JPS6142424B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing semiconductor pellets used for high output transistors, thyristors, etc.

For example, a semiconductor pellet (hereinafter simply referred to as a pellet) for an inverted mesa transistor has a side cross section of a pellet 1 formed in an inverted mesa shape, as shown in FIG.
A rubber material (for example, silicone rubber) 3 serving as a protective substance is applied to the PN junction exposed on the side wall 2 to protect it and increase the pressure resistance. Further, E, B, and C are electrode layers formed on the front surface 1m and the back surface 1n of the pellet 1.

A plurality of pellets 1 are manufactured at once from one semiconductor wafer (hereinafter simply referred to as a wafer). An example of this manufacturing will be explained from each step shown in FIGS. 2 to 10. That is, first, wax 5 is applied to the front surface 4m of the wafer 4 on which electrode formation has been completed, and is fixed to the quartz substrate 6. For example, a photoresist 7 is applied to the back surface 4n, a predetermined pattern is exposed, and the exposed portion is removed. Then, open the window 7a (see Figures 2 and 3). Then, by etching, a mesa groove 8 is formed in the wafer 4 from the window 7a (the fourth
(see figure). This mesa groove 8 reaches the surface of the wafer 4 and separates the wafer into individual pellets 1.
Thus, each pellet 1 is fixed by the wax 5 and maintains the shape of the wafer 4'. Then, a fluid protective substance, for example, a rubber material 3 such as silicone rubber, is applied to the entire rear surface side of the wafer 4', and the mesa groove 8 is filled with the rubber material 3 (see FIG. 5). Then, this rubber material 3 is cured, and the rubber material 3 and photoresist 7 applied to the back surface 1n of each pellet 1 of this wafer 4' are removed, leaving the rubber material 3 only in the mesa groove 8 (Fig. 6). and Figure 9). Next, the wafer 4' formed by bonding a plurality of pellets 1 with the rubber material 3 is peeled off from the substrate 6 by removing the wax 5 with an organic solvent, and the surface of the wafer 4', that is, the 1 m side of the surface of each pellet 1 is removed. is adhered to the elastic sheet 10 (see FIG. 7). Finally, the rubber material 3 is cut along the center line of the mesa groove 8.

The rubber material 3 was cut in the manner shown in FIGS. 8 and 10. First, the sheet 10 of the wafer 4' shown in FIG. 7 is placed on the bracket stage 11.
The wafer 4' is positioned in a flat state by being fixed at the top. Then, a sharp cutter 12 like a razor blade is applied to the rubber material 3 from above the wafer 4' along the center line of the mesa groove 8, and the cutter 12 or stage 11 is moved in the X direction, which is the direction in which the mesa groove 2 is formed. The rubber material 3 was cut by moving horizontally in the Y direction. However, this method of cutting rubber material has the following problems.

That is, the rubber material 3 has flexibility and adhesiveness peculiar to rubber after curing, and the wafer 4' is a flexible sheet 1.
Since it is a thin piece glued to cutter 1,
2 along the center line of the rubber material 3, the area around the cut portion of the wafer 4' moves due to the frictional resistance between the cutter 12 and the rubber material 3, and the cut surface of the rubber material 3 deviates from the center line and bends. Something happened. Therefore, it is necessary to always be careful not to deviate greatly from the cutting direction, making it difficult to automate the cutting process. Furthermore, since the rubber material 3 is cut by pressing the surface to be cut against the cutter 12, if the cutter 12 becomes even slightly worn, the frictional resistance during cutting increases, causing the rubber material 3 to be cut. The cut surface may become wavy and have a poor appearance, cracks may appear on the cut surface, and sometimes the rubber material 3 may peel off from the side wall 2, resulting in deterioration of characteristics such as a decrease in pressure resistance.

The present invention has been made in view of the above-mentioned conventional problems and has solved them.
The explanation is as follows when applied to the production of.

One of the features of the present invention is that a UV-curable material is used as the protective material, for example, a rubber material made of silicone rubber mixed with a curing agent that hardens when irradiated with UV light.
It is manufactured by the same conventional method up to the steps shown in FIG. 5 (see FIG. 11). However, the same reference numerals as in FIG. 5 indicate the same contents, 13 is the above-mentioned ultraviolet curable rubber material, and 14 is a wafer in which a plurality of pellets 1 are connected by the rubber material 13. According to the present invention, the rubber material 13 is cut in the following manner to separate individual pellets 1 from the wafer 14.

First, the rubber material 13 is partially cured. For this curing, as shown in FIGS. 12 and 15, a mesh-like mask 15 is positioned and placed on the back surface of the wafer 14 on the substrate 6, covering only the middle surface portion 13a of the rubber material 13. Then, ultraviolet rays 16 are irradiated from above the wafer 14 in a direction perpendicular to and parallel to the surface of the wafer 14. Then, the ultraviolet rays 16 are irradiated to the entire back surface of the wafer except for the middle part 13a of the rubber material 13 that is hidden by the mask 15, and only the both side parts 13b of the rubber material 13 are cured by this ultraviolet irradiation, and the middle part 13a remains uncured. . When the hardening of the rubber material 13 is completed in this way, the photoresist 7 and the rubber material 13 on the surface are removed, and the wax 5 is also removed and the wafer 14 is peeled off from the substrate 6.
A stretchable sheet 17 is adhered as shown in the figure. When this sheet 17 is stretched radially, the pellets 1 move away from each other, and at this time, the uncured rubber material 13 is separated from the intermediate portion 13a, and the wafer 14 is separated into individual pellets as shown in FIG. be divided. In this way, the cutting process using a cutter can be omitted, and various troubles associated with cutting with a cutter can therefore be eliminated.

Note that after partially curing the rubber material 13 with the mask 15, the mask 15 is removed and the rubber material 13 is cured again.
The entire surface of the wafer 14 is irradiated with ultraviolet rays 16 to slightly harden the intermediate portion 13a of the rubber material 13.
It is also possible to adhere the rubber material 13 to the sheet 17 and then cut the intermediate portion 13a of the rubber material 13 with a cutter. In this case, since the intermediate portion 13a of the rubber material 13 is in a semi-hardened state, it is easy to insert the cutter into the rubber material 13, and smooth and reliable cutting is possible.

As explained above, according to the present invention, since the cut portion of the rubber material is in an uncured state, cutting can be performed easily and reliably, and semiconductor pellets with good appearance and stable characteristics can be produced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a mesa semiconductor pellet, FIGS. 2 to 10 are diagrams explaining a conventional method for manufacturing a mesa semiconductor pellet, and FIGS. 11 to 14 are diagrams explaining the present invention. 15 is a partial plan view of FIG. 12. 1... Semiconductor pellet, 13... Ultraviolet curing protective substance, 16... Ultraviolet light.

Claims (1)

[Claims] 1 A step of filling a plurality of semiconductor pellets arranged at regular intervals with an ultraviolet curable protective substance to connect and integrate the semiconductor pellets, and irradiating ultraviolet rays while masking the intermediate part of the protective substance between the semiconductor pellets. and a step of applying an external force to the semiconductor pellets connected and integrated by the protective substance to separate them from the middle part of the uncured protective substance to obtain individual semiconductor pellets. manufacturing method.