| 摘要 |
<p>918,425. Semi-conductor devices. PACIFIC SEMICONDUCTORS Inc. May 11, 1959 [May 23, 1958], No. 16107/59. Class 37. A voltage-sensitive capacitor consists of a semiconductor body 10a with an alloyed region which decreases in diameter towards the interior of the region, a regrown region of opposite conductivity type from the body being formed at the interface, the arrangement being that the remaining base region thickness is less than the radius of the alloyed region at the top of the semi-conductor. The first step in production is an ohmic back contact. A silicon body 10a (Fig. 1) of about 1¢ inches diameter formed from a single crystal and having a resistivity in the range from 0.1 to 1.5 ohm centimetres is selected. The wafer is then lapped or etched in known manner to reduce the wafer thickness to 15 mils. The surface 13 of the wafer is then wet-lapped with a 600-mesh abrasive to roughen the etched surface. A 99% gold, 1 % antimony foil is then placed on the lapped wafer which is itself positioned on a lavite plate 20. A second lavite plate 22 and a weight 23 are then placed on the gold foil and the whole is then placed in an atmosphere of 85% nitrogen, 15% hydrogen heated to 450‹ C. as quickly as possible, held in equilibrium five minutes, cooled at not more than 12‹ C. per minute until 200‹ C. is reached and then cooled at room temperature. Body member 10a, Fig. 2, is then diced from silicon wafer 10. The body is a cylinder of diameter 0.042 inches and thickness 0.015 plus or minus 0.002 inch. The PN junction is formed by alloying a small quantity of aluminium from a wire about 10 mils. in diameter and heating the body to about 150‹ C. The aluminium alloys with the silicon and upon cooling produces the frustoconical shape shown with a re-grown P-type conducting region 12. The top diameter D 1 is 10 to 30 mils. while D 2 is 6 mils. Œ 3 mils. The thickness wb is between 1 and 5 mils. A solution of one part nitric, one part hydrochloric acid will etch the outside silicon to the slope shown in Fig. 3, reducing the capacity of the device. Fig. 4 shows the device encapsulated in a central glass cylinder to which are sealed metal tubes 26, 27 in which are metal pins 30, 31, and spot-welded electrodes 32, 33.</p> |
