JPS6233347Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is based on an electrode structure of a Darlington semiconductor device in which a drive transistor and an output transistor are connected in a so-called Darlington connection on one semiconductor substrate.

Conventionally, in Darlington transistors, the input is the base of the drive transistor, and the output is the emitter of the output transistor, so the base of the drive transistor and the emitter of the output transistor are made of aluminum or
Thin wires such as Au are bonded to connect to external leads, but in this case, bonding wires of the same diameter are usually used for the emitter and base to simplify the bonding equipment and reduce man-hours. By the way, the base current of the drive transistor is 1/h of the emitter current of the output transistor.
For example, if the emitter current is 10A _, h _FE
When is 1000, even though the base current flows only 10 mA, the bonding wire diameter is determined based on the bonding wire current density of the emitter, so a large diameter is used.
Further, the width of the base electrode of the drive transistor depends almost on the diameter of the bonding wire, and as described above, a large area is required because an excessively large bonding wire is used. Furthermore, in the conventional structure, the base electrode is structured along the emitter-base junction, and as mentioned above, the base electrode requires a large area, so the base area has to be made larger than necessary. . In order to avoid this, several bonding wires with small diameters are used in parallel for the emitter of the output transistor, and one wire is used for the base of the drive transistor, but as mentioned above, this method requires a large amount of bonding equipment and man-hours. A problem arises.

The object of the present invention is to eliminate the above-mentioned drawbacks and provide an electrode structure in which bonding wires of the same diameter can be used for input and output electrodes without making the base region of the drive transistor unnecessarily large.

The basic configuration of the present invention to achieve such an objective is to include at least a drive transistor and an output transistor that are connected to each other in a so-called Darlington on the same substrate, and to connect the base of the drive transistor and the external base lead with a bonding wire. In a Darlington semiconductor device in which the emitter of the output transistor and the external emitter lead are connected with a bonding wire, the emitter region of the drive transistor is penetrated below the base bonding part, which is necessary for the bonding wire that uses the base electrode. The emitter region is disposed so as to extend over a portion of the emitter region with an insulating film interposed therebetween.

The present invention will be specifically explained below using the drawings.

1 and 2 are diagrams showing the conventional structure,
The width of the base electrode 5 of the drive transistor 10 is determined according to the bonding wire, and the base region 2a is equal to or slightly wider than the electrode 5. In order to obtain the desired emitter junction length, the width of the base electrode 5 is determined according to the bonding wire. It is usually comb-shaped.
For this reason, there was a drawback that the base region 2a became larger than necessary.

By the way, in the structure of such a Darlington transistor, as shown in FIGS. 3 and 4 as a first embodiment, the base region 2a' is narrowed and the comb-shaped emitters 3a' are inserted into the base region 2a'.

Alternatively, as a second embodiment, as shown in FIGS. 5 and 6, the base region is surrounded and separated by a plurality of emitter regions 3a''. Thereafter, a portion that makes ohmic contact with the electrode on the base region along the emitter junction Only the insulating film 4'' is removed, leaving the insulating film 4'' on the emitter region 3a'' that has entered inside the base region, and then the base electrode 5'' is expanded to above the emitter region 3a'' to ensure the desired bonding width. For example, a Darlington transistor with a proper base region driving transistor can be obtained.

The semiconductor device of the present invention shown in FIGS. 3 and 4 and 5 and 6 can be manufactured through the following steps. That is, a P-type impurity such as boron or potassium is diffused into an N-type silicon substrate 1 to form a base region 2.
a', 2a'' and 2b' are formed. Next, oxide films 4',
The oxide films 4' and 4'' are selectively coated with a photoresist or the like, and the oxide films 4' and 4'' are selectively etched using a buffered hydrofluoric acid solution or the like to open a window that will become an emitter electrode extraction area. After that, an N-type impurity such as phosphorus is diffused to form emitter regions 3a', 3a'' and 3.
b is formed and covered again with oxide films 4' and 4''.Next, a window is opened for ohmic contact, a conductor such as aluminum is vapor deposited, a photoresist etc. is selectively coated and selectively etched with phosphoric acid etc. electrode 5',
Next, heat treatment is performed at a temperature of 400℃ to 500℃ for about 30 minutes to 2 hours to alloy aluminum and silicon.Finally, after covering the mesa with photoresist or wax, hydrofluoric acid, Mesa etching is performed using a mixture of nitric acid and glacial acetic acid to form a transistor element.

The above embodiments have been described for NPN mesa type transistors, but PNP mesa type transistors, NPN
It is obvious that a similar structure can be applied to planar transistors and PNP planar transistors.

[Brief explanation of drawings]

1 and 2 are a plan view and a sectional view of a conventional transistor, FIGS. 3 and 4 are a plan view and a sectional view showing a first embodiment of the present invention, and FIG. 5 is a plan view and a sectional view of a conventional transistor.
FIG. 6 is a plan view and a sectional view showing a second embodiment of the present invention. 1...Silicon substrate, 2a, 2a', 2a'', 2b
...Base region, 3a, 3a', 3a'', 3b... Emitter region, 4, 4', 4''... Oxide film, 5,
5', 5''...electrode.

Claims (1)

[Scope of utility model registration request] A drive transistor and an output transistor are connected in Darlington, both transistors are provided on one semiconductor substrate, the base electrode of the drive transistor and the external base lead are connected by a first bonding wire, and the emitter electrode of the output transistor and the external emitter lead are connected. and connected by a second bonding wire having the same diameter as the first wire, the emitter region of the drive transistor is inserted below the bonded portion of the base electrode of the drive transistor, and further A Darlington semiconductor device, wherein the base electrode is formed to extend on an insulating film covering the emitter region of the drive transistor to a width necessary for bonding the first bonding wire.