基于背向曝光的GaN基脊型LD制备工艺改进

Improved Process of GaN-based Ridge Laser Diodes Based on Back-ward Exposure

GaN基脊型激光二极管(LD)的制备工艺中,面临的一个主要困难是p电极和窄脊结构的制备受到光刻对准精度的严重制约。设计和验证了一种基于背向曝光技术的激光器制备工艺。通过预先沉积一层200nm的铝作为挡光掩模和牺牲层,利用ICP蚀刻制备出宽为2.5μm的脊型结构,并使用PECVD沉积SiO2绝缘层。随后采用背向曝光实现二次光刻,将脊型图形精确地转移到电极窗口,继而采用湿法腐蚀SiO2绝缘层打开窗口,借助对的铝掩模腐蚀实现对残余绝缘层的辅助剥离,从而同时解决了目前脊型激光器电极窗口对准困难和绝缘层侧向腐蚀条件难于把握的问题。

In the process of GaN-based laser diodes, a major difficulty suffered is how to make accurate alignment of p-electrode with narrow ridge structure. The process of laser diodes based on back-ward exposure process was designed and verified. A 200 nm thick A1 mask was deposited before the erosion of a 2.5μm wide ridge by ICP and the deposition of a SiO2 isolating layer by PECVD. When the p-electrode was to be deposited, a back-ward exposure was used to transfer the pattern of the ridges to the photoresist to form a window. Then wet-etching was used to erode the SiO2 isolating layer to get through the window, and this process was assisted by the lift-off of buried A1 mask. This technic can effectively improve the accuracy of alignment and etching of isolating layer.