Etching method and etching device

Abstract

In order to satisfactorily etch a SiOCN film, the present invention provides a method for etching a SiOCN film formed on a substrate, wherein the SiOCN film is etched through exposure to plasma generated from an etching gas containing an oxygen-containing gas, hydrogen gas, and a fluorine-containing gas that does not contain N.

Description

Etching method and etching apparatus

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

[0002] In the manufacture of semiconductor devices, it is sometimes necessary to etch the carbon-containing silicon oxide film formed on the surface of the semiconductor wafer (hereinafter also referred to as wafer), which is the substrate. Patent Document 1 describes NH ３ and C ｘ F ｙ This document describes etching a carbon-containing silicon oxide film having less than 30 atomic percent of carbon and less than 50 atomic percent of hydrogen using a plasma of a gas having [a specific gas].

[0003] Japan Special Table No. 2004-512673

[0004] The technology described herein provides a technology that can effectively etch a SiOCN film.

[0005] One aspect of the present disclosure is an etching method for 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.

[0006] According to this disclosure, the SiOCN film can be etched effectively.

[0007] This is a longitudinal cross-sectional side view of an etching apparatus performing etching. This is a longitudinal cross-sectional side view of a heat shield in the etching apparatus. NF ３ HF, F ２ This graph shows the amount of etching when plasma etching is performed using NF as the etching gas. ３ These are SEM images of the film surface when using a gas containing nitrogen and when using a fluorine-containing gas that does not contain nitrogen.

[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 Apparatus> FIG. 1 is a longitudinal sectional view showing an outline of the configuration of an etching apparatus 1 according to the present embodiment. The etching apparatus 1 includes a processing container 11 for storing a substrate W (hereinafter also referred to as a 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 upper wall and the upper side of the side wall of the processing container 11. A horizontal partition plate 21 is provided in the processing container 11, and the inside of the processing container 11 is partitioned into a processing space S surrounded by the container body 12 and a plasma generation space P surrounded by the lid 13. Further, below the partition plate 21, a heat insulating plate 23 is horizontally arranged so as to partition the inside of the processing container 11 vertically in the same manner as the partition plate 21.

[0010] At the bottom of the container body 12, an exhaust mechanism 14 including a vacuum pump is connected to evacuate the inside of the processing container 11 to a reduced-pressure (vacuum) atmosphere of a desired pressure. A stage 15 is provided in the processing space S, and the wafer W is processed while being horizontally placed on the upper surface of the stage 15. The upper surface of this stage 15 faces the heat insulating plate 23. In one embodiment, two stages 15 may be provided so that two wafers W can be processed together. In that case, since these two stages 15 are arranged in the X direction in FIG. 1, only one of the stages 15 is shown in FIG. 1.

[0011] A temperature adjustment mechanism 16 for adjusting the temperature of the placed wafer W is embedded in the stage 15. The temperature adjustment mechanism 16 is constituted by, for example, a flow path through which a fluid whose temperature is adjusted by a chiller flows, a heater, or the like. Reference numeral 17 in the figure is a transfer port of the wafer W, which is opened in the side wall of the container body 12 so that a transfer mechanism (not shown) can transfer the wafer W to and from the stage 15, and is opened and closed by a gate valve 18. 15A in the figure is a lifting mechanism for lifting and lowering the stage 15 for this transfer.

[0012] Outside the processing container 11, a first gas supply unit 31 and a second gas supply unit 32 are provided. The first gas supply unit 31 supplies HF gas, F ２ gas, O ２ gas, H ２The system is equipped with a storage section for each of the gases and noble gases, and a flow rate adjustment mechanism for adjusting the flow rate of the gases from the storage section to the plasma generation space P, so that these gases can be supplied to the plasma generation space P. The flow rate adjustment mechanism is composed of, for example, valves or 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 supplies an inert gas, such as N2. ２ In order to supply (nitrogen) gas to the processing space S via the heat shield plate 23, it is equipped with a gas storage section and a flow rate adjustment mechanism, similar to the first gas supply section 31. ２ The gas is used as a pressure regulating gas and a diluent for the etching gas in the processing container 11.

[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. By shifting the positions of the through holes 22 in this way, the two partition plates 21 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, in the processing space S, radicals are selectively supplied from among the ions and radicals that are active species of the plasma, and etching is performed.

[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 vessel 11 is made of, for example, quartz and serves 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 supply 35 via a matching unit 34. When high-frequency power of a predetermined frequency (for example, 13.56 MHz or higher) is output from the high-frequency power supply 35, inductively coupled plasma is generated from each gas supplied to the plasma generation space P. The high-frequency antenna 33, the matching unit 34, and the high-frequency power supply 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. The operations controlled in this way 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 to the processing container 11 from the first gas supply unit 31 and the second gas supply unit 32, the amount of exhaust 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 storage 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 apparatus 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, an SiOCN film is etched. The SiOCN film is used, for example, in the ISP (Inner Spacer) of a CFET (Compliant Field Effect Transistor), and etching of the SiOCN film is used, for example, as one step in the manufacturing process of the CFET. This CFET has a structure in which NMOS transistors and PMOS transistors are stacked in the thickness direction of the wafer W on the wafer W. More specifically, the gates that constitute each of these transistors overlap each other in the thickness direction of the wafer W.

[0020] Then, semiconductor films made of materials such as Si (silicon) or SiGe (silicon germanium), called nanowires or nanosheets, extend through these gates in a direction perpendicular to the thickness direction of the wafer W, and each semiconductor film is formed in multiple layers in the thickness direction of the wafer W. In this way, each semiconductor film is surrounded by the gate, and the CFET has a so-called GAA (gate all around) structure.

[0021] As a method for etching a SiOCN film, NF is used as the etching gas. ３ A technique using a gas containing NF is known. ３ By using a gas containing SiO, for example, when manufacturing a CFET having the above GAA structure, ２ It is possible to selectively etch materials such as SiN, Si, and SiGe.

[0022] When etching a SiOCN film, NF is used as the etching gas. ３ When using a gas containing NF, surface roughness is observed, and a smooth film cannot be obtained (see Figure 4 below). This is because NF is used as the etching gas. ３ When using NF ３It is presumed that the nitrate is decomposed into NF and 2F radicals, and that the N radicals affect the surface roughness of the film. The results of the surface roughness observation of the SiOCN film by etching will be described later with reference to the photograph (Figure 4).

[0023] In the etching method according to this embodiment, for example, HF or F ２ An etching gas containing fluorine, oxygen, and hydrogen gas, which does not contain nitrogen, is used. In this case, the nitrogen-free fluorine-containing gas is decomposed into H and F radicals or F radicals, and the C-C bonds are dissociated by the F radicals, causing the etching of the SiOCN film to proceed. With this etching method, since there are no nitrogen 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 methods such as 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, the selective etching of Si-containing films such as SiO2, SiN, Si, and SiGe, and the SiOCN film was evaluated and confirmed 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 were a pressure of 100 mT to 1000 mT, a supply power of the high-frequency power source of 100 W to 1000 W, a wafer temperature of 15°C to 100°C, and the flow rate ratios of the respective gases were the F source (NF ２ , HF, F ２ ) of 10 sccm to 50 sccm, hydrogen gas of 30 sccm to 100 sccm, oxygen gas of 100 sccm to 2000 sccm, and inert gas of 200 sccm to 两千 sccm.

[0027] FIG. 3 is a graph showing the etching amounts when plasma etching is performed under the above etching conditions with the F source being NF ３ , HF, F ２ respectively. In FIG. 3, the etching amounts of three types of SiOCN films with different compositions and thicknesses, SiN film, O ｘ film, Si film, and SiGe film are shown. 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. < 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 NF ３ as the etching gas with the case of using a fluorine-containing gas containing HF or F ２ , 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 ｘFor the film, Si film, and SiGe film, an increase in the etching amount is suppressed, and it has been shown that it is possible to selectively etch the SiOCN film with respect to these films.

[0029] That is, for example, when manufacturing a CFET having a GAA structure, in a manufacturing process in which Si-containing films such as SiO ２ , SiN, Si, and SiGe are exposed, the SiOCN film can be selectively etched, indicating that the technology according to the present disclosure is effective.

[0030] <Evaluation of surface roughness> Fig. 4 is a SEM (scanning electron microscope) image of the surface of a SiOCN film (carbon content: 44 atomic %) when a gas containing NF ３ is used as the etching gas and when a fluorine-containing gas not containing N is used. (a) is NF ３ , (b) is F ２ , and (c) is the case when a gas containing HF is used.

[0031] As shown in Fig. 4(a), when a gas containing NF ３ is used as the etching gas, unevenness is observed on the surface of the film after etching, indicating that a smooth surface property is not obtained. On the other hand, as shown in Fig. 4(b) and (c), when a fluorine-containing gas not containing N is used as the etching gas, it can be seen that the surface of the film after etching has a smooth property.

[0032] It was confirmed that by using a fluorine-containing gas not containing N as the etching gas, an etching process can be performed such that the surface of the film becomes smooth. As a result, the surface property of the SiOCN film after the etching process becomes good, and an etching process of the SiOCN film useful in the manufacture of semiconductor devices and the like can be performed.

[0033] <Operational effects of the technology of the present disclosure> According to the etching method and the etching apparatus according to the present embodiment described above, when performing an etching process on a SiOCN film, good etching can be performed so that the surface of the film has a smooth surface property. For example, when etching the ISP of a CFET, an etching process can be performed such that the surface has a smooth property.

[0034] Also, SiN film, O ｘ It is possible to selectively etch SiOCN films against films, Si films, SiGe films, etc. This allows for, for example, the manufacturing of CFETs with a GAA structure. ２ In manufacturing processes where Si-containing films such as SiN, Si, and SiGe are exposed, the SiOCN film can be selectively etched without affecting other semiconductor arrays during manufacturing.

[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] The following configuration examples also fall within the technical scope of this disclosure: (1) An etching method comprising etching a SiOCN film formed on a substrate 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 etching method according to any one of (1) to (3), wherein the substrate is provided with the SiOCN film and a silicon-containing film, and the SiOCN film and the silicon-containing film are exposed to the plasma, and the SiOCN film is selectively etched from the SiOCN film and the silicon-containing film. (5) A processing container for storing a substrate on which a SiOCN film is formed, and HF or F ２ An etching apparatus comprising: a gas supply unit that supplies an etching gas containing a fluorine-containing gas, an oxygen-containing gas, and a hydrogen gas; and a plasma generation mechanism that generates a plasma for etching the SiOCN film by exposing it to the plasma of the etching gas. (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 etching apparatus according to any one of (5) to (7), wherein the substrate has the SiOCN film and the silicon-containing film formed on it, and the SiOCN film and the silicon-containing film are exposed to the plasma to selectively etch the SiOCN film from the SiOCN film and the silicon-containing film.

[0039] W wafer

Claims

1. An etching 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.

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

5. An apparatus for etching a SiOCN film formed on a substrate, comprising: a processing container for storing the substrate; and HF or F ２ An etching apparatus comprising: a gas supply unit that supplies an etching gas containing a fluorine-containing gas, an oxygen-containing gas, and a hydrogen gas; and a plasma generation mechanism that generates the plasma for etching the SiOCN film by exposing it to the plasma of the etching gas.

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

Images