JPH02238631A - Semiconductor device - Google Patents

Abstract

PURPOSE:To form an HBT which is provided with a high amplification factor and a good high-frequency characteristic while a sufficient throughput for its industrial production is kept by a method wherein an emitter region is constituted of a plurality of semiconductor substance layers whose band gap is reduced one after another stepwise toward an end of a collector of a base region. CONSTITUTION:An n-type single-crystal Si film is formed as a collector region 102 on an n-type low-resistance single-crystal Si substrate 101; three layers of p-type SiCx films are formed as a base 103 on it. In addition, an SiO2 insulating layer 105 is formed; a window for emitter-region use is formed by a photoetching process; after that, three layers of n-type SiCx films are formed again; an emitter 104 is formed by the photoetching process. In this manner, a plurality of semiconductor substance layers whose band gap is reduced one after another stepwise toward an end of a collector of the base region 103 from an emitter region 104 are formed. Thereby, a manufacturing apparatus can be controlled easily; industrial productivity can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high performance (high speed) half barrel device having a wide ganope emitter.

[Prior Art] In recent years, semiconductor junctions using heterojunctions, ie, junctions made of different semiconductors, have been actively developed using methods such as molecular beam epitaxy (MBE). Heterojunction bipolar transistors (hereinafter referred to as HBTs) with wide gas emitters have high emitter injection efficiency and can set the base impurity concentration higher than usual, which reduces parasitic elements such as base resistance and enables high speed operation. HBT, which is the subject of particularly active research, is capable of achieving
In this case, the spike-like barrier formed when the bandgap is stepped at the base-emitter junction impairs the injection of electrons from the emitter to the base. Since this reduction in emitter injection efficiency leads to a reduction in transistor performance, a method has been proposed in which the bandgap changes continuously at the base-emitter junction. Furthermore, since carrier transit time in the base region greatly contributes to speeding up the transistor,
A high-performance HB'[' has been proposed that has a structure in which the bandgap is continuously changed (tilted) even in the base region. (Fig. 3) Fig. 6 (a) is a conceptual diagram of an npn-type HBT with a structure in which the band gap of the base-emitter junction and the base region is continuously changed, and Fig. 3 (b) is a conceptual diagram of the band gap of the base-emitter junction and the base region. It is a diagram.

[Problem to be solved by the invention] However, in order to achieve such a smooth band gap change, it is necessary to precisely control the flanks of the molecular beam in the MBE method and the gas flow rate in the MOCvD method. However, controlling manufacturing equipment is extremely difficult, and industrial productivity (mass production) is lacking.

[Means for Solving the Problems] A semiconductor device of the present invention includes a base region made of a first semiconductor having a first conductivity type, and an emitter made of a second semiconductor having a second conductivity type and having a wider band gap than the first semiconductor. The semiconductor device is characterized in that it comprises a plurality of semiconductor material layers having a region and a band width gradually decreasing from the emitter region to the collector end of the base region.

[Example] The present invention will be explained below according to the examples.

Figure 1 shows an npn type HB' to which the semiconductor device of the present invention is applied.
This is an example of T. 101 is a low-resistance n-type single-crystal Si substrate, and a collector region 102 is formed by forming an n-hole single-crystal Si film thereon using the MBE method. Three layers of p-type SiOx films are formed thereon using the MBK method to form a base 103. Furthermore, an insulating layer 105 of S102 is formed on the surface using the low pressure CvD method, and a window for the emitter region is formed using a photoetching process, and then an n-type SiC! Three layers of x films are formed, and an emitter 104 is formed by a photo-etching process. Next, using the sputtering method, S10
After forming the insulating layer 106 of No. 2 and forming a window for the base electrode and emitter tl'M by a photo-etching process, an A7 film is formed on the surface by a sputtering process, and a base electrode 108 and an emitter electrode 109 are formed by a photo-etching process. form.

Finally, a collector electrode 107 of A7 film is formed on the back side of the substrate by sputtering.

Carbon content ratio X of the composition of p-type Si-Ox in the base layer
are x=o, x, , x2 from the collector side, and x=x3 from the base side in the n-type SiOx emitter layer.
, 4, r. (Figure 2(b)) where xi
(i=1~5) is 0〈x1〈x2〈x3 (x
The relationship is 4 < x H < 1. Figure 2 (α
) is the band diagram for the embodiment shown in Figure 1. As can be seen from the band diagram, when a step-like inclined junction is used, a barrier is formed at the interface of each layer, but the height of the barrier is simply the same as the step-like junction. It is much smaller than the place where it was.

In addition, it is possible to convert sloped joints into multiple stepped joints (stepped sloped joints).
Forming the HBT can greatly reduce the burden of the process when manufacturing the HBT. In order to smoothly change the material composition, it is necessary to precisely control the growth conditions during the formation of the semiconductor layer, and it is also necessary to keep the growth rate sufficiently low.

However, when replacing it with multiple step-like compositional changes, it becomes much easier to control the area and increase the growth rate, resulting in a significant improvement in production throughput. .

The number of layers of the base and collector layers may be plural. The larger the number, the smaller the difference in band gaps at the interfaces between the layers, but if there are too many, it will be disadvantageous in terms of the process, so the optimum number is about 2 to 10.

The present invention is applicable not only to vertical type bibolar transistors but also to horizontal type bibolar transistors.

In this example, single crystal S1 and SiC! x film is formed, but OV at reduced pressure or normal pressure
A vapor phase growth method such as the D method may be used, and other methods such as liquid phase growth or solid phase growth after forming a non-single crystal film by a plasma OVD method are also possible. Further, although a Sin film is used as the insulating layer, SiNx or the like may also be used.Also, plasma CVD method, optical OVD method, etc. may be used as a method for forming the film. As for the electrode, other than AI-, metals such as Cjr and Mo, silicide, etc. can be used, and the forming method can be vapor deposition or the like.

FIG. 4 shows O M L l (
This is an example in which a Current Mode Logic (Current Mode Logic) circuit was created. By using the semiconductor of the present invention, high-speed logic elements can be stably supplied industrially. This applies not only to digital circuits, but also to analog circuits.

By combining the semiconductor device of the present invention and a CMOS circuit, a high-performance BiOMOS (HBTCMOS) circuit can be stably supplied industrially.

It is also possible to form the semiconductor device of the present invention on an insulating substrate or an insulating layer. In this case, not only the emitter top type as in the embodiment shown in FIG. 1 but also the collector top type are possible. Furthermore, element separation becomes easier and application to tertiary elements becomes possible, so high-speed arithmetic devices,
Application in a wide range of fields such as imaging devices becomes possible.

Above, we have described an example using SiOx as a semiconductor, but elemental semiconductors such as Si and Ge may also be used.
Compound semiconductors such as GaAs and InP may also be used. Furthermore, the bandgain knob may be changed using a non-single crystal semiconductor. Further, although the npn type has been described, a pnp type may also be used.

[Effects of the Invention] As described above, by using the semiconductor device of the present invention, it is possible to form an HBT with a high amplification factor and good high frequency characteristics while maintaining sufficient throughput for industrial production. It becomes possible.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a PNP type transistor of a semiconductor device shown in an embodiment of the present invention. FIGS. 2(a) and 2(b) are a band diagram and a carbon-mixed diagram of the embodiment shown in FIG. 1. Fig. 6 (+7.), (b'I is a conceptual diagram and band diagram of a conventional example. Fig. 4 is a diagram of an example in which an OML circuit is manufactured using the semiconductor device of the present invention. 101... ...N-type single crystal 81 substrate 102, 2
03,303...Collector 103,202,3
02... Base 104, 201, 401...
・・・Emitter 105, 106 ・・・・・・
Insulating layer 107...Collector electrode 108.
...Heath electrode 109 ...Emitter electrode 604 ...
...Base-emitter inclined junction 605...
...Grand Heas and above Applicant Seiko Epson Co., Ltd. Agent Patent attorney Kisaburo Suzuki (and one other person) Figure 1 (a) Figure 2 (b) Figure 2 301 Ivy 30) Baseno I3 collector (a) ( b) Figure 3

Claims (1)

[Claims] a base region made of a first semiconductor having a first conductivity type; and an emitter region made of a second semiconductor having a second conductivity type and having a wider bandgap than the first semiconductor; 1. A semiconductor device comprising a plurality of semiconductor material layers whose band gaps gradually decrease toward a collector end.