JPH0485967A - Passivating method for semiconductor device - Google Patents

Abstract

PURPOSE:To facilitate a passivation by coating the inner surface of a collar of a cylindrical member having the collar at one opening with nonfluidized passivation rubber, then inserting a semiconductor element into the member, and supplying fluidized passivation rubber into a gap between both. CONSTITUTION:A cylindrical member 12 having a collar 12a is prepared therein, and the collar 12a of the member 12 is coated with nonfluidized passivation material 13 inside an opening end. Then, a semiconductor element S which is beveled and in which its working distortion is removed, is inserted into the member 12, and placed on the coated material 13, fluidized passivation material 9 is fed to a gap formed between the element S and the member 12 and cured. In this case, the material 9 is blocked by the material 13, and entirely covered with the passivation material having sufficient thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a passivation method for semiconductor devices for power use and the like.

B9 Summary of the Invention The present invention involves preparing a semiconductor element using the alloy-free method, applying a non-flowing passivation material to the inside of the flange of this cylindrical member, and applying the above-described semiconductor onto the passivation material. By placing the element and injecting a fluid passivation material into the gap formed between the two and curing it, the passivation process in the alloy-free method is facilitated and the passivation effect is enhanced.

BACKGROUND OF THE INVENTION C0 Conventional Technology Power semiconductor devices, such as gate turn-off thyristors, generally abbreviated as GTO, are increasingly exhibiting their characteristics as self-extinguishing devices in the field of high withstand voltages and large currents.

FIG. 2 shows a configuration diagram of this conventional GTO element, which basically has a four-layer structure of PNPN. Usually, the thermal buffer plate 8 is made of a tungsten disk or a molybdenum disk, which has a coefficient of thermal expansion similar to that of Si. That is, ① is the N emitter layer, 2 is the P base layer, 3 is the N base layer,
4 is a P emitter layer that constitutes a semiconductor element. still,
In FIG. 2, 5 is an N buffer layer, 6 is an N short layer,
7b is an anode electrode, and 8 is a thermal buffer plate. The thermal buffer plate 8 is usually a tungsten disk or a molybdenum disk having a coefficient of thermal expansion similar to that of Si.

The anode electrode 7b is formed by alloying an Al-8i thin film brazing material containing 2 to 20% by weight of Si to the thermal buffer plate 8 with Si semiconductor pellets. Further, K indicates a cathode terminal, A indicates an anode terminal, and G indicates a gate terminal.

In this type of semiconductor element, the electric field concentrates on the end face, so in order to alleviate the electric field concentration and achieve a high withstand voltage, the end face of the semiconductor element is beveled and the end face is covered with a highly insulating dielectric. A so-called passivation process is performed.

In this passivation process, as shown in FIG. 2, after the semiconductor element is beveled, processing distortion is removed by machining and sawching to create a gap in the beveled surface, and passivation rubber 9 is poured into the gap and hardened.

The poured passivation rubber is blocked by the thermal buffer plate 8 so as to cover the beveled surface with a sufficient thickness.

However, in the anode electrode formation method using the above alloy method,
There is a problem in that the difference in thermal expansion coefficient between the semiconductor element and the thermal buffer plate causes warpage of the element and thermal fatigue of the cathode electrode, so it is necessary to make the thermal buffer plate thicker and arrange the cathode emitters radially. Treatment was required.

As a result, in the alloy method, the amount of expensive thermal buffer plates used increases, which is a major cause of cost increase.Furthermore, the radial arrangement of cathode emitters has geometrical inefficiencies in the area of the element, resulting in an increase in the size of the element. It has a configuration that is disadvantageous to electric current.

Furthermore, due to the use of an alloy, the alloy surface side, which is the anode emitter side of the semiconductor device, is eroded by 10 μm or more, resulting in nonuniform device characteristics and the need to form an excessively deep diffusion layer on the anode emitter side. This problem also arises.

In order to solve the above problems, a so-called alloy-free method has been proposed in which the anode electrode is formed without using an alloy, and some semiconductor devices have been commercialized using this manufacturing method.

FIG. 3 shows an explanatory diagram of a semiconductor device produced by this alloy-free method.

In the figure, 78 indicates an anode electrode, and the semiconductor element S
Comparing FIG. 3 with FIG. 2, the differences are that there is no thermal buffer plate 8 and that the anode electrode 1 is not formed of an alloy but is formed by pressure welding.

Passivation processing of semiconductor elements by this alloy-free method is performed by removing processing distortion by etching after bevel processing, applying polyimide 10 to the beveled surface, and then transfer-molding silicone resin 11 on top of it. There is.

D1 Problems to be Solved by the Invention However, in the above-mentioned alloy-free method, there is no thermal buffer plate 8, and therefore there is no member to stop the flowable passivation rubber when it is poured.

For this reason, it is necessary to apply polyimide to the beveled surface and transfer-mold silicone resin thereon.

Therefore, in the alloy method, passivation processing is a series of operations in which passivation rubber is applied and heat treated (cured), but in the alloy free method, polyimide is applied and heat treated as described above, and then silicone The process is complicated because it requires two steps: resin transfer molding.

Furthermore, when applying polyimide to the bevel surface, there are problems such as the polyimide being repelled by the bevel surface, air bubbles being formed, and air bubbles and voids easily forming between the applied polyimide and silicone resin. However, there is a problem in that it is difficult to obtain a good passivation effect.

The present invention was made against this background, and an object of the present invention is to provide a passivation processing method using an alloy-free method that is as simple as the conventional alloy method and has a high passivation effect.

E1 Means for Solving the Problem The means for solving the above problem in the present invention is to provide a cylindrical member having a flange inside in a passivation processing method using an alloy-free method for a semiconductor element, A non-flowing passivation material is applied to the inside of the open end of the flange of this cylindrical member, and then a semiconductor element that has been beveled to remove processing distortion is inserted into the cylindrical member. It is placed on the applied passivation material, and a fluid passivation material is poured into the gap formed between the semiconductor element and the cylindrical member and hardened.

F0 effect As described above, a non-flowable passivation material is applied to the inside of the open end of the flange of a cylindrical member having a flange inside, and a semiconductor element is placed on top of the non-flowable passivation material. When a fluid passivation material is poured into the gap between the beveled surface and the cylindrical member, this passivation material is dammed up by a non-flowable passivation material, and the entire surface is covered with a sufficiently thick passivation material.

G. Example A semiconductor passivation processing method according to this example will be described below with reference to FIG.

In FIG. 1, the basic configuration of the semiconductor element S is the same as that in FIG. 3, so a description thereof will be omitted.

Reference numeral 12 denotes a preferably cylindrical member made of Teflon or silicone resin, and has a flange 12a and an opening formed by the flange 12a at one end thereof.

Reference numeral 13 indicates a non-flowable passivation rubber applied to the inside of the opening end near the opening of the flange 12a, 14 indicates a non-flowable passivation rubber applied to the edge of the upper surface of the semiconductor element S, and 9 indicates a flowable passivation rubber. Showing passivation rubber.

The passivation process according to this embodiment will be described below.

First, the cylindrical member 12 is prepared. Next, this cylindrical member 12
A non-flowable passivation rubber 13 is uniformly applied to the inside of the opening side of the flange 12a in a ring shape having a diameter slightly smaller than the diameter of the lower surface of the semiconductor element S, and raised to an appropriate height.

Thereafter, the semiconductor element S, which has been subjected to bevel processing and etching to remove processing distortion, is inserted into the cylindrical resin 12 and fixed onto the non-flowable passivation rubber 13, as shown in FIG. .

In addition, non-flowable passivation rubber 14 is also applied in a ring shape near the edge of the upper surface of the semiconductor element S. In this way, a gap is formed between the semiconductor element S and the cylindrical member into which the fluid passivation rubber can flow.

Next, fluid passivation rubber 9 is poured into this gap. At this time, the non-flowable passivation rubber 13 blocks the outflow of the passivation rubber 9, and the non-flowable passivation rubber 14 prevents it from flowing into the cathode electrode side.

After this operation is completed, the flowable passivation rubber 9 is cured in a conventional manner.

By configuring the cylindrical member 12 and the semiconductor element S as described above, the present invention allows fluid passivation rubber 9 to flow into the gap and harden, similar to the conventional alloy method passivation process. The passivation process can be performed in a series of operations similar to the conventional alloy method.

In this embodiment, the cylindrical member and the semiconductor element S are bonded together using the non-flowable passivation rubber 13 to prevent the flowable passivation rubber 9 from leaking from the gap, but other bonding means may be used. Alternatively, a configuration may be adopted in which leakage of the passivation rubber from the above-mentioned gap is prevented by using a passivation rubber with low fluidity for this processing without using an adhesive means.

Further, in the above embodiment, in order to prevent the flowable passivation rubber 9 from flowing into the cathode electrode, a non-flowable passivation rubber 14 is applied to the upper surface of the cathode electrode to prevent this intrusion. If the outflow is prevented by other means, this non-flowable passivation rubber 14
is not necessarily necessary.

H8 Effects of the Invention According to the present invention, a non-flowing passivation rubber is applied to the inner surface of the flange of a cylindrical member having a flange at one opening, and then a semiconductor element is inserted into the cylindrical member. However, a gap is formed between the two.

With this configuration, similarly to the alloy method, passivation processing can be easily performed by flowing the fluid passivation rubber into the above-mentioned gap.

Furthermore, compared to the passivation process in the conventional alloy-free method, the semiconductor element is evenly covered with a sufficiently thick rubber, so the passivation effect is high and the yield and reliability are excellent.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a semiconductor device that has been passivated using the present invention, Fig. 2 is a block diagram of a semiconductor device that has been passivated using the alloy method, and Fig. 3 is a block diagram of a semiconductor device that has been passivated using the alloy method. It is a block diagram of the semiconductor element used. 1...N emitter layer, 2...P base layer, 3...
N base layer, 4... P emitter layer, 5... N buffer layer, 6... N short layer, 7... anode electrode,
8... Thermal buffer plate, 9... Fluid passivation rubber, 10... Polyimide, 11 Silicone resin, 12...
...Cylindrical member, 12a...Flame portion 13, 14...Non-flowable passivation rubber Fig. 1 A structural diagram of a semiconductor element in the present invention Fig. 2 A structural diagram of a semiconductor element f in a conventional example Fig. 3

Claims (1)

[Claims] (1) In a passivation processing method using an alloy-free method for semiconductor devices, a cylindrical member having a flange inside is prepared, and a non-flowing material is placed inside the open end of the flange of this cylindrical member. A passivation material is applied, and then the semiconductor element, which has been beveled to remove processing distortion, is inserted into the cylindrical member and placed on the applied passivation material, and the semiconductor elements and the cylindrical member are placed on top of the applied passivation material. A semiconductor device passivation processing method, characterized in that a fluid passivation material is poured into a gap formed between the two and hardened.