Etching method and etching apparatus

Abstract

To reduce residues after etching a silicon germanium film while suppressing etching of a film adjacent to the silicon germanium film when etching the silicon germanium film.SOLUTION: An etching method is a method for etching a silicon germanium film formed on a substrate, includes: a first step of supplying a first etching gas which is a fluorine-containing gas to the substrate for a first period of time; and a second step of supplying, after the first step, a second etching gas which is a fluorine-containing gas different in type from the first etching gas to the substrate for a second period of time shorter than the first period of time.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] When manufacturing a semiconductor device, there are cases where a SiGe film formed on the surface of a semiconductor wafer (hereinafter referred to as a wafer), which is a substrate, is etched. In Patent Document 1, a laminated film composed of a Si film and a SiGe film is formed on a wafer, and it is shown that HF gas and ClF3 gas are simultaneously supplied when selectively etching the SiGe film of this laminated film.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides a technique capable of reducing residues after etching while suppressing etching of a film adjacent to a silicon germanium film when etching the silicon germanium film.

Means for Solving the Problems

[0005] The etching method of the present disclosure is a method for etching a silicon germanium film formed on a substrate, a first step of supplying a first etching gas, which is a fluorine-containing gas, to the substrate for a first time; a second step, after the first step, of supplying a second etching gas, which is a fluorine-containing gas different in type from the first etching gas, to the substrate for a second time shorter than the first time; and includes The first step is to selectively etch the silicon germanium film and the silicon film, respectively, which are exposed on the surface of the substrate. The second step is to etch the remaining portion of the silicon germanium film. the law of nature, The second etching gas is chlorine trifluoride gas. . [Effects of the Invention]

[0006] This disclosure makes it possible to reduce the amount of residue after etching while suppressing the etching of films adjacent to the silicon germanium film when etching a silicon germanium film. [Brief explanation of the drawing]

[0007] [Figure 1] This is a longitudinal cross-sectional side view of a wafer subjected to etching according to one embodiment of the present disclosure. [Figure 2] This is a chart showing the flow of the etching process. [Figure 3] This chart shows the timing of the supply and cut-off of the gas used in the etching process and the changes in the pressure of the processing vessel. [Figure 4] This is a longitudinal cross-sectional side view of the wafer after the etching process. [Figure 5] This is a longitudinal cross-sectional side view of one embodiment of the apparatus for performing the etching process. [Figure 6] This is a graph showing the results of the evaluation test. [Figure 7] This is an explanatory diagram showing images of the substrate chips obtained during evaluation testing and various test results. [Figure 8] This is a graph showing the results of the evaluation test. [Figure 9] This is a graph showing the results of the evaluation test. [Figure 10] This is an explanatory diagram showing images of the substrate chips obtained during evaluation testing and various test results. [Figure 11]This is an explanatory diagram showing images of the substrate chips obtained during evaluation testing and various test results. [Figure 12] This is a longitudinal cross-sectional side view of the substrate used in the evaluation test. [Modes for carrying out the invention]

[0008] In describing one embodiment of the etching method of this disclosure, a film structure formed on a wafer W, which is the substrate to be etched, will be described. Figure 1 is a longitudinal cross-sectional front view of the film structure. In the figure, two mutually orthogonal directions in the planar direction of the wafer W are shown as the X direction and the Y direction, and the direction in the thickness direction of the wafer W that is orthogonal to the X direction and the Y direction is shown as the Z direction. In the following description, assuming that the wafer W is placed horizontally, the X direction may be described as the left-right direction, the Y direction as the front-back direction, and the Z direction as the vertical direction.

[0009] A large number of laminates 15, each composed of a Si (silicon) film 12, a SiGe (silicon germanium) film 13, and a porous film 14, are provided on a base film 11 formed on a wafer W. The SiGe film 13 in these laminates 15 is the film to be etched. Multiple laminates 15 are provided at intervals from each other in both the front-to-back and left-to-right directions, and are arranged in a matrix in a plan view. The porous film 14 is, for example, an insulating film, and more specifically, a low-k film made of, for example, SiOC (carbon-doped silicon oxide), SiCOH, or SiOCN (a film composed of Si, oxygen, nitrogen, and carbon).

[0010] The structure of the above laminate 15 will be further described. Porous films 14 are formed adjacent to the left and right sides of the SiGe film 13, respectively. Therefore, the direction in which the SiGe film 13 and the Si film 12 are arranged and the direction in which the SiGe film 13 and the porous films 14 are arranged intersect each other. If the SiGe film 13 and the porous films 14 adjacent to the left and right are called adjacent bodies, the laminate 15 is composed of a plurality of adjacent bodies and a plurality of Si films 12 laminated, and the adjacent bodies and the Si films 12 are alternately positioned when viewed in the vertical direction (Z direction). The upper end portion of the laminate 15 is composed of the Si film 12 among the adjacent bodies and the Si films 12. And a semiconductor film 16 is provided between the laminates 15 arranged side by side, and the laminate 15 and the semiconductor film 16 are adjacent to each other. The semiconductor film 16 is a film that forms a source or a drain in a semiconductor product manufactured from the wafer W and is composed of, for example, Si or SiGe.

[0011] Also, an upper layer film 17 is provided on the laminate 15 and the semiconductor film 16. A plurality of grooves 18 extending in the front-rear direction are formed at intervals in the left-right direction in the upper layer film 17, so that the upper layer film 17 is divided into left and right parts, and each groove 18 is provided at a position overlapping the SiGe film 13 in the vertical direction (Z direction). And the lower side of the upper layer film 17 extends toward between the laminates 15 arranged in the front-rear direction and is configured as a recessed portion (not shown). A recess 10 is formed with the recessed portion and the Si film 12 and the SiGe film 13 in the laminate 15 serving as side walls, and this recess 10 is connected to the groove 18. That is, this recess 10 opens between the upper layer 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 side walls of the recess 10 and are exposed to the etching gas supplied above the wafer W. Note that the semiconductor film 16 is covered by the upper layer film 17 and is not exposed on the surface of the wafer W.

[0012] Although the detailed configuration is not described, the upper layer film 17 is composed of a plurality of types of films such as a silicon oxide (SiO2) film and an insulating film made of SiOCN. Note that the upper layer film 17 has resistance to an etching gas described later, and etching of the semiconductor film 16 from above by the etching gas is prevented.

[0013] Due to the above-described film structure, the etching gas supplied above the wafer W flows into the recess 10 through the groove 18, and the SiGe film 13 can be etched laterally. More specifically, the gas flowing into the recess 10 in this manner flows in the front-back direction (Y direction) of the paper surface of FIG. 1 to etch the SiGe films 13 at each stage. By the way, the Si film 12 and the SiGe film 13 are adjacent to each other. Among these Si film 12 and SiGe film 13, it is required to selectively etch the SiGe film 13 and suppress the roughness (surface roughness) of the Si film 12 after the etching is completed. Further, it is also required that no residue of Ge (germanium) derived from the SiGe film 13 remains on the surface of the Si film 12 after the etching is completed.

[0014] Also, the SiGe film 13 is adjacent to the semiconductor film 16 through the porous film 14. Even during the progress of etching of the SiGe film 13, the semiconductor film 16 is covered with the upper layer film 17 and the porous film 14 and is not exposed on the surface of the wafer W. However, during the progress of this etching, the etching gas can pass through the pores of the porous film 14 and be supplied to the semiconductor film 16. It is also required to etch the SiGe film 13 so as to suppress the etching of the semiconductor film 16. The etching in the present embodiment can meet those requirements.

[0015] The etching process of this embodiment will be described in detail below with reference to the flowchart in Figure 2 and the timing chart in Figure 3. This etching process is performed by supplying two types of fluorine-containing etching gases to a processing container in which a vacuum atmosphere is formed, while the wafer W described in Figure 1 is placed. The timing chart shows the timing of the supply and interruption of each etching gas to the processing container, and the timing of the change in pressure inside the processing container.

[0016] First, the wafer W, as explained in Figure 1, is brought into the processing container. Then, by evacuating the processing container, a vacuum atmosphere with a predetermined first pressure is created inside the processing container. Next, for example, F2 (fluorine) gas is supplied into the processing container as the first etching gas (time t1, step S1). This selectively etches the SiGe film 13 out of the Si film 12. When a predetermined first time has elapsed from time t1 to time t2, the supply of F2 gas into the processing container is stopped, while the supply of ClF3 (chlorine trifluoride) gas, which is the second etching gas, into the processing container is started. Furthermore, by adjusting the exhaust flow rate inside the processing container, the pressure inside the processing container is reduced to a second pressure lower than the first pressure (step S2). The supplied ClF3 gas purges the F2 gas remaining inside the processing container, and the remaining portion of the SiGe film 13 is etched.

[0017] When a predetermined second time has elapsed from time t2 to time t3, the supply of ClF3 gas into the processing container is stopped. This second time (time t2 to t3) is shorter than the first time (time t1 to t2). Figure 4 shows a frontal cross-section of the wafer W after the etching process is complete. An inert gas is supplied into the processing container to purge the ClF3 gas from within the container, completing the etching process, and the wafer W is removed from the processing container.

[0018] In this embodiment, the etching process involves changing the type of gas and performing a two-stage etching. The reason for this is that, when etching the SiGe film of a structure adjacent to a Si film, as shown in the evaluation test described later, using ClF3 gas suppresses the adhesion of Ge residue to the Si film and the roughness of the Si film after etching compared to using F2 gas. However, this ClF3 gas has high etching properties for Si films, and the Si film is easily etched. In other words, it is difficult to selectively etch the SiGe film.

[0019] Therefore, F2 gas is first supplied to the wafer W in Figure 1 for a relatively long period of time. As will be shown in the evaluation test described later, the Si film 12 is difficult to etch with F2 gas. In other words, the SiGe film 13 can be etched with high selectivity relative to the Si film 12. Then, after the SiGe film 13 is largely removed with F2 gas, ClF3 gas is supplied for a relatively short time. This suppresses etching of the Si film 12, while reducing the roughness of the Si film 12 and reducing the amount of Ge residue adhering to the Si film 12.

[0020] Incidentally, as mentioned above, ClF3 gas has relatively high etching properties for Si films, but as will be shown in the evaluation tests described later, it also has relatively high etching properties for SiGe films. Therefore, although the semiconductor film 16 formed on the wafer W is composed of Si or SiGe as previously described, regardless of whether it is composed of Si or SiGe, it will have high etching properties to this ClF3 gas. However, since the supply time of the ClF3 gas in this embodiment is relatively short, the supply of the ClF3 gas to the semiconductor film 16 through the pores of the porous film 14 is suppressed. As a result, etching of the semiconductor film 16 can also be suppressed.

[0021] Furthermore, due to the exhaust of the processing chamber, the second pressure at time t2-t3 when ClF3 gas is supplied is lower than the first pressure at time t1-t2 when F2 gas is supplied. For ClF3 gas, maintaining a relatively low pressure in the processing chamber prevents it from remaining in the chamber for an extended period. Therefore, etching of the Si film 12 and semiconductor film 16 is more reliably suppressed. Conversely, for F2 gas, maintaining a relatively high pressure in the processing chamber allows it to remain in the chamber for a relatively longer period and act on the SiGe film 13. This prevents a decrease in the etching rate.

[0022] Next, we will describe etching apparatus 2, which is an example of an etching apparatus capable of performing the etching process described in Figures 2 and 3. Figure 5 is a longitudinal cross-sectional side view of etching apparatus 2. In the figure, 21 is the processing container described above and constitutes etching apparatus 2. In the figure, 22 is a wafer W transport port opening in the side wall of processing container 21, which is opened and closed by a gate valve 23. A stage 31 on which wafers W are placed is provided inside processing container 21, and the stage 31 is provided with lifting pins (not shown). Wafers W are transferred between the substrate transport mechanism located outside processing container 21 and the stage 31 via these lifting pins.

[0023] A temperature control unit 22 is embedded in the stage 31, and the wafer W placed on the stage 31 is temperature-controlled. This temperature control unit 22 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 22 is not limited to a flow path for such a fluid, and may be configured as, for example, a heater for resistance heating.

[0024] Furthermore, one end of the exhaust pipe 24 is open inside the processing container 21, and the other end of the exhaust pipe 24 is connected to an exhaust mechanism 26, which is composed of, for example, a vacuum pump, via a valve 25, which is a pressure changing mechanism. By adjusting the opening of the valve 25, the exhaust flow rate inside the processing container 21 is adjusted, and the pressure inside the processing container 21 is set to the desired vacuum pressure. In other words, as described above, switching between the first pressure and the second pressure can be done by changing the opening of the valve 25.

[0025] A shower plate 32 is provided on the upper side of the processing container 21, facing the stage 31. The downstream sides of gas supply passages 41 to 44 are connected to the shower plate 32, and the upstream sides of gas supply passages 41 to 44 are connected to gas supply sources 51 to 54 via flow rate adjustment units 40. Each flow rate adjustment unit 40 is equipped with a valve and a mass flow controller. The supply of each gas from gas supply sources 51 to 54 is controlled by opening and closing the valves included in the flow rate adjustment unit 40 to the downstream side. The flow rate supplied to the downstream side of each gas is also adjusted by each flow rate adjustment unit 40. Each gas supplied to the gas passages provided in the shower plate 32 is discharged downward from a number of discharge ports provided on the lower surface of the shower plate 32.

[0026] F2 gas, ClF3 gas, N2 gas, and Ar gas are supplied from gas supply sources 51, 52, 53, and 54, respectively, and each of these gases is supplied into the processing container 21 via the shower plate 32. The supply of each of these gases can be controlled independently by each flow rate adjustment unit 40. The inert gas N2 gas is supplied to the processing container 21 via the shower plate 32 as a carrier gas during the etching process, along with the etching gases (F2 gas and ClF3 gas). It is also supplied into the processing container after the supply of etching gases has ended, and acts as a purge gas to purge the inside of the processing container. The inert gas Ar gas is used to adjust the partial pressure of each etching gas and is supplied into the processing container along with the etching gases. The first gas supply unit is comprised of a gas supply passage 41 through which F2 gas flows, a flow rate adjustment unit 40 interposed in the gas supply passage 41, and a shower plate 32. The second gas supply unit is comprised of a gas supply passage 42 through which ClF3 gas flows, a flow rate adjustment unit 40 interposed in the gas supply passage 42, and a shower plate 32.

[0027] Furthermore, the etching apparatus 2 is equipped with a control unit 20, which is a computer, and this control unit 20 is equipped with a program, memory, and 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 on the control unit 20. The control unit 20 outputs control signals to each part of the etching apparatus 2 using this program, thereby controlling the operation of each part. Specifically, the operations of the etching apparatus 2 that are controlled in this manner include, for example, adjusting the temperature of the fluid supplied to the stage 31 (i.e., the processing temperature of the wafer W), cutting off the supply of each gas from the shower plate 32, and adjusting the exhaust flow rate by the valve 25 (i.e., adjusting the pressure inside the processing container 21).

[0028] By adjusting the opening of valve 25 of etching apparatus 2, the first pressure at time t1 to t2 is set to, for example, 1.33 Pa (10 mTorr) to 133 Pa (1000 mTorr), and the second pressure at time t2 to t3 is set to, for example, 0 Pa to 133 Pa. In addition, the temperature control unit 22 sets the temperature of wafer W at time t1 to t3 to, for example, -50°C to 150°C. The supply flow rates of each gas into the processing container are within the following ranges: F2 gas 1 to 500 sccm, ClF3 gas 0.1 to 10 sccm, N2 gas 50 to 1000 sccm, and Ar gas 10 to 1000 sccm.

[0029] Furthermore, as described above, inert gases (N2 gas and Ar gas) are supplied into the processing container along with F2 gas and ClF3 gas. Regarding the flow rates of F2 gas, ClF3 gas and inert gas supplied into the processing container, for example, the flow rate of F2 gas / flow rate of inert gas is greater than the flow rate of ClF3 gas / flow rate of inert gas. In other words, when supplying F2 gas and ClF3 gas to the wafer W, the ClF3 gas may be supplied with a higher dilution ratio by the inert gas than the F2 gas. By adjusting the flow rates of each gas in this way, the etching effect of ClF3 gas on the Si film 12 and the semiconductor film 16 is more reliably suppressed.

[0030] Although F2 gas is shown as the first etching gas, other fluorine-containing gases capable of selectively etching the SiGe film 13 with respect to the Si film 12 may be used. For example, a mixture of HF gas and F2 gas may be used instead of F2 gas. Furthermore, a fluorine-containing gas with a relatively large etching effect on the SiGe film 13 can be used as the second etching gas instead of the ClF3 gas. For example, IF7 (iodine heptafluoride) gas or NF3 (nitrogen trifluoride) gas may be used as the second etching gas. Note that "containing fluorine" here means containing fluorine as a constituent component, not containing it as an impurity.

[0031] In the processing example shown in the chart in Figure 3, ClF3 gas is supplied simultaneously with the cessation of F2 gas supply, and the F2 gas is purged from the processing container 21 using ClF3 gas. However, there may be an interval between the point in time when the F2 gas supply is stopped and the point in time when the ClF3 gas supply is started. During that interval, the F2 gas in the processing container may be purged with an inert gas such as N2 gas. However, in order to shorten the processing time, it is preferable to supply ClF3 gas simultaneously with the cessation of F2 gas supply, as shown in Figure 3, and to purge the F2 gas using ClF3 gas.

[0032] Incidentally, the etching method described in this embodiment suppresses the roughness of the Si film 12 adjacent to the SiGe film 13, as mentioned above, so it is particularly effective when performed on substrates where the SiGe film 13 and Si film 12 are adjacent to each other. However, since this etching method can reduce the amount of residual Ge after etching the SiGe film, it may also be used when etching a SiGe film 13 that is not adjacent to the Si film 12.

[0033] 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.

[0034] [Evaluation Test 1] The evaluation tests conducted in relation to the technology of this disclosure will now be described. In Evaluation Test 1, multiple wafers W, each with two chips fixed to its surface, were prepared. Then, using the etching apparatus 2 shown in the embodiment, the etching gas type and etching time were changed for each wafer W. One of the two chips had a SiGe film laminated as an upper layer on top of a Si film as an underlayer. The thickness of this SiGe film was 50 nm, and the Ge content in the film was 25%. The other chip was a polysilicon film. For the chip with 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 by AFM (atomic force microscope), images were acquired by SEM (scanning electron microscope), and the amount of etching of the SiGe film was measured. The amount of etching was also measured for the polysilicon film chip.

[0035] Etching was performed by supplying F2 gas, ClF3 gas, and F2 gas and ClF3 gas to wafer W as etching gases. The tests using F2 gas, ClF3 gas, and F2 gas and ClF3 gas are designated as evaluation tests 1-1, 1-2, and 1-3, respectively. In evaluation test 1-3, the start and end timings of supplying F2 gas and ClF3 gas were synchronized and supplied simultaneously. In each of evaluation tests 1-1 to 1-3, the etching gas supply time (etching time) was changed for each wafer W. When performing etching, the temperature of wafer W, the pressure inside the processing container 21, and the flow rate of each gas supplied into the processing container were set to values ​​within the range shown in the embodiment.

[0036] In explaining the test results, the etching time set so that the amount of etching of the SiGe film on the chip becomes the same as the film thickness of the SiGe film, 50 nm (i.e., the SiGe film is exactly removed), is sometimes expressed as the JE (Just Etching) time. The time for further etching beyond that, resulting in excess etching of the 50 nm SiGe film, is sometimes expressed as the OE (Over Etching) time. Specifically, if the film thickness of the SiGe film on the chip is assumed to be 100 nm, 150 nm, 300 nm, and 550 nm, the time for which the amount of etching of the SiGe film becomes the same as the film thickness is expressed as the OE time for 100%, 200%, 500%, and 1000%, respectively. The OE time for each is calculated based on the relationship between the amount of etching of the SiGe film of 50 nm or less and the corresponding etching time (see graph in Figure 6).

[0037] Figure 7 shows the SEM images, Ge detection amount, RMS, and polysilicon film etching amount obtained for each evaluation test 1-1 to 1-3, including JE and each OE treatment. As previously mentioned, the SEM images, Ge detection amount, and RMS were obtained from chips on which the SiGe film was formed (i.e., chips on which the surface was formed of Si after the SiGe film was removed). In reality, the Ge detection amount was obtained as a percentage, and the RMS and polysilicon film etching amount were obtained as values ​​in nm, but the values ​​shown in the table are normalized values ​​obtained in this way by dividing them by a predetermined coefficient. For Ge detection amount, a larger value in the figure indicates a larger amount remaining on the Si film; for RMS, a larger value indicates greater roughness; and for polysilicon film etching amount, a larger value indicates greater etching. In Figure 7, for comparison, an image of the surface of the chip on which the SiGe film was formed before etching, and the normalized RMS are also shown in the lower right corner of the figure.

[0038] Figure 8 shows a graph illustrating the relationship between etching time with ClF3 gas and the amount of etching of the SiGe and polysilicon films, which served as the basis for evaluation test 1-2. Figure 9 shows a graph illustrating the relationship between etching time with F2 and ClF3 gases and the amount of etching of the SiGe and polysilicon films, which served as the basis for evaluation test 1-3. Similar to evaluation test 1-1, the JE and OE times were determined from the correspondence between the amount of etching of the SiGe film and the etching time, and evaluation tests 1-2 and 1-3 were conducted. The vertical axis of each graph shows the etching amount of each film, but the values ​​shown are normalized by dividing the obtained values ​​by a predetermined coefficient. This predetermined coefficient is the same as the coefficient used to normalize the etching amount of the polysilicon film in Figure 6.

[0039] The results of evaluation test 1-1 using F2 gas will be explained. In evaluation test 1-1 shown in Figure 7, the specific etching times for JE, OE100%, OE200%, OE500%, and OE1000% were 82 seconds, 145 seconds, 208 seconds, 397 seconds, and 712 seconds, respectively. As shown in Figure 6, the amount of etching of the SiGe film increases as the etching time with F2 gas increases. On the other hand, as shown in Figure 7, the amount of etching of the polysilicon film is generally constant and relatively low for the etching times of JE and each OE. Therefore, as described in the embodiment, it can be seen that the SiGe film can be etched with high selectivity when etching the Si film and SiGe film using F2 gas.

[0040] However, the detected amount of Ge is relatively large. As the percentage of OE increases, the detected amount of Ge decreases, but it was confirmed that Ge remains even at OE 1000%. Furthermore, for RMS, the value decreases as the percentage of OE increases, but it was confirmed that the value is relatively large (i.e., the roughness is relatively large) when the percentage is low and in the case of JE.

[0041] Next, we will explain the results of evaluation test 1-2 using ClF3 gas. As shown in Figure 7, the etching times for JE, OE100%, and OE200% in this evaluation test 1-2 were 50 seconds, 115 seconds, and 179 seconds, respectively. Regarding the amount of Ge detected, the value was relatively low for JE, and no Ge was detected for OE100% and OE200%. Regarding RMS, the RMS values ​​for JE, OE100%, and OE200% were similar to the RMS values ​​before etching, and were lower than the RMS values ​​for JE, OE100%, and OE200% in evaluation test 1-1. The RMS values ​​for OE100% and OE200% were particularly low.

[0042] However, as shown in Figure 8, when using ClF3 gas, as the etching time increases, not only the etching amount of the SiGe film but also the etching amount of the polysilicon film increases. As a result, the etching amounts of the JE, OE100%, and OE200% polysilicon films in Evaluation Test 1-2 were greater than the etching amounts of the JE and each OE polysilicon film in Evaluation Test 1-1.

[0043] Next, we will explain the results of evaluation test 1-3 using F2 gas + ClF3 gas. In evaluation test 1-3, shown in Figure 7, the etching times for JE, OE100%, and OE200% were 24 seconds, 54 seconds, and 85 seconds, respectively. Regarding the amount of Ge detected, similar to test 1-2, the value was relatively low for JE, and no Ge was detected for OE100% and OE200%. Furthermore, the RMS values ​​were particularly low for OE100% and OE200%, and were about the same as the RMS values ​​before etching.

[0044] However, as shown in Figure 9, even when using F2 gas + ClF3 gas, as the etching time increases, not only the etching amount of the SiGe film but also the etching amount of the polysilicon film increases. As a result, the etching amounts of the JE, OE100%, and OE200% polysilicon films in Evaluation Test 1-3 were greater than the etching amounts of the JE and each OE polysilicon film in Evaluation Test 1-1.

[0045] As described above, the results of this evaluation test 1 confirmed that using ClF3 gas as the etching gas can reduce the amount of Ge remaining on the Si film after etching (residue amount) and suppress the roughness of the Si film. However, it was shown that the amount of etching of the Si film is relatively larger compared to when using F2 gas.

[0046] [Evaluation Test 2] As Evaluation Test 2, etching was performed on wafer W with the same configuration as Evaluation Test 1, under the same conditions as those used in Evaluation Test 1-1 for OE 100%. That is, etching was performed using F2 gas. Following this F2 gas etching, F2 gas and NH3 gas were supplied into the processing container to perform purging of F2 gas and etching within the processing container. The pressure inside the processing container was set lower during the period when only F2 gas was supplied (the purging period) than during the period when only F2 gas was supplied. After this etching, SEM images, Ge detection amount, and RMS were obtained from the chip with the SiGe film formed on it, as in Evaluation Test 1, and the etching amount was obtained from the chip with the polysilicon film. The supply time of F2 gas and NH3 gas (purging time) was changed for each wafer W, and the tests performed with settings of 5 seconds, 10 seconds, and 20 seconds are designated as Evaluation Tests 2-1, 2-2, and 2-3, respectively.

[0047] [Evaluation Test 3] For Evaluation Test 3, the test was conducted under the same processing conditions as Evaluation Test 2, except that there was no period during which etching was performed by supplying F2 gas alone. Therefore, in Evaluation Test 3, etching was performed only during the period when both F2 gas and NH3 gas were supplied to wafer W simultaneously (corresponding to the purging period in Evaluation Test 2). The supply times for F2 gas and NH3 gas were set to 5 seconds, 10 seconds, and 20 seconds, respectively, as in Evaluation Test 2, and the tests conducted with these time settings are designated as Evaluation Tests 3-1, 3-2, and 3-3, respectively. In Evaluation Test 3, the etching amounts of the SiGe film and the polysilicon film were measured.

[0048] The results of evaluation tests 2 and 3 are shown in Figure 10. Each value in the table is normalized in the same way as in evaluation test 1. Looking at the results of evaluation test 2, the Ge detection amount and RMS were relatively high in each of evaluation tests 2-1 to 2-3. Furthermore, between evaluation tests 2-1 to 2-3, the longer the supply time of F2 gas and NH3 gas, the greater the etching amount of the polysilicon film. Looking at the results of evaluation test 3, there was no significant difference in the etching amount of the SiGe film between evaluation tests 3-1 to 3-3, but the etching amount of the polysilicon film increased with longer etching time. Therefore, from the results of evaluation tests 2 and 3, it can be seen that the polysilicon film is etched relatively significantly by the action of F2 gas and NH3 gas.

[0049] [Evaluation Test 4] For Evaluation Test 4, the treatment was carried out under the same conditions as Evaluation Test 2, except that the purging was performed by supplying ClF3 gas instead of F2 gas and NH3 gas as in Evaluation Test 2, and the range of the length of the purging period was different from the range of 5 seconds to 20 seconds set in Evaluation Test 2. Therefore, in Evaluation Test 4, as in the embodiment, ClF3 gas was supplied after F2 gas. The pressure inside the treatment container was also set lower during the period of supplying ClF3 gas than during the period of supplying F2 gas, as in the embodiment. The supply time of ClF3 gas was set to 5 seconds, 20 seconds, and 60 seconds, respectively, and the tests conducted with these time settings are designated as Evaluation Tests 4-1, 4-2, and 4-3, respectively.

[0050] [Evaluation Test 5] For Evaluation Test 5, the same processing conditions as Evaluation Test 4 were used, except that there was no period for supplying F2 gas and performing etching. Therefore, in Evaluation Test 5, etching was performed using only ClF3 gas. The supply time for the ClF3 gas was set to 5 seconds, 20 seconds, and 60 seconds, the same as in Evaluation Test 4, and the tests performed with these time settings are designated as Evaluation Tests 5-1, 5-2, and 5-3, respectively. In Evaluation Test 5, as in Evaluation Test 3, the etching amounts of the SiGe film and the polysilicon film were measured.

[0051] The results of evaluation tests 4 and 5 are shown in Figure 11. Each value in the table is normalized in the same way as in evaluation test 1. Looking at the results of evaluation test 4, the Ge detection amount was kept low in each of evaluation tests 4-1 to 4-3, and was lower than any of the Ge detection amounts in evaluation tests 2-1 to 2-3. Similarly, the RMS was kept low in each of evaluation tests 4-1 to 4-3, and was lower than any of the RMS values ​​in evaluation tests 2-1 to 2-3. Furthermore, the etching amount of the polysilicon film was relatively low in each of evaluation tests 4-1 to 4-3, and was about the same as the values ​​in evaluation tests 2-1 to 2-3.

[0052] From the results of the above evaluation test 4, it can be seen that when processing the wafer W having the film structure shown in Figure 1 using the method described in the embodiment above, it is possible to selectively etch the SiGe film 13 out of the Si film 12 and SiGe film 13, thereby suppressing the remaining Ge residue. Furthermore, it can be seen that the roughness of the Si film 12 after etching can be suppressed.

[0053] Furthermore, the results of Evaluation Test 5 show that, similar to Evaluation Test 1, the amount of etching of the SiGe film and the polysilicon film increases as the supply time of ClF3 gas increases. The amount of etching of the polysilicon film is relatively large in Evaluation Test 5-2, but relatively small in Evaluation Test 5-1. From these results, it is considered preferable that the time (second time) for supplying ClF3 gas from time t2 to time t3 shown in Figure 3 be shorter than 20 seconds, and more preferably 5 seconds or less.

[0054] [Evaluation Test 6] For evaluation test 6-1, a substrate having the film structure shown in Figure 12 was prepared. This film structure comprises a laminate 62 in which Si films 12 and SiGe films 13 are alternately and repeatedly stacked upwards, with a SiN (silicon nitride) film 61 formed on the uppermost Si film 12. A porous film 63, which is a low-k film, is formed to cover this laminate 62 from the side to the top, and the porous film 63 is exposed on the surface of the substrate. In other words, when etching gas is supplied, the porous film 63 is exposed to the etching gas. After supplying etching gas to the substrate in which each film is formed as described in Figures 2 and 3 of the embodiment, the state of the SiGe film 13 was observed. Furthermore, for evaluation test 6-2, the state of the SiGe film 13 was observed after supplying etching gas to a substrate having a film structure that is generally the same except that the porous film 63 is not formed, as described in Figures 2 and 3.

[0055] In evaluation test 6-2, the SiGe film 13 was etched from the side, but in evaluation test 6-1, no etching of the SiGe film 13 from the side was observed. From these test results, it is expected that when etching is performed on a wafer W having the film structure shown in Figures 1 and 2, as explained in Figures 2 and 3, etching of the semiconductor film 16 adjacent to the porous film 14 will be suppressed. [Explanation of symbols]

[0056] W wafer 13 SiGe film

Claims

1. In a method for etching a silicon germanium film formed on a substrate, A first step involves supplying a first etching gas, which is a fluorine-containing gas, to the substrate for a first time. After the first step, a second step is performed in which a second etching gas, which is a fluorine-containing gas of a different type from the first etching gas, is supplied to the substrate for a second time that is shorter than the first time. Includes, The first step is to selectively etch the silicon germanium film and the silicon film, respectively, that are exposed on the surface of the substrate. The second step is to etch the remaining portion of the silicon germanium film, The etching method wherein the second etching gas is chlorine trifluoride gas.

2. The aforementioned substrate includes: Silicon-containing film and A porous film interposed between the silicon-containing film and the silicon-germanium film, The etching method according to claim 1, wherein a feature is provided.

3. The first and second steps are steps of supplying the first etching gas and the second etching gas, respectively, to the substrate stored in the processing container. The etching method according to claim 1, further comprising the step of setting the pressure inside the processing vessel in the second step to a pressure lower than the pressure inside the processing vessel in the first step.

4. In an apparatus for etching a silicon germanium film formed on a substrate, A processing container for storing the substrate, A first gas supply unit for carrying out a first step of supplying a first etching gas, which is a fluorine-containing gas, into the processing container for a first time, A second gas supply unit for carrying out a second step in which, after supplying the first etching gas, a second etching gas, which is a fluorine-containing gas of a different type from the first etching gas, is supplied into the processing container for a second time shorter than the first time, Equipped with, The first step is to selectively etch the silicon germanium film and the silicon film, respectively, which are exposed on the surface of the substrate. The second step is to etch the remainder of the silicon germanium film, and the etching apparatus is wherein the second etching gas is chlorine trifluoride gas.

Images