Etching Method

Abstract

To provide a technique for efficiently etching a plurality of types of films.SOLUTION: An etching method includes: a step of setting the inside of a process chamber to a reduced pressure state; a first etching step of supplying a first etching gas and a first flow rate of water vapor into the process chamber to etch a second film; and a second etching step of supplying a second etching gas and a second flow rate of water vapor different from the first flow rate into the process chamber after the first etching step to etch a third film.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a substrate etching technology. Substrates to be processed include, for example, semiconductor wafers, glass substrates for liquid crystal displays, substrates for flat panel displays (FPDs) such as organic electroluminescence (EL) displays, substrates for optical disks, substrates for magnetic disks, substrates for magneto-optical disks, glass substrates for photomasks, ceramic substrates, substrates for field emission displays (FEDs), and substrates for solar cells. [Background technology]

[0002] 2. Description of the Related Art Semiconductor device manufacturing processes include etching a coating film formed on a substrate, such as a silicon oxide film or a silicon nitride film.

[0003] Conventionally, wet etching based on hydrofluoric acid has been used to etch silicon oxide films, for example. However, as semiconductor devices become more highly integrated and the patterns they form become finer, wet etching has become problematic, as the surface tension of water can cause the patterns to collapse.

[0004] Therefore, a vapor phase etching technique using hydrofluoric acid vapor or anhydrous hydrogen fluoride gas has been adopted (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6782140 Summary of the Invention [Problem to be solved by the invention]

[0006] When etching a plurality of types of films using the above techniques, if a method is adopted in which a chamber is prepared for each of the target films, the time required for the etching process will be long.

[0007] The technology disclosed in the present specification has been made in consideration of the problems described above, and is a technology for efficiently etching a plurality of types of films. [Means for solving the problem]

[0008] An etching method that is a first aspect of the technology disclosed in the present specification is an etching method for etching a second film and a third film each formed on a first film (including the side surfaces) in the same processing chamber, and includes a step of reducing the pressure in the processing chamber, a first etching step of supplying a first etching gas and water vapor at a first flow rate into the processing chamber to etch the second film, and a second etching step of supplying a second etching gas and the water vapor at a second flow rate, which is different from the first flow rate, into the processing chamber after the first etching step to etch the third film.

[0009] An etching method according to a second aspect of the technology disclosed in the present specification is related to the etching method according to the first aspect, and the first etching gas and the second etching gas are both etching gases containing hydrogen fluoride.

[0010] An etching method that is a third aspect of the technology disclosed in the present specification is related to the etching method of the first or second aspect, in which the first film is a silicon oxide film, the second film is a BSG film, and the third film is a silicon nitride film.

[0011] An etching method that is a fourth aspect of the technology disclosed in the present specification is related to the etching method that is any one of the first to third aspects, in which the first film and the third film form a plurality of stacked structures, and the second film is formed between adjacent stacked structures. [Effects of the Invention]

[0012] According to at least the first aspect of the technology disclosed in the present specification, by performing etching processes with different flow rate settings, each of the films to be processed can be etched more efficiently than when the same etching process is continuously performed without changing the flow rate setting.

[0013] Furthermore, objects, features, aspects, and advantages associated with the technology disclosed herein will become more apparent from the detailed description and accompanying drawings set forth below. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a side view schematically illustrating an example of the configuration of an etching apparatus according to an embodiment. [Figure 2] 4 is a flowchart illustrating an example of the operation of the etching apparatus according to the embodiment. [Figure 3] 1A and 1B are diagrams schematically illustrating examples of coating films that are the subject of an etching process. [Figure 4] 1A and 1B are diagrams schematically illustrating examples of coating films that are the subject of an etching process. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments will be described with reference to the accompanying drawings. In the following embodiments, detailed features will be shown for the purpose of explaining the technology, but these are merely examples and are not necessarily essential features for enabling the embodiments to be implemented.

[0016] The drawings are schematic, and for the sake of convenience, components may be omitted or simplified as appropriate. The relative sizes and positions of components shown in different drawings are not necessarily accurately depicted and may be changed as appropriate. Hatching may also be used in drawings such as plan views that are not cross-sectional views to facilitate understanding of the embodiments.

[0017] In the following description, the same components are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed descriptions of them may be omitted to avoid duplication.

[0018] Furthermore, in the description given in this specification, when a certain component is described as "comprising," "including," or "having," unless otherwise specified, this is not an exclusive expression that excludes the presence of other components.

[0019] Furthermore, although ordinal numbers such as "first" or "second" may be used in the descriptions in this specification, these terms are used for convenience to facilitate understanding of the contents of the embodiments, and the contents of the embodiments are not limited to the order that may result from these ordinal numbers.

[0020] Furthermore, in the description provided in this specification, terms that indicate specific positions or directions, such as "top," "bottom," "left," "right," "side," "bottom," "front," or "back," may be used, but these terms are used for convenience to facilitate understanding of the contents of the embodiments and have no relation to the positions or directions when the embodiments are actually implemented.

[0021] <Embodiment> The etching method according to this embodiment will be described below.

[0022] <Configuration of the etching equipment> 1 is a side view schematically showing an example of the configuration of an etching apparatus 1 according to this embodiment. The etching apparatus 1 is a single-wafer etching apparatus that processes substrates W such as semiconductor wafers one by one.

[0023] In this embodiment, the silicon-containing coating film to be etched is a silicon nitride film and a BSG (Boron Silicate Glass) film obtained by a CVD method, but the coating film is not limited to this and may be, for example, another silicon oxide film, etc. Furthermore, the silicon oxide film may be a thermal silicon oxide film formed by thermal oxidation, or may be a silicon oxide film such as a TEOS (Tetra Ethoxy Silane) film, a PSG (Phospho Silicate Glass) film, or a BPSG (Boron-doped Phospho Silicate Glass) film obtained by a chemical vapor deposition (i.e., CVD) method.

[0024] 1, the etching apparatus 1 includes a processing chamber 2, such as a chamber for processing a substrate W, and a control unit 3 that controls the operation of devices provided in the etching apparatus 1 or the opening and closing of valves. The control unit 3 includes a determination unit 31 that makes a predetermined determination based on input information, and a memory unit 32 that stores the input information, the results of the determination by the determination unit 31, information output from the determination unit 31, and the like.

[0025] The processing chamber 2 has, for example, a cylindrical shape and has an internal processing space for processing the substrate W. A substrate holder 4 that holds the substrate W in a substantially horizontal position is installed in the processing chamber 2. The substrate W is transported into the processing chamber 2 by a transport system (not shown) and then placed on the substrate holder 4.

[0026] Within the processing chamber 2 are provided a substrate holder 4 for holding the substrate W, a heating mechanism 5 built into the substrate holder 4 for heating the substrate W, a gas distribution plate 6 located above the substrate holder 4 within the processing chamber 2, an exhaust pipe 7 connected to and communicating with the processing chamber 2 for reducing the pressure inside the processing chamber 2, a pressure sensor 10 connected to the processing chamber 2, and a pipe 11 (mixed gas pipe) connected to and communicating with the upper part of the processing chamber 2.

[0027] The substrate holder 4 may hold the substrate W by means of a chuck pin or the like, or may hold the substrate W on its upper surface by suction.

[0028] The substrate W is heated to a predetermined temperature in the range of 30° C. to 200° C. by a heating mechanism 5 built into the substrate holder 4. As the heating mechanism 5, for example, a resistance heating type electric heater is assumed.

[0029] The gas dispersion plate 6 has a plurality of openings 61 formed therein, and is provided above the substrate W so as to separate the upper and lower sections of the processing chamber 2. The gas supplied from the pipes 11 is dispersed through the plurality of openings 61 in the gas dispersion plate 6 and further supplied below the gas dispersion plate 6. In this embodiment, the gas dispersion plate 6 has a plurality of openings 61 with an inner diameter of 0.1 mm formed therein at intervals of 5 mm. However, the inner diameter and intervals of the openings are not limited to these. The gas dispersion plate 6 may also be provided in multiple stages.

[0030] The pressure sensor 10 is a sensor that measures the pressure (degree of vacuum) inside the processing chamber 2, and can output the pressure measurement results to the control unit 3 via wired or wireless communication means.

[0031] The exhaust pipe 7 is provided with a valve 21, an APC (Auto Pressure Controller) valve 9 located downstream of the valve 21, and a decompression pump 8 located downstream of the APC valve 9 and which reduces the pressure inside the processing chamber 2 via the exhaust pipe 7. The APC valve 9 adjusts the pressure inside the processing chamber 2 by adjusting the exhaust flow rate from the processing chamber 2. A determination unit 31 in the control unit 3 can adjust the opening of the APC valve 9 so that the pressure inside the processing chamber 2 measured by the pressure sensor 10 becomes the desired pressure.

[0032] In this embodiment, the decompression pump 8 is described as the means for decompressing the interior of the processing chamber 2, but the decompression means is not limited to this, and for example, the decompression may be achieved by factory utility exhaust.

[0033] Pipe 11 is connected to pipes 12, 13, and 14 on the upstream side, and is a pipe where gases supplied from each pipe join together. The gases joined in pipe 11 are supplied to the upper part of processing chamber 2.

[0034] The piping 12 is provided with a valve 22, a nitrogen flow controller 82 located upstream of the valve 22, and a nitrogen supply source 42 located upstream of the nitrogen flow controller 82. The opening and closing of the valve 22 is adjusted by the control of the nitrogen flow controller 82, thereby controlling the flow rate of nitrogen (inert gas) supplied from the nitrogen supply source 42 to the piping 12. The nitrogen flow controller 82 measures the flow rate of nitrogen and controls the flow rate based on the obtained measurement value.

[0035] Pipe 13 is provided with a valve 23, a hydrogen fluoride gas flow rate controller 83 located upstream of valve 23, and a hydrogen fluoride gas supply source 43 located upstream of hydrogen fluoride gas flow rate controller 83. The opening and closing of valve 23 is adjusted by control of hydrogen fluoride gas flow rate controller 83, thereby controlling the flow rate of hydrogen fluoride gas supplied from hydrogen fluoride gas supply source 43 to pipe 13. Note that a high-pressure cylinder of anhydrous hydrogen fluoride is used as hydrogen fluoride gas supply source 43, for example. Note that hydrogen fluoride gas flow rate controller 83 measures the flow rate of hydrogen fluoride gas and controls the flow rate based on the obtained measurement value.

[0036] Pipe 14 is provided with valve 24, vaporizer 25 located upstream of valve 24, water flow controller 84 located upstream of vaporizer 25, and water supply source 44 located upstream of water flow controller 84. Furthermore, upstream of pipe 14A branching off from pipe 14 at vaporizer 25, nitrogen flow controller 85 and nitrogen supply source 45 located upstream of nitrogen flow controller 85 are provided. Note that water flow controller 84 measures the flow rate of water vapor and controls the flow rate based on the obtained measurement value. Also, nitrogen flow controller 85 measures the flow rate of nitrogen and controls the flow rate based on the obtained measurement value.

[0037] In vaporizer 25, water supplied from water supply source 44 is vaporized by nitrogen (inert gas) supplied from nitrogen supply source 45 and pressure-fed. Then, valve 24 controls the flow rate of the vaporized water vapor supplied from pipe 14 to pipe 11. The flow rates of the water vapor supplied to vaporizer 25 are controlled by water flow rate controller 84, and the flow rate of the nitrogen (inert gas) supplied to vaporizer 25 is controlled by nitrogen flow rate controller 85.

[0038] The judgment unit 31 of the control unit 3 performs temperature adjustment of the heating mechanism 5 in the etching apparatus 1, adjustment of the opening / closing degree of the valve 22 via the nitrogen flow controller 82, adjustment of the opening / closing degree of the valve 23 via the hydrogen fluoride gas flow controller 83, adjustment of the opening / closing degree of the valve 24, adjustment of the opening / closing degree of the valve 21, exhaust operation of the pressure reducing pump 8, measurement operation of the pressure sensor 10, adjustment of the opening degree of the APC valve 9, etc.

[0039] The control unit 3 controls each valve to select the gas to be supplied from the pipe 11 into the processing chamber 2 from nitrogen, hydrogen fluoride gas, and water vapor. The selected gas then passes through the gas distribution plate 6 in the processing chamber 2 and reaches the substrate W.

[0040] The supply rate of the hydrogen fluoride gas supplied to etch the multiple types of coating films formed on the substrate W is, for example, 100 cc / min to 2000 cc / min. The supply rate of the water vapor mixed with the hydrogen fluoride gas is, for example, 300 cc / min to 10000 cc / min.

[0041] In addition, in the step of cleaning the substrate surface after etching the coating film (described later), the supply rate of water vapor is, for example, 300 cc / min to 10,000 cc / min.

[0042] During processing of the substrate W, the pressure inside the processing chamber 2 is maintained, for example, at not less than 1 Pa and not more than 30,000 Pa. The pressure inside the processing chamber 2 is controlled by the control unit 3 adjusting the aperture of the APC valve 9 in accordance with the supply amount of water vapor and the supply amount of the mixed gas of water vapor and hydrogen fluoride gas so that the pressure inside the processing chamber 2 indicated by the pressure sensor 10 becomes a predetermined pressure.

[0043] <Operation of the etching equipment> The operation of the etching apparatus according to this embodiment will be described below. Fig. 2 is a flowchart showing an example of the operation of the etching apparatus according to this embodiment. The following operation is executed under the control of the control unit 3.

[0044] Here, the coating films of the substrate W to be processed are a silicon nitride film and a BSG film. A silicon oxide film (thermal oxide film) is formed on the upper surface of the substrate W, and the silicon nitride film is formed on the upper surface of the silicon oxide film, and the BSG film is formed on the side surface of the silicon oxide film.

[0045] First, the substrate W is transported into the processing chamber 2 by a transport system (not shown), and then placed on the substrate holder 4 (step ST1). After the substrate W is placed on the substrate holder 4, the substrate W is heated to a predetermined temperature in the range of 30°C to 200°C by the heating mechanism 5 built into the substrate holder 4.

[0046] Next, after the substrate W is placed on the substrate holder 4, the vacuum pump 8 starts to evacuate the processing chamber 2 (step ST2). The vacuum pumping is continued until the pressure in the processing chamber 2 reaches about 0.1 Pa, and the atmospheric air in the processing chamber 2 is exhausted.

[0047] The evacuation time is determined by the capacity of the vacuum pump used for evacuation and the allowable evacuation time, but reducing the pressure as much as possible will allow the atmospheric atmosphere inside the processing chamber 2 to be exhausted and the processing chamber 2 to be clean.

[0048] Next, the hydrogen fluoride gas serving as an etching gas is adjusted to a predetermined supply flow rate by opening and closing valve 23, and further, the vaporized water vapor is adjusted to a predetermined supply flow rate by opening and closing valve 24, and the hydrogen fluoride gas and water vapor are mixed in vaporizer 25 to form a mixed gas. Then, after the pressure in processing chamber 2 reaches approximately 0.1 Pa, nitrogen is supplied from nitrogen supply source 42 through pipe 12 into processing chamber 2. After the pressure in processing chamber 2 is adjusted to a predetermined range of 1 Pa to 30,000 Pa, the mixed gas is supplied into processing chamber 2 through pipe 11.

[0049] The mixed gas supplied into the processing chamber 2 passes through the multiple openings in the gas distribution plate 6 and is uniformly supplied to the entire surface of the substrate W, and further etches the coating film to be processed (first etching step of step ST3).

[0050] At this time, the pressure inside the processing chamber 2 is monitored by a pressure sensor 10 so that the pressure inside the processing chamber 2 is maintained at a predetermined vacuum level, and the opening degree of the APC valve 9 is adjusted by the control unit 3 based on the pressure indicated by the pressure sensor 10.

[0051] Here, prior to step ST3, water vapor may be supplied into the processing chamber 2 from the pipe 11. The water vapor passes through the plurality of openings 61 in the gas distribution plate 6 and is supplied to the entire surface of the substrate W. The water vapor that has reached the entire surface of the substrate W forms a thin layer of water on the upper surface of the substrate W.

[0052] If the water layer is formed, the etching gas, hydrogen fluoride gas, dissolves in the water layer and forms HF2 - Fluorine ions are generated, and etching can begin immediately. The supply time of water vapor is not particularly limited, but may be long enough to form a thin layer of water over the entire surface of the substrate W (for example, about 1 second or more and 10 seconds or less).

[0053] 3 is a diagram schematically illustrating an example of a coating film that is the target of the first etching step. As illustrated in the example in FIG. 3, a silicon nitride film 90 is formed on the upper surface of a silicon oxide film 70, and a BSG film 92 is formed on the side surface of the silicon oxide film 70. The example illustrated in FIG. 3 shows a layered structure in which the silicon oxide films 70 and the silicon nitride films 90 are alternately stacked. The BSG film 92 is formed in a trench 94 formed between the layered structures and in contact with both adjacent layered structures.

[0054] In the first etching step, the BSG film 92 is mainly etched. In the first etching step, the supply flow rates of the water vapor and hydrogen fluoride gas in the mixed gas are set so as to increase the etching rate (selectivity) of the BSG film 92 relative to the silicon oxide film 70. For example, the supply flow rate of the water vapor is set in the range of 300 cc / min to 10,000 cc / min, and the supply flow rate of the hydrogen fluoride gas is set in the range of 100 cc / min to 2,000 cc / min.

[0055] After the BSG film 92 has been sufficiently removed and the first etching step has been completed, the mixed gas is supplied into the processing chamber 2 while changing the supply flow rates of the water vapor and hydrogen fluoride gas in the mixed gas and the degree of vacuum in the processing chamber 2, and the coating film to be processed is etched (second etching step of step ST4). The mixed gas supplied into the processing chamber 2 passes through the multiple openings in the gas distribution plate 6 and is supplied uniformly over the entire surface of the substrate W.

[0056] At this time, the pressure inside the processing chamber 2 is monitored by a pressure sensor 10 so that the pressure inside the processing chamber 2 is maintained at a predetermined vacuum level, and the opening degree of the APC valve 9 is adjusted by the control unit 3 based on the pressure indicated by the pressure sensor 10.

[0057] 4 is a diagram schematically illustrating an example of a coating film that is the target of the second etching step. As shown in the example in FIG. 4, the BSG film 92 is removed in the first etching step, and the side surface of the silicon nitride film 90 is exposed inside the trench 94.

[0058] In the second etching step, the silicon nitride film 90 is mainly etched. In the second etching step, the supply flow rates of the water vapor and the hydrogen fluoride gas in the mixed gas are set so as to increase the etching rate (selectivity) of the silicon nitride film 90 relative to the silicon oxide film 70. Specifically, the mixed gas supplied in the second etching step has a different water vapor supply ratio (supply flow rate) from the mixed gas supplied in the first etching step.

[0059] After the silicon nitride film 90 has been sufficiently removed and the second etching step has ended, the valve 23 is closed under the control of the control unit 3 to stop the supply of the hydrogen fluoride gas, which is the etching gas. Meanwhile, water vapor is supplied by adjusting the valve 24, and is supplied from the pipe 14 into the processing chamber 2 (step ST5).

[0060] The water vapor supplied after the second etching step passes through the plurality of openings 61 in the gas distribution plate 6 and reaches the entire surface of the substrate W. Then, the water vapor cleans (washes away) the substrate W after the second etching step, thereby removing fluorine (SiF-based residues) remaining on the surface of the substrate W.

[0061] The cleaning step of step ST5 may also be performed after the first etching step.

[0062] <Supply ratio of mixed gas> In the first etching step, a gas mixture of hydrogen fluoride gas at a supply rate sufficient to etch the BSG film 92 to be processed and water vapor at a predetermined supply rate (first flow rate) is supplied to the substrate W.

[0063] Here, a thermal oxide film is formed on the surface of the substrate W before it is loaded into the etching apparatus 1. In this embodiment, the substrate W is a silicon substrate, and the thermal oxide film is a silicon oxide film 70.

[0064] The thermal oxide film is formed by oxidizing the substrate W from its surface to its interior. Specifically, by exposing the substrate W to oxygen or water vapor in a high-temperature atmosphere, silicon (Si) and oxygen (O2) chemically react to form a thin film (thermal oxide film) of silicon dioxide (SiO2). The density (film density) of this thermal oxide film is relatively high, at 2.2 g / cm3. 3 That's about it.

[0065] On the other hand, the density (film density) of the BSG film 92 formed on the side surface of the silicon oxide film 70 is 1.8 g / cm3 The density of the thermal oxide film is about 2.2 g / cm 3 ) is smaller than

[0066] A film with low film density can be said to be porous, and generally, water vapor penetrates into the film, facilitating the etching reaction. Therefore, under the condition that water vapor is supplied at the first flow rate, the BSG film 92 is etched while maintaining a high selectivity relative to the silicon oxide film 70.

[0067] Next, in the second etching step, a gas mixture of hydrogen fluoride gas in an amount sufficient to etch the silicon nitride film 90 to be processed and water vapor in a predetermined amount (second flow rate) is supplied to the substrate W.

[0068] The selectivity of the silicon nitride film 90 to the silicon oxide film 70 increases as the amount of water vapor decreases, so the second flow rate is set to a flow rate equal to or lower than the flow rate of water vapor corresponding to the desired selectivity.

[0069] The coating film to be processed in the first etching step and the second etching step is not limited to the above case, and for example, the coating film to be processed in the first etching step may be the silicon nitride film 90, and the coating film to be processed in the second etching step may be the BSG film 92. Also, one of the first flow rate and the second flow rate may be zero.

[0070] Here, in the first etching step, the coating film to be etched in the second etching step is present, and therefore the first flow rate set in the first etching step is set to a flow rate that provides a sufficiently high selectivity ratio of the coating film to be etched in the first etching step to the coating film to be etched in the second etching step, or a flow rate that allows etching of the coating film to be processed in the first etching step to be completed sufficiently quickly.

[0071] By performing the etching processes with different flow rate settings as described above, each of the coating films to be processed can be etched more efficiently than when the same etching process is continuously performed without changing the flow rate setting.

[0072] This shortens the overall processing time required to etch both coating films (the BSG film 92 and the silicon nitride film 90), thereby preventing unintentional removal of films that are not the target of processing (for example, the silicon oxide film 70 in FIGS. 3 and 4). Therefore, even when removing multiple types of coating films in a complex structure such as a three-dimensional NAND having a three-dimensional structure, it becomes easier to achieve a desired structure.

[0073] Furthermore, by performing the first etching step and the second etching step in the same processing chamber 2, the etching processes can be performed continuously without moving the substrate W. This makes it possible to shorten the processing time required to etch both coating films (the BSG film 92 and the silicon nitride film 90).

[0074] Between the first etching step and the second etching step, the pressure and temperature within the processing chamber 2 and the supply flow rate of the nitrogen or hydrogen fluoride gas can also be changed as appropriate.

[0075] In both the first etching step and the second etching step, it is sufficient that the coating film to be treated is at least partially removed, and it is not necessarily necessary that the entire film is removed.

[0076] <Effects of the above-described embodiments> Next, examples of effects obtained by the above-described embodiments will be described. Note that in the following description, the effects will be described based on the specific configurations exemplified in the above-described embodiments, but these may be replaced with other specific configurations exemplified in the present specification as long as the same effects are obtained. In other words, for convenience, only one of the corresponding specific configurations may be described as a representative below, but the representatively described specific configuration may be replaced with another corresponding specific configuration.

[0077] According to the embodiment described above, the etching method is a method for etching a BSG film 92 as a second film and a silicon nitride film 90 as a third film, each formed on (including the top and side surfaces of) a silicon oxide film 70 as a first film, in the same processing chamber 2. In this etching method, the processing chamber 2 is depressurized. Then, a first etching gas (hydrogen fluoride gas) and water vapor at a first flow rate are supplied into the processing chamber 2 to etch the BSG film 92 (first etching step). Then, after the first etching step, a second etching gas (hydrogen fluoride gas) and water vapor at a second flow rate, which is different from the first flow rate, are supplied into the processing chamber 2 to etch the silicon nitride film 90 (second etching step).

[0078] According to this configuration, by performing each etching step with a different flow rate setting, each coating film to be processed can be etched more efficiently than when the same etching step is continuously performed without changing the flow rate setting. Therefore, the overall processing time required to etch both coating films (the BSG film 92 and the silicon nitride film 90) can be shortened, which prevents unintentional removal of a film that is not the processing target (e.g., the silicon oxide film 70 in FIGS. 3 and 4). Furthermore, by performing the first etching step and the second etching step in the same processing chamber 2, the etching process can be performed continuously without moving the substrate W. Therefore, the processing time required to etch both coating films can be shortened.

[0079] Furthermore, even if other configurations shown as examples in this specification are appropriately added to the above configuration, that is, even if other configurations in this specification that were not mentioned as the above configuration are appropriately added, the same effect can be achieved.

[0080] Furthermore, according to the embodiment described above, both the first etching gas and the second etching gas contain hydrogen fluoride, and with this configuration, the BSG film 92 and the silicon nitride film 90 can be removed in separate etching steps by the action of the hydrogen fluoride gas.

[0081] Furthermore, according to the embodiment described above, the first film is a silicon oxide film, the second film is a BSG film, and the third film is a silicon nitride film. With this configuration, in the first etching step, the BSG film 92 can be removed while maintaining the selectivity of the BSG film 92 to the silicon oxide film 70, and in the second etching step, the silicon nitride film 90 can be removed while maintaining the selectivity of the silicon nitride film 90 to the silicon oxide film 70.

[0082] Furthermore, according to the embodiment described above, the silicon oxide film 70 and the silicon nitride film 90 form a plurality of stacked structures. Furthermore, the BSG film 92 is formed between adjacent stacked structures. With this configuration, the BSG film 92 between the stacked structures (trench 94) is removed in the first etching step, thereby exposing the side surfaces of the silicon nitride film 90. Then, in the second etching step, the exposed silicon nitride film 90 can be effectively etched.

[0083] <Modifications of the above-described embodiments> In the embodiments described above, the material, composition, dimensions, shape, relative positional relationship, or implementation conditions of each component may also be described, but these are merely examples in all aspects and are not limiting.

[0084] Thus, numerous variations and equivalents not shown are contemplated within the scope of the technology disclosed herein, including, for example, the modification, addition, or omission of at least one component.

[0085] Furthermore, in the embodiments described above, when a material name is mentioned without any particular specification, it is assumed that the material may contain other additives, such as an alloy, unless a contradiction arises. [Explanation of symbols]

[0086] 2. Processing chamber 70 Silicon oxide film 90 Silicon nitride film 92 BSG membrane

Claims

1. An etching method for etching a second film and a third film formed on a first film (including side surfaces) in the same processing chamber, creating a reduced pressure inside the processing chamber; a first etching step of supplying a first etching gas and water vapor at a first flow rate into the processing chamber to etch the second film; a second etching step of supplying, after the first etching step, a second etching gas and the water vapor at a second flow rate different from the first flow rate into the processing chamber to etch the third film; Etching method.

2. 2. The etching method according to claim 1, the first etching gas and the second etching gas are both etching gases containing hydrogen fluoride; Etching method.

3. 3. The etching method according to claim 1 or 2, the first film is a silicon oxide film, the second film is a BSG film, and the third film is a silicon nitride film; Etching method.

4. 4. The etching method according to claim 1, the first film and the third film form a multi-layer structure; the second film is formed between adjacent stacked structures; Etching method.

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