Etching method and etching apparatus

Abstract

The present invention provides an etching method and an etching apparatus that make the shape of a germanium-containing film after etching a desired shape. The etching method includes the following steps: a step of storing a substrate in a processing container, the substrate having a recess composed of a side wall that is a germanium-containing film; an etching step of supplying an etching gas containing a first fluorine-containing gas and a second fluorine-containing gas to the processing container to etch the side wall; and a shape control step included in the etching step, in which the shape control step, 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 supplied to the processing container relative to the first fluorine-containing gas is adjusted to control the shape of the side wall after etching.

Description

Technical Field

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

[0002] When manufacturing semiconductor devices, various films formed on the surface of a semiconductor wafer (hereinafter referred to as a wafer) serving as a substrate are etched. Patent Document 1 describes supplying ClF3 gas and HF gas to a wafer composed of alternating layers of Si films and SiGe films, which are silicon-containing films, to suppress damage to the Si films and selectively etch the SiGe films. Furthermore, Patent Document 2 describes etching the Si film embedded in the pores of an oxide film on the wafer surface by alternately supplying ClF3 gas and a mixed gas consisting of F2 gas and NH3 gas, thereby suppressing surface roughness after etching.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-53448

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 2012-201102 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] The present disclosure provides a technology capable of making the shape of a germanium-containing film after etching into a desired shape.

[0009] Solutions for solving problems

[0010] The etching method of the present invention comprises the following steps:

[0011] a step of storing a substrate having a recessed portion formed of a germanium-containing film in a processing container; and

[0012] A shape control process includes supplying an etching gas containing a first fluorine-containing gas and a second fluorine-containing gas into the processing container, and 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 supplied to the processing container relative to the first fluorine-containing gas to control the shape of the side wall etched by the etching gas.

[0013] Effects of the Invention

[0014] According to the present disclosure, the shape of the germanium-containing film after etching can be made into a desired shape. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1It is a longitudinal sectional side view of a wafer being processed according to one embodiment of the present disclosure.

[0016] Figure 2 It is a longitudinal sectional side view of the above-mentioned wafer after etching process.

[0017] Figure 3 It is a graph which shows the result of an experiment.

[0018] Figure 4 It is a graph which shows the result of an experiment.

[0019] Figure 5 It is a longitudinal sectional side view of the above wafer.

[0020] Figure 6 It is a longitudinal sectional side view of the above wafer.

[0021] Figure 7 It is a longitudinal sectional side view of the above wafer.

[0022] Figure 8 It is a longitudinal sectional side view of the above wafer.

[0023] Figure 9 It is a longitudinal sectional side view of the etching device. DETAILED DESCRIPTION

[0024] To illustrate the process involved in one embodiment of the etching method disclosed herein, Figure 1 The wafer W to be etched is described below. Figure 1 11 is a longitudinal sectional side view of the surface of the wafer W. 11 in the figure is a substrate constituting the wafer W, which is made of Si (silicon). On the substrate 11, SiGe (silicon germanium) films 12 and Si (silicon) films 13 are repeatedly stacked in the longitudinal direction (the thickness direction of the wafer W) in an alternating manner in the order described. This stacked structure is formed by a large number of SiGe films 12 and a large number of Si films 13. Figure 1 , to avoid complication, the number of layers is omitted, but a stacked structure consisting of three SiGe films 12 and three Si films 13 is shown. Furthermore, a mask film 14 is formed on the topmost Si film 13 of the stacked structure. During etching, the mask film 14 serves as a mask for the stacked structure. Furthermore, due to this structure, the Si film 13, serving as an insertion film, is inserted between the SiGe films 12 in the thickness direction of the wafer W.

[0025] Moreover, a plurality of recesses are formed on the surface of the wafer W, each recess being formed to have a depth from the surface of the mask film 14 to the surface of the substrate 11. Thus, the sidewalls of each recess are formed by a stack (referred to as a stack 15) consisting of the SiGe film 12, the Si film 13, the mask film 14, and the surface of the substrate 11. Thus, it can also be considered that a plurality of stacks 15 are arranged at intervals from each other on the surface of the wafer W. The recesses are formed in such a way as to form a denser area (Dense) of the stacks 15 and an area (ISO) that is more widely separated from the stacks 15. Thus, the plurality of recesses include a first recess 21 having a first width L1, and a second recess 22 having a second width L2 that is wider than the first width L1.

[0026] Furthermore, the difference between the first width L1 and the second width L2 is not unavoidable or inadvertent due to processing errors, but is designed. For example, the designed width L2 / width L1 is greater than 2. Figure 1 The first recess 21 and the second recess 22 shown in the figure are grooves extending in the front-to-back direction of the paper, but may be holes. In the case of holes, the first width L1 and the second width L2 are the diameters of the holes.

[0027] The SiGe film 12 is a germanium-containing film to be etched. The portion of the SiGe film 12 facing the first recess 21 forms a first side wall, and the portion facing the second recess 22 forms a second side wall. In this embodiment, the wafer W is placed in a processing container, and F2 (fluorine) gas and ClF3 (chlorine trifluoride) gas are simultaneously supplied to the processing container as etching gases. The etching gas enters the first recess 21 and the second recess 22, as shown in FIG. Figure 2 As shown, each stage of the SiGe film 12 constituting the stacked body 15 is etched from the side. Since this etching is performed so as to remove only a portion of the sidewall of each SiGe film 12, each stage of the SiGe film 12 remains on the wafer W after etching.

[0028] In this etching, the SiGe film 12 is selectively etched out of the SiGe film 12 and the Si film 13. Thus, by etching, recesses having openings in the lateral direction are formed so as to face the first recess 21 and the second recess 22, respectively. Figure 2 In the figure, the recess facing the first recess 21 is referred to as a first side recess 23 , and the recess facing the second recess 22 is referred to as a second side recess 24 .

[0029] In order to specifically explain the etching process of this embodiment, first, an experiment on the etching of the above-mentioned wafer W is described. In this experiment, different processing conditions are set for the multiple wafers W mentioned above to etch the SiGe film 12. As this etching, in addition to the above-mentioned etching gases (F2 gas and ClF3 gas), Ar (argon) gas and N2 (nitrogen) gas are also supplied to the processing container at the same time as the etching gas. These Ar gas and N2 gas have the function of serving as carrier gases for the etching gas and the function of adjusting the partial pressures of the gases in the processing container. Moreover, as the above-mentioned processing conditions that are changed for each wafer W, there are the flow rates of the gases supplied to the processing container and the pressure (total pressure) in the processing container. In addition, along with the changes in these flow rates and total pressures, the partial pressures of the F2 gas and the partial pressures of ClF3 in the processing container are also changed for each wafer W to perform etching.

[0030] Furthermore, during the experiment, the etching amount of each section of the SiGe film 12 facing the first recess 21 (i.e., each section in the Dense) and the etching amount of each section of the SiGe film 12 facing the second recess 22 (i.e., each section in the ISO) were measured. Hereinafter, the etching amount of the portion of the SiGe film 12 facing the first recess 21 will sometimes be referred to as the DENSE etching amount, and the etching amount of the portion facing the second recess 22 will sometimes be referred to as the ISO etching amount. Furthermore, as described above, multiple sections of the SiGe film 12 are provided in the stack 15. The upper SiGe film 12 will sometimes be referred to as the top, the lower SiGe film 12 as the bottom, and the SiGe film 12 positioned between the top and bottom as the middle.

[0031] There are 8 processing conditions that are set, which are referred to as processing conditions 1 to 8. Table 1 below summarizes processing conditions 1 to 8. In addition, in Table 1, the pressure in the processing container is expressed as a total pressure (unit: mTorr). The unit of each flow rate in Table 1 is sccm. The partial pressures of F2 gas and ClF3 gas in the table (unit: mTorr) are partial pressures in the processing container, which are values ​​calculated based on the flow rate of each gas and the pressure in the processing container. In addition, in processing conditions 1 to 8, the temperature of the wafer W in the etching process is a temperature in the range of -40°C to 80°C, and is a common temperature between the conditions. In addition, in order to prevent the description from being complicated, in the following description, the partial pressure in the processing container is recorded only as partial pressure, and the flow rate of the gas supplied to the processing container is recorded only as flow rate.

[0032] In Table 1, except for the partial pressure of ClF3 gas, each set value is represented by a letter. Specifically, regarding the pressure (total pressure) of the processing container, the letter A is used to represent the specified pressure value (unit: mTorr), and the total pressure is represented by multiplying the value by A before A. Thus, for example, the total pressure (2A) in processing conditions 1 to 4, 6, and 8 is twice the total pressure (A) in processing conditions 5 and 7.

[0033] The flow rates of F2 gas, ClF3 gas, and N2 gas are also represented by the letters B to D and the multiplication values ​​multiplied by B to D, as in the above-mentioned total pressure. In addition, the flow ratio shown in Table 1 is the ratio of the flow rate of F2 gas (second fluorine-containing gas) to the flow rate of ClF3 gas (first fluorine-containing gas), and the flow ratio is represented by "B / C" and the multiplication value multiplied therewith in Table 1. In addition, the flow ratio is recorded as the F2 / ClF3 flow ratio below. In addition, the partial pressure of F2 gas (unit: mTorr) is also represented by the letter (F) and the multiplication value multiplied therewith, as in the total pressure and the F2 / ClF3 flow ratio. However, with respect to the flow rate of Ar gas (unit: sccm), since its value varies slightly between the processing conditions, its representation in the table is different from that of other gases and is not represented based on the multiplication value. E1 to E8 shown as the flow rate of Ar gas in the table are separate values.

[0034] (Table 1)

[0035]

[0036] B / C=24.46

[0037] exist Figure 3 In the figure, a bar graph showing the DENSE etching amount and ISO etching amount for each processing condition is shown as experimental results. The vertical axis of the graph is scaled in units of a specified etching amount, so the etching amount between each scale mark represents the same amount. The bar graph showing the DENSE etching amount is shaded, while the bar graph showing the ISO etching amount is not shaded. The etching amounts shown in the bar graphs in this figure are the averages of the etching amounts at the top, middle, and bottom regions described above.

[0038] Moreover, in this Figure 3 In the figure, the bar graphs are shown from left to right in the order of process conditions 7, 5, 6, 2, 4, 1, and 3. When observing the partial pressure of ClF3 gas, the partial pressure of ClF3 gas is 0.2 mTorr (0.267×10- 1 Pa), and 0.4 mTorr (0.533 × 10- 1Pa), and 0.7 mTorr (0.933×10- 1 Pa). Thus, in Figure 3 In the figure, the histograms for each processing condition are shown separately according to the partial pressure of ClF3 gas. Furthermore, for processing conditions with the same partial pressure of ClF3 gas, the histograms for each processing condition are shown in the above arrangement, assuming that the closer the histogram is to the right in the figure, the smaller the F2 / ClF3 flow rate ratio of the processing condition.

[0039] like Figure 3 As shown in Figure 1, when the DENSE etching amount under process conditions 1 and 3, where the ClF3 gas partial pressure is 0.7 mTorr, is compared with the ISO etching amount, the ISO etching amount is greater. Furthermore, when the DENSE etching amount under process conditions 5 and 7, where the ClF3 gas partial pressure is 0.2 mTorr, is compared with the ISO etching amount, the DENSE etching amount is greater. Therefore, the experimental results show that when the ClF3 gas partial pressure is high, the ISO etching amount is higher, regardless of the aforementioned F2 / ClF3 flow rate ratio, and when the ClF3 gas partial pressure is low, the DENSE etching amount is higher, regardless of the aforementioned F2 / ClF3 flow rate ratio.

[0040] Furthermore, when observing process conditions 2, 4, and 6, where the partial pressure of ClF3 gas was 0.4 mTorr, the DENSE etching amount and the ISO etching amount were approximately equal under process condition 4, which had the smallest F2 / ClF3 flow ratio among these process conditions 2, 4, and 6. Furthermore, under process condition 2, where the F2 / ClF3 flow ratio was only slightly larger than that of process condition 4, when comparing the DENSE etching amount with the ISO etching amount, the ISO etching amount was greater. Under process condition 6, when comparing the DENSE etching amount with the ISO etching amount, the DENSE etching amount was greater.

[0041] As described above, it can be seen that the DENSE etching amount and the ISO etching amount each change depending on the partial pressure of the ClF3 gas, thereby changing the magnitude relationship between these etching amounts. Specifically, it can be seen that the DENSE etching amount and the ISO etching amount can change to the same or approximately the same level, or one can change more significantly than the other, depending on the partial pressure.

[0042] Furthermore, ClF3 gas is more reactive with the SiGe film 12 than F2 gas. When the ClF3 gas partial pressure is low, the concentration of the ClF3 gas within the larger second recess 22 becomes very low, making it difficult for the ClF3 gas to react with the SiGe film 12. However, when the ClF3 gas partial pressure is high, the concentration of the ClF3 gas within the second recess 22 becomes high, allowing the ClF3 gas to react efficiently with the SiGe film 12. Specifically, when the ClF3 gas partial pressure is greater than 0.7 mTorr, the ISO etching amount is greater, similar to process conditions 1 and 3 with a partial pressure of 0.7 mTorr. When the ClF3 gas partial pressure is less than 0.3 mTorr, the DENSE etching amount is greater, similar to process conditions 5 and 7 with a partial pressure of 0.3 mTorr.

[0043] In other words, when processing within the partial pressure range of 0.7 mTorr or higher (the second range), the ISO etching amount becomes larger, and when processing within the partial pressure range of 0.2 mTorr or lower (the third range), the DENSE etching amount becomes larger. Furthermore, according to the above experimental results, when processing within the partial pressure range of greater than 0.2 mTorr and less than 0.7 mTorr (the first range), the DENSE etching amount and the ISO etching amount change depending on the F2 / ClF3 flow rate ratio, resulting in a change in the magnitude relationship between these etching amounts.

[0044] In the above-described experiments, the relationship between the etching amounts at the top, middle, and bottom portions was obtained for each wafer W processed under process conditions 2, 4, and 8 in which the partial pressure of the ClF 3 gas was 0.4 mTorr, which is a value within the first range. Figure 4 This is a diagram showing the relationship of the etching amount as a bar graph. Figure 4 The vertical axis of the graph is marked with a scale in units of the specified etching amount difference, so the etching amount difference between each scale is the same. Figure 4 In the figure, the top etching amount - the middle etching amount is represented by a bar graph with diagonal lines, and the middle etching amount - the bottom etching amount is represented by a bar graph without diagonal lines. The bar graphs are arranged so that the F2 / ClF3 flow rate ratio of the processing condition decreases as the bar graph moves to the right. Therefore, the bar graphs are arranged from left to right in the order of processing conditions 2, 8, and 4.

[0045] like Figure 4As shown, with respect to the etching amount in the middle portion and the etching amount in the bottom portion, the etching amount in the bottom portion is larger under any of the processing conditions 2, 4, and 8. However, the difference in etching amount between the middle portion and the bottom portion decreases in the order of processing conditions 4, 8, and 2, and is very small under processing condition 2. Since the F2 / ClF3 flow ratios in processing conditions 2, 8, and 4 are 4B / C, 3B / C, and 2B / C, respectively, it can be seen that when the F2 / ClF3 flow ratio is within the range of 2B / C to 4B / C, the larger the F2 / ClF3 flow ratio, the smaller the difference in etching amount between the middle portion and the bottom portion.

[0046] Furthermore, when examining the difference in etching amount between the top and middle portions, the difference is positive under Process Conditions 4 and 8. Therefore, the etching amount at the top is greater. Between Process Conditions 4 and 8, the difference in etching amount under Process Condition 8 is smaller. Furthermore, under Process Condition 2, the difference is negative, indicating that the etching amount at the middle portion is greater than that at the top. This indicates that within the F2 / ClF3 flow ratio range of 2B / C to 4B / C, the greater the F2 / ClF3 flow ratio, the greater the etching amount at the middle portion relative to the etching amount at the top. Furthermore, the absolute values ​​of the etching amount differences between Process Conditions 2 and 8 are similar.

[0047] Thus, it is shown that when the partial pressure of the ClF3 gas is within the first range described above, by changing the above-mentioned F2 / ClF3 flow ratio for the SiGe film 12 facing the first recess 21 and the second recess 22, respectively, the etching amount at each of the top, middle, and bottom portions can be adjusted. Moreover, regarding the F2 / ClF3 flow ratio, it can be inferred that within the range of greater than 3B / C and less than 4B / C, there is a preferred value that can make the difference in etching amount between the top and the middle zero or approximately zero and can make the difference in etching amount between the middle and the bottom extremely small. As shown in Table 1, since B / C = 24.46, in order to make the etching amount values ​​consistent between the top, middle, and bottom portions, it is preferred to set the F2 / ClF3 flow ratio to greater than 3×24.46=73.38 and less than 4×24.46=97.84. In addition, regarding the F2 / ClF3 flow ratio Figure 4 The dotted line and a1, b1, and c1 in the graph will be described later as an example of the F2 / ClF3 setting used in the experiment.

[0048] The etching process of this embodiment is based on the insights gained from the experiments described above. Specifically, the shape of the surface of the wafer W after etching is controlled to achieve a desired shape. Several specific examples of this shape control are described below. In each of these specific examples, the goal is to perform etching so that the shapes of the stacked bodies 15 after etching are identical or substantially identical. In other words, etching is performed so that the stacked bodies 15 have a bilaterally symmetrical shape.

[0049] First, a first specific example is shown. Regarding the wafer W as an etching target that is transported into the processing container, as shown in FIG. Figure 1 As shown in FIG. 1 , the sidewalls of the SiGe film 12 and the sidewalls of the Si film 13 in each stack 15 are aligned in the lateral direction. In this case, for example, the partial pressure of the ClF3 gas is set to 0.4 mTorr, which is the same as the partial pressure in process conditions 2, 4, 6, and 8, and the F2 / ClF3 flow ratio is set to a reference value for etching. The reference value of the F2 / ClF3 flow ratio is set to, for example, Figure 4 The reference value is a value within the range of greater than 3B / C and less than 4B / C as described in the graph of FIG. That is, the reference value is a value of the F2 / ClF3 flow ratio close to the process condition 4 that makes the ISO etching amount and the DENSE etching amount approximately the same (see FIG. Figure 3 ), therefore, by etching based on this reference value, the ISO etching amount and the DENSE etching amount can be made to be approximately the same value.

[0050] Thus, after etching, Figure 2 As shown, the depth of the first side recess 23 can be made consistent with the depth of the second side recess 24, so that the shapes of the stacked bodies 15 are the same or substantially the same. Figure 4 As described above, since the F2 / ClF3 flow rate ratio is set as described above, the etching amount values ​​are consistent among the top, middle, and bottom portions. In other words, the depth uniformity of each of the first side recesses 23 at the top, middle, and bottom portions is improved, and the uniformity of each of the second side recesses 24 at the top, middle, and bottom portions is also improved, which is preferable.

[0051] Next, the second specific example is described. Figure 5 The upper half of FIG. 1 shows the wafer W before etching in this example. The wafer W is Figure 1 The wafer W shown has a substantially similar structure. However, in a pre-etching step, the side (DENSE side) of each SiGe film 12 facing the first recess 21 is etched to pre-form a first side recess 23. The sidewalls of the Si film 13 facing the first recess 21 are not aligned with the sidewalls of the SiGe film 12 in the lateral direction.

[0052] Therefore, in order to Figure 5 To etch the upper half of the wafer W to make the shapes of the stacked bodies 15 consistent, the ISO etching amount needs to be greater than the DENSE etching amount. Therefore, the partial pressure of the ClF3 gas is set to 0.4 mTorr, and the F2 / ClF3 flow ratio is set to be lower than the reference value. As an example, the F2 / ClF3 flow ratio is set to the same as in Figure 3Etching was performed at 4B / C, which was the same as the process conditions 2 described in the previous section. By performing etching in this manner, the ISO etching amount was greater than the DENSE etching amount. Figure 5 The lower half of FIG shows the wafer W after etching. Figure 5 As shown in the lower half of , due to the above-mentioned difference in etching amount, the depth of the first side recess 23 and the depth of the second side recess 24 are consistent, and the shapes of the stacked bodies 15 after etching are the same or substantially the same.

[0053] Next, the third specific example is described. Figure 6 The upper half of FIG. 1 shows the wafer W before etching in this example. The wafer W is Figure 1 The wafer W shown has a substantially similar structure. However, in a pre-etching step, the side (ISO side) of each SiGe film 12 facing the second recess 22 is etched, pre-forming a second side recess 24. Consequently, the sidewalls of the Si film 13 facing the second recess 22 and the sidewalls of the SiGe film 12 are not aligned in the lateral direction.

[0054] Therefore, in order to Figure 6 To etch the upper half of the wafer W to make the shapes of the stacked bodies 15 consistent, the DENSE etching amount needs to be greater than the ISO etching amount. Therefore, the partial pressure of the ClF3 gas is set to 0.4 mTorr, and the F2 / ClF3 flow ratio is set to be higher than the reference value. As an example, the flow ratio is set to Figure 3 Etching is performed at 6B / C, which is the same as the process condition 6 described in the previous section. By performing etching in this manner, the DENSE etching amount becomes larger than the ISO etching amount. Figure 6 The lower half of FIG shows the wafer W after etching. Figure 6 As shown in the lower half of , due to the above-mentioned difference in etching amount, the depth of the first side recess 23 and the depth of the second side recess 24 are consistent, and the shapes of the stacked bodies 15 after etching are the same or substantially the same.

[0055] The fourth specific example is described. Figure 7 The upper half of FIG. 1 shows the wafer W before etching in this example. The wafer W is Figure 1 The wafer W shown has a substantially similar structure. However, in the pre-etching process, the positions of the sidewalls of the SiGe film 12 sections facing the first recess 21 and the second recess 22 are offset, causing the middle portion to be etched more significantly than the top and bottom portions, forming the first side recess 23 and the second side recess 24. The top and bottom portions are barely etched.

[0056] Therefore, the partial pressure of ClF3 gas is set to 0.4 mTorr and the F2 / ClF3 flow ratio is set to a value lower than the reference value to perform etching. Figure 4 As shown in FIG, compared with the case where etching is performed at the reference value, the etching amount at the top and bottom becomes larger than the etching amount at the middle. Figure 7 As shown in the lower half of FIG, the depth of the first side recess 23 of each stage and the depth of the second side recess 24 of each stage of the wafer W after etching can be made uniform.

[0057] The fifth specific example is described. In this example, as in the fourth specific example, in the pre-process, the positions of the side walls of the SiGe film 12 of the wafer W before etching, which are facing the first recess 21 and the second recess 22, are deviated. Specifically, Figure 8 As shown in the upper half of FIG, the top is etched more significantly than the middle and bottom to form a first side recess 23 and a second side recess 24. The middle and bottom are hardly etched.

[0058] In this case, etching is performed by setting the partial pressure of ClF3 gas to 0.4 mTorr and the F2 / ClF3 flow ratio to a value higher than the reference value. Figure 4 As shown, the etching amount of the middle portion relative to the top portion becomes larger than when etching is performed at the reference value. In addition, the difference in etching amount between the middle portion and the bottom portion becomes smaller. As a result, the depth of the first side recess 23 of each section of the etched wafer W and the depth of the second side recess 24 of each section can be made consistent. In addition, regarding Figure 7 、 Figure 8 In the fourth and fifth specific examples, the F2 / ClF3 flow rate ratio is set to a value smaller than 4B / C in process condition 2. In other words, it is set to a value closer to the F2 / ClF3 flow rate ratio in process condition 4, which makes the DENSE etching amount and the ISO etching amount substantially the same, so that the DENSE etching amount and the ISO etching amount are consistent.

[0059] As described above, in Examples 1 to 5, the ClF3 partial pressure in the processing container is set to 0.4 mTorr, and the F2 / ClF3 flow ratio is set according to the wafers W transported into the processing container. This allows the stacked structure 15 after etching to be controlled so that variations in shape between wafers W are suppressed.

[0060] In addition, regarding the above specific examples 1 to 5, the partial pressure of the ClF3 gas is not limited to being set to 0.4 mTorr. It is also possible to control the shape of the wafer W after etching by changing the F2 / ClF3 flow ratio in the same manner while setting the partial pressure to other values ​​within the first range described above. In addition, the reference value of the flow ratio is not limited to being set to the above value. For example, it can be set to 4B / C as in process condition 4, and Figures 5 to 8As described above, the etching process is performed by changing the reference value according to the shape of the wafer W.

[0061] Next, the specific example 6 is described. In the specific example 6, it is assumed that the Figure 5 The wafer W shown in the upper half of the etching is etched and the partial pressure is set to be within the range of 0.7mTorr or more (the second range) for processing. Figure 3 As explained in , by setting the partial pressure in this way, the ISO etching amount is greater than the DENSE etching amount. Figure 5 As shown in the lower half of the figure, the shapes of the stacked bodies 15 after etching are the same or substantially the same. Furthermore, the F2 / ClF3 flow ratio can be set to any value. It is clear that under the aforementioned process conditions 1 and 3, when the F2 / ClF3 flow ratio is B / C or 2B / C, the DENSE etching amount is less than the ISO etching amount. Therefore, the F2 / ClF3 flow ratio can be set to a value within the range of B / C to 2B / C, for example.

[0062] Next, the specific example 7 is described. In the specific example 7, it is assumed that the Figure 6 The wafer W shown in the upper half of FIG is etched, and the partial pressure is set within a range below 0.2 mTorr (within the third range) to perform etching. Figure 3 As described in [ 15 ], by setting the partial pressure in this manner to perform etching, the DENSE etching amount is greater than the ISO etching amount, and the shapes of the stacked bodies 15 after etching are the same or substantially the same. Furthermore, the F2 / ClF3 flow rate ratio can be set to any value. It is clear that under the aforementioned process conditions 5 and 7, when the F2 / ClF3 flow rate ratio is 3B / C or 9B / C, the DENSE etching amount is greater than the ISO etching amount. Therefore, the F2 / ClF3 flow rate ratio can be set to a value within the range of 3B / C to 9B / C, for example.

[0063] As described above, in Examples 1 to 3, the ISO etching amount (the etching amount of the first sidewall) and the DENSE etching amount (the etching amount of the second sidewall) are controlled separately by adjusting the F2 / ClF3 flow rate ratio, thereby controlling the magnitude relationship between these etching amounts. However, as in Examples 6 and 7, the ISO etching amount and the DENSE etching amount can also be controlled separately by adjusting the ClF3 gas partial pressure, thereby controlling this magnitude relationship. Furthermore, it is assumed that the temperature of the wafer W is set within the above-described range during the processing of each of the aforementioned Examples.

[0064] Next, refer to Figure 9The etching apparatus 3 will be described with reference to a longitudinal sectional side view of FIG. The etching apparatus 3 can select and implement any of the various specific examples for a single wafer W. The etching apparatus 3 includes a processing container 31. 32 in the figure denotes a transfer port for the wafer W, which is opened and closed by a gate valve 33. A loading platform 41 for loading the wafer W is provided within the processing container 31, and lift pins (not shown) are provided on the loading platform 41. The wafer W is transferred between a substrate transfer mechanism (not shown) and the loading platform 41 via the lift pins.

[0065] A temperature adjustment unit 42 is embedded in the mounting table 41. This temperature adjustment unit 42 maintains the temperature of the wafer W placed on the mounting table 41 within the aforementioned range. The temperature adjustment unit 42 is configured, for example, as a flow path forming part of a circulation path through which a temperature adjustment fluid, such as water, flows. The temperature adjustment unit 42 adjusts the temperature of the wafer W through heat exchange with the fluid. However, the temperature adjustment unit 42 is not limited to such a fluid flow path and may also be configured as a heater, for example, a resistance heater.

[0066] One end of an exhaust pipe 43 opens into the processing chamber 31, and the other end of the exhaust pipe 43 is connected to an exhaust mechanism 45, such as a vacuum pump, via a valve 44 serving as a pressure changing mechanism. The exhaust flow rate changes as the opening of the valve 44 changes, thereby changing the total pressure within the processing chamber 31.

[0067] A gas showerhead 46, serving as an etching gas supply unit, is installed in the upper portion of the processing chamber 31, facing the mounting table 41. The gas showerhead 46 is connected to the downstream side of gas supply lines 51-54. The upstream sides of the gas supply lines 51-54 are connected to gas supply sources 56-59 via flow control units 55, respectively. Each flow control unit 55 includes a valve and a mass flow controller. Thus, the gas supplied from the gas supply sources 56-59 is regulated by the flow control unit 55 so that the flow rate is adjusted toward the downstream side.

[0068] F2 gas, ClF3 gas, Ar gas, and N2 gas are supplied from gas supply sources 56, 57, 58, and 59, respectively. Thus, these F2 gas, ClF3 gas, Ar gas, and N2 gas can be supplied from the gas showerhead 46 into the processing container 31. Due to the above structure, the F2 / ClF3 flow ratio can be adjusted by operating the flow control units 55 provided in the gas supply lines 51 and 52, respectively. Furthermore, the partial pressure of the ClF3 gas within the processing container 31 can be adjusted by operating the flow control unit 55 provided in the gas supply line 52 and the valve 44 provided in the exhaust pipe 43. In other words, the F2 / ClF3 flow ratio and the partial pressure of the ClF3 gas within the processing container 31 can be set to the values ​​for each of the aforementioned processing examples, and each of the processes can be performed. The flow control unit 55 and valve 44 described above constitute an adjustment unit.

[0069] In addition, if Figure 4 As shown, the etching apparatus 3 includes a control unit 30, which is a computer. This control unit 30 includes a program, memory, and a CPU. The program contains commands (steps) for performing the processing described in the specific examples described above. This program is stored on a storage medium such as an optical disk, hard disk, magneto-optical disk, or DVD, and is installed in the control unit 30. The control unit 30 uses this program to output control signals to various components of the etching apparatus 3, thereby controlling the operation of each component. Specifically, this includes, for example, adjusting the flow rate of each gas supplied downstream via the aforementioned flow rate adjustment units 55 and adjusting the opening of the valve 44.

[0070] The material is transported into the processing container 31 of the etching device 3. Figure 1 The wafer W shown in FIG. 1 is placed on the mounting table 41 and the temperature of the wafer W is adjusted to preferably -40°C to 20°C. Then, with the desired pressure (total pressure) in the processing container 31, F2 gas, ClF3 gas, Ar gas, and N2 gas are supplied into the processing container 31 to perform etching. As described above, the partial pressure of each gas and the F2 / ClF3 flow ratio are set to desired values.

[0071] Alternatively, the user of the etching apparatus 3 may manually set the F2 / ClF3 flow ratio and the partial pressure of the ClF3 gas in the processing container 31 according to the wafer W transported into the processing container 31. However, the control unit 30 may also be configured to automatically set these parameters. Specifically, the parameter setting may be described, for example, by sending information for determining the shape of the wafer W transported into the etching apparatus 3 from the control unit of the apparatus for pre-processing the etching to the control unit 30. More specifically, the parameter setting may be described, for example, by setting the parameter setting according to the processing procedures of other apparatuses for pre-processing the etching. Figure 2 The shape of the wafer W shown, Figure 5The upper part of the wafer W is shown as well as Figure 6 In this case, information for specifying which process the wafer W transported to the etching apparatus 3 has been processed by is sent to the control unit 30, and the control unit 30 acquires the information.

[0072] The control unit 30 then sets the partial pressure of the ClF3 gas in the processing container 31 to a value within the first range and, based on the above information, selects and determines whether the F2 / ClF3 flow ratio should be set to the value described in Specific Example 1, the value described in Specific Example 2, or the value described in Specific Example 3. By performing etching at these determined values, the ISO etching amount and the DENSE etching amount are controlled as described in the respective figures, so that the shapes of the stacked bodies 15 are uniform.

[0073] Furthermore, instead of determining the F2 / ClF3 flow rate ratio based on information from other devices as described above, the aforementioned magnitude relationship can also be controlled by selecting the ClF3 gas partial pressure within the processing container 31 from a first range of values, a second range of values, or a third range of values. Therefore, the control unit 10 can also select the ClF3 gas partial pressure to control the aforementioned magnitude relationship of the etching amount. In other words, the control unit 30 can also determine which of the processing conditions described in Specific Examples 1, 6, and 7 to perform the process.

[0074] In addition, for example, it is assumed that the etching amount of the SiGe film 12 facing the first recess 21 changes according to the processing process of other devices, and the side walls of the top, middle, and bottom of the SiGe film 12 become Figure 1 The positional relationship shown, Figure 7 The positional relationship shown and Figure 8 Which of the positional relationships shown changes? Alternatively, the control unit 30 sets the partial pressure of the ClF3 gas to a value within the first range and, based on information related to the aforementioned process recipe, determines whether the F2 / ClF3 flow ratio should be set to 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. In other words, the control unit 30 determines which of the processing conditions described in Specific Examples 1, 4, and 5 to perform processing under and switches the F2 / ClF3 flow ratio. Specifically, the F2 / ClF3 flow ratio is adjusted based on the wafer W stored in the processing container 31, thereby controlling the etching profile of each SiGe film segment facing the first recess 21.

[0075] In addition, other application examples of the experimental results are shown. Figure 4The dashed line in FIG. 1 is a graph showing the relationship between the experimentally obtained F2 / ClF3 flow ratio and the top etching amount versus the middle etching amount, approximated as a linear function. This linear function is assumed to be stored in the memory of the control unit 30. Furthermore, for example, a single wafer W is processed under the conditions of a ClF3 gas partial pressure of 0.4 mTorr and an arbitrary first F2 / ClF3 flow ratio. This single wafer W is inspected, and a measured value a1 is obtained, which relates to the top etching amount versus the middle etching amount.

[0076] Then, the displacement amount c1 of the F2 / ClF3 flow ratio between the point b1 where the etching amount of the top-middle portion is 0 and the point corresponding to the measured value a1 is read out using the above-mentioned linear function, and is set to a flow ratio shifted by c1 from the first flow ratio (set as the second flow ratio) so that the top-middle portion is zero when the subsequent wafer W is processed. That is, the value of the etching amount of the top-middle portion is shifted by the linear function by an amount corresponding to the amount of the offset of the F2 / ClF3 flow ratio, and the F2 / ClF3 flow ratio is determined based on the top-middle portion obtained from the previously processed wafer W so that the top-middle portion of the subsequent wafer W becomes 0nm. The above-mentioned second flow ratio is determined, for example, by the control unit 30. Although it is shown that the top-middle portion is made 0nm, it can also be controlled in the same way so that the middle-bottom portion becomes 0nm. In this way, the shape control of the wafer W based on the above-mentioned experiment is not limited to the control based on Figures 5 to 8 This is performed based on the shape of the wafer W before etching shown in the figure.

[0077] In each etching process performed by the etching apparatus 3 as described above, the 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, the etching amount can be freely selected to be larger or equal. This allows control to be performed so that the shape of the stacked body 15 after etching is consistent, that is, to achieve the desired shape. Furthermore, the etching amount at the top, middle, and bottom of each section of the SiGe film 12 facing the first recess 21 can be controlled, and the shape of these top, middle, and bottom sections, more specifically, the sidewalls of the SiGe film 12 at these height positions, can be controlled.

[0078] In addition, in each of the examples described above, the shape of the stack 15 is made consistent by making the depths of the first side recess 23 and the second side recess 24 consistent after etching, but the processing conditions can also be selected in a manner that increases either of these side recesses 23 and 24. In other words, when controlling the etching amount, it is not limited to controlling it in a manner that makes the shapes of the stacks 15 consistent. In addition, instead of having the Si film 13 between the SiGe films 12 as in the examples described above, it is also possible to have a structure in which only the SiGe film 12 is provided between the mask film 14 and the substrate 11. Furthermore, the first recess 21 and the second recess 22 are not limited to having openings in the longitudinal direction, but can also have openings in the transverse direction. In other words, the sidewalls of the recess refer to the sidewalls observed from the bottom of the recess and are not limited to being located in the transverse direction.

[0079] In this example, F2 gas is used as the second fluorine-containing gas, which has a low etching performance against SiGe films, and ClF3 gas is used as the first fluorine-containing gas, which has a high etching performance against SiGe films. However, this combination of gases is not limited to this one. 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 as the first fluorine-containing gas instead of ClF3 gas. Furthermore, the germanium-containing film to be etched is not limited to SiGe films; a germanium film may also be used.

[0080] The embodiments disclosed herein are to be considered in all respects as illustrative and non-restrictive, and the embodiments described above may be omitted, replaced, modified, or combined in various ways without departing from the scope of the appended claims and the spirit thereof.

[0081] Description of Reference Numerals

[0082] W: wafer; 12: SiGe film; 15: laminated body; 21: first recessed portion; 22: second recessed portion.

Claims

1. An etching method comprising the following steps: a step of storing a substrate in a processing container, the substrate having a recessed portion formed by a sidewall comprising a germanium-containing film; an etching step of supplying an etching gas containing a first fluorine-containing gas and a second fluorine-containing gas into the processing container to etch the sidewall; as well as a shape control step included in the etching step, wherein the partial pressure of the first fluorine-containing gas in the processing container is adjusted to control the shape of the sidewall after etching; Wherein, the recess comprises: a first recess formed by a first sidewall and having a first width; and a second recessed portion, which is formed by a second sidewall and has a second width wider than the first width; In the shape control step, the magnitude of each of the etching amount of the first side wall and the etching amount of the second side wall in the etching step is controlled.

2. The etching method according to claim 1, wherein The first fluorine-containing gas is chlorine trifluoride gas, The shape control process includes the following steps: The etching is performed by setting the partial pressure of the first fluorine-containing gas to a partial pressure within a first range in which the etching amount of the first side wall and the etching amount of the second side wall can be changed according to the ratio of the flow rate of the second fluorine-containing gas supplied into the processing container relative to the first fluorine-containing gas.

3. The etching method according to claim 2, wherein: The method includes determining the ratio of the flow rates according to the substrates stored in the processing container.

4. The etching method according to claim 2 or 3, wherein: The first range is greater than 0.267×10 -1 Pa and less than 0.933×10 -1 Pa range.

5. The etching method according to claim 1, wherein The first fluorine-containing gas is chlorine trifluoride gas, The shape control step includes performing etching with the partial pressure of the first fluorine-containing gas set to a partial pressure within a second range where the etching amount of the second sidewall is greater than the etching amount of the first sidewall.

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

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

8. The etching method according to claim 7, wherein: The third range is 0.267×10 -1 Below Pa.

9. The etching method according to any one of claims 1 to 3, wherein The first fluorine-containing gas is chlorine trifluoride gas, The shape control process is carried out in the following manner: The partial pressure of the first fluorine-containing gas is set to a partial pressure within a range selected according to the substrate stored in the processing container, among a first range in which the etching amount of the first side wall and the etching amount of the second side wall can be changed according to the ratio of the flow rate of the second fluorine-containing gas supplied into the processing container relative to the first fluorine-containing gas, a second range in which the etching amount of the second side wall is greater than the etching amount of the first side wall, and a third range in which the etching amount of the first side wall is greater than the etching amount of the second side wall.

10. The etching method according to claim 1, wherein The sidewall of the recess is composed of a plurality of sections of the germanium-containing film and an insertion film inserted between the sections of the germanium-containing film. The shape controlling step includes adjusting a ratio of a flow rate of the second fluorine-containing gas to a flow rate of the first fluorine-containing gas supplied into the processing container to control a shape of each section of the germanium-containing film on the sidewall after etching.

11. The etching method according to any one of claims 1 to 3, wherein: The germanium-containing film is a SiGe film.

12. An etching device comprising: a processing container for storing a substrate having a recessed portion formed by a sidewall comprising a germanium-containing film; an etching gas supply unit for supplying an etching gas containing a first fluorine-containing gas and a second fluorine-containing gas into the processing container to etch the sidewall; an adjusting unit for adjusting the partial pressure of the first fluorine-containing gas in the processing container during the etching to control the shape of the sidewall after the etching, in, The recess includes: a first recess formed by a first sidewall and having a first width; as well as a second recessed portion, which is formed by a second sidewall and has a second width wider than the first width; The adjustment unit controls the magnitude of each of an etching amount of the first sidewall and an etching amount of the second sidewall.

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