Inductively coupled plasma etching for large format HgCdTe focal plane array fabrication

Abstract

Inductively coupled plasma (ICP) using hydrogen-based gas chemistry has been developed to meet requirements for deep HgCdTe mesa etching and shallow CdTe passivation etching in large format HgCdTe infrared focal plane array (FPA) fabrication. Large format 2048 ϫ 2048, 20-µm unit-cell short wavelength infrared (SWIR) and 2560 ϫ 512, 25-µm unit-cell midwavelength infrared (MWIR) double-layer heterojunction (DLHJ) p-on-n HgCdTe FPAs fabricated using ICP processing exhibit Ͼ99% pixel operability. The HgCdTe FPAs are grown by molecular beam epitaxy (MBE) on Si substrates with suitable buffer layers. Midwavelength infrared detectors fabricated from 4-in. MBE-grown HgCdTe/Si substrates using ICP for mesa delineation and CdTe passivation etching demonstrate measured spectral characteristics, RoA product, and quantum efficiency comparable to detectors fabricated using wet chemical processes. Mechanical samples prepared to examine physical characteristics of ICP reveal plasma with high energy and low ion angle distribution, which is necessary for fine definition, high-aspect ratio mesa etching with accurate replication of photolithographic mask dimensions.

Achieving Manufacturing Readiness for 6-Inch HgCdTe on Silicon

“…dev./mean) on the order of 2% with ICP, as opposed to 3% with ECR and 4% for wet etch chemistries. 8 Today, ICP dry etching is used for mesa delineation in all HgCdTe programs with pixel pitch at or below 15 lm. The current ICP tool has also demonstrated the ability to routinely etch trenches greater than 10 lm deep for advanced HgCdTe products.…”

Status of HgCdTe Bicolor and Dual-Band Infrared Focal Arrays at LETI

“…The use of electron cyclotron resonance (ECR) plasma reactors and inductively coupled plasma (ICP) reactors has been studied in several laboratories. [8][9][10] We have focused recently on processes based on CH 4 /H 2 /Ar gas mixture in an ICP reactor. Some results on the influence of plasma parameters (electron density and temperature, ion flux) on the etching rate and mechanisms can be found in Ref.…”

A review of advances in EO/IR focal plane array technology for space system applications

“…Wet etch processing may be replaced by dry etch processing (plasma and ICP) to give precise dimensional control producing nearly vertical sidewalls, enabling higher aspect ratios [20,21] . These anisotropic processes and their potential to offer better uniformity will facilitate optimization of detector array performance.…”