Etching method and etching apparatus

Abstract

The etching method according to the present disclosure includes an etching step in which a halogen-containing gas, an ammonia gas, and an amine gas are supplied as etching gases to a substrate having a silicon oxide film formed on the surface thereof, and the silicon oxide film is etched.

Description

TECHNICAL FIELD

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

[0002] In a manufacturing process of a semiconductor device, for example, an oxide silicon film formed on a substrate that is a semiconductor wafer (hereinafter, referred to as a wafer) is etched. It is shown in Patent Literature 1 that the oxide silicon film is supplied with amine gas to be etched.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: WO2020 / 054476A1 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] The present disclosure provides a technology capable of setting a shape of an etched oxide silicon film to a desired shape when etching an oxide silicon film formed on a substrate.

[0008] SOLUTION TO PROBLEM

[0009] The etching method of the present disclosure includes an etching process in which a substrate on which an oxide silicon film is formed on a surface is supplied with a halogen-containing gas, ammonia gas, and amine gas as etching gas to etch the oxide silicon film.

[0010] EFFECT OF THE INVENTION

[0011] The present disclosure is capable of setting a shape of an etched oxide silicon film to a desired shape when etching an oxide silicon film formed on a substrate. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a longitudinal sectional view of a wafer that is a subject of an etching method that is one embodiment of the present disclosure.

[0013] Figure 2 is a longitudinal sectional view of a wafer that shows an etching process of a comparative example.

[0014] Figure 3 is a longitudinal sectional view of a wafer that shows an etching process of a comparative example.

[0015] Figure 4 is a longitudinal sectional view of a wafer that shows an etching process of another comparative example.

[0016] Figure 5 is an explanatory diagram for showing an outline of the present embodiment.

[0017] Figure 6 is a longitudinal sectional view for showing an etching process of the present embodiment.

[0018] Figure 7 is a view showing an etching process of the present embodiment.

[0019] Figure 8 is a longitudinal sectional view of an apparatus for carrying out the etching process of the present embodiment.

[0020] Figure 9 is a chart showing the results of the evaluation test.

[0021] Figure 10 is an explanatory view of an image showing the results of the evaluation test.

[0022] Figure 11 is an explanatory view of an image showing the results of the evaluation test.

[0023] Figure 12 is an explanatory view of an image showing the results of the evaluation test. DETAILED DESCRIPTION

[0024] An embodiment (Example) of the etching method of the present disclosure is described. The outline of the etching method is described, and a SiOx (silicon oxide) film 11 of a surface of a wafer W is etched by supplying a halogen-containing gas, an NH3 (ammonia) gas, and an amine gas as etching gases to the wafer W as a substrate. As shown in FIG. 1, a Si film 12 is formed on the surface of the wafer W, and a groove is formed in the Si film 12. Thus, a recess 14 that opens in a thickness direction of the wafer W is formed by the Si film 12 and a lower layer film 13 formed on a lower side of the Si film 12, and the Si film 12 is configured as a side wall of the recess 14. Further, the display of the lower layer film 13 is omitted in several drawings described later. Figure 1

[0025] Further, the SiOx film 11 is formed in the recess 14 described above. By using the etching gases described above, the SiOx film 11 is selectively etched in the SiOx film 11 and the Si film 12 that are each a silicon-containing film and exposed on the surface of the wafer W. After the etching, a process is performed to leave a part of the SiOx film 11 in the recess 14. Further, when the etching is performed, a plasma is not formed around the wafer W.

[0026] The etching of the example is described more specifically, and the SiOx film 11 of a desired amount is etched by repeatedly performing the supply of the etching gases to the wafer W and sublimation (also including vaporization) of a reaction product in a state where the supply of the etching gases to the wafer W is stopped. Further, in the present example, for example, an HF (hydrogen fluoride) gas is used as one of the etching gases, that is, a halogen-containing gas.

[0027] ​As described above, the etching gas contains NH3 gas and amine gas, both of which are alkaline gases. By using both NH3 gas and amine gas, the purpose is to achieve relatively high flatness on the upper surface (surface) of the SiOx film 11 remaining in the recess 14 after etching, and to prevent performance degradation of semiconductor devices manufactured from the wafer W due to this low flatness. Furthermore, in this embodiment, HF gas is used as the halogen-containing gas, and trimethylamine (TMA) gas is used as the amine gas.

[0028] Below, we will first describe the comparative example process to clearly demonstrate the effects of the etching gases used in the examples. Comparative Example 1 describes the process using HF gas and NH3 gas as etching gases, and Comparative Example 2 describes the process using HF gas and TMA gas as etching gases. First, the etching process in Comparative Example 1 will be described. Figure 2 、 Figure 3 1 is a longitudinal sectional side view of a wafer W showing changes in the SiOx film 11 that are estimated to occur during the processing of Comparative Example 1. In the figure, etching gases composed of HF gas and NH3 gas are represented as etching gas 21. In the following description, unless otherwise specified, references to left and right ends and left and right center portions of the SiOx film 11 refer to the left and right ends and left and right center portions, respectively, in the longitudinal sectional view.

[0029] By supplying the etching gas 21 ( Figure 2 (a)), the surface of the SiOx film 11 in the recess 14 reacts with the etching gas 21 to form a layer 15 composed of ammonium fluorosilicate [(NH4)SiF6:AFS] as a reaction product. The thickness of the AFS layer 15 varies between the left and right ends and the center of the SiOx film 11 ( Figure 2 (b)).

[0030] More specifically, the etching gas 21 is supplied to the left and right central portions of the SiOx film 11 (i.e., regions relatively far from the interface with the Si film 12) in greater quantities than to the left and right end portions (i.e., regions close to the interface with the Si film 12). Consequently, the thickness of the left and right central portions of the AFS layer 15 is greater than that of the left and right end portions. The reason for this variation in the amount of etching gas 21 supplied to various portions of the SiOx film is due to the Si film 12, as described in detail in the description of Comparative Example 2.

[0031] As for the central portions on the left and right in the SiOx film 11, there is a tendency that the contact of the central portions on the left and right with the etching gas 21 is hindered due to the formation of the AFS layer 15 having a relatively large thickness. On the other hand, the AFS layer 15 formed on the upper side of the end portions on the left and right of the SiOx film 11 has a relatively small thickness, and thus easily comes into contact with the etching gas 21. Therefore, the reaction is more advanced at the end portions on the left and right than at the central portions on the left and right of the SiOx film 11, and the height of the surface of the SiOx film 11 is uniform between the central portions on the left and right and the end portions on the left and right Figure 2 The AFS has a low adsorptivity to Si, as shown in the evaluation test to be described later, and on the other hand, has a high adsorptivity to AFS, and thus easily aggregates. For these reasons, the AFS in the vicinity of the interface of the Si film 12 in the AFS layer 15 is separated from the AFS layer 15. That is, when the supply of the etching gas 21 is continued, the thickness of the AFS layer 15 on the end portions on the left and right of the SiOx film 11 decreases Figure 2

[0032] The thickness of the AFS layer 15 decreases like this, and thus the reaction with the etching gas 21 is more greatly advanced at the end portions on the left and right of the SiOx film 11 than at the central portions on the left and right. Also, since the thickness of the AFS layer 15 becomes large on the end portions on the left and right of the SiOx film 11 and on the central portions on the left and right, the contact with the etching gas 21 is hindered, and the reaction is stopped Figure 3 (a). At the time when the reaction is stopped, since the reaction has been advanced as described thus far, as for the SiOx film 11, its surface becomes a shape in which the central portions on the left and right are higher than the end portions on the left and right (a convex shape). Also, after the supply of the etching gas 21 to the wafer W is stopped, the AFS layer 15 is removed by the temperature adjustment of the wafer W and the exhaust of the surroundings of the wafer W, and the SiOx film 11 maintains the above-described convex shape Figure 3 (b). Thus, the planarity of the surface of the SiOx film 11 is relatively low.

[0033] Next, the differences from Comparative Example 1 will be described with reference to Figure 4 The etching in Comparative Example 2 will be described. Figure 4 is a longitudinal sectional side view of the wafer W showing the change of the SiOx film 11 estimated to occur in the processing of this Comparative Example 2. Figure 4 is a longitudinal sectional side view showing the case of the change of the wafer W estimated to occur in the etching. In Figure 4 In, the etching gas is shown as the etching gas 22, which is a mixture of an HF gas and a TMA gas. By supplying this etching gas 22 to the wafer W adjusted to a prescribed temperature Figure 4 ​(a)), the surface of the SiOx film 11 in the recess 14 reacts with the etching gas 22 to produce a reaction product 16. Compared to the AFS produced by the NH3 gas described above, the sublimation temperature of the reaction product 16 is lower. Therefore, the reaction product 16 sublimates quickly after being produced, and the contact between the etching gas 22 and the SiOx film 11 is not easily hindered by the reaction product 16 ( Figure 4 (b)).

[0034] Moreover, with respect to the etching gas 22, a part thereof is supplied downwardly along the opening direction of the recess 14, and another part thereof is supplied obliquely with respect to the opening direction. A part of the etching gas 22 supplied in this way collides with the Si film 12 on the way downward and rebounds, whereby the etching gas 22 is supplied to the left and right central portions of the SiOx film 11 in the longitudinal cross-sectional view. That is, the molecules of the etching gas 22 are directly supplied to the left and right central portions, or the molecules rebounded by the Si film 12 are supplied to the left and right central portions. In other words, a relatively large number of the molecules of the etching gas 22 collide with the left and right central portions of the SiOx film 11, but due to the above-mentioned rebound, it is difficult for the molecules to collide with the left and right end portions. That is, due to the difference in the collision probability of the molecules, with respect to the SiOx film 11, etching progresses more significantly in its central portion than in its left and right end portions ( Figure 4 (c)). Therefore, after the etching is completed, the SiOx film 11 becomes a shape (set as a concave shape) in which the center portion of the left and right sides of the surface is located lower than the left and right ends in the longitudinal cross-sectional view ( Figure 4 (d)). Therefore, the flatness of the surface of the SiOx film 11 is relatively low.

[0035] Figure 5 : is a conceptual diagram showing etching in the embodiment. Figures 2-4 As described above, the SiOx film 11 is etched using either NH3 gas or TMA gas. Since the sublimation properties of the generated reaction products are different when NH3 gas is used as the etching gas and when TMA gas is used as the etching gas, the difference in which side of the SiOx film 11 becomes higher after etching is different, the center or the peripheral part. Therefore, in the embodiment, both gases are used. By doing so, the effects of these gases can be balanced, thereby achieving a better effect than, for example, Figure 5 As shown in the lower right section of the figure, the case where NH3 gas is used alone suppresses the center portion on the left and right from becoming higher than the end portion, or Figure 5 As shown in the upper right section of FIG, the case where TMA gas is used alone suppresses the left and right ends from becoming higher than the center. Figure 5 As shown in the right central section of , the heights of the central and end portions on the left and right sides can also be made consistent.

[0036] ReferenceFigure 6 The longitudinal side view and Figure 7 The etching process of the embodiment is described with a timing chart. This timing chart shows the timing of supplying each gas to the wafer W. As described later, since the wafer W is stored in the processing container and processed, Figure 7 The timing of supplying and shutting off each gas into the processing container is shown. Etching is performed while the processing container is evacuated to a vacuum atmosphere at a predetermined pressure and the wafer W is adjusted to a predetermined temperature.

[0037] HF gas, NH3 gas and TMA gas are supplied as etching gas to the wafer W in the processing container (time t1 in the figure). Figures 2-4 The gases represented as etching gases 21 and 22 ( Figure 6 (a)). In this gas, HF gas and NH3 gas (etching gas 21) act on the SiOx film 11, forming the AFS layer 15 as described in Comparative Example 1. However, by including TMA gas as the alkaline gas, the partial pressure of NH3 gas can be made relatively low, thereby making the thickness of the AFS layer 15 relatively small. Thus, the relatively small thickness of the AFS layer 15 allows each etching gas to pass through the AFS layer 15 and act on the SiOx film 11.

[0038] As described in Comparative Example 1, the AFS layer 15 is formed so that its thickness in the left and right center portions is greater than that in the left and right end portions. Therefore, due to the gas shielding effect of the AFS layer 15 on the SiOx film 11, the center portion of the SiOx film 11 is thicker than the left and right end portions, suppressing etching in this center portion. However, as described in Comparative Example 2, the etching gas 22 has a higher probability of impinging on the left and right center portions of the SiOx film 11 through the Si film 12, resulting in the generation and sublimation of reaction products 16. Furthermore, similarly to the etching gas 22, the etching gas 21 also collides more frequently with the left and right center portions.

[0039] In this way, the difference in the shielding effect of the AFS layer 15 and the difference in the collision probability of each gas are balanced, so that the denaturation uniformity of the left and right center portions and end portions of the SiOx film 11 is highly developed ( Figure 6 (b)). Then, the supply of HF gas, NH3 gas, and TMA gas to the wafer W is stopped (time t2). Furthermore, by adjusting the temperature of the wafer W and exhausting the inside of the processing container, the AFS layer 15 is sublimated and removed ( Figure 6 (c)) Furthermore, when other reaction products such as the reaction product 16 remain on the SiO film 11, these other reaction products are also sublimated and removed, and the surface of the SiO film 11 is exposed.

[0040] After a predetermined time has passed from time t2, HF gas, NH3 gas, and TMA gas are supplied to the wafer W as etching gases again (time t3), and these gases react with the SiOx film 11. Then, the supply of the etching gas to the wafer W is stopped (time t4), and the reaction products on the SiOx film 11 are removed by sublimation of the reaction products and exhaust of the processing container, so that etching progresses and the SiOx film 11 is exposed. Next, after a predetermined time has passed from time t4, HF gas, NH3 gas, and TMA gas are supplied to the wafer W as etching gases again (time t5).

[0041] If the process from time t1 to immediately before time t3 is defined as the first cycle, a second cycle similar to the first cycle is performed from time t3 to immediately before time t5, and the SiOx film 11 is etched. The same cycle is repeated after time t5, and the etching progresses each time the cycle is performed. When the cycle is repeated a predetermined number of times and the SiOx film 11 is etched by the desired amount, the process on the wafer W is terminated ( Figure 6 (d)). In each cycle, the left and right center portions and left and right end portions of the SiOx film 11 are etched with high uniformity. Therefore, the surface flatness of the SiOx film 11 is relatively high at the end of the treatment.

[0042] In addition, in each cycle, the period during which at least one of the etching gases is supplied corresponds to the etching period, and the period during which no etching gas is supplied corresponds to the exhaust period. Figure 7 When the etching process is performed in this manner, the time t1 to t2 and the time t3 to t4 correspond to the etching period, and the time t2 to t3 and the time t4 to t5 correspond to the exhaust period.

[0043] Use the above Figure 5 The shape of the SiOx film 11 after etching will be supplemented. As already mentioned, the AFS generated by the etching gas significantly interferes with the flatness and shape of the SiOx film 11 after etching. Figure 6 、 Figure 7 When the treatment is carried out as described in , if the generation of AFS is suppressed or the sublimation of AFS is high, then Figure 5 As shown in the upper right portion of , the influence of the collision probability of the TMA gas is strong, and the shape is likely to be concave.

[0044] Specifically, the SiOx film 11 is easily made into a concave shape by: making the inside of the processing vessel relatively low in pressure; making the flow rate of the TMA gas supplied into the processing vessel relatively large in comparison with the flow rate of the NH3 gas supplied into the processing vessel; making the temperature of the wafer W relatively high; and / or making the time from the end of the supply of the etching gas until the next supply of the etching gas (the time of t2 to t3, t4 to t5 of the above processing) relatively long. In contrast, the SiOx film 11 is easily made into a convex shape after etching as shown in the lower right section by: making the inside of the processing vessel relatively high in pressure; making the flow rate of the TMA gas supplied into the processing vessel relatively small in comparison with the flow rate of the NH3 gas supplied into the processing vessel; making the temperature of the wafer W relatively low; and / or making the exhaust time after etching relatively short. Figure 5 Specifically, the SiOx film 11 is easily made into a concave shape by: making the inside of the processing vessel relatively low in pressure; making the flow rate of the TMA gas supplied into the processing vessel relatively large in comparison with the flow rate of the NH3 gas supplied into the processing vessel; making the temperature of the wafer W relatively high; and / or making the time from the end of the supply of the etching gas until the next supply of the etching gas (the time of t2 to t3, t4 to t5 of the above processing) relatively long. In contrast, the SiOx film 11 is easily made into a convex shape after etching as shown in the lower right section by: making the inside of the processing vessel relatively high in pressure; making the flow rate of the TMA gas supplied into the processing vessel relatively small in comparison with the flow rate of the NH3 gas supplied into the processing vessel; making the temperature of the wafer W relatively low; and / or making the exhaust time after etching relatively short.

[0045] That is, by adjusting various processing conditions in addition to using both the amine gas and the NH3 gas as the etching gas, it is possible to control the shape of the surface of the SiOx film 11 after etching, and thus it is possible to further improve the planarity. In the evaluation test later, the preferable range of the flow rate of the TMA gas in comparison with the flow rate of the NH3 gas in the above processing conditions on the basis of improving the planarity of the surface of the SiOx film 11 is described.

[0046] Next, the etching apparatus 3 that performs the etching processing according to the present disclosure is described with reference to a longitudinal sectional view of Fig. 1. Figure 8 31 is a processing vessel that constitutes the etching apparatus 3. 39 is a wafer W carrying port that is opened in the side wall of the processing vessel 31, and is opened and closed by a gate valve 33. A mounting table 41 on which the wafer W is mounted is provided in the processing vessel 31, and an unillustrated lift pin is provided in the mounting table 41. The wafer W is exchanged between a substrate carrying mechanism provided outside the processing vessel 31 and the mounting table 41 via the lift pin.

[0047] A temperature adjusting section 32 is embedded in the mounting table 41 to adjust the temperature of the wafer W mounted on the mounting table 41. The temperature adjusting section 32 is configured as a flow path that constitutes a part of a circulation path through which a temperature adjusting fluid such as water flows, and the temperature of the wafer W is adjusted by heat exchange with the fluid. However, the temperature adjusting section 32 is not limited to be such a flow path of the fluid, and for example, can be configured by a heater for performing resistance heating. The temperature of the wafer W (the temperature of the surface of the mounting table 41) at the time of supplying the etching gas is preferably set to, for example, -20°C to 150°C to perform sublimation of AFS.

[0048] Further, one end of an exhaust pipe 33, which is open in the processing container 31, is connected to an exhaust mechanism 35, which is constituted by a vacuum pump, for example, via a valve 34 as a pressure changing mechanism. By adjusting the opening degree of the valve 34, the pressure in the processing container 31 is set to a prescribed pressure, and the wafer W is subjected to etching processing. The pressure is, for example, 0.133 Pa to 1.3 x 10 4 Pa.

[0049] A gas shower plate 46 is provided in the processing container 31 on the upper side in a manner facing the mounting table 41. The downstream side of the gas supply paths 51 to 54 is connected to the gas shower plate 46, and the upstream side of the gas supply paths 51 to 54 is connected to the gas supply sources 61 to 64, respectively, via the flow rate adjusting sections 50. Each flow rate adjusting section 50 is provided with a valve and a mass flow controller. The supply and cutoff of each gas to the downstream side are performed by the opening and closing of the valve included in the flow rate adjusting section 50 with respect to each gas supplied from the gas supply sources 61 to 64. Further, the flow rate of the supply to the downstream side is adjusted by each flow rate adjusting section 50 with respect to each gas. Each gas supplied to the gas flow path provided in the shower plate 46 is ejected downward from a plurality of ejection ports provided in the lower surface of the shower plate 46. The gas supply mechanism is constituted by the gas shower plate 46, the flow rate adjusting sections 50, and the gas supply sources 61 to 64.

[0050] HF gas, TMA gas, N2 gas, and NH3 gas are supplied from the gas supply sources 61, 62, 63, and 64, respectively, and these each gas is supplied into the processing container 31 via the gas shower plate 46. The supply of these each gas can be performed independently of each other by each flow rate adjusting section 50. The N2 gas as an inactive gas is supplied into the processing container 31 via the gas shower plate 46 as a carrier gas together with the etching gas. Further, the N2 gas is supplied into the processing container 31 as a purge gas during the period in which the etching gas is not supplied in the implementation of the above-described circulation. That is, the N2 gas is supplied into the processing container 31 at all times during the above-described processing of the wafer W.

[0051] Further, the etching apparatus 3 is provided with a control section 30 as a computer, which is provided with a program, a memory, and a CPU. The program in which commands (each step) to perform the above-described processing of the wafer W and the conveyance of the wafer W are incorporated is stored in a storage medium such as a compact disc, a hard disc, a magneto-optical disc, a DVD, or the like, and is installed in the control section 30. The control section 30 outputs a control signal to each section of the etching apparatus 3 by the program to control the operation of each section. Specifically, the operation of the above-described etching apparatus 3 as controlled as such includes, for example, the temperature of the fluid supplied to the mounting table 41, the supply and cutoff of each gas from the gas shower plate 46, the adjustment of the exhaust flow rate by the valve 34, and the like.

[0052] Further, in the processing described above, TMA gas is used as the amine gas, but an amine gas other than TMA gas can also be used. Specifically, a gas of dimethylamine, dimethylethylamine, diethylamine, triethylamine, mono-tert-butylamine, tetrahydro-pyrrole, pyridine, or the like can be used. Thus, any one of a primary amine, a secondary amine, and a tertiary amine can also be used as the etching gas. Furthermore, as the etching gas, an appropriate one can be selected depending on the material of the film to be etched. In the case of etching the SiOx film 11, for example, in addition to HF, each of HCl, HBr, HI, SF6, and the like can be used as the halogen-containing gas.

[0053] In Figure 7 the processing shown in the timing chart, the cycle is repeated a plurality of times, but in the case where the amount of etching required is small, the cycle can be performed only once without repeating the cycle. In addition, in the example shown in the timing chart, each of the gases is supplied in a manner in which the supply period of the HF gas, the supply period of the TMA gas, and the supply period of the NH3 gas overlap each other, but the supply periods of these gases can also be non-overlapping. Thus, for example, the HF gas, the TMA gas, and the NH3 gas can be sequentially supplied one by one to the wafer W. In addition, it is also possible to supply the remaining one after the two of the three etching gases have been supplied to the wafer W in advance. That is, it is also possible that only the supply periods of the two of the three gases overlap each other.

[0054] Even in the case where the supply periods of the three etching gases are deviated as described above, it is sufficient to provide the exhaust period in which each of the etching gases is not supplied after each of the etching gases is supplied to the wafer W in order to sublimate the reaction product on the wafer W as one cycle. That is, it is sufficient to perform the etching of the SiOx film 11 by repeating the cycle consisting of the etching period in which at least any one of the three etching gases is supplied and the exhaust period after the etching period.

[0055] Further, the supply periods of the three etching gases can be staggered as described above, but from the viewpoint of increasing the partial pressure of the etching gas around the wafer W to increase the etching rate, it is preferable that the supply periods of the three etching gases overlap each other, and it is more preferable that the supply of the three etching gases be performed at the same time (the start time point of the supply period coincides, and the stop time point of the supply coincides) as shown in Figure 7

[0056] In addition, the case where the etching gas contains halogen, amine, and NH3 as components is described. In this specification, the fact that the etching gas and the film to be etched contain a certain specific component as described above does not mean that the component is contained as an impurity, but means that the component is contained as a constituent component.

[0057] ​The structure of the apparatus is arbitrary, for example, with respect to the gas supply paths 51 to 53 that constitute the flow paths of the etching gases, a tank is provided as a storage portion that stores the gases, and a valve is provided on the downstream side of the tank. The supply and cutoff of the gases from the tank into the processing container 31 are switched by the opening and closing of the valve. Also, the apparatus can be structured such that the gases are stored in the tank in a state in which the valve is closed, and each of the etching gases is supplied into the processing container 31 in a relatively large flow rate within a relatively short period by opening the valve in a state in which the tank is pressurized. Further, the downstream sides of the gas supply paths 52 and 54 can be merged and shared, and the NH3 gas and the TMA gas can be stored in the shared tank and supplied into the processing container 31 via the shared valve by providing the above-described tank and valve at the shared portion. Also, with respect to the HF gas, it is preferable to store it in a tank other than the tank for storing the NH3 gas and the TMA gas and supply it into the processing container 31 in order to prevent unnecessary reactions of the HF gas with the NH3 gas and the TMA gas. That is, it is sufficient to store the HF gas in the tank of the gas supply path 51 and supply it into the processing container 31 via the valve of the gas supply path 51.

[0058] In addition, with respect to the recess 14 in which the SiOx film 11 is provided, it is not limited to a structure that is open toward the upper side (the thickness direction of the substrate), but can be a structure that is open toward the side. In addition, with respect to the positional relationship between the SiOx film 11 and the Si film 12, as long as the SiOx film 11 and the Si film 12 are adjacent to each other and each of them is exposed on the surface of the substrate W, the etching amount of the SiOx film 11 between the region in the vicinity of the interface of the Si film 12 and the region that is relatively separated from the interface can be controlled by the present technology. That is, the SiOx film 11 is not limited to being provided in the recess 14 in which the Si film 12 constitutes a side wall. Further, the present technology is not limited to being applied to a case in which the SiOx film and another kind of silicon-containing film are both exposed on the surface of the substrate as formed like this, but can be applied to a case in which the SiOx film 11 is provided on the entire surface of the substrate and etched.

[0059] Further, the side wall of the recess 14 in which the SiOx film 11 is provided is constituted by the Si film 12, and it is estimated that the level of the adsorptivity of the Si film 12 to the reaction product will intervene in the shape after the etching of the SiOx film 11 as described. The silicon-containing film other than the Si film 12 such as the SiGe film has low adsorptivity to the reaction product as with the Si film 12, and has high resistance to the etching gas (the halogen-containing gas and the alkaline gas) as described. Therefore, in a case in which the side wall of the recess 14 is not constituted by the Si film 12 but by the silicon-containing film other than the Si film 12 such as the SiGe film described above, it is considered that the etching using the etching gas is also effective.

[0060] The embodiments disclosed this time are to be considered merely illustrative and not restrictive in all aspects. The above-described embodiments can be omitted, substituted, altered, combined in various ways without departing from the scope of the appended claims and the subject matter thereof.

[0061] An evaluation test performed in association with the present technology is described below.

[0062] [Evaluation Test 1]

[0063] As the evaluation test 1, the energy (ΔG / eV) required for the adsorption of HF, NH3, TMA, AFS to SiN (silicon nitride), SiO (silicon oxide), Si, AFS respectively was calculated by simulation. The result thereof is shown as Table 1. Each value in the table is the energy thereof, and the smaller the value, the higher the adsorptivity.

[0064] [Table 1]

[0065] SiN SiO SI AFS HF -0.21 -0.02 0.24 -0.4 NH3 0.19 0.01 0.28 -0.23 TMA 0.18 -0.05 0.31 -0.24 AFS -0.31 -0.51 0.17 -1.24

[0066] As shown in this Table 1, the adsorptivity between AFS is high, and there is a tendency that molecules easily gather among each other. Also, AFS and NH3 are easily adsorbed to SiO, but AFS and NH3 are difficult to adsorb to Si. Therefore, in the case where NH3 gas is included as the etching gas, it is estimated that the reaction progresses as described by Figure 2 and the like. That is, it is considered that the selective etching of the SiOx film 11 with respect to the Si film 12, and the thickness of the AFS layer 15 becomes relatively small at the left and right end portions of the SiOx film 11 as shown in (d) of Figure 2 .

[0067] In addition, the adsorptivity of TMA with respect to SiO is relatively high, but the adsorptivity of TMA with respect to Si is relatively low. The adsorptivity of NH3 with respect to SiO, Si also has the same tendency as the adsorptivity of TMA with respect to SiO, Si. Therefore, as described by Figure 6 , it is known that in the case where both TMA gas and NH3 gas are used as the etching gas, it is possible to selectively etch the SiOx film 11 with respect to the Si film 12.

[0068] Also, as shown in Table 1, the adsorptivity of SiN to AFS is high compared to Si. Thus, in the case where etching is performed using NH3 gas as described by Figure 2 , it is difficult for the peeling of AFS to occur in the case where the side wall of the recess 14 is assumed to be formed by a SiN film, and it is estimated that the etching amount of the left and right end portions is suppressed. Thus, the side wall of the recess 14 can also be constituted by a SiN film, but it is considered that the effectiveness of the present technology is higher in the case where it is constituted by a Si film.

[0069] [Evaluation Test 2]

[0070] As the evaluation test 2, the same test apparatus as the etching apparatus 3 was used to etch the SiOx film 11 in the recess 14 by supplying the substrate on which each film was formed with the HF gas, the NH3 gas, and the TMA gas as described in the embodiment. These HF gas, NH3 gas, and TMA gas were supplied into the processing container 31 as shown in the drawing. Figure 1 Figure 7 Thus, each gas was supplied to the substrate at the same time as each other.

[0071] In this evaluation test 2, the processing was performed while changing the flow rate ratio of the NH3 gas to the TMA gas supplied into the processing container 31 for each substrate. Also, after the etching, the SEM image of each substrate was acquired, and the state of the recess 14 was observed. Specifically, the difference in height between the top of the Si film 12 and the central part of the SiOx film 11 on the left and right (which was set as the central etching depth), and the difference in height between the top of the Si film 12 and the end part of the SiOx film 11 on the left and right (which was set as the end etching depth) were acquired, respectively. Also, the difference between the end etching depth and the central etching depth was calculated as the difference in etching depth. Thus, the smaller the absolute value of the difference in etching depth, the higher the uniformity of the height of the surface of the SiOx film 11. That is, the higher the uniformity of the etching at the surface of the SiOx film. In the following description, sometimes the value obtained by dividing the flow rate of the TMA gas supplied into the processing container 31 by the flow rate of the NH3 gas supplied into the processing container 31 (that is, the ratio of the flow rate of the amine gas to the flow rate of the ammonia gas) is noted as "TMA gas flow rate / NH3 gas flow rate".

[0072] As for the above TMA gas flow rate / NH3 gas flow rate, in the evaluation test 2-1, it was set to 11:1, in the evaluation test 2-2, it was set to 9:3, in the evaluation test 2-3, it was set to 7:5, in the evaluation test 2-4, it was set to 1:1, in the evaluation test 2-5, it was set to 5:7, in the evaluation test 2-6, it was set to 3:9, and in the evaluation test 2-7, it was set to 1:11. Thus, as for the flow rate ratio, in the evaluation test 2-1, it was 11 (=11 / 1), in the evaluation test 2-2, it was 3 (=9 / 3), in the evaluation test 2-3, it was 1.4 (=7 / 5), in the evaluation test 2-4, it was 1 (=1 / 1), in the evaluation test 2-5, it was 0.71 (=5 / 7), in the evaluation test 2-6, it was 0.33 (=3 / 9), and in the evaluation test 2-7, it was 0.09 (=1 / 11).

[0073] Figure 9 Figure 10 Figure 11 ​​​The image shows the results of Evaluation Test 2. The graph only shows the results of Evaluation Tests 2-1, 2-3, 2-5, and 2-7. The horizontal axis of the graph represents the TMA gas / NH3 gas flow rate ratio, and the vertical axis represents the above-mentioned etching depth difference, with the scale marked in intervals of specified numerical values ​​(denoted as A in the graph). As can be seen from the graph, the absolute value of the etching depth difference is relatively large in Evaluation Test 2-1, but the absolute value of the etching depth difference is relatively small in Evaluation Tests 2-3, 2-5, and 2-7, indicating that the height uniformity of the SiOx film 11 is high.

[0074] Furthermore, the images show that, for the SiOx film 11, as the TMA gas flow rate / NH3 gas flow rate ratio decreases, the surface of the SiOx film 11 becomes more convex, with the left and right edges lower than the center. Furthermore, as the TMA gas flow rate / NH3 gas flow rate ratio increases, the surface of the SiOx film 11 becomes more concave, with the left and right edges higher than the center. In Evaluation Tests 2-1 and 2-2, the SiOx film 11 exhibits a pronounced concave shape, with a significant difference between the left and right center and the left and right edges. However, in Evaluation Tests 2-3 to 2-7, this difference between the left and right center and the left and right edges is minimized, resulting in a relatively high surface flatness for the SiOx film 11. The images show that the surface flatness is particularly high in Evaluation Tests 2-3 to 2-6. Therefore, Evaluation Test 2 demonstrates that, when supplying TMA gas and NH3 gas to a substrate with overlapping supply periods, it is preferable to set the TMA gas flow rate / NH3 gas flow rate ratio to a value less than 3, and more preferably to a value between 0.33 and 1.4.

[0075] [Evaluation Test 3]

[0076] As the evaluation test 3, the same as the evaluation test 2 was performed. Figure 7 As shown in the figure, each etching gas was supplied to each of the multiple substrates to etch the SiOx film 11. In this evaluation test 3, etching was performed at different temperatures for each substrate, rather than maintaining a constant TMA gas flow rate and NH3 gas flow rate for each substrate. Specifically, in evaluation tests 3-1, 3-2, and 3-3, the substrate temperatures were set to 80°C, 90°C, and 100°C, respectively.

[0077] Figure 12 The image shows the results of Evaluation Test 3. In Evaluation Test 3-3, the tendency to become a concave shape was the greatest, while in Evaluation Test 3-1, the tendency to become a concave shape was the smallest.

[0078] It is considered that this is caused by sublimation of AFS as explained in the embodiment. Also, in Evaluation Test 3-1, 3-2, the planarity of the surface of the SiOx film 11 was relatively high. Thus, according to this Evaluation Test 3, it was confirmed that as the temperature of the substrate at the time of etching treatment, it is preferable to be set to less than 100°C, and more preferable to be set to 90°C or less.

[0079] BRIEF DESCRIPTION OF DRAWINGS

[0080] W: wafer; 11: SiOx (silicon oxide) film; 21: etching gas (HF gas, NH3 gas); 22: etching gas (HF gas, TMA gas).

Claims

1. An etching method, comprising an etching step, In the etching step, a halogen-containing gas, ammonia gas, and amine gas are supplied as etching gases to a substrate having a silicon oxide film formed on a surface thereof to etch the silicon oxide film.

2. The etching method according to claim 1, wherein The silicon oxide film and the silicon-containing film of a different type from the silicon oxide film are provided on the surface of the substrate so as to be adjacent to each other and to be exposed. The etching process includes the following steps: The silicon oxide film is selectively etched from among the silicon oxide film and the silicon-containing film.

3. The etching method according to claim 2, wherein: The silicon-containing film of a different kind from the silicon oxide film is a silicon film.

4. The etching method according to claim 3, wherein: A concave portion having sidewalls formed by the silicon film is provided on the surface of the substrate. The etching step includes etching the silicon oxide film formed in the recess.

5. The etching method according to claim 1, wherein A cycle consisting of an etching period and an exhaust period is repeated, wherein The etching period is a period during which at least one of the etching gases is supplied to the substrate. The exhaust period is a period during which the supply of each etching gas to the substrate is stopped after the etching period, and the area around the substrate is exhausted.

6. The etching method according to claim 5, wherein: The periods during which the halogen-containing gas, the ammonia gas, and the amine gas are supplied to the substrate overlap with each other.

7. The etching method according to claim 5, wherein: The periods during which the ammonia gas and the amine gas are supplied to the substrate overlap with each other. A ratio of a flow rate of the amine gas supplied to the substrate to a flow rate of the ammonia gas is less than 3.

8. An etching device comprising: a processing container that stores a substrate having a silicon oxide film formed on a surface thereof; and The gas supply mechanism supplies a halogen-containing gas, an ammonia gas, and an amine gas as etching gas to etch the silicon oxide film.

Images