JPH0718456U - Pressure contact type semiconductor device - Google Patents

Abstract

(57) [Summary] [Object] To provide a pressure contact type semiconductor device using an alloy free method and having a structure capable of easily positioning a semiconductor pellet. [Structure] A fixing member 14 is incorporated in a step portion 20 formed on a semiconductor pellet, and relative positioning is performed by contact with an inner wall surface of a flat package 19. Further, a cutout portion 14a is provided in a part of the fixing member 14, and the gate lead 22 is inserted into the cutout portion 14a to prevent the fixing member 14 and the silicon substrate 100 from moving in the circumferential direction. Therefore, it is possible to prevent the semiconductor pellet from being displaced even if vibration or the like is applied after the assembly.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a pressure contact type semiconductor device in which a semiconductor wafer and a temperature compensation plate are not fixed to each other (hereinafter referred to as an alloy free type).

[0002]

[Prior art]

 This type of power semiconductor device, for example, a gate turn-off thyristor (hereinafter abbreviated as GTO) and the like, is characterized as a self-arc-extinguishing element in the fields of high breakdown voltage and large current. The schematic structure of the GTO and its problems will be described below. FIG. 4 is an explanatory view showing one of the conventional schematic structures of the GTO. In the figure, the silicon substrate 100 has a PNPN structure, and an N ↑ + short-circuit layer 6 that selectively penetrates the P emitter layer 7 is provided on the anode side. Further, the silicon substrate 100 is brazed to the temperature compensating plate 8 that serves as an anode electrode. The temperature compensating plate 8 is made of molybdenum or tungsten having a thermal expansion coefficient similar to that of the silicon substrate 100.

However, the formation of the anode electrode using the alloying method by brazing causes warping of the element due to the bimetal effect due to the difference in thermal expansion between the silicon substrate 100 and the temperature compensating plate 8. However, the erosion of N ↑ + short-circuit layer 6 of aluminum silicide may cause defective characteristics of the element. As means for suppressing these, it was necessary to thicken the temperature compensation plate 8 and deeply form the N ↑ + short-circuit layer 6 and the P emitter layer 7. On the other hand, increasing the thickness of the temperature compensating plate 8 causes an increase in cost, and increasing the thickness of the N ↑ + short-circuit layer 6 and the P emitter layer 7 increases the switching loss. This is disadvantageous as an element because it has a trade-off relationship with the suppression of warpage and characteristic defects. In the figure, 1 is a cathode electrode provided in the N emitter region, 2 is a gate electrode provided on the P base layer 4 so as to have a step with the cathode electrode 1, 5 is an N base layer, Reference numeral 9 denotes a passivation rubber used as a protective material for the beveled surface of the silicon substrate 100.

In order to overcome the above problems, an alloy-free technique for forming an anode electrode without using a brazing method has already been proposed. A structural diagram of a semiconductor device using this method is shown in FIG. In FIG. 5, the anode electrode 10 has an aluminum layer formed by vapor deposition or the like instead of the alloy method, and is not alloyed with the temperature compensation plate. In the passivation process for semiconductor devices by this alloy-free method, after beveling the end face, the process strain is removed with a hydrofluoric acid or nitric acid-based chemical, the polyimide resin 11 is applied to the bevel face, and then firing is performed. A silicone resin 12 is formed on the polyimide resin 11 by a transfer molding method. Further, as shown in FIG. 6, the silicone resin 12 molded by this transfer molding method was housed in a flat package 19 and used for positioning with the flat package inner wall 21 as shown in FIG. . The same parts as those in FIG. 4 are designated by the same reference numerals and the other description is omitted.

[0005]

[Problems to be solved by the device]

 In the structure of the conventional pressure contact type semiconductor device as described above, there is a molding step of the silicone resin 12 by the transfer molding method, and there is a problem to be solved such that the step is complicated as a whole.

[0006]

[The purpose of the device]

 The present invention has been made in order to solve the above problems, and uses an alloy-free method, and does not require molding of silicone resin as a positioning member, and can easily position a semiconductor pellet. It is an object of the present invention to provide a pressure contact type semiconductor device having a structure.

[0007]

The pressure contact type semiconductor device of the present invention has a structure in which a semiconductor pellet is sandwiched between an anode post of a flat package and a cathode post, and the anode of the semiconductor pellet is Side or cathode side is provided with a step on the outer peripheral portion of one main surface thereof, and a fixing member is fitted in the step so as to be positioned relative to the flat package inner wall surface. . Further, a part of the fixing member is cut out to form a cutout portion, and a gate pipe is passed through the cutout portion to prevent semiconductor pellets from moving in the circumferential direction of the fixing member. Is.

[0008]

[Action]

 In the pressure contact type semiconductor device of the present invention, the fixing member is fitted in the step portion, so that the outer peripheral surface of the fixing member enables relative positioning in the flat package. Further, since a notch is provided in a part of the fixing member and the gate pipe is inserted into the notch, the fixing member can be prevented from moving in the circumferential direction, and can be flat-shaped after assembly. It is possible to prevent the displacement of the semiconductor pellet even if vibration or the like is applied to the package.

[0009]

【Example】

 Embodiments of the present invention will be described below in detail with reference to the drawings. First, as shown in FIG. 7, P base layer 4 is formed by diffusing Group 3 impurities such as gallium and boron into silicon substrate 100. Further, the anode short-circuit layer (N ↑ + short-circuit layer) 6 is formed by diffusing phosphorus, and the P emitter layer 7 is formed by diffusing gallium, boron or the like. Next, phosphorus is diffused to form the N emitter layer 13. Since the above steps are the same as those in the conventional method, detailed description thereof is omitted.

Further, in the GTO, in order to form a multi-cathode which is generally divided into a large number of islands, the gate portion 2a is dug with a hydrofluoric acid / nitric acid-based etching solution. At this time, a step 20 having a depth of about 30 μm is formed at the end portion on the cathode side at the same time as the gate portion 2a. Then, an oxide film 13a for protecting the N emitter layer 13 is grown and an electrode window is opened. Next, as shown in FIG. 8, aluminum is vapor-deposited on the anode side (upper part in the drawing) to form the anode electrode 10. Further, the cathode electrode 1 (downward in the figure) and the gate electrode 2 are also formed by vapor deposition. Next, after the beveling of the end surface, the processing strain is removed by hydrofluoric acid and nitric acid-based chemicals, and a fixing member that considers the size and tolerance to the inner wall of the flat package at the step 20 of the end surface on the cathode side. Insert 14. As a material of the fixing member 14, an insulating material such as Teflon or silicon rubber is suitable. Further, with the anode electrode 10 facing upward, passivation rubber (silicon rubber) 9 is applied to the beveled portion of the end face.

Next, the semiconductor pellet obtained through the above steps is incorporated into the flat package 19 as shown in FIG. In this case, since the step 20 is provided on the semiconductor pellet, the fixing member 14 can be fitted into the step 20, and the outer surface of the fixing member 14 and the silicon substrate 100 can be used to form the flat package inner wall 21. It can be used for positioning. Further, as shown in FIG. 2, a part of the outer periphery of the fixing member 14 is cut out to form a cutout portion 14a, and the gate lead 22 is inserted into the cutout portion 14a, so that the fixing member 14 is circumferentially formed. Is prevented from moving due to vibration or the like. Further, the etching of the silicon substrate 100 for providing the step 20 is not limited to the order of the above-mentioned steps, and after the oxide film 3 for protecting the N emitter layer 13 is grown, the gate engraving step is It is also possible to carry out by another process. In this case, the depth of the step 20 is not limited to about 30 μm, and it is possible to etch to the limit value where the depletion layer extends to the P base layer 4. Further, the method of forming the step 20 is not limited to the chemical etching method as described above, but may be a mechanical forming method.

Next, a modified example of the present invention will be described. Also in this modification, the steps up to the step of digging the gate are the same. Next, as shown in FIG. 9, after the oxide film 3 for protecting the N emitter layer 13 is grown, the end face portion on the anode side is selectively removed to form a step 20. The removal method may be either chemical etching or mechanical method, as in the above-mentioned embodiment. Further, the etching depth needs to be precisely set in consideration of the width of the depletion layer extending to the N base layer 5, but may be about 30 μm. Then, as shown in FIG. 10, aluminum is vapor-deposited on the anode side to form the anode electrode 10, and the cathode electrode 1 and the gate electrode 2 are also vapor-deposited.

Next, after beveling, the processing strain is removed by a chemical such as hydrofluoric acid or nitric acid, and the dimensional tolerance up to the inner wall of the flat package 20 is taken into consideration at the step 20 of the end face on the anodic side. The fixing member 14 is fitted, and the cathode electrode is faced up, and as shown in FIG. 10, passivation rubber (silicone rubber) 9 is applied to the beveled surface. The semiconductor pellet obtained as described above is incorporated into the flat package 19 as shown in FIG. It should be noted that the flat package 19 has a cathode electrode post 17 and an anode electrode post 18 at the open end, and the above semiconductor pellets are made into the above cathode electrode member by interposing the cathode electrode member 15 and the anode electrode member 16. It is sandwiched between the post 17 and the anode electrode post 18. Further, a bottomed hole 26 is formed in the center of the cathode electrode post 17, and the gate electrode parts such as the insulating spacer 23, the gate electrode member 25, and the disc spring 27 are inserted into the bottomed hole 26 to The electrode member 25 is pressed against the gate electrode 2, and one end of the gate lead 22 connected to the electrode member 25 is pulled out to the outside of the flat package 19 through an insulating pipe 28.

[0014]

[Effect of device]

 According to the present invention, a semiconductor pellet and a flat package can be positioned easily and accurately, and a highly reliable alloy-free pressure-contact type semiconductor device can be provided. In addition, since the fixing member for insulation is fitted and fixed to the step provided on the outer periphery of the silicon semiconductor substrate, the transfer molding process as in the past is not necessary and the excellent effects such as simplification of the manufacturing process are achieved. Play.

[Brief description of drawings]

FIG. 1 is an assembly view of a power pressure contact type semiconductor device according to an embodiment of the present invention.

FIG. 2 is an external view of a fixing member used in the above device.

FIG. 3 is an assembly view of a power pressure contact type semiconductor device showing a modification of the present invention.

FIG. 4 is an explanatory view showing a semiconductor pellet of a conventional power pressure contact type semiconductor device.

FIG. 5 is an explanatory diagram of a conventional semiconductor pellet.

FIG. 6 is an explanatory view showing a state in which the semiconductor pellet is incorporated in a flat package.

FIG. 7 is an explanatory diagram of a silicon semiconductor substrate used in an embodiment of the present invention.

FIG. 8 is an explanatory view of a semiconductor pellet similarly used in the above embodiment.

FIG. 9 is an explanatory view of a semiconductor pellet used in a modified example of the present invention.

FIG. 10 is an explanatory diagram of a semiconductor pellet similarly used in the modified example.

[Explanation of symbols]

 1 Cathode Electrode 2 Gate Electrode 2a Gate Part 3 Oxide Film 4 P Base Layer 5 N Base Layer 6 N ↑ + Short-Circuit Layer 7 P Emitter Layer 8 Temperature Compensation Plate 9 Passivation Rubber 10 Anode Electrode 11 Polyimide Resin 12 Silicone Resin 13 N Emitter Layer 13a Oxide film 14 Fixing member 15 Cathode electrode member 16 Anode electrode member 17 Cathode electrode post 18 Anode electrode post 19 Flat package 20 Step 21 Flat package inner wall 22 Gate lead 23 Insulating spacer 24 Gate electrode component 25 Gate electrode member 26 Bottomed Hole 27 Disc spring 100 Silicon semiconductor substrate

Claims (2)

[Scope of utility model registration request] 1. A pressure contact type semiconductor device having a structure in which a semiconductor pellet is sandwiched between an anode post and a cathode post of a flat package, wherein the semiconductor pellet is provided on an outer peripheral portion of one of the anode-side and cathode-side main surfaces of the semiconductor pellet. A pressure contact type semiconductor device characterized in that a step is provided, and a fixing member is fitted into the step to perform relative positioning with respect to the inner wall surface of the package. 2. A portion of the fixing member is cut out to form a notch, and a gate pipe is passed through the notch to prevent the fixing member and the semiconductor pellet from moving in the circumferential direction. The pressure contact type semiconductor device according to claim 1.