JPH08203874A - Method and system for ashing and mixture gas therefor - Google Patents

Abstract

PURPOSE: To obtain a mixture gas for ashing an organic compound at a high rate in which the selection ratio the organic compound to a silicon nitride film is elevated by specifying the ratio of gases containing hydrogen element and halogen element to a mixture gas containing oxygen gas. CONSTITUTION: A gas pipe 21 coupled with a reaction gas introduction pipe 20 provided on the side face of a plasma generation chamber 14a is branched into gas pipes 22, 23 coupled, respectively, with an oxygen gas vessel 25 and a hydrogen and fluorine vessel 26 encapsulating a gas containing hydrogen element and halogen element, i.e., CHF3 gas. The gas pipes 22, 23 are provided, respectively, with regulation valves 27, 28 and gas flowmeters 29, 30. A mixed gas introduction controller 31 receives detection signals from the gas flowmeters 29, 30 and controls the opening of the regulation valve 27, 28 such that the ratio of CHF3 gas to the total quantity of gas will be in the range of 0.2-8% when oxygen gas and the CHF3 gas are mixed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a semiconductor element manufacturing process and surface treatment in various fields, and uses an ashing mixed gas used to remove organic compounds such as photoresist and the like. The present invention relates to an ashing method and an apparatus therefor.

[0002]

2. Description of the Related Art In a microfabrication technique in a manufacturing process of semiconductor devices or the like, or a machining technique in other fields, for example, a liquid crystal display, a print processing, a compact disc, a laser disc, a photo-resist, an organic compound such as a photoresist is used. Photo-etching process using a film resist is an important and essential process.

This resist is used as a base mask in the exposure process and is removed at the stage when the exposure process is completed. As a method of removing this resist, H ₂ SO
₄ and H ₂ O ₂ mixed solution or H _{2 in} this mixed solution
It is used to remove using a solution containing O, or to remove in a solution represented by an alkaline solution.

However, the removal method using such a solution has problems in terms of solution management, work safety, and the like. In particular, in the manufacturing process of semiconductor devices, the process using liquid is disliked.

Further, in the manufacturing process of semiconductor elements and the like, patterning of metal such as aluminum is used as an electrode material. When the photoresist of the organic compound film is used for patterning such a metal, the metal for patterning is corroded in the mixed solution of H ₂ SO ₄ and H ₂ O ₂ .

Therefore, the removal method using a solution has limited applications. On the other hand, a dry ashing (ashing) method is used as a means for solving the problems when such a solution is used.

According to this dry ashing method, an object to be processed having a resist formed therein is placed in a processing container, and O ₂ gas or O ₂ + CF ₄ gas is introduced into the processing container to cause an electric discharge. The resist is removed by dry ashing with.

In this dry ashing method, the resist can be peeled off more easily than the method using a solution. As a specific example, a photo etching process using O ₂ + CF ₄ gas plasma will be described. FIG.
2 shows a step of forming a silicon nitride film 2 which is an etching stopper of a thin film transistor (TFT).

A hydrogenated amorphous silicon film 3 is formed on the surface of the glass substrate 1 as shown in FIG.
A silicon nitride film 2 serving as an etching stopper is formed on the hydrogenated amorphous silicon film 3, and then a resist film 4 of an organic compound is applied on the entire surface.

Next, pattern exposure and development are performed.
A resist layer 4 having a desired pattern as shown in (b).
Only a remains. Next, chemical dry etching (CDE), wet etching or the like is performed using the resist layer 4a as a mask. As a result of this etching, the portion of the silicon nitride film 2 masked by the resist layer 4a, that is, the etching stopper 2a remains, as shown in FIG.
The other part of the silicon nitride film 2 is removed.

After that, the resist layer 4a is removed by ashing with O ₂ + CF ₄ gas plasma.
The etching stopper 2a remains as shown in FIG. However, in the ashing method using O ₂ gas plasma among such ashing methods, even if the base material for applying the resist is a metal or the like, it is not necessary to limit this base material, but in order to obtain a practical predetermined removal rate. Requires a high removal rate unless the substrate is heated to a high temperature, for example, 200 ° C. or higher.

Further, in the ashing method using O ₂ + CF ₄ gas, the silicon nitride film as the base material is etched together with the resist layer 4a, and a high selection ratio of the silicon nitride film to the resist layer 4a cannot be obtained.

That is, the resist layer 4a is removed by O ₂ + CF ₄ gas plasma. Since this gas contains a fluorine-based gas, the etching stopper 2a
Is etched and film loss occurs.

When a thin film transistor is manufactured through the process of reducing the film thickness of the etching stopper 2a, the characteristics of the thin film transistor are adversely affected. The problem of the film reduction of the etching stopper 2a and the film irregularity of the surface thereof occurs even when any of the barrel type and parallel plate type and microwave plasma processing ashing devices is used.

Particularly in the barrel type and the parallel plate type, charged particles are much incident on the substrate surface during discharge, and the film reduction is more remarkable than that in the apparatus by the microwave plasma treatment.

[0016]

As described above, in the method of using a solution for removing an organic compound film such as a resist, it is difficult to manage the solution and ensure safety, and the material of the base is limited. . On the other hand, in dry ashing using O ₂ gas plasma, a high removal rate cannot be obtained unless the substrate is heated to a high temperature.

Further, in the dry ashing using O ₂ + CF ₄ gas plasma, the silicon nitride film as the base material is etched together with the resist film, and a high selection ratio of the organic compound film to the silicon nitride film cannot be obtained.

Therefore, an object of the present invention is to provide an ashing mixed gas which can increase the ashing rate for organic compounds and can increase the selection ratio of the organic compound film to the silicon nitride film.

It is another object of the present invention to provide an ashing method and an apparatus for ashing an organic compound at a high ashing rate by increasing the selection ratio of the organic compound film to the silicon nitride film.

[0020]

According to a first aspect of the present invention, there is provided an oxygen gas, a gas containing a hydrogen element and a halogen element, and a mixture of the oxygen gas, a gas containing the hydrogen element and a halogen element. Is a mixed gas for ashing in which the gas containing hydrogen element and halogen element is mixed at a ratio of 0.2 to 8% with respect to the total gas amount of (1).

According to claim 2, the halogen element gas is
It is a mixed gas for ashing which is a fluorine element gas. According to claim 3, in the ashing method for selectively ashing the organic compound with respect to the silicon nitride film by supplying and exciting a reaction gas to the object having the organic compound formed on the silicon nitride film, As a reaction gas, oxygen gas, a gas containing a hydrogen element and a halogen element are mixed, and the mixing ratio at this time is a total gas when a gas containing an oxygen gas, a hydrogen element and a halogen element is mixed. The ashing method is intended to achieve the above object by using a mixed gas for ashing in which the ratio of the gas containing the hydrogen element and the halogen element is 0.2 to 8% with respect to the amount.

According to claim 4, the halogen element gas is
This is an ashing method using a fluorine element gas. According to the fifth aspect, the object to be processed having the organic compound formed on the silicon nitride film is placed in the processing container, and the reaction gas is supplied to the processing container to excite the organic compound into the silicon nitride film. In the ashing device for selectively ashing, the gas containing oxygen gas, hydrogen element and halogen element is used as the total gas amount when the gas containing oxygen gas, hydrogen element and halogen element is mixed. On the other hand, the ashing apparatus is intended to achieve the above object by including a mixing and introducing unit that mixes the gas containing the hydrogen element and the halogen element so as to have a ratio of 0.2 to 8% and introduces the mixed gas into the processing container. .

[0023]

According to the present invention, the ratio of the gas containing the hydrogen element and the halogen element to the total gas amount when the oxygen gas, the gas containing the hydrogen element and the halogen element is mixed is 0. Since it mixes at a low concentration of 2-8%,
By reacting with the silicon nitride film, a product is generated on this silicon nitride film, and this product serves as a protective film to suppress etching of the silicon nitride film. As a result, since the ashing rate is high in the ashing in which the halogen element gas is added to the oxygen gas, the ashing rate for the organic compound can be increased and the selection ratio for the silicon nitride film is increased.

According to the second aspect, the ratio of the gas containing hydrogen element and the fluorine element to the total gas amount when oxygen gas, the gas containing the hydrogen element and the fluorine element is mixed is 0. Since it is mixed at a low concentration of 2 to 8%, it reacts with the silicon nitride film to generate a product on this silicon nitride film, and this product serves as a protective film to suppress etching of the silicon nitride film. As a result, since the ashing rate is high in the ashing in which the fluorine element gas is added to the oxygen gas, the ashing rate for the organic compound can be increased and the selection ratio for the silicon nitride film is increased.

According to the third aspect, the ratio of the gas containing the hydrogen element and the halogen element to the total gas amount when the gas containing the oxygen gas, the hydrogen element and the halogen element is mixed is 0. When the reaction gas mixed at a low concentration of 2 to 8% is supplied to the object to be processed and excited, the organic compound is removed, and at the same time, a product is generated on the silicon nitride film by reacting with the silicon nitride film, This product serves as a protective film and suppresses etching of the silicon nitride film. As a result, the organic compound is removed at a high ashing rate with a high selection ratio for the silicon nitride film.

According to the present invention, the ratio of the gas containing hydrogen element and fluorine element to the total gas amount when oxygen gas, the gas containing hydrogen element and fluorine element is mixed is 0. When the reaction gas mixed at a low concentration of 2 to 8% is supplied to the object to be processed and excited, the organic compound is removed, and at the same time, a product is generated on the silicon nitride film by reacting with the silicon nitride film, This product serves as a protective film and suppresses etching of the silicon nitride film. This allows
The selection ratio to the silicon nitride film is high, and the organic compound is removed at a high ashing rate.

According to the fifth aspect of the present invention, the object to be processed having the organic compound formed on the silicon nitride film is placed in the processing container, and oxygen gas, hydrogen element and fluorine element are introduced into the processing container by the mixing introduction means. A reaction gas in which the ratio of the gas containing the hydrogen element and the fluorine element is mixed at a low concentration of 0.2 to 8% with respect to the total gas amount when the containing gas is mixed is introduced. Then, by discharging the reaction gas, the organic compound is removed, and at the same time, the reaction with the silicon nitride film produces a product on the silicon nitride film, and the product serves as a protective film to form the silicon nitride film. Suppresses etching. As a result, the organic compound is removed at a high ashing rate with a high selection ratio for the silicon nitride film.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The present invention provides a method of supplying a reaction gas to a semiconductor element having a resist film formed of an organic compound on a silicon nitride film to excite the resist film with respect to the silicon nitride film by exciting the reaction gas. Is composed of a gas containing oxygen gas, a hydrogen element and a halogen element, and the hydrogen element and the halogen element are added to the total gas amount when the oxygen gas, a gas containing the hydrogen element and a halogen element are mixed. This is an ashing method using a mixed gas for ashing in which the ratio of the gas contained is 0.2 to 8%.

FIG. 1 is a block diagram of a dry ashing apparatus for microwave plasma processing to which such an ashing method is applied. The microwave generator 10 has, for example, a frequency of 2.
Microwave 10a with 45 GHz and microwave power of 1 kW
Has the function of generating.

Radiation port 11 of the microwave generator 10
A waveguide 12 is connected to the. A microwave radiation port 13 is formed in the waveguide 12, and a processing container 14 is connected to the microwave radiation port 13.

The processing chamber 14 has a plasma generation chamber 14a in the plasma generation region formed in the upper portion and a processing chamber 14b in the treatment region formed in the lower portion thereof. The space between the plasma generation chamber 14a and the processing chamber 14b is formed between them. Are in communication.

Of these, a microwave passage window 15 is provided above the plasma generation chamber 14a so as to fit into the microwave radiation port 13. The μ wave passage window 15 vacuum-seals the processing container 14, and is made of quartz or ceramics.

The processing chamber 14b has a stage 1 which can be raised and lowered.
6 is provided, and a semiconductor element 17 as an object to be processed having an organic compound formed on a silicon nitride film is arranged on the stage 16.

An exhaust port 18 connected to the exhaust system is provided in the lower part of the processing chamber 14b. The exhaust system is equipped with an exhaust pump and the like. A metal mesh 19 is arranged between the plasma generating chamber 14a and the processing chamber 14b.

The metal mesh 19 is formed by a punch plate having a variable opening diameter that shields the plasma generated in the plasma generating chamber 14a. However, since the stage 16 can be raised and lowered and the opening diameter of the metal mesh 19 is variable, the distance between the metal mesh 19 and the semiconductor element 17 is 2 when dry ashing.
5 to 100 mm, the opening diameter of the metal mesh 19 is 2 mm,
Optimum is about 4 mm, 6 mm, and 220 mm.

On the other hand, on the side surface of the plasma generating chamber 14a,
A reaction gas introduction pipe 20 is provided. A gas pipe 21 is connected to the reaction gas introduction pipe 20, and the gas pipe 21 is branched into two gas pipes 22 and 23.

An oxygen gas container 25 and a hydrogen and fluorine container 26 are connected to the gas pipes 22 and 23, respectively. The oxygen gas container 25 is filled with oxygen gas (O ₂ gas), and the hydrogen and fluorine container 26 is filled with a gas containing hydrogen element and fluorine element, that is, CHF ₃ gas.

The gas pipes 22 and 23 are provided with control valves 27 and 28 and gas flow meters 29 and 30, respectively. These gas flow meters 29 and 30 have a function of detecting the flow rates of the gases flowing through the gas pipes 22 and 23 and sending the respective detection signals to the mixing introduction control device 31.

This mixing introduction control device 31 inputs each detection signal output from each gas flow meter 29, 30 and outputs O ₂
Gas, CHF ₃ gas in the range of 0.2 to 8% of the total gas amount when mixing CHF ₃ gas,
If the total amount of the mixed gas for ashing, for example, the mixture gas of O ₂ / CHF ₃ is 1000, the optimum ratio is within the range of 3 to 5%, the O ₂ gas is 970, C
Each control valve 27, 2 so that the ratio of HF ₃ gas is 30
8 is controlled, and each control valve 27, 28 is controlled so that the gas flow rate of O ₂ + CHF ₃ at this time is 1000 sccm.
It has a function of controlling the opening degree of.

O ₂ + CH in the processing container 14
As shown in FIG. 2, the introduction of the F ₃ gas was carried out in advance with O ₂ gas and C.
An ashing gas mixture consisting of HF ₃ gas, which is a mixture of O ₂ gas and CHF ₃ gas in the range of 0.2 to 8% of CHF ₃ gas with respect to the total gas amount. The container 30 for ashing gas may be sealed and connected to the reaction gas introduction pipe 20 through the gas pipe 21.

In this case, the gas flow meter 31 and the control valve 32
Is provided in the gas pipe 21, and the flow control device 33 controls the control valve 3
2 is controlled to control the gas flow rate of the O ₂ + CHF ₃ gas to be a predetermined flow rate.

Further, a gas containing a hydrogen element and a gas containing a halogen element may be mixed to obtain an O ₂ + CHF ₃ gas. Next, the ashing action of the apparatus configured as described above will be described.

As described above, as shown in FIG. 5A, the hydrogenated amorphous silicon film 3 is formed on the surface of the glass substrate 1, and the silicon nitride film serving as an etching stopper is formed on the hydrogenated amorphous silicon film 3. 2 is formed,
After this, a resist film 4 of an organic compound is applied to the entire surface.

Next, pattern exposure and development are performed.
As shown in (b), only the resist layer 4a in a portion according to the desired pattern remains. Next, chemical dry etching, wet etching or the like is performed using the resist layer 4a as a mask. As a result of this etching, the portion of the silicon nitride film 2 masked by the resist layer 4a, that is, the etching stopper 2a remains, and the other portions of the silicon nitride film 2 are removed by this etching.

After that, dry ashing by O ₂ + CHF ₃ gas plasma is performed. That is, the semiconductor element 17 shown in FIG. 3C is placed on the stage 16 of the processing container 14.

The mixing / introduction control device 31 is used for each gas flow meter 2
Each detection signal output from 9, 30 is input, and O ₂ and C
C for the total amount of gas when mixed with HF ₃
The ratio of HF ₃ gas is in the range of 0.2 to 8%, for example O ₂
If the total amount of gas mixed with / CHF ₃ gas is 1000, the opening degree of each control valve 27, 28 is controlled so that the ratio of O ₂ gas is 970 and CHF ₃ gas is 30.

At this time, the mixing introduction control device 31 is
_The openings of the control valves 27 and 28 are controlled so that the gas flow rate of ₂ + CHF ₃ is 1000 sccm. Thus, the O ₂ gas flowing out from the oxygen gas container 25 and the CHF ₃ gas flowing out from the hydrogen / fluorine container 26 are connected to the gas pipes 22,
23, and mixed by the gas pipe 21 and the reaction gas introduction pipe 2
It is introduced into the plasma generation chamber 14a of the processing container 14 through 0.

[0048] That is, in the plasma generation chamber 14a of the processing vessel 14 made of an O ₂ gas and CHF ₃ gas, CHF ₃ gas to the gas volume of the total when mixing these O ₂ gas and CHF ₃ gas The mixed gas O ₂ + CHF ₃ gas for ashing having a ratio of 0.2 to 8% is introduced.

In the case of the configuration shown in FIG. 2, the flow control device 33 controls the opening of the control valve 32 so that the O ₂ + CHF ₃ in the ashing gas container 30 has a gas flow rate of 100.
Plasma generation chamber 14 of processing container 14 controlled to 0 sccm
is introduced into a.

At this time, the pressure inside the plasma generating chamber 14a and the processing chamber 14b is reduced to 47 Pa by the exhaust system. On the other hand, the microwave generator 10 has a frequency of 2.4.
The microwave 10a of 5 GHz and microwave power of 1 kW is generated.

The microwave 10a propagates in the waveguide 12, passes through the μ wave passage window 15, and is transmitted to the plasma generation chamber 14
is emitted to a. Radiation of this microwave 10a causes O
_{The 2} + CHF ₃ gas is excited and acts as an active species, and this plasma generation causes the resist layer 4a of the semiconductor element 17 to be excited.
Is etched.

[0052] In this case, ashing was added CHF ₃ gas at low concentrations against O ₂ gas mixed gas O ₂ + CHF
By using ₃ , the selection ratio of the resist layer 4a which is an organic compound film / the silicon nitride film 2 becomes high.

That is, the mechanism of increasing the selection ratio of the resist layer 4a with respect to the silicon nitride film 2 will be explained. By mixing a low-concentration CHF ₃ gas with the O ₂ gas, it reacts with the silicon nitride film 2. As a result, a product is generated on the silicon nitride film 2.

It was confirmed by FT-IR (Fourier transform infrared absorption) analysis shown in FIG. 3 that this product was an ammonium salt. In this FT-IR analysis, N
-H, NH, high absorption of SiF, which indicates that it is a composition with ammonium salts are products similar to (NH _{4) 2} SiF _6.

In this way, (NH
₄ ) When a product similar to ₂ SiF ₆ is produced, this product serves as a protective film and suppresses etching of the silicon nitride film 2. The product is easily removed by washing with water.

Therefore, in ashing with O ₂ ,
By adding the low-concentration CHF ₃ gas, the ashing rate for the resist layer 4a is high, and the selection ratio of the resist layer 4a for the silicon nitride film 2 is high.

FIG. 4 shows the results of the concentration dependence of the ashing rate and the selection ratio by adding CHF ₃ gas to O ₂ gas. Here, the ashing rate was obtained from each film thickness before and after the processing of the resist layer 4a, and the etching rate was obtained from each film thickness of the silicon nitride film 2 deposited on the glass substrate 1 before and after the processing.

As shown in the figure, when the conventional mixed gas with CF ₄ gas was used, the ashing speed was about 1000 nm / min.
It can be seen that the speed became as high as nm / min.

On the other hand, the resist layer 4a / silicon nitride film 2
The selection ratio of O ₂ + CF ₄ using the conventional long-lived active species is
It can be seen that the gas downflow ashing was about 100, but was improved to 1000 or more in the present invention.

The lower the CHF ₃ concentration with respect to the O ₂ gas, the faster the ashing rate. As described above, in the above-described embodiment, the resist layer 4a which is the organic compound film is used.
Is selectively etched with respect to the silicon nitride film 2, the ratio of CHF ₃ to the total amount of gas when O ₂ gas and CHF ₃ gas are mixed is set to a low concentration in the range of 0.2 to 8%. By using the mixed gas for ashing, the ashing rate for the resist layer 4a can be increased, and the selection ratio of the resist layer 4a for the silicon nitride film 2 can be increased.

In particular, the ratio of CHF ₃ gas to the total gas amount when O ₂ gas and CHF ₃ gas are mixed is 3
By setting it in the range of ˜5%, the ashing speed for the resist layer 4a is increased, and the selection ratio of the resist layer 4a to the silicon nitride film 2 can be increased, so that the ashing process can be further improved.

For example, the ashing speed is 2000 nm / min
As a result, the resist layer 4a / silicon nitride film 2 selection ratio becomes 1000 or more. As a result, the film thickness of the etching stopper 2a does not decrease, and the characteristics of the thin film transistor are not adversely affected even when the thin film transistor is manufactured. Therefore, a thin film transistor having excellent characteristics can be manufactured by using any of the barrel type, parallel plate type, and microwave plasma ashing devices in which the film thickness of the etching stopper 2a has been conventionally reduced.

Further, the ratio of CHF ₃ gas to the total amount of gas when O ₂ gas and CHF ₃ gas are mixed is set to a low concentration in the range of 0.2 to 8%. Each control valve 27, 28 by the introduction control device 31
By adjusting the opening degree, it is possible to variably control the ashing speed and the optimum selection ratio of the resist layer 4a / the silicon nitride film 2 to a value.

The present invention is not limited to the above-mentioned embodiment but may be modified as follows. For example, for addition to O ₂ gas is not limited to CHF _3, H and a halogen element gas to O ₂ gas (Cl, Br, I, At ) may be used.

[0065]

As described above in detail, according to the present invention, it is possible to provide a mixed gas for ashing which can increase the ashing rate for an organic compound and increase the selection ratio of the organic compound film to the silicon nitride film.

Further, according to the present invention, it is possible to provide an ashing method and an apparatus for ashing an organic compound at a high ashing rate by increasing the selection ratio of the organic compound film to the silicon nitride film.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a dry ashing apparatus for microwave plasma processing to which an ashing method according to the present invention is applied.

FIG. 2 is a configuration diagram showing another introduction of an ashing mixed gas into a processing container.

FIG. 3 is a reaction product F formed on a silicon nitride film.
The figure which shows a T-IR analysis result.

FIG. 4 is a diagram showing concentration dependence of an ashing rate and a selection ratio by adding a gas containing a hydrogen element and a fluorine element to oxygen gas.

FIG. 5 is a process drawing of forming a silicon nitride film which is an etching stopper of a thin film transistor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Microwave generator, 12 ... Waveguide, 14 ... Processing container, 14a ... Plasma generation chamber, 14b ... Processing chamber, 15
... μ wave passage window, 16 ... Stage, 17 ... Semiconductor element, 1
9 ... Metal mesh, 20 ... Reactive gas introduction pipe, 25 ... Oxygen gas container, 26 ... Hydrogen and fluorine container, 27, 28 ... Control valve, 29, 30 ... Gas flow meter, 31 ... Mixing introduction control device, 40 ... Ashing Gas container.

Claims (5)

[Claims] 1. An oxygen gas, a gas containing a hydrogen element and a halogen element, wherein the hydrogen element is contained with respect to a total gas amount when the oxygen gas, a gas containing the hydrogen element and a halogen element are mixed. And a mixed gas for ashing, wherein the ratio of the gas containing the halogen element is mixed in the range of 0.2 to 8%. 2. The mixed gas for ashing according to claim 1, wherein the halogen element gas is a fluorine element gas. 3. An ashing method for selectively ashing the organic compound with respect to the silicon nitride film by supplying and exciting a reaction gas to a target object on which an organic compound is formed on the silicon nitride film, As the reaction gas, a gas containing oxygen gas, a hydrogen element and a halogen element is mixed, and the mixing ratio at this time is a value when the gas containing the oxygen gas, the hydrogen element and the halogen element is mixed. An ashing method comprising using a mixed gas for ashing in which a ratio of a gas containing the hydrogen element and the halogen element is mixed in a range of 0.2 to 8% with respect to a total gas amount. 4. The ashing method according to claim 3, wherein the halogen element gas is a fluorine element gas. 5. An object to be processed having an organic compound formed on a silicon nitride film is placed in a processing container, and a reaction gas is supplied to the processing container to excite the organic compound on the silicon nitride film. In the ashing device that selectively ashes the oxygen gas, the gas containing hydrogen element and halogen element, the total gas amount when mixing the gas containing oxygen gas, hydrogen element and halogen element On the other hand, a mixing and introducing means for mixing the gas containing the hydrogen element and the halogen element so as to be in a range of 0.2 to 8% and introducing the mixture into the processing container is provided. Ashing device.