Low-temperature formation of polycrystalline semiconductor films via enhanced metal-induced crystallization
View Patent ↗A method for forming polycrystalline semiconductor film from amorphous semiconductor film at reduced temperatures and/or accelerated rates. The inclusion of a small percentage of semiconductor material, such as 2% within the metal layer, reduces the temperatures required for crystallization of the amorphous semiconductor by at least 50° C. in comparison to the use of the metal layer without the small percentage of semiconductor material. During a low temperature isothermal annealing process adjacent Al-2% Si and a-Si films undergo a layer exchange resulting in formation of a continuous polycrystalline silicon film having good physical and electrical properties. Formation of polycrystalline-semiconductor in this manner is suitable for use with low temperature substrates (e.g., glass, plastic) as well as with numerous integrated circuit and MEMs fabrication devices and practices.
1. In a method for metal-induced crystallization of a semiconductor material during formation of a polycrystalline semiconductor film, the improvement comprising:
incorporating a small percentage, between 0.5 to 5 percent, of said semiconductor material within the metal used for inducing crystallization;
wherein an initial crystallization temperature is reduced.
2. A method for lowering the initial crystallization temperature during metal-induced crystallization of a semiconductor material during formation of a semiconductor film, comprising:
incorporating a small percentage of the semiconductor material, between 0.5 to 5 percent, within the metal used for inducing crystallization.
3. A method of fabricating a semiconductor film, comprising:
incorporating a small percentage of a semiconductor material, between 0.5 to 5 percent, into a metal material to create a semiconductor-metal composite; and
forming a film of said semiconductor material from said semiconductor-metal composite.
4. A method as recited in any of claims 1 through 3 , wherein said semiconductor material is selected from the group consisting essentially of Si, Ge, Si 1-x Ge x , Si 1-y C y and SiC.
5. A method as recited in any of claims 1 through 3 , wherein the temperature required for metal-induced crystallization is lowered by at least approximately 50° C.
6. A method as recited in any of claims 1 through 3 :
wherein said metal comprises aluminum;
wherein said semiconductor material comprises amorphous silicon; and
wherein aluminum-induced crystallization of said amorphous silicon is reduced by at least approximately 100° C. by incorporating approximately 2% Si into said aluminum.
7. A method as recited in any of claims 1 through 3 , wherein polycrystalline silicon films are formed at temperatures at or below the range of approximately 300° C. to 350° C.
8. A method as recited in any of claims 1 through 3 , further comprising pulsed excimer laser annealing (ELA) comprising all or a portion of an annealing step wherein said amorphous semiconductor film is crystallized during metal-induced crystallization.
9. A method of forming polycrystalline semiconductor films, comprising:
depositing a metal-semiconductor layer over a substrate;
said metal-semiconductor layer comprises a metal into which is incorporated between 0.5 to 5 percent of a semiconductor material;
forming an interfacial membrane over said metal-semiconductor layer;
depositing an amorphous semiconductor material over said interfacial membrane; and
sufficiently annealing said semiconductor material to induce a layer exchange between said metal-semiconductor layer and said amorphous semiconductor layer which crystallizes to form a polycrystalline semiconductor layer.
10. A method as recited in claim 9 , wherein the thickness of the amorphous semiconductor layer should be at least as thick as the metal-semiconductor layer to ensure formation of a continuous polycrystalline semiconductor film in response to said annealing.
11. A method as recited in claim 9 , wherein the thickness of the amorphous semiconductor layer should be at least 1.4 times as thick as the metal-semiconductor layer to ensure formation of a continuous polycrystalline semiconductor film in response to said annealing.
12. A method as recited in claim 9 , wherein said semiconductor material comprises less than 10% of the metal-semiconductor layer.
13. A method as recited in claim 9 , wherein said semiconductor material comprises from 0.5% to 5% of the metal-semiconductor layer.
14. A method as recited in claim 9 , wherein said semiconductor material comprises approximately 2% of the metal-semiconductor layer.
15. A method as recited in claim 9 , wherein the resultant polycrystalline semiconductor film is conductive due to the incorporation of some metal from said metal-semiconductor layer.
16. A method as recited in claim 9 , wherein said reduced temperatures comprise temperatures at or below a range of approximately 300° C. to 350° C.
17. A method as recited in claim 9 , wherein said sufficient annealing comprises isothermal annealing in the range from approximately 300° C. to 350°.
18. A method as recited in claim 9 , wherein said sufficient annealing comprises isothermal annealing for approximately one to three hours.
19. A method as recited in claim 9 , further comprising pulsed excimer laser annealing (ELA) comprising all or a portion of said annealing step wherein said amorphous semiconductor film is crystallized.
20. A method as recited in claim 19 , wherein said laser annealing is utilized for completing the annealing process.
21. A method as recited in claim 9 , wherein said metal comprises Aluminum.
22. A method as recited in claim 9 , wherein said semiconductor is selected from the group of semiconductor materials consisting of Si, Ge, Si 1-x Ge x , Si 1-y C y and SiC.
23. A method as recited in claim 9 , wherein said semiconductor material comprises silicon.
24. A method as recited in claim 9 , wherein said semiconductor material comprises polycrystalline-silicon-germanium (poly-Si 1-x Ge x , 0<×1).
25. A method as recited in claim 9 , wherein said method is suitable for forming polycrystalline semiconductor films on substrates which would be damaged by high temperatures exceeding the range of approximately 300° C. to 350° C.
26. A method as recited in claim 9 , wherein said method is suitable for forming polycrystalline semiconductor films on glass substrates, plastic substrates and/or substrates containing completed CMOS circuitry.
27. A method as recited in claim 9 , wherein said method can be applied using the same equipment as is utilized to perform aluminum-induced crystallization (AIC).
28. A method as recited in claim 9 , wherein said polycrystalline semiconductor comprises transistor gate electrodes in complementary metal-oxide-semiconductor (CMOS) integrated circuits.
29. A method as recited in claim 9 , wherein said polycrystalline semiconductor comprises structural layers in surface-micromachined microelectromechanical systems (MEMS).
30. A method as recited in claim 9 , wherein said polycrystalline semiconductor is utilized in CMOS electronics according to a MEMS-last process flow.
31. In a method for metal-induced crystallization of a semiconductor material during formation of a polycrystalline semiconductor film, the improvement comprising:
incorporating a small percentage of the semiconductor material within the metal used for inducing crystallization;
wherein an initial crystallization temperature is reduced;
wherein said metal comprises aluminum;
wherein said semiconductor material comprises amorphous silicon; and
wherein aluminum-induced crystallization of said amorphous silicon is reduced by at least approximately 100° C. by incorporating approximately 2% Si into said aluminum.
32. A method for lowering the initial crystallization temperature during metal-induced crystallization of a semiconductor material during formation of a semiconductor film, comprising:
incorporating a small percentage of the semiconductor material within the metal used for inducing crystallization;
wherein said metal comprises aluminum;
wherein said semiconductor material comprises amorphous silicon; and
wherein aluminum-induced crystallization of said amorphous silicon is reduced by at least approximately 100° C. by incorporating approximately 2% Si into said aluminum.
33. A method of fabricating a semiconductor film, comprising:
incorporating a small percentage of a semiconductor material into a metal material to create a semiconductor-metal composite; and
forming a film of said semiconductor material from said semiconductor-metal composite;
wherein said metal comprises aluminum;
wherein said semiconductor material comprises amorphous silicon; and
wherein aluminum-induced crystallization of said amorphous silicon is reduced by at least approximately 100° C. by incorporating approximately 2% Si into said aluminum.
34. A method as recited in any of claims 31 through 33 , wherein said semiconductor material is selected from the group consisting essentially of Si, Ge, Si 1-x Ge x , Si 1-y C y and SiC.
35. A method as recited in any of claims 31 through 33 , wherein the temperature required for metal-induced crystallization is lowered by at least approximately 50° C.
36. A method as recited in any of claims 31 through 33 , wherein polycrystalline silicon films are formed at temperatures at or below the range of approximately 300° C. to 350° C.
37. A method as recited in any of claims 31 through 33 , further comprising pulsed excimer laser annealing (ELA) comprising all or a portion of an annealing step wherein said amorphous semiconductor film is crystallized during metal-induced crystallization.