JPS63114259A - Bipolar type transistor - Google Patents

Abstract

PURPOSE:To decrease the temperature of an external connecting part for an emitter, by arranging the external connecting part for the emitter, which is formed on the surface electrode of the emitter for electrical connection to the outside, at a position which is protruded from a part surrounded by the emitter region. CONSTITUTION:A rear stage emitter electrode 7 is formed on the main surface of a semiconductor substrate and arranged at the inside parts of finger parts 41-48 of an emitter. The electrode 7 is also formed at the central part of the finger parts. The electrode is extended toward the direction perpendicular to the longitudinal direction of the finger parts 41-48 of the emitter. A protruding region 71, on which an external connecting part 13 of the emitter, is provided at the outside of a part surrounded with the finger parts 41-48 of the emitter. The external connecting part 13 of the emitter comprises a metallized layer and is formed in the protruding region 71. Electrical connection to the outside is performed at this part. Thus the effect of heating at the emitter region can be decreased, thermal fatigue at this part is alleviated and the life of the products can be elongated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a bipolar transistor, and more particularly, to a bipolar transistor having an emitter external connection portion formed on an emitter surface electrode for electrical connection with the outside.

[Conventional technology]

FIG. 3 shows a Darlington-connected bipolar transistor (hereinafter referred to as "rDTr") as a conventional bipolar transistor. 4(a) is a top view thereof, and FIG. 2(b) is a cross-sectional view taken along the line CC in FIG. 2(a). In the figure, log+ is an N-type low-resistance collector layer, and 10a
8 is the low-resistance collector layer 10a, and the N- layer layered thereon.
type high-resistance collector layer, and a low-resistance collector layer 10a
+ and the high-resistance collector layer 10 a z constitute a semiconductor substrate that becomes the collector regions of the front and rear stages. 2a is the base region of the front-stage transistor (hereinafter referred to as "front-stage base") made of a P-type scattered layer formed in the high-resistance collector layer 10a2, and 2a is an N-type scattered layer formed in the front-stage base la. 3a is a high-resistance collector 1i10a, the base region of a rear-stage transistor (hereinafter referred to as "back-stage base") is a P-type diffusion layer formed therein, and 4a is a high-resistance collector 1i10a; This is the emitter region of the subsequent transistor (hereinafter referred to as "subsequent emitter") made of an N0 type diffusion layer formed in the subsequent base 3a, and its peripheral length is increased to improve characteristics such as current capacity and current amplification factor. It has a plurality of finger-like portions 41a to 50a for this purpose. 5a is a surface electrode of the front stage base 1a (hereinafter referred to as "front stage base electrode"), and 6a is a surface electrode of the front stage emitter 2a and the rear stage base 3a, electrically connecting the two. 7a is the surface electrode of the latter emitter (hereinafter referred to as the "later emitter electrode")
, 8a is an oxide film formed on the main surface of the semiconductor substrate to protect the PN junction, and 9a is a surface protection film.

11a is a collector electrode, 12a is a base external connection portion formed at the center on the surface electrode 5a, 13a is an emitter external connection portion formed at the center on the rear emitter electrode 7a, and 14a is formed on the collector electrode 11a. This is the collector external connection part. Here, the emitter external connection portion 13a is arranged in the center on the rear emitter electrode 7a because the emitter external connection portion 13a and each finger-shaped portion 4
This is because it is the position where the difference in current path distance between 1a to 50a can be reduced most.

Next, the operation of this DTr will be explained. Front stage base electrode 5
When the front stage transistor is operated by applying a positive bias to a and causing a base current to flow from the front stage base 1a to the front stage emitter 2a, the base current is amplified by the current amplification factor of the front stage transistor. The current flows from the low resistance collector layer 10a to the high resistance collector layer N.
10 a.

and flows to the front-stage emitter 2a. Since the front-stage emitter 2a and the rear-stage base 3a are electrically connected by the surface electrode 6a, the collector current is transmitted to the rear-stage base 3a.
a flows to the second-stage emitter 4a to operate the second-stage transistor, and a collector current whose current is amplified by the current amplification factor of the second-stage transistor passes from the low-resistance collector layer 10a1 to the high-resistance collector ii10a2. It flows to the subsequent emitter 4a. In this way, when the base current of the transistor is passed, a large output current can be obtained.

[Problem that the invention seeks to solve]

When the DTr is operated as described above, heat is generated in the collector region immediately below the front-stage emitter 2a and the rear-stage emitter 4a. In particular, as described above, a large current flows directly under the rear-stage emitter 4a, so the amount of heat generated therefrom increases. According to the above-mentioned DTr, the temperature is likely to be the highest immediately below the latter-stage emitter 4a, which is the heat-generating part, and furthermore, since the emitter external connection part 13a is arranged above the central part, that part is affected by the heat generation. becomes larger.

Furthermore, when the current flowing through the rear emitter 4a becomes even larger, the resistance component of the rear emitter electrode 7a cannot be ignored, and the potential of the rear emitter 4a rises due to the potential drop due to the resistance component.
The bias voltage across a becomes smaller as the distance from the emitter external connection portion 13a increases. Therefore, emitter external connection part 1
Since the operation of the transistor is suppressed in the part away from the emitter external connection part 13a,
The amount of heat generated is concentrated in the vicinity, and the amount of heat generated around this portion becomes even larger.

In the emitter external connection part 13a and the base external connection part 12a, the metal wire 13a1 is wire-bonded as shown in the schematic perspective view of FIG.
Electrical connection with the outside is made by bonding the L lead 13a2 with solder 13a (FIG. 2(b)), and as mentioned above, if the amount of heat generated in this part increases, thermal fatigue may occur, for example. The possibility that cracks will occur in the solder 13a3 increases, and reliability at the connection portion decreases.

The above description was about Darlington-connected bipolar transistors, but the same applies to single bipolar transistors, and although the degree of difference is different compared to DTr, 1. Heat generation at the external connection of the emitter is still a problem, and consideration must be given to thermal fatigue, especially when these devices are used in automobiles with severe thermal environmental conditions or for high power applications. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide a bipolar transistor structure in which the temperature at the external connection portion of the emitter is reduced.

[Means for solving problems]

In order to achieve the above object, the present invention includes a semiconductor substrate of a first conductivity type that is electrically connected to a collector electrode and serves as a collector region, and a semiconductor substrate that is formed on the main surface side of the semiconductor substrate and that is formed on the main surface side. A bipolar transistor comprising: a base region of a second conductivity type electrically connected to a surface electrode; and an emitter region of a first conductivity type formed in the base region and electrically connected to an emitter surface electrode on the main surface. , employing a bipolar transistor characterized in that an emitter external connection portion formed on the emitter surface electrode is disposed at a position protruding from a portion surrounded by the emitter region in order to make an electrical connection with the outside. are doing.

〔Example〕

Hereinafter, the present invention will be explained using embodiments shown in the drawings. FIG. 1 shows an embodiment of the present invention, in which the present invention is applied to a DTr. The figure (a) is a top view, the figure (b)
is a cross-sectional view taken along the line A--A in FIG. 5A, and FIG. First, let's focus on Φ) in the same figure.
10. The N-type impurity concentration is l×IQ! 11 atoms/C
10□ is an N0-type low resistance collector layer with an N type impurity concentration of about 1×IQ14 atoms/ctl, and the low resistance collector layer 10. An N-type high-resistance collector layer is laminated thereon, and the low-resistance collector layer 101 and the high-resistance collector layer 10□ constitute a semiconductor substrate that becomes the front-stage and rear-stage collector regions. l is high resistance collector layer 1
0 is a pre-stage base formed in the pre-stage base 1, 2 is a pre-stage emitter formed in the pre-stage base 1, 3 is a post-stage base formed in the high-resistance collector layer 102, and 4 is formed in the post-stage base 3. This is the latter stage emitter. In addition, the P-type impurity concentration of the first stage base 1 and the second stage base 3 is lXl01
h″″′? The N-type impurity concentration of the front-stage emitter 2 and the rear-stage emitter 4 may be approximately 1X10'' atoms/d.

Next, the layout will be mainly explained with reference to FIGS. The aforementioned front stage base 1 and rear stage base 3 are electrically connected through a connecting path 15, and a resistor 75 Rl is inserted through this connecting path 15. Note that a resistor R1 is inserted in parallel between the rear-stage emitter 4 and the rear-stage base 3. The rear emitter 4 has an emitter finger portion 4 whose planar shape is finger-like.
1, 42, 43, 44, and emitter finger portions 45, 46, 47.
appears on the surface, and the portion 31 is directly electrically connected to the subsequent emitter electrode 7. Further, protrusions 49 . . . extend from the emitter fingers 41 , 45 in a direction perpendicular to the longitudinal direction of the emitter fingers 41 , 45 so that a portion thereof is electrically connected to an emitter external connection portion 13 to be described later. ．． 49□ is formed.

The above-mentioned portion 31 appears on the surface between the protrusions 4L and 49z, and reaches the emitter external connection portion 13. Furthermore, the protrusions 4L and 49z are formed to insert a resistor into the rear stage base 3 directly below the protrusions 4L and 49z, and do not necessarily need to be connected to the emitter external connection portion 13, and may be arranged in the vicinity thereof. That's fine. Note that this protrusion 49
．． .

No substantial transistor operation is performed in the 49□ portion.

A rear emitter electrode 7 electrically connected to the rear emitter 4 and formed on the main surface of the semiconductor substrate is connected to the emitter finger portion 4 .
1 to 48, the emitter finger portions 41 to 48 are arranged inside the emitter finger portions 41 to 48, and are also formed in their central portions, and extend from the central portions in a direction perpendicular to the longitudinal direction of the emitter finger portions 41 to 48. It has a protruding region 71 on which the emitter external connection portion 13 is mounted outside the portion surrounded by the emitter fingers 41 to 48 . Further, a cutout portion 72.73 (that is, a portion where the rear emitter electrode 7 is not formed) is formed from the vicinity of the portion perpendicular to the protrusion region 71 and the emitter finger portion 41.45 toward the center portion. .

The emitter external connection part 13 consists of a metallization layer and is formed in a raised area 71, in which the electrical connection to the outside is made.

Next, in the front-stage transistor, the front-stage emitter 2 also has a plurality of finger-like parts, and the end thereof is connected to the connection path 15.
It extends to The surface electrode (previous base electrode) 5 of the pre-stage base l has a finger-like part so as to fit into the indentation formed by the finger-like part of the pre-stage emitter 2, and the base electrode is located at the corner on the semiconductor substrate. It has a large area portion 51 for mounting the external connection portion 12. A surface electrode 6 is formed on a predetermined area on the surface of the front emitter 2 and the rear emitter 3. To explain in detail the arrangement of the front surface electrode 6 that electrically connects the two, the front emitter 2 is located on the inside of the front emitter 2. In the rear stage base 3 portion, base finger parts 61 to 66 are formed so as to fit into the indentation formed between the emitter finger parts 41 to 48 of the rear stage emitter 4. a part 67 electrically connecting 63 and 66, and a base finger part 6 disposed on the side of the emitter external connection part 13 next to the emitter finger part 41.45.
8.69 is formed. Here the base fingers 69
is its tip 69. is formed apart from the protrusion 49□.

A collector electrode 11 is formed on the other main surface of the semiconductor substrate, electrically connected to the low-resistance collector layer lO1, and a collector external connection portion 14 is formed on the collector electrode 11. Note that since the collector electrode 11 is normally electrically connected directly by soldering or the like, there is no need to newly form this collector external connection portion 14. 8 is an oxide film formed on the main surface of the semiconductor substrate to protect the PN junction; 9
is a surface protective film.

Therefore, in this embodiment, the operation is similar to that of the DTr shown in FIG. 3 described as the conventional technique, but in this case, the emitter external connection portion 13 is a portion surrounded by the rear-stage emitter 4 where heat easily accumulates. The protruding area 7 is not located on the central part of the
1, so even if a large current flows through the rear emitter 4 and the collector region directly under the rear emitter 4 generates heat, its influence is reduced.

Here, in the present invention, a position that protrudes from a portion surrounded by the emitter region means a region surrounded by the emitter region that contributes to substantial transistor operation (hereinafter referred to as "effective emitter region") in its planar shape. ) means that the emitter external connection part is placed outside the area surrounded by the envelope line of
As shown in the partial top view in FIG. 1(a) of FIG. 11, the area formed by the envelope line is the area surrounded by the dotted line in the figure, and the emitter external connection portion 13 is disposed outside of the area. I can see that it is.

In the past, as shown in the schematic top views of FIGS. 9(a) and 10(a), the emitter external connection portion 1 is
30 and a base external connection portion 120 are formed to face each other along opposite sides of the semiconductor substrate, and a recess is formed in the effective emitter region 400 in its planar shape, and the emitter external connection portion 130 is disposed within the recess. What you have (
Figure 9(a)). And, the emitter external connection portion 131 and the base external connection portion 121 are arranged at diagonal corners of the semiconductor substrate, respectively, and the effective emitter region 401 is arranged so as to surround the emitter external connection bone 131 (
10(a)), each of these bipolar transistors also has an emitter external connection portion 130 within the region surrounded by the envelope line as shown by the dotted line in the figure.
, 131 are arranged, so it is not within the scope of the present invention,
In such a bipolar transistor, the emitter external connection portion 130 of the bipolar transistor shown in FIG.
In addition, as a result of the heat conduction from the two adjacent sides 401a and 401b of the emitter external connection portion 131 of the bipolar transistor shown in FIG. 10, the temperature reduction effect is as shown in FIG. 9(b). As shown in the isotherm diagrams in Figure 10 and Figure 10, these results are not very promising.

According to the temperature measurement results obtained by the present inventors, the temperature distributions of the conventional DTr with the arrangement shown in Fig. 3 and the DTr with the arrangement of this embodiment are as shown in Fig. 7(a), respectively.
As shown in the isothermal diagram of FIG. 7 □□□), the emitter external connection portions 13a, 13. Base external connection part 12a
, the temperature of 12 is the latter stage emitter current It-6m, the collector-emitter voltage 10 V, ON OF F (7)
Under the condition of 20 Hz, the 7th
As shown in FIG.
It can be seen that the temperature has been reduced.

According to this embodiment, the temperature at the emitter external connection portion 13 can be reduced as described above and the object of the present invention can be achieved. For example, fingers 43, 44, 47, 48 where the difference in distance to the point becomes large.
Since the finger-shaped portions 41, 42, 45, and 46 are closer to each other, when the current flowing to the subsequent emitter 4a becomes large, the transistor operation is biased around this area due to the difference in wiring resistance, and the emitter external connection Although it is conceivable that the temperature of the portion 13 will increase, according to this embodiment, the notch portions 72 and 73 are formed in the rear emitter electrode 7, so that the temperature of the portion 13 in FIG. As shown in the partially enlarged view, for example, the current i flowing through the finger-shaped portion 45.41
flows bypassing the notches 72 and 73, respectively, so
The current path distance becomes correspondingly longer, and therefore the wiring resistance becomes correspondingly larger. Therefore, the current path distance near the emitter external connection portion 13 can be increased, so for example, the current path distance from the emitter external connection portion 13 to the finger-like portions 43, 44, 47, 48 and the finger-like portion can be increased. The distances from 41°, 42°, 45° to 46° can be made approximately the same, the wiring resistance is made uniform as a whole, and the bias in transistor operation can be alleviated. The experimental results of the present inventors are shown in the graph of FIG. The horizontal axis represents the distance from the emitter external connection portion 13 to each point on the subsequent emitter 4, and the vertical axis represents the emitter current i at each point.

The total emitter current is 1. =8A, which is the detected value when the collector-emitter voltage is -3V. As can be seen from the graph, in the configuration without cutouts 72 and 73 (white circles), the emitter current i increases as the distance from the emitter external connection portion 13 increases.

However, by forming the notches 72 and 73 (hatched circles), the emitter current 10 is made uniform.

Further, according to this embodiment, as shown in FIG. 2, the tip portion 69 of the base finger portion 69. is formed at a distance l from the protrusion 49 □, and a part of the current injected from the surface electrode 6 into the rear base 3 flows through the rear base 3 at a distance l.
The current flows through the emitter external connection portion 13, but the amount becomes smaller as the distance 2 becomes longer. According to this embodiment, the amount of current is relatively small, and the current flow near the emitter external connection portion 13 decreases as the length of the distance 2 increases. Transistor operation can be suppressed, and therefore, heat generation due to the operation can be suppressed.

In this embodiment, since the base fingers 69 and 68 are arranged symmetrically in FIG. 1, the tips of the base fingers 68 are relatively close to the protrusion 49°; For the purpose of further suppressing transistor operation near the emitter external connection portion 13, the tip and protrusion 49. In other words, the length of the base finger-like portion 68 in the longitudinal direction may be shortened.

Furthermore, according to this embodiment, the emitter external connection portion 13
The rear-stage emitter 4 is not formed in the entire area below, but is formed in a relatively small area, so the transistor structure is formed only in that small area under the emitter external connection part 13. . Furthermore, since this portion is electrically connected to the subsequent base 3 by the emitter external connection portion 13, the transistor operation in this portion is suppressed. Since other parts do not have a transistor structure, they do not operate, so heat generation is suppressed. Moreover, by adopting such a structure, the rear stage base 3 is electrically connected to the emitter external connection part 13 over a large area, so that the internal emitter external connection part 13 is electrically connected to the rear stage base 3 during reverse bias between the base and the emitter. Carriers can escape more easily, and the breakdown resistance due to current concentration in this area is improved.

Next, FIG. 5 shows another embodiment of the present invention, in which the present invention is applied to a single bipolar transistor. Figure (a) is a top view, Figure (b) is Figure (a).
It is a sectional view taken along the line BB inside. This embodiment is formed in the same way as the transistor in the latter stage of the embodiment shown in FIG. 1, and the same effect can be expected. 10b1 is a low-resistance collector layer, 10b2 is a high-resistance collector layer, and llb is a collector layer. The electrode, 14b is the collector external connection part, 3b and 4b are the rear base 3 and rear emitter 4 in FIG. 1, respectively.
The base region and emitter region correspond to the . Reference numeral 6b denotes a base electrode, one end of which is placed in a corner of the semiconductor substrate over a relatively large area, and a base external connection portion 1 is placed on top of the base electrode.
2b. The base electrode 6b has a finger-like portion formed so as to enter the recessed portion formed by the finger-like portion of the emitter region 4b, and the other end 6b+ is inserted into the recessed portion 6bz closest to the emitter external connection portion 13b. is not formed, but is formed up to this side.

The emitter region 4b has a plurality of emitter finger-shaped parts, the central part of which is not formed, and a protruding part is formed so that a part thereof is electrically connected to the emitter external connection part 13b. . The emitter electrode 7b is formed on the inside of the emitter finger-shaped portion and also on the center portion, and one end thereof is placed at a corner of the semiconductor substrate at a position protruding from the emitter region 4b, and an emitter electrode 7b is formed on the top of the emitter finger-shaped portion. It has a connecting portion 13b. Furthermore, the notch 72 in FIG.
．． Notches 72b and 73b are bent and formed for the same purpose as 73. In the figure, 8b is an oxide film, 9
b is a surface protective film.

Next, FIG. 8 shows still another embodiment of the present invention, in which the present invention is applied to a multi-emitter bipolar transistor. The figure (a) is a top view, the figure (b)
) is an enlarged view of section E in figure (a), and figure (C) is an enlarged view of section E in figure (a).
b) is a cross-sectional view of the stairs taken along line D-D in FIG. In the figure, 3c
4c is a base region, 4c is an emitter region, 6C is a base electrode, 7c is an emitter electrode, 8c is an oxide film, 9c is a surface protection film, 10c+ is a low resistance collector layer, 10c2 is a high resistance collector layer, 11. c is a collector electrode, 12c is a base external connection part, and 13c is an emitter external connection part. A large number of emitter regions 4c are formed in the base region 3c, and in each emitter region 40 part, the base region 3c, high resistance One transistor unit is constituted by the collector layer 11 cz and the low resistance collector 1lOcl, and one transistor is constituted by electrically connecting these many transistor units to the base electrode 6c and the emitter electrode 7cT. Also in this embodiment, the emitter external connection portion 13c is arranged at a position protruding from the portion surrounded by the emitter region 4C, and notches 72c and 73c are formed in the emitter electrode 7C. .

Therefore, in this embodiment as well, the temperature of the emitter external connection portion 13c can be reduced as in the above embodiment, and the notch portion 72c
, 73c, it is possible to suppress heat generation due to transistor operation near the emitter external connection portion 13c.

Note that the present invention is not limited to the above two embodiments,
Various modifications can be made without departing from the spirit of the invention. For example, although the above embodiment uses an NPN type bipolar transistor, a PNP type may also be used, or a structure in which two or more bipolar type transistors are connected can also be adopted. be.

〔Effect of the invention〕

As described above, according to the present invention, since the emitter external connection part is placed in a position that protrudes from the part surrounded by the emitter region, the influence of heat generation in the emitter region can be reduced, thereby reducing thermal fatigue in that part. However, it has the excellent effect of prolonging the product life.

[Brief explanation of the drawing]

FIG. 1(a) is a top view of an embodiment of the present invention, and FIG. 1(b) is a top view of an embodiment of the present invention.
) is a sectional view taken along the line A-A in Figure 1(a), Figure 1(C) is its equivalent circuit diagram, Figure 2 is a partially enlarged view of Figure 1(a), Figure 3(a) is a top view of a conventional DTr, and Figure 3 (
B) is a cross-sectional view taken along the line CC in FIG. 4(a), FIG. 4 is a schematic perspective view of the emitter external connection part, FIG. Figure 5 (°C) is B in Figure (a).
-B cross-sectional view, Figure 6 is a graph showing the current distribution at each point of the emitter, Figure 7 (a) is an isothermal diagram of the conventional DTr,
Figure 7 (b) is an isothermal diagram of the example in Figure 1;
Figure (C) is a graph showing the temperature at each external connection part,
FIG.
Figure (b) is an enlarged view of section E in Figure (a), Figure 8 (C)
9(a) and 10(a) are schematic top views of conventional bipolar transistors, and FIG. 9(a) and 10(b) are schematic top views of conventional bipolar transistors. are the isothermal diagrams of FIG. 1(a), and FIG. 11 is a partial top view of FIG. 1(a). 1... Front stage base, 2... Front stage emitter, 3...
Rear stage base, 4... Rear stage emitter, 5... Front stage base electrode. 6... Surface electrode, 7... Later emitter electrode, 101
...Low resistance collector layer, tOW...High resistance collector layer. 11...Collector electrode, 12...Base external connection part. 13...Emitter external connection part, 14...Collector external connection part, 71...Protrusion part, 12.13...Notch part.

Claims (5)

[Claims] (1) A semiconductor substrate of a first conductivity type that is electrically connected to a collector electrode and serves as a collector region, and a second conductivity type that is formed on the main surface side of the semiconductor substrate and electrically connected to a base surface electrode on the main surface. and a first conductivity type emitter region formed in the base region and electrically connected to the emitter surface electrode on the main surface, in order to make an electrical connection to the outside. A bipolar transistor characterized in that an emitter external connection portion formed on the emitter surface electrode is located at a position protruding from a portion surrounded by the emitter region. (2) The emitter surface electrode is provided with a notch portion of the electrode extending from the emitter external connection portion side toward the center portion of the portion surrounded by the emitter region. bipolar transistor. (3) The bipolar transistor according to claim 1 or 2, wherein the emitter region has an emitter finger-like portion in a part of its planar shape. (4) The emitter region has a protrusion that protrudes toward the emitter external connection portion in a part of its planar shape, and the base surface electrode has a base finger-like part in a part thereof. According to any one of claims 1 to 3, wherein the tip of the base finger-like portion close to the emitter external connection portion and the protrusion are formed apart from each other. The bipolar transistor described. (5) The bipolar transistor according to any one of claims 1 to 4, wherein at least a portion of the base region is electrically connected to the emitter surface electrode under the emitter external connection portion. .