JPH0320090A - Manufacture of compound semiconductor element - Google Patents

Abstract

PURPOSE:To form a highly reliable protective film by realizing low resistivity by alloying silicon with electrode metal in an electrode section. CONSTITUTION:After gold germanium (Au/Ge) alloy 2 is deposited on an Si doped N-type GaAs substrate 1, a silicon thin film 3 is formed through a plasma CVD method. In an electrode formation section, an allow section 4 of Au/Ge electrode and silicon is formed for resistivity just as a thin film 3 is formed. Therefore, after a protective film of high resistance silicon is formed, shaping of an aperture for electrode formation becomes unnecessary, thereby eliminating troubles caused by etching of a protective film. Since silicon has a thermal expansion coefficient and a lattice constant which are comparatively in the neighborhood of those of a compound semiconductor such as GaAs or InP, and has a good thermal conductivity, stresses due to heat distortion, etc., can be reduced. A protective film having good reliability can be formed in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing a compound semiconductor device for extremely easily forming a protective film on a compound semiconductor device on which electrodes are formed.

Conventional technology GaAs, GaAIAs, InP or InGaAs
Compound semiconductors such as P have high electron mobility and can be used as direct transition materials, allowing them to realize functions that cannot be found in semiconductor devices made from ordinary St, such as optical semiconductor devices such as ultra-high-speed transistors and light-emitting diodes. It is an extremely useful semiconductor material.

Generally, in semiconductor devices, a thin film must be used to prevent deterioration of the device surface from moisture and oxygen in the air, or to form partial electrodes. Conventionally, Si02 or SiN has been used as a thin film for the above purpose.
Such recording films have been used. The formation of a thin film in the prior art will be explained.

Figure 4 shows I n P / I n Ga As
FIG. 2 is an explanatory diagram showing a case in which current confinement is performed by forming electrodes only on a portion of a light emitting diode (LED) made of P as a column. N-type InP 11, P-type 1nGaAsP active layer 12
, P type! 4 of nP13 and P-type InGaAsP14
After an epitaxial substrate for a light emitting diode consisting of layers is fabricated by liquid phase epitaxial growth, a Si02 film 61 is deposited over the entire surface to insulate areas other than the electrodes by chemical vapor deposition (CVD) using silane and oxygen as gas sources.
Shaped by law. After that, the Si02 film in the electrode forming part was removed by photolithography and chemical etching,
The electrode 21 is partially formed in accordance with that position. moreover,
The element fabrication is completed by forming the metal 5 for facilitating bonding and the back electrode 71 having a hole for extracting light in accordance with the position of the electrode 21. In this light emitting diode, current flows in a concentrated manner in the region below the electrode of the active layer 12 due to the Si02 film 61, which is an insulator, and correspondingly, light emission is also limited to the region below the electrode, resulting in extremely narrow light emission. A region can be formed. Thereby, the coupling efficiency with an optical fiber having a small core diameter can be increased, and the application value as a light source for optical fiber transmission can be increased.

FIG. 5 is an explanatory diagram of another conventional technique in which a surface protective film is formed on a light emitting diode made of GaAIAs as an example. P-type GaAIA on P-type CaAs substrate 15
s (mixed crystal ratio X=0.7) 16, P-type GaArAs active layer (X=0.35) 17, and N-type CaAIAs (
After elongating the three layers 18 (X=0.7) by a liquid phase epitaxial method and separating the elements by mesa etching, a SiN film 62 is formed on the surface by a plasma CVD method.

Thereafter, a portion of the SiN film is removed using photophosphorography technology and dry etching using SF6 gas to form the electrode 22, and the back electrode 72 is further formed to complete the device fabrication. When the GaAIAs mixed crystal ratio becomes high, it is easily oxidized by oxygen and moisture in the air to form light-absorbing oxides, reducing the light-emitting efficiency of the light-emitting diode. To prevent this, SiN film 62 is used.

Problems to be Solved by the Invention In the above-mentioned conventional techniques for forming a protective film, SiO2 and S
Since an insulator such as iN is used, after the protective film is formed, it is necessary to use techniques such as etching to open a window for the electrode shape, which complicates the manufacturing process.

Furthermore, in the example shown in Fig. 4, stress is generated internally due to the difference in thermal expansion coefficient between the S i O z film and the compound semiconductor, and with the passage of high current, element deterioration occurs in which the luminous efficiency decreases and reliability is reduced. This was the cause of the decline. Furthermore, in the example shown in FIG. 5, the resist is broken at the mesa edge, so the SiN film at the mesa portion may be removed at the same time as the etching for forming the electrode. In this case as well, the aforementioned oxidation occurs during energization at high temperatures, impairing reliability. The above problems cannot be improved in any way even if a protective film is formed after forming the electrode.

The present invention eliminates the problems associated with the above-mentioned prior art, is simple,
Another object of the present invention is to provide a manufacturing method for forming a highly reliable protective film.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention forms a thin film of silicon with high resistivity on the surface of a compound semiconductor element partially formed with metal electrodes, and As a means for achieving this goal, the electrode metal and silicon are alloyed to reduce the resistance, and the high-resistance silicon is used as a surface protection film on the surface of the element other than the electrode portion.

Function: High-resistance silicon is easily alloyed with metals, mainly gold and aluminum, resulting in low resistance. After forming a high-resistance silicon protective film, there is no need to open a window for electrode formation, and this process is attached to the etching of the protective film. You can eliminate inconvenience. In addition, silicon has a thermal expansion coefficient and lattice constant that are relatively similar to those of compound semiconductors such as GaAs and InP, and also has good thermal conductivity, so silicon can reduce stress caused by thermal distortion and other factors, making it a highly reliable protective film. It can be formed.

EXAMPLES The present invention, which has been explained above, will be explained in more detail using examples.

FIG. 1 is an example in which the effect of the present invention was confirmed using N-type CaAs as a compound semiconductor. Si-doped N-type C
Gold germanium (A u / G
e) After depositing Alloy 2 to a thickness of 200 nm, by plasma CVD method using silane (SiH4) gas,
A silicon thin film 3 was formed to have a thickness of about 50 nm.

An electrode was applied to this sample to examine the surface conductivity with and without the Au/Ge electrode. In the electrode forming part, the alloy part 4 of the A u / G e electrode and silicon is formed at the same time as the thin film is formed.
However, the resistance remained high in the silicon-only part, indicating that the above-mentioned effect can actually be used.

In contrast to the prior art shown in FIG. 4, FIG.
FIG. 2 is a configuration diagram when used for current confinement of a GaAsP light emitting diode. N-type 1nP11, P-type 1nGaAsP active layer 12, P-type 1nP13, and P-type 1nGaAs
An electrode of gold/zinc (Au/Zn) alloy 21 with a diameter of 35 μm was placed on the tuffle heterojunction formed in the order of P14.
1 is formed to a thickness of 400 nm, and silicon 3 is formed to a thickness of 50 nm.
The thickness was estimated at m. Furthermore, gold 5 (2 μm) for bonding is formed on it by sandwiching titanium (Ti), and on the back side, an A u /G e electrode 71 is formed with a hole corresponding to the Au / Zn electrode 21 . was formed. In the fabricated device, light emission occurs at the bottom of the electrode 21, and its diameter is approximately 40 mm.
It was confirmed that the current was well constricted due to the high resistance silicon.

The results of conducting an electric current test on the same sample in a high-temperature atmosphere showed that the lifespan was estimated to be two orders of magnitude better than that of the conventional technology shown in Figure 4, and the results of the coefficient of thermal expansion were extremely reliable. It was confirmed that the present invention is effective.

Similarly, FIG. 3 is a structural diagram when the present invention is applied to the conventional example shown in FIG. P on the P-type GaAs substrate 15
type GaAIAs (X=0.7)16, P-type GaAIAs
(X=0.35)17, P-type GaAIAs (X=0.7
) 18, an A u / G e electrode 22 with a diameter of 100 μm is placed on the surface of a double heterojunction of about 1 μm.
After forming the semiconductor device to a thickness of 1, the elements were separated by mesa etching. After that, Au/Zn alloy 72 was used as the back electrode.
After that, silicon 3 was formed to a thickness of 50 nm over the entire surface. In this case as well, the electrode 22 and the silicon 3 easily formed an alloyed portion 4, and the other surfaces were covered with high-resistance silicon. In this example, since there was no etching step after forming the silicon thin film 3, even the mesa edges were completely protected and a good protective film was formed. For this reason, there was almost no deterioration in luminous efficiency even in current tests at high temperatures and high humidity, and a significant reliability improvement effect was observed.

In the above embodiments, it is desirable that the thickness of the silicon thin film to the thickness of the metal electrode be several tens of percent or less. There was a tendency for it to get worse.

Effects of the Invention The present invention makes it possible to fabricate a protective film for a compound semiconductor device using a simple method, and further improves the reliability of the device significantly.The industrial value of the present invention when actually used is It can be said that this is extremely high.

In the embodiments of the present invention, GaAIAs-based and InP-based light emitting diodes have been described, but as types of compound semiconductors, InGaAIAs, InGaA I P
It goes without saying that other materials may be used instead of the light emitting diode, and similar effects can be obtained by using other elements such as a semiconductor laser, a light receiving element, a field effect transistor, or a plurality of the above elements instead of the light emitting diode.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the structure of an example for confirming the effect of the present invention, FIG. 2 is a cross-sectional view showing the structure of an example in which the present invention is applied to an InP-based light emitting diode, and the wi
A cross-sectional view showing the structure of another embodiment applied to an aAIAs-based light emitting diode, FIG. 4 is a cross-sectional view of an InP-based light emitting diode according to the prior art, and FIG. 5 is a cross-sectional view of a GaAIAs-based light emitting diode according to the prior art. .

Claims (4)

[Claims] (1) A thin film of silicon having high resistivity is formed on the surface of a compound semiconductor element formed by partially forming a metal electrode, including the upper part of the electrode, and the silicon and the electrode metal are formed in the electrode part. A method for manufacturing a compound semiconductor device, characterized in that the resistance is reduced by alloying, and the device surface other than the electrode portion is covered with the high-resistance silicon thin film. (2) The method for manufacturing a compound semiconductor device according to claim 1, wherein the electrode metal is mainly made of gold or aluminum. (3) The method for manufacturing a compound semiconductor device according to claim 1 or 2, wherein a protrusion or a depression is partially formed on the surface of the compound semiconductor device. (4) A compound semiconductor according to claim 1, 2 or 3, wherein the thickness of the silicon thin film formed on the metal electrode is within several tens of percent of the thickness of the metal electrode. Method of manufacturing elements.