Etching method and etching apparatus

Abstract

To effectively etch the SiOCN film. [Solution] A method for etching a SiOCN film formed on a substrate, wherein the SiOCN film is etched by exposing it to a plasma generated from an etching gas containing a fluorine-containing gas, an oxygen-containing gas, and a hydrogen gas that does not contain nitrogen. When etching the SiOCN film, good etching can be performed so that the film surface has a smooth surface texture, and also the SiN film, O x It is possible to selectively etch SiOCN films against films such as Si films and SiGe films.

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 may be a case of etching a carbon-containing silicon oxide film formed on the surface of a semiconductor wafer (hereinafter also referred to as a wafer) which is a substrate. In Patent Document 1, it describes etching a carbon-containing silicon oxide film having less than about 30 atomic% carbon and containing less than about 50 atomic% hydrogen using a plasma of a gas having NH3 and C x F y and being.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The technology according to the present disclosure provides a technology capable of etching a SiOCN film well.

Means for Solving the Problems

[0005] One aspect of the present disclosure is a method for etching a SiOCN film formed on a substrate, the method comprising exposing the SiOCN film to a plasma generated from an etching gas containing a fluorine-containing gas not containing N, an oxygen-containing gas, and hydrogen gas for etching.

Effects of the Invention

[0006] According to the present disclosure, a SiOCN film can be etched well.

Brief Description of the Drawings

[0007] [Figure 1] This is a longitudinal cross-sectional side view of an etching apparatus that performs etching. [Figure 2] This is a longitudinal cross-sectional side view of a heat shield plate in an etching apparatus. [Figure 3] This graph shows the amount of etching when plasma etching is performed using NF3, HF, and F2. [Figure 4] These are SEM images of the film surface when using a gas containing NF3 as the etching gas and when using a fluorine-containing gas that does not contain nitrogen. [Modes for carrying out the invention]

[0008] The etching method and etching apparatus according to this embodiment will be described below with reference to the drawings. In this specification, elements having substantially the same functional configuration are denoted by the same reference numerals, and redundant explanations will be omitted.

[0009] <Wafer Processing Equipment> Figure 1 is a longitudinal cross-sectional view showing a schematic configuration of the etching apparatus 1 according to this embodiment. The etching apparatus 1 includes a processing container 11 for storing a substrate W (hereinafter also referred to as wafer W). This processing container 11 includes a container body 12 and a lid 13. The container body 12 forms the bottom wall and the lower side of the side wall of the processing container 11, and the lid 13 forms the top wall and the upper side of the side wall of the processing container 11. A horizontal partition plate 21 is provided inside the processing container 11, dividing the inside of the processing container 11 into a processing space S surrounded by the container body 12 and a plasma generation space P surrounded by the lid 13. Below the partition plate 21, a heat shield plate 23 is horizontally arranged to divide the inside of the processing container 11 vertically, similar to the partition plate 21.

[0010] An exhaust mechanism 14 equipped with a vacuum pump is connected to the bottom of the container body 12, which exhausts the inside of the processing container 11 to create a reduced pressure (vacuum) atmosphere of the desired pressure. A stage 15 is provided in the processing space S, and the wafer W is processed while placed horizontally on the upper surface of the stage 15. The upper surface of this stage 15 faces the heat shield plate 23. In one embodiment, two stages 15 may be provided so that two wafers W can be processed at once. In that case, these two stages 15 are aligned in the X direction in Figure 1, so only one of the stages 15 is shown in Figure 1.

[0011] A temperature control mechanism 16 for adjusting the temperature of the wafer W placed on it is embedded in the stage 15. The temperature control mechanism 16 consists of, for example, a flow path through which a fluid whose temperature has been controlled by a chiller flows, and a heater. Reference numeral 17 in the figure indicates the wafer W transfer port, which is an opening in the side wall of the container body 12 so that a transfer mechanism (not shown) can transfer the wafer W to the stage 15, and is opened and closed by a gate valve 18. In the figure, 15A is a lifting mechanism that raises and lowers the stage 15 for this transfer.

[0012] Outside the processing vessel 11, a first gas supply unit 31 and a second gas supply unit 32 are provided. The first gas supply unit 31 includes a storage unit for each of the following gases, HF gas, F2 gas, O2 gas, H2 gas, and noble gases, so that these gases can be supplied to the plasma generation space P, and a flow rate adjustment mechanism for adjusting the flow rate of the gases from the storage unit to the plasma generation space P. The flow rate adjustment mechanism is composed of, for example, valves and a mass flow controller. The noble gas, which is an inert gas, is specifically, for example, Ar (argon) gas, and plays a role in plasma formation and regulating the pressure inside the processing vessel 11.

[0013] The second gas supply unit 32 is equipped with a gas storage unit and a flow rate adjustment mechanism, similar to the first gas supply unit 31, so that it can supply an inert gas, such as N2 (nitrogen) gas, to the processing space S via the heat shield plate 23. This N2 gas is used as a pressure regulating gas in the processing container 11 and as a diluent gas for the etching gas.

[0014] Figure 2 is a longitudinal cross-sectional side view of the heat shield plate 23 in the etching apparatus 1. As shown in Figure 2, two partition plates 21 are provided side by side, one above the other, with a gap between them. Each of these two partition plates 21 has multiple through holes 22. The positions of the through holes 22 in the upper partition plate 21 and the through holes 22 in the lower partition plate 21 are different in a plan view. This offset in the positions of the through holes 22 allows the two partition plates 21 to function as a so-called ion trap, suppressing the supply of ions in the plasma generated in the plasma generation space P to the processing space S. Therefore, radicals, which are among the ions and radicals that are active species of the plasma, are selectively supplied to the processing space S to perform etching.

[0015] The heat shield 23 plays a role in suppressing the influence of heat accumulated on the partition plate 21 by repeated plasma generation in the plasma generation space P on the distribution of radicals in the processing space S. The peripheral edge of the heat shield 23 forms a flange embedded in the side wall of the container body 12, and the heat shield 23 is cooled by a cooling mechanism 24 embedded in this flange. This cooling mechanism 24 is composed of, for example, a flow path through which a fluid whose temperature has been regulated by a chiller flows, or a Peltier element.

[0016] Multiple through-holes 26 are formed in the heat shield plate 23 to allow radicals to be introduced from the plasma generation space P to the processing space S. In a plan view, each through-hole 26 overlaps with the through-holes 22 of the lower partition plate 21. In addition, numerous gas outlets 27 are opened on the lower surface of the heat shield plate 23. The gas supplied from the second gas supply unit 32 is supplied to the processing space S in a shower-like manner from the gas outlets 27 through a flow path formed inside the heat shield plate 23. Therefore, the heat shield plate 23 is configured as a showerhead. Note that the through-holes 26 of the heat shield plate 23 and the through-holes 22 of the partition plate 21 are omitted from Figure 1 to avoid cluttering the diagram.

[0017] The lid 13 of the processing container 11 is made of, for example, quartz and is configured as a dielectric window. An annular high-frequency antenna 33 is formed on the lid 13, and the high-frequency antenna 33 is connected to a high-frequency power source 35 via a matcher 34. By outputting high-frequency power of a predetermined frequency (for example, 13.56 MHz or higher) from the high-frequency power source 35, an inductively coupled plasma is generated from each gas supplied to the plasma generation space P. The high-frequency antenna 33, the matcher 34, and the high-frequency power source 35 constitute a plasma generation mechanism.

[0018] The etching apparatus 1 described above is provided with at least one control unit 10. This control unit 10 is, for example, a computer and includes a program, memory, and a CPU. The program incorporates instructions (each step) to perform the wafer W processing and wafer W transport as described above. This program is stored on a 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 using the program, and controls the operation of each part. Such controlled operations include, for example, adjusting the temperature of the stage 15 (i.e., the processing temperature of the wafer W), the flow rate of each gas supplied from the first gas supply unit 31 and the second gas supply unit 32 into the processing container 11, the exhaust volume by the exhaust mechanism 14 (i.e., adjusting the pressure inside the processing container 11), and switching between plasma formation and stopping plasma formation by turning the high-frequency power supply 35 on and off. In one embodiment, part or all of the control unit 10 may be included in the etching apparatus 1. The control unit 10 may also include a processing unit, a memory unit, and a communication interface. The processing unit may be configured to read a program from the memory unit that provides logic or routines enabling various control operations, and to perform various control operations by executing the read program. This program may be stored in the memory unit in advance, or it may be obtained via a medium when needed. The obtained program is stored in the memory unit and read from the memory unit and executed by the processing unit. The medium may be various storage media readable by a computer, or it may be a communication line connected to a communication interface. The storage medium may be temporary or permanent. The processing unit may be a CPU (Central Processing Unit), or it may be one or more circuits. The memory unit may include RAM (Random Access Memory), ROM (Read Only Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), or a combination thereof.The communication interface may communicate with the etching device 1 via a communication line such as a LAN (Local Area Network).

[0019] <Etching Method> An embodiment of the etching method according to this embodiment will be described. In this embodiment, etching of the SiOCN film is performed. The SiOCN film is used, for example, as an ISP (Inner Spacer) of a CFET (Complimentary Field Effect Transistor), and the etching of the SiOCN film is used, for example, as one step in the manufacturing process of a CFET. This CFET has a structure in which an NMOS transistor and a PMOS transistor are stacked in the thickness direction of the wafer W on the wafer W. More specifically, the gates constituting these transistors overlap each other in the thickness direction of the wafer W.

[0020] And through these gates, a semiconductor film composed of Si (silicon), SiGe (silicon germanium), etc., called a nanowire or nanosheet, extends in a direction orthogonal to the thickness direction of the wafer W, and each semiconductor film is formed in multiple stages in the thickness direction of the wafer W. By passing through the gates in this way, the CFET has a so-called GAA (gate all around) structure in which each semiconductor film is surrounded by the gates.

[0021] As a method for etching the SiOCN film, a technique using a gas containing NF3 as an etching gas is known. By using a gas containing NF3 as the etching gas, it is possible to selectively etch SiO2, SiN, Si, SiGe, etc. when manufacturing a CFET having the above GAA structure, for example.

[0022] When etching a SiOCN film, using an etching gas containing NF3 results in surface roughness, and a smooth film cannot be obtained (see Figure 4 below). This is presumed to be because, when NF3 is used as an etching gas, it decomposes into NF and 2F radicals, and the N radicals affect the surface roughness of the film. The results of the surface roughness observation of the SiOCN film due to etching will be described later with reference to the photograph (Figure 4).

[0023] In the etching method according to this embodiment, etching gases containing fluorine-containing gases such as HF or F2 but no N, oxygen-containing gases, and hydrogen gases are used. In this case, the fluorine-containing gas that does not contain N is decomposed into H and F radicals or F radicals, and the bonds between C and C are dissociated by the F radicals, and etching of the SiOCN film proceeds. With this etching method, since there are no N radicals that affect the surface roughness of the film, it is presumed that a film with a smoother surface can be obtained. Note that the oxygen-containing gas mentioned above may be oxygen gas.

[0024] The SiOCN film according to this embodiment contains, for example, 35 atomic percent or more of carbon. Preferably, it contains 30 atomic percent to 40 atomic percent of silicon, 5 atomic percent to 20 atomic percent of oxygen, 30 atomic percent to 50 atomic percent of carbon, and 5 atomic percent to 20 atomic percent of nitrogen. These atomic percent can be measured by secondary ion mass spectrometry (SIMS) or X-ray photoelectron spectroscopy (XPS).

[0025] <Evaluation Test> In relation to the disclosed technology, for example, when manufacturing a CFET with the above-mentioned GAA structure, we evaluated and confirmed the selective etching of Si-containing films such as SiO2, SiN, Si, and SiGe, and the SiOCN film, as follows: Specifically, three types of SiOCN films with different compositions and thicknesses, and a SiN film, O xFor each of the film, Si film, and SiGe film, an etching process was performed under predetermined conditions and an evaluation test was conducted on the etching amount. A wafer W on which chips with each film formed on the surface was prepared, loaded into the etching apparatus 1 described with reference to FIG. 1, and plasma etching was performed for a predetermined time. Then, after the etching process, the etching amount of the film formed on the chip was measured.

[0026] The conditions for the etching process are as follows: pressure 100 mT to 1000 mT, supply power of the high-frequency power source 100 W to 1000 W, wafer temperature 15°C to 100°C, and the flow rate ratios of each gas are as follows: F source (NF2, HF, F2) 10 sccm to 50 sccm, hydrogen gas 30 sccm to 100 sccm, oxygen gas 100 sccm to 2000 sccm, and inert gas 200 sccm to 2000 sccm.

[0027] FIG. 3 is a graph showing the etching amount when plasma etching is performed under the above etching process conditions with the F source being NF3, HF, and F2 respectively. In FIG. 3, it shows the etching amounts of three types of SiOCN films with different compositions and thicknesses, SiN film, O x film, Si film, and SiGe film. The relationships of SiOCN films No. 1 to No. 3 in the figure are as follows. For Si, No. 2 and No. 3 are larger than No. 1, and No. 2 and No. 3 are the same. Also, for O, the relationship is No. 2 < No. 1 < No. 3. Also, for C, the relationship is No. 2 > No. 1 > No. 3. Also, for N, No. 1 and No. 2 are smaller than No. 3, and No. 1 and No. 2 are the same.

[0028] As shown in FIG. 3, when comparing the case of using a gas containing NF3 as the etching gas and the case of using a fluorine-containing gas containing HF or F2, the etching amount of at least one type of composition of the SiOCN film has increased. On the other hand, for the SiN film, O x film, Si film, and SiGe film, the increase in the etching amount is suppressed, indicating that it is possible to selectively etch the SiOCN film with respect to these films.

[0029] In other words, for example, when manufacturing a CFET with a GAA structure, it has been shown that the SiOCN film can be selectively etched in a manufacturing process where Si-containing films such as SiO2, SiN, Si, and SiGe are exposed, demonstrating the effectiveness of the technology according to this disclosure.

[0030] <Evaluation of surface roughness> Figure 4 shows SEM (scanning electron microscope) images of the surface of a SiOCN film (carbon content 44 atoms%) when an etching gas containing NF3 was used and when a fluorine-containing gas without nitrogen was used. (a) shows the case when an NF3 gas was used, (b) shows the case when an F2 gas was used, and (c) shows the case when an HF gas was used.

[0031] As shown in Figure 4(a), when a gas containing NF3 is used as the etching gas, irregularities are observed on the surface of the etched film, indicating that a smooth surface texture is not achieved. On the other hand, as shown in Figures 4(b) and (c), when a fluorine-containing gas without nitrogen is used as the etching gas, the surface of the etched film is smooth.

[0032] It was confirmed that using a fluorine-containing gas that does not contain nitrogen as the etching gas allows for etching that results in a smooth film surface. As a result, the surface properties of the SiOCN film after etching are improved, enabling etching of SiOCN films that are useful in the manufacture of semiconductor devices and the like.

[0033] <Effects and Effects of the Technology Disclosed in This Disclosure> According to the etching method and etching apparatus of this embodiment described above, when etching a SiOCN film, good etching can be performed so that the film surface has a smooth surface texture. For example, when etching the ISP of a CFET, the etching process can be carried out so that the surface has a smooth texture.

[0034] Also, SiN film, O xIt is possible to selectively etch SiOCN films against other films, such as Si films and SiGe films. This allows for selective etching of SiOCN films in manufacturing processes that expose Si-containing films such as SiO2, SiN, Si, and SiGe during the production of CFETs with a GAA structure, without affecting other semiconductor arrays during the etching process.

[0035] The embodiments disclosed herein should be considered in all respects as illustrative and not restrictive. The embodiments described above may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims. For example, the constituent elements of the embodiments described above can be combined in any way. Such any combination will naturally yield the functions and effects of each constituent element in the combination, as well as other functions and effects that will be apparent to those skilled in the art from the description herein.

[0036] Furthermore, the effects described herein are merely descriptive or illustrative and not limiting. In other words, the technology relating to this disclosure may produce other effects that are obvious to those skilled in the art from the description herein, in addition to or instead of the effects described herein.

[0037] For example, the above embodiment does not specifically mention the flow rate ratio of each gas constituting the etching gas, but this can be set arbitrarily. For example, in an etching gas containing a fluorine-containing gas that does not contain nitrogen, an oxygen-containing gas, and a hydrogen gas, the flow rates of the fluorine-containing gas, oxygen-containing gas, and hydrogen gas may be set to 1:1:1.

[0038] Furthermore, the following configuration examples also fall within the technical scope of this disclosure. (1) An etching method in which an SiOCN film formed on a substrate is etched by exposing it to a plasma generated from an etching gas containing a fluorine-containing gas, an oxygen-containing gas, and a hydrogen gas that does not contain nitrogen. (2) The etching method according to (1), wherein the oxygen-containing gas is oxygen. (3) The etching method according to (1) or (2), wherein the carbon content in the SiOCN film is 35 atomic percent or more. (4) The substrate is provided with the SiOCN film and the silicon-containing film, The etching method according to any one of (1) to (3), comprising the step of exposing the SiOCN film and the silicon-containing film to the plasma and selectively etching the SiOCN film among the SiOCN film and the silicon-containing film. (5) A processing container for storing a substrate on which an SiOCN film has been formed, A gas supply unit that supplies etching gases containing fluorine-containing gas (including HF or F2), oxygen-containing gas, and hydrogen gas into the processing container, To perform etching by exposing the SiOCN film to the plasma of the etching gas, a plasma generation mechanism for generating the plasma is provided, An etching apparatus equipped with the following features. (6) The etching apparatus according to (5), wherein the oxygen-containing gas is oxygen. (7) The etching apparatus according to (5) or (6), wherein the carbon content in the SiOCN film is 35 atomic percent or more. (8) The substrate has the SiOCN film and the silicon-containing film formed on it. An etching apparatus according to any one of (5) to (7), wherein the SiOCN film and the silicon-containing film are exposed to the plasma to selectively etch the SiOCN film among the SiOCN film and the silicon-containing film. [Explanation of symbols]

[0039] W wafer

Claims

1. A method for etching a SiOCN film formed on a substrate, An etching method comprising etching the SiOCN film by exposing it to a plasma generated from an etching gas containing a fluorine-containing gas, an oxygen-containing gas, and a hydrogen gas that does not contain nitrogen.

2. The etching method according to claim 1, wherein the oxygen-containing gas is oxygen.

3. The etching method according to claim 1, wherein the carbon content in the SiOCN film is 35 atomic percent or more.

4. The substrate has the SiOCN film and the silicon-containing film formed on it. The etching method according to claim 1, wherein the SiOCN film and the silicon-containing film are exposed to the plasma to selectively etch the SiOCN film among the SiOCN film and the silicon-containing film.

5. An apparatus for etching a SiOCN film formed on a substrate, A processing container for storing the substrate, A gas supply unit that supplies etching gases containing fluorine-containing gas, oxygen-containing gas, and hydrogen gas that do not contain nitrogen into the processing container, To etch the SiOCN film by exposing it to the plasma of the etching gas, a plasma generation mechanism is provided to generate the plasma, An etching apparatus equipped with the following features.

6. The etching apparatus according to claim 5, wherein the oxygen-containing gas is oxygen.

7. The etching apparatus according to claim 5, wherein the carbon content in the SiOCN film is 35 atomic percent or more.

8. The substrate has the SiOCN film and the silicon-containing film formed on it. The etching apparatus according to claim 5, wherein the SiOCN film and the silicon-containing film are exposed to the plasma to selectively etch the SiOCN film among the SiOCN film and the silicon-containing film.

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