JPS6156474A - Manufacture of gallium nitride semiconductor device - Google Patents

Abstract

PURPOSE:To enable the formation of electrodes to the lower GaN layer by forming an apertuer in the surface GaN layer by a method wherein two or more of GaN layers are formed on a substrate, and a protection film is formed on the surface; next, an aperture is formed in the protection film, and heat treatment is carried out in a gas atmosphere containing hydrogen chloride gas. CONSTITUTION:An N type GaN layer 2 and a P type GaN layer 3 of insulation or high resistivity are formed on a sapphire substrate 1, and an Si dioxide film 10 is deposited on the GaN layer 3 of the outermost surface. Using this Si dioxide film 10 as the protection mask member, after an aperture is selectively provided thereto, heat treatment is carried out at 500 deg.C with flows of the mixed gas of AR and HCl, when the GaN layer 3 of the outermost surface exposed to this aperture is removed; accordingly, the lower GaN layer 2 is exposed. Next, the Si dioxide film 10 the protection film is removed; thereafter, an Al film is formed by evaporation and patterned into the first electrode layer 4 and the second electrode layer 11.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing a gallium nitride (hereinafter referred to as GaN) semiconductor device, and more particularly to a method for forming electrodes on GaN.

Conventional configurations and their problems Although GaN is seen as a promising semiconductor material for blue light-emitting devices, large single crystals are difficult to realize, and usually
It is epitaxially grown on an electrically insulating sapphire substrate using a vapor phase method.

GaN is a crystal with strong ionic bonding properties, and is a crystal with strong ionic bonding properties.
Compared to covalent crystals such as t) and gallium arsenide (GaAs), the crystal is incomplete and contains many crystal defects such as nitrogen (N) vacancies. Furthermore, in this GaN crystal, nitrogen vacancies act as donors, so it often becomes a low-resistance n-type semiconductor even without adding impurities. Therefore, even if an acceptor impurity is added, most of it will be spent on charge compensation, and at most it will become an insulator or a high-resistance p-type (also called π-type) semiconductor. A p-type semiconductor cannot be obtained. For this reason, GaN blue light emitting elements often have an i(π)n junction structure rather than a perfect pm junction structure. 1st
The figure is a schematic cross-sectional view of a conventional GaN light emitting device.
Zinc (Z) is added to n-type GaN layer 2 on sapphire substrate 1.
High resistivity i(π) type GaN layer 3 added with n)
is formed to a thickness of about 1 μm, and this i(π) type G
a A metal electrode layer 4 is provided on the N layer 3, and a thin metal wire 5 is crimped onto it.

However, forming electrodes on the n-type GaN layer 2 is quite troublesome. In other words, GaN crystal is a highly chemically stable substance and is difficult to chemically etch using chemicals.
A method is used in which an indium electrode part 6 is provided on the side surface of the N layer 2 and the other electrode part 7 is electrically connected to the metal stem 9 by a thin needle wire 8. However, n-type Ga
The thickness of the N layer 2 was only 20 to 30 μm at most, and it was extremely difficult to form the indium electrode portion 6 and to connect the thin needle wire 8 to this portion, resulting in poor productivity.

OBJECTS OF THE INVENTION The present invention has developed a technique that can selectively remove the GaN layer, thereby forming an opening in the surface GaN layer, through which the underlying GaN layer is exposed. The present invention provides a manufacturing method capable of forming electrodes.

Structure of the Invention In summary, the present invention provides at least two layers of G on a substrate.
a After forming the N layer, a protective film is formed on the surface of the outermost layer of the structure, and then the protective film is selectively removed to form an opening, and the film is exposed to a gas atmosphere containing hydrogen chloride gas. The step of removing the GaN layer of the outermost surface layer exposed to the opening through heat treatment and forming an electrode on the GaN layer below the outermost surface layer exposed to the opening. As a result, the uppermost surface and the G immediately below it
Since a flat electrode layer can be formed on each surface of the aN layer, GaN semiconductor devices can be assembled using normal wire bonding technology, greatly improving the manufacturability of GaN semiconductor devices. improves.

Description of examples Next, the present invention will be explained in detail using examples.

2A to 2C are cross-sectional views in the order of steps of the embodiment of the present invention, in which an n-type Ga with a thickness of about 30 μm is formed on a sapphire substrate 1.
This is a manufacturing process of a semiconductor device having an N layer 2 and an insulating or high resistivity p-type GaN layer 3 with a thickness of about 1 μm.

First, as shown in FIG. 2a, a silicon dioxide film 10 is deposited on the outermost GaN layer 3. Then, this silicon dioxide film 1o is used as a protective mask material, and after selectively providing openings in it, it is filled with a mixed gas of argon (Ar) and hydrogen chloride (HCl) gas with a mixing ratio of 2=1. When heat treatment is performed at 50°C for 20 minutes while flowing at a flow rate of 1.51 per minute, the Ga of the outermost surface exposed in this opening is
The N layer 3 is removed and the underlying G layer is removed as shown in Figure 2.
a N layer 2 is exposed. In addition, in this heat treatment,
When the heat treatment temperature is aOO℃, it is about 8 μm, and similarly, it is 60 μm.
Approximately 4 μm at 0°C, and approximately 2 μm at 500°C
The thickness of the GaN layer 3 on the outermost surface is at most 1 μm, so if heat treatment is performed under conditions exceeding this, the thickness of the GaN layer 3 on the outermost surface will be removed.
a The N layer 3 is reliably decomposed and removed, and the underlying GaN layer 2
surface appears.

Next, after removing the silicon dioxide film 10 as a protective coating,
An aluminum (CAl) film is deposited and patterned to form a first electrode layer 4 and a second electrode layer 11 as shown in FIG. 2C.

FIG. 3 is a schematic cross-sectional view of the semiconductor device of the embodiment shown in FIG. 2C installed on a metal stem 9. Electrode connections were made using a thin metal wire 5 by ordinary wire bonding technology. It is something.

Effects of the Invention According to the present invention, silicon dioxide is used as a protective film, and silicon dioxide is used as a mask to heat-treat the exposed surface of the GaN layer through the opening in a gas atmosphere containing hydrogen chloride gas. , selective removal of the GaN layer is performed, and by using this technique, it becomes possible to form a planar electrode portion in a semiconductor device using GaN crystal, and the manufacturability is significantly improved.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a conventional GaN light emitting device, FIG. 2 a-C is a step-by-step sectional view of an example of the present invention, and FIG. 3 is a GaN light emitting device obtained in an example of the present invention. FIG. 1... Sapphire substrate, 2... N-type G
a N layer, 3...i (π) type Ga N layer,
4, 11...electrode layer, 5...metal thin wire (bonding wire). Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure ○ ■ Figure 2 Figure 3

Claims (2)

[Claims] (1) After forming at least two gallium nitride layers on the substrate, forming a protective film on the surface of the gallium nitride layer, which is the outermost layer, and then selectively removing the protective film,
An opening is formed, and the gallium nitride layer of the outermost surface layer exposed to the opening is removed by heat treatment in a gas atmosphere containing hydrogen chloride gas, and the nitride layer below the outermost surface layer exposed to the opening is removed. A method for manufacturing a gallium nitride semiconductor device, which includes a step of forming an electrode on a gallium layer. (2) Claim 1 in which the outermost gallium nitride layer is insulating or has a conductivity opposite to that of the underlying gallium nitride layer.
A method for manufacturing a gallium nitride semiconductor device as described in 1.