Off-axis epitaxial lift process

Abstract

Embodiments described herein provide processes for forming and removing epitaxial films and materials from growth wafers by epitaxial lift off (ELO) processes. In some embodiments, the growth wafer has edge surfaces with an off-axis orientation which is utilized during the ELO process. The off-axis orientation of the edge surface provides an additional variable for controlling the etch rate during the ELO process and therefore the etch front may be modulated to prevent the formation of high stress points which reduces or prevents stressing and cracking the epitaxial film stack. In one embodiment, the growth wafer is rectangular and has an edge surface with an off-axis orientation rotated by an angle greater than 0° and up to 90° relative to an edge orientation of <110> at 0°.

I/We claim: 
     
         1 . A growth wafer, comprising:
 a single substrate having a crystalline lattice structure, wherein:   the single substrate has multiple edges that are non-parallel and non-perpendicular to a cleave plane, and   the single substrate has a facial surface with a <001> orientation, off by up to 12°.   
     
     
         2 . The growth wafer of  claim 1 , wherein the edges being non-parallel and non-perpendicular to the cleave plane corresponds to the edges having an off-axis orientation that is rotated from the cleave plane by an angle from 0° to 90°. 
     
     
         3 . The growth wafer of  claim 1 , wherein the edges being non-parallel and non-perpendicular to the cleave plane corresponds to the edges having an off-axis orientation that is rotated from the cleave plane by an angle from 30° to 60°. 
     
     
         4 . The growth wafer of  claim 1 , wherein the edges being non-parallel and non-perpendicular to the cleave plane corresponds to the edges having an off-axis orientation that is rotated from the cleave plane by a 45° angle. 
     
     
         5 . The growth wafer of  claim 1 , wherein the growth wafer has a rectangular shape or square shape, and the edges correspond to the sides of the rectangular shape or the square shape. 
     
     
         6 . The growth wafer of  claim 1 , wherein the growth wafer is cut or diced from a circular growth wafer. 
     
     
         7 . The growth wafer of  claim 6 , wherein the circular growth wafer has a flat cut or a notch that indicates the cleave plane. 
     
     
         8 . The growth wafer of  claim 1 , wherein the cleave plane is a <110> orientation. 
     
     
         9 . The growth wafer of  claim 1 , wherein the single substrate includes elements from Group III, Group IV, or Group V. 
     
     
         10 . The growth wafer of  claim 1 , wherein the single substrate is configured to have a sacrificial layer deposited on the single substrate, and the sacrificial layer is configured to have an epitaxial film stack formed on the sacrificial layer. 
     
     
         11 . A sacrificial layer for an epitaxial lift off process, comprising:
 a layer formed on a single substrate having a crystalline lattice structure, wherein:
 the single substrate has multiple edges that are non-parallel and non-perpendicular to a cleave plane, and 
 the single substrate has a facial surface with a <001> orientation, off by up to 12°, 
   wherein the layer is configured to have an epitaxial film stack formed on the layer and to be etched away to separate the epitaxial film stack from the single substrate.   
     
     
         12 . The sacrificial layer of  claim 11 , wherein the edges being non-parallel and non-perpendicular to the cleave plane corresponds to the edges having an off-axis orientation that is rotated from the cleave plane by an angle from 0° to 90°. 
     
     
         13 . The sacrificial layer of  claim 11 , wherein the edges being non-parallel and non-perpendicular to the cleave plane corresponds to the edges having an off-axis orientation that is rotated from the cleave plane by an angle from 30° to 60°. 
     
     
         14 . The sacrificial layer of  claim 11 , wherein the edges being non-parallel and non-perpendicular to the cleave plane corresponds to the edges having an off-axis orientation that is rotated from the cleave plane by a 45° angle. 
     
     
         15 . The sacrificial layer of  claim 11 , wherein the growth wafer has a rectangular shape or square shape, and the edges correspond to the sides of the rectangular shape or the square shape. 
     
     
         16 . The sacrificial layer of  claim 11 , wherein the growth wafer is cut or diced from a circular growth wafer. 
     
     
         17 . The sacrificial layer of  claim 16 , wherein the circular growth wafer has a flat cut or a notch that indicates the cleave plane. 
     
     
         18 . The sacrificial layer of  claim 11 , wherein the cleave plane is a <110> orientation. 
     
     
         19 . The sacrificial layer of  claim 11 , wherein the single substrate includes elements from Group III, Group IV, or Group V. 
     
     
         20 . The sacrificial layer of  claim 11 , wherein the layer includes edges that correspond to the edges of the single substrate, and wherein corners between the edges of the layer etch faster during the epitaxial lift off process than the sides of the edges of the layer.