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Method of Patterning II-VI Compounds

IP.com Disclosure Number: IPCOM000105777D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 75K

Publishing Venue

IBM

Related People

Brady, MJ: AUTHOR [+2]

Abstract

Growth of epitaxial layers of II-VI type compounds by molecular beam techniques have gained in popularity due to recent advances in achieving light emission in the visible wavelength in thin films of Zn,Cd,(Se) grown on certain substrate materials. One difficulty that exists in the epitaxial growth is the high temperatures that are required, usually in the range of 300 to 800° C, thus restricting the use of organic photoresist stencils for patterning and lift-off techniques. An additional restriction is that many of the substrates of choice are not oxidizable, i.e., GaAs, MgO, CdS, etc., as is the case, for example, in the use of a single crystal silicon substrate.

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Method of Patterning II-VI Compounds

      Growth of  epitaxial layers of II-VI type compounds by
molecular beam techniques have gained in popularity due to recent
advances in achieving light emission in the visible wavelength in
thin films of Zn,Cd,(Se) grown on certain substrate materials.  One
difficulty that exists in the epitaxial growth is the high
temperatures that are required, usually in the range of 300 to
800&deg C, thus restricting the use of organic photoresist stencils
for patterning and lift-off techniques.  An additional restriction is
that many of the substrates of choice are not oxidizable, i.e., GaAs,
MgO, CdS, etc., as is the case, for example, in the use of a single
crystal silicon substrate.

      Disclosed is a method of depositing epitaxial II-VI films on
patterned substrates that allows for high temperature processing.  A
single crystal <100> silicon substrate with 500 nm of thermally grown
silicon dioxide is patterned using standard semiconductor
photolithographic processing.  The resist stencil allows for a
pattern in the silicon dioxide to be fabricated.  The substrate is
then outgassed at 150&deg C in a load-lock chamber to remove water
vapor.  Then it is positioned in the main chamber, and heated to
850&deg C to remove the 30-angstrom native oxide.

      Blanket deposition of films of CdTe are grown at a rate of 2 to
3 angstroms per second with a background pressure of less than 8E10-9
and a substrate temperature of 250&deg C.  The substrate is then
immersed in a solution of 50:1 mixture of 50 parts by volume of 40%
NHF solution with 1 part of 49% HF.  This etchant selectively removes
the silicon dioxide, but does not attack the II-VI film, thus in
effect allowing for a lift-off process.  An additional embodiment,
for substrates such as GaAs, which are not oxidizable, consists of
the following.  A spin on glass (SOG) is deposited on the GaAs
substrate, at a spin speed of 2000 rpm, prebaked at 100&deg C for 15
minutes in air, to drive o...