Freestanding thickness of single crystal material and method having carrier lifetimes.docx

1、Freestanding thickness of single crystal material and method having carrier lifetimes ( 31 of 137 )United States Patent Application20100052105 Kind Code A1 Henley; Francois J. ; et al. March 4, 2010 Free-standing thickness of single crystal material and method having carrier lifetimes AbstractA meth

2、od of fabricating a thickness of silicon material includes providing a silicon ingot material having a surface region and introducing a plurality of particles having an energy of about 1-5 MeV through the surface region to a depth to define a cleave region and a thickness of detachable material betw

3、een the cleave region and the surface region. Additionally, the method includes processing the silicon ingot material to free the thickness of detachable material at a vicinity of the cleave region and causing formation of a free-standing thickness of material characterized by a carrier lifetime abo

4、ut 10 microseconds and a thickness ranging from about 20 microns to about 150 microns with a thickness variation of less than about five percent. Furthermore, the method includes treating the free-standing thickness of material using a thermal treatment process to recover the carrier lifetime to abo

5、ut 200 microseconds and greater. Inventors:Henley; Francois J.; (Aptos, CA) ; Kang; Sien; (Dublin, CA) ; Liu; Zuqin; (Palo Alto, CA) ; Tian; Lu; (Milpitas, CA) Correspondence Address: TOWNSEND AND TOWNSEND AND CREW, LLP TWO EMBARCADERO CENTER, EIGHTH FLOOR SAN FRANCISCO CA 94111-3834 USAssignee:Sili

6、con Genesis CorporationSan JoseCASerial No.: 460899Series Code: 12 Filed: July 23, 2009Current U.S. Class:257/618; 257/E21.215; 257/E23.002; 438/705 Class at Publication:257/618; 438/705; 257/E21.215; 257/E23.002 International Class: H01L 21/306 20060101 H01L021/306; H01L 23/58 20060101 H01L023/58Cl

7、aims1. A method of fabricating a thickness of silicon material, the method comprising: providing a silicon ingot material having a surface region; introducing a plurality of particles having an energy of about 1-5 MeV and greater through the surface region to a depth to define a cleave region and a

8、thickness of detachable material between the cleave region and the surface region; processing the silicon ingot material to free the thickness of detachable material at a vicinity of the cleave region; causing formation of a free-standing thickness of material characterized by a carrier lifetime of

9、about 10 microseconds and less, a first thickness ranging from about 20 microns to about 150 microns with a total thickness variation of less than about five percent; treating the free-standing thickness of material using at least an etching process; and performing a thermal/passivation process on t

10、he free-standing thickness of material to recover the carrier lifetime to greater than about 200 microseconds. 2. The method of claim 1 wherein the free-standing thickness of material after the etching process is substantially free from surface damage. 3. The method of claim 1 wherein the free-stand

11、ing thickness of material after the thermal treatment process is substantially free from sub-surface damage. 4. The method of claim 1 wherein the etching process removes about 5-10% of the thickness of material from a front surface of the free-standing thickness of material and from a back surface o

12、f the free-standing thickness of material to have a second thickness ranging from about 16 microns to about 120 microns. 5. The method of claim 4 wherein the free-standing thickness of material after the etching process retains the thickness variation substantially the same as that before the etchin

13、g process. 6. the method of claim 4 wherein the etching process leads to a RMS surface roughness between about 100-300 nm. 7. The method of claim 4 wherein the etching process develops a texture on either the front surface or the back surface characterized by higher light trapping capability. 8. The

14、 method of claim 1 wherein the thermal/passivation process is characterized by a temperature of about 400 Degrees Celsius to about 800 Degrees Celsius and usage of iodine/methanol solution. 9. The method of claim 1 wherein the free-standing thickness of material is characterized by a strength of abo

15、ut 1 to 5 GPa fracture stress as measured by a ring on ring. 10. The method of claim 1 wherein the etching process comprises dipping the free-standing thickness of material into a solution of HF, nitric and acetic acid for a predetermined time and with a predetermined speed. 11. A method of fabricat

16、ing a thickness of silicon material having a total thickness variation of less than about 5% (change in thickness/thickness), the method comprising: providing a silicon ingot material having a surface region; introducing a plurality of particles having an energy of about 1-5 MeV through the surface

17、region to a depth to define a cleave region and a thickness of detachable material between the cleave region and the surface region; processing the silicon ingot material to free the thickness of detachable material at a vicinity of the cleave region; causing formation of a free-standing thickness o

18、f material characterized by a carrier lifetime of about 10 microseconds and less, a first thickness substantially equal to that of the thickness of detachable material; treating the free-standing thickness of material using at least an etching process; performing a thermal/passivation process on the

19、 free-standing thickness of material to recover the carrier lifetime to greater than about 200 microseconds; and wherein the free-standing thickness of material has a strength about 1 GPa and greater in fracture stress. 12. The method of claim 11 wherein the free-standing thickness of material after

20、 the etching process is substantially free from surface damage. 13. The method of claim 11 wherein the free-standing thickness of material after the thermal treatment process is substantially free from sub-surface damage. 14. The method of claim 11 wherein the etching process removes about 5-10% of

21、the first thickness of the free-standing thickness of material to provide a second thickness with a total thickness variation. 15. The method of claim 14 wherein the first thickness ranges from about 20 microns to about 150 microns; the second thickness ranges from about 16 microns to about 120 micr

22、on; the total thickness variation is less than 5%. 16. The method of claim 15 wherein the etching process leads to a RMS surface roughness of about 1000 nm and less as measured by atomic force microscopy (AFM). 17. The method of claim 11 wherein the thermal/passivation process is characterized by an

23、 annealing temperature of about 400 Degrees Celsius to about 800 Degrees Celsius and usage of iodine/methanol solution. 18. The method of claim 11 wherein the free-standing thickness of material is characterized by a strength of about 1 GPa and greater in fracture stress as measured by a ring-on-rin

24、g test. 19. The method of claim 11 wherein the free-standing thickness of material is characterized by a strength of about 5 GPa and greater in fracture stress as measured by a ring-on-ring test. 20. The method of claim 11 wherein the silicon ingot is P type characterized by a resistivity of about 0

25、.2 to 12 Ohm centimeter 21. The method of claim 11 wherein the etching process comprises dipping the free-standing thickness of material in a solution of HF, nitric and acetic acid. 22. A silicon wafer having a total thickness variation of less than about 5% (change in thickness/thickness) comprisin

26、g: a free-standing thickness of silicon material having a thickness ranging from about 20 microns to about 150 microns; a first surface region overlying the free-standing thickness of silicon material; a second surface region overlying the free-standing thickness of silicon material; a total thickne

27、ss variation of less than about five percent from a first surface region of the free-standing thickness of silicon material to a second surface region of the free-standing thickness of silicon material; a carrier lifetime to greater than about 200 microseconds; and a strength of about 1 GPa and grea

28、ter in fracture stress. 23. The silicon wafer of claim 22 wherein the first surface region has a RMS surface roughness of about 1000 nanometers. 24. The silicon wafer of claim 22 wherein the second surface region has a RMS surface roughness of about 1000 nanometers and less. 25. The silicon wafer of

29、 claim 22 further comprising a resistivity of about 0.2 to 12 Ohm centimeter. 26. The silicon wafer of claim 22 wherein the free-standing thickness of silicon material comprises a single crystal silicon, a polycrystalline silicon, or a metallurgical silicon. DescriptionCROSS-REFERENCE TO RELATED APP

30、LICATION 0001 The instant nonprovisional patent application claims priority to U.S. provisional patent application No. 61/093,248 filed on Aug. 29, 2009 and incorporated by reference in its entirety herein for all purposes. BACKGROUND OF THE INVENTION 0002 The present invention relates generally to

31、technique including a method and a structure for forming a solar cell structure using layer transfer techniques for photovoltaic applications. But it will be recognized that the invention has a wider range of applicability; it can also be applied to other types of applications such as for three-dime

32、nsional packaging of integrated semiconductor devices, photonic devices, piezoelectronic devices, flat panel displays, microelectromechanical systems (MEMS), nano-technology structures, sensors, actuators, integrated circuits, biological and biomedical devices, and the like. 0003 From the beginning of time, human beings have relied upon the sun to derive almost all useful forms of energy. Such energy comes from petro