Method for etching and etching device

Abstract

To provide a method for etching and an etching device which can etch a carbon-containing silicon oxide film with an excellent selectivity.SOLUTION: The method for etching according to the present disclosure includes: exposing a carbon-containing silicon oxide film 14 formed on a wafer W to plasma generated from an etching gas containing fluorine-containing gas, oxygen-containing gas, and hydrogen gas; and etching the film.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In manufacturing a semiconductor device, a carbon-containing silicon oxide film formed on the surface of a semiconductor wafer (hereinafter, referred to as a wafer) serving as a substrate may be etched. Patent Document 1 describes the etching of a carbon-containing silicon oxide film that is said to contain less than about 30 atomic % of carbon and less than about 50 atomic % of hydrogen using plasma of a gas containing NH3 and CxFy. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2004-512673 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique capable of satisfactorily etching a carbon-containing silicon oxide film. [Means for solving the problem]

[0005] In the etching method of the present disclosure, a carbon-containing silicon oxide film formed on a substrate is etched by exposing it to plasma generated from an etching gas containing a fluorine-containing gas, an oxygen-containing gas, and a hydrogen gas. Effect of the Invention

[0006] The present disclosure can satisfactorily etch a carbon-containing silicon oxide film. [Brief description of the drawings]

[0007] [Figure 1]FIG. 2 is a vertical cross-sectional side view of a wafer undergoing an etching process according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a vertical cross-sectional side view of the wafer during etching. [Diagram 3] FIG. 2 is a vertical cross-sectional side view of the wafer W after etching. [Figure 4] 2 is a vertical sectional side view of an etching apparatus that performs the etching process. FIG. [Diagram 5] FIG. 4 is a vertical sectional side view of a heat shield plate in the etching apparatus. [Figure 6] FIG. 13 is a vertical cross-sectional side view of another wafer before etching processing; [Figure 7] FIG. 4 is a vertical cross-sectional side view of the other wafer after etching processing. [Figure 8] FIG. 11 is a graph showing the results of an evaluation test. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] An embodiment of the etching method of the present disclosure will be described. The plasma etching method shown in this embodiment is used as one of the manufacturing processes of a CFET (Complimentary Field Effect Transistor). This CFET has a structure in which an NMOS transistor and a PMOS transistor are stacked on a substrate in the thickness direction of the substrate. More specifically, the gates constituting each of these transistors overlap each other in the thickness direction of the substrate.

[0009] Then, through these gates, semiconductor films made of Si (silicon) or SiGe (silicon germanium), called nanowires or nanosheets, extend in a direction perpendicular to the thickness direction of the substrate, and each semiconductor film is formed in multiple stages in the thickness direction of the substrate. By penetrating the gate in this way, each semiconductor film is surrounded by the gate, and the CFET has a so-called GAA (gate all around) structure. Note that the process during the manufacture of this CFET is shown as an example of the application of this technology, and it should be noted that the application of this technology is not limited to the manufacture of CFETs.

[0010] With reference to FIG. 1, a wafer W, which is a substrate to be etched, will be described. FIG. 1 is a vertical cross-sectional side view of a surface layer of the wafer W. In the figure, two mutually orthogonal directions in the surface direction of the wafer W are indicated as the X direction and the Y direction, and a thickness direction of the wafer W, which is orthogonal to each of the X direction and the Y direction, is indicated as the Z direction. FIG. 1 shows the wafer W as viewed toward the X direction. In the following description of the film structure of the surface layer of the wafer W, the wafer W will be described as being placed on a horizontal surface. Therefore, the Z direction is the up-down direction.

[0011] On the wafer W, a SiGe (silicon germanium) film 11 is formed so as to extend in the X direction. A large number of SiGe films 11 are provided in the Z direction at intervals, and each extends in the X direction. When viewed in the X direction, each SiGe film 11 except for the bottommost SiGe film 11 is surrounded by a SiOx (silicon oxide) film 12 as shown in the figure. The bottommost SiGe film 11 is also covered with a SiOx film 12 like the other SiGe films 11. However, since the bottommost SiGe film 11 is formed so as to protrude upward from the surface of the wafer W, the SiOx film 12 is not formed below the SiGe film 11. The SiGe films 11 of some stages among the SiGe films 11 formed in multiple stages as described above form the above-mentioned nanowires or nanosheets.

[0012] For ease of explanation, the plurality of SiGe films 11 covered with the SiOx film 12 and arranged in the Z direction will be collectively referred to as a semiconductor film array 13. Although not shown, in the wafer W, a plurality of the semiconductor film arrays 13 are arranged in the Y direction. A SiOC film 14, which is a carbon-containing silicon oxide film, is formed so as to cover each semiconductor film array 13. More specifically, the SiOC film 14 is formed so as to straddle the left side of the semiconductor film array 13, pass through the upper side, and then straddle to the right side as viewed in the X direction. The SiOC film 14 is formed so as to enter the gaps between the adjacent SiGe films 11 from the left and right sides of the semiconductor film array 13 and fill the gaps.

[0013] The SiOC film 14 contains, for example, 20 atomic % or more and 40 atomic % or less of carbon. The atomic % can be measured by secondary ion mass spectrometry (SIMS) or X-ray photoelectron spectroscopy (XPS). The plasma etching of this embodiment removes portions of the SiOC film 14 located on the left side, right side, and upper side of the semiconductor film array 13 as viewed in the X direction. Therefore, the etching is performed so that the portions of the SiOC film 14 interposed between the SiGe films 11 remain after the processing.

[0014] Incidentally, when etching the SiOC film formed on the wafer W, a method of forming an etching gas containing HF (hydrogen fluoride) gas and NH3 (ammonia) into plasma and exposing the SiOC film to the plasma may be used. However, when etching a SiOC film having a relatively high carbon content such as the SiOC film 14 of this embodiment, the amount of etching per unit time is relatively small. In addition, the etching selectivity of such plasma etching to Si-containing films other than the SiOC film is relatively small. In other words, the Si-containing film is etched relatively largely.

[0015] In this embodiment, a mixed gas consisting of fluorine-containing gas NF3 (nitrogen trifluoride), O2 (oxygen) and H2 (hydrogen) is supplied as an etching gas together with an inert gas for plasma generation into a processing vessel housing the wafer W. A vacuum atmosphere of a predetermined pressure is maintained inside the processing vessel. The wafer W is then exposed to the plasmatized etching gas to etch the SiOC film 14.

[0016] As shown in FIG. 2, during this etching, a part of the SiOx film 12 is still covered by the SiOC film 14, while another part is exposed to the surface. That is, both the SiOx film 12 and the SiOC film 14 are exposed to the surface of the wafer W. The arrows in the figure indicate plasma. Even if the SiOx film 12 is exposed to the surface of the wafer W in this way, the plasma has high etching selectivity to the SiOC film 14, so the SiOC film 14 is selectively etched and the etching of the SiOx film 12 is suppressed. Then, when the parts of the SiOC film 14 that covered the left side, right side, and upper side of the semiconductor film array 13 are removed, as shown in FIG. 3, the generation of plasma is stopped and the etching process is completed.

[0017] As described above, the SiOC film 14 is etched with high selectivity to the SiOx film 12. Moreover, as shown in the evaluation test described later, the etching rate (amount etched per unit time) of the SiOC film 14 is relatively high, and the etching process of the SiOC film 14 can be completed in a relatively short time. In FIG. 2 showing the state during etching, the upper portion of the SiOC film 14 is shown to be removed before the lower portion, but it is not limited to the upper portion being removed first as shown in the figure.

[0018] Next, an etching apparatus 2, which is one embodiment of an apparatus for performing the above-mentioned plasma etching process, will be described with reference to the vertical cross-sectional side view of Fig. 4. The etching apparatus 2 includes a processing vessel 21 for storing a wafer W. The processing vessel 21 includes a vessel body 22 and a lid 23, the vessel body 22 forming the bottom wall and the lower side of the side wall of the processing vessel 21, and the lid 23 forming the upper wall and the upper side of the side wall of the processing vessel 21. A horizontal partition plate 31 is provided inside the processing vessel 21, and the inside of the processing vessel 21 is divided into a processing space S surrounded by the vessel body 22 and a plasma generation space P surrounded by the lid 23. A heat shield plate 33 is horizontally disposed below the partition plate 31 so as to divide the inside of the processing vessel 21 into upper and lower parts, similar to the partition plate 31.

[0019] An exhaust mechanism 24 equipped with a vacuum pump is connected to the bottom of the vessel body 22, and exhausts the inside of the processing vessel 21 to create a vacuum atmosphere of a desired pressure. A stage 25 is provided in the processing space S, and the wafer W is processed while being placed horizontally on the upper surface of the stage 25. The upper surface of the stage 25 faces a heat shield plate 33. Two stages 25 are provided so that two wafers W can be processed at the same time. However, since the two stages 25 are lined up in the front-back direction of FIG. 4, only one stage 25 is shown in FIG. A temperature adjustment mechanism 26 for adjusting the temperature of the wafer W placed thereon is embedded in the stage 25. The temperature adjustment mechanism 26 is composed of, for example, a flow path through which a fluid whose temperature is adjusted by a chiller flows, a heater, and the like. In the figure, 27 denotes a transfer port for the wafer W, which opens in a side wall of the vessel body 22 so that a transfer mechanism (not shown) can transfer the wafer W to the stage 25, and is opened and closed by a gate valve 28. In the figure, reference numeral 25A denotes a lifting mechanism for lifting and lowering the stage 25 for this transfer.

[0020] A first gas supply unit 41 and a second gas supply unit 42 are provided outside the processing vessel 21. The first gas supply unit 41 includes a storage unit for storing each of NF3 gas, O2 gas, H2 gas, and a rare gas so that these gases can be supplied to the plasma generating space P, and a flow rate adjustment mechanism for adjusting the flow rate of the gas from the storage unit to the plasma generating space P. The flow rate adjustment mechanism is, for example, a valve or a mass flow controller. The rare gas, which is an inert gas, is, for example, Ar (argon) gas, and plays a role in forming plasma and adjusting the pressure inside the processing vessel 21.

[0021] The second gas supply unit 42 includes a gas storage unit and a flow rate adjustment mechanism, similar to the first gas supply unit 41, so that an inert gas, for example, N2 (nitrogen) gas, can be supplied to the processing space S via a heat shield plate 33 described later. This N2 gas is used as a pressure adjustment gas in the processing vessel 21 and a dilution gas for the etching gas.

[0022] The partition plate 31 and the heat shield plate 33 will be described with reference to the vertical side view of FIG. 5. Two partition plates 31 are arranged vertically with a gap therebetween, and each of the two partition plates 31 has a plurality of through holes 32. The through holes 32 of the upper partition plate 31 and the through holes 32 of the lower partition plate 31 are located at different positions in a plan view. By shifting the positions of the through holes 32 in this way, the two partition plates 31 function as so-called ion traps that suppress the supply of ions in the plasma generated in the plasma generation space P to the processing space S. Therefore, radicals are selectively supplied to the processing space S from among ions and radicals, which are active species of plasma.

[0023] The heat shield 33 serves to suppress the influence of heat accumulated in the partition plate 31 due to repeated plasma generation in the plasma generation space P on the distribution of radicals in the processing space S. The peripheral portion of the heat shield 33 forms a flange embedded in the side wall of the vessel body 22, and the heat shield 33 is cooled by a cooling mechanism 34 embedded in this flange. This cooling mechanism 34 is composed of a flow path through which a fluid whose temperature is adjusted by a chiller flows, for example, or a Peltier element.

[0024] A plurality of through holes 36 are formed in the heat shield 33 so that radicals can be introduced from the plasma generation space P to the processing space S. Each through hole 36 overlaps with a through hole 32 of the lower partition plate 31 in a plan view. A number of gas outlets 37 are opened on the lower surface of the heat shield 33. Gas supplied from the second gas supply unit 42 is supplied in a shower-like manner from the gas outlets 37 through a flow path formed inside the heat shield 33. Therefore, the heat shield 33 is configured as a shower head. Note that the through holes 36 of the heat shield 33 and the through holes 32 of the partition plate 31 are omitted from FIG. 4 to prevent the drawing from becoming too complicated.

[0025] Returning to FIG. 4, the lid 23 of the processing vessel 21 is made of, for example, quartz and configured as a dielectric window. A ring-shaped high-frequency antenna 43 is formed on the lid 23, and the high-frequency antenna 43 is connected to a high-frequency power supply 45 via a matching box 44. When high-frequency power of a predetermined frequency (for example, 13.56 MHz or higher) is output from the high-frequency power supply 45, inductively coupled plasma is generated from each gas supplied to the plasma generation space P. The high-frequency antenna 43, the matching box 44, and the high-frequency power supply 45 configure a plasma generation mechanism.

[0026] The etching apparatus 2 includes a control unit 20, which is a computer, and the control unit 20 includes a program, a memory, and a CPU. The program includes commands (each step) for performing the above-mentioned processing of the wafer W and transport of the wafer W. The program is stored in a storage medium, such as a compact disk, a hard disk, a magneto-optical disk, a DVD, etc., and is installed in the control unit 20. The control unit 20 outputs control signals to each part of the etching apparatus 2 according to the program, and controls the operation of each part. The operations controlled in this way include, for example, adjustment of the temperature of the stage 25 (i.e., the processing temperature of the wafer W), the flow rates of each gas supplied from the first gas supply unit 41 and the second gas supply unit 42 to the processing chamber 21, the amount of exhaust by the exhaust mechanism 24 (i.e., adjustment of the pressure in the processing chamber 21), switching between forming and stopping plasma formation by turning on and off the high-frequency power supply 45, and the like.

[0027] The procedure for processing the wafer W by the etching apparatus 2 described above will be described. The wafer W shown in FIG. 1 is placed on the stage 25. Then, with the pressure in the processing chamber 21 set to, for example, 1.33 Pa to 133 Pa and the temperature of the wafer W set to 0° C. to 120° C., each gas is supplied into the processing chamber 21 from the first gas supply unit 41 and the second gas supply unit 42 at a predetermined flow rate. An example of the flow rate ratio of each gas will be described in the evaluation test described later. Then, a power of, for example, 200 W to 800 W is supplied from the high frequency power source 45 to the high frequency antenna 43, and each gas supplied to the plasma generation space P is turned into plasma.

[0028] Radicals constituting the plasma are supplied from the plasma generating space P to the processing space S to proceed with the etching of the SiOC film 14 described in Figs. 1 to 3, and even if the SiOx film 12 is exposed during this etching, the etching of the SiOx film 12 is suppressed. In addition, in the etching device 2, the supply of ions having relatively high energy among the active species constituting the plasma to the wafer W is suppressed. Therefore, the etching of the SiOC film 14 proceeds while the etching of the SiOx film 12 is more reliably suppressed. Then, as shown in Fig. 3, when the desired portion of the SiOC film 14 is etched, the power supply from the high frequency power source 45 and the supply of each gas into the processing vessel 21 are stopped, and the processing is completed.

[0029] As will be shown in the evaluation test described later, the plasma etching of the present technology makes it possible to etch the SiOC film with high selectivity with respect to the Si-containing film, even when a Si-containing film other than SiGe, such as Si or SiOx, and a SiOC film are present on the surface of the wafer W. The film structure of the wafer W shown in Fig. 6 is a film structure for manufacturing a CFET, like that shown in Fig. 1, but differs from that shown in Fig. 1 in that the SiOx film 12 is not formed on the surface of each SiGe film 11 constituting the semiconductor film array 13, and a SiOC film 14 is in contact with the SiGe film 11.

[0030] Since the plasma etching of the present technology has the above-mentioned selectivity, even if the SiGe film 11 is exposed during etching of the SiOC film 14 formed as shown in Fig. 6, it is possible to etch the SiOC film 14 around the semiconductor film array 13 while suppressing etching of the SiGe film 11. Fig. 7 shows the state at the end of this etching.

[0031] 1 and 6 show an example in which the semiconductor film array 13 is constituted by the SiGe film 11, but it may be formed by a Si film instead of the SiGe film 11. Therefore, in Fig. 6, the Si film is exposed on the surface during the etching of the SiOC film 14, but even in this case, the Si film can be etched while the etching of the Si film is suppressed due to the above-mentioned etching selectivity.

[0032] Incidentally, so far, an example of the manufacturing process of a CFET has been described in which the SiOC film 14 covering the semiconductor film array 13 is plasma etched. That is, an example has been shown in which the SiOC film 14, which has projections and recesses corresponding to the shape of a pattern formed on the surface of the wafer W, is etched. However, as described above, the present technology is not limited to application to the manufacturing process of a CFET, and the shape of the etched SiOC film 14 is arbitrary. Therefore, for example, the SiOC film 14 formed as a flat film may be etched using the plasma already described.

[0033] In each of the etching examples described above, any one of the Si film, the SiGe film 11, and the SiOx film 12, which are Si-containing films, is exposed to the surface during etching, and the SiOC film 14 is selectively etched out of the Si-containing film and the SiOC film 14. As described above, the SiOC film 14 and the Si-containing film are not limited to being both exposed to the surface during etching, and these films may be exposed on the surface of the wafer W before the start of etching, and the SiOC film 14 may be selectively etched from the beginning of etching. Therefore, for example, the wafer W formed so that the SiOC film 14 and the Si-containing film are both aligned in the surface direction of the wafer W and exposed to the surface may be carried into the etching device 2, and the SiOC film 14 may be selectively etched.

[0034] The above-mentioned Si-containing film is a film containing Si and different from the carbon-containing silicon oxide film to be etched, for example, a film not containing carbon. More specifically, the Si-containing film may be, for example, the above-mentioned Si film, SiGe film, SiOx film, or SiN (silicon nitride). In addition, the above-mentioned plasma etching also increases the etching selectivity of the carbon-containing silicon oxide film to the SiN film, as shown in the evaluation test described below. The reason why the etching of each Si-containing film is suppressed in this way is thought to be that the active species of the plasma generated from the O2 gas and H2 gas constituting the etching gas adhere to the surface of the Si-containing film and function as a protective film against the plasma.

[0035] Furthermore, when etching the SiOC film 14 with the above-mentioned plasma, it is not limited to forming a state in which both the SiOC film 14 and the Si-containing film are exposed on the surface. In other words, etching may be performed such that only the SiOC film 14 is exposed on the surface of the substrate from the start to the end of the process. Even in this case, according to the present technology, the effect of being able to etch the SiOC film 14 at a relatively high etching rate is achieved.

[0036] Now, a supplementary explanation will be given about the Si-containing film. Here, the film containing Si does not mean that Si is inevitably contained as an impurity, but that Si is contained as a constituent. In this specification, the description that a film other than the Si-containing film or an etching gas contains a specific component means that the film or the etching gas contains the component as a constituent, not that it contains the component as an impurity, just like Si in this Si-containing film. And, for example, it has been described that the Si-containing film is a film that does not contain carbon, but this carbon-free means that it does not contain carbon as a constituent, and does not mean that it does not contain carbon that is inevitably mixed in as an impurity.

[0037] The carbon-containing silicon oxide film to be etched is not limited to the SiOC film 14. Specifically, the etching target may be, for example, a film constituted as a SiCOH film by containing hydrogen in addition to Si, O, and C, or a film constituted as a SiOCN film by containing nitrogen. The atomic % of carbon contained in these SiCOH films and SiOCN films is the same as the range of atomic % of carbon contained in the SiOC film 14 described above.

[0038] The fluorine-containing gas constituting the etching gas is not limited to NF3 gas, and other gases containing fluorine such as F2 (fluorine) gas may be used. Also, although an example in which oxygen is used as the oxygen-containing gas constituting the etching gas has been shown, it is considered that the same effect as when oxygen gas is used can be obtained even if O3 (ozone) gas, CO (carbon monoxide) gas, CO2 (carbon dioxide) gas, etc. are used, since oxygen radicals can be supplied to the wafer W.

[0039] Although the etching apparatus 2 described above is configured to form inductively coupled plasma, any method for forming plasma may be used. For example, a shower head and a stage provided in a processing vessel may be configured as parallel plate electrodes facing each other, and a capacitively coupled plasma may be formed by gas supplied from the shower head toward the stage, and a wafer W on the stage may be etched. In addition, a so-called remote plasma processing may be performed in which plasma formed at a location away from the processing vessel is supplied to the processing vessel for processing. However, in the apparatus configuration in which inductively coupled plasma is formed in the processing vessel for processing, it is advantageous to place a partition plate 31 serving as an ion trap as described in FIG. 4 and FIG. 5, since this can suppress etching of the Si-containing film due to the action of ions.

[0040] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The above-described embodiments may be omitted, substituted, modified, or combined in various forms without departing from the scope and spirit of the appended claims.

[0041] [Evaluation test] An evaluation test carried out in relation to the technology of the present disclosure will be described. A wafer W with five chips mounted on its surface was prepared. A film was formed on the top surface of each chip, and the type of film formed differs between chips. Specifically, the films formed were a SiOC film, a SiN film, a SiOx film, a polysilicon film, and a SiGe film, and one of these films was formed on each chip. In this evaluation test, the SiOC film contained carbon at 30 atomic % or more and 40 atomic % or less.

[0042] As an evaluation test, the above wafer W was loaded into the etching device 2 described in the embodiment, and plasma etching was performed for a predetermined time. Then, the etching amount of the film formed on each chip after the etching process was measured. Furthermore, for films other than the SiOC film, the etching selectivity was calculated based on the etching amount of the SiOC film. This etching selectivity is a value calculated by dividing the etching amount of the SiOC film by the etching amount of the film for which the etching selectivity is to be calculated. Therefore, the larger the etching selectivity, the more the etching amount of the film is suppressed, and the higher the etching selectivity to the SiOC film.

[0043] For the etching process in this evaluation test, the pressure inside the processing vessel 21 and the power supplied from the high frequency power source 45 were set to values ​​within the ranges described in the embodiment. In addition, the flow rate ratio of the gases supplied into the processing vessel 21 was set to NF3:H2 gas:O2 gas:N2 gas:Ar gas=1:1:1:14:1.

[0044] FIG. 8 is a graph showing the results of this evaluation test. The vertical axis of the graph shows the amount of etching, and the vertical axis is scaled at a predetermined interval A. The etching selectivity ratios were 26.8, 97.7, 157.9, and 42.3 for the SiN film, SiOx film, polysilicon film, and SiGe film, respectively. Thus, the etching selectivity ratios were relatively high for all of the SiN film, SiOx film, polysilicon film, and SiGe film. Therefore, as described in the embodiment, it was confirmed that when etching a SiOC film using this technology, the etching amount of Si-containing films other than the SiOC film is suppressed, and a high etching rate can be obtained for the SiOC film. In particular, since the etching selectivity ratios of the SiOx film, polysilicon film, and SiGe film are high, it can be seen that this technology is effective when etching a SiOC film with respect to these films. Therefore, as described in the embodiment, it was shown that it is effective to apply this technology to the manufacturing process of CFETs in which these films are exposed during the etching of the SiOC film.

[0045] Since such a high etching selectivity ratio can be obtained for each Si-containing film, it is expected that a practically sufficient selectivity can be obtained even if the carbon atom content of the SiOC film is less than 30 atomic %. Specifically, as described in the embodiment, it is considered that a sufficient etching selectivity can be obtained if the SiOC film contains 20 atomic % or more of carbon.

[0046] In addition, the flow rate ratio of NF3, O2 gas, and H2 gas constituting the etching gas is 1:1:1 in this evaluation test, but since a very high etching selectivity is obtained for each Si-containing film as described above, it is considered that even if the flow rate ratio is slightly changed, sufficient effect can be obtained in practice. It is expected that etching can be performed with sufficient selectivity even if each gas is supplied to the wafer W at a ratio of 0.2 to 10 for O2 gas and 0.2 to 10 for H2 gas when the flow rate of NF3 gas is 1, and if the flow rate of O2 gas and the flow rate of H2 gas are each set to 0.5 to 1.5 when the flow rate of NF3 gas is 1, which is closer to the conditions set in the test, etching with a good selectivity can be performed more reliably. Although detailed results are omitted, when H2 gas is not contained in the etching gas and only NF3 and O2 gas are supplied, high etching selectivity for the SiOC film as shown in this evaluation test was not obtained. Therefore, in order to increase the etching selectivity of the SiOC film, it is effective to make the etching gas contain H2 gas. [Explanation of symbols]

[0047] W wafer 14 SiOC film

Claims

1. An etching method for etching a carbon-containing silicon oxide film formed on a substrate by exposing the film to plasma generated from an etching gas containing a fluorine-containing gas, an oxygen-containing gas, and a hydrogen gas.

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

3. 3. The etching method of claim 2, wherein said fluorine-containing gas is nitrogen trifluoride.

4. 4. The etching method according to claim 3, wherein the carbon-containing silicon oxide film is a SiOC film.

5. 2. The etching method according to claim 1, wherein the carbon content in said carbon-containing silicon oxide film is 20 atomic % or more and 40 atomic % or less.

6. The carbon-containing silicon oxide film and a silicon-containing film are provided on the substrate, 2. The etching method according to claim 1, further comprising the step of exposing the carbon-containing silicon oxide film and the silicon-containing film to the plasma, and selectively etching the carbon-containing silicon oxide film out of the carbon-containing silicon oxide film and the silicon-containing film.

7. 7. The etching method according to claim 6, wherein the silicon-containing film is a silicon film, a silicon oxide film or a silicon germanium film.

8. a processing vessel for storing a substrate on which a carbon-containing silicon oxide film is formed; a gas supply unit for supplying an etching gas containing a fluorine-containing gas, an oxygen-containing gas, and a hydrogen gas into the processing chamber; a plasma generating mechanism for generating plasma of the etching gas so as to expose the carbon-containing silicon oxide film to the plasma and etch the carbon-containing silicon oxide film; An etching apparatus comprising:

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