Method for porogen removal and mechanical strength enhancement of low-k carbon doped silicon oxide using low thermal budget microwave curing

• US 7,892,985 B1
• Filed: 11/15/2005
• Issued: 02/22/2011
• Est. Priority Date: 11/15/2005
• Status: Active Grant

• Current Assignee: Novellus Systems Incorporated (LAM Research Corporation)
• Original Assignee: Novellus Systems Incorporated (LAM Research Corporation)
• Inventors: Papasouliotis, George D., Cho, Seon-Mee, Barnes, Mike
• Primary Examiner(s): Wilczewski; Mary
• Assistant Examiner(s): Thomas; Toniae M
• Application Number:
  US11/280,113
• Time in Patent Office: 1,925 Days
• Field of Search: 438/623, 438/781, 427/553, 427/255.6, 257/E21.242, 257/E21.576
• US Class Current: 438/781
• CPC Class Codes: H01L 21/02126 the material containing Si, O, and at least one of H, N, C, F, or other non-metal elements, e.g. SiOC, SiOC:H or SiONC
• CPC Class Codes: H01L 21/02203 the layer being porous
• CPC Class Codes: H01L 21/02274 in the presence of a plasma [PECVD]
• CPC Class Codes: H01L 21/02337 treatment by exposure to a gas or vapour
• CPC Class Codes: H01L 21/02345 treatment by exposure to radiation, e.g. visible light
• CPC Class Codes: H01L 21/76825 by exposing the layer to particle radiation, e.g. ion implantation, irradiation with UV light or electrons etc. plasma treatment H01L21/76826
• CPC Class Codes: H01L 2221/1047 the air gaps being formed by pores in the dielectric

Abstract

Improved methods for preparing a low-k dielectric material on a substrate using microwave radiation are provided. The use of microwave radiation allows the preparation of low-k films to be accomplished at low temperatures. According to various embodiments, microwave radiation is used to remove porogen from a precursor film and/or to increase the strength of the resulting porous dielectric layer. In a preferred embodiment, methods involve (a) forming a precursor film that contains a porogen and a structure former on a substrate, (b) exposing the precursor film to microwave radiation to remove the porogen from the precursor film to thereby create voids within the dielectric material and form the porous low-k dielectric layer and (c) exposing the dielectric material to microwave radiation in a manner that increases the mechanical strength of the porous low-k dielectric layer.

Claims

1. A method of preparing a porous low-k dielectric layer on a substrate, the method comprising:

(a) providing a precursor film on the substrate, the precursor film comprising a dielectric material and a porogen;

(b) exposing the precursor film to microwave radiation to remove the porogen to thereby create voids within the dielectric material and form the porous low-k dielectric layer; and

(c) exposing the dielectric material to microwave radiation in a manner that increases the mechanical strength of the porous low-k dielectric layer, wherein at least part of (b) and (c) occur simultaneously.

2. The method of claim 1 wherein (a) comprises forming a precursor film on the substrate, the precursor film comprising the porogen and a structure former.

3. The method of claim 1 wherein the substrate temperature is below about 400°

C. during microwave exposure.

4. The method of claim 1 wherein the substrate temperature is below about 300°

C. during microwave exposure.

5. The method of claim 1 wherein the substrate temperature is below about 100°

C. during microwave exposure.

6. The method of claim 1 wherein the microwave power ranges between about 100 W and 7 kW.

7. The method of claim 6 wherein the microwave power ranges between about 1 kW-3 kW.

8. The method of claim 1 wherein the microwave frequency is between about 1 and 4 GHz.

9. The method of claim 8 wherein the microwave frequency is about 2.45 GHz.

10. The method of claim 1, wherein the substrate is a semiconductor wafer.

11. The method of claim 1, wherein the precursor film comprises a porogen and a silicon-containing structure former.

12. The method of claim 11 wherein the precursor film is formed by co-depositing the porogen with the structure former.

13. The method of claim 11, wherein the structure former is produced from at least one of a silane, an alkylsilane, an alkoxysilane, siloxane, carbon-doped variation thereof, or combination thereof.

14. The method of claim 13, wherein the structure former is produced from diethoxymethylsilane (DEMS), octamethylcyclotetrasiloxane (OMCTS), tetramethylcyclotetrasiloxane (TMCTS), dimethyldimethoxysilane (DMDMOS), carbon-doped oxides or a combination thereof.

15. The method of claim 1, wherein the porogen comprises a polyfunctional cyclic non-aromatic compound.

16. The method of claim 15, wherein the polyfunctional cyclic non-aromatic compound is a limonene compound.

17. The method of claim 1, wherein (b) comprises exposing the precursor film to pulses of microwave radiation.

18. The method of claim 1, wherein (b) is performed under an ambient comprising at least one of argon, nitrogen, helium, hydrogen and a combination thereof.

19. The method of claim 1, wherein the porous low-k dielectric layer has a k-value of about 2.5 or lower.