Pocl < Sub > 3 < / Sub > Process Establishment And Optimization

POCL3 technology is the simple form of Phosphorus Oxychloride diffusion, which is a basic type of gas resource diffusion. On the process of semiconductor manufactory, diffusion is the way which penetrate into the silicon substrate using a constant surface concentration of the impurity diffusion at the high temperature, and then re-distribution by the second Limited source surface diffusion for the purpose to doping. Phosphorus Oxychloride is decomposed to produce P2O5 deposited on the surface of the wafer, P2O5 and silicon reaction of SiO2 and phosphorus atoms, which form a layer of phosphorus silicon glass on the surface, the phosphorus atoms will diffuse into the silicon at last.This article writes at the angle of process, establish a set of complete diffusion model by analyze the variables of POCL3 process:nitrogen, oxygen, phosphorus oxychloride carried by nitrogen, deposition time and temperature. Using the tube volume to calculate the main flow of nitrogen, calculating carried nitrogen flow by the steam pressure of phosphorus oxychloride, select the oxygen.In the study of improving doping uniformity, several effective methods were made out: placement, role of the baffle, self-doping effect and the specificity of oxygen in the reaction. With these points, the uniformity within wafer improved greatly in application. Although the doped uniformity can be improved to 2%, but it is still lower than the way which doped by implant. In order to solve the problem of bottleneck, we often switch these two processes. The article also lists the progress which transforms diffusion to implant at the emitter drive. During the verification process, there were many problem happened, such as HFEN low, VTP low and Cap low. Now we get the purpose after adjustment, the production achieves the ideal expected. At present, the yield rate is in 95% above on the bipolar process in diffusion and implant.In recent years, Polycrystalline doping is used widely, due to solar cell manufacturing field is used more and more frequently, it has more meaningful to study this process theory and applications. Compare with the sheet resistance from the monocrystalline silicon and polysilicon doped, we can explained the difference, and the contact between the substrate reflectivity and resistance relations, from the phenomenon of production.My unit is one which manufactures 6-inch wafers that is mainly including Bipolar, CMOS, and BiCMOS technologies. POCL3 technology is used in ISO layer of bipolar and polycrystalline doping on MOS device. Therefore, the yield must reach certain level, which needs better stability, uniformity, and controllability. During 4 years improvement and optimization, POCL technology control system is ripe step by step, and can satisfy the needs of productivity and quality.