Method for promoting adhesion between dielectric substrates and metal layers

Abstract

The present invention relates to novel processes for metallization of dielectric substrate surfaces applying organosilane compositions followed by oxidative treatment. The method results in metal plated surfaces exhibiting high adhesion between the substrate and the plated metal while at the same time leaves the smooth substrate surface intact.

1 . A method for treating a surface of a dielectric substrate to prepare said surface for subsequent wet chemical metal plating, such method comprising in this order the steps of
 (i) treating said surface with a solution comprising at least one organosilane compound;   (ii) treating said surface with a solution comprising an oxidizing agent selected from aqueous acidic or alkaline solutions of a permanganate salt.   
     
     
         2 . Method according to  claim 1  wherein the concentration of permanganate salt ranges from 20-100 g/l. 
     
     
         3 . Method according to  claim 1  wherein the organosilane compound is selected from the group represented by the formula
   A (4-x) SiB x    
 wherein 
 each A is independently a hydrolyzable group, 
 x is 1 to 3, and 
 each B is independently selected from the group consisting of C 1 -C 20  alkyl, aryl, amino aryl and a functional group represented by the formula
   C n H 2n X, 
 
 wherein 
 n is from 0 to 15, preferably 0 to 10 even more preferably 1 to 8, most preferably 1, 2, 3, 4 and 
 X is selected from the group consisting of amino, amido, hydroxy, alkoxy, halo, mercapto, carboxy, carboxy ester, carboxamide, thiocarboxamide, acyl, vinyl, allyl, styryl, epoxy, epoxycyclohexyl, glycidoxy, isocyanato, thiocyanato, thioisocyanato, ureido, thioureido, guanidino, thioglycidoxy, acryloxy, methacryloxy groups; or X is a residue of a carboxy ester; or X is Si(OR) 3 , and wherein R is a C 1 -C 5  alkyl group. 
 
     
     
         4 . Method according to  claim 3  wherein the hydrolyzable group A is selected from the group consisting of —OH, —OR 1  and wherein R 1  is C 1 -C 5  alkyl, —(CH 2 ) y OR 2  and wherein y is 1, 2 or 3 and R 2  is H or C 1 -C 5  alkyl, —OCOR 3  and and wherein R 3  is H or C 1 -C 5  alkyl. 
     
     
         5 . Method according to  claim 4 , wherein R 1 , R 2  and R 3  are independently selected from methyl, ethyl, propyl and isopropyl. 
     
     
         6 . Method according to  claim 1  wherein the organosilane compound is selected from the group consisting of vinylsilanes, aminoalkylsilanes, ureidoalkylsilanes, methacryloxy silanes and epoxyalkylsilanes. 
     
     
         7 . Method according to  claim 1  wherein the organosilane is applied in a concentration of between 0.5 wt. % and 20 wt. %. 
     
     
         8 . Method according to  claim 1  wherein the organosilane is dissolved in a polar organic solvent organic solvent having boiling point in the range of 60 to 250° C. 
     
     
         9 . Method according to  claim 1  wherein the organosilane is dissolved in a polar organic solvent selected from diethyleneglycol, 2-isopropoxyethanol (IPPE), di(propyleneglycol)methyletheracetate (DPGMEA), and 2-ethyl-1-hexanol. 
     
     
         10 . Method according to  claim 1  wherein the oxidizing agent according to step 1 ii) is an alkaline aqueous solution of permanganate ions. 
     
     
         11 . Method according to  claim 1 , wherein
 (i) treating said surface with a solution comprising at least one organosilane compound is carried out for a period of time of between 10 s and 10 min. at a temperature of between 15 and 50° C., and   (ii) treating said surface with a solution comprising an oxidizing agent selected from an alkaline aqueous solution of permanganate salt is carried out in a concentration of 20-100 g/l for a period of time of between 1 and 30 min. at a temperature of between 20 and 95° C. to obtain a roughened surface having an average surface roughness Ra of less than 150 nm.   
     
     
         12 . Method according to  claim 1  further comprising
 (iii) metallizing the substrate after step (ii) with a wet chemical plating method. 
 
     
     
         13 . Method according to  claim 12  wherein metallizing is a copper metallizing. 
     
     
         14 . Method according to  claim 13  wherein
 (iii) metallizing the substrate after step (ii) with a wet chemical plating method comprises the following steps to render the surface conductive 
 (iii a) contacting the substrate with an activator solution, that contains colloidal or ionic catalysing metal causing the substrate's surface to become catalytic, 
 and optionally, particularly if the activator contains ionic catalysing metal, 
 (iii b) contacting the substrate with a reducer, wherein the metal ions of an ionic activator are reduced to elemental metal, 
 or, if the activator contains colloidal catalysing metal, 
 (iii c) contacting the substrate with an accelerator, wherein the components of the colloid, for example a protective colloid, is removed from the catalysing metal. 
 
     
     
         15 . Method according to  claim 1  wherein the dielectric substrate is a substrate comprising a bare dielectric build-up layer having a back side and a top surface, having on at least a portion of the back side a contact area and a second dielectric layer attached to the back side of the build-up layer, having at least one opening in the build-up layer which extends through the substrate to the contact area,
 (i) treating said surface with a solution comprising at least one organosilane compound as defined in  claim 1 , 
 (ii) treating said surface with a solution comprising an oxidizing agent as defined in  claim 1 , 
 (iii) depositing a conductive seed layer onto the top surface of the dielectric build-up layer and the dielectric side walls of the at least one opening, and 
 selectively depositing a copper layer into openings of a patterned resist layer by electroplating. 
 
     
     
         16 . The method of  claim 14  wherein the ionic catalysing metal is a noble metal. 
     
     
         17 . Method according to  claim 12  wherein
 (iii) metallizing the substrate after step (ii) with a wet chemical plating method comprises the following steps to render the surface conductive 
 (iii a) contacting the substrate with an activator solution, that contains colloidal or ionic catalysing metal causing the the substrate's surface to become catalytic, 
 and optionally, particularly if the activator contains ionic catalysing metal, 
 (iii b) contacting the substrate with a reducer, wherein the metal ions of an ionic activator are reduced to elemental metal, 
 or, if the activator contains colloidal catalysing metal, 
 (iii c) contacting the substrate with an accelerator, wherein the components of the colloid, for example a protective colloid, is removed from the catalysing metal. 
 
     
     
         18 . The method of  claim 17  wherein the ionic catalysing metal is a noble metal.