Etching method and etching apparatus

Abstract

To make the shape of a germanium-containing film after etching be a desired one.SOLUTION: An etching method includes: a step of storing a substrate comprising recesses constituted by side walls that are germanium-containing films, in a processing container; an etching step of supplying etching gas containing first fluorine-containing gas and second fluorine-containing gas into the processing container to perform etching on a first side wall and a second side wall; and a shape control step, included in the etching step, of controlling the shapes of the side walls after the etching by adjusting the partial pressure of the first fluorine-containing gas in the processing container or the ratio of the flow rate of the second fluorine-containing gas to that of the first fluorine-containing gas to be supplied into the processing container.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] In manufacturing a semiconductor device, etching is performed on each film formed on the surface of a semiconductor wafer (hereinafter referred to as a wafer) that is a substrate. Patent Document 1 describes a method of supplying ClF gas and HF gas to a wafer in which Si films and SiGe films, which are silicon-containing films, are alternately stacked, thereby selectively etching the SiGe film while suppressing damage to the Si film. Patent Document 2 describes a method of etching a Si film embedded in pores in an oxide film on the wafer surface so as to suppress surface roughness after etching by alternately supplying ClF gas and a mixed gas consisting of F gas and NH gas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-53448 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-201102 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique that can achieve a desired shape of a germanium-containing film after etching. [Means for solving the problem]

[0005] The etching method of the present disclosure includes the steps of: storing a substrate having a recess with a sidewall formed of a germanium-containing film in a processing chamber; An etching gas containing a first fluorine-containing gas and a second fluorine-containing gas is supplied into the processing chamber; Each side wall an etching step of etching the first sidewall and the second sidewall; The etching step includes: Adjust the partial pressure a shape control step of adjusting the shape of the sidewall after etching; Equipped with 、 The recessed portion is a first recess defined by the first sidewall and having a first width; a second recess defined by the second sidewall and having a second width greater than the first width; The shape control step includes: The etching amount of the first side wall and the etching amount of the second side wall in the etching step are controlled. [Effects of the Invention]

[0006] According to the present disclosure, the shape of the germanium-containing film after etching can be made as desired. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a cross-sectional side view of a wafer undergoing processing according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a longitudinal sectional side view of the wafer after etching processing. [Figure 3] FIG. 10 is a graph showing test results. [Figure 4] FIG. 10 is a graph showing test results. [Figure 5] FIG. 2 is a vertical cross-sectional side view of the wafer. [Figure 6] FIG. 2 is a vertical cross-sectional side view of the wafer. [Figure 7] FIG. 2 is a vertical cross-sectional side view of the wafer. [Figure 8] FIG. 2 is a vertical cross-sectional side view of the wafer. [Figure 9] FIG. 2 is a vertical cross-sectional side view of the etching apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0008] To explain a process according to an embodiment of the etching method of the present disclosure, a wafer W to be etched will be described with reference to FIG. 1 . FIG. 1 is a longitudinal side view of the surface of the wafer W. Reference numeral 11 in the figure denotes a substrate constituting the wafer W, which is made of silicon (Si). SiGe (silicon germanium) films 12 and Si (silicon) films 13 are alternately and repeatedly stacked on the substrate 11 in the longitudinal direction (thickness direction of the wafer W). This stacked structure is formed of multiple SiGe films 12 and multiple Si films 13. For clarity, FIG. 1 omits the number of layers and shows the structure as consisting of three layers of SiGe films 12 and three layers of Si films 13. A mask film 14 is formed on the Si film 13, which is the top layer of this stacked structure. This mask film 14 serves as a mask for the stacked structure during etching. Due to this configuration, Si films 13 are interposed between the SiGe films 12 in the thickness direction of the wafer W.

[0009] A plurality of recesses are formed on the surface of the wafer W, each recess having a depth extending from the surface of the mask film 14 to the surface layer of the substrate 11. Therefore, the sidewalls of each recess are formed by a stack (referred to as stack 15) consisting of the SiGe film 12, the Si film 13, the mask film 14, and the surface layer of the substrate 11. Therefore, it can be seen that a plurality of stacks 15 are arranged at intervals on the surface of the wafer W. The recesses are formed so as to form regions where the stacks 15 are relatively densely packed (Dense) and regions where the stacks 15 are relatively widely spaced apart (ISO). Therefore, the plurality of recesses includes a first recess 21 having a first width L1 and a second recess 22 having a second width L2 greater than the first width L1.

[0010] The difference in size between the first width L1 and the second width L2 is not an unavoidable or unintentional result of processing errors or the like, but is formed by design, and for example, the designed width L2 / width L1 is 2 or more. The first recess 21 and the second recess 22 illustrated in FIG. 1 are grooves extending in the direction of the paper, but may also be holes. If they are holes, the first width L1 and the second width L2 are the diameters of the holes.

[0011] The SiGe film 12 is a germanium-containing film to be etched. A portion of the SiGe film 12 facing the first recess 21 forms a first sidewall, and a portion facing the second recess 22 forms a second sidewall. In this embodiment, the wafer W is placed in a processing chamber, and F2 (fluorine) gas and ClF3 ( Chlorine trifluoride ) gas is simultaneously supplied as an etching gas. This etching gas enters the first recess 21 and the second recess 22, and laterally etches the SiGe film 12 of each stage constituting the stack 15, as shown in FIG. 2. This etching is performed so as to remove only a portion of the sidewall of each SiGe film 12, so that the SiGe film 12 of each stage remains on the wafer W after etching.

[0012] This etching selectively etches the SiGe film 12 out of the SiGe film 12 and the Si film 13. Therefore, recesses that open laterally are formed by the etching so as to face the first recess 21 and the second recess 22. The recesses facing the first recess 21 and the second recess 22 are shown in FIG. 2 as a first lateral recess 23 and a second lateral recess 24, respectively.

[0013] To specifically explain the etching process of this embodiment, an experiment conducted on the etching of the wafers W will be described first. In this experiment, the SiGe film 12 was etched for multiple wafers W under different processing conditions. For this etching, in addition to the etching gases (F2 gas and ClF3 gas), Ar (argon) gas and N2 (nitrogen) gas were supplied into the processing chamber simultaneously with the etching gas. These Ar gas and N2 gas serve as carrier gases for the etching gas and to adjust the partial pressure of each gas in the processing chamber. The processing conditions that were changed for each wafer W were the flow rates of each gas supplied into the processing chamber and the pressure (total pressure) within the processing chamber. Note that, in accordance with the changes in the flow rates and total pressure, the partial pressures of F2 gas and ClF3 gas in the processing chamber were also changed for each wafer W during etching.

[0014] In the experiment, the etching amount of the SiGe film 12 at each step facing the first recess 21 (i.e., each step in the Dense configuration) and the etching amount of the SiGe film 12 at each step facing the second recess 22 (i.e., each step in the ISO configuration) were measured. Hereinafter, the etching amount of the portion of the SiGe film 12 facing the first recess 21 may be referred to as the Dense etching amount, and the etching amount of the portion facing the second recess 22 may be referred to as the ISO etching amount. As described above, the SiGe film 12 is provided in multiple steps in the stacked body 15. The upper SiGe film 12 may be referred to as the top, the lower SiGe film 12 as the bottom, and the SiGe film 12 at a height between the top and bottom as the middle.

[0015] Eight processing conditions were set, designated as processing conditions 1 to 8. Table 1 below summarizes processing conditions 1 to 8. The pressure inside the processing vessel is shown in Table 1 as the total pressure (unit: mTorr). The units for each flow rate in Table 1 are sccm. The partial pressures (unit: mTorr) of F2 gas and ClF3 gas in the table are the partial pressures inside the processing vessel, and are values ​​calculated from the flow rates of each gas and the pressure inside the processing vessel. Under processing conditions 1 to 8, the temperature of the wafer W during etching is a common temperature within the range of -40°C to 80°C. To avoid complication, in the following description, the partial pressure inside the processing vessel will be simply referred to as the partial pressure, and the flow rate of the gas supplied into the processing vessel will be simply referred to as the flow rate.

[0016] In Table 1, each set value, except for the partial pressure of ClF3 gas, is shown as a value using an alphabet. Specifically, for the pressure (total pressure) of the processing vessel, a predetermined pressure value (unit: mTorr) is designated as the alphabet A, and the multiplied value of this A is displayed before A to indicate the total pressure. Therefore, for example, the total pressure (2A) under processing conditions 1 to 4, 6, and 8 is twice the total pressure (A) under processing conditions 5 and 7.

[0017] As with the total pressure, the flow rates of F2 gas, ClF3 gas, and N2 gas are indicated by letters B through D and the multiplication of B through D. The flow rate ratios shown in Table 1 are the ratios of the flow rate of F2 gas (second fluorine-containing gas) to the flow rate of ClF3 gas (first fluorine-containing gas), and are expressed in Table 1 by "B / C" and its multiplication. Hereinafter, these flow rate ratios will be referred to as the F2 / ClF3 flow rate ratio. Similarly to the total pressure and F2 / ClF3 flow rate ratio, the partial pressure of F2 gas (unit: mTorr) is also indicated by the letter F and its multiplication. However, unlike the other gases, the Ar gas flow rate (unit: sccm) is not expressed by its multiplication because its value varies slightly depending on the processing conditions. E1 through E8, shown as Ar gas flow rates in the table, are individual values.

[0018] (Table 1) TIFF0007803047000001.tif73140

[0019] Figure 3 shows experimental results, with bar graphs showing the DENSE etching amount and ISO etching amount for each processing condition. The vertical axis of the graph is scaled in increments of a specified etching amount, so the etching amount between each scale indicates the same amount. The bars showing the DENSE etching amount are shaded, while the bars showing the ISO etching amount are not shaded. Note that the etching amounts shown in the bars in this figure are the average of the top, middle, and bottom etching amounts mentioned above.

[0020] In Figure 3, the bar graphs are shown from left to right in the order of process conditions 7, 5, 6, 2, 4, 1, and 3. Looking at the partial pressure of ClF3 gas, under process conditions 5 and 7, the pressure was 0.2 mTorr (0.267 x 10 -1 Pa), and 0.4 mTorr (0.533 × 10 -1 Pa), and under processing conditions 1 and 3, 0.7 mTorr (0.933 × 10 -1 Pa). Therefore, in Figure 3, the bar graphs for each processing condition are divided by the partial pressure of ClF3 gas. For processing conditions with the same partial pressure of ClF3 gas, the bar graphs for processing conditions with smaller F2 / ClF3 flow ratios are arranged toward the right side of the figure, so the bar graphs for each processing condition are arranged in the above order.

[0021] As shown in Figure 3, under process conditions 1 and 3, where the ClF3 gas partial pressure was 0.7 mTorr, the ISO etching rate was greater than the DENSE etching rate. Furthermore, under process conditions 5 and 7, where the ClF3 gas partial pressure was 0.2 mTorr, the DENSE etching rate was greater than the ISO etching rate. Therefore, the experimental results showed that when the ClF3 gas partial pressure was relatively high, the ISO etching rate was greater regardless of the F2 / ClF3 flow rate ratio. On the other hand, when the ClF3 gas partial pressure was relatively low, the DENSE etching rate was greater regardless of the F2 / ClF3 flow rate ratio.

[0022] Additionally, under process conditions 2, 4, and 6, where the ClF3 gas partial pressure is 0.4 mTorr, the DENSE etching amount and the ISO etching amount are approximately equal for process condition 4, which has the smallest F2 / ClF3 flow ratio among these process conditions 2, 4, and 6. And under process condition 2, which has the second smallest F2 / ClF3 flow ratio among process conditions 2, 4, and 6 after process condition 4, the ISO etching amount is larger than the DENSE etching amount. Under process condition 6, the DENSE etching amount is larger than the ISO etching amount.

[0023] As described above, the DENSE etching rate and the ISO etching rate each change depending on the partial pressure of ClF3 gas, and the magnitude relationship between these etching rates changes. Specifically, depending on the partial pressure, the DENSE etching rate and the ISO etching rate can be the same or approximately the same, or one can be larger than the other.

[0024] ClF gas has a higher reactivity with the SiGe film 12 than F gas. When the partial pressure of ClF gas is relatively low, the ClF gas concentration in the relatively large second recess 22 is very low, making it difficult for the ClF gas to react with the SiGe film 12. However, when the partial pressure of ClF gas is relatively high, the ClF gas concentration in the second recess 22 is relatively high, allowing the ClF gas to react efficiently with the SiGe film 12. That is, when the partial pressure of ClF gas is greater than 0.7 mTorr, the ISO etching amount is larger, as in process conditions 1 and 3, where the partial pressure is 0.7 mTorr. When the partial pressure of ClF gas is less than 0.3 mTorr, the DENSE etching amount is larger, as in process conditions 5 and 7, where the partial pressure is 0.3 mTorr. In summary, the ISO etching amount is larger when the partial pressure is 0.7 mTorr or higher (within the second range), and the DENSE etching amount is larger when the partial pressure is 0.2 mTorr or lower (within the third range).The above experimental results show that when the partial pressure is greater than 0.2 mTorr and less than 0.7 mTorr (within the first range), the DENSE etching amount and ISO etching amount change depending on the F2 / ClF3 flow rate ratio, and as a result, the relationship between these etching amounts fluctuates.

[0025] In the above experiment, the relationship between the top, middle, and bottom etching amounts was obtained for each wafer W processed under process conditions 2, 4, and 8, where the ClF3 gas partial pressure was 0.4 mTorr, a value within the first range. Figure 4 shows this relationship in the form of a bar graph. The vertical axis of the graph in Figure 4 is scaled in increments of a predetermined difference in etching amount, so the difference in etching amount between each scale is the same. In Figure 4, the top etching amount minus the middle etching amount is shown as a shaded bar, and the middle etching amount minus the bottom etching amount is shown as an unshaded bar. Each bar graph indicates a process condition with a decreasing F2 / ClF3 flow rate ratio, as shown in Figure 4, so the bars are arranged in the order of process conditions 2, 8, and 4 toward the right.

[0026] 4, regarding the etching amount of the middle and the etching amount of the bottom, the etching amount of the bottom was larger under all of process conditions 2, 4, and 8, but the difference between the etching amounts of the middle and the bottom became smaller under process conditions 4, 8, and 2, and the difference was slight under process condition 2. Since the F2 / ClF3 flow ratios under process conditions 2, 8, and 4 were 4B / C, 3B / C, and 2B / C, respectively, it can be seen that within the F2 / ClF3 flow ratio range of 2B / C to 4B / C, the difference between the etching amounts of the middle and the bottom became smaller as the F2 / ClF3 flow ratio increased.

[0027] Furthermore, looking at the difference in etching amount between the top and middle, the difference in etching amount is a positive value under process conditions 4 and 8. Therefore, the etching amount of the top is larger, and between process conditions 4 and 8, the difference in etching amount is smaller under process condition 8. And under process condition 2, the difference in etching amount is a negative value, and the etching amount of the middle is larger than that of the top. As such, it can be seen that the larger the value is within the range of F2 / ClF3 flow rate ratio 2B / C to 4B / C, the greater the etching amount of the middle relative to the etching amount of the top. Note that the absolute value of the difference in etching amount is similar between process conditions 2 and 8.

[0028] As described above, when the partial pressure of ClF3 gas is within the first range, the etching amounts of the top, middle, and bottom portions of the SiGe film 12 facing the first and second recesses 21 and 22 can be adjusted by changing the F2 / ClF3 flow rate ratio. Furthermore, it is estimated that a preferable F2 / ClF3 flow rate ratio greater than 3B / C and less than 4B / C exists that can reduce the difference in etching amount between the top and middle portions to zero or nearly zero and minimize the etching amount between the middle and bottom portions. As shown in Table 1, since B / C = 24.46, to equalize the etching amounts between the top, middle, and bottom portions, it is preferable to set the F2 / ClF3 flow rate ratio greater than 3 × 24.46 = 73.38 and less than 4 × 24.46 = 97.84. The dotted line and a1, b1, and c1 in the graph of Figure 4 will be described later as an example of F2 / ClF3 settings based on this experiment.

[0029] The etching process of this embodiment is performed based on the findings obtained from the experiments described above. Specifically, the shape of the surface of the wafer W after etching is controlled to a desired shape. Several specific examples of this shape control are described below. In each of these specific examples, the objective is to perform etching so that the shapes of the laminates 15 after etching are the same or approximately the same. In other words, etching is performed so that the laminates 15 have bilaterally symmetrical shapes.

[0030] First, a first specific example will be described. For a wafer W to be etched, as shown in FIG. 1, the sidewalls of the SiGe film 12 and the Si film 13 in each stack 15 are laterally aligned with each other. In this case, etching is performed by setting the ClF gas partial pressure to 0.4 mTorr, the same as the partial pressure under process conditions 2, 4, 6, and 8, and the F / ClF flow ratio to a reference value. This reference value for the F / ClF flow ratio is set to, for example, a value greater than 3B / C and less than 4B / C, as described in the graph of FIG. 4. That is, this reference value is close to the F / ClF flow ratio under process condition 4, in which the ISO etching amount and the DENSE etching amount were approximately the same (see FIG. 3). Therefore, etching under this reference value allows the ISO etching amount and the DENSE etching amount to be approximately the same.

[0031] Therefore, after etching, the depths of the first lateral recesses 23 and the second lateral recesses 24 are uniform, as shown in Fig. 2, and the shapes of the laminates 15 can be made the same or approximately the same. Furthermore, as described in Fig. 4, since the F2 / ClF3 flow rate ratio is set as described above, the etching amount is uniform among the top, middle, and bottom. That is, this is preferable because the uniformity of the depths of the first lateral recesses 23 at the top, middle, and bottom, and the uniformity of the second lateral recesses 24 at the top, middle, and bottom are each high.

[0032] Next, a second specific example will be described. The wafer W before etching in this example is shown in the upper part of Fig. 5, and this wafer W has substantially the same configuration as the wafer W shown in Fig. 1. However, in a pre-etching process, the side (dense side) of each SiGe film 12 facing the first recess 21 is etched, and a first lateral recess 23 is formed in advance. The side walls of the Si film 13 and the SiGe film 12 facing the first recess 21 are not aligned in the lateral direction.

[0033] Therefore, to etch the wafer W shown in the upper part of Figure 5 to uniform the shapes of the laminated bodies 15, it is necessary to increase the ISO etching rate relative to the DENSE etching rate. Therefore, the ClF3 gas partial pressure is set to 0.4 mTorr, and the F2 / ClF3 flow rate ratio is set lower than the reference value. For example, the F2 / ClF3 flow rate ratio is set to 4B / C, the same as process condition 2 described in Figure 3, and etching is performed. By performing etching in this manner, the ISO etching rate is increased relative to the DENSE etching rate. The lower part of Figure 5 shows the wafer W after etching. Due to the difference in etching rate, the depths of the first and second lateral recesses 23 and 24 are uniform, as shown in the lower part of Figure 5, and the shapes of the laminated bodies 15 after etching are uniform or approximately the same.

[0034] Next, a third specific example will be described. The wafer W before etching in this example is shown in the upper part of Fig. 6, and this wafer W has substantially the same configuration as the wafer W shown in Fig. 1. However, in a pre-etching process, the side (ISO side) of each SiGe film 12 facing the second recess 22 is etched, and a second lateral recess 24 is formed in advance. Therefore, the side walls of the Si film 13 and the SiGe film 12 facing the second recess 22 are not aligned in the lateral direction.

[0035] Therefore, to etch the wafer W shown in the upper row of FIG. 6 to uniform the shapes of the laminates 15, it is necessary to increase the DENSE etching rate relative to the ISO etching rate. Therefore, the ClF3 gas partial pressure is set to 0.4 mTorr, and the F2 / ClF3 flow rate ratio is set higher than the reference value. For example, the flow rate ratio is set to 6B / C, the same as process condition 6 described in FIG. 3, for etching. By performing etching in this manner, the DENSE etching rate is increased relative to the ISO etching rate. The lower row of FIG. 6 shows the wafer W after etching. Due to the difference in the etching rate, the depths of the first and second side recesses 23 and 24 are uniform, as shown in the lower row of FIG. 6, and the shapes of the laminates 15 after etching are uniform or approximately the same.

[0036] A fourth specific example will now be described. The wafer W before etching in this example is shown in the upper part of Figure 7, and this wafer W has substantially the same configuration as the wafer W shown in Figure 1. However, in the pre-etching process, variations occur in the positions of the sidewalls of the SiGe film 12 at each stage facing the first recess 21 and the second recess 22, respectively, and the middle is etched more than the top and bottom, forming a first lateral recess 23 and a second lateral recess 24. The top and bottom are substantially etched.

[0037] Therefore, etching is performed by setting the ClF3 gas partial pressure to 0.4 mTorr and the F2 / ClF3 flow rate ratio to a value lower than the reference value. As a result of these settings, the etching amounts at the top and bottom are greater than the etching amount at the middle, as shown in Figure 4. Therefore, as shown in the lower part of Figure 7, the depths of the first lateral recesses 23 and the second lateral recesses 24 of each stage can be made uniform for the etched wafer W.

[0038] A fifth specific example will now be described. In this example, as in the fourth specific example, in the pre-etching process of the wafer W, variations occur in the positions of the sidewalls of the SiGe film 12 at each stage facing the first recess 21 and the second recess 22. Specifically, as shown in the upper part of FIG. 8, the top is etched more than the middle and bottom, forming a first lateral recess 23 and a second lateral recess 24. The middle and bottom are substantially etched.

[0039] In this case, etching is performed by setting the ClF3 gas partial pressure to 0.4 mTorr and the F2 / ClF3 flow rate ratio to a value higher than the reference value. As shown in FIG. 4, this setting results in a larger middle etching amount relative to the top than when etching is performed at the reference value. Furthermore, the difference in etching amount between the middle and bottom is reduced. This allows the depths of the first lateral recesses 23 and the second lateral recesses 24 of each stage of the etched wafer W to be uniform. Note that in the fourth and fifth specific examples shown in FIGS. 7 and 8, the F2 / ClF3 flow rate ratio is set to a value smaller than, for example, 4B / C under process condition 2. In other words, this setting is relatively close to the F2 / ClF3 flow rate ratio under process condition 4, which results in the DENSE etching amount and the ISO etching amount being approximately the same, thereby ensuring that the DENSE etching amount and the ISO etching amount are uniform.

[0040] As described above, in Examples 1 to 5, the partial pressure of ClF3 in the processing chamber is set to 0.4 mTorr, and the F2 / ClF3 flow rate ratio is set according to the wafers W transferred into the processing chamber. This makes it possible to control the etched stack 15 so that the shape variation among the wafers W is suppressed.

[0041] In the above specific examples 1 to 5, the partial pressure of the ClF3 gas is not limited to 0.4 mTorr, and may be set to another value within the first range described above, and the F2 / ClF3 flow rate ratio may be similarly varied to control the shape of the etched wafer W. The reference value of the flow rate ratio is also not limited to the value described above, and may be set to, for example, 4B / C, the same as in process condition 4, and the etching process may be performed by changing the reference value depending on the shape of the wafer W, as described with reference to Figures 5 to 8.

[0042] Next, Specific Example 6 will be described. In Specific Example 6, the wafer W shown in the upper part of FIG. 5 described in Specific Example 2 is etched, and the processing is performed with the partial pressure set within a range of 0.7 mTorr or more (within the second range). As described in FIG. 3, by setting the partial pressure in this way, the ISO etching amount becomes larger than the DENSE etching amount, and as shown in the lower part of FIG. 5, the shapes of the respective laminates 15 after etching are the same or substantially the same. Note that the F2 / ClF3 flow rate ratio may be set to any value. From the fact that it has been confirmed that the DENSE etching amount < ISO etching amount when the F2 / ClF3 flow rate ratio is B / C or 2B / C under the above processing conditions 1 and 3, for example, a value within the range of B / C to 2B / C may be used.

[0043] Next, Specific Example 7 will be described. In Specific Example 7, the wafer W shown in the upper part of FIG. 6 described in Specific Example 3 is etched, and the etching process is performed with the partial pressure set within a range of 0.2 mTorr or less (within the third range). As described in FIG. 3, by setting the partial pressure in this way and performing etching, the DENSE etching amount becomes larger than the ISO etching amount, and the shapes of the respective laminates 15 after etching are the same or substantially the same. Note that the F2 / ClF3 flow rate ratio may be set to any value. From the fact that it has been confirmed that the DENSE etching amount > ISO etching amount when the F2 / ClF3 flow rate ratio is 3B / C or 9B / C under the above processing conditions 5 and 7, for example, a value within the range of 3B / C to 9B / C may be used.

[0044] As described above, in the above Specific Examples 1 to 3, by adjusting the F2 / ClF3 flow rate ratio, the ISO etching amount (etching amount of the first side wall) and the DENSE etching amount (etching amount of the second side wall) are controlled respectively, and thereby the magnitude relationship between these etching amounts is controlled. However, by adjusting the partial pressure of the ClF3 gas as in Specific Examples 6 and 7, it is also possible to control the ISO etching amount and the DENSE etching amount respectively, and thereby control the magnitude relationship. In the processing of each of the above-described specific examples, the temperature of the wafer W is set to a temperature within the range described above.

[0045] Next, the etching apparatus 3 will be described with reference to the vertical cross-sectional side view of FIG. 9. This etching apparatus 3 can be implemented by selecting any one of the specific examples for one wafer W. The etching apparatus 3 includes a processing vessel 31. In the figure, reference numeral 32 denotes a transfer port for the wafer W that opens into the side wall of the processing vessel 31 and is opened and closed by a gate valve 33. A stage 41 on which the wafer W is placed is provided within the processing vessel 31, and the stage 41 is provided with lift pins (not shown). The wafer W is transferred between the stage 41 and a substrate transfer mechanism (not shown) via the lift pins.

[0046] A temperature adjustment unit 42 is embedded in the stage 41, and the temperature of the wafer W placed on the stage 41 is adjusted to within the aforementioned range. This temperature adjustment unit 42 is configured as a flow path that forms part of a circulation path through which a temperature adjustment fluid such as water flows, and adjusts the temperature of the wafer W by heat exchange with the fluid. However, the temperature adjustment unit 42 is not limited to being a flow path for such a fluid, and may be configured as a heater that is, for example, a resistance heating element.

[0047] One end of an exhaust pipe 43 opens into the processing vessel 31, and the other end of the exhaust pipe 43 is connected to an exhaust mechanism 45, which is constituted by, for example, a vacuum pump, via a valve 44, which is a pressure change mechanism. Changing the opening of the valve 44 changes the exhaust flow rate, and thereby changes the total pressure inside the processing vessel 31.

[0048] A gas shower head 46, which serves as an etching gas supply unit, is provided at the upper side of the processing vessel 31, facing the stage 41. The downstream sides of gas supply paths 51 to 54 are connected to the gas shower head 46, and the upstream sides of the gas supply paths 51 to 54 are connected to gas supply sources 56 to 59 via flow rate adjusters 55, respectively. Each flow rate adjuster 55 includes a valve and a mass flow controller. Therefore, the flow rate of the gas supplied from the gas supply sources 56 to 59 to the downstream side is adjusted by the flow rate adjuster 55.

[0049] Gas supply sources 56, 57, 58, and 59 supply F2 gas, ClF3 gas, Ar gas, and N2 gas, respectively. Therefore, the gas shower head 46 can supply these gases into the processing vessel 31. With the above configuration, the F2 / ClF3 flow rate ratio can be adjusted by operating the flow rate adjusters 55 installed in the gas supply lines 51 and 52, respectively. Furthermore, the partial pressure of the ClF3 gas in the processing vessel 31 can be adjusted by operating the flow rate adjuster 55 installed in the gas supply line 52 and the valve 44 installed in the exhaust pipe 43. That is, the F2 / ClF3 flow rate ratio and the partial pressure of the ClF3 gas in the processing vessel 31 can be adjusted to the values ​​of the respective processing examples described above, and the respective processing steps can be performed. The flow rate adjusters 55 and the valve 44 are configured as an adjustment unit.

[0050] 4, the etching apparatus 3 is equipped with a control unit 30, which is a computer, and this control unit 30 is equipped with a program, a memory, and a CPU. The program contains instructions (each step) for performing the processes described in each of the specific examples above. This program is stored on a storage medium, such as a compact disc, a hard disk, a magneto-optical disc, or a DVD, and is then installed in the control unit 30. The control unit 30 outputs control signals to each part of the etching apparatus 3 using the program, and controls the operation of each part. Specifically, these operations include, for example, adjusting the flow rate of each gas supplied downstream by each of the flow rate adjusters 55 described above, and adjusting the opening of the valve 44.

[0051] 1 and the like is transferred into the processing chamber 31 of the etching apparatus 3, and placed on the stage 41. The temperature of the wafer W is then adjusted, preferably to a temperature of -40°C to 20°C. Then, with the interior of the processing chamber 31 at a desired pressure (total pressure), F2 gas, ClF3 gas, Ar gas, and N2 gas are supplied into the processing chamber 31 to perform the etching process. The partial pressures of each gas and the F2 / ClF3 flow ratio are set to desired values ​​as described above.

[0052] The user of the etching apparatus 3 may manually set the F2 / ClF3 flow rate ratio and the partial pressure of the ClF3 gas in the processing vessel 31 depending on the wafer W to be transferred into the processing vessel 31. However, the control unit 30 may automatically set these parameters. Specifically, for example, a control unit provided in an apparatus that performs pre-etching processing transmits information for identifying the shape of the wafer W to be transferred to the etching apparatus 3 to the control unit 30. More specifically, for example, the wafer W shape shown in FIG. 2, the wafer W shape shown in the upper part of FIG. 5, or the wafer W shape shown in the upper part of FIG. 6 may be switched depending on the processing recipe of another apparatus that performs pre-processing. In this case, information for identifying the processing recipe used for the wafer W to be transferred to the etching apparatus 3 is transmitted to the control unit 30, and the control unit 30 acquires the information.

[0053] Then, the control unit 30 sets the partial pressure of the ClF3 gas in the processing vessel 31 to a value within the first range, and selects and determines the F2 / ClF3 flow rate ratio based on the above information from the values ​​described in Specific Example 1, Specific Example 2, and Specific Example 3. By performing etching with the determined values, the ISO etching amount and DENSE etching amount are each controlled as described in each figure, and the shapes of the laminates 15 are made uniform.

[0054] As described above, instead of determining the F2 / ClF3 flow rate ratio based on information from another apparatus, the magnitude relationship can also be controlled by selecting the partial pressure of ClF3 gas in the processing vessel 31 from a first range, a second range, or a third range. Therefore, the control unit 10 may select the partial pressure of ClF3 gas to control the magnitude relationship of the etching amount. In other words, the control unit 30 may determine under which processing conditions from those described in Specific Example 1, Specific Example 6, or Specific Example 7 the processing should be performed.

[0055] Furthermore, the etching amount of the SiGe film 12 facing the first recess 21 varies depending on the process recipe of the other device, and the positional relationship of the top, middle, and bottom sidewalls of the SiGe film 12 varies, whether it is as shown in FIG. 1, FIG. 7, or FIG. 8. The control unit 30 may set the partial pressure of the ClF gas to a value within the first range, and may determine the F2 / ClF3 flow rate ratio based on information about the process recipe, whether it is the aforementioned reference value, a value greater than the reference value by a predetermined amount, or a value less than the reference value by a predetermined amount. That is, the control unit 30 determines which of the process conditions described in Specific Examples 1, 4, and 5 is used for processing, and switches the F2 / ClF3 flow rate ratio accordingly. That is, the F2 / ClF3 flow rate ratio is adjusted depending on the wafer W stored in the process vessel 31, thereby controlling the etched profile of the SiGe film at each level facing the first recess 21.

[0056] Here is another example of how the experimental results can be used. The dotted line in Figure 4 represents the experimentally obtained correlation between the F2 / ClF3 flow rate ratio and the top-middle etching amount, approximated as a linear function. This linear function is stored in the memory of the control unit 30. For example, suppose one wafer W is processed with a ClF3 gas partial pressure of 0.4 mTorr and an arbitrary first F2 / ClF3 flow rate ratio. This wafer W is inspected, and measurement values ​​a1 for the top-middle etching amount are obtained.

[0057] Then, using the linear function, the amount of change c1 in the F2 / ClF3 flow rate ratio between point b1, where the top-middle etching amount is zero, and the point corresponding to measurement value a1 is read, and a flow rate ratio (referred to as the second flow rate ratio) is set that is shifted by c1 from the first flow rate ratio so that the top-middle etching amount is zero when processing the subsequent wafer W. In other words, the amount of change in the F2 / ClF3 flow rate ratio is considered to shift according to the linear function, and the F2 / ClF3 flow rate ratio is determined from the top-middle etching amount obtained from the previously processed wafer W so that the top-middle etching amount of the subsequent wafer W is 0 nm. The determination of the second flow rate ratio is performed, for example, by the control unit 30. While the top-middle etching amount is shown to be 0 nm, control may also be performed to similarly set the middle-bottom etching amount to 0 nm. Thus, the shape control of the wafer W based on the above experiments is not limited to being performed based on the shape of the wafer W before etching, as shown in Figures 5 to 8, etc.

[0058] As described above, for each etching process performed by the etching apparatus 3, the magnitude relationship between the etching amount of the SiGe film facing the first recess 21 and the etching amount of each SiGe film 12 facing the second recess 22 is controlled. More specifically, it is possible to freely select which etching amount should be larger or equal. This allows the shapes of the stacked body 15 after etching to be controlled so that they are uniform, that is, to have the desired shape. Furthermore, the etching amounts of the top, middle, and bottom of the SiGe film 12 at each level facing the first recess 21 are also controlled, and the shapes of the top, middle, and bottom, more specifically, the positions of the sidewalls of the SiGe film 12 at each height, can also be controlled.

[0059] In the above-described examples, the shape of the stack 15 is made uniform by making the depths of the first lateral recess 23 and the second lateral recess 24 uniform after etching. However, the processing conditions may be selected so that either of these lateral recesses 23, 24 is larger. In other words, the etching amount does not necessarily have to be controlled so that the shapes of the stacks 15 are uniform. Furthermore, the Si film 13 does not have to be interposed between the SiGe films 12 as in the above-described examples. A configuration in which only the SiGe film 12 is provided between the mask film 14 and the substrate 11 may also be used. Furthermore, the first recess 21 and the second recess 22 do not necessarily have to open vertically, but may also open horizontally. In other words, the sidewall of a recess refers to the sidewall as viewed from the bottom of the recess, and is not limited to being located horizontally.

[0060] In this example, F2 gas is used as the second fluorine-containing gas, which has a relatively low etching ability for SiGe films, and ClF3 gas is used as the first fluorine-containing gas, which has a relatively high etching ability for SiGe films, but the combination of gases is not limited to this. Specifically, for example, HF gas may be used as the second fluorine-containing gas, and SF6 gas, IF5 gas, or IF7 gas may be used instead of ClF3 gas as the first fluorine-containing gas. Furthermore, the germanium-containing film to be etched is not limited to a SiGe film, but may also be a germanium film.

[0061] It should be noted that the embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive, and various omissions, substitutions, modifications, and combinations may be made to the above-described embodiments without departing from the scope and spirit of the appended claims. [Explanation of symbols]

[0062] W wafer 12 SiGe film 15 Laminate 21 First recess 22 Second recess

Claims

1. storing a substrate having a recess with a sidewall formed of a germanium-containing film in a processing chamber; an etching step of supplying an etching gas containing a first fluorine-containing gas and a second fluorine-containing gas into the processing chamber and etching the first sidewall and the second sidewall, respectively; a shape control step, included in the etching step, of adjusting a partial pressure of the first fluorine-containing gas in the processing vessel to control a shape of the sidewall after etching; Equipped with The recessed portion is a first recess defined by the first sidewall and having a first width; a second recess defined by the second sidewall and having a second width greater than the first width; The shape control step includes: an etching amount of the first sidewall and an etching amount of the second sidewall in the etching step are controlled.

2. the first fluorine-containing gas is chlorine trifluoride gas; The shape control step is performed by adjusting the partial pressure of the first fluorine-containing gas as follows:

2. The etching method according to claim 1, further comprising the step of performing etching by setting partial pressures within a first range in which the magnitudes of the etching amounts of the first sidewall and the second sidewall can be changed according to a flow rate ratio of the second fluorine-containing gas to the first fluorine-containing gas supplied into the processing vessel.

3. 3. The etching method according to claim 2, further comprising the step of determining the flow rate ratio in accordance with the substrate stored in the processing vessel.

4. The first range is 0.267×10 －1 Pa, 0.933 x 10 －1 4. The etching method according to claim 2, wherein the pressure is in the range of less than 100 Pa.

5. the first fluorine-containing gas is chlorine trifluoride gas; 2. The etching method according to claim 1, wherein the shape control step includes a step of performing etching by setting the partial pressure of the first fluorine-containing gas in a second range in which the etching amount of the second sidewall is larger than the etching amount of the first sidewall.

6. The second range is 0.933×10 －1 6. The etching method according to claim 5, wherein the pressure is 1 Pa or more.

7. the first fluorine-containing gas is chlorine trifluoride gas; 2. The etching method according to claim 1, wherein the shape control step includes a step of adjusting the partial pressure of the first fluorine-containing gas to a partial pressure in a third range in which the etching amount of the first sidewall is larger than the etching amount of the second sidewall.

8. The third range is 0.267 x 10 －1 8. The etching method according to claim 7, wherein the pressure is 0.1 Pa or less.

9. the first fluorine-containing gas is chlorine trifluoride gas; The shape control step is performed by adjusting the partial pressure of the first fluorine-containing gas as follows: a first range in which the etching amount of the first sidewall and the etching amount of the second sidewall can be changed according to a flow rate ratio of the second fluorine-containing gas to the first fluorine-containing gas supplied into the processing chamber; a second range in which the etching amount of the second sidewall is larger than the etching amount of the first sidewall; and a third range in which the etching amount of the first sidewall is larger than the etching amount of the second sidewall.

2. The etching method according to claim 1, wherein the etching is performed so that the partial pressure is within a range selected according to the substrate stored in the processing vessel.

10. a sidewall of the recess is formed by a plurality of steps of the germanium-containing film and an intervening film interposed between the germanium-containing films; 10. The etching method according to claim 2, wherein the shape control step includes a step of adjusting the flow rate ratio to control the shape of the germanium-containing film at each stage on the sidewall after etching.

11. 11. The etching method according to claim 1, wherein the germanium-containing film is a SiGe film.

12. a processing vessel for storing a substrate having a recess with a sidewall formed of a germanium-containing film; an etching gas supply unit that supplies an etching gas containing a first fluorine-containing gas and a second fluorine-containing gas into the processing vessel to etch the first sidewall and the second sidewall, respectively; an adjusting unit that adjusts a partial pressure of the first fluorine-containing gas in the processing chamber during the etching in order to control a shape of the sidewall after the etching; Equipped with the recess includes a first recess defined by the first sidewall and having a first width, and a second recess defined by the second sidewall and having a second width greater than the first width; an etching apparatus in which the control of the shape of the sidewall is performed by controlling the etching amount of the first sidewall and the etching amount of the second sidewall by adjusting the partial pressure;

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