JPH0329299B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multi-cell transistor having an emitter stabilizing resistor that is difficult to burn out.

[Conventional technology]

In order to meet the demands for improved characteristics such as larger currents, faster switching, and higher frequencies, there are many types of transistors such as multi-emitter type or mesh emitter type (base island type) that are made up of a large number of cells (small transistors). It has been commercialized.

In this multi-cell transistor, it is known to connect a resistor (called an emitter stabilizing resistor) in series to the emitter of each cell in order to ensure uniform operation of each cell and to improve secondary breakdown resistance. FIG. 14 is a partial plan view showing an example of a conventional multi-emitter transistor. 1
2 is a unit emitter region constituting a cell, and 2 is a base region. Although not shown in the figure, an insulating film is formed on the surfaces of the unit emitter region 1 and the base region 2. 3 is an opening for emitter connection provided in this insulating film, 4 and 5 are emitter wiring conductors, 6 and 7 are polysilicon resistive films, 8 is an opening for base connection provided in the above insulating film, and 9 is a base. It is a wiring conductor. In this structure, the resistors R ₁ and R ₂ obtained by the polysilicon resistive films 6 and 7 are connected between the emitter region 1 and the emitter wiring conductor 4, and act as emitter stabilizing resistors. There are various connection structures for the emitter stabilizing resistor, but the structure in which two resistive films 6 and 7 are connected in parallel, as shown in Figure 14, is often used because it is easy to obtain an appropriate resistance value and is convenient for pattern design. has been done.

[Problem that the invention seeks to solve]

However, there was a need for further improvement regarding the reverse bias secondary breakdown resistance of L-load switching circuits and the like. That is, when the test conditions for reverse bias secondary breakdown strength are made stricter, the resistance film 6 or 7 is damaged by the transient current flowing during switch-off in the cell near the bonding butt (external connection) of the emitter electrode. There is a problem in that the resistance value of these cells decreases due to burnout, and current concentrates in the cell, leading to secondary destruction, and there is a desire to improve this problem.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a multi-cell transistor that prevents burnout of the emitter stabilizing resistor and has a high reverse bias secondary breakdown resistance.

[Means for solving problems]

To achieve the above object, the present invention will be described with reference to the reference numerals in the drawings showing the embodiments for ease of understanding. a base region of a second conductivity type, the first base region having a plurality of island-like portions, net-like portions, or stripe-like portions, the base region being arranged adjacent to the base region on the opposite side from the collector region; an emitter region of a conductivity type, an insulating film provided on the surfaces of the emitter region and the base region, and an emitter connection provided on each of the insulating films on a plurality of unit emitter regions constituting the emitter region. an emitter wiring conductor for connecting the plurality of unit emitter areas in parallel, a base wiring conductor connected to the base area, and an emitter wiring conductor provided between the unit emitter area and the emitter wiring conductor. In a multi-cell transistor having a resistive film, first and second emitter connection holes 21 and 22 are provided corresponding to the unit emitter region 11a, and the center of the first emitter connection hole 21 and the A region along the first straight line connecting the center of the second emitter connecting hole 22 and a region perpendicular to the first straight line at approximately the center between the first and second emitter connecting holes 21 and 22. Approximately cross-shaped resistive films 18 and 33 having regions along the second straight line are provided, and both ends of the resistive film in the region along the first straight line are connected to the first straight line.
and connect to the unit emitter region 11a directly through the second emitter connection openings 21 and 22 or via the emitter connection electrodes 16a and 16b, and connect both ends of the resistive film in the region along the second straight line. The present invention relates to a multi-cell transistor characterized in that it is connected to the emitter wiring conductors 15a and 15b, respectively.

[Effect]

Since the resistive films 18 and 33 of the present invention are formed in a substantially cross shape, the emitter wiring conductors 15a and 15b
Resistive films 18, 33 from to emitter connection openings 21, 22 or emitter connection electrodes 16a, 16b
The length can be increased. That is, only the portion of the resistive films 18, 33 extending along the first straight line connecting the emitter connection openings 21, 22 is smaller than the conventional example shown in FIGS. 14 and 6.
The length of can be increased. In the present invention, when obtaining the same resistance value with the same film thickness as in the past, the resistance film 18, 33 is lengthened by the length of the resistance film 18, 33.
33 can be made wider. As a result, it becomes possible to lower the current density in the resistive films 18 and 33, making it difficult for the resistive films 18 and 33 to burn out.

〔Example〕

Next, a multi-emitter type silicon transistor according to an embodiment of the present invention will be explained based on FIGS. 1 to 4. Figure 1 is a plan view showing the transistor with the insulating film omitted, and Figure 2 is the same as in Figure 1.
3 is a cross-sectional view taken along line A-A in FIG.
FIG. 4 is a sectional view taken along line BB in FIG. In order to clearly distinguish each part, the emitter and base connecting conductors 15 and 17 are shaded in the plan views of FIGS. 1 and 2 and in other embodiments to be described later.

In the figure, 11 is an N ⁺ type (first conductivity type) emitter region, 12 is a P-type (second conductivity type) base region, 13 is an N-type high resistance collector region, 14 is a low resistance collector region, 15a, 15b is the first and second emitter wiring conductor made of Al film, 16a,
16b is an emitter connection electrode, 17a is a base wiring conductor made of an Al film, 18 is an emitter stabilizing resistor made of a polysilicon film, 19 is a collector electrode made of a Ni film, and 20 is a two-layer film of SiO ₂ -Si ₃ N ₄ The insulating film 21, 22, and 23 are openings provided in the insulating film 20.

The emitter region 11 includes a large number of unit emitter regions 11a arranged in an island shape, and the base region 12 is arranged in a mesh shape on the chip surface. Although only 12 unit emitter regions 11a are shown in FIG. 1, in reality there may be many, for example.
There are 200 of them.

First and second emitter wiring conductors 15a and 15b are provided corresponding to each unit emitter region 11a, and a common connection portion 15 that connects these in common
c is provided. The first and second emitter wiring conductors 15a and 15b are connected to the first and second emitter connection openings 21 and 22 provided in the insulating film 20.
It is parallel to the first straight line L ₁ connecting the lines and has equal intervals.

The base wiring conductor 17a is the emitter wiring conductor 1
5a and 15b, and is connected to the base region 12 via a base connection opening 23 provided in the insulating film 20. Note that each base wiring conductor 17a is connected to a common connection portion 17b. Further, the openings 23 are provided corresponding to the corners of the unit emitter regions 11a.

The emitter stabilizing resistive film 18 is formed in a substantially cross shape, and is connected to the emitter connecting electrodes 16a, 16b of the first and second openings 21, 22.
First and second emitter wiring conductors 15a, 15b
It is connected to the. First and second openings 21, 2
2 is provided on the first straight line _L1 corresponding to the bisector of the unit emitter area 11a in one direction, and at an equal distance from the second straight line _L2 corresponding to the bisector in the other direction. is placed above. Note that the second straight line L ₂ is perpendicular to the first straight line L ₁ and passes through the center between the first aperture 21 and the second aperture 22 . The emitter stabilizing resistive film 18 is
It is formed symmetrically about the first and second straight lines L ₁ and L ₂ . One end 18a of the emitter stabilizing resistive film 18 along the first straight line _L1 is connected to the first emitter connecting electrode 16a, and the other end 18a is connected to the first emitter connecting electrode 16a.
b is connected to the second emitter connection electrode 16b,
One end 18c of the area along the second straight line _L2 is the first
is connected to the emitter wiring conductor 15a of the other end 1.
8d is connected to the second emitter wiring conductor 15b.

A base current having a waveform 24 as shown in FIG. 5 is caused to flow through the transistor configured as described above to cause a switching operation, and the collector current I _S/B is caused to cause secondary destruction.
(averaged value) was calculated. At this time, a voltage of 800V was applied between the collector and emitter using a diode clamp method, and L=
Connect a 2.8 mH coil, fix the positive direction base current I _B1 in Figure 5 to 2.5 A, and change the collector current I _C by changing the pulse width W of this positive direction base current I _B1 . Collector current leading to destruction
The value of I _S/B was measured. In addition, the base current in the reverse direction
The value of I _B2 was varied in three steps: -1.0A, -2.0A, and -3.0A, and each I _S/B was determined.

As a result, I _S/B is 12 A when I _B2 = -1.0 A, I _S/B is 11 A when I _B2 = -2.0 A, and I _S/B is 10 A when I _B2 = -0.3 A. It was hot.

For comparison, the first example except that the resistive film 18 is not provided
When I _S/B was measured in the same manner as in the example, I _B2
I _S/B when = -1.0A is 2A, I _B2 = -2.0A and
I _S/B was less than 2 A when I _B2 = -3.0 A. Also,
The resistance value was the same as that of the resistive film 18 of the first example, but the pattern was changed to the resistive films 6 and 7 shown in _FIG. However, when I _B2 = -1.0A, I _S/B is 7A, when I _B2 = -2.0A, I _S/B is 2A, and when I _B2 = -3.0A, I _S/B is 2A. It was hot.

As is clear from this measurement result, I _B2 = −1.0A
The effect of improving secondary fracture resistance was already visible at the time of
Significant improvement is achieved when I _B2 = -2.0A. This improvement effect can be seen at arrows 29, 30, 31, and 32 in Figure 7.
The length of the current path between the emitter connection openings 21, 22 and the emitter wiring conductors 15a, 15b, that is, the length of the resistive film 18, becomes longer, and in order to obtain the same resistance value as before, the resistive film It becomes possible to increase the width or thickness of 18, which results from the lower current density there. In addition, the resistive film 1
If 8 is made into a cross shape, the current density in the central regions indicated by E and F will be low, and no burnout will occur in these central regions.

Next, a transistor according to a second embodiment shown in FIGS. 8 to 11 will be explained. However, this second
12 and 1 which will be described later.
In FIGS. 3 and 15, parts common to those in FIGS. 1 to 4 are designated by the same reference numerals, and their explanations will be omitted.

In this second embodiment, an emitter stabilizing resistor film 33 made of an Al film is provided in place of the emitter stabilizing resistor film 18 made of a polysilicon film in FIGS. 1 to 4. This resistive film 33 includes emitter wiring conductors 15a, 15b, emitter connection electrode 16
Although it is made of the same material Al as a and 16b, it is formed so that a desired resistance value can be obtained by reducing the width and/or thickness and reducing the cross-sectional area. For example, while the emitter wiring conductors 15a and 15b have a width of 30 μm and a thickness of 5 μm, the resistive film 33 has a width of 30 μm and a thickness of 1 μm. The transistors shown in FIGS. 8 to 11 have the same structure as the transistors shown in FIGS. 1 to 4, except that the material of the resistive film 24 is changed.

When the collector current I _S/B leading to secondary breakdown of the transistor in the second embodiment was measured using the same method as in the first embodiment, I _S/B was 6 A when I _B2 = -1.0 A, and I When _B2 = -2.0A, I _S/B was 5A, and when I _B2 = -3.0A, I _S/B was 5A.

As is clear from this result, when I _B2 is large,
That is, an improvement in secondary breakdown resistance was observed during deep reverse bias. In the second embodiment, although the resistance value of the emitter stabilizing resistive film 33 is smaller than the resistance value of the conventional resistors 6 and 7 shown in FIG. 14, which is a disadvantageous value for emitter stabilization, First, the reason why the instantaneous breakdown resistance is improved during deep reverse bias is that the resistive film 33 is formed in a cross shape. In addition,
When this Al film is used as the resistive film 33, the emitter becomes open due to burnout, increasing the burden on other cells and leading to destruction.

If the resistive film 33 is made of the same material as the emitter wiring conductors 15a, 15b, etc. as in this embodiment, the manufacturing process can be simplified and costs can be reduced. Note that if it is attempted to construct the resistors 6 and 7 of the structure shown in FIG. 14 using Al films as in the second embodiment, it will be difficult to obtain the necessary resistance value within a practical length range. Even if the required resistance value is obtained, secondary destruction is likely to occur.

[Modified example]

The present invention is not limited to the above-described embodiments, and, for example, the following modifications are possible.

(A) As shown in FIGS. 12 and 13, the present invention can also be applied to a mesh emitter type transistor (pace island type transistor) in which the base region 12 is arranged in an island shape and the emitter region 11 is arranged in a mesh shape. is possible. In this case, first and second openings 21 and 22 are provided corresponding to the unit emitter region 11a, and the first and second emitter wiring conductors 15a and 15 are connected to each other.
A resistive film 18 made of the same polysilicon film as in the first embodiment is provided as shown in FIG. 12, or a resistive film 18 made of the same Al film as in the second embodiment is provided as shown in FIG. 33 will be provided. This results in
Exactly the same effects as in the first and second embodiments can be obtained.

(B) As shown in Figure 15, in a mesh emitter type transistor, the emitter connection opening 2
1 and 22 are regularly arranged repeatedly, and the opening 2 is
A resistive film 18 made of a cross-shaped polysilicon film or a resistive film made of an Al film may be provided between each of 1 and 22. In this case, the opening 2
1 and 22 are also used as adjacent unit emitter regions 11a.

(C) The resistive films 18 and 33 may be formed of polysilicon, a resistive material other than Al, or a metal material. In short, the resistive films 18 and 33 may be made of any material as long as it provides resistance.

(D) The patterns of the resistive films 18 and 33 may not be exactly cross-shaped, but may have a curvature at the intersection. In addition, the first straight line of the resistive films 18 and 24
The pattern may be modified so that the length of the portion along L ₁ approaches or becomes equal to the width of the portion along the second straight line L ₂ .

(E) The resistive films 18 and 33 may also be provided in the openings 21 and 22 and connected directly to the emitter region 11.

〔Effect of the invention〕

As is clear from the above, according to the present invention, a resistive film is provided along the first straight line connecting the pair of openings, and a resistive film is also provided along the second straight line orthogonal to the first straight line. If both ends of the resistive film along this second straight line are connected to the emitter wiring conductor, the resistive film is less likely to be burnt out and the secondary breakdown resistance is improved.

[Brief explanation of the drawing]

1 is a plan view showing a transistor according to a first embodiment of the present invention, FIG. 2 is a partially enlarged plan view of FIG. 1, FIG. 3 is a sectional view taken along line A-A in FIG. The figure is a sectional view taken along the line B-B in Figure 2, Figure 5 is a current waveform diagram for measuring the secondary breakdown collector current, Figure 6 is a plan view showing a conventional emitter stabilizing resistor, and Figure 7 is a A plan view showing how current flows in the emitter stabilizing resistor film of the present invention, FIG. 8 is a plan view showing the transistor of the second embodiment of the present invention, and FIG.
A partially enlarged plan view of the figure, Figure 10 is A-A of Figure 9.
A line sectional view, FIG. 11 is a BB line sectional view of FIG. 9,
12 and 13 are plan views showing a transistor of a modified example, FIG. 14 is a plan view showing a part of a conventional transistor, and FIG. 15 is a plan view showing a part of a transistor of a modified example. DESCRIPTION OF SYMBOLS 11... Emitter area, 11a... Unit emitter area, 12... Base area, 13... Collector area, 1
5a, 15b... Emitter wiring conductor, 18... Emitter stabilizing resistance film, 20... Insulating film, 21, 22... Opening.

Claims (1)

[Scope of Claims] 1: a collector region of a first conductivity type; a base region of a second conductivity type adjacent to the collector region; and a base region adjacent to the base region on a side opposite to the collector region; an emitter region of a first conductivity type, which is disposed on the surface of the emitter region and has a plurality of island-like portions, net-like portions, or stripe-like portions; an insulating film provided on the surfaces of the emitter region and the base region; , emitter connection openings provided in the insulating film on the plurality of unit emitter regions constituting the emitter region; an emitter wiring conductor for connecting the plurality of unit emitter regions in parallel; and an emitter wiring conductor in the base region. In a multi-cell transistor having a connected base wiring conductor and a resistive film provided between the unit emitter region and the emitter wiring conductor, a first base wiring conductor corresponding to the unit emitter region 11a is provided.
and a region along a first straight line connecting the center of the first emitter connecting hole 21 and the center of the second emitter connecting hole 22; and a substantially cross-shaped resistive film 18, 33 having a region extending along a second straight line orthogonal to the first straight line approximately in the center between the first and second emitter connection openings 21, 22; Both ends of the resistive film in the region along the first straight line are
and connect to the unit emitter region 11a directly through the second emitter connection openings 21 and 22 or via the emitter connection electrodes 16a and 16b, and connect both ends of the resistive film in the region along the second straight line. A multi-cell transistor characterized in that it is connected to the emitter wiring conductors 15a and 15b, respectively. 2 The resistive film is connected to the emitter wiring conductor 15.
The multi-cell transistor according to claim 1, wherein the transistors a and 15b are made of different materials. 3. The multi-cell transistor according to claim 2, wherein the resistive film is a polysilicon film. 4. The resistive film is connected to the emitter wiring conductor 15a,
2. The multi-cell transistor according to claim 1, which is made of the same material as said emitter wiring conductor 15b and whose cross-sectional area is smaller than that of said emitter wiring conductor 15a, 15b. 5 The resistive film and the emitter wiring conductor are both
The multi-cell transistor according to claim 4, which is an Al film.