Abstract Technology

Abstract

The unit operations characterizing planar technology have been briefly mentioned in Sect. 4.2. Of course, the accurate description of processes like the deposition of poly-Si or Si₃N₄, the oxidation of silicon, the plasma or sputter etching of Si, SiO₂, Si3N4, metals, etc., requires a detailed knowledge of the reaction kinetics and the solution of the diffusion–reaction equations with moving boundary conditions, coupled with the rheological equations of each reactant and product. Designing a process architecture, however, does not require of all the above, and to some extent one may deal, for instance, with poly-Si or Si₃N₄ depositions as representative of a unique process (conformal deposition), the difference being given by the constituting materials only (poly-Si instead of Si3N4, in the considered example). Most of the unit operations considered in this book may ultimately be reduced to the following: Conformal deposition Isotropic etching Selective etching Directional etching Directional deposition in addition to the one at the basis of microelectronics, Lithographic definition Each of these can be thought of as a transformation that operates on assigned bodies transforming them into other bodies.