Substrate processing method and substrate processing apparatus

Abstract

To selectively etch a first film, which is a silicon oxide film, on a substrate having a surface exposed with the first film and a second film, which are silicon-containing films of different types.SOLUTION: When supplying process gas to a substrate with exposed surfaces of a first film and a second film, which are silicon-containing films of different types, to selectively etch the first film, which is a silicon oxide film, there are performed a protective process for supplying a fluid containing a sililation agent to the substrate to form a protective film on the surface layer of the second film to prevent etching of the second film and an etching process for supplying the process gas to the substrate on which the protective film is formed and selectively etching the first film.SELECTED DRAWING: Figure 2B

Description

[Technical Field]

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

[0002] In the manufacture of semiconductor devices, a silicon oxide film formed on the surface of a semiconductor wafer (hereinafter referred to as a wafer) serving as a substrate may be etched. Patent Document 1 describes a technique for modifying a silicon oxide film and then removing the resulting reaction products by heating, comprising a first modification step using HF gas and NH3 gas and a second modification step using HF gas. Patent Document 2 describes a technique for etching a silicon film while protecting the silicon oxide film by forming a protective film made of amine on the silicon oxide film. Patent Document 3 describes a device for performing plasma processing on a substrate, in which a water-repellent silicon-containing protective film is formed on each component in the processing chamber by generating a plasma of TMSDMA gas, thereby preventing moisture from adhering to the components during maintenance of the device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6812284 [Patent Document 2] Japanese Patent Publication No. 2021-174938 [Patent Document 3] Patent No. 7357182 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique for selectively etching a first film, which is a silicon oxide film, in a substrate having a first film and a second film, which are different types of silicon-containing films, exposed on the surface. [Means for solving the problem]

[0005] The substrate processing method of the present disclosure includes: A substrate processing method for selectively etching a silicon oxide film by supplying a processing gas to a substrate having a first film and a second film, the first film being different types of silicon-containing films, exposed on a surface thereof, the method comprising: a protection step of supplying a fluid containing a silylation agent to the substrate to form a protection film on a surface of the second film that prevents etching of the second film; and an etching step of supplying the processing gas to the substrate on which the protective film is formed, and selectively etching the first film. [Effects of the Invention]

[0006] According to the present disclosure, in a substrate having a first film and a second film, which are different types of silicon-containing films, exposed on the surface, the first film, which is a silicon oxide film, can be selectively etched. [Brief explanation of the drawings]

[0007] [Figure 1A] 1 is a cross-sectional side view of a wafer undergoing processing according to an embodiment of the present disclosure. [Figure 1B] FIG. 2 is a longitudinal sectional side view of the wafer. [Figure 2A] FIG. 2 is a longitudinal sectional side view of the wafer. [Figure 2B] FIG. 2 is a longitudinal sectional side view of the wafer. [Figure 3] 1 is a chemical reaction formula showing the reaction that proceeds in the protection step of the treatment. [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. 4 is a chart showing the timing of supply of each gas. [Figure 7] FIG. 10 is a characteristic diagram showing the results of an evaluation test. [Figure 8] FIG. 10 is a graph showing the results of an evaluation test. [Figure 9] FIG. 10 is a graph showing the results of an evaluation test. DETAILED DESCRIPTION OF THE INVENTION

[0008] An outline of a process that is one embodiment of a substrate processing method according to the present disclosure will be described below. Fig. 1A is a longitudinal sectional side view of the surface of a wafer W, which is a substrate before processing. The wafer W has a silicon (Si) layer 10.

[0009] Above the Si layer 10, structures each consisting of an upper layer film 11 and a SiN film 13 that covers and surrounds the upper layer film 11 from the top surface to the side surfaces are formed at regular intervals. FIG. 1 shows a portion sandwiching a recess 12 between two adjacent structures. A SiO2 film (silicon oxide film) 14 is formed at the bottom of the recess 12. A portion of this SiO2 film 14 is formed below the upper layer film 11 and the SiN film 13, and the other portion is formed on the bottom surface of the recess 12. Furthermore, the SiO2 film 14 is formed from below one structure to below another structure, so that a portion of it is covered by each structure, and the other portion is exposed to the surface of the wafer W as the bottom surface of the recess 12. The recess 12 has a relatively high ratio D / W of its depth D to its opening width W, i.e., it is formed to have a high aspect ratio. For example, the opening width W is 25 nm. The recess 12 is used, for example, as a contact hole.

[0010] The SiO2 film 14 serves as a first film, and the SiN film 13 serves as a second film, so that the first film and the second film, which are different types of silicon-containing films, are exposed on the surface of the substrate wafer W. The SiO2 film 14 may be an oxide film formed by various methods, such as a thermal oxide film, an oxide film formed by a CVD method, or an oxide film formed using a TEOS (Tetra Ethoxy Silane) raw material.

[0011] In this embodiment, the SiO2 film 14 is selectively etched from the SiO2 film 14 and the SiN film 13 by supplying a processing gas. As described above, a portion of the SiO2 film 14 is formed below the structure made up of the SiN film 13 and the upper film 11, and therefore, this etching is performed by supplying the processing gas to the SiO2 film 14 through the recess 12. Due to the diffusion of the processing gas, the processing gas is supplied from the side to the portion of the SiO2 film 14 formed below the structure, and the portion formed below this is also etched.

[0012] When etching the SiO2 film 14, even if a process gas capable of selectively etching the SiO2 film 14 is used, the SiN film 13 may be etched along with the SiO2 film 14. This is presumably because the surface layer is oxidized by the processes performed before etching the SiO2 film, resulting in properties similar to those of the SiO2 film 14. Etching the SiN film 13 increases the line width of the pattern and shortens the distance between the patterns, which may increase leakage current and cause short circuits. This ultimately reduces the yield of semiconductor devices manufactured from the wafer W. The process in this embodiment is performed to address this problem.

[0013] 1B to 3, the processing performed on the wafer W will be described in order. The processing shown in each figure is performed after the wafer W is loaded into a processing chamber and the processing chamber is evacuated to create a vacuum atmosphere at a predetermined pressure. During processing, the wafer W is adjusted to a desired temperature.

[0014] First, the protection step will be described. In this step, the processing chamber is evacuated to, for example, 5.0 Pa to 40.0 Pa, and the temperature of the wafer W is adjusted to, for example, 20°C to 120°C. With the pressure in the processing chamber and the temperature of the wafer W adjusted in this manner, a gas containing a silylation agent is supplied into the processing chamber. The silylation agent may be a compound containing silicon (Si) and an alkyl group, such as trimethylsilyldimethylamine (TMSDMA). In this example, TMSDMA gas is supplied into the processing chamber, and the SiN film 13 is silylated by this gas, forming a protective film 15 on the surface of the SiN film 13, as shown in FIG. 1B.

[0015] In the protection step, it is presumed that the chemical reaction shown in Fig. 3 progresses in the surface layer of the SiN film 13, resulting in the formation of the protective film 15. As shown in Fig. 3, in the surface layer of the SiN film 13, some of the Si-N bonds are broken, and hydroxyl groups (-OH) are bonded to Si, forming Si-OH bonds. Therefore, since the surface layer of the SiN film 13 contains oxygen (O), it is presumed that the surface layer has properties similar to those of an oxide film, as described above.

[0016] In the chemical reaction formula shown in Figure 3, the silylating agent is SiR3X. R is an alkyl group, and when the silylating agent is TMSDMA, R is a methyl group (-CH3) and X is an amino group (-N(CH3)2). When TMSDMA gas is supplied to the SiN film 13, a chemical reaction occurs in which the hydrogen (H) in the hydroxyl group (-OH) bonded to Si is replaced with a trimethylsilyl group (-Si(CH3)3), forming a protective film 15. Meanwhile, the H released from the Si-OH bond bonds with an amino group (-N(CH3)2) to generate dimethylamine (NH(CH3)2) gas, which is removed by exhausting the processing chamber.

[0017] The protective film 15 thus formed is a modified surface layer of the SiN film 13, and the thickness of the SiN film 13 including the protective film 15 hardly changes before and after the formation of the protective film 15. However, since the OH group of the SiN film 13 containing oxygen in the surface layer is hydrophilic and the trimethylsilyl group is hydrophobic, the formation of the protective film 15 makes the surface layer of the SiN film 13 hydrophobic.

[0018] During the protection process, TMSDMA gas is supplied into the processing chamber, so not only the SiN film 13 but also the SiO2 film 14 exposed in the recess 12 comes into contact with the TMSDMA gas and is silylated. However, since it has been confirmed that the SiO2 film 14 continues to be etched in the etching process described below even after the protection process is performed, it is presumed that the effect of the silylation agent on the SiO2 film 14 is small. For this reason, FIGS. 1B and 2A depict the protective film 15 only on the surface of the SiN film 13. Note that, because the reaction proceeds as described in FIG. 3, it is presumed that the protective film 15 is formed in a manner corresponding to the oxidized portions of the SiN film 13. Therefore, although FIGS. 1B and 2A show the entire surface of the SiN film 13 as being converted into the protective film 15, it is conceivable that the protective film 15 may be formed locally.

[0019] Next, the etching process performed after the protection process will be described. In this example, the etching process includes a modification process in which a processing gas is supplied to modify the first film, SiO2 film 14, and a heating process in which the wafer W is heated to sublimate and remove the modified SiO2 film 14. In this example, the modification process and the protection process are performed on the wafer W in the same processing chamber.

[0020] In the modification step, the processing chamber is evacuated to, for example, 5.0 Pa to 40.0 Pa, and the temperature of the wafer W is adjusted to, for example, 20°C to 120°C. With the pressure in the processing chamber and the temperature of the wafer W adjusted in this manner, hydrogen fluoride (HF) gas and ammonia (NH3) gas are supplied as processing gases for etching. By supplying these gases to the surface of the wafer W in this manner, a first COR (Chemical Oxide Removal) process is performed on the wafer W. In this first COR process, the pressure in the processing chamber is adjusted to, for example, 5.0 Pa to 40.0 Pa, and the temperature of the wafer W is adjusted to, for example, 20°C to 120°C.

[0021] In the first COR process, the SiO2 film 14 present at the bottom of the recess 12 of the wafer W is altered by chemical reaction with HF gas molecules and NH3 gas molecules, and is transformed into reaction products (see FIG. 2A). This chemical reaction proceeds downward and horizontally from the surface of the SiO2 film 14 exposed in the recess 12 toward the back (away from the surface), and ammonium fluorosilicate (AFS), moisture, etc. are generated as reaction products.

[0022] Subsequently, in the modification step of this embodiment, after the first COR process, a second COR process is further performed on the wafer W. In this second COR process, only HF gas is supplied to the wafer W without using NH gas, which is a basic gas. The supply of HF gas modifies the SiO film 14 at the interface between the reaction product (first reaction product) generated in the first COR process and the SiO film 14 located horizontally further back than the first reaction product, thereby generating a second reaction product.

[0023] The second reaction product, which contains dihydrogen hexafluorosilicate (H2SiF6) and other compounds, is produced by a chemical reaction with HF gas molecules using the water contained in the first reaction product as a catalyst. Figure 2A shows the state in which the first and second COR processes are performed, resulting in the production of the first and second reaction products. The first and second reaction products are not distinguished from each other and are collectively referred to as reaction product 16.

[0024] In the second COR process, HF gas is supplied instead of NH gas, which allows the HF gas to easily permeate the first reaction product, thereby generating the second reaction product at the back of the SiO film 14. This second COR process is performed in the same processing chamber as the first COR process, and the pressure in the processing chamber and the temperature of the wafer W in the second COR process are set, for example, similarly to those in the first COR process.

[0025] Once the second COR process is completed and a sufficient layer of the second reaction product is formed, a heating step is performed. In this example, this heating step is performed in a processing vessel different from the processing vessel used for the first and second COR processes. During the heating step, high-temperature heated gas is supplied into the processing vessel while the processing vessel is evacuated. This heats and vaporizes the reaction product 16 (the first and second reaction products) generated by the COR process. The reaction product 16 is then exhausted from below the recess 12 through the recess 12 and discharged to the outside of the wafer W. In this manner, as shown in FIG. 2B, the heating step is performed after the first and second COR processes, removing the reaction product 16 and etching the SiO2 film 14.

[0026] As described above, the first COR process and the second COR process proceed quickly because the silylating agent has little effect on the surface of the SiO2 film 14 during the protection process. On the other hand, the protective film 15 formed on the surface of the SiN film 13 prevents the SiN film 13 from coming into contact with the processing gases (HF gas, NH3 gas), thereby suppressing the generation of reaction products 16 in the SiN film 13.

[0027] 3, even after the formation of the protective film 15, oxygen (O) is present in the surface layer of the SiN film 13, but silicon (Si) bonds to the oxygen to form siloxane bonds (Si-O-Si). From the perspective of the process gas, the oxidized portions of the SiN film 13 appear as if they are coated and masked, and the portions appear as if they are repaired by Si, a constituent element of the SiN film 13, which is thought to reduce the reactivity between the process gas and the portions. Therefore, the formation of the protective film 15 suppresses etching of the SiN film 13.

[0028] As described above, since the protective film 15 is also formed on the surface layer of the SiO2 film 14, the etching rate of the SiO2 film 14 in the etching process is lower than when the protective process is not performed. As a result, in order to etch the SiO2 film 14 to a set amount, the etching process time is longer than when the protective process is not performed. Even in such a case, it has been confirmed that the loss amount (etching amount) of the SiN film 13 is smaller than when the protective process is not performed.

[0029] 1 and 2, one embodiment of a substrate processing apparatus 2 that performs the series of processes described with reference to Fig. 1 and Fig. 2 will now be described with reference to the plan view of Fig. 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, respectively, and two processing modules 4 provided adjacent to the two heat treatment modules 30, respectively.

[0030] 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 on the side of the atmospheric pressure transfer chamber 23 on which a carrier 24 for accommodating a wafer W is mounted. In the drawing, reference numeral 26 denotes an aligner 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 aligner 26, and the load lock chamber 31.

[0031] A second substrate transfer mechanism 32 having, for example, an articulated arm structure is provided in 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. A vacuum atmosphere is maintained inside the treatment vessel constituting the heat treatment module 30 and the treatment vessel constituting the treatment module 4. The load lock chamber 31 can be switched between an atmospheric pressure atmosphere and a vacuum atmosphere so that wafers W can be transferred between the vacuum atmosphere treatment vessels and the atmospheric pressure transfer chamber 23.

[0032] 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 heating process described above.

[0033] The processing module 4 will be described with reference to the vertical cross-sectional side view of FIG. 5. This processing module 4 performs the protection process and the modification process (first COR process, second COR process) described above. In the figure, 41 denotes a processing vessel constituting the processing module 4. A transfer port 42 for the wafer W is opened in the sidewall of the processing vessel 41, and this transfer port 42 is opened and closed by the gate valve 33 described above. A stage 51 for placing the wafer W is provided within the processing vessel 41, and this stage 51 has lift pins (not shown) for transferring the wafer W to and from the second substrate transfer mechanism 32 described above.

[0034] A temperature adjustment unit 52 is embedded in the stage 51, and the wafer W placed on the stage 51 is adjusted 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.

[0035] 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 formed of, for example, a vacuum pump. The exhaust pipe 53 is provided with a valve 54, which is a pressure change mechanism, and 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.

[0036] A gas shower head 56 is provided at the upper side of the processing vessel 41 so as to face the stage 51. The downstream sides of gas supply paths 61 to 65 are connected to the gas shower head 56, and the upstream sides of the gas supply paths 61 to 65 are connected to gas supply sources 71 to 75 via flow rate adjusters 66, respectively. Each flow rate adjuster 66 includes a valve and a mass flow controller, and the gas supplied from the gas supply sources 71 to 75 is supplied to the downstream side by opening or closing a valve included in the flow rate adjuster 66.

[0037] Silylation agents, TMSDMA gas, HF gas, NH gas, Ar (argon) gas, and N (nitrogen) gas, are supplied from gas supply sources 71, 72, 73, 74, and 75, respectively, and these gases are supplied into processing chamber 41 via gas showerhead 56. Ar gas and N gas are used as carrier gases.

[0038] TMSDMA is a liquid at room temperature. In the protection step, a container containing TMSDMA is heated to vaporize it, and a carrier gas is supplied to the container, whereby TMSDMA is supplied together with the carrier gas into the process vessel 41. In this example, the protective film forming fluid supply unit includes a gas supply source 71, a gas supply path 61, a flow rate regulator 66 provided in the gas supply path 61, and a gas shower head 56. HF gas and NH3 gas are supplied together with the carrier gas into the process vessel 41 in the first COR process, and HF gas is supplied together with the carrier gas in the second COR process. In this example, the process gas supply unit includes gas supply sources 72 and 73, gas supply paths 62 and 63, and flow rate regulators 66 and gas shower heads 56 provided in the gas supply paths 62 and 63, respectively. The inert gas supply unit includes gas supply sources 74 and 75, gas supply paths 64 and 65, and flow rate regulators 66 and gas shower heads 56 provided in the gas supply paths 64 and 65, respectively.

[0039] 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 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 aligner 26. Examples of the operation of the processing module 4 controlled by the control signals include the temperature of the fluid supplied to the stage 51, the supply and cutoff of gases from the gas shower head 56 by the flow rate regulator 66, the adjustment of the flow rate of each gas supplied into the processing chamber 41, and the adjustment of the exhaust flow rate by the valve 54.

[0040] The transfer path of the wafer W in the substrate processing apparatus 2 will now be described. As explained in FIG. 1A, the carrier 24 storing the wafer W on which each film has been formed is placed on the carrier mounting table 25. Then, the wafer W is transferred in the order of the atmospheric pressure transfer chamber 23 → aligner 26 → atmospheric pressure transfer chamber 23 → load lock chamber 31, and then transferred to the processing module 4 via the heat treatment module 30. Then, as already mentioned, TMSDMA gas is supplied and the process described as the protection step is performed to form the protective film 15.

[0041] Next, in the processing module 4, the supply of TMSDMA gas is stopped and the TMSDMA gas is exhausted from the processing vessel 41. Then, as described above, HF gas and NH3 gas are supplied as processing gases to perform the first COR process to form the first reaction product (AFS layer). After this, the supply of NH3 gas is stopped and only HF gas is supplied as processing gas to perform the second COR process to form the second reaction product.

[0042] Next, the wafer W is transferred to the heat treatment module 30, where a heating process is performed to sublimate the reaction product 16. As a result, a portion of the SiO2 film 14 is selectively etched. In addition, the wafer W may be transported back and forth between the processing module 4 and the heat treatment module 30, so that the cycle of protection process → first COR process → second COR process → heating process is repeated a predetermined number of times. Thereafter, the wafer W is transferred from the heat treatment module 30 to the load lock chamber 31 and then to the atmospheric pressure transfer chamber 23, and then returned to the carrier 24. A further explanation of the repeated cycle described above is provided. In FIGS. 1 and 2, the process gas penetrates the SiO2 film 14 laterally, causing the film to change, and the portions of the SiO2 film 14 located below the upper film 11 and the SiN film 13 are also etched. By repeating the cycle without the process gas penetrating in this manner, the SiO2 film 14 exposed at the bottom of the recess 12 is first etched downward, increasing the depth of the recess 12 and forming a space in the portion of the SiO2 film 14 located below the upper film 11 and the SiN film 13. In the subsequent cycle, the process gas is supplied laterally through this space to the portion of the SiO2 film 14 located below the upper film 11 and the SiN film 13, thereby etching that portion. Alternatively, the protection process may be performed only once, and the etching process (first COR process → second COR process → heating process) may be repeated.

[0043] According to the processing method shown in this embodiment, as described above, in a wafer W having a first film, SiO2 film 14, and a second film, SiN film 13, exposed on the surface, a protective film 15 is formed on the surface of the SiN film 13, so that the SiO2 film 14 can be selectively etched. In this way, the protective film 15 suppresses etching of the SiN film 13, thereby suppressing deformation of the recesses 12 during etching of the SiO2 film 14. This suppresses an increase in leakage current and the occurrence of short circuits due to the leakage current, thereby increasing the yield of semiconductor products manufactured from the wafers W after the etching process.

[0044] In the above-described embodiment, the protection process and the modification process are performed on wafers W in the same processing chamber using a gas containing a silylation agent. This allows for a more compact substrate processing apparatus 2 than when these processes are performed in separate processing chambers. Furthermore, since there is no need to transfer wafers W to a separate processing chamber for the modification process after the protection process, throughput can be improved, and the yield of semiconductor products can be further increased. When the protection process and the modification process are performed in the same processing chamber in this manner, the processing temperature of the wafer W (i.e., the temperature of the stage 51) may be kept constant. In other words, after the protection process is completed, the modification process may be started immediately without changing the temperature of the stage 51, thereby increasing throughput.

[0045] Other examples of silylating agents for forming the protective film 15 include dimethylsilyldimethylamine (DMSDMA), hexamethyldisilazane (HMDS), tetramethyldisilazane (TMDS), TMSPyrole (1-trimethylsilylpyrole), N,O-Bis(trimethylsilyl)trifluoroacetamide (BSTFA), and Bis(dimethylamino)dimethylsilane (BDMADMS). For convenience, the silylating agent is represented as SiR3X in FIG. 3. While all three Rs in TMSDMA are alkyl groups, the silylating agent is not limited to one in which all three Rs are alkyl groups. Alternatively, a silylating agent in which one or more Rs are halogenated alkyl groups may be used. A halogenated alkyl group is an alkyl group in which one or more hydrogen atoms are replaced with halogen atoms. Regarding DMSDMA, which is an example of a silylating agent, one of the three Rs is represented as H (hydrogen atom). Thus, the silylating agent may be a compound in which some of the three R's are H.

[0046] In the above, the fluid containing the silylation agent may be a liquid containing the silylation agent. For example, the liquid may be applied to the surface of the wafer W by a method such as spin coating in an air atmosphere to form the protective film 15. Thereafter, the wafer W may be transported to the substrate processing apparatus 2 for subsequent processing. Before and after the protection process, TMSDMA liquid was dropped onto the surface of the oxidized SiN film 13, and the contact angle was measured. After the formation of the protective film 15, the contact angle was about five times larger than before the formation, confirming that the film had become hydrophobic. In other words, the formation of the protective film 15 by silylation as described in FIG. 3 was confirmed.

[0047] Furthermore, the modification process is not limited to using HF gas. For example, F2 gas, IF7 gas, IF5 gas, ClF3 gas, or SF6 gas can also be used to modify the SiO2 film (first film) and generate reaction products, thereby performing a similar process. Various fluorine-containing gases can be used. Furthermore, in the above-described process example, the first and second COR processes were performed in the modification process to etch the SiO2 film 14. However, only the first COR process may be performed. Furthermore, the method disclosed herein is not limited to horizontal etching of the SiO2 film 14 in the above-described device structure. For example, the method disclosed herein can also be used when the SiO2 film 14 and the SiN film 13 are formed on the wafer W so that they are aligned horizontally and the top surfaces of these films are exposed, and the SiO2 film 14 is etched from above.

[0048] Furthermore, in the above-described substrate processing apparatus 2, the alteration process and the heating process may be performed in the same processing chamber, for example, by changing the temperature of the stage 51 of the processing module 4. However, since it takes time to adjust the temperature of the stage 51, it is preferable to perform the alteration process and the heating process in different processing chambers, as described above. Furthermore, in the above example, HF gas and NH gas are simultaneously supplied to the wafer W in the first COR process, but the HF gas supply period and the NH gas supply period may be supplied so that they do not overlap each other, or so that the supply periods of these gases only partially overlap each other. Even in this case, one of the HF gas and the NH gas adsorbed on the SiO film 14 reacts with the other gas, thereby generating a first reaction product.

[0049] Incidentally, FIG. 2B shows the protective film 15 remaining on the wafer W after the etching process is completed. As described above, the protective film 15 is formed on the surface layer of the SiN film 13, and is therefore considered to be very thin. Therefore, in reality, the surface layer of the SiN film 13 is also slightly etched along with the SiO2 film 14, and is therefore considered to be removed by the end of etching. In other words, a removal process for removing the protective film 15 after the etching process is not necessarily performed. However, a removal process may be performed to more reliably prevent any influence on the processes after etching. This removal process may be performed, for example, by heating in a heat treatment module 30 to cause a deprotection reaction.

[0050] The configuration of the processing module 4 and the processing performed in the processing module 4 described in Fig. 5 will be described in more detail. By supplying the TMSDMA gas to the wafer W in the processing chamber 41 as described above, the reaction described in Fig. 3 occurs, and the SiN film 13 is silylated. During this silylation, dimethylamine (hereinafter referred to as DMA) gas is generated, which is shown as X in Fig. 3.

[0051] As described above, HF gas is supplied to wafer W in processing vessel 41 to perform the first and second COR processes after silylation of SiN film 13. The applicant has confirmed that if DMA gas remains in processing vessel 41 during the supply of HF gas into processing vessel 41 and both HF gas and DMA gas are supplied to aluminum (Al) components in processing vessel 41, the surfaces of the components may be corroded. Examples of such Al components include the inner wall of processing vessel 41 and gas shower head 56. The corrosion of these components generates Al fluoride, which vaporizes and adheres to wafer W and various components in processing vessel 11, potentially causing metal contamination.

[0052] Gas supply paths 61-65 provided in processing module 4 are each composed of metal piping, and the metal constituting this piping contains Al. Therefore, to prevent contamination by Al, gas supply path 61 for TMSDMA gas and gas supply path 62 for HF gas are configured as separate entities leading to gas shower head 56, as shown in the figure. Furthermore, within gas shower head 56, the TMSDMA gas flow path and the HF gas flow path are formed as separate flow paths that do not communicate with each other.

[0053] The controller 20 controls the operation of the processing module 4 to prevent Al contamination in the processing vessel 41. Specifically, the controller 20 is programmed to prevent a valve included in the flow rate regulator 66 in the TMSDMA gas supply line 61 and a valve included in the flow rate regulator 66 in the HF gas supply line 62 from being simultaneously opened to supply each gas into the processing vessel 41. Furthermore, a user of the apparatus can set the supply period of each gas individually or change the preset supply period by performing a predetermined operation on the controller 20. In this case, the program may be programmed to prevent Al contamination in the processing vessel 41 from overlapping the supply period of the TMSDMA gas and the supply period of the HF gas into the processing vessel 41.

[0054] 6, the gases are preferably supplied into processing vessel 41 to process wafer W. This time chart shows not only the change in the supply amount of each gas into processing vessel 41 and whether or not it is supplied, but also the change in pressure inside processing vessel 41. During the period from time t1 to time t7 shown in the time chart, the inside of processing vessel 41 is constantly evacuated by exhaust mechanism 55 to maintain a vacuum pressure.

[0055] First, wafer W is loaded into processing vessel 41 and placed on stage 51, and its temperature is adjusted. Meanwhile, inert gases N2 gas and Ar gas are supplied into processing vessel 41, and the pressure inside processing vessel 41 is set to A1 (time t1). Thereafter, at time t2, supply of TMSDMA gas into processing vessel 41 begins, while the flow rates of N2 gas and Ar gas supplied into processing vessel 41 are reduced, and the pressure inside processing vessel 41 is reduced to A2.

[0056] At subsequent time t3, the supply of TMSDMA gas into processing vessel 41 is stopped, while the flow rates of N2 gas and Ar gas supplied into processing vessel 41 are increased. N2 gas and Ar gas act as purge gases to purge and remove TMSDMA gas and DMA gas remaining in processing vessel 41 from processing vessel 41. Thereafter, at time t4, the supply of N2 gas and Ar gas into processing vessel 41 is stopped, and the pressure inside processing vessel 41 drops to A3. As evacuation continues in this manner and the degree of vacuum inside processing vessel 41 increases, the removal of TMSDMA gas and DMA gas from processing vessel 41 progresses further.

[0057] Then, at time t5, the supply of HF gas, NH3 gas, N2 gas, and Ar gas into processing vessel 41 begins, and the pressure inside processing vessel 41 rises to A4. The HF gas and NH3 gas perform a first COR process, altering SiO2 film 14. Because the DMA gas and TMSDMA gas, which is a source of DMA gas, have been removed from processing vessel 41 by time t5, the supply of HF gas prevents corrosion of the inner wall of processing vessel 41 and the surface of gas showerhead 56. Thereafter, at time t6, the supply of HF gas, NH3 gas, N2 gas, and Ar gas into processing vessel 41 is stopped. After the remaining gases in processing vessel 41 are exhausted, wafer W is unloaded from processing vessel 41.

[0058] In addition to processing the wafer W by controlling the supply of each gas as described above, corrosion may be more reliably prevented by coating the inner wall of the processing vessel 41 and the surface of the gas shower head 56 with, for example, a Ni-P plating film. Note that, although only the first COR process using HF gas and NH gas is performed among the first and second COR processes in the example shown in the time chart of FIG. 6, as described above, the second COR process may be performed by continuing to supply HF gas after the first COR process.

[0059] 6, in order to more reliably remove DMA gas and TMSDMA gas from processing vessel 41, a period (time t4 to t5) is provided during which only evacuation of processing vessel 41 is performed, among the supply of inert purge gas and evacuation of processing vessel 41. However, if the period (time t3 to t4) during which purge gas is supplied and evacuation of processing vessel 41 is performed before this period is set relatively long, the period from time t4 to t5 during which only evacuation is performed without supplying purge gas may be omitted. The supply of purge gas into processing vessel 41 and evacuation of processing vessel 41 during the period from time t3 to t4 corresponds to a first removal step, and the evacuation of processing vessel 41 during the period from time t4 to t5 corresponds to a second removal step.

[0060] 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.

[0061] [Evaluation test] An evaluation test conducted in relation to the technology of the present disclosure will be described below. In this evaluation test (Evaluation Test 1), etching was performed using the above-mentioned processing gas on a SiN film and an SiO2 film, both with and without a protection process, and the amount of etching was evaluated. The SiN and SiO2 films to be evaluated were each formed on a blanket wafer. The protection process was performed by applying TMSDMA liquid as a fluid containing a silylation agent to the wafer W using the method described above.

[0062] Then, regardless of whether or not the protection process was performed, the etching process was performed by performing the modification process (first COR process and second COR process) and the heating process, and the etching amount was measured. In the modification process, Ar gas and N gas were also supplied into the processing vessel together with HF gas and NH gas.

[0063] The measurement results of the etching amount are shown in Figure 7. In the figure, the vertical axis represents the etching amount. The horizontal axis represents "Example 1," "Comparative Example 1," "Comparative Example 2," and "Comparative Example 3," as follows: Example 1: SiN film (with protection process) Comparative Example 1: SiN (no protective step) Comparative Example 2: SiO2 film (with protection process) Comparative Example 3: SiO2 film (no protection process)

[0064] 7, it was confirmed that the etching amount of the SiN film in Example 1, in which the protective process was performed, was smaller than that in Comparative Example 1, in which the protective process was not performed, and that performing the protective process can suppress etching by the processing gas (HF gas, NH3 gas). On the other hand, it was confirmed that the SiO2 film can be etched even when the protective process is performed.

[0065] Another evaluation test (Evaluation Test 2) will be described. In Evaluation Test 2, a comparison was made between a wafer W having the device structure shown in FIG. 1 , in the same manner as in Evaluation Test 1, with a case in which the protection process and the etching process were performed, and a case in which the etching process was performed without the protection process. As a result, if the etching amount of the SiN film 13 without the protection process was 1, the etching amount of the SiO2 film 14 without the protection process was 1.24. The etching amounts of the SiN film 13 and the SiO2 film 14 with the protection process were 0.29 and 1.08, respectively. The supply time of the process gas was approximately the same in both the cases in which the protection process was performed and the case in which the protection process was not performed, and the time in which the protection process was performed was set to 1.2 times longer than the time in which the protection process was not performed. The processing conditions other than the supply time of the process gas were the same in each case. As described above, even when a protective film was formed, the change in the etching amount of the SiO2 film 14 was suppressed, and the etching amount of the SiN film 13 was smaller than the etching amount of the SiO2 film 14. Therefore, it was confirmed from the evaluation test 2 that the SiO2 film 14 can be selectively etched as explained in the embodiment.

[0066] As described above, the results of evaluation tests 1 and 2 showed different etching selectivity for the SiO2 film 14, which is presumably due to the influence of differences in the surface structure of the wafers to which the silylation agent was supplied. However, as described above, in evaluation test 1, the amount of etching of the SiN film 13 was reduced by supplying the silylation agent, and in evaluation test 2, the amount of etching of the SiN film 13 was also reduced by supplying the silylation agent. Therefore, overall, evaluation tests 1 and 2 confirmed that forming a protective film is effective in suppressing the etching of the SiN film 13.

[0067] Next, evaluation test 3 will be described. In evaluation test 3-1, a substrate was placed on stage 51 in processing chamber 41 of processing module 4, and gases were supplied into processing chamber 41 according to the procedure described at times t1 to t6 in the time chart of FIG. 6. Therefore, in evaluation test 3-1, the gases were supplied into processing chamber 41 so that the period during which TMSDMA gas was supplied did not overlap with the period during which HF gas and NH3 gas were supplied. This series of gas supplies from times t1 to t6 constituted one cycle, and the number of cycle repetitions was varied for each substrate. In other words, the number of times TMSDMA gas, HF gas, and NH3 gas were supplied varied depending on the substrate. After a predetermined number of cycles had been performed, the substrate was removed from processing chamber 41, and the amount of Al atoms attached to each of the front and back surfaces of the substrate was measured.

[0068] In addition, evaluation test 3-2 was performed in the same manner as evaluation test 3-1, except that TMSDMA gas, HF gas, and NH3 gas were simultaneously supplied for a predetermined period of time as one cycle, and the amount of Al atoms attached to the substrate was measured. Therefore, in evaluation test 3-2, TMSDMA gas, HF gas, and NH3 gas were supplied into processing vessel 41 the same number of times as the number of cycles. The supply times of TMSDMA gas, HF gas, and NH3 gas in one cycle were the same between evaluation tests 3-1 and 3-2. Therefore, comparing evaluation tests 3-1 and 3-2, the more cycles there were, the longer the exposure time of the processing vessel 41 to TMSDMA gas, HF gas, and NH3 gas. In evaluation test 3-1, the number of cycles (number of cycles performed) was set to 1, 25, 50, 100, and 300, respectively, and gas was supplied to each substrate. In evaluation test 3-1, the number of cycles (1) means that the series of gas supplies shown at times t1 to t6 was performed only once, without repeating them. In evaluation test 3-2, the number of cycles was set to 5, 10, and 25, respectively.

[0069] 8 and 9 are graphs showing the results of evaluation tests 3-1 and 3-2 on the front surface side of the substrate, respectively, and show the number of Al atoms (unit: atoms / cm) measured for each cycle number. 2) are shown. A on the vertical axis of the graph is a positive number. Looking at the results of Evaluation Test 3-1 in Figure 8, the measured value when the cycle number was 1 was larger than the measured value when the cycle number was 25 to 100, but smaller than the measured value when the cycle number was 300. Except for the result when the cycle number was 1, in each graph, the measured value of the number of Al atoms generally tends to increase as the cycle number increases in both Evaluation Tests 3-1 and 3-2. Furthermore, the measurement results for the number of Al atoms at each cycle number in Evaluation Test 3-1 were smaller than the measurement results for any cycle number in Evaluation Test 3-2.

[0070] Although the results are not shown, the number of Al atoms on the back surface of the substrate also tended to generally increase as the number of cycles increased, just as on the front surface of the substrate, and the number of Al atoms at each number of cycles in Evaluation Test 3-1 was smaller than the number of Al atoms at any number of cycles in Evaluation Test 3-2. Therefore, in order to prevent Al contamination inside the processing vessel 41, it was shown that supplying each gas to the wafer W and performing processing as described in FIG. [Explanation of symbols]

[0071] W Semiconductor wafer 13 SiN film (second film) 14 SiO2 film (first film) 15 Protective film

Claims

1. 1. A substrate processing method for selectively etching a silicon oxide film by supplying a processing gas to a substrate having a first film and a second film, the first film being different types of silicon-containing films, exposed on a surface thereof, the method comprising: a protection step of supplying a fluid containing a silylation agent to the substrate to form a protection film on a surface of the second film to prevent etching of the second film; an etching step of supplying the processing gas to the substrate on which the protective film is formed, and selectively etching the first film; A substrate processing method comprising:

2. 2. The substrate processing method according to claim 1, wherein the fluid containing the silylation agent is a gas containing the silylation agent.

3. The etching step includes: a modification step of supplying the processing gas to modify the first film; 3. The substrate processing method according to claim 2, further comprising a heating step of heating the substrate to remove the altered first film.

4. 4. The substrate processing method according to claim 3, wherein the modifying step and the protecting step are performed on the substrate in the same processing chamber.

5. 2. The substrate processing method according to claim 1, wherein the second film is a silicon nitride film.

6. the etching step is performed after the protection step, 5. The substrate processing method according to claim 4, wherein a first removal step is performed between the protection step and the etching step, in which an inert gas is supplied into the processing vessel while the processing vessel is evacuated, in order to remove the gas containing the silylation agent from the processing vessel.

7. After the first removal step and before the etching step, 7. The substrate processing method according to claim 6, further comprising the step of: performing a second removal step of evacuating the processing vessel while stopping the supply of the inert gas into the processing vessel.

8. 1. A substrate processing apparatus that supplies a processing gas to a substrate having a first film and a second film, the first film being a silicon oxide film, exposed on a surface thereof, the first film being a silicon oxide film, the processing gas being supplied to the substrate. a protective film forming fluid supply unit that supplies a fluid containing a silylation agent to the substrate in order to form a protective film on a surface layer of the second film that prevents etching of the second film; a processing gas supply unit that supplies the processing gas to the substrate on which the protective film is formed, and selectively etches the first film; A substrate processing apparatus comprising:

9. the fluid containing the silylation agent is a gas containing the silylation agent, an inert gas supply unit for supplying an inert gas to the substrate; a processing vessel in which the substrate is housed and the interior thereof is evacuated, and into which the gas containing the silylation agent supplied from the protective film forming fluid supply unit, the processing gas supplied from the processing gas supply unit, and the inert gas supplied from the inert gas supply unit are supplied; a control unit that outputs a control signal to perform an etching step of supplying the processing gas into the processing vessel after the gas containing the silylating agent has been supplied into the processing vessel, and a first removal step of supplying the inert gas into the processing vessel while the processing vessel is being evacuated during the period from when the gas containing the silylating agent is supplied into the processing vessel until the processing gas is supplied, in order to remove the gas containing the silylating agent from the processing vessel; The substrate processing apparatus according to claim 8 , further comprising:

10. The control unit 10. The substrate processing apparatus according to claim 9, wherein a control signal is output so that a second removal step is performed after the first removal step and before the etching step, in which the supply of the inert gas into the processing vessel is stopped and the inside of the processing vessel is evacuated.

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