JPH06132281A - Manufacture of silicon oxide film - Google Patents

Abstract

PURPOSE:To obtain a silicon oxide film excelling in breakdown voltage, by using an atmospheric CVD method. CONSTITUTION:The volume flow rate ratio R of oxygen gas to a silane based gas is higher than 30, preferably higher than 40, a silicon oxide film is manufactured by an atmospheric chemical vapor growth method. The atmospheric chemical vapor growth method is conducted sequentially by a single-wafer processing system. The formed silicon oxide film is utilized as an layer insulation film and an ONO film beside a field oxide film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a silicon oxide film by atmospheric pressure chemical vapor deposition, and more particularly to a method for producing a silicon oxide film having an excellent withstand voltage.

[0002]

2. Description of the Related Art A chemical vapor deposition method (hereinafter referred to as a CVD method) is a method in which a raw material is supplied as a gas and a thin film is deposited by a chemical reaction on a vapor phase or on a substrate surface.
Compared with other thin film deposition methods such as vacuum evaporation method and sputtering method, it is possible to form a wider and more versatile thin film and to provide various useful thin film deposition forms in the LSI manufacturing process. Is widely used, including.

Production of silicon oxide film by atmospheric pressure CVD method
Is a silane gas Si as a raw material gas._nH 2_{n +}2 (eg
For example, monosilane SiH_Four ) And oxygen O₂ And using, for example
SiH at a temperature of 300-500 ° C_Four +20₂ → SiO₂ + 2H₂ O or SiH_Four + O₂ → SiO₂ + H₂ By inducing a chemical reaction

[0004]

However, atmospheric pressure CVD
Since the silicon oxide film formed by the thermal oxidation method is not denser than the silicon oxide film formed by the thermal oxidation method, the electric field strength of the silicon oxide film formed by the thermal oxidation method is 9 MV / cm.
On the other hand, the electric field strength of the silicon oxide film formed by the atmospheric pressure CVD method is generally about 7 MV / cm. Therefore, there is a drawback that the reliability with respect to electrical breakdown voltage is inferior to that of a silicon oxide film formed by thermal oxidation.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to obtain a silicon oxide film having an excellent withstand voltage by the atmospheric pressure CVD method.

[0006]

In order to achieve the above object, in the method for producing a silicon oxide film according to the present invention, the volume flow ratio of oxygen to silane-based gas is 30 or more, preferably 4 or less.
A value of 0 or more is characterized in that a silicon oxide film is manufactured by an atmospheric pressure chemical vapor deposition method.

[0007] The atmospheric pressure chemical vapor deposition method is preferably carried out by sequentially processing in a single plate mode. Further, the silicon oxide film may be stacked on and under the silicon nitride film to be used as an ONO film.

[0008]

It is undeniable that the silicon oxide film formed by the thermal oxidation method is superior in electric field strength to the silicon oxide film formed by the CVD method because it is formed in a denser film than the silicon oxide film formed by the CVD method. According to this, when the silicon oxide film is manufactured by the CVD method, if the volume flow ratio of the silane-based gas as the raw material and oxygen is appropriately configured, a silicon oxide film having an electric field strength comparable to that of the thermal oxide film can be obtained. It was discovered that

That is, when a silicon oxide film is formed on a silicon substrate as shown in FIG. 2 and a voltage is sequentially applied to the silicon oxide film and the leak current flowing at that time is observed, the result shown in FIG. 1 (A) is obtained. was gotten.

According to this result, at the volume flow rate ratio R = 10 adopted in the conventional atmospheric pressure CVD method, the leak current also increases as the applied voltage increases, which is especially remarkable as compared with the thermal oxide film. There is a problem with the stability on the high voltage side. However, it is understood that when the volume flow ratio R of oxygen to the silane-based gas is increased to 30 or more, there is not much difference in the leak current on the low voltage side, but the leak current becomes stable when a high voltage is applied. To be done.

In particular, as shown in FIG. 1 (B), R = 30
Shows a remarkable limit value of the leak current, and in that sense, if R = 30, preferably R = 40 or more is set, a silicon oxide film having an electric field strength comparable to that of a thermal oxide film can be obtained. . This is because SiH ₄ + 2O ₂ → SiO ₂ + 2H ₂ O or SiH ₄ + O ₂ → SiO ₂ + H ₂ grows when the volume flow ratio of oxygen contained in the raw material is small in the vapor phase growth reaction process. This is considered to be because the oxygen in the silicon oxide film is insufficient and the above reaction is incomplete, the hydrogen-mediated polymerized film and the silicon Si are bonded to each other to lower the insulating property, and as a result, the leak current increases. .

Therefore, if the volumetric flow rate of oxygen is increased as in the present invention, the above reaction proceeds smoothly, and a more dense silicon oxide film SiO ₂ having a low leak property can be obtained.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the present invention, the silicon oxide film is manufactured by atmospheric pressure chemical vapor deposition using silane-based gas and oxygen as raw materials. Examples of the silane-based gas include SiH ₄ ,
SiHCl ₃ , SiH ₂ Cl ₂ , SiH ₃ Cl, SiC
l ₄ , SiBr ₄ , SiI ₄ , SiF ₄ , Si (OC ₂
H ₄ ) _{4 and the} like can be exemplified, but not limited thereto. Also, oxygen is not limited to oxygen gas only, and NO, NO ₂ , N ₂ O, CO, CO ₂
+ H ₂ , H ₂ O, O ₃ or the like can be used.

The volumetric flow rate ratio R (= oxygen / silane-based gas) of silane-based gas and oxygen supplied as a raw material is set to 30 or more, preferably 40 or more. This is because by setting the volumetric flow rate ratio of the source gas in such a range, the leak current with respect to the applied voltage can be reduced, which will be described later. When forming the silicon oxide film of the present invention, the substrate is grown at a low temperature of 300 to 500 ° C. by using the atmospheric pressure CVD method.

Such a silicon oxide film is shown in FIG.
It can be manufactured by the atmospheric pressure vapor phase growth apparatus (hereinafter also referred to as atmospheric pressure CVD apparatus) shown in. FIG. 3 is a conceptual diagram showing an apparatus for producing a silicon oxide film according to an embodiment of the present invention. Such a single-wafer CVD apparatus is superior to a batch-type vapor phase growth apparatus for simultaneously processing a large number of wafers. This is advantageous in that it is possible to easily cope with an increase in the diameter of the wafer and also to cope with the diversification of the silicon oxide film to be deposited.

In this atmospheric pressure CVD apparatus, the transfer conveyor 3
0, semiconductor substrates 31 such as semiconductor wafers are arranged in, for example, two rows at a predetermined interval, and a silicon oxide film is continuously formed on the surface of each semiconductor substrate 31 above the transfer conveyor 30. Three injectors 32 for film formation are arranged along the transport direction of the transport conveyor 30.

The injector 32 is provided with respective supply sources (silane gas supply source 33 and oxygen gas supply source 3).
From 4), the silane-based gas as a raw material gas and oxygen are introduced through the respective pipes 35 and 36. Then, the raw material gas blown out from the three injectors 32 sequentially reacts and deposits on the surface of the semiconductor substrate 31 transported by the transport conveyor 30 to form a silicon oxide film having a predetermined thickness.

Next, the reason why the volume flow rate ratio R of the source gas is set to R = 30 or more, preferably 40 or more as described above will be explained. FIG. 1A is a graph showing the relationship between the applied voltage and the leak current of the silicon oxide film according to one embodiment of the present invention, and FIG. 1B is the same with respect to the volumetric flow rate ratio of the raw material (oxygen / silane-based gas). Graph showing the relationship of leakage current,
FIG. 2 is a sectional view showing a semiconductor device used for performing the measurement shown in FIG.

First, as shown in FIG. 2, a silicon substrate 1
A silicon oxide film 2 is formed on the above by a CVD method to prepare a test piece, and a voltage is sequentially applied to the silicon oxide film 2,
The leak current flowing at that time was observed. When forming the silicon oxide film 2, the substrate temperature is set to 400 to 42 under normal pressure.
Maintained at 0 ° C, monosilane SiH ₄ as silane-based gas
Is fixed to 40cc and oxygen gas is 400cc
(R = 10), 800 cc (R = 20), 1200 cc
By changing to (R = 30), three types of test pieces were obtained. The thickness of each silicon oxide film 2 was 100 nm, and the aluminum electrode film 3 was formed on the surface of the silicon oxide film 2.

Then, the silicon substrate 1 and the aluminum electrode film 3
A voltage was applied between and, and the leak current value of the silicon oxide film with respect to the applied voltage value was measured. This result is shown in Figure 1.
It shows in (A).

By the way, for the purpose of comparison with a silicon oxide film formed by the thermal oxidation method, a thermal oxide film and an aluminum electrode film are formed on a silicon substrate in the same structure, and the silicon oxide film with respect to the applied voltage value is formed under the same conditions as above. The leak current value was measured. Further, based on this measured value, the relationship between the leak current and the volume flow ratio R of oxygen gas / monosilane was plotted to obtain the graph of FIG. 1 (B).

According to this result, when the volume flow rate ratio R = 10 adopted in the conventional atmospheric pressure CVD method, the leak current also increases as the applied voltage increases, and especially compared with the thermal oxide film. There is a problem with the stability on the high voltage side. For example,
In Fig. 1 (A), before breaking down, 50V
The leakage current tends to increase sharply at applied voltages of 70 V and 70 V.

However, when the volume flow rate ratio R of oxygen to silane-based gas is increased to 30 or more, the leak current on the low voltage side is not so different from that when R = 10, but as the high voltage is applied, Particularly, in the example shown in FIG. 1A, it is understood that the leakage current becomes low and becomes stable at an applied voltage of 50 V or higher.

Further, as shown in FIG. 1 (B), R = 30
Shows a remarkable limit value of the leak current, and in that sense, if R = 30, preferably R = 40 or more is set, a silicon oxide film having an electric field strength comparable to that of a thermal oxide film can be obtained. Be understood.

This is because when the volume flow ratio of oxygen contained in the raw material is small in the vapor phase growth reaction process of SiH ₄ + 2O ₂ → SiO ₂ + 2H ₂ O or SiH ₄ + O ₂ → SiO ₂ + H _2. , The oxygen in the growing silicon oxide film is insufficient and the above reaction becomes incomplete, and the hydrogenated intervening polymer film or silicon Si bonds with each other to lower the insulating property, resulting in an increase in leak current. it is conceivable that.

Therefore, since the silicon oxide film formed by the thermal oxidation method is denser than the silicon oxide film formed by the CVD method, it cannot be denied that it has excellent electric field strength. In manufacturing the film, if the volume flow ratio of the silane-based gas as the raw material and oxygen is appropriately configured, a silicon oxide film having an electric field strength comparable to that of the thermal oxide film can be obtained.

The above-described method for producing a silicon oxide film according to the present invention can be applied to the following various thin films.

FIG. 4 is a sectional view showing a specific example in which the silicon oxide film of the present invention is used as a field insulating film of a bipolar transistor. In this bipolar transistor (for example, NPN type transistor), a silicon oxide film (field insulating film) 5 is formed on an N type silicon substrate 4, a base diffusion region 6 is formed, and then the silicon oxide film 5 is photoetched. The emitter diffusion hole 7 and the collector diffusion hole 8 are opened by the
To form an emitter region 9 and a collector diffusion region 10.

Further, the base electrode lead-out hole 11 is opened by photoetching, an electrode metal is formed on the surface thereof, and then the base electrode 1 is formed by photoetching.
2, the emitter electrode 13 and the collector electrode 14 are formed.

In forming the field oxide film 5 of such a bipolar transistor, if a silicon oxide film is formed by using the method of the present invention, a base B-emitter E and a base B-collector C are formed. The breakdown voltage of the pn junction is significantly improved.

FIG. 5 is a sectional view showing a specific example in which the silicon oxide film of the present invention is also used as an interlayer insulating film. For example, a polysilicon film 15 formed on a silicon substrate 19 is shown.
The silicon oxide film 1 is formed on the surface of the substrate by the manufacturing method of the present invention.
7 is formed, and a polysilicon film 16 is further formed, and the silicon oxide film 17 is used as an interlayer insulating film between the polysilicon films 15 and 16.

In the figure, an electric field is particularly likely to concentrate at the edge portion 18 of the lower polysilicon film 15 formed on the silicon substrate 19, so that the breakdown voltage effect of the silicon oxide film 17 formed according to the present invention is effective. . In this case,
It is not limited to the polysilicon film, and an aluminum electrode film has the same effect.

The silicon oxide film of the present invention can also be used as a so-called ONO film. For example,
When thinning the interlayer insulating film between polysilicons used for the stack gate of EPROM, it is necessary to minimize the leak current. However, in order to form a good-quality silicon oxide film on a polysilicon film in which phosphorus is diffused at a high concentration, thermal oxidation at a high temperature of 1100 ° C. or higher is necessary. Due to various reasons such as speed, the controllability of the film thickness is reduced, and it is extremely difficult to reduce the film thickness.

Therefore, a three-layer insulating film (ONO film) has been developed in which a silicon nitride film (for example, Si ₃ N ₄ ) is formed on a silicon oxide film, and a silicon oxide film is further formed.

When the silicon oxide film of the ONO film is formed by using the manufacturing method of the present invention, the electrical withstand voltage is excellent, so that the insulating performance of the ONO film can be further improved.

The embodiments described above are provided for facilitating the understanding of the present invention, but not for limiting the present invention. Therefore, each element disclosed in the above-described embodiments is intended to include all design changes and equivalents within the technical scope of the present invention.

[0037]

As described above, according to the present invention, the silicon oxide film is produced by the atmospheric pressure chemical vapor deposition method with the volume flow ratio of oxygen to silane-based gas being 30 or more, preferably 40 or more. Moreover, the electric field strength can be increased, and a silicon oxide film having excellent electrical withstand voltage can be obtained.

For example, the electric field strength of the conventional silicon oxide film formed by atmospheric pressure vapor deposition was 7 MV / cm, whereas the electric field strength of the silicon oxide film manufactured by the manufacturing method of the present invention was 8 MV / cm or more. Therefore, it has electrical withstand voltage comparable to 9 MV / cm of the silicon oxide film formed by the thermal oxidation method.

[Brief description of drawings]

FIG. 1A is a graph showing a relationship between an applied voltage and a leak current of a silicon oxide film according to an embodiment of the present invention,
(B) is a graph showing the relationship of the leak current with respect to the volumetric flow rate ratio of the raw material (oxygen / silane-based gas).

FIG. 2 is a cross-sectional view showing a semiconductor device used for performing the measurement shown in FIG.

FIG. 3 is a conceptual diagram showing a silicon oxide film manufacturing apparatus according to an embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a specific example in which the silicon oxide film of the present invention is used as a field insulating film.

FIG. 5 is a sectional view showing a specific example in which the silicon oxide film of the present invention is also used as an interlayer insulating film.

[Explanation of symbols]

 1 ... Silicon substrate 2 ... Silicon oxide film 3 ... Aluminum electrode film

Claims (4)

[Claims] 1. A method for producing a silicon oxide film, which comprises producing a silicon oxide film by atmospheric pressure chemical vapor deposition with a volume flow ratio of oxygen to silane-based gas of 30 or more. 2. The method for producing a silicon oxide film according to claim 1, wherein the volumetric flow rate ratio of oxygen to the silane-based gas is 40 or more. 3. The method for producing a silicon oxide film according to claim 1, wherein the atmospheric pressure chemical vapor deposition method is sequentially processed in a single wafer mode. 4. The silicon oxide film is used by being stacked above and below a silicon nitride film.
4. The method for manufacturing a silicon oxide film according to any one of 1 to 3.