Method of integrating epitaxial film onto assembly substrate
A method of growing an epitaxial film and transferring it to an assembly substrate is disclosed. The film growth and transfer are made using an epitaxy lateral overgrowth technique. The formed epitaxial film on an assembly substrate can be further processed to form devices such as solar cell, light emitting diode, and other devices and assembled into higher integration of desired applications.
1. A method of forming an epitaxial thin film comprising:
providing an assembly substrate including a plurality of openings and defining a first pattern for an epitaxial layer;
directing a liquid phase epitaxial material into said plurality of openings;
maintaining a crystalline seed substrate in fixed contact with said assembly substrate for at least a first duration in which said liquid phase epitaxial material is introduced into said plurality of openings;
arranging said assembly substrate and said crystalline seed substrate such that epitaxial layer growth is initiated at a surface region of said crystalline seed substrate situated at a bottom of said plurality of openings and can be controlled until said epitaxial layer is formed within said first pattern.
2. The method of claim 1 , wherein said epitaxial layer can be grown laterally across a top surface of said assembly substrate.
3. The method of claim 1 , further including a step: processing said assembly substrate and epitaxial layer as an integrated epitaxial packaged structure within a semiconductor processing apparatus to form active devices on said assembly substrate and/or said thin film epitaxial layer.
4. The method of claim 1 wherein said epitaxial layer includes a graded composition throughout a thickness direction of said assembly substrate.
5. The method of claim 1 wherein said liquid phase epitaxial material is adapted with thermal characteristics matching said assembly substrate.
6. The method of claim 1 wherein said crystalline seed substrate is detachable from said assembly substrate.
7. The method of claim 6 , wherein said crystalline seed substrate is detached by a shearing action.
8. The method of claim 6 , wherein said crystalline seed substrate is detached by a chemical etchant.
9. The method of claim 1 further including a step: forming one or more second separate epitaxial layers on said epitaxial layer.
10. The method of claim 9 wherein said one or more second separate epitaxial layers and said epitaxial layer include different dopant species.
11. The method of claim 1 further including a step: forming one or more second separate assembly substrates on said epitaxial layer.
12. The method of claim 1 wherein said epitaxial layer has a multidimensional structure including lines and via interconnects.
13. The method of claim 1 , wherein said epitaxial layer forms part of a p-n junction.
14. The method of claim 1 , wherein said epitaxial layer forms part of an integrated circuit device.
15. The method of claim 1 further including a step of forming a sacrificial layer attached between a bottom surface of said assembly substrate and said surface of said crystalline seed substrate.
16. The method of claim 1 further including a step of forming a spacer situated adjacent said assembly substrate and above said crystalline seed substrate.
17. The method of claim 1 further including a step: controlling heating and cooling of said liquid phase epitaxial material.
18. The method of claim 6 wherein said crystalline seed substrate can be re-used after said epitaxial layer is separated for growing a second epitaxial layer.
19. The method of claim 1 further including a step: controlling a side profile of said openings to be vertical, step recessed or sloped to any desired angle.
20. A method of forming an epitaxial thin film comprising:
providing an assembly substrate including a plurality of openings and defining a first pattern for an epitaxial layer;
directing a liquid phase epitaxial (LPE) material into said plurality of openings;
maintaining a crystalline seed substrate in fixed contact with said assembly substrate for at least a first duration in which said liquid phase epitaxial material is introduced into said plurality of openings;
controlling a temperature of said LPE material and arranging said assembly substrate and said crystalline seed substrate such that epitaxial layer growth is initiated at a surface region of said crystalline seed substrate situated at a bottom of said plurality of openings and can be controlled until said epitaxial layer is formed within said first pattern.
21. The method of claim 20 further including a step of controlling said temperature of said LPE material to be at or below a re-melting temperature of a bulk of said LPE material for said epitaxial layer so as to separate said epitaxial layer from said crystalline seed substrate.
22. The method of claim 20 wherein a constant temperature lower than a melt temperature of said liquid phase epitaxial material is maintained at an interface to said crystalline seed substrate so that said liquid phase epitaxial material precipitates and grows epitaxially on said crystalline seed substrate.
23. The method of claim 20 wherein said assembly substrate, said crystalline seed substrate and a melt situate for the LPE material are independently temperature controlled.
24. The method of claim 23 wherein said assembly substrate, said crystalline seed substrate and said melt situate are controlled to have a temperature at or slightly above a bulk melting temperature of said liquid phase epitaxial material during a first phase of said growing of said epitaxial layer.
25. The method of claim 24 wherein said assembly substrate, said crystalline seed substrate and said melt situate are slowly cooled to have a temperature at or slightly below a super-cooling point of said liquid phase epitaxial material during a second phase of said growing of said epitaxial layer.
26. The method of claim 25 wherein said assembly substrate and said crystalline seed substrate are further cooled to an ambient temperature after a separation during a third phase of said growing of said epitaxial layer.