JPH05315269A - Forming method for thin film - Google Patents

Abstract

PURPOSE:To react GeF4 with silane gas and to deposit a uniform SiGe thin film at a low temperature by supplying mixture gas of the GeF4 and the silane gas to a substrate heated to a special temperature. CONSTITUTION:An Si single crystalline substrate is mounted on a substrate holder 3, which is evacuated to 10<-6>Torr or less through an evacuation system 4. The substrate is heated by a heater contained therein to 200-600 deg.C, and held thereat. After the temperature of the substrate is stabilized, GeF4, SiH4 are introduced from a nozzle 2 through a gas tube 1, and He is further introduced. It is so held that an entire pressure becomes 520mTorr, and a Ge epitaxial thin film is deposited. A suitable flow rate ratio of the used GeF4 and silane gas is 0.5-20. Thus, the GeF4 and the silane gas are reacted to easily form a Ge or SiGe deposited film at a low temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film forming method for depositing a Ge or SiGe thin film used for a thin film device on a substrate by a CVD method.

[0002]

2. Description of the Related Art Deposited thin films of Ge and SiGe are widely used in thin film devices such as solar cells, photosensors, and thin film transistors. Several methods for producing these thin films have been proposed, and vacuum deposition method, ion plating method, sputtering method, CVD method and the like are well known.

In particular, formation of an epitaxial film of Ge includes vapor phase epitaxy and liquid phase epitaxy. In general, liquid phase epitaxy has high crystallinity but has a non-uniform film thickness and poor surface condition and mass production. It is not used very often because it has bad sex.

On the other hand, vapor phase epitaxy includes the above-mentioned vacuum deposition method, ion plating method, sputtering method and CV.
Although it is performed by the D method or the like, for example, in the CVD method, it is necessary to supply some energy in order to induce decomposition of the raw material and maintain it. In the plasma CVD method, it is given by collision with high-energy electrons in plasma, and in the thermal CVD method and the photo CVD method, it is given by substrate heating and light irradiation, respectively.

However, in the formation of the deposited film by these methods, the energy supplying means itself often limits the usefulness and practicality. In the thermal CVD method, for example, when depositing a Ge thin film, a temperature of 500 ° C. or higher is required, the selection of the substrate material is limited, the apparatus itself becomes complicated, and a technique for industrial scale production has not been established.

The object of the present invention is to form a Ge and SiGe thin film at a low temperature and in a uniform ratio by selecting the starting material and designing the production process in consideration of the physical and chemical properties of the substance. It is to provide manufacturing technology.

[0007]

The present inventors have problems To achieve the] a result of various investigations on these problems, GeF ₄ and silane gas _{(Si n H 2n + 2,} n is an integer of 1 to 3) is reacted with As a result, a method of depositing a Ge or SiGe thin film was found, and the present invention was reached.

That is, according to the present invention, the substrate temperature is 200 to
A heating substrate which is a temperature range of 600 ° C., GeF ₄ and silane gas _{(Si n H 2n + 2,} n is an integer of 1 to 3), wherein the depositing a Ge or SiGe thin film by supplying a mixed gas of Is a method for forming a thin film.

In the present invention, the substrate temperature is 200 to 600 ° C.
On a heated substrate which is the temperature range, GeF ₄ and silane gas _{(Si n H 2n + 2,} n is an integer of 1 to 3) Ge by supplying a mixed gas, but is intended to deposit a SiGe film, When the substrate temperature is lower than 200 ° C., the reaction rate is slow and the thermal decomposition is insufficient to cause film deposition, which is not preferable. Further, when the temperature is 600 ° C. or higher, the raw material gas is decomposed and a uniform film cannot be formed, which is not preferable. In particular, it is most preferable to react in the range of 300 to 450 ° C.

In the present invention, the carrier gas may be H ₂ , N ₂ , He or Ar, if necessary. In the present invention, it is preferable to use a single crystal substrate such as Si or Ge as the substrate material to be used, but other glass substrates, Si polycrystalline substrates, Si amorphous substrates,
Ge polycrystal substrate, Ge amorphous substrate, etc. are used,
It is not limited to these. Particularly in epitaxial growth, the Ge deposition rate is affected by the plane orientation of the substrate. In the case of a Si substrate, the deposition rate on the (100) plane is high, and then on the (110) plane, there is almost no deposition on the (111) plane.

Next, in the present invention, silane gas (Si _n
H _{2n + 2} , n is an integer of 1 to 3)
A Ge or SiGe thin film can be deposited from eF _4, but it is extremely useful to be able to deposit a Ge epitaxial thin film by suppressing the incorporation of Si or the formation of an alloy by selecting the conditions. A thin film cannot be deposited only by decomposing the GeF ₄ alone or with a carrier gas. In particular, when deposited on the Si substrate, Si substrate is introduced along with GeF ₄ alone or carrier gas is etched, if silane _{(Si n H 2n + 2,} n is an integer of 1 to 3) is present, it occurs in the etching Becomes large, and the speed becomes several tens to one hundred Å / s.

In the present invention, the ratio of the amounts of GeF ₄ and silane gas (Si _n H _{2n + 2} , n being an integer of 1 to 3) used varies depending on the film forming conditions and the like, but the flow rate ratio [silane gas (Si _n H _{2n +} 2, _n is an integer of 1 to 3) / GeF _4] is suitably from 0.5 to 20 is preferably is desirably 0.5 to 10. Further, the deposition rate of the deposited film, the more the partial pressure of silane gas _{(Si n H 2n + 2,} n is an integer of 1 to 3) is increased, also the higher the substrate temperature increases.

In the present invention, not only the low pressure CVD method but also the high vacuum vapor deposition method can be used as the deposition method for the Ge deposited thin film and the like. Generally, the pressure is preferably low pressure, but considering the dilution ratio, sufficient deposition is possible even at atmospheric pressure, and the pressure range is not particularly limited.

[0014]

The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.

Example 1 A Si single crystal substrate was attached to the substrate holder 3 shown in FIG. 1, and the pressure was reduced to 10 ⁻⁶ Torr or less through an exhaust system 4.
The distance between the nozzle 2 and the substrate is 40 mm. The substrate was heated to and held at 375 ° C. by the built-in heater. After the substrate temperature is stabilized, G is passed from the nozzle 2 through the gas introduction pipe 1.
Introducing 5 sccm of eF ₄ and 30 sccm of SiH ₄ , and further introducing He to maintain the total pressure at 520 mTorr to deposit a Ge epitaxial thin film. The film forming rate at this time was 1 Å / s. The deposited film was analyzed by RHEED pattern by X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction and electron beam diffraction.
It was a Ge epitaxial thin film having a (00) plane.

Example 2 A Si (100) substrate patterned by SiO ₂ was used, adjusted under the same conditions as in Example 1, and after stabilizing the substrate temperature, GeF ₄ 5 sccm and SiH ₄ 30 s from nozzle 2.
ccm is introduced, and He is further introduced so that the total pressure is 520 m.
The Ge thin film was deposited while holding it at Torr. The deposited film was analyzed by X-ray photoelectron spectroscopy, Raman spectroscopy, RHEED pattern by X-ray diffraction and electron beam diffraction, and a scanning electron microscope. As a result, no deposition of the film was observed on SiO ₂ and Si (100 ) Surface was selectively deposited with Ge epitaxial thin film.

Example 3 After adjusting under the same conditions as in Example 1 and stabilizing the substrate temperature,
GeF ₄ 30 sccm from the nozzle 2, SiH ₄ 30sc
cm and then He to bring the total pressure to 520 mT.
The Ge epitaxial thin film was deposited while holding it at orr. The film forming rate at this time was 0.5 Å / s. This deposited film is subjected to X-ray photoelectron spectroscopy, Raman spectroscopy, X
As a result of analysis by a RHEED pattern by a line diffraction method and an electron diffraction method, it was a Ge epitaxial thin film having a (100) plane.

Example 4 SiO₂Uses Si (100) substrate patterned by
The substrate temperature was stabilized by adjusting under the same conditions as in Example 1.
After that, GeF from nozzle 2_Four1.5 sccm, Si ₂H₆
Introduce 15 sccm and further introduce He to bring the total pressure to 4
Hold to 20 mTorr and deposit Ge thin film
It was The film formation rate at this time was 6.5 Å / s. this
X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction and X-ray diffraction
And RHEED pattern by electron diffraction method, scanning electron
As a result of analysis with a child microscope, selective growth on the Si substrate
Seen and grown Ge is epitaxy with (400) plane orientation.
It was a thin film.

Example 5 A glass substrate was used and adjusted under the same conditions as in Example 1, and after the substrate temperature was kept stable at 420 ° C. and stabilized, Ge was discharged from the nozzle 2.
Introducing F ₄ 10sccm and Si ₂ H ₆ 30sccm,
He was further introduced to maintain the total pressure at 600 mTorr, and a Ge thin film was deposited. The film forming rate at this time was 50 Å / s. The deposited film was analyzed by RHEED pattern by X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction and electron diffraction, and as a result, it was a Ge polycrystalline thin film.

Example 6 An amorphous Si substrate was attached to the substrate holder 3, and the pressure was reduced to 10 ⁻⁶ Torr or less through the exhaust system 4. The distance between the nozzle 2 and the substrate is 40 mm. The substrate was heated to and held at 350 ° C. by the built-in heater. After the substrate temperature was stabilized, GeF ₄ 5sccm, SiH
_After introducing 20 sccm and further introducing He, the total pressure was kept at 550 mTorr and a Ge epitaxial thin film was deposited. The deposition rate at this time is 0.6Å /
It was s. The deposited film was analyzed by RHEED pattern by X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction and electron diffraction, and as a result, it was a Ge polycrystal thin film of (100) plane.

Example 7 The substrate was adjusted to the same conditions as in Example 1 and the substrate was heated to 420 ° C. by a built-in heater and held. After the substrate temperature is stabilized, GeF ₄ 2.7 sccm, Si ₂ H is discharged from the nozzle 2.
_A thin film was deposited by introducing 630 sccm and further introducing He to maintain the total pressure at 600 mTorr. The film forming rate at this time was 45 Å / s. The deposited film was analyzed by X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction and electron diffraction to find that it was a SiGe polycrystalline thin film.

Comparative Example 1 After adjusting under the same conditions as in Example 1 and stabilizing the substrate temperature,
GeF ₄ 30sccm was introduced from nozzle 2, and further H
An attempt was made to deposit a Ge epitaxial thin film by introducing e and maintaining the total pressure at 520 mTorr, but no deposited film could be confirmed on the substrate. At this time, the Si substrate was etched.

[0023]

According to the method of the present invention, Ge or S
It has made it possible to form iGe deposited films at lower temperatures than conventional methods and without the need for complicated manufacturing equipment.

[Brief description of drawings]

FIG. 1 shows a schematic view of a thin film deposition apparatus used in the present invention.

[Explanation of symbols]

 1. Gas inlet pipe 2. Nozzle 3. Substrate holder 4. Exhaust system

Claims (1)

[Claims] 1. GeF ₄ and silane gas (Si _n H 2) on a heated substrate having a substrate temperature of 200 to 600 ° C.
_{2n + 2} , n is an integer of 1 to 3) A Ge or SiGe thin film is deposited by supplying a mixed gas to form a thin film.