is smaller than when the flow rate is 5 sccm, it is desirable for the difference in etching amount to be even smaller in practice.

[0066] When the flow rate of the NH3 gas was 10 sccm or more, the difference in the etching amount was sufficiently small. This result was probably due to the fact that when the flow rate of the NH3 gas was 10 sccm or more, the NH3 gas was sufficiently supplied from the opening to the back of the recess 73, and the AFS layer 13 was sufficiently formed on the surfaces of the upper and lower walls of the Si film 74 that constitute the recess 73.

[0067] As described above, in Evaluation Test 4, when F2 gas and NH3 gas are supplied into processing chamber 41 in parallel to etch each portion of recess 73 with high uniformity, the flow rate of NH3 gas is preferably greater than 8 sccm, and more preferably 10 sccm or greater. As described above, F2 gas is supplied at 500 sccm. Therefore, in Evaluation Test 4, the ratio of the flow rate of NH3 gas to the flow rate of F2 gas is preferably greater than 8 sccm / 500 sccm = 0.016, and more preferably 10 sccm / 500 sccm = 0.02 or greater. [Explanation of symbols]

[0068] W wafer 11 Si film 13 AFS layer

Claims

1. a first step of supplying a process gas containing a halogen-containing gas and a basic gas to a substrate having a silicon film formed on its surface and having a first temperature, thereby modifying the surface of the silicon film and generating a reaction product; a second step of heating the substrate to a second temperature after the first step and removing the reaction product; Including, The substrate processing method, wherein the second temperature is higher than the first temperature.

2. 2. The substrate processing method according to claim 1, further comprising the step of repeating the first step and the second step in order.

3. 3. The substrate processing method according to claim 2, wherein the silicon film remains on the substrate at the end of the repeating step.

4. a first step of supplying a process gas containing a halogen-containing gas and a basic gas to a substrate having a silicon film formed on its surface and having a first temperature, thereby modifying the surface of the silicon film and generating a reaction product; a second step of heating the substrate to a second temperature after the first step and removing the reaction product; Including, the substrate has a silicon-containing film different from the silicon film formed on a surface thereof; the first step and the second step are steps of selectively modifying and removing the silicon film relative to the silicon-containing film, The substrate processing method, wherein the silicon-containing film is a SiGe film.

5. a first step of supplying a process gas containing a halogen-containing gas and a basic gas to a substrate having a silicon film formed on its surface and having a first temperature, thereby modifying the surface of the silicon film and generating a reaction product; a second step of heating the substrate to a second temperature after the first step and removing the reaction product; Including, The substrate processing method, wherein the first temperature is between -20°C and 60°C.

6. 6. The substrate processing method according to claim 1, wherein in the first step, the halogen-containing gas and the basic gas are simultaneously supplied to the substrate.

7. 7. The substrate processing method according to claim 6, wherein in the first step, the halogen-containing gas and the basic gas are simultaneously supplied to the substrate for 40 seconds or more.

8. a first step of supplying a process gas containing a halogen-containing gas and a basic gas to a substrate having a silicon film formed on its surface and having a first temperature, thereby modifying the surface of the silicon film and generating a reaction product; a second step of heating the substrate to a second temperature after the first step and removing the reaction product; Including, the halogen-containing gas is fluorine gas, the basic gas is ammonia gas, In the first step, the supply of the fluorine gas into a processing vessel storing the substrate and the supply of the ammonia gas into the processing vessel are performed in parallel; a ratio of a flow rate of ammonia gas supplied into the processing vessel to a flow rate of fluorine gas supplied into the processing vessel being greater than 0.016;

9. a first step of supplying a process gas containing a halogen-containing gas and a basic gas to a substrate having a silicon film formed on its surface and having a first temperature, thereby modifying the surface of the silicon film and generating a reaction product; a second step of heating the substrate to a second temperature after the first step and removing the reaction product; Including, The first step includes: a first supply step in which the halogen-containing gas and the basic gas are supplied to the substrate in parallel; a second supply step of supplying only one of the halogen-containing gas and the basic gas to the substrate after the first supply step; A substrate processing method comprising:

10. The halogen-containing gas is a first fluorine-containing gas supplied to the substrate in the first supply step; a second fluorine-containing gas supplied to the substrate in the second supply step; 10. The substrate processing method according to claim 9, wherein the first fluorine-containing gas and the second fluorine-containing gas are different in kind from each other.

11. the first fluorine-containing gas is a fluorine gas; 11. The substrate processing method according to claim 10, wherein the second fluorine-containing gas is hydrogen fluoride gas.

12. a processing vessel for storing a substrate having a silicon film formed on its surface; a processing gas supply mechanism for supplying a processing gas containing a halogen-containing gas and a basic gas into the processing vessel; a temperature adjusting unit that adjusts the temperature of the substrate in the processing chamber; a control unit that outputs a control signal so that a first step of supplying the processing gas to the substrate at a first temperature to modify the surface of the silicon film and generate a reaction product, and a second step of heating the substrate to a second temperature after the first step to remove the reaction product, are performed; Equipped with The substrate processing apparatus, wherein the second temperature is higher than the first temperature.

13. a processing vessel for storing a substrate having a silicon film formed on its surface; a processing gas supply mechanism for supplying a processing gas containing a halogen-containing gas and a basic gas into the processing vessel; a temperature adjusting unit that adjusts the temperature of the substrate in the processing chamber; a control unit that outputs a control signal so that a first step of supplying the processing gas to the substrate at a first temperature to modify the surface of the silicon film and generate a reaction product, and a second step of heating the substrate to a second temperature after the first step to remove the reaction product, are performed; Equipped with the substrate has a silicon-containing film different from the silicon film formed on a surface thereof; the first step and the second step are steps of selectively modifying and removing the silicon film relative to the silicon-containing film, The substrate processing method, wherein the silicon-containing film is a SiGe film.

14. a processing vessel for storing a substrate having a silicon film formed on its surface; a processing gas supply mechanism for supplying a processing gas containing a halogen-containing gas and a basic gas into the processing vessel; a temperature adjusting unit that adjusts the temperature of the substrate in the processing chamber; a control unit that outputs a control signal so that a first step of supplying the processing gas to the substrate at a first temperature to modify the surface of the silicon film and generate a reaction product, and a second step of heating the substrate to a second temperature after the first step to remove the reaction product, are performed; Equipped with The substrate processing apparatus, wherein the first temperature is in the range of -20°C to 60°C.

15. a processing vessel for storing a substrate having a silicon film formed on its surface; a processing gas supply mechanism for supplying a processing gas containing a halogen-containing gas and a basic gas into the processing vessel; a temperature adjusting unit that adjusts the temperature of the substrate in the processing chamber; a control unit that outputs a control signal so that a first step of supplying the processing gas to the substrate at a first temperature to modify the surface of the silicon film and generate a reaction product, and a second step of heating the substrate to a second temperature after the first step to remove the reaction product, are performed; Equipped with the halogen-containing gas is fluorine gas, the basic gas is ammonia gas, In the first step, the supply of the fluorine gas into a processing vessel storing the substrate and the supply of the ammonia gas into the processing vessel are performed in parallel; A substrate processing apparatus, wherein a ratio of a flow rate of ammonia gas supplied into the processing vessel to a flow rate of fluorine gas supplied into the processing vessel is greater than 0.

016.

16. a processing vessel for storing a substrate having a silicon film formed on its surface; a processing gas supply mechanism for supplying a processing gas containing a halogen-containing gas and a basic gas into the processing vessel; a temperature adjusting unit that adjusts the temperature of the substrate in the processing chamber; a control unit that outputs a control signal so that a first step of supplying the processing gas to the substrate at a first temperature to modify the surface of the silicon film and generate a reaction product, and a second step of heating the substrate to a second temperature after the first step to remove the reaction product, are performed; Equipped with The first step comprises: a first supply step in which the halogen-containing gas and the basic gas are supplied to the substrate in parallel; a second supply step of supplying only one of the halogen-containing gas and the basic gas to the substrate after the first supply step; A substrate processing apparatus comprising:

Images