JPS62143464A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form base electrodes separated from an emitter electrode with a minute interval in a small number of processes, by forming base electrodes in self-alignment by the use of overhanging structure generated by wet etching. CONSTITUTION:Pattern formation of an emitter electrode 11 made of AuGe/Ni/ Au making ohmic contact is performed on an emitter layer 1. By wet etching with the electrode 11 serving as mask, a base layer 2 is exposed to form an overhanging part 12. Then, pattern formation of base electrodes 13 is performed in self-alignment on the base layer 2 by lift-off process, in which resist is formed on a given part, and evaporated with CrAu from the surface, and then removed. Thereafter, removing a given region of the base layer 2 makes a collector layer 3 become exposed to form collector electrodes 14 on it.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of manufacturing a bipolar transistor.

(Prior Art) In a bipolar transistor, the performance of the device is greatly improved by forming the base electrode near the emitter electrode. However, in the past, since the emitter electrode and the base electrode were formed separately, the distance between these electrodes had to be increased. Recently, a self-line heterojunction bipolar transistor has been described in the Proceedings of the General Conference of the Institute of Electronics and Communication Engineers (Spring 1985), pages 2-370 and 2-371. When forming the base electrode, the base layer is exposed by reactive ion etching technology (using the SiNx film with the emitter electrode pattern as a mask), and the sidewalls of the remaining emitter layer are etched with SiO□. cover with This SiO2 film is used as a frame film between the emitter layer and base electrode to form a base electrode.

Thereafter, the base electrode is buried with an insulator, unnecessary material on the emitter layer is removed, and an emitter electrode is formed on the emitter layer.

In this way, the base electrode is formed in a self-aligned manner. This reduces the distance between the base electrode and the emitter electrode.

(Problems to be Solved by the Invention) However, this method has the problem that the number of steps required to form the base electrode and the number of steps required to form the emitter electrode thereafter are large and complex.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing high-performance bipolar transistors using self-line technology with fewer man-hours and simple steps by eliminating the large number of man-hours and complexity described above.

(Means for Solving the Problems) In order to solve the above problems, the present invention prepares a semiconductor substrate on which an emitter layer, a base layer, and a collector layer are formed in order from the surface, and places an emitter electrode on the emitter layer. - By forming a mother turn and performing wet etching using the emitter electrode as a mask, the emitter layer including a part under the emitter electrode is removed and the base layer is exposed, and the base layer is etched from a direction perpendicular to the surface of the substrate. Base electrodes are formed on the base electrical layer by depositing metal on the emitter layer with minute intervals, and then a collector electrode connected to the collector layer is formed.

(Function) According to the present invention, as explained above, by performing wet etching using the emitter electrode as a mask, the base layer is exposed, and a part of the emitter layer under the emitter charge is side-etched, and the emitter layer is etched in the direction perpendicular to the substrate surface. Since the base electrode is formed in a self-aligned manner by depositing metal from the base electrode, it is possible to easily form the base electrodes spaced apart from each other with minute intervals in the emitter layer.

(Embodiment) FIGS. 1(a) to 1(d) are cross-sectional views of a bipolar transistor for explaining one embodiment of the present invention, which will be explained below along with the drawings.

As shown in Figure 1(,), from the surface, 1 is layered Ga.
2 is an emitter layer consisting of an As layer and an n-type kAGaAs layer, 2 is a base layer consisting of a p-type AlGaAs layer or a p-type GaAs layer, and 3 is a collector layer consisting of an n-type GaAs layer and a square-type GaAs layer. Yes, 4 is semi-insulating G
The substrate is aAa or n-type GaAs.

First, as shown in FIG. 1(a), an AuGe/Ni/Au emitter electrode 11 making ohmic contact is patterned on the emitter layer 1 using a lift-off method. Next, as shown in FIG. 1(b), using this emitter electrode 11 as a mask, wet etching is performed using an NH40H-H20□H2O-based etching solution to expose the base layer 2 and to -Hang part 1
form 2. Next, a renost (not shown) is formed in a predetermined portion, and as shown in FIG. 1(c), CrAu is deposited from the surface to form an ohmic contact, and the resist is removed to lift off the base layer in a self-aligned manner. A base electrode 13 is patterned on 2. After that,
As shown in FIG. 1(d), a bipolar transistor is formed by removing a predetermined region of the base layer 2 to expose the collector layer 3, and forming a collector electrode 14 on the collector layer 3. be done.

In addition, in the embodiment of the present invention, the opening part 1
The width of the base electrode 13 is approximately the same as the depth of the wet etching, and the thickness of the base electrode 13 and the width of the base electrode 1 can be adjusted by selecting the etching depth and the width of the over-etching part 12.
The distance between the 3m emitter layers 1 can be varied.

According to the embodiment of the present invention, the performance of the Pipo2 transistor can be improved because the base electrodes α13 spaced apart from each other with a small interval can be easily formed in the emitter layer l.

(Effects of the Invention) As described in detail above, according to the present invention, the base electrode is formed in a self-line manner using the over/under structure formed by wet etching, so that the emitter can be formed in an extremely simple manner with a small number of steps. Since the base electrodes can be created with minute intervals between the electrodes, and the electrodes are formed in a self-aligned manner, the distance between the electrodes and the active area does not depend on the accuracy of mask alignment, and therefore, high-performance bipolar electrodes can be created. - Transistors can be created with good uniformity.

[Brief explanation of drawings]

FIGS. 1(a) to 1(d) are schematic cross-sectional views of a bipolar transistor for explaining the present invention in detail. DESCRIPTION OF SYMBOLS 1... Emitter layer, 2... Base layer, 3... Collector layer, 4... Substrate, 11... Emitter electrode, 12
... Overhang part, 13 ... Base electrode, 1
4...Collector electrode. Patent applicant: Oki Electric Industry Co., Ltd. Fig.1

Claims (1)

[Claims] A step of preparing a semiconductor substrate on which an emitter layer, a base layer, and a collector layer are formed in order from the surface, a step of patterning an emitter electrode on the emitter layer, and a step of wet-wetting using the emitter electrode as a mask. a step of removing the emitter layer including a part under the emitter electrode and exposing the base layer by etching, and depositing metal from a direction perpendicular to the surface of the substrate to form minute intervals in the emitter layer. A method for manufacturing a semiconductor device, comprising the steps of: forming spaced apart base electrodes on the base electrode layer; and then forming a collector electrode connected to the collector layer.