Substrate processing method and substrate processing apparatus

Abstract

To suppress surface roughness after etching of a silicon film forming a recess, and control the shape of the recess.SOLUTION: A first process of supplying process gas including halogen-containing gas and basic gas to a substrate on which a recess, in which sidewalls are formed of a silicon film and a depth wall is formed of a germanium-containing film, is formed, and altering the surface of the silicon film to generate a reaction product; a second process of removing the reaction product to widen the depth of the recess; a process of performing a cycle consisting of the first process and the second process a plurality of times; and a process of performing the first process of the cycle performed first under a first processing condition, and performing the first process of the cycle performed later under a second processing condition different from the first processing condition are executed.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] In manufacturing a semiconductor device, there are cases where the Si film among the Si film and the SiGe film formed on the surface of a semiconductor wafer (hereinafter referred to as a wafer), which is a substrate, is selectively etched. For example, in Patent Document 1, it is described that by using F2 gas and NH3 gas as etching gases and setting the ratio of NH3 gas to the etching gas to a predetermined value, the above-mentioned selective etching is performed.

Prior Art Documents

Patent Documents

[0003] [[ID=2;3]]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides a technique capable of suppressing the surface roughness after etching and controlling the shape of a recess for a silicon film forming the recess.

Means for Solving the Problems

[0005] The substrate processing method of the present disclosure supplies a processing gas containing a halogen-containing gas and a basic gas to a substrate in which a recess having side walls formed of a silicon film and a back wall formed of a germanium-containing film is formed, to alter the surface of the silicon film and generate reaction products in a first step; a second step of removing the reaction products to widen the width of the recess; a step of performing a plurality of cycles including the first step and the second step; A step in which the first step of the cycle performed earlier is carried out under first processing conditions, and the first step of the cycle performed later is carried out under second processing conditions different from the first processing conditions, Includes. [Effects of the Invention]

[0006] This disclosure provides a silicon film that forms recesses, which can suppress the surface roughness after etching and control the shape of the recesses. [Brief explanation of the drawing]

[0007] [Figure 1] This is a longitudinal cross-sectional side view of a wafer on which a process according to one embodiment of the present disclosure is performed. [Figure 2] This is an explanatory diagram showing the changes in the recessed area before and after etching. [Figure 3] This is a longitudinal cross-sectional side view of the wafer after etching. [Figure 4] This is an explanatory diagram showing the changes in the Si film forming the recess. [Figure 5] This is an explanatory diagram showing the changes in the Si film forming the recess. [Figure 6] This is an explanatory diagram showing the changes in the Si film forming the recess. [Figure 7] This is an explanatory diagram showing the changes in the recessed area during etching. [Figure 8] This is an explanatory diagram showing how the recess takes on a rectangular shape. [Figure 9] This is an explanatory diagram showing how the aforementioned recess has a rounded shape. [Figure 10] A flowchart illustrating the processing in this embodiment. [Figure 11] This is a plan view showing one embodiment of a substrate processing apparatus for performing the aforementioned processing. [Figure 12] This is a longitudinal cross-sectional side view showing an example of a processing module provided in the aforementioned substrate processing apparatus. [Figure 13] This is a graph showing the results of the evaluation test. [Figure 14]This is a graph showing the results of the evaluation test. [Figure 15] This is a graph showing the results of the evaluation test. [Modes for carrying out the invention]

[0008] An embodiment of the substrate processing method of this disclosure will be described. Figure 1 is a longitudinal cross-sectional side view of the surface of a wafer W, which is a substrate, showing the state before the etching process according to this embodiment. An underlayer film 11 is formed on the wafer W. On the underlayer film 11, a SiGe (silicon germanium) film 12 and a Si (silicon) film 13 are alternately and repeatedly stacked. By forming such a repeating structure, each of the SiGe film 12 and Si film 13 is formed in multiple layers in the thickness direction of the wafer W. This thickness direction of the wafer W will be described as the longitudinal direction. The Si film 13 is formed, for example, by epitaxial growth.

[0009] A mask film 14 is stacked on the uppermost Si film 13 of the repeating structure described above, preventing etching from above the Si film 13. A recess is formed extending vertically from the mask film 14 to the upper side of the lower film 11. This recess is a groove 15 extending in the front-to-back direction of the paper in Figure 1. The groove 15 opens to the upper surface of the mask film 14. The side walls of the groove 15 are composed of the mask film 14, the Si film 13, and the surface layer of the lower film 11, respectively, while each SiGe film 12 is located away from the side walls of the groove 15. As a result, in a vertical cross-sectional view, the left wall of the groove 15 has multiple recesses facing left, spaced apart from each other, and the right wall of the groove 15 has multiple recesses facing right, spaced apart from each other. These recesses facing left and right are referred to as recesses 16. Therefore, the recesses 16 are formed in multiple steps in the thickness direction of the wafer W, and are also formed to open in directions intersecting this thickness direction.

[0010] The groove 15 and the recess 16 are formed so as to form a bilaterally symmetric structure, and the vertical widths of the respective recesses 16 are the same or approximately the same. Hereinafter, the upper recess 16, the lower recess 16, and the recess 16 between the upper side and the lower side in the Si film 13 may be described as the top recess 16, the bottom recess 16, and the middle recess 16, respectively. As described above, the height of the laminate formed by the SiGe film 12 and the Si film 13 (= the height from the upper surface of the lower layer film 11 to the lower end of the mask film 14) is, for example, 4 μm.

[0011] FIG. 2 shows an enlarged view of one of the recesses 16. The left side corresponds to the state before etching in FIG. 1 described above, and the right side is the state after the etching described later. Since it is the film structure described above, regarding the recess 16, the side wall is composed of the Si film 13, and the back wall (bottom wall) is composed of the SiGe film 12. Hereinafter, for the sake of convenience of explanation, the walls forming each recess 16 may be described as the upper wall 21, the lower wall 22, and the side wall 23. The upper wall 21 and the lower wall 22 are composed of the Si film 13, and the upper wall 21 of any one recess 16 is the lower wall 22 of the recess 16 above the one recess 16. The side wall 23 is composed of the SiGe film 12 before etching. Regarding the recess 16 before etching, the upper wall 21 and the lower wall 22 are perpendicular or approximately perpendicular to the side wall 23, and each of the upper wall 21 and the lower wall 22 and the side wall 23 forms a corner portion in a longitudinal sectional view, and the angle is 90° or approximately 90°.

[0012] When gas is supplied to the wafer W, the gas is introduced into the groove 15 and further into the recesses 16 of each stage. In this embodiment, by introducing the processing gas into each recess 16 from the surface of the wafer W in this way, the lower surface side of the upper wall 21 and the upper surface side of the lower wall 22 are etched. That is, the thickness of the Si film 13 forming the side wall of the recess 16 is reduced, and the longitudinal width of the recess 16 is increased. By this widening, the side wall 2 of the recess 16 after etching will be composed of the SiGe film 12 and the Si film 13. Note that FIG. 2 is a schematic diagram showing a desirable state in which the shape of the recess 16 after etching becomes a rectangular shape described later and the roughness of the lower surface of the upper wall 21 and the upper surface of the lower wall 22 is suppressed.

[0013] Specifically describing the above etching process, F2 (fluorine) gas, which is a halogen-containing gas, and NH3 gas, which is a basic gas, are supplied to the wafer W as processing gases to alter the surface of the Si film 13 that constitutes the upper wall 21 and the lower wall 22 and generate reaction products. The step of altering the Si film 13 with the processing gas is defined as the processing gas supply step. Subsequently, by heating the wafer W, a heating step is performed to sublime this reaction product and widen the concave portion 16. The reaction product to be sublimed is various products such as AFS described later. By repeatedly performing the cycle consisting of the processing gas supply step, which is the first step, and the heating step, which is the second step, the vertical width of the concave portion 16 is set to a desired size. Note that each of the processing gas supply step and the heating step is performed in a processing container in which a vacuum atmosphere of a predetermined pressure is formed with the wafer W housed therein.

[0014] The above processing gas mainly acts on the Si film 13 among the Si film 13 and the SiGe film 12. Therefore, the etching of the Si film 13 is selectively performed with respect to the SiGe film 12. The above reaction product is ammonium fluorosilicate [AFS: ((NH4)SiF6)]. In the following description, unless otherwise specified, the supply time of the processing gas refers to the supply time of the processing gas in one cycle described above, which is the time when both the F2 gas, which is a halogen-containing gas, and the NH3 gas, which is a basic gas, are supplied to the wafer W.

[0015] Regarding the recessed portion 16 after etching, it is desirable that it meets the following first to third requirements. The first requirement is that the roughness (surface roughness) of the lower surface of the upper wall 21 and the upper surface of the lower wall 22, which are Si films 13, be relatively small. The second requirement is as follows: After etching, just as before etching, a 90° or approximately 90° angle is formed at the back of the recessed portion 16 between the upper wall 21, the lower wall 22, and the side wall 23. The formation of such an angle results in high uniformity of the vertical width between the opening and back sides of the recessed portion 16. For the sake of explanation, below, the shape of the recessed portion 16 with such an angle and high uniformity of vertical width will be described as rectangular. On the other hand, the shape of the recessed portion 16 where such an angle is not formed, and the recessed portion 16 is in a U-shape when viewed in vertical section, with a smaller vertical width at the back compared to the opening, will be described as rounded. The second requirement is that the shape of the recessed portion 16 should be closer to a rectangular shape (to increase its rectangularity).

[0016] The third requirement is that variations in the vertical width of each recess 16 at each height be suppressed. This means that variations in the amount of etching are suppressed between the top, middle, and bottom recesses 16. Figure 3 is a schematic diagram showing the wafer W of Figure 1 after etching to satisfy the above first to third requirements, and the recess 16 after etching in Figure 2 mentioned above is one of the recesses 16 of the wafer W shown in Figure 3.

[0017] The roughness of the Si film 13, as per the first requirement, will be explained in detail. The Si film 13 reacts with the processing gases, F2 gas and NH3 gas, as shown in Equation 1 below, producing the product (SiF4). This SiF4 reacts as shown in Equation 2 to generate AFS. The roughness of the Si film 13 after etching varies depending on the processing conditions, but it is thought that the amount of AFS generated during the processing gas supply process is a contributing factor. Si+F2+NH3→SiF4+NH3...Formula 1 SiF4+H2+F2+2NH3→(NH4)SiF6...Formula 2

[0018] The following explains the differences in roughness that are thought to be caused by differences in the amount of AFS generated, referring to Figures 4 to 6. Figures 4 to 6 schematically show the change in the upper surface of the lower wall 22 of the recess between the time of processing gas supply and after the end of etching, but the lower surface of the upper wall 21 also changes in a similar way to the upper surface of the lower wall 22. The amount of AFS generated during the processing gas supply process is greater in Figures 4, 5, and 6, respectively.

[0019] Figure 4 shows that, due to the relatively small amount of AFS generated, the AFS layer 31 is formed in a scattered manner on the upper surface of the lower wall 22 during the processing gas supply process. On this upper surface, the areas covered by the AFS layer 31 have reduced contact with the processing gas, making it less likely for alteration to occur due to reaction with the processing gas. In other words, the areas on the upper surface of the lower wall 22 where the AFS layer 31 is formed and the areas where the AFS layer 31 is not formed have different reactivity to the processing gas. Due to this difference in reactivity, irregularities are formed on the surface of the lower wall 22 after etching. As described above, since the AFS layer 31 is formed in a scattered manner, the surface roughness of the upper surface of the lower wall 22 is small. That is, the width of the recesses and the width of the protrusions in the above-mentioned irregularities are relatively small.

[0020] Figure 5 shows that during the processing gas supply process, the AFS layer 31 is formed as a thin layer covering the entire upper surface of the lower wall 22, thereby suppressing the reaction with the processing gas to a similar degree in each part of the upper surface. As a result, the entire upper surface of the lower wall 22 is etched with high uniformity, and the surface becomes flat or generally flat after etching.

[0021] Figure 6 shows that a relatively large amount of AFS is generated during the processing gas supply process, causing the AFS layer 31 to cover the entire upper surface of the lower wall 22, and resulting in variations in the thickness of the AFS layer 31 across different parts of the upper surface. In other words, the AFS layer 31 has a large surface roughness. The larger the thickness of the AFS layer 31, the less likely the processing gas is to come into contact with the lower wall 22, resulting in a larger surface roughness for the lower wall 22 after etching. Specifically, the width of the recesses and protrusions become relatively large.

[0022] As shown in Figure 4, a state with relatively small surface roughness is defined as microroughness, and as shown in Figure 6, a state with relatively large surface roughness is defined as large roughness. As described above, if the amount of AFS generated shifts from the appropriate range to the lower side, the surface roughness of the Si film 13 due to microroughness increases, and if it shifts to the higher side, the surface roughness of the Si film 13 due to large roughness increases. From equations 1 and 2 above, the amount of AFS generated is influenced by the flow rate ratio of F2 gas and NH3 gas, which are the processing gases supplied to the wafer W. If the flow rate of NH3 gas is relatively large relative to the flow rate of F2 gas, the amount of AFS generated increases. Also, the amount of AFS generated increases with longer processing gas supply time. By the way, the flow rate of NH3 gas relative to the flow rate of F2 gas in the processing gas (NH3 gas flow rate / F2 gas flow rate) may be referred to as the NH3 gas flow rate ratio below. Therefore, a large NH3 gas flow rate ratio means that the flow rate of NH3 gas is large relative to the flow rate of F2 gas (= the proportion of NH3 gas to the proportion of F2 gas in the processing gas is large).

[0023] Next, we will explain the shape of the recess 16 after etching, as per the second requirement. Depending on the processing conditions, the shape of the recess 16 after etching changes between a rectangular shape and a round shape. The processes that are presumed to occur before these rectangular and round shapes are formed will be explained below. First, with reference to Figures 7 and 8, we will explain the presumed process for forming a rectangular shape. The processing gases, F2 gas 41 and NH3 gas 42, enter the recess 16 (upper part of Figure 7) and react with the lower surface of the upper wall 21 and the upper surface of the lower wall 22, which are the Si film 13, as shown in equation 1 above, to produce SiF4. Of this SiF4, some is released into the recess 16 as a gas, while other parts react as shown in equation 2 above to form the AFS layer 31.

[0024] F2 gas 41 and NH3 gas 42 act not only on the upper wall 21 and lower wall 22 but also on the side wall 23, altering and slightly etching the surface layer of the SiGe film 12 that constitutes the side wall 23, and releasing GeF4 (germanium tetrafluoride) gas 43. As the side wall 23 is etched in this way, a portion of the Si film 13 is newly exposed inside the recess 16 at the back of the recess 16, thereby forming the upper wall 21 and lower wall 22 of the recess 16 (Figure 7, lower panel). This portion is referred to as the newly exposed portion 44.

[0025] Since the newly exposed area 44 is exposed to the recess 16 during the supply of processing gas, the time it is exposed to F2 gas 41 and NH3 gas 42 is shorter compared to the area of ​​the Si film 13 that formed the upper wall 21 and lower wall 22 before etching. Therefore, the amount of reaction with these F2 gases 41 and NH3 gases 42 is relatively small. Also, the further back you are in the recess 16, the less likely F2 gases 41 and NH3 gases 42 are to penetrate. As a result, the upper wall 21 and lower wall 22, including the newly exposed area 44, react less with F2 gases 41 and NH3 gases 42 towards the back of the recess 16. However, GeF4 gas 43 is reactive with the Si film 13 and reacts relatively strongly with the Si film 13 at the back of the recess 16 when generated from the SiGe film 12. Therefore, the Si film 13 reacts with high uniformity from the opening to the back of the recess 16 (Figure 8, upper panel). Therefore, after the removal of each reaction product generated in the heating process and the processing gas supply process, the recess 16 becomes rectangular in shape (Figure 8, lower panel). The AFG layer, which is a reaction product formed in the SiGe film 12, is shown as 45 in the figure, and the reaction product between GeF4 gas 43 and the Si film 13 is shown as 46. These AFG layers 45 and reaction products 46 are also removed along with the AFS layer 45. The AFG layer 45 will be described later.

[0026] Next, we will explain the estimation of the process by which the round shape is formed. As the reaction between the surface layer of the SiGe film 12 and the processing gas proceeds from the state shown in the lower part of Figure 7, the surface layer gradually changes into an AFG [(NH4)GeF6] layer 45. As this change to the AFG layer 45 progresses, the amount of GeF4 gas 44 released decreases. Therefore, for the upper wall 21 and the lower wall 22, the amount of reaction with GeF4 gas 44 and / or F2 gas 41 and NH3 gas 42 decreases as you move towards the back of the recess 16 (upper part of Figure 9). Consequently, after the removal of reaction products by the heating process, the recess 16 becomes round (lower part of Figure 9). From the above, it can be concluded that the longer the processing gas supply time, or the larger the flow rate ratio of NH3 gas, the easier it is for the AFG layer 45 to form (= the easier it is for the release of GeF4 gas 44 to be reduced), and thus the easier it is for the shape to become round.

[0027] Next, we will explain the variation in etching amount between the top, middle, and bottom sections regarding the third requirement. Since it is more difficult for the processing gas to enter the deeper parts of the groove 15, if the processing gas supply time is relatively short, the upper wall 21 and lower wall 22 of the recess 16 are more likely to come into contact with the processing gas and react with it in the order of top > middle > bottom. Therefore, the etching amount increases in this order.

[0028] However, as shown in the evaluation tests described later, it has been confirmed that as the supply time of the processing gas increases, the amount of etching tends to increase towards the bottom (i.e., the amount of etching follows the pattern of top < middle < bottom). This is thought to be partly due to the fact that a longer supply time of the processing gas causes the AFS layer 31 formed towards the top (the opening side of the groove 15) to become thicker, hindering the reaction of the upper wall 21 and lower wall 22 with respect to the processing gas. In addition, the greater the flow rate of NH3 gas, the easier it is for the thickness of the AFS layer 31 at the top to increase, and the more likely it is that the amount of etching will be greater towards the bottom.

[0029] As described above, by using processing conditions where the NH3 gas flow rate ratio is relatively small and / or the processing gas supply time is relatively short, the recesses 16 after etching tend to have micro-roughness, a rectangular shape, and a larger etching amount on the top side. Conversely, by using processing conditions where the NH3 gas flow rate ratio is relatively large and / or the processing gas supply time is relatively long, the recesses 16 after etching tend to have large-scale roughness, a round shape, and a larger etching amount on the bottom side. The NH3 gas flow rate ratio and processing gas supply time do not necessarily coincide with the appropriate range for keeping the roughness within an acceptable range, the appropriate range for creating a rectangular shape, or the appropriate range for equalizing the etching amount between the top and bottom. Therefore, when repeating a cycle consisting of a processing gas supply process and a heating process, it was difficult to adequately satisfy all of the above requirements 1 to 3 if the processing gas supply process in each cycle was set to the same processing conditions.

[0030] Therefore, in this embodiment, the processing conditions are made different for the processing gas supply process performed in the preceding cycle and the processing gas supply process performed in the succeeding cycle. Figure 10 shows the processing flow in this embodiment. Assuming that the cycle is set to be performed a total of Z times, the processing gas supply process is performed under the first processing conditions, followed by a heating process. This is repeated X times to perform the preceding cycle (step S1). After that, the processing gas supply process is performed under the second processing conditions, followed by a heating process. This is repeated Y times (Z times - X times) to perform the succeeding cycle (step S2).

[0031] By changing the processing conditions as described above, it is possible to prevent a strong tendency in specific areas regarding roughness, recess shape, and etching amount between the top, middle, and bottom, compared to processing with a single processing condition, thereby meeting the first to third requirements. However, as will be shown later in the evaluation tests, it has been confirmed that the processing conditions performed in the preceding cycle have a relatively greater influence on the shape and roughness of the recess 16 after etching than those in the subsequent cycle. In other words, if the processing gas supply process of the preceding cycle is set to conditions that form a rectangular shape and micro-roughness, the recess 16 after etching tends to have a rectangular shape and micro-roughness. Conversely, if the processing gas supply process of the preceding cycle is set to conditions that form a round shape and large roughness, the recess 16 after etching tends to have a round shape and large roughness.

[0032] Regarding roughness, it is acceptable as long as it remains within an acceptable range, even if it is formed to a small extent. Therefore, in order to achieve a rectangular shape, the first processing conditions in the preceding cycle may be set to conditions that tend to form a rectangular shape and micro-roughness, and the second processing conditions in the subsequent cycle may be set to conditions that tend to form a round shape and large-scale roughness compared to the first processing conditions. Specifically, the flow rate ratio of NH3 gas should be made smaller in the first processing conditions than in the second processing conditions, or the supply time of the processing gas should be made shorter in the first processing conditions than in the second processing conditions. Furthermore, in order to increase the tendency to form a rectangular shape, it is preferable to set the first processing conditions in the preceding cycle and the second processing conditions in the subsequent cycle in this way, and then, for example, set the number of times the preceding cycle is performed (X times) ≥ the number of times the subsequent cycle is performed (Y times).

[0033] Furthermore, there are cases where it is more important to address the first requirement (requirement to suppress roughness) than the second requirement (requirement to increase rectangularity). In such cases, as described above, the recess 16 after etching is relatively heavily influenced by the first processing conditions in the preceding cycle, so the first processing conditions should be selected to suppress roughness relatively well. Then, as the second processing conditions in the subsequent cycle, conditions should be selected to correct the etching amount between the top, middle, and bottom and to modify the shape of the recess 16 so that rectangularity is increased. Specifically, the flow rate ratio of NH3 gas should be made greater in the first processing conditions than in the second processing conditions, or the supply time of the processing gas should be made greater in the first processing conditions than in the second processing conditions. In such cases, when trying to obtain a high level of roughness suppression, it is preferable to set, for example, the number of times the preceding cycle is performed (X times) ≥ the number of times the subsequent cycle is performed (Y times) in order to maximize that effect.

[0034] In this embodiment, in order to increase rectangularity, the flow rate ratio of NH3 gas is set to be greater in the first processing condition than in the second processing condition, and the supply time of the processing gas is set to be shorter in the first processing condition than in the second processing condition, and the number of times the preceding cycle is performed (X times) > the number of times the subsequent cycle is performed.

[0035] To give a more specific example of processing conditions, based on the results of subsequent evaluation tests, the flow rate ratio of NH3 gas (flow rate of NH3 gas / flow rate of F2 gas) will be set to within the range of 0.01 to 0.014 for each of the first and second processing conditions. Therefore, the flow rate ratio of NH3 gas in at least one of the first and second processing conditions will be less than 0.014. In addition, the supply time of the processing gas will be set to within the range of 10 to 15 seconds for each of the first and second processing conditions. In this specification, the supply time of the processing gas refers to the time during which the halogen-containing gas (F2 gas in this embodiment) and the basic gas (NH3 gas in this embodiment) constituting the processing gas are simultaneously supplied to the wafer W (i.e., the time during which they are supplied into the processing container containing the wafer W).

[0036] A substrate processing apparatus 5, which is one embodiment of the apparatus that performs the processing described in the flowchart of Figure 10, will be described with reference to the plan view of Figure 11. The substrate processing apparatus 5 includes an loading / unloading section 51 for loading and unloading wafers W, two load lock chambers 61 provided adjacent to the loading / unloading section 51, two heat treatment modules 60 provided adjacent to each of the two load lock chambers 61, and two processing modules 7 provided adjacent to each of the two heat treatment modules 60. The processing module 7 corresponds to the first processing unit, and the heat treatment module 60 corresponds to the second processing unit.

[0037] The loading / unloading section 51 includes a first substrate transport mechanism 52 and an atmospheric pressure transport chamber 53, and a carrier mounting table 55 provided on the side of the atmospheric pressure transport chamber 53 on which a carrier 54 for storing wafers W is placed. In the figure, 56 is an aligner adjacent to the atmospheric pressure transport chamber 53, and is provided to rotate the wafer W to optically determine the eccentricity and align the wafer W with respect to the first substrate transport mechanism 52. The first substrate transport mechanism 52 transports the wafer W between the carrier 54 on the carrier mounting table 55, the aligner 56, and the load lock chamber 61.

[0038] Each load lock chamber 61 is provided with a second substrate transport mechanism 62, for example, having a multi-joint arm structure, which transports the wafer W between the load lock chamber 61, the heat treatment module 60, and the processing module 7. The processing containers constituting the heat treatment module 60 and the processing containers constituting the processing module 7 are under a vacuum atmosphere, and the load lock chamber 61 can be switched between an atmospheric pressure atmosphere and a vacuum atmosphere to allow for the transfer of wafer W between these vacuum-atmosphere processing containers and the atmospheric pressure transport chamber 53.

[0039] In the figure, 63 is a gate valve that can be opened and closed, and is provided between the atmospheric pressure transport chamber 53 and the load lock chamber 61, between the load lock chamber 61 and the heat treatment module 60, and between the heat treatment module 60 and the processing module 7. The heat treatment module 60 includes the processing container, an exhaust mechanism for evacuating the inside of the processing container to form a vacuum atmosphere, and a stage provided inside the processing container that can heat the wafer W placed on it, and is configured to perform the heating process described above.

[0040] The processing module 7 will be described with reference to the longitudinal cross-sectional side view in Figure 12. This processing module 7 performs the processing gas supply process described above. In the figure, 71 is a processing container that constitutes the processing module 7. In the figure, 72 is a wafer W transport port opening in the side wall of the processing container 71, which is opened and closed by the gate valve 63 described above. A stage 81 on which the wafer W is placed is provided inside the processing container 71, and the stage 81 is provided with a lifting pin (not shown). The wafer W is transferred between the second substrate transport mechanism 62 and the stage 81 via this lifting pin.

[0041] A temperature control unit 82 is embedded in the stage 81, and the wafer W placed on the stage 81 is brought to the temperature described above. This temperature control unit 82 is configured as a flow path that forms part of a circulation path through which a temperature-controlling fluid, such as water, flows, and the temperature of the wafer W is adjusted by heat exchange with the fluid. However, the temperature control unit 82 is not limited to such a fluid flow path, and may be configured as, for example, a heater for resistance heating.

[0042] Furthermore, one end of an exhaust pipe 83 is open inside the processing container 71, and the other end of the exhaust pipe 83 is connected to an exhaust mechanism 85, which is composed of, for example, a vacuum pump, via a valve 84, which is a pressure changing mechanism. By adjusting the opening of the valve 84, the pressure inside the processing container 71 is set to a pressure within the range described later, and processing is carried out.

[0043] In the upper part of the processing container 71, a gas showerhead 86, which is a processing gas supply mechanism, is provided facing the stage 81. The downstream side of gas supply passages 91 to 94 is connected to the gas showerhead 86, and the upstream side of gas supply passages 91 to 94 is connected to gas supply sources 96 to 99 via flow rate adjustment units 95. Each flow rate adjustment unit 95 is equipped with a valve and a mass flow controller. The supply of gas from gas supply sources 96 to 99 is cut off to the downstream side by opening and closing the valves included in the flow rate adjustment unit 95.

[0044] F2 gas, NH3 gas, Ar (argon) gas, and N2 (nitrogen) gas are supplied from gas sources 96, 97, 98, and 99, respectively. Therefore, the gas showerhead 86 can supply these HF gases, NH3 gases, Ar gases, and N2 gases into the processing container 71. Ar gas and N2 gas are supplied into the processing container 71 as carrier gases along with F2 gas and NH3 gas.

[0045] As shown in Figure 11, the substrate processing apparatus 5 is equipped with a control unit 50, which is a computer. This control unit 50 includes a program, memory, and a CPU. The program incorporates instructions (each step) to perform the wafer W processing and wafer W transport as described above. This program is stored in a storage medium, such as a compact disk, hard disk, magneto-optical disk, or DVD, and installed in the control unit 50. The control unit 50 outputs control signals to each part of the substrate processing apparatus 5 using this program, thereby controlling the operation of each part. Specifically, the operation of the processing module 7, the operation of the heat treatment module 60, the operation of the first substrate transport mechanism 52, the operation of the second substrate transport mechanism 62, and the operation of the aligner 56 are controlled by the control signals. The operation of the processing module 7 includes, for example, the temperature of the fluid supplied to the stage 81, the supply and cut of each gas from the gas shower head 86, and the adjustment of the exhaust flow rate by the valve 84.

[0046] The transport path of the wafer W in the substrate processing apparatus 5 will now be explained. As explained in Figure 1, a carrier 54 containing wafers W on which each film has been formed is placed on a carrier mounting table 55. The wafer W is then transported in the following order: atmospheric pressure transport chamber 53 → aligner 56 → atmospheric pressure transport chamber 53 → load lock chamber 61, and then transported to the processing module 7 via the heat treatment module 60. Then, as previously described, the processing gas supply process is performed, and the surface layers of the upper wall 21 and lower wall 22 that form the recess 16 are altered to become the AFS layer 31. Subsequently, the wafer W is transported to the heat treatment module 60, where the AFS layer 31 and other reaction products are sublimated. After that, the wafer W is transported back and forth between the processing module 7 and the heat treatment module 60, so that the cycle consisting of the processing gas supply process and the heating process is repeated.

[0047] In the cycle described above, the processing gas supply process is performed under the first processing conditions from the 1st to the Xth cycle, as shown in Figure 10. Then, from the X+1th cycle onward, the processing gas supply process is performed under the second processing conditions, in which the flow rate ratio of NH3 gas is significantly increased and the processing gas supply time is extended. This cycle under the second processing conditions is repeated Y times, and when a total of Z (X+Y) cycles are completed and each recess 16 reaches the desired vertical width as shown in Figure 3, the wafer W is transported from the heat treatment module 60 to the load lock chamber 61 → atmospheric pressure transport chamber 53 in that order and returned to the carrier 54.

[0048] The following is a supplementary explanation of the processing gas supply process in the cycle described above. In this processing gas process, the processing container 71 of the processing module 7 is evacuated to, for example, 100 mTorr (13.3 Pa) to 10 Torr (1333 Pa), and the temperature of the wafer W is adjusted to, for example, -20°C to 60°C. F2 gas and NH3 gas are supplied to the processing container 71 in parallel (step T1). The supply time of F2 gas and NH3 gas and the flow rate ratio of F2 gas and NH3 gas in step T1 correspond to the processing gas supply time and NH3 gas flow rate ratio described above. After the supply of F2 gas and NH3 gas is stopped, N2 gas is supplied to the processing container 71 along with the evacuation of the processing container 71, thereby purging any remaining F2 gas and NH3 gas in the processing container 71 (step T2). After this purging, the wafer W is removed from the processing container 71. Furthermore, to add to the explanation of the heating process in the above cycle, in this heating process, the wafer W is heated to a higher temperature than the temperature of the wafer W in steps T1 and T2, for example, 80°C to 300°C, which causes the sublimation of the reaction product.

[0049] As described above, the first to third requirements can be met by setting the processing conditions in the processing gas supply process to be different for the preceding and succeeding cycles. Specifically, for the recessed area 16 after etching, the roughness of the Si film 13 forming the upper wall 21 and lower wall 22 can be suppressed, the recessed area 16 can be made rectangular, and variations in the vertical width of the recessed area 16 between the top, middle, and bottom can be suppressed. Therefore, the yield of semiconductor products manufactured from the wafer W after etching can be increased.

[0050] Although we have described the number of times the preliminary cycle (X) and the number of times the subsequent cycle (Y) are performed as multiple times, these X and / or Y cycles may be performed only once. Therefore, the preliminary and subsequent cycles do not need to be repeated. Furthermore, in the examples described so far, the process is divided into two stages: a preliminary cycle and a subsequent cycle, by changing the flow rate ratio of NH3 gas or the supply time of the process gas only once in the process gas supply process. However, the process is not limited to two stages; it may be divided into three or more stages by changing the processing conditions two or more times.

[0051] Furthermore, when performing a two-stage process, it is preferable to either make the flow rate ratio of NH3 gas greater in the first cycle than in the second cycle in order to achieve a rectangular shape, or to make the supply time of the processed gas shorter in the first cycle than in the second cycle. It is also preferable that the number of cycles be greater than or equal to the number of cycles in the first stage. When performing a process with three or more stages, for example, the processing conditions for the first stage and the processing conditions for any subsequent stages should be such that they have a similar relationship, and the number of cycles should be such that, for example, the number of cycles for the first stage is greater than or equal to the number of cycles for any stage.

[0052] In this embodiment, the atmosphere surrounding the wafer W is maintained in a vacuum from the start of the first cycle to the end of the last cycle. However, for example, each stage of the cycle may be performed in a different device, and the wafer W may be moved between devices by passing it through an atmospheric environment. However, from the viewpoint of preventing a decrease in throughput, it is preferable that the wafer W is processed in a vacuum from the first cycle to the last cycle, as in the case where the substrate processing device 5 described above is used.

[0053] Incidentally, after the processing gas supply process in any cycle, but before the heating process, a secondary fluorine-containing gas may be supplied to further suppress the roughness of the Si film 13 after etching is complete. This secondary fluorine-containing gas (i.e., halogen-containing gas) is, for example, HF (hydrogen fluoride) gas, and is therefore a different type of gas from the F2 gas, which is the primary fluorine-containing gas that constitutes the processing gas. The HF gas is supplied to the wafer W by the processing module 7.

[0054] The processing procedure in the processing module 7 when supplying HF gas is described as follows: after the supply of the processing gas (step T1) and purging of the processing container 71 (step T2) are performed in order, HF gas is supplied to the processing container 71 (step T3). After the supply of HF gas is stopped, in step T4, N2 gas is supplied to the processing container 71 and exhaust is performed, similar to step T2, and any remaining HF gas is purged. After that, the wafer W is removed from the processing module 7. When supplying HF gas, which is a roughness suppression gas, in this manner, steps T1 to T4 constitute the first process, step T1, which supplies both halogen-containing gas (F2 gas) and basic gas (NH3 gas), corresponds to the first supply process, and step T3, which supplies only one of these gases, corresponds to the second supply process.

[0055] It is believed that the supply of the HF gas described above causes the NH3 contained in the AFS layer 31 formed in step T1 to react with the HF gas to produce reaction products, and these reaction products slightly etch the surface layer of the Si film 13 coated on the AFS layer 31, thereby suppressing roughness.

[0056] The processing module 7 that performs the above steps T1 to T4 is configured such that, in addition to the gas supply sources 96 to 99 described above, an HF gas supply source is provided, and the HF gas supply source and the gas shower head 86 are connected via a flow path. A flow rate adjustment unit 95 is interposed in the HF gas flow path, similar to the flow paths of the other gases, and the HF gas is supplied into the processing container 71 via the gas shower head 86 at a desired flow rate. When supplying this HF gas into the processing container 71, for example, Ar gas and N2 gas are also supplied into the processing container 71 as carrier gases.

[0057] Alternatively, instead of supplying HF gas to the wafer W as a gas to suppress roughness, NH3 gas may be supplied to the wafer W. When NH3 gas is supplied in this way, it is thought that the NH3 gas reacts with the fluorine component contained in the AFS layer 31 formed in step T1 to produce a reaction product, and that this reaction product slightly etches the surface layer of the Si film 13 coated on the AFS layer 31, thereby suppressing roughness.

[0058] Furthermore, when using NH3 gas as the roughness suppression gas, for example, F2 gas and NH3 gas can be supplied together as processing gases, and the NH3 gas can be continued to be supplied to the wafer W even after the F2 gas supply is stopped, thereby omitting the N2 gas purge in step T2. In addition, the supply of each of the above roughness suppression gases can be carried out in any cycle. For example, it can be done in the last cycle of each stage cycle, or in every cycle.

[0059] While it was stated that the temperature of the wafer W is raised above the temperature during the processing gas supply process to remove the reaction products, this is not the only method of removal. For example, after performing steps T1 and T2 in the processing module 7, the sublimation temperature of the reaction products may be lowered by increasing the opening of the valve 74 interposed in the exhaust pipe 73 to reduce the pressure inside the processing container 71. Therefore, it is not limited to performing a single cycle in different processing containers.

[0060] Regarding the processing gases, F2 gas and NH3 gas, as previously mentioned, the timing of the end and start of supply may be staggered. Furthermore, the fluorine-containing gas included in the processing gas is not limited to F2 gas; for example, IF7 gas, IF5 gas, ClF3 gas, and SF6 gas may also be used. Note that "containing fluorine" does not mean containing fluorine as an impurity, but rather containing it as a constituent component. Similarly, the containing of Ge, as described later, also means containing it as a constituent component, not as an impurity.

[0061] Furthermore, the recess 16 is not limited to being horizontal; it may also be open in the vertical direction, and this technology can be applied when etching the Si film forming the side wall of such a recess 16. In that case, the recess 16 can be etched to conform to the first and second requirements (requirements for roughness and rectangular shape) of the first to third requirements described above.

[0062] Even if a Ge film forms the side wall 23 of the recess 16 instead of the SiGe film 12, it is thought that GeF4 can be produced using a fluorine-containing gas to etch the back side of the recess 16. Therefore, the side wall 23 of the recess 16 is not limited to being made of the SiGe film 12, but can be made of any film containing a Ge film.

[0063] The embodiments disclosed herein should be considered in all respects as illustrative and not restrictive. The above embodiments may be omitted, replaced, modified, or combined in various ways without departing from the scope and spirit of the appended claims.

[0064] [Evaluation Test] The following describes evaluation tests 1 to 5 conducted with respect to this technology. In each test, a cycle consisting of a processing gas supply process and a heating process was performed on a substrate having the film structure described in Figure 1 using the apparatus described in the embodiment, and the dimensions of each part were measured from SEM images acquired before and after processing. For evaluation tests 1 to 4, no changes were made to the processing conditions between the preceding and succeeding cycles described in Figure 10, and processing was performed under a single set of processing conditions. In evaluation tests 1 to 5, the period for supplying F2 gas and the period for supplying NH3 gas in the processing gas supply process coincided. That is, the timing of the start of supplying these gases to the processing container 71 was the same, and the timing of the end of supplying these gases to the processing container 71 was also the same.

[0065] The following three dimensions were measured in each evaluation test: 1. The width of the groove 15, which will be referred to as the groove width dimension below. 2. The vertical width of the recess 16 at a predetermined distance slightly away from the opening of the recess 16, which will be referred to as the opening-side dimension below. 3. The final vertical width of the recess 16 at a predetermined distance slightly away from the side wall 23 of the recess 16, which will be referred to as the back-side dimension below.

[0066] In the evaluation test, among the multi-stage recesses 16, a plurality of recesses 16 in a predetermined stage are designated as the top recesses 16. For each of the groove width dimension, opening side dimension, and back side dimension of the top recesses 16, (dimension after etching - dimension before etching) / 2 is calculated. This calculation is performed for each of the plurality of top recesses 16. Then, the average value obtained from the calculated value from the groove width dimension, the calculated value obtained from the calculated value from the opening side dimension, and the calculated value obtained from the back side dimension is calculated among the recesses 16, and the resulting average value is designated as the groove width etching amount, opening side etching amount, and back side etching amount for the top recesses 16. The groove width dimension of each top recess 16 is obtained from between the upper walls 21 of the horizontally opposing recesses 16.

[0067] Similarly, multiple recesses 16 in a predetermined step are designated as middle recesses 16 and bottom recesses 16, respectively, and the groove width etching amount, opening side etching amount, and back side etching amount are calculated for each of the middle recesses 16 and bottom recesses 16. The etching amounts calculated in this way are divided by a predetermined standard amount, and the normalized values ​​are shown in Figures 13 to 15 below. The larger the normalized value, the larger the actual etching amount. Note that the etching amounts obtained in each evaluation test before test normalization (i.e., measured values) are values ​​of 20 nm or less. Regarding evaluation tests 3-5, the test results include tables describing the shape of the recessed area 16 after etching and the state of its roughness. In each table, areas that are clearly rectangular and clearly round are represented as "rectangular" and "round," respectively, while other shapes are represented as "intermediate." Therefore, even if an area is not clearly rectangular but has a relatively high degree of rectangularity and is at a level that does not pose a practical problem, it is also shown as "intermediate" in the table, meaning that the processing conditions resulting in "rectangular" are not the only practical processing conditions. In addition, in the table, areas where neither micro-roughness nor large-roughness was observed and the smoothness was high are represented as "smooth."

[0068] • Evaluation Test 1 In evaluation tests 1-1 to 1-3, etching was performed on the substrate by repeating the cycle of the processing gas supply process and the heating process. Between evaluation tests 1-1 to 1-3, the combination of the number of cycles and the pressure inside the processing container 71 during the processing gas supply process was changed. In evaluation test 1-1, the pressure inside the processing container 71 was 200 Pa (1.5 Torr), and the number of cycles was 9. In evaluation test 1-2, the pressure inside the processing container 71 was 666.6 Pa (5 Torr), and the number of cycles was 9. In evaluation test 1-3, the pressure inside the processing container 71 was 666.6 Pa (5 Torr), and the number of cycles was 3. Each processing condition, such as the temperature of the wafer W during processing gas supply, the processing gas supply time, and the flow rate ratio of NH3 gas, was set to values ​​within the range described in the embodiment.

[0069] The results of this evaluation test 1 show the average values ​​obtained from each of the top, middle, and bottom recesses 16. In evaluation test 1-1, the groove width etching amount was 1.26, the opening side etching amount was 1.62, and the back side etching amount was 1.66. In evaluation test 1-2, the etching progressed so much that the upper wall 21 and lower wall 22 disappeared, making it impossible to measure the etching amount for each. In evaluation test 1-3, the disappearance of the upper wall 21 and lower wall 22 was prevented, and the groove width etching amount was 1.78, the opening side etching amount was 1.9, and the back side etching amount was 1.9.

[0070] From the results of the above evaluation test 1, it can be seen that it is preferable to set the pressure inside the processing container 71 relatively high when supplying the processing gas, as this can increase the etching rate, and that excessive etching can be prevented by appropriately setting the number of cycles. Furthermore, it can be seen that it is preferable to set the pressure inside the processing container 71 to be greater than 1.5 Torr (200 Pa), and even more preferable to set it to 5 Torr (666.6 Pa) or higher.

[0071] • Evaluation Test 2 In evaluation tests 2-1 to 2-5, each substrate was processed by performing the processing gas supply process and the heating process only once, without repeating the cycle of these processes. The processing gas supply time was set to different values ​​for evaluation tests 2-1 to 2-5, being 5 seconds, 10 seconds, 15 seconds, 25 seconds, and 35 seconds, respectively, for evaluation tests 2-1, 2-2, 2-3, 2-4, and 2-5. Furthermore, each processing condition, such as the NH3 gas flow rate ratio, the temperature of the wafer W during processing gas supply, and the pressure inside the processing container 71, was set to values ​​within the range described in the embodiment.

[0072] The graphs in Figures 13 to 15 below summarize the etching amounts in Evaluation Test 2. Each graph shows the relationship between the etching amount and the treatment gas supply time, with the etching amount on the vertical axis and the supply time on the horizontal axis. Figure 13 shows the etching amount at the groove width, Figure 14 shows the etching amount at the opening side, and Figure 15 shows the etching amount at the back side.

[0073] As is clear from the graph in Figure 13, the correlation between the processing gas supply time and the etching amount is low for the top, middle, and bottom of the groove 15 in the lateral direction. Furthermore, as is clear from the graphs in Figures 14 and 15, for the etching amount on the opening side and the etching amount on the back side of the recess 16, the etching amount on the top side is relatively small when the etching time is relatively long. This is thought to be because a large amount of AFS was generated on the top side, as explained in the embodiment. In addition, the graphs in Figures 14 and 15 show that, as explained in the embodiment, the etching amount is larger at the top when the etching time is short, and larger at the bottom when the etching time is long. From the graphs in Figures 14 and 15, the slope of the graphs is generally the same for the top, middle, and bottom when the processing gas supply time is in the range of 10 to 15 seconds, and the difference in etching amount between the top, middle, and bottom is suppressed.Therefore, this evaluation test 2 shows that it is preferable to set the processing gas supply time in one cycle to 10 to 15 seconds.

[0074] • Evaluation Test 3 In evaluation tests 3-1 to 3-6, the combination of the NH3 gas flow rate ratio and the processing gas supply time was varied for each substrate, and the substrate was processed accordingly. The number of cycles was 3. The processing gas supply time was set to 10 seconds in evaluation tests 3-1 to 3-3, and to 15 seconds in evaluation tests 3-1 to 3-3. The NH3 gas flow rate ratio was set to 0.01 in evaluation tests 3-1 and 3-4, to 0.014 in evaluation tests 3-2 and 3-5, and to 0.02 in evaluation tests 3-3 and 3-6. Other processing conditions were the same as in evaluation test 2. Table 1 below summarizes the results obtained in evaluation test 3. In this evaluation test 3, as in evaluation test 2, the etching amount of each part was also obtained.

[0075] [Table 1]

[0076] Regarding the roughness of the upper wall 21 and lower wall 22 of the recessed area 16 after etching, micro-roughness was observed in the middle and bottom recessed areas 16 of evaluation test 3-1. Large-scale roughness was observed in the top recessed area 16 of evaluation test 3-3, and in the top, middle, and bottom recessed areas 16 of evaluation test 3-6. Furthermore, regarding the shape of the recessed area 16 after etching, the top, middle, and bottom recessed areas 16 of evaluation tests 3-1 and 3-4, and the bottom recessed area 16 of evaluation test 3-2, were rectangular in shape.

[0077] Therefore, this evaluation test 3 confirmed that microroughness is formed when the NH3 gas flow rate ratio is relatively small and the etching time is relatively short. Furthermore, it was confirmed that large roughness is formed when the NH3 gas flow rate ratio is relatively large. As described in the embodiment, it is thought that the difference in roughness state is due to the difference in the amount of AFS generated. In addition, this evaluation test 3 confirmed that a rectangular shape tends to form when the NH3 gas flow rate ratio is relatively small. And it can be seen that in order to form a rectangular shape, it is preferable to make the flow rate ratio smaller than 0.014, and more preferably 0.01 or less.

[0078] However, in evaluation tests 3-1, 3-4, and 3-5, where the NH3 gas flow rate ratio was set to 0.01 and the resulting shape was rectangular, the variation in etching amount between the top and bottom was relatively large. Consequently, the results of evaluation tests 3-1 to 3-6 did not adequately meet one or more of the first to third requirements.

[0079] • Evaluation Test 4 In evaluation tests 4-1 to 4-5, the combination of the NH3 gas flow rate ratio, processing gas supply time, and number of cycles was varied for each substrate, and each substrate was processed accordingly. The processing gas supply time was set to 10 seconds, 15 seconds, 15 seconds, 12.5 seconds, and 10 seconds for evaluation tests 4-1, 4-2, 4-3, 4-4, and 4-5, respectively. The NH3 gas flow rate ratio in the processing gas was set to 0.01 for evaluation tests 4-1, 4-2, and 4-4, and to 0.014 for evaluation tests 4-3 and 4-5. The number of cycles was set to 3 for evaluation tests 4-1 to 4-4, and to 4 for evaluation test 4-5. Other processing conditions were the same as those for evaluation tests 2 and 3. Table 2 below summarizes the results of evaluation test 4. In evaluation test 4 and evaluation test 5, which will be described next, the etching amount of each part was obtained, similar to evaluation test 3.

[0080] [Table 2]

[0081] Regarding the roughness of the upper wall 21 and lower wall 22 of the recess 16 after etching, micro-roughness was observed in the middle and bottom recesses 16 of evaluation tests 4-1 and 4-4, and in the bottom recess 16 of evaluation test 4-5. For the other recesses 16, the roughness was kept within a desirable range. A comparison between evaluation tests 4-1, 4-2, and 4-4, which had the same number of cycles and NH3 gas flow rate ratio, shows that, as described in the embodiment, a shorter processing gas supply time makes it easier for micro-roughness to form.

[0082] Regarding the shape of the recesses 16 after etching, the top, middle, and bottom recesses 16 in evaluation tests 4-1 and 4-2, and the middle and bottom recesses 16 in evaluation tests 4-4 and 4-5 were rectangular in shape, while the other recesses 16 were round in shape. A comparison between evaluation tests 4-1, 4-2, and 4-4 shows that, as described in the embodiment, when the processing gas supply time is relatively short, there is a tendency for the recesses to be rectangular in shape. Furthermore, in evaluation tests 4-1, 4-2, and 4-4, where the NH3 gas flow rate ratio was set to 0.01, two or three of the top, middle, and bottom recesses were rectangular in shape, indicating that it is preferable to set the ratio to 0.01 or less in order to obtain a rectangular shape.

[0083] Looking at the etching amounts on the opening side and the back side, in evaluation tests 4-2, 4-4, and 4-5, the etching amount at the top was greater than that at the middle and bottom. In other words, there was a relatively large variation in etching amounts between the top, middle, and bottom. Also, in evaluation test 4-3, the etching amount at the top was smaller than that at the middle and bottom. As a result of these findings, the recesses 16 of each substrate in evaluation test 4 did not adequately meet one or more of the first to third requirements.

[0084] Further examination of the results of evaluation test 4 revealed that when the NH3 gas flow rate ratio is 0.01, the recesses 16 tend to be rectangular in shape, and the etching amount at the top tends to be larger. Furthermore, when the NH3 gas flow rate ratio is 0.014, the recesses 16 tend to be round in shape, and the tendency for the etching amount at the top to be larger is mitigated compared to the case of a flow rate ratio of 0.01. Additionally, in both cases where the NH3 gas flow rate ratio is 0.01 and 0.014, the roughness is sometimes kept within a desirable range. However, regarding roughness, when the NH3 gas flow rate ratio in the processing gas is 0.01 and 0.014, the desired results were not obtained with a processing gas supply time of 10 seconds.

[0085] Considering the results of Evaluation Test 4 and the results of Evaluation Test 2, which indicated that a processing gas supply time of 10 to 15 seconds is desirable, it is conceivable to set the flow rate ratio of NH3 gas in the processing gas to a range greater than 0.01 and less than 0.014, and the processing gas supply time to a range greater than 10 seconds and less than or equal to 15 seconds. In other words, within these ranges of each parameter, it is conceivable to explore an acceptable range that better conforms to the first to third requirements than the processing conditions set in Evaluation Test 4, and to perform the processing using values ​​within that acceptable range. However, the acceptable range for the NH3 gas flow rate ratio is a very narrow range within the relatively narrow range of 0.01 to 0.014. Therefore, it is difficult to deal with changes in the flow rate ratio, for example, if the film structure to be etched changes slightly, raising concerns about its practicality. Accordingly, the multi-stage processing by changing the processing conditions, as described in the embodiment, is effective.

[0086] • Evaluation Test 5 In evaluation tests 5-1 to 5-5, a two-stage process (preliminary cycle and secondary cycle) was performed by changing the processing conditions as described in the embodiment. The combination of processing conditions for the preliminary cycle and the secondary cycle was changed for each substrate. Note that the processing conditions other than the NH3 gas flow rate ratio, processing gas supply time, and number of cycles were the same as those in evaluation test 4.

[0087] The flow rate ratio of NH3 gas and the supply time of the processed gas in the preceding cycle of evaluation tests 5-1, 5-2, and 5-4, and in the subsequent cycle of evaluation tests 5-3 and 5-5, were set to the same processing conditions as those used in evaluation test 4, where a rectangular shape was obtained. Furthermore, the flow rate ratio of NH3 gas and the supply time of the processed gas in the subsequent cycle of evaluation tests 5-1, 5-2, and 5-4, and in the preceding cycle of evaluation tests 5-3 and 5-5, were set to the same processing conditions as those used in evaluation test 4, where roughness was kept within a desirable range. Table 3 below summarizes the processing conditions and results of evaluation test 5.

[0088] Furthermore, considering the differences in the number of cycles in addition to the flow rate ratio of NH3 gas and the supply time of the processed gas, the tendency to form a rectangular shape is as follows: pre-stage of evaluation test 5-1 > pre-stage of evaluation test 5-2 and post-stage of evaluation test 5-3 > pre-stage of evaluation test 5-4 > post-stage of evaluation test 5-5. And the tendency to suppress roughness is as follows: post-stage of evaluation test 5-2, pre-stage of 5-3 and pre-stage of 5-5 > post-stage of evaluation test 5-1 and post-stage of 5-4.

[0089] [Table 3]

[0090] The results of evaluation tests 5-1 to 5-5 will be used to verify the difference in etching amount between the top and bottom. To summarize this verification, the difference in etching amount of the recess 16 between the top and bottom obtained from evaluation test 4 will be corrected according to the number of cycles. This will allow us to calculate the expected difference in etching amount between the top and bottom when only the preceding cycle in evaluation test 5 is performed, and the expected difference in etching amount when only the subsequent cycle in evaluation test 5 is performed. These expected differences in etching amount will be summed to obtain the predicted difference in etching amount between the top and bottom. This predicted difference in etching amount, and the predicted difference in etching amount obtained in the process of obtaining this predicted difference, will be compared with the actual difference in etching amount between the top and bottom obtained from evaluation test 5.

[0091] To explain in more detail, in evaluation test 5-1, the etching amounts on the opening side and the back side of the top section were designated as A1X1 and A2X2, respectively, and their average value was set to A3X3. The etching amounts on the opening side and the back side of the bottom section were designated as B1Y1 and B2Y2, respectively, and their average value was set to B3Y3. The value calculated as A3X3 - B3Y3 was taken as the difference in etching amounts between the top and bottom sections in evaluation test 5-1. The difference in etching amounts between the top and bottom sections calculated in this way was a positive value. Therefore, in evaluation test 5-1, the etching amount at the top section was greater than that at the bottom section.

[0092] Except for the number of cycles, evaluation tests 4-1 and 4-3 were conducted under the same conditions as the pre- and post-cycles of evaluation test 5-1. For evaluation test 4-1, C1A1 was obtained as (average of etching amount on the top opening side and etching amount on the top back side) - (average of etching amount on the bottom opening side and etching amount on the back side) = C1A1. Although the number of cycles in evaluation test 4-1 was 3, the number of pre-cycles in evaluation test 5-1 was 4, so it was corrected by multiplying by 4 / 3, and the resulting value was taken as the difference in expected etching amount C2A2 (= C1A1 × 4 / 3). Note that this value of C2A2 was positive. That is, the etching amount is greater at the top than at the bottom.

[0093] Similarly, for evaluation test 4-3, which was under the same conditions as the subsequent cycle, the difference in expected etching amount was calculated. Specifically for evaluation test 4-3, the following formula was calculated: (average of etching amount on the top opening side and etching amount on the top back side) - (average of etching amount on the bottom opening side and etching amount on the bottom back side) = C1A'1. Although the number of cycles in evaluation test 4-3 is 3, the number of subsequent cycles in evaluation test 5-1 is 1, so this was corrected by multiplying by 1 / 3, and this value was taken as the difference in expected etching amount C2A'2 (= C'A'1 × 1 / 3). This C'A'2 was a negative value. In other words, the etching amount is greater at the bottom than at the top.

[0094] Comparing the estimated total etching amount C2A2 + C2A′2 with A3X3 - B3Y3 from evaluation test 5-1, the values ​​were approximately the same. Furthermore, C2A2 was greater than A3X3 - B3Y3. The above calculation results indicate that, when performing the two-stage processing described in the embodiment, even if a relatively large bias in etching amount occurs between the top and bottom sides at the end of the first stage, this bias can be offset by performing a second stage of processing that increases the etching amount on the opposite side of the top or bottom side compared to the first stage.

[0095] Furthermore, as described above, in evaluation test 4-1, each recess 16 was rectangular in shape, and micro-roughness was formed in the middle and bottom recesses 16. In evaluation test 4-3, each recess 16 was of an intermediate shape, and the roughness of each recess 16 was within a desirable range. In contrast, the test results of evaluation test 5-1 showed that the middle and bottom recesses 16 were rectangular in shape, and micro-roughness was confirmed in the top, middle, and bottom recesses 16. Therefore, the shape and roughness of the recesses 16 were found to be relatively heavily influenced by the processing conditions of the preceding cycle.

[0096] For evaluation tests 5-2 to 5-5, the same calculations as for evaluation test 5-1 were used for verification. The results suggest that the bias in etching amount between the top and bottom sides is offset by the execution of the preceding and succeeding cycles. For verification, evaluation tests 5-2 and 5-3 used the same processing conditions as evaluation tests 4-1 and 4-3 as evaluation test 5-1, but evaluation tests 5-4 and 5-5 used the processing conditions of evaluation test 4-2, so the data from evaluation test 4-2 was used for verification. Furthermore, the pre- and post-cycles of evaluation test 5-2 were the same as those of evaluation tests 4-1 and 4-3, respectively, except for the number of cycles, just like in evaluation test 5-1. As shown in Table 3, in evaluation test 5-2, the bottom recess 16 was rectangular in shape, and micro-roughness was observed in both the middle and bottom recesses 16. Therefore, in evaluation test 5-2, as in evaluation test 5-1, the processing conditions of the pre-cycle had a relatively large influence on the shape and roughness of the recesses 16.

[0097] Regarding evaluation test 5-3, the preceding and succeeding cycles were the same as in evaluation tests 4-3 and 4-1, respectively, except for the number of cycles. As shown in Table 3, in evaluation test 5-3, the top, middle, and bottom recesses 16 had an intermediate shape, while the roughness was kept within an acceptable range. In evaluation test 4-3, each recess 16 had an intermediate shape, and the roughness of each recess 16 was within an acceptable range, while in evaluation test 4-1, each recess 16 had a rectangular shape, and micro-roughness was formed in the middle and bottom recesses 16. Therefore, in evaluation test 5-3 as well, the processing conditions of the preceding cycle had a relatively large influence on the shape and roughness of the recesses 16.

[0098] For evaluation test 5-4, the preceding and succeeding cycles were the same as in evaluation tests 4-2 and 4-3, respectively, except for the number of cycles. As shown in Table 3, in evaluation test 5-4, the bottom recess 16 was rectangular in shape, and microroughness was observed in the bottom recess 16. On the other hand, in evaluation test 4-2, each recess 16 was rectangular in shape, and microroughness was formed in the bottom recess 16. In evaluation test 4-3, each recess 16 was an intermediate shape, and the roughness of each recess 16 was within a desirable range. Therefore, in evaluation test 5-4 as well, the processing conditions of the preceding cycle had a relatively large influence on the shape and roughness of the recess 16.

[0099] For evaluation test 5-5, the preceding and succeeding cycles were the same as in evaluation tests 4-3 and 4-2, respectively, except for the number of cycles. As mentioned above, in evaluation test 5-5, the roughness of each of the top, middle, and bottom recesses 16 was kept within an acceptable range and had an intermediate shape. On the other hand, in evaluation test 4-3, each of the recesses 16 had an intermediate shape, and the roughness of each recess 16 was within a desirable range. In evaluation test 4-2, each of the recesses 16 had a rectangular shape, and microroughness was formed in the bottom recess 16. Therefore, in evaluation test 5-5 as well, the processing conditions of the preceding cycle had a relatively large influence on the shape and roughness of the recesses 16. Incidentally, in evaluation test 5-5, the roughness of the top, middle, and bottom was suppressed, and the difference in etching amount between the top and bottom (X3-Y3) was the smallest among all evaluation tests 5. Furthermore, while the shape of each recess 16 was slightly more rounded than the shape of the recess 16 in evaluation test 5-1, it was more rectangular than the shape of each recess 16 in evaluation test 4-3, making it practical. Therefore, among evaluation tests 5-1 to 5-5, evaluation test 5-5 yielded the most favorable results.

[0100] As described above, evaluation test 5 confirmed that the bias in etching amount between the top and bottom sides in the preceding and succeeding cycles cancels out, resulting in highly uniform etching from the top to the bottom side. It was also confirmed that the processing conditions performed in the preceding cycle greatly affect the shape and roughness of the recessed area 16 after etching. As mentioned above, in evaluation tests 5-3 and 5-5, roughness is suppressed at the top, middle, and bottom. Therefore, in order to suppress roughness in this way, it was shown that it is preferable to make the flow rate ratio of NH3 gas greater for the first processing condition in the preceding cycle than for the second processing condition in the succeeding cycle, as described in the embodiment. Comparing evaluation tests 5-3 and 5-5, the difference in etching amount between the top and bottom differs, with the difference in etching amount being smaller in evaluation test 5-5. Since the supply time of the processing gas under the second processing condition differs between evaluation tests 5-3 and 5-5, it can be seen that by adjusting the supply time of the processing gas between the first and second processing conditions, the balance of etching amounts between the top, middle, and bottom can be controlled while suppressing the roughness of each recess 16.

[0101] Regarding the rectangularity of the recess 16, the results of evaluation tests 5-1, 5-2, and 5-4 indicated that to improve the rectangularity, it is preferable to make the flow rate ratio of NH3 gas smaller in the first treatment condition than in the second treatment condition. Furthermore, since evaluation test 5-1 showed the highest rectangularity, it was indicated that to obtain even higher rectangularity, it is preferable to make the supply time of the treatment gas shorter in the first treatment condition than in the second treatment condition. [Explanation of Symbols]

[0102] W wafer 12 SiGe film 13 Si film 41 F2 gas 42 NH3 gas

Claims

1. A first step involves supplying a treatment gas containing a halogen-containing gas and a basic gas to a substrate in which a recess is formed, in which the side walls are formed by a silicon film and the back wall is formed by a germanium-containing film, thereby altering the surface of the silicon film and generating a reaction product. A second step involves removing the reaction product to widen the width of the recess, A process of performing a cycle consisting of the first step and the second step multiple times, A step in which the first step of the cycle performed earlier is carried out under first processing conditions, and the first step of the cycle performed later is carried out under second processing conditions different from the first processing conditions, A substrate processing method including the following.

2. The substrate processing method according to claim 1, wherein the first processing condition and the second processing condition differ in at least one of the ratio of the basic gas to the halogen-containing gas in the processing gas, or the supply time of the processing gas.

3. The substrate processing method according to claim 2, wherein the ratio of the basic gas to the halogen-containing gas is smaller in the first processing condition than in the second processing condition, or the supply time of the processing gas is shorter in the first processing condition than in the second processing condition.

4. The substrate processing method according to claim 2, wherein the ratio of the basic gas to the halogen-containing gas is greater in the first processing condition than in the second processing condition, or the supply time of the processing gas is longer in the first processing condition than in the second processing condition.

5. The recess is formed in multiple stages in the thickness direction of the substrate, The substrate processing method according to claim 3 or 4, wherein the plurality of recesses each open in a direction intersecting the thickness direction.

6. The substrate processing method according to claim 2, wherein the halogen-containing gas is a first fluorine-containing gas and the basic gas is ammonia gas.

7. The substrate processing method according to claim 6, wherein the first fluorine-containing gas is a fluorine gas.

8. The substrate processing method according to claim 1, wherein the germanium-containing film is a silicon germanium film.

9. The substrate processing method according to claim 2, wherein in one of the first processing conditions and the second processing conditions, the ratio of the basic gas to the halogen-containing gas is less than 0.

014.

10. The substrate processing method according to claim 2, wherein in the first processing conditions and the second processing conditions, the supply time of the processing gas is 10 seconds to 15 seconds.

11. The substrate processing method according to claim 10, wherein the first step includes supplying the processing gas into the processing container while the pressure inside the processing container containing the substrate is greater than 200 Pa.

12. The first step is, A first supply step is performed in parallel by supplying the halogen-containing gas to the substrate and supplying the basic gas to the substrate, A second supply step is performed after the first supply step, in which only one of the halogen-containing gas and the basic gas is supplied to the substrate. A substrate processing method according to claim 1, including the following:

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

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

15. A first processing unit supplies a processing gas containing a halogen-containing gas and a basic gas to alter the surface of the silicon film in a substrate in which a recess is formed, where the side walls are formed of a silicon film and the back wall is formed of a germanium-containing film, in order to generate a reaction product. A second processing unit that removes the reaction product and widens the width of the recess, A control unit outputs a control signal such that a cycle consisting of processing by the first processing unit and processing by the second processing unit is performed multiple times, and the processing by the first processing unit in the earlier cycle is performed under first processing conditions, and the processing by the first processing unit in the later cycle is performed under second processing conditions different from the first processing conditions. A substrate processing apparatus including a substrate processing device.

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