JP2518413B2 - Semiconductor integrated circuit - Google Patents

Description

The present invention relates to a semiconductor integrated circuit, and more particularly to a power bipolar IC excellent in high frequency characteristics.

[Conventional technology]

Conventionally, in a high-frequency bipolar IC, a so-called comb-shaped (interdigital) electrode has been adopted because of its easy manufacturing method or simple process. This is not an exception, especially in power ICs that handle large currents.

An example of a plan view and a structural sectional view of a normal power IC,
It is shown in FIGS. 6 (a), (b) and (c).

The figure (a) is a top view, the figure (b) is the XX sectional view, and the figure (c) is the YY sectional view.

However, in FIG. 6, the central portion is simplified for simplification. 1 is a base electrode, 2 is an emitter electrode, 3 is a collector electrode, 4 is a surface protection film, for example, an oxide film, 5 is an isolation oxide film, 6 is an emitter, 7 is a base, 8 is a collector (epitaxial layer), 9 Is a buried layer, 10 is a collector pulling part,
Reference numeral 11 is a P-type semiconductor substrate.

[Problems to be Solved by the Invention]

On the other hand, in order to increase the power consumption, it is necessary to flow a large current, but the current that can be passed per electrode is limited by the material and size of the electrode, so the number of electrodes must be increased. I don't get it.

However, in the conventional IC, as shown in FIG. 6, by having the collector electrodes 3 facing each other, the collector resistance r
_{Although SC} is being reduced, when the number of electrodes is increased to increase the power, not only the collector resistance r _SC inevitably increases, but, for example, in the central portion and the vicinity of the collector electrode 3, Since the collector resistances r _SC are greatly different, current imbalance occurs and problems such as thermal runaway occur.

Further, in the conventional structure, as shown in FIG. 6 (c), the base electrode 1 is arranged on, for example, an oxide film of the surface protection film 4, and the surface protection film 4 includes an emitter, a base, Since the contacts of the collector are usually opened at the same time, it is desirable to be as thin as possible for forming a fine emitter. However, if the thickness of only the periphery of the collector is increased to reduce the capacitance of the base electrode described later, it becomes difficult to form the fine emitter. .

In order to avoid this, it is necessary to add one more mask for collector contact, which makes the process longer. On the other hand, when it comes to a power IC, the number of electrodes is considerably large, and therefore the length of the base electrode to be drawn around becomes too long to be ignored. Therefore, when the thickness of the surface protection film 4 is thin, the collector resistance C _P becomes extremely high. growing.

Further, since a large base area of the IC for power, since the collector-base junction capacitance C _JC itself is large, the actual collector-base capacitance C _CB = C _JC + C _P becomes extremely large, the collector resistance r _SC described above In consideration of the above, the cutoff frequency f _T and the power gain (for example, | S _21e | ² ) are greatly deteriorated, and there is a drawback that an IC having excellent high frequency characteristics cannot be realized.

In contrast to the conventional power IC described above, according to the present invention, at least three sides of the base region are surrounded by the high-concentration collector pull-up portion, and a thick insulating layer film is provided between the base region and the collector resistance r _SC . The difference lies in that the capacitance is reduced and made uniform, and the capacitance of the base electrode with respect to the collector is reduced.

[Means for solving the problem]

The present invention provides a bipolar semiconductor having a second conductivity type collector region on a first conductivity type semiconductor substrate, a first conductivity type base in the collector region, and a second conductivity type emitter in the base. In the integrated circuit, at least three sides of the base region are surrounded by a high-concentration second-conductivity-type collector pull-up part, and at least one side surrounded by the collector pull-up part has a distance of at least 5000Å between the base region and the collector pull-up part. A semiconductor integrated circuit in which a base electrode separated by an insulating film having the above thickness and connected to a first portion of the base region extends over the insulating film and is connected to a second portion of the base region. Is.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

1 (a), (b), and (c) show a first embodiment of the present invention. This example is an example in which three sides of the base region are surrounded by a collector pull-up portion. A plan view is shown in FIG. 10A, an X-X cross-sectional view thereof is shown in FIG. A sectional view is shown. Further, in FIG. 1, the central portion is omitted for simplicity.

Here, 1 is a base electrode, 2 is an emitter electrode, 3 is a collector electrode, 4 is a surface protection film, for example, an oxide film, and 5
Is an isolation oxide film, 6 is an emitter, 7 is a base, 8 is a collector (epitaxial layer), 9 is a buried layer, 10 is a high-concentration region of the collector pulling portion, 11 is a P-type semiconductor substrate, and 12 is for capacitance reduction. It is an insulating film.

As the capacitance reducing insulating film 12, a material having a low dielectric constant,
For example, an oxide film is desirable, and the method of forming the oxide film may be thermal oxidation or a method of burying the oxide film after etching S _i . Its thickness and width are 5000Å for capacity reduction
The above is desirable, and it may be determined in consideration of the epitaxial thickness, the electrode width, and the like.

According to this embodiment, the collector resistance shown in FIG.
Collector resistance in the Y-Y direction shown in Fig. (c) from r _SC '
Since r _SC ″ can be made much smaller, the collector resistance r _SC is also small as a whole, and a balanced transistor operation can be performed regardless of the positions of all the emitters.

Further, in order to further reduce the collector resistance, as in the second embodiment shown in the plan views of FIGS. 2A and 2B and the Y-Y sectional view thereof, the collector pull-up portion 10 is used to form the base region. All 7 may be enclosed.

In addition, in order to reduce the capacitance when the base electrode 1 is drawn out, a capacitance reducing insulating film 12 may surround all four sides. Further, if the impurity concentration of the collector pulling portion 10 is about 1 × 10 ¹⁸ / cm ³ or more, the effect can be sufficiently exhibited.

FIG. 3 is a plan view of the third embodiment of the present invention, in which the collector pull-up portions 10 are provided at three locations in order to further reduce the collector resistance. Of course, if necessary, the collector pull-up portions 10 may be provided in four or more places as well.

The plan view of FIG. 4 shows a fourth embodiment in which the present invention is applied to a power IC with a ballast resistor. Originally, if the ballast resistor 13 is used, it is not suitable for a power IC because it causes a decrease in gain due to negative feedback due to the resistance and it is difficult to design a resistance value for balancing. Therefore, even if it is unavoidable to use it, the value of the ballast resistance may be constant by applying the present invention, and since a small resistance value contributes to sufficient stabilization, the decrease in gain can be reduced. It will be possible.

〔The invention's effect〕

As described above, according to the present invention, the collector resistance is reduced and the stray capacitance of the base electrode with respect to the collector is also reduced. Therefore, stable operation can be realized and the high frequency characteristics can be greatly improved as compared with the conventional structure.

A transistor having the structure shown in FIG. 1 in Fig. 5 the present invention, the high frequency characteristics of the transistor of the conventional structure shown in FIG. 6, cut-off frequency f _T and power gain | About ^2, | S _21e
It is a graph obtained by actual measurement and comparison, and both transistors have the same design rule, emitter size, number, and the like.

From Fig. 5, it can be seen that f _T is about
It can be seen that 2GH _Z and | S _21e | ² improve by about 1 dB, and the collector current I _c max at which f _T becomes maximum is improved by about 10 mA or more. These data fully demonstrate the effectiveness of the present invention.

[Brief description of drawings]

1 is a first embodiment of the present invention, FIG. 1 (a) is a plan view,
Figure (b) is its XX cross section, Figure (c) is its YY cross section, Figure 2 is a second embodiment of the present invention, Figure (a) is a plan view, and Figure (b). FIG. 3 is a plan view of a third embodiment of the present invention, FIG. 4 is a plan view of a fourth embodiment of the present invention, and FIG. 5 is a conventional structure and the present invention. FIG. 6 is a graph showing comparison (measurement) of high frequency characteristics of transistors having a structure, FIG. 6 is a diagram showing an example of a conventional structure, FIG. 6A is a plan view, FIG. c) is the YY sectional view. 1 ... Base electrode, 2 ... Emitter electrode, 3 ... Collector electrode, 4 ... Surface protection film, 5 ... Separation oxide film, 6
...... Emitter, 7 …… Base, 8 …… Collector (epitaxial layer), 9 …… Buried layer, 10 …… Collector pull-up part, 11 …… P-type semiconductor substrate, 12 …… Capacitance reduction insulating film.

Claims (1)

(57) [Claims] 1. A bipolar having a second conductivity type collector region on a first conductivity type semiconductor substrate, a first conductivity type base in the collector region, and a second conductivity type emitter in the base. In a semiconductor integrated circuit, at least three sides of the base region are surrounded by a high-concentration second-conductivity-type collector pulling-up portion, and at least one side surrounded by the collector pulling-up portion extends at least between the base region and the collector pulling-up portion. The base electrode, which is separated by an insulating film with a thickness of 5000 Å or more and is connected to the first part of the base region, extends over the insulating film and is connected to the second part of the base region. A characteristic semiconductor integrated circuit.