JPS6043035B2 - semiconductor equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION With recent advances in variable voltage and variable frequency control technology, the capacity of control devices has increased and the scope of application is expanding to include vehicle drive induction motors.

Along with this, semiconductor elements used in variable voltage and variable frequency control devices have also increased in capacity, and elements with special ratings have become necessary. For example, variable voltage for vehicle drive induction motors,
Even in the semiconductor device used in the variable frequency control device, the commutation thyristor of the device has a reverse blocking ability of 2.5 KV,
The turn-off time is 30 psec, the average on-current is 400 A, but the pulse current is 5000 A). A special thyristor is required that has a conduction period of 60 μsec di/dt of 300 A/μsec. If the thyristor is realized by a thyristor having a normal structure, the ignition characteristics of the thyristor will deteriorate and it will not be suitable for practical use. The present invention has been made to fulfill the above-mentioned requirements.

The present invention utilizes the characteristics of the thyristor portion (reverse conduction type thyristor) of the reverse conduction thyristor currently used in vehicle armature choppers since it has the forward direction characteristics of the thyristor described above. In other words, 2.5 KV is required to compensate for the reverse blocking ability of the 2.5 KV high speed reverse conduction type thyristor.
By integrating KV high-speed diodes in series,
It becomes possible to realize the above-required element which has a reverse blocking ability of 2.5 KV and has excellent ignition characteristics as a thyristor. A feature of the present invention is that when diode wafers are fixedly integrated in series in a direction that supplements the reverse blocking ability of the reverse conduction type thyristor wafer, a negative bevel is given to the voltage blocking junction of both wafers.

One of the reasons for this is improved mechanical reliability due to the element structure, and the other is that in 2.5KV class high-speed diodes, the leakage current at high temperatures is higher with a negative bevel than with a positive bevel. The aim is to improve the reliability of the device based on the experimental fact that the An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a vertical cross-sectional view of an embodiment of the semiconductor device of the present invention, and the semiconductor device 1 is a PNIP
A reverse conductivity type thyristaulic wafer 2 having an N junction, a guiode wafer 3 having one PN junction, an anode electrode 24 and a cathode electrode 24' are integrated.

Thyristauer Furia 2 has a specific resistance of 100 to 130 Ωα.
It is made of silicon and has a diameter of 4" and a thickness of 400μ. P for this
By selectively diffusing type and N type impurities, five layers as shown are formed. That is, 5 is an N-type base material layer having a thickness of 270μ, 6 is a resistivity 0.1Ω layer formed by epitaxial growth, and a thickness of 40μ.
7 is a P-type emitter layer formed by boron diffusion with a sheet resistance of 5 Ω/hole and a thickness of 10 μ; 8
9 is a P-type layer formed by gallium diffusion and has a sheet resistance of 30 Ω/hole and a thickness of 90 μm, and 9 is an N-type emitter layer formed by phosphorus diffusion and has a sheet resistance of 0.4 Ω/hole and a thickness of 20 μm. 10 is an anode emitter junction formed by N type base layer 6 and P type emitter layer 7, 11 is a central PN junction formed by N type base material layer 5 and P type base layer 8, and 12 is P type emitter junction. The cathode-emitter junction is formed by the N-type base layer 8 and the N-type emitter layer 9.

From the surface of the P-type emitter layer 7 and the low resistivity N+ layer 6, the thyristue air 2 is heated at a temperature of 820 to 860°C in order to shorten the turn-off time of the thyristau air 2.
Gold diffusion between @ will be implemented. The surfaces of the P-type emitter layer 7 and the low-resistivity N+ layer 6 are in low-resistance contact with the intermediate support plate 22 via the metal solder layer 23'', and the metal solder layer 23 and the P-type low-resistivity silicon 25 and It is fixed to the diode wafer 3 via a metal brazing layer 23''.
A cathode electrode 24'' and a gate electrode 21 are provided in low resistance contact on the surfaces of the N-type emitter layer 9 and the low resistivity P-type layer 8. In order to supplement the capacity, we use a PN junction 1 whose forward blocking capacity has the same or higher reverse breakdown voltage.
8 is formed, and the specific resistance of N-type silicon is 100~
Phosphorus, an N-type impurity, is removed from one side of a silicon wafer with a diameter of 130 f1, a diameter of 4 mm, and a thickness of 370 μ. Sheet resistance 0.4
An N+ type layer 17 is formed by diffusing 50 μm with a sheet resistance of 5Ω/portion to form an N+ type layer 17, and a P type layer 16 is formed by diffusing boron as a P type impurity from the other side by 50 μm with a sheet resistance of 5Ω/portion. Therefore, the thickness of the N-type base material layer 15 is 270μ. From the low resistivity P-type layer 16 of the diode wafer 3 (to reduce the reverse recovery charge of the diode wafer 3, gold diffusion is carried out at a temperature of 820 to 860° C. for 6 minutes. Its surface is fixed to the P-type low resistivity silicon 25 by a metal solder layer 23'' with low resistance contact.The intermediate support plate 22 is preferably made of a highly conductive metal with a small coefficient of thermal expansion, such as tungsten or molybdenum, and is made of metal solder. 23, 23'', and 23'' are preferably thin foils mainly made of aluminum.As a first step, the thyristaulic flame 2, intermediate support plate 22, and P-type low resistivity silicon 25 are made of metal solder 23, 23 during the manufacturing process. '' in the order shown in the detailed explanation above and 7 in an inert gas.
By heating to 750°C (20~), they are bonded and integrated.

As a second step, the diode wafer 3 with respect to the P-type low resistivity silicon 25 is heated at a temperature of 660 DEG C. in an inert gas via the metal solder layer 23''.

As a result, the thyristor wafer 2, the intermediate support plate 22, the P-type low resistivity silicon 25, and the diode wafer 3 are fixed together. Thereafter, the cathode electrode 24'' and gate electrode 21 of the thyristor wafer fabric 2 are coated with aluminum to a thickness of about 10μ using a metal mask.The anode electrode 24 of the diode wafer fabric 3 is also formed by aluminum vapor deposition, A heat treatment is carried out at a temperature of 0.degree. The bevel 19 is provided in order to reduce the surface electric field intensity with respect to the central PN junction (forward blocking junction) 11.The inclination angle of the bevel 19 is as shown in the figure for the P-type base layer 8 with a high impurity concentration. The bevel 20 of the diode wafer 3 has a negative bevel because it forms an obtuse angle with respect to the central PN junction 11 in the direction of the N-type base material layer 5.The bevel 20 of the diode wafer 3 has a surface electric field strength As shown in the figure, the inclination angle of the bevel 20 is a negative bevel that forms an obtuse angle with respect to the PN junction 18 in the direction from the P-type layer 16 with a high impurity concentration to the N-type base material layer 15. The characteristics of the semiconductor device of the present invention formed in this manner are listed below.

(1) By using P-type low resistivity silicon on the diode wafer surface of the intermediate support plate, aluminum can be fixed to the N+ layer of the diode wafer near the eutectic temperature of aluminum and silicon (57rC), which is good. ohmic contact can be obtained.

By the way, if you compare it to the case where P-type low resistivity silicon is not used, it is 0.3 to 0.4 at a forward current of 1500A.
It is possible to improve V.

(2) By using a metal plate with good conductivity as the intermediate support plate, the uneven current distribution that occurs in P-type low resistivity silicon, which has lower conductivity than the metal plate, is made uniform by the intermediate support plate. After that, a forward current is supplied to the thyristor air side, making it possible to increase current surge resistance.

In the case where there is no intermediate support plate made of metal, the current surge withstand capacity is 10 rT1secC, but when the intermediate support plate is inserted into a 5500A thyristor, the withstand capacity increases to 7500 to 8000A. (3) Since both the thyristor wafer and the diode wafer form a negative bevel, a semiconductor device with low leakage current at high temperatures can be easily realized. In the device according to the present application, the leakage current at 2.5 KV at a temperature of 125° C. is about 15 to 20 rT1A in both forward and reverse directions, whereas in the device with a positive bevel formed on both wafers, the leakage current is about 30 to
It is 40mA. (4) It is possible to achieve a turn-off time of 30 μSec by fixing and integrating a diode in series with a reverse conductivity type thyristor in a 2.5K■ thyristor with a withstand voltage, which was impossible to achieve with conventional reverse blocking thyristors. (5) Since this thyristor is controlled by applying a gate signal between the low resistivity P-type layer 8 and the N-type emitter layer 9 of the reverse conductivity type thyristor fan, it is more sensitive to the gate signal than a remote gate type thyristor. Fast response speed.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of one embodiment of the semiconductor device of the present invention. 1...Semiconductor device, 2...Thyrist wafer, 3...Diode wafer, 24.
... Anode electrode, 2 "... Cathode electrode, 23
, 23″, 23″...metal brazing layer, 21...
... Gate electrode, 22 ... Intermediate support plate, 25.
...P type low resistivity silicon plate.

Claims (1)

[Claims] 1 When connecting and integrating diode wafers in series in a direction that supplements the reverse blocking ability of the reverse conductivity type thyristaulic wafer, a metal plate with good conductivity and a small coefficient of thermal expansion is used to securely integrate both wafers. An intermediate support plate is used, and the outer diameter of both wafers decreases as the distance from the intermediate support plate increases. 1. A semiconductor device having a structure using resistive silicon, and characterized in that a voltage blocking junction of the reverse conductivity type thyristor wafer and a voltage blocking junction of the diode wafer are both shaped to have a negative bevel.