Etching method and etching apparatus

Abstract

An etching method according to the present disclosure includes an etching step of etching a silicon germanium film provided on a substrate by supplying, to the substrate, a first etching gas containing fluorine atoms and a second etching gas that is a compound of germanium and fluorine.

Description

Etching method and etching apparatus

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

[0002] In the manufacture of semiconductor devices, it is sometimes necessary to selectively etch one of the Si film and SiGe film formed on the surface of a semiconductor wafer (hereinafter referred to as a wafer), which is a substrate. Patent Document 1 describes a structure in which Si films and SiGe films are alternately stacked, and describes the selective etching of the SiGe film using the etching gas ClF ３ It has been shown that by supplying HF gas in addition to the gas, the Si film is hydrogen-terminated and etching is suppressed. Patent Document 2 describes how GeF is used to selectively etch the Si film in the above-mentioned structure. ４ It is stated that the gas will be used as an etching gas.

[0003] Patent No. 7113711 Patent No. 7317201

[0004] This disclosure provides a technique for etching a silicon germanium film in a manner that allows for good etching control.

[0005] The etching method of this disclosure includes an etching step of supplying a first etching gas containing fluorine atoms and a second etching gas which is a compound of germanium and fluorine to a substrate, and etching a silicon germanium film provided on the substrate.

[0006] This disclosure enables etching of a silicon germanium film in a manner that provides good etching controllability.

[0007] This is a longitudinal cross-sectional side view of a wafer etched by an etching method according to one embodiment of the present disclosure. This is a longitudinal cross-sectional side view of a wafer etched by the comparative example. This is a longitudinal cross-sectional side view of a wafer etched by the comparative example. This is a longitudinal cross-sectional side view of a wafer etched by the comparative example. This is a longitudinal cross-sectional side view of a wafer etched by the comparative example. This is a longitudinal cross-sectional side view of a wafer in the process of etching in the embodiment. This is a longitudinal cross-sectional side view of a wafer in the process of etching in the embodiment. This is a longitudinal cross-sectional side view of a wafer after etching in the embodiment. This is a chart showing the gas supply timing in the process of the embodiment. This is a longitudinal cross-sectional side view of the etching apparatus. This is a chart showing the timing of other gas supply examples. This is a chart showing the timing of other gas supply examples. This is a graph showing the results of the evaluation test.

[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. A lower layer film 11 is formed on the wafer W. On the lower layer 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. Hereafter, 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. In the example shown in Figure 1, the thickness of the SiGe film 12 is greater than that of the Si film 13, but conversely, the Si film 13 may be larger than the SiGe film 12. The germanium content in the SiGe film 12 is, for example, 20 atomic percent or less.

[0009] A mask film 14 is stacked on the uppermost Si film 13 in the repeating structure described above. The mask film 14 is made of, for example, a silicon nitride film or a silicon oxide film, and prevents etching of the Si film 13 from above. A recess 15 extending in the vertical direction is formed so as to open into the mask film 14, and the lower end of the recess 15 reaches the lower layer film 11. Therefore, the bottom surface of the recess 15 is formed by the lower layer film 11. In the following description, the recess 15 may be referred to as a vertical recess 15 to distinguish it from the horizontal recess 16 described later. With the formation of the vertical recess 15 in this way, the SiGe film 12 and the Si film 13 are exposed on the surface of the wafer W.

[0010] In this embodiment, etching gas is supplied to the wafer W and introduced into the vertical recesses 15, with the objective of selectively etching the SiGe film 12 from the side, out of the Si film 12 and Si film 13. That is, the SiGe film 12 is etched in a direction intersecting the thickness direction of the wafer W. Plasma is not formed during etching. This etching is carried out so that a portion of the SiGe film 12 remains. In other words, etching is performed so that recesses 16 (not shown in Figure 1) are formed laterally. When etching the SiGe film 12 in this way, it is required to etch the SiGe film 12 in each stage with high uniformity and to make the depth L of the lateral recesses 16 the same in each stage.

[0011] Before describing the etching process of this embodiment in detail, a comparative example will be described. Generally, ClF is used as the etching gas for SiGe films. ３ (Chlorine trifluoride) gas and F ２ Gases containing fluorine atoms, such as (fluorine) gas, are known. When etching the SiGe film 12 on wafer W in Figure 1, ClF is used as the etching gas. ３Assume that gas is used. In that case, it has been confirmed by tests conducted by the applicant on a substrate having the same configuration as the wafer W in FIG. 1 that, as shown in FIG. 2, the SiGe films 12 at each stage are etched. As shown in the figure, there is a relatively large variation in the etching amount of the SiGe films 12 at each stage. More specifically, for the recesses 16 located on the upper stage side, the depth L is large, and this depth L decreases as it goes towards the lower stage. Although not shown in the figure, for ClF ３ When using gas, the etching amount of the Si film 13 is relatively large. That is, the etching selectivity with respect to the SiGe film 12 is low.

[0012] As a reason for the increase in the depth of the recesses 16 on the upper stage side, for ClF ３ gas, the reactivity is high, the incubation time is short, and since it reacts with the SiGe film 12 and the Si film 13 above the vertical recess 15, it is considered that it is difficult to supply ClF ３ gas to the lower side of the vertical recess 15 compared to the upper side of the vertical recess 15. The incubation time is the time required from the start of supplying the etching gas to the object to be etched until the etching starts.

[0013] On the other hand, when etching the SiGe film 12 of the wafer W in FIG. 1, assume that F ３ gas is used instead of ClF ２ [[ID=I6]] gas. Note that GeF ４ gas to be described later is not supplied. When using only F ２ gas as the etching gas, it has been confirmed that the etching of the Si film 13 is suppressed and the etching selectivity with respect to the SiGe film 12 is high.

[0014] However, when using F ２ gas, since the reactivity with respect to the SiGe film 12 is low, in order to obtain a relatively large etching amount, the etching time becomes long. Also, for F ２When using gas, it has been confirmed that there is a relatively large variation in the amount of etching in each stage of the SiGe film 12, as shown in Figure 3. To describe this variation in detail, the recess 16 located on the lower side of the vertical recess 15 has a large depth L, and etching is performed such that the depth L of the recess 16 decreases as you move towards the upper part of the vertical recess 15.

[0015] And as will be shown in the evaluation test described later, F ２ When using gas, it has been confirmed that the processing stability is low. Specifically, low processing stability means that when processing multiple substrates sequentially, there is a large variation in the depth L of the recesses 16 between substrates when the processing conditions are the same, and, as shown in Figures 4 and 5, when the processing conditions other than the etching time (etching gas supply time) are the same, the depth L does not increase in proportion to the length of the etching time.

[0016] In that way F ２ The reasons why the depth L of the lower recess 16 increases when gas is used and why the processing stability is low are F ２ In addition to the relatively low reactivity of the gas with the SiGe film 12 and the relatively long incubation time, F ２ It is presumed that the reaction products produced by the reaction between the gas and the SiGe film 12 have an influence. These reaction products are thought to be SiF ４ GeF ４ GeF ２ These and other things occur, but at least GeF ４ (Germanium tetrafluoride) is F ２ It exhibits relatively high etching properties for the SiGe film 12 in the presence of gas. Therefore, GeF formed in the film ４ When the concentration of the GeF is low, etching of the SiGe film 12 is suppressed, and the GeF ４ As the concentration of increases, the etching rate (amount of etching per unit time) of the SiGe film 12 increases. The reaction product is GeF ４ is, F ２ The SiGe film 12 is in a gaseous state at the temperature at which etching by the gas occurs.

[0017] F ２Regarding the gas, due to its low reactivity with the SiGe film 12, ClF ３ Unlike gas, it is supplied sufficiently not only to the upper side of the vertical recess 15 but also to the lower side. Furthermore, the lower side of the vertical recess 15 is supplied with more GeF gas generated during etching compared to the upper side. ４ It is difficult for it to be released outside the vertical recess 15 and tends to accumulate. Therefore, the GeF in the environment in contact with the SiGe film 12 is lower on the lower side of the vertical recess 15 compared to the upper side. ４ Because the concentration of F tends to be high, ２ Etching of the SiGe film 12 begins and progresses rapidly from the moment the gas supply starts. In other words, it is presumed that the incubation time was shorter on the lower side of the vertical recess 15 compared to the upper side, resulting in a difference in the amount of etching (= depth L) between the recesses 16. Also, F ２ When using gas, the incubation time is relatively long, so GeF is used between the substrates. ４ The relatively large variation in the timing of these events is thought to be the reason for the low stability of the process described above.

[0018] Therefore, when etching the SiGe film 12, it is required to obtain good etching controllability. Obtaining this good etching controllability includes some or all of the following: suppressing variations in the etching amount of each recess 16, obtaining a relatively large etching amount in a relatively short time, and increasing the stability of the process.

[0019] In the process of this embodiment, the etching gas is the first etching gas, F ２ The gas and GeF, a second etching gas which is a compound of germanium and fluorine. ４ Gas and are supplied to the wafer W. As a result, each SiGe film 12 is relatively GeF ４The material is exposed to an environment with a high concentration of the material, so that etching is started quickly (i.e., the incubation time is shortened), and then etching proceeds at a high etching rate. By performing etching in this manner, variations in the amount of etching in the recesses 16 of each stage formed after processing are suppressed, a relatively large amount of etching can be obtained in a relatively short time, and the stability of the process is increased.

[0020] The processing of this embodiment will be explained below using the longitudinal cross-sectional side views of the wafer W shown in Figures 6 to 8 and Figure 9, which is a time chart showing the supply state of each gas to the wafer W. In this embodiment, the wafer W is processed while it is stored in a processing container where a vacuum atmosphere of a predetermined pressure is formed. During processing, the wafer W is placed on a stage and adjusted to a predetermined temperature.

[0021] First, with respect to the wafer W shown in Figure 1, F ２ Gas 21 and GeF ４ Start supplying gas 22 (time t1 in the chart). This F ２ Gas 21 and GeF ４ Gas 22 enters the vertical recess 15 and is supplied to the SiGe film 12 from the side. ２ Gas and GeF ４ When gas is supplied, the reaction shown in Equation 1 below proceeds. Note that the stoichiometric ratios on both sides of this reaction equation are not the same. As the reaction proceeds in this way, from the perspective of the SiGe film 12, GeF ４ F is the comparative example. ２ In addition to being supplied as a reaction product generated by the etching gas, just as when only the gas is supplied as the etching gas, it is also supplied as the etching gas itself. ２ Gas + GeF ４ +SiGe→SiF ４ (gas) + GeF ４ (gas) + GeF ２ (Solid) + GeFx...Formula 1

[0022] As shown in Figure 6, the reaction of Equation 1 proceeds on the surface layer of each SiGe film 12 facing the vertical recess 15, initiating the transformation into the reaction product layer 17. F explained in the comparative example ２ Similar to the case where only gas 21 is supplied as the etching gas, GeF is present on the lower side of the vertical recess 15. ４ The reaction products containing the accumulators accumulate, and the lower SiGe film 12 is GeF ４ This will result in exposure to an environment with relatively high concentrations of [the substance]. On the other hand, GeF ４ Gas 22 is supplied into the vertical recess 15, and in particular, the GeF is supplied to the upper side of the vertical recess 15 near the opening. ４ The concentration of gas 22 increases. Therefore, the SiGe film 12 in each stage becomes GeF ４ The film is exposed to an environment with a sufficiently high concentration of [the substance]. As a result, the transformation into the reaction product layer 17 proceeds uniformly and rapidly among the SiGe films 12 in each stage. Furthermore, the generated reaction product layer 17 is removed by vaporization. In this way, etching of each stage of the SiGe film 12 is started with high uniformity with a relatively short incubation time.

[0023] Then etching proceeds, and the depth L of the recesses 16 in each step increases. The reaction product is GeF ４ and GeF ４ Due to the presence of gas, this etching proceeds with a high etching rate. At time t2, a predetermined time has elapsed from time t1, GeF is applied to the wafer W. ４ The gas supply was cut off, F ２ The supply of gas only will continue. As explained in the comparative example, F ２ Even when supplying only gas, F ２ GeF is produced from the gas and the SiGe film 12. ４ This is generated. Therefore, the uniformity of the depth L between the recesses 16 is maintained, and F continues. ２ Gas and GeF ４ The etching of each SiGe film 12 progresses due to the action of (Figure 7). Subsequently, after a predetermined time has elapsed from time t2 and a recess 16 of the desired depth L is formed, F is applied to the wafer W. ２The gas supply is stopped (time t3), and the etching process is completed. Figure 8 shows the wafer W after the etching is complete.

[0024] As described above, in the etching process of this embodiment, F ２ From the start of gas etching until partway through, GeF ４ By supplying gas, the GeF environment on the surface of each SiGe film 12 in the depth direction of the vertical recess 15 is controlled. ４ The concentration of the solvent is standardized. This ensures that each SiGe film 12 is etched uniformly and relatively extensively with a short etching time. As will be shown in the evaluation tests later, it has been confirmed that the etching process of this embodiment also improves the stability of the process. Furthermore, it has been confirmed that the etching of the Si film 13 can be suppressed by the method of this embodiment.

[0025] Next, an etching apparatus 3, which is an example of an etching apparatus capable of performing the etching process of this embodiment described above, will be explained. Figure 10 is a longitudinal cross-sectional side view of the etching apparatus 3. In the figure, 31 is the processing container described above and constitutes the etching apparatus 3. In the figure, 32 is a wafer W transport port opening in the side wall of the processing container 31, which 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 lifting pins (not shown). Wafers W are transferred between the substrate transport mechanism located outside the processing container 31 and the stage 41 via these lifting pins.

[0026] A temperature control unit 42 is embedded in the stage 41, and the wafer W placed on the stage 41 is temperature-controlled. This temperature control unit 42 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 42 is not limited to such a fluid flow path, and may be configured as, for example, a heater for resistance heating.

[0027] Furthermore, one end of an exhaust pipe 34 is open inside the processing container 31, and the other end of the exhaust pipe 34 is connected to an exhaust mechanism 36, which is composed of, for example, a vacuum pump, via a valve 35, which is a pressure changing mechanism. By adjusting the opening of the valve 35, the exhaust flow rate inside the processing container 31 is adjusted, and the pressure inside the processing container 31 is set to the desired vacuum pressure.

[0028] A showerhead 43 is provided on the upper side of the processing container 31, facing the stage 41. The downstream side of the gas supply passages 51 to 54 is connected to the showerhead 43, and the upstream side of the gas supply passages 51 to 54 is connected to the gas supply sources 61 to 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 the gas supply sources 61 to 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. Therefore, each of the times t1 to t3 shown in the time chart is the timing when the opening and closing of the valves in the gas supply passages 51 and 52 is switched. In addition, the flow rate supplied to the downstream side for each gas is adjusted by each flow rate adjustment unit 50. Each gas supplied to the gas passage provided in the showerhead 43 is discharged downward from a number of discharge ports provided on the lower surface of the showerhead 43.

[0029] From gas supply sources 61, 62, 63, and 64, F ２ Gas, GeF ４ Gas, N ２ Gas and Ar gas are supplied separately, and each of these gases is supplied into the processing container 31 via the showerhead 43. Each of these gases can be supplied independently by the flow rate adjustment units 50. The flow rate adjustment units 50 provided in the gas supply sources 61 and 62 and the gas supply paths 51 and 52 correspond to the gas supply mechanism that supplies etching gas into the processing container 31. ２ The gas and Ar gas are used as carrier gases, and the etching gas is F ２ Gas and GeF ４ It is supplied into the processing container 31 along with the gas. ２The gas and Ar gas are supplied after the supply of etching gas to the processing container 31 is stopped, and also act as purge gases to purge any remaining processing gas from the processing container 31.

[0030] 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, adjusting the temperature of the fluid supplied to the stage 41 (i.e., the processing temperature of the wafer W), cutting off the supply of each gas from the shower head 43, and adjusting the exhaust flow rate by the valve 35 (i.e., adjusting the pressure inside the processing container 31).

[0031] Using the etching apparatus 3 described above, etching gas is supplied into the processing container 31 as shown in the time chart of Figure 9, and the wafer W is processed as shown in Figures 6 to 8. There are no particular restrictions on the pressure inside the processing container 31 during the etching process, but for example, it is set to 1.33 Pa (10 mTorr) to 1333 Pa (10 Torr). F ２ Gas and GeF ４ The preferred partial pressures of each gas will be described later. The processing temperature of the wafer W (the temperature of the wafer W during etching gas supply) should be a temperature that can vaporize and remove each product constituting the reaction product layer 17, for example, -20°C to 150°C.

[0032] By the way, the time chart shown in Figure 11 shows a different processing example from the processing example shown in the time chart in Figure 9. In this processing example in Figure 11, F ２ GeF during the supply of gas to wafer W ４ Without stopping the supply of gas to wafer W, F ２ At time t3, when the gas supply is stopped, GeF４ The supply of gas to the wafer W is stopped. As shown in the example of FIG. 11, GeF ４ The supply of gas to F ２ The supply of gas is not limited to stopping during the supply. However, as described above, GeF ４ Even if the supply of gas is stopped during the supply, etching can proceed due to GeF generated from the SiGe film 12. Therefore, from the viewpoint of avoiding the supply of unnecessary gas, GeF ４ Regarding the supply of gas, it is preferable to stop during the supply of F ４ gas (that is, during etching). ２

[0033] Incidentally, as shown in the evaluation test described later, F ２ gas and GeF ４ Among the gases, even if only GeF ４ gas is supplied to the wafer W, the SiGe film 12 cannot be etched. Therefore, GeF ４ gas is not used alone as an etching gas, but is supplied as an etching gas together with F ２ gas. That is, these gases are supplied to the wafer W so that the period during which F ２ gas is supplied to the wafer W overlaps with the period during which GeF ４ gas is supplied to the wafer W.

[0034] In making the supply periods of the gases overlap with each other, if F ２ gas is supplied to the wafer W before GeF ４ gas, as described in the comparative example, the amounts of GeF generated from the SiGe films 12 at each stage are different from each other, and the etching rates between the SiGe films 12 at each stage will be different. Therefore, as shown in FIGS. 9 and 11, F ４ gas and GeF ２ gas are preferably supplied to the wafer W simultaneously. ４ [[ID=四十二]] ４ [[ID=四十三]] [[ID=四十四]] [[ID=四十五]]

[0035] Furthermore, the etching apparatus 3 may be configured to supply HF (hydrogen fluoride) gas into the processing container 31 in addition to the etching gas and inert gas described above. Specifically, in addition to the apparatus configuration shown in Figure 10, the etching apparatus 3 is configured to include an HF gas supply source, a gas supply path connecting the HF gas supply source and the shower head 43, and a flow rate adjustment unit 50 interposed in the gas supply path. Then, as shown in the time chart in Figure 12, F ２ During the time t1 to t3 while gas is being supplied, HF gas is also supplied to the wafer W. As described in Patent Document 1, the surface of the Si film 13 is hydrogen-terminated by the HF gas, which protects it from etching gas, and this is preferable because it more reliably suppresses etching of the Si film 13. In the example shown in Figure 12, F ２ Although HF gas is continuously supplied to the wafer W between time t1 and time t3 when the gas is supplied, the supply of HF gas is not limited to this method, F ２ HF gas may be supplied only for a portion of the time range between time t1 and time t3.

[0036] The wafer W to be etched is not limited to having the structure shown in Figure 1. For example, even when a SiGe film forms the upper surface of the wafer W and the SiGe film is etched from above, the etching method of this embodiment described above can be used. Furthermore, the etching method described above is not limited to wafers W on which both a Si film and a SiGe film are formed on the surface; the etching method of this embodiment may also be used when only a SiGe film is formed on the surface of the wafer W. Even when selective etching of the Si film is not performed in this way, this embodiment is preferable because it is possible to obtain a relatively large amount of etching of the SiGe film in a short etching time and to obtain high stability in the process.

[0037] Also, as an etching gas, F ２ ClF instead of gas ３ You may supply gas. That is, ClF ３ Gas and GeF ４The gas may be supplied to the wafer W as an etching gas. However, as mentioned in the comparative example, ClF ３ Because the gas has high etching properties for Si films, F is used to selectively etch the SiGe film among the Si film and SiGe film. ２ It is preferable to use gas.

[0038] Up to this point, wafers have been used as an example of substrates to be processed, but the substrates processed in the processing container 31 include, in addition to wafers, substrates for manufacturing flat panel displays, substrates for manufacturing exposure masks used in photolithography, and dummy substrates processed for the purpose of testing and setting processing parameters in the substrate processing apparatus. Furthermore, the embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The above embodiments may be omitted, replaced, modified, and combined in various ways without departing from the scope and spirit of the attached claims.

[0039] [Evaluation Tests] The evaluation tests conducted in relation to this embodiment will be described below. • Evaluation Test 1 As Evaluation Test 1, a substrate having a film structure similar to the wafer W described in Figure 1 was placed on the stage 41 of the etching apparatus 3, F ２ Gas, N ２ The SiGe film 12 was etched by supplying gas and Ar gas into the processing container 31. Therefore, in this evaluation test 1, GeF ４ The process described as a comparative example was performed without supplying gas to the substrate. The combination of etching time and substrate processing temperature was changed for each substrate, and the process was performed on each substrate. After processing, an SEM image was acquired, and the depth L of the recess 16 (i.e., etching amount) was measured from the image, and the average value was calculated. The substrate processing temperature was set to 20°C or 40°C, and the pressure in the processing container 31 during etching gas supply was set to a pressure within the range described in the embodiment. Some of the multiple substrates were processed under the same processing conditions.

[0040] Tables 1 and 2 below show the results of Evaluation Test 1. Table 1 shows the test results when the substrate processing temperature was 20°C, and Table 2 shows the test results when the substrate processing temperature was 40°C. In each table, the average value calculated for depth L is normalized by dividing it by a predetermined positive number. Unless otherwise specified, the depth L shown in the following explanation is the same as the depth L shown in the results of Evaluation Test 1, normalized from the average value. Furthermore, for each result of substrates processed under the same processing conditions, the results of the first processing and the results of the second processing are shown in the table, respectively. In the substrate, multiple vertical recesses 15 are formed, and the SiGe film 12 is etched from the left and right. For this reason, there is a limit to the depth L of the recesses 16, and if etching exceeds this limit, the left and right recesses 16 are connected. The description of a depth L of 42.5 or more in Tables 1 and 2 indicates that the limit for depth L is 42.5, and etching was performed to exceed this limit, resulting in the left and right recesses 16 being connected to each other. Furthermore, when presenting the results of each evaluation test other than evaluation test 1, if the depth L exceeds the limit value, the word "greater than or equal to" will be added to indicate that limit value.

[0041]

[0042]

[0043] As is clear from Tables 1 and 2, when the processing temperature is the same between substrates, the depth L does not increase as the etching time increases, and the phenomena shown in Figures 4 and 5 occur. Furthermore, when the etching time is the same, the difference in depth L is relatively large. In addition, even when the etching time is set to a relatively long time, the depth L before normalization was generally small. From these results, it is desirable to obtain a relatively large etching amount with a short etching time, and to increase the stability of the process (suppressing the variation in the depth L of the recesses 16 between substrates and making the depth L increase in proportion to the length of the etching time).

[0044] • Evaluation Test 2 This section will explain Evaluation Test 2, focusing on the differences from Evaluation Test 1. In Evaluation Test 2, for some of the multiple substrates, F was used as described in the embodiment. ２Gas and GeF ４ The gas was used as the etching gas for the process, and for the other parts, the same as in evaluation test 1, F ２ The process was carried out using only gas as the etching gas. In evaluation tests 2-1 and 2-3, the etching gas was F ２ Only gas is used, and in evaluation tests 2-2 and 2-4, the etching gas is F ２ Gas and GeF ４ It was gas.

[0045] In evaluation tests 2-1 and 2-2, and in evaluation tests 2-3 and 2-4, the processing conditions are the same except for the flow rate of each gas supplied to the substrate. To describe the setting of this gas flow rate in more detail, in evaluation tests 2-1 to 2-4, N is supplied along with the etching gas. ２ Gas and Ar gas are supplied into the processing container 31. The flow rates of each gas supplied into the processing container 31 are as follows. Evaluation test 2-1: F ２ Gas = A1 sccm, GeF ４ Gas = 0 sccm, Ar gas = C 1 sccm, N ２ Gas = D1sccm Evaluation Test 2-2: F ２ Gas = A1 sccm, GeF ４ Gas = B1 sccm, Ar gas = C2 sccm, N ２ Gas = D1sccm Evaluation Test 2-3: F ２ Gas = A1 sccm, GeF ４ Gas = 0 sccm, Ar gas = C 1 sccm, N ２ Gas = D2sccm Evaluation Test 2-4: F ２ Gas = A1 sccm, GeF ４ Gas = B1 sccm, Ar gas = C2 sccm, N ２ Gas = D2sccm

[0046] Between evaluation tests 2-1 and 2-2, and between evaluation tests 2-3 and 2-4, the etching gas and N supplied into the processing container 31 ２The sum of the individual gas and Ar gas flow rates (total flow rate) is set to be equal in each case. That is, (A1 + C1 + D1) sccm in evaluation test 2-1 is equal to (A1 + B1 + C1 + D1) sccm in evaluation test 2-2, and (A1 + C1 + D2) sccm in evaluation test 2-3 is equal to (A1 + B1 + C2 + D2) sccm in evaluation test 2-2. Therefore, in evaluation tests 2-2 and 2-4, GeF ４ The flow rate of Ar gas supplied into the processing container 31 is set lower than in evaluation tests 2-1 and 2-3, respectively, by the amount of the gas flow rate. ２ Regarding the gas flow rate, D1 sccm in evaluation tests 2-1 and 2-2 < D2 sccm in evaluation tests 2-3 and 2-4, indicating that the total gas flow rate in evaluation tests 2-3 and 2-4 is higher than in evaluation tests 2-1 and 2-2, and that the dilution rate of the etching gas by the inert gas is higher. Note that in evaluation tests 2-2 and 2-4, F ２ The gas flow rate is GeF ４ Greater than the gas flow rate, specifically F ２ Gas flow rate A1 sccm / GeF ４ The gas flow rate B1sccm = 2.

[0047] In this evaluation test 2 and the evaluation tests described later, F ２ Gas and GeF ４ When supplying gas to the substrate, F ２ GeF ４ Without stopping the gas supply, F as shown in Figure 11 ２ During the supply of gas to the substrate, GeF to the substrate ４ The gas supply is kept continuous. Regarding processing conditions other than the gas flow rate, in evaluation tests 2-1 to 2-4, the processing temperature of the substrate was set to 20°C. Also, in evaluation tests 2-1 to 2-4, the pressure inside the processing container 31 was set to a value within the range described in the embodiment, with E1 Torr in evaluation tests 2-1 and 2-2, and E2 Torr (higher than E1 Torr) in evaluation tests 2-3 and 2-4. The etching time was set to 2400 seconds in evaluation tests 2-1 and 2-2, and to 1600 seconds in evaluation tests 2-3 and 2-4.

[0048] Table 3 below summarizes the results of evaluation test 2. As indicated in the table, GeF was obtained between evaluation tests 2-1 and 2-2, and between evaluation tests 2-3 and 2-4, respectively. ４ Evaluation tests 2-2 and 2-4, where gas was supplied, had a greater depth L. Therefore, F was used as the etching gas. ２ GeF along with gas ４ Supplying gas resulted in favorable outcomes.

[0049]

[0050] - Evaluation Test 3 Evaluation Test 3 (3-1 to 3-8) was conducted in the same manner as Evaluation Test 2, except that the substrate processing temperature and etching time were different. For Evaluation Tests 3-1, 3-2, 3-3, and 3-4, the substrate processing temperature was set to 35°C and the substrate processing time (etching time) was set to 1200 seconds, 1200 seconds, 600 seconds, and 600 seconds, respectively, but the processing conditions were the same as for Evaluation Tests 2-1, 2-2, 2-3, and 2-4, respectively. Therefore, for Evaluation Tests 3-2 and 3-4, F was used as the etching gas. ２ Gas and GeF ４ Both gases are supplied to the substrate, and in evaluation tests 3-3 and 3-4, the total flow rate of supplied gas is greater than in evaluation tests 3-1 and 3-2, resulting in a higher dilution ratio of the etching gas.

[0051] For evaluation tests 3-5, 3-6, 3-7, and 3-8, the processing conditions were the same as for evaluation tests 2-1, 2-2, 2-3, and 2-4, respectively, except that the processing temperature of the substrate was set to 50°C and the processing times were 1200 seconds, 1200 seconds, 480 seconds, and 480 seconds. Therefore, in evaluation tests 3-6 and 3-8, F was used as the etching gas. ２ Gas and GeF ４ Both gases are supplied to the substrate.

[0052]

[0053]

[0054] Tables 4 and 5 above summarize the results of evaluation tests 3-1 to 3-8. Note that the depth L of the recess 16 in evaluation test 3-3 was too small to be accurately measured. As is clear from Tables 4 and 5, GeF ４ When comparing evaluation tests 3-1 and 3-2, 3-3 and 3-4, 3-5 and 3-6, and 3-7 and 3-8, which differ in terms of the presence or absence of gas supply, GeF ４ The test in which gas was supplied showed a larger value for depth L.

[0055] Also, GeF ４ In evaluation tests 3-4 and 3-8, where gas was supplied and the size of the recesses 16 did not exceed the limit, the acquired images showed no significant difference in depth L between the recesses 16 in each stage, confirming that the SiGe film 12 was etched with high uniformity in each stage. Thus, in evaluation test 3 as in evaluation test 2, F was used as the etching gas. ２ GeF along with gas ４ Supplying gas resulted in favorable outcomes.

[0056] As described above, evaluation tests 2 and 3 were F ２ Gas and GeF ４ By supplying gas as etching gas, F ２ It was shown that the depth L of the recess 16 becomes larger compared to when only gas is supplied as the etching gas. This is because, as explained in the embodiment, GeF ４ This is presumably due to a shorter incubation time resulting from the supply of gas.

[0057] - Evaluation Test 4 Evaluation Tests 4-1 to 4-4 were performed on the substrate using the same processing conditions as in Evaluation Test 2-2, except that the etching time was changed. Also, Evaluation Tests 4-5 to 4-8 were performed on the substrate using the same processing conditions as in Evaluation Test 2-4, except that the etching time was changed. Therefore, in Evaluation Tests 4-1 to 4-8, F ２ Gas and GeF ４The gas is supplied to the substrate as an etching gas. In evaluation tests 4-1, 4-2, 4-3, and 4-4, the etching times were set to 900 seconds, 1200 seconds, 1800 seconds, and 2400 seconds, respectively. In evaluation tests 4-5, 4-6, 4-7, and 4-8, the etching times were set to 1200 seconds, 1400 seconds, 1400 seconds, and 1500 seconds, respectively. Therefore, the etching time is the same between evaluation tests 4-6 and 4-7.

[0058]

[0059]

[0060] Tables 6 and 7 above summarize the results of evaluation tests 4-1 to 4-8. Looking at the results of evaluation tests 4-1 to 4-4, where only the etching time differs, the depth L of the recess 16 increases as the etching time increases. Looking at the results of evaluation tests 4-5 to 4-8, where only the etching time differs, the depth L of the recess 16 increases as the etching time increases, and there is no significant difference in depth L between evaluation tests 4-6 and 4-7, where the etching time is the same. From the results of evaluation tests 4 above, F ２ Gas and GeF ４ It was confirmed that supplying the gas to the wafer W as an etching gas can significantly improve the stability of the process.

[0061] - Evaluation Test 5: Evaluation Test 5 was F ２ Gas, GeF ４ Gas, N ２ Gas and Ar gas were supplied to the wafer W, and etching was performed on multiple substrates in the same manner as in other evaluation tests. The state of the Si film 13 and SiGe film 12 was observed from the images acquired after etching. When etching multiple substrates in this manner, GeF was supplied into the processing container 31 between the substrates. ４ The gas flow rate is kept constant, F ２ Gas flow rate and N ２ The combination with the gas flow rate was changed. Note that among the multiple substrates, F ２ Gas flow rate or GeF ４Some samples were processed with the gas flow rate set to 0 sccm. The total gas flow rate supplied to the processing container 31 was kept constant between substrates. Therefore, in this evaluation test 5, the F inside the processing container 31 ２ Gas, GeF ４ The combination of partial pressures for each gas is set differently for each substrate. Other than the gas flow rate, the processing conditions are the same for all substrates. The processing temperature for each substrate (i.e., the temperature of stage 41) is set to 40°C, and the etching time is set to 300 seconds.

[0062] Images obtained after etching confirmed etching of the Si film 13 on some substrates. The graph in Figure 13 shows F inside the processing container 31. ２ Gas and GeF ４ This graph shows the relationship between the gas partial pressure setting and whether or not the Si film 13 is etched. The horizontal axis of the graph represents the F inside the processing container 31. ２ Partial pressure of the gas, the vertical axis of the graph is GeF inside the processing container 31. ４ The partial pressures of each gas are set. As shown in the graph, GeF ４ With the partial pressure of the gas set to 100 mTorr (13.3 Pa), F ２ The tests are being conducted with the partial pressure of the gas varied within the range of 0 mTorr to 200 mTorr (26.6 Pa). ４ A partial pressure of 100 mTorr of gas refers to the GeF supplied into the processing container 31. ４ The gas flow rate / total gas flow rate supplied into the processing container 31 × pressure inside the processing container 31 = 100 mTorr, and GeF ４ The partial pressures of other gases will be calculated in the same manner.

[0063] The above F ２ Within the range of gas partial pressure from 0 mTorr to 200 mTorr, F ２ When the partial pressure of the gas is 0 mTorr (i.e., F ２ When the gas flow rate was 0 sccm, the Si film 13 was not etched, but the SiGe film 12 was also not etched. Therefore, as described in the embodiment, GeF ４The SiGe film 12 cannot be etched by the gas alone; in order to perform this etching, GeF ４ F along with gas ２ It was shown that supplying gas is necessary.

[0064] Also, as shown in the graph, F ２ With the partial pressure of the gas set to 200 mTorr, GeF ４ The partial pressure of the gas is changed within the range of 0 mTorr to 300 mTorr (39.9 Pa). Within this range, F ２ In the gas partial pressure range of 0 mTorr to 200 mTorr, etching of the Si film 13 was not observed, and the SiGe film 12 was selectively etched, but GeF ４ When the gas partial pressure was set to 300 mTorr, etching of the Si film 13 was confirmed.

[0065] As described above, F ２ Gas and GeF ４ When supplying gas to wafer W, F ２ Partial pressure of gas and GeF ４ The etching selectivity for the SiGe film 12 changes depending on the relationship with the partial pressure of the gas. Specifically, F ２ If the partial pressure of the gas is too low, the selectivity will decrease. Based on the results of this evaluation test 5, F is used to prevent this decrease in selectivity. ２ Regarding the partial pressure of the gas, it has been shown that it is preferable to have a pressure greater than, for example, 150 mTorr, and more preferably 200 mTorr or higher. Also, as shown in the graph, GeF ４ If the partial pressure of the gas is too high, the etching selectivity for the SiGe film 12 will also decrease. From the results of this evaluation test 5, it is possible to prevent this decrease in selectivity by using GeF ４ It has been shown that the partial pressure of the gas is preferably less than, for example, 300 mTorr, and more preferably 200 mTorr or less.

[0066] W wafer 21 F ２ (Fluorine) gas 22 GeF ４ (Germanium tetrafluoride) gas

Claims

1. An etching method comprising an etching step of supplying a first etching gas containing fluorine atoms and a second etching gas which is a compound of germanium and fluorine to a substrate, thereby etching a silicon germanium film provided on the substrate.

2. The etching method according to claim 1, wherein the second etching gas is germanium tetrafluoride gas.

3. The etching method according to claim 2, wherein the first etching gas is fluorine gas.

4. The etching method according to claim 3, wherein a silicon film is formed on the substrate, the silicon film and the silicon germanium film are exposed on the surface of the substrate, and the etching step is a step of selectively etching the silicon germanium film among the silicon film and the silicon germanium film.

5. The etching method according to claim 4, wherein the substrate is provided with a laminate comprising a plurality of silicon germanium films and a plurality of silicon films, the silicon germanium films and the silicon films are alternately laminated in the thickness direction of the substrate, and the etching step is a step of etching the silicon germanium films in a direction intersecting the thickness direction of the substrate.

6. The etching method according to claim 3, further comprising the step of stopping the supply of the second etching gas to the substrate while the first etching gas is being supplied to the substrate.

7. The etching method according to claim 3, further comprising the step of supplying hydrogen fluoride gas to the substrate while the first etching gas is being supplied to the substrate.

8. An etching apparatus comprising: a processing container for storing a substrate on which a silicon germanium film is provided; and a gas supply mechanism for supplying both a first etching gas containing fluorine atoms and a second etching gas which is a compound of germanium and fluorine into the processing container in order to etch the silicon germanium film.

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