JPH0611052B2 - Transistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an improvement of a transistor, particularly a transistor having a high frequency and a high current capacity.

(B) Conventional Technology As a structure for increasing the current capacity of a transistor, it has been known to increase the effective area of the emitter. As this structure, there is a mesh base structure or an island-shaped emitter structure shown in FIG. In FIG.
(1) is a collector region made of a semiconductor substrate, (2) is a base region, (3) is an island-shaped emitter region, (4) shown by a dotted line is a base electrode in ohmic contact with the base region (2), (5) ) Is an emitter electrode in ohmic contact with each of the island-shaped emitter regions (3) ... (3).

In the above structure, the peripheral length of the base-emitter junction can be increased by the large number of island-shaped emitter regions (3) ... (3), and high current capacity can be easily achieved. However, as is clear from FIG. 2, as the area of the island-shaped emitter regions (3) ... (3) increases, the area of the mesh-shaped base region (2) also increases and the chip area increases. However, since only 1 / h _FE of collector current flows through the base electrode, the base region (2)
The increase of 1 does not contribute to the increase in current capacity of the transistor.

Therefore, a transistor having a mesh emitter structure as shown in FIG. 3 was considered. In FIG. 3, (10) is a collector region made of a semiconductor substrate, (11) is a base region, (12) is a mesh-shaped emitter region, and (13) shown by a dotted line is an emitter region (12). Ohmic contacted emitter electrode, (14)
Is a base electrode in ohmic contact with the scattered base regions (11).

In the above structure, only the area of the emitter can be increased by the mesh-shaped emitter region (12), which is quite effective in preventing the increase of the chip area. However, the third
As is clear from the figure, the emitter electrode (13) and the base electrode (1
In order to form 4) in the shape of a comb, the emitter electrode (13) can make ohmic contact with only about half the area of the mesh-shaped emitter region (12), and the increase of the area of the emitter region (12) is realized. However, the area of the emitter electrode (13) cannot be increased. Therefore, the mesh-shaped emitter region (12) cannot be fully utilized, and the mesh-shaped emitter region (12) does not work sufficiently to increase the current capacity.

Therefore, after further improvement, a transistor having a mesh emitter having a multilayer electrode structure as shown in FIGS. 4 (a) and 4 (b) was considered. Such a transistor comprises a collector region (20) made of a silicon semiconductor substrate, a base region (21), and a mesh-shaped emitter region (22), and the emitter region (22) is almost the entire surface of the base region (21). The contact regions (23) ... (23) of the base region (21) are arranged in a multi-island shape within the emitter region (22) so as to be completely surrounded by the emitter region (22).
A first base electrode (25) and a first emitter electrode (26) of a first layer shown by a dotted line are formed on the silicon oxide film (24) on the surface of the substrate (20), and the first base electrode (25) is a base region. Each of the contact regions (23) of (21) is ohmic-contacted with each other to form a number of islands, and the first emitter electrode (26) is an emitter region (22).
Has a mesh-like shape with ohmic contact with almost the entire surface. The first base electrode (25) and the first emitter electrode (26) are covered with an interlayer insulating film (27) of polyimide or the like, and the second base electrode of the second layer indicated by a dashed line is formed on the interlayer insulating film (27). (28) and the second emitter electrode (29) are formed. The second base electrodes 28 are formed in ohmic contact with a large number of island-shaped first base electrodes 25, ..., 25, respectively, and extend in one direction like comb teeth. Second emitter electrode (29)
Makes ohmic contact at the outer peripheral portion of the mesh-shaped first emitter electrode (26) indicated by the diagonal lines and extends to the bonding pad.

(C) Problems to be Solved by the Invention According to the above structure, the first emitter electrode (26) can be arranged on almost the entire surface of the mesh-shaped emitter region (22). It can be operated efficiently and the current capacity can be increased.

However, in order to increase the frequency, it is necessary to reduce the width of the mesh-shaped emitter region (22) and miniaturize the pattern. When the pattern shown in FIG. 4 (a) is miniaturized as it is, each contact region (23) ... (23) of the base region (21) is also reduced to be a fine pattern. As a result, each contact region (23) ... (23) of the base region (21) and the first base electrode (25) ... (25)
Since the contact area of is also small, the resistance for taking out the base increases. In particular, a power transistor, which is required to have a high current, is also required to increase the base current, and this pattern has a drawback that this requirement cannot be satisfied. Further, since the electrostatic breakdown resistance is also concentrated on the base region side, there is a drawback that such a pattern does not increase much.

(D) Means for Solving the Problems The present invention has been made in view of the above drawbacks, and a transistor in which the conventional drawbacks are completely eliminated by forming each of the island-shaped contact regions of the base region in a rectangular shape is provided. It is provided.

(E) Function In the present invention, by making each contact region of the base region rectangular, the contact area with the base electrode is increased, while the base current is increased without reducing the area of the mesh-shaped emitter region. is doing.

(F) Embodiment An embodiment of the transistor according to the present invention will be described with reference to FIGS. FIG. 1 (a) is a top view of a transistor according to the present invention, and FIG. 1 (b) is a sectional view taken along line I--I of FIG. 1 (a).

The transistor according to the present invention comprises a collector region (30) made of a silicon semiconductor substrate, a base region (31), and a mesh-shaped emitter region (32), and the emitter region (32) is almost the same as the base region (31). The contact regions (33) ... (33) of the base region (31) are arranged on the entire surface, and the emitter regions (32) are formed in a multi-island shape.
It is located within and completely surrounded by the emitter region (32). On the silicon oxide film (34) on the surface of the substrate (30), the first base electrode (35) and the first emitter electrode (36) of the first layer shown by the dotted line
, The first base electrode (35) is ohmic-contacted with each contact region (33) ... (33) of the base region (31) to form a large number of islands, and the first emitter electrode (36) is an emitter region.
It has a mesh shape with ohmic contact with almost the entire surface of (32). The first base electrode (35) and the first emitter electrode (36) are covered with an interlayer insulating film (37) made of polyimide or the like, and on the interlayer insulating film (37), the second layer of the second layer shown by a dashed line is drawn.
A base electrode (38) and a second emitter electrode (39) are formed. The second base electrodes 38 are formed in ohmic contact with a large number of island-shaped first base electrodes 35, ... 35, respectively, and extend in one direction like comb teeth. The second emitter electrode (39) is in ohmic contact with the mesh-shaped first emitter electrode (36) in a strip shape and extends to the bonding pad in a comb shape.

The feature of the present invention resides in that each contact region (33) ... (33) of the base region (31) is formed in a rectangular shape. The contact region (33) of the present invention is formed by connecting two or three square contact regions shown in FIG. 4 (A) in the related art. With this structure, each contact region (33) ... (33) of the base region (31) and the mesh-shaped emitter region (3
It is clear that this can be realized while keeping the area ratio with 2) the same as the conventional one shown in FIG. 4 (a), and the current capacity can be kept the same as the conventional one. While each contact area
Since the contact holes (33) ... (33) with the first base electrode (35) can be rectangular, the contact area can be greatly increased. Specifically, the connection of two can realize a contact area about twice as large as the conventional one. As a result, the extraction resistance of the base region (31) can be greatly reduced, and the base current can be easily increased. Also, each contact area (33) of the base area (31) ...
Since (33) has a rectangular shape, the peripheral length per cell can be increased as compared with the conventional one, and specifically, the two connected cells can realize the peripheral length 1.5 times that of the conventional one. As a result, with respect to electrostatic breakdown resistance, the electric field can be dispersed as the peripheral length of each contact region (33) ... (33) increases, and breakdown of the first base electrode (35) can be prevented.

The effect of the present invention will be described with reference to FIGS.
FIG. 5 shows the characteristics of the base extraction resistance γ′bb, where a is the width of the contact region (33) of one base region (31),
b means the vertical width. In the conventional structure (a / b = 1), γ'bb was about 1Ω, but when the shape of the present invention with a / b = 2, γ'bb can be improved to about 0.7Ω. This is because the contact area of the first base electrode (31) to the contact region (33) is increased.

FIG. 6 shows the characteristics of electrostatic breakdown withstand capability. This characteristic is to obtain a breakdown strength of a transistor by connecting a capacitor charged in advance to the base electrode to the base electrode and discharging the capacitor. From FIG. 6, the structure of the present invention (for example, a / b = 2)
In, the breaking strength is greatly increased compared to the conventional one. This is because the first base electrode (35) can be formed larger than in the conventional case, so that the breakdown due to the concentration of the electric field in the first base electrode (35) can be greatly relaxed.

FIG. 7 shows the characteristic of the switching time tf (fall time). With the structure of the present invention, tf can be improved as compared with the conventional case. This is for each contact area (33) of the base area (31)… (3
Since the base area can be strengthened with the stripe formation in 3),
Further, it is possible to realize a finer pattern of the mesh-shaped emitter region (32).

(G) Effect of the Invention The first effect of the present invention is to stripe the contact regions (33) ... (33) of the base region (31) while maintaining the ratio of the emitter area to the base area of the base electrode. Since the contact area can be increased, the base extraction resistance γ′bb can be greatly reduced and the base current capacity can be increased. This makes it possible to realize a high-current, high-frequency power transistor.

The second effect of the present invention is that the peripheral length of each contact region (33) ... (33) of the base region (31) can be increased, so that the electrostatic breakdown resistance can be increased.

[Brief description of drawings]

1A and 1B are a top view and a cross-sectional view taken along the line I-I of a transistor according to the present invention, FIG. 2 is a top view of a conventional mesh-based structure transistor, and FIG. 3 is a conventional view. 4B is a top view for explaining a transistor having a mesh emitter structure of FIG. 4, FIGS. 4A and 4B are top views for explaining an improved transistor of a conventional mesh emitter structure and cross-sectional views taken along line IV-IV, FIGS. FIG. 7 is a characteristic diagram for explaining each characteristic of the present invention. Description of main drawing numbers (30) is collector region, (31) is base region, (32) is mesh emitter region, (33) ... (33) is base contact region, (35) is first base electrode, (36) is the first emitter electrode,
(38) is a second base electrode, and (39) is a second emitter electrode.

Claims (1)

[Claims] 1. A collector region, a base region and an emitter region are provided, the emitter region is provided on substantially the entire surface of the base region, and the contact regions of the base region are arranged in a large number of islands in the emitter region. A lattice-shaped first-layer emitter electrode that makes ohmic contact is provided on almost the entire surface of the emitter region, and an island-shaped first-layer base electrode that makes ohmic contact is provided in the contact region of the base region. And a second layer which is insulated from the base electrode of the first layer through an insulating film and which makes ohmic contact with the emitter electrode of the first layer and extends between the base electrode rows of the island-shaped first layer. A transistor comprising: an emitter electrode and a base electrode row of the island-shaped first layer, the base electrode of the second layer extending between the emitter electrodes of the second layer; The contact region of the base region is rectangular, and the second
A transistor characterized in that the longitudinal direction of the rectangle is provided in a direction orthogonal to the extending direction of the base electrode of the layer, and the long side and the short side are approximately 2: 1 to 3: 1.