Silicon planar integrated circuitry - Devices and circuits fabricated using multiple epitaxial and diffusion techniques

By the alternate application of epitaxial growth and selective diffusion, it is possible to construct integrated circuits layer by layer. In this manner, the electrical properties of internal regions can be modified and multiple epitaxial layers electrically isolated. The additional freedom resulting from the ability to work within the silicon block opens new modes of device design. This technique has been successfully used to construct both bipolar and unipolar field-effect transistors. Adjacent but electrically isolated active devices exhibit excellent and well matched characteristics. The characteristics of typical devices and their method of fabrication will be discussed. These active devices are taken from two integrated circuits--first, a differential amplifier stage containing two n-p-n bipolar transistors and five resistors, and second, a differential amplifier stage containing two p-channel, n-gate unipolar transistors and six resistors. Possible future applications of this technique will be presented. The advantages and disadvantages of the technique will be pointed out.