JPS63124465A - Manufacture of bipolar transistor - Google Patents

Abstract

PURPOSE:To obtain a bipolar transistor having excellent high-speed and high-frequency characteristics and consisting of a compound semiconductor by forming a collector electrode self-aligning with a fine base electrode by shaping an insulating film having superior adhesion onto the base electrode. CONSTITUTION:An N GaAs layer 2, a P-GaAs layer 3 and an N-AlGaAs layer 4 are superposed onto semi-insulating GaAs 1 through an MBE method, H ions are implanted and dielectric isolation 5 is conducted, and ohmic AuGeNi 6a and SiO2 7 are stacked. A photo-resist mask 8 is executed, an emitter electrode 6 is shaped through ion milling, and the N layer 4 is etched in an isotropic manner by HPO4+H2O2+H2O to expose the P layer 3. The mask 8 is removed, a photo-resist 9 is formed, and AuZnNi 10a is superposed on the emitter electrode 6 through self-alignment. The resist 9 is gotten rid of and AuZnNi 10a is coated with SiO2 11, a resist 13 is executed, SiO2 11 and the P layer 3 are taken off through etching to expose the P layer 3, AuGeNi 12a is evaporated, and a collector electrode 12 self-aligning with a base electrode 10 is shaped onto the layer 2. The layer 12a is lifted off, thus completing a bipolar transistor.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing a bipolar transistor.

[Conventional technology]

Bipolar transistors have an excellent feature of higher current driving capability than field effect transistors. Therefore, in recent years, research and development of bipolar transistors using not only Sj but also compound semiconductors such as GaAs have been actively conducted. In particular, bipolar transistors using compound semiconductors are developed by using molecular beam epitaxy (hereinafter referred to as MBE) technology.
It has many advantages, such as the base junction can be configured as a heterojunction, and the emitter injection efficiency can be maintained high even if the base is highly doped.

In order to increase the frequency of such compound semiconductor bipolar transistors, it is necessary to miniaturize the emitter and base electrodes, and at the same time arrange them in a self-aligned manner. Must be placed in a self-consistent manner.

FIGS. 3(a) to 3(c) are cross-sectional views of a semiconductor chip shown in order of steps for explaining a conventional method of manufacturing a bipolar transistor.

In this conventional example, first, as shown in FIG.
A semiconductor layer 2' made of n-GaAs, a semiconductor layer 3' made of P-GaAs, and an n-
Sequentially M
It is formed by the BE method, and furthermore, A IJ of a predetermined pattern is formed.
After forming an emitter electrode 6' made of a GeNi layer and an Si02 film 7 thereon, an AuZnNi layer 10a' is formed on the entire semiconductor layer 3' using this as a mask. Here, on the emitter electrode 6' made of an AuGeNi layer, a 5i02 film 7' and an A u Z n
1 oa' of the Ni layer remains.

Subsequently, a photoresist film 13' having a predetermined pattern is formed to cover the emitter electrode 6' so that the width WB of the base electrode becomes a predetermined value.

Next, as shown in FIG. 3(b), the photoresist film 13
Using the photoresist film 15 as a mask, the entire AuZnNi layer 10a' is etched to form the base electrode 10', and the surfaces of the semiconductor layer 3' and the semiconductor layer 2' are removed by isotropic etching. semiconductor layer 2
An ohmic metal AuGeNi layer 12a' is deposited on the surface of the substrate 12a' from above.

Next, as shown in FIG. 3(c), the photoresist film 13' is dissolved and removed in an organic solvent to form the collector electrode 12'.

[Problem that the invention seeks to solve]

In the conventional bipolar transistor manufacturing method described above, the base electrode is patterned using a photoresist formed thereon, but at this time, the adhesion between the photoresist 1 and the A u Z n N i layer of the base electrode is poor, so that it is not normally used. There is a drawback that the phosphoric acid or sulfuric acid-based etching solution used in the etching soaks in and etches the AuZnNi layer as well.

Therefore, in this method, the lower limit of the width Wa of the base electrode is about 2 μm, and it is extremely difficult to make the base electrode smaller than that.

Therefore, in the structure according to the conventional method, the parasitic base-collector junction capacitance under the base electrode is large, which hinders the improvement of the high-speed and high-frequency characteristics of the bipolar transistor.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a bipolar transistor having extremely excellent high-speed and high-frequency performance by miniaturizing the base electrode and forming a collector electrode in self-alignment with the base electrode.

[Means for solving problems]

The method for manufacturing a bipolar transistor of the present invention includes forming an emitter layer of one conductivity type and an emitter layer in a predetermined pattern on a first semiconductor layer of one conductivity type and a second semiconductor layer of the opposite conductivity type, which are sequentially deposited on a semi-insulating substrate. a step of forming an electrode; a step of selectively forming a first conductor layer on the second semiconductor layer;
forming an insulating film and a photoresist film with a predetermined pattern on the emitter electrode and the first conductor layer; using the photoresist film as a mask, the insulating film, the first conductor layer, and the second semiconductor layer are formed; Forming a base electrode made of the first conductor layer by sequentially removing it by anisotropic and isotropic etching, and forming a collector electrode on the first conductor layer using the photoresist film and the base electrode as a mask. The collector electrode is formed in self-alignment with the base electrode.

[Effect]

In the present invention, since an insulating film made of an oxide film or a nitride film with good adhesion is formed on the base electrode to protect it, even if the width WB of the base electrode is narrowed to about 0.5 μm, the photoresist film is The underlying A u Z nNj layer is not etched, a fine base electrode and a collector electrode self-aligned thereto can be formed, and a compound bipolar transistor with extremely excellent high speed and high frequency performance can be realized.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

1(a) to (f) are cross-sectional views of a semiconductor chip shown in the order of steps for explaining one embodiment of the present invention.In this embodiment, first, as shown in FIG. 1(a), A semiconductor layer 2 made of n-GaAs is sequentially formed on the surface of the GaAs semi-insulating substrate 1.
The semiconductor layer 3 consisting of A, s and n-Δ(! G a A
A semiconductor layer 4 made of S is formed by the MBE method, and then hydrogen ions H are ion-implanted into other parts except for the part where the bipolar transistor is to be formed to form the insulating region 5.

Next, as shown in FIG. 1(b), the ohmic metal AuGcNi layers 6a and 5j02 of the semiconductor layer 4 are
The films 7 and 7 are sequentially formed.

Next, as shown in FIG. 1(c), a photoresist film 8 of a predetermined pattern is formed, and using this as a mask, 5i02
The film 7 and the AuGeN i layer 6a are removed by anisotropic etching using Ar4 ion milling to form the emitter electrode 6, and the semiconductor layer 4 is isotropically etched using a mixture of phosphoric acid, hydrogen peroxide, and water. The surface of the semiconductor layer 3 is exposed by etching. Here, the emitter electrode 6 is protected by a Si 02 film 7 with good adhesion.

Next, as shown in FIG. 1(d), the photoresist 1 to film 8
After removing the ohmic metal A of the semiconductor layer 2, a photoresist film 9 is formed on the insulating region 5.
A uZnNi layer 10a is deposited on the emitter electrode 6 in a self-aligned manner.

As shown in the above process, even if the emitter electrode 6 is miniaturized to 2 μm or less, since there is a protective film made of the SiO2 film 7, the emitter electrode 6 will not be over-etched and will remain self-aligned as designed. AuZnNi layer 10a
Layer 0a.

Next, as shown in FIG. 1(e), after cleaning with an organic solvent to dissolve the photoresists 1 to 9, a Si○2 film 11 is deposited on the entire surface by CVD, and then the collector electrode After forming the photoresist film 13 for formation, the entire SiO2 film 11 is etched with buffered hydrofluoric acid, and further,
The semiconductor layer 3 is etched using a mixture of phosphoric acid, hydrogen peroxide, and water to expose the semiconductor layer 2. Subsequently, an ohmic metal AuGeNi layer 1.2a of the semiconductor layer 4 made of n-GaAs is deposited from above. At this time, a collector electrode 12 is formed on the surface of the semiconductor layer 2 in a self-aligned manner with the base electrode 10.

Finally, as shown in FIG. 1(f>), the AuGeNi layer 12a is lifted off using an organic solvent to form a bipolar 1-helangister of the compound semiconductor layer 2a.

Therefore, by the process shown here, even if the width of the base electrode 10 becomes 2 μm or less, the base electrode 10 is not over-etched because of the protective film made of the SjO□ film 11, and the self-aligned arrangement of the collector electrode 12 is maintained. can be done.

FIG. 2 is a plan view of a semiconductor chip for explaining one embodiment of the present invention.

In this embodiment, by the manufacturing method described above, an emitter electrode 6 and a self-aligned emitter electrode 6 are formed in an element formation region surrounded by an insulating region 5 on a semi-insulating substrate 1, as shown in FIG. A bipolar transistor made of a compound semiconductor is produced, which includes a base electrode 10 disposed at the base electrode 10 and a collector electrode 12 disposed in self-alignment with the base electrode 10.

In the embodiment of the present invention, 5i02 is used as the insulating film.
Although a film is used, the effect is the same even if a nitride film such as SiNx is used.

Furthermore, although GaAs has been described as a semiconductor, other compound semiconductors such as JnP may be used instead of GaAs.

〔Effect of the invention〕

As explained above, the present invention provides an insulating film on the base electrode, forms the base electrode into an extremely fine pattern with a width of 0.5 to 0.2 μIn, and furthermore, the collector electrode is formed in a self-aligned manner to the base electrode. This arrangement has the effect of realizing a compound semiconductor bipolar transistor with excellent high speed and high frequency performance.

This makes it possible to mass-produce bipolar transistors with cut-off frequencies of 300H or more, thereby reducing costs, and to integrate frequency dividers with operating frequencies of 20 GH2 or more.

[Brief explanation of the drawing]

1(a) to (f) are cross-sectional views of a semiconductor chip shown in the order of steps for explaining an embodiment of the present invention, and FIG. 2 is a cross-sectional view of a semiconductor chip for explaining an embodiment of the present invention. The plan view and FIGS. 3(a) to 3(c) are cross-sectional views of a semiconductor chip shown in order of steps for explaining a conventional method of manufacturing a bipolar transistor. 1.1'...semi-insulating substrate, 2.2', 3.3'
. 4.4'...Semiconductor layer, 5...Insulating region, 6.6'
...Emitter electrode, 6a-...AuGeNi layer, 7.
7′...5i02 film, 8,9...photoresist film,
10°10'--Base electrode, 10a, 10a'-
AuZnNi layer, 1l-3i02 film, 12.12'...
・Collector electrode, 12a, 12a''-AuGeNi layer,
13... Photoresist film. Foil 2 figure

Claims (1)

[Claims] forming an emitter layer and an emitter electrode of one conductivity type in a predetermined pattern on a first semiconductor layer of one conductivity type and a second semiconductor layer of an opposite conductivity type sequentially deposited on a semi-insulating substrate; a step of selectively forming a first conductor layer on the semiconductor layer; a step of forming an insulating film and a photoresist film in a predetermined pattern on the emitter electrode and the first conductor layer; using the photoresist film as a mask, a step of sequentially removing the insulating film, the first conductor layer, and the second semiconductor layer by anisotropic and isotropic etching to form a base electrode made of the first conductor layer, and the photoresist film and the second semiconductor layer. A method for manufacturing a bipolar transistor, comprising the step of forming a collector electrode on the first conductor layer using the base electrode as a mask, and forming the collector electrode in a self-aligned manner with the base electrode.