Plating bath and surface treatment compositions for thin film deposition
View Patent ↗An aqueous substrate surface treatment composition includes cysteine and an acidic solution having a pH of about 7 or less. The composition enables a selective deposition of a metal ion sensitizer and a subsequent selective plating of a metallic cap layer. Various CoWP plating bath compositions are also provided which may be used to form the cap layer.
1. An aqueous CoWP plating bath composition, comprising:
a cobalt salt;
a reducing agent;
a metal chelator;
a buffer; and
a tungstate salt;
wherein a ratio of molar concentrations of the cobalt salt to the reducing agent is from about 1:3 to about 1:5, and a ratio of molar concentrations of the cobalt salt to the metal chelator is from about 1:2.5 to about 1:3.5, wherein at least one of the (i) reducing agent and (ii) metal chelator comprises an alkali metal.
2. The composition of claim 1 , wherein the reducing agent comprises a hypophosphite salt.
3. The composition of claim 2 , wherein the hypophosphite salt is selected from a group consisting of H 3 PO 2 , NaH 2 PO 2 , KH 2 PO 2 , or NH 4 H 2 PO 2 .
4. The composition of claim 1 , wherein the metal chelator comprises a citrate salt.
5. The composition of claim 4 , wherein the citrate salt is selected from a group consisting of H 3 C 6 H 5 O 7 , Na 3 C 6 H 5 O 7 , K 3 C 6 H 5 O 7 or (NH 4 ) 3 C 6 H 5 O 7 .
6. The composition of claim 1 , wherein the buffer is selected from a group consisting of H 3 BO 3 , ethanolamine, TAPS, bicine, or CHES.
7. The composition of claim 1 , wherein:
the cobalt salt is selected from a group consisting of CoSO 4 , CoCl 2 or Co(OH) 2 ;
the reducing agent comprises a hypophosphite salt selected from a group consisting of H 3 PO 2 , NaH 2 PO 2 , KH 2 PO 2 , or NH 4 H 2 PO 2 ;
the metal chelator comprises a citrate salt selected from a group consisting of H 3 C 6 H 5 O 7 , Na 3 C 6 H 5 O 7 , K 3 C 6 H 5 O 7 or (NH 4 ) 3 C 6 H 5 O 7 ;
the buffer is selected from a group consisting of H 3 BO 3 , ethanolamine, TAPS, bicine, or CHES; and
the tungstate salt is selected from a group consisting of Na 2 WO 4 , K 2 WO 4 , or (NH 4 ) 2 WO 4 .
8. An aqueous CoWP plating bath composition, comprising
a cobalt salt selected from a group consisting of CoSO 4 or Co(OH) 2 ;
a reducing agent comprising a hypophosphite salt selected from a group consisting of H 3 PO 2 or NH 4 H 2 PO 2 ;
a metal chelator comprising (NH 4 ) 3 C 6 H 5 O 7 ;
a buffer selected from a group consisting of H 3 BO 3 , ethanolamine, TAPS, bicine, or CHES; and
a tungstate salt comprising (NH 4 ) 2 WO 4 ;
wherein a ratio of molar concentrations of the cobalt salt to the reducing agent is from about 1:3 to about 1:5, and a ratio of molar concentrations of the cobalt salt to the metal chelator is from about 1:2.5 to about 1:3.5;
wherein the composition comprises cysteine; and
wherein the composition comprises an alkali-free bath solution.
9. An aqueous CoWP plating bath composition, comprising:
from about 0.03 to about 0.15 M Co(OH) 2 ;
from about 0.05 to about 0.3 M H 3 PO 2 ;
from about 0.1 to about 0.5 M Na 3 C 6 H 5 O 7 ;
from about 0.3 to about 0.6 M H 3 BO 3 ; and
from about 0.01 to about 0.08 M Na 2 WO 4 ;
wherein the composition has a pH of about 8.0 to about 10.0 at a temperature from about 65 to about 85° C.
10. An aqueous CoWP plating bath composition, comprising:
from about 0.03 to about 0.15 M Co(OH) 2
from about 0.05 to about 0.3 M H 3 PO 2 ;
from about 0.1 to about 0.5 M (NH 4 ) 3 C 6 H 5 O 7 ;
from about 0.3 to about 0.6 M H 3 BO 3 ; and
from about 0.01 to about 0.08 M H 2 WO 4
wherein the composition has a pH of about 8.0 to about 10.0 at a temperature from about 70 to about 85° C.; and
wherein the composition comprises cysteine.
11. The composition of claim 1 , further comprising cysteine.
12. The composition of claim 9 , further comprising cysteine.