Method for Increasing Adhesion of Copper to Polymeric Surfaces

Abstract

Disclosed herein are methods and systems for conditioning a polymeric layer on a substrate to enable adhesion of a metal layer to the polymeric layer. Techniques may include conditioning the polymeric layer with nitrogen-containing plasma to generate a nitride layer on the surface of the polymeric layer. In another embodiment, the conditioning may include depositing a CuN layer using a lower power copper sputtering process in a nitrogen rich environment. Following the condition process, a higher power copper deposition or sputtering process may be used to deposit copper onto the polymeric layer with good adhesion properties.

What is claimed: 
     
         1 . A method for adhering metal to a polymeric material, comprising:
 exposing a substrate to a nitrogen-containing environment to increase adhesion of first and second metal-containing layers to the substrate, the substrate comprising a tray of semiconductor devices that are at least partially covered with polymeric material;   depositing, at a first power level, the first metal-containing layer onto the polymeric material surface present on the substrate; and   depositing, at a second power level, the second metal-containing layer onto the first metal-containing layer,   wherein the second power level is different from the first power level.   
     
     
         2 . The method of  claim 1 , wherein the depositing and exposing are performed concurrently. 
     
     
         3 . The method of  claim 1 , wherein the exposing is performed prior to the depositing the first and second metal-containing layers. 
     
     
         4 . The method of  claim 1 , wherein the first metal-containing layer comprises CuNx proximate to the polymeric surface that transitions to substantially Cu as the second metal-containing layer is deposited to achieve a target layer thickness. 
     
     
         5 . The method of  claim 1 , wherein the first metal-containing layer comprises CuNx, and wherein the nitrogen content of the second metal-containing layer decreases with distance from the polymeric surface. 
     
     
         6 . The method of  claim 1 , wherein the substrate comprises an encapsulated electronic device that can be coupled to a printed circuit board or another electronic device. 
     
     
         7 . The method of  claim 1 , wherein the depositing the first and second metal-containing layers includes performing a physical vapor deposition (PVD) process. 
     
     
         8 . The method of  claim 1 , wherein the exposing includes exposing the polymeric surface to a nitrogen-containing plasma. 
     
     
         9 . The method of  claim 1 , wherein the exposing includes exposing the polymeric surface to a nitrogen or nitrogen-containing ion beam. 
     
     
         10 . A method for depositing a metal layer on a packaged electronic device, the method comprising:
 receiving the packaged electronic device comprising an exposed polymeric surface;   applying a nitrogen-containing plasma to the exposed polymeric surface;   depositing, at a first power level, a first metal-containing layer on the exposed polymeric surface after having been activated using the nitrogen-containing plasma; and   depositing, at a second power level, a second metal-containing layer onto the first metal-containing layer,   wherein the second power level is different from the first power level.   
     
     
         11 . A method for depositing a metal layer on a packaged electronic device, comprising:
 receiving a packaged electronic device comprising an exposed polymeric material;   activating the exposed polymeric material by treating the exposed polymeric material with a nitrogen-containing plasma;   depositing, at a first power level, a first metal layer on exposed polymeric material via a physical vapor deposition process, the first metal layer providing electromagnetic shielding for the packaged electronic device; and   depositing, at a second power level, a second metal layer onto the first metal layer,   wherein the second power level is different from the first power level.   
     
     
         12 . The method of  claim 11 , wherein activating the exposed polymeric material occurs in a first processing chamber, and wherein depositing the first and second metal layers occurs in a second processing chamber. 
     
     
         13 . The method of  claim 12  wherein the first processing chamber comprises an etching chamber that includes an electrode or an antenna, and wherein the second processing chamber comprises a physical vapor deposition chamber that includes a magnetron. 
     
     
         14 . The method of  claim 11 , wherein treating the exposed polymeric material with the nitrogen plasma includes isotropically bombarding the exposed polymeric material with the nitrogen plasma comprising nitrogen-containing species, including but not limited to, atomic nitrogen (N), diatomic nitrogen (N 2 ), atomic nitrogen ions (N + ), diatomic nitrogen ions (N 2   + ), or metastable nitrogen (N*, N 2 *). 
     
     
         15 . The method of  claim 11 , wherein treating the exposed polymeric material with nitrogen plasma includes anisotropically bombarding the exposed polymeric material with the nitrogen plasma comprising nitrogen-containing species, including but not limited to, atomic nitrogen (N), diatomic nitrogen (N 2 ), atomic nitrogen ions (N + ), diatomic nitrogen ions (N 2   + ), or metastable nitrogen (N*, N 2 *). 
     
     
         16 . The method of  claim 11 , wherein the depositing the first metal layer comprises performing a physical vapor deposition (PVD) process that includes:
 introducing a first process gas containing a noble gas and nitrogen-containing gas; and   sputtering metal from a metal target operated at a power condition that includes a sputtering power per unit area equal to or greater than 1 W per cm2.   
     
     
         17 . The method of  claim 11 , wherein activating the exposed polymeric material further comprises mixing argon with the nitrogen plasma, the mixture comprising at least 25% argon. 
     
     
         18 . The method of  claim 11 , wherein the encapsulated semiconductor devices comprise metal contacts that can be coupled to circuitry that is external to the packaged electronic device. 
     
     
         19 . The method of  claim 11 , wherein the polymeric material comprises an epoxy resin or a silicone impregnated epoxy. 
     
     
         20 . The method of  claim 11 , wherein the packaged electronic device comprises electrical leads or ball contacts.