Low sodium, low metals silica polishing slurries

Claim 2

A colloidal silica slurry comprising: a low metals ammonium-stabilized silica sol formed by: (a) diluting said silica-containing solution with water to obtain a dilute silica-containing solution containing from about 5.0 to about 8.0 weight percent silica, as SiO 2 ; (b) exposing said dilute silica-containing solution to a cation exchange resin in the acid form and in sufficient capacity to remove essentially all sodium values, thereby forming a dilute silicic acid solution, said silicic acid solution comprising from about 5.0 to about 8.0 weight percent silicic acid as SiO 2 ; (c) adding to said silicic acid solution at least 0.10 weight percent, based on SiO 2 , of oxalic acid crystals and at least 0.25 weight percent, based on total silicic acid solution, of an inorganic acid, thereby forming an oxalate-containing, low pH silicic acid solution having a pH ranging from about 0.5 to about 2.5; (d) mixing said oxalate-containing, low pH silicic acid solution to recover silicic acid solution which contains from about 5.0 to about 8.0 weight percent silicic acid, as SiO 2 ; (e) exposing said silicic acid solution to an anion exchange resin in the hydroxide form, and in sufficient amount and with sufficient capacity to replace essentially all negatively charged species contained therein with hydroxide ions, thereby forming a hydroxide-neutralized silicic acid solution having a pH ranging between about 2.5 to about 4.0; (f) exposing said hydroxide-neutralized silicic acid solution to a cation exchange resin in the acid form and in sufficient amount and with sufficient capacity to replace all positively charged species contained therein with hydrated protons, thereby forming a low metals silicic acid solution; (g) chilling said low metals silicic acid solution to a temperature ranging between about 40° F. to about 50° F., and storing for from one minute to about fifty hours, thereby forming a chilled low metals silicic acid solution; (h) adding up to 50 volume percent of the low metals silicic acid solution to a preformed ammonium hydroxide solution made by adding concentrated ammonium hydroxide to deionized or softened water in sufficient quantity to achieve the preformed ammonium hydroxide solution having a pH ranging between about 8.0 to about 11.2, thereby forming an ammonium-neutralized silicic acid heel solution having a pH ranging between about 8.0 to about 11.2; (i) heating said heel solution to a temperature ranging between about 75° C. to about 150° C., under sufficient pressure to prevent boiling, and then maintaining this temperature for from about 0.5 hours to about twenty-four hours thereby forming silica sol particles, while adding, with stirring, the remainder of the low metals silicic acid solution, thereby reacting same with said silica sol particles, while simultaneously adding sufficient ammonium hydroxide solution to maintain a pH ranging from about 8.0 to about 11.2, and finally forming a dilute ammonium-stabilized low metals silica sol admixture; (j) reacting this final admixture, at a temperature from 75° C. to about 150° C., at pressure sufficient to prevent boiling, for an additional 0.5 to about 8 hours, thereby forming a dilute, low metals silica sol solution containing from about 2.0 to about 6.0 weight percent silica, as SiO 2 ; and (k) concentrating the dilute, low metals sol solution thereby forming said low metals ammonium-stabilized silica sol; said low metals ammonium-stabilized silica sol having the following characteristics: SiO 2 present in the range between about 8.5 to about 11.3; a particle diameter in the range between about 4.0 to about 130 nm; aluminum, as Al, present in an amount less than about 100 ppm, based on SiO 2 ; iron, as Fe, present in an amount less than about 50 ppm, based on SiO 2 ; potassium, as K, present in an amount less than about 25 ppm, based on SiO 2 ; and sodium, as Na, present in an amount less than about 500 ppm, based on SiO 2 ; a bactericide present in an amount between about 0.08 to about 5%, said bactericide is at least one compound selected from the group consisting of tetramethylammonium chloride, tetraethylammonium chloride, tetrapropylammonium chloride, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, alkylbenzyldimethylammonium chloride, and alkylbenzyldimethylammonium hydroxide, wherein the alkyl chain ranges from 1 to about 20 carbon atoms; and sodium chlorite or sodium hypochlorite present in an amount between about 1 to about 1000 ppm.

Claim 3

The colloidal silica slurry according to claim 1, wherein said bactericide is present in an amount between about 0.1 to about 1.25%.

Claim 4

The colloidal silica slurry according to claim 2, wherein said bactericide is present in an amount between about 0.5 to about 0.75%.

Claim 5

The colloidal silica slurry according to claim 1, wherein said sodium chlorite or sodium hypochlorite is present in an amount between about 65 ppm to about 100 ppm.

Claim 6

The colloidal silica slurry according to claim 1, further comprising a fungicide present in an amount between about 0.1 to about 2.0%.

Claim 7

The colloidal silica slurry according to claim 5, wherein said fungicide is present in an amount between about 0.1 to about 0.8%.

Claim 8

The colloidal silica slurry according to claim 6, wherein said fungicide is present in an amount between about 0.1 to about 0.5%.

Claim 9

The colloidal silica slurry according to claim 5, wherein said fungicide is sodium pyrithione.

Claim 10

The colloidal silica slurry according to claim 1, further comprising a polishing rate accelerator which is present in an amount between about 0.5 to about 5%, said polishing rate accelerator is at least one compound selected from the group consisting of: primary amines, secondary amines, heterocyclic amines, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and aminoethylethanolamine, and mixtures thereof.

Claim 11

The colloidal silica slurry according to claim 9, wherein said primary amines are selected from the group consisting of: monoethanolamine, isopropylamine, ethylenediamine, and propanediamine.

Claim 12

The colloidal silica slurry according to claim 9, wherein said secondary amines are selected from the group consisting of: diethanolamine, dipropylamine, and dibutylamine.

Claim 13

The colloidal silica slurry according to claim 9, wherein said heterocyclic amines are selected from the group consisting of: hexamethylenediamine, bis(aminopropyl) piperazine, and piperazine.

Claim 14

A colloidal silica slurry comprising: a low metals ammonium-stabilized silica sol formed by: (a) diluting said silica-containing solution with water to obtain a dilute silica-containing solution containing from about 5.0 to about 8.0 weight percent silica, as SiO 2 ; (b) exposing said dilute silica-containing solution to a cation exchange resin in the acid form and in sufficient capacity to remove essentially all sodium values, thereby forming a dilute silicic acid solution, said silicic acid solution comprising from about 5.0 to about 8.0 weight percent silicic acid as SiO 2 ; (c) adding to said silicic acid solution at least 0.10 weight percent, based on SiO 2 , of oxalic acid crystals and at least 0.25 weight percent, based on total silicic acid solution, of an inorganic acid, thereby forming an oxalate-containing, low pH silicic acid solution having a pH ranging from about 0.5 to about 2.5; (d) mixing said oxalate-containing, low pH silicic acid solution to recover silicic acid solution which contains from about 5.0 to about 8.0 weight percent silicic acid, as SiO 2 ; (e) exposing said silicic acid solution to an anion exchange resin in the hydroxide form, and in sufficient amount and with sufficient capacity to replace essentially all negatively charged species contained therein with hydroxide ions, thereby forming a hydroxide-neutralized silicic acid solution having a pH ranging between about 2.5 to about 4.0; (f) exposing said hydroxide-neutralized silicic acid solution to a cation exchange resin in the acid form and in sufficient amount and with sufficient capacity to replace all positively charged species contained therein with hydrated protons, thereby forming a low metals silicic acid solution; (g) chilling said low metals silicic acid solution to a temperature ranging between about 40° F. to about 50° F., and storing for from one minute to about fifty hours, thereby forming a chilled low metals silicic acid solution; (h) adding up to 50 volume percent of the low metals silicic acid solution to a preformed ammonium hydroxide solution made by adding concentrated ammonium hydroxide to deionized or softened water in sufficient quantity to achieve the preformed ammonium hydroxide solution having a pH ranging between about 8.0 to about 11.2, thereby forming an ammonium-neutralized silicic acid heel solution having a pH ranging between about 8.0 to about 11.2; (i) heating said heel solution to a temperature ranging between about 75° C. to about 150° C., under sufficient pressure to prevent boiling, and then maintaining this temperature for from about 0.5 hours to about twenty-four hours thereby forming silica sol particles, while adding, with stirring, the remainder of the low metals silicic acid solution, thereby reacting same with said silica sol particles, while simultaneously adding sufficient ammonium hydroxide solution to maintain a pH ranging from about 8.0 to about 11.2, and finally forming a dilute ammonium-stabilized low metals silica sol admixture; (j) reacting this final admixture, at a temperature from 75° C. to about 150° C., at pressure sufficient to prevent boiling, for an additional 0.5 to about 8 hours, thereby forming a dilute, low metals silica sol solution containing from about 2.0 to about 6.0 weight percent silica, as SiO 2 ; and (k) concentrating the dilute, low metals sol solution thereby forming said low metals ammonium-stabilized silica sol; said low metals ammonium-stabilized silica sol having the following characteristics: SiO 2 present in the range between about 8.5 to about 11.3; a particle diameter in the range between about 4.0 to about 130 nm; aluminum, as Al, present in an amount less than about 100 ppm, based on SiO 2 ; iron, as Fe, present in an amount less than about 50 ppm, based on SiO 2 ; potassium, as K, present in an amount less than about 25 ppm, based on SiO 2 ; and sodium, as Na, present in an amount less than about 500 ppm, based on SiO 2 ; and a polishing rate accelerator present in an amount between about 0.5 to about 5%.

Claim 15

A colloidal silica slurry comprising: a low metals ammonium-stabilized silica sol formed by: (a) diluting said silica-containing solution with water to obtain a dilute silica-containing solution containing from about 5.0 to about 8.0 weight percent silica, as SiO 2 ; (b) exposing said dilute silica-containing solution to a cation exchange resin in the acid form and in sufficient capacity to remove essentially all sodium values, thereby forming a dilute silicic acid solution, said silicic acid solution comprising from about 5.0 to about 8.0 weight percent silicic acid as SiO 2 ; (c) adding to said silicic acid solution at least 0.10 weight percent, based on SiO 2 , of oxalic acid crystals and at least 0.25 weight percent, based on total silicic acid solution, of an inorganic acid, thereby forming an oxalate-containing, low pH silicic acid solution having a pH ranging from about 0.5 to about 2.5; (d) mixing said oxalate-containing, low pH silicic acid solution to recover silicic acid solution which contains from about 5.0 to about 8.0 weight percent silicic acid, as SiO 2 ; (e) exposing said silicic acid solution to an anion exchange resin in the hydroxide form, and in sufficient amount and with sufficient capacity to replace essentially all negatively charged species contained therein with hydroxide ions, thereby forming a hydroxide-neutralized silicic acid solution having a pH ranging between about 2.5 to about 4.0; (f) exposing said hydroxide-neutralized silicic acid solution to a cation exchange resin in the acid form and in sufficient amount and with sufficient capacity to replace all positively charged species contained therein with hydrated protons, thereby forming a low metals silicic acid solution; (g) chilling said low metals silicic acid solution to a temperature ranging between about 40° F. to about 50° F., and storing for from one minute to about fifty hours, thereby forming a chilled low metals silicic acid solution; (h) adding up to 50 volume percent of the low metals silicic acid solution to a preformed ammonium hydroxide solution made by adding concentrated ammonium hydroxide to deionized or softened water in sufficient quantity to achieve the preformed ammonium hydroxide solution having a pH ranging between about 8.0 to about 11.2, thereby forming an ammonium-neutralized silicic acid heel solution having a pH ranging between about 8.0 to about 11.2; (i) heating said heel solution to a temperature ranging between about 75° C. to about 150° C., under sufficient pressure to prevent boiling, and then maintaining this temperature for from about 0.5 hours to about twenty-four hours thereby forming silica sol particles, while adding, with stirring, the remainder of the low metals silicic acid solution, thereby reacting same with said silica sol particles, while simultaneously adding sufficient ammonium hydroxide solution to maintain a pH ranging from about 8.0 to about 11.2, and finally forming a dilute ammonium-stabilized low metals silica sol admixture; (j) reacting this final admixture, at a temperature from 75° C. to about 150° C., at pressure sufficient to prevent boiling, for an additional 0.5 to about 8 hours, thereby forming a dilute, low metals silica sol solution containing from about 2.0 to about 6.0 weight percent silica, as SiO 2 ; and (k) concentrating the dilute, low metals sol solution thereby forming said low metals ammonium-stabilized silica sol; said low metals ammonium-stabilized silica sol having the following characteristics: SiO 2 present in the range between about 8.5 to about 11.3; a particle diameter in the range between about 4.0 to about 130 nm; aluminum, as Al, present in an amount less than about 100 ppm, based on SiO 2 ; iron, as Fe, present in an amount less than about 50 ppm, based on SiO 2 ; potassium, as K, present in an amount less than about 25 ppm, based on SiO 2 ; and sodium, as Na, present in an amount less than about 500 ppm, based on SiO 2 ; and a polishing rate accelerator present in an amount between about 0.5 to about 5%.

Claim 16

The colloidal silica slurry according to claim 13, wherein said polishing rate accelerator is at least one compound selected from the group consisting of: primary amines, secondary amines, tertiary amines, heterocyclic amines, and mixtures thereof.

Claim 17

The colloidal silica slurry according to claim 14, wherein said primary amines are selected from the group consisting of: monoethanolamine, isopropylamine, ethylenediamine, and propanediamine.

Claim 18

The colloidal silica slurry according to claim 14, wherein said secondary amines are selected from the group consisting of: diethanolamine, dipropylamine, and dibutylamine.

Claim 19

The colloidal silica slurry according to claim 14, wherein said tertiary amine is triethanolamine.

Claim 20

The colloidal silica slurry according to claim 14, wherein said heterocyclic amines are selected from the group consisting of: hexamethylenediamine, bis(aminopropyl) piperazine, and piperazine.

Claim 21

The colloidal silica slurry according to claim 13, wherein said polishing rate accelerator includes at least one quaternary amine.

Claim 22

The colloidal silica slurry according to claim 19, wherein said quaternary amine is selected from the group consisting of: tetramethylammonium chloride, tetraethylammonium chloride, tetrapropylammonium chloride, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, alkylbenzyldimethylammonium chloride, and alkylbenzyldimethylammonium hydroxide, wherein the alkyl chain ranges from 1 to about 20 carbon atoms.

Claim 23

The colloidal silica slurry according to claim 13, wherein said polishing rate accelerator is selected from the group consisting of diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and aminoethylethanolamine.

Claim 24

The colloidal silica slurry according to claim 13, further comprising either sodium chlorite or sodium hypochlorite in an amount between about 1 ppm to about 1000 ppm.

Claim 25

The colloidal silica slurry according to claim 22, wherein either the sodium chlorite or sodium hypochlorite are present in an amount between about 65 ppm to about 100 ppm.

Claim 26

The colloidal silica slurry according to claim 13 further comprising a fungicide in an amount between about 0.1 to about 2%.

Claim 27

The colloidal silica slurry according to claim 24, wherein said fungicide is present in an amount between about 0.1 to about 0.8%.

Claim 28

The colloidal silica slurry according to claim 25, wherein said fungicide is present in an amount between about 0.1 to about 0.5%.

Claim 29

The colloidal silica slurry according to claim 24, wherein said fungicide is sodium pyrithione.

Claim 30

A process for polishing a silicon wafer which includes the step of recirculating a colloidal silica slurry comprising: a low metals ammonium-stabilized silica sol formed by: (a) diluting said silica-containing solution with water to obtain a dilute silica-containing solution containing from about 5.0 to about 8.0 weight percent silica, as SiO 2 ; (b) exposing said dilute silica-containing solution to a cation exchange resin in the acid form and in sufficient capacity to remove essentially all sodium values, thereby forming a dilute silicic acid solution, said silicic acid solution comprising from about 5.0 to about 8.0 weight percent silicic acid as SiO 2 ; (c) adding to said silicic acid solution at least 0.10 weight percent, based on SiO 2 , of oxalic acid crystals and at least 0.25 weight percent, based on total silicic acid solution, of an inorganic acid, thereby forming an oxalate-containing, low pH silicic acid solution having a pH ranging from about 0.5 to about 2.5; (d) mixing said oxalate-containing, low pH silicic acid solution to recover silicic acid solution which contains from about 5.0 to about 8.0 weight percent silicic acid, as SiO 2 ; (e) exposing said silicic acid solution to an anion exchange resin in the hydroxide form, and in sufficient amount and with sufficient capacity to replace essentially all negatively charged species contained therein with hydroxide ions, thereby forming a hydroxide-neutralized silicic acid solution having a pH ranging between about 2.5 to about 4.0; (f) exposing said hydroxide-neutralized silicic acid solution to a cation exchange resin in the acid form and in sufficient amount and with sufficient capacity to replace all positively charged species contained therein with hydrated protons, thereby forming a low metals silicic acid solution; (g) chilling said low metal silicic acid solution to a temperature ranging between bout 40° F. to about 50° F., and storing for from one minute to about fifty hours, thereby forming a chilled low metals silicic acid solution; (h) adding up to 50 volume percent of the low metals silicic acid solution to a preformed ammonium hydroxide solution made by adding concentrated ammonium hydroxide to deionized or softened water in sufficient quantity to achieve the preformed ammonium hydroxide solution having a pH ranging between about 8.0 to about 11.2, thereby forming an ammonium-neutralized silicic acid heel solution having a pH ranging between about 8.0 to about 11.2; (i) heating said heel solution to a temperature ranging between about 75° C. to about 150° C., under sufficient pressure to prevent boiling, and then maintaining this temperature for from about 0.5 hours to about twenty-four hours thereby forming silica sol particles, while adding, with stirring, the remainder of the low metals silicic acid solution, thereby reacting same with said silica sol particles, while simultaneously adding sufficient ammonium hydroxide solution to maintain a pH ranging from about 8.0 to about 11.2, and finally forming a dilute ammonium-stabilized low metals silica sol admixture; (j) reacting this final admixture, at a temperature from 75° C. to about 150° C., at pressure sufficient to prevent boiling, for an additional 0.5 to about 8 hours, thereby forming a dilute, low metals silica sol solution containing from about 2.0 to about 6.0 weight percent silica, as SiO 2 ; and (k) concentrating the dilute, low metals sol solution thereby forming said low metals ammonium-stabilized silica sol; said low metals ammonium-stabilized silica sol having the following characteristics: SiO 2 present in the range between about 8.5 to about 11.3; a particle diameter in the range between about 4.0 to about 130 nm; aluminum, as Al, present in an amount less than about 100 ppm, based on SiO 2 ; iron, as Fe, present in an amount less than about 50 ppm, based on SiO 2 ; potassium, as K, present in an amount less than about 25 ppm, based on SiO 2 ; and sodium, as Na, present in an amount less than about 500 ppm, based on SiO 2 ; a bactericide present in an amount between about 0.08 to about 5%, said bactericide is at least one compound selected from the group consisting of tetramethylammonium chloride, tetraethylammonium chloride, tetrapropylammonium chloride, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, alkylbenzyldimethylammonium chloride, and alkylbenzyldimethylammonium hydroxide, wherein the alkyl chain ranges from 1 to about 20 carbon atoms; and sodium chlorite or sodium hypochlorite present in an amount between about 1 to about 1000 ppm, between a polishing plate containing a polishing pad and said silicon wafer.

Claim 31

A process for polishing a silicon wafer which includes the step of recirculating a colloidal silica slurry comprising: a low metals ammonium-stabilized silica sol formed by: (a) diluting said silica-containing solution with water to obtain a dilute silica-containing solution containing from about 5.0 to about 8.0 weight percent silica, as SiO 2 ; (b) exposing said dilute silica-containing solution to a cation exchange resin in the acid form and in sufficient capacity to remove essentially all sodium values, thereby forming a dilute silicic acid solution, said silicic acid solution comprising from about 5.0 to about 8.0 weight percent silicic acid as SiO 2 ; (c) adding to said silicic acid solution at least 0.10 weight percent, based on SiO 2 , of oxalic acid crystals and at least 0.25 weight percent, based on total silicic acid solution, of an inorganic acid, thereby forming an oxalate-containing, low pH silicic acid solution having a pH ranging from about 0.5 to about 2.5; (d) mixing said oxalate-containing, low pH silicic acid solution to recover silicic acid solution which contains from about 5.0 to about 8.0 weight percent silicic acid, as SiO 2 ; (e) exposing said silicic acid solution to an anion exchange resin in the hydroxide form, and in sufficient amount and with sufficient capacity to replace essentially all negatively charged species contained therein with hydroxide ions, thereby forming a hydroxide-neutralized silicic acid solution having a pH ranging between about 2.5 to about 4.0; (f) exposing said hydroxide-neutralized silicic acid solution to a cation exchange resin in the acid form and in sufficient amount and with sufficient capacity to replace all positively charged species contained therein with hydrated protons, thereby forming a low metals silicic acid solution; (g) chilling said low metal silicic acid solution to a temperature ranging between bout 40° F. to about 50° F., and storing for from one minute to about fifty hours, thereby forming a chilled low metals silicic acid solution; (h) adding up to 50 volume percent of the low metals silicic acid solution to a preformed ammonium hydroxide solution made by adding concentrated ammonium hydroxide to deionized or softened water in sufficient quantity to achieve the preformed ammonium hydroxide solution having a pH ranging between about 8.0 to about 11.2, thereby forming an ammonium-neutralized silicic acid heel solution having a pH ranging between about 8.0 to about 11.2; (i) heating said heel solution to a temperature ranging between about 75° C. to about 150° C., under sufficient pressure to prevent boiling, and then maintaining this temperature for from about 0.5 hours to about twenty-four hours thereby forming silica sol particles, while adding, with stirring, the remainder of the low metals silicic acid solution, thereby reacting same with said silica sol particles, while simultaneously adding sufficient ammonium hydroxide solution to maintain a pH ranging from about 8.0 to about 11.2, and finally forming a dilute ammonium-stabilized low metals silica sol admixture; (j) reacting this final admixture, at a temperature from 75° C. to about 150° C., at pressure sufficient to prevent boiling, for an additional 0.5 to about 8 hours, thereby forming a dilute, low metals silica sol solution containing from about 2.0 to about 6.0 weight percent silica, as SiO 2 ; and (k) concentrating the dilute, low metals sol solution thereby forming said low metals ammonium-stabilized silica sol; said low metals ammonium-stabilized silica sol having the following characteristics: SiO 2 present in the range between about 8.5 to about 11.3; a particle diameter in the range between about 4.0 to about 130 nm; aluminum, as Al, present in an amount less than about 100 ppm, based on SiO 2 ; iron, as Fe, present in an amount less than about 50 ppm, based on SiO 2 ; potassium, as K, present in an amount less than about 25 ppm, based on SiO 2 ; and sodium, as Na, present in an amount less than about 500 ppm, based on SiO 2 ; a bactericide present in an amount between about 0.08 to about 5%, said bactericide is at least one compound selected from the group consisting of tetramethylammonium chloride, tetraethylammonium chloride, tetrapropylammonium chloride, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, alkylbenzyldimethylammonium chloride, and alkylbenzyldimethylammonium hydroxide, wherein the alkyl chain ranges from 1 to about 20 carbon atoms; and sodium chlorite or sodium hypochlorite present in an amount between about 1 to about 1000 ppm, between a polishing plate containing a polishing pad and said silicon wafer.

Claim 32

The process according to claim 28, wherein said bactericide is present in an amount between about 0.1 to about 1.25%.

Claim 33

The process according to claim 29, wherein said bactericide is present in an amount between about 0.5 to about 0.75%.

Claim 34

The process according to claim 28, wherein said sodium chlorite or sodium hypochlorite is present in an amount between about 65 ppm to about 100 ppm.

Claim 35

The process according to claim 28, further comprising a fungicide present in an amount between about 0.1 to about 2.0%.

Claim 36

The process according to claim 32, wherein said fungicide is present in an amount between about 0.1 to bout 0.8%.

Claim 37

The process according to claim 33, wherein said fungicide is present in an amount between about 0.1 to about 0.5%.

Claim 38

The process according to claim 32, wherein said fungicide is sodium pyrithione.

Claim 39

The process according to claim 28, further comprising a polishing rate accelerator which is present in an amount between about 0.5 to about 5%, said polishing rate accelerator is at least one compound selected from the group consisting of: primary amines, secondary amines, heterocyclic amines, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and aminoethylethanolamine, and mixtures thereof.

Claim 40

The process according to claim 36, wherein said primary amines are selected from the group consisting of: monoethanolamine, isopropylamine, ethylenediamine, and propanediamine.

Claim 41

The process according to claim 36, wherein said secondary amines are selected from the group consisting of: diethanolamine, dipropylamine, and dibutylamine.

Claim 42

The process according to claim 36, wherein said heterocyclic amines are selected from the group consisting of: hexamethylenediamine, bis(aminopropyl) piperazine, and piperazine.

Claim 43

A process for polishing a silicon wafer which includes the step of recirculating a colloidal silica slurry comprising: a low metals ammonium-stabilized silica sol formed by: (a) diluted said silica-containing solution with water to obtain a dilute silica-containing solution containing from about 5.0 to about 8.0 weight percent silica, as SiO 2 ; (b) exposing said dilute silica-containing solution to a cation exchange resin in the acid form and in sufficient capacity to remove essentially all sodium values, thereby forming a dilute silicic acid solution, said silicic acid solution comprising from about 5.0 to about 8.0 weight percent silicic acid as SiO 2 ; (c) adding to said silicic acid solution at least 0.10 weight percent, based on SiO 2 , of oxalic acid crystals and at least 0.25 weight percent, based on total silicic acid solution, of an inorganic acid, thereby forming an oxalate-containing, low pH silicic acid solution having a pH ranging from about 0.5 to about 2.5; (d) mixing said oxalate-containing, low pH silicic acid solution to recover silicic acid solution which contains from about 5.0 to about 8.0 weight percent silicic acid, as SiO 2 ; (e) exposing said silicic acid solution to an anion exchange resin in the hydroxide form, and in sufficient amount and with sufficient capacity to replace essentially all negatively charged species contained therein with hydroxide ions, thereby forming a hydroxide-neutralized silicic acid solution having a pH ranging between about 2.5 to about 4.0; (f) exposing said hydroxide-neutralized silicic acid solution to a cation exchange resin in the acid form and in sufficient amount and with sufficient capacity to replace all positively charged species contained therein with hydrated protons, thereby forming a low metals silicic acid solution; (g) chilling said low metals silicic acid solution to a temperature ranging between about 40° F. to about 50° F., and storing for from one minute to about fifty hours, thereby forming a chilled low metals silicic acid solution; (h) adding up to 50 volume percent of the low metals silicic acid solution to a preformed ammonium hydroxide solution made by adding concentrated ammonium hydroxide to deionized or softened water in sufficient quantity to achieve the preformed ammonium hydroxide solution having a pH ranging between about 8.0 to about 11.2, thereby forming an ammonium-neutralized silicic acid heel solution having a pH ranging between about 8.0 to about 11.2; (i) heating said heel solution to a temperature ranging between about 75° C. to about 150° C., under sufficient pressure to prevent boiling, and then maintaining this temperature for from about 0.5 hours to about twenty-four hours thereby forming silica sol particles, while adding, with stirring, the remainder of the low metals silicic acid solution, thereby reacting same with said silica sol particles, while simultaneously adding sufficient ammonium hydroxide solution to maintain a pH ranging from about 8.0 to about 11.2, and finally forming a dilute ammonium-stabilized low metals silica sol admixture; (j) reacting this final admixture, at a temperature from 75° C. to about 150° C., at pressure sufficient to prevent boiling, for an additional 0.5 to about 8 hours, thereby forming a dilute, low metals silica sol solution containing from about 2.0 to about 6.0 weight percent silica, as SiO 2 ; and (K) concentrating the dilute, low metals sol solution thereby forming said low metals ammonium-stabilized silica sol; said low metals ammonium-stabilized silica sol having the following characteristics: SiO 2 present in the range between about 8.5 to about 11.3; a particle diameter in the range between about 4.0 to about 130 nm; aluminum, as Al, present in an amount less than about 100 ppm, based on SiO 2 ; iron, as Fe, present in an amount less than about 50 ppm, based on SiO 2 ; potassium, as K, present in an amount less than about 25 ppm, based on SiO 2 ; and sodium, as Na, present in an amount less than about 500 ppm, based on SiO 2 ; and a polishing rate accelerator present in an amount between about 0.5 to about 5%, between a polishing plate containing a polishing pad and said silicon wafer.

Claim 44

A process for polishing a silicon wafer which includes the step of recirculating a colloidal silica slurry comprising: a low metals ammonium-stabilized silica sol formed by: (a) diluted said silica-containing solution with water to obtain a dilute silica-containing solution containing from about 5.0 to about 8.0 weight percent silica, as SiO 2 ; (b) exposing said dilute silica-containing solution to a cation exchange resin in the acid form and in sufficient capacity to remove essentially all sodium values, thereby forming a dilute silicic acid solution, said silicic acid solution comprising from about 5.0 to about 8.0 weight percent silicic acid as SiO 2 ; (c) adding to said silicic acid solution at least 0.10 weight percent, based on SiO 2 , of oxalic acid crystals and at least 0.25 weight percent, based on total silicic acid solution, of an inorganic acid, thereby forming an oxalate-containing, low pH silicic acid solution having a pH ranging from about 0.5 to about 2.5; (d) mixing said oxalate-containing, low pH silicic acid solution to recover silicic acid solution which contains from about 5.0 to about 8.0 weight percent silicic acid, as SiO 2 ; (e) exposing said silicic acid solution to an anion exchange resin in the hydroxide form, and in sufficient amount and with sufficient capacity to replace essentially all negatively charged species contained therein with hydroxide ions, thereby forming a hydroxide-neutralized silicic acid solution having a pH ranging between about 2.5 to about 4.0; (f) exposing said hydroxide-neutralized silicic acid solution to a cation exchange resin in the acid form and in sufficient amount and with sufficient capacity to replace all positively charged species contained therein with hydrated protons, thereby forming a low metals silicic acid solution; (g) chilling said low metals silicic acid solution to a temperature ranging between about 40° F. to about 50° F., and storing for from one minute to about fifty hours, thereby forming a chilled low metals silicic acid solution; (h) adding up to 50 volume percent of the low metals silicic acid solution to a preformed ammonium hydroxide solution made by adding concentrated ammonium hydroxide to deionized or softened water in sufficient quantity to achieve the preformed ammonium hydroxide solution having a pH ranging between about 8.0 to about 11.2, thereby forming an ammonium-neutralized silicic acid heel solution having a pH ranging between about 8.0 to about 11.2; (i) heating said heel solution to a temperature ranging between about 75° C. to about 150° C., under sufficient pressure to prevent boiling, and then maintaining this temperature for from about 0.5 hours to about twenty-four hours thereby forming silica sol particles, while adding, with stirring, the remainder of the low metals silicic acid solution, thereby reacting same with said silica sol particles, while simultaneously adding sufficient ammonium hydroxide solution to maintain a pH ranging from about 8.0 to about 11.2, and finally forming a dilute ammonium-stabilized low metals silica sol admixture; (j) reacting this final admixture, at a temperature from 75° C. to about 150° C., at pressure sufficient to prevent boiling, for an additional 0.5 to about 8 hours, thereby forming a dilute, low metals silica sol solution containing from about 2.0 to about 6.0 weight percent silica, as SiO 2 ; and (K) concentrating the dilute, low metals sol solution thereby forming said low metals ammonium-stabilized silica sol; said low metals ammonium-stabilized silica sol having the following characteristics: SiO 2 present in the range between about 8.5 to about 11.3; a particle diameter in the range between about 4.0 to about 130 nm; aluminum, as Al, present in an amount less than about 100 ppm, based on SiO 2 ; iron, as Fe, present in an amount less than about 50 ppm, based on SiO 2 ; potassium, as K, present in an amount less than about 25 ppm, based on SiO 2 ; and sodium, as Na, present in an amount less than about 500 ppm, based on SiO 2 ; and a polishing rate accelerator present in an amount between about 0.5 to about 5%, between a polishing plate containing a polishing pad and said silicon wafer.

Claim 45

The process according to claim 40, wherein said polishing rate accelerator is at least one compound selected from the group consisting of: primary amines, secondary amines, tertiary amines, heterocyclic amines, and mixtures thereof.

Claim 46

The process according to claim 41, wherein said primary amines are selected from the group consisting of: monoethanolamine, isopropylamine, ethylenediamine, and propanediamine.

Claim 47

The process according to claim 41, wherein said secondary amines are selected from the group consisting of: diethanolamine, dipropylamine, and dibutylamine.

Claim 48

The process according to claim 41, wherein said tertiary amine is triethanolamine.

Claim 49

The process according to claim 41, wherein said heterocyclic amines are selected from the group consisting of: hexamethylenediamine, bis(aminopropyl) piperazine, and piperazine.

Claim 50

The process according to claim 40, wherein said polishing rate accelerator includes at least one quaternary amine.

Claim 51

The process according to claim 46, wherein said quaternary amine is selected from the group consisting of: tetramethylammonium chloride, tetraethylammonium chloride, tetrapropylammonium chloride, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, alkylbenzyldimethylammonium chloride, and alkylbenzyldimethylammonium hydroxide, wherein the alkyl chain ranges from 1 to about 20 carbon atoms.

Claim 52

The process according to claim 40, wherein said polishing rate accelerator is selected from the group consisting of diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and aminoethylethanolamine.

Claim 53

The process according to claim 40, further comprising either sodium chlorite or sodium hypochlorite in an amount between about 1 ppm to about 1000 ppm.

Claim 54

The process according to claim 49, wherein either the sodium chlorite or sodium hypochlorite are present in an amount between about 65 ppm to about 100 ppm.

Claim 55

The process according to claim 40 further comprising a fungicide in an amount between about 0.1 to about 2%.

Claim 56

The process according to claim 51, wherein said fungicide is present in an amount between about 0.1 to about 0.8%.

Claim 57

The process according to claim 52, wherein said fungicide is present in an amount between about 0.1 to about 0.5%.

Claim 58

The process according to claim 51, wherein said fungicide is sodium pyrithione.