Etching method and etching apparatus

Abstract

When etching a silicon oxide film formed on a substrate, the shape of the silicon oxide film after etching is to be as desired. [Solution] The etching method of the present disclosure includes an etching step of etching a silicon oxide film formed on a substrate on which a silicon oxide film is formed on the surface by supplying a halogen-containing gas, ammonia gas, and an amine gas as etching gases.

Description

Technical Field

[0001] The present disclosure relates to an etching method and an etching apparatus.

Background Art

[0002] In the manufacturing process of semiconductor devices, for example, etching is performed on a silicon oxide film formed on a substrate such as a semiconductor wafer (hereinafter referred to as a wafer). Patent Document 1 shows that etching is performed by supplying an amine gas to the silicon oxide film.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] <​​​​​​​​​​​​​​​​​ [Figure 1] This is a longitudinal cross-sectional side view of a wafer on which an etching method, which is one embodiment of the present disclosure, is to be performed. [Figure 2] This is a longitudinal cross-sectional side view of a wafer showing the etching process of a comparative example. [Figure 3] This is a longitudinal cross-sectional side view of a wafer showing the etching process of a comparative example. [Figure 4] This is a longitudinal cross-sectional side view of a wafer showing the etching process for another comparative example. [Figure 5] This is an explanatory diagram illustrating the outline of this embodiment. [Figure 6] This is a longitudinal cross-sectional side view illustrating the etching process of this embodiment. [Figure 7] This is a chart illustrating the etching process of this embodiment. [Figure 8] This is a longitudinal cross-sectional side view of the apparatus for carrying out the etching process of this embodiment. [Figure 9] This is a graph showing the results of the evaluation test. [Figure 10] This is an explanatory diagram showing images of the results of the evaluation test. [Figure 11] This is an explanatory diagram showing images of the results of the evaluation test. [Figure 12] This is an explanatory diagram showing images of the results of the evaluation test. [Modes for carrying out the invention]

[0008] An embodiment (example) of the etching method of the present disclosure will be described below. In summary, this etching method involves supplying a halogen-containing gas, NH3 (ammonia) gas, and an amine gas as etching gases to a wafer W, which is a substrate, to etch the SiOx (silicon oxide) film 11 on the surface of the wafer W. As shown in Figure 1, a Si film 12 is formed on the surface of the wafer W, and grooves are formed in the Si film 12. Therefore, a recess 14 opening in the thickness direction of the wafer W is formed by the Si film 12 and an underlying film 13 formed below the Si film 12, and the Si film 12 is configured as a side wall forming the recess 14. Note that the underlying film 13 will be omitted from the display in some of the figures described later.

[0009] A SiOx film 11 is formed within the recess 14 described above. By using the etching gas described above, the SiOx film 11 is selectively etched from the SiOx film 11 and the Si film 12, both of which are silicon-containing films and are exposed on the surface of the wafer W. After etching, a process is carried out so that a portion of the SiOx film 11 remains within the recess 14.

[0010] More specifically, the etching process in this embodiment involves repeatedly supplying an etching gas to the wafer W and then sublimating (including vaporizing) the reaction product while the supply of the etching gas to the wafer W is stopped, thereby etching a desired amount of SiOx film 11. In this embodiment, for example, HF (hydrogen fluoride) gas is used as one of the etching gases, specifically a halogen-containing gas.

[0011] As described above, this etching gas contains NH3 gas and amine gas, both of which are basic gases. By using both NH3 gas and amine gas, the aim is to make the upper surface (surface) of the SiOx film 11 remaining in the recess 14 after etching relatively flat, thereby preventing performance degradation of semiconductor devices manufactured from wafer W due to low flatness. In this embodiment, HF gas is used as the halogen-containing gas, and trimethylamine (TMA) gas is used as the amine gas.

[0012] Hereinafter, in order to clearly show the effects of the etching gas in the embodiments, the processes of the comparative examples will be described first. The process using HF gas and NH3 gas as the etching gas is Comparative Example 1, and the process of performing etching using HF gas and TMA gas as the etching gas is Comparative Example 2. First, the etching in Comparative Example 1 will be described. FIGS. 2 and 3 are longitudinal side views of the wafer W showing the changes in the SiOx film 11 presumed to occur during the process of this Comparative Example 1. In the figure, the etching gas, which is HF gas and NH3 gas, is shown as the etching gas 21. In the following description, unless otherwise specified, the descriptions of the left and right ends and the left and right central portions of the SiOx film 11 respectively mean the left and right ends and the left and right central portions in the longitudinal cross-sectional view.

[0013] By supplying the above-described etching gas 21 to the wafer W in a state where it is heated to a predetermined temperature (FIG. 2(a)), the surface of the SiOx film 11 in the concave portion 14 reacts with the etching gas 21, and a layer 15 made of ammonium silicofluoride [(NH4)SiF6: AFS], which is a reaction product, is formed. A variation occurs in the thickness of the AFS layer 15 between the left and right ends and the central portion on the SiOx film 11 (FIG. 2(b)).

[0014] More specifically, the etching gas 21 is supplied relatively more to the left and right central portions (i.e., the regions relatively far from the interface with the Si film 12) of the SiOx film 11 than to the left and right ends (i.e., the regions close to the interface with the Si film 12). As a result, in the AFS layer 15, the thickness of the left and right central portions becomes larger than the thickness of the left and right ends. The reason for the variation in the supply amount of the etching gas 21 in each part of the SiOx film is due to the Si film 12, which will be described in detail in the description of Comparative Example 2.

[0015] Regarding the left and right central portions of the SiOx film 11, the formation of the relatively thick AFS layer 15 tends to prevent contact with the etching gas 21. On the other hand, since the thickness of the AFS layer 15 formed above the left and right ends of the SiOx film 11 is relatively small, it is likely to come into contact with the etching gas 21. Therefore, the reaction proceeds at the left and right ends of the SiOx film 11 rather than at the left and right central portions, and the surface height of the SiOx film 11 is made uniform between the left and right central portions and the left and right ends (Fig. 2(c)). However, as shown in the evaluation test described later, AFS has low adsorptivity to Si, while AFS has high adsorptivity to AFS and tends to aggregate. Due to these factors, among the AFS constituting the AFS layer 15, the AFS near the interface of the Si film 12 desorbs from the AFS layer 15. That is, when the supply of the etching gas 21 is continued, the thickness of the AFS layer 15 on the left and right ends of the SiOx film 11 decreases (Fig. 2(d)).

[0016] Due to the decrease in the thickness of the AFS layer 15 as described above, the reaction with the etching gas 21 proceeds relatively greatly at the left and right ends of the SiOx film 11, but the reaction is relatively suppressed at the left and right central portions. Then, when the thickness of the AFS layer 15 increases on the left and right ends and the left and right central portions of the SiOx film 11, contact with the etching gas 21 is prevented and the reaction stops (Fig. 3(a)). At the time of this reaction stop, as described above, due to the progress of the reaction, the surface of the SiOx film 11 has a shape where the left and right central portions are higher than the left and right ends (a convex shape). After the supply of the etching gas 21 to the wafer W is stopped, the AFS layer 15 is removed by heating the wafer W and exhausting the surroundings of the wafer W, but the SiOx film 11 remains in the above-described convex shape (Fig. 3(b)). Therefore, the flatness of the surface of the SiOx film 11 is relatively low.

[0017] Next, the etching in Comparative Example 2 will be explained with reference to Figure 4, focusing on the differences from Comparative Example 1. Figure 4 is a longitudinal cross-sectional side view of wafer W showing the changes in the SiOx film 11 that are estimated to occur during the processing of Comparative Example 2. Figure 4 is a longitudinal cross-sectional side view showing the changes in wafer W that are estimated to occur during this etching. In Figure 4, the etching gas, which is HF gas and TMA gas, is shown as etching gas 22. When the etching gas 22 is supplied to wafer W that has been heated to a predetermined temperature (Figure 4(a)), the surface of the SiOx film 11 in the recess 14 reacts with the etching gas 22, and a reaction product 16 is produced. Compared to the AFS produced from the NH3 gas described above, the sublimation temperature of this reaction product 16 is low. Therefore, this reaction product 16 sublimes rapidly after its formation, and the contact of the etching gas 22 with the SiOx film 11 is not easily hindered by this reaction product 16 (Figure 4(b)).

[0018] Regarding the etching gas 22, some is supplied downward along the opening direction of the recess 14, while other portions are supplied obliquely to the opening direction. Some of the etching gas 22 supplied in this way collides with the Si film 12 on its way downward and bounces back, supplying the left and right central parts of the SiOx film 11 in a vertical cross-sectional view. That is, the left and right central parts are supplied either directly by the etching gas 22 molecules or by the molecules that have bounced back from the Si film 12. In other words, a relatively large number of etching gas 22 molecules collide with the left and right central parts of the SiOx film 11, but due to the aforementioned bounce, the molecules are less likely to collide with the left and right edges. That is, due to the difference in molecular collision probability, etching of the SiOx film 11 proceeds relatively more in the central part than at the left and right edges (Figure 4(c)). Therefore, after etching is complete, the surface of the SiOx film 11 has a shape in which the left and right central parts are lower than the left and right edges in a vertical cross-sectional view (concave shape) (Figure 4(d)). Therefore, the surface flatness of the SiOx film 11 is relatively low.

[0019] Figure 5 is a conceptual diagram showing etching in the embodiment. The left side of the figure shows the SiOx film 11 etched using either NH3 gas or TMA gas, as explained in Figures 2 to 4. As previously mentioned, the sublimation properties of the reaction products differ depending on whether NH3 gas or TMA gas is used as the etching gas, resulting in differences in whether the central or peripheral part of the SiOx film 11 becomes higher after etching. Therefore, in this embodiment, both of these gases are used. By doing so, the effects of these gases are balanced, and as shown in the lower right panel of Figure 5, the central part on both sides becomes less higher than the edges compared to when NH3 gas is used alone, and as shown in the upper right panel of Figure 5, the edges on both sides become less higher than the central part compared to when TMA gas is used alone. Furthermore, as shown in the middle right panel of Figure 5, it becomes possible to make the heights of the central part on both sides and the edges equal.

[0020] The etching process of the embodiment will be explained with reference to the longitudinal cross-sectional side view in Figure 6 and the timing chart in Figure 7. This timing chart shows the timing of supplying each gas to the wafer W. As will be described later, the wafer W is stored in a processing container for processing, so Figure 7 shows the timing of supplying and cutting off each gas to the processing container. Furthermore, the processing container is evacuated to create a vacuum atmosphere at a predetermined pressure, and the wafer W is heated to a predetermined temperature before etching is performed.

[0021] HF gas, NH3 gas, and TMA gas are supplied as etching gases to the wafer W in such a processing container (time t1 in the chart). That is, the gases shown as etching gases 21 and 22 in Figures 2 to 4 are supplied to the wafer W (Figure 6(a)). Of these gases, HF gas and NH3 gas (etching gas 21) act on the SiOx film 11, and the AFS layer 15 is formed as described in Comparative Example 1. However, because TMA gas is included as a basic gas, the partial pressure of NH3 gas can be made relatively small, and thus the thickness of the AFS layer 15 can be made relatively small. Because the thickness of the AFS layer 15 is relatively small, each etching gas can pass through the AFS layer 15 and act on the SiOx film 11.

[0022] As described in Comparative Example 1, the AFS layer 15 is formed such that the thickness of the central part on both sides is greater than the thickness of the edges on both sides. Therefore, regarding the gas shielding effect of this AFS layer 15 on the SiOx film 11, the shielding effect is greater in the central part than at the edges on both sides of the SiOx film 11, and etching is suppressed in the central part. However, as described in Comparative Example 2, the Si film 12 causes a relatively high probability of collision of etching gas 22 in the central part on both sides of the SiOx film 11, resulting in the generation of reaction products 16 and the progression of sublimation. Similarly, etching gas 21 also collides relatively frequently in the central part on both sides, just like etching gas 22.

[0023] In this way, the differences in the shielding effect of the AFS layer 15 and the differences in collision probabilities of each gas are balanced, and the alteration proceeds with high uniformity in the central and edge parts of the SiOx film 11 (Figure 6(b)). Then the supply of HF gas, NH3 gas, and TMA gas to the wafer W is stopped (time t2). Then, the AFS layer 15 is sublimated and removed by heating the wafer W and exhausting the processing container (Figure 6(c)). If other reaction products such as reaction products 16 remain on the SiO film 11, these other reaction products are also sublimated and removed, and the surface of the SiO film 11 is exposed.

[0024] After a predetermined time has elapsed from time t2, etching gases HF gas, NH3 gas, and TMA gas are supplied to the wafer W again (time t3) and react with the SiOx film 11. Thereafter, the supply of the etching gases to the wafer W is stopped (time t4), and the reaction products on the SiOx film 11 are removed by sublimation of the reaction products and exhaust of the processing container, allowing etching to proceed and exposing the SiOx film 11. Subsequently, after a predetermined time has elapsed from time t4, etching gases HF gas, NH3 gas, and TMA gas are supplied to the wafer W again (time t5).

[0025] If the processing immediately before time t1 to time t3 is considered the first cycle, then a second cycle similar to the first cycle is performed immediately before time t3 to time t5, etching the SiOx film 11. The same cycle is repeated after time t5, and etching progresses with each cycle. When the cycle is repeated a predetermined number of times and a desired amount of the SiOx film 11 is etched, the processing on the wafer W is completed (Figure 6(d)). In each cycle, the SiOx film 11 is etched with high uniformity in the center and at the edges, so the SiOx film 11 at the end of processing has relatively high surface flatness.

[0026] In each cycle, the period during which at least one of the etching gases is supplied corresponds to the etching period, and the period during which neither etching gas is supplied corresponds to the exhaust period. Therefore, when performing the etching process as shown in Figure 7, times t1-t2 and t3-t4 correspond to the etching period, and times t2-t3 and t4-t5 correspond to the exhaust period.

[0027] Using Figure 5 above, we will provide further explanation regarding the shape of the SiOx film 11 after etching. As previously mentioned, AFS generated from the etching gas significantly influences the shape and flatness of the SiOx film 11 after etching. As explained in Figures 6 and 7, if the generation of AFS is suppressed or if the sublimation rate is high during processing, the influence of the collision probability of the TMA gas becomes relatively strong, as shown in the upper right of Figure 5, and a concave shape tends to form.

[0028] Specifically, by setting the pressure inside the processing container to a relatively low level, setting the flow rate of TMA gas supplied to the processing container to a relatively high level relative to the flow rate of NH3 gas supplied to the processing container, setting the temperature of the wafer W to a relatively high level, and / or by setting the time from the end of supplying etching gas to the next supply of etching gas (the time t2-t3 and t4-t5 in the above-mentioned processing) to a relatively long level, the SiOx film 11 tends to become concave. Conversely, by setting the pressure inside the processing container to a relatively high level, setting the flow rate of TMA gas supplied to the processing container to a relatively low level relative to the flow rate of NH3 gas supplied to the processing container, setting the temperature of the wafer W to a relatively low level, and / or by setting the exhaust time after etching to a relatively short level, the SiOx film 11 after etching tends to become convex, as shown in the lower right panel of Figure 5.

[0029] In other words, in addition to using both amine gas and NH3 gas as etching gases, the shape of the surface of the SiOx film 11 after etching can be controlled and its flatness improved by adjusting various processing conditions. In subsequent evaluation tests, the preferred range of the flow rate of TMA gas relative to the flow rate of NH3 gas among the above processing conditions for improving the flatness of the surface of the SiOx film 11 will be explained.

[0030] Next, the etching apparatus 3 that performs the etching process according to this disclosure will be described with reference to the longitudinal cross-sectional side view of Figure 8. In the figure, 31 is a processing container that constitutes the etching apparatus 3. In the figure, 39 is a wafer W transport port that opens in the side wall of the processing container 31 and is opened and closed by a gate valve 33. A stage 41 on which wafers W are placed is provided inside the processing container 31, and the stage 41 is provided with a lifting pin (not shown). Wafers W are transferred between the substrate transport mechanism located outside the processing container 31 and the stage 41 via the lifting pin.

[0031] A temperature control unit 32 is embedded in the stage 41, and the temperature of the wafer W placed on the stage 41 is controlled. This temperature control unit 32 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 controlled by heat exchange with the fluid. However, the temperature control unit 32 is not limited to a flow path for such a fluid, and may be configured as, for example, a heater for resistance heating. The temperature of the wafer W (the surface temperature of the stage 41) when supplying etching gas is preferably set to, for example, -20°C to 150°C in order to perform AFS sublimation.

[0032] Furthermore, one end of an exhaust pipe 33 is open inside the processing container 31, and the other end of the exhaust pipe 33 is connected to an exhaust mechanism 35, which is composed of, for example, a vacuum pump, via a valve 34, which is a pressure changing mechanism. By adjusting the opening of the valve 34, the pressure inside the processing container 31 is set to a predetermined pressure and etching is performed on the wafer W. This pressure is, for example, 0.133 Pa to 1.3 × 10⁻⁶. 4 It is Pa.

[0033] A gas shower plate 46 is provided on the upper side of the processing container 31, facing the stage 41. The downstream sides of gas supply passages 51-54 are connected to the gas shower plate 46, and the upstream sides of gas supply passages 51-54 are connected to gas supply sources 61-64 via flow rate adjustment units 50. Each flow rate adjustment unit 50 is equipped with a valve and a mass flow controller. The supply of each gas from gas supply sources 61-64 is controlled by opening and closing the valves included in the flow rate adjustment unit 50 to cut off the supply to the downstream side. The flow rate supplied to the downstream side of each gas is also adjusted by each flow rate adjustment unit 50. Each gas supplied to the gas passages provided in the shower plate 46 is discharged downward from numerous discharge ports provided on the lower surface of the shower plate 46. The gas shower plate 46, flow rate adjustment units 50, and gas supply sources 61-64 constitute the gas supply mechanism.

[0034] HF gas, TMA gas, N2 gas, and NH3 gas are supplied from gas supply sources 61, 62, 63, and 64, respectively, and each of these gases is supplied into the processing container 31 via the gas shower plate 46. The supply of each of these gases can be controlled independently by each flow rate adjustment unit 50. The inert gas, N2 gas, is supplied as a carrier gas to the processing container 31 via the gas shower plate 46 along with the etching gas. In addition, N2 gas is supplied to the processing container 31 as a purge gas even during periods when the etching gas is not supplied during the execution of the above cycle. That is, it is constantly supplied to the processing container 31 during the processing of the wafer W as described above.

[0035] Furthermore, the etching apparatus 3 is equipped with a control unit 30, which is a computer. This control unit 30 includes a program, memory, and a CPU. The program incorporates instructions (each step) to perform the processing and transport of the wafer W as described above. This program is stored on a storage medium, such as a compact disk, hard disk, magneto-optical disk, DVD, etc., and installed in the control unit 30. The control unit 30 outputs control signals to each part of the etching apparatus 3 using this program, thereby controlling the operation of each part. Specifically, the operations of the etching apparatus 3 controlled in this manner include, for example, the temperature of the fluid supplied to the stage 41, the supply and cut-off of each gas from the gas shower plate 46, and the adjustment of the exhaust flow rate by the valve 34.

[0036] In the above process, TMA gas is used as the amine gas, but other amine gases may also be used. Specifically, various amine compounds such as dimethylamine, dimethylethylamine, diethylamine, triethylamine, monotertiary butylamine, pyrrolidine, and pyridine can be used as etching gases. Therefore, any of primary, secondary, or tertiary amines may be used as the etching gas. The etching gas should be appropriately selected according to the material of the film to be etched. When etching the SiOx film 11, for example, in addition to HF, other halogen-containing gases such as HCl, HBr, HI, and SF6 can be used.

[0037] In the process shown in the chart in Figure 7, the cycle is repeated multiple times. However, if the required etching amount is very small, the cycle may be omitted and the process may be performed only once. Also, in the example shown in the time chart, the supply periods for HF gas, TMA gas, and NH3 gas overlap, but the supply periods for these gases may not overlap. For example, HF gas, TMA gas, and NH3 gas may be supplied to the wafer W one at a time in sequence. Alternatively, two of these three etching gases may be supplied to the wafer W first, and then the remaining one may be supplied. In other words, the supply periods for only two of the three gases may overlap.

[0038] Even if there is a difference in the supply periods for the three etching gases, one cycle can be structured such that after supplying each etching gas to the wafer W, there is an exhaust period during which the etching gas is not supplied in order to sublimate the reaction products on the wafer W. In other words, etching of the SiOx film 11 can be performed by repeating a cycle consisting of an etching period during which at least one of the three etching gases is supplied, followed by an exhaust period.

[0039] While the supply periods for the three etching gases may be staggered, it is preferable to overlap the supply periods of the three etching gases from the viewpoint of increasing the partial pressure of the etching gas around the wafer W and thereby increasing the etching rate. It is even more preferable that the three etching gases are supplied simultaneously, as shown in Figure 7 (the start and end times of the supply periods are the same).

[0040] Incidentally, we have stated that etching gases contain halogens, amines, and NH3 as components. In this specification, when we say that an etching gas or the film to be etched contains a particular component, it does not mean that the component is contained as an impurity, but rather that it is contained as a constituent component.

[0041] The configuration of the apparatus is arbitrary. For example, for the gas supply passages 51 to 53 that form the path for etching gas, a tank may be interposed as a storage section for the gas, and a valve may be interposed downstream of the tank. The gas may be stored in the tank when the valve is closed, and by opening the valve when the tank is pressurized, the apparatus can be configured to supply each etching gas into the processing container 31 at a relatively large flow rate over a relatively short period of time. The downstream sections of the gas supply passages 52 and 53 may be merged and made common, and the above-mentioned tank and valve may be provided in this common section so that the NH3 gas and TMA gas are stored in a common tank and supplied into the processing container 31 via a common valve. As for HF gas, in order to prevent unwanted reactions with the NH3 gas and TMA gas, it is preferable to store it in a separate tank from the tank in which the NH3 gas and TMA gas are stored and supply it into the processing container 31. In other words, it is sufficient for it to be stored in the tank of the gas supply passage 51 and supplied into the processing container 31 via the valve of the gas supply passage 51.

[0042] Incidentally, the recess 14 in which the SiOx film 11 is provided is not limited to opening upward (in the thickness direction of the substrate), but may also be configured to open laterally. Furthermore, regarding the positional relationship between the SiOx film 11 and the Si film 12, as long as the SiOx film 11 and the Si film 12 are adjacent to each other and exposed on the surface of the substrate W, the amount of etching of the SiOx film 11 between the region near the interface of the Si film 12 and the region relatively far from the interface can be controlled by this technology. In other words, the SiOx film 11 is not limited to being provided within the recess 14 in which the Si film 12 forms a side wall. Moreover, this technology is not limited to being applied when both the SiOx film and other types of silicon-containing films are exposed on the surface of the substrate, but may also be applied when the SiOx film 11 is provided over the entire surface of the substrate and this SiOx film 11 is etched.

[0043] Furthermore, the sidewalls of the recesses 14 where the SiOx film 11 is provided are composed of Si film 12, and it is presumed that the low adsorption capacity of this Si film 12 for reaction products is related to the shape of the SiOx film 11 after etching, as described above. Silicon-containing films other than Si film 12, such as SiGe films, also have low adsorption capacity for reaction products, similar to Si film 12, and have high resistance to the etching gases (halogen-containing gases and basic gases) described above. Therefore, even when the sidewalls of the recesses 14 are composed of these silicon-containing films other than Si film 12 instead of Si film 12, etching using these etching gases is considered effective.

[0044] 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.

[0045] The evaluation tests conducted in connection with this technology are described below. [Evaluation Test 1] As part of Evaluation Test 1, the amount of energy (ΔG / eV) required for adsorption of SiN (silicon nitride), SiO, Si, and AFS for each of HF, NH3, TMA, and AFS was calculated by simulation. The results are shown in Table 1. Each value in the table represents the amount of energy, and a smaller value indicates higher adsorption.

[0046] [Table 1]

[0047] As shown in Table 1, AFS molecules exhibit high adsorption to each other, and tend to aggregate easily. Furthermore, AFS and NH3 are readily adsorbed onto SiO, but not readily adsorbed onto Si. Therefore, when NH3 gas is included as the etching gas, it is presumed that the reaction proceeds as explained in Figure 2, etc. Specifically, it is conceivable that selective etching of the SiOx film 11 onto the Si film 12 occurs, and that the thickness of the AFS layer 15 becomes relatively smaller at the left and right edges of the SiOx film 11, as shown in Figure 2(d).

[0048] Furthermore, while TMA has relatively high adsorption properties to SiO, its adsorption properties to Si are relatively low. The adsorption properties of NH3 to SiO and Si show a similar trend to those of TMA to SiO and Si. Therefore, as explained in Figure 6, when both TMA gas and NH3 gas are used as etching gases, it can be seen that the SiOx film 11 can be etched selectively from the Si film 12.

[0049] Furthermore, as shown in Table 1, SiN has higher adsorption properties to AFS compared to Si. Therefore, when etching using NH3 gas as explained in Figure 2, if the sidewalls of the recess 14 are formed with a SiN film, it is estimated that peeling of the AFS will be less likely to occur, and the amount of etching at the left and right ends will be suppressed. Thus, although the sidewalls of the recess 14 may be made of a SiN film, it is considered that the effectiveness of this technology is higher when they are made of a Si film.

[0050] [Evaluation Test 2] As part of evaluation test 2, using a test apparatus similar to etching apparatus 3, HF gas, NH3 gas, and TMA gas were supplied to the substrate on which each film was formed, as shown in Figure 1, and etching of the SiOx film 11 in the recesses 14 was performed. These HF gases, NH3 gases, and TMA gases were supplied into the processing container 31 as shown in the chart in Figure 7. Therefore, each gas was supplied to the substrate simultaneously.

[0051] In this evaluation test 2, the flow rate ratio of NH3 gas and TMA gas supplied to the processing container 31 was changed for each substrate, and processing was performed. After etching, SEM images were acquired for each substrate, and the state of the recesses 14 was observed. Specifically, the height difference between the top of the Si film 12 and the left and right central parts of the SiOx film 11 (referred to as the central etching depth), and the height difference between the top of the Si film 12 and the left and right edges of the SiOx film 11 (referred to as the edge etching depth) were acquired. The difference in etching depth was then calculated as edge etching depth - central etching depth. Therefore, the smaller the absolute value of the difference in etching depth, the higher the uniformity of the surface height of the SiOx film 11. In other words, the uniformity of etching on the surface of the SiOx film is high. In the following explanation, the value obtained by dividing the flow rate of TMA gas supplied to the processing container 31 by the flow rate of NH3 gas supplied to the processing container 31 (i.e., the ratio of the flow rate of the amine gas to the flow rate of ammonia gas) may be expressed as "TMA gas flow rate / NH3 gas flow rate".

[0052] Regarding the TMA gas flow rate / NH3 gas flow rate mentioned above, the ratio was 11:1 in evaluation test 2-1, 9:3 in evaluation test 2-2, 7:5 in evaluation test 2-3, 1:1 in evaluation test 2-4, 5:7 in evaluation test 2-5, 3:9 in evaluation test 2-6, and 1:11 in evaluation test 2-7. Therefore, the flow rate ratios were 11 (=11 / 1) in evaluation test 2-1, 3 (=9 / 3) in evaluation test 2-2, 1.4 (=7 / 5) in evaluation test 2-3, 1 (=1 / 1) in evaluation test 2-4, 0.71 (=5 / 7) in evaluation test 2-5, 0.33 (=3 / 9) in evaluation test 2-6, and 0.09 (=1 / 11) in evaluation test 2-7.

[0053] The graph in Figure 9 and the images in Figures 10 and 11 show the results of Evaluation Test 2. The graphs are representative and show only the results for Evaluation Tests 2-1, 2-3, 2-5, and 2-7. The horizontal axis of the graph represents the TMA gas / NH3 gas flow rate ratio, and the vertical axis represents the difference in etching depth, with scales marked at predetermined numerical increments (indicated as A in the figure). From the graphs, it can be seen that the absolute value of the difference in etching depth is relatively large in Evaluation Test 2-1, but relatively small in Evaluation Tests 2-3, 2-5, and 2-7, indicating high uniformity in the height of the SiOx film 11.

[0054] Furthermore, from each image, it can be seen that for the SiOx film 11, the smaller the TMA gas flow rate / NH3 gas flow rate, the more convex the surface of the SiOx film 11 becomes, with the left and right edges being lower than the left and right central parts. Conversely, the larger the TMA gas flow rate / NH3 gas flow rate, the more concave the surface of the SiOx film 11 becomes, with the left and right edges being higher than the left and right central parts. In evaluation tests 2-1 and 2-2, the SiOx film 11 exhibits a pronounced concave shape, with a relatively large difference between the left and right central parts and the left and right edges. However, in evaluation tests 2-3 to 2-7, the difference between the left and right central parts and the left and right edges is suppressed, indicating relatively high flatness of the SiOx film 11 surface. From the images, it can be seen that this flatness is particularly high in evaluation tests 2-3 to 2-5. Therefore, from this evaluation test 2, it can be seen that when supplying TMA gas and NH3 gas to the substrate so that their supply periods overlap, it is preferable to set the TMA gas flow rate / NH3 gas flow rate to a value less than 3, and more preferably to 0.33 to 1.4.

[0055] [Evaluation Test 3] For Evaluation Test 3, as in Evaluation Test 2, each etching gas was supplied to multiple substrates as shown in the chart in Figure 7, and the SiOx film 11 was etched. In this Evaluation Test 3, instead of keeping the TMA gas flow rate / NH3 gas flow rate constant for each substrate, the temperature of each substrate was set to a different temperature for etching. Specifically, in Evaluation Tests 3-1, 3-2, and 3-3, the substrate temperatures were set to 80°C, 90°C, and 100°C, respectively.

[0056] Figure 12 shows the results of evaluation test 3. The tendency towards a concave shape was most pronounced in evaluation test 3-3, while the tendency towards a concave shape was least pronounced in evaluation test 3-1. This is thought to be due to the sublimation properties of AFS, as explained in the embodiment. Furthermore, the surface flatness of the SiOx film 11 was relatively high in evaluation tests 3-1 and 3-2. Therefore, from evaluation test 3, it was confirmed that the substrate temperature during etching is preferably lower than 100°C, and more preferably 90°C or lower. [Explanation of Symbols]

[0057] W wafer 11. SiOx (silicon oxide) film 21 Etching gases (HF gas, NH3 gas) 22 Etching gases (HF gas, TMA gas)

Claims

1. The method includes an etching step in which a silicon oxide film formed in a recess and a silicon-containing film other than the silicon film forming the side wall of the recess are adjacent to each other and exposed on the surface of a substrate, to which a halogen-containing gas, ammonia gas, and amine gas are supplied as etching gases to selectively etch the silicon oxide film among the silicon oxide film and the silicon-containing film, The periods during which each of the halogen-containing gas, ammonia gas, and amine gas is supplied to the substrate overlap. The etching step is a step of supplying the etching gas to the substrate while the reaction product between the etching gas and the silicon oxide film remains on the silicon oxide film, wherein the ratio of the flow rate of the amine gas to the flow rate of the ammonia gas supplied to the substrate is less than 3.

2. The etching method according to claim 1, wherein the silicon-containing film other than the silicon film is a SiGe film or a nitrogen-containing film.

3. An etching period during which at least one of the etching gases is supplied to the substrate, The etching method according to claim 1, wherein a cycle consisting of stopping the supply of each etching gas to the substrate after the etching period and exhausting the area around the substrate is repeated.

4. The etching method according to claim 1, wherein only one type of amine gas is supplied as the amine gas.

5. The etching method according to claim 4, wherein the single amine gas is trimethylamine gas.

6. The etching method according to claim 1, wherein the etching step is a step of supplying the etching gas while the temperature of the substrate is lower than 100°C.

7. A processing container for storing a substrate in which a silicon oxide film formed in a recess and a silicon-containing film other than the silicon film forming the side wall of the recess are adjacent to each other and are exposed on the surface, A gas supply mechanism for selectively etching the silicon oxide film, among the silicon oxide film and the silicon-containing film, by supplying a halogen-containing gas, ammonia gas, and amine gas as etching gases, Equipped with, The periods during which each of the halogen-containing gas, ammonia gas, and amine gas is supplied to the substrate overlap. The aforementioned gas supply mechanism supplies the etching gas to the substrate while the reaction products between the etching gas and the silicon oxide film remain on the silicon oxide film, and the ratio of the flow rate of the amine gas to the flow rate of the ammonia gas supplied to the substrate is less than 3.

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