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Study On Temperature Field And Stress Field Distribution Of Grating Micro-scale Wafers In Laser Spike Thermal Annealing Process

Posted on:2018-07-26Degree:MasterType:Thesis
Country:ChinaCandidate:S TianFull Text:PDF
GTID:2428330572959136Subject:Power engineering
Abstract/Summary:PDF Full Text Request
In recent years,with the development of the semiconductor industry,the number of transistors per unit area on the chip increases following the Moore's Law,and it will be double about every two years,which results in decreasing of the corresponding size for the semiconductor components and the corresponding size has been reduced to micro-nano-level.In the semiconductor component manufacturing process,heat treatment is an important part of the process.As a new annealing method,the laser spike annealing process has some advantages for its fast heating speed,single chip processing and easily controlling,so it has become the main technology of rapid annealing for semiconductor devices.Due to the micro-nano-scale pattern on the surface of the wafer,the uneven temperature distribution of the wafer is caused during the laser spike annealing process,leading to excessive thermal stress,which leads to crystal defect and failure of the wafer and it is called "Pattern Effect"Therefore,it is important to study the temperature field and stress field distribution of the wafer during laser spike annealing under different pattern parameters,which is of great significance to improve the laser annealing process and weaken the "Pattern Effect".In this paper,the grating wafer is taken as the research object,the temperature distribution and stress distribution of the wafer are simulated by the finite element simulation software Comsol Multiphysics,using the CO2 laser with wavelength of 10.6?m as the heat source,with the different parameters of the grating and the annealing process.And the preliminary selection of the annealing process parameters under the fixed structure parameters was discussed.Firstly,the physical model of the grating wafer is established.The heat source is regarded as the heat source with the moving body.The energy distribution in the horizontal direction of the wafer is in accordance with the Gaussian distribution function,the exponential attenuation function in the vertical direction.The influence of laser power and laser beam scanning speed on temperature and temperature uniformity was analyzed.The temperature distribution of the wafer with different grating structure parameters(grating width and gating pitch)was simulated numerically.The results show that laser energy penetrates very little in the depth direction of the wafer,below 100?m,and the wafer peak temperature point lags behind the laser beam center point,and the lag distance is about 100?m.Increasing the gate width and decreasing the gate pitch can increase the temperature level of the wafer and promote temperature uniformity.The temperature level of the wafer can be increased by increasing the laser power and decreasing the scanning speed while ensuring that the material is not melted.Then,the results of the temperature field are loaded into the structural mechanics module as the temperature load.Based on the theory of total increment,the stress distribution of the wafer under different grating structural parameters during the heat treatment process is analyzed.And the influence of laser power and laser beam scanning velocity on the stress distribution is analyzed too.The results show that the stress distribution on the top surface of the wafer is very irregular,and the shape of the grating substrate and the grating substrate changes sharply,the stress concentration is obvious and the stress is large.The grating part can be free to deform and the stress can be free to release,so the stress is very small,and the smallest stress on the grating is at the corners of the gratings.Increasing the gating pitch and decreasing the gating width can decrease the stress level.Reducing the laser power and increasing the scanning speed can reduce stress level during the process.Finally,the selection of annealing process parameters is considered from the viewpoint of temperature and stress under the fixed structure parameters(grating width is140?m,grating pitch is 160?m).From the temperature point of view,the scanning speed is higher than 60mm/s and the laser power is lower than 48W,ensuring the material is not melted,and from the stress point of view,the annealing process parameters are not limited.
Keywords/Search Tags:grating wafer, laser annealing, temperature distribution, stress distribution, influence of parameters
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