Etching method and etching apparatus

Abstract

To increase the controllability of the etching amount in each portion in a plane of a substrate when etching an oxygen-containing silicon film embedded in a plurality of concave portions different from each other in opening width in the substrate.SOLUTION: An etching method is arranged to supply an etching gas to a substrate having a plurality of concave portions different from each other in opening size, and to etch an oxygen-containing silicon film embedded in each concave portion. The etching method comprises: an adsorption step of supplying an organic amine compound gas to the substrate to cause the oxygen-containing silicon film to adsorb the gas; a desorption step of causing an excess amount of the organic amine compound gas to desorb from the substrate; and an etching step of supplying the halogen-containing etching gas to the substrate with the organic amine compound adsorbed thereon to selectively etch the oxygen-containing silicon film for each concave portion.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] When forming a semiconductor device, etching is performed on a silicon film containing oxygen, such as a SiOx (silicon oxide) film, formed on a semiconductor wafer (hereinafter referred to as a wafer) which is a substrate. For example, Patent Document 1 describes supplying HF (hydrogen fluoride) gas and an organic amine compound gas to etch the SiOx film.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides a technique capable of enhancing controllability of an etching amount in each part in the plane of a substrate when etching a silicon film containing oxygen embedded in a plurality of recesses having different opening widths from each other in the substrate.

Means for Solving the Problems

[0005] The etching method of the present disclosure is an etching method of supplying an etching gas to a substrate having a plurality of recesses with different opening sizes from each other and etching a silicon film containing oxygen embedded in each of the recesses, an adsorption step of supplying an organic amine compound gas to the substrate and adsorbing it on the silicon film containing oxygen; a desorption step of desorbing the excess organic amine compound gas from the substrate; the organic amine compound GasAn etching step of supplying the etching gas containing halogen to the substrate adsorbed with oxygen and selectively etching the silicon film containing oxygen with respect to each of the recesses; comprising; When a preset time has elapsed since the supply of the organic amine compound gas and the etching gas was started, the supply of the organic amine compound gas is stopped, while the supply of the etching gas continues.

[0006] Another etching method of the present disclosure is an etching method of supplying an etching gas to a substrate to etch a silicon film containing oxygen, an adsorption step of supplying an organic amine compound gas to the substrate and adsorbing it on the silicon film containing oxygen; Next, an inert gas is supplied to the substrate to desorb the excess organic amine compound gas from the substrate; Subsequently, an etching step of supplying the etching gas containing halogen to the substrate adsorbed with the organic amine compound to etch the silicon film containing oxygen; comprising.

Advantages of the Invention

[0007] When etching a silicon film containing oxygen embedded in a plurality of recesses having different opening widths from each other on a substrate, the present disclosure can improve the controllability of the etching amount in each part in the plane of the substrate.

Brief Description of the Drawings

[0008]

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Embodiments for Carrying Out the Invention

[0009] The etching apparatus 1 according to an embodiment of the etching apparatus of the present disclosure is shown in FIG. 1, and this etching apparatus 1 is configured to be able to perform the first to third etching methods described later. To describe the outlines of the first to third etching methods first, for the SiOx film, which is a silicon (Si) film containing oxygen formed on the surface of the wafer W, etching is performed using HF (hydrogen fluoride) gas, which is an etching gas, and trimethylamine (TMA) gas, which is an organic amine compound gas.

[0010] More specifically, as shown in the evaluation test later, the TMA gas has a high adsorptivity to the SiOx film and reacts with the HF gas to enhance the etching property of the HF gas with respect to the SiOx film. Utilizing this property, in the first to third etching methods, the SiOx film is selectively etched with respect to the films other than the SiOx film formed on the surface of the wafer W. Note that plasma is not used for etching.

[0011] The etching apparatus 1 includes a processing chamber 11, a stage 12, a shower head 13, an exhaust mechanism 14, and a piping system 15. The inside of the processing chamber 11 is evacuated by the above-described exhaust mechanism 14 including, for example, a vacuum pump, an exhaust pipe, and a valve provided in the exhaust pipe, and is set to a vacuum atmosphere at a desired pressure. Further, the above-described stage 12 provided in the processing chamber 11 includes a heater, and the wafer W placed on the stage 12 is heated to a desired temperature by the heater. Note that the processing chamber 11 is provided with a transport port for the wafer W that can be opened and closed, and the stage 12 is provided with a pin that can move up and down. The wafer W is transported between the transport mechanism of the wafer W that has entered the processing chamber 11 through the transport port and the stage 12, but illustration of these transport port and pin is omitted.

[0012] The shower head 13, which is an organic amine compound gas supply unit and an etching gas supply unit, is provided at the ceiling portion in the processing chamber 11 so as to face the stage 12, and supplies gas to the entire surface of the wafer W placed on the stage 12. The piping system 15 is configured to supply the above-described HF gas and TMA gas to the wafer W via the shower head 13. Next, the configuration of the piping system 15 will be described. The piping system 15 includes pipes 21A and 21B whose downstream sides are respectively connected to the shower head 13. The upstream side of the pipe 21A is connected to the supply source 23A of HF gas via the gas supply device 22A, and the upstream side of the pipe 21B is connected to the supply source 23B of TMA gas via the gas supply device 22B.

[0013] The downstream side of the pipe 25A is connected to the downstream side of the gas supply device 22A in the pipe 21A, and the upstream side of the pipe 25A is connected to the supply source 27 of an inert gas, for example, N 2 (nitrogen) gas via the gas supply device 26A. The downstream side of the pipe 25B is connected to the downstream side of the gas supply device 22B in the pipe 21B, and the upstream side of the pipe 25B is connected to N 2It is connected to the gas supply source 27. The gas supply devices 22A, 22B, 26A, and 26B are equipped with flow control devices such as valves and mass flow controllers so as to be able to control the on / off and flow rate of each gas supplied from the gas supply source to the downstream side.

[0014] In addition, the above N 2 The gas is used as the carrier gas for TMA gas, the carrier gas for HF gas, and the purge gas for purging the inside of the processing container 11. For example, during the processing of the wafer W, N is constantly supplied to the pipes 21A and 21B. 2 The gas is supplied. Thereby, when TMA gas or HF gas is supplied into the processing container 11, it is used as the carrier gas for the TMA gas or HF gas, and when neither HF gas nor TMA gas is supplied, it is used as the purge gas. In addition, N 2 Instead of the N gas, other inert gases such as Ar (argon) gas may be used as the carrier gas and the purge gas. Also, the shower head 13 that supplies the purge gas in this way, the heater of the stage 12 described above, and the exhaust mechanism 14 form a desorption mechanism for desorbing the excess TMA gas adsorbed on the wafer W in each etching method described later.

[0015] The etching apparatus 1 includes a control unit 10, and this control unit 10 is equipped with a program. Commands (each step) are incorporated into the program so that the processing of the wafer W described later is performed. This program is stored in a computer storage medium, such as a compact disk, hard disk, magneto-optical disk, DVD, etc., and installed in the control unit 10. The control unit 10 outputs control signals to each part of the etching apparatus 1 according to the program and controls the operation of each part. Specifically, the temperature of the wafer W by the heater of the stage 12, the on / off of each gas to the shower head 13 by the gas supply devices 22A, 22B, 26A, 26B, the pressure inside the processing container 11 by the exhaust mechanism 14, etc. are controlled.

[0016] FIG. 2 shows an example of the surface of the wafer W processed by the above-described etching apparatus 1, and the first to third etching methods described below will be described by taking as an example the case where processing is performed on this wafer W. A SiN (silicon nitride) film 31 is formed on the surface of the wafer W. Recesses 32 and 33 are formed in the SiN film 31 as patterns having different widths from each other. In FIG. 2, vertical cross-sections orthogonal to the extending direction of the recesses 32 and 33, which are grooves, are shown. That is, the recesses 32 and 33 extend in the front and back directions of the paper surface, respectively.

[0017] The width of the recess 32 is larger than the width of the recess 33. Therefore, the size of the opening (= width L1) of the recess 32 is larger than the size of the opening (= width L2) of the recess 33. The width L1 is, for example, 100 nm or more, and the width L2 is, for example, 100 nm or less. When the width L2 is within such a relatively small range, it is considered that clogging by TMA described below is likely to occur. The recesses 32 and 33 are filled with a SiOx film 34, and the SiOx film 34 and the SiN film 31 are exposed on the surface of the wafer W.

[0018] (First Etching Method) Subsequently, the first etching method according to an embodiment of the etching method of the present disclosure will be described with reference to FIG. 3, which is a flowchart showing the processing procedure, and FIG. 4, which is a timing chart showing the supply and cutoff of HF gas and TMA gas into the processing container 11. Also, schematic diagrams showing the surface state of the wafer W in FIGS. 5 to 10 will be appropriately referred to. In these schematic diagrams, the TMA gas is shown as 41 and the HF gas is shown as 42, respectively.

[0019] First, the wafer W described in FIG. 2 is placed on the stage 21 and heated to a preset temperature, and at the same time, the inside of the processing container 11 is evacuated so as to reach a preset pressure. In a state where the temperature of the wafer W and the pressure inside the processing container 11 are thus controlled, TMA gas 41 is supplied into the processing container 11 (time t1, step S1). Since the TMA gas 41 has a high adsorptivity to the SiOx film 34 and a low adsorptivity to the SiN film 31, it is selectively adsorbed on the surface of the SiOx film 34 embedded in the recesses 32 and 33 respectively (FIGS. 5A and 5B). Then, the supply of the TMA gas 41 into the processing container 11 is stopped (time t2, step S2), and the inside of the processing container 11 is purged with a purge gas.

[0020] Due to the supply of thermal energy from the heated wafer W, the evacuation inside the processing container 11, and the action of the purge gas, a part of the TMA gas 41 adsorbed on the wafer W desorbs from the wafer W, and a thin layer 43 of TMA is formed on the surface of the SiOx film 34 in each of the recesses 32 and 33 (FIG. 6A). This thin layer 43 is, for example, a molecular layer of TMA of about one layer. That is, it is a monolayer or a layer in which several molecules are overlapped.

[0021] When a preset time has elapsed from time t2, HF gas 42 is supplied into the processing container 11 (time t3, step S3). The HF gas 42 reacts with the TMA gas 41 forming the thin layer 43 on the SiOx film and is activated. The HF gas 42 thus activated reacts with the SiOx film 34, and the resulting reaction product sublimes. That is, the SiOx film 34 is etched (FIGS. 6B and 7A). Since the thickness of the above-described thin layer 43 is extremely small, the etching amount (etched film thickness) of each SiOx film 34 due to the above reaction is small. That is, the SiOx film 34 embedded in the recess 32 and the SiOx film 34 embedded in the recess 33 are both etched little by little, and the etching amounts are uniform. And, as shown in the evaluation test described later, the etching property of the HF gas 42 with respect to the SiN film 31 is low. Therefore, among the SiN film 31 and the SiOx film 34, the SiOx film 34 is selectively etched.

[0022] When a preset time has elapsed since time t3, the supply of HF gas 42 into the processing container 11 stops (time t4, step S4), and the HF gas 42 remaining in the processing container 11 is purged by the purge gas supplied into the processing container 11. Then, after a preset time has elapsed since time t4, TMA gas 41 is supplied into the processing container 11 (time t5), selectively adsorbed onto the surface of the SiOx film 34 etched at the above-mentioned times t3 to t4 (FIGS. 7B and 8A), and thereafter, the supply of TMA gas 41 into the processing container 11 stops (time t6). That is, the above-described steps S1 and S2 are executed again.

[0023] After the supply of TMA gas 41 stops at time t6, the inside of the processing container 11 is purged with the purge gas, and a part of the TMA gas 41 adsorbed on the SiOx film 34 is desorbed by the purge gas, exhaust, and supply of heat from the wafer W in the same manner as at times t2 to t3. Then, a thin layer 43 of TMA is formed again on the surface of each SiOx film 34 (FIG. 8B), and thereafter, HF gas 42 is supplied into the processing container 11 (time t7). That is, step S3 is executed again, and each SiOx film 34 is etched (FIGS. 9A and 9B). Also at the time of this re-etching, since TMA gas 41 is adsorbed on the surface of each SiOx film 34 and the thin layer 43 is formed, the SiOx films 34 in the recesses 32 and 33 are selectively etched with high uniformity and a slight reduction in film thickness. Thereafter, the supply of HF gas 42 into the processing container 11 stops (time t8). That is, step S4 is executed again.

[0024] For example, the cycle consisting of steps S1 to S4 is repeatedly performed thereafter, and the selective adsorption step of the TMA gas 41 onto the SiOx film 34, the desorption step of the excess TMA gas 41 from the SiOx film 34, and the etching step of the SiOx film 34 with the HF gas 42 are repeatedly performed in order. As a result, selective etching of the SiOx film 34 proceeds with high uniformity and in small amounts at each part within the plane of the wafer W. When the above cycle is repeated a preset number of times, the processing of the wafer W is completed, and the wafer W is carried out from the processing container 11. Regarding the wafer W after the completion of this processing, due to the progress of etching as described above, the uniformity of the etching amount of the SiOx film 34 in the concave portions 32 and 33 is high, and SiOx films 34 with a desired thickness remain in the concave portions 32 and 33, respectively (FIG. 10).

[0025] Although it has been described that desorption of the TMA gas from the wafer W occurs while the supply of the TMA gas and the HF gas is stopped, as described above, heat supply from the wafer W and exhaust in the processing container 11 contribute to desorption. Therefore, for example, such desorption also occurs during the supply of the TMA gas to the wafer W. That is, the desorption step of the TMA gas from the wafer W is not limited to being performed at a timing different from the adsorption step of the TMA gas, and may be performed in parallel with the adsorption step.

[0026] Further, the thin layer 43 during the supply of the HF gas is not limited to the configuration in which a single molecular layer or several molecules are stacked as described above, and may be a thicker layer, and its thickness is arbitrary. Since the adsorption amount of the TMA gas can be changed by controlling processing conditions such as the supply amount of the TMA gas to the wafer W and the temperature of the wafer W, the thickness of the thin layer 43 can be adjusted by changing the processing conditions.

[0027] By the way, in the above processing example, it has been described that the cycle consisting of steps S1 to S4 is repeated two or more times, but the number of repetitions of this cycle may be two. Also, the number of cycles may be one, that is, the steps S1 to S4 may be performed only once without repetition.

[0028] (Second Etching Method) Regarding the second etching method, with reference to FIG. 11, which is a timing chart showing the supply and cutoff of TMA gas 41 and HF gas 42 into the processing vessel 11, and FIGS. 12 to 13 showing the surface state of the wafer W, the differences from the first etching method will be mainly described. As described with reference to FIG. 2, the wafer W is placed on the stage 21 and heated to a preset temperature, and at the same time, the inside of the processing vessel 11 is evacuated so as to reach a preset pressure. In this state, TMA gas 41 and HF gas 42 are supplied into the processing vessel 11 (FIG. 12A, time t11).

[0029] TMA gas 41 is adsorbed on the surface of each SiOx film 34 in the recesses 32 and 33. Since both TMA gas 41 and HF gas 42 are being supplied, HF gas 42 quickly reacts with the adsorbed TMA gas 41, and the surface of the SiOx film 34 is etched. Then, newly TMA gas 41 is adsorbed on the etched surface of the SiOx film 34 and reacts with HF gas 42, so that the surface of the SiOx film 34 is further etched (FIG. 12B). Then, when a preset time has elapsed since the start of the supply of TMA gas 41 and HF gas 42, the supply of TMA gas 41 is stopped, while the supply of HF gas 42 into the processing vessel 11 continues (FIG. 13A, time t12).

[0030] The reason for changing to supply only HF gas 42 out of TMA gas 41 and HF gas 42 will be explained. In the explanation, FIGS. 14A and 14B, which are schematic diagrams showing the states considered to occur in the recess 33 of the SiN film 31, will also be referred to. FIG. 14A shows the state immediately before the supply of TMA gas 41 is stopped, and FIG. 14B shows the state after the supply of TMA gas 41 is stopped, respectively.

[0031] Until the supply of the TMA gas 41 is stopped, in the recesses 32 and 33 of the SiN film 31, as described above, the etching of the SiOx film 34 proceeds, the height of the surface of the SiOx film 34 decreases, and the depth of the groove having the surface of the SiOx film 34 as the bottom surface increases. For the groove having the SiOx film 34 as the bottom surface, the groove formed in the recess 32 is designated as 32A, and the groove formed in the recess 33 is designated as 33A.

[0032] When the depths of the grooves 32A and 33A increase in this way, for the groove 32A, due to its wide opening width, the TMA gas 41 and the HF gas 42 easily flow in. Therefore, the etching of the SiOx film 34 continues to proceed. On the other hand, for the groove 33A, due to its narrow opening width, the TMA gas 41 and the HF gas 42 hardly flow in. However, since the adsorptivity of the TMA gas 41 to the SiOx film 34 is high as described above, once the TMA gas 41 that has entered the groove 33A tends to adsorb and stay on the surface of the SiOx film 34 as shown in Fig. 14A, and further molecules of the TMA gas 41 adsorb and deposit on the adsorbed molecules of the TMA gas 41.

[0033] Thus, the deposition amount of the TMA molecules on the SiOx film 34 in the groove 33A increases, and the groove 33A is blocked. As a result, the supply of the HF gas 42 to the surface of the SiOx film 34 is inhibited. That is, the HF gas 42 cannot react with the TMA gas 41 adsorbed on the surface of the SiOx film 34 to etch the SiOx film 34. Therefore, in the recess 33, the etching of the SiOx film 34 stops or the etching rate decreases.

[0034] Therefore, as described above, at time t12, the supply of only the TMA gas 41 among the TMA gas 41 and the HF gas 42 is stopped. After the supply of the TMA gas 41 is stopped, due to the evacuation in the processing container 11, the application of thermal energy from the wafer W, and the purging action of the HF gas 42, the TMA gas 41 gradually desorbs from the surface of the SiOx film 34 in the groove 33A. On the other hand, the continuously supplied HF gas 42 enters the groove 33A and can react with the TMA gas 41 directly adsorbed on the surface of the SiOx film 34 due to the above-mentioned desorption. That is, the etching of the SiOx film 34 is resumed in the concave portion 33. Thus, after the supply of the TMA gas 41 is stopped, in the concave portion 33, the etching of the SiOx film 34 proceeds due to the remaining TMA gas 41 and the newly supplied HF gas 42.

[0035] In addition, when the supply of the TMA gas 41 is stopped at time t12 and the TMA gas 41 is adsorbed and remains on the surface of the SiOx film 34 also in the groove 32A, the SiOx film 34 in the groove 32A is etched by the HF gas supplied after time t12 and the TMA gas 41. When a preset time has elapsed from the time t12, the supply of the HF gas 42 into the processing container 11 is stopped (time t13), and the etching process is completed (Fig. 13B).

[0036] As described above, according to the second etching method, first, the adsorption process and the etching process of the TMA gas 41 are performed in parallel. After time t12 when the supply of the TMA gas is stopped, the desorption process of the excess TMA gas 41 and the etching process are performed in parallel. Thereby, it is possible to prevent the etching of the SiOx film 34 from stopping due to the excessive retention of the TMA gas 41 in the concave portion 33 with a relatively narrow opening width. Therefore, since the SiOx film 34 in the concave portion 33 can be etched deeper, the film thickness of the SiOx can be made the desired film thickness.

[0037] (Third etching method) In the above-described second etching method, as shown in FIG. 13B at the end of etching, it was shown that the etching amount of the SiOx film 34 differed between the recess 32 and the recess 33, but the etching amounts can also be made the same. In this third etching method, for example, similar to the second etching method, TMA gas 41 and HF gas 42 are supplied into the processing chamber 11 along the timing chart described with reference to FIG. 11, and the wafer W described with reference to FIG. 2 is processed.

[0038] Therefore, in this third etching method, the supply of TMA gas 41 and HF gas 42 to the wafer W is started at time t11 (FIG. 12A). Then, by these TMA gas 41 and HF gas 42, after etching progresses in each of the SiOx films 34 of the recesses 32 and 33 as described above, in the recess 33 with a narrow opening width, TMA gas 41 accumulates on the SiOx film 34, molecules of TMA are deposited, and the etching stops. On the other hand, for the recess 32, since the opening width is wide, both TMA gas 41 and HF gas 42 easily enter, so the etching of the SiOx film 34 progresses. As a result, as shown in FIG. 12B, the etching amount in the recess 32 becomes larger than the etching amount in the recess 33.

[0039] Thereafter, the supply of TMA gas 41 is stopped at time t12. When the supply of TMA gas 41 is stopped, in the recess 32, since the TMA gas 41 has been consumed due to the continuous etching until then, the amount of TMA gas 41 adsorbed on the SiOx film 34 is relatively small. Therefore, after the supply of TMA gas 41 is stopped, the etching amount of the SiOx film 34 in the recess 32 is zero or a very small amount.

[0040] On the one hand, as described in the explanation of the second etching method, at the above time t12, a large amount of TMA gas 41 is adsorbed on the SiOx film 34 in the recess 33. After the time t12, the desorption of the TMA gas 41 proceeds, and the etching of the SiOx film 34 resumes. However, even if the desorption proceeds to a certain extent, since a large amount of the TMA gas 41 was originally adsorbed on the SiOx film 34, the etching amount after the time t12 becomes relatively large. As a result, when the supply of the HF gas 42 is stopped at the time t13, as shown in FIG. 15, the etching amounts of the SiOx film 34 are made uniform between the recess 32 and the recess 33.

[0041] As described above, according to the third etching method, by utilizing the difference in the adsorption amount of the TMA gas 41 in the recesses 32 and 33 when the supply of the TMA gas is stopped, the etching amounts of the SiOx film 34 are made uniform between these recesses 32 and 33 having different opening widths. Regarding the adsorption amount of the TMA gas 41 on the SiOx film 34 in the recesses 32 and 33 at the time of stopping the supply of the TMA gas 41, it may be controlled by appropriately setting various processing conditions such as the flow rate of the TMA gas 41 and the temperature of the wafer W. However, although the third etching method has been described as making the etching amounts of the SiOx film 34 uniform between the recesses 32 and 33, various processing conditions may be set so that a desired difference occurs in the etching amount.

[0042] Incidentally, in the second and third etching methods, it was described that before the time t12 when the supply of HF gas alone is started, by simultaneously supplying TMA gas 41 and HF gas 42, a difference in the adsorption amount of TMA gas 41 occurs between the concave portion 32 and the concave portion 33. However, even if the TMA gas 41 and the HF gas 42 are supplied in order as in the first etching method, depending on the processing conditions such as the flow rate of the TMA gas 41, a relatively large amount of the TMA gas 41 is adsorbed on the concave portion 33, and a difference occurs between the concave portions 32 and 33. That is, regarding the second etching method and the second etching method described above, the TMA gas 41 and the HF gas 42 may be supplied in order before the time t12, and therefore, they are not necessarily supplied simultaneously. However, it is preferable because the etching time can be shortened by supplying these gases simultaneously.

[0043] As an example of the processing conditions for performing the first to third etching methods described above, the pressure in the processing container 11 is 0.13332 Pa to 13332 Pa. Also, the flow rate of the HF gas supplied into the processing container 11 is 0.1 sccm to 2000 sccm, the flow rate of the TMA gas supplied into the processing container 11 is 0.1 sccm to 1000 sccm, and the flow rate of the N 2 gas supplied into the processing container 11 is 0.1 sccm to 2000 sccm. And the temperature of the wafer W is -50°C to 200°C. By performing the processing with the wafer W at such a temperature, it is possible to adsorb a gas of an organic amine compound such as TMA and etch SiOx (that is, sublime the reaction product). That is, it is preferable because there is no need to change the temperature of the wafer W during the processing described in the first to third etching methods above.

[0044] Incidentally, although the film for forming the recesses 32 and 33 in which the SiOx film 34 is embedded has been described as being composed of SiN, it is not limited to being composed of the SiN, and may be composed of other silicon-containing materials. For example, it may be composed of Si, SiC (silicon carbide), SiOC, SiCN, or SiOCN. Even in that case, by selectively adsorbing the TMA gas to the SiOx film 34, the SiOx film 34 can be selectively etched. Further, as the silicon film containing oxygen that is selectively etched with respect to the recesses 32 and 33, in addition to the SiOx film, an SiOCN film described later, tetraethyl ortho silicate (TEOS) shown in the evaluation test described later, etc. may be used. Therefore, the silicon film containing oxygen is not limited to the SiOx film. Note that containing oxygen means containing as a main component constituting the film, not containing as an impurity.

[0045] Incidentally, although an example in which trimethylamine (TMA) gas is used as the organic amine compound gas has been shown, it is not limited to the TMA gas, and a gas of a known organic amine compound can be used. Specifically, for example, gases of organic amine compounds such as monomethylamine, dimethylamine, dimethylethylamine, diethylmethylamine, monoethylamine, diethylamine, triethylamine, mononormalpropylamine, dinormalpropylamine, monopropylamine, monoisopropylamine, diisopropylamine, monobutylamine, dibutylamine, monotertiarybutylamine, ditertiarybutylamine, pyrrolidine, piperidine, piperazine, pyridine, pyrazine can be used.

[0046] As other specific examples of the organic amine compound, compounds in which some or all of the C-H bonds of the above compounds are C-F bonds (such as trifluoromethylamine, 1,1,1-trifluorodimethylamine, perfluorodimethylamine, 2,2,2-trifluoroethylamine, perfluoroethylamine, bis(2,2,2-trifluoroethyl)amine, perfluorodiethylamine, 3-fluoropyridine, etc.) can be used. These organic amine compounds have a pKa of the conjugate acid of 3.2 or higher than that of HF, can form a salt with HF, have a certain vapor pressure in the temperature range of 20 to 100 °C, and furthermore do not decompose in this temperature range and can be supplied as a gas, which is preferable.

[0047] In addition, as the etching gas, those containing halogen can be used. Besides HF containing fluorine as the halogen, gases of compounds such as HCl, HBr, HI, SF 4 etc. can be used. In FIG. 2, although the recesses of the SiN film in which SiOx is embedded are described as grooves, they may also be holes. That is, the present technology can also be applied when a plurality of holes having different opening diameters (= sizes of the openings) are provided in the SiN film and the SiOx film embedded in each hole is selectively etched.

[0048] It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The above embodiments may be omitted, substituted, changed, and / or combined in various forms without departing from the scope and spirit of the appended claims.

[0049] Subsequently, the evaluation tests conducted in relation to the present technology will be described. · Evaluation Test 1 As Evaluation Test 1, the adsorption energies of TMA on each of the SiN film and the SiOx film in the range of -50 °C to 200 °C were measured by simulation. Regarding the adsorption energy, the lower value indicates a more stable state as a molecule of TMA, that is, it is more likely to be adsorbed.

[0050] Figure 16 is a graph showing the results of this evaluation test 1. For this graph, the horizontal axis represents temperature (unit: °C), and the vertical axis represents the adsorption energy (unit: eV), respectively. As shown in this graph, when comparing the adsorption energy for the SiOx film and the adsorption energy for the SiN film at the same temperature, the adsorption energy for the SiOx film is lower.

[0051] Also, as shown in the graph, for each of the SiN film and the SiOx film, as the temperature increases, the value of the adsorption energy increases. However, for the SiOx film, even at 200 °C, the adsorption energy was still slightly higher than 0 eV. That is, in the temperature range (-50 °C to 200 °C) of this evaluation test 1, it can be seen that TMA has a high adsorption property for SiOx. Therefore, from the results of this evaluation test 1, it was confirmed that for TMA, in the range of -50 °C to 200 °C, among the SiN film and the SiOx film, it selectively adsorbs to the SiOx film. Such a result is considered to be due to the formation of a hydrogen bond between the nitrogen atom of TMA and the hydrogen atom (existing bonded to the oxygen atom) in the SiOx film, and the dipole interaction acting between the polarized TMA and the polarized SiOx. It is considered that other organic amines than TMA also selectively adsorb to the SiOx film for the same reason.

[0052] · Evaluation Test 2 As evaluation test 2, an etching process was performed by supplying TMA gas and HF gas to each of the SiOx film and the SiN film formed on the substrate. This etching process was performed on a plurality of substrates, and for each process, the combination of the pressure in the processing container 11 and the supply time of each gas was changed. Then, the etching amount of each film was measured for the processed substrates, and the etching selectivity was calculated as the etching amount of the SiOx film / the etching amount of the SiN film.

[0053] The SiOx film was formed by heat-treating Si in an oxygen-containing atmosphere, and the SiN film was formed by ALD. The pressure in the processing chamber 11 was set to 2.1 Torr (280 Pa), 3 Torr (400 Pa), or 4 Torr (533.2 Pa), and the supply time of each gas was set to 5 seconds, 10 seconds, or 30 seconds. Each etching process was performed with the temperature of the wafer W set to 140°C.

[0054] The results of Evaluation Test 2 are shown in Fig. 17. In Fig. 17, the bar graph represents the etching amount of the SiOx film, and the line graph represents the etching selectivity. Note that in each etching process, the etching amount of the SiN film was extremely small (less than 1 nm), so it is not shown in the graph. As is clear from the graph, for any combination of the supply time of each gas and the pressure in the processing chamber 11, the etching amount and etching selectivity of the SiOx film were relatively large values. Also, from the graph, it can be seen that the higher the pressure in the processing chamber 11, the greater the tendency for the etching amount of the SiOx film to be larger, and thus the etching selectivity also becomes larger. Specifically, when the pressure in the processing chamber 11 was 4 Torr and the supply time of the gas was 30 seconds, the etching amount of SiOx was 205 nm and the etching selectivity was 316, which were the largest values for each of the etching amount and etching selectivity.

[0055] From the results of this Evaluation Test 2, it can be seen that when etching the SiOx film with HF gas, the SiOx film can be selectively etched with respect to the SiN film by supplying TMA gas. Furthermore, from the results of this Evaluation Test 2, it was confirmed that the SiOx film can be etched at the temperature at which the TMA gas is adsorbed. That is, it was confirmed that there is no need to switch the temperature of the wafer W between when the TMA is adsorbed and when the reaction product generated by the reaction of TMA, HF gas, and SiOx is sublimated.

[0056] · Evaluation Test 3 As Evaluation Test 3, the supply of TMA gas and HF gas was performed according to the cycle of FIG. 3 described in the above-described first etching method, and each of the SiOx film and the TEOS film formed on the substrate was etched. The number of cycles was changed for each etching process. The SiOx film was formed by heat-treating Si in an oxygen atmosphere, similar to the SiOx film in Evaluation Test 2.

[0057] The graph in FIG. 18 shows the results of Evaluation Test 3. The horizontal axis and the vertical axis of the graph indicate the number of cycles and the etching amount (unit: nm), respectively. As shown in the graph, for each of the SiOx film and the TEOS film, the number of cycles and the etching amount are generally in a proportional relationship, and the etching amount in one cycle is about 5 nm for the SiOx film and about 6 nm for the TEOS film. Thus, for each of the SiOx film and the TEOS film, the etching amount in one cycle was at the atomic layer level.

[0058] As described above, from the results of Evaluation Test 3, by performing the cycle described in the first etching method, atomic layer etching is possible for a silicon film containing oxygen, and it was confirmed that by repeating the cycle, it can be controlled to obtain a desired etching amount. Therefore, as described as the first etching method, it is considered that the etching amount of the silicon film containing oxygen in each part in the plane of the wafer W can be set to a desired value and the uniformity in the plane of the wafer W can be made high.

[0059] · Evaluation Test 4 For a substrate provided with a SiN film in which a recess that is a groove is formed and the SiOx film is embedded in the recess, the SiOx film was etched. Then, the longitudinal side surface of the substrate after the etching process was imaged, and the depth of the groove formed by the etching (= etching amount of the SiOx film) was measured. The width at the opening of the recess is 1 nm.

[0060] In this evaluation test 4, the above etching is performed by changing the gas supply method for each substrate. For one substrate, HF gas and TMA gas were simultaneously supplied to the wafer W as shown by the time t11 to t12 in the timing chart of FIG. 11. However, the supply of HF gas alone after the time t12 in this timing chart was not performed. The test conducted by supplying each gas in this manner is defined as evaluation test 4-1.

[0061] For other substrates, the gas was supplied as shown in the timing chart of FIG. 11. That is, after simultaneously supplying HF gas and TMA gas, the supply of HF gas alone was performed. Except for performing the supply of HF gas alone, etching was performed under the same processing conditions as in evaluation test 4-1. The test conducted by supplying each gas in this manner is defined as evaluation test 4-2.

[0062] FIG. 19 is a schematic diagram of the images obtained from the substrates in evaluation tests 4-1 and 4-2. Regarding the depth of the formed grooves, they were 21 nm and 36 nm in evaluation test 4-1 and evaluation test 4-2 respectively, and the value in evaluation test 4-2 was larger. In evaluation test 4-1, after the adsorption of TMA gas progressed and the deposition of TMA molecules became excessive, it is considered that the etching stopped because HF gas was no longer supplied to the SiOx film. On the other hand, in evaluation test 4-2, after the supply of TMA gas stopped, as explained in the second etching method, the desorption of TMA gas from the wafer W progressed, so HF gas was supplied to the SiOx film, and it is considered that the etching progressed more than in evaluation test 4-1. Therefore, according to this evaluation test 4, it was confirmed that by supplying HF gas alone after supplying TMA gas and HF gas, it is possible to increase the etching amount.

[0063] · Evaluation test 5 As Evaluation Test 5-1, the cycle consisting of Steps S1 to S4 described in FIGS. 3 and 4 was performed 5 times on a substrate with a SiOx film formed on its surface. Therefore, in one cycle, HF gas was supplied after the supply of TMA gas. When repeating the cycle, during the supply of TMA gas and HF gas, purge gas was supplied into the processing container storing the substrate and the processing container was evacuated. The time for one cycle was 30 seconds, and the temperature of the substrate during processing was 40°C. After performing etching in this way, water was supplied to the surface of the processed substrate to elute the components contained in the substrate into the water. Then, the fluorine content was measured for the water by ion chromatography.

[0064] Also, as Evaluation Test 5-2, the same substrate with a SiOx film formed on its surface as in Evaluation Test 5-1 was treated with TMA gas and HF gas, and the fluorine content was measured for the water supplied to the surface of the processed substrate using ion chromatography. For this Evaluation Test 5-2, the simultaneous supply of TMA gas and HF gas to the substrate for 4 seconds can be cited as the difference from Evaluation Test 5-1. Note that in both Evaluation Tests 5-1 and 5-2, the etching process was performed with the substrate temperature within the range described above.

[0065] In Evaluation Test 5-1, the fluorine content was 3.0×10 14 atom / cm 2 and in Evaluation Test 5-2, the fluorine content was 5.8×10 14 atom / cm 2 Thus, the fluorine content in Evaluation Test 5-1 was a smaller value. Therefore, it can be understood from this Evaluation Test 5 that by supplying an etching gas containing a halogen after an organic amine compound gas and etching a silicon film containing oxygen, the amount of halogen remaining on the substrate after etching can be kept low. The above test results were obtained because, as described above, the organic amine compound has a relatively high adsorptivity to the SiOx film, forming a protective film on the SiOx film and suppressing the penetration of the subsequently supplied HF gas into the substrate.

[0066] In Evaluation Test 5, TMA gas, that is, an organic amine compound gas in which an amino group is bonded to a branched alkyl group, was used as the organic amine compound gas. However, it is more preferable to use a gas of an organic amine compound in which an amino group is bonded to a linear alkyl group without branching. To explain the reason, it is considered that the adsorption of the organic amine compound to the oxygen-containing silicon film is caused by the adsorption of the amino group in the organic amine compound to the oxygen-containing silicon film. When the organic amine compound is composed of a branched alkyl group, it is considered that the side chain of the alkyl group interferes with the film, thereby preventing the contact of the amino group in the same molecule as the alkyl group with the film. Further, if a large number of molecules of the organic amine compound are adsorbed on the film, the side chains of the respective molecules will interfere with each other. In order to prevent such interference, the number of molecules of the organic amine compound adsorbed per unit area of the film is considered to be relatively small, and the gaps between the molecules are considered to be relatively large.

[0067] However, when an organic amine compound having a linear alkyl group is used, since there is no side chain of the alkyl group, the above-described inhibition of the adsorption of the amino group to the film by the side chain and the interference between the side chains of the molecules do not occur. Therefore, the adsorption of the molecules of the organic amine compound to the oxygen-containing silicon film is more reliably and densely performed, and thus it is considered that the effect as a protective film for suppressing the penetration of halogen into the substrate can be more reliably obtained.

[0068] By the way, as described above, when the amino group adsorbs to the film, as a linear alkyl group viewed from the amino group, it extends toward the opposite side of the film. Therefore, the longer the number of carbons in this linear alkyl group, the longer it is, and when viewed as the above protective film, it is thicker and the function as the protective film is higher, which is more preferable. From the above, as the organic amine compound gas, C n H 2n+1 which has a linear alkyl group represented as and indicates the number of carbon atoms C n H 2n+1It is preferable to use an organic amine compound in which n in the formula is an integer of 4 or more. Specifically, for example, it is preferable to use butylamine, hexylamine, octylamine, decylamine, or the like.

[0069] Even if the alkyl group has a branched structure, if the above-mentioned n (= number of carbon atoms) is relatively large, it is considered that the penetration of halogen can be sufficiently prevented. In addition to octylamine and decylamine having a linear alkyl group exemplified as a specific example, for example, decylamine having a branched alkyl group represented by the following Molecular Formula 1 is known to have relatively high corrosion resistance with respect to the metal surface, that is, to have high protective performance. Therefore, even when used as a protective film for the above-mentioned oxygen-containing silicon film, it is considered that the above-mentioned penetration can be sufficiently prevented. Therefore, for example, it is more preferable that n is 10 or more. Each of the amines described above can be used in each of the etching methods described in the embodiments. Therefore, while obtaining the effects described in each embodiment, it is possible to suppress the residual of halogen such as fluorine in the processed wafer W, and suppress the influence of the halogen on the post-etching process of the wafer W. Molecular Formula 1 TIFF0007683343000001.tif2472

[0070] W wafer 32, 33 recesses 34 SiOx film 41 TMA gas 42 HF gas

Claims

1. In an etching method of supplying an etching gas to a substrate having a plurality of recesses with different opening sizes and etching a silicon film containing oxygen embedded in each of the recesses, an adsorption step of supplying an organic amine compound gas to the substrate and adsorbing it on the silicon film containing oxygen; a desorption step of desorbing the excess organic amine compound gas from the substrate; an etching step of supplying the etching gas containing halogen to the substrate on which the organic amine compound gas is adsorbed and selectively etching the silicon film containing oxygen with respect to each of the recesses; comprising: When a preset time has elapsed since the supply of the organic amine compound gas and the etching gas was started, the supply of the organic amine compound gas is stopped while the supply of the etching gas continues.

2. After the adsorption step, the desorption step and the etching step are performed in parallel, The etching method according to claim 1, wherein the desorption step includes a step of supplying only the etching gas among the organic amine compound gas and the etching gas to the substrate.

3. The etching method according to claim 2, wherein the adsorption step and the etching step are performed in parallel.

4. The etching method according to any one of claims 1 to 3, wherein the recess is made of a material containing silicon.

5. The etching method according to claim 4, wherein the material containing silicon is silicon nitride.

6. The organic amine compound gas is a gas of a compound having a linear alkyl group represented by C ｎ H ２ｎ＋１ and having n of 4 or more, and the etching method according to any one of claims 1 to 5.

7. In an etching apparatus for supplying an etching gas to a substrate having a plurality of recesses with different opening widths and etching a silicon film containing oxygen embedded in each of the recesses, a processing chamber; a stage for placing the substrate provided in the processing chamber; an organic amine compound gas supply unit for supplying an organic amine compound gas into the processing chamber so as to be adsorbed on the silicon film containing oxygen; a desorption mechanism for desorbing the excess organic amine compound gas from the substrate; an etching gas supply unit for supplying the etching gas containing halogen into the processing chamber and selectively etching the silicon film containing oxygen on which the organic amine compound gas is adsorbed with respect to each of the recesses; comprising: An etching apparatus that stops the supply of the organic amine compound gas while continuing the supply of the etching gas when a preset time has elapsed since the start of the supply of the organic amine compound gas and the etching gas.

Images