Surface treatment and protection method for cadmium zinc telluride crystals
AssigneeSandia Corporation
InventorsGomez W. Wright, Ralph B. James, Arnold Burger, Douglas A. Chinn
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Abstract
A method for treatment of the surface of a CdZnTe (CZT) crystal that provides a native dielectric coating to reduce surface leakage currents and thereby, improve the resolution of instruments incorporating detectors using CZT crystals. A two step process is disclosed, etching the surface of a CZT crystal with a solution of the conventional bromine/methanol etch treatment, and after attachment of electrical contacts, passivating the CZT crystal surface with a solution of 10 w/o NH4F and 10 w/o H2O2 in water.
Claims75
A method for reducing leakage current and improving spectral resolution in CdZnTe crystals, comprising the steps of:
- a) etching the surface of a CdZnTe crystal with a solution of bromine in methanol;
- b) applying electrodes onto the etched surface of the CdZnTe crystal;
- and
- c) passivating CdZnTe crystal by growing a dielectric layer on said etched surface so as to form a coherent, continuous layer consisting essentially of CdO.
A method for forming a detector sensitive to ionizing radiation, comprising the steps of:
- a) etching the surface of a CdZnTe crystal with a solution of bromine in methanol;
- b) passivating the CdZnTe crystal by growing a dielectric layer on said etched surface forming thereby a passivated surface;
- c) applying a photoresist layer onto said dielectric layer;
- d) exposing a portion of said photoresist using electromagnetic radiation and a lithography means;
- e) developing and removing said exposed portion thereby creating an image pattern in said photoresist and exposing a corresponding portion of said passivated surface;
- f) removing said corresponding portion and thereby replicating said image onto said CdZnTe crystal surface;
- g) depositing a metal conductor onto said surface image thereby forming an electrode on said exposed CdZnTe crystal surface;
- and
- h) removing the remaining photoresist layer.
33 The method of claim 32, wherein said polymer layer comprises HumiSeal® type 1B12.
A method for forming a detector sensitive to ionizing radiation, comprising the steps of:
- a) etching the surface of a CdZnTe crystal with a solution of bromine in methanol;
- b) applying a photoresist layer onto said etched surface;
- c) exposing a portion of said photoresist using an electromagnetic radiation and a lithography means;
- d) developing and removing said exposed photoresist thereby leaving a portion of said surface uncovered;
- e) passivating said uncovered surface portion by growing a dielectric layer on said surface portion;
- f) removing said photoresist layer to create a pattern image in said dielectric layer and exposing a corresponding portion of said CZT crystal surface;
- and
- g) depositing a metal conductor onto said exposed surface thereby forming an electrode on said CdZnTe crystal surface.
A method for forming a detector sensitive to ionizing radiation, comprising the steps of:
- a) etching the surface of a CdZnTe crystal with a solution of bromine in methanol;
- b) applying a photoresist layer onto said etched surface;
- c) exposing said photoresist using a lithographic means to create an exposed image of an electrode contact pattern in said photoresist;
- d) developing and removing said exposed photoresist to create a pattern image in said photoresist;
- e) depositing a metal conductor into said pattern and onto said etched surface;
- f) removing the remaining photoresist;
- and
- g) passivating the etch CdZnTe crystal surface by growing a dielectric layer on said uncovered surface.
An ionizing radiation detector, comprising:
- a CdZnTe crystal having one or more surfaces;
- and
- a passivating dielectric layer grown on said surfaces, said layer consisting essentially of CdO.
Dependencies are inferred from the claim text.