JPS61283120A - Ohmic electrode - Google Patents

Abstract

PURPOSE:To form an ohmic electrode having high reliability and low contacting resistance by forming a metal film made by sequentially laminating Ti and Pt on a semiconductor of specific carrier density. CONSTITUTION:A collector contact layer 2, a collector layer 3, a base layer 4, an emitter layer 5 and an emitter contact layer 6 are sequentially formed on a substrate 1 made of an Fe-doped insulating InP of a bipolar transistor. A portion made of InP and a portion made of In0.76Ga0.24As0.56P0.44 are selectively mesa etched with etchants of hydrochloric acid, phosphoric acid and sulfuric acid, hydrogen peroxide, water. Then, emitter base and collector electrodes 7, 8, 9 formed by sequentially laminating Ti and Pt are formed by a lifting-OFF method using a resist, an SiO2 is further accumulated by CVD, patterned to form a protective film 11, and a cover electrode 10 is formed by lifting OFF of the resist. Since the Ti lacks a reaction with the semiconductor and the Pt prevents Au of the cover electrode 10 from invading to the semiconductor layer, the decrease of the reliability due to the deterioration of the electrodes can be largely suppressed. The electrodes made of the Ti and the Pt are ohmic for the P-type semiconductor to be simply manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ohmic electrode for a semiconductor device, and particularly to a highly reliable ohmic electrode.

[Conventional technology]

In recent years, research and development has been actively conducted on electronic devices using compound semiconductors such as InP and GaAS because they can operate at higher speeds than devices using 81. By the way, in these compound semiconductors, the mobility of electrons is generally higher than that of holes, so they are used in n-channel field effect transistors,
Types that inject a high current into the n-type semiconductor, such as npn-type bipolar transistors, can operate at higher speeds, but in the above types of devices, in order to obtain high reliability, it is necessary to The ohmic electrode formed in this way occupies a very important position. Conventionally, electrodes using AuGe have been known (magazine' IEEE, ELECT
RONDliVICE LE'rTEBjS' vo
1, EDL-5 No. 6214 (1984)).

[Problem that the invention seeks to solve]

However, in electrodes using such alloys, the noodles tend to react with the semiconductor, and especially when used as an electrode for injecting high current, heat is generated at the electrode part, promoting the reaction between the semiconductor and the electrode, and deteriorating the element. It had a drawback that was a major factor.

An object of the present invention is to eliminate the above-mentioned drawbacks and provide an ohmic electrode having high reliability and low contact resistance.

[Means for solving problems]

The present invention uses at least 1X10c! This is an ohmic electrode characterized by forming a metal film formed by sequentially laminating at least Ti and PT on a semiconductor containing n-type impurities of IL or higher. Examples will be described in detail.

FIG. 1 is a cross-sectional view of a quapolar transistor according to an embodiment of the present invention. This bipolar transistor has a layer thickness of 1μ on a substrate 1 made of Fe-doped insulating InP and a carrier concentration of I x 10 ``cm''.
Type Ino, 7=Gc 6. uAa 6.44P o,
Collector contact layer 2 consisting of ss, layer thickness 0.3
The collector layer 3 is made of n-type InP with a carrier concentration of 1X10 cm at 0.21 Lm, and the p-type InP (A+, xAa6
, 44Pe, ss, the layer thickness is 0.24
Yaria concentration is 2×10CI! The emitter layer 5 is made of L n-type InP, the layer thickness is 0.2μ, and the carrier concentration is lX1.
An emitter electrode 7 having an emitter contact layer 6 made of 0cIrL n-type InP, and having Ti and steam laminated in sequence;
A pace electrode 8, a collector electrode 9, a cover electrode 10 for wire bonding made of noodles, and S10. protective film 11
It is composed of

To form a device with the structure of the present invention, a collector contact ! ! ``ia2's'' From the layer where the collector layer 3, base layer 4, emitter layer 5, and emitter contact layer 6 are formed, the InP portion is etched using an etching solution of hydrochloric acid and phosphoric acid with Ino, ?1Gao, and 5AI.
5o, saP 6. An emitter electrode 7 and a base electrode in which T1 and PT are sequentially laminated by a lift-off method using a 0-order resist in which the portion consisting of M is selectively mesa-etched using an etching solution consisting of sulfuric acid, hydrogen peroxide, and water. 8. Form the collector electrode 9, and further perform S10. After depositing and patterning using G2 to form a protective film 11 ft thick, a cover electrode 10 is formed by lift-off using a resist.

In the above examples, the carrier concentration was set to 1×10cIIL.
A type semiconductor is provided as an electrode contact layer, and a Ti
Since the electrode is made of PT and PT, the contact resistance can be made comparable to that of conventional non-alloy electrodes, so there is no deterioration of the device characteristics due to an increase in parasitic resistance. Moreover, since PT prevents the noodles of the cover electrode 10 from penetrating into the semiconductor layer, it is said that reliability is greatly reduced due to deterioration of the electrode. It is known that electrodes made of TI and PT can also serve as ohmic electrodes for p-type semiconductors, and can be used as ohmic electrodes for both pens, which simplifies the manufacturing process. . Therefore, it is possible to manufacture a highly reliable element without deteriorating the characteristics compared to the conventional method, and the manufacturing yield can be improved because the post-process steps can be simplified.

In addition, in the present invention, any mixed crystal composition may be used as long as it is an n-type conductive semiconductor having a carrier concentration of lXl0"m' or more, the TI serving as the TFC electrode may be of any thickness, and the PT may be of any thickness. It can be of any thickness as long as it can prevent noodles from entering.

〔Effect of the invention〕

As explained above, according to the present invention, at least lX1
An ohmic electrode with high reliability and low contact resistance formed by gold J[, which is formed by sequentially laminating at least Ti and PT on an n-type conductive semiconductor having a carrier concentration of 0 cm or more. It has the effect of being able to obtain the following.

[Brief explanation of drawings]

FIG. 3 is a schematic cross-sectional view of a register. 1... Substrate, 2... Collector contact layer, 3...
- Collector layer, 4... Base layer, 5... Emitter layer, 6... Emitter, contact layer, 7... Emitter electrode, 8... Base electrode, 9... Collector electrode, 1
0...Cover electrode, 11...Protective film

Claims (1)

[Claims] (1) A metal film formed by sequentially laminating at least Ti and Pt is formed on an n-type conductive semiconductor having a carrier concentration of at least 1×10^1^9 cm^-^3 or more. Ohmic electrode.