Deep wet etching of borosilicate glass and fused silica with dehydrated AZ4330 and a Cr/Au mask

作者：Jin Joo Young^*; Yoo Sunghyun; Bae Jae Sung; Kim Yong Kweon

来源：Journal of Micromechanics and Microengineering, 2014, 24(1): 015003.

DOI：10.1088/0960-1317/24/1/015003

• glass wet etching
• borosilicate glass
• fused silica
• deep wet etching
• through-via

This research highlights a superior glass-wet-etch technique which enables a glass wafer to be etched for more than 20 h in 49 wt% hydrofluoric acid (HF) only with Cr/Au film and a common positive photoresist, AZ4330. We demonstrated that pits on the wet-etched glass wafer were generated not only due to HF diffusion through the Cr/Au film but also due to pinholes on the Cr/Au films created by the diffusion of the Cr/Au etchant through a photoresist etching-mask during the Cr/Au wet etching process. These two types of diffusion, HF diffusion and Cr/Au etchant diffusion, were eliminated by the thermal curing of a photoresist (PR), AZ4330, before the Cr/Au wet etching process. The curing process allowed the PR to dehydrate, increased the hydrophobicity, and prevented the diffusion of the hydrophilic HF and Cr/Au etchant. Optimization of the curing process was performed, showing that curing at 130 degrees C for 20 min was the proper condition. With the optimized process, a 525 mu m thick borosilicate glass wafer was penetrated with 49% wt HF. A fused silica wafer 525 mu m thick was also wet-etched and penetrated with 49 wt% HF at 10 h. Moreover, no pits were found in wet etching of the fused silica for 20 h in 49 wt% HF. These findings demonstrate that the proposed technique allows the wet etching of a glass wafer for more than 20 h in 49% wt HF, the best result thus far. We fabricated a glass substrate with a 217.0 mu m deep cavity and a penetrating through-via using the proposed technique, proving the feasibility of the product as an optical component with a surface roughness of 45.5 angstrom in the cavity.

• 出版日期2014-1