Etching method and etching apparatus

Abstract

To design the shape of a silicon layer after etching when etching a silicon layer.SOLUTION: An etching method includes an etching step of supplying a halogen-containing gas and an amine gas to a substrate having a silicon layer formed on its surface, to etch the silicon layer.SELECTED DRAWING: Figure 5

Description

Technical Field

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

Background Art

[0002] When manufacturing a semiconductor device, there are cases where the Si layer among the Si layer and the SiGe layer formed on the surface of a semiconductor wafer (hereinafter referred to as a wafer), which is a substrate, is selectively etched. Note that Patent Document 1 describes etching a silicon oxide layer using hydrogen fluoride gas and trimethylamine gas.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides a technique capable of making the shape of a silicon layer after etching a desired shape when etching the silicon layer.

Means for Solving the Problems

[0005] The etching method of the present disclosure includes an etching step of supplying Fluorine gas, a halogen-containing gas and an amine gas to a substrate having a silicon layer formed on its surface to etch the silicon layer. fruit, A germanium-containing layer is formed adjacent to the silicon layer on the substrate. The silicon layer and the germanium-containing layer are each exposed on the surface of the substrate. The etching process is a process of selectively etching the silicon layer from the silicon layer and the germanium-containing layer. . The etching method of this disclosure includes an etching step of supplying a fluorine gas and an amine gas, which are halogen-containing gases, to a substrate on which a silicon layer is formed on the surface, and etching the silicon layer. The etching process includes supplying ammonia gas to the substrate. The etching method disclosed herein is The process includes an etching step in which a silicon layer is formed on a substrate, and a halogen-containing gas and trimethylamine gas (an amine gas) are supplied to etch the silicon layer. [Effects of the Invention]

[0006] This disclosure allows for the desired shape of the silicon layer after etching when etching the silicon layer. [Brief explanation of the drawing]

[0007] [Figure 1] This is a longitudinal cross-sectional front view of a wafer on which processing is performed according to each embodiment of the present disclosure. [Figure 2] This is an explanatory diagram showing the changes in recesses due to etching treatment of the comparative form. [Figure 3] This is an explanatory diagram showing the changes in recesses due to etching treatment of the comparative form. [Figure 4] This is an explanatory diagram showing the changes in the recessed areas due to the etching process in the first embodiment. [Figure 5] This is an explanatory diagram showing the changes in the recessed areas due to the etching process in the first embodiment. [Figure 6] This is a longitudinal cross-sectional front view of the wafer after etching according to the first embodiment. [Figure 7] This is an explanatory diagram showing the changes in the recessed areas due to the etching process in the second embodiment. [Figure 8] This is an explanatory diagram showing the changes in the recessed areas due to the etching process in the second embodiment. [Figure 9] This is a front cross-sectional view of the wafer after etching according to the second embodiment. [Figure 10] This is a longitudinal cross-sectional front view showing an example of an etching apparatus that performs the processing described herein. [Figure 11] This is a graph showing the results of the evaluation test. [Figure 12] This is an SEM image showing the results of the evaluation test. [Figure 13] This is an SEM image showing the surface of the wafer before evaluation testing. [Figure 14] This is an SEM image showing the results of the evaluation test. [Figure 15] This is a graph showing the results of the evaluation test. [Figure 16] It is a SEM image showing the results of the evaluation test. [Figure 17] It is a SEM image showing the results of the evaluation test. [Figure 18] It is a SEM image showing the results of the evaluation test.

Embodiments for Carrying Out the Invention

[0008] (Overview of Etching and Structure of Each Layer on the Substrate) The etching method (etching process) in one embodiment of the present disclosure will be described. This etching process is used, for example, in the process of manufacturing a GAA (Gate all around) transistor such as a nanosheet or a nanowire from a substrate W in which a large number of Si (silicon) layers 11 and SiGe (silicon germanium) layers 12 each having a thickness of several nm are laminated, and is performed without forming plasma around the substrate W. FIG. 1 is a longitudinal front view of the substrate W which is a wafer, and shows the state before the etching process is performed.

[0009] The surface layer of the substrate W is shown as 13. On this surface layer 13, when the thickness direction of the substrate W is taken as the vertical direction, the Si layer 11 and the SiGe layer 12 are alternately and repeatedly laminated in this vertical direction. Therefore, the SiGe layer 12 is in contact with the Si layer 11 in the vertical direction. The uppermost stage of the repetition of the Si layer 11 and the SiGe layer 12 is formed by the Si layer 11, and a mask film 14 for preventing the etching of the Si layer 11 from above is laminated on the Si layer 11. When the mask film 14, the Si layer 11, and the SiGe layer 12 laminated with each other are taken as the laminated structure 10, grooves 15 are formed from the upper end to the lower end of the laminated structure 10 so as to divide the laminated structure 10 in the horizontal direction in a longitudinal sectional view, and a plurality of these grooves 15 are formed apart from each other in the horizontal direction. Therefore, each side surface of the Si layer 11 and the SiGe layer 12 is exposed to the surface of the substrate W through the groove 15 and is exposed to the etching gas supplied from above the substrate W and introduced into the groove 15.

[0010] In this embodiment, the Si layer 11 is selectively etched from the side, compared to the Si layer 11 and the SiGe layer 12. This etching is performed so that a portion of each Si layer 11 remains. Therefore, after etching, a recess 18 is formed by the SiGe layer 12 and the Si layer 11 toward the center of the width of the laminated structure 10. It is desirable that this recess 18 has high rectangularity in a vertical cross-sectional view. To explain this rectangularity in more detail, the recess 18 is considered rectangular when the side surface (back wall surface) of the recess 18 formed by the Si layer 11 and the top and bottom surfaces of the recess 18 form a 90° angle in a front view. A recess 18 whose shape approximates such a recess 18 is a recess 18 with high rectangularity.

[0011] In addition to increasing the rectangularity of the recess 18, it is also desirable that the roughness (surface roughness) of the side surface of the Si layer 11 forming the back wall of the recess 18 be suppressed. More specifically, it is preferable that the formation of irregularities on the side surface be suppressed and that it be highly smooth. The above-mentioned determination of the desired shape of the silicon layer after etching includes the determination of a shape in which such roughness is suppressed.

[0012] (Comparative form) To clearly explain the etching process according to the embodiment, we will first describe the etching process of a comparative form based on Figures 2 and 3. Figures 2 and 3 correspond to partially enlarged views of the longitudinal cross-sectional front view shown in Figure 1, and are explanatory diagrams showing the change in shape of the substrate W during the etching process, while Figure 3 shows the state of the substrate W at the end of the etching process.

[0013] A method for etching a Si layer using halogen-containing gases, F2 (fluorine) gas and NH3 gas, as etching gases is known, and in the etching process in the comparative configuration, these F2 and NH3 gases are supplied simultaneously to the substrate W described above. As will be shown later in the evaluation test, by supplying such etching gases, the Si layer 11 is selectively etched relative to the SiGe layer 12. However, it was confirmed that the region near the interface between the Si layer 11 and the SiGe layer 12 (hereinafter referred to as the near-interface region 19) is etched more significantly toward the center of the width of the laminated structure 10 compared to other regions. Therefore, when viewed in the vertical direction, the depth in the horizontal direction differs in each part of the formed recess 18, resulting in low rectangularity as described above.

[0014] The etching of the Si layer 11 in this manner is thought to be due to the diffusion of Ge (germanium) atoms from the adjacent SiGe layer 12 in the interface region 19 of the Si layer 11. More specifically, it is estimated that this diffusion results in a higher Ge atom concentration in the interface region 19 than in other regions of the Si layer 11, leading to a higher etching rate (etching amount / etching time) compared to other regions, as shown in Figures 2 and 3. Although the SiGe layer 12, which is the source of Ge atom diffusion, has a higher Ge atom concentration than the interface region 19 of the Si layer 11, etching is almost nonexistent in it, as shown in the evaluation test. The SiGe layer 12 contains a relatively large amount of Ge atoms, and therefore its layer properties differ from those of the interface region 19, where only trace amounts of Ge are present in the Si layer due to diffusion. This is thought to be the reason for the difference in resistance to the etching gas.

[0015] Furthermore, the results of the evaluation tests described later show that the roughness of the Si layer 11 increases after etching compared to before etching. This increase in roughness is due to by-products generated by the reaction between the etching gas and the Si layer 11. Specifically, ammonium silicofluoride ((NH4)2SiF6) is produced as a by-product during etching, and a layer of this by-product is formed on the Si layer 11, but its thickness varies in different parts of the Si layer 11. In areas of the Si layer 11 where the thickness of the by-product layer is relatively large, contact with the etching gas is hindered, and etching is inhibited. In other words, the amount of etching varies in different parts of the surface of the Si layer 11, and as a result, the roughness after etching increases as described above.

[0016] (First Embodiment) Next, the etching process according to this embodiment will be explained based on Figures 4 to 6. Figures 4 and 5 are explanatory diagrams showing the shape change of the substrate W during the etching process, similar to Figures 2 and 3, and Figure 5 shows the state of the substrate W at the end of the etching process. Figure 6 is a longitudinal cross-sectional front view of the entire laminated structure 10 after the etching process, similar to Figure 1, and Figure 5 is an enlarged view of a part of Figure 6.

[0017] In this embodiment, the etching gas consists of F2 gas and trimethylamine ((CH3)3N, hereafter referred to as TMA) gas, which is an amine gas, and these F2 gas and TMA gas are supplied to the substrate W simultaneously. It is thought that etching proceeds so that the amount of etching is roughly the same between the region near the interface 19 in the Si layer 11 and other regions (Figure 4), and as will be shown later in the evaluation test results, the recessed area 18 after etching is highly rectangular (Figures 5 and 6). In other words, when using the etching gas of this embodiment, the Ge atom content in the Si layer 11 does not significantly affect the etching properties of the etching gas.

[0018] Furthermore, the results of the evaluation tests described later show that using the etching gas of this embodiment suppresses the increase in roughness of the Si layer 11 after etching, and the sides of the Si layer 11 after etching are smoother compared to when using the etching gas of the comparative embodiment. This is thought to be due to the difference in the by-products generated between this embodiment and the comparative embodiment. The by-products in this embodiment are assumed to be substances in which the constituent elements of ammonia contained in ammonium silicate, a by-product of the comparative embodiment, are replaced with the constituent elements of trimethylamine. It is thought that because these by-products have a higher vapor pressure than ammonium silicate, they vaporize immediately after generation and separate from the sides of the Si layer 11, thus not interfering with the contact between the etching gas and the sides of the Si layer 11, and the sides of the Si layer 11 are etched with high uniformity.

[0019] As described above, the etching process in this embodiment makes it possible to increase the rectangularity of the recesses 18 formed by etching, and to suppress the roughness (increase the smoothness) of the side surface of the Si layer 11 after etching. Furthermore, as shown in the evaluation test, it is possible to achieve a relatively high etching rate for the Si layer 11.

[0020] (Second Embodiment) The etching process in this embodiment will be explained based on Figures 7 to 9. In this explanation, the differences from the first embodiment will be the main focus, and the same configuration as in the first embodiment will not be described. Figure 7 is a longitudinal cross-sectional front view of the entire laminated structure 10 after etching, similar to Figure 1, and Figure 8 is an enlarged view of a part of Figure 9.

[0021] As previously described, the rectangular shape of the recess 18 formed in the first embodiment is high, but as shown in Figures 5 and 6, the etching amount in the region near the interface 19 in the Si layer 11 may be smaller than in other regions of the Si layer 11. That is, the depth of the recess 18 decreases as it approaches the SiGe layer 12 located above or below, and the recess 18 may be formed such that the upper and lower parts at the back form an arc when viewed in a vertical cross-section. This is generally thought to be because, when gas flows through a gap, the flow velocity tends to decrease near the walls forming the gap. In other words, when etching gas flows through the recess 18 toward the back, the flow velocity of the etching gas is small near the upper and lower walls of the recess 18, and it is thought that the effect of this etching gas is relatively small, resulting in a smaller etching amount in the region near the interface 19.

[0022] In this second embodiment, etching is performed to increase the rectangularity of the recess 18. Specifically, the etching gas in this embodiment consists of F2 gas, TMA gas, and NH3 gas, and these F2, TMA gas, and NH3 gas are supplied to the substrate W simultaneously.

[0023] As explained in the comparative form, the inclusion of F2 gas and NH3 gas as etching gas results in a relatively high etching rate in the interface region 19. Consequently, compared to the etching process in the first embodiment, the etching process in this second embodiment proceeds with a more uniform etching amount between the interface region 19 and other regions in the Si layer 11 (Figure 7), and the rectangularity of the recess 18 is higher at the end of etching (Figures 8 and 9). Furthermore, as will be shown in the evaluation tests later, this second embodiment allows for etching at a higher etching rate compared to the first embodiment.

[0024] Next, an etching apparatus 1A that performs etching processing according to the present disclosure will be described with reference to the longitudinal cross-sectional front view of Figure 10. This etching apparatus 1A can be implemented by selecting one of the etching methods from the first embodiment and the second embodiment. In the figure, 71 is a processing container that constitutes the etching apparatus 1A. In the figure, 72 is a substrate W transport port opening in the side wall of the processing container 71, which is opened and closed by the gate valve 63 described above. A stage 81 on which the substrate W is placed is provided inside the processing container 71, and the stage 81 is provided with a lifting pin (not shown). The substrate W is transferred between the substrate transport mechanism located outside the processing container 71 and the stage 81 via the lifting pin.

[0025] A temperature control unit 82 is embedded in the stage 81, and the substrate W placed on the stage 81 is kept at the temperature described above. This temperature control unit 82 is configured as a flow path that forms part of a circulation path through which a temperature-controlling fluid, such as water, flows, and the temperature of the substrate W is adjusted by heat exchange with the fluid. However, the temperature control unit 82 is not limited to such a fluid flow path, and may be configured as, for example, a heater for resistance heating. The temperature of the substrate W (the surface temperature of the stage 81) when the etching gas is supplied is, for example, -50°C to 200°C.

[0026] Furthermore, one end of an exhaust pipe 83 is open inside the processing container 71, and the other end of the exhaust pipe 83 is connected to an exhaust mechanism 85, which is composed of, for example, a vacuum pump, via a valve 84, which is a pressure changing mechanism. By adjusting the opening of the valve 84, the pressure inside the processing container 71 is set to a predetermined pressure, and etching is performed on the substrate W. This pressure is, for example, 0.133 Pa to 1.3 × 10⁻⁶. 4 It is Pa.

[0027] A gas shower head 86 is provided in the upper part of the processing container 71, facing the stage 81. The downstream side of gas supply passages 91 to 94 is connected to the gas shower head 86, and the upstream side of gas supply passages 91 to 94 is connected to gas supply sources 96 to 99 via flow rate adjustment units 95. Each flow rate adjustment unit 95 is equipped with a valve and a mass flow controller. The supply of each gas from gas supply sources 96 to 99 is controlled by opening and closing the valves included in the flow rate adjustment unit 95 to cut off the supply to the downstream side. Furthermore, the flow rate supplied to the downstream side of each gas is adjusted by each flow rate adjustment unit 95. The gas shower head 86, flow rate adjustment units 95, and gas supply sources 96 to 99 constitute the gas supply mechanism.

[0028] F2 gas, TMA gas, N2 gas, and NH3 gas are supplied from gas supply sources 96, 97, 98, and 99, respectively, and each of these gases is supplied into the processing container 71 via the gas shower head 86. Each of these gases can be supplied independently by the flow rate adjustment unit 95. N2 gas, which is an inert gas, is supplied as a carrier gas to the processing container 71 via the gas shower head 86 along with the etching gas. When implementing the etching method of the first embodiment, F2 gas and TMA gas are supplied to the gas shower head 86 as etching gases, and when implementing the etching method of the second embodiment, F2 gas, TMA gas, and NH3 are supplied to the gas shower head 86 as etching gases.

[0029] Furthermore, the etching apparatus 1A is equipped with a control unit 50, which is a computer. This control unit 50 includes a program, memory, and a CPU. The program incorporates instructions (each step) to process the substrate W and transport the substrate W as described above. This program is stored in a storage medium, such as a compact disk, hard disk, magneto-optical disk, DVD, etc., and installed in the control unit 50. The control unit 50 outputs control signals to each part of the etching apparatus 1A using this program, thereby controlling the operation of each part. Specifically, the operations of the etching apparatus 1A controlled in this manner include, for example, the temperature of the fluid supplied to the stage 81, the supply and cut-off of each gas from the gas shower head 86, and the adjustment of the exhaust flow rate by the valve 84.

[0030] (modified version) The etching methods of the first and second embodiments are not limited to being applied to a substrate W having the structure described in Figure 1. For example, they can also be applied to a substrate W in which the Si layer 11 and each SiGe layer 12 are adjacent to each other in the lateral direction and exposed on the surface, when selectively etching the Si layer 11. In this case as well, it is possible to prevent the etching rate of the region 19 near the interface of the Si layer 11 from becoming larger than when etching is performed in the comparative embodiment, and to control the shape of the Si layer 11 after etching. In other words, the direction of adjacency of the Si layer 11 and SiGe layer 12 is not limited to the vertical direction.

[0031] Furthermore, even if another germanium-containing layer, such as a Ge layer, is adjacent to the Si layer 11 instead of the SiGe layer 12, and the Ge content in the interface region 19 of the Si layer 11 becomes relatively high, it is considered that the etching rate of the interface region 19 can be suppressed by the etching method of the first or second embodiment. In other words, even when a germanium-containing layer other than the SiGe layer 12 is adjacent to the Si layer 11, it is considered that the shape of the Si layer 11 can be controlled by this technology. Note that etching is not limited to the Si layer adjacent to other types of layers; for example, only the Si layer 11 exposed over almost the entire surface of the substrate W may be simply etched. In that case, the roughness of the Si layer 11 after etching can be suppressed. In addition, although a polysilicon layer is etched as the silicon layer in the evaluation test described later, the silicon layer etched by this technology is not limited to polysilicon, but may be amorphous silicon. It may also be a silicon layer containing doping elements such as phosphorus.

[0032] Furthermore, in the first and second embodiments, the partial pressure of the etching gas around the substrate W is increased by simultaneously supplying multiple gases that constitute the etching gas, thereby increasing the etching rate. However, the gases constituting the etching gas are not limited to being supplied simultaneously, but may be supplied sequentially. Specifically, in the first embodiment, F2 gas and TMA gas may be supplied sequentially, and in the second embodiment, F2 gas, TMA gas, and NH3 gas may be supplied sequentially to the processing container 71. When supplying the gases constituting the etching gas sequentially in this manner, an inert gas such as N2 gas may be supplied to the processing container as a purge gas between the supply of one gas constituting the etching gas and the other gases to purge any gases remaining in the processing container 71.

[0033] In this specification, supplying each gas to the substrate W simultaneously means that the start timing of supplying each gas to the substrate W is synchronized, and the end timing of supplying each gas to the substrate W is synchronized. Therefore, supplying each gas simultaneously includes the overlapping of the periods during which each gas is supplied to the substrate W. As described above, it is preferable to supply each gas simultaneously in order to increase the etching gas pressure around the substrate W, but the start timing and / or end timing of supply may be staggered among the gases that make up the etching gas. In other words, the period during which one gas that makes up the etching gas is supplied may overlap only partially with the period during which another gas that makes up the etching gas is supplied.

[0034] Furthermore, while the etching gas described above contains F2 gas, a fluorine-containing gas, as a halogen-containing gas, other halogen-containing gases containing other halogen molecules such as Cl (chlorine) or Br (bromine) may be used instead of fluorine-containing gas. Also, the fluorine-containing gas is not limited to F2 gas; for example, IF7 gas, IF5 gas, ClF3 gas, or SF6 gas may be used.

[0035] Furthermore, while the etching gas described above contains TMA gas, it is not limited to this and may also contain other amine gases. The other amine gas may be a gas composed of primary, secondary, or tertiary amines. Specifically, monomethylamine (CH3NH2), a primary amine; dimethylamine ((CH3)2NH), a secondary amine; and triethylamine ((CH3CH2)3N), a tertiary amine, can be used.

[0036] Incidentally, we have stated that etching gases may contain components such as F2, amines, and NH3, and that Ge may be contained as a component of the layer (film) adjacent to the Si layer to be etched. In this specification, when we say that a gas or film contains a certain component, we mean that it contains that component as a constituent component, not as an impurity.

[0037] The embodiments described above in this disclosure should be considered in all respects as illustrative and not restrictive. The embodiments described above may be omitted, replaced, modified, or combined in various ways without departing from the scope and spirit of the appended claims.

[0038] [Evaluation Test] The evaluation tests conducted regarding the etching process described herein are described below. <Evaluation Test 1> As Evaluation Test 1, a comparative etching process was performed on a test substrate B1 having the layer structure described in Figure 1 using an etching apparatus 1A. Specifically, in Evaluation Test 1, F2 gas and NH3 gas were used as etching gases. Multiple substrates B1 were prepared, and different etching times (etching gas supply times) were set for each substrate B1. Specifically, these etching times were set to 60 seconds, 120 seconds, and 175 seconds. The processing conditions other than the etching time were set similarly for all substrates B1. The pressure inside the processing container 71 and the temperature of the substrate B1 were set to values ​​within the range described in the embodiment, and the flow rates of F2 gas and NH3 gas supplied to the substrate W (i.e., supplied into the processing container 71) were set to NH3 gas flow rate / F2 gas flow rate = 0.02. Then, SEM images of substrate B1 acquired before and after the etching process were compared to detect the etching amount of the side walls of multiple Si layers 11, and the average value was calculated. Similarly to the Si layer 11, the etching amount of the sidewalls of the SiGe layer 12 was detected from multiple layers and the average value was calculated. The N2 gas and F2 gas supplied to the substrate W were set to a ratio of N2 gas flow rate / F2 gas flow rate = 1.6, and this ratio was also used in subsequent evaluation tests.

[0039] Figure 11 shows the results of evaluation test 1. The horizontal axis of the graph represents etching time, and the vertical axis represents the average etching amount of the Si layer 11 and the average etching amount of the SiGe layer 12, respectively. The vertical axis scales for the Si layer 11 and the SiGe layer 12 are marked with constant etching amount increments. However, the size of these increments differs. That is, the etching amount per division of the Si layer 11 (denoted as Anm) is different from the etching amount per division of the SiGe layer 12 (denoted as Bnm), where Anm > Bnm. The divisions of the Si layer 11 and SiGe layer 12 located at the same height in the graph are shown as α and β, respectively, where α is approximately 3.3 times β.

[0040] As shown in the graph, the average etching amount of the Si layer 11 increases as the etching time increases, and this etching time and the average etching amount of the Si layer 11 are roughly proportional. On the other hand, the average etching amount of the SiGe layer 12 remains roughly constant. Furthermore, the average etching amount of the Si layer 11 at the shortest etching time of 60 seconds is greater than the average etching amount of the SiGe layer 12 at each etching time. Thus, in evaluation test 1, selective etching of the Si layer 11 occurred compared to the Si layer 11 and the SiGe layer 12.

[0041] However, as described in the embodiment, the rectangularity of the recess 18 was low in this evaluation test 1. Figure 12 shows an SEM image of substrate B1 processed with an etching time set to 175 seconds. From this image, it was confirmed that the region 19 near the interface of the Si layer 11 was etched more significantly than other regions, as explained in Figures 2 and 3.

[0042] <Evaluation Test 2> A substrate B2 with a polysilicon layer formed on its surface was subjected to etching for a predetermined time, in the same manner as in Evaluation Test 1. All processing conditions except for the etching time were the same as those in Evaluation Test 1. The surface of substrate B2 was imaged and observed before and after the etching process. The polysilicon layer was formed on a flat substrate B2 without any patterns. Therefore, the laminated structure 10 described in Figure 1 was not formed on this substrate B2.

[0043] Figure 13 shows the surface of substrate B2 before etching, and Figure 14 shows the surface of substrate B2 after etching. From Figures 13 and 14, it can be seen that the etching process created many irregularities on the surface, resulting in increased roughness. As described in the embodiment, by-products are generated during etching, and the polysilicon layer is etched while covered with these by-products, which is thought to be the reason for this increase in roughness. Similarly, by-products are generated when etching the Si layer 11 that constitutes the laminated structure 10, so it is thought that the roughness of the Si layer 11 after etching will also increase.

[0044] <Evaluation Test 3> As Evaluation Test 3, the test substrate B1 was etched using the F2 gas and TMA gas described in the first embodiment, and the average etching amount of the Si layer 11 and SiGe layer 12 was calculated in the same manner as in Evaluation Test 1. Therefore, in Evaluation Test 3, TMA gas was used as the etching gas instead of the NH3 gas used in Evaluation Test 1. The etching times for each substrate in Evaluation Test 3 were 60 seconds, 90 seconds, and 120 seconds. Except for the setting of the etching time and the use of TMA gas as the etching gas, the etching process in Evaluation Test 3 was the same as in Evaluation Test 1. The flow rate of TMA gas / flow rate of F2 gas supplied to the substrate W in Evaluation Test 3 was 0.02, the same as the flow rate of NH3 gas / flow rate of F2 gas in Evaluation Test 1.

[0045] Figure 15 shows the results of Evaluation Test 3. The vertical and horizontal axes of the graph in Figure 15 are set to be the same as those of the graph in Figure 13 for Evaluation Test 1. As shown in the graph, the average amount of etching of the Si layer 11 increases as the etching time increases, and this etching time and the average amount of etching of the Si layer 11 are roughly proportional. On the other hand, the average amount of etching of the SiGe layer 12 remains roughly constant. Furthermore, the average amount of etching of the Si layer 11 at the shortest etching time of 60 seconds is greater than the average amount of etching of the SiGe layer 12 at each etching time. From these results, it can be seen that even when TMA gas is used instead of NH3 gas, the etching selectivity for the Si layer 11 of the SiGe layer 12 is maintained.

[0046] Furthermore, comparing the graph in Figure 15 with the graph in Figure 13, it can be seen that, for the same etching time, the average amount of Si etched is greater in Evaluation Test 3 than in Evaluation Test 1. In other words, in Evaluation Test 3, it was confirmed that the etching rate of the Si layer 11 can be increased by using TMA gas instead of NH3 gas as the etching gas. The average amount of etching of the Si layer 11 in Evaluation Test 3 compared to the average amount of etching of the Si layer 11 in Evaluation Test 1 at etching times of 60 seconds and 120 seconds was 1.67 times and 2.67 times, respectively. Figure 16 shows an SEM image of substrate B1 etched at an etching time of 90 seconds in Evaluation Test 3. As shown in this image, the rectangularity of the formed recess 18 is high.

[0047] <Evaluation Test 4> Except for using F2 gas and TMA gas as the etching gases in Evaluation Test 3, the substrate B2 was etched under the same processing conditions as in Evaluation Test 2, and the surface of substrate B2 was imaged and observed after the process. Figure 17 shows the surface of substrate B2 after this etching process. Compared with the image in Figure 13 before etching, as explained in Evaluation Test 2, it can be seen that there is no significant change in the surface roughness of the polysilicon layer in the image in Figure 17. Furthermore, compared with the image in Figure 14 after etching in Evaluation Test 2, it can be seen that the surface roughness of the polysilicon layer is suppressed in the image in Figure 17. This is thought to be due to the fact that the by-products generated differ when TMA gas is used and when NH3 gas is used, as described in the embodiment, and that the sublimation properties of these by-products differ. Therefore, it is predicted that when etching the Si layer 11 that constitutes the laminated structure 10, the roughness of the Si layer 11 will be suppressed in the same way as the polysilicon layer in Evaluation Test 4.

[0048] As shown above, the results of evaluation tests 1 to 4 demonstrate that by using F2 gas and TMA gas as etching gases, the etching rate, the rectangularity of the formed recesses 18, and the smoothness of the Si layer after etching can all be made relatively high when etching the Si layer 11 of the laminated structure 10.

[0049] <Evaluation Test 5> As evaluation test 5, the test substrate B1 was etched using the F2 gas, TMA gas, and NH3 gas described in the second embodiment, and the average etching amount of the Si layer 11 and SiGe layer 12 was calculated, similar to evaluation tests 1 and 3. Therefore, in evaluation test 5, the types of gases that make up the etching gas are the same as those used in evaluation test 3, plus the NH3 gas used in evaluation test 1. In evaluation test 5, the etching time was set to 90 seconds.

[0050] Regarding the flow rates of each gas supplied to substrate W in this evaluation test 5, the F2 gas flow rate / (TMA gas flow rate + NH3 gas flow rate) is 0.02, the same as the F2 gas flow rate / NH3 gas flow rate in evaluation test 1 and the F2 gas flow rate / TMA gas flow rate in evaluation test 3. In this evaluation test 5, the TMA gas flow rate / NH3 gas flow rate is set to 1. Other processing conditions other than gas flow rates, such as the temperature of substrate B1, are the same as the processing conditions set in evaluation tests 1 and 3.

[0051] Comparing the results of evaluation test 3, which had the same etching time of 90 seconds as evaluation test 5, with the results of evaluation test 5, the average etching amount of Si layer 11 in evaluation test 5 was 3.69 times higher than the average etching amount of Si layer 11 in evaluation test 3. Furthermore, the average etching amount of SiGe layer 12 in evaluation test 5 was 1.28 times higher than the average etching amount of SiGe layer 12 in evaluation test 3. Therefore, comparing the results of evaluation test 5 with those of evaluation test 3, it can be seen that there was no significant change in the etching amount of SiGe layer 12, but the etching amount of Si layer 11 increased significantly. In other words, the etching selectivity for Si layer 11 among Si layer 11 and SiGe layer 12 was ensured, while the etching rate of Si layer 11 was higher than in evaluation test 3, which is a favorable result. Figure 18 shows an image of substrate B1 after etching in evaluation test 5. As is clear from comparing it with the image in Figure 16 of evaluation test 3, the rectangularity of the recess 18 is higher.

[0052] Incidentally, regarding the TMA gas flow rate / F2 gas flow rate, as mentioned above, it was set to 0.02 in evaluation test 3. Then, in evaluation test 5, since the TMA gas flow rate was half that of evaluation test 3, the TMA gas / F2 gas flow rate was 0.01. Since etching treatment was favorably performed in both evaluation tests 3 and 5, it can be seen that it is preferable to set the TMA gas / F2 gas flow rate to 0.01 or higher.

[0053] Furthermore, in evaluation test 5, the balance between the effect of suppressing etching in the near-interface region 19 by using TMA gas and the effect of promoting etching in the near-interface region 19 by using NH3 gas is considered to have resulted in the etching progressing and the rectangularity of the recess 18 being increased, as explained in Figures 7 to 9. As mentioned above, in evaluation test 5, the TMA gas flow rate / NH3 gas flow rate was set to 1, but it is considered that the above balance will not be significantly disrupted even if the ratio of TMA gas flow rate to NH3 gas flow rate deviates slightly from this ratio. However, if the value of TMA gas flow rate / NH3 gas flow rate is too small, the effect of NH3 gas will be too large, and the problems described in the comparison form will occur. Also, if the value of TMA gas flow rate / NH3 gas flow rate is too large, the effect of NH3 gas will be too small, and the etching rate of the near-interface region 19 will decrease, as explained in Figures 7 to 9. Taking this into consideration, it is considered preferable to set the TMA gas flow rate / NH3 gas flow rate to, for example, 0.25 to 4.0. [Explanation of Symbols]

[0054] W board 11 Si layer

Claims

1. The process includes an etching step in which a silicon layer is formed on a substrate, and halogen-containing gases, namely fluorine gas and amine gas, are supplied to etch the silicon layer. A germanium-containing layer is formed adjacent to the silicon layer on the substrate. The silicon layer and the germanium-containing layer are each exposed on the surface of the substrate. The etching step is an etching method in which the silicon layer is selectively etched from the silicon layer and the germanium-containing layer.

2. The etching method according to claim 1, wherein the germanium-containing layer is a silicon germanium layer.

3. The etching method according to claim 2, wherein the substrate is provided with the silicon layer and the silicon germanium layer alternately stacked on it.

4. The etching method according to claim 1, wherein the etching step includes a step of supplying the halogen-containing gas and the amine gas to the substrate such that the period for supplying the halogen-containing gas and the period for supplying the amine gas overlap with each other.

5. The etching method according to claim 4, wherein the flow rate of the amine gas supplied to the substrate / the flow rate of the halogen-containing gas supplied to the substrate is 0.01 or more.

6. The process includes an etching step in which a silicon layer is formed on a substrate, and halogen-containing gases, namely fluorine gas and amine gas, are supplied to etch the silicon layer. The etching step is an etching method that includes the step of supplying ammonia gas to the substrate.

7. The etching method according to claim 6, wherein the etching step includes a step of supplying the halogen-containing gas, the amine gas, and the ammonia gas to the substrate such that the periods for which each gas is supplied overlap.

8. An etching method comprising an etching step of supplying a halogen-containing gas and trimethylamine gas, which is an amine gas, to a substrate on which a silicon layer has been formed on its surface, thereby etching the silicon layer.

9. The etching method according to claim 8, wherein the halogen-containing gas is fluorine gas.

10. The etching method according to claim 9, wherein the etching step includes a step of supplying ammonia gas to the substrate.

11. The etching method according to claim 10, wherein the etching step includes a step of supplying the halogen-containing gas, the amine gas, and the ammonia gas to the substrate such that the periods for which each gas is supplied overlap.

12. A silicon layer and a germanium-containing layer adjacent to the silicon layer are formed on the surface, and the silicon layer and the germanium-containing layer are each exposed on the surface of the substrate in the processing container, A gas supply mechanism supplies halogen-containing gases, namely fluorine gas and amine gas, into the processing container in order to selectively etch the silicon layer from the aforementioned silicon layer and the aforementioned germanium-containing layer. An etching apparatus equipped with the following features.

13. A processing container for storing a substrate having a silicon layer formed on its surface, A gas supply mechanism supplies halogen-containing gases, such as fluorine gas, amine gas, and ammonia gas, into the processing container in order to etch the silicon layer. An etching apparatus equipped with the following features.

14. A processing container for storing a substrate having a silicon layer formed on its surface, A gas supply mechanism that supplies a halogen-containing gas and a trimethylamine gas, which is an amine gas, into the processing container in order to etch the silicon layer, An etching apparatus equipped with the following features.

Images