System and method of selectively cleaning copper substrate surfaces, in-situ, to remove copper oxides

• US 5,939,334 A
• Filed: 05/22/1997
• Issued: 08/17/1999
• Est. Priority Date: 05/22/1997
• Status: Expired due to Term

• Current Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.), Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Nguyen, Tue, Hsu, Sheng Teng, Evans, David R., Charneski, Lawrence J.
• Primary Examiner(s): Bowers, Charles
• Assistant Examiner(s): NGUYEN, THANH T
• Application Number:
  US08/861,808
• Time in Patent Office: 817 Days
• Field of Search: 438/907, 438/629, 438/637-640, 438/668, 438/672, 438/675, 438/677, 438/689, 438/706, 438/709-711, 148/DIG. 17, 148/DIG. 20
• US Class Current: 438/689
• CPC Class Codes: C23G 5/00 Cleaning or de-greasing metallic material by other methods; Apparatus for cleaning or de-greasing metallic material with organic solvents
• CPC Class Codes: H01L 21/02063 the processing being the formation of vias or contact holes
• CPC Class Codes: H01L 21/02068 during, before or after processing of conductive layers, e.g. polysilicon or amorphous silicon layers
• CPC Class Codes: H01L 21/31111 by chemical means
• CPC Class Codes: H01L 21/31138 by dry-etching
• CPC Class Codes: H01L 21/32134 by liquid etching only
• CPC Class Codes: H01L 21/76838 characterised by the formation and the after-treatment of the conductors etching for patterning the conductors H01L21/3213

Abstract

A system and method of selectively etching copper surfaces free of copper oxides in preparation for the deposition of an interconnecting metallic material is provided. The method removes metal oxides with β-diketones, such as Hhfac. The Hhfac is delivered into the system in vapor form, and reacts almost exclusively to copper oxides. The by-products of the cleaning process are likewise volatile for removal from the system with a vacuum pressure. Since the process is easily adaptable to most IC process systems, it can be conducted in an oxygen-free environment, without the removal of the IC from the process chamber. The in-situ cleaning process permits a minimum amount of copper oxide to reform before the deposition of the overlying interconnection metal. In this manner, a highly conductive electrical interconnection between the copper surface and the interconnecting metal material is formed. An IC having a metal interconnection, in which the underlying copper layer is cleaned of copper oxides, in-situ with Hhfac vapor, is also provided.

Claims

1. In an integrated circuit (IC) having a dielectric interlevel with a dielectric surface, and a plurality of metal levels underlying the dielectric interlevel, a method for selectively cleaning metal oxides, in-situ, from a surface on a first metal level, accessed through a via from the dielectric surface, the method comprising the steps of:

a) providing an atmosphere surrounding the integrated circuit;

b) controlling the atmosphere to be substantially free of oxygen, whereby the formation of metal oxides on the first metal level surface is minimized;

c) introducing a β

-diketone vapor into the atmosphere; and

d) volatilizing the metal oxides from the first metal level surface using the β

-diketone vapor introduced in step c), whereby a minimal amount of material is removed from the first metal level surface in preparation for an electrical connection with subsequently deposited metal levels.

2. A method as in claim 1 wherein the first metal level is a metal selected from the group consisting of copper and silver.

3. A method as in claim 1 in which step c) includes using a β

-diketone having the following structural formula;

##STR1## in which the R and R¹ groups are selected from the set of groups consisting of C1 to C6 alkyls, perfluoroalkyls, and other substitutions, and the X group is selected from the functional groups consisting of H, F, CL, Br, I, alkyls, perfluoroalkyls, and substitutions.

4. A method as in claim 3 in which step c) includes using hexafluoroacetylacetonate (Hifac) as the β

-diketone to volatilize the metal oxides on the first metal level surface.

5. A method as in claim 4 in which step c) includes delivering the Hhfac at a pressure of less than approximately 85 Torr and a temperature of approximately 20°

C.

6. A method as in claim 1 including the further step, following step d), of:

e) creating a vacuum to remove the volatile metal oxides obtained in step d) from the atmosphere, whereby the cleaning by-products are easily removed from the area of the IC.

7. A method as in claim 1 including the further step, before step c), of:

f) controlling the IC temperature to be in the range between 100 and 450°

C.

8. A method as in claim 1 including the further step, following step d), of:

g) while maintaining the atmosphere established in step b), depositing a second metal level overlying the first metal level surface to electrically interface to the first metal level, whereby the cleaning process facilitates a low resistance electrical connection.

9. A method as in claim 8 in which step g) includes depositing a second metal level selected from the group consisting of TiN, TiSi_x N_y, TaSi_x N_y, TaN, WN, WSi_x N_y, Ti, Ta, W, Cu, Al, Ag, and Au.