JPS58121671A - Semiconductor device - Google Patents

Abstract

PURPOSE:To reduce Ic (collector current) dependability of hFE by dividing a transistor into numerous number more than two and automatically increasing the number of the transistors which sequentially operate in response to the level of Ic. CONSTITUTION:After collector layers 11, 12 and a base layer 13 are formed, an emitter layer is divided into two regions, and the first and second emitter layers 18, 14 are formed by selectively diffusing doner impurity for auxiliary and main transistors Q1 and Q2. Then, auxiliary transistor Q1 and main transistor Q2 ae shortcircuited at the collectors and emitters with common electrodes by depositing collector electrodes 15, emitter electrodes 16 and base electrodes 17, the transistor Q1 is simultaneously disposed between the base electrode and the transistor Q2, and an insulating film 19 is formed to prevent the base layer 13 from shortcircuiting to the emitter electrode 16.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device, and particularly relates to a semiconductor device having a current amplification rate of 11FIi.
! Concerning a transistor with reduced dependence on collector current 1c 〇 In general, the common emitter current amplification rate hrz (hereinafter simply referred to as current amplification rate or 5), which is a superimposed electrical characteristic of a transistor, is; Due to its dependent nature, the pace current l depends on the level of lc in actual use! It has the disadvantage that 1 must be controlled.

SUMMARY OF THE INVENTION An object of the present invention is to improve such drawbacks and provide a transistor in which the dependence of hp''g on IC is reduced.

The features of the present invention are as follows: - An impurity of one conductivity type is diffused on one main surface side of a conductivity type semiconductor substrate to form a collector layer, and an impurity of opposite conductivity type is diffused on the other main surface side to form a base layer.
In a semiconductor device in which an emitter layer is formed by diffusing impurities of one conductivity type into the base layer, an impurity region of one conductivity type is provided in the base layer so that its planar shape completely surrounds the emitter layer. It is found in semiconductor devices that are

With such a configuration, a plurality of transistors are formed on a semiconductor substrate, and each of the transistors has a common collector electrode and a common emitter electrode, and constitutes one main transistor and a large number of auxiliary transistors. The semiconductor device has a structure in which the auxiliary transistor is disposed between the base electrode and the main transistor. That is, the feature of the present invention is that the hFE is
The objective is to reduce the lc dependence of

According to the present invention, flat hF with less lc dependence.

Next, the present invention will be explained with reference to the drawings.
Figure r is a plan view of the pattern seen from the emitter side, Figure (b) is a cross-sectional view of the chip along the line A-A', Figure (C) is an equivalent circuit,
(The dJ diagram is a general example showing the lc dependence of hFE. This transistor is made by diffusing donor impurities at a high concentration from one side of a hemispherical semiconductor substrate 1 to form an N+ layer, that is, a collector layer 2, and from the other side. After the acceptor impurity is diffused to form one layer, that is, the base layer 3, donor impurities are selectively diffused into a desired portion to surround the first layer, that is, the emitter layer 4, and the core emitter layer 4. By forming another unnecessary base part on the surface, and depositing a metal electrode 5 on the collector C@ side, a metal electrode 6 on the emitter E side, and a gold electrode 7 on the exposed base part 5 on the corresponding edge, The transistor manufactured in this way is generally shown in an equivalent circuit (cJ diagram), and its current amplification factor hFE shows a strong dependence on the collector current 1c. In the region where lc is small /JS, the base −
The recombination mechanism of carriers becomes dominant near the surface of the junction between emitters, lowering hyE, and as the density of carriers (holes) injected into the base layer increases in the region where lc is large, Electrical neutrality condition is no longer maintained,
To neutralize this, electrons are supplied from pace electrons,
The electron density in the spacer layer also decreases, reducing the injection efficiency of the emitter junction, so the phenomenon that hFE decreases is a well-known phenomenon. For example, in the case of a Darlington connection type large capacity transistor with a rating of 1c = 50A and VCE (SVS) = 500V,
c=IAteh,,=soo, IC=11rF at 25A,=a4001c=5OAtebFg=L300
．． 1c=10OAteh, E=27, which changes significantly. When using such a transistor for switching purposes,
It was necessary to variably control the base current according to lc, and at the same time to adjust the base current for all transistors since the hFEW characteristics differ between individual transistors.

Next, a transistor according to an embodiment of the present invention is shown in FIG.
To explain with reference to d), after forming the collector layers 11 and 12 and the base layer 13 in the same manner as in the conventional method,
The emitter layer is divided into two regions, and the first emitter layer 18 and the second emitter layer 14 are formed by selective diffusion of donor impurities, and the auxiliary transistor section Q
, and the main transistor part Q! Then, by depositing a collector electrode 15, an emitter electrode 16, and a base electrode 17, the collector and emitter of the auxiliary transistor Q and the main transistor q are short-circuited by a common electrode, and at the same time, the auxiliary transistor Q1 is connected to the base electrode. The base layer 13 is placed between the main transistors q and the emitter electrode 16.
The device is manufactured by providing an insulating film 19 to prevent short circuits. In the transistor with this new structure, the base region of q contributes to q as a base resistance 20 (as shown in the equivalent circuit of the CJ diagram, a relatively small auxiliary transistor Q and a relatively large main transistor q are connected in parallel). Therefore, h of this transistor is
This is the combined result of hyEe properties21, 22.If the sizes of Ql and Ql are excessively selected, in the region where lc is small, it will be located close to the base electrode 17. Ql that exists operates dominantly,
As lC increases, the hFE of q decreases and the collector-emitter voltage drop VCE(sat)Q increases, so that the current flows dominantly to l c rd Qt.
The transition from l to q is based on a base resistance of 20 and hFE of % Ql.
Determined by the interrelationship of characteristics. That is, in the region (C) where lc is small, that is, 1B is J\, the base resistance r suppresses IBI, so Q, 1B:lB1+lB2...
...(1) 1c=lcx-1-1cz
...(2) VBg(sat)Q,
=rxlBx+Vi+z(sat)Qg ------
・(s)lc:=hp,x1m
・・・・・・(4) IcI = hFE1x IB
I-e-(5)lC2=h
FE2 XIB!・・・・・・
...(6) However, VnE(sat)Qt: pace-emitter saturation voltage of Qt, VnE(sat)C4: Q
Base 12 saturation voltage of a, IBI: pace current flowing in Q, lB2: base current flowing in q, lc
Collector current flowing in l, Q, IC2: Collector current flowing in Q, hpl, 1: Current amplification rate of Qt, hF
+, +: Current amplification rate of Qt, since it flows dominantly,
The collector current is also dominated by lC1, but in the region where lc is dog, that is, IB is dog, VaE(sat)Q, is IBI
Since it increases with the increase of , lB determined by equation (8)
2 starts to drive the ants, and 1C2 becomes dominant.

As a result of the above, since Qt and Qt automatically change the operating level according to the level of lc, the total hFE is (d)
Although we have described an example of a 0 or more, 2-split type transistor that can obtain a flat characteristic as shown in 23 in the figure, the effect is the same even when the emitter is divided into 2 or more pieces, as shown in Fig. 3. (aJ~(cl shows an example of dividing into 3 parts,
Qt, Qt are auxiliary transistors, q is the main transistor, and the principle of operation is the same as in the case of two divisions.
Flat hFE characteristics with little dependence can be obtained.

Figure 4 +a), (bl is the output stage of a Darlington coupled transistor to which the present invention is applied, and the equivalent circuit is shown in Figure 4 (b). It is clear from the above description that fewer transistors can be realized.

Furthermore, in explaining the present invention, an example using a hemi-type semiconductor substrate has been shown, but if a p-type semiconductor substrate is used, it is possible to create a transistor of the opposite type by replacing the acceptor and donor impurities. are obvious and have exactly the same effect. Furthermore, even in the case of a transistor with a structure in which the pace electrode is located in the center, the auxiliary transistor is placed between the main transistor and the base electrode. I
It goes without saying that the effects of the present invention can be expected by using Imfk.

[Brief explanation of the drawing]

Fig. 1(al~(dlU) is an example of a conventional transistor, Fig. 1(a) is a plan view of the pattern seen from the emitter side, and Fig. 1(b) is A-(dlU) of Fig. 1(a). A cross-sectional view at A', Fig. 1 (cl is an equivalent circuit, Fig. 1 (dJ is a graph showing the relationship between current amplification factor hFE and collector current IC), Fig. 2 (al to +d) is a graph showing the relationship between current amplification factor hFE and collector current IC. In one embodiment of the invention, the second figure (a) is a plan view of the pattern seen from the emitter side;
Fig. 2(b) is a cross-sectional view taken along line 3-B' of Fig. 2(a),
Figure 2 (C) is an equivalent circuit, #! Figure 2(d) shows bFE and l
This is a glass showing the relationship with c. Figure 3 (a) to (C)
3(a) is a cross-sectional view of the device, FIG. 3(bJ is an equivalent circuit, and FIG. 3(C1 is hFo
Figure 4(a) is a graph showing the relationship between Ic and Ic.
4(b) shows yet another embodiment of the present invention 1 applied to the output stage of a Darlington coupled transistor, FIG. 4(a) is a cross-sectional view of the element, and FIG. 4(b) is its equivalent circuit. . In the figure, 1... a hemi-shaped semiconductor substrate, 2...
... Collector layer, 3 ... Base layer, 4.
...Emitter layer, 5...Collector metal electrode, 6...Emitter metal electrode, 7...
Pace metal electrode, 11.12... Collector layer,
13... Base layer, 14... Second emitter layer, 15... Collector electrode, 16...
... Emitter electrode, 17 ... Base electrode, 1
8...First emitter layer, 19...Insulating layer, 20...Pace resistor, 21...
hFE% of Q, 22...Q! The hFE characteristics of 23...Qs are the hFE% characteristics. (a/) Shikub") Figure 1 (C>(tL') Figure 1 (oJ) Figure 3 Figure 3

Claims (1)

[Claims] Impurities of one conductivity type are diffused on the main surface side of the semiconductor substrate of one conductivity type to form a collector layer, impurities of opposite conductivity type are diffused on the other main surface side to form a base layer, and one conductivity type is formed in the base layer. A semiconductor device in which an emitter layer is formed by diffusion of type impurities, characterized in that a nine-conductivity type impurity region is provided in the base layer so that its planar shape surrounds the emitter mt. Semiconductor equipment.