Abstract: To address the challenges of chemical residue, particle contamination, surface haze, and oxide thickness control on 6-inch germanium wafers after wet cleaning, this paper presents an optimization study of the cleaning process. An L₉(3⁴) orthogonal experiment was designed with four factors at three levels, namely SC1 (NH₄OH-H₂O₂-H₂O) cleaning time, temperature, solution ratio, and developer cleaning time, to systematically investigate the effects of these parameters on wafer surface quality. Range analysis results indicate that the ratio of SC1 plays a decisive role in controlling oxide thickness and surface haze, while developer cleaning time has a significant influence on particle removal from the substrate surface. The optimized process parameters are determined as follows: SC1 cleaning time 20 s, temperature 8 ℃, solution ratio 1∶2∶10, and developer cleaning time 60 s. Under these conditions, chemical residue on the 6-inch germanium wafer surface is significantly reduced, and the oxide thickness is stably controlled at 0.8–0.9 nm. Surface quality was also compared between wafers cleaned at room temperature and low temperature using the same solution ratio. Wafers cleaned at low temperature exhibit a more uniform surface with a thinner oxide layer and fewer oxides, which is beneficial to the uniformity of surface passivation prior to epitaxial growth and oxide desorption during epitaxy.