Experiments showed that increasing water concentration in the bath results in higher selectivity: more Si3N4 etched and less SiO2 etched. With the installations of a water concentration monitor and a water spiking apparatus, the bath is able to control the water concentration. The partial replacement of the chemical bath after each product lot reduces dissolved silicon concentration. The addition of H2SO4 saves initial conditioning time. With all of the efforts, the bath starts at a high selectivity and maintain this selectivity for an extended bath life.
Archive for category: Technical Article
How to Overcome the Effects of Silicon Build-Up During Solar Cell Wet Chemical Processing
Although the chemical reaction is well known, the anisotropic etching of Si in alkaline solutions is a complex process. This is particularly true in the solar industry where a large mass of silicon is typically introduced into the etch bath. The etch by-products (silicates) affect the balance of the etching specie. If adequate compensation is not made for these by- products, a significant drop in etch rate and an increase in contamination levels is typically noticed. Because of this contamination, production lines would suffer from unpredictable wafer characteristics and hence lower cell performance.
Optimized Wet Processes and PECVD for High-Efficiency Solar Cells
In this study, we highlight the effect of pre-cleans, texturization and final cleans on cell parameters. We also studied the importance of coupling these wet cleaning and texturization steps with the PECVD steps to achieve the film quality required for highest solar cell efficiency.