Substrate processing method and substrate processing apparatus

Abstract

In removing a silicon-containing film formed on a surface of a substrate, each portion in-plane of the substrate is subjected to removal processing with high uniformity. An etching method includes the following steps: a substrate on which a silicon-containing film is formed on a surface is stored in a processing vessel, a processing gas containing a halogen-containing gas and an alkali gas is supplied, and the silicon-containing film is converted to generate a reaction product; in order to remove a portion of the reaction product, supply of a non-reactive gas into the processing vessel and evacuation of the processing vessel are performed in a state where supply of the processing gas into the processing vessel is stopped; the first step and the second step are alternately repeated; and in each of the second steps, the processing vessel is set to a pressure higher than 200 Pa, so that the processing gas is supplied to the substrate on which the reaction product remains in the first step of the second time and thereafter in the repeated steps.

Description

Technical Field

[0001] This disclosure relates to a substrate processing method and a substrate processing apparatus. Background Technology

[0002] In the manufacture of semiconductor devices, etching of silicon-containing films such as SiO2 films (silicon oxide films) formed on the surface of a semiconductor wafer (hereinafter referred to as a wafer) that serves as a substrate is sometimes performed. Patent Document 1 describes that when etching the SiO2 film by sequentially supplying an alkaline gas to the substrate in a first step and a fluorine-containing gas to the wafer in a second step, the processing container holding the substrate is purged after the second step is completed and before the first step begins.

[0003] Patent document 2 describes a process whereby, after supplying a processing gas containing halogenated gas and alkaline gas to the wafer to generate reaction products on the surface of the SiO2 film, the processing container holding the wafer is depressurized to 0 Pa to 200 Pa in such a way that a portion of the reaction products remain on the SiO2 film while the other portion is removed. Then, the pressure inside the processing container is increased, and the processing gas is supplied to the wafer again, thereby removing the SiO2 film.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2021-180281

[0007] Patent Document 2: Japanese Patent Application Publication No. 2021-118250 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] This disclosure provides a technique for performing highly uniform removal processing on all parts of the substrate surface when removing a silicon-containing film formed on the surface of a substrate.

[0010] Solution for solving the problem

[0011] The etching method disclosed herein includes the following steps: storing a substrate with a silicon-containing film formed on its surface in a processing container; a first step, supplying a processing gas containing a halogen-containing gas and an alkaline gas into the processing container to convert the silicon-containing film into reaction products; a second step, in order to remove a portion of the reaction products, supplying an inactive gas into the processing container and venting the processing container while the supply of the processing gas into the processing container is stopped; a repeating step, alternately repeating the first step and the second step; and a pressure control step, in each of the second steps, setting the pressure inside the processing container to a level higher than 200 Pa, so that the processing gas is supplied to the substrate containing the residual reaction products in the second and subsequent first steps of the repeating step.

[0012] Invention Effects

[0013] This disclosure enables highly uniform removal of silicon-containing films formed on the surface of a substrate. Attached Figure Description

[0014] Figure 1 It is a longitudinal cross-section of the surface structure of the substrate before the etching process in the illustrated embodiment.

[0015] Figure 2 This is an enlarged longitudinal section of a portion of the surface structure of a substrate before etching.

[0016] Figure 3A This is a graph showing the surface changes of the silicon oxide film after etching treatment based on a comparative method.

[0017] Figure 3B This is a graph showing the surface changes of the silicon oxide film after etching treatment based on a comparative method.

[0018] Figure 4A This is a diagram showing the surface changes of the silicon oxide film after etching treatment based on the embodiment.

[0019] Figure 4B This is a diagram showing the surface changes of the silicon oxide film after etching treatment based on the embodiment.

[0020] Figure 4C This is a diagram showing the surface changes of the silicon oxide film after etching treatment based on the embodiment.

[0021] Figure 4D This is a diagram showing the surface changes of the silicon oxide film after etching treatment based on the embodiment.

[0022] Figure 5 This is a longitudinal sectional side view of the substrate processing apparatus according to an embodiment.

[0023] Figure 6 This is a timing diagram illustrating the processing operations in the substrate processing apparatus of the embodiment.

[0024] Figure 7 This is a graph showing the results of the evaluation of Experiment 1.

[0025] Figure 8 This is a graph showing the results of the evaluation of experiment 2. Detailed Implementation

[0026] (Substrate surface structure)

[0027] Figure 1 This is a longitudinal cross-sectional side view of the surface structure of the substrate before etching, illustrating an embodiment. As shown in the figure, on the surface layer of wafer W, a large number of protrusions, for example, formed of a polysilicon film 11, are formed on the lower layer film 10 and arranged laterally, thereby forming a plurality of recesses. Thus, the polysilicon film 11 forms the sidewalls of the recesses. A silicon oxide film 12 is formed within each recess. In this embodiment, each silicon oxide film 12 is etched such that its lower end remains. This etching is performed selectively relative to the polysilicon film 11. Furthermore, the aforementioned lower layer film 10... Figure 1 Other than those shown in the diagram.

[0028] When forming a silicon oxide film 12 within a recess, the silicon oxide film 12 grows from various points on the sidewalls of the polycrystalline silicon film 11 and fuses together, thereby sometimes forming a seam 13 at the central portion in the lateral direction of the silicon oxide film 12. This seam 13 is a junction where the interfaces of the silicon oxide films 12 join together, a void formed in the silicon oxide film 12. Laterally, the direction from the surface side of the wafer W towards the back side is sometimes referred to as the vertical direction or the height direction. The lateral length (width), height length, and other dimensions of the seam 13, as well as its formation position in the height direction, vary between the recesses.

[0029] (Comparison method)

[0030] To illustrate the effect of the etching method disclosed herein, the etching process of the comparative method will be described first. Figure 2 The wafer W before processing is shown. In the description, two silicon oxide films 12a and 12b are shown as silicon oxide films 12. No seam 13 is formed in silicon oxide film 12a, while a seam 13 is formed in silicon oxide film 12b. Furthermore, in both the comparative processing method and the processing of the embodiments described later, the wafer W is stored in a processing container and adjusted to a predetermined temperature. The wafer W is processed by supplying various gases into the processing container. In the processing of the wafer W, a vacuum atmosphere at a desired pressure is created inside the processing container by adjusting the exhaust volume.

[0031] Figure 3A, Figure 3B The surface changes of silicon oxide films 12a and 12b under the etching process involved in the comparative method are shown. First, a process gas is supplied into the processing container. This process gas is a halogen-containing gas and an alkaline gas; specifically, HF (hydrogen fluoride) gas is supplied as the halogen-containing gas, and NH3 (ammonia) gas is supplied as the alkaline gas. The surface portions of the silicon oxide films 12a and 12b reacting with the process gas are converted into ammonium fluorosilicate (AFS) as a reaction product, forming an AFS layer. Moreover, as the reaction progresses, the thickness of the AFS layer increases.

[0032] When the AFS layer thickness is relatively small, the processing gas can pass through the AFS layer, causing the silicon oxide films 12a and 12b to transform. However, if the AFS layer thickness is relatively large, such passage is difficult to occur. Therefore, after supplying the processing gas for a specified time, the supply of the processing gas is stopped, and the pressure inside the processing container is maintained at a relatively low level. As a result, the AFS sublimates, thereby removing the AFS layer and exposing the surfaces of the silicon oxide films 12a and 12b. By alternately repeating the supply of the processing gas and the exposure of the surfaces of the silicon oxide films 12a and 12b based on the removal of the AFS layer, the etching of each silicon oxide film 12a and 12b downwards progresses. Figure 3A In addition, the arrows on the dotted lines in the diagram represent sublimated AFS.

[0033] However, when etching proceeds as described above and processing gas is supplied to the region in the silicon oxide film 12b where the seam 13 is formed, the processing gas flows downward within the seam 13 (specifically, the tiny gap between the interfaces of the silicon oxide film 12 and the voids forming the seam 13). Then, the region surrounding the seam 13 transforms into an AFS (Alternating Field Freeze-Form), which then sublimates. In other words, etching in the silicon oxide film 12b proceeds downwards more than etching in the silicon oxide film 12a. Specifically, etching proceeds faster at the region where the seam 13 is formed.

[0034] Therefore, such as Figure 3B As shown, at the end of etching, there may be a significant difference in the amount of etching between the silicon oxide films 12a and 12b (i.e., a significant difference in surface height between the silicon oxide films 12a and 12b). Furthermore, in the silicon oxide film 12b, when etching is performed around the seam 13 as described above, the seam 13 is etched to extend laterally. Therefore, the central portions on the left and right sides of the recess are etched more extensively, thus... Figure 3B As shown, at the end of etching, the surface height deviation of various parts of the silicon oxide film 12b may become large.

[0035] Assuming that a large number of recesses are formed in the wafer W, as described above, the width, length in the height direction, and position in the height direction of the seams in the silicon oxide film 12 within the recesses may differ between the recesses. Therefore, although FIG. 3 shows a deviation in the amount of etching between the silicon oxide film 12b with seams 13 and the silicon oxide film 12a without seams 13, the aforementioned deviation in the amount of etching may also occur between silicon oxide films 12 with seams 13 due to differences in the state of such seams 13.

[0036] (This implementation method)

[0037] This embodiment is implemented to prevent the adverse conditions described in the comparison method from occurring. Similar to the comparison method, the processing is illustrated. Figure 2 The situation of wafer W. Figures 4A-4D This is a diagram showing the surface changes of the silicon oxide films 12a and 12b based on the etching process involved in this embodiment.

[0038] First, similar to the comparison method, HF gas and NH3 gas are supplied as processing gases to the wafer W stored in a processing container that has been degassed and set to a vacuum atmosphere, causing the surfaces of silicon oxide films 12a and 12b to transform and form an AFS layer 14. Figure 4A Furthermore, the processing gas selectively acts on the silicon oxide film 12 of the polycrystalline silicon film 11 and silicon oxide film 12 forming the sidewalls of the recess, thereby transforming it. The arrows on the dotted lines in the figure indicate the processing gas.

[0039] Then, the supply of processing gas to wafer W is stopped. During this process gas supply stoppage, the processing container is vented (pressure control process) to achieve a relatively high pressure inside the processing container, specifically higher than 200 Pa. On the other hand, a purge gas, which is an inactive gas, is supplied to remove any remaining processing gas inside the processing container.

[0040] Regarding AFS layer 14, the high pressure within the processing container suppresses rapid sublimation. Furthermore, as the wafer W is heated, AFS slightly sublimates from the surface of AFS layer 14 and is released into the nearby gas phase. Due to the flow of purge gas in the gas phase near the surface, the AFS concentration in that gas phase decreases. Therefore, to maintain a balance in the AFS concentration of that gas phase, sublimation of AFS from the surface of AFS layer 14 is promoted. In this way, with the supply of purge gas, the surface portion of AFS layer 14 continues to sublimate slowly. Figure 4BIn the diagram, solid lines represent purge gas, and dotted lines represent vaporized AFS. The process of supplying processing gas to form AFS layer 14 is designated as the first process, and the process of removing the surface portion of AFS layer 14 by supplying purge gas at a pressure higher than 200 Pa within the processing container is designated as the second process.

[0041] Before the AFS layer 14 disappears, the processing gas is supplied to the processing container again. Figure 4C That is, the first process is performed again. Because of the second process, the thickness of the AFS layer 14 is thinner than at the end of the first process, so the processing gas passes through the AFS layer 14 and acts on the surface of the underlying silicon oxide film 12, which changes to AFS. That is, the thickness of the AFS layer 14 increases. Then, the second process is performed again, thereby removing the surface layer of the AFS layer 14. The first and second processes are then repeated sequentially to advance etching below the silicon oxide film 12. In each first process, similar to the second first process described above, processing gas is supplied to the silicon oxide film 12, which is covered by the remaining AFS layer 14.

[0042] As the etching process progresses through a cycle consisting of the first and second steps, the silicon oxide film 12b is etched downwards. The surface of the AFS layer 14 approaches the formation site of the seam 13, creating a condition where process gas is supplied into the seam 13. Even in this condition, permeation is suppressed by the AFS layer 14, thereby preventing excessive flow of process gas into the depths of the seam 13. Furthermore, assuming the formed AFS flows on the wafer W, the lower part of the AFS layer 14 can penetrate into the seam 13. Figures 4A-4C The diagram shows the AFS layer 14 in such a state. In this case, the AFS layer 14 has a large thickness in the portion where the seam 13 is formed, thus more reliably preventing the permeation of the processing gas and more reliably preventing the flow of processing gas into the seam 13.

[0043] Based on the above, in the implementation of the above-described cycle in this embodiment, the portion where the seam 13 is formed, as shown in the comparative embodiment, is prevented from being etched at a relatively fast speed, and from being etched to cause the seam 13 to expand laterally. As a result, the etching uniformity between the silicon oxide films 12a and 12b is highly advanced, and the etching uniformity within the recesses of the silicon oxide film 12b is also highly advanced.

[0044] After repeating the first and second processes a predetermined number of times, the pressure inside the processing container is set to a specified pressure, and purge gas is supplied to the processing container to remove the AFS layer 14 from the wafer W, thus ending the etching process. Figure 4D The image shows the wafer W after etching is complete.

[0045] exist Figures 4A-4D The diagram illustrates how to suppress the deviation in etching amount between a silicon oxide film 12b with seam 13 and a silicon oxide film 12a without seam 13. Even between silicon oxide films 12 with seam 13, as described above, the deviation in etching amount is suppressed by preventing the portions with seam 13 from being etched at a faster rate.

[0046] Figure 5 This is a longitudinal sectional side view showing the substrate processing apparatus according to this embodiment. The substrate processing apparatus 1 includes a processing container 21, which contains a processing space for processing wafers W as described above. Figure 22 shows a wafer W transfer port with an opening in the side wall of the processing container 21, which is opened and closed by a gate valve 23. A stage 24 for holding wafers W is provided inside the processing container 21, and a lifting pin (not shown) is provided on the stage 24, the upper end of which protrudes into the upper surface of the stage 24. The wafers W are transferred between the stage 24 and the substrate transfer mechanism (not shown) via this lifting pin.

[0047] A temperature adjustment unit 25, for example a heater for resistance heating, is embedded in the stage 24. The wafer W placed on the stage 24 is heated to a set temperature, for example, 80°C or higher. A gas spray head 30 is provided on the upper side of the processing container 21, facing the stage 24. The gas spray head 30 is connected to the downstream side of gas supply paths 31 and 32. Gas supply paths 31A and 31B are branched on the upstream side of gas supply path 31, and gas supply paths 32A and 32B are branched on the upstream side of gas supply path 32. Furthermore, the upstream sides of gas supply paths 31A, 31B, 32A, and 32B are connected to gas supply sources 41, 42, 43, and 44 respectively via flow adjustment units 35. Each flow adjustment unit 35 is equipped with a valve and a mass flow controller to cut off the downstream supply of gas from gas supply sources 41 to 44 and to adjust the flow rate.

[0048] HF gas, Ar (argon) gas, NH3 gas, and N2 (nitrogen) gas are supplied from gas supply sources 41, 42, 43, and 44 to their respective connected flow paths. Furthermore, N2 gas and Ar gas constitute the purge gas described above. The flow adjustment units 35 described above allow for switching the gas supplied from these gas supply sources 41 to 44 to the processing container 21. The gas supply source 41 supplying HF gas and the flow adjustment unit 35 in gas supply path 31A, and the gas supply source 43 supplying NH3 gas and the flow adjustment unit 35 in gas supply path 32A, constitute the processing gas supply mechanism. The gas supply source 42 supplying Ar gas and the flow adjustment unit 35 in gas supply path 31B, and the gas supply source 44 supplying N2 gas and the flow adjustment unit 35 in gas supply path 32B, constitute the inactive gas supply mechanism.

[0049] The upstream end of the exhaust passage 51 is connected to the bottom of the processing container 21, and the processing container 21 has an opening. A valve V1 and an exhaust mechanism 52 are sequentially arranged downstream of the exhaust passage 51. The exhaust mechanism 52 consists of a vacuum pump or the like. The valve V1 is, for example, an APC (Auto Pressure Control) valve, which can be adjusted in its opening degree during wafer W processing according to a control signal output from the control unit 20 (described later), so that the pressure inside the processing container 21 reaches a preset value.

[0050] The substrate processing apparatus 1 includes a control unit 20, which functions as a computer. This control unit 20 includes a program, memory, and a CPU. Commands (steps) are programmed into the program to perform the described wafer W processing and wafer W transport. This program is stored on a storage medium, such as an optical disc, hard disk, optical disc drive, or DVD, and installed on the control unit 20. The control unit 20 outputs control signals to each part of the substrate processing apparatus 1 via this program, controlling the operation of each part. Operations controlled in this way include, for example, adjusting the temperature of the stage 24 (i.e., the temperature of the wafer W), operating the exhaust mechanism 52, adjusting the opening of valve V1 (i.e., adjusting the pressure within the processing container 21), and cutting off the supply of gases from gas supply sources 41-44 to the processing container 21 and adjusting the flow rate, as performed by the flow rate adjustment unit 35.

[0051] Next, the actions shown in the two cycles are illustrated. Figure 6 The timing diagram is used for... Figures 4A-4D The processing operations in the substrate processing apparatus 1 described herein will be explained. Regarding... Figure 6 The timing diagram shows the timing of the cutoff of the supply of processing gas to the processing container 21 and the change in the supply of purge gas. The timing of the cutoff of the processing gas supply is the timing of the opening and closing of the valve of the flow adjustment unit 35, and the timing of the change in the supply of purge gas can also be said to be the timing of the flow adjustment performed by the mass flow controller of the flow adjustment unit 35.

[0052] If passed Figures 4A-4DAs explained, the process involves alternating between a first step of supplying processing gas to wafer W and a second step of supplying purge gas under a relatively high-pressure, reduced-pressure atmosphere to remove AFS. In each of the first and second steps illustrated here, the processing container 21 is adjusted to the same pressure P0. The times t1~t2 and t3~t4 shown in the graph represent the periods for the first step, and the times t2~t3 and t4~t5 represent the periods for the second step. Hereinafter, the time for one cycle of the first step (i.e., the lengths of time t1~t2 and t3~t4 respectively) is sometimes referred to as the processing gas supply time, and the time for one cycle of the second step (i.e., the lengths of time t2~t3 and t4~t5 respectively) is referred to as the purge time. To prevent the silicon oxide film 12 from being exposed as described above, the purge time is set relatively short; therefore, the processing gas supply time is, for example, longer than the purge time.

[0053] Will Figure 2 The wafer W shown is placed into the processing container 21, placed on the stage 24, and heated to the aforementioned temperature. Then, HF and NH3 gases are supplied as processing gases, and Ar and N2 gases are supplied as purge gases into the processing container 21. The opening of valve V1 is adjusted to set the pressure inside the processing container 21 to P0. Figure 4A , Figure 5 (Time t1 in the text). The pressure P0 is, for example, above 800 Pa (6 Torr), and more specifically, for example, from 1000 Pa (7.5 Torr) to 4000 Pa (30 Torr), which is a pressure higher than the vapor pressure of AFS.

[0054] Next, the supply of processing gas is stopped, and the supply of purge gas is increased (time t2). As a result, the processing gas in the processing container 21 is purged, thus stopping the generation of new AFS, and removing the surface of the AFS layer 14. The removed AFS is discharged along with the purge gas. Figure 4B At time t3, after a predetermined time has elapsed from time t2, the processing gas is supplied to the processing container 21 again, and the supply of purge gas is reduced. At this time, the removal of the AFS layer 14 stops, the second process ends, and the second first process begins. The same actions as at times t1-t2 are performed from time t3 to t4, and the same actions as at times t2-t3 are performed from time t4 to t5.

[0055] An example of the volumetric flow rate (hereinafter referred to simply as flow rate) of each gas per unit time in the etching process of this embodiment will be described. In the first step described above, the flow rate of the processing gas is set in the range of 10 sccm to 1000 sccm, for example, the flow rate of NH3 gas is greater than the flow rate of HF gas. The flow rate of the purge gas in the first step is set in the range of 0 sccm to 10000 sccm, for example, the flow rate of N2 gas is set to approximately twice the flow rate of Ar gas. In the second step described above, the flow rates of the purge gases are each set in the range of 10 sccm to 25000 sccm, for example, the flow rate of N2 gas is set to approximately twice the flow rate of Ar gas. Furthermore, regarding the flow rate of the purge gas in the second step, it is preferable to set it to approximately twice or more than twice the flow rates of the processing gas and the purge gas in the first step.

[0056] (Modified Example)

[0057] The purging gas in this embodiment is not necessarily Ar and N2; either one or other inert gases may be used. The treatment gas is not limited to HF and NH3; any halogen-containing or alkaline gas is acceptable. The halogen-containing gas is not limited to fluorine-containing gases; gases containing other halogen molecules such as Cl (chlorine) and Br (bromine) may also be used. The same applies to alkaline gases.

[0058] Regarding the pressure of the first and second processes in this disclosure, setting it to the same pressure P0 is not a necessary condition; they can be different and can be appropriately set separately. Furthermore, in Figure 6 In the processing example shown, the amount of purge gas supplied is assumed to be different in the first process and the second process, but it can also be the same.

[0059] The surface shape of wafer W is not limited to Figure 1 , Figure 2 The shape shown can also have a silicon oxide film 12 provided on its surface instead of a polysilicon film 11. That is, it is not limited to etching the silicon oxide film 12 formed in the recess, but seams 13 are easily formed in the silicon oxide film 12 formed in the recess due to the film growth as described above. Therefore, this technique is particularly effective for etching the silicon oxide film 12 formed in the recess. In addition, the recess in which the silicon oxide film 12 is formed is not limited to opening upward (i.e., in the thickness direction of the wafer W), but can also open to the side (i.e., in the direction along the main surface of the wafer W).

[0060] Furthermore, the silicon-containing film used for etching is not limited to silicon oxide film 12; for example, it can also be a SiON film (silicon nitride film). When etching a SiON film in this way, AFS as a reaction product can be generated from the SiON film using the aforementioned processing gas, thus achieving the same effect as when etching the silicon oxide film 12. Alternatively, a SiN film (silicon nitride film) can also be used as the silicon-containing film. When etching this SiN film, AFS is generated from the SiN film by supplying NF3 gas, NH3 gas, and O2 gas as processing gases. Therefore, similar to the case of etching the silicon oxide film 12 described above, highly uniform etching can be performed within the plane of the wafer W.

[0061] It should be considered that the above-described embodiments involved in this disclosure are illustrative in all respects and not restrictive. The above-described embodiments may be omitted, substituted, modified, or combined in various ways without departing from the appended claims and their spirit.

[0062] [Evaluation Test]

[0063] The following describes the evaluation tests conducted on the etching process described in this disclosure.

[0064] <Evaluation Experiment 1>

[0065] As evaluation test 1, a first process was performed on multiple test substrates with a flatly formed silicon oxide film on their surface, ensuring the thickness of the AFS layer was within a specified range. Then, for each substrate, the time until the AFS layer was completely removed (defined as the purge out time) was investigated by varying the combination of pressure within the processing container and the flow rate of the purge gas supplied to the processing container. The pressure within the processing container was set to 1000 Pa (7.5 Torr), 2000 Pa (15 Torr), or 4000 Pa (30 Torr). Tests conducted with pressures set to 1000 Pa, 2000 Pa, and 4000 Pa were designated as evaluation tests 1-1, 1-2, and 1-3, respectively. Furthermore, as a comparative test, for one substrate with an AFS layer formed as described above, valve V1 was fully open, the pressure within the processing container was set to approximately 0 Torr, and the flow rate of the purge gas was set to 0 sccm to investigate the purge out time.

[0066] Figure 7This is a graph showing the results of evaluation tests 1-1 to 1-3 and comparative tests. The horizontal axis represents the flow rate of the purge gas, and the vertical axis represents the purge discharge time. As shown in the graph, according to the results of evaluation tests 1-1 to 1-3, the higher the pressure inside the processing container, the longer the purge discharge time; the lower the flow rate of the purge gas, the longer the purge discharge time. If the purge discharge time is too short, it is difficult to leave an appropriate amount of AFS on the silicon oxide film at the end of the second process as described in the embodiment. In the comparative test, the purge discharge time was as short as 10 seconds, so it was difficult to leave such residue. However, in evaluation tests 1-1 to 1-3, it was shown that by setting the flow rate of the purge gas appropriately, it was possible to leave AFS residue for a relatively long time. In evaluation tests 1-1 to 1-3, the pressure inside the processing container was set to 7.5 Torr or higher, so according to this evaluation test, it is preferable to set the pressure inside the processing container to 7.5 Torr or higher. Furthermore, it is believed that even a pressure slightly lower than 7.5 Torr is sufficient to allow the AFS to remain on the substrate for a sufficient time, depending on the setting of the purge gas flow rate. Therefore, it is believed that the pressure in the processing container during the second process should be, for example, 800 Pa (6 Torr) or higher.

[0067] <Evaluation Experiment 2>

[0068] As evaluation test 2, for those that passed this Figure 1 , Figure 2 Multiple substrates with the described surface structure underwent etching processing according to this embodiment. In this etching, the purging time for each substrate was varied, and 55 cycles consisting of a first process and a second process were performed. The purging time was set to 2 seconds, 2.4 seconds, 2.6 seconds, 2.7 seconds, 2.8 seconds, or 3.0 seconds. For the etched substrates, the surface shape, etching amount, and deviation of the surface height of the silicon oxide film 12 were evaluated by acquiring SEM images. Regarding the etching amount, it was obtained by measuring at multiple locations within a recess to obtain the average value of these measurements, and then using this average value to obtain the average value among the multiple recesses. Regarding the deviation of the surface height of the silicon oxide film 12, it was obtained by averaging the heights of multiple locations on the surface of the silicon oxide film 12 within a recess and calculating a 3σ value based on this average value obtained among the recesses, thus representing the deviation of the etching amount among the recesses.

[0069] As other processing conditions, the pressure inside the processing container was set to 4000 Pa (30 Torr), the wafer temperature was set to 130°C, and the processing gas supply time was 4 seconds. Regarding the purge gas flow rate in the second process, N2 gas was set to 14800 sccm and Ar gas was set to 6000 sccm.

[0070] Figure 8The graph shows the results of evaluation experiment 2. The horizontal axis of the graph represents the purging time [sec], the left vertical axis represents the etching amount [nm], and the right vertical axis represents the deviation of the surface height of the silicon oxide film 12 [nm]. As shown in the graph, it is confirmed that the etching amount increases with the increase of purging time. This is believed to be because the longer the purging time, the less AFS remains on the silicon oxide film 12 at the end of the second process (the smaller the thickness of the AFS layer 14), and therefore the greater the thickness of the silicon oxide film 12 that is transformed into the AFS layer 14 in the subsequent first process.

[0071] Furthermore, regarding the deviation in surface height of the silicon oxide film 12, the deviation decreases as the purging time shortens within a range of 2.6 seconds or more, but increases compared to a purging time of 2.6 seconds when the purging time is lower than 2.6 seconds. In other words, a purging time of 2.6 seconds best suppresses the deviation in etching amount between recesses. Additionally, based on SEM images, the flatness of the surface of the silicon oxide film 12 within the recesses was also confirmed to be highest when the purging time is set to 2.6 seconds. It is estimated that when the purging time is long within a range of 2.6 seconds or more, the amount of AFS residue on the silicon oxide film 12 is low during the first process (the thickness of the AFS layer 14 is small), therefore, as explained in the comparison method, the etching rate at the formation portion of the seam 13 increases, thereby increasing the deviation in surface height of the silicon oxide film 12. When the purging time is shorter than 2.6 seconds, it is believed that the amount of AFS residue on the silicon oxide film 12 is too large during the first process (the thickness of AFS layer 14 is too large), which greatly hinders the permeation of the processing gas in a part of the recess, thus causing a deviation.

[0072] As described above, evaluation test 2 confirmed that the purging time has an appropriate range. The preferred purging time may be affected by surface shape, processing space volume, wafer temperature, processing gas supply conditions, etc., but in this evaluation test it was a relatively short time of 2.6 seconds, so it is considered to be less than 30 seconds, and even if it is longer, it is less than 1 minute.

[0073] Explanation of reference numerals in the attached figures

[0074] W: Wafer

[0075] 12: Silicon oxide film

[0076] 14: AFS layer

[0077] 21: Handling Containers

Claims

1. A substrate processing method, comprising the following steps: The substrate with a silicon-containing film formed on its surface is stored in the processing container; In the first step, a processing gas containing halogenated gas and alkaline gas is supplied into the processing container to convert the silicon-containing membrane into reaction products. In the second step, in order to remove a portion of the reaction product, the supply of inactive gas to the processing container and the venting of the processing container are carried out while the supply of the processing gas to the processing container is stopped. Repeating the process, alternately repeating the first process and the second process; and In a pressure control step, the pressure inside the processing container is set to a level higher than 200 Pa in each of the second steps, so that the processing gas is supplied to the substrate containing the reaction products in the second and subsequent first steps of the repeated steps.

2. The substrate processing method according to claim 1, wherein, The pressure control process is a process of setting the pressure inside the processing container to a pressure of 800 Pa or higher.

3. The substrate processing method according to claim 2, wherein, The silicon-containing film is a silicon oxide film.

4. The substrate processing method according to claim 3, wherein, The halogen-containing gas is hydrogen fluoride gas, and the alkaline gas is ammonia gas.

5. The substrate processing method according to claim 4, wherein, The silicon-containing film is formed within the recess formed on the substrate. The first step is a step of selectively converting the silicon-containing film in such a way that the sidewalls of the recess and the silicon-containing film in the silicon-containing film are selectively removed in the second step.

6. The substrate processing method according to claim 5, wherein, The silicon-containing membrane contains voids or joints where the interfaces of the silicon-containing membranes are joined together before being supplied with the processing gas.

7. A substrate processing apparatus comprising: A processing container, which is stored on a substrate with a silicon-containing film formed on its surface; A processing gas supply mechanism supplies processing gas containing halogenated gas and alkaline gas into the processing container; An inactive gas supply mechanism that supplies inactive gas into the processing container; An exhaust mechanism that exhausts air from the processing container; and The control unit outputs control signals to execute a first step, a second step, a repeating step, and a pressure control step. In the first step, the processing gas is supplied to the processing container to convert the silicon-containing film into reaction products. In the second step, in order to remove a portion of the reaction products, the supply of inactive gas to the processing container and the venting of the processing container are performed while the supply of the processing gas to the processing container is stopped. In the repeating step, the first step and the second step are repeated alternately. In the pressure control step, the pressure inside the processing container is set to a pressure higher than 200 Pa in each of the second steps, so that the processing gas is supplied to the substrate containing the residual reaction products in the second and subsequent first steps of the repeating step.

8. The substrate processing apparatus according to claim 7, wherein, In the pressure control step, the pressure inside the processing container is set to 800 Pa or higher in each of the second steps.

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