Correlation of Cleaning Conditions and Wafer Out-Gassing

Abstract

To remove the oxide layer, BOE (Buffered Oxide Etchant) is widely used solution in semiconductor fabrication process. When using the BOE solution in single type equipment, NH3 ions are created by the chemical reaction. Because BOE is a mixture solution of NH4F and HF. And created NH3 ions make some problems during device fabrication process. As the device is shrinked, NH3 ion control in process chamber becomes more important. We studied the thickness change caused by NH3 ion.When backside cleaning process using the BOE solution, surface of backside was changed. And it affected the next poly layer deposition process. As a result, poly layer deposition thickness dispersion problem was occurred. We find that the difference between normal wafer and issued wafer about backside layer and fumed NH3 ion is main factor of this problem. In this paper, we will explain the cause of poly thickness dispersion issue that occurred at poly film deposition and analyze measurement of cleaning conditions by NH3 out-gassing.Key Words: Poly deposition thickness, NH3+ ion, BOE(Buffered Oxide Etchant),APM(Ammonium Peroxide Mixture), Out-gassing