Novel application of a supercritical CO2 system for curing low k dielectric materials

• US 20040175958A1
• Filed: 03/07/2003
• Published: 09/09/2004
• Est. Priority Date: 03/07/2003
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Inventors: Lin, Chun-Hsien, Lo, Henry, Lin, Yu-Liang, Liu, Anthony
• Granted Patent: US 6,875,709 B2
• Time in Patent Office: Days
• US Class Current: 438/778
• CPC Class Codes: H01L 21/02118 carbon based polymeric organic or inorganic material, e.g. polyimides, poly cyclobutene or PVC polymers per se C08G, photoresist per se G03F
• CPC Class Codes: H01L 21/02134 the material comprising hydrogen silsesquioxane, e.g. HSQ
• CPC Class Codes: H01L 21/02137 the material comprising alkyl silsesquioxane, e.g. MSQ
• CPC Class Codes: H01L 21/02203 the layer being porous
• CPC Class Codes: H01L 21/02282 liquid deposition, e.g. spin-coating, sol-gel techniques, spray coating
• CPC Class Codes: H01L 21/02343 treatment by exposure to a liquid
• CPC Class Codes: H01L 21/31058 of organic layers
• CPC Class Codes: H01L 21/312 Organic layers, e.g. photoresist H01L21/3105, H01L21/32 take precedence; photoresists per se G03C
• CPC Class Codes: H01L 21/3124 layers comprising hydrogen silsesquioxane
• CPC Class Codes: H01L 21/76826 by contacting the layer with gases, liquids or plasmas
• CPC Class Codes: H01L 21/76829 characterised by the formation of thin functional dielectric layers, e.g. dielectric etch-stop, barrier, capping or liner layers

Abstract

A method and apparatus for curing and-modifying a-low k dielectric layer in an interconnect structure is disclosed. A spin-on low k dielectric layer comprised of an organic silsesquioxane, polyarylether, bisbenzocyclobuene, or SiLK is spin coated on a substrate. The substrate is placed in a process chamber in a supercritical CO₂ system and is treated at a temperature between 30° C. and 150° C. and at a pressure from 70 to 700 atmospheres. A co-solvent such as CF₃—X or F—X is added that selectively replaces C—CH₃ bonds with C—CF₃ or C—F bonds. Alternatively, H₂O₂ is employed as co-solvent to replace a halogen in a C-Z bond where Z=F, Cl, or Br with an hydroxyl group. Two co-solvents may be combined with CO₂ for more flexibility. The cured dielectric layer has improved properties that include better adhesion, lower k value, increased hardness, and a higher elastic modulus.

Claims

1. A method of curing and modifying a low k dielectric layer on a substrate, comprising:

(a) providing a substrate;

(b) coating a spin-on low k dielectric layer on said substrate;

(c) positioning said substrate in a process chamber; and

(d) treating said substrate with a supercritical fluid (SCF) comprised of CO₂ and a co-solvent which is H₂O₂, CF₃—

X, or Y—

F wherein X═

NR₁R₂, —

OR₃, —

O₂CR₃, —

(C═

O)R₃, or R₃ and wherein Y═

H or an alkyl group and R₁, R₂, R₃═

H or an alkyl group.

2. The method of claim 1 wherein said dielectric layer is a low k material selected from a group including inorganic silsesquioxanes₇ organic silsesquioxanes, polyarylethers, bisbenzocyclobutenes, and SiLK from Dow Corning.

3. The method of claim 1 wherein the process chamber is part of a supercritical CO₂ system that is capable of a continuous flow.

4. The method of claim 1 wherein the process chamber is designed for a single wafer mode.

5. The method of claim 1 wherein the low k dielectric layer has a pore volume between about 20% and 40% of the total solid volume of said layer.

6. The method of claim 1 wherein said low k dielectric layer has a thickness in a range of about 1000 to 9000 Angstroms.

7. The method of claim 1 wherein said substrate is treated with a supercritical fluid at a temperature of about 30°

C. to 150°

C.

8. The method of claim 1 wherein said substrate is treated with a supercritical fluid at a pressure between about 70 atmospheres and 700 atmospheres.

9. The method of claim 1 wherein said substrate is treated with a SCF comprised of CO₂ and CF₃—

X wherein the CO₂ flow rate is from about 1000 to 15000 standard cubic centimeters per minute (sccm) and the CF₃—

X flow rate is from about 50 to 100 sccm.

10. The method of claim 1 wherein said substrate is treated with a SCF comprised of CO₂ and Y—

F wherein the CO₂ flow rate is from about 1000 to 15000 sccm and the Y—

F flow rate is from about 50 to 100 sccm

11. The method of claim 1 wherein said substrate is treated with a SCF comprised of CO₂ and H₂O₂ wherein the CO₂ flow rate is from about 1000 to 15000 standard cubic centimeters per minute (sccm) and the H₂O₂ flow rate is between 0 and about 1000 sccm.

12. The method of claim 1 wherein said SCF is further comprised of a second co-solvent that is selected from the aforementioned co-solvents CF₃—

X, Y—

F, and H₂O₂ and wherein the second co-solvent is different than the first co-solvent.

13. The method of claim 12 wherein the SCF is comprised of CO₂, CF₃—

X and Y—

F wherein the CO₂ flow rate is from about 1000 to 15000 sccm, the CF₃—

X flow rate is between about 50 and 1000 sccm and the Y—

F flow rate is from about 50 to 100 sccm.

14. The method of claim 12 wherein the SCF is comprised of CO₂, H₂O₂, and Y—

F wherein the CO₂ flow rate is from about 1000 to 15000 sccm, the H₂O₂ flow rate is between about 50 and 1000 sccm and the Y—

F flow rate is from about 50 to 100 sccm.

15. A damascene process comprising the steps of:

(a) providing a substrate upon with an etch stop layer formed thereon;

(b) coating a spin-on low k dielectric layer on said etch stop layer;

(c) curing and modifying said low k dielectric layer by treating with a supercritical fluid comprised of CO₂ and a co-solvent which is H₂O₂, CF₃—

X, or Y—

F wherein X═

NR₁R₂, —

OR₃, —

O₂CR₃, —

(C═

O)R₃, or R₃ and wherein Y═

H or an alkyl group and R₁, R₂, R₃═

H or an alkyl group;

(d) forming an opening in the stack comprised of said low k dielectric layer and said etch stop layer;

(e) depositing a barrier metal liner in said opening;

(f) depositing a metal on said barrier metal liner to fill said opening; and

(g) planarizing said metal so that it is coplanar with said low k dielectric layer.

16. The method of claim 15 further comprised of forming a cap layer which is silicon nitride or silicon oxynitride on said cured low k dielectric layer prior to forming said opening.

17. The method of claim 16 wherein said etch stop layer is comprised of silicon nitride, silicon oxynitride or silicon carbide.

18. The method of claim 15 wherein said low k dielectric layer is comprised of a material selected from a group including inorganic silsesquioxanes, organic silsesquioxanes, polyarylethers, bisbenzocyclobutenes, and SiLK from Dow Corning.

19. The method of claim 15 wherein said low k dielectric layer is cured in a process chamber in a single wafer mode.

20. The method of claim 15 wherein said low k dielectric layer is cured in a supercritical CO₂ system in a continuous flow process.

21. The method of claim 15 wherein said low k dielectric layer has a pore volume between about 20% and 40% of the total solid volume of said layer.

22. The method of claim 15 wherein said low k dielectric layer has a thickness in a range of about 1000 to 9000 Angstroms.

23. The method of claim 15 wherein said substrate is treated with a supercritical fluid at a temperature between about 30°

C. and 150°

C.

24. The method of claim 15 wherein said substrate is treated with a supercritical fluid at a pressure between about 70 atmospheres and 700 atmospheres.

25. The method of claim 15 wherein said substrate is treated with a SCF comprised of CO₂ and CF₃—

X wherein the CO₂ flow rate is from about 1000 to 15000 sccm and the CF₃—

X flow rate is from about 50 to 100 sccm.

26. The method of claim 15 wherein said substrate is treated with a SCF comprised of CO₂ and Y—

F wherein the CO₂ flow rate is from about 1000 to 15000 sccm and the Y—

F flow rate is from about 50 to 100 sccm

27. The method of claim 15 wherein said substrate is treated with a SCF comprised of CO₂ and H₂O₂ wherein the CO₂ flow rate is from about 1000 to 15000 standard cubic centimeters per minute (sccm) and the H₂O₂ flow rate is between 0 and about 1000 sccm.

28. The method of claim 15 wherein said SCF is further comprised of a second co-solvent that is selected from the aforementioned co-solvents CF₃—

X, Y—

F, and H₂O₂ and wherein the second co-solvent is different than the first co-solvent.

29. The method of claim 28 wherein the SCF is comprised of CO₂, CF₃—

X and Y—

F wherein the CO₂ flow rate is from about 1000 to 15000 sccm, the CF₃—

X flow rate is between about 50 and 1000 sccm and the Y—

F flow rate is from about 50 to 100 sccm.

30. The method of claim 28 wherein the SCF is comprised of CO₂, H₂O₂, and Y—

F wherein the CO₂ flow rate is from about 1000 to 15000 sccm, the H₂O₂ flow rate is between about 50 and 1000 sccm and the Y—

F flow rate is from about 50 to 100 sccm.

31. The method of claim 15 wherein said opening is a via hole or a trench or a trench formed above a via hole.

32. The method of claim 15 wherein said barrier metal layer is comprised of Ta, TaN, W, WN, Ti, TiN, or TaSiN.

33. The method of claim 15 wherein said metal layer is comprised of copper, aluminum, or a Cu/Al alloy.

34. An apparatus for curing and modifying a low k dielectric material on a substrate, comprising a continuous loop SCF system that can withstand pressures from about 70 to 700 atmospheres and temperatures of about 30°

C. to 150°

C., comprising;

(a) a process chamber capable of holding a 300 mm wafer in place during a supercritical fluid (SCF) treatment;

(b) a port with a connection to an end point detection system;

(c) a separator for removing co-solvents, solids, monomers, O₂, and N₂ from the SCF;

(d) a hydrocarbon knock out chamber;

(e) a chiller;

(f) a working CO₂ tank;

(g) a make up tank for CO₂ and a source tank for a first co-solvent and a second source tank for a second co-solvent;

(h) a preheater for heating the SCF in the loop before entering the process chamber;

(i) a CO₂ pump and pumps for introducing co-solvents into the continuous loop system;

(j) tubing and valves for directing, regulating, and containing the SCF flow within the continuous loop; and

(k) a supercritical fluid comprised of CO₂ and one or more co-solvents selected from a group including H₂O₂, CF₃—

X, or Y—

F wherein X═

NR₁R₂, —

OR₃, —

O₂CR₃, —

(C═

O)R₃, or R₃ and wherein Y═

H or an alkyl group and R₁, R₂, R₃═

H or an alkyl group.

35. The apparatus of claim 34 wherein the CO₂ make-up tank is connected to the continuous loop system between the chiller and the CO₂ working tank.

36. The apparatus of claim 34 wherein the inlet valves for the co-solvents are connected to a point on the continuous loop system between the CO₂ pump and the preheater.

37. The apparatus of claim 34 wherein the continuous loop from the CO₂ pump passes through a preheater or a by-pass loop around said preheater just prior to entering the process chamber.

38. The apparatus of claim 34 wherein the port for the end point detect measurement device is located in the continuous loop immediately downstream from the process chamber.

39. The apparatus of claim 34 wherein the continuous loop between the process chamber and the CO₂ pump successively passes through a separator, a hydrocarbon knock out chamber, a chiller, and a working CO₂ tank.

40. The apparatus of claim 34 wherein the process chamber may be isolated and the continuous flow stopped to allow pressure to be reduced to 1 atmosphere and to allow temperature to be lowered to room temperature within said chamber so that a finished substrate may be removed and replaced with an untreated substrate.

41. The apparatus of claim 34 which is capable of maintaining a SCF flow rate of 1 to 15 liters per minute.