JP2015130427A - Dry etching device and dry etching method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use an etching gas with a low global warming coefficient in dry etching and to simplify facilities and processes.SOLUTION: An insulating film 20 on a substrate S is subjected to dry etching. The following steps are carried out: (a) a first step S100 of etching a part of the insulating film 20 not covered with a resist mask 10 by using a first mixture gas containing CHand COF, in which a mixing ratio of CHto COFin the first mixture gas is less than 0.60; (b) a second step S200 of forming a protective film 44 on a side wall 23 of the etched insulating film 20 by using a second mixture gas containing CHand COF, in which a mixing ratio of CHto COFin the second mixture gas is higher than 0.60; and (c) (S300) repeating the first step S100 and the second step S200.

Description

  The present invention relates to a dry etching apparatus and a dry etching method.

Conventionally, CF ₄ has been used as an etching gas in dry etching of an insulating film in a pre-process of semiconductor manufacturing. However, as a countermeasure against global warming in recent years, CF ₄ having a high global warming potential is being replaced with an alternative gas having a low global warming potential. As an alternative gas, a gas having a high ratio of x to _y and having a low C—F bond, for example, C ₄ F ₆ is used as C _x F _y (Patent Document 1).

JP-T-2006-514783 JP 2010-73935 A JP 4090492 A JP 2007-520080 A JP 2007-528610 A

However, C ₄ F ₆ has a high vapor pressure. For this reason, when using C ₄ F ₆ as an etching gas, a constant temperature facility for vaporizing C ₄ F ₆ is required. Further, a C _x F _y, the ratio of x against y uses high etching gas, C is likely to adhere to the inner wall of the processing chamber. For this reason, there is a possibility that the deposits may be peeled off during the processing to contaminate the semiconductor product, and the inner wall of the processing chamber needs to be frequently cleaned.

On the other hand, conventionally, as a technique for performing deep etching, a BOSH method in which a passivation mode and an etching mode are repeatedly performed has been performed. In the passivation mode, a protective film is formed on the side wall of the structure using C ₄ F ₈ as an etching gas. On the other hand, in the etching mode, etching is performed using SF ₆ as an etching gas, and the bottom surface of the structure is etched. At this time, the protective film on the side wall is also etched, but the side wall of the structure itself is protected by the protective film. As a result, only the bottom surface of the structure is etched, and high aspect ratio etching is achieved.

  However, in the above method, there is room for improvement in terms of manufacturing lead time and manufacturing cost because it is necessary to exchange gases in the passivation mode and the etching mode.

  For this reason, in dry etching, it has been desired to use an etching gas having a low global warming potential and to simplify equipment and processes. In addition, in the conventional dry etching, it has been desired to reduce the size of the processing apparatus, to reduce the cost, to save resources, to facilitate manufacturing, and to improve usability.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms.

(1) According to one aspect of the present invention, a method for performing dry etching on an insulating film on a substrate is provided. This method is (a) a first step of etching a portion of the insulating film not covered with a resist mask by using a first type mixed gas containing CH ₄ and COF ₂ . The first step in which the mixing ratio of CH _{4 to} COF ₂ is lower than 0.60 in one kind of mixed gas; and (b) the etching using the second kind mixed gas containing CH ₄ and COF _2. A second step of forming a protective film on the sidewall of the insulating film, wherein the mixing ratio of CH _{4 to} COF ₂ is higher than 0.60 in the second type mixed gas; (C) including the step of repeating the first step and the second step. With such an embodiment, dry etching can be performed on the insulating film on the semiconductor substrate using an etching gas having a low warming coefficient as compared with an embodiment using CF ₄ as the processing gas. In addition, since no constant temperature equipment for etching gas is required, etching can be performed with simple equipment as compared with an embodiment using C ₄ F ₆ as a processing gas. By repeating the formation of the protective film on the sidewall and the etching of the insulating film, the high aspect ratio etching can be performed. Furthermore, since the etching gas used in the first step and the second step is common, switching between the first step and the second step is easy. Note that “a portion of the insulating film not covered with the resist mask” means a portion of the insulating film that is not covered with the resist mask in the stacking direction of the insulating film and the resist mask.

(2) In the first step of the dry etching method of the above aspect, the CH ₄ and COF ₂ mixing ratio may be lower than 0.45. With such an embodiment, the insulating film can be etched more efficiently in the first step.

(3) In the second step of the method for performing dry etching in the above form, the mixing ratio of CH ₄ and COF ₂ may be higher than 0.70. If it is set as such an aspect, a protective film can be formed more efficiently in a 2nd process.

(4) In the dry etching method of the above aspect, the insulating film can be made of a metal oxide, SiO ₂ , SiN, AlN, or GaO. In each of these embodiments, the method of performing the dry etching in the above form is effective.

(5) According to one embodiment of the present invention, an apparatus for performing dry etching on an insulating film on a substrate is provided. This apparatus is a first processing unit that etches a portion of the insulating film that is not covered with a resist mask by using a first type mixed gas containing CH ₄ and COF ₂ , wherein the first type in a mixed gas of the mixing ratio of CH ₄ for COF ₂ is less than 0.60, the first processing section; using a second type of mixed gas containing CH ₄ and COF ₂ the insulation was the etching A second processing unit for forming a protective film on a sidewall of the film, wherein the second processing unit has a CH _{4 to} COF ₂ mixing ratio higher than 0.60 in the second type mixed gas; And a third processing unit that repeatedly performs etching and formation of the protective film.

  A plurality of constituent elements of each aspect of the present invention described above are not indispensable, and some or all of the effects described in the present specification are to be solved to solve part or all of the above-described problems. In order to achieve the above, it is possible to appropriately change, delete, replace with another new component, and partially delete the limited contents of some of the plurality of components. In order to solve part or all of the above-described problems or to achieve part or all of the effects described in this specification, technical features included in one embodiment of the present invention described above. A part or all of the technical features included in the other aspects of the present invention described above may be combined to form an independent form of the present invention.

  The present invention can be implemented in various forms other than the method and the apparatus. For example, the present invention can be realized in the form of a semiconductor substrate manufacturing method, a control device and control method for a dry etching apparatus, a computer program for realizing the control method, a non-temporary recording medium on which the computer program is recorded, and the like. .

Explanatory drawing of the dry etching system as 1st Embodiment of this invention. The flowchart which shows the process of the etching performed using the dry etching system of FIG. FIG. 3 is a cross-sectional view showing a configuration of a substrate S. Sectional drawing which shows the structure of the board | substrate S after the process of step S100 of the 1st time. Sectional drawing which shows the structure of the board | substrate S after the process of step S200 of the 1st time. The microscope picture of the board | substrate S used as experiment object. The graph which shows the result of an experiment. Photomicrograph of the substrate S after processing when the flow mixing ratio of CH ₄ to the flow rate of COF ₂ is 0.20. Photomicrograph of the substrate S after processing when the flow mixing ratio of CH ₄ to the flow rate of COF ₂ is 0.28. Photomicrograph of the substrate S after processing when the flow mixing ratio of CH ₄ to the flow rate of COF ₂ is 0.70.

A. First embodiment:
FIG. 1 is an explanatory diagram of a dry etching system as a first embodiment of the present invention. The dry etching system includes a cylinder cabinet 100 and a dry etching apparatus 300 connected to the cylinder cabinet 100 via a processing gas supply pipe 200.

The cylinder cabinet 100 includes a high-pressure tank 101 containing CH ₄ as a processing gas, a pressure regulator 102 for supplying the processing gas in the high-pressure tank 101 to the outside while reducing the pressure of the processing gas to a predetermined pressure, Is provided. The cylinder cabinet 100 also has a high-pressure tank 103 containing COF ₂ as a processing gas, and a pressure regulator 104 for supplying the processing gas in the high-pressure tank 103 to the outside while reducing the pressure of the processing gas to a predetermined pressure. And comprising. The COF ₂ and CH ₄ as processing gases stored in the tanks 101 and 103 are individually reduced in pressure by the pressure regulators 102 and 104, and then individually dry etching apparatus via the processing gas supply pipe 200. 300. Here, configurations and supplying CH _4, constituting the supplying COF _2, has been described, the cylinder cabinet 100, other may be provided with a similar configuration to supply Ar.

The processing gas supply pipes 200 are a plurality of pipes that can supply gas such as COF ₂ and CH ₄ supplied from the cylinder cabinet 100 to the dry etching apparatus 300 independently.

The dry etching apparatus 300 is an inductive coupled plasma (ICP) plasma etching apparatus. The dry etching apparatus 300 includes a stage 301 that holds the substrate S to be processed in the processing container 308 and functions as a lower electrode, an antenna 302, and a mass flow controller that supplies a processing gas controlled to a predetermined amount to the processing container 308. 303, a first high-frequency power supply 304 that supplies high-frequency power to the stage 301, a second high-frequency power supply 305 that supplies high-frequency power to the antenna 302, and a control unit 306 that controls these units. Note that the mass flow controller 303 can independently control the mass flow rates of COF ₂ and CH ₄ that are independently supplied from the cylinder cabinet 100 via the processing gas supply pipes 200 that are a plurality of pipes. The dry etching apparatus 300 can control each unit to generate plasma on the substrate S to be processed and etch the substrate S to be processed. Thus, deposition can be performed.

  FIG. 2 is a flowchart showing an etching process performed using the dry etching system of FIG. In performing the process of FIG. 2, the substrate S is set on the stage 301 in advance (see FIG. 1). The substrate S is disposed on the stage 301 so that the upper surface thereof coincides with the horizontal direction. As a result, the stacking direction of the layers included in the substrate S coincides with the vertical direction. In the dry etching apparatus 300, the direction from the antenna 302 toward the stage 301 matches the vertical direction.

FIG. 3 is a cross-sectional view showing the configuration of the substrate S. Note that FIG. 3 does not accurately reflect the dimensions of the configuration of the substrate S in order to facilitate understanding of the technology. FIG. 3 shows a part of the cross section of the configuration of the substrate S, and the shapes of the left and right ends and the lower end of FIG. 3 do not reflect the configuration of the substrate S. The same applies to the dimensions of each part of the substrate S shown in FIGS. 4 and 5 and the shapes of the left and right ends and the lower end. The substrate S includes a semiconductor substrate 30, a SiO ₂ insulating film 20 formed on the semiconductor substrate, and a polymer organic compound resist mask 10 formed on the insulating film 20.

In step S <b> 100 of FIG. 2, the control unit 306 first controls the mass flow controller 303 so that a mixed gas containing COF ₂ and CH ₄ having a first mixing ratio is supplied into the processing container 308. Then, high-frequency power is supplied from the high-frequency power sources 304 and 305 to the antenna 302 and the stage 301 to accelerate and collide ion species in the plasma toward the stage 301, that is, the substrate S, thereby etching the substrate S. . Here, the first mixing ratio is a mixing ratio in which the mixing ratio of the flow rate of CH _{4 to} the flow rate of COF ₂ is lower than 0.60. The flow rate of the processing gas is evaluated by sccm (standard cc / min), that is, cc / min under an atmospheric pressure of 1013 hPa and 0 ° C. Hereinafter, the same applies when referring to the “mixing ratio” in the present specification. By performing the process of step S100, a portion of the insulating film 20 that is not covered with the resist mask 10 is etched. A functional unit of the control unit 306 that controls each unit and executes step S100 is shown as a first processing unit 311 in FIG.

  FIG. 4 is a cross-sectional view showing the configuration of the substrate S after the first step S100. In FIG. 4, the direction in which the ion species collides with the substrate S in step S100 of FIG. 2 is indicated by an arrow P1. In step S100, the ion species is accelerated in a direction from the side where the antenna 302 exists toward the stage 301, that is, perpendicularly to the upper surface of the stage 301 and the upper surface of the substrate S (see FIG. 1). For this reason, in the substrate S, the upper surface 21 of the insulating film 20 and the upper surface 11 of the resist mask 10 are mainly etched (see FIG. 3). However, the resist mask 10 is made of a material that is harder to etch than the insulating film 20. For this reason, the resist mask 10 is not etched as much as the insulating film 20. As a result, in step S100, a portion of the insulating film 20 that is not covered with the resist mask 10 is mainly etched. Note that “a portion of the insulating film that is not covered with the resist mask” means a portion of the insulating film that is not covered with the resist mask in the stacking direction of the insulating film and the resist mask (see FIG. 4P1). .

  Then, the side surface 23 of the insulating film 20 that is substantially perpendicular to the upper surface of the insulating film 20 is exposed. The upper surface of the insulating film 20 exposed by etching the portion of the insulating film 20 that is not covered with the resist mask 10 is shown as an upper surface 22 in FIG. A side surface of the insulating film 20 exposed by etching a portion of the insulating film 20 not covered with the resist mask 10 is shown as a side surface 23 in FIG.

In step S <b> 200 of FIG. 2, the control unit 306 controls the mass flow controller 303 so that a mixed gas containing COF ₂ and CH ₄ having a second mixing ratio is supplied into the processing container 308. Then, high-frequency power is supplied from the high-frequency power sources 304 and 305 to the antenna 302 and the stage 301 to accelerate and collide ion species in the plasma toward the stage 301, that is, the substrate S. As a result, a fluorine compound deposit 40 is deposited on the surface of the substrate S (see FIG. 5). Here, the second mixing ratio is a mixing ratio in which the mixing ratio of the CH ₄ flow rate to the COF ₂ flow rate is higher than 0.60. By performing the process of step S200, the surface of the insulating film 20 and the surface of the resist mask 10 are covered with the deposit 40. A functional unit of the control unit 306 that controls each unit and executes step S200 is illustrated as a second processing unit 312 in FIG.

  FIG. 5 is a cross-sectional view showing the configuration of the substrate S after the first processing in step S200. In FIG. 5, the direction in which the ion species collides with the substrate S in step S200 of FIG. 2 is indicated by an arrow P2. As shown in FIG. 5, in step S200 of FIG. 2, in addition to the upper surface 22 of the insulating film 20 and the upper surface 11 of the resist mask 10 etched in step S100, the side surface 12 of the resist mask 10 is etched. The side surface 23 of the insulating film 20 exposed by the above is also covered with the deposit 40. These deposits 40 function as a protective film in etching performed later. In FIG. 5, the deposit 40 deposited on the upper surface 22 of the insulating film 20 is shown as a protective film 41. A deposit 40 deposited on the upper surface 11 of the resist mask 10 is shown as a protective film 42. A deposit 40 deposited on the side surface 12 of the resist mask 10 is shown as a protective film 43. The deposit 40 deposited on the side surface 23 of the insulating film 20 is shown as a protective film 44.

  In step S300 of FIG. 2, it is determined whether or not steps S100 and S200 are repeated N times (N is an integer of 2 or more). If the number of repetitions of steps S100 and S200 is N, the process ends. If the number of repetitions of steps S100 and S200 is less than N, the process returns to step S100. N is a predetermined number. N can be determined according to the shape and size of the structure formed by etching the substrate S.

  In step S100 of FIG. 2, etching is performed on the substrate S (see FIG. 5) whose surface is covered with the deposit 40. At that time, etching proceeds mainly in the direction from the antenna 302 toward the stage 301 (see arrow P1 in FIG. 4). For this reason, the protective film 41 deposited on the upper surface 22 of the insulating film 20 and the protective film 42 deposited on the upper surface 11 of the resist mask 10 are mainly etched (see FIG. 5). Thereafter, the upper surface 22 of the insulating film 20 and the upper surface 11 of the resist mask 10 are also etched (see FIG. 4). The resist mask 10 is not etched as much as the insulating film 20 because the resist mask 10 is formed of a material that is less easily etched than the insulating film 20.

  On the other hand, the protective film 43 deposited on the side surface 12 of the resist mask 10 and the side surface 12 of the resist mask 10, the protective film 44 deposited on the side surface 23 of the insulating film 20, and the side surface 23 of the insulating film 20 have ionic species. Since it is arranged in a direction perpendicular to the collision direction, it is not etched as compared with the upper surface 22 of the insulating film 20 (see FIG. 5). As a result, etching of the upper surface 22 of the insulating film 20 exposed by etching proceeds. Etching of other portions does not proceed as compared with the upper surface 22 of the insulating film 20.

  Thereafter, the process of step S200 is performed. Then, the processes of steps S100 and S200 are repeatedly performed until the number of repetitions of steps S100 and S200 reaches N (step S300 in FIG. 2). A functional unit of the control unit 306 that controls each unit to perform the process of step S300 and executes the processes of steps S100 and S200 a predetermined number of times is shown as a third processing unit 313 in FIG.

  2 is performed, the upper surface 22 of the insulating film 20 is most etched (see FIGS. 4 and 5). As a result, deep etching is performed on the insulating film 20 in a direction perpendicular to the surface. Done.

Table 1 shows the warming coefficients of CH ₄ and COF ₂ used as process gases in this embodiment, and other gases.

As is apparent from Table 1, CH ₄ and COF ₂ used as processing gases in this embodiment have a warming coefficient of about 1/10 to 1/10000 compared to other gases. For this reason, according to the present embodiment, dry etching is performed on the insulating film on the semiconductor substrate using a gas that does not easily promote global warming as compared with an embodiment in which CF ₄ or C ₂ F ₆ is used as a processing gas. It can be carried out.

Further, CH ₄ and COF ₂ have a lower vapor pressure than C ₄ F ₆ or the like. For this reason, unlike C ₄ F ₆ , there is no need for a thermostatic facility for heating and vaporizing the target to keep it warm. Therefore, etching can be performed with simple equipment as compared with an embodiment using C ₄ F ₆ or the like as the processing gas.

  Furthermore, in this embodiment, the etching gas used in step S100 and step S200 is common. For this reason, when repeating Step S100 and Step S200, it is not necessary to completely replace the processing gas in the processing container 308. Etching and deposition can be repeated by controlling the flow rate for each gas. That is, it is easy to switch between the etching process and the deposition process, and to repeat them. As a result, etching with a high aspect ratio can be easily performed.

B. Example:
ICP-RIE etching was performed on the substrate S (see FIG. 3) having the SiO ₂ insulating film 20 and the resist mask 10 by changing the flow rate ratio of CH ₄ and COF ₂ in various ways. The processing conditions are as follows.
Equipment used: RIE-200iP, manufactured by Samco Corporation
ICP = 1.7 W / cm ² (RF = 13.56 MHz)
Bias = 0.8 W / cm ²
Pressure = 0.5Pa
Etching time = 1 minute Deposition time = 1 minute Number of repetitions N = 5 (Total time = 10 minutes)

FIG. 6 is a photomicrograph of the substrate S that was the subject of the experiment (see FIG. 3). The composition and configuration of the substrate S are as follows. The resist mask 10 is made of a material containing 35 to 60% by weight of propylene glycol monomethyl ether acetate, 15 to 25% of n-butyl acetate, 1 to 5% of cresol, and 25 to 45% of novolak resin. The following resist mask was used. The resist mask 10 has a pattern resolution of 2 μm, that is, a mask having a width of 2 μm is arranged with an interval of 2 μm. Ten samples were prepared for each condition.
Semiconductor substrate Composition: Si
Insulating film Composition: SiO ₂
Thickness: 1.0μm
Resist mask Manufacturer name: Tokyo Ohka Kogyo Co., Ltd. Product name: TCIR-ZR8800PB
Thickness: 1.8μm
Resolution: 2μm

Under the above conditions, and various changes in flow ratio of CH ₄ and COF _2, and supplies the CH ₄ and COF ₂ and Ar into the processing chamber 308, and out the ICP-RIE etching, the insulating film 20, The etching rate of the resist mask 10 was measured. For example, when the mixing ratio was 0.20, the flow rate ratio of COF ₂ , CH _4, and Ar was 25: 5: 5. The results of the experiment are shown in Table 2. In Table 2, the column “CH ₄ / COF ₂ ” indicates the mixing ratio of the flow rate of CH _{4 to} the flow rate of COF ₂ . The column “SiO ₂ ” indicates the etching rate (nm / min) of the insulating film 20. The column “PR” indicates the etching rate (nm / min) of the resist mask 10. The column “selectivity” indicates the ratio of the etching rate of the insulating film 20 to the etching rate of the resist mask 10. The values in Table 2 are average values of 10 samples.

FIG. 7 is a graph showing the results of the experiment. In the graph of FIG. 7, the horizontal axis represents the mixing ratio of the flow rate of CH _{4 to} the flow rate of COF ₂ , and the vertical axis represents the etching rate. A graph G10 represents the etching rate of the resist mask 10. A graph G20 represents the etching rate of the insulating film 20.

From Table 2 and FIG. 7, it can be seen that the insulating film 20 (SiO ₂ ) is etched in a region where the mixing ratio of the flow rate of CH _{4 to} the flow rate of COF ₂ is less than 0.60. Further, in the region where the insulating film 20 is etched, the value of “selectivity” in Table 2 is 1 or more, and it can be seen that the insulating film 20 is etched more than the resist mask 10. Therefore, in step S100 of FIG. 2, it can be seen that the etching is performed by setting the mixing ratio of the flow rate of CH _{4 to} the flow rate of COF ₂ lower than 0.60.

From the results in Table 2, the mixing ratio of the CH ₄ flow rate to the COF ₂ flow rate is preferably less than 0.50 and more preferably less than 0.45 from the viewpoint of etching selectivity. The mixing ratio of the flow rate of CH _{4 to} the flow rate of COF ₂ is preferably 0.20 or more, more preferably 0.25 or more, and 0.35 or more from the viewpoint of etching selectivity. More preferably it is.

FIG. 8 is a photomicrograph of the substrate S after processing when the mixing ratio of the flow rate of CH _{4 to} the flow rate of COF ₂ is 0.20. FIG. 9 is a photomicrograph of the substrate S after processing when the mixing ratio of the flow rate of CH _{4 to} the flow rate of COF ₂ is 0.28. 8 and 9, it can be seen that the angle of the etching sidewall can be controlled by controlling the mixing ratio of the CH ₄ flow rate to the COF ₂ flow rate. More specifically, when the mixing ratio of the flow rate of CH _{4 to} the flow rate of COF ₂ is smaller (see FIG. 8), the resist mask 10 (especially the side surface 12) is more etched, and the side surface of the etched insulating film 20 It can be seen that the inner angle of the surface 23 with respect to the surface of the insulating film 20 (horizontal plane) becomes small.

FIG. 10 is a micrograph of the substrate S after processing when the mixing ratio of the flow rate of CH _{4 to} the flow rate of COF ₂ is 0.70. In FIG. 10, the resist mask 10 is highlighted to facilitate understanding of the technique. In the above experiment, deposits were confirmed on the insulating film 20 under the condition that the etching rate of the insulating film 20 in Table 2 is 0 and the mixing ratio is 0.64 or more. For example, FIG. 10 shows that the deposit 40 is deposited on the side surface 12 and the upper surface 11 of the resist mask 10 under the condition that the mixing ratio of the flow rate of CH _{4 to} the flow rate of COF ₂ is 0.70. More deposit 40 is deposited on the side surface 12 of the resist mask 10 than on the upper surface 11.

The deposition of the deposit 40 is presumed to occur through the following reaction. That is, by applying a high frequency voltage, COF ₂ and CH ₄ are excited, and CH-based, CF, and CF ₂ monomers are adsorbed on the resist mask 10 and the insulating film 20 (SiO ₂ ). With respect to these monomers, H * by excitation of CH ₄ causes a polymerization reaction to form a CF-based polymer, which becomes the protective film 40. Therefore, the protective film 40 is more easily generated as the amount of CH ₄ that supplies H * increases.

Therefore, the growth rate of the protective film 40 can be controlled mainly by the mixing ratio of the flow rate of CH _{4 to} the flow rate of COF ₂ . That is, as CH ₄ / COF ₂ increases, the growth rate increases. When CH ₄ / COF ₂ exceeds 0.60, the growth rate of the protective film 40 exceeds the etching rate, so that etching does not occur (see Table 2). ). From this, it can be seen that in step S200 of FIG. 2, the deposit 40 is deposited by setting the mixing ratio of the flow rate of CH _{4 to} the flow rate of COF ₂ higher than 0.60. It can also be seen that the deposit 40 is deposited more as the mixing ratio of the CH ₄ flow rate to the COF ₂ flow rate exceeds 0.60 and becomes higher. For example, the protective film forming step is preferably performed by setting the mixing ratio of the flow rate of CH _{4 to} the flow rate of COF _{2 to} a value higher than 0.70, and the protective film forming step is performed at a value higher than 0.80. More preferably, the protective film forming step is more preferably performed at a value higher than 0.90.

C. Variation:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

C1. Modification 1:
In the above embodiment, a mixed gas containing CH ₄ and COF ₂ at a predetermined ratio is used as the processing gas in steps S100 and S200. However, CHF ₃ can be used instead of COF ₂ .

C2. Modification 2:
In the above embodiment, the insulating film 20 is made of SiO ₂ . However, even when the insulating film is made of another material, etching with a high aspect ratio can be performed by the processing of the above embodiment. In addition to SiO ₂ , the insulating film can be, for example, AlN, GaO, or SiN. The insulating film can be a metal oxide. Note that the insulating film is preferably made of a material that easily vaporizes when a fluoride is formed by reaction.
The semiconductor substrate 30 can be composed of GaN, SiC, Si, AlN, GaO, or the like.

When AlN or GaO is used as an insulator material, an AlN or GaO thin film of 1 μm or less that does not contain impurities that generate carriers is used as a gate insulating film of a (power) transistor or an element (such as a transistor or a diode). It can be used as a protective film. Further, when AlN or GaO is adopted as the material of the gate insulating film, it can be adopted in the form of oxynitride such as AlON or GaON, if necessary. On the other hand, when AlN and GaO are employed as the material of the substrate (semiconductor), AlN and GaO doped with impurities that generate carriers (1014 to 1020 cm ⁻³ ) can be employed. When AlN or GaO is used as the material of the substrate (semiconductor), it is preferable that the substrate has a thickness of 100 μm or more that is easy to handle as a support substrate.

  In the above embodiment, TCIR-ZR8800PB manufactured by Tokyo Ohka Kogyo Co., Ltd. was used as the resist mask 10. However, not only when using TCIR-ZR8800PB manufactured by Tokyo Ohka Kogyo Co., Ltd., but by selecting the resist mask 10 appropriately according to the insulating film 20, the same effect can be achieved by the above embodiment.

C3. Modification 3:
In the above embodiment, the etching in step S100 and the deposition process in step S200 are repeated N times. However, the number of repetitions of the etching and deposition processes can be determined by other methods. For example, the depth of the concave portion of the insulating film formed by etching or the thickness of the bottom of the concave portion of the insulating film can be monitored, and the repetition of the etching and deposition processing can be terminated when they become a predetermined size. That is, the etching and deposition processes can be performed repeatedly according to some criteria.

  In the above-described embodiment, each processing gas is independently supplied from the cylinder cabinet 100 to the dry etching apparatus 300 via the processing gas supply pipes 200 that are a plurality of pipes. However, it is also possible to adopt a mode in which two or more process gases are supplied from the cylinder cabinet to the dry etching apparatus using a common pipe. And all the gas which should be supplied to a dry etching apparatus can also be set as the aspect supplied to a dry etching apparatus from a cylinder cabinet by a common pipe | tube.

  In the above embodiment, inductively coupled plasma reactive ion etching (RIE) was performed. However, the etching can also be performed by other reactive ion etching such as capacitively coupled plasma-RIE (CCP-RIE), ECR-RIE (Electron Cyclotron Resonance-RIE), or magnetron RIE. Etching is not limited to reactive ion etching, and can be performed by other methods such as ion milling.

DESCRIPTION OF SYMBOLS 100 ... Cylinder cabinet 101 ... High pressure tank 102 ... Pressure regulator 103 ... High pressure tank 104 ... Pressure regulator 200 ... Processing gas supply pipe 300 ... Dry etching apparatus 301 ... Stage 302 ... Antenna 303 ... Mass flow controller 304 ... 1st high frequency power supply 305 ... Second high frequency power supply 306 ... Control unit 10 ... Resist mask 11 ... Upper surface of resist mask 10 12 ... Side surface of resist mask 10 20 ... Insulating film 21 ... Upper surface of insulating film 20 22 ... Upper surface of exposed insulating film 20 The exposed side surface 30 of the insulating film 30 The semiconductor substrate 40 The deposit 41 The protective film deposited on the upper surface 22 of the insulating film 20 The protective film deposited on the upper surface 11 of the resist mask 10 43 The side surface 12 of the resist mask 10 Protective film 44 deposited on the side surface 23 of the insulating film 20 Stacked protective film S ... Substrate G10 ... Graph showing the etching rate of the resist mask 10 G20 ... Graph showing the etching rate of the insulating film 20

Claims (5)

A method of performing dry etching on an insulating film on a substrate,
(A) a first step of etching a portion of the insulating film not covered with a resist mask using a first type mixed gas containing CH ₄ and COF ₂ , wherein the first type mixed A first step in which the mixing ratio of CH _{4 to} COF ₂ is less than 0.60 in the gas;
(B) a second step of forming a protective film on the side wall of the etched insulating film using a second type mixed gas containing CH ₄ and COF ₂ , wherein the second type mixed gas; A second step wherein the mixing ratio of CH _{4 to} COF ₂ is higher than 0.60;
(C) A method comprising: repeating the first step and the second step. The method of claim 1, comprising:
In the first step, the mixing ratio of CH ₄ and COF ₂ is lower than 0.45. The method according to claim 1 or 2, comprising:
A method wherein the mixing ratio of CH ₄ and COF ₂ is higher than 0.70 in the second step. A method according to any one of claims 1 to 3,
The method, wherein the insulating film is a metal oxide, SiO ₂ , SiN, AlN, or GaO. An apparatus for performing dry etching on an insulating film on a substrate,
A first processing unit that etches a portion of the insulating film that is not covered with a resist mask using a first type mixed gas containing CH ₄ and COF ₂ . A first processing section, wherein the mixing ratio of CH _{4 to} COF ₂ is lower than 0.60;
A second processing unit that forms a protective film on a side wall of the etched insulating film using a second type mixed gas containing CH ₄ and COF ₂ , wherein in the second type mixed gas, A _second processing section, wherein the mixing ratio of CH _{4 to} COF ₂ is higher than 0.60;
A third processing unit that repeatedly executes the etching and the formation of the protective film.