Fabrication of a semiconductor device with air gaps for ultra-low capacitance interconnections

• US 6,165,890 A
• Filed: 01/21/1998
• Issued: 12/26/2000
• Est. Priority Date: 01/21/1997
• Status: Expired due to Term

• Current Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Inventors: Bidstrup Allen, Sue Ann, Zhao, Qiang, Kohl, Paul A.
• Primary Examiner(s): Everhart, Caridad
• Application Number:
  US09/009,952
• Time in Patent Office: 1,070 Days
• Field of Search: 438/619, 438/623, 438/780, 438/781, 438/421
• US Class Current: 438/619
• CPC Class Codes: H01L 21/7682 the dielectric comprising air gaps
• CPC Class Codes: H01L 23/5222 Capacitive arrangements or effects of, or between wiring layers other capacitive arrangements H01L23/642
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/12044 OLED

Abstract

A method of forming an air gap or gaps within solid structures and specifically semiconductor structures to reduce capacitive coupling between electrical elements such as metal lines, wherein a norbornene-type polymer is used as a sacrificial material to occupy a closed interior volume in a semiconductor structure. The sacrificial material is caused to decompose into one or more gaseous decomposition products which are removed, preferably by diffusion, through an overcoat layer. The decomposition of the sacrificial material leaves an air gap or gaps at the closed interior volume previously occupied by the norbornene-type polymer. The air gaps may be disposed between electrical leads to minimize capacitive coupling therebetween.

Claims

1. A method of forming an air gap within a semiconductor structure comprising the steps of:

using a sacrificial material to occupy a closed interior volume in a semiconductor structure;

causing the sacrificial material to decompose into one or more gaseous decomposition products; and

removing at least one of the one or more gaseous decomposition products by passage through at least one solid layer contiguous to the interior volume; and

wherein the decomposition of the sacrificial material leaves an air gap at the closed interior volume previously occupied thereby, and the sacrificial material comprises a norbornene-type polymer.

2. A method as set forth in claim 1, wherein the at least one solid layer is a dielectric material through which the at least one of the one or more gaseous decomposition products can pass by diffusion under conditions not detrimental to the semiconductor structure.

3. A method as set forth in claim 1, wherein the at least one solid layer is a porous dielectric material through which the at least one of the one or more gaseous decomposition products can pass through pores in the porous dielectric material under conditions not detrimental to the semiconductor structure.

4. A method as set forth in claim 1, wherein said norbornene-type polymer comprises repeat units of the general formula:

##STR16## wherein R¹ and R⁴ independently represent hydrogen or linear or branched (C₁ to C₂₀) alkyl;

R² and R³ independently represent hydrogen, linear or branched (C₁ to C₂₀) alkyl or the groups;

##STR17## R⁹ independently is hydrogen, methyl, or ethyl;

R¹⁰, R¹¹, and R¹² independently represent linear or branched (C₁ to C₂₀) alkyl, linear or branched (C₁ to C₂₀) alkoxy, linear or branched (C₁ to C₂₀) alkyl carbonyloxy, linear or branched (C₁ to C₂₀) alkyl peroxy, and substituted or unsubstituted (C₆ to C₂₀) aryloxy;

m is a number from 0 to 4; and

n is a number from 0 to 5; and

at least one of substituents R² and R³ is selected from the silyl group represented by the formula set forth under Ia.

5. A method as set forth in claim 4, wherein at least one of R¹⁰, R¹¹, or R¹² is selected from a linear or branched (C₁ to C₁₀) alkoxy group and R⁹ is hydrogen.

6. A method as set forth in claim 5, wherein each of R¹⁰, R¹¹, and R¹² are the same and are selected from methoxy, ethoxy, propoxy, butoxy, and pentoxy.

7. A method as set forth in claim 6, wherein n is 0 and R¹⁰, R¹¹, and R¹² are each ethoxy groups.

8. A method as set forth in claim 7, wherein R² or R³ is a triethoxysilyl substituent.

9. A method as set forth in claim 1, wherein in Formula I above, m is preferably 0 or 1 as represented by structures Ib and Ic, respectively:

##STR18## wherein R¹ to R⁴ are as previously defined and at least one of R² and R³ is a silyl substituent represented by Ia.

10. A method as set forth in claim 1, wherein R¹ and R⁴ taken together with the two ring carbon atoms to which they are attached comprise a repeat unit of the following structure:

##STR19## wherein B is a methylene group, q is a number from 2 to 6, and R² and R³ are as defined above.

11. A method as set forth in claim 1, wherein said norbornene-type polymer further comprises hydrocarbyl substituted polycyclic repeating units selected from units represented by Formula II below:

##STR20## wherein R⁵, R⁶, R⁷, and R⁸ independently represent hydrogen, linear and branched (C₁ to C₂₀) alkyl, hydrocarbyl substituted and unsubstituted (C₅ to C₁₂) cycloalkyl, hydrocarbyl substituted and unsubstituted (C₆ to C₄₀) aryl, hydrocarbyl substituted and unsubstituted (C₇ to C₁₅) aralkyl, (C₃ to C₂₀) alkynyl, linear and branched (C₃ to C₂₀) alkenyl, or vinyl;

any of R⁵ and R⁶ or R⁷ and R⁸ can be taken together to form a (C₁ to C₁₀) alkylidenyl group, R⁵ and R⁸ when taken with the two ring carbon atoms to which they are attached can represent saturated and unsaturated cyclic groups containing 4 to 12 carbon atoms or an aromatic ring containing 6 to 17 carbon atoms; and

p is 0, 1, 2, 3, or 4.

12. A method as set forth in claim 1, wherein said norbornene-type polymer comprises hydrocarbyl substituted polycyclic repeating units selected from units represented by Formula II below:

##STR21## wherein R⁵, R⁶, R⁷, and R⁸ independently represent hydrogen, linear and branched (C₁ to C₂₀) alkyl, hydrocarbyl substituted and unsubstituted (C₅ to C₁₂) cycloalkyl, hydrocarbyl substituted and unsubstituted (C₆ to C₄₀) aryl, hydrocarbyl substituted and unsubstituted (C₇ to C₁₅) aralkyl, (C₃ to C₂₀) alkynyl, linear and branched (C₃ to C₂₀) alkenyl, or vinyl;

any of R⁵ and R⁶ or R⁷ and R⁸ can be taken together to form a (C₁ to C₁₀) alkylidenyl group, R⁵ and R⁸ when taken with the two ring carbon atoms to which they are attached can represent saturated and unsaturated cyclic groups containing 4 to 12 carbon atoms or an aromatic ring containing 6 to 17 carbon atoms; and

p is 0, 1, 2, 3, or 4.

13. A method as set forth in claim 1, wherein said norbornene-type polymer comprises repeating units represented by Formula III below:

##STR22## wherein R⁹ to R¹² independently represent a polar substituent selected from the group;

--(A)_n --C(O)OR", --(A)_n --OR", --(A)_n --OC(O)R", --(A)_n --OC(O)OR", --(A)_n --C(O)R", --(A)_n --OC(O)C(O)OR", --(A)_n --O--A'"'"'--C(O)OR", --(A)_n --OC(O)--A'"'"'--C(O)OR", --(A)_n --C(O)O--A'"'"'--C(O)OR", --(A)_n --C(O)--A'"'"'--OR", --(A)_n --C(O)O--A'"'"'--OC(O)OR", --(A)_n --C(O)O--A'"'"'--O--A'"'"'--C(O)OR", --(A)_n --C(O)O--A'"'"'--OC(O)C(O)OR", --(A)_n --C(R")₂ CH(R")(C(O)OR"), and --(A)_n --C(R")₂ CH(C(O)OR")₂ ;

the moieties A and A'"'"' independently represent a divalent bridging or spacer radical selected from divalent hydrocarbon radicals, divalent cyclic hydrocarbon radicals, divalent oxygen containing radicals, and divalent cyclic ethers and cyclic diethers; and

n is an integer 0 or 1.

14. A method as set forth in claim 1, wherein said norbornene-type polymer comprises copolymers comprising a combination of repeating units represented by Formulae I and II, Formulae I and III, Formulae II and III or Formulae I, II and III, where Formula I is:

##STR23## wherein R¹ and R⁴ independently represent hydrogen or linear or branched (C₁ to C₂₀) alkyl;

R² and R³ independently represent hydrogen, linear or branched (C₁ to C₂₀) alkyl or the groups;

##STR24## R⁹ independently is hydrogen, methyl, or ethyl;

R¹⁰, R¹¹, and R¹² independently represent linear or branched (C₁ to C₂₀) alkyl, linear or branched (C₁ to C₂₀) alkoxy, linear or branched (C₁ to C₂₀) alkyl carbonyloxy, and substituted or unsubstituted (C₆ to C₂₀) aryloxy;

m is a number from 0 to 4; and

n is a number from 0 to 5; and

at least one of substituents R² and R³ is selected from the silyl group represented by the formula set forth under Ia;

Formula II is ##STR25## wherein R⁵, R⁶, R⁷, and R⁸ independently represent hydrogen, linear and branched (C₁ to C₂₀) alkyl, hydrocarbyl substituted and unsubstituted (C₅ to C₁₂) cycloalkyl, hydrocarbyl substituted and unsubstituted (C₆ to C₄₀) aryl, hydrocarbyl substituted and unsubstituted (C₇ to C₁₅) aralkyl, (C₃ to C₂₀) alkynyl, linear and branched (C₃ to C₂₀) alkenyl, or vinyl;

any of R⁵ and R⁶ or R⁷ and R⁸ can be taken together to form a (C₁ to C₁₀) alkylidenyl group, R⁵ and R⁸ when taken with the two ring carbon atoms to which they are attached can represent saturated and unsaturated cyclic groups containing 4 to 12 carbon atoms or an aromatic ring containing 6 to 17 carbon atoms; and

p is 0, 1, 2, 3, or 4; and

Formula III is ##STR26## wherein R⁹ to R¹² independently represent a polar substituent selected from the group;

--(A)_n --C(O)OR'"'"', --(A)_n --OR", --(A)_n --OC(O)R", --(A)_n --OC(O)OR", --(A)_n --C(O)R", --(A)_n --OC(O)C(O)OR", --(A)_n --O--A'"'"'--C(O)OR", --(A)_n --OC(O)--A'"'"'--C(O)OR", --(A)_n --C(O)O--A'"'"'--C(O)OR", --(A)_n --C(O)--A'"'"'--OR", --(A)_n --C(O)O--A'"'"'--OC(O)OR", --(A)_n --C(O)O--A'"'"'--O--A'"'"'--C(O)OR", --(A)_n --C(O)O--A'"'"'--OC(O)C(O)OR", --(A)_n --C(R")₂ CH(R")(C(O)OR"), and --(A)_n --C(R")₂ CH(C(O)OR")₂ ;

the moieties A and A'"'"' independently represent a divalent bridging or spacer radical selected from divalent hydrocarbon radicals, divalent cyclic hydrocarbon radicals, divalent oxygen containing radicals, and divalent cyclic ethers and cyclic diethers; and

n is an integer 0 or 1.

15. A method as set forth in claim 1, wherein the repeating units containing silyl functional groups comprise at least 1 mole percent of the polymer.

16. A method as set forth in claim 15, wherein the repeating units containing silyl functional groups comprise at least 5 mole percent of the polymer.

17. A method as set forth in claim 1, wherein the sacrificial material is provided in the semiconductor structure by:

forming a patterned layer of the sacrificial material on a substrate corresponding to a pattern of one or more gaps to be formed in the semiconductor structure; and

forming another layer of material overlying the patterned layer of sacrificial material.

18. A method as set forth in claim 1, wherein the sacrificial material is provided in the semiconductor structure by:

forming a patterned layer of sacrificial material on a substrate corresponding to a pattern of one or more gaps to be formed in the semiconductor structure;

depositing a second material on the substrate within regions bordered by the sacrificial material;

forming another layer of material overlying the patterned layer of sacrificial material and second material in the regions bordered by the sacrificial material.

19. A method as set forth in claim 18, wherein the depositing step includes using a conductive material as the second material to form conductive leads.

20. A method of forming one or more air gaps in a semiconductor structure comprising the steps of:

forming a patterned layer of sacrificial material on a substrate corresponding to a pattern of one or more gaps to be formed in the semiconductor structure;

depositing a second material on the substrate within regions bordered by the sacrificial material;

forming an overcoat layer of material overlying the patterned layer of sacrificial material and second material in the regions bordered by the sacrificial material;

causing the sacrificial material to decompose into one or more gaseous decomposition products; and

removing at least one of the one or more gaseous decomposition products by passage through the overcoat layer so that one or more air gaps are formed within the semiconductor structure.

21. A method as set forth in claim 20, wherein said depositing of the second material includes using a conductive material to form conductive leads on opposite sides of portions of the sacrificial material.

22. A method as set forth in claim 21, wherein prior to said forming of the overcoat layer, the conductive material is formed with a height less than the height of the adjacent sacrificial material.

23. A method as set forth in claim 20, wherein said sacrificial material is a cyclic olefin.

24. A method as set forth in claim 23, wherein said cyclic olefin is a dicyclic olefin.

25. A method as set forth in claim 20, wherein said sacrificial material is a norbornene-type polymer.

26. A method as set forth in claim 25, wherein said norbornene-type polymer comprises repeat units of the general formula:

##STR27## wherein R¹ and R⁴ independently represent hydrogen or linear or branched (C₁ to C₂₀) alkyl;

R² and R³ independently represent hydrogen, linear or branched (C₁ to C₂₀) alkyl or the groups;

##STR28## R⁹ independently is hydrogen, methyl, or ethyl;

R¹⁰, R¹¹, and R¹² independently represent linear or branched (C₁ to C₂₀) alkyl, linear or branched (C₁ to C₂₀) alkoxy, linear or branched (C₁ to C₂₀) alkyl carbonyloxy, and substituted or unsubstituted (C₆ to C₂₀) aryloxy;

m is a number from 0 to 4; and

n is a number from 0 to 5; and

at least one of substituents R² and R³ is selected from the silyl group represented by the formula set forth under Ia.

27. A method as set forth in claim 26, wherein in Formula I above, m is preferably 0 or 1 as represented by structures Ib and Ic, respectively:

##STR29## wherein R¹ to R⁴ are as previously defined and at least one of R² and R³ is a silyl substituent represented by Ia.

28. A method as set forth in claim 26, wherein R¹ and R⁴ taken together with the two ring carbon atoms to which they are attached comprise a repeat unit of the following structure:

##STR30## wherein B is a methylene group, q is a number from 2 to 6, and R² and R³ are as defined above.

29. A method as set forth in claim 26, wherein said norbornene-type polymer further comprises hydrocarbyl substituted polycyclic repeating units selected from units represented by Formula II below:

##STR31## wherein R⁵, R⁶, R⁷, and R⁸ independently represent hydrogen, linear and branched (C₁ to C₂₀) alkyl, hydrocarbyl substituted and unsubstituted (C₅ to C₁₂) cycloalkyl, hydrocarbyl substituted and unsubstituted (C₆ to C₄₀) aryl, hydrocarbyl substituted and unsubstituted (C₇ to C₁₅) aralkyl, (C₃ to C₂₀) alkynyl, linear and branched (C₃ to C₂₀) alkenyl, or vinyl;

any of R⁵ and R⁶ or R⁷ and R⁸ can be taken together to form a (C₁ to C₁₀) alkylidenyl group, R⁵ and R⁸ when taken with the two ring carbon atoms to which they are attached can represent saturated and unsaturated cyclic groups containing 4 to 12 carbon atoms or an aromatic ring containing 6 to 17 carbon atoms; and

p is 0, 1, 2, 3, or 4.

30. A method of forming an air gap within a structure comprising the steps of:

using a sacrificial material to occupy a closed interior volume in the structure;

heating the sacrificial material to cause it to decompose into one or more gaseous decomposition products; and

removing at least one of the one or more gaseous decomposition products by passage through at least one solid layer contiguous to the interior volume; and

wherein the decomposition of the sacrificial material leaves an air gap at the closed interior volume previously occupied by the sacrificial material.

31. A method as set forth in claim 30, wherein the at least one solid layer is a dielectric material through which the at least one of the one or more gaseous decomposition products can pass by diffusion under conditions not detrimental to the semiconductor structure.

32. A method as set forth in claim 30, wherein the at least one solid layer is a porous dielectric material through which the at least one of the one or more gaseous decomposition products can pass through pores in the porous dielectric material under conditions not detrimental to the semiconductor structure.

33. A method as set forth in claim 30, wherein said sacrificial material is a cyclic olefin.

34. A method as set forth in claim 33, wherein said cyclic olefin is a bicycloolefin.

35. A method as set forth in claim 30, wherein said sacrificial material is a norbornene-type polymer.

36. A method as set forth in claim 35, wherein said norbornene-type polymer comprises repeat units of the general formula:

##STR32## wherein R¹ and R⁴ independently represent hydrogen or linear or branched (C₁ to C₂₀) alkyl;

R² and R³ independently represent hydrogen, linear or branched (C₁ to C₂₀) alkyl or the groups;

##STR33## R⁹ independently is hydrogen, methyl, or ethyl;

R¹⁰, R¹¹, and R¹² independently represent linear or branched (C₁ to C₂₀) alkyl, linear or branched (C₁ to C₂₀) alkoxy, linear or branched (C₁ to C₂₀) alkyl carbonyloxy, and substituted or unsubstituted (C₆ to C₂₀) aryloxy;

m is a number from 0 to 4; and

n is a number from 0 to 5; and

at least one of substituents R² and R³ is selected from the silyl group represented by the formula set forth under Ia.

37. A method as set forth in claim 36 wherein in Formula I above, m is preferably 0 or 1 as represented by structures Ib and Ic, respectively:

##STR34## wherein R¹ to R⁴ are as previously defined and at least one of R² and R³ is a silyl substituent represented by Ia.

38. A method as set forth in claim 36, wherein R¹ and R⁴ taken together with the two ring carbon atoms to which they are attached comprise a repeat unit of the following structure:

##STR35## wherein B is a methylene group, q is a number from 2 to 6, and R² and R³ are as defined above.

39. A method as set forth in claim 36, wherein said norbornene-type polymer further comprises hydrocarbyl substituted polycyclic repeating units selected from units represented by Formula II below:

##STR36## wherein R⁵, R⁶, R⁷, and R⁸ independently represent hydrogen, linear and branched (C₁ to C₂₀) alkyl, hydrocarbyl substituted and unsubstituted (C₅ to C₁₂) cycloalkyl, hydrocarbyl substituted and unsubstituted (C₆ to C₄₀) aryl, hydrocarbyl substituted and unsubstituted (C₇ to C₁₅) aralkyl, (C₃ to C₂₀) alkynyl, linear and branched (C₃ to C₂₀) alkenyl, or vinyl;

any of R⁵ and R⁶ or R⁷ and R⁸ can be taken together to form a (C₁ to C₁₀) alkylidenyl group, R⁵ and R⁸ when taken with the two ring carbon atoms to which they are attached can represent saturated and unsaturated cyclic groups containing 4 to 12 carbon atoms or an aromatic ring containing 6 to 17 carbon atoms; and

p is 0, 1, 2, 3, or 4.