JPH0138378B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor integrated circuit device.

As one of the PNP transistors constituting a semiconductor integrated circuit device, there has been an epitaxial base PNP transistor, which is shown in FIG. In FIG. 1, 1 is a P-type semiconductor substrate, 2 is an N-type epitaxial layer grown on the main surface of this substrate 1, and 3 is a PNP formed by selectively diffusing P-type impurities on the same layer 2. The collector regions of the transistors, 4, are similarly grown on top of these
type epitaxial layer, 5 is a collector extraction diffusion layer formed by selectively diffusing P type impurities on the same layer 4;
Reference numeral 6 designates an emitter region similarly formed by selectively diffusing P-type impurities, and reference numeral 7 designates a contact diffusion layer of the base region 4' as the same layer 4, similarly formed by selectively diffusing N-type impurities. And the high frequency characteristics of this conventional epitaxial base PNP transistor,
That is, f _T : _IE is shown in FIG. 2, and its impurity concentration profile is shown in FIG. 3.

Here, such a conventional epitaxial base
In a PNP transistor, since the base region is formed by an epitaxial layer, the minority carriers injected from the emitter region into the base region are not subjected to an accelerating electric field, and therefore the diffused base
It had the disadvantage of inferior f _T :I _E characteristics compared to PNP transistors. This is known from the following equation.
That is, 1/2πf _T = τ _B + r _e (Ce + Cc) Here, τ _B is the base running time of the minority carrier,
r _e is emitter resistance, Ce is emitter transition capacitance, Cc
is the collector transition capacitance and is the epitaxial
Since a PNP transistor is normally a uniform base transistor, it is not subjected to an accelerating electric field due to a diffusion gradient, and thus has a larger τ _B and a smaller f _T than a diffused base transistor.

In view of these conventional drawbacks, the present invention selectively diffuses N-type impurities into the collector region made of the P-type diffusion layer to form an active base region, and epitaxially diffuses the emitter region made of the P-type diffusion layer. The active base region is formed to reach the active base region within the layer, and the active base region forms an accelerating electric field, thereby improving high frequency characteristics.

Hereinafter, one embodiment of the method of this invention will be described in detail with reference to FIGS. 4 to 6.

In FIG. 4, in this embodiment method, after the collector region 3 is formed by the P-type diffusion layer, the N
The active base region 8 is formed by selectively diffusing type impurities, and then the N-type epitaxial layer 4 is grown thereon, and then the collector lead-out diffusion layer 5 reaching the collector region 3 is formed by selectively diffusing P-type impurities. At the same time, an emitter region 9 reaching the active base region 8 is formed, and a base contact diffusion layer 7 is further formed by selectively diffusing N-type impurities.

FIG. 5 shows the impurity concentration profile of an epitaxial base PNP transistor obtained by the method of this embodiment, and as is clear from FIG. The minority carriers injected from the region have a concentration gradient such that they are subjected to an accelerating electric field, and the sixth
The f _T :I _E characteristics shown in the figure, that is, the high frequency characteristics, are sufficiently excellent, as is clear from the comparison with FIG. 2 above.

As detailed above, according to the method of the present invention, it is possible to form an epitaxial base PNP transistor in a semiconductor integrated circuit device that has high frequency characteristics similar to that of a diffusion base PNP transistor as an individual semiconductor element, and also to form a PNP, NPN This invention has the advantage of making it easier to implement so-called complementary transistors in an integrated circuit device.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a PNP transistor formed in a semiconductor integrated circuit device by a conventional method;
Figures 2 and 3 show f _T : I _E of the same transistor as above.
FIG. 4 is an explanatory diagram showing the characteristics and impurity concentration distribution, respectively, and FIG.
5 and 6 are cross-sectional views showing the transistor, and the impurity concentration distribution and f _T :
FIG. 3 is an explanatory diagram showing _IE characteristics respectively. DESCRIPTION OF SYMBOLS 1... P-type semiconductor substrate, 2... N-type epitaxial layer, 3... P-type collector region, 4... N-type epitaxial layer, 5... P-type collector extraction diffusion layer, 7... N-type base Contact diffusion layer, 8...
N-type active base region, 9...P-type emitter region.

Claims (1)

[Claims] 1. A step of growing a first N-type epitaxial layer on the main surface of a P-type semiconductor substrate, and selectively diffusing P-type impurities onto the first N-type epitaxial layer to form a collector region. selectively diffusing N-type impurities into the collector region to form an active base region; growing a second N-type epitaxial layer thereon; selectively diffusing P-type impurities from the surface of the epitaxial layer to reach the collector region and the active base region, respectively, to form a collector lead-out diffusion region and an emitter region; N from layer surface
1. A method for manufacturing a semiconductor integrated circuit device, comprising forming a PNP transistor by selectively diffusing type impurities to form a base contact diffusion layer.