Planar microlenses for near infrared CMOS image sensors

Abstract

In this paper we present planar microlenses designed to improve the sensitivity of SPAD pixels. We designed diffractive and metasurface planar microlens structures based on rigorous optical simulations. The current melted microlens solution and designed diffractive microlens were implemented on STMicroelectronics 40nm CMOS testchips (32 × 32 SPAD array), and average gains of 1.9 and 1.4 in sensitivity respectively were measured, compared to a SPAD without microlens.