JPH02263478A - Manufacture of semiconductor element - Google Patents

Abstract

PURPOSE:To prevent the leakage of an electric current and improve the yielding rate of manufactured by forming an imperfect crystal region of a semiconductor film in the direction where cracks are liable to develop and taking a step so as not to allow the semiconductor film at a lower part of an electrode that is alloyed by heat treatment to be cracked. CONSTITUTION:An n-type GaAs film 2 and a p-type GaAs film 3 contain an amorphous GaAs layer which is allowed to grow at a low temperature. Including the surface of an SiN film 6, the preceding two films make the film 6 perform epitaxial growth on the n-type Si substrate 1. After making a semiconductor film grow, if a temperature is lowered up to a room temperature, difference in coefficients of thermal expansion of Si and GaAs may apply stress on both GaAs films 2 and 3. However, the GaAs films on the upper part of the SiN film 6 is not completely crystallized but its films are in the state of polycrystals or amorphous conditions. As these parts are in imperfect crystal regions, the development of cracks C is only centered at these parts and no cracks develop at the other part. This state of the semiconductor film prevents the abnormal leakage of a current and improves a yielding rate.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor element used in a photoelectric conversion element, etc., and particularly relates to a method for manufacturing a semiconductor element used in a photoelectric conversion element, etc. The present invention relates to a method of manufacturing a semiconductor element by epitaxially growing a semiconductor film.

[Conventional technology]

Compound semiconductors such as GaAs are often used as materials for semiconductor elements such as highly efficient photoelectric conversion elements. As a manufacturing method thereof, from the viewpoint of reducing the cost of the device, it is common to epitaxially grow these compound semiconductors on a semiconductor substrate such as a Si substrate. Hereinafter, a conventional method for manufacturing a semiconductor device will be briefly described using a photoelectric conversion device having an n-junction as an example.

FIG. 3 is a schematic cross-sectional view showing the steps of this conventional manufacturing method. First, on the n-Si substrate 11, a Se-doped n-GaA layer containing a regular amorphous GaAs layer with a thickness of approximately 200 mm is prepared.
sJl! 12. MOCVD (Metalorganic Carbon
Chemical Vapor Depositton
) method (FIG. 3(a)).

Next, an Au/Zn film 14 is patterned on the p-GaAs film 13, and an A/Zn film 14 is formed on the lower surface of the n-5i substrate 11.
An I film 15 is deposited and heat treated at about 450°C to form an ohmic electrode (FIG. 3(b)). Finally, p
- In order to reduce the leakage current flowing to the end face of the n-junction diode, the n-GaAs film 12 and the p-GaAs film 13 are
A photoelectric conversion element is manufactured by etching the end face of the semiconductor film (FIG. 3(C)).

[Problems to be Solved by the Invention] Among the photoelectric conversion elements manufactured by the method described above, there are many elements that generate an abnormally large leakage current, and there is a problem that the manufacturing yield is extremely low. there were.

The cause of this leakage current is Si and GaA.
The present inventor has experimentally determined that this is because Au/Zn abnormally diffuses into cracks that occur in the GaAs film due to the difference in thermal expansion coefficient between the Au/Zn film 14 and the n-GaAs film 12. It was proved. It was also found that most of the directions in which these cracks occur are in a specific crystal direction of the n-5i substrate 11 and in a direction perpendicular to this.

The present invention has been made in view of the above circumstances, and it is possible to form an imperfectly crystalline region of a semiconductor film in a direction in which cracks are likely to occur, thereby causing cracks in the semiconductor film under the electrode that is heat-treated and alloyed. It is an object of the present invention to provide a method for manufacturing a semiconductor device that can prevent leakage current from occurring and improve manufacturing yield by preventing leakage current from occurring.

[Means to solve the problem]

A method for manufacturing a semiconductor device according to the present invention is a method for manufacturing a semiconductor device in which a plurality of layers of semiconductor films having different conductivity types are epitaxially grown on a semiconductor substrate. a step of forming imperfectly crystalline regions of the semiconductor film in a lattice shape in the vertical direction thereof; a step of forming electrodes in each region except the imperfectly crystalline regions and subjecting them to heat treatment; The method is characterized by comprising a step of connecting wires using a conductive film.

[Effect]

In the manufacturing method of the present invention, imperfectly crystalline regions of a semiconductor film are formed in a lattice pattern over a specific direction of a semiconductor substrate where cracks are likely to occur and in a direction perpendicular thereto. If this is done, when the temperature is lowered to room temperature, cracks will occur intensively only in this imperfect crystal region, and no cracks will occur in the region where the electrodes will be formed. Therefore, the conventional abnormal diffusion of the material constituting the electrode into the semiconductor film is prevented, and no leakage current occurs.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on drawings showing embodiments thereof.

FIG. 1 is a schematic cross-sectional view showing the steps of the manufacturing method of the present invention,
FIG. 2 is also a top view thereof. In this embodiment, a method for manufacturing a semiconductor device will be described using as an example a photoelectric conversion element having a structure in which a rectangular n-Si substrate is divided into 3×3 photoelectric conversion sections.

First, a photoelectric conversion unit with a thickness of 100 μm is placed on an n-Si substrate 1, which is a semiconductor substrate, tilted 2 degrees in the [011] direction from the (100) plane.
The width is 10μ at 100μm intervals so that it is divided into m intervals.
A SiN film 6 having a thickness of approximately 2,000 m is patterned into a lattice shape (FIG. 1(a)). This SiN film 6 is
The SiN film 6 is formed in a strip shape in the [011] direction and in a direction perpendicular thereto, and the SiN film 6 forms a lattice pattern as shown in FIG. 2(a). Further, the patterning in this step uses ordinary photolithography and etching.

Next, an n-GaAs film with a thickness of about 3 um including an amorphous GaAs layer with a thickness of 200 Å or less is grown at a low temperature of 450° C. using the MOCVD method. A p-GaAs film 3 and a p-GaAs film 3 are epitaxially grown in this order on the n-5i substrate 1 including the surface of the SiN film 6 at a growth temperature of about 700°C (FIG. 1(b)). After growing a semiconductor film, when the temperature is lowered to room temperature, stress is applied to the GaAs film due to the difference in thermal expansion coefficients between St and GaAs. However, in the present invention, the GaAs film above the SiN film 6 is not completely crystallized and is polycrystalline or amorphous.
In other words, since this part (the GaAs film on top of the SiN film 6) is an imperfect crystal region, cracks C occur intensively only in this part as shown in FIG. 1(b), and in other parts. No crank occurs.

Next, by a lift-off method using photolithography, the thickness of the p-GaAs film 3 of each photoelectric conversion section is 5000 mm.
A 0 Au/Zn (Zn content: 5%) film 4 is formed, and an Al film 5 is vapor-deposited on the lower surface of the n-5t substrate 1 (
Fig. 1(C), Fig. 2(b)). Then at 450°C 2
Heat treatment is performed for a minute to alloy the p-GaAs film 3 and the Au/Zn film 4 and to alloy the n-Si substrate 1 and the AI film 5. At this time, since no cracks have occurred in the lower part of the Au/Zn film 4, the n-Ga
Abnormal diffusion reaching the As film 2 does not occur.

Next, in order to eliminate the leakage current between the p-n junction in the imperfectly crystalline region and the leakage current at the end face of the pn junction, the GaAs film portion, which is the imperfectly crystalline region, was
04. H20□,! Etching is performed using photolithography using a mixed solution of 1□0 (FIG. 1(d)).

Finally, an Au film 8, which is a conductive film with a thickness of about 1 μm, is selectively formed on the surface of the heat-resistant glass 7 having light transmittance by a lift-off method, and is bonded to each electrode (Au/Zn film 4). A photoelectric conversion element is manufactured by connecting each electrode (FIG. 1(e), FIG. 2(C)). Here, heat-resistant glass 7
has the function of protecting the element.

In this example, the incomplete crystalline region was removed by etching, but if this region has high resistance, it is etched directly onto the n-GaAs film 2 by a lift-off method without etching. A 0^U film having a thickness of about 2000 layers may be deposited to connect each electrode.

(Effects of the Invention) As detailed above, in the manufacturing method of the present invention, cranks are selectively generated in the imperfectly crystalline regions of the semiconductor film, and cranks are not generated in the semiconductor film below the electrode. The present invention has excellent effects, such as being able to prevent the occurrence of abnormal leakage current in the manufactured semiconductor element.As a result, the manufacturing yield can be significantly improved.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing the steps of the manufacturing method according to the present invention, FIG. 2 is a top view thereof, and FIG. 3 is a schematic cross-sectional view showing the steps of the conventional manufacturing method. 1...n-5i substrate 2-n-GaAs film 3-p
-GaAs film 4--・Au/Zn film 5・AI film 5
=SiN film 7...Heat-resistant glass 8...Au film

Claims (1)

[Claims] 1. A method for manufacturing a semiconductor device in which a plurality of layers of semiconductor films of different conductivity types are epitaxially grown on a semiconductor substrate, wherein a specific crystal direction of the semiconductor substrate and its perpendicular direction are formed on the semiconductor substrate. forming imperfectly crystalline regions of the semiconductor film in a lattice shape across directions; forming electrodes in each region excluding the imperfectly crystalline regions and subjecting them to heat treatment; and connecting each of the formed electrodes to a conductive film. 1. A method of manufacturing a semiconductor device, comprising the step of connecting wires.