Substrate processing method and substrate processing apparatus

Abstract

To provide a substrate processing method capable of ensuring the reproducibility of etching results even when etching is repeated a plurality of times on the same substrate.SOLUTION: In a substrate processing method, a silicon oxide film TG formed on a substrate W is etched. A substrate processing method includes a first etching step S43 and a second etching step S47. In the first etching step S43, in a state in which the pressure inside a chamber 2 exhibits a first pressure P1 lower than the atmospheric pressure, hydrogen fluoride gas is supplied into the chamber 2 to selectively etch the silicon oxide film TG for another film FL. In the second etching step S47, in a state in which the pressure inside the chamber 2 exhibits a second pressure P2 lower than the atmospheric pressure, hydrogen fluoride gas is supplied into the chamber 2 to selectively etch the silicon oxide film TG for the other film FL. The second pressure P2 is lower than the first pressure P1.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a substrate processing method and a substrate processing apparatus. [Background technology]

[0002] The etching method described in Patent Document 1 includes the steps of preparing a substrate W on which a CVD oxide film and an ALD oxide film are formed, adjusting the temperature of the prepared substrate W to a first temperature greater than 0°C and less than 100°C, and supplying hydrogen fluoride gas and water vapor to the surface of the substrate whose temperature is adjusted to the first temperature, thereby selectively etching the CVD oxide film.

[0003] By contacting a substrate on which an ALD oxide film and a CVD oxide film have been formed with hydrogen fluoride gas and water vapor at a first temperature greater than 0° C. and less than 100° C., the CVD oxide film can be etched while suppressing etching of the ALD oxide film. This allows the CVD oxide film to be etched with a high selectivity relative to the ALD oxide film. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-114628 Summary of the Invention [Problem to be solved by the invention]

[0005] The inventors of the present application have made a new discovery in relation to the etching method described in Patent Document 1.

[0006] That is, the inventors of the present application have found that when etching is repeated multiple times on the same substrate, the reproducibility of the etching results (for example, the amount of etching) may become insufficient.

[0007] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a substrate processing method and a substrate processing apparatus that can ensure reproducibility of etching results even when etching processes are repeated multiple times on the same substrate. [Means for solving the problem]

[0008] According to one aspect of the present invention, a substrate processing method includes etching a silicon oxide film formed on a substrate. The substrate processing method includes a first etching step and a second etching step. In the first etching step, ,blood In a state where the pressure in the chamber indicates a first pressure lower than atmospheric pressure, hydrogen fluoride gas is supplied into the chamber to selectively etch the silicon oxide film relative to other films. In a second etching step, in a state where the pressure in the chamber indicates a second pressure lower than atmospheric pressure, hydrogen fluoride gas is supplied into the chamber to selectively etch the silicon oxide film relative to other films. The second pressure is lower than the first pressure. The first etching step is preferably a step of setting the pressure in the chamber to a first pressure lower than atmospheric pressure while stopping the supply of hydrogen fluoride gas into the chamber, and then supplying hydrogen fluoride gas into the chamber while the pressure in the chamber is maintained at the first pressure, thereby selectively etching the silicon oxide film relative to other films. The second etching step is preferably a step of, after completion of the first etching step, setting the pressure in the chamber to a second pressure lower than atmospheric pressure while stopping the supply of hydrogen fluoride gas into the chamber, and then supplying hydrogen fluoride gas into the chamber while maintaining the pressure in the chamber at the second pressure, thereby selectively etching the silicon oxide film relative to the other films. In the second etching step, the pressure in the chamber is preferably set to the second pressure, thereby lowering the melting point and boiling point of the reaction product remaining on the substrate from the first etching step.

[0009] In one aspect of the present invention, the first etching step and the second etching step preferably constitute a two-stage etching process, and the two-stage etching process is preferably performed a plurality of times.

[0010] In one aspect of the present invention, the second pressure is preferably 50 Torr or less.

[0011] In one aspect of the present invention, the first pressure is preferably 600 Torr or less and 100 Torr or more.

[0012] In one aspect of the present invention, in the second etching step, the silicon oxide film is preferably etched while sublimating reaction products on the silicon oxide film that are produced in the first etching step.

[0013] According to another aspect of the present invention, a substrate processing apparatus etches a silicon oxide film formed on a substrate with hydrogen fluoride gas. The substrate processing apparatus includes a chamber, a hydrogen fluoride supply unit, a pressure control unit, and a control unit. The substrate is placed in the chamber. The hydrogen fluoride supply unit supplies hydrogen fluoride gas into the chamber. The pressure control unit controls the pressure in the chamber. The control unit controls the pressure control unit. The control unit controls the pressure control unit so that the pressure in the chamber becomes a first pressure lower than atmospheric pressure. The control unit controls the hydrogen fluoride supply unit to supply hydrogen fluoride gas into the chamber when the pressure in the chamber indicates the first pressure. The control unit controls the pressure control unit so that the pressure in the chamber becomes a second pressure lower than atmospheric pressure. The control unit controls the hydrogen fluoride supply unit to supply hydrogen fluoride gas into the chamber when the pressure in the chamber indicates the second pressure. The second pressure is lower than the first pressure. The control unit preferably controls the hydrogen fluoride supply unit and the pressure control unit. It is preferable that the control unit controls the hydrogen fluoride supply unit and the pressure control unit to perform a first etching step in which the pressure in the chamber is set to a first pressure lower than atmospheric pressure while the supply of hydrogen fluoride gas into the chamber is stopped, and then hydrogen fluoride gas is supplied into the chamber while the pressure in the chamber is maintained at the first pressure, thereby selectively etching the silicon oxide film relative to other films; and after the first etching step, the control unit controls the hydrogen fluoride supply unit and the pressure control unit to perform a second etching step in which the pressure in the chamber is set to a second pressure lower than atmospheric pressure while the supply of hydrogen fluoride gas into the chamber is stopped, and then hydrogen fluoride gas is supplied into the chamber while the pressure in the chamber is maintained at the second pressure, thereby selectively etching the silicon oxide film relative to the other films. The first pressure is preferably 100 Torr or more and 600 Torr or less, and the second pressure is preferably 50 Torr or less. In the second etching step, the pressure in the chamber is preferably set to the second pressure, thereby lowering the melting point and boiling point of the reaction product remaining on the substrate from the first etching step. In the second etching step, the silicon oxide film is preferably etched while sublimating reaction products formed on the silicon oxide film in the first etching step. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a substrate processing method and a substrate processing apparatus that can ensure reproducibility of etching results even when the same substrate is subjected to multiple etching processes. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a side view showing the inside of a substrate processing apparatus according to an embodiment of the present invention. [Figure 2] 10 is a graph showing the amount of etching by an etching process according to a comparative example. [Figure 3] 3 is a graph showing the amount of etching by the etching process according to Example 1 of the present invention. [Figure 4] 1 is a time chart showing a two-stage etching process according to the present embodiment. [Figure 5] 1 is a flowchart showing a substrate processing method according to the present embodiment. [Figure 6] 1 is a flowchart showing the first stage of a two-stage etching process according to the present embodiment. [Figure 7] 10 is a flowchart showing the latter stage of the two-stage etching process according to the present embodiment. [Figure 8] 10 is a flowchart showing the first stage of a two-stage etching process according to a modified example of the present embodiment. [Figure 9] 10 is a flowchart showing the latter stage of a two-stage etching process according to a modified example of the present embodiment. [Figure 10] 10 is a graph showing the amount of etching by a two-stage etching process according to Example 2 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and description thereof will not be repeated.

[0017] Furthermore, unless otherwise specified, expressions indicating relative or absolute positional relationships (e.g., "in one direction," "along one direction," "parallel," "orthogonal," "center," "concentric," "coaxial," etc.) not only express that positional relationship exactly, but also express a state in which there is a relative displacement in terms of angle or distance within a range in which tolerance or equivalent functionality is obtained. Expressions indicating an equal state (e.g., "identical," "equal," "homogeneous," etc.) not only express a state in which there is strict quantitative equality, but also express a state in which there is a difference in which tolerance or equivalent functionality is obtained, unless otherwise specified. Expressions indicating shape (e.g., "square shape" or "cylindrical shape") not only express the geometrically strict shape, but also express a shape with, for example, irregularities or chamfers, within a range in which equivalent effects are obtained. The expressions "comprise," "include," or "have" a component are not exclusive expressions that exclude the presence of other components. The expression "at least one of A, B, and C" includes A only, B only, C only, any two of A, B, and C, and all of A, B, and C. This is not limited to the case where there are three selection elements (A, B, and C), but also applies to the case where there are two selection elements and the case where there are four or more selection elements.

[0018] A substrate processing apparatus 1 according to an embodiment of the present invention will be described with reference to Figures 1 to 7. First, the substrate processing apparatus 1 will be described with reference to Figure 1. Figure 1 is a side view showing the interior of the substrate processing apparatus 1 according to this embodiment.

[0019] 1, the substrate processing apparatus 1 is a single-wafer type substrate processing apparatus that etches substrates W such as semiconductor wafers one by one. The substrate processing apparatus 1 is, for example, a gas-phase substrate processing apparatus that does not use plasma. In this embodiment, the substrate processing apparatus 1 etches a silicon oxide film formed on the substrate W using hydrogen fluoride gas (hereinafter referred to as "HF gas").

[0020] The substrate processing apparatus 1 can be applied as part of an apparatus for manufacturing semiconductor devices. The substrate W is not necessarily limited to a substrate for a semiconductor device. The substrate W is, for example, a substrate for a liquid crystal display device, a substrate for a plasma display, a substrate for a field emission display (FED), a substrate for an optical disk, a substrate for a magnetic disk, a substrate for a magneto-optical disk, a substrate for a photomask, a ceramic substrate, or a substrate for a solar cell. Hereinafter, as an example, the substrate W is a silicon substrate.

[0021] A silicon oxide film is formed on the surface of the substrate W, for example, in a pre-process before the substrate W is loaded into the substrate processing apparatus 1. However, the location where the silicon oxide film is formed is not particularly limited. The silicon oxide film may be, for example, a silicon thermal oxide film, a TEOS (Tetra Ethoxy Silane) film, a BSG (Boron Silicate Glass) film, a PSG (Phospho Silicate Glass) film, a BPSG (Boron doped Phospho Silicate Glass) film, or an ALD (Atomic layer deposition) oxide film.

[0022] The silicon thermal oxide film is formed, for example, by a method of oxidizing the substrate W from its surface to its interior. Specifically, the substrate W is exposed to oxygen or water vapor in a high-temperature atmosphere, causing silicon (Si) and oxygen (O2) to chemically react with each other to form a thin film (thermal oxide film) of silicon dioxide (SiO2). The silicon thermal oxide film is dense. In other words, the density (film density) of the silicon thermal oxide film is high.

[0023] The TEOS film, BSG film, PSG film, and BPSG film are formed, for example, by chemical vapor deposition (CVD). In CVD, for example, the substrate W is exposed to a source gas containing components of the target thin film, and a chemical reaction is caused on the substrate W using heat or plasma. The target thin film is formed on the substrate W by the chemical reaction. For example, when a BSG film is formed by CVD, the source gas contains boron (B). The density (film density) of each of the TEOS film, BSG film, PSG film, and BPSG film is smaller than that of a thermal oxide film.

[0024] ALD oxide films are formed by atomic layer deposition (ALD). In the ALD process, a substrate W placed in a chamber is first exposed to precursor A. Next, precursor A is removed from the chamber by purging, and the substrate is then exposed to another precursor B (e.g., ozone). Then, precursor B is removed from the chamber again by purging. By repeating these processes, a film at the single-molecular level is formed layer by layer. Specifically, when a silicon oxide film is to be formed as the ALD oxide film, aminosilane is used as the source gas (precursor A), and when an aluminum oxide (Al2O3) film is to be formed, trimethylaluminum is used as the source gas. The density (film density) of an ALD oxide film is smaller than that of a thermal oxide film.

[0025] In this embodiment, the substrate processing apparatus 1 etches a silicon oxide film formed on a substrate W.

[0026] Hereinafter, the silicon oxide film to be etched by the substrate processing apparatus 1 will be referred to as a "silicon oxide film TG."

[0027] For example, not only the silicon oxide film TG but also other films (hereinafter referred to as "other films FL") are formed on the surface of the substrate W. The other films FL are formed, for example, in another pre-process before the substrate W is loaded into the substrate processing apparatus 1. However, the location where the other films FL are formed is not particularly limited. Furthermore, the other films FL are not particularly limited and may be, for example, a silicon oxide film different from the silicon oxide film TG or a film other than a silicon oxide film. For example, the silicon oxide film TG is a silicon thermal oxide film, and the other films FL are a TEOS film, a BSG film, a PSG film, a BPSG film, or an ALD oxide film.

[0028] For example, a silicon oxide film TG and another film FL are exposed on the surface of the substrate W. The substrate processing apparatus 1 then selectively etches the silicon oxide film TG relative to the other film FL.

[0029] The substrate processing apparatus 1 includes a chamber 2, a control unit 3, a substrate holder 4, a heating mechanism 5 for the substrate W, a gas distribution plate 6, an exhaust pipe 7, a vacuum pump 8, a pressure control valve 9, a pressure sensor 10, a gas supply pipe 11, a water vapor supply unit 30, an HF (hydrogen fluoride) supply unit 40, and a nitrogen supply unit 50.

[0030] The chamber 2 is hollow and can accommodate the substrate W. That is, the substrate W is placed in the chamber 2. The internal space of the chamber 2 corresponds to a processing chamber in which the etching process is performed on the substrate W.

[0031] The control unit 3 controls the substrate holder 4 , the heating mechanism 5 , the vacuum pump 8 , the pressure control valve 9 , the pressure sensor 10 , the water vapor supply unit 30 , the HF supply unit 40 , and the nitrogen supply unit 50 .

[0032] The control unit 3 includes a processor and a storage device. The processor is, for example, a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The storage device stores data and computer programs. The storage device includes a main storage device and an auxiliary storage device. The main storage device is, for example, a semiconductor memory. The auxiliary storage device is, for example, a semiconductor memory, a solid state drive, or a hard disk drive. The storage device may include removable media. The storage device corresponds to an example of a non-transitory computer-readable storage medium.

[0033] In the chamber 2, a substrate holder 4, a heating mechanism 5, a gas distribution plate 6 and a pressure sensor 10 are arranged.

[0034] The substrate holder 4 holds the substrate W in a substantially horizontal position within the chamber 2. "Horizontal position" indicates that the substrate W is parallel to a horizontal plane. The substrate W is carried into the chamber 2 from the outside by a transport mechanism (not shown) and placed on the substrate holder 4. The substrate holder 4 may hold the substrate W by suction, or may clamp the peripheral edge of the substrate W with multiple chuck pins. Note that the substrate holder 4 does not necessarily have to hold the substrate W, and may simply support the substrate W. In other words, the substrate holder 4 may be a mounting table on which the substrate W is placed.

[0035] The heating mechanism 5 heats the substrate W held by the substrate holder 4. Specifically, the heating mechanism 5 heats the substrate W to set the temperature of the substrate W to a target temperature. In the example of FIG. 1, the heating mechanism 5 is built into the substrate holder 4. The heating mechanism 5 is, for example, a resistance heating type electric heater. Note that the heating mechanism 5 may include, for example, a lamp instead of an electric heater. The lamp may irradiate the substrate W with infrared rays to set the substrate W to the target temperature.

[0036] The gas dispersion plate 6 is disposed above the substrate holder 4 within the chamber 2. The gas dispersion plate 6 is disposed between the substrate holder 4 and the outlet of the gas supply pipe 11 within the chamber 2. The gas dispersion plate 6 is formed in the shape of a plate that extends horizontally within the chamber 2. The gas dispersion plate 6 has a plurality of openings 6H. Specifically, the gas dispersion plate 6 has a plurality of openings 6H that penetrate through the plate in the thickness direction and are distributed horizontally.

[0037] An exhaust pipe 7 is connected to the chamber 2. In the example of FIG. 1, the exhaust pipe 7 is connected to the bottom of the chamber 2 and is in communication with the interior of the chamber 2. A vacuum pump 8 is connected to the exhaust pipe 7. The vacuum pump 8 reduces the pressure inside the chamber 2 by sucking in gas from the chamber 2 through the exhaust pipe 7. Specifically, the vacuum pump 8 reduces the pressure inside the chamber 2, thereby creating a vacuum inside the chamber 2. A vacuum refers to a state in which the pressure inside the chamber 2 is lower than atmospheric pressure. As an example, a vacuum refers to a state in which the pressure inside the chamber 2 is 600 Torr or less.

[0038] A pressure control valve 9 is disposed in the exhaust pipe 7. The pressure control valve 9 adjusts the exhaust flow rate of the gas in the chamber 2 by adjusting the opening of the exhaust pipe 7. As a result, the pressure in the chamber 2 is adjusted. In other words, the pressure control valve 9 controls the pressure in the chamber 2 by adjusting the exhaust flow rate of the gas in the chamber 2. The pressure control valve 9 is, for example, an APC (Auto Pressure Controller) valve. The pressure control valve 9 corresponds to an example of the "pressure control unit" of the present invention.

[0039] Specifically, the pressure control valve 9 controls the degree of vacuum in the chamber 2 by adjusting the opening of the exhaust pipe 7. In other words, the pressure control valve 9 controls the degree of vacuum in the chamber 2 by adjusting the exhaust flow rate of the gas in the chamber 2.

[0040] The degree of vacuum indicates the degree of vacuum within the chamber 2. In other words, the degree of vacuum is an index showing the state of vacuum within the chamber 2. As an example, the degree of vacuum is indicated by the pressure within the chamber 2. The higher the degree of vacuum, the lower the pressure within the chamber 2, indicating a high vacuum state. On the other hand, the lower the degree of vacuum, the higher the pressure within the chamber 2, indicating a low vacuum state.

[0041] The pressure sensor 10 is connected to the chamber 2 and detects the pressure inside the chamber 2. The pressure sensor 10 outputs an electrical signal indicating the detected pressure inside the chamber 2 to the control unit 3. The control unit 3 controls the pressure control valve 9 so that the pressure detected by the pressure sensor 10 becomes a target pressure. In this embodiment, the target pressure is a first pressure P1, a second pressure P2, or a third pressure P3, which will be described later.

[0042] In other words, the control unit 3 controls the pressure control valve 9 based on the detection result of the pressure sensor 10. Specifically, the control unit 3 controls the pressure control valve 9 so that the pressure detected by the pressure sensor 10 indicates the target vacuum. In this embodiment, the target vacuum is a first vacuum VC1, a second vacuum VC2, or a third vacuum VC3, which will be described later.

[0043] After the substrate W is held by the substrate holder 4, the vacuum pump 8 is activated to begin evacuating the chamber 2. In this embodiment, the vacuum pump 8 is used as a means for reducing the pressure inside the chamber 2, but this is not limiting. For example, the pressure can also be reduced by exhausting factory utilities. In short, the specific configuration of the exhaust unit that exhausts gas inside the chamber 2 can be changed as appropriate.

[0044] A gas supply pipe 11 is connected to the chamber 2. In the example of FIG. 1, the gas supply pipe 11 is connected to the upper part of the chamber 2 in a state of communication with the interior of the chamber 2. In the example of FIG. 1, the gas supply pipe 11 includes a common pipe 111 and branch pipes 112 to 114. One end of the common pipe 111 is connected to the upper part of the chamber 2.

[0045] The branch pipe 112 connects the common pipe 111 and the water vapor supply unit 30. The water vapor supply unit 30 vaporizes water to generate water vapor. The water vapor supply unit 30 then supplies water vapor into the chamber 2 via the gas supply pipe 11 (the branch pipe 112 and the common pipe 111).

[0046] Specifically, the water vapor supply unit 30 includes a vaporizer 12, a water flow rate controller 13A, a nitrogen gas flow rate controller 13B, and an on-off valve 16. The control unit 3 controls the vaporizer 12, the water flow rate controller 13A, the nitrogen gas flow rate controller 13B, and the on-off valve 16.

[0047] Branch pipe 112 connects common pipe 111 and vaporizer 12. Vaporizer 12 vaporizes water to generate water vapor. Pipes 112A and 112B are connected to vaporizer 12. Pipe 112A is connected to a water supply source (not shown). Pipe 112A supplies water to vaporizer 12. A water flow controller 13A is arranged in pipe 112A. The water flow controller 13A controls the flow rate of water supplied to vaporizer 12. Pipe 112B is connected to a nitrogen supply source (not shown). Pipe 112B supplies nitrogen gas to vaporizer 12. A nitrogen gas flow controller 13B is arranged in pipe 112B. The nitrogen gas flow controller 13B controls the flow rate of nitrogen gas supplied to vaporizer 12. Water flow controller 13A and nitrogen gas flow controller 13B are, for example, mass flow controllers.

[0048] Vaporizer 12 generates water vapor by vaporizing water supplied from pipe 112A and supplies the water vapor to branch pipe 112. The flow rate of water is controlled by water flow rate controller 13A, thereby adjusting the flow rate of water vapor supplied from vaporizer 12 to branch pipe 112. In other words, the flow rate of water vapor supplied from vaporizer 12 to chamber 2 is adjusted by controlling the flow rate of water by water flow rate controller 13A.

[0049] An on-off valve 16 is disposed in branch pipe 112. On-off valve 16 opens and closes the flow path of branch pipe 112. When on-off valve 16 opens the flow path of branch pipe 112, water vapor generated in vaporizer 12 is supplied from gas supply pipe 11 (branch pipe 112 and common pipe 111) into chamber 2. In this case, nitrogen gas supplied from pipe 112B is used as a carrier gas for water vapor. Therefore, the nitrogen gas transports water vapor generated in vaporizer 12 into chamber 2 via gas supply pipe 11 (branch pipe 112 and common pipe 111).

[0050] The branch pipe 113 connects the common pipe 111 and the HF supply unit 40. The HF supply unit 40 supplies HF gas (hydrogen fluoride gas) into the chamber 2 via the gas supply pipe 11 (the branch pipe 113 and the common pipe 111).

[0051] Specifically, the HF supply unit 40 includes an HF (hydrogen fluoride) gas flow rate controller 14 and an on-off valve 17. The control unit 3 controls the HF gas flow rate controller 14 and the on-off valve 17.

[0052] The branch pipe 113 connects the common pipe 111 and an HF (hydrogen fluoride) supply source (not shown). The HF supply source supplies HF gas into the branch pipe 113. The HF gas may be, for example, anhydrous HF gas. Anhydrous HF gas is HF gas that contains almost no moisture, for example, a moisture content (volume ratio) of several tens (e.g., 10) vol. ppm or less. An HF gas flow controller 14 is disposed in the branch pipe 113. The HF gas flow controller 14 controls the flow rate of the HF gas supplied into the chamber 2. The HF gas flow controller 14 is, for example, a mass flow controller.

[0053] An on-off valve 17 is disposed in the branch pipe 113. The on-off valve 17 opens and closes the flow path of the branch pipe 113. When the on-off valve 17 opens the flow path of the branch pipe 113, HF gas is supplied from the gas supply pipe 11 (branch pipe 113 and common pipe 111) into the chamber 2. The flow rate of the HF gas supplied into the chamber 2 is adjusted by controlling the flow rate of the HF gas with the HF gas flow rate controller 14.

[0054] The branch pipe 114 connects the common pipe 111 and the nitrogen supply unit 50. The nitrogen supply unit 50 supplies nitrogen gas into the chamber 2 via the gas supply pipe 11 (the branch pipe 114 and the common pipe 111).

[0055] Specifically, the nitrogen supply unit 50 includes a nitrogen gas flow rate controller 15 and an on-off valve 18. The control unit 3 controls the nitrogen gas flow rate controller 15 and the on-off valve 18.

[0056] The branch pipe 114 connects the common pipe 111 and a nitrogen supply source (not shown). The nitrogen supply source supplies nitrogen gas into the branch pipe 114. The nitrogen gas also contains almost no moisture, and the moisture content (volume ratio) in the nitrogen gas is, for example, several tens (e.g., 10) vol.ppm or less. A nitrogen gas flow controller 15 is disposed in the branch pipe 114. The nitrogen gas flow controller 15 controls the flow rate of the nitrogen gas supplied into the chamber 2. The nitrogen gas flow controller 15 is, for example, a mass flow controller.

[0057] An on-off valve 18 is disposed in the branch pipe 114. The on-off valve 18 opens and closes the flow path of the branch pipe 114. When the on-off valve 18 opens the flow path of the branch pipe 114, nitrogen gas is supplied from the gas supply pipe 11 (branch pipe 114 and common pipe 111) into the chamber 2. The flow rate of the nitrogen gas is controlled by the nitrogen gas flow rate controller 15, so that the flow rate of the nitrogen gas supplied into the chamber 2 is adjusted.

[0058] The nitrogen gas supplied from the branch pipe 114 is supplied into the chamber 2 to adjust the pressure (vacuum level) inside the chamber 2 or to purge the chamber 2 after etching processing under reduced pressure. Note that an inert gas such as a rare gas (e.g., argon gas) may be used instead of nitrogen gas. The inert gas is a gas that has poor reactivity with both the HF gas and the substrate W.

[0059] Water vapor (containing nitrogen gas as a carrier gas) and HF gas are supplied into chamber 2 via gas supply pipe 11, which is connected to the internal space of chamber 2, and pass through gas dispersion plate 6 to reach substrate W. Specifically, a mixed gas of water vapor (containing nitrogen gas as a carrier gas) and HF gas supplied above gas dispersion plate 6 in chamber 2 moves below gas dispersion plate 6 by passing through a plurality of openings 6H provided in gas dispersion plate 6, and is then uniformly supplied onto substrate W. The inner diameter of opening 6H is, for example, 0.1 mm. The distance between adjacent openings 6H is, for example, 5 mm.

[0060] When water vapor and HF gas flow onto the surface of the silicon oxide film TG of the substrate W, the silicon oxide film TG is etched. - (hydrogen fluoride ion) is known to contribute. HF2 - is generated by a reaction between HF gas and water vapor (HO). Specifically, when water vapor and HF gas flow onto the surface of the silicon oxide film TG of the substrate W, the silicon oxide film TG is selectively etched relative to other films FL.

[0061] 1, only one gas distribution plate 6 is installed in the chamber 2, but multiple gas distribution plates 6 may be installed in multiple layers one above the other. Furthermore, if it is not necessary for the water vapor and HF gas supplied into the chamber 2 to act uniformly on the substrate W, or if the water vapor and HF gas can be rectified by a configuration other than the gas distribution plate 6, the gas distribution plate 6 is not necessary.

[0062] Next, to facilitate understanding of this embodiment, etching results of a comparative example and etching results of a basic experiment of this embodiment (Example 1 of the present invention) will be described with reference to FIGS. 2 and 3. FIG.

[0063] 2 is a graph showing the etching amount by the etching process according to the comparative example. The vertical axis represents the etching amount (nm). In this specification, the etching amount represents the difference between the thickness of the silicon oxide film TG before etching and the thickness of the silicon oxide film TG after etching. The horizontal axis represents the order of the etching process.

[0064] In the comparative example, an experiment was carried out using a substrate processing apparatus having the same hardware configuration as the substrate processing apparatus 1 shown in Fig. 1. For ease of explanation, the following description will be given with the same reference numerals as the elements of the substrate processing apparatus 1 in the comparative example.

[0065] In the comparative example, the silicon oxide film TG formed on the substrate W was a low pressure (LP)-TEOS film. The silicon oxide film TG was etched using HF gas. The pressure in the chamber 2 was 150 Torr. The flow rate of the HF gas supplied from the HF supply unit 40 to the chamber 2 was 1 slm. The flow rate of the water vapor supplied from the water vapor supply unit 30 to the chamber 2 was 1 slm. The flow rate of the nitrogen gas supplied from the nitrogen supply unit 50 to the chamber 2 was 7 slm. "slm" stands for "standard liter / min," a unit representing the flow rate in liters per minute. The temperature of the substrate W was 100°C. These conditions were the same for both the first etching process (horizontal axis "1") and the second etching process (horizontal axis "2").

[0066] A first etching process (horizontal axis "1") was performed using HF gas in chamber 2. After the first etching process was completed, the substrate W was removed from chamber 2 and the thickness of the silicon oxide film TG was measured. The first etching amount was calculated based on the film thickness measurement results. As a result, the etching amount in the first etching process was 3.2 [nm]. The etching time was 300 seconds.

[0067] Next, the same substrate W, i.e., the substrate W after the first etching process, was returned to chamber 2 and subjected to a second etching process (horizontal axis "2") under the same conditions as the first etching process. After the second etching process was completed, the substrate W was removed from chamber 2 and the film thickness of the silicon oxide film TG was measured. The second etching amount was calculated based on the film thickness measurement results. As a result, the etching amount in the second etching process was 5.6 [nm]. The etching time was 300 seconds.

[0068] The difference between the etching amount in the first and second etching processes was 2.3 [nm]. Thus, when the pressure in chamber 2 was 150 [Torr], the reproducibility of the etching amount between the first and second etching processes was insufficient.

[0069] The inventors of the present application speculated that the reason for the insufficient reproducibility of the etching amount was as follows. Specifically, the inventors of the present application speculated that a layer containing reaction products generated during the first etching process remained on the surface of the silicon oxide film TG of the substrate W. The reaction products remaining on the surface of the silicon oxide film TG were silicon fluoride-based reaction products. For example, it was speculated that a mixed gas of water vapor and HF gas reacted with the silicon oxide film TG to generate silicon fluoride-based reaction products. However, it was speculated that the reaction products remaining on the surface of the silicon oxide film TG could include reaction products other than silicon fluoride-based reaction products. The inventors of the present application speculated that the reaction products remaining on the surface of the silicon oxide film TG affected the second etching process using the same substrate W, resulting in insufficient reproducibility of the etching amount.

[0070] Therefore, in order to ensure the reproducibility of the etching amount by promoting the sublimation and exhaust of the reaction products, the pressure in chamber 2 was set to 50 Torr, which is lower than 150 Torr, and a basic experiment (Example 1) of this embodiment was conducted.

[0071] 3 is a graph showing the etching amount by the etching process according to Example 1 of the present invention, where the vertical axis represents the etching amount (nm) and the horizontal axis represents the order of the etching process.

[0072] In Example 1, the silicon oxide film TG formed on the substrate W was an LP-TEOS film. The silicon oxide film TG was etched using HF gas. The pressure inside the chamber 2 was 50 Torr. The flow rate of the HF gas supplied from the HF supply unit 40 to the chamber 2 was 1.5 slm. The flow rate of the water vapor supplied from the water vapor supply unit 30 to the chamber 2 was 2 slm. The flow rate of the nitrogen gas supplied from the nitrogen supply unit 50 to the chamber 2 was 4 slm. The temperature of the substrate W was 100°C. These conditions were the same for both the first etching process (horizontal axis "1") and the second etching process (horizontal axis "2").

[0073] A first etching process (horizontal axis "1") was performed using HF gas in chamber 2. When the first etching process was completed, the substrate W was removed from chamber 2, and the film thickness of the silicon oxide film TG was measured. The first etching amount was calculated based on the film thickness measurement results. As a result, the etching amount in the first etching process was 1.2 [nm]. The etching time was 240 seconds.

[0074] Next, the same substrate W, i.e., the substrate W after the first etching process, was returned to chamber 2 and subjected to a second etching process (horizontal axis "2") under the same conditions as the first etching process. After the second etching process was completed, the substrate W was removed from chamber 2 and the film thickness of the silicon oxide film TG was measured. The second etching amount was calculated based on the film thickness measurement results. As a result, the etching amount in the second etching process was 1.5 [nm]. The etching time was 240 seconds.

[0075] The difference between the etching amount in the first and second etching processes was 0.3 nm. Thus, when the pressure in chamber 2 was 50 Torr, the reproducibility of the etching amount was ensured between the first and second etching processes.

[0076] The inventors of the present application speculate that the reason why the etching amount can be reproducibly maintained is as follows. That is, by reducing the pressure in chamber 2 from 150 Torr to 50 Torr, the melting point and boiling point of the reaction products remaining on the surface of the silicon oxide film TG by the first etching process were lowered. Therefore, the reaction products became more likely to sublimate. As a result, the inventors of the present application speculate that the sublimation and exhaust of the reaction products was promoted in the second etching process, thereby reducing the influence of the reaction products on the etching. Therefore, the etching amount could be reproducibly maintained between the first and second etching processes.

[0077] Therefore, in this embodiment, the substrate processing apparatus 1 shown in FIG. 1 performs a two-stage etching process. The two-stage etching process refers to a process in which an etching process of a silicon oxide film TG using HF gas is performed at a first pressure P1, an etching process of a silicon oxide film TG using HF gas at the first pressure P1 is performed, and then an etching process of a silicon oxide film TG using HF gas at a second pressure P2 is performed. In this specification, the first pressure P1 is lower than atmospheric pressure. Also, the second pressure P2 is lower than atmospheric pressure. Furthermore, the second pressure P2 is lower than the first pressure P1.

[0078] In other words, the two-stage etching process is a process in which an etching process of the silicon oxide film TG using HF gas is performed at a first vacuum degree VC1, an etching process of the silicon oxide film TG using HF gas at the first vacuum degree VC1 is performed, and then an etching process of the silicon oxide film TG using HF gas is performed at a second vacuum degree VC2. The second vacuum degree VC2 indicates a higher vacuum degree than the first vacuum degree VC1. The second vacuum degree VC2 indicates a second pressure P2. The first vacuum degree VC1 indicates a first pressure P1.

[0079] Specifically, the control unit 3 controls the pressure control valve 9 so that the pressure in the chamber 2 becomes a first pressure P1 that is lower than atmospheric pressure. As a result, the pressure control valve 9 sets the pressure in the chamber 2 to the first pressure P1.

[0080] In other words, the control unit 3 controls the pressure control valve 9 so that the degree of vacuum in the chamber 2 becomes the first degree of vacuum VC1. As a result, the pressure control valve 9 sets the degree of vacuum in the chamber 2 to the first degree of vacuum VC1.

[0081] Furthermore, the control unit 3 controls the HF supply unit 40 to supply HF gas into the chamber 2 when the pressure inside the chamber 2 indicates the first pressure P1. As a result, the HF supply unit 40 supplies HF gas into the chamber 2 when the pressure inside the chamber 2 indicates the first pressure P1. Therefore, under the first pressure P1, the silicon oxide film TG formed on the substrate W is etched by the HF gas. Specifically, under the first pressure P1, the silicon oxide film TG is selectively etched by the HF gas relative to other films FL.

[0082] In other words, the control unit 3 controls the HF supply unit 40 to supply HF gas into the chamber 2 when the degree of vacuum in the chamber 2 indicates the first degree of vacuum VC1. As a result, the HF supply unit 40 supplies HF gas into the chamber 2 when the degree of vacuum in the chamber 2 indicates the first degree of vacuum VC1. Therefore, at the first degree of vacuum VC1, the silicon oxide film TG formed on the substrate W is etched by the HF gas. Specifically, at the first degree of vacuum VC1, the silicon oxide film TG is selectively etched by the HF gas relative to other films FL.

[0083] Next, the control unit 3 controls the pressure control valve 9 so that the pressure in the chamber 2 becomes a second pressure P2 that is lower than atmospheric pressure. As a result, the pressure control valve 9 sets the pressure in the chamber 2 to the second pressure P2.

[0084] In other words, the control unit 3 controls the pressure control valve 9 so that the degree of vacuum in the chamber 2 becomes the second degree of vacuum VC2. As a result, the pressure control valve 9 sets the degree of vacuum in the chamber 2 to the second degree of vacuum VC2.

[0085] Furthermore, the control unit 3 controls the HF supply unit 40 to supply HF gas into the chamber 2 when the pressure in the chamber 2 indicates the second pressure P2. As a result, the HF supply unit 40 supplies HF gas into the chamber 2 when the pressure in the chamber 2 indicates the second pressure P2. Therefore, under the second pressure P2, the silicon oxide film TG formed on the substrate W is etched by the HF gas. Specifically, under the second pressure P2, the silicon oxide film TG is selectively etched by the HF gas relative to the other films FL.

[0086] In other words, the control unit 3 controls the HF supply unit 40 to supply HF gas into the chamber 2 when the degree of vacuum in the chamber 2 indicates the second degree of vacuum VC2. As a result, the HF supply unit 40 supplies HF gas into the chamber 2 when the degree of vacuum in the chamber 2 indicates the second degree of vacuum VC2. Therefore, at the second degree of vacuum VC2, the silicon oxide film TG formed on the substrate W is etched by the HF gas. Specifically, at the second degree of vacuum VC2, the silicon oxide film TG is selectively etched by the HF gas relative to the other films FL.

[0087] As described above with reference to FIG. 1 , according to this embodiment, after a first etching step under a first pressure P1, a second etching step is performed under a second pressure P2 lower than the first pressure P1 (two-stage etching process). Therefore, in the second etching step, the melting point and boiling point of the reaction products on the silicon oxide film TG resulting from HF gas are lower than those in the first etching step. As a result, in the second etching step, the sublimation and exhaust of the reaction products on the silicon oxide film TG generated in the first etching step are promoted. This reduces the influence of the reaction products on the second etching step, ensuring reproducibility of the etching amount between the first and second etching steps. In other words, even when the same substrate W is subjected to multiple etching steps, reproducibility of the etching results can be ensured. The reaction products on the silicon oxide film TG are silicon fluoride-based reaction products. Furthermore, the reaction products on the silicon oxide film TG may include reaction products other than silicon fluoride-based reaction products.

[0088] That is, in this embodiment, in the second etching process of the two-stage etching process, the silicon oxide film TG is selectively etched relative to the other films FL while the reaction products on the silicon oxide film TG are removed by sublimation.

[0089] Next, the two-stage etching process will be described in detail with reference to Figures 1 and 4. Figure 4 is a time chart showing the two-stage etching process according to this embodiment.

[0090] As shown in FIG. 4, at time t0, the vacuum pump 8 reduces the pressure in the chamber 2, and the pressure control valve 9 sets the pressure in the chamber 2 to a third pressure P3. That is, the pressure control valve 9 sets the vacuum level in the chamber 2 to a third vacuum level VC3. The third vacuum level VC3 indicates the third pressure P3. The third pressure P3 is, for example, 2×10 -2 At time t0, the on-off valves 16 to 18 close the flow paths of the branch pipes 112 to 114, respectively.

[0091] At time t1, the on-off valve 18 opens the flow path of the branch pipe 114. As a result, nitrogen gas is supplied from the nitrogen supply unit 50 into the chamber 2. Nitrogen gas is supplied into the chamber 2 for a predetermined period T11. Also, at time t1, the pressure control valve 9 sets the pressure in the chamber 2 to a first pressure P1. That is, the pressure control valve 9 sets the vacuum level in the chamber 2 to a first vacuum level VC1. The first vacuum level VC1 indicates the first pressure P1. The first pressure P1 is higher than the third pressure P3. Therefore, the first vacuum level VC1 indicates a vacuum level lower than the third vacuum level VC3. The first pressure P1 is, for example, 150 Torr. In the chamber 2, the first pressure P1 (first vacuum level VC1) is maintained for a predetermined period T12.

[0092] At time t2, the on-off valve 16 opens the flow path of the branch pipe 112. As a result, water vapor is supplied from the water vapor supply unit 30 into the chamber 2. Water vapor is supplied into the chamber 2 for a predetermined period T13.

[0093] At time t3, the on-off valve 17 opens the flow path of the branch pipe 113. As a result, HF gas is supplied from the HF supply unit 40 into the chamber 2. This starts etching the silicon oxide film TG formed on the substrate W. HF gas is supplied into the chamber 2 for a predetermined period T14.

[0094] At time t4, the on-off valve 16 closes the flow path of the branch pipe 112, and the on-off valve 17 closes the flow path of the branch pipe 113. As a result, the supply of water vapor and HF gas into the chamber 2 is stopped. This completes the etching of the silicon oxide film TG formed on the substrate W.

[0095] At time t5, the pressure control valve 9 sets the pressure in the chamber 2 to a third pressure P3. That is, the pressure control valve 9 sets the vacuum level in the chamber 2 to a third vacuum level VC3. The on-off valve 18 also closes the flow path of the branch pipe 114. As a result, the supply of nitrogen gas from the nitrogen supply unit 50 into the chamber 2 is stopped. During the period from time t4 to time t5, the gas in the chamber 2 is purged with nitrogen gas.

[0096] At time t6, the on-off valve 18 opens the flow path of the branch pipe 114. As a result, nitrogen gas is supplied from the nitrogen supply unit 50 into the chamber 2. Nitrogen gas is supplied into the chamber 2 for a predetermined period T21. Also, at time t6, the pressure control valve 9 sets the pressure in the chamber 2 to a second pressure P2. That is, the pressure control valve 9 sets the vacuum level in the chamber 2 to a second vacuum level VC2. The second vacuum level VC2 represents the second pressure P2. The second pressure P2 is higher than the third pressure P3 and lower than the first pressure P1. Therefore, the second vacuum level VC2 represents a vacuum level lower than the third vacuum level VC3 and higher than the first vacuum level VC1. The second pressure P2 is, for example, 50 Torr. In the chamber 2, the second pressure P2 (second vacuum level VC2) is maintained for a predetermined period T22.

[0097] At time t7, the on-off valve 16 opens the flow path of the branch pipe 112. As a result, water vapor is supplied from the water vapor supply unit 30 into the chamber 2. Water vapor is supplied into the chamber 2 for a predetermined period T23.

[0098] At time t8, the on-off valve 17 opens the flow path of the branch pipe 113. As a result, HF gas is supplied from the HF supply unit 40 into the chamber 2. This starts etching the silicon oxide film TG formed on the substrate W. In this case, the silicon oxide film is etched while reaction products on the silicon oxide film TG are sublimated and exhausted. HF gas is supplied into the chamber 2 for a predetermined period T24.

[0099] At time t9, the on-off valve 16 closes the flow path of the branch pipe 112, and the on-off valve 17 closes the flow path of the branch pipe 113. As a result, the supply of water vapor and HF gas into the chamber 2 is stopped. Thus, etching of the silicon oxide film formed on the substrate W is completed.

[0100] At time t10, the pressure control valve 9 sets the pressure in the chamber 2 to a third pressure P3. That is, the pressure control valve 9 sets the vacuum level in the chamber 2 to a third vacuum level VC3. Also, at time t10, the on-off valve 18 closes the flow path of the branch pipe 114. As a result, the supply of nitrogen gas from the nitrogen supply unit 50 into the chamber 2 is stopped. During the period from time t9 to time t10, the gas in the chamber 2 is purged with nitrogen gas.

[0101] Hereinafter, for convenience of explanation, the process from time t1 to time t4 may be referred to as the "first etching process," and the process from time t6 to time t9 may be referred to as the "second etching process." When the substrate W is unloaded from the chamber 2 after the second etching process is completed, for example, the vacuum pump 8 stops suction, and the pressure control valve 9 sets the pressure in the chamber 2 to atmospheric pressure. In this case, it is preferable that the nitrogen supply unit 50 supplies nitrogen gas into the chamber 2.

[0102] In the first etching step, the timing of setting the pressure in chamber 2 to first pressure P1 and the timing of supplying nitrogen are not limited to the order shown in FIG. 4 and may be in any order. In the second etching step, the timing of setting the pressure in chamber 2 to second pressure P2 and the timing of supplying nitrogen are not limited to the order shown in FIG. 4 and may be in any order. Furthermore, in each of the first and second etching steps, the timing of supplying nitrogen and the timing of supplying HF gas are not limited to the order shown in FIG. 4 and may be in any order, or may be simultaneous. Furthermore, in each of the first and second etching steps, the timing of stopping the supply of HF gas and the timing of stopping the supply of water vapor are not limited to the order shown in FIG. 4 and may be in any order. Furthermore, in each of the first and second etching steps, the timing of setting the pressure in chamber 2 to third pressure P3 and the timing of stopping the supply of nitrogen gas are not limited to the order shown in FIG. 4 and may be in any order.

[0103] The two-stage etching process has been described above with reference to FIG. 4. In this case, in the second etching step, the silicon oxide film TG is etched while the reaction products on the silicon oxide film TG generated in the first etching step are sublimated. Specifically, in the second etching step, the silicon oxide film is selectively etched relative to other films FL while the reaction products on the silicon oxide film generated in the first etching step are sublimated. Therefore, the influence of the reaction products on the etching in the second etching step is reduced, and the reproducibility of the etching amount can be ensured between the first etching step and the second etching step.

[0104] Furthermore, the second pressure P2 during the second etching step is preferably 50 Torr or less. This preferred example effectively promotes sublimation and exhaust of reaction products (e.g., silicon fluoride-based reaction products). Specifically, the second pressure P2 is 50 Torr or less and 1 Torr or more.

[0105] Furthermore, the first pressure P1 during the first etching step is preferably 600 Torr or less and 100 Torr or more. This preferred example allows for a larger etching amount compared to the second etching step. This is because the higher the pressure in the chamber 2, the greater the etching amount of the silicon oxide film TG. This point is also clear from the comparison of the first etching amount (150 Torr) in FIG. 2 with the first etching amount (50 Torr) in FIG. 3.

[0106] Next, a substrate processing method according to this embodiment will be described with reference to Figures 1 and 5 to 7. In the substrate processing method, a silicon oxide film TG formed on a substrate W is etched. The substrate processing method is performed by a substrate processing apparatus 1.

[0107] 5 is a flowchart showing the substrate processing method according to this embodiment. As shown in FIG. 5, the substrate processing method includes steps S1 to S6.

[0108] First, in step S1, a substrate W to be etched by the substrate processing apparatus 1 is prepared. A silicon oxide film TG is formed and exposed on the upper surface of the substrate W. Specifically, a silicon oxide film TG and another film FL are formed and exposed on the upper surface of the substrate W.

[0109] Next, in step S2, a transfer mechanism (not shown) loads the substrate W into the chamber 2 and places the substrate W on the substrate holder 4. In this case, the substrate W is placed in an orientation in which the surface on which the silicon oxide film TG and the other film FL are formed faces upward.

[0110] Next, in step S3, the control unit 3 controls the heating mechanism 5 to set the temperature of the substrate W to the target temperature. As a result, the heating mechanism 5 heats the substrate W to set the temperature of the substrate W to the target temperature. The target temperature is a temperature higher than room temperature. The target temperature is, for example, 100°C.

[0111] Next, in step S4, the substrate processing apparatus 1 performs a two-stage etching process. The two-stage etching process is a process in which the silicon oxide film TG is etched with HF gas (hydrogen fluoride gas) under a first pressure P1, the silicon oxide film TG is etched with HF gas under the first pressure P1, and then the silicon oxide film TG is etched with HF gas under a second pressure P2 (see FIG. 4). Specifically, the two-stage etching process is a process in which the silicon oxide film TG is selectively etched with HF gas under the first pressure P1, the silicon oxide film TG is selectively etched with HF gas under the first pressure P1, and then the silicon oxide film TG is selectively etched with HF gas under the second pressure P2.

[0112] Hereinafter, step S4 may be referred to as "two-stage etching treatment step S4."

[0113] Next, in step S5, the control unit 3 determines whether the two-stage etching process in step S4 has been performed a predetermined number of times NM.

[0114] If it is determined in step S5 that the two-stage etching process has not been performed the predetermined number of times NM (No in step S5), the process proceeds to step S4. Therefore, step S4 is repeated until the two-stage etching process has been performed the predetermined number of times NM.

[0115] The predetermined number of times NM is, for example, 1. However, the predetermined number of times NM may be multiple times (2 or more).

[0116] On the other hand, if it is determined in step S5 that the two-stage etching process has been performed the predetermined number of times NM (Yes in step S5), the process proceeds to step S6.

[0117] Next, in step S6, a transfer mechanism (not shown) transfers the substrate W out of the chamber 2. Then, the substrate processing method ends.

[0118] Next, the two-stage etching process of step S4 in Fig. 5 will be described in detail with reference to Fig. 1, Fig. 6, and Fig. 7. Fig. 6 and Fig. 7 are flowcharts showing the two-stage etching process. As shown in Fig. 6 and Fig. 7, the two-stage etching process includes steps S41 to S49. Before step S41 is performed, the on-off valves 16 to 18 close the flow paths of the branch pipes 112 to 114.

[0119] As shown in FIG. 6, first, in step S41, the control unit 3 starts the vacuum pump 8. Then, the control unit 3 controls the pressure control valve 9 so that the degree of vacuum in the chamber 2 indicates a third degree of vacuum VC3. In other words, the control unit 3 controls the pressure control valve 9 so that the pressure in the chamber 2 indicates a third pressure P3 (FIG. 4). As a result, the pressure control valve 9 sets the pressure in the chamber 2 to the third pressure P3. Step S41 may also be referred to as a "chamber pressure reduction step S41."

[0120] Next, in step S42, the control unit 3 controls the nitrogen supply unit 50 to supply nitrogen gas into the chamber 2. As a result, the nitrogen supply unit 50 opens the flow path of the branch pipe 114 using the on-off valve 18, thereby supplying nitrogen gas into the chamber 2. The nitrogen supply unit 50 continues to supply nitrogen gas until step S44. Specifically, the nitrogen supply unit 50 continues to supply nitrogen gas for a predetermined period T11 (FIG. 4). Step S42 may be referred to as a "nitrogen gas supply step S42."

[0121] Next, in step S43, the substrate processing apparatus 1 performs a first etching process. The first etching process refers to supplying HF gas into the chamber 2 in a state where the pressure in the chamber 2 indicates a first pressure P1 that is lower than atmospheric pressure, and selectively etching the silicon oxide film TG relative to other films FL. In other words, the first etching process refers to supplying HF gas into the chamber 2 in a state where the vacuum level in the chamber 2 indicates a first vacuum level VC1, and selectively etching the silicon oxide film TG relative to other films FL. Step S43 may be referred to as a "first etching step S43."

[0122] Specifically, step S43 includes steps S431 to S433.

[0123] First, in step S431, the control unit 3 controls the pressure control valve 9 so that the pressure in the chamber 2 indicates a first pressure P1 (FIG. 4) that is lower than atmospheric pressure. As a result, the pressure control valve 9 sets the pressure in the chamber 2 to the first pressure P1. Specifically, the pressure control valve 9 sets the pressure in the chamber 2 to the first pressure P1 for a predetermined period T12 (FIG. 4) and maintains the degree of vacuum in the chamber 2 at a first degree of vacuum VC1. Step S431 may be referred to as a "first pressure control step S431."

[0124] Next, in step S432, the control unit 3 controls the water vapor supply unit 30 to supply water vapor into the chamber 2. As a result, the water vapor supply unit 30 generates water vapor using the vaporizer 12 and opens the flow path of the branch pipe 112 using the on-off valve 16, thereby supplying the water vapor into the chamber 2. The water vapor supply unit 30 continues to supply water vapor for a predetermined period T13 (FIG. 4). Step S432 may be referred to as a "first water vapor supply step S432."

[0125] Next, in step S433, the control unit 3 controls the HF supply unit 40 to supply HF gas into the chamber 2. As a result, the HF supply unit 40 opens the flow path of the branch pipe 113 with the on-off valve 17, thereby supplying HF gas into the chamber 2. The HF supply unit 40 continues to supply HF gas for a predetermined period T14 (FIG. 4). Step S433 may be referred to as a "first HF gas supply step S433."

[0126] The mixed gas of water vapor and HF gas supplied into chamber 2 passes through the multiple openings 6H formed in gas dispersion plate 6 and comes into substantially uniform contact with the entire surface of substrate W. As a result, the silicon oxide film TG is selectively etched relative to other films FL by the water vapor and HF gas. Then, when HF supply unit 40 stops supplying HF gas after a predetermined period T14 has elapsed since the start of supply of HF gas, etching is completed. In other words, step S43 (first etching step S43) is completed.

[0127] Next, in step S44, the nitrogen supply unit 50 continues to supply nitrogen gas even after the supply of water vapor and HF gas has stopped. As a result, the gas in the chamber 2 is purged. Then, the control unit 3 controls the nitrogen supply unit 50 to stop the supply of nitrogen gas after a predetermined period T11 has elapsed since the start of the nitrogen gas supply in step S42. As a result, the nitrogen supply unit 50 stops the supply of nitrogen gas, completing the purge with nitrogen gas. Step S44 may be referred to as a "nitrogen gas purge step S44."

[0128] Next, as shown in FIG. 7, in step S45, the control unit 3 controls the pressure control valve 9 so that the degree of vacuum in the chamber 2 indicates a third degree of vacuum VC3. In other words, the control unit 3 controls the pressure control valve 9 so that the pressure in the chamber 2 indicates a third pressure P3 (FIG. 4). As a result, the pressure control valve 9 sets the pressure in the chamber 2 to the third pressure P3. Step S45 may also be referred to as a "chamber pressure reduction step S45."

[0129] Next, in step S46, the control unit 3 controls the nitrogen supply unit 50 to supply nitrogen gas into the chamber 2. As a result, the nitrogen supply unit 50 opens the flow path of the branch pipe 114 using the on-off valve 18, thereby supplying nitrogen gas into the chamber 2. The nitrogen supply unit 50 continues to supply nitrogen gas until step S48. Specifically, the nitrogen supply unit 50 continues to supply nitrogen gas for a predetermined period T21 (FIG. 4). Step S46 may be referred to as a "nitrogen gas supply step S46."

[0130] Next, in step S47, the substrate processing apparatus 1 performs a second etching process. The second etching process refers to supplying HF gas into the chamber 2 in a state where the pressure in the chamber 2 indicates a second pressure P2 lower than atmospheric pressure, and selectively etching the silicon oxide film TG relative to other films FL. In other words, the second etching process refers to supplying HF gas into the chamber 2 in a state where the vacuum level in the chamber 2 indicates a second vacuum level VC2, and selectively etching the silicon oxide film TG relative to other films FL. Step S47 may be referred to as a "second etching step S47."

[0131] Specifically, step S47 includes steps S471 to S473.

[0132] First, in step S471, the control unit 3 controls the pressure control valve 9 so that the pressure in the chamber 2 indicates a second pressure P2 (FIG. 4) that is lower than atmospheric pressure. As a result, the pressure control valve 9 sets the pressure in the chamber 2 to the second pressure P2. Specifically, the pressure control valve 9 sets the pressure in the chamber 2 to the second pressure P2 for a predetermined period T22 (FIG. 4) and maintains the degree of vacuum in the chamber 2 at the second degree of vacuum VC2. Step S471 may be referred to as a "second pressure control step S471."

[0133] Next, in step S472, the control unit 3 controls the water vapor supply unit 30 to supply water vapor into the chamber 2. As a result, the water vapor supply unit 30 generates water vapor using the vaporizer 12 and opens the flow path of the branch pipe 112 using the on-off valve 16, thereby supplying the water vapor into the chamber 2. The water vapor supply unit 30 continues to supply water vapor for a predetermined period T23 (FIG. 4). Step S472 may be referred to as a "second water vapor supply step S472."

[0134] Next, in step S473, the control unit 3 controls the HF supply unit 40 to supply HF gas into the chamber 2. As a result, the HF supply unit 40 opens the flow path of the branch pipe 113 with the on-off valve 17, thereby supplying HF gas into the chamber 2. The HF supply unit 40 continues to supply HF gas for a predetermined period T24 (FIG. 4). Step S473 may be referred to as a "second HF gas supply step S473."

[0135] The mixed gas of water vapor and HF gas supplied into chamber 2 passes through the multiple openings 6H formed in gas dispersion plate 6 and comes into substantially uniform contact with the entire surface of substrate W. As a result, the silicon oxide film TG is selectively etched relative to other films FL by the water vapor and HF gas. Then, when HF supply unit 40 stops supplying HF gas after a predetermined period T24 has elapsed since the start of supply of HF gas, etching is completed. In other words, step S47 (second etching step S47) is completed.

[0136] Next, in step S48, the nitrogen supply unit 50 continues to supply nitrogen gas even after the supply of water vapor and HF gas has stopped. As a result, the gas in the chamber 2 is purged. Then, the control unit 3 controls the nitrogen supply unit 50 to stop the supply of nitrogen gas after a predetermined period T21 has elapsed since the start of the nitrogen gas supply in step S46. As a result, the nitrogen supply unit 50 stops the supply of nitrogen gas, completing the purge with nitrogen gas. Step S48 may be referred to as a "nitrogen gas purge step S48."

[0137] Next, in step S49, the control unit 3 controls the pressure control valve 9 so that the degree of vacuum in the chamber 2 indicates a third vacuum degree VC3. That is, the control unit 3 controls the pressure control valve 9 so that the pressure in the chamber 2 indicates a third pressure P3 (FIG. 4). As a result, the pressure control valve 9 sets the pressure in the chamber 2 to the third pressure P3. Step S49 may be referred to as a "chamber pressure reduction step S49." After step S49, the process returns to the main routine of FIG. 5 and proceeds to step S5.

[0138] 5 to 7, according to the substrate processing method of this embodiment, the two-stage etching process S4 is performed a predetermined number of times NM (step S5). If the predetermined number of times NM is multiple, the two-stage etching process S4 is performed multiple times. Therefore, the total etching amount can be increased compared to when the two-stage etching process S4 is performed only once.

[0139] Additionally, in this embodiment, in each of the two-stage etching processes S4, after the first etching process S43 under the first pressure P1, the second etching process S47 is performed under the second pressure P2, which is lower than the first pressure P1. Therefore, in the second etching process S47, the melting point and boiling point of the reaction products on the silicon oxide film TG resulting from the HF gas are lower than in the first etching process S43. As a result, in the second etching process S47, the sublimation and exhaust of the reaction products on the silicon oxide film TG is promoted. This reduces the influence of the reaction products on the second etching process S47, ensuring reproducibility of the etching amount between the first etching process S43 and the second etching process S47. In other words, even when the same substrate W is subjected to multiple etching processes, reproducibility of the etching results is ensured.

[0140] Furthermore, in this embodiment, since the reproducibility of the etching results can be ensured in each of the two-step etching treatment steps S4, the reproducibility of the etching results can be ensured even between multiple two-step etching treatment steps S4, as demonstrated in Example 2 described below.

[0141] As a result of the above, according to this embodiment, by performing the two-stage etching process S4 multiple times, it is possible to increase the total etching amount while ensuring the reproducibility of the etching results even when the same substrate W is subjected to multiple etching processes.

[0142] The first etching step S43 and the second etching step S47 are part of the two-stage etching process S4. Therefore, the first etching step S43 and the second etching step S47 constitute the two-stage etching process S4.

[0143] (Variation) 1, 8, and 9, a substrate processing apparatus 1 and a substrate processing method according to a modified example of the present embodiment will be described. The modified example differs from the present embodiment mainly in that water vapor is not supplied into the chamber 2. The following mainly describes the differences between the modified example and the present embodiment.

[0144] The substrate processing apparatus 1 according to the modified example does not include the water vapor supply unit 30 and the branch pipe 112 shown in Fig. 1. Alternatively, in the substrate processing apparatus 1 according to the modified example, the water vapor supply unit 30 does not supply water vapor into the chamber 2.

[0145] The substrate processing method according to the modified example is similar to the substrate processing method shown in Fig. 5. However, the details of the two-stage etching process in step S4 according to the modified example are different from those of the two-stage etching process shown in Fig. 6 and Fig. 7. The differences will be mainly described below.

[0146] 8 and 9 are flowcharts showing a two-stage etching process according to a modified example. As shown in Fig. 8 and 9, in this modified example, the two-stage etching process of step S4 in Fig. 5 includes steps S41, S42, S43A, S44, S45, S46, S47A, S48, and S49. Steps S41, S42, S44, S45, S46, S48, and S49 in the modified example are the same as steps S41, S42, S44, S45, S46, S48, and S49 shown in Fig. 6 and Fig. 7.

[0147] In the modified example, step S43A includes step S431 and step S433, as shown in FIG. 8. Steps S431 and S433 of the modified example are similar to steps S431 and S433 shown in FIG. 6, respectively. However, the substrate processing method according to the modified example does not include step S432 shown in FIG. 6. Therefore, the silicon oxide film TG formed on the substrate W is selectively etched relative to other films FL by the HF gas in step S433. Step S43A may be referred to as a "first etching step 43A."

[0148] 1, HF gas supplied into chamber 2 via gas supply pipe 11 passes through gas dispersion plate 6 and reaches substrate W. More specifically, HF gas supplied to chamber 2 above gas dispersion plate 6 moves below gas dispersion plate 6 by passing through a plurality of openings 6H provided in gas dispersion plate 6. The flow of HF gas is rectified by passing through the plurality of openings 6H, and is supplied uniformly onto substrate W. The HF gas is preferably anhydrous HF gas.

[0149] When the HF gas flows onto the surface of the substrate W, it acts on the surface of the substrate W and etches the silicon oxide film TG. The etching of the silicon oxide film TG is mainly performed using HF2 - (hydrogen fluoride ion) is known to contribute. HF2 - is produced by the reaction between HF gas and water (H2O) in the silicon oxide film.

[0150] In the above embodiment, not only HF gas but also water vapor is supplied into chamber 2, causing the HF gas and water vapor to react with each other to generate hydrogen fluoride ions. In contrast, in the modified example, attention is focused on the moisture in the silicon oxide film TG, and HF gas is supplied into chamber 2, causing the HF gas to react with the moisture in the silicon oxide film TG to generate hydrogen fluoride ions. Therefore, there is no need to supply water vapor into chamber 2, which reduces running costs. Furthermore, the water vapor supply unit 30 and branch pipe 112 for supplying water vapor into chamber 2 can be omitted. In this case, the size and manufacturing costs of the substrate processing apparatus 1 can be reduced.

[0151] 9, step S47A includes step S471 and step S473. Steps S471 and S473 of the modified example are similar to steps S471 and S473 shown in FIG. 7, respectively. However, the substrate processing method according to the modified example does not include step S472 shown in FIG. 7. Therefore, the silicon oxide film TG formed on the substrate W is selectively etched with the HF gas in step S473 relative to other films FL. The principle of etching is similar to that of step S43A shown in FIG. 8. Step S47A may be referred to as a "second etching step S47A."

[0152] 8 and 9, in the modified example, the first etching step S43A and the second etching step S47 are performed in the same manner as in the above-described embodiment. As a result, even when the etching process is repeated multiple times on the same substrate W, the reproducibility of the etching result can be ensured.

[0153] Next, the present invention will be described in detail based on examples, but the present invention is not limited to the following examples. [Example]

[0154] Example 2 of the present invention will be described with reference to Figures 1, 5, 6, 7, and 10. In Example 2, the substrate processing apparatus 1 shown in Figure 1 was used. In Example 2, step S4 (Figure 5) of performing the two-stage etching process, i.e., the two-stage etching process S4, was performed twice (the predetermined number of times NM of step S5=2).

[0155] In Example 2, the silicon oxide film TG formed on the substrate W was an LP-TEOS film. The silicon oxide film TG was etched with HF gas.

[0156] Specifically, in the first etching step S43 (FIG. 6), the flow rate of HF gas supplied from the HF supply unit 40 to the chamber 2 was 1 [slm]. The flow rate of water vapor supplied from the water vapor supply unit 30 to the chamber 2 was 1 [slm]. The flow rate of nitrogen gas supplied from the nitrogen supply unit 50 to the chamber 2 was 7 [slm]. The temperature of the substrate W was 100 (°C). The pressure inside the chamber 2 was 150 [Torr].

[0157] In the second etching step S47 (FIG. 6), the flow rate of the HF gas supplied from the HF supply unit 40 to the chamber 2 was 1.5 [slm]. The flow rate of the water vapor supplied from the water vapor supply unit 30 to the chamber 2 was 2 [slm]. The flow rate of the nitrogen gas supplied from the nitrogen supply unit 50 to the chamber 2 was 4 [slm]. The temperature of the substrate W was 100°C. The pressure inside the chamber 2 was 50 [Torr].

[0158] 10 is a graph showing the etching amount in the two-stage etching process according to Example 2. The vertical axis represents the etching amount (nm), and the horizontal axis represents the order of the two-stage etching process.

[0159] In Example 2, a first two-stage etching process (horizontal axis "1") was performed using HF gas in chamber 2. In this case, the first etching step S43 and the second etching step S47 were performed while the substrate W was held by the substrate holder 4.

[0160] After the first two-stage etching process was completed, the substrate W was removed from the chamber 2 and the thickness of the silicon oxide film TG was measured. Based on the film thickness measurement results, the etching amount in the first two-stage etching process was calculated. As a result, the etching amount in the first two-stage etching process was 4.5 [nm]. The etching time was 540 seconds.

[0161] Next, the same substrate W, i.e., the substrate W after the first two-stage etching process, was returned to chamber 2 and subjected to a second two-stage etching process (horizontal axis "2") under the same conditions as the first process. After the second two-stage etching process was completed, the substrate W was removed from chamber 2 and the film thickness of the silicon oxide film TG was measured. Based on the film thickness measurement results, the etching amount in the second two-stage etching process was calculated. As a result, the etching amount in the second two-stage etching process was 4.9 [nm]. The etching time was 540 seconds.

[0162] The difference between the etching amount by the first two-stage etching process and the etching amount by the second two-stage etching process was 0.4 [nm]. In this way, in each of the two two-stage etching process steps S4 performed twice, by setting the pressure in chamber 2 to 50 [Torr] in the second etching step S47, it was possible to ensure reproducibility of the etching amount between the first two-stage etching process and the second two-stage etching process.

[0163] The embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to the above embodiments and can be implemented in various forms without departing from the spirit of the present invention. Furthermore, the components disclosed in the above embodiments can be modified as appropriate. For example, some of the components shown in one embodiment may be added to the components of another embodiment, or some of the components shown in one embodiment may be deleted from the embodiment.

[0164] Furthermore, the drawings mainly show each component in a schematic manner to facilitate understanding of the invention, and the thickness, length, number, spacing, etc. of each component shown in the drawings may differ from the actual ones due to the convenience of creating the drawings. Furthermore, the configuration of each component shown in the above embodiment is merely an example and is not particularly limited, and it goes without saying that various modifications are possible within a range that does not substantially deviate from the effects of the present invention. [Industrial Applicability]

[0165] The present invention relates to a substrate processing method and a substrate processing apparatus, and has industrial applicability. [Explanation of symbols]

[0166] 1. Substrate processing equipment 3. Control Unit 9 Pressure control valve (pressure control section) 40 Hydrogen fluoride supply unit (HF supply unit) W substrate

Claims

1. 1. A substrate processing method for etching a silicon oxide film formed on a substrate, comprising: a first etching step of setting the pressure in the chamber to a first pressure lower than atmospheric pressure while stopping the supply of hydrogen fluoride gas into the chamber, and then supplying hydrogen fluoride gas into the chamber while maintaining the pressure in the chamber at the first pressure, thereby selectively etching the silicon oxide film relative to other films; a second etching step in which, after the first etching step is completed, the pressure in the chamber is set to a second pressure lower than atmospheric pressure while the supply of hydrogen fluoride gas into the chamber is stopped, and then, while the pressure in the chamber is maintained at the second pressure, hydrogen fluoride gas is supplied into the chamber to selectively etch the silicon oxide film relative to the other film; Including, the first pressure is equal to or less than 600 Torr and equal to or greater than 100 Torr, the second pressure is 50 Torr or less, In the second etching step, the pressure in the chamber is set to the second pressure to lower the melting point and boiling point of reaction products remaining on the substrate from the first etching step; In the second etching step, the silicon oxide film is etched while sublimating reaction products on the silicon oxide film that are produced in the first etching step.

2. the first etching step and the second etching step constitute a two-step etching process; The substrate processing method of claim 1 , wherein the two-stage etching process is performed multiple times.

3. 1. A substrate processing apparatus for etching a silicon oxide film formed on a substrate with hydrogen fluoride gas, comprising: a chamber in which the substrate is placed; a hydrogen fluoride supply unit that supplies hydrogen fluoride gas into the chamber; a pressure control unit for controlling the pressure in the chamber; a control unit that controls the hydrogen fluoride supply unit and the pressure control unit; Equipped with The control unit controls the hydrogen fluoride supply unit and the pressure control unit, a first etching step of setting the pressure in the chamber to a first pressure lower than atmospheric pressure while stopping the supply of hydrogen fluoride gas into the chamber, and then supplying hydrogen fluoride gas into the chamber while maintaining the pressure in the chamber at the first pressure, thereby selectively etching the silicon oxide film relative to other films; after completion of the first etching step, a second etching step is carried out in which the pressure in the chamber is set to a second pressure lower than atmospheric pressure while the supply of hydrogen fluoride gas into the chamber is stopped, and then hydrogen fluoride gas is supplied into the chamber while the pressure in the chamber is maintained at the second pressure, thereby selectively etching the silicon oxide film relative to the other film; the first pressure is equal to or less than 600 Torr and equal to or greater than 100 Torr, the second pressure is 50 Torr or less, In the second etching step, the pressure in the chamber is set to the second pressure to lower the melting point and boiling point of reaction products remaining on the substrate from the first etching step; In the second etching step, the silicon oxide film is etched while sublimating reaction products on the silicon oxide film that are produced in the first etching step.

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