SELECTIVE METAL WET ETCH COMPOSITION AND PROCESS
Composition and a process using the composition for selectively wet etching metal including depositing metal on a silicon surface; applying energy to cause respective portions of the metal and silicon to form silicide, leaving a quantity of unreacted metal; selectively wet etching the unreacted metal by applying to the unreacted metal a composition including HCl, HBr, an ammonium halide, an amine hydrohalide salt, a quaternary ammonium halide, a quaternary phosphonium halide or a mixture of any two or more thereof; a nitrogen oxide compound; a stabilizer for the nitrogen oxide, comprising a glycol, a glyme, an ether, a polyol or a mixture of any two or more thereof; and water. In one embodiment, the composition includes an ammonium halide, an amine hydrohalide salt, a quaternary ammonium halide, a quaternary phosphonium halide or a mixture of any two or more thereof; a nitrogen oxide compound; and water.
1 . A process for forming a structure containing a silicide comprising:
forming a silicide by reaction of silicon and a metal, wherein the forming leaves a quantity of unreacted metal associated with the silicide;
selectively wet etching the unreacted metal by applying to the unreacted metal a composition comprising:
an ammonium halide, an amine hydrohalide salt, a quaternary ammonium halide, a quaternary phosphonium halide or a mixture of any two or more thereof;
a nitrogen oxide compound; and
water.
2 . The process of claim 1 wherein the forming comprises:
depositing a metal on a silicon surface;
applying energy to cause respective portions of the metal and the silicon to react to form a silicide, leaving the quantity of unreacted metal.
3 . The process of claim 1 wherein in the etching, the metal is etched selectively to one or more of silicides, polysilicon, silicon, silicon-germanium, nitrides and oxides with a selectivity in the range from about 10:1 to about 5000:1.
4 . The process of claim 1 wherein the amine hydrohalide salt comprises a C 1 -C 18 alkyl mono- or polyamine, a C 1 -C 18 alkanol mono- or polyamine or a C 6 -C 14 aryl mono- or polyamine or a mixture of any two or more thereof, wherein
each amine may be primary, secondary or tertiary;
each amine may comprise any combination of said alkyl, alkanol or aryl groups;
said alkyl and alkanol groups may be branched or unbranched; and
said aryl groups may be substituted with one or more C 1 to C 18 alkyl groups.
5 . The process of claim 1 wherein the quaternary ammonium halide comprises a tetraalkyl quaternary ammonium halide, a trialkylaryl quaternary ammonium halide, a dialkyldiaryl quaternary ammonium halide, an alkyltriaryl quaternary ammonium halide or a mixture of any two or more thereof, wherein the alkyl groups independently may be branched or unbranched C 1 to C 18 alkyl groups and the aryl groups independently may be C 6 -C 14 aryl, and the aryl groups may be substituted with one or more C 1 to C 18 alkyl groups, and wherein the quaternary ammonium halide may be a polyquaternary ammonium halide, comprising from 2 to about 6 quaternary ammonium atoms, wherein each quaternary ammonium atom may be separated from adjacent quaternary ammonium atom by a C 1 -C 6 alkylene or hydroxyalkylene group.
6 . The process of claim 1 wherein the quaternary phosphonium halide comprises a tetraalkyl quaternary phosphonium halide, a trialkylaryl quaternary phosphonium halide, a dialkyldiaryl quaternary phosphonium halide, an alkyltriaryl quaternary phosphonium halide or a mixture of any two or more thereof, wherein the alkyl groups independently may be branched or unbranched C 1 to C 18 alkyl groups and the aryl groups independently may be C 6 -C 14 aryl, and the aryl groups may be substituted with one or more C 1 to C 18 alkyl groups, and wherein the quaternary phosphonium halide may be a polyquaternary phosphonium halide comprising from 2 to about 6 quaternary phosphonium atoms, wherein each quaternary phosphonium atom may be separated from adjacent quaternary phosphonium atom by a C 1 -C 6 alkylene or hydroxyalkylene group.
7 . The process of claim 1 wherein the nitrogen oxide compound comprises one or more of nitric acid, nitrous acid, nitrosyl tetrafluoroborate, a nitrosyl halide, a nitrite salt, an organic nitrite compound.
8 . The process of claim 1 wherein the composition further comprises a stabilizer for the nitrogen oxide, said stabilizer comprising a glycol, a glyme, an ether, a polyol or a mixture of any two or more thereof.
9 . The process of claim 8 wherein the stabilizer for the nitrogen oxide comprises a crown ether, a diglyme, a triglyme, a tetraglyme, a pentaglyme, a hexaglyme or a mixture of any two or more thereof.
10 . The process of claim 8 wherein the stabilizer for the nitrogen oxide comprises a polyalkylene glycol, a polyalkylene glycol monoalkyl ether, a polyalkylene glycol dialkyl ether or a mixture of any two or more thereof, wherein the alkylene and alkyl groups are C 1 to about C 8 alkylene or alkyl.
11 . The process of claim 1 wherein the composition further comprises one or more of an alkyl or aryl mono- or poly-sulfonic acid, sulfuric acid, phosphoric acid, or a carboxylic acid.
12 . The process of claim 1 wherein the unreacted metal comprises one or more of Ti, Ni, Ni(Pt), Co, Pt, Ru, W, Mo, Nb, Ta and Re.
13 . An abrasive-free selective metal wet etch composition comprising:
(a) HCl, HBr, an ammonium halide, an amine hydrohalide salt, a quaternary ammonium halide, a quaternary phosphonium halide or a mixture of any two or more thereof;
(b) a nitrogen oxide compound;
(c) a stabilizer for the nitrogen oxide, said stabilizer comprising a glycol, a glyme, an ether, a polyol or a mixture of any two or more thereof; and
(d) water.
14 . The composition of claim 13 wherein the amine hydrohalide salt comprises a C 1 -C 18 alkyl mono- or polyamine, a C 1 -C 18 alkanol mono- or polyamine or a C 6 -C 14 aryl mono- or polyamine or a mixture of any two or more thereof, wherein
each amine may be primary, secondary or tertiary;
each amine may comprise any combination of said alkyl, alkanol or aryl groups;
said alkyl and alkanol groups may be branched or unbranched; and
said aryl groups may be substituted with one or more C 1 to C 18 alkyl groups.
15 . The composition of claim 13 wherein the quaternary ammonium halide comprises a tetraalkyl quaternary ammonium halide, a trialkylaryl quaternary ammonium halide, a dialkyldiaryl quaternary ammonium halide, an alkyltriaryl quaternary ammonium halide or a mixture of any two or more thereof, wherein the alkyl groups independently may be branched or unbranched C 1 to C 18 alkyl groups and the aryl groups independently may be C 6 -C 14 aryl, and the aryl groups may be substituted with one or more C 1 to C 18 alkyl groups and wherein the quaternary ammonium halide may be a polyquaternary ammonium halide, comprising from 2 to about 6 quaternary ammonium atoms, wherein each quaternary ammonium atom may be separated from adjacent quaternary ammonium atom by a C 1 -C 6 alkylene or hydroxyalkylene group.
16 . The composition of claim 13 wherein the quaternary phosphonium halide comprises a tetraalkyl quaternary phosphonium halide, a trialkylaryl quaternary phosphonium halide, a dialkyldiaryl quaternary phosphonium halide, an alkyltriaryl quaternary phosphonium halide or a mixture of any two or more thereof, wherein the alkyl groups independently may be branched or unbranched C 1 to C 18 alkyl groups and the aryl groups independently may be C 6 -C 14 aryl, and the aryl groups may be substituted with one or more C 1 to C 18 alkyl groups, and wherein the quaternary phosphonium halide may be a polyquaternary phosphonium halide, comprising from 2 to about 6 quaternary phosphonium atoms, wherein each quaternary phosphonium atom may be separated from adjacent quaternary phosphonium atom by a C 1 -C 6 alkylene or hydroxyalkylene group.
17 . The composition of claim 13 wherein the nitrogen oxide compound comprises one or more of nitric acid, nitrous acid, nitrosyl tetrafluoroborate, a nitrosyl halide, a nitrite salt, an organic nitrite compound.
18 . The composition of claim 13 wherein the stabilizer for the nitrogen oxide comprises a crown ether, a diglyme, a triglyme, a tetraglyme, a pentaglyme, a hexaglyme or a mixture of any two or more thereof.
19 . The composition of claim 13 wherein the stabilizer for the nitrogen oxide comprises a polyalkylene glycol, a polyalkylene glycol monoalkyl ether, a polyalkylene glycol dialkyl ether or a mixture of any two or more thereof, wherein the alkylene and alkyl groups are C 1 to about C 8 alkylene or alkyl.
20 . The composition of claims 13 wherein the composition further comprises one or more of an alkyl or aryl mono- or poly-sulfonic acid, sulfuric acid, phosphoric acid, or a carboxylic acid.
21 . A process for forming a structure containing a silicide comprising:
forming a silicide by reaction of silicon and a metal, wherein the forming leaves a quantity of unreacted metal associated with the silicide;
selectively wet etching the unreacted metal by applying to the unreacted metal a composition comprising:
(a) HCl, HBr, an ammonium halide, an amine hydrohalide salt, a quaternary ammonium halide, a quaternary phosphonium halide or a mixture of any two or more thereof;
(b) a nitrogen oxide compound;
(c) a stabilizer for the nitrogen oxide, said stabilizer comprising a glycol, a glyme, an ether, a polyol or a mixture of any two or more thereof; and
(d) water.
22 . The process of claim 21 wherein the forming comprises:
depositing a metal on a silicon surface;
applying energy to cause respective portions of the metal and the silicon to react to form a silicide, leaving the quantity of unreacted metal.