High resistivity silicon structure and a process for the preparation thereof
View Patent ↗The present invention generally relates to a high resistivity CZ silicon wafer, or a high resistivity silicon structure derived therefrom, and a process for the preparation thereof. In particular, the high resistivity silicon structure comprises a large diameter CZ silicon wafer as the substrate thereof, wherein the resistivity of the substrate wafer is decoupled from the concentration of acceptor atoms (e.g., boron) therein, the resistivity of the substrate being substantially greater than the resistivity as calculated based on the concentration of said acceptor atoms therein.
1. A process for preparing a high resistivity silicon structure, the process comprising:
subjecting a silicon structure, which comprises a CZ single crystal silicon substrate having an initial resistivity of at least about 50 ohm-cm, to a heat-treatment for a duration and at a temperature such that the resulting substrate of the heat-treated structure has a concentration of thermal donors [TD] and acceptors [A] wherein the ratio [TD]:[A] is between about 0.8:1 and about 1.2:1.
2. The process of claim 1 wherein said ratio is between about 0.9:1 and 1.1:1.
3. The process of claim 1 wherein the resulting resistivity of the heat-treated substrate is at least about 10 times greater than the resistivity as calculated based on the acceptor concentration therein.
4. The process of claim 1 wherein the substrate of the silicon structure has an oxygen concentration ranging from about at least about 5 to less than about 20 ppma.
5. The process of claim 1 wherein the substrate of the silicon structure has an initial resistivity ranging from at least about 100 to less than about 300 ohm-cm.
6. The process of claim 1 wherein after the heat-treatment the resulting substrate of the heat-treated silicon structure has a resistivity of at least about 1000 ohm-cm.
7. The process of claim 1 wherein boron atoms are the acceptor and oxygen clusters are the thermal donors.
8. The process of claim 7 wherein the boron concentration [B] and the oxygen concentration [Oi] of the substrate of the structure, and the temperature, T, of the heat-treatment, are related by the following equation:
[ B]= 1 e 14([ O i ]/[O i ] ref ) n exp( E/kT−E/kT ref )
wherein:
[B] is the boron concentration;
[Oi] ref is the reference interstitial oxygen concentration and is about 6.6e17 cm −3 ;
[Oi] is the actual interstitial oxygen concentration of the substrate of the structure;
n is the oxygen exponent and is about 7;
E is the activation energy and is about 4 eV;
k is the Boltzmann constant;
T is the actual temperature of the heat-treatment; and,
T ref is the reference temperature and is about 520° C., and further wherein:
(i) for a given boron concentration, [B], the oxygen concentration may be about +/−0.5 ppma of the calculated concentration and the temperature of the heat-treatment may be about +/−10° C. of the calculated temperature;
(ii) for a given oxygen concentration, [Oi], the boron concentration may be about +/−20% of the calculated concentration and the temperature of the heat-treatment may be about +/−10° C. of the calculated temperature; and,
(iii) for a given temperature of the heat-treatment, T, the oxygen concentration may be about +/−0.5 ppma of the calculated concentration and the boron concentration may be about +/−20% of the calculated concentration.
9. The process of claim 1 wherein the substrate of the structure has a front stratum and a back stratum, a circumferential edge, a central axis which is substantially perpendicular to each of said front and back stratums, and a radius extending from said central axis substantially parallel to each of said front and back stratums and toward the circumferential edge, said substrate having an oxygen concentration which varies along said radius.
10. The process of claim 9 wherein said oxygen concentration along said radius varies from about 5 ppma to about 20 ppma.
11. The process of claim 1 wherein the substrate of the structure has a front stratum and a back stratum, a circumferential edge, a central axis which is substantially perpendicular to each of said front and back stratums, and a radius extending from said central axis substantially parallel to each of said front and back stratums and toward the circumferential edge, said substrate having a boron concentration which varies along said radius.
12. The process of claim 11 wherein said boron concentration along said radius varies from at least about 1% to less than about 20%.
13. The process of claim 1 wherein the temperature of said heat-treatment is in the range of greater than about 480 to less than about 600° C.
14. The process of claim 13 wherein said heat-treatment is for a time of about 10 to about 250 minutes.
15. A process for preparing a high resistivity CZ single crystal silicon wafer, the process comprising:
subjecting a CZ single crystal silicon wafer having a nominal diameter of at least 150 mm and an initial resistivity of at least about 50 ohm-cm to a heat-treatment for a duration and at a temperature such that the resulting heat-treated wafer has a concentration of thermal donors [TD] and acceptors [A] wherein the ratio [TD]:[A] is between about 0.8:1 and about 1.2:1.
16. The process of claim 15 wherein said ratio is between about 0.9:1 and 1.1:1.
17. The process of claim 15 wherein the resulting resistivity of the heat-treated wafer is at least about 10 times greater than the resistivity as calculated based on the acceptor concentration therein.
18. The process of claim 15 wherein said wafer has an oxygen concentration ranging from about at least about 5 to less than about 20 ppma.
19. The process of claim 15 wherein said wafer has an initial resistivity ranging from at least about 100 to less than about 300 ohm-cm.
20. The process of claim 15 wherein said wafer has a resistivity after said heat-treatment of at least about 1000 ohm-cm.
21. The process of claim 15 wherein boron atoms are the acceptor and oxygen clusters are the thermal donors.
22. The process of claim 21 wherein the boron concentration [B] and the oxygen concentration [Oi] of the wafer, and the temperature, T, of the heat-treatment, are related by the following equation:
[ B]= 1 e 14([ O i ]/[O i ] ref ) n exp( E/kT−E/kT ref )
wherein:
[B] is the boron concentration;
[Oi] ref is the reference interstitial oxygen concentration and is about 6.6e17 cm −3 ;
[Oi] is the actual interstitial oxygen concentration of the wafer;
n is the oxygen exponent and is about 7;
E is the activation energy and is about 4 eV;
k is the Boltzmann constant;
T is the actual temperature of the heat-treatment; and,
T ref is the reference temperature and is about 520° C., and further wherein:
(i) for a given boron concentration, [B], the oxygen concentration may be about +/−0.5 ppma of the calculated concentration and the temperature of the heat-treatment may be about +/−10° C. of the calculated temperature;
(ii) for a given oxygen concentration, [Oi], the boron concentration may be about +/−20% of the calculated concentration and the temperature of the heat-treatment may be about +/−10° C. of the calculated temperature; and,
(iii) for a given temperature of the heat-treatment, T, the oxygen concentration may be about +/−0.5 ppma of the calculated concentration and the boron concentration may be about +/−20% of the calculated concentration.
23. The process of claim 15 wherein the wafer has a front surface and a back surface, a circumferential edge, a central axis which is substantially perpendicular to each of said front and back surfaces, and a radius extending from said central axis substantially parallel to each of said front and back surfaces and toward the circumferential edge, said wafer having an oxygen concentration which varies along said radius.
24. The process of claim 23 wherein said oxygen concentration along said radius varies from about 5 ppma to about 20 ppma.
25. The process of claim 15 wherein the wafer has a front surface and a back surface, a circumferential edge, a central axis which is substantially perpendicular to each of said front and back surfaces, and a radius extending from said central axis substantially parallel to each of said front and back surfaces and toward the circumferential edge, said wafer having a boron concentration which varies along said radius.
26. The process of claim 25 wherein said boron concentration along said radius varies from at least about 1% to less than about 20%.
27. The process of claim 15 wherein the temperature of said heat-treatment is in the range of greater than about 480 to less than about 600° C.
28. The process of claim 27 wherein said heat-treatment for a time of about 10 to about 250 minutes.
29. A high resistivity silicon structure comprising a CZ single crystal silicon substrate, said substrate having an oxygen concentration between at least about 5 ppma and about 20 ppma, and a concentration of thermal donors [TD] and acceptors [A] wherein the ratio [TD]:[A] is between about 0.8:1 and about 1.2:1.
30. The structure of claim 29 wherein said ratio is between about 0.9:1 and 1.1:1.
31. The structure of claim 29 wherein said structure is an electronic device.
32. The structure of claim 29 wherein said structure is passive electrical device.
33. The structure of claim 29 wherein the substrate of said structure is not Au-doped.
34. The structure of claim 29 wherein the substrate of said structure has a resistivity of at least about 1000 ohm-cm.
35. The structure of claim 29 wherein said structure further comprises an epitaxial layer deposited on a surface of said substrate.
36. The structure of claim 29 wherein said structure is a silicon on insulator structure, said structure further comprising an oxide layer on a surface of said substrate, and a device layer on said oxide layer.
37. The structure of claim 29 wherein boron atoms are the acceptor and wherein oxygen clusters are the thermal donors.
38. The structure of claim 37 wherein the resistivity is substantially greater than the resistivity as calculated based on said boron concentration.
39. The structure of claim 38 wherein the resistivity is at least about 10 times greater than the resistivity as calculated based on the boron concentration.
40. The structure of claim 29 wherein the substrate of the structure has a front stratum and a back stratum, a circumferential edge, a central axis which is substantially perpendicular to each of said front and back stratums, and a radius extending from said central axis substantially parallel to each of said front and back stratums and toward the circumferential edge, said substrate having an oxygen concentration and/or a boron concentration which varies along said radius.
41. The structure of claim 40 wherein said boron concentration along said radius varies from at least about 1% to less than about 20%.
42. The structure of claim 40 wherein said oxygen concentration along said radius varies from at least about 5 ppma to less than about 20 ppma.
43. A high resistivity CZ single crystal silicon wafer, the wafer having a nominal diameter of at least 150 mm and an oxygen concentration between at least about 5 ppma and about 20 ppma, and comprising a concentration of thermal donors [TD] and acceptors [A], wherein the ratio [TD]:[A] is between about 0.8:1 and about 1.2:1.
44. The wafer of claim 43 wherein said ratio is between about 0.9:1 and 1.1:1.
45. The wafer of claim 43 wherein said wafer is not Au-doped.
46. The wafer of claim 43 wherein said wafer has a resistivity of at least about 1000 ohm-cm.
47. The wafer of claim 43 wherein said wafer further comprises an epitaxial layer deposited on a surface of said wafer.
48. A silicon-on-insulator structure comprising the wafer of claim 43 as the handle wafer thereof, said handle wafer having an oxide layer on a surface thereof, and a device layer on a surface of the oxide layer.
49. The wafer of claim 43 wherein boron atoms are the acceptor and wherein oxygen clusters are the thermal donors.
50. The wafer of claim 49 wherein the resistivity is substantially greater than the resistivity as calculated based on said boron concentration.
51. The wafer of claim 50 wherein the resistivity is at least about 10 times greater than the resistivity as calculated based on the boron concentration.
52. The wafer of claim 43 wherein the wafer has a front surface and a back surface, a circumferential edge, a central axis which is substantially perpendicular to each of said front and back surfaces, and a radius extending from said central axis substantially parallel to each of said front and back surfaces and toward the circumferential edge, said wafer having an oxygen concentration and/or a boron concentration which varies along said radius.
53. The wafer of claim 52 wherein said boron concentration along said radius varies from at least about 1% to less than about 20%.
54. The wafer of claim 52 wherein said oxygen concentration along said radius varies from at least about 5 ppma to less than about 20 ppma.