Innovative anisotropic etching processes for emergent architectures of HgCdTe photodetectors – GRAINE

The project GRAINE concerns etching technologies for HgCdTe infrared photodectors of 3rd generation.
These detectors require mastering the etching of µm-deep vias or trenches in the material, with a perfectly controlled dimension and geometry. Plasma etching is today the only processing technology able to produce such patterns. But some very important issues need to be solved, among which: electrical damage, stoichiometry changes, surface roughness, lack of anisotropy in the etching, aspect ratio dependent etching, and mask material dependent etching.
Our aim is to achieve a significant step in the etching technology of HgCdTe in order to waive these various issues. We propose to:
- explore new plasma processes
- explore the interest of using new gas mixtures for their potentiality in the protection of the pattern sidewall during the etching
- study the capability of these new concepts to control the etching anisotropy as well as the pattern dimension and geometry, for a large range of pattern dimension and aspect ratio.
Our research strategy is based on plasma diagnostics and surface characterisations. It is focused on the understanding of the etching mechanisms using patterned samples (and not uniquely blank samples), and on the development of an etching process.

Two research laboratories are involved in GRAINE: The Institute of materials Jean Rouxel (IMN) at CNRS/University of Nantes - France and the Department of Optronics (Leti/DOPT) at CEA-Leti, Grenoble - France. These two labs have ten years old collaboration on the topic of etching HgCdTe in methane/hydrogen based plasmas.
GRAINE will increase IMN's and Leti/DOPT's knowledge in the etching mechanisms of HgCdTe; it will increase their know-how in the etching processes of these compounds. Results and outcomes will be integrated in other currently and future projects.
The approach is ambitious as it aims at exploring new plasma and etching concepts, which are not presently used in the field of HgCdTe device fabrication. This project should open new opportunities for the development of new architectures in HgCdTe IR detectors.