JP2004200393A - Transistor - Google Patents

Abstract

Provided is a transistor in which a current is dispersed and flows throughout a semiconductor chip without being concentrated near an emitter pad.
A base region is formed in a collector region, and an emitter region is formed in the base region. Further, inside the emitter region 3, a plurality of multi-base regions 4 having a uniform size are arranged and formed in a row direction and a column direction. It is assumed that the size of the base contact portion 51 closer to the emitter pad 10 is relatively smaller than the size of the base contact portion 53 closer to the base pad 7.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a transistor, and more particularly to a transistor such as a power transistor having a high withstand voltage and a large current capacity used for a switching power supply.
[0002]
[Prior art]
For example, in a power transistor that requires a large current, such as a high-voltage power transistor used in a switching power supply for a telephone or the like, the operating current, that is, the collector current, which is an absolute maximum rating, mainly depends on the area and peripheral length of the emitter region. Therefore, in order to increase the operating current, it is necessary to increase the area and peripheral length of the emitter region. However, increasing the area of the chip constituting the transistor in order to increase the area and perimeter of the emitter region is disadvantageous in terms of mounting on a small device.
[0003]
Therefore, within the limited chip area, the contact portion and the aluminum wiring in the base region and the emitter region are made uniform, and the junction area between the base region and the emitter region and the perimeter of the emitter are increased. There has been proposed a transistor having a configuration in which a base region and an emitter region are formed in a comb shape, and a configuration in which a multi-base region is formed between comb-shaped emitter electrode wirings.
[0004]
FIG. 3 is a plan view schematically illustrating the layout of each part of a conventional transistor viewed from the front side. Reference numeral 31 denotes a collector region of a transistor formed of a semiconductor substrate. A base region 32 is formed in the collector region 31, and an emitter region 33 is formed in the base region 32. Further, inside the emitter region 33, a plurality of multi-base regions 34 having a uniform size are formed in a row direction and a column direction.
[0005]
A base contact portion 35 is formed in each of the multiple base regions 34, and a comb-shaped base electrode wiring 36 connecting the base contact portions 35 is formed. The base electrode wiring 36 extends and is integrated to form a base pad 37. Also, between the base electrode wirings 36, like the base electrode wiring 36, comb-shaped emitter electrode wirings 39 connecting the lateral emitter contact portions 38 are formed, and the emitter electrode wirings 39 are extended and collected. An emitter pad 40 is formed.
[0006]
On the other hand, there has been proposed a transistor in which the size of the multi-base region is not uniform. Specifically, the size of the multi-base region is formed large near the emitter pad, and the size of the multi-base region is formed small near the base pad (for example, see Patent Document 1).
[0007]
[Patent Document 1]
Japanese Patent No. 2895327
[Problems to be solved by the invention]
In the conventional transistor shown in FIG. 3, when a multi-base region is formed between comb-shaped emitter electrode wirings and a base contact portion, an emitter contact portion, an aluminum wiring, and the like are made uniform, an emitter is formed. The current flows intensively between the emitter electrode wiring and the base contact portion in the vicinity of the emitter pad for supplying power to the region, and there has been a problem that transistor breakdown due to overcurrent occurs.
[0009]
The present invention has been made in view of such a problem, and the operating current and the instantaneous inrush current (surge current) are uniformly distributed over the entire semiconductor substrate (semiconductor chip) without being concentrated near the emitter pad. It is an object of the present invention to provide a transistor which is configured to flow and can achieve high breakdown current resistance, that is, high breakdown voltage resistance.
[0010]
Another object of the present invention is to provide a transistor capable of more reliably achieving uniform current distribution.
[0011]
[Means for Solving the Problems]
In the transistor according to the first invention, a base region is formed in a collector region, an emitter region is formed in the base region, and a base is provided via a base electrode wiring and an emitter electrode wiring to supply power to the base region and the emitter region, respectively. In the transistor in which the pad and the emitter pad are formed, the plurality of uniform-sized multi-base regions formed between the base pad and the emitter pad are connected to the base electrode wiring and the multi-base region. Therefore, a base contact portion formed in a multi-base region is provided, and a distance between a boundary of the multi-base region and the base contact portion becomes shorter as the distance from the emitter pad increases.
[0012]
In the first invention, the pattern of the base contact portion is changed so that the distance between the boundary between the multi-base region and the emitter region and the base contact portion becomes shorter as the distance from the emitter pad increases. The ballast resistance in the base region can be increased nearer to the emitter pad, and smaller when farther from the emitter pad. That is, the current hardly flows in the multi-base region arranged on the side closer to the emitter pad where the current easily flows, and the current flows in the multi-base region arranged on the base pad side (far side from the emitter pad) where the current hardly flows. Can be easier. As a result, the easiness of current flow and the difficulty of current flow can be offset, and the same level of current easiness can flow in any region near the base pad, near the emitter pad, or at an intermediate position between the base pad and the emitter pad. Can be. Therefore, the current distribution can be made uniform, and the operating current and the instantaneous inrush current (surge current) do not concentrate near the emitter pad, but flow in a distributed manner throughout the semiconductor substrate (semiconductor chip). Element destruction due to local concentration of current in the vicinity can be prevented.
[0013]
A transistor according to a second invention is characterized in that in the first invention, the multi-base region and the base contact portion are formed concentrically.
[0014]
In the second invention, since the multi-base region and the base contact portion are formed in a concentric pattern, local concentration of current in each multi-base region can be prevented, and the uniformity of current distribution can be further improved. . The reliability in surge voltage and surge current can be further improved.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described with reference to the drawings showing the embodiments.
FIG. 1 is an explanatory plan view schematically illustrating the layout of each part of a transistor according to the present invention as viewed from the front side. FIG. 2 is a cross-sectional explanatory diagram for explaining a schematic cross-section taken along arrow AA in FIG. In FIG. 2, hatching indicating a cross section is attached to only a part for easy understanding, but all parts in the figure are cross sections of each part. Reference numeral 1 denotes a collector region of a transistor formed of a semiconductor substrate such as silicon. A base region 2 is formed in the collector region 1, and an emitter region 3 is formed in the base region 2. Further, inside the emitter region 3, a plurality of multi-base regions 4 having a uniform size (a uniform plane pattern) are arranged and formed in a row direction and a column direction.
[0016]
As is well known, in the case of a PNP transistor, the collector region 1 is a P-type semiconductor substrate, the base region 2 is formed by diffusing an N-type impurity, and the emitter region 3 is formed by a P-type impurity. Is formed by diffusing. In the case of an NPN transistor, the collector region 1 is an N-type semiconductor substrate, the base region 2 is formed by diffusing a P-type impurity, and the emitter region 3 is formed by diffusing an N-type impurity. You.
[0017]
A base contact portion 5 is formed in each of the plurality of multi-base regions 4 concentrically with respect to the multi-base region 4, and the base contact portion 5 in the lateral direction in the figure is a comb-shaped base electrode wiring 6 (understanding). (Indicated by a two-dot chain line in order to facilitate the above). The base electrode wiring 6 is further extended and collected to form a base pad 7 (shown by broken lines for easy understanding). Further, between or outside the base electrode wirings 6, the emitter contact portions 8 are arranged and formed in the row direction and the column direction. The emitter contact portions 8 in the horizontal direction in the figure are interconnected and connected by a comb-shaped emitter electrode wire 9 (shown by a two-dot chain line for easy understanding) formed similarly to the base electrode wire 6. ing. The emitter electrode wiring 9 is further extended and collected to form an emitter pad 10 (shown by broken lines for easy understanding). The base contact portion 5 and the emitter contact portion 8 are formed by providing openings in the insulating film 11 (FIG. 2) formed on the semiconductor substrate, as is well known. The transistor is formed using other well-known semiconductor processes. For example, the base electrode wiring 6, the base pad 7, the emitter electrode wiring 9, and the emitter pad 10 are formed simultaneously by vapor deposition or plating of a metal such as aluminum or copper.
[0018]
The size of the base contact portion 5 (51) closer to the emitter pad 10 is formed relatively smaller than the size of the base contact portion 5 (53) closer to the base pad 7. The size of the base contact portion 5 (52) located in the middle is formed to be an intermediate size between the size of the base contact portion 5 (51) and the size of the base contact portion 5 (53). That is, distance L1 (distance between the boundary of multi-base region 4 and base contact portion 51 on the side closer to emitter pad 10)> distance L2 (distance between the boundary of multi-base region 4 and base contact portion 52 at an intermediate position)> A relationship of a distance L3 (the distance between the boundary of the multi-base region 4 and the base contact portion 53 closer to the base pad 7) is provided. That is, the distance (for example, L1, L2, L3) between the boundary of the multi-base region 4 and the base contact part 5 (for example, 51, 52, 53) is equal to the base contact part 5 (for example, 51, 52, 53). It is formed so as to be shorter as the distance from the emitter pad 10 increases (for example, L1>L2> L3).
[0019]
The resistance between the base contact part 5 and the emitter contact part 8 is the resistance of the multi-base region 4 between them (ballast resistance, for example, Rb1, Rb2, Rb3 respectively corresponding to the base contact parts 51, 52, 53) and the emitter. It is determined by the sum with the resistance of the region 3. Since the impurity concentration in the emitter region 3 is generally about 100 to 10000 times higher than the impurity concentration in the multi-base region 4, the resistance in the emitter region 3 becomes smaller than the resistance in the multi-base region 4, and the base contact portion 5 and the emitter contact portion 8 The effect on the resistance between them is small. That is, the resistance between the base contact portion 5 and the emitter contact portion 8 is basically determined by the resistance (Rb1, Rb2, Rb3) of the multi-base region 4.
[0020]
That is, on the side closer to the emitter pad 10, the resistance between the base contact part 5 and the emitter contact part 8 is determined by, for example, Rb1, and on the side closer to the base pad 7, the resistance between the base contact part 5 and the emitter contact part 8 is smaller. Is determined by, for example, Rb3, and the resistance between the base contact portion 5 and the emitter contact portion 8 located in the middle is determined by, for example, Rb2. Since the resistances Rb1, Rb2, Rb3 occur in the multi-base region 4 formed with the same impurity profile, the magnitudes of the resistances Rb1, Rb2, Rb3 are substantially proportional to the corresponding distances L1, L2, L3, respectively. Rb1>Rb2> Rb3.
[0021]
Therefore, on the side closer to the emitter pad 10, the current is easy to flow because it is close to the emitter pad 10, but the resistance between the base contact portion 5 and the emitter contact portion 8 is large, for example, Rb 1, so that the current hardly flows. On the other hand, on the side close to the base pad 7, the current is difficult to flow because it is far from the emitter pad 10, but the resistance between the base contact part 5 and the emitter contact part 8 is small, for example, Rb3, and the current easily flows. At an intermediate position between the base pad 7 and the emitter pad 10, an intermediate current easily flows. In other words, the distance from the emitter pad 10 and the boundary of the multi-base region 4 and the base contact in any of the region near the emitter pad 10, the side near the base pad 7, and the intermediate position between the base pad 7 and the emitter pad 10. The ease of current flow and the difficulty of current flow, which are determined by the distance to the part 5, are offset.
[0022]
As a result of the easiness of current flow and the difficulty of current flow depending on the distance from the emitter pad 10, the current flow is reduced in any of the vicinity of the base pad 7, the vicinity of the emitter pad 10, and the intermediate position between the base pad 7 and the emitter pad 10. Can be set to the same level of current flow. The operating current and the instantaneous inrush current (surge current) do not concentrate in the vicinity of the emitter pad 7 but flow evenly over the entire semiconductor substrate (semiconductor chip), thereby preventing element breakdown due to local concentration of current. And high breakdown current resistance, that is, high breakdown voltage resistance. In the case of three distances L1, L2, and L3, the length may be large, medium, or small. For example, when the number of multi-base regions 4 increases in the same row direction, the pattern of each part of the transistor may be increased. May be appropriately set so that the uniformity of the current distribution can be improved in accordance with the above. For example, the current distribution may be changed linearly, or may be changed stepwise (for example, in the case of six multi-base regions, large, medium, medium, small, To be set as described above).
[0023]
Since the multi-base region 4 and the base contact portion 5 are formed concentrically, the resistance (Rb1, Rb2, Rb3) of each multi-base region 4 can be made uniform in all directions on the circumference. Localization of the current can be prevented from occurring in the multi-base region 4, and the uniformity of the current distribution can be further improved. If the area of the base contact portion 5 (53) close to the base pad 7 is too large, the base contact portion 53 can be formed in a ring shape.
[0024]
Further, in the above description, the multi-base region 4 is assumed to have a uniform size, but a slight variation and a non-uniformity of the dimensions are permissible as long as they do not depart from the gist of the present invention. For example, even when the size of the multi-base region 4 is made non-uniform, the base contact portion 5 (for example, 53) closer to the base pad 7 is separated from the base contact portion 5 (for example, 51) closer to the emitter pad 10. Needless to say, if the distance between the base contact portion and the boundary of the multi-base region 4 becomes shorter as the distance from the emitter pad 10 increases, the same operation and effect as the present invention can be obtained.
[0025]
【The invention's effect】
As described in detail above, in the first invention, the pattern of the base contact portion is changed so that the distance between the boundary of the multi-base region and the emitter region and the base contact portion becomes shorter as the distance from the emitter pad increases. Therefore, the ballast resistance in each multi-base region can be increased nearer to the emitter pad, and reduced when farther from the emitter pad. In other words, it is difficult for the current to flow in the multi-base region located on the side closer to the emitter pad where current easily flows, and it is easier for the current to flow in the multi-base region located far from the emitter pad where current does not easily flow due to parasitic resistance. Configuration. As a result, the easiness of current flow and the difficulty of current flow can be offset on the entire surface of the chip, and the current flow is nearly equal in the vicinity of the base pad, the vicinity of the emitter pad, and the intermediate position between the base pad and the emitter pad. Current can easily flow. With such a configuration, the distribution of the current flowing through the emitter electrode wiring can be made uniform, the operating current and the instantaneous rush current (surge current) can be prevented from being concentrated near the emitter pad, and can be spread over the entire semiconductor substrate (semiconductor chip). Since it can be made to flow in a dispersed manner, element destruction due to local concentration of current near the emitter pad can be prevented. That is, a transistor (bipolar transistor) having excellent breakdown current characteristics and breakdown voltage characteristics can be realized.
[0026]
In the second invention, since the multi-base region and the base contact portion are formed in a concentric pattern, local concentration of current in each multi-base region can be prevented, and the uniformity of current distribution can be further improved. . A transistor with further improved reliability in surge voltage and surge current can be realized.
[Brief description of the drawings]
FIG. 1 is an explanatory plan view schematically illustrating a layout of each part when a transistor according to the present invention is viewed from a front surface side.
FIG. 2 is an explanatory cross-sectional view schematically illustrating a cross-section taken along arrow AA in FIG. 1;
FIG. 3 is a plan view schematically illustrating a layout of each part of a conventional transistor viewed from the front side.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Collector region 2 Base region 3 Emitter region 4 Multi-base region 5, 51, 52, 53 Base contact part 6 Base electrode wiring 7 Base pad 8 Emitter contact part 9 Emitter electrode wiring 10 Emitter pad 11 Insulating film L1, L2, L3 Distance Rb1, Rb2, Rb3 resistance (ballast resistance)

Claims (2)

A base region is formed in the collector region, an emitter region is formed in the base region, and a base pad and an emitter pad are formed through the base electrode wiring and the emitter electrode wiring to supply power to the base region and the emitter region, respectively. Transistor
A plurality of uniformly sized multi-base regions formed between the base pad and the emitter pad;
A base contact portion formed in a multi-base region to connect the base electrode wiring and the multi-base region,
A transistor wherein a distance between a boundary of the multi-base region and a base contact portion decreases as the distance from the emitter pad increases. The transistor according to claim 1, wherein the multi-base region and the base contact portion are formed concentrically.

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