JP2593650B2 - Method for producing amorphous silicon semiconductor coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is to industrially propose a third semiconductor material. The present invention relates to a method for producing a novel amorphous silicon semiconductor film which is slightly different from a crystalline semiconductor or an amorphous (amorphous) semiconductor made of single crystal or polycrystal and can be used for a semiconductor device.

[Conventional technology]

Conventionally, as a semiconductor, a single crystal semiconductor has been regarded as a material having the most crystallographically stable and most ideal characteristics. As a single crystal semiconductor, a polycrystalline or amorphous semiconductor is known as a non-single crystal semiconductor.

A polycrystalline semiconductor is made up of a large number of crystalline masses, and at the grain boundaries, a so-called grain boundary (G.
B) was present. The grain boundary has a large number of dangling bonds at the grain boundary portion, which serve as recombination centers, and promotes precipitation of impurities at the grain boundaries. For this reason, even if a part of the crystal is a single crystal, most of its electric characteristics are determined by the grain boundary, and the characteristics are not similar to those of the single crystal.

By the way, this grain boundary not only precipitates impurities such as boron or phosphorus but also precipitates oxygen and the like. As a result, only this grain boundary increases its energy gap as compared with other parts, Was caused locally. Thus, despite the very crystalline, electrically conductive had gone 1/10 ^{4 to} the small single crystals reaches about 1/10 ^9.

On the other hand, amorphous semiconductors are amorphous in crystallinity, the interatomic distances in the micro are indefinitely varied, and have pure infinite lattice strain. He uses the geometric irregularities as the starting point to unravel its energy structure.

In particular, in the case of amorphous semiconductors, typically, a method of forming the semiconductor at room temperature to 300 ° C. by a glow discharge method of silane (SiH ₄ ) is known. Thus, the energy band width is larger than 1.0 eV to 1.1 eV of single crystal silicon and becomes 1.6 eV to 1.8 eV, and it has been found that N-type or P-type conductivity type can be obtained by adding a small amount of boron or phosphorus. I have. And this shows that this semiconductor can be applied to devices.
Currently expected.

[Problems to be solved by the invention]

However, this amorphous semiconductor also has a preferable surface as compared with a single crystal semiconductor in some characteristics.
For example, when the transition of light is an amorphous semiconductor,
This is a direct transition, and a single crystal semiconductor is an indirect transition. On the other hand, in terms of mobility, a single crystal semiconductor has electrons 15
00cm ² V / S, whereas a hole 500cm ² V / S, to the conduction Kuti Activity is sigma = 10 ^-3 not very small as 10 ^-4 (Ωcm) ^-1 (room temperature). Furthermore, the conductivity of an intrinsic semiconductor is 10 ⁻⁴ (Ωcm) ⁻¹ for a single crystal, whereas the conductivity of a non-single crystal semiconductor is 10 ⁻⁹ to 10
^-12 (Ωcm) ^-1 is extremely small. In addition, the non-single-crystal semiconductor, while the diffusion length of the minority carriers also single crystals have also 10 ² [mu] m to 10 ⁴ [mu] m, 300 Å to 400Å and 1/10 ⁵
Was also small.

An object of the present invention is to solve the above-described problems, and to provide an amorphous silicon semiconductor film in which the surface superior to the single crystal semiconductor of the amorphous semiconductor is left as it is and the inferior points are improved. .

[Means for solving the problem]

In order to achieve the above object, the method for producing an amorphous semiconductor film of the present invention comprises the steps of: forming a silicon oxide film on a crystal surface 110 having irregularities, and then forming an amorphous semiconductor film containing hydrogen or a halogen element thereon by a high-speed CVD method. It is characterized by forming a coating.

〔Example〕

FIG. 1A is an electron micrograph showing the crystal structure of a cross section of the semiconductor film of the present invention. FIG. 1 (B) is a simulated view of the photograph of FIG. 1 (A).

As is clear from FIG. 1 (A), countless regular streaks (2) are seen in the vertical direction.
It is observed that the amorphous silicon semiconductor (1) has a columnar or layered crystal structure.

One feature of the semiconductor of the present invention is that an amorphous silicon semiconductor is formed at a high speed by a plasma CVD method under ECR (Electron Cyclotron Resonance) conditions.

That is, since amorphous silicon semiconductors are successively deposited on the substrate at a high speed by the ECR plasma CVD method, the deposited amorphous silicon semiconductor does not sufficiently react on the substrate, and therefore, the stripes are regularly formed in the vertical direction. It can be estimated that 2) appears.

Further, in addition to the features described above, it is necessary that irregularities having regularity are formed on the substrate on which the amorphous silicon semiconductor is formed.

For example, when forming regular irregularities on a silicon single crystal substrate, anisotropic etching of silicon is performed through a known photolithography process, and the silicon is anisotropically etched at a pitch of about 5 μm.
The unevenness having the zero plane is formed.

Further, an SiO ₂ film was formed on the uneven surface at a thickness of about 2000 ° so that epitaxial crystal growth did not occur on the substrate. An amorphous silicon semiconductor is formed on the substrate by the ECR plasma CVD method.

Then, as shown in FIG. 1 (A), the amorphous silicon semiconductor (1) is bounded by the streaks (2) having regularity.
Has a columnar or layered crystal structure. At this time, the crystal structure formed on the amorphous silicon semiconductor substrate is 100
The direction had a surface.

This is very similar to that found in conventionally known graphoepitaxy, but in the case of the present invention, it is clearly an amorphous semiconductor, and even when analyzed by X-ray diffraction, electronic diffraction, etc., it is unique to amorphous. The result was shown.

FIG. 2 (A) is a micrograph showing a cross-sectional crystal structure of amorphous silicon on a glass substrate as a comparative example. FIG. 2 (B) is a photograph of the photograph of FIG. 2 (A).

When a substrate having no regular irregularities is similarly formed on a mere glass substrate, the amorphous semiconductor film formed as shown in FIGS. 2 (A) and 2 (B) clearly has a regular vertical direction. No streaks. As is evident from this, one of the features of the present invention is to manufacture a substrate on a substrate having a regular irregular shape.

The semiconductor film of the present invention is characterized by anisotropy in electric conductivity among electric characteristics.

That is, in FIG. 1 (B), when a current flows in the direction of arrow A, the photoconductivity is σp = 10 ⁻⁶ to 10 as in a general amorphous silicon semiconductor.
^-4 (Ωcm) ^-1 and dark conductivity is σd = 10
^-11 to 10 ^-9 (Ωcm) ^-1 . However, when the direction of current flow is the direction of arrow B in FIG. 1B, the photoconductivity is σp = 10 ⁻² to 10 ⁻⁴ (Ωc
m) ^-1 , dark conductivity is σd = 10 ^-5 or 1
At 0 ^-6 (Ωcm) ^-1 , anisotropy was observed in the electrical conductivity.

 The electric conductivity was measured as follows.

The measurement of the electric conductivity in the direction of arrow A in FIG.
Photoconductivity was measured by providing a pair of electrodes by ITO on the surface of amorphous silicon, applying an electric field of 10 V / cm to 1000 V / cm to the silicon film, and irradiating AM1 (100 mW / cm ² ) light.

The dark conductivity is measured without irradiating light.

The measurement of the electric conductivity in the direction of arrow B in FIG.
An electrode was formed so as to sandwich amorphous silicon, and a voltage was applied between the electrodes. That is, Cr was formed as an electrode on the SiO ₂ film, and an ITO electrode was formed on amorphous silicon. Then, an electric field of 10 to 10000 V / cm is applied between both electrodes, and AM1 (100 mV / cm
Photoconductivity was measured by irradiating the light of ² ).

The dark conductivity is measured without irradiating light.

One of the applications of the semiconductor film of the present invention is as follows.
There is an optical conversion device having a PIN structure.

In other words, when the film of the present invention is used as the semiconductor of the I layer and formed so as to have regularity in the direction of the PN electric field,
Due to the anisotropy of the electric conductivity, carriers generated inside the I layer by light irradiation are generated by the internal electric field of PN.
Much more move to the P and N layers than a general amorphous silicon semiconductor.

Therefore, it is possible to generate more current than when a general amorphous silicon semiconductor is used as the I layer.

 Hereinafter, a method for producing the film of the present invention will be described by way of examples.

Example As a substrate on which a film was formed, a silicon single crystal substrate on which irregularities having 110 surfaces were formed at a pitch of 8 μm was used.

This unevenness was formed by a conventionally known photolithography and anisotropic etching of silicon.

An SiO ₂ film was deposited on this substrate so that the film formed on the substrate did not grow epitaxially.

This substrate was set in an ECR plasma CVD apparatus, and a reaction was performed at a substrate temperature of 400 ° C., a reaction pressure of 4.0 × 10 ⁻⁴ torr, a microwave output of 300 W, and a SiH ₄ gas of 15 SCCM, and the temperature was increased to 1500 ° C.
A film was formed for about 5 minutes at a film formation rate of 1 minute / minute, and a semiconductor film having a thickness of 7500 ° was formed.
As shown in the electron micrograph of the above, an amorphous silicon semiconductor film having a columnar or layered crystal structure could be formed with a vertical streak as a boundary.

〔The invention's effect〕

According to the present invention, after forming a silicon oxide film on the crystal face 110 having irregularities, an amorphous semiconductor film containing hydrogen or a halogen element formed thereon is formed. A column or a layered crystal structure, with a streak showing regularity in the vertical direction as a border,
Electric conductivity can be made anisotropic. Therefore, when the amorphous silicon semiconductor film of the present invention is applied to a photoelectric conversion device, it has become possible to generate a larger amount of current than when a general amorphous silicon semiconductor is used as an I layer.

[Brief description of the drawings]

FIG. 1A is an electron micrograph showing the crystal structure of a cross section of the semiconductor film of the present invention. FIG. 1 (B) shows the first
It is the figure which copied the photograph of figure (A). FIG. 2 is a micrograph showing the crystal structure of a cross section of amorphous silicon on a glass substrate as a comparative example. 1 ... amorphous silicon semiconductor film of the present invention 2 ... streaks regularly appearing in amorphous silicon semiconductor film 3 ... substrate

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shunpei Yamazaki 398 Hase, Atsugi-shi Semiconductor Energy Laboratory Co., Ltd. (56) References JP-A-57-68017 (JP, A)

Claims (1)

(57) [Claims] An amorphous silicon semiconductor film comprising: a silicon oxide film formed on a crystal surface having irregularities; and an amorphous silicon semiconductor film containing hydrogen or a halogen element formed thereon by a high-speed CVD method. Manufacturing method.