JPH11251291A - Manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form sidewalls of an SiC film on the side faces of a semiconductor and element by etching the SiC film, using a gas plasma contg. atoms of Cl, H and O, without containing F. SOLUTION: On an Si substrate 12 an Si oxide film 30 which is to become a gate insulation film is formed by the thermal oxidation method, a polycrystalline Si film 32 is formed on the Si oxide film 30 by the CVD method, an SiC film 34 is formed on the polycrystalline Si film 32 by the CVD method, the SiC film 34 and polycrystalline Si film 32 are patterned to form gate wirings, an SiC film 36 is deposited on the entire Si substrate 12 surface and etched, using a gas plasma which does not contain F but containing atoms of Cl, H and O to form the sidewalls of the SiC film 36 on the side faces of the gate wirings.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for dry etching a silicon nitride film, and more particularly to a method for manufacturing a semiconductor device using a method for selectively etching a silicon nitride film with respect to a silicon oxide film. .

[0002]

2. Description of the Related Art In recent years, RIE (Reactive Ion Etching: RIE) using reactive gas plasma is generally used in an etching process in fine processing of a semiconductor device. In RIE, a wafer (silicon semiconductor substrate) is placed on an electrode placed in an etching chamber and etching is performed by a synergistic effect of neutral active species and reactive gas ions. Etching can be performed.

FIGS. 9 and 10 show an example of a conventional process using RIE, and are cross-sectional views of a process of forming a side wall of a silicon nitride film on a side surface of a gate wiring. FIG. 9 shows a structure before the RIE is performed, and FIG. 10 shows a structure after the sidewall is formed by the RIE.

A gate oxide film 102 made of a silicon oxide film and a gate wiring 104 are formed on a semiconductor substrate 100, and a cap film 106 is formed on the gate wiring 104. Further, on the gate oxide film 102 and the cap film 106 on the gate wiring 104, a silicon nitride film 108 for forming a side wall is formed. FIG. 10 shows a structure after performing RIE on the semiconductor substrate having such a structure and forming the side wall.

[0005]

As shown in FIG. 9, in the formation of the side wall of the wiring and the element using the silicon nitride film 108, when the base is very thin like the gate oxide film 102, the silicon During the over-etching of the nitride film 108, there is a problem that a large amount of the base of the film to be etched such as the thin gate oxide film (silicon oxide film) 102 and the semiconductor substrate 100 are etched. In addition, damages such as contamination due to subsequent ion implantation and disorder of the crystal due to the ion implantation can be prevented.
There is a problem that occurs at 00. Further, in the formation of the side wall, the silicon nitride film 108 needs to be processed with good controllability.
Is isotropically etched, and the side wall becomes thin.

However, conventionally, the silicon nitride film 1
When the selectivity between the silicon oxide film 08 and the underlying silicon oxide film 102 is increased, the isotropic etching is performed, that is, the side wall is narrowed. As the selectivity with the oxide film 102 decreases, the underlying silicon oxide film 102
Is etched.

The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to etch a silicon nitride film having a high selectivity to a silicon oxide film and to anisotropically process the silicon nitride film. Accordingly, it is an object of the present invention to provide a method of manufacturing a semiconductor device using a dry etching method capable of forming side walls of a silicon nitride film on side surfaces of wirings and elements.

[0008]

According to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising introducing a gas into an etching chamber, and using a gas plasma obtained by converting the gas into a plasma. A method of manufacturing a semiconductor device using a dry etching apparatus for performing etching by using the gas plasma containing at least chlorine (Cl), hydrogen (H), and oxygen (O) atoms without containing fluorine. And etching the silicon nitride film.

According to a second aspect of the present invention, there is provided a method for manufacturing a semiconductor device, comprising: forming a substrate on which a silicon oxide film and a silicon nitride film are present;
1) The silicon nitride film is etched by a dry etching apparatus using a gas plasma containing atoms of l), hydrogen (H) and oxygen (O).

According to a third aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: forming a wiring or a conductive thin film element on a silicon oxide film; and forming an entire surface on the silicon oxide film on which the wiring or electrode is formed. Forming a silicon nitride film on at least chlorine (Cl) containing no fluorine,
Etching the silicon nitride film with a dry etching apparatus using a gas plasma containing hydrogen (H) and oxygen (O) atoms.

According to a fourth aspect of the present invention, in the method of manufacturing a semiconductor device, in the step of forming a side wall of a silicon nitride film on a side surface of a wiring or a conductive thin film element formed on a silicon oxide film, Forming a silicon nitride film on the entire surface of the silicon oxide film on which the conductive thin film element is formed;
1) forming a side wall of the silicon nitride film by a dry etching apparatus using a gas plasma containing atoms of hydrogen (H) and oxygen (O).

Further, according to a fifth aspect of the present invention, in the method of manufacturing a semiconductor device according to any one of the first to fourth aspects, the chlorine (Cl), the hydrogen (H), and the oxygen (O) A gas plasma containing each atom is generated from a mixed gas containing Cl ₂ , fluorine-free hydrogen halide, and O ₂ .

Further, a method of manufacturing a semiconductor device according to a sixth aspect is characterized in that, in the configuration according to the fifth aspect, the hydrogen halide is HCl. Also,
According to a seventh aspect of the present invention, in the semiconductor device manufacturing method according to the sixth aspect, the gas flow ratio of the mixed gas is HCl: Cl ₂ : O ₂ = 20: 5: 1. And

Further, in the method of manufacturing a semiconductor device according to the present invention, the pressure in the etching chamber when etching the silicon nitride film is set to 500 in the structure according to any one of the first to seventh aspects. [MTorr] or less.

According to a ninth aspect of the present invention, in the method of manufacturing a semiconductor device according to any one of the first to eighth aspects, the high frequency power density when etching the silicon nitride film is 0.76. [W / cm ² ] to 1.15 [W
/ Cm ² ].

[0016]

Embodiments of the present invention will be described below with reference to the drawings. First, the configuration of a dry etching apparatus used in the method for manufacturing a semiconductor device according to the embodiment of the present invention will be described.

FIG. 1 is a diagram showing an example of the configuration of a dry etching apparatus used in the method of manufacturing a semiconductor device according to this embodiment. As shown in FIG. 1, a silicon semiconductor substrate (hereinafter, a silicon substrate) 12 as an object to be processed is accommodated in a processing chamber 10, and the silicon substrate 12 is placed on a stage 14. The stage 14 has a temperature control mechanism (not shown) so that the temperature of the silicon substrate 12 can be controlled.

A gas inlet 16 is provided at an upper portion of the side surface of the processing chamber 10, and an unillustrated gas inlet 16 for introducing a mixed gas of HCl / Cl ₂ / O ₂ used as a reaction gas is provided in the gas inlet 16. The gas supply system is connected. further,
A high-frequency power supply 20 is connected to a cathode electrode 18 provided on the stage 14 in the processing chamber 10, and the cathode electrode 18 and the outer frame 22 form a counter electrode.

Further, a vacuum exhaust port 24 is provided at a lower portion of the side surface of the processing chamber 10, and air in the processing chamber 10 is exhausted by a vacuum pump or the like (not shown) connected to the vacuum exhaust port 24 to reduce the pressure. You. Then, the high-frequency power supply 20 applies a high frequency, so that the cathode electrode 18 and the outer frame 22 are applied.
A plasma discharge is generated between the electrodes, and the reaction gas is turned into plasma.

Further, permanent magnets 26a and 26b are provided on the left and right sides of the processing chamber 10, respectively.
A horizontal magnetic field is formed on the surface of the silicon substrate 12 by a and 26b. The magnetron discharge is generated by a horizontal magnetic field and an electric field generated by the high-frequency power supply 20 orthogonal to the horizontal magnetic field, thereby promoting the ionization of the reaction gas HCl / Cl ₂ / O ₂ .

In this embodiment, an apparatus for forming a horizontal magnetic field on the surface of the silicon substrate 12 to be processed is used, but an apparatus having no such horizontal magnetic field forming means may be used. Further, a different dry etching apparatus may be used.

Next, a method of manufacturing a semiconductor device according to an embodiment of the present invention using the dry etching apparatus will be described. 2 to 4 are cross-sectional views before and after processing showing a method for manufacturing a semiconductor device according to an embodiment of the present invention.
FIG. 2 shows the structure of the semiconductor device before processing, and FIGS. 3 and 4 show the structure of the semiconductor device after processing.

First, as shown in FIG. 2, a silicon oxide film 30 as a gate insulating film is formed on a silicon substrate 12 made of a silicon wafer or the like by a thermal oxidation method. Further, a polycrystalline silicon film 32 is formed on the silicon oxide film 30 by a CVD method. Thereafter, a silicon nitride film 34 is formed on the polycrystalline silicon 32 film by a CVD method, and then the silicon nitride film 3 is formed by a lithography method.
4 and the polysilicon film 32 are patterned to form the gate wiring 32.

Subsequently, the entire surface of the silicon substrate 12 is subjected to CVD.
A silicon nitride film 36 is deposited by a method, and the silicon nitride film 36 is formed on the side surfaces of the gate wiring 32 and the silicon nitride film 34, on the upper portion of the silicon nitride film 34, and on the silicon oxide film 30.

Next, the silicon substrate 12 having such a structure will be described.
Is placed on the stage 14 of the dry etching apparatus shown in FIG. 1, and the silicon nitride film 36 is formed under the following conditions.
Is etched.

First, for example, the power of the high frequency power supply 20 applied to the cathode electrode 18 is set to 0.76 to 1.15 [W / cm].
² ] The pressure in the processing chamber 10 is set to 500 [mTorr] or less, and the temperature of the processing surface of the silicon substrate 12 is set to about 70 ° C. Then, the gas flow ratio of the mixed gas supplied from the gas inlet 16 is set to be HCl / Cl ₂ / O ₂ = 20: 5: 1. Preferably, the power of the high frequency power supply 20 applied to the cathode electrode 18 is 0.76 [W / cm ² ],
The internal pressure is fixed at 125 [mTorr], and the temperature of the processing surface of the silicon substrate 12 is fixed at about 70 ° C. And gas inlet 1
The gas flow rate of the mixed gas supplied from
[Sccm], Cl ₂ is 50 [sccm], O ₂ is 10 [sccm]
And

Under the above-described etching conditions, the silicon nitride film 36 is etched, and as shown in FIG. 3, only the silicon nitride film 36 formed on the surface parallel to the silicon substrate 12 is etched to form the gate wiring 32. Is formed on the side surfaces of the silicon nitride film 36.

At this time, a residue 36a of the silicon nitride film 36 may remain on the silicon oxide film 30 in some cases. Therefore, the silicon nitride film 36 is further etched just before over-etching, and as shown in FIG.
6a is completely removed.

That is, when etching is carried out under the above-mentioned conditions using a dry etching apparatus as shown in FIG. 1, the silicon nitride film 3 existing on a plane parallel to the silicon substrate 12
The anisotropic etching can be performed such that the etching rate of the silicon nitride film 36 on the side of the gate wiring 32 becomes very low and the etching rate on the side of the silicon nitride film 36 on the side of the gate wiring 32 becomes very low. Further, after the silicon nitride film 36 existing on the plane parallel to the silicon substrate 12 is etched,
Even if further etching is performed, the etching rate of the silicon oxide film 30 is very slow, so that the underlying silicon oxide film 30 is not etched in a large amount.

Here, the results of examining the change in the etching rates of the silicon nitride film and the silicon oxide film and the change in the etching selectivity of the silicon nitride film with respect to the silicon oxide film under the above etching conditions will be described. The etching selectivity is (etching rate of silicon nitride film) / (etching rate of silicon oxide film).

At this time, the setting conditions of the dry etching apparatus are the same as those described above,
Is 0.76 [W / cm ² ], the pressure in the processing chamber 10 is 125 [mTorr], and the temperature of the processing surface of the silicon substrate 12 is about 70 ° C.

First, the dependency of the etching rate and the etching selectivity on the amount of HCl added when HCl is added to the gas system of Cl ₂ and O ₂ will be described. FIG.
H when HCl was added to the l ₂ and O ₂ gas system
FIG. 4 is a diagram showing changes in an etching rate and an etching selectivity with respect to the amount of Cl added.

The etching rate of the silicon nitride film (SiN) increases as the added amount of HCl increases from 0 to 100 [sccm] and reaches a maximum at 100 [sccm]. ] As it increases.

Such characteristics are considered to be due to the following reasons. The etching of the silicon nitride film is performed using Cl2
In such a system, the reaction is carried out by the reaction shown in the following formula (1). Si ₃ N ₄ + 6Cl ₂ ↑ → 3 (SiCl ₄ ) ↑ + 2N ₂ … (1) That is, in this system, it is considered that the reaction proceeds by Cl in the plasma.

On the other hand, when HCl is used, the etching of the silicon nitride film is performed by a reaction represented by the following equation (2). Si ₃ N ₄ +12 HCl ↑ → 3 (SiCl ₄ ) ↑ + 4NH ₃ ↑ (2) That is, when HCl is added to the gas system of Cl ₂ and O ₂ , both Cl and H in the plasma are changed. It is considered to react with the silicon nitride film. However, when the added amount of HCl is more than 100 [sccm], a reaction product at the time of etching is deposited on the silicon nitride film, and the increase in the deposited amount exceeds the increase in the etched amount, so that the etching of the silicon nitride film is suppressed. It is thought to be done. Therefore, as the addition amount of HCl increases, the etching rate of the silicon nitride film increases.
The etching rate of the silicon nitride film decreases from 00 [sccm].

On the other hand, a silicon oxide film (SiO ₂ )
The etching rate of HCl is 0 to 100.
As it increases to [sccm], it will drop slightly,
Further, as the amount of addition increases from 100 to 200 [sccm], the descending rate increases. This is probably because the reaction product gas represented by the formula (2) is recombined on the surface of the silicon oxide film, a deposited layer is easily formed, and the etching of the silicon oxide film is hindered.

That is, as the addition amount of HCl increases, the etching rate of the silicon nitride film increases.
Further, when the added amount of HCl increases, it falls. On the other hand, the etching rate of the silicon oxide film continues to decrease. Due to such a difference in the etching rate, the etching selectivity of the silicon nitride film to the silicon oxide film slightly increases as the addition amount of HCl increases from 0 to 100 [sccm], and the addition amount further increases from 100 to 20 sccm.
As the value increases to 0 [sccm], the rate of increase increases. From this result, it is understood that the optimal HCl gas flow rate is 200 [sccm] as described above.

Next, the dependence of the etching rate and the etching selectivity on the amount of Cl ₂ when Cl ₂ is added to the gas system of HCl and O ₂ will be described. FIG.
C when adding Cl ₂ to the gas system of Cl and O ₂
FIG. 4 is a diagram showing changes in an etching rate and an etching selectivity with respect to an added amount of l ₂ .

The etching rate of the silicon nitride film (SiN) increases as the added amount of Cl ₂ increases from 0 to 50 [sccm].
cm], the rate of increase decreases.

On the other hand, a silicon oxide film (SiO ₂ )
Etching rate, the amount of Cl ₂ is 0 to 50 [sc of
cm], but only slightly,
Further, as the added amount increases to 50 to 100 [sccm], the amount gradually increases from 50 [sccm] as a boundary.

That is, as the addition amount of Cl ₂ increases, the etching rate of the silicon nitride film increases.
When the addition amount is 50 [sccm] or more, the rate of increase decreases. On the other hand, the etching rate of the silicon oxide film decreases and then increases, and the lowest etching rate is around 50 [sccm]. Due to such a difference in the etching rate, the etching selectivity of the silicon nitride film to the silicon oxide film increases as the added amount of Cl ₂ increases from 0 to 50 [sccm], and becomes maximum at 50 [sccm]. It decreases as the added amount increases to 50 to 100 [sccm]. From this result, it is understood that the optimal Cl ₂ gas flow rate is 50 [sccm] as described above.

Next, the etching rate of the silicon nitride film and the silicon oxide film when O ₂ is added to the gas system of HCl and Cl ₂ , and the etching selectivity of the silicon nitride film to the silicon oxide film, O _2. The dependence on the amount of addition will be described.

FIG. 7 is a graph showing changes in the etching rate and the etching selectivity with respect to the amount of O ₂ when O ₂ is added to the gas system of HCl and Cl ₂ . As shown in FIG. 7, as the added amount of O ₂ increases (0 to 10 sccm), the etching rate of the silicon oxide film decreases. This is probably because O ₂ contributes to the suppression of etching of the silicon oxide film. In other words, the reaction products Si-O and Si-Cl
Since O is more stable, a reaction for forming Si—O tends to occur in a system in which O and Cl coexist. The reaction product Si—O is deposited on both the silicon oxide film and the silicon nitride film. However, since the silicon oxide film has a larger polarization action on the surface, the reaction product Si—O is more easily deposited on the surface of the silicon oxide film.

However, since this reaction product is also deposited on the surface of the silicon nitride film, the etching rate of the silicon nitride film decreases as the added amount of O ₂ increases (0 to 15 sccm).

From such a difference in etching rate,
Etching selectivity of the silicon nitride film to the silicon oxide film is increased maximum at 10 [sccm] with as amount of O ₂ is increased to 0 [sccm], further added the amount of 10 to 15 [sccm] As it increases.
From this result, it is understood that the optimum O ₂ gas flow rate is 10 [sccm] as described above.

Next, in the dry etching apparatus shown in FIG. 1, the etching rates of the silicon nitride film and the silicon oxide film when the power of the high frequency power supply 20 is changed, and the etching of the silicon nitride film with respect to the silicon oxide film. The power dependence of the selection ratio will be described. here,
The gas flow rate of the mixed gas supplied is 200 [scc
m], Cl ₂ is 50 [sccm], O ₂ is 10 [sccm], other setting conditions of the dry etching apparatus are as follows: the pressure in the processing chamber 10 is 125 [mTorr], and the temperature of the processing surface of the silicon substrate 12 is About 70 ° C.

FIG. 8 is a diagram showing changes in the etching rate and the etching selectivity when the power of the high frequency power supply 20 applied in the dry etching apparatus is changed. The etching rate of the silicon nitride film (SiN)
The power (RFPower) of the high frequency power supply 20 is 0.76 to 1.1
It increases as it increases to 5 [W / cm ² ]. On the other hand, the etching rate of the silicon oxide film (SiO ₂ ) is 0.76 to
It increases as it increases to 1.15 [W / cm ² ].

However, the etching selectivity of the silicon nitride film to the silicon oxide film decreases as the power (RF Power) of the high frequency power supply 20 increases to 0.76 to 1.15 [W / cm ² ]. From this result, it can be seen that the optimum power of the high frequency power supply 20 applied in the dry etching apparatus shown in FIG. 1 is 0.76 [W / cm ² ] as described above.

The following is a summary of the experimental results described above. First, the optimal gas flow rate of the mixed gas is HCl
Is 200 [sccm], Cl ₂ is 50 [sccm], and O ₂ is 10
[Sccm], expressed as a gas flow ratio, HCl: Cl
₂ : O ₂ = 20: 5: 1. It should be noted that the gas flow ratio of this mixed gas is as described above for HCl: Cl ₂ : O ₂
It can easily be inferred that etching with a high etching selectivity is possible even if the flow rate ratio is other than = 20: 5: 1. For example, HCl: Cl ₂ : O ₂ = 0 to 40: 0-0
20: 1 to 3 is sufficient.

The condition for setting the dry etching apparatus at this time is that the high frequency power supply 2 applied to the cathode electrode 18 is used.
0 to 0.76 to 1.15 [W / cm ² ], processing chamber 1
The pressure within 0 is 500 [mTorr] or less and the silicon substrate 12
Is set to about 70 ° C. Preferably, the power of the high-frequency power supply 20 is 0.76 [W / cm ² ], the pressure in the processing chamber 10 is 125 [mTorr], and the temperature of the processing surface of the silicon substrate 12 is about 70 ° C.

As described above, according to this embodiment, the silicon nitride film having a high selectivity with respect to the silicon oxide film can be etched, and the silicon nitride film can be anisotropically etched. The side wall of the silicon nitride film can be formed on the side surface of the element or the like.

Further, since the gate insulating film made of the silicon oxide film is not etched during the over-etching of the silicon nitride film, damages such as contamination and disorder of the crystal due to ion implantation or the like in the subsequent steps are prevented. Can be prevented.

In the above embodiment, HCl, Cl
_Although a reaction gas containing Cl, H, and O was generated by introducing a mixed gas of ₂ and O _2, the reaction gas was not limited to the mixed gas of HCl, Cl ₂ , and O _2.
What is necessary is just to introduce the mixed gas which can generate the reaction gas containing.

The reaction gas is formed into active species (ions, radicals) by being turned into plasma and is selectively etched by the etched reaction product gas, and therefore contains at least Cl, H and O. In order to generate gas plasma, H ₂ , H ₂ O, HCl
Gases such as O and HBr, and N ₂ and NH that contribute to the reaction
It is easy to imagine that a gas mixture with ₃ is effective enough.

The silicon substrate 12 may be glass or another substrate, and the gate wiring 32 may be another wiring or a pad of an element. Also,
In the above embodiment, when the side wall of the silicon nitride film is to be processed into a more vertical shape, after etching is performed under a condition of high vertical workability until the underlying silicon oxide film is exposed, a part thereof is partially removed. The remaining silicon nitride film can be used as over-etching for removing the underlying silicon oxide film with high selectivity.

Further, when strict dimensional control is particularly required, in the conventional processes, the side wall made of the silicon nitride film is narrowed by the isotropic etching, and the dimensional control is not good. By using the above-described embodiment, it is possible to etch a thin silicon nitride film.

[0057]

As described above, according to the present invention, by etching a silicon nitride film having a high selectivity with respect to a silicon oxide film and anisotropically processing the silicon nitride film, wiring and devices can be obtained. It is possible to provide a method of manufacturing a semiconductor device using a dry etching method capable of forming a side wall of a silicon nitride film on a side surface of a semiconductor device.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a configuration of a dry etching apparatus used in a method of manufacturing a semiconductor device according to an embodiment.

FIG. 2 is a cross-sectional view before processing illustrating a method for manufacturing a semiconductor device of this embodiment.

FIG. 3 is a cross-sectional view after processing illustrating the method for manufacturing a semiconductor device of this embodiment;

FIG. 4 is a cross-sectional view after processing illustrating the method for manufacturing a semiconductor device of this embodiment;

FIG. 5 is a diagram showing changes in an etching rate and an etching selectivity with respect to an added amount of HCl.

FIG. 6 is a diagram showing changes in an etching rate and an etching selectivity with respect to an added amount of Cl ₂ .

FIG. 7 is a diagram showing a change in an etching rate and an etching selectivity with respect to an added amount of O ₂ .

FIG. 8 is a diagram showing changes in an etching rate and an etching selectivity when the power of a high-frequency power supply is changed in the dry etching apparatus shown in FIG. 1;

FIG. 9 is a cross-sectional view before processing illustrating a conventional method for manufacturing a semiconductor device.

FIG. 10 is a cross-sectional view after processing illustrating a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Processing chamber 12 ... Silicon semiconductor substrate (silicon substrate) 14 ... Stage 16 ... Gas introduction port 18 ... Cathode electrode 20 ... High frequency power supply 22 ... Outer frame 24 ... Vacuum exhaust port 26a, 26b ... Permanent magnet 30 ... Silicon oxide film 32 ... Polycrystalline silicon film 34, 36 ... Silicon nitride film 36a ... Residue

Claims (9)

[Claims] 1. A method of manufacturing a semiconductor device using a dry etching apparatus in which a gas is introduced into an etching chamber and etching is performed using gas plasma obtained by converting the gas into plasma, wherein at least chlorine (Cl) ), Hydrogen (H),
And etching the silicon nitride film using the gas plasma containing atoms of oxygen and oxygen (O). 2. A gas plasma containing at least chlorine (Cl), hydrogen (H), and oxygen (O) atoms without containing fluorine is used for a substrate on which a silicon oxide film and a silicon nitride film are present. By dry etching equipment,
A method for manufacturing a semiconductor device, comprising etching the silicon nitride film. A step of forming a wiring or a conductive thin film element on the silicon oxide film; a step of forming a silicon nitride film on the entire surface of the silicon oxide film on which the wiring or the electrode is formed; At least chlorine (Cl), hydrogen (H),
And a step of etching the silicon nitride film by a dry etching apparatus using a gas plasma containing each atom of oxygen and oxygen (O). 4. A step of forming a side wall of a silicon nitride film on a side surface of a wiring or a conductive thin film element formed on a silicon oxide film, wherein the side wall of the silicon nitride film is formed on the silicon oxide film on which the wiring or the conductive thin film element is formed. A step of forming a silicon nitride film on the entire surface, at least chlorine (Cl), hydrogen (H) containing no fluorine,
Forming a sidewall of the silicon nitride film by a dry etching apparatus using a gas plasma containing atoms of oxygen and oxygen (O). 5. The gas plasma containing atoms of chlorine (Cl), hydrogen (H), and oxygen (O) is generated from a mixed gas containing Cl ₂ , hydrogen halide not containing fluorine, and O _2. The method for manufacturing a semiconductor device according to claim 1, wherein the method is performed. 6. The method according to claim 5, wherein the hydrogen halide is HCl. 7. The gas flow ratio of the mixed gas is HCl:
_{Cl 2: O 2 = 20:} 5: The method of manufacturing a semiconductor device according to claim 6, characterized in that the 1. 8. The method for manufacturing a semiconductor device according to claim 1, wherein the pressure of the etching processing chamber when etching the silicon nitride film is 500 [mTorr] or less. 9. The high-frequency power density when etching the silicon nitride film is 0.76 [W / cm ² ] to 1.15.
9. The method for manufacturing a semiconductor device according to claim 1, wherein [W / cm ² ].