Etching method and etching apparatus

Abstract

The etching method includes the steps of: placing a substrate having a three-layer laminated film of a first silicon oxide film, a silicon nitride film, and a second silicon oxide film laminated together in a chamber; and etching the three-layer laminated film in the chamber using an HF-NH3 gas while adjusting the gas ratio in each film.

Description

Technical Field

[0001] This disclosure relates to etching methods and etching apparatus. Background Technology

[0002] Recently, in the manufacturing process of semiconductor devices, a method known as Chemical Oxide Removal (COR) is used to chemically etch the silicon oxide film (SiO2 film) in a chamber without generating plasma. As COR, a technique is known to use hydrogen fluoride (HF) gas (a fluorine-containing gas) and ammonia (NH3) gas (an alkaline gas) in the silicon oxide film (SiO2 film) on the surface of the semiconductor wafer, which serves as a substrate (e.g., Patent Documents 1 and 2). In this technique, HF gas and NH3 gas react with the silicon oxide film to generate ammonium fluoride silicon ((NH4)2SiF6; AFS), which is then sublimated by heating, thereby etching the silicon oxide film.

[0003] Existing technical documents

[0004] Patent Document 1: Japanese Patent Application Publication No. 2005-39185

[0005] Patent Document 2: Japanese Patent Application Publication No. 2008-160000 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] This disclosure provides an etching method and etching apparatus capable of simultaneously removing a three-layer laminated film consisting of a first silicon oxide film, a silicon nitride film, and a second silicon oxide film.

[0008] Solution for solving the problem

[0009] The etching method of this disclosure includes the following steps: placing a substrate having a three-layered film consisting of a first silicon oxide film, a silicon nitride film, and a second silicon oxide film in a chamber; and etching the three-layered film in the chamber while adjusting the gas ratio in each film using an HF-NH3 gas.

[0010] The effects of the invention

[0011] According to this disclosure, an etching method and etching apparatus are provided that can simultaneously remove a three-layer laminated film consisting of a first silicon oxide film, a silicon nitride film, and a second silicon oxide film. Attached Figure Description

[0012] Figure 1 A cross-sectional view illustrating an example of an etching apparatus used in an implementation of an etching method according to one embodiment.

[0013] Figure 2A flowchart illustrating an etching method according to one embodiment.

[0014] Figure 3 A cross-sectional view illustrating an example of the structure of a substrate to which an etching method of one embodiment is applied is shown for illustrative purposes.

[0015] Figure 4 For illustrative purposes only Figure 3 A cross-sectional view of the ONO laminate in the substrate, showing the state of etching.

[0016] Figure 5 A diagram illustrating the etching process of step ST2 in an etching method according to one embodiment is provided.

[0017] Figure 6 The graph illustrates the relationship between HF / (HF+NH3) and the selectivity ratio of SiO2 to SiN when etching SiO2 and SiN films by changing the ratio of NH3 gas to HF gas.

[0018] Figure 7 A graph showing the relationship between stage temperature and etching amount of each film, and the selectivity ratio of ALD-SiN film to Th-SiO2 film when etching ALD-SiN film and Th-SiO2 film by varying stage temperature within 90–120 °C.

[0019] Figure 8 This diagram illustrates the mechanism by which Si is etched when an ONO laminate is etched.

[0020] Figure 9 A graph showing the relationship between the etching amount of the Th-SiO2 film and the etching amount of the a-Si film when HF gas and NH3 gas are used to etch the Th-SiO2 film at various temperatures. Detailed Implementation

[0021] The embodiments will now be described with reference to the accompanying drawings.

[0022] <Etching Device>

[0023] Figure 1 A cross-sectional view illustrating an example of an etching apparatus used in an implementation of an etching method according to one embodiment.

[0024] like Figure 1 As shown, the etching apparatus 1 has a sealed chamber 10, and a mounting stage 12 is provided inside the chamber 10 to place the substrate W in a generally horizontal state.

[0025] In addition, the etching apparatus 1 includes a gas supply mechanism 13, which supplies processing gas to the chamber 10, and an exhaust mechanism 14, which exhausts gas from the chamber 10.

[0026] The chamber 10 is composed of a chamber body 21 and a cover 22. The chamber body 21 has a generally cylindrical side wall portion 21a and a bottom portion 21b, and the upper part is an opening, which is closed by the cover 22 having a recess inside. The side wall portion 21a and the cover 22 are sealed by a sealing member (not shown) to ensure the airtightness of the chamber 10.

[0027] Inside the cover 22, a nozzle 26 serving as a gas inlet component is embedded, facing the mounting platform 12. The nozzle 26 has a cylindrical body 31 and a spray plate 32 disposed at the bottom of the body 31. In the space formed by the body 31 and the spray plate 32, an intermediate plate 33 is provided parallel to the spray plate 32. The space between the upper wall 31a of the body 31 and the intermediate plate 33 forms a first space 34a, and the space between the intermediate plate 33 and the spray plate 32 forms a second space 34b.

[0028] A first gas supply pipe 61, in which a gas supply mechanism 13 is inserted, is located in the first space 34a. Multiple gas passages 35, connected to the first space 34a, extend from the intermediate plate 33 through spacers 36 located in the second space 34b to the upper surface of the spray plate 32. These gas passages 35 are connected to multiple first gas discharge holes 37 formed in the spray plate 32. Conversely, a third gas supply pipe 63, in which a gas supply mechanism is inserted, is located in the second space 34b. This second space 34b is connected to multiple second gas discharge holes 38 formed in the spray plate 32.

[0029] Furthermore, the gas supplied from the first gas supply pipe 61 to the first space 34a is discharged into the chamber 10 via the gas passage 35 and the first gas discharge port 37. Additionally, the gas supplied from the third gas supply pipe 63 to the second space 34b is discharged through the second gas discharge port 38. That is, it becomes a post-mixing type where the gas supplied from the first gas supply pipe 61 and the gas supplied from the third gas supply pipe 63 are mixed after being discharged from the nozzle 26.

[0030] It should be noted that it can also be a premixed type in which the gas supplied from the first gas supply pipe 61 and the gas supplied from the third gas supply pipe 63 are mixed in the nozzle.

[0031] The side wall portion 21a of the chamber body 21 is provided with a loading / unloading outlet 41 for loading / unloading substrate W. The loading / unloading outlet 41 can be opened and closed by a gate valve 42, so that substrate W can be transported between adjacent components.

[0032] The mounting stage 12 is roughly circular in plan view and is fixed to the bottom 21b of the chamber 10. A temperature regulator 45 for adjusting the temperature of the mounting stage 12 is provided inside the mounting stage 12. The temperature regulator 45 may be, for example, a temperature regulating medium flow path for circulating a temperature regulating medium (e.g., water) or a resistance heater. The temperature regulator 45 adjusts the temperature of the mounting stage 12 to the desired temperature, thereby controlling the temperature of the substrate W placed on the mounting stage 12.

[0033] The gas supply mechanism 13 has an HF gas supply source 51, an Ar gas supply source 52, an NH3 gas supply source 53, and an N2 gas supply source 54.

[0034] HF gas supply source 51 supplies HF gas, and NH3 gas supply source 53 supplies NH3 gas. Ar gas supply source 52 and N2 gas supply source 54 supply dilution gas, purge gas, and inert gas N2 gas (which also functions as a carrier gas), and Ar gas. Both N2 and Ar can be either Ar or N2 gas. Furthermore, the inert gas is not limited to Ar and N2 gas; other rare gases such as He gas can also be used.

[0035] These gas supply sources 51-54 are respectively connected to one end of the first to fourth gas supply pipes 61-64. The first gas supply pipe 61, connected to the HF gas supply source 51, is as described above, with its other end inserted into the first space 34a of the nozzle 26. The other end of the second gas supply pipe 62, connected to the Ar gas supply source 52, is connected to the first gas supply pipe 61. The third gas supply pipe 63, connected to the NH3 gas supply source 53, is as described above, with its other end inserted into the second space 34b of the nozzle 26. The other end of the fourth gas supply pipe 64, connected to the N2 gas supply source 54, is connected to the third gas supply pipe 63.

[0036] HF gas and NH3 gas, together with Ar gas and N2 gas (which are inactive gases), arrive at the first space 34a and the second space 34b of the nozzle 26, respectively, and are discharged into the chamber 10 through the first gas discharge hole 37 and the second gas discharge hole 38.

[0037] Gas supply pipes 61 to 64, numbered 1 to 4, are equipped with flow control units 65 for switching on and off the flow path and controlling the flow rate. The flow control unit 65 is composed, for example, of a switching valve and a flow controller such as a mass flow controller (MFC) or a flow control system (FCS).

[0038] The exhaust mechanism 14 has an exhaust pipe 72 connected to an exhaust port 71 formed at the bottom 21b of the chamber 10, and further includes an automatic pressure control valve (APC) 73 disposed on the exhaust pipe 72 for controlling the pressure inside the chamber 10 and a vacuum pump 74 for the exhaust chamber 10.

[0039] Two capacitive galvanometers 76a and 76b, for high and low pressure respectively, are provided on the side wall of chamber 10 to control the pressure inside chamber 10. A temperature sensor (not shown) for detecting the temperature of substrate W is provided near the substrate W placed on the mounting stage 12.

[0040] The chamber 10, nozzle 26, and stage 12 constituting the etching apparatus 1 are made of a metallic material such as aluminum. Coatings such as oxide films can be formed on their surfaces.

[0041] The etching apparatus 1 also includes a control unit 80. The control unit 80 is configured as a computer and includes: a main control unit equipped with a CPU, an input device, an output device, a display device, and a storage device (storage medium). The main control unit controls the operation of each component of the etching apparatus 1. Control of each component based on the main control unit is performed based on a control program stored in a storage medium (hard disk, optical disk, semiconductor memory, etc.) embedded in the storage device. The storage medium stores a processing procedure as the control program, and based on the processing procedure, the etching apparatus 1 performs processing.

[0042] <Etching Method>

[0043] Next, an etching method according to one embodiment performed in the etching apparatus 1 configured as described above will be described. The etching method described below is performed based on control by the control unit 80.

[0044] Figure 2 A flowchart illustrating an etching method according to one embodiment.

[0045] First, a substrate W having three layers of films, consisting of a first silicon oxide film, a silicon nitride film, and a second silicon oxide film, is placed in the chamber 10 (step ST1).

[0046] Then, in chamber 10, the three-layer film is etched by adjusting the gas ratio in each film using HF-NH3 gas (step ST2).

[0047] At this time, the etching of the first silicon oxide film, the silicon nitride film, and the second silicon oxide film is carried out by controlling the gas ratio in a manner that appropriately etches each film with a good selectivity ratio to minimize loading. In addition, the etching of each film is carried out by appropriately controlling the temperature of the stage 12 and the pressure inside the chamber 10.

[0048] When silicon oxide and silicon nitride films are etched using HF-NH3-based gas, ammonium fluoride silicide (AFS) is generated as a reaction product. Therefore, in order to simultaneously etch each of the three-layered films within chamber 10, cyclic etching, which involves repeatedly supplying HF-NH3-based gas and purging chamber 10, is preferably employed. This allows etching to proceed by the generation of AFS during the repeated supply of HF-NH3-based gas and the sublimation of AFS generated during purging. The number of repetitions can be appropriately set according to the thickness of each film.

[0049] The following is a more detailed explanation.

[0050] In step ST1, the substrate W has no restrictions on its structure or stacking direction as long as it has three laminated films. For example, the following structures can be cited: Figure 3 The figure is shown schematically. Figure 3 In this example, a Si film 101 is formed on a substrate (not shown), and an ONO stacked film 102, consisting of three layers to be etched, is formed on the substrate W. The ONO stacked film 102 is constructed by sequentially stacking a second silicon oxide film 113, a silicon nitride film 112, and a first silicon oxide film 111 from below. The thickness of each of the first silicon oxide film 111, the silicon nitride film 112, and the second silicon oxide film 113 is preferably in the range of 6 to 12 nm. A Si film 103 and a SiN film 104 are formed on the ONO stacked film 102, and recesses (grooves or holes) 105 are formed on the Si film 103 and the SiN film 104. It should be noted that the Si films 101 and 103 can be poly-Si films or amorphous Si films (a-Si films).

[0051] for Figure 3 On the substrate W, the first silicon oxide film 111, the silicon nitride film 112, and the second silicon oxide film 113 of step ST2 are simultaneously etched, thereby achieving the following: Figure 4 As shown, the Si film 101 that forms the substrate is exposed.

[0052] The first silica-based film 111 and the second silica-based film 113 use Si and O as the main components and may contain additives. The first silica-based film 111 and the second silica-based film 113 can be made of the same material, but are preferably made of different materials. Examples of the first silica-based film include thermally oxidized films (Th-SiO2 films) and TEOS films (CVD-SiO2 films). A TEOS film refers to a film formed using tetraethoxysilane (TEOS) as a Si precursor via CVD. A TEOS film can be a PTEOS film formed by plasma CVD. Examples of the second silica-based film 113 include SiO2 films formed by ALD (ALD-SiO2 films) and SiON films. These are lower density films compared to the thermally oxidized films and TEOS films used as the first silica-based film 111. By making the second silicon oxide film 113 a film with a lower density than the first silicon oxide film, the second silicon oxide film 113 can be selectively etched onto the first silicon oxide film 111.

[0053] The silicon nitride-based film 112 uses Si and N as the main components and may contain additives. Examples of silicon nitride-based films 112 include SiN films formed by CVD and ALD methods (CVD-SiN films, ALD-SiN films).

[0054] In step ST2, such as Figure 5 As shown, the etching process includes three stages: etching the first silicon oxide film 111 (ST2-1), etching the silicon nitride film 112 (ST2-2), and etching the second silicon oxide film 113 (ST2-3). To achieve the desired etching in these stages, the gas ratio of the HF-NH3 system gas is adjusted during the etching stages ST2-1 and ST2-3 of the silicon oxide film and during the etching stage ST2-2 of the silicon nitride film.

[0055] Figure 6This diagram illustrates the relationship between the ratio of HF gas to NH3 gas (HF / (HF+NH3)×100) and the selectivity of SiO2 to SiN (SiO2 / SiN) when etching SiO2 films (Th-SiO2 films) and SiN films by varying the ratio of NH3 gas to HF gas. As shown in the diagram, SiO2 films are easily etched within a range rich in NH3 gas, achieving a high selectivity of over 100 for silicon nitride films with an HF gas ratio of 20% or less. However, the reaction becomes difficult if the HF gas ratio falls below 3%. On the other hand, SiN films are easily etched within a range rich in HF gas, achieving a high selectivity of approximately 99% or more. Specifically, when the HF gas ratio is 100%, the SiO2 / SiN ratio becomes 0.01 or less, meaning the selectivity of SiN to SiO2 is over 100.

[0056] Therefore, in the etching stages ST2-1 and ST2-3 of the silicon oxide film, the HF gas ratio is preferably 3 to 20%, more preferably in the range of 3 to 9%. Within this range, sufficient etching amount can be obtained in addition to the selectivity.

[0057] On the other hand, in the etching stage of the silicon nitride film, namely ST2-2, the HF gas ratio is preferably 99% or more. More preferably, the HF gas ratio is 100%.

[0058] In the etching process of step ST2, when the second silicon oxide film 113 is etched (i.e., ST2-3), it is preferable to selectively etch the first silicon oxide film 111. When the first silicon oxide film 111 is a Th-SiO2 film or a CVD-SiO2 film, and the second silicon oxide film 113 is an ALD-SiO2 film or a SiON film, the second silicon oxide film 113 can be selectively etched by reducing the ratio of HF gas during the etching of the second silicon oxide film 113 compared to the etching of the first silicon oxide film 111.

[0059] When etching each film with the above-mentioned preferred gas ratio, the gas flow rate is preferably within the following range.

[0060] • Etching stage of the first silicon oxide film 111 (ST2-1)

[0061] HF gas: 50–100 sccm

[0062] NH3 gas: 450~550sccm

[0063] N2 gas + Ar gas: 300~600sccm

[0064] • Etching stage of silicon nitride film 112 (ST2-2)

[0065] HF gas: 800~1000sccm

[0066] NH3 gas: 0~10sccm

[0067] N2 gas + Ar gas: 300~600sccm

[0068] • Etching stage of the second silicon oxide film 113 (ST2-3)

[0069] HF gas: 30–50 sccm (less than during the etching of the first silicon oxide film).

[0070] NH3 gas: 450~550sccm

[0071] N2 gas + Ar gas: 300~600sccm

[0072] Regarding the pressure in step ST2, in the stages of etching the first and second silicon oxide films 111 and 113 (ST2-1 and ST2-3), it is preferable to set the pressure relatively low compared to the stage of etching the silicon nitride film 112. This allows for selective etching of the first and second silicon oxide films 111 and 113 with respect to the silicon nitride film 112. On the other hand, in the stage of etching the silicon nitride film 112 (ST2-2), it is preferable to set the pressure relatively high compared to the stage of etching the first and second silicon oxide films 111 and 113. This allows for selective etching of the silicon nitride film 112 with respect to the first and second silicon oxide films 111 and 113.

[0073] More preferably, in the etching stages (ST2-1 and ST2-3) of the first and second silicon oxide films 111 and 113, the etching temperature is 5 Torr (667 Pa) or less, and in the etching stage (ST2-2) of the silicon nitride film 112, the etching temperature is 5 to 100 Torr (667 to 13332 Pa).

[0074] The substrate temperature (stage temperature) for the etching stage (ST2-2) of the silicon nitride film 112 is preferably 80-100°C, more preferably 90-100°C. By setting the temperature within this range, the silicon nitride film 112 can be etched with a high selectivity for the first and second silicon oxide films 111 and 113 with a realistic etching amount.

[0075] Figure 7This graph illustrates the relationship between stage temperature and etching amount for each film, and the selectivity of ALD-SiN film to Th-SiO2 film, when etching ALD-SiN and Th-SiO2 films under varying stage temperatures of 90–120°C at 100% HF gas pressure of 20 Torr and 50 Torr. As shown in the graph, at 90–100°C, SiN films can be etched with realistic etching amounts and high selectivity for SiO2 films. At 105°C, the selectivity is high, but the etching amount decreases.

[0076] in addition, Figure 3 In the substrate W with the structure of ONO laminate 102, the etching of each film requires a high selectivity for Si films 101 and 103, but if the temperature is low, Si will be etched. The model is as follows. Figure 8 This diagram illustrates a model of Si being etched during the etching of an ONO multilayer film. For example, when etching the first and second silicon oxide films 111 and 113, as shown... Figure 8 As shown, H2O is generated during the etching process using HF and NH3 gases to produce AFS. Furthermore, if the temperature is low, H2O remains, and it reacts with the NH3 gas used as the introduction gas, causing alkaline etching of Si. To suppress this reaction, it is preferable to raise the substrate temperature to remove H2O. Figure 9 A graph showing the relationship between the etching amount of the Th-SiO2 film and the etching amount of the a-Si film when HF and NH3 gases are used to etch the Th-SiO2 film at various temperatures is presented. As shown in the graph, there is a tendency for a low selectivity of the Th-SiO2 film to the a-Si film at 85°C, but a certain degree of high selectivity can be obtained at 90°C, and the etching amount of a-Si decreases as the temperature increases. Therefore, in step ST2, in order to selectively etch each film for Si, the stage temperature (substrate temperature) is preferably 90°C or higher. As mentioned above, the etching amount of the SiN film is low at 105°C; therefore, 90–100°C is preferred.

[0077] Taking into account the selectivity of the SiN film for the SiO2 film and the selectivity of the SiO2 film for the Si film, the substrate temperature (stage temperature) during etching of the ONO laminate 102 in step ST2 is preferably 80–100°C, more preferably 90–100°C. The temperature can be varied during the etching stages (ST2-1 to ST2-3) of each film within this range, but it is preferable to set it to the same temperature substantially.

[0078] In the etching stage of each film in step ST2 (ST2-1 to ST2-3), as described above, it is preferable to repeatedly perform cyclic etching by supplying HF-NH3-based gas to generate reaction products and purging the chamber 10 to sublimate the reaction products. Furthermore, after the etching of the ONO laminate 102 is completed, it is preferable to remove the substrate W from the chamber 10 and perform heat treatment for residue removal using a heating device.

[0079] The time for supplying HF-NH3 gas during each cyclic etching of the films is preferably in the range of 20 to 60 seconds. Furthermore, from the viewpoint of thoroughly removing AFS, the time for one purging operation is preferably 3 minutes or more, more preferably 3 to 5 minutes. Where a heat treatment for removing residue is performed after the etching of the ONO laminate 102, the purging time during the final etching stage (ST2-3) of the second silicon oxide film 113 can be shorter, preferably in the range of 30 to 60 seconds.

[0080] Alternatively, the purging operation can be performed by simply evacuating the chamber 10, or by supplying purging gas while evacuating. The purging gas can be Ar gas supplied from Ar gas supply source 52 and / or N2 gas supply source 54. For effective removal of AFS, evacuation alone is preferable.

[0081] During the purging operation, the temperature of the stage 12 is set to the temperature at which the sublimation energy of the AFS generated on the substrate W is achieved. If the temperature of the stage 12 is within the aforementioned temperature range of 80 to 100°C, the AFS, which is a reaction product, can be sufficiently removed by the purging operation during cyclic etching.

[0082] Figure 3 In the substrate W with the structure, when etching the ONO laminate 102, selectivity for the SiN film 104 is also required. The SiN film 104 and the silicon nitride film 112 of the ONO laminate 102 are of the same type, but by extending the blow-off time during cyclic etching of the silicon nitride film 112 to minimize AFS and H2O, the loss of the SiN film 104 can be reduced. Therefore, selectivity for the SiN film 104 can also be ensured when etching the silicon nitride film 112. The preferred blow-off time is in the range of 3 to 5 minutes.

[0083] After the etching of each film is completed, the chamber 10 is purged. Ar gas and / or N2 gas supplied from Ar gas supply source 52 and / or N2 gas supply source 54 can be used as the purging gas. After the etching of the second silicon oxide film 113 is completed, the chamber is purged in this manner, and then the substrate W is removed from the chamber 10.

[0084] As shown in Patent Document 1 above, it is known in the past that SiO2 films are etched using HF and NH3 gases. On the other hand, in the structure of semiconductor devices, ONO stacked films, which are the subject of this embodiment, are mostly used, requiring the etching of ONO stacked films. When etching ONO stacked films, in order to suppress loading to a minimum, it is necessary to etch SiO2 films and SiN films with high selectivity. In the past, gas etching of SiO2 films and wet etching of SiN films were gradually combined.

[0085] In contrast, in this embodiment, by optimizing conditions such as the gas ratio of the first silicon oxide film, the silicon nitride film, and the second silicon oxide film constituting the ONO laminate, and further applying cyclic etching, the ONO laminate can be etched simultaneously with gas etching. Therefore, the ONO laminate can be etched with high production capacity using a simpler process than before.

[0086] Furthermore, when a Si film is present adjacent to the ONO layer, it is required to etch the ONO layer with a high selectivity towards the Si film. Specifically, as... Figure 3 Since the Si film 101, which forms the substrate of the ONO stacked film 102, mostly serves as the functional part (channel, etc.) of the transistor, it is required that the ONO stacked film 102 be etched as infrequently as possible. In contrast, in this embodiment, as described above, the Si film can also be etched onto the ONO stacked film with a high selectivity.

[0087] <Other Applications>

[0088] The embodiments have been described above, but the embodiments disclosed herein are illustrative in all respects and should not be considered limiting. The above embodiments may be omitted, substituted, or modified in various ways without departing from the appended claims and their spirit.

[0089] For example, the apparatus described in the above embodiments is merely an example, and various configurations of apparatus can be applied. Furthermore, while a semiconductor wafer is used as the substrate in the example, other substrates such as FPD (flat panel display) substrates or ceramic substrates can also be used.

[0090] Explanation of reference numerals in the attached figures

[0091] 1; Etching apparatus; 10; Chamber; 12; Stage; 13; Gas supply mechanism; 14; Exhaust mechanism; 26; Nozzle; 45; Temperature regulator; 51; HF gas supply source; 53; NH3 gas supply source; 80; Control unit; 101; 103; Si film; 102; ONO laminated film; 104; SiN film; 105; Recess; 111; First silicon oxide film; 112; Silicon nitride film; 113; Second silicon oxide film; W; Substrate

Claims

1. An etching method, comprising the following steps: The process of placing a substrate comprising a three-layer laminated film consisting of a first silicon oxide film, a silicon nitride film, and a second silicon oxide film into a cavity; and, The process of etching the three-layer laminated film by using HF-NH3 gas and adjusting the gas ratio during etching of each film within the chamber.

2. The etching method according to claim 1, wherein, The etching of the first silicon oxide film, the silicon nitride film, and the second silicon oxide film is performed by cyclic etching that repeatedly performs the operation of supplying HF-NH3 gas to generate reaction products and the operation of purging the chamber to sublimate the reaction products.

3. The etching method according to claim 2, wherein, The time for the purging operation during etching of the first silicon oxide film, the silicon nitride film, and the second silicon oxide film is set to 3 to 5 minutes.

4. The etching method according to claim 2, wherein, After the etching process, the method further includes the following steps: removing the substrate from the chamber; and heating the removed substrate to remove residue. The purging time for the first silicon oxide film and the silicon nitride film is set to 3-5 minutes, and the purging time for the second silicon oxide film is set to 30-60 seconds.

5. The etching method according to claim 2, wherein, The substrate contains a SiN film in the portion outside the three-layer stacked film, and the time for the purging operation is set to 3 to 5 minutes when etching the silicon nitride film.

6. The etching method according to any one of claims 1 to 5, wherein, When etching the first silicon oxide film and the second silicon oxide film, HF gas and NH3 gas are supplied as the HF-NH3 gas with a gas ratio of 3 to 20% for HF / (HF+NH3). When etching the silicon nitride film, HF gas and NH3 gas are supplied as the HF-NH3 gas with a gas ratio of 99% or more for HF / (HF+NH3).

7. The etching method according to any one of claims 1 to 5, wherein, When etching the first silicon oxide film and the second silicon oxide film, the pressure inside the chamber is set to below 667 Pa. When etching the silicon nitride film, the pressure inside the chamber is set to the range of 667 to 13332 Pa.

8. The etching method according to any one of claims 1 to 5, wherein, The temperature of the substrate during etching of the silicon nitride film is 80~100℃.

9. The etching method according to claim 8, wherein, The temperature of the substrate during etching of the three-layer laminated film is 80~100℃.

10. The etching method according to claim 9, wherein, The substrate includes a Si film adjacent to the three-layer stacked film, and the temperature of the substrate during etching of the three-layer stacked film is in the range of 90~100°C.

11. The etching method according to any one of claims 1-5, 9-10, wherein, The etching of the three-layer stacked film begins with the first silicon oxide film and ends with the second silicon oxide film. The first silicon oxide film is a thermally oxidized film or a TEOS film, and the second silicon oxide film is a silicon oxide film formed by ALD or a SiON film.

12. The etching method according to claim 11, wherein, During the etching of the second silicon oxide film, the HF gas flow rate becomes less than the HF gas flow rate during the etching of the first silicon oxide film.

13. An etching apparatus comprising: The chamber contains a substrate comprising a three-layered film consisting of a first silicon oxide film, a silicon nitride film, and a second silicon oxide film. A stage that holds the substrate within the cavity; A gas supply unit supplies alkaline gas and fluorine-containing gas into the chamber; An exhaust section that exhausts air from the chamber; A temperature regulating unit that regulates the temperature of the substrate on the mounting stage; and, Control Department The control unit controls the gas supply unit, the exhaust unit, and the temperature regulation unit so that the substrate placed on the mounting stage in the chamber is etched using HF-NH3 gas while adjusting the gas ratio during etching of each film.

14. The etching apparatus according to claim 13, wherein, The control unit controls the etching of each of the first silicon oxide film, the silicon nitride film, and the second silicon oxide film, thereby repeatedly performing the operation of supplying HF-NH3 gas to generate reaction products and the operation of purging the chamber to sublimate the reaction products.

15. The etching apparatus according to claim 13 or claim 14, wherein, In the control unit, when etching the first silicon oxide film and the second silicon oxide film, HF gas and NH3 gas are supplied as the HF-NH3 gas with a gas ratio of 3 to 20% for HF / (HF+NH3). When etching the silicon nitride film, HF gas and NH3 gas are supplied as the HF-NH3 gas with a gas ratio of 99% or more for HF / (HF+NH3).

16. The etching apparatus according to claim 13 or claim 14, wherein, For the control unit, when etching the first silicon oxide film and the second silicon oxide film, the pressure inside the chamber is controlled to be below 667 Pa, and when etching the silicon nitride film, the pressure inside the chamber is controlled to be in the range of 667 to 13332 Pa.

17. The etching apparatus according to claim 13 or claim 14, wherein, The control unit controls the temperature of the substrate to 80~100°C when etching the three-layer laminated film.

18. The etching apparatus according to claim 13 or claim 14, wherein, The etching of the three-layer stacked film begins with the first silicon oxide film and ends with the second silicon oxide film. The first silicon oxide film is a thermally oxidized film or a TEOS film, and the second silicon oxide film is a silicon oxide film formed by ALD or a SiON film. The control unit controls the flow rate of HF gas to be less than that of HF gas during the etching of the second silicon oxide film.

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