Microlenses and photodetectors integration for augmenting photocurrent

Abstract

This paper presents two approaches in microlenses (MLs) and photodiodes (PDs) integration for improving the light-photocurrent conversion. The first one consists in fabricating MLs with AZ4562 photoresist on a glass substrate: The integration of MLs with a focal length of 170 μm on a 150 μm thickness glass substrate aligned on top of a 240 μm square CMOS photodiode resulted in a decrease of ≈38% for the light-current conversion under white light. In the second approach the MLs were fabricated also with AZ4562 in 24-5 μm width-thickness (at the apex) on top of a 240 μm and 24 μm square CMOS photodiodes. The results showed an increase in light-current conversion in both cases: The 240 μm photodiode presented an increase of ≈2.6% and ≈5.2% under white and red light respectively, while the 24 μm photodiode presented an increase of ≈2.3% and ≈14.5% also under white and red light respectively.