JPH0365434B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method and apparatus for producing high-quality silicon-containing thin films, and in particular to a method and apparatus for producing high-quality silicon-containing thin films, and in particular, a method and apparatus for producing high-quality silicon-containing thin films.
This invention relates to a method and apparatus for producing high-quality silicon-containing thin films by CVD.

(Prior Art) Amorphous semiconductor thin films such as amorphous silicon are currently formed by discharging and decomposing silane or the like. Therefore, when a solar cell or the like is formed by stacking various amorphous semiconductor films in multiple layers, the interfaces between the layers are subject to plasma damage due to discharge, which puts a limit on the improvement of their properties. As a way to solve this,
Attempts have been made to form amorphous semiconductors through photochemical reactions, but there are problems with the method of introducing light into the film deposition area and the light source itself.

On the other hand, in the production of semiconductor devices such as MOS transistors, it is desired to develop a technology for forming high-quality insulating films at low temperatures. For this reason, insulating film deposition methods using plasma reactions or photoreactions are being considered, but these methods also have the same problems as the amorphous semiconductor thin film manufacturing method described above.

(Problems to be Solved by the Invention) The starting point of the present invention is the idea that in order to solve the problems of the prior art, thermal CVD may be used. There is. In other words, if a good amorphous semiconductor with high photosensitivity could be made by thermal CVD, not only would the film formation equipment become simpler and cheaper, but the film formation itself would become more stable. Furthermore, if a high-quality insulating film can be made using thermal CVD at low temperatures, including room temperature, it will be an ideal insulation formation method that does not cause damage to the semiconductor device itself.

Therefore, the present invention uses only a thermal CVD method without using plasma reactions or photoreactions to produce high-quality silicon-containing films such as amorphous semiconductor thin films such as amorphous silicon and insulating films such as silicon nitride. An object of the present invention is to provide a method and apparatus for forming a thin film.

(Means for Solving the Problems) The method of the present invention uses species in an intermediate state that does not exist in nature, particularly silicon difluoride S _i F ₂ or silicon monofluoride S, which has an unusually long life. Using _iF ,
This is mixed with decomposed species obtained by thermally decomposing hydrogen H ₂ , silane S _i H ₄ , disilane S _i2 H ₆ , ammonia NH ₃ , hydrazine N ₂ H ₄ near the substrate, and a material whose main component is this mixed gas is mixed. Heat for supplying gas to the substrate and depositing it
The present invention relates to a thin film forming method characterized by forming high-quality thin films containing silicon, such as amorphous semiconductor thin films such as amorphous silicon and insulating films such as silicon nitride, by CVD.

In the method of the present invention, silicon difluoride,
S _i F ₂ or a fragment thereof, silicon monofluoride S _i F, is a combination of solid silicon and silicon tetrafluoride S _i
It is produced by a chemical reaction with _F4 at temperatures above 900℃. In addition, silicon difluoride S _i F ₂ etc. is di-silicon hexafluoride S _i2 F ₆ etc. SimF _2n+2 (m=
1, 2, 3,...) or S _i
It can also be obtained by decomposing a molecule such as F ₂ H ₂ in which part of the fluorine in the molecule is replaced with hydrogen by thermal reaction, plasma reaction, or photoreaction.

In the method of the present invention, these silicon difluoride S _i F ₂ or silicon monofluoride S _i F are mixed with hydrogen H ₂ ,
Silane S _i H ₄ , disilane S _i2 H ₆ , ammonia NH ₃ or hydrazine N ₂ H ₄ is mixed with species decomposed by a thermal reaction, and the mixed gas is thermally decomposed onto a substrate (so-called thermal chemical vapor deposition).
(CVD)). At this time,
intermediate state species such as silicon difluoride S _i F ₂ ;
Even when plasma reactions are used to generate various decomposition species such as hydrogen _H2 decomposition species (hydrogen atoms), after they are transported onto the substrate surface, the substrate surface is exposed to plasma, high-energy light, etc. The key point of the invention is to thermally CVD a silicon-containing thin film onto a substrate without being damaged by exposure.

The amorphous semiconductor thin film to be formed is amorphous silicon, amorphous silicon carbide, amorphous silicon germanium, or
It is composed of these fluorine-containing substances, and includes thin films in which these are microcrystalline or polycrystalline.

In addition, the insulating film to be formed contains silicon such as silicon nitride, silicon oxide, or silicon nitride, but these films may also contain fluorine, hydrogen, or both at the same time. be.

The substrate on which the thin film is deposited is at room temperature or above;
In particular, when forming an amorphous semiconductor thin film, it is desirable that the substrate temperature be in the range of 150°C to 400°C.

As a method for generating decomposition species, there is a method of bringing hydrogen, silane, disilane, ammonia, hydrazine, etc. into contact with a metal that causes a thermal catalytic reaction, such as incandescent or red-hot tungsten, platinum, or palladium.

The apparatus of the present invention includes an intermediate state seed generation section, a film deposition section equipped with a heating device communicating with the intermediate state seed generation section and accommodating a substrate therein and heating it to a predetermined temperature, and an intermediate state generation section. It is composed of a decomposition species source gas introduction section provided near the connection part of the film deposition section, and a decomposition species generation section provided in the gas passage between this introduction section and the substrate heating section or near the film deposition section. ing.

An example of the decomposition species generating section is a metal heater that causes a thermal catalytic reaction, such as tungsten, platinum, or palladium.

(Example) Next, an example of the method and apparatus for manufacturing a silicon-containing thin film of the present invention will be described with reference to the accompanying drawings.

Figure 1 shows an example of the method of the present invention in which silicon difluoride S _i F ₂ is generated by a chemical reaction between solid silicon and silicon tetrafluoride S _i F ₄ , and the heat generated by hydrogen and incandescent tungsten is generated. This figure schematically shows an apparatus that generates hydrogen decomposition species, that is, hydrogen atoms, through a catalytic reaction, and forms amorphous silicon using a mixed gas of silicon difluoride and hydrogen atoms. This device includes an intermediate state species generating section 1 consisting of a high heat resistant tube 5 such as a quartz tube filled with solid silicon 6 and an electric furnace 3 for heating this high heat resistant tube, and a quartz tube accommodating a substrate 8 therein. A film deposition section 2 consisting of a second high heat resistant tube 7 such as the like, and a second electric furnace 4 that heats the substrate to a predetermined temperature through the high heat resistant tube.
, the outlet of the first high heat resistant tube 5 and the second high heat resistant tube 7
A raw material gas inlet 9 for decomposed species such as hydrogen is provided near the connection with the inlet of the tungsten gas inlet 9 and a tungsten gas inlet 9 is provided in the gas passage between the inlet 9 and the heating section of the substrate or in the vicinity of the substrate 8. It mainly consists of a heater 10.

The silicon tetrafluoride S _i F ₄ is introduced into a quartz tube or high temperature tube 5 filled with solid silicon 6 . At that time, the tube 5 is heated to 900℃ or higher and 1200℃ using the electric furnace 3.
It is heated back and forth, and a chemical reaction produces silicon difluoride S _i F ₂ . The produced silicon difluoride S _i F ₂ is immediately introduced into the film deposition section 2 . In the film deposition section 2, the temperature of the substrate 8 is maintained at a set value by an electric furnace 4. Furthermore, hydrogen H ₂ is also simultaneously introduced into the film deposition section 2 from the decomposed species raw material gas inlet 9 . The introduced hydrogen H ₂ comes into contact with the tungsten heater 10 placed on the gas introduction side of the film deposition section 2 or near the substrate 8, and is decomposed into hydrogen atoms by a thermal catalytic reaction. Platinum, palladium, and the like are also used as metals that can cause this thermal catalytic reaction. Then, the hydrogen atoms and silicon difluoride S _i F ₂ are transported onto the substrate 8 to form amorphous silicon. Amorphous silicon with good photosensitivity is produced when the substrate temperature is between 150°C and 400°C.
Its photosensitivity reaches its maximum between 200°C and 350°C.

FIG. 2 shows the deposition rate of amorphous silicon as a function of the current flowing through the tungsten heater 10 and the temperature of the tungsten heater 10 at that time as measured by a pyrometer.
As the tungsten heater current increases, the dissociation rate of hydrogen increases, and the film formation rate also increases accordingly. In the case of this apparatus, the deposition rate can be improved to at least 47 Å/sec.

Figure 3 shows the photoconductivity △σ _p , dark conductivity σ _d , and photosensitivity △σ _p /σ _d of the deposited amorphous silicon as a function of the tungsten heater temperature. The conductivity △σ _p is 100mW/cm ²
Measured using AM-1 light. When the tungsten heater current is less than 8A, the photosensitivity △σ _p /σ _d is
¹⁰⁶ , and the photosensitivity of amorphous silicon made by the conventional discharge decomposition method is ¹⁰⁴ .
It can be seen that amorphous silicon of higher quality than that of 10 ⁵ is formed. Also,
The spin density corresponding to defects due to dangling bonds in silicon determined by ESR measurement of this amorphous silicon is 10 ¹⁵ cm ^-3 , which is a typical value of 10 for amorphous silicon made by the conventional discharge decomposition method. lower than ¹⁶ cm ^-3 .

When the tungsten heater current is increased, the film formation rate increases as shown in FIG. 2, but tungsten is mixed into the film and the film quality deteriorates. For example, if the heater current is 13A, 200ppm of tungsten will be mixed in. When the heater current is 6A, it is suppressed to less than 9ppm. This metal contamination can be prevented by using a metal that causes a thermal catalytic reaction at low temperatures, such as platinum.

In addition, among the symbols representing the film forming conditions shown in FIGS. 2 and 3, FR (G), T _s , and P _g are respectively,
The flow rate of gas G (sccm), substrate temperature (°C), and gas pressure (Torr) are shown.

(Effects of the Invention) The silicon-containing thin film produced by the method and apparatus of the present invention is not damaged by plasma or the like, so it has low defects and high quality, as shown using amorphous silicon as an example. It is something. Therefore, if the formed thin film is an amorphous semiconductor such as amorphous silicon, amorphous silicon carbide, or amorphous silicon germanium, it can be used for highly efficient solar cells, electrophotographic photoreceptors, thin film transistors, photographic tubes, etc. . In addition, when the formed thin film is an insulating thin film such as silicon nitride or silicon oxide, it can be used for local oxidation (LOCOS) technology in gate insulating films, field insulating films, field insulating films of transistors, and integrated circuits. It can be used as a silicon nitride film for a mask. When the present invention is applied to electronic devices such as transistors and integrated circuits, a great advantage of the present invention is that insulating films such as silicon nitride and silicon oxide can be formed by low-temperature thermal CVD.

The present invention relates not only to amorphous semiconductors or their microcrystalline or polycrystalline thin films, but also to the formation of silicon-containing insulating films, and has an extremely large and wide-ranging impact on industry.

Note that the generation of decomposed species by thermal decomposition in the method of the present invention is not limited to the method using a catalytic reaction as in the above-mentioned example. In addition to thermal decomposition, decomposition species can also be generated by decomposition by plasma reaction, decomposition by photoreaction, etc.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an example of the apparatus according to the present invention, Fig. 2 is a graph of a characteristic curve showing the relationship between heater current and film growth rate, and Fig. 3 is a graph of the characteristic curve showing the relationship between heater current and film growth rate. It is a graph illustrating photoconductivity Δσ _p , dark conductivity σ _d , and photosensitivity Δσ _p /σ _d as examples. 1: Intermediate state species generation section, 2: Film deposition section, 3: First electric furnace, 4: Second electric furnace, 5: First high heat resistant tube, 6: Solid silicon, 7: Second high temperature heat resistant tube,
8: Substrate, 9: Decomposed species raw material gas inlet, 10: Tungsten heater, 11: Thermocouple.

Claims (1)

[Claims] 1 Silicon difluoride SiF ₂ , silicon monofluoride
Intermediate species such as SiF include hydrogen H ₂ , silane SiH ₄ , disilane Si ₂ H ₆ , ammonia NH ₃ or hydrazine.
A method for producing a silicon-containing thin film, which comprises forming a silicon-containing thin film by mixing and supplying decomposed species obtained by thermally catalytically decomposing N ₂ H ₄ or the like near a substrate. 2 Silicon difluoride SiF ₂ , silicon monofluoride
Intermediate species such as SiF include hydrogen H ₂ , silane SiH ₄ , disilane Si ₂ H ₆ , ammonia NH ₃ or hydrazine.
The method for producing a silicon-containing thin film according to claim 1, characterized in that a reactive gas such as N ₂ H ₄ is mixed, the mixed gas is thermally catalytically decomposed near the substrate, and then supplied to the substrate. 3. The silicon-containing film to be formed is amorphous silicon, fluorine-containing amorphous silicon, amorphous silicon carbide, fluorine-containing amorphous silicon carbide, amorphous silicon germanium, fluorine-containing amorphous silicon germanium, etc. 3. The method of manufacturing a silicon-containing thin film according to claim 1 or 2, wherein the amorphous semiconductor thin film is a microcrystalline or polycrystalline film. 4 The silicon-containing film formed is silicon nitride,
3. The method of manufacturing a silicon-containing thin film according to claim 1 or 2, wherein the insulating thin film is made of silicon oxide, silicon nitride, or the like. 5 The silicon-containing film formed is silicon nitride,
The silicon-containing silicon-containing material according to claim 1 or 2, which is an insulating thin film of silicon oxide, silicon nitride, etc., and the insulating thin film contains fluorine or hydrogen or both. Method for manufacturing thin films. 6. Claim 1, characterized in that the thermal catalytic decomposition temperature when depositing the thin film is room temperature or higher.
A method for producing a silicon-containing thin film according to any one of Items 1 to 5. 7 Substrate temperature when depositing thin film is from 150℃
7. The method for producing a silicon-containing thin film according to claim 6, wherein the temperature is in the range of 400°C. 8. Bringing a reactive gas such as hydrogen H ₂ , silane SiH ₄ , disilane Si ₂ H ₆ , ammonia NH ₃ or hydrazine N ₂ H ₄ into contact with a metal that causes a thermal catalytic reaction such as incandescent or red-hot tungsten, platinum or palladium. 8. A method for producing a silicon-containing thin film according to any one of claims 1 to 7, characterized in that decomposed species are generated by a method of producing a silicon-containing thin film. 9. An intermediate state generation section, a film deposition section connected to the intermediate state generation section and equipped with a heating device that accommodates a substrate therein and heats it to a predetermined temperature, and a connection between the intermediate state species generation section and the film deposition section. The method is characterized by comprising a decomposition species source gas introduction section provided near the section, a decomposition species generation section provided in the gas passage between the introduction section and the substrate heating section, and near the film deposition section. A device for manufacturing silicon-containing thin films. 10. The apparatus for producing a silicon-containing thin film according to claim 9, wherein the decomposition species generating section is a heater made of a metal that causes a thermal catalytic reaction, such as tungsten, platinum, or palladium.