Multi-physical Field Simulation Of Tubular LF-PECVD-SiN_x:H Deposition Of PERC Solar Cell

Plasma-enhanced chemical vapor deposition（PECVD）technology has achieved wide application in the preparation of silicon nitride（SiN_x:H）for Passivated Emitterand Rear Cell（PERC）cells.The low-frequency tubular PECVD equipment studied in this paper has unique advantages in such equipment and is an important breakthrough in improving the production efficiency and reducing the production cost of PV cells.However,the process of high-throughput SiN_x:H films and their composition and thickness uniformity in the production of mass-produced crystalline silicon cells are still very problematic.Therefore,it is of great importance to establish a reasonable multi-physics field simulation model for the thin film silicon nitride process grown by tubular LF-PECVD equipment and to optimize the simulation of process parameters and upgrade the chamber structure for this process system.In this study,a multi-physics coupled model of SiN_x:H thin film deposition with flow,thermal,plasma and chemical reaction fields is developed based on the COMSOL Multiphysics simulation platform to address the key problem of low film formation rate and low uniformity control caused by the increase of equipment size in the large-capacity tubular LF-PECVD equipment currently used in industrial production.The main research works are summarized as follows.（1）Simulation model construction,validation and relevant parameters study of the subsystems of flow field,thermal field and plasma field involved in this film-forming process based on the finite element method,respectively.A theoretical basis was established for the construction of a multi-field coupled model for the SiN_x:H film formation process,and a reference direction was provided for the regulation of the relevant process parameters.（2）A multi-physics field simulation model of tubular LF-PECVD-SiN_x:H deposition was established.Based on the validated simulation model,the effects of temperature,pressure,NH₃/Si H₄ fractionation ratio and total gas flow rate on deposition rate and film uniformity were investigated.The simulation results showed that the effect of temperature on deposition rate was the most obvious,and the effect of pressure and temperature on film uniformity was the most prominent.（3）The influence of the chamber structure on the film uniformity was analyzed,and a parallel gas transport structure was proposed.It is found that the change of chamber structure further improves the deposition effect of SiN_x:H film,and the uniformity of deposited film is improved from 97.0%to 98.1%,and the uniformity and deposition rate are better than the original structure.（4）The SiN_x:H homogeneity and its deposition rate were further optimized for the large-size,high-throughput LF-PECVD tube furnace by considering the results of multi-field simulations.A set of process parameters was optimized,and the performance index of deposited SiN_x:H films was significantly improved compared with the original process.The performance of the SiN_x:H film obtained from the process combination with the implementation temperature at 450-550°C;pressure at 260-300Pa;total reaction gas flow rate at 13000-18000 sccm;NH₃/Si H₄ shunt ratio of 8-10 can improve the film formation rate by 11.6%and the uniformity performance can be better than 97%compared with the original process.This dissertation provides a reference for solving the problems of low deposition rate and poor uniformity caused by the increased size of tubular LF-PECVD equipment,which is conducive to improving the production efficiency of the equipment and the quality of the films,thus reducing the production cost and improving the performance of PV cells.