Etching method and etching apparatus

Abstract

An etching method according to the present disclosure is a method for etching a silicon germanium film formed on a substrate, the etching method including: a first step of supplying a first etching gas for a first time to the substrate, the first etching gas being a fluorine-containing gas; and a second step in which, after the first step, a second etching gas is supplied to the substrate for a second time that is shorter than the first time, the second etching gas being a fluorine-containing gas of a different type from the first etching gas.

Description

Technical Field

[0001] The present disclosure relates to an etching method and an etching device. Background Art

[0002] When manufacturing a semiconductor device, a SiGe film formed on the surface of a semiconductor wafer (hereinafter referred to as a wafer) serving as a substrate is sometimes etched. Patent Document 1 shows that a stacked film consisting of a Si film and a SiGe film is formed on a wafer, and when the SiGe film of the stacked film is selectively etched, HF gas and ClF3 gas are simultaneously supplied.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-170380 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] The present disclosure provides a technology capable of reducing the residue after etching while suppressing the etching of a film adjacent to the silicon germanium film when etching a silicon germanium film.

[0008] Solutions for solving problems

[0009] The etching method disclosed herein is a method for etching a silicon germanium film formed on a substrate, and the etching method comprises the following steps:

[0010] In a first step, a first etching gas is supplied to the substrate for a first time, wherein the first etching gas is a fluorine-containing gas; and

[0011] In a second step, after the first step, a second etching gas is supplied to the substrate for a second time shorter than the first time, wherein the second etching gas is a fluorine-containing gas of a different type from that of the first etching gas.

[0012] Effects of the Invention

[0013] The present disclosure can reduce the residue after etching while suppressing the etching of a film adjacent to the silicon germanium film when etching a silicon germanium film. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a longitudinal sectional side view of a wafer subjected to an etching process according to one embodiment of the present disclosure.

[0015] Figure 2 : is a graph showing the flow of the etching process.

[0016] Figure 31 is a graph showing the timing of supply cutoff of the gas used in the etching process and the pressure change of the processing container.

[0017] Figure 4 is a longitudinal sectional side view of the wafer after the etching process.

[0018] Figure 5 It is a longitudinal sectional side view related to one embodiment of the apparatus for performing the etching process.

[0019] Figure 6 It is a graph showing the results of the evaluation test.

[0020] Figure 7 These are explanatory diagrams showing images of chips on substrates obtained in evaluation tests and various test results.

[0021] Figure 8 It is a graph showing the results of the evaluation test.

[0022] Fig. 9 It is a graph showing the results of the evaluation test.

[0023] Fig.10 These are explanatory diagrams showing images of chips on substrates obtained in evaluation tests and various test results.

[0024] Fig.11 These are explanatory diagrams showing images of chips on substrates obtained in evaluation tests and various test results.

[0025] Fig.12 This is a longitudinal sectional side view of a substrate used in the evaluation test. DETAILED DESCRIPTION

[0026] When describing one embodiment of the etching method of the present disclosure, a film structure formed on a wafer W that is a substrate to be etched will be described. Figure 1 This is a longitudinal sectional front view of the film structure. In the figure, two directions orthogonal to each other in the surface direction of the wafer W are represented as the X direction and the Y direction, and the direction which is the thickness direction of the wafer W and is orthogonal to the X direction and the Y direction is represented as the Z direction. In the following description, it is assumed that the wafer W is placed horizontally, and sometimes the X direction is recorded as the left-right direction, the Y direction is recorded as the front-back direction, and the Z direction is recorded as the vertical direction.

[0027] A large number of stacked bodies 15 composed of Si (silicon) films 12, SiGe (silicon germanium) films 13 and porous films 14 are provided on the base film 11 formed on the wafer W. The SiGe film 13 in the stacked body 15 is a film to be etched. The stacked body 15 is provided with a plurality of layers spaced apart from each other in the front-back direction and the left-right direction, and is arranged in a matrix shape when viewed from above. The porous film 14 is, for example, an insulating film, more specifically, a low-k film composed of SiOC (silicon oxide with carbon added), SiCOH, SiOCN (a film composed of Si, oxygen, nitrogen and carbon), etc.

[0028] The structure of the above-mentioned stacked body 15 is further described. A porous film 14 is formed adjacent to the left and right sides of the SiGe film 13. Therefore, the direction in which the SiGe film 13 and the Si film 12 are arranged intersects with the direction in which the SiGe film 13 and the porous film 14 are arranged. When the SiGe film 13 and the porous film 14 adjacent to it on the left and right are called adjacent bodies, the stacked body 15 is composed of a plurality of adjacent bodies and a plurality of Si films 12 stacked, and the adjacent bodies and the Si film 12 exist alternately when observed in the vertical direction (Z direction). The upper end of the stacked body 15 is composed of the adjacent bodies and the Si film 12 in the Si film 12. Moreover, a semiconductor film 16 is provided between the stacked bodies 15 arranged on the left and right, and the stacked body 15 and the semiconductor film 16 are adjacent to each other. The semiconductor film 16 is a film that forms a source or drain in a semiconductor product manufactured by a wafer W, for example, composed of Si or SiGe.

[0029] In addition, an upper film 17 is provided on the stack 15 and the semiconductor film 16. A plurality of grooves 18 extending in the front-to-back direction are formed in the upper film 17 at intervals to the left and right, thereby dividing the upper film 17 to the left and right, and each groove 18 is provided at a position overlapping with the SiGe film 13 in the vertical direction (Z direction). Moreover, the lower side of the upper film 17 is formed as a recessed portion (not shown) by extending toward the stack 15 arranged in the front-to-back direction. A recess 10 is formed with the recessed portion and the Si film 12 and the SiGe film 13 in the stack 15 constituting the side wall, and the recess 10 is connected to the groove 18. That is, the recess 10 opens between the upper films 17 in the left-right direction (X direction) and extends in the Z direction. Therefore, the Si film 12 and the SiGe film 13 are exposed on the surface of the wafer W as the side wall of the recess 10, and are exposed to the etching gas supplied to the upper part of the wafer W. In addition, the semiconductor film 16 is covered with the upper film 17 and is not exposed on the surface of the wafer W.

[0030] Although the detailed structure is omitted, the upper film 17 is composed of multiple types of films such as a silicon oxide (SiO2) film and an insulating film composed of SiOCN. In addition, the upper film 17 has resistance to etching gas described later, preventing the etching gas from etching the semiconductor film 16 from above.

[0031] Due to the above-mentioned film structure, the etching gas supplied to the upper side of the wafer W can flow into the recess 10 through the groove 18 to etch the SiGe film 13 toward the side. More specifically, the gas flowing into the recess 10 in this way flows toward the inner side of the recess 10. Figure 1 The SiGe film 13 of each layer is etched by flowing in the front and back direction (Y direction) of the paper surface. In addition, although the Si film 12 and the SiGe film 13 are adjacent to each other, it is required to selectively etch the SiGe film 13 of these Si films 12 and SiGe films 13, and to suppress the roughness (surface roughness) of the Si film 12 after the etching is completed. It is also required that no Ge (germanium) residues originating from the SiGe film 13 remain on the surface of the Si film 12 after the etching is completed.

[0032] In addition, the SiGe film 13 is adjacent to the semiconductor film 16 via the porous film 14, and even during the etching of the SiGe film 13, the semiconductor film 16 is covered by the upper film 17 and the porous film 14 and is not exposed on the surface of the wafer W. However, during the etching, the etching gas may be supplied to the semiconductor film 16 through the holes of the porous film 14. It is also required to etch the SiGe film 13 in a manner that suppresses the etching of the semiconductor film 16. The etching in this embodiment can meet these requirements.

[0033] Below, refer to Figure 2 Flowchart and Figure 3 The etching process of this embodiment is specifically described in detail with reference to the time chart of FIG. Figure 1 The wafer W described in the above is stored in a processing container with a vacuum atmosphere and two etching gases are supplied. The two etching gases are two fluorine-containing gases. The timing chart shows the timing of supplying and shutting off each etching gas into the processing container and the timing of changing the pressure in the processing container.

[0034] First, load the Figure 1The wafer W described in the above is then formed in the processing container by exhausting the processing container to form a vacuum atmosphere of a predetermined first pressure. Then, a first etching gas such as F2 (fluorine) gas is supplied into the processing container (time t1, step S1). Thus, selective etching of the Si film 12 and the SiGe film 13 is performed. When a predetermined first time has passed since time t1 and it becomes time t2, the supply of F2 gas into the processing container is stopped, and on the other hand, the supply of ClF3 (chlorine trifluoride) gas into the processing container as a second etching gas is started. Furthermore, the pressure in the processing container is reduced by adjusting the exhaust flow rate in the processing container, and the pressure in the processing container is set to a second pressure lower than the first pressure (step S2). The F2 gas remaining in the processing container is purged from the processing container by the supplied ClF3 gas, and the remaining portion of the SiGe film 13 is etched.

[0035] When a preset second time elapses from time t2 to time t3, the supply of ClF3 gas into the processing container is stopped. The second time (time t2 to t3) is shorter than the first time (time t1 to t2). Figure 4 The longitudinal cross-sectional front view of the wafer W after the etching process is completed is shown. The etching process is completed by supplying an inert gas into the processing container to purge the ClF3 gas from the processing container, and the wafer W is unloaded from the processing container.

[0036] As described above, in the etching process of this embodiment, the type of gas is changed to perform two-stage etching. The reason is that when etching the SiGe film of a structure where the Si film and the SiGe film are adjacent, as shown in the evaluation test described later, the case of using ClF3 gas can suppress the attachment of Ge residue to the Si film after etching and the roughness of the Si film compared with the case of using F2 gas. However, the ClF3 gas has a high etching property for the Si film, so it is easy to etch the Si film. That is, it is difficult to selectively etch the SiGe film when only ClF3 gas is used.

[0037] Therefore, for Figure 1 First, the F2 gas is supplied for a relatively long time to the wafer W. As shown in the evaluation test described later, the F2 gas does not easily etch the Si film 12. That is, the SiGe film 13 can be etched with high selectivity to the Si film 12.

[0038] Then, after the SiGe film 13 is substantially removed by the F2 gas, the ClF3 gas is supplied for a short time. This can reduce the roughness of the Si film 12 and the Ge residue attached to the Si film 12 while suppressing etching of the Si film 12.

[0039] In addition, as for ClF3 gas, as described above, the etching property for Si film is relatively high, but as shown in the evaluation test described later, the etching property for SiGe film is also relatively high. Therefore, although the semiconductor film 16 formed on the wafer W is composed of Si or SiGe as described above, no matter which one is composed of Si or SiGe, the etching property for ClF3 gas is high. However, the supply time of ClF3 gas in this embodiment is relatively short, so the ClF3 gas is suppressed from passing through the holes of the porous membrane 14 and being supplied to the semiconductor film 16. Therefore, it is also possible to suppress the semiconductor film 16 from being etched.

[0040] In addition, by exhausting the processing container, the second pressure at time t2 to t3 when the ClF3 gas is supplied is lower than the first pressure at time t1 to t2 when the F2 gas is supplied. For the ClF3 gas, by setting the pressure in the processing container to a relatively low pressure in this way, the ClF3 gas is prevented from being retained in the processing container for a long time. Therefore, the Si film 12 and the semiconductor film 16 are more reliably suppressed from being etched. On the contrary, for the F2 gas, by setting the pressure in the processing container to a relatively high pressure, the F2 gas is retained in the processing container for a long time and acts on the SiGe film 13. Therefore, a decrease in the etching rate is prevented.

[0041] Next, as a Figure 2 , Figure 3 An etching device 2 which is an example of an etching device for the etching process described in . Figure 5 2 is a longitudinal sectional side view of the etching device 2. Reference numeral 21 in the figure is the processing container mentioned above, which constitutes the etching device 2. Reference numeral 22 in the figure is a transfer port for the wafer W opened in the side wall of the processing container 21, which is opened and closed by a gate valve 23. A workbench 31 on which the wafer W is placed is provided in the processing container 21, and a lifting pin (not shown) is provided on the workbench 31. The wafer W is transferred between the substrate transfer mechanism arranged outside the processing container 21 and the workbench 31 via the lifting pin.

[0042] A temperature adjustment unit 22 is embedded in the workbench 31 to adjust the temperature of the wafer W placed on the workbench 31. The temperature adjustment unit 22 is configured as, for example, a flow path, which constitutes a part of a circulation path for a fluid for temperature adjustment such as water to flow, and the temperature adjustment unit 22 adjusts the temperature of the wafer W by heat exchange with the fluid. However, the temperature adjustment unit 22 is not limited to being a flow path of such a fluid, and may be configured as, for example, a heater for resistance heating.

[0043] In addition, one end of the exhaust pipe 24 opens in the processing container 21, and the other end of the exhaust pipe 24 is connected to an exhaust mechanism 26, such as a vacuum pump, via a valve 25 as a pressure changing mechanism. The exhaust flow rate in the processing container 21 is adjusted by adjusting the opening of the valve 25, and the pressure in the processing container 21 is set to a desired vacuum pressure. That is, as described above, the first pressure and the second pressure can be switched by changing the opening of the valve 25.

[0044] A shower plate 32 is provided on the upper side of the processing container 21 so as to face the workbench 31. The shower plate 32 is connected to the downstream side of gas supply paths 41 to 44, and the upstream sides of the gas supply paths 41 to 44 are connected to gas supply sources 51 to 54 via flow adjustment sections 40, respectively. Each flow adjustment section 40 is provided with a valve and a mass flow controller. For each gas supplied from the gas supply sources 51 to 54, the supply to the downstream side is cut off by opening and closing the valve included in the flow adjustment section 40. In addition, for each gas, the flow rate supplied to the downstream side is adjusted by each flow adjustment section 40. Each gas supplied to the gas flow path provided in the shower plate 32 is ejected downward from a large number of ejection ports provided on the lower surface of the shower plate 32.

[0045] F2 gas, ClF3 gas, N2 gas, and Ar gas are supplied from gas supply sources 51, 52, 53, and 54, respectively, and these gases are supplied into the processing container 21 via the shower plate 32. Through each flow adjustment unit 40, the supply of these gases can be performed independently of each other. N2 gas, which is an inactive gas, is used as a carrier gas during the etching process and is supplied into the processing container 21 together with the etching gas (F2 gas and ClF3 gas) via the shower plate 32. In addition, it is also supplied into the processing container after the supply of the etching gas is completed, and also acts as a purge gas for purging the processing container. In addition, Ar gas, which is an inactive gas, is a gas used to adjust the partial pressure of each etching gas, and is supplied into the processing container together with the etching gas. The first gas supply part is composed of a gas supply path 41 for supplying F2 gas, a flow adjustment part 40 arranged on the gas supply path 41, and a shower plate 32, and the second gas supply part is composed of a gas supply path 42 for supplying ClF3 gas, a flow adjustment part 40 arranged on the gas supply path 42, and a shower plate 32.

[0046] In addition, the etching device 2 includes a control unit 20 as a computer, and the control unit 20 includes a program, a memory, and a CPU. In the program, commands (various steps) are incorporated in a manner to perform the processing of the wafer W and the conveyance of the wafer W as described above, and the program is stored in a storage medium such as an optical disk, a hard disk, a magneto-optical disk, a DVD, etc., and installed in the control unit 20. The control unit 20 outputs a control signal to each part of the etching device 2 through the program to control the operation of each part. Specifically, the operation of the etching device 2 controlled in this way includes, for example, the adjustment of the temperature of the fluid supplied to the workbench 31 (i.e., the processing temperature of the wafer W), the supply and cut-off of each gas from the shower plate 32, the adjustment of the exhaust flow rate using the valve 25 (i.e., the adjustment of the pressure in the processing container 21), and other operations.

[0047] By adjusting the opening of the valve 25 of the etching device 2, the first pressure at the time t1 to t2 is set to, for example, 1.33Pa (10mTorr) to 133Pa (1000mTorr), and the second pressure at the time t2 to t3 is set to, for example, 0Pa to 133Pa. In addition, the temperature of the wafer W is set to, for example, -50°C to 150°C at the time t1 to t3 by the temperature adjustment unit 22. In addition, as the supply flow rate of each gas into the processing container, the F2 gas is in the range of 1sccm to 500sccm, the ClF3 gas is in the range of 0.1sccm to 10sccm, the N2 gas is in the range of 50sccm to 1000sccm, and the Ar gas is in the range of 10sccm to 1000sccm.

[0048] In addition, as described above, inert gas (N2 gas and Ar gas) is supplied into the processing container together with F2 gas and ClF3 gas. As the relationship between the flow rates of F2 gas, ClF3 and inert gas supplied into the processing container, for example, the flow rate of F2 gas / the flow rate of inert gas is greater than the flow rate of ClF3 gas / the flow rate of inert gas. In other words, when F2 gas and ClF3 gas are supplied to the wafer W respectively, ClF3 gas can be supplied at a dilution rate of inert gas higher than that of F2 gas. By adjusting the flow rates of each gas in this way, the etching effect of ClF3 gas on Si film 12 and semiconductor film 16 can be more reliably suppressed.

[0049] It is shown that F2 gas is used as the first etching gas, but other fluorine-containing gases that can selectively etch the SiGe film 13 relative to the Si film 12 can also be used. For example, a mixed gas of HF gas and F2 gas can be used instead of F2 gas. In addition, a fluorine-containing gas that has a relatively large etching effect on the SiGe film 13 can be used instead of the ClF3 gas as the second etching gas. For example, IF7 (iodine heptafluoride) gas or NF3 (nitrogen trifluoride) gas can also be used as the second etching gas. In addition, the term "containing fluorine" here means that fluorine is included as a constituent component, not as an impurity.

[0050] exist Figure 3 In the processing example shown in the diagram of FIG. 1 , ClF3 gas is supplied while the supply of F2 gas is stopped, and the F2 gas is purged from the processing container 21 by the ClF3 gas. However, an interval may be left from the time when the supply of F2 gas is stopped to the time when the supply of ClF3 gas is started. Furthermore, it may be set that the F2 gas in the processing container is purged by an inactive gas such as N2 gas during this interval. However, in order to shorten the processing time, it is preferably set that, as in FIG. Figure 3 As shown in , ClF3 gas is supplied while the supply of F2 gas is stopped, and the F2 gas is purged using the ClF3 gas.

[0051] In addition, the etching method described in this embodiment suppresses the roughness of the Si film 12 adjacent to the SiGe film 13 as described so far, and is therefore particularly effective for a substrate in which the SiGe film 13 and the Si film 12 are adjacent to each other. However, according to this etching method, the amount of Ge remaining after etching of the SiGe film can be reduced, and therefore, it can also be used in the case of etching the SiGe film 13 that is not adjacent to the Si film 12.

[0052] The embodiments disclosed herein are illustrative in all respects and should not be construed as limiting. The embodiments described above may be omitted, replaced, modified, or combined in various ways without departing from the appended claims and the gist thereof.

[0053] [Evaluation Test 1]

[0054] The evaluation tests conducted in connection with the technology of the present disclosure will be described. In Evaluation Test 1, a plurality of wafers W having two chips fixed on the surface were prepared. Then, using the etching apparatus 2 shown in the embodiment, each wafer W was processed while changing the type of etching gas and the etching time. One of the two chips was obtained by laminating a SiGe film as an upper layer film on the upper side of a lower layer film that was a Si film. The thickness of the SiGe film was 50 nm, and the Ge content in the film was 25%. The other chip was a polysilicon film. For the chip having the SiGe film, after etching, the amount of Ge was measured by XPS (X-ray photoelectron spectroscopy), the RMS (root mean square roughness) was measured using AFM (atomic force microscope), an image was acquired using SEM (scanning electron microscope), and the etching amount of the SiGe film was measured. The etching amount of the polysilicon film chip was also measured.

[0055] As the etching gas, F2 gas, ClF3 gas, and a mixture of F2 gas and ClF3 gas were supplied to the wafer W for etching, respectively. The tests using F2 gas, ClF3 gas, and the mixture of F2 gas and ClF3 gas were designated as Evaluation Tests 1-1, 1-2, and 1-3, respectively. In addition, in Evaluation Test 1-3, the start timing and end timing of the supply were made consistent between the F2 gas and the ClF3 gas, and the supply was performed simultaneously. In each of Evaluation Tests 1-1 to 1-3, each wafer W was processed while changing the supply time (etching time) of the etching gas. In addition, when performing etching, the temperature of the wafer W, the pressure in the processing container 21, and the flow rate of each gas supplied into the processing container were set to the values within the ranges shown in the embodiment, respectively.

[0056] When explaining the test results, the etching time set so that the etching amount of the SiGe film of the above chip becomes the same as the film thickness of the SiGe film, i.e., 50 nm (i.e., exactly removing the SiGe film), is sometimes referred to as the time for performing JE (just etching). The time for further extending the etching time to etch the 50-nm SiGe film excessively (in Japanese: surplus) is sometimes referred to as the time for performing OE (over etching). Specifically, when the film thickness of the SiGe film of the chip is assumed to be 100 nm, 150 nm, 300 nm, and 550 nm, the times for making the etching amount of the SiGe film the same as the film thickness are respectively referred to as the times for performing 100%, 200%, 500%, and 1000% of OE. In addition, for the time for performing each OE, the relationship between the etching amount of the SiGe film of 50 nm or less and the etching time corresponding to the etching amount is obtained (refer to Figure 6 the curve), and the calculation is based on the obtained relationship.

[0057] Figure 7 This is a graph showing the SEM image, Ge detection amount, RMS, and polysilicon film etching amount obtained in the JE and each OE process for each evaluation test in the evaluation tests 1-1 to 1-3. As already mentioned, the SEM image, Ge detection amount, and RMS are obtained from a chip on which a SiGe film has been formed (that is, a chip whose surface is formed of Si by removing the SiGe film). In addition, in practice, the Ge detection amount is obtained as a percentage value, and the RMS and polysilicon film etching amount are obtained as values ​​in nm units, but each value shown in the table is a value obtained by dividing the values ​​obtained in this way by a prescribed coefficient for standardization. Regarding the Ge detection amount, the larger the value in the graph, the more the amount remaining on the Si film. Regarding the RMS, the larger the value in the graph, the greater the roughness. Regarding the polysilicon film etching amount, the larger the value in the graph, the greater the etching amount. In addition, Figure 7 In the figure, for comparison, an image of the surface of the chip on which the SiGe film is formed before etching and the normalized RMS are also shown in the lower right corner.

[0058] exist Figure 8 , which is the basis for the evaluation test 1-2, shows a curve showing the relationship between the etching time using ClF3 gas and the etching amount of SiGe film and polysilicon film. Fig. 9 The graphs showing the relationship between the etching time using F2 gas and ClF3 gas and the etching amount of SiGe film and polysilicon film, which are the basis for the evaluation test 1-3, are shown. As in the evaluation test 1-1, the times of JE and OE are determined based on the correspondence between the etching amount of SiGe film and the etching time, and the evaluation tests 1-2 and 1-3 are carried out. The vertical axis of each curve shows the etching amount of each film, but the value obtained by dividing the obtained value by a predetermined coefficient is shown. In addition, the predetermined coefficient is used for the purpose of Figure 6 The coefficient used to normalize the etching amount of the polysilicon film is the same.

[0059] The results of the evaluation test 1-1 using F2 gas are described below. Figure 7 The specific etching times of JE, OE100%, OE200%, OE500%, and OE1000% in the evaluation test 1-1 are 82 seconds, 145 seconds, 208 seconds, 397 seconds, and 712 seconds, respectively. Figure 6 As shown in FIG. 1 , as the etching time using F2 gas becomes longer, the etching amount of SiGe film becomes larger. Figure 7As shown, the etching amount of the polysilicon film is substantially constant and relatively low under the etching time of JE and each OE. Therefore, it can be seen that, as described in the embodiment, when the Si film and the SiGe film are etched using F2 gas, the SiGe film can be etched with high selectivity.

[0060] However, a relatively large value is shown as the amount of Ge detected. As the percentage of OE increases, the amount of Ge detected decreases, but Ge residue is confirmed even at OE1000%. In addition, regarding RMS, as the percentage of OE increases, the value of RMS decreases, but in the case of low percentage and JE, a relatively large value is confirmed (i.e., the roughness is relatively large).

[0061] Next, the results of the evaluation test 1-2 using ClF3 gas will be described. Figure 7 The JE, OE100%, and OE200% in the evaluation test 1-2 shown have specific etching times of 50 seconds, 115 seconds, and 179 seconds, respectively. Regarding the amount of Ge detected, it is a relatively low value in the case of JE, and no Ge is detected in the cases of OE100% and OE200%. Regarding RMS, the RMS values ​​of JE, OE100%, and OE200% are the same as the RMS before etching, and are lower than any RMS value of JE, OE100%, and OE200% in the evaluation test 1-1. Moreover, the RMS of OE100% and OE200% are particularly low values.

[0062] However, if Figure 8 As shown in the figure, when ClF3 gas is used, as the etching time becomes longer, not only the etching amount of SiGe film but also the etching amount of polysilicon film increases. Moreover, the following results are obtained: the etching amount of each polysilicon film of JE, OE100%, and OE200% in Evaluation Test 1-2 is larger than the etching amount of any polysilicon film in JE and each OE in Evaluation Test 1-1.

[0063] Next, the results of evaluation tests 1-3 using F2 gas + ClF3 gas are described. Figure 7 The specific etching times of JE, OE100%, and OE200% in the evaluation test 1-3 are 24 seconds, 54 seconds, and 85 seconds, respectively. As for the amount of Ge detected, similar to the test 1-2, it is a relatively low value in the case of JE, and no Ge is detected in the case of OE100% and OE200%. In addition, regarding RMS, it becomes a particularly low value in the case of OE100% and OE200%, which is a value of the same degree as the RMS before etching.

[0064] However, if Fig. 9As shown, in the case of using F2 gas + ClF3 gas, as the etching time becomes longer, not only the etching amount of SiGe film but also the etching amount of polysilicon film increases. Moreover, the following results are obtained: the etching amount of each polysilicon film of JE, OE100%, and OE200% in Evaluation Test 1-3 is larger than the etching amount of any polysilicon film in JE and each OE in Evaluation Test 1-1.

[0065] As described above, it was confirmed from the results of the evaluation test 1 that when ClF3 gas is used as the etching gas, the amount of Ge (residue amount) remaining on the Si film after etching can be reduced, and the roughness of the Si film can be suppressed. However, it is shown that the etching amount of the Si film is also larger than that of the case where F2 gas is used.

[0066] [Evaluation Test 2]

[0067] As evaluation test 2, the wafer W having the same structure as that of evaluation test 1 was etched under the same conditions as those of OE100% as evaluation test 1-1. That is, etching was performed using F2 gas. And, following the etching of F2 gas, the F2 gas in the processing container was purged and etched by supplying F2 gas and NH3 gas into the processing container. In addition, the pressure in the processing container was made lower during the period when F2 gas alone was supplied (during the purging) than during the period when F2 gas and NH3 gas were supplied. After such etching, as in evaluation test 1, SEM images, Ge detection amount, and RMS were obtained from the chip on which the SiGe film was formed, and the etching amount was obtained from the chip of the polysilicon film. The time for supplying F2 gas and NH3 gas (the time for purging) was changed for each wafer W, and the tests set to 5 seconds, 10 seconds, and 20 seconds were set as evaluation tests 2-1, 2-2, and 2-3, respectively.

[0068] [Evaluation Test 3]

[0069] As evaluation test 3, the same processing conditions as those of evaluation test 2 were used except that the period in which F2 gas was supplied alone from among F2 gas and NH3 gas for etching was not provided. Therefore, in this evaluation test 3, etching was performed only during the period in which both F2 gas and NH3 gas were supplied to the wafer W at the same time (a period that corresponds to the purging in evaluation test 2). The time for supplying F2 gas and NH3 gas was set to 5 seconds, 10 seconds, and 20 seconds, respectively, as in evaluation test 2, and the tests performed with the time set in this way were respectively designated as evaluation tests 3-1, 3-2, and 3-3. In this evaluation test 3, the etching amounts of SiGe film and polysilicon film were measured.

[0070] exist Fig.10The results of evaluation tests 2 and 3 are shown in the table. The values ​​in the table are standardized values, similar to those in evaluation test 1. Observing the results of evaluation test 2, in each of evaluation tests 2-1 to 2-3, the Ge detection amount and RMS are relatively large. In addition, between evaluation tests 2-1 to 2-3, the following results are obtained: the longer the supply time of F2 gas and NH3 gas, the greater the etching amount of the polysilicon film. Observing the results of evaluation test 3, the following results are obtained: between evaluation tests 3-1 to 3-3, there is no significant difference in the etching amount of the SiGe film, but the longer the etching time, the greater the etching amount of the polysilicon film. Therefore, according to the results of evaluation tests 2 and 3, it can be seen that the polysilicon film is etched relatively greatly due to the action of F2 gas and NH3 gas.

[0071] [Evaluation Test 4]

[0072] As evaluation test 4, the same conditions as those of evaluation test 2 were used except that ClF3 gas was supplied for purging instead of the purging performed by F2 gas and NH3 gas in evaluation test 2, and the range of the length of the period for performing the purging was different from the range of 5 seconds to 20 seconds set in evaluation test 2. Therefore, in this evaluation test 4, ClF3 gas was supplied after the supply of F2 gas, as in the embodiment. As for the pressure in the processing container, the pressure during the period of supplying ClF3 gas was also made lower than the pressure during the period of supplying F2 gas, as in the embodiment. The time for supplying ClF3 gas was set to 5 seconds, 20 seconds, and 60 seconds, respectively, and the tests performed with the time set in this way were respectively designated as evaluation tests 4-1, 4-2, and 4-3.

[0073] [Evaluation Test 5]

[0074] As evaluation test 5, the same processing conditions as those of evaluation test 4 were used except that the period for etching by supplying F2 gas was not provided. Therefore, in this evaluation test 5, etching was performed using only ClF3 gas. The time for supplying ClF3 gas was set to 5 seconds, 20 seconds, and 60 seconds, respectively, as in evaluation test 4, and the tests performed with such time settings were respectively designated as evaluation tests 5-1, 5-2, and 5-3. In this evaluation test 5, the etching amounts of SiGe film and polysilicon film were measured, as in evaluation test 3.

[0075] exist Fig.11The results of evaluation tests 4 and 5 are shown in the table. The values ​​in the table are standardized values, similar to those in evaluation test 1. Observing the results of evaluation test 4, the amount of Ge detected was suppressed to a low level in each of evaluation tests 4-1 to 4-3, and became a value lower than any Ge detection amount in evaluation tests 2-1 to 2-3. In addition, the RMS was also suppressed to a low level in each of evaluation tests 4-1 to 4-3, and became a value lower than any RMS in evaluation tests 2-1 to 2-3. In addition, the etching amount of the polysilicon film was relatively low in each of evaluation tests 4-1 to 4-3, and was at the same level as the values ​​in evaluation tests 2-1 to 2-3.

[0076] According to the results of the above evaluation test 4, it can be seen that the method shown in the above-mentioned embodiment is used to treat the Figure 1 When the wafer W having the film structure shown in , the SiGe film 13 can be selectively etched out of the Si film 12 and the SiGe film 13 and Ge residue can be suppressed from remaining. In addition, it can be seen that the roughness of the Si film 12 after etching can be suppressed.

[0077] In addition, the results of evaluation test 5 show that, similar to evaluation test 1, as the supply time of ClF3 gas increases, the etching amount of SiGe film and polysilicon film increases. The etching amount of the polysilicon film is a relatively large value in evaluation test 5-2, but a relatively small value in evaluation test 5-1. Based on this result, it is considered that the preferred Figure 3 The time (second time) from time t2 to time t3 for supplying the ClF 3 gas is shorter than 20 seconds, and more preferably, less than or equal to 5 seconds.

[0078] [Evaluation Test 6]

[0079] As evaluation test 6-1, a Fig.12 The film structure shown in the figure is a substrate. The film structure includes a stacked body 62, in which Si films 12 and SiGe films 13 are stacked alternately and repeatedly upward, and a SiN (silicon nitride) film 61 is formed on the uppermost Si film 12. In addition, a porous film 63 as a low-k film is formed in a manner covering the stacked body 62 from the side to the top, and the porous film 63 is exposed on the surface of the substrate. That is, when the etching gas is supplied, the porous film 63 is exposed to the etching gas. For a substrate having each film formed thereon, as in the embodiment Figure 2 , Figure 3 After the etching gas was supplied as described in the above, the state of the SiGe film 13 was observed. In addition, as an evaluation test 6-2, a substrate having substantially the same film structure except that the porous film 63 was not formed was subjected to the same test as in the above. Figure 2 , Figure 3After the etching gas was supplied as described in , the state of the SiGe film 13 was observed.

[0080] In the evaluation test 6-2, the SiGe film 13 was etched from the side, but in the evaluation test 6-1, no etching of the SiGe film 13 from the side was observed. Figure 1 , Figure 2 The film structure of the wafer W is as in Figure 2 , Figure 3 When etching is performed as described in , the semiconductor film 16 adjacent to the porous film 14 is suppressed from being etched.

[0081] Description of Reference Numerals

[0082] W: wafer; 13: SiGe film.

Claims

1. An etching method is a method for etching a silicon germanium film formed on a substrate, the etching method comprising the following steps: In a first step, a first etching gas is supplied to the substrate for a first time, wherein the first etching gas is a fluorine-containing gas; and In a second step, after the first step, a second etching gas is supplied to the substrate for a second time shorter than the first time, wherein the second etching gas is a fluorine-containing gas of a different type from that of the first etching gas.

2. The etching method according to claim 1, wherein: The first step is a step of selectively etching the silicon germanium film of the silicon germanium film and the silicon film respectively exposed on the surface of the substrate. The second step is a step of etching the remaining portion of the silicon germanium film.

3. The etching method according to claim 2, wherein: The second etching gas is chlorine trifluoride gas.

4. The etching method according to claim 3, wherein: The substrate is provided with a silicon-containing film and a porous film interposed between the silicon-containing film and the silicon germanium film.

5. The etching method according to claim 1, wherein: The first step is a step of supplying the first etching gas to the substrate stored in the processing container, and the second step is a step of supplying the second etching gas to the substrate stored in the processing container. The etching method further includes the step of setting the pressure in the processing container in the second step to a pressure lower than the pressure in the processing container in the first step.

6. An etching device for etching a silicon germanium film formed on a substrate, the etching device comprising: a processing container that holds the substrate; A first gas supply unit supplies a first etching gas into the processing container for a first time, wherein the first etching gas is a fluorine-containing gas; and A second gas supply unit supplies a second etching gas into the processing container for a second time shorter than the first time after the first etching gas is supplied, wherein the second etching gas is a fluorine-containing gas of a type different from that of the first etching gas.

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