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Laser-induced Proliferation Of Non-uniform Field Diffusion Theory Research

Posted on:2007-11-07Degree:MasterType:Thesis
Country:ChinaCandidate:Y L WangFull Text:PDF
GTID:2208360185956524Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
Laser induced diffusion is a technology that dope the impurities into a certain region of semiconductor by a focused laser. It has the advantages of"low temperature processing"and"direct writing", and it is promising to use this technology in the fabrication of monolithically optoelctronic integrated circuits (OEICs) to solve the incompatibility problem between optoelctronic and electronic components.The performance of devices is directly decided by the impurity distribution in the diffused region, and the impurity distribution may be affected by the material thermal properties, the mechanism of diffusion, the power of laser and the diffusion time. In order to optimize the processing parameters more effectively and quickly, it is necessary to establish a mathematical physical model to simulate the actual diffusion process.Laser induced diffusion is performed within a non-homogenous 4-D temperature field, which is different with the normal closed-ampoule diffusion in a homogenous and steady temperature field. It is well known that the diffusion coefficient is temperature dependent strongly. The available equipments can not measure the temperature of the substrate in the diffusion process, and so it is necessary to study the 4-D temperature distribution in the processed region beforehand.The purpose of this work is to theoretically study the laser induced diffusion process, which is performed within a non-homogenous temperature field. The main conclusions and contributions include:1. The mechanism of temperature rise in the small processed region has been analyzed theoretically. Then the mathematical problem of nonlinear heat diffusion with temperature dependent thermal conductivity has been derived during laser irradiation of two-layer structures. To solve this problem, a kirchhoff transformation and further time variable transformation has been used. An approximate analytical formulation of 4-D temperature distribution has been derived. This method is expected to be useful in investigating the 4-D temperature distribution in other laser assisted processing.
Keywords/Search Tags:laser induced diffusion, temperature field, impurity concentration distribution, numerical simulation
PDF Full Text Request
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