Electroplating in presence of co2

Abstract

The present invention provides a method for conducting electroplating in the presence of CO 2 and a metal salt-containing aqueous solution, wherein the CO 2 is in the form of liquid, subcritical or supercritical, the method being characterized in that a nonionic compound having a CO 2 -affinitive moiety is further added to the system where the aqueous solution and CO 2 coexist. The method of the present invention improves the efficiency of the electrochemical reaction process and enables formation of an excellent metal film.

1 . A method for conducting electroplating in the presence of CO 2  and a metal salt-containing aqueous solution, the CO 2  being liquid, subcritical or supercritical, the method further comprising a step of adding a nonionic compound having a CO 2 -affinitive moiety to a system wherein the aqueous solution and CO 2  coexist, the CO 2 -affinitive moiety being at least one member selected from the group consisting of: 
 (1) homopolymers, bicopolymers and tricopolymers of polyoxypropylene, polyoxybutylene and/or polyoxyethylene;    (2) fluorine-containing alkyl groups in which some or all of the hydrogen atoms are substituted by fluorine;    (3) fluorine-containing polyether groups in which some or all of the hydrogen atoms are substituted by fluorine; and    (4) dialkylsiloxy groups.    
   
   
       2 . The method according to  claim 1 , wherein the nonionic compound is an ether-based or ester-based compound.  
   
   
       3 . The method according to  claim 1 , wherein the nonionic compound is an alcohol-based compound.  
   
   
       4 . The method according to  claim 1 , wherein the nonionic compound is a fluorinated hydrocarbon.  
   
   
       5 . The method according to  claim 1 , wherein the nonionic compound is a polyalkylsiloxane.  
   
   
       6 . The method according to  claim 1 , wherein the nonionic compound is a fluorine-containing polymer.  
   
   
       7 . A plating bath comprising a metal salt-containing aqueous solution, CO 2 , and a nonionic compound having a CO 2 -affinitive moiety, the CO 2  being liquid, subcritical or supercritical, the CO 2 -affinitive moiety being at least one member selected from the group consisting of: 
 (1) homopolymers, bicopolymers and tricopolymers of polyoxypropylene, polyoxybutylene and/or polyoxyethylene;    (2) fluorine-containing alkyl groups in which some or all of the hydrogen atoms are substituted by fluorine;    (3) fluorine-containing polyether groups in which some or all of the hydrogen atoms are substituted by fluorine; and    (4) dialkylsiloxy groups.    
   
   
       8 . An additive for use in electroplating conducted in the presence of liquid, subcritical or supercritical CO 2 , the additive comprising a nonionic compound having a CO 2 -affinitive moiety, 
 the CO 2 -affinitive moiety being at least one member selected from the group consisting of:    (1) homopolymers, bicopolymers and tricopolymers of polyoxypropylene, polyoxybutylene and/or polyoxyethylene;    (2) fluorine-containing alkyl groups in which some or all of the hydrogen atoms are substituted by fluorine;    (3) fluorine-containing polyether groups in which some or all of the hydrogen atoms are substituted by fluorine; and    (4) dialkylsiloxy groups.    
   
   
       9 . A method for preprocessing conducted before plating comprising the step of degreasing and washing a plating substrate prior to plating using a nonionic compound having a CO 2 -affinitive moiety, 
 the CO 2 -affinitive moiety being at least one member selected from the group consisting of:    (1) homopolymers, bicopolymers and tricopolymers of polyoxypropylene, polyoxybutylene and/or polyoxyethylene;    (2) fluorine-containing alkyl groups in which some or all of the hydrogen atoms are substituted by fluorine;    (3) fluorine-containing polyether groups in which some or all of the hydrogen atoms are substituted by fluorine; and    (4) dialkylsiloxy groups.    
   
   
       10 . A method for postprocessing conducted after plating comprising the step of washing a plated film after plating using a nonionic compound having a CO 2 -affinitive moiety, the CO 2 -affinitive moiety being at least one member selected from the group consisting of: 
 (1) homopolymers, bicopolymers and tricopolymers of polyoxypropylene, polyoxybutylene and/or polyoxyethylene;    (2) fluorine-containing alkyl groups in which some or all of the hydrogen atoms are substituted by fluorine;    (3) fluorine-containing polyether groups in which some or all of the hydrogen atoms are substituted by fluorine; and    (4) dialkylsiloxy groups.    
   
   
       11 . A plated film having 
 (1) per cm 2 , not more than one pinhole having a diameter of at least 1 μm;    (2) a film thickness of not more than 1 μm; and    (3) a plated film surface roughness of not greater than 10 nm.    
   
   
       12 . The method according to  claim 1 , wherein the nonionic compound used is (CO 2 -affinitive moiety)-X— or X—(CO 2 -affinitive moiety)-X— of 1) or 2) below respectively: 
 1) F—(CF 2 ) q —(OCF 3 F 6 ) m —(OC 2 F 4 ) n —(OCF 2 ) o —(CH 2 ) p —X—, or    2) —X—(CH 2 ) p —(CF 2 O) o —(C 2 F 4 ) n —(C 3 F 6 O) m —(CF 2 ) q —(OC 3 F 6 ) m —(OC 2 F 4 ) n —(OCF 2 ) o —(CH 2 ) p —X—,    wherein m, n, o, p, and q are integers not smaller than 0, m and n are integers from 0 to 15 but not both 0, n+m≦20, o=0 to 20, p=0 to 2, and q=1 to 10; the sequence of the repeating units not being fixed; —(OC 3 F 6 ) m — represents —(OCF 2 CF 2 CF 2 ) m — or —(OCF(CF 3 )CF 2 ) m —, and —(OC 2 F 4 ) n — represents —(OCF 2 CF 2 ) n — or —(OCF(CF 3 )) n —, and    each X may be the same or different, and represents a single bond, or O, S, NH, NR (R a : alkyl group), C═O, C(O)O, OC(O), C(O)S, SC(O), C(O)NH, C(O)NR a  (R a : alkyl group), NH(O)C, NR(O)C, CH 2 , CHR a , CR a   2  (R a : alkyl group), SO 2 NH, or NHSO 2 .    
   
   
       13 . The method according to  claim 1 , wherein the nonionic compound is one of 1) to 3): 
 1) F—(CF 2 ) q —(OC 3 F 6 ) m —(OC 2 F 4 ) n —(OCF 2 ) o —(CH 2 ) p X—R h ,    2) F—(CF 2 ) q —(OC 3 F 6 ) m —(OC 2 F 4 ) n —(OCF 2 ) o —(CH 2 ) p X—R h —X—(CH 2 ) p —(CF 2 O) o —(C 2 F 4 O) n —(C 3 F 6 O) m —(CF 2 ) q —F, and    3) R h —X(CH 2 ) p —(CF 2 O) o —(C 2 F 4 O) n —(C 3 F 6 O) m —(CF 2 ) q —(OC 3 F 6 ) m —(OC 2 F 4 ) n —(OCF 2 ) o —(CH 2 ) p X—R h ,    wherein m, n, o, p, and q are integers not smaller than 0, m and n are integers from 0 to 15 but not both 0, n+m≦20, o=0 to 20, p=0 to 2, and q=1 to 10; the sequence of the repeating units not being fixed; —(OC 3 F 6 ) m — represents —(OCF 2 CF 2 CF 2 ) m — or —(OCF(CF 3 )CF 2 ) m —, and —(OC 2 F 4 ) n — represents —(OCF 2 CF 2 ) n — or —(OCF(CF 3 )) n —, and    each X may be the same or different, and represents a single bond, or O, S, NH, NR (R a : alkyl group), C═O, C(O)O, OC(O), C(O)S, SC(O), C(O)NH, C(O)NR a  (R a : alkyl group), NH(O)C, NR(O)C, CH 2 , CHR a , CR a   2  (R a : alkyl group), SO 2 NH, or NHSO 2 , and each R h  is a hydrophilic moiety and a straight or branched chain hydrocarbon group that may contain hetero atoms.    
   
   
       14 . The method according to  claim 13 , wherein R h  is a polyoxyalkylene group.  
   
   
       15 . The method according to  claim 13 , wherein the nonionic compound comprises a CO 2 -affinitive moiety whose number of carbon atoms is the same as or greater than that of the R h  group.  
   
   
       16 . The method according to  claim 1 , wherein the nonionic compound comprises (CO 2 -affinitive moiety)-X— or X—(CO 2 -affinitive moiety)-X— of 1) or 2) below respectively: 
 1) Y—(CF 2 )—(CH 2 ) n1 —X, or    2) X—(CH 2 ) n1 —(CF 2 ) m1 —(CH 2 ) n1 —X,    wherein Y is F or H, each X may be the same or different and represents one member selected from the group consisting of COO, O, S, CONH, NHCO, SO 2 NH, and NHSO 2 , m1 is an integer from 3 to 20, and each n1 may be the same or different and represents an integer from 0 to 2.    
   
   
       17 . The method according to  claim 16 , wherein the nonionic compound is one of 1) to 3) below respectively: 
 1) Y—(CF 2 ) m1 —(CH 2 ) n1 —X—R h ,    2) Y—(CF 2 ) n —(CH 2 ) n1 —X—R h —X—(CH 2 ) n1 —(CF 2 ) m —Y, or    3) R h —X—(CH 2 ) n1 —(CF 2 ) m1 —(CH 2 ) n1 —X—R h ,    wherein Y is F or H, each X may be the same or different and represents one member selected from the group consisting of COO, O, S, CONH, NHCO, SO 2 NH, and NHSO 2 , each m1 may be the same or different and represents an integer from 3 to 20, each n1 may be the same or different and represents an integer from 0 to 2, and each R h  is a hydrophilic moiety and straight or branched chain hydrocarbon group that may contain hetero atoms.    
   
   
       18 . The method according to  claim 17 , wherein R h  is a polyoxyalkylene group.  
   
   
       19 . The method according to  claim 17 , wherein the nonionic compound comprises a CO 2 -affinitive moiety whose number of carbon atoms is the same as or greater than that of each R h  group.