JPH02140939A - Manufacture of bipolar transistor - Google Patents

Abstract

PURPOSE:To increase the operation speed by laminating a base layer, laminating an amorphous film or a polycrystalline film on or on and around the surface of the base layer, on which base electrodes are to be formed, and then forming an emitter layer. CONSTITUTION:In a process of exposing a base layer 3, an amorphous film 4 is formed beforehand on the top of the base layer 3 over a range of etching for forming base electrodes 7. Etching automatically stops when it reaches the amorphous film 4 and the amorphous film 4 is etched with a different etching liquid. Therefore, the base layer 3 can be securely exposed even if it is thin. Thereby a high-operation-speed bipolar transistor having the thin base layer 3 can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a bipolar transistor.

[Conventional technology]

FIG. 4 is a cross-sectional view showing the manufacturing method and structure of a conventional bipolar transistor, for example. In the figure, 1 is a substrate, 2 is a collector layer deposited on this substrate 1, and 3 is a collector layer deposited on the collector layer 2. The base Fm, 5'a is an emitter deposited on the base layer 3. 6 is emitter 5a
7 is a base electrode formed on the base layer 3 , and 8 is a collector electrode formed on the collector layer 2 . 31 is a resist for emitter mesa, and 32 is a resist for base mesa.

Next, a method for manufacturing this bipolar transistor will be explained.

A collector layer 2, a base layer 3, and an emitter layer 5 are formed on the substrate 1.
Each layer of A is deposited in turn using a crystal growth method (4th A).
figure). Next, a resist is applied to the entire surface of the emitter 5a and lithography is performed to form an emitter mesa resist 31, and etching is performed using this resist as a mask. This etching is carried out until the etched surface reaches the base layer 3 (FIG. 4B). Next, the emitter mesa resist 31 is removed, a resist is applied again to the entire surface, lithography is performed, a base mesa resist 32 is formed, and etching is performed using this resist as a mask. This etching is performed until the etched surface reaches the collector layer 2 (the fourth
(Figure C), Next, the base mesa resist 32 is removed, and then resist coating, lithography, electrode deposition, and resist removal are repeated to form the emitter electrode 6. Base electrode 7
．． A collector electrode 8 is formed to complete the bipolar transistor (FIG. 4D).

[Problem to be solved by the invention]

Conventional bipolar transistors are manufactured through the steps described above. By the way, when trying to increase the operating speed of a bipolar transistor, it is necessary to make the base layer thinner. However, since this process uses normal etching to expose the base layer to the surface, when the base layer is made thin, it is difficult to stop the etching with good control when the base layer is exposed to the surface.

This invention was made to solve the above-mentioned problems, and it is possible to expose a thin base layer to the surface with good control, and it is possible to obtain a bipolar transistor with a thin base layer and a high operating speed. The purpose of this study is to obtain a method for manufacturing bipolar transistors that can be used.

[Means to solve the problem]

The method for manufacturing a bipolar transistor according to the present invention includes:
After the base layer is deposited, an amorphous or polycrystalline film is deposited on or around the surface of the base layer where a base electrode will be formed in the future, and then an emitter layer is formed.

[Effect]

In this invention, in the step of exposing the base layer, the structure is such that an amorphous film is formed in advance on the upper layer of the base layer in the area where etching is performed to form the base electrode, and this etching removes the amorphous film. Etching is automatically stopped when this point is reached, and the amorphous film is etched using a different etching solution, so even if the base layer is thin, the base layer can be exposed reliably.

〔Example〕

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

1 to 3 show a method for manufacturing a bipolar transistor according to an embodiment of the present invention. In the figures, 1 is a substrate, 2 is a collector layer deposited on this substrate 1, and 3 is a collector layer 2. a base layer 4 deposited on the collector layer 2 and an amorphous film 5a deposited on the base layer 3;
is an emitter electrode deposited on the base layer 3, 5b is a high resistance part of the emitter layer deposited on the amorphous film 4, 6 is an emitter electrode formed on the emitter 5a, and 7 is an emitter electrode formed on the base layer 3. A base electrode 8 is a collector electrode formed on the collector base 2.

In FIG. 2, 21 is a resist for emitter electrode, 22
23 is a base electrode resist, and 23 is a collector electrode resist.

Next, a method for manufacturing a bipolar transistor according to the present invention will be described.

After depositing a collector layer 2 and a base layer 3 on a substrate 1 using a crystal growth method, lithography is performed to etch the base layer in a portion where a collector electrode will be formed in the future to expose the collector layer 2 (Second A). figure). An amorphous film 4 is deposited on the entire surface, and lithography is performed to etch the amorphous film in the area where the emitter 5a will be deposited in the future to form the base layer 3.
(Figure 2B). An emitter layer is deposited over the entire surface using a crystal growth method. However, at this time, a part of the emitter layer deposited on the exposed part of the single-crystal base layer 3 becomes the single-crystal emitter 5a, whereas a part of the emitter layer deposited on the amorphous film 4 becomes the single-crystal emitter 5a. A part becomes a polycrystalline emitter layer high resistance portion 5b (FIG. 20). Next, a resist is applied to the entire surface and lithography is performed to expose the emitter 5a.
A resist 21 for an emitter electrode is formed (FIG. 2D).

Emitter electrode metal is deposited on the entire surface, and a lift-off operation is performed using emitter electrode resist 21 to form emitter electrode 6 (FIG. 2E).

Resist is again applied to the entire surface and lithography is performed to form a base electrode resist 22 (FIG. 2F). A part of the high resistance portion 5b of the emitter layer is etched using an etchant that does not etch the amorphous film 4. When the etching progresses to the amorphous film 4, the etching automatically stops.

Furthermore, this time, a part of the amorphous film 4 is etched using an etchant that does not etch the semiconductor crystal. Then, when the etching progresses to the base layer 3, the etching automatically stops (FIG. 2G). A metal for the base electrode is deposited on the entire surface, and a lift-off operation is performed using the resist 22 for the base electrode to form the base electrode 7 (FIG. 2H).

A resist is again applied to the entire surface and lithography is performed to form a resist 23 for the collector electrode (FIG. 2J). A part of the emitter layer high resistance part 5b and a part of the amorphous film 4 are etched to expose the collector layer (see the second figure). The metal for the collector electrode is vapor-deposited, and the resist 23 for the collector electrode is deposited.
The bipolar transistor is completed by performing the lift-off process using

FIG. 3 shows a second embodiment of the present invention, which is an improved version of the first embodiment.
2 shows the structure of a bipolar transistor obtained in this embodiment. In the manufacturing method of the second embodiment, the base layer 3 is deposited thicker in advance than in the above case in order to obtain a predetermined resistance between the base and the emitter in the method of the first embodiment. Process, that is, 2nd B
In the state shown in the figure, the process includes a step of etching away the portion of the base layer 3 where the emitter is to be deposited to a predetermined depth. This structure has the effect of providing the required base-emitter resistance.

〔Effect of the invention〕

As described above, according to the method of manufacturing a bipolar transistor of the present invention, in the step of exposing the base layer, an amorphous film is formed in advance on the upper layer of the base layer in the area to be etched to form the base electrode, and this etching is performed. Etching automatically stops when the amorphous film is reached, and this amorphous film is then etched with a different etching solution, ensuring that the base layer is exposed even if it is thin. This has the effect of making it possible to obtain a bipolar transistor with an inexpensive base layer and a high operating speed.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of a bipolar transistor obtained by an embodiment of the present invention, and FIG. 2 is a sectional view showing the manufacturing process of the bipolar transistor of the above embodiment.
FIG. 3 is a sectional view of the structure of a bipolar transistor obtained according to another embodiment of the present invention, and FIG. 4 is a sectional view showing the manufacturing process and completed structure of a conventional bipolar transistor. 1 is a substrate, 2 is a collector layer, 3 is a base layer, 4 is an amorphous film, 5a is an emitter, 5b is a high resistance part of the emitter layer, 6 is an emitter electrode, 7 is a base electrode, 8 is a collector electrode, 2
1 is a resist for the emitter electrode, 22 is a resist for the base electrode, 23 is a resist for the collector electrode, 31 is a resist for the emitter mesa, and 32 is a resist for the base layer mesa. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1) a step of depositing first and second single crystal semiconductor layers on one main surface of a semiconductor substrate; depositing an amorphous film on the second single crystal semiconductor layer; Applying and patterning a photoresist to remove a region of the amorphous film where an emitter is to be formed, and depositing a single crystal semiconductor on the amorphous film and the second single crystal semiconductor layer in the region where an emitter is to be formed. a step of forming a polycrystalline semiconductor on the amorphous film and a single crystal semiconductor emitter on the second single crystal semiconductor layer in the emitter formation area, and applying and patterning a photoresist. After that, a step of etching a predetermined region of the polycrystalline semiconductor layer with a first etchant, and then etching a predetermined region of the amorphous film with a second etchant, and depositing a metal film on the entire surface and applying a photoresist. A method of manufacturing a bipolar transistor, comprising: forming a base electrode by removing the base electrode.