A PNP high frequency silicon transistor produced by double diffusion and oxide masking techniques

Solid state diffusion techniques with all of its advantages are used to produce a PNP transistor that has desirable high frequency characteristics. The processes used in making the device provide a high degree of uniformity and ease of manufacturing. Oxide masking by means of silicon dioxide and photolithographic methods provide an exposed base area at the surface and localized emitters. Measurements from photomicrographs have given base widths of about .00005 inch to .00007 inch and the emitter layer is about .0001 inch thick. Stripe geometry is used in fabricating transistors from diffused material, and the emitter and base stripes are pure gold, .001 inch by .006 inch spaced about .001 inch apart. High-frequency parameters for the experimental devices have been equal to those of NPN units measured to date. Cut-off frequencies as high as 300 Mc/s have been measured and several diffusion runs have yielded devices with cut-off frequencies of 100-150 Mc/s. The input resistance is about 60 - 140 ohms and collector capacitance is about 2 - 3 µµfd. The breakdown voltage for most units is about 20 - 30 volts; however, the transistors with higher cut-off frequencies have lower breakdown voltages.