JPS6142932A - Manufacture of mesa-type semiconductor device - Google Patents

Abstract

PURPOSE:To prevent damages of a wafer by dividing a semiconductor substrate into each individual semiconductor device after fixing an enforcing plate via alloy to one part of the at least one main face of the semiconductor substrate having P-type and N-type layers formed thereon in advance and next drilling mesa grooves on the substrate to clad and calcine glass therein and cladding electrode material on the substrate. CONSTITUTION:An enforcing plate 8 composed of polycrystalline silicon or single crystal silicon, molybdenum or tungsten is fixed to one part of the at least one main force of a semocinductor substrate 1 having P-type and N-type layers formed thereon via aluminum or alloy 19 containing aluminum. After mesa-type grooves 2 are drilled on the semiconductor substrate 1, glass 5 is cladded and calcined on the substrate 1 and furthermore, electrode material is cladded. After this, ths substrate 1 is divided into each individual semiconductor device. Said enforcing plate 8 is formed, for example, by fixing a polycrystalline silicon ring 8 to the wafer 1 via aluminum foil 9 at 700 deg.C in a vacuum. This allows damages of the wafer to be prevented and the caliber of the wafer to be made large.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improved method of manufacturing a mesa-type semiconductor device. .

[Prior art]

Fig. 1 shows the manufacturing process of this 81 conventional mesa type thyristor device, and Fig. 1A shows a semiconductor substrate (hereinafter referred to as wafer) 1 with four layers of P-N-P-N designed in advance. Figure 1B shows a state formed by the impurity diffusion method, in which mesa grooves 2 are dug in wafer 1, and PN junctions 3 and 4 are formed.
FIG.
This is a diagram showing a state in which electrodes are metallized on a wafer 1, where 6 is an anode made of gold, 7 is a cathode made of aluminum, and 12 is a cathode made of aluminum.
is a gate electrode made of aluminum.

Note that the anode 6, cathode 7, and gate 12 are each deposited by vacuum evaporation. In this way, each electrode 8,? 1.1
After 2 is deposited, the wafer process is completed by dividing the wafer into individual silice elements using a diamond cutter as shown by the broken lines in FIG. 1C.

Now, in the case of a thyristor element as described above, wafer 1 is
As shown in the figure, after the step B, that is, after the step of digging the mesa groove 2, wafer breakage occurs rapidly and the manufacturing yield tends to decrease. The first reason for this is:
Due to the mesa groove 2 being dug on the main surface of the wafer 1,
This mesa groove 2 reduces the material strength of the wafer 1. That is, the blocking voltage value is generally 400 to 150.
In the case of 0V class Cyrisk, the thickness of Ueno 11 is 200
Approximately 300 μm is suitable, and in this wafer 1, for example, when an N-type substrate is used, the depth of the P-type emitter region from the substrate surface χ”) is 50 to 70 μm5! Therefore, the depth of the mesa groove 2 needs to be about 60 to 80 μrn in order to exceed χj. Therefore, if the mesa grooves 2 are dug from both main surfaces of the wafer 1, the thickness of the thinnest part of the wafer 1 will be 80 to 140 μm, and it will be extremely susceptible to damage. Furthermore, for discrete elements such as thyristors, diodes, and triacs, it is easier to obtain a large capacity by controlling the current in the vertical direction of the wafer 1 than in the lateral direction; This means that it cannot be made thicker.

The second problem is that distortion is applied to the wafer 1 due to the difference in thermal expansion coefficient between the material of the wafer 1 (silicon) and the passivation glass 5.

For this reason, the sea urchin 1 has a mesa groove 2, as shown in the area A in Figure 2.
The degree of wafer damage was generally tolerable until the mesa groove 2 was formed, but as shown in ranges B and C in Figure 2, after the mesa groove 2 was dug, the degree of wafer damage was proportional to the number of times the wafer 1 was handled. There were increasing problems.

To solve this problem, the following methods for reinforcing the wafer have been proposed. One method is to thicken the dimensions of the wafer, remove only the main part of the originally thick wafer by etching, leave a part of the original surface of the wafer, and use this remaining part as a reinforcing frame. The element is formed in the recessed portion. However, this method has the serious problem that the seated portions that form the elements cannot be finished flat, and conversely, polycrystalline silicon is partially deposited on an originally thin wafer, and this deposited portion is Although a method of using a reinforcing frame has been considered, both of these methods were insufficient.

[Summary of the invention]

This invention was made to eliminate the above-mentioned drawbacks.
After forming p2 and n-type 11 in advance on a semiconductor substrate, a portion of at least one main surface of the semiconductor substrate is made of polycrystalline silicon, single crystal silicon, molybdenum or tungsten via aluminum or an alloy containing aluminum as a component. A step of digging a mesa groove in the semiconductor substrate to which the reinforcing plate is fixed with an alloy, and then coating and firing glass on the semiconductor substrate.After this step, an electrode is attached to the semiconductor substrate. The present invention provides a method for manufacturing a mesa-type semiconductor device that can prevent damage to the wafer and increase the diameter of the wafer by including the steps of depositing a material and then dividing the wafer into individual semiconductor devices. be.

[Embodiments of the invention]

An embodiment will be described below with reference to the drawings. Figure 3 shows a state in which a polycrystalline silicon ring 8 is bonded to a wafer 1 through an aluminum foil 9 in a vacuum at 700°C for 15 minutes.
FIG.

By the way, as is well known, the polycrystalline silicon ring 8 is C
It is mass-produced using the VD method, in which silicon is deposited around the carbon rod, and then the carbon rod is burned out, or
Alternatively, a circle I is obtained by pulling it out, and then the polycrystalline silicon ring 8 is obtained by cutting this circular tube into rings.
can be obtained. I wonder if it can be obtained using a similar method for single crystal silicon. By the way, the thickness of this polycrystalline silicon ring 8 is arbitrary, but the thickness of the wafer 1 is 2.
When the thickness is 00 .mu.m, empirically, it is appropriate to have a thickness of about 200 to 500 .mu.m. Further, the aluminum foil 9 can be obtained by punching it into a ring shape, and the appropriate thickness is, for example, about 30 to 50 μm.

Further, the alloy material (brazing material) is not limited to aluminum, but any material containing aluminum as a component, such as aluminum-silicon eutectic foil, can provide good alloy adhesion. This is because the AI-Si eutectic alloy is stable and strong.

However, when the polycrystalline silicon ring 8 is fixed to the alloy in this manner, the strength of the wafer 1 becomes extremely large, and empirically it has been increased by 2 to 4 times.

FIG. 3B shows a conventional method in which the area other than the mesa groove 2 is masked by photolithography using a photoresist, a silicon oxide film, or a silicon nitride film, mesa etching is performed using a CP-4 etchant, and then Inochik's This figure shows the state in which IP760 glass was deposited and fired at 750°C. Therefore, up to the step of forming mesa groove 2 on wafer 1, it takes 1,200 to 13
It is relatively I & humidity temperature work like impurity diffusion in high humidity of 00℃, but after digging mesa trench, 750'CPI
! If the reinforcing plate is fixed with an alloy, the fixed portion will be able to withstand the temperature sufficiently since the temperature is relatively low just by glass deposition firing or metallization with electrode material.

By the way, a point that should be taken into consideration when comparing this embodiment with the conventional method is that the print method is more suitable than the direct method in photolithography when obtaining two patterns of mesa grooves. Furthermore, when firing glass, the alloy brazing filler metal 9 may soften at one point, so it is preferable to stack the wafers 1 horizontally and perform the firing process, but even when firing the wafers upright, the polycrystalline silicon ring 8 The direction is not particularly limited as long as there is no fear that the brazing filler metal 9 will flow out due to misalignment.

Furthermore, the effect is the same even if a ring made of molybdenum or tungsten, which is similar to the wafer 1 and the thermal W tensioning wheel, is used as the reinforcing material.

In addition, the reinforcing plate is a cross-shaped reinforcing plate 1 as shown in Fig. 4A.
A similar effect can be obtained using a reinforcing material 11 in which a ring pattern is combined with a cross pattern as shown in FIG. 0 and FIG. 4B.

Incidentally, if the pattern of the reinforcing plate becomes complicated, the brazing material may be formed by vacuum evaporation or sputtering.

In the above description, the reinforcing plate is attached to both main surfaces of the wafer 1, but it is clear that the effect can be exerted even if the reinforcing plate is attached to only one of the main surfaces. By the way, after the step shown in FIG. 3B, the anode 6 is made of gold, the cathode 7 is made of gold,
The wafer process is completed by vacuum-depositing aluminum onto each gate electrode 12.

Now, the wafer completed in this way will be cut into individual cyrisk elements using a diamond cutter, etc., as in the past, but in the case of O, a suitable diamond cutter can cut along the periphery of the sea urchin. Polycrystalline or single-crystalline silicon is used as a reinforcing plate because of the dicing process.In this case, it can be easily cut together with the wafer, but when tungsten or molybdenum is used, sulfuric acid-nitric acid-water system and nitric acid-hydrofluoric acid-system are used before dicing. It is necessary to remove only the reinforcing plate by etching with a water-based etchant and then dicing.

〔Effect of the invention〕

As described above, in the present invention, after forming P-type and N-type layers on a semiconductor substrate in advance, polycrystalline silicon or A step of fixing a reinforcing plate made of single crystal silicon, molybdenum, or tungsten with an alloy, and a step of digging a mesa groove in the semiconductor substrate to which the reinforcing plate is fixed with an alloy, and then applying glass and firing it. After that, the semiconductor substrate is coated with electrode material and then divided into individual semiconductor devices, which has the effect of preventing damage to the sea urchin and making it possible to increase the diameter of the sea urchin. .

[Brief explanation of the drawing]

Figures 1A, B, and C are cross-sectional views of main parts showing the manufacturing process of a conventional mesa-type thyristor device, Figure 2 is a graph showing changes in conventional wafer breakage by process, and Figures 3A and B are the main parts of the conventional mesa-type thyristor device. FIG. 4 is a sectional view of a main part showing the steps of one embodiment of the invention, FIG. 4 is a perspective view of another embodiment of the invention, and FIG. 5 is a perspective view of still another embodiment of the invention. In the figure, 1 is a semiconductor substrate, 2 is a mesa groove, and 8 is io. 11 is a reinforcing plate, and 9 is a brazing material. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] After forming P-type and N-type layers in advance on a semiconductor substrate, polycrystalline silicon, single crystal silicon, molybdenum, or tungsten is applied to a portion of at least one main surface of the semiconductor substrate via aluminum or an alloy containing aluminum as a component. A step of drilling a mesa groove in the semiconductor substrate to which the reinforcing plate is fixed with an alloy and then depositing and firing glass thereon; After this step, applying an electrode material to the semiconductor substrate. A method for manufacturing a mesa-type semiconductor substrate device, comprising the steps of deposition and then dividing into individual semiconductor devices.