Glass-based SOI structures

• US 7,605,053 B2
• Filed: 04/09/2008
• Issued: 10/20/2009
• Est. Priority Date: 02/18/2003
• Status: Active Grant

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Couillard, James G., Gadkaree, Kishor P., Mach, Joseph F.
• Primary Examiner(s): Sarkar; Asok K
• Application Number:
  US12/082,211
• Publication Number:
  US 20080224254A1
• Time in Patent Office: 559 Days
• Field of Search: 257/347, 257/E27.112, 257/E21.48, 438/455
• US Class Current: 438/455
• CPC Class Codes: H01L 21/2007 Bonding of semiconductor wafers to insulating substrates or to semiconducting substrates using an intermediate insulating layer H01L21/2011 takes precedence; bonding of semiconductor wafers to semiconductor wafers for junction formation H01L21/187
• CPC Class Codes: H01L 21/76254 with separation/delamination along an ion implanted layer, e.g. Smart-cut, Unibond

Abstract

Semiconductor-on-insulator (SOI) structures, including large area SOI structures, are provided which have one or more regions composed of a layer of a substantially single-crystal semiconductor (e.g., doped silicon) attached to a support substrate composed of an oxide glass or an oxide glass-ceramic. The oxide glass or oxide glass-ceramic is preferably transparent and preferably has a strain point of less than 1000° C., a resistivity at 250° C. that is less than or equal to 10¹⁶ Ω-cm, and contains positive ions (e.g., alkali or alkaline-earth ions) which can move within the glass or glass-ceramic in response to an electric field at elevated temperatures (e.g., 300-1000° C.). The bond strength between the semiconductor layer and the support substrate is preferably at least 8 joules/meter². The semiconductor layer can include a hybrid region in which the semiconductor material has reacted with oxygen ions originating from the glass or glass-ceramic. The support substrate preferably includes a depletion region which has a reduced concentration of the mobile positive ions.

Claims

1. A method for producing a semiconductor-on-insulator structure, comprising:

(A) providing first and second substrates wherein;

(1) the first substrate comprises a first external surface for bonding to the second substrate (the first bonding surface), a second external surface for applying force to the first substrate (the first force-applying surface), and an internal zone for separating the first substrate into a first part and a second part (the separation zone), where;

(a) the second part is between the separation zone and the first bonding surface, and (b) the first substrate comprises a substantially single-crystal semiconductor material; and

(2) the second substrate comprises two external surfaces, one for bonding to the first substrate (the second bonding surface) and another for applying force to the second substrate (the second force-applying surface), where;

(a) the second bonding surface and the second force-applying surface are separated from one another by a distance D₂, and (b) the second substrate comprises an oxide glass or an oxide glass-ceramic;

(B) bringing the first and second bonding surfaces into contact;

(C) for a period of time sufficient for the first and second substrates to bond to one another at the first and second bonding surfaces, and for positive ions within the oxide glass or oxide glass-ceramic to move within the second substrate in a direction away from the second bonding surface and towards the second force-applying surface, such that the second substrate includes;

(i) a first substrate layer adjacent the second bonding surface having a reduced positive ion concentration in which substantially no modifier positive ions are present, and (ii) a second substrate layer adjacent the first substrate layer and having an enhanced positive ion concentration of modifier positive ions, including at least one alkaline earth modifier ion;

(1) applying force to the first and second force-applying surfaces to press the first and second bonding surfaces together;

(2) subjecting the first and second substrates to an electric field which is characterized by first and second voltages V₁ and V₂ at the first and second force-applying surfaces, respectively, V₁ being higher than V₂ so that the electric field is directed from the first substrate to the second substrate; and

(3) heating the first and second substrates, said heating being characterized by first and second temperatures T₁ and T₂ at the first and second force-applying surfaces, respectively; and

(D) separating the first and second parts at the separation zone.

2. A method for producing a semiconductor-on-insulator structure, comprising:

(A) providing a first substrate of substantially single-crystal semiconductor material having first and second surfaces, and an internal separation zone located therebetween;

(B) providing a second substrate of an oxide glass or an oxide glass-ceramic having a first surface for bonding to the first surface of the first substrate and a second surface;

(C) bringing the first surfaces of the first and second substrates into contact with one another and applying force to press them together;

(D) subjecting the first and second substrates to an electric field directed from the first substrate to the second substrate;

(E) heating the first and second substrates by applying first and second sources of heat, at temperatures T₁ and T₂, respectively, to the respective second surfaces of the first and second substrates;

(F) maintaining one or more of the force, the electric field, and the heat for a period of time sufficient to bond the first and second substrates to one another, and for positive ions within the second substrate to move in a direction away from the first surface towards the second surface thereof, such that the second substrate includes;

(i) a first substrate layer, adjacent the first surface thereof, having a reduced positive ion concentration in which substantially no modifier positive ions are present, and (ii) a second substrate layer adjacent the first substrate layer and having an enhanced positive ion concentration of modifier positive ions, including at least one alkaline earth modifier ion; and

(G) separating the first substrate at the separation zone such that a layer of the substantially single-crystal semiconductor material remains bonded to the second substrate.

3. The method of claim 2, wherein the oxide glass or oxide glass-ceramic further comprises non-bridging oxygens which during the maintaining step, move within the second substrate in a direction away from the first surface and towards the second surface thereof.

4. The method of claim 2, wherein the oxide glass or oxide glass-ceramic of the second substrate has a 0-300°

C. coefficient of thermal expansion CTE and a 250°

C. resistivity ρ

which satisfy the relationships;

5×

10<sup>−

7</sup>/°

C.≦

CTE≦

75×

10<sup>−

7</sup>/°

C., and

ρ

≦

10¹⁶ Ω

-cm.

5. The method of claim 2, wherein the first and second substrates, at least in part, bond to one another through the reaction of the semiconductor material of the first substrate with oxygen originating from the second substrate.

6. The method of claim 5, wherein the reaction of the semiconductor material of the first substrate with oxygen originating from the second substrate produces a region (the hybrid region) of enhanced oxygen concentration which begins at the first surface of the first substrate and extends towards the separation zone.

7. The method of claim 2, wherein the movement of the positive ions forms a region which is depleted in positive ions (the positive ion depletion region) which begins at the first surface of the second substrate and extends into the second substrate towards the second surface thereof, wherein:

(i) the oxide glass or oxide glass-ceramic comprises one or more of the following positive ions;

Li⁺¹, Na⁺¹, K⁺¹, Cs⁺¹, Mg⁺², Ca⁺², Sr⁺², and/or Ba⁺² (the alkali/alkaline-earth ions); and

(ii) the positive ion depletion region is depleted of one or more of said alkali/alkaline-earth ions.

8. The method of claim 7, wherein:

(i) each of the alkali/alkaline-earth ions which the oxide glass or oxide glass-ceramic contains has a reference concentration C_i/Ref at a reference surface which is within the second substrate and spaced from the first surface thereof by a distance D₂/2; and

(ii) the positive ion depletion region has a distal edge and the movement of the positive ions forms a region in the vicinity of said distal edge (the pile-up region) in which the concentration of at least one type of positive ion is enhanced relative to C_i/Ref for that ion.

9. The method of claim 2, further comprising maintaining one or more of the force, the electric field, and the heat to:

produce a first layer within the second substrate adjacent to the first surface thereof with a reduced positive ion concentration having substantially no modifier positive ions; and

produce a second layer adjacent to the first layer within the second substrate with an enhanced positive ion concentration of modifier positive ions, including at least one alkaline earth modifier ion from the first layer of the second substrate.

10. The method of claim 9, wherein relative degrees to which the modifier positive ions are absent from the first layer and the modifier positive ions exist in the second layer are such that substantially no ion re-migration from the second substrate into the first substrate may occur.

11. The method of claim 2, further comprising cooling the first and second substrates such that the first substrate separates at the separation zone.

12. The method of claim 11, wherein the first substrate separates at the separation zone when respective temperatures of the first and second substrates are falling.

13. The method of claim 2, wherein the first substrate separates at the separation zone during the heating of the first and second substrates.

14. The method of claim 13, wherein the first substrate separates at the separation zone when respective temperatures of the first and second substrates are rising.

15. The method of claim 2, wherein the first substrate separates at the separation zone when respective temperatures of the first and second substrates are neither substantially rising nor falling.

16. The method of claim 2, wherein the first substrate separates at the separation zone in response to temperature profiles of the respective temperatures of the first and second substrates during at least one of the heating step and a cooling step.

17. The method of claim 16, wherein characteristics of the temperature profiles at which the first substrate separates at the separation zone are a function of a strain point of the second substrate.

18. The method of claim 17, wherein the characteristics of the temperature profiles vary between:

(i) respective temperatures of the first and second substrates falling or having fallen during cooling to achieve separation, where the strain point of the second substrate is relatively low; and

(ii) respective temperatures of the first and second substrates rising or having risen during heating to achieve separation, where the strain point of the second substrate is relatively high.

19. The method of claim 2, wherein one of:

T₁ and T₂ are different temperatures, and T₁ and T₂ are substantially the same temperature.

20. The method of claim 2, wherein the strain point, T_s, and T₁ and T₂ of the oxide glass or oxide glass-ceramic are in degrees centigrade and satisfy the relationships:

T_s−

350≦

T₁≦

T_s+350; and

 

 

(i)

T_s−

350≦

T₂≦

T_s+350. 

 

(ii)

21. The method of claim 2, wherein:

300°

C.≦

T₁≦

800°

C.; and

 

 

(i)

300°

C.≦

T₂≦

800°

C. 

 

(ii)

22. The method of claim 2, wherein the step of maintaining one or more of the force, the electric field, and the heat is performed in an inert atmosphere.

23. The method of claim 2, wherein the force per unit area P applied to the second surfaces satisfies the relationship:

1 psi≦

P≦

100 psi.

24. The method of claim 2, wherein the electric field is produced by applying respective voltages V₁ and V₂ to the second surfaces of the first and second substrates, respectively, where V_{1 and V2} satisfy the relationship:

100 volts/cm≦

(V₁ −

V₂)/D≦

40 kilovolts/cm,

where D is the distance between the second surfaces.

25. The method of claim 2, wherein:

CTE₁−

20×

10<sup>−

7</sup>/°

C.≦

CTE₂≦

CTE₁+20×

10<sup>−

7</sup>/°

C.

where CTE₁ is the 0°

C. coefficient of thermal expansion of the substantially single-crystal semiconductor material and CTE₂ is the 0-300°

C. coefficient of thermal expansion of the oxide glass or oxide glass-ceramic.

26. The method of claim 2, wherein the oxide glass or oxide glass-ceramic is transparent.

27. The method of claim 2, wherein the first substrate is taken from the group consisting of:

silicon (Si), germanium-doped silicon (SiGe), silicon carbide (SiC), germanium (Ge), gallium arsenide (GaAs), GaP, and InP.

28. The method of claim 2, wherein the bond strength between the second surfaces after separation is at least 8 joules/meter².

29. A method of forming a semiconductor on glass structure, comprising:

establishing an exfoliation layer on a semiconductor wafer;

contacting the exfoliation layer of the semiconductor wafer to a glass substrate; and

applying pressure, temperature and voltage to the semiconductor wafer and the glass substrate, such that a bond is established therebetween via electrolysis, and such that the glass substrate includes;

(i) a first substrate layer adjacent the exfoliation layer having a reduced modifier positive ion concentration, and (ii) a second substrate layer adjacent the first substrate layer having an enhanced modifier positive ion concentration,

wherein the first substrate layer with the reduced modifier positive ion concentration is operable to inhibit ion re-migration from the glass substrate into the exfoliation layer.

30. The method of claim 29, wherein the step of applying pressure, temperature and voltage includes causing at least one alkaline earth modifier ion to move from the first substrate layer to the second substrate layer.

31. The method of claim 29, wherein the step of applying pressure, temperature and voltage includes substantially depleting the first substrate layer of all of alkali/alkaline-earth modifier positive ions.

32. The method of claim 29, wherein the step of applying pressure, temperature and voltage includes maintaining one or more network forming ions in the first substrate layer.

33. The method of claim 29, wherein the step of applying pressure, temperature and voltage includes causing non-bridging oxygens in the first substrate layer to move in a direction away from the exfoliation layer.

34. The method of claim 29, wherein the modifier positive ions include at least one of:

Li⁺¹, Na⁺¹, K⁺¹, Cs⁺¹, Mg⁺², Ca⁺², Sr⁺², and/or Ba⁺².

35. A semiconductor on glass structure, comprising:

a semiconductor layer; and

a glass substrate to which the semiconductor layer is bonded via electrolysis, the glass substrate including;

(i) a first substrate layer adjacent the semiconductor layer having a reduced modifier positive ion concentration, and (ii) a second substrate layer adjacent the first substrate layer having an enhanced modifier positive ion concentration,

wherein the first substrate layer with the reduced modifier positive ion concentration is operable to inhibit ion re-migration from the glass substrate into the semiconductor layer.

36. The semiconductor on glass structure of claim 35, wherein at least one alkaline earth modifier ion is present in the second substrate layer, which alkaline earth modifier ion moved from the first substrate layer as a result of the bonding of the semiconductor layer to the glass substrate via electrolysis.

37. The semiconductor on glass structure of claim 35, wherein the first substrate layer is substantially depleted of all of alkali/alkaline-earth modifier positive ions.

38. The semiconductor on glass structure of claim 35, wherein the first substrate layer maintains one or more network forming ions therein.

39. The semiconductor on glass structure of claim 35, wherein the first substrate layer includes non-bridging oxygens that have moved away from the semiconductor layer.

40. The semiconductor on glass structure of claim 35, wherein the modifier positive ions include at least one of:

Li⁺¹, Na⁺¹, K⁺¹, Cs⁺¹, Mg⁺², Ca⁺², Sr⁺², and/or Ba⁺².