JPS5945230B2 - Emitter short-circuit thyristor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an emitter-shorted thyristor in which a cathode emitter region and an adjacent cathode base region are partially short-circuited by a cathode, and in particular to shortening the turn-off time thereof. It's about structure.

For thyristors that require high-speed switching, many improvements have been made in terms of design and structure, but these efforts have mainly focused on improving turn-off characteristics and other characteristics that are compatible with these ( gate trigger current, on-voltage, etc.)
has been paid to improve the correlation.

Generally, in order to shorten the turn-off time, recombination centers are introduced by diffusion of heavy metals or radiation irradiation,
Providing a short emitter promotes the disappearance of excess carriers at turn-off, but these factors also result in an increase in gate trigger current and on-voltage. In order to minimize the deterioration of other characteristics and shorten the turn-off time, various improvements have been made in the diffusion specifications and short emitter structure, but very satisfactory results have not been obtained. . A short emitter thyristor having a conventional structure will be explained below.

FIG. 1 is a sectional view showing a conventional short-circuited emitter thyristor, and FIG. 2 is a top view thereof. Such a thyristor is manufactured by forming a P-type base region 2, a P-type emitter region 3, and an N-type emitter region 4 on an N-type semiconductor substrate 1, and then diffusing a heavy metal such as gold into the semiconductor substrate 1. A cathode electrode 5, a gate electrode 6, and an anode electrode 8 are formed on the substrate. At this time, a partial molecule short-circuited to the cathode electrode 5 of the P-type base region 2 (hereinafter referred to as a short emitter)
is formed. In conventional devices, these short emitters T are sparsely formed within the cathode region.
Short emitter T closest to a point in the cathode region
The maximum value of the distance reached was about 300 Itm or more.
For this reason, excellent turn-off characteristics could not be obtained. If the short emitters T are formed more densely, the turn-off characteristics are improved, but there is a problem that the gate trigger current increases and the effective cathode area decreases, resulting in an increase in the on-state voltage. The present invention has been made in view of the above points, and an object of the present invention is to provide a short-circuited emitter thyristor that can improve turn-off characteristics without impairing other characteristics. This invention will be explained below.

FIG. 3 is a sectional view showing an embodiment of the present invention, and FIG. 4 is a top view thereof. In the figure, the same reference numerals as in FIGS. 1 and 2 indicate the same or corresponding parts, and the difference from FIGS. It is a point formed to be located at the intersection of a group of equally spaced parallel straight lines that are orthogonal to each other so that the

At this time, the diffusion depths of the N-type region 4, P-type region 2, and P-type region 3 are respectively D, d2, d3, the thickness of the N-type region between the P-type regions 2 and 3 is D4, and the semiconductor substrate 1 Assuming that the thickness is t1, the distance between the centers of adjacent shot emitters 7 is DSEl, and the diameter of each shot emitter 7 is r, each of the above parameters is determined by the following relationships. t may be determined by the blocking voltage required for the element, but
When the blocking voltage is low (500 to 800), it is often determined based on the wafer thickness required to prevent a decrease in yield due to wafer cracking during the manufacturing process.

For example, when using a 50 mmφ wafer, t is 200
When the thickness is less than μm, a decrease in yield due to wafer cracking becomes a problem. In particular, in the case of a glass stiction type, a mesa groove is formed in the wafer, so if a 507n11φ wafer is used, a thickness of about 220 μm or more is required. As D4 becomes thicker, the on-voltage increases, and especially when cutting off a pulsed large current, the power loss in the on-state increases and the temperature of the element increases, resulting in a longer turn-off time. Therefore, D4 needs to be as small as possible to satisfy the required blocking voltage. Further, the P-type base region 2 and the P-type emitter region 3 are often formed at the same time to simplify the manufacturing process, and in this case, it is necessary to increase D2 in order to decrease D4. Also, when D2-d1 increases, the short emitter 7
The combined resistance R of the P-type base region 2 from to the gate electrode 6
As SE becomes smaller, the efficiency of injection from the N-type emitter region 4 decreases, and the gate trigger current increases.

Furthermore, increasing r or decreasing DSE improves the turn-off characteristics, but increases the gate trigger current.

The specific values of each of the above-mentioned parameters according to the present invention will be shown by taking a thyristor for controlling a series automatic light control flash as an example.

In the thyristor, a pulse current with a current peak value of 100 to 300 A as shown in FIG.
In this case, it is required to shut off the power in a time of several microseconds or less.

In this case, the turn-off time depends on Tw and is usually Tw
There is a point where the turn-off time is maximum in the range of 600 to 1000 μSec. The maximum value of this turn-off time is hereinafter referred to as pulse turn-off time Tq. T below
q is the value for the pulse current in FIG. Figure 6 shows pulse turn-off Tq and gate trigger current 1 using DSE as a parameter. The experimental results of the correlation of T are shown.
At this time, t=220 μm, D2=D3=65 μM, . d
l=37μM,. d4=90μM,. r=40ttm. In Figure 6, A and B are each required T
, and I.

Indicates the maximum value of T, and C, D, E, F, and G are each Ds
This is a line showing the characteristics of E-600, 4001280, 200, and 150 μm. As is clear from this graph, I
As GT increases, T9 decreases, and once a certain value is reached, t becomes approximately constant as IGT increases. The value of TqOq at this time is defined as Tqmin, and the relationship between Tqmm and DSE is shown in FIG.

When the DSE is 400 μm or more, the Tq dragon hardly depends on the DSE, and the short emitter effect does not appear.
When DSE becomes 300 ttm or less, the short emitter effect becomes significant and TqTnm becomes small. As is clear from straight lines A and B in Fig. 6, if D8E is set to 400 μm or more, it is difficult to control T and IGT to values that satisfy both, but if DSE is set to 300 μm or less, this becomes easy. This effect becomes even more remarkable when the DSE is set to 150 μm or less. FIG. 8 shows the experimental results of the phase opening/opening relationship between Tq and 10T using D2-d1 as a parameter.

In this case, t-220 μM, . d2=D3=65 μM, .
d4=90μM. r=40 μm. Moreover, H, I, and J are graphs of D2-d1-27μMl3OμMl35μm, respectively. As shown in this graph, as D2-d1 increases, IGT for a constant T value increases, and when D2-d1 is 30 μm or more, IGT and T,
It becomes difficult to control both of them to a value that satisfies them. Therefore, D2-d1 is 30! It is necessary to keep it below Tm. In addition,
By setting D4 to 110 μm or less, it is possible to prevent significant deterioration of the pulse turn-off characteristics due to a temperature rise during energization to increase the on-state voltage.

Further, by setting r to 50 μm or less, deterioration of pulse turn-off characteristics due to increase in IGT and decrease in effective cathode area can be prevented. As mentioned above, DSE is 300It
m (the effect is even more pronounced below 150 μm), t
If D2 and D3 are determined so that D4 is 200 μm or more, D4 is 110 μm or less, d1 is determined so that D2-d1 is 30 μm or less, and r is 50 μm or less,
Compared to the conventional structure, devices having better turn-off characteristics can be obtained at a higher yield without deteriorating other characteristics.

Of course, it is clear that the turn-off characteristics can be improved simply by reducing the DSE to 3001 tm or less. In the above example, the short emitter 7 is arranged so as to be located on the intersection of a group of equally spaced parallel straight lines that are orthogonal to each other, but it does not necessarily have to be in this shape, and as shown in FIG. It is also possible to arrange them at the intersections of equally spaced parallel straight lines that intersect with each other at an angle of 600°.

In other words, the effect of the short emitter in the case of DsE-300 μm in the above example is similar to the effect of the short emitter in the case of DsE-300 μm.
× 300 μm - 9 × 104 μm area at a rate of 1,
It is clear that this can be achieved with shot emitters uniformly distributed over the entire cand area. Similarly, the effect of DsE-150μm is 2.25×104μ
This is similar to the effect of short emitters uniformly distributed in the area of d. Note that the shape of the short emitter does not necessarily have to be circular; for example, the effect of a short emitter with a diameter of 40 μm is π×20 μM,
It can be obtained with a short emitter of arbitrary shape having an area of 1.3×10 3 μm.

It is clear that the present invention can also be applied to a structure in which the periphery of the cathode region is a short emitter, as shown in FIG.

Although the thyristor for a series automatic light control strobe has been described above as an example, the present invention can be applied to thyristors that generally require high-speed switching.

Further, the numerical values used in the above explanation, such as the diffusion depth and wafer thickness, are just one example, and the present invention can be applied to other cases as well. For example, the present invention is also effective in the case of D2Sd3.
Furthermore, the present invention can be applied not only to thyristors with a center gate structure but also to thyristors with a corner gate structure.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing a conventional short-emitter thyristor, Fig. 2 is a top view thereof, Fig. 3 is a sectional view showing an embodiment of the present invention, Fig. 4 is a top view thereof, and Fig. 5 is a sectional view showing a conventional short-circuited emitter thyristor. Figures 6 and 8 are diagrams showing the pulse current waveform, Figures 6 and 8 are diagrams showing the correlation between GT and Tq, Figure 7 is a diagram showing the relationship between DSE and T, mm, and Figures 9 and 10 are diagrams showing the correlation between GT and Tq. FIG. 7 is a top view showing another embodiment of the invention. In the figure, 1 is an N-type semiconductor substrate, 2 is a P-type base region, 3 is a P-type emitter region, 4 is an N-type emitter region, 5 is a cathode electrode, 6 is a gate electrode, 7 is a short emitter, and 8 is an anode electrode. be.

Claims (1)

[Scope of Claims] 1. A semiconductor substrate having a cathode emitter region, a cathode base region, an anode base region, and an anode emitter region bonded in sequence, wherein the cathode emitter region and the cathode base region are partially connected by a cathode. In the short-circuited thyristor, a plurality of the short-circuited portions are uniformly distributed within the cathode at a density of one or more in 9×10^4 μm^2, and the thickness of the semiconductor substrate is 200 μm or more, and the anode The thickness of the base region is 110μm or less, and the thickness of the cathode base region is 30μm or less.
A short-circuited emitter thyristor characterized by being formed to a size of micrometer or less. 2. The emitter short-circuited thyristor according to claim 1, wherein the short-circuited portions are provided at a density of one piece per 2.25×10^4 μm^2. 3. The emitter short-circuited thyristor according to claim 1, wherein one short-circuited portion has an area of 1.3×10^3 μm^2 or less.