Abstract:
A method of adhering a silicate layer to dielectric layer comprising the following steps. A structure having an overlying dielectric layer formed thereover is provided. An adhesion promoter layer is formed upon the dielectric layer. The adhesion promoter layer including adhesion promotion molecules. The dielectric layer and the adhesion promoter layer are treated to a low-temperature treatment to bind at least some of the adhesion promotion molecules to the dielectric layer. A silicate layer is formed upon the low-temperature treated adhesion promoter layer. The silicate layer and the low-temperature treated adhesion promoter layer are treated to a high-temperature treatment to bind at least some of the adhesion promotion molecules to the silicate layer whereby the silicate layer is adhered to the dielectric layer.

Description:
BACKGROUND OF THE INVENTION 
     Adhesion between chemical vapor deposition (CVD) barrier dielectric layers, or via etch-stop layers, and silicate (SiO based materials) low-k films, or solution-gelation (SOL-GEL) processed films, is a major concern in microelectronics integration. Weak adhesion at this interface results in film delamination during subsequent processing. In current practice, such adhesion is very low, on the order of less than about 0.12 GPa/M (giga parcel/square root meter), which results in severe peeling. 
     U.S. Pat. No. 6,303,524 B1 to Sharangpani et al. describes low-k curing methods that affect adhesion. 
     U.S. Pat. No. 6,303,523 B2 to Cheung et al. describes a low-k film deposition process to improve adhesion. 
     U.S. Pat. No. 6,180,518 B1 to Layadi et al. describes a method of forming vias in a low-k dielectric material and discusses low-k layer adhesion problems. 
     U.S. Pat. No. 4,238,528 to Angelo et al. describes adhesion promoters for polyamides. 
     U.S. Pat. No. 5,965,202 to Taylor-Smith et al. describes coupling agents between low-k layers. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of one or more embodiments of the present invention to provide enhanced adhesion between dielectric films and silicate films. 
     It is another object of one or more embodiments of the present invention to provide enhanced adhesion between CVD dielectric films and spin-on low-k silicate films. 
     Other objects will appear hereinafter. 
     It has now been discovered that the above and other objects of the present invention may be accomplished in the following manner. Specifically, a structure having an overlying dielectric layer formed thereover is provided. An adhesion promoter layer is formed upon the dielectric layer. The adhesion promoter layer including adhesion promotion molecules. The dielectric layer and the adhesion promoter layer are treated to a low-temperature treatment to bind at least some of the adhesion promotion molecules to the dielectric layer. A silicate layer is formed upon the low-temperature treated adhesion promoter layer. The silicate layer and the low-temperature treated adhesion promoter layer are treated to a high-temperature treatment to bind at least some of the adhesion promotion molecules to the silicate layer whereby the silicate layer is adhered to the dielectric layer. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be more clearly understood from the following description taken in conjunction with the accompanying drawings in which like reference numerals designate similar or corresponding elements, regions and portions and in which: 
     FIGS. 1 to  4  schematically illustrates a preferred embodiment of the present invention. 
     FIGS. 5 to  7  illustrate the first series of adhesion promotion molecules. 
     FIGS. 8A,  8 B,  9 A and  9 B illustrate the second series of adhesion promotion molecules. 
     FIGS. 10 and 11 illustrate the third series of adhesion promotion molecules. 
     FIGS. 12A,  12 B and  12 C illustrate the mechanism believed to enhance adhesion between the CVD dielectric layer and the spin-on low-k layer using a sample first series of adhesion promotion molecules. 
     FIGS. 13A,  13 B and  13 C illustrate the mechanism believed to enhance adhesion between the CVD dielectric layer and the spin-on low-k layer using a sample second series of adhesion promotion molecules. 
     FIGS. 14A,  14 B and  14 C illustrate the mechanism believed to enhance adhesion between the CVD dielectric layer and the spin-on low-k layer using a sample third series of adhesion promotion molecules. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Initial Structure 
     As shown in FIG. 1, structure  10  has an overlying layer  12  formed thereover. Layer  12  may function as, for example a barrier layer or a via etch-stop layer. 
     Structure  10  is preferably understood to possibly include a semiconductor wafer or substrate, active and passive devices formed within the wafer, conductive layers and dielectric layers (e.g., inter-poly oxide (IPO), intermetal dielectric (IMD), etc.) formed over the wafer surface. The term “semiconductor structure” is meant to include devices formed within a semiconductor wafer and the layers overlying the wafer. Structure  10  may be a silicon wafer or a silicon substrate. 
     Layer  12  may be a chemical vapor deposition (CVD) dielectric layer or a spin-on dielectric layer and is preferably comprised of silicon dioxide (SiO 2 ), silicon carbide (SiC), silicon oxynitride (SiON), carbon-doped silicon oxide (SiOC), silicon nitride (SiN) or silicon carbo-oxynitride (SiCNO). Layer  12  may also be a metal layer preferably such as copper (Cu), aluminum (Al), gold (Au) or silver (Ag). 
     It is noted that if layer  12  is a CVD dielectric layer, then layer  18  is a spin-on dielectric layer and if layer  12  is a spin-on dielectric layer, then layer  18  is a CVD dielectric layer. 
     Layer  12  has a thickness of preferably from about 300 to 5000 Å and more preferably from about 300 to 600 Å. 
     In one key step of the invention, an adhesion promoter layer  14  is then coated upon layer  12  to improve the adhesion between layer  12  and Adhesion promoter layer  14  has a thickness of preferably from about 20 to 300 Å and more preferably from about 50 to 150 Å. 
     Adhesion promoter layer  14  is comprised of adhesion promotion molecules selected from one of three series of adhesion promotion molecules such as (1) a first series: dihydroxyl-terminated molecules; (2) a second series: hydroxyl-/alkoxysilyl-terminated molecules; or (3) a third series: hydroxylvinyl or hydroxylacryl-terminated molecules. That is, for example: 
     1. first series of adhesion promotion molecules as shown in FIGS. 5 to  7 , i.e.: 
     a) dihydroxyl terminated molecules as shown in FIG. 5; 
     b) alkoxysilyl hydroxyl terminated molecules as shown in FIG. 6; or 
     c) alkoxysilyl terminated molecules as shown in FIG. 7; 
     where R is —CH 2 —, —CH 2 —CH 2 —, —CH 2 —CH 2 —CH 2 —, etc.; and where R may further include an ether [—CH 2 —O—CH 2 —] or ester                           
     linkage; 
     2. second series of adhesion promotion molecules as shown in FIGS. 8A,  8 B,  9 A and  9 B, i.e.: 
     a) alkoxysilyl vinyl terminated molecules as shown in FIG. 8A; 
     b) hydroxyl vinyl terminated molecules as shown in FIG. 8B; 
     c) alkoxysilyl acryl terminated molecules as shown in FIG. 9A; or 
     d) hydroxyl acryl terminated molecules as shown in FIG. 9B; 
     where R is —CH 2 —, —CH 2 —CH 2 —, —CH 2 —CH 2 —CH 2 —, etc.; and where R further include an ether [—CH 2 —O—CH 2 —]or ester                           
     linkage; or 
     3. third series of adhesion promotion molecules as shown in FIGS. 10 and 11, i.e.: 
     a) (RO) x Si(OR′) 4-x  as shown in FIG. 10; or 
     b) (RO) x Si(OR′) 3-H  as shown in FIG. 11 
     where R is methyl (—CH 3 ), ethyl (—CH 2 CH 3 ), propyl (—CH 2 CH 2 CH 3 ), etc. and 
     where R′is —CH 2 —, —CH 2 —CH 2 —, —CH 2 —CH 2 —CH 2 —, etc.; and where R may further include an ether or ester                           
     linkage. 
     Of the three series of molecules, the first series (as a group) is more preferred. Of the molecules, the alkoxysilyl hydroxyl terminated molecules as shown in FIG. 6, the alkoxysilyl terminated molecules as shown in FIG. 7, the alkoxysilyl vinyl terminated molecules as shown in FIG.  8 A and the alkoxysilyl acryl terminated molecules as shown in FIG. 9A are more preferred with the alkoxysilyl terminated molecules as shown in FIG. 7 being most preferred. 
     Low-Temperature Treatment  16   
     As shown in FIG. 2, the structure of FIG. 1 is subjected to a low-temperature treatment  16  to bind the adhesion promotion molecules of adhesion promoter layer  14  to layer  12 , forming low-temperature treated adhesion promoter layer  14 ′. 
     The low temperature treatment  16  is conducted under the following conditions for: 
     I. the first series of adhesion promotion molecules as shown in FIGS. 5 to  7 : 
     temperature: preferably from about 150 to 250° C. and more preferably from about 180 to 230° C.; and 
     time: preferably from about 3 to 10 minutes and more preferably from about 5 to 8 minutes; and 
     II. the second series of adhesion promotion molecules as shown in FIGS. 8A,  8 B,  9 A and  9 B, and the third series of adhesion promotion molecules as shown in FIGS.  10  and  11 : 
     temperature: preferably from about 150 to 250° C. and more preferably from about 180 to 230° C.; and 
     time: preferably from about 3 to 30 minutes and more preferably from about 10 to 20 minutes. 
     Formation of Spin-on Low-k Silicate Layer  18   
     As shown in FIG. 3, a layer  18  is formed over low-temperature treated adhesion promoter layer  14 ′ to a thickness of preferably from about 500 to 8000 Å and more preferably from about 3000 to 6000 Å. As noted above, if layer  12  is a CVD dielectric layer, then layer  18  is a spin-on dielectric layer and if layer  12  is a spin-on dielectric layer, then layer  18  is a CVD dielectric layer. 
     Preferably, layer  12  is a CVD dielectric layer and layer  18  is a spin-on low-k silicate/SiO based material as will be used for illustrative purposes hereafter. 
     Spin-on low-k silicate layer  18  is comprised of silicon (Si), oxygen (O) and carbon (C) atoms (also see the description of layer  12 ). 
     High-Temperature Treatment  20   
     As shown in FIG. 4, the structure of FIG. 3 is subjected to a high-temperature treatment  20  to bind the spin-on low-k silicate layer  18  to CVD dielectric layer  12  via the high-temperature treated adhesion promoter layer  14 ″. 
     The high temperature treatment  20  is conducted under the following conditions for the first, second and third series of adhesion promotion molecules: 
     temperature: preferably from about 300 to 450° C. and more preferably from about 350 to 420° C.; and 
     time: preferably from about 1 to 6 hours and more preferably from about 2 to 4 hours. 
     The high-temperature treatment  20  cures the double bonds of the second series of adhesion promotion molecules being either vinyl or acryl terminated molecules. Please see FIGS. 13A,  13 B and  13 C. 
     The adhesion between the CVD dielectric layer  12  and the spin-on low-k silicate layer  18  using the adhesion promoter layer  14  in accordance with the method of the present invention is improved to preferably greater than about 0.30 GPa/M (giga parcel/square root meter) and more preferably greater than about 0.5 GPa/M so that subsequent chemical mechanical polishing processes do not delaminate the spin-on low-k silicate layer  18  from the CVD dielectric layer  12 . 
     Proposed Mechanisms of Adhesion Enhancement 
     FIGS. 12A,  12 B and  12 C illustrate the mechanism believed by the inventors to enhance adhesion between the CVD dielectric layer and the spin-on low-k layer using a sample first series of adhesion promotion molecules; FIGS. 13A,  13 B and  13 C illustrate the mechanism believed to enhance adhesion between the CVD dielectric layer and the spin-on low-k layer using a sample second series of adhesion promotion molecules and FIGS. 14A,  14 B and  14 C illustrate the mechanism believed to enhance adhesion between the CVD dielectric layer and the spin-on low-k layer using a sample third series of adhesion promotion molecules. 
     Each series of FIGS. 12A,  13 A and  14 A illustrate the upper surface of CVD dielectric layer  12  (with exposed —OH molecules) after being coated with adhesion promoter layer  14  comprising sample adhesion promotion molecules from the first, second and third series of adhesion promotion molecules, respectively. 
     Each series of FIGS. 12B,  13 B and  14 B illustrate (1) the upper surface of CVD dielectric layer  12  after the low-temperature treatment  16  so that the upper surface of CVD dielectric layer  12  is bound to the sample adhesion promotion molecules from the first, second and third series of adhesion promotion molecules of the low-temperature treated adhesion promoter layer  14 ′, respectively, and (2) the spin-on low-k silicate layer  18  is formed over the low-temperature treated adhesion promoter layer  14 ′. 
     Each series of FIGS. 12C,  13 C and  14 C illustrate (1) the lower surface of spin-on low-k silicate layer  18  after the high-temperature treatment  20  so that the lower surface of spin-on low-k silicate layer  18  is bound to the sample adhesion promotion molecules from the first, second and third series of adhesion promotion molecules of the high-temperature treated adhesion promoter layer  14 ″, respectively, and (2) the upper surface of CVD dielectric layer  12  bound to the sample adhesion promotion molecules from the first, second and third series of adhesion promotion molecules of the high-temperature treated adhesion promoter layer  14 ″, respectively. 
     It is noted that FIG. 13C also demonstrates double bond cross-linking that also may occur. 
     Advantages of the Present Invention 
     The advantages of one or more embodiments of the present invention include greatly improving the adhesion between CVD dielectric layers and spin-on silicate layers. 
     While particular embodiments of the present invention have been illustrated and described, it is not intended to limit the invention, except as defined by the following claims.