High-frequency power transistor

Details High-frequency power transistor High-frequency power transistor

1989-03-27

1991-07-16

Hille, Rolf

357 14, 357 49, 357 53, 357 81, H01L 2972

Patent

active

050328867

DESCRIPTION:

BRIEF SUMMARY
PRIOR ART

The invention is directed to a high-frequency power transistor using bipolar epitaxy technique and having a plurality of emitters with emitter and base contact strips arranged in its base region, the emitter and base contacts are located at a main surface of the silicon layer.
High-frequency transistors for power output stages in high-frequency amplifiers are usually produced with the epitaxy technique. In known constructions, they are usually insulated against the heat sinks, which are conventionally connected to ground, with thin beryllium oxide layers because of the good heat conductivity. However, this isolation technique is not only expensive, but is also critical with respect to handling, since beryllium oxide is poisonous.
In addition, it is known to construct transistors in monolithic integration technology, wherein the individual components of such a semiconductor arrangement are isolated relative to one another and to the substrate by means of depletion or barrier layers, possibly also dielectric layers of SiO.
However, the losses of the depletion layer insulation increase as the operating frequency increases, since the depletion layer capacitances which are formed are loaded with ohmic bulk resistors. For this reason, the previously known monolithically integrated transistors are unsuitable in practice as high-frequency power transistors.


ADVANTAGES OF THE INVENTION

In contrast, the high-frequency power transistor of the invention has the advantage that an isolating intermediate layer which is applied during the wafer production process, can comprise a depletion or barrier layer, but preferably comprises a dielectric such as an oxide or a nitride layer, and is accordingly inexpensive and easy to use. An alloyable or solderable coating can be applied to this layer, which enables a connection with a heat sink. This is made possible in that the emitter, base and collector electrodes lie on the other main surface of the silicon layer, wherein the base region and the emitter contact strips are arranged between collector contact strips. This measure enables a simple, inexpensive production of a high-frequency power transistor, wherein the oxide or nitride layers can be deposited on the silicon as an intermediate layer using the plasma method during the wafer production process. A polysilicon layer can be applied additionally to the intermediate layer as alloyable coating. An aluminum nickel layer can serve as solderable coating, wherein a gold layer can be applied additionally as surface protection.
The heat sink connected with the transistor can be connected to ground relative to high frequency, but preferably also relative to direct current.
In order to prevent reflected capacitances, it is advantageous to arrange a highly doped shield grid in the silicon under the base connection lines and under the base contact spot, respectively, which shield grid is connected to ground potential at least relative to high frequency.
In order to create permanent defined conditions at the circumference of the semiconductor layer, it is also advantageous to provide an isolating diffusion region having the same doping as the substrate at least at the locations not connected to ground. The correspondingly constructed regions are accordingly passivated.
In order to stabilize the current distribution, resistors can be diffused into the feed lines to the individual emitter fingers, wherein these resistors can be formed by means of highly doped n-regions.


DRAWING

The invention is explained in more detail in the following description and with the aid of the drawing, in which:
FIG. 1 shows the equivalent circuit diagram of a known bipolar monolithically integrated high-frequency transistor;
FIG. 2 shows the equivalent circuit of a monolithically integrated high-frequency transistor with an additional substrate diode according to the invention;
FIG. 3 shows the equivalent circuit of a monolithically integrated high-frequency transistor with shield grid and corresponding oxide capacitance;
FIG. 4 shows a top

REFERENCES:
patent: 3896475 (1975-07-01), Bonis
patent: 4106048 (1978-08-01), Khajezadeh
patent: 4377029 (1983-03-01), Ozawa
patent: 4651192 (1987-03-01), Matsushita et al.
Electric Design News, vol. 26, No. 15, 5 Aug. 1981, (Boston, MA, U.S.), "High-Voltage bipolar Darlington provides true Dielectric isolation".

Affiliated with

Also associated with

Rating

High-frequency power transistor does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with High-frequency power transistor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High-frequency power transistor will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-135140