Substrate processing method and substrate processing apparatus

Abstract

To perform a removal process with high uniformity at each portion within a plane of a substrate when removing a silicon-containing film formed on a surface of the substrate.SOLUTION: An etching method includes the steps of: storing a substrate having a silicon-containing film formed on a surface thereof in a processing container, supplying a processing gas containing a halogen-containing gas and a basic gas, and modifying the silicon-containing film to generate a reaction product; supplying an inert gas into the processing container and exhausting the inside of the processing container in a state where the supply of the processing gas into the processing container is stopped in order to remove a part of the reaction product; alternately repeating the first step and the second step; and setting a pressure in the processing container to a pressure higher than 200 Pa in each of the second steps so that the processing gas is supplied to the substrate on which the reaction product remains in the first steps in second and subsequent rounds in the repeating step.SELECTED DRAWING: Figure 4B

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, etching of a silicon-containing film such as an SiO2 film (silicon oxide film) formed on the surface of a semiconductor wafer (hereinafter referred to as a wafer) serving as a substrate may be performed. Patent Document 1 describes that when etching an SiO2 film by sequentially repeating a first step of supplying a basic gas to the substrate and a second step of supplying a fluorine-containing gas to the wafer, the inside of a processing vessel containing the substrate is purged after the second step is completed and before the first step is started.

[0003] Patent Document 2 describes a method in which a process gas containing a halogen-containing gas and a basic gas is supplied to a wafer to generate a reaction product on the surface of the SiO2 film, and then the pressure inside a process vessel containing the wafer is reduced to 0 to 200 Pa so that some of the reaction product remains on the SiO2 film and other parts are removed.Then, the pressure inside the process vessel is increased, and the process gas is supplied to the wafer again to remove the SiO2 film. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-180281 [Patent Document 2] Patent Publication No. 2021-118250 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure provides a technique for removing a silicon-containing film formed on a surface of a substrate, which is capable of performing a highly uniform removal process in each part of the surface of the substrate. [Means for solving the problem]

[0006] The etching method of the present disclosure includes the steps of: storing a substrate having a silicon-containing film formed on a surface thereof in a processing chamber; a first step of supplying a processing gas containing a halogen-containing gas and a basic gas into the processing vessel to modify the silicon-containing film and generate a reaction product; a second step of supplying an inert gas into the processing vessel and evacuating the processing vessel while stopping the supply of the processing gas into the processing vessel in order to remove a portion of the reaction product; a repeating step of alternately repeating the first step and the second step; a pressure control step of maintaining a pressure in the processing chamber higher than 200 Pa in each of the second steps so that the processing gas is supplied to the substrate on which the reaction product remains in the second or subsequent first steps in the repeating step; Includes. [Effects of the Invention]

[0007] The present disclosure makes it possible to perform a highly uniform removal process in each part of the surface of a substrate when removing a silicon-containing film formed on the surface of the substrate. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a longitudinal cross-sectional side view illustrating a surface structure of a substrate before etching processing according to an embodiment. [Figure 2] 1 is an enlarged longitudinal cross-sectional side view illustrating a portion of the surface structure of a substrate before etching processing. [Figure 3A] FIG. 10 is a diagram showing changes in the surface of a silicon oxide film caused by etching treatment in a comparative example. [Figure 3B] FIG. 10 is a diagram showing changes in the surface of a silicon oxide film caused by etching treatment in a comparative example. [Figure 4A] 1A and 1B are diagrams illustrating changes in the surface of a silicon oxide film due to an etching process according to an embodiment. [Figure 4B]1A and 1B are diagrams illustrating changes in the surface of a silicon oxide film due to an etching process according to an embodiment. [Figure 4C] 1A and 1B are diagrams illustrating changes in the surface of a silicon oxide film due to an etching process according to an embodiment. [Figure 4D] 1A and 1B are diagrams illustrating changes in the surface of a silicon oxide film due to an etching process according to an embodiment. [Figure 5] 1 is a vertical sectional side view showing a substrate processing apparatus according to an embodiment; [Figure 6] 4 is a time chart showing a processing operation in the substrate processing apparatus according to the embodiment. [Figure 7] 1 is a graph showing the results of evaluation test 1. [Figure 8] 10 is a graph showing the results of evaluation test 2. DETAILED DESCRIPTION OF THE INVENTION

[0009] (surface structure of the board) FIG. 1 is a longitudinal side view illustrating the surface structure of a substrate before etching in this embodiment. As shown in the figure, in the surface layer of the wafer W, a number of protrusions, each made of, for example, a polysilicon film 11, are formed on an underlying film 10 and aligned horizontally, thereby forming a plurality of recesses. The polysilicon film 11 therefore forms the sidewalls of the recesses. A silicon oxide film 12 is formed within each recess. In this embodiment, etching is performed so that the bottom end of each silicon oxide film 12 remains. This etching is selective to the polysilicon film 11. The underlying film 10 is not shown in any figures other than FIG. 1.

[0010] When the silicon oxide film 12 is formed in the recess, the silicon oxide film 12 grows from various parts of the sidewalls of the polysilicon film 11 and joins together, which may result in the formation of a seam 13 in the horizontal center of the silicon oxide film 12. This seam 13 is a junction between the interfaces of the silicon oxide film 12 or a void formed in the silicon oxide film 12. Hereinafter, the direction from the front side to the back side of the wafer W may also be referred to as the up-down direction or the height direction. The size of the seam 13, such as the horizontal length (width) and height length, and its position in the height direction, vary between recesses.

[0011] (Comparative form) To clarify the effects of the etching method of the present disclosure, a comparative etching process will be described first. FIG. 2 shows a wafer W before processing. For the purposes of the description, two silicon oxide films 12a and 12b are shown as the silicon oxide film 12, with no seam 13 formed in the silicon oxide film 12a and a seam 13 formed in the silicon oxide film 12b. In both the process of this comparative example and the processes of the embodiments described below, the wafer W is stored in a processing vessel and adjusted to a predetermined temperature, and processing is performed by supplying various gases into the processing vessel. During processing of the wafer W, the amount of exhaust gas from the processing vessel is adjusted to create a vacuum atmosphere at a desired pressure.

[0012] 3A and 3B show the surface changes of silicon oxide films 12a and 12b due to an etching process according to a comparative example. First, a process gas is supplied into a process chamber. This process gas is a halogen-containing gas and a basic gas, specifically, HF (hydrogen fluoride) gas as the halogen-containing gas and NH3 (ammonia) gas as the basic gas. The surface portions of the silicon oxide films 12a and 12b react with the process gas and are transformed into the reaction product ammonium fluorosilicate (AFS), forming an AFS layer. As this reaction progresses, the thickness of the AFS layer increases.

[0013] When the AFS layer is relatively thin, the processing gas can penetrate the AFS layer and alter the silicon oxide films 12a and 12b. However, as the AFS layer becomes thicker, such penetration becomes more difficult. Therefore, after supplying the processing gas for a predetermined time, the supply of processing gas is stopped to maintain a relatively low pressure inside the processing chamber. This causes the AFS to sublimate, removing the AFS layer and exposing the surfaces of the silicon oxide films 12a and 12b. By alternately repeating this supply of processing gas and the removal of the AFS layer to expose the surface of the silicon oxide film 12, downward etching of each of the silicon oxide films 12a and 12b progresses (Figure 3A). Note that the dotted arrows in the figure indicate the sublimated AFS.

[0014] However, as etching progresses in this manner, when processing gas is supplied to the portion of silicon oxide film 12b where seam 13 has formed, the processing gas flows downward within seam 13 (specifically, the voids forming seam 13 and the minute gaps between the interfaces of silicon oxide film 12). The portion around seam 13 then transforms into AFS, and then sublimes. In other words, etching progresses downward in silicon oxide film 12b more than in silicon oxide film 12a. That is, etching progresses relatively quickly in the portion where seam 13 has formed.

[0015] Therefore, as shown in Figure 3B, there is a risk that the etching amount will differ relatively greatly between the silicon oxide films 12a and 12b (i.e., the surface heights will differ relatively greatly between the silicon oxide films 12a and 12b) at the end of etching. Furthermore, when the periphery of the seam 13 in the silicon oxide film 12b is etched as described above, the seam 13 is etched so as to expand laterally. Therefore, the central portions on both sides of the recess are etched relatively largely, and there is a risk that the surface heights of the respective portions of the silicon oxide film 12b will vary relatively greatly at the end of etching, as shown in Figure 3B.

[0016] Assuming that a large number of recesses are formed in the wafer W, as described above, the width, height, and height position of the seam in the silicon oxide film 12 within the recesses may vary among the recesses. Therefore, although Fig. 3 shows that the etching amount varies between the silicon oxide film 12b in which the seam 13 is formed and the silicon oxide film 12a in which the seam 13 is not formed, the above-mentioned etching amount may also vary among the silicon oxide films 12 in which the seam 13 is formed due to differences in the state of the seam 13.

[0017] (Present embodiment) This embodiment is performed to prevent the problems described in the comparative embodiment from occurring. As in the comparative embodiment, the case where the wafer W shown in FIG. 2 is processed will be described as an example. FIGS. 4A to 4D are diagrams showing changes in the surfaces of silicon oxide films 12a and 12b due to the etching process according to this embodiment.

[0018] First, as in the comparative example, HF gas and NH3 gas are supplied as processing gases to a wafer W stored in a processing chamber that has been evacuated to a vacuum atmosphere, thereby modifying the surfaces of silicon oxide films 12a and 12b and forming an AFS layer 14 (FIG. 4A). Note that the processing gas selectively acts on and modifies the silicon oxide film 12 of the polysilicon film 11 and silicon oxide film 12 that form the sidewall of the recess. The chain arrows in the figure indicate the processing gas.

[0019] Thereafter, the supply of the processing gas to the wafer W is stopped. While the supply of the processing gas is stopped, the processing vessel is evacuated to a relatively high pressure, specifically, a pressure higher than 200 Pa (pressure control process). Meanwhile, a purge gas, which is an inert gas, is supplied to remove the processing gas remaining in the processing vessel.

[0020] The AFS layer 14 is prevented from rapidly sublimating because the pressure inside the processing vessel is relatively high. When the wafer W is heated, a small amount of AFS sublimes from the surface of the AFS layer 14 and is released into the gas phase near the surface. The flow of purge gas in the gas phase near the surface reduces the AFS concentration in the gas phase. Therefore, sublimation of AFS from the surface of the AFS layer 14 is promoted so that the equilibrium of the AFS concentration in the gas phase is maintained. Thus, while the purge gas is being supplied, the surface portion of the AFS layer 14 continues to sublimate slowly. In FIG. 4B, the purge gas is indicated by a solid line, and the vaporized AFS is indicated by a dotted line. Hereinafter, the process of supplying the processing gas to form the AFS layer 14 will be referred to as the first process, and the process of removing the surface portion of the AFS layer 14 by increasing the pressure inside the processing vessel to more than 200 Pa and supplying the purge gas will be referred to as the second process.

[0021] Before the AFS layer 14 disappears, the supply of processing gas into the processing chamber is resumed ( FIG. 4C ). That is, the first step is performed again. Because the second step has made the AFS layer 14 thinner than at the end of the first step, the processing gas penetrates the AFS layer 14 and acts on the surface layer of the silicon oxide film 12 underneath, converting the surface layer into AFS. That is, the thickness of the AFS layer 14 increases. The second step is then performed again, removing the surface layer of the AFS layer 14. The first and second steps are then repeated in sequence, etching the silicon oxide film 12 downward. In each first step, processing gas is supplied to the silicon oxide film 12, which remains covered with the AFS layer 14, as in the second first step described above.

[0022] As etching progresses by repeating the cycle consisting of the first and second steps, etching of the silicon oxide film 12b progresses downward, and the surface of the AFS layer 14 approaches the portion where the seam 13 is formed, resulting in a state in which the process gas is supplied into the seam 13. Even in this state, the AFS layer 14 suppresses permeation, preventing a large amount of process gas from flowing deep into the seam 13. Furthermore, the formed AFS flows on the wafer W, and the lower portion of the AFS layer 14 can penetrate into the seam 13. FIGS. 4A to 4C show the AFS layer 14 in such a state. In this case, the thickness of the AFS layer 14 is large in the portion where the seam 13 is formed, so that permeation of the process gas is more reliably prevented, and the process gas is more reliably prevented from flowing into the seam 13.

[0023] For these reasons, during the above cycle in this embodiment, the area where seam 13 is formed is prevented from being etched at a relatively high rate, as shown in the comparative example, and etching that would laterally expand seam 13 is prevented. As a result, etching proceeds with high uniformity between silicon oxide films 12a and 12b, and also in each portion of the recess where silicon oxide film 12b is formed.

[0024] After the cycle of the first and second steps is repeated a predetermined number of times, the pressure inside the processing chamber is increased to a predetermined level and a purge gas is supplied into the processing chamber, thereby removing the AFS layer 14 from the wafer W and completing the etching process. Figure 4D shows the wafer W after etching has been completed.

[0025] 4A to 4D show that variation in the amount of etching is suppressed between silicon oxide film 12b on which seam 13 is formed and silicon oxide film 12a on which seam 13 is not formed. As described above, the high-speed etching of the portion on which seam 13 is formed is suppressed, thereby suppressing variation in the amount of etching even between silicon oxide films 12 on which seam 13 is formed.

[0026] 5 is a longitudinal side view showing a substrate processing apparatus according to this embodiment. As described above, the substrate processing apparatus 1 includes a processing chamber 21 that contains a processing space for processing a wafer W. In the figure, reference numeral 22 denotes a transfer port for the wafer W that opens into the sidewall of the processing chamber 21 and is opened and closed by a gate valve 23. A stage 24 on which the wafer W is placed is provided within the processing chamber 21, and the stage 24 is provided with lift pins (not shown), the upper ends of which protrude and retract into the upper surface of the stage 24. The wafer W is transferred between the stage 24 and a substrate transfer mechanism (not shown) via the lift pins.

[0027] A temperature adjustment unit 25, which is, for example, a heater that performs resistance heating, is embedded in the stage 24, and heats the wafer W placed on the stage 24 to a set temperature of, for example, 80°C or higher. A gas shower head 30 is provided at an upper portion of the processing chamber 21, facing the stage 24. The downstream sides of gas supply paths 31 and 32 are connected to the gas shower head 30. The upstream side of the gas supply path 31 branches to form gas supply paths 31A and 31B, and the upstream side of the gas supply path 32 branches to form gas supply paths 32A and 32B. The upstream sides of the gas supply paths 31A, 31B, 32A, and 32B are connected to gas supply sources 41, 42, 43, and 44, respectively, via flow rate adjustment units 35. Each flow rate adjustment unit 35 includes a valve and a mass flow controller, and controls the supply and cutoff of gases supplied from the gas supply sources 41 to 44 to the downstream side and adjusts the flow rate.

[0028] Gas supply sources 41, 42, 43, and 44 supply HF gas, Ar (argon) gas, NH3 gas, and N2 (nitrogen) gas to their respective connected flow paths. N2 gas and Ar gas constitute the aforementioned purge gas. The flow rate regulators 35 can switch the gases supplied from these gas supply sources 41 to 44 into the processing chamber 21. The gas supply source 41 and flow rate regulator 35 for supplying HF gas in the gas supply path 31A, and the gas supply source 43 and flow rate regulator 35 for supplying NH3 gas in the gas supply path 32A, correspond to a processing gas supply mechanism. The gas supply source 42 and flow rate regulator 35 for supplying Ar gas in the gas supply path 31B, and the gas supply source 44 and flow rate regulator 35 for supplying N2 gas in the gas supply path 32B, correspond to an inert gas supply mechanism.

[0029] The upstream end of an exhaust path 51 is connected to the bottom of the processing vessel 21 and opens into the processing vessel 21. A valve V1 and an exhaust mechanism 52 are sequentially provided on the exhaust path 51 toward the downstream side, and the exhaust mechanism 52 is configured by a vacuum pump or the like. The valve V1 is, for example, an APC (Auto Pressure Control) valve, and its opening degree can be changed during processing of the wafer W in accordance with a control signal output from the control unit 20, which will be described later, so that the pressure inside the processing vessel 21 becomes a preset value.

[0030] The substrate processing apparatus 1 includes a control unit 20, which is a computer, and the control unit 20 includes a program, a memory, and a CPU. The program includes instructions (steps) for performing the aforementioned wafer W processing and wafer W transfer. 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 installed in the control unit 20. The control unit 20 outputs control signals to each component of the substrate processing apparatus 1 based on the program, thereby controlling the operation of each component. The operations controlled in this manner 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 the valve V1 (i.e., adjusting the pressure inside the processing chamber 21), and supplying and cutting off the supply of each gas from the gas supply sources 41 to 44 into the processing chamber 21 by the flow rate adjustment unit 35, adjusting the flow rate, etc.

[0031] 4A to 4D, the processing operation of the substrate processing apparatus 1 for performing the processing described with reference to FIGS. 4A to 4D will be described using the time chart of FIG. 6, which shows two cycles of operation. The time chart of FIG. 6 shows the timing of supply and cutoff of the processing gas into the processing vessel 21 and the timing of changes in the supply amount of the purge gas. The timing of this supply and cutoff of the processing gas corresponds to the timing of opening and closing the valve of the flow rate adjuster 35, and the timing of changes in the supply amount of the purge gas corresponds to the timing of flow rate adjustment by the mass flow controller of the flow rate adjuster 35.

[0032] As described with reference to FIGS. 4A to 4D, the process alternates between a first process in which a process gas is supplied to the wafer W and a second process in which a purge gas is supplied in a relatively high-pressure, reduced-pressure atmosphere to remove the AFS. In the illustrated first and second processes, the interior of the process vessel 21 is adjusted to the same pressure P0. The first process is performed from time t1 to time t2 and from time t3 to time t4, respectively, during the time periods indicated in the chart. The second process is performed from time t2 to time t3 and from time t4 to time t5, respectively. Hereinafter, the time during which the first process is performed in one cycle (i.e., the length between times t1 and t2 and between times t3 and t4) may be referred to as the process gas supply time, and the second process is performed in one cycle (i.e., the length between times t1 and t2 and between times t3 and t4) may be referred to as the purge time. As described above, the second step is performed so as to prevent the silicon oxide film 12 from being exposed, and therefore the purge time is set to be relatively short. Therefore, the processing gas supply time is, for example, longer than the purge time.

[0033] 2 is loaded into the processing chamber 21, placed on the stage 24, and heated to the above-mentioned temperature. Then, HF gas and NH3 gas as processing gases and Ar gas and N2 gas as purge gases are supplied into the processing chamber 21, and the opening of the valve V1 is adjusted to set the pressure inside the processing chamber 21 to P0 (time t1 in FIGS. 4A and 5). The pressure P0 is, for example, 800 Pa (6 Torr) or higher, more specifically, for example, 1000 Pa (7.5 Torr) to 4000 Pa (30 Torr), which is a pressure range higher than the vapor pressure of the AFS.

[0034] Next, the supply of the processing gas is stopped, and the supply rate of the purge gas is increased (time t2). As a result, the processing gas in the processing vessel 21 is purged, stopping the generation of new AFS, and the surface of the AFS layer 14 is removed, and the removed AFS is exhausted together with the purge gas (FIG. 4B). At time t3, a preset time after time t2, the supply of the processing gas into the processing vessel 21 is resumed, and the supply rate of the purge gas is reduced. At this time, the removal of the AFS layer 14 is stopped, the second step is completed, and a second round of the first step is started. From time t3 to t4, the same operations as from time t1 to t2 are performed, and from time t4 to t5, the same operations as from time t3 to t4 are performed.

[0035] Regarding an example of the volumetric flow rate per unit time (hereinafter simply referred to as flow rate) of each gas in the etching process of this embodiment, the flow rate of the process gas in the first step is set in the range of 10 sccm to 1000 sccm, with the flow rate of NH gas being higher than that of HF gas, for example. The flow rate of the purge gas in the first step is set in the range of 0 sccm to 10,000 sccm, with the flow rate of N gas being approximately twice that of Ar gas, for example. The flow rates of the purge gas in the second step are each set in the range of 10 sccm to 25,000 sccm, with the flow rate of N gas being approximately twice that of Ar gas, for example. The flow rate of the purge gas in the second step is preferably approximately twice or more than twice that of the process gas and purge gas in the first step.

[0036] (Variation) The purge gas in this embodiment does not necessarily have to be Ar gas and N2 gas; only one of these gases may be used, or another inert gas may be used. The process gas is not limited to HF gas and NH3 gas, but may be a halogen-containing gas or a basic gas. The halogen-containing gas is not limited to a fluorine-containing gas, but may also be a halogen-containing gas containing other halogen molecules such as Cl (chlorine) or Br (bromine). The same applies to the basic gas.

[0037] Regarding the pressures in the first and second steps of the present disclosure, it is not essential that they be the same as the pressure P0, but they may be different and can be set appropriately for each step. Also, in the processing example shown in Fig. 6, the supply amount of purge gas is different between the first step and the second step, but it may be the same.

[0038] The surface shape of the wafer W is not limited to the shapes shown in FIGS. 1 and 2 . For example, the polysilicon film 11 may not be provided on the surface, and a silicon oxide film 12 may be uniformly provided. In other words, the present technology is not limited to etching the silicon oxide film 12 formed in the recesses, but as described above, seams 13 are likely to form in the silicon oxide film 12 formed in the recesses due to film growth. Therefore, the present technology is particularly effective for etching the silicon oxide film 12 formed in the recesses. Furthermore, the recesses having the silicon oxide film 12 formed therein are not limited to opening upward (i.e., in the thickness direction of the wafer W), but may also open sideways (i.e., in the direction along the main surface of the wafer W).

[0039] Furthermore, the silicon-containing film to be etched is not limited to the silicon oxide film 12, but may be, for example, a SiON film (silicon oxynitride film). Even when etching a SiON film, the AFS can be generated as a reaction product from the SiON film by using the process gas described above, thereby achieving the same effect as when etching the silicon oxide film 12. Furthermore, the silicon-containing film may be a SiN film (silicon nitride film). When etching this SiN film, AFS is generated from the SiN film by supplying NF3 gas, NH3 gas, and O2 gas as process gases. This allows for highly uniform etching across the wafer W, similar to the etching of the silicon oxide film 12 described above.

[0040] The above-described embodiments of the present disclosure should be considered to be illustrative in all respects and not restrictive, and various omissions, substitutions, modifications, and combinations may be made in the above-described embodiments without departing from the scope and spirit of the appended claims.

[0041] [Evaluation test] The following describes evaluation tests conducted on the etching process of the present disclosure. Evaluation Test 1 In Evaluation Test 1, the first process was performed on multiple test substrates with a flat silicon oxide film on their surfaces to achieve a predetermined AFS layer thickness. The combination of the pressure in the processing chamber and the flow rate of the purge gas supplied into the processing chamber was changed for each substrate, and the time required for the AFS layer to be completely removed (referred to as the purge-out time) was measured for each substrate. The pressure in the processing chamber was set to 1000 Pa (7.5 Torr), 2000 Pa (15 Torr), or 4000 Pa (30 Torr). The tests performed at these pressure settings of 1000 Pa, 2000 Pa, and 4000 Pa were designated Evaluation Tests 1-1, 1-2, and 1-3, respectively. As a comparative test, the purge-out time was measured for one of the substrates with the AFS layer formed as described above, with valve V1 fully opened to set the pressure in the processing chamber to approximately 0 Torr and the purge gas flow rate to 0 sccm.

[0042] FIG. 7 is a graph showing the results of Evaluation Tests 1-1 to 1-3 and the Comparative Test. The horizontal axis represents the purge gas flow rate, and the vertical axis represents the purge-out time. As shown in the graph, the results of Evaluation Tests 1-1 to 1-3 reveal that the higher the pressure in the processing vessel, the longer the purge-out time, and the lower the purge gas flow rate, the longer the purge-out time. If the purge-out 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 short purge-out time of 10 seconds makes it difficult to leave such an amount of AFS. However, Evaluation Tests 1-1 to 1-3 demonstrated that it is possible to leave AFS for a relatively long time by appropriately setting the purge gas flow rate. In Evaluation Tests 1-1 to 1-3, the pressure in the processing vessel was set to 7.5 Torr or higher. This Evaluation Test 1 demonstrates that it is preferable to set the pressure in the processing vessel to 7.5 Torr or higher. It is believed that even at a pressure slightly lower than 7.5 Torr, the AFS can remain on the substrate for a sufficient period of time depending on the flow rate of the purge gas. Therefore, it is believed that the pressure inside the processing vessel during the second step should be, for example, 800 Pa (6 Torr) or higher.

[0043] Evaluation Test 2 In Evaluation Test 2, the etching process of this embodiment was performed on multiple substrates having the surface layer structure described in FIGS. 1 and 2. In this etching, a cycle consisting of the first and second steps was performed 55 times, with the purge time varied for each substrate. The purge time was set to 2, 2.4, 2.6, 2.7, 2.8, or 3.0 seconds. The surface shape, etching amount, and surface height variation of the silicon oxide film 12 were evaluated by acquiring SEM images of the substrates after the etching process. The etching amount was measured at multiple positions within a single recess, the average value of the measured values ​​was calculated, and then the average value was used to calculate the average value across multiple recesses. The variation in the surface height of the silicon oxide film 12 was calculated as a 3σ value obtained by averaging the heights of multiple positions on the surface of the silicon oxide film 12 within a single recess and then averaging the average values ​​across the recesses. This value represents the variation in the etching amount across the recesses.

[0044] Other processing conditions were a pressure in the processing chamber of 4000 Pa (30 Torr), a wafer temperature of 130° C., and a processing gas supply time of 4 seconds. The flow rates of the purge gases in the second step were 14800 sccm for N2 gas and 6000 sccm for Ar gas.

[0045] 8 is a graph showing the results of Evaluation Test 2, with the horizontal axis representing purge time [sec], the vertical axis on the left representing the etching amount [nm], and the vertical axis on the right representing the variation in surface height [nm] of the silicon oxide film 12. As shown in the figure, it was confirmed that the etching amount increased as the purge time increased. This is thought to be because the longer the purge time, the smaller the amount of AFS remaining on the silicon oxide film 12 at the end of the second step (the smaller the thickness of the AFS layer 14), and therefore the thickness of the silicon oxide film 12 that is transformed into the AFS layer 14 in the subsequent first step increases.

[0046] The variation in the surface height of the silicon oxide film 12 decreased as the purge time decreased within the range of 2.6 seconds or more. However, when the purge time was shorter than 2.6 seconds, the variation in the etching amount between the recesses was greater than when the purge time was 2.6 seconds. In other words, the variation in the etching amount between the recesses was minimized with a purge time of 2.6 seconds. Furthermore, SEM images confirmed that the surface flatness of the silicon oxide film 12 within the recesses was also highest with a purge time of 2.6 seconds. When the purge time is longer within the range of 2.6 seconds or more, the amount of AFS remaining on the silicon oxide film 12 during the first step is small (the thickness of the AFS layer 14 is small). This increases the etching rate in the area where the seam 13 is formed, as described in the comparative example, presumably resulting in the increase in the variation in the surface height of the silicon oxide film 12. When the purge time is shorter than 2.6 seconds, it is thought that the amount of AFS remaining on the silicon oxide film 12 during the first process is too large (the thickness of the AFS layer 14 is too large), which significantly hinders the permeation of the processing gas in some recesses, resulting in variations. As described above, it was confirmed that there is an appropriate range for the purge time from Evaluation Test 2. The preferable purge time can be affected by factors such as the surface shape, the volume of the processing space, the wafer temperature, and the processing gas supply conditions, but since the time was relatively short at 2.6 seconds in this evaluation test, it is thought that the appropriate purge time should be 30 seconds or less, and at most 1 minute or less. [Explanation of symbols]

[0047] W wafer 12 Silicon oxide film 14 AFS layer 21 Processing container

Claims

1. storing the substrate having the silicon-containing film formed on the surface thereof in a processing chamber; a first step of supplying a processing gas containing a halogen-containing gas and a basic gas into the processing vessel to modify the silicon-containing film and generate a reaction product; a second step of supplying an inert gas into the processing vessel and evacuating the processing vessel while stopping the supply of the processing gas into the processing vessel in order to remove a portion of the reaction product; a repeating step of alternately repeating the first step and the second step; a pressure control step of maintaining a pressure in the processing chamber higher than 200 Pa in each of the second steps so that the processing gas is supplied to the substrate on which the reaction product remains in the second or subsequent first steps in the repeating step; A substrate processing method comprising:

2. 2. The substrate processing method according to claim 1, wherein the pressure control step is a step of controlling the pressure inside the processing vessel to 800 Pa or more.

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

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

5. the silicon-containing film is formed in a recess formed in the substrate; 5. The substrate processing method according to claim 4, wherein the first step is a step of selectively modifying the silicon-containing film so that the silicon-containing film is selectively removed from the sidewall of the recess and the silicon-containing film in the second step.

6. 6. The substrate processing method according to claim 5, wherein the silicon-containing film before the processing gas is supplied includes voids or bonding portions between interfaces of the silicon-containing film.

7. a processing vessel for storing a substrate having a silicon-containing film formed on a surface thereof; a processing gas supply mechanism for supplying a processing gas containing a halogen-containing gas and a basic gas into the processing vessel; an inert gas supply mechanism for supplying an inert gas into the processing chamber; an exhaust mechanism for exhausting the inside of the processing vessel; a control unit that outputs a control signal to execute a first step of supplying the processing gas into the processing vessel to modify the silicon-containing film and generate a reaction product; a second step of supplying an inert gas into the processing vessel and evacuating the processing vessel while stopping the supply of the processing gas into the processing vessel in order to remove a portion of the reaction product; a repeating step of alternately repeating the first step and the second step; and a pressure control step of maintaining a pressure in the processing vessel at a level higher than 200 Pa in each of the second steps so that the processing gas is supplied to the substrate on which the reaction product remains in the first step from the second time onwards in the repeating step. A substrate processing apparatus comprising:

8. 8. The substrate processing apparatus according to claim 7, wherein the pressure control step maintains the pressure inside the processing vessel at 800 Pa or higher in each of the second steps.

Images