JPS5931219B2 - semiconductor equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device, and particularly to a high frequency, high power transistor.

A high frequency, high power transistor is required to be able to flow a large current and at the same time have good high frequency characteristics.

For good high frequency characteristics, the capacitance of each junction must be minimized as it acts as a parasitic capacitance and has an adverse effect on the operation of the transistor. On the other hand, it is generally well known that when a high-frequency, high-output transistor operates at a large current, the current flows in a concentrated manner around the emitter region, both in direct current and alternating current, due to the peripheral effect. Therefore, in order to handle large currents and operate efficiently at high frequencies, the length of the peripheral portion is increased, and the area of the portion that exercises the transistor function is made as small as possible. That is, the structure is such that the circumferential length of the emitter can be made as large as possible within a small area. This results in the shape of the emitter region becoming finer and more complex. On the other hand, in order to be suitable for high frequency applications, the base region must be as narrow as possible according to the frequency of use. It is also well known that in conventional impurity diffusion techniques, this must be achieved by forming a shallow diffusion layer. Therefore, the emitter layer needs to be made shallower as the frequency increases, and the diffusion layer forming the emitter region inevitably has an increased electrical resistance. This increase in electrical resistance makes it impossible to flow a large current required for a high-output transistor, or causes adverse effects such as a reduction in power gain in transistor characteristics. Furthermore, as mentioned above, high-frequency transistors require a fine structure, but from the viewpoint of structural technology or reliability of the element, in order to form transistors efficiently, the emitter region is formed in a lattice shape or a fishbone shape, and a part of the emitter region is A structure is often adopted in which a non-rectifying contact is formed to derive the electrical characteristics to the outside, but in this case, the increase in the electrical resistance of the emitter layer is due to the fact that the diffusion layer is the only current path. Since it accounts for a large proportion,
The potential drop will significantly adversely affect the high frequency characteristics of the transistor. The present invention has been made mainly in view of the above points, and therefore, an object of the present invention is to provide a novel high-frequency, high-output transistor that reduces the high resistance of the emitter layer and provides good high-frequency characteristics. .

The above objects of the present invention include a collector, a base, and an emitter region, an insulating layer that covers at least the emitter region and has a plurality of openings on the emitter region, and a collector, a base, and an emitter region; A semiconductor device comprising means for taking out an electrode, characterized in that the emitter region under the insulating layer between the openings has a low resistance layer in resistive contact with the emitter region. It will be achieved.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of the structure of a transistor (having a lattice-shaped emitter) to which the present invention is applied will be described below with reference to the accompanying drawings, while comparing it with a conventional method.

The same reference numerals will be used for equivalent parts in each figure below. Fig. 1 is a plan view showing an example of a transistor having a lattice emitter structure using conventional technology, and Fig. 2 is a cross section taken along line 2-2 in Fig. 1 and viewed in the direction of the arrow. It is a diagram.

In the figure, inside a high resistivity layer 1b of a semiconductor substrate 1 consisting of two layers, a low resistivity layer 1a and a high resistivity layer 1b, there is a base region 2 having a conductivity type opposite to that of the substrate, and a base region 2 having a conductivity type opposite to that of the substrate. A conductive type emitter region 3 is formed. Further, the entire surfaces of the emitter region 3 and the base region 2 are covered with an insulating film 5 such as SiO2, and an emitter electrode drawing window 6 and a base electrode drawing window 7 are opened in the insulating film. Although not shown in the figure, a non-rectifying connection is made through a window opened in each of the emitter region and the base region using an electrode material such as Al, and electrical characteristics are derived to the outside. As described above, this structure allows a large emitter circumference in a small area, and is suitable for high frequency, high output transistors. However, in order to achieve high frequency characteristics, it is necessary to form the base region extremely thin, and for this purpose, when forming the base region and emitter region by impurity diffusion, the emitter region is generally made extremely thin. Since it has to be formed by diffusion, the lateral resistance of the diffusion layer is necessarily large, and the unexposed emitter region 3 is electrically connected only by the diffusion layer under the insulating film.
a ends up occupying most of the total emitter area. Therefore, a significant potential drop occurs due to the large electrical resistance of the emitter layer, and the area away from the window for drawing out the emitter electrode, for example, the middle part between two windows for drawing out the emitter electrode, hardly contributes to the current. , it will no longer function effectively as an emitter. For this reason, there is a fundamental problem that a large current necessary for a high-output transistor cannot flow, and at the same time, the effective circumferential length of the emitter is reduced, resulting in a reduction in power gain and output power. FIGS. 3 and 4 show examples of high frequency, high power transistors having a shape similar to that shown in FIG. 1 according to the present invention. FIG. 3 is a plan view thereof, and FIG. 4 is a sectional view taken along line 4--4 in FIG. 3 and viewed in the direction of the arrow. A feature of the present invention, in addition to the description shown in FIG. 1, is that the surface of the emitter region 3 is provided with a low resistance layer 4 made of a metal-semiconductor compound or the like. As a method for forming this low resistance layer, for example, after forming the emitter diffusion region, platinum (Pt) or the like is deposited over the entire surface of the substrate and heat-treated, and then platinum (Pt) is deposited on unnecessary parts.
) etc., but other methods such as directly depositing a metal-semiconductor compound etc. on the emitter diffusion region may also be used. After that, an insulating film such as a SiO2 layer is formed by a low-temperature pyrolysis method using silane (SiH4 traces), a window for exposing the emitter electrode and base electrode is opened in the insulating film, and a normal method is applied from that part. A well-known method may be used to derive electrical characteristics using a metal material for electrodes, etc. By additionally forming this low resistance layer 4, the emitter region other than the emitter window directly connected to the electrode metal can be The lateral resistance of the large part (the part under the insulating film) can be made considerably small, and therefore the potential drop can also be made very small.

As a result, the entire area around the emitter can effectively contribute to current injection, and the desired function can be effectively achieved without losing any of the advantages of the transistor with the structure shown in Figure 1. A high frequency, high output transistor having excellent high frequency characteristics can be obtained. In the above example, an intermetallic compound of Pt and a semiconductor was used as the material for the low resistance layer, but any other metal such as molybdenum (MO) that does not change the conductivity type of the diffusion layer may be used. Can be implemented. Note that the present invention is not limited to high frequency, high output transistors, but is applicable to semiconductor devices in which a shallow diffusion junction is formed in a semiconductor substrate and the electrical resistance needs to be reduced, for example, the diffusion layer is used as a resistance layer. However, when it is impossible to introduce a large amount of impurities or form a deep diffusion layer due to various manufacturing technology constraints, we provide a method that makes it possible to reduce the resistance of the diffusion layer. It can be applied to general structures. Although the present invention has been described above according to preferred embodiments thereof with reference to the accompanying drawings, it is needless to say that these are merely illustrative and do not have a restrictive meaning.

Therefore, the present invention can be practiced with various changes without departing from the spirit and scope of the invention, but all of them are included within the scope of the claims of the present application.

[Brief explanation of the drawing]

Figure 1 is a schematic plan view of a conventional semiconductor device, and Figure 2 is a schematic plan view of a conventional semiconductor device.
A schematic cross-sectional view taken along line 2-2 in the figure and seen in the force direction of the arrow, FIG. 3 is a schematic plan view showing one embodiment of a semiconductor device according to the present invention, and FIG. FIG. 4 is a schematic cross-sectional view taken along line 4-4 of FIG. 1... N-type silicon substrate, 1a... Low resistivity layer, 1b... High resistivity layer, 2...
・p-type base region, 3...n-type emitter region,
3a...Unexposed portion in the n-type emitter region, 4...Silicon and platinum compound layer, 5...
. . . Insulating coating, 6 . . . Exposed portion in n-type emitter region, 7 . . . Exposed portion in p-type base region.

Claims (1)

[Claims] 1: an insulating layer covering an emitter region; a plurality of holes provided in the insulating layer to expose a plurality of surface portions of the emitter region; and an electrode layer contacting the emitter region through the plurality of holes. and a low resistance layer formed in contact with an emitter region portion under the insulating layer between the plurality of openings.