Layer transfer of films utilizing controlled shear region

Abstract

A film of material may be formed by providing a semiconductor substrate having a surface region and a cleave region located at a predetermined depth beneath the surface region. During a process of cleaving the film from the substrate, shear in the cleave region is carefully controlled. According to certain embodiments, an in-plane shear component (KII) is maintained near zero, sandwiched between a tensile region and a compressive region. In one embodiment, cleaving can be accomplished using a plate positioned over the substrate surface. The plate serves to constrain movement of the film during cleaving, and together with a localized thermal treatment reduces shear developed during the cleaving process. According to other embodiments, the KIT component is purposefully maintained at a high level and serves to guide and drive fracture propagation through the cleave sequence.

What is claimed is: 
     
         1 . A method for cleaving a film of material, the method comprising;
 providing a substrate having a face and an underlying cleave region;   applying a thermal source having a predetermined energy in a direction perpendicular to the face to create a volume of heated material between the cleave region and the face, the heated volume exhibiting a substantially uniform temperature profile followed by a sharp drop in temperature at the cleave region; and   cleaving the film from the substrate at the cleave region.   
     
     
         2 . The method of  claim 1  wherein application of the thermal source heats the volume of material in an adiabatic process. 
     
     
         3 . The method of  claim 1  wherein the sharp drop in temperature is 10° C./μm or greater. 
     
     
         4 . The method of  claim 1  wherein the thermal source is a photon source. 
     
     
         5 . The method of  claim 4  wherein the photon source comprises a laser. 
     
     
         6 . The method of  claim 1  wherein the sharp drop in temperature results in a controlled shear at the cleave region. 
     
     
         7 . The method of  claim 6  wherein the thermal source comprises a laser scanned with a propagating crack to generate shear dominant cleave conditions within the cleave region. 
     
     
         8 . The method of  claim 6  wherein:
 the thermal source is applied at a distance ahead of the crack; 
 a thermal gradient arises from the substantially uniform temperature profile followed by the sharp drop in temperature; and 
 energy from the thermal gradient is coupled across the distance through to the crack by moments and stresses within the cleave region. 
 
     
     
         9 . The method of  claim 1  wherein the cleaving comprises applying a pressure to propagate a crack in the cleave region. 
     
     
         10 . The method of  claim 9  further comprising modulating the pressure to control a depth of crack propagation. 
     
     
         11 . The method of  claim 9  wherein the pressure is applied by a jet of gas or by insertion of a blade. 
     
     
         12 . The method of  claim 1  wherein the thermal source is an energetic electron beam source. 
     
     
         13 . The method of  claim 12  wherein the thermal source comprises a plurality of energetic electrons applied in a vacuum environment having a pressure of between about 10 −4  to 10 6  Torr. 
     
     
         14 . The method of  claim 12  wherein a vacuum environment facilitates the cleaving. 
     
     
         15 . The method of  claim 12  wherein the energetic electron beam source causes a temperature rise volumetrically within an uncleaved propagation area close to a crack. 
     
     
         16 . The method of  claim 1  further comprising fixing the substrate in position during application of the thermal source and the cleaving. 
     
     
         17 . The method of  claim 16  wherein fixing the substrate in position comprises clamping edges of the substrate. 
     
     
         18 . The method of  claim 16  wherein fixing the substrate in position comprises securing the substrate from below. 
     
     
         19 . The method of  claim 1  further comprising bending the substrate during application of the thermal source and the cleaving. 
     
     
         20 . The method of  claim 1  further comprising heating the substrate from below during application of the thermal source and the cleaving.