第二章 掺杂技术（The second chapter doping technology）.doc

第二章 掺杂技术（The second chapter doping technology） The second chapter doping technology Objective: to reconstruct the electrical characteristics of Semiconductors Definition: the artificial method is used to incorporate the required impurities into a specified area of the semiconductor substrate in a certain manner and to achieve a specified quantity and conformity to the required distribution. Applications: making PN junction, resistance in IC, ohmic contact area, silicon gate, polysilicon interconnect line Methods: thermal diffusion and ion implantation Section 1 diffusion Definition: the doped gas is introduced into a high temperature furnace with silicon wafers, so as to achieve the purpose of diffusing impurities into the silicon wafer. Method： Liquid source diffusion Powder source diffusion Sheet source diffusion Diffusion of latex source Diffusion of solid source (CVD doped SiO2) Section 1 diffusion Diffusion principle In essence, diffusion is the statistical result of microscopic particles undergoing irregular thermal motion. Direction: high concentration to low concentration diffusion. The 1. Fick first law of J=-D at N D - diffusion coefficient (cm2/s) At N concentration gradient - - diffusion from high concentration to low concentration J diffusion current density Section 1 diffusion 2. diffusion model (institution) Energy Pohl Seidman distribution of impurity atoms Gap diffusion - impurity motion in the interstitial space Substitution (substitution) diffusion - impurity atoms move from one lattice point to another Premise: there is an empty space near the grid Diffusion principle 3. diffusion coefficient D=D0, exp (-Ea, /kT) D0 - apparent diffusion coefficient, the diffusion coefficient is 1/kT to 0 Ea - activation energy; gap diffusion: Ea = Ei, Substitutional diffusion: Ea = Es+ Ev D is a physical quantity describing the speed of particle diffusion, and is a macroscopic description of microscopic diffusion. Diffusion principle D is inversely proportional t