Abstract: Defects in varistors are detected by pulsing a high current through the varistors and shortly thereafter mapping the temperature distribution of a main varistor surface by heat sensitive equipment. The presence of a localized hot spot sufficiently higher in temperature than a reference temperature level in the varistor indicates the presence of a defect. The disclosed technique is especially adapted for detecting defects that manifest themselves as incipient hot spots but which quickly disappear from observation because their heat rapidly disperses into surrounding varistor material.

Abstract: A system for controlling the blade-to-boule feedrate of a wafer cutting saw to regulate the blade-to-boule force in accordance with predetermined criteria and for monitoring the cutting efficiency of the blade and determining when the blade needs to be dressed to increase its cutting efficiency. A constant blade-to-boule force is preferred.

Abstract: Accurate metering and dispensing of small quantities of abrasive material comprised of particles or powder, or both is accomplished by feed apparatus comprising a rotatable tubular member having a threaded interior surface for transporting the abrasive material through the tubular member in response to rotation of the member about the axis thereof. The discharge portion of the tube is particularly adapted to dispense frequent, small quantities of the material rather than less frequent larger quantities.

Abstract: A method of fabricating a semiconductor device comprising the steps of disposing a layer of dopant material over exposed portions of a surface of a semiconductor body and over portions of a masking layer adjacent the exposed portions, the dopant material having a diffusion coefficient through the masking layer at least about as large as its diffusion coefficient into the body. The dopant material is selectively etched to remove portions overlying the masking layer and thereafter remaining portions of the masking layer are etched to remove any dopant material which might still remain thereover.

Abstract: A diffusion apparatus, particularly useful for diffusing aluminum into semiconductor wafers, comprises a quartz evaporation tube in combination with a restrictor plate which is inserted in an open end thereof. The restrictor plate preferably has substantially the same shape as, but a slightly smaller cross-section than, the evaporation tube. In practice, the relatively small gap between the restrictor plate and the evaporation tube results in a substantially negligible leak in the diffusion apparatus. As a result the apparatus effectively operates as if it were a sealed ampule while in fact it is open, i.e. not sealed.

Abstract: Uniform aluminum diffusion into monocrystalline silicon is obtained by forming a polycrystalline silicon underlayer on the surface of a monocrystalline silicon body, depositing a layer of aluminum on the polycrystalline silicon underlayer by evaporation at a temperature of less than about 250.degree. C., depositing a silicon overlayer over said aluminum layer at a temperature less than about 250.degree. C. and raising the temperature of said structure to between 900.degree. C. and 1300.degree. C. to cause the aluminum to diffuse into said monocrystalline silicon.

Abstract: A semiconductor device package comprises a plurality of walls extending from a base member which has a pellet mounting surface associated therewith. The walls form an enclosure and each one of the walls has a lid receiving surface associated therewith. All of the lid receiving surfaces lie in a single geometric plane which intersects the geometric plane of the pellet mounting surface at an included angle of less than about 90.degree.. External leads protrude into the enclosures through one of the walls. A lid can be affixed to the lid receiving surfaces to hermetically seal the enclosure. The package is particularly useful when made to conform to the dimensions of the well known TO-220 package.

Abstract: A semiconductor device comprises a body of semiconductor material having a PN junction terminating at a major surface thereof. At least one field limiting ring is within the body and extends around a portion of the PN junction. Each field limiting ring is spaced apart from the surface.

Abstract: A contact clip, primarily for use in semiconductor devices comprises a layer of material having a relatively high coefficient of thermal expansion and another layer of relatively low coefficient of thermal expansion. Such a clip improves the contact between the clip and the semiconductor pellet to which it is soldered not only during device assembly but also at high operating temperatures as well.

Abstract: A gate controlled semiconductor controlled rectifier comprises an integral combination of a regenerative thyristor section and an adjacent non-regenerative section. The non-regenerative section includes rectifying contact means to reduce the lateral current needed to turn on the regenerative section.