Wet etching characterization of InSb for thermal imaging applications

Abstract

A citric acid/hydrogen peroxide-based chemical system has been reported for the first time to meet the requirements of continuously scaling down the pixel area for InSb high-density infrared camera applications. This chemical system with a reaction-rate-limited mechanism was concluded to have superior etching performance compared with the nitric acid-based Solution. It is established that this etching mechanism has better control over device structure uniformity due to its linear proportionality to etching time and its nondependence oil agitation and exposed etched area. Two different chemical systems have been studied to form the high-density mesa structures ill this Study. The wet etching characteristics corresponding to these chemical Solutions were measured and analyzed. From atomic force microscopy (AFM), the results clearly indicate that the surface-reaction-rate-limited dominant-control mechanism for InSb mesa etching in citric acid/hydrogen peroxide produces a fairly smooth morphology near junction edges and well-controlled sidewall profiles. Good step coverage for dielectric deposition as shown by field-emission scanning electron microscopy and a highly uniformly distributed dark current of InSb pn junction arrays at 77 K have proven the feasibility of the citric acid/hydrogen pet-oxide wet etching process to bring superior etching performance compared with the nitric acid-based Solution.