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A method of manipulating the rate of homogeneous nucleation of silicon as either a particulate solid or liquid settling out of the gaseous phase during the pyrolysis of silane homologs by controlling the quantity of halogen within the pyrolysis medium. The rate of homogeneous nucleation can be maint

A method of manipulating the rate of homogeneous nucleation of silicon as either a particulate solid or liquid settling out of the gaseous phase during the pyrolysis of silane homologs by controlling the quantity of halogen within the pyrolysis medium. The rate of homogeneous nucleation can be maintained sufficiently low (below 1 silicon nucleus/cm 3 /sec) so as to avoid power formation with a minimum amount of halogen.

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1. A method of decreasing the homogeneous nucleation of particulate solid silicon in the gas phase during the pyrolysis of silane homologs and hydrogen mixtures thereof at temperatures below about 1700 Kelvin, said method comprising: (a) adding halogen to a gaseous feedstock comprised of silane h

1. A method of decreasing the homogeneous nucleation of particulate solid silicon in the gas phase during the pyrolysis of silane homologs and hydrogen mixtures thereof at temperatures below about 1700 Kelvin, said method comprising: (a) adding halogen to a gaseous feedstock comprised of silane homologs, in the form of one or more members of the group consisting of HI, HBr, HF, Cl 2, Br 2, F 2, I 2, SiX 3 H and SiX 4, wherein X is halogen in a quantity at least equi-molar to the silane homolog content of said feedstock, with the quantity of SiX 3 H added to the feedstock being limited to less than about 30 mole percent of said feedstock and (b) pyrolyzing the silane homologs within the feedstock of step (a). 2. A method as in claim 1 wherein the feedstock is comprised of silane homologs selected from the group consisting of SiH 4, SiH 3 Cl, SiH 2 Cl 2 and the halogen added is in the form of Cl 2, SiHCl 3, SiCl 4 and mixtures thereof. 3. A method as in claim 2 wherein the concentration of silane homologs within said feedstock is within the range of about 0.1 mole percent to about 20 mole percent of said feedstock. 4. A method as in claim 3 wherein the total concentration of Cl 2, SiHCl 3 and SiCl 4 added to the feedstock is within the range of about 1 to 30 mole percent of said feedstock. 5. A method as in claim 4 wherein the pyrolysis temperature falls within the range of about 800 to about 1700 Kelvin. 6. A method of decreasing the homogeneous nucleation of liquid silicon in the gas phase during the pyrolysis of silane homologs and hydrogen mixtures thereof at temperatures above about 1700 Kelvin, said method comprising: (a) adding halogen to a gaseous feedstock comprised of silane homologs selected from the group consisting of SiH 4, SiH 3 X, SiH 2 X 2 and mixtures thereof in the form of one or more members of the group consisting of HI, HBr, HF, Cl 2, I 2, Br 2, F 2, SiX 4 and SiH 3 X 3 wherein X is halogen, in a concentration at least equi-molar to the silane homolog content of said feedstock, with the quantities of SiHX 3 added being greater than about 10 mole percent of said feedstock and the quantities of SiX 4 added being greater than about 2 mole percent of said feedstock and (b) pyrolyzing the silane homologs within the feedstock of step (a). 7. A method as in claim 6 wherein the feedstock is comprised of one or more members of the group consisting of SiH 4, SiH 3 Cl, SiH 2 Cl 2, and the halogen added is in the form of Cl 2, SiHCl 3, SiCl 4 and mixtures thereof. 8. A method as in claim 5 wherein the concentration of silane homologs comprising said feedstock falls within the range of about 0.1 mole percent to about 20 mole percent of said feedstock. 9. A method as in claim 6 wherein the total concentration of Cl 2, SiHCl 3 and SiCl 4 added to the feedstock falls within the range of about 1 mole percent to about 30 mole percent of said feedstock. 10. A method of decreasing the homogeneous nucleation of particulate solid and liquid silicon in the gaseous phase during the pyrolysis of silane homologs and hydrogen mixtures thereof having the formula SiH 2 X 2, wherein X is halogen, said method comprising the steps of (a) adding halogen to a gaseous feedstock comprised of silane homologs having the formula SiH 2 X 2 in the form of one or more members of the group consisting of HF, HI, HBr, Cl 2, Br 2, I 2, F 2, SiHX 3 and SiX 4, wherein X is halogen, in a concentration within the range of about 0.1 to 1.0 the molar concentration of the silane homologs in said feedstock and (b) pyrolyzing the silane homologs within the feedstock of step (a). 11. A method as in claim 10 wherein the silane homolog is SiH 2 Cl 2 and the halogen added to the feedstock is in the form of Cl 2, SiHCl 3, SiCl 4 and mixtures thereof. 12. A method of reducing the homogeneous nucleation of particulate solid and liquid silicon in the gaseous phase to one silicon nucleus/cm 3 /sec and less when pyrolyzing silane homologs comprising: (a) selecting silane homologs from the group consisting of SiH 4, SiH 3 X, SiH 2 X 2 and mixtures thereof, wherein X is halogen, (b) diluting the silane homologs of step (a) with hydrogen to provide a gaseous feedstock having a concentration of silane homologs in the range of about 0.001 to 20 mole percent, (c) adding a member of the group consisting of Cl 2 and F 2 in a concentration with the range of about 0.001 to 90 mole percent of said feedstock, (d) selecting a pyrolysis temperature from a group of values within the range of 800 to 3000 K. which correspond to loci on and outside of one or more curves of FIG. 4, said curves corresponding to concentrations of silane homologs which are greater than and equal to the concentration of silane homologs in step (b) and (e) pyrolyzing the feedstock of step (c) at said pyrolysis temperature. 13. A process as in claim 12 wherein the pyrolysis temperature is additionally limited to values corresponding to loci on a curve selected from FIG. 4, the selected curve corresponding to the lowest SiH 4 concentration which is greater than or equal to the concentration of silane homologs in step (b). 14. A method of reducing the homogeneous nucleation of particulate solid and liquid silicon in the gaseous phase to 1 silicon nucleus cm 3 /sec and less when pyrolyzing silane homologs comprising (a) selecting silane homologs from the group consisting of SiH 4, SiHX 3, SiH 2 X 2 and mixtures thereof, wherein X is halogen; (b) diluting the silane homologs of step (a) with hydrogen to provide a gaseous feedstock having a concentration of silane homologs in the range of about 0.001 to 20 mole percent; (c) adding a member of the group consisting of HCl, and HF in a concentration within the range of about 0.001 to 90 mole percent of said feedstock; (d) selecting a pyrolysis temperature from a group of values within the range of 800 to 3000 K. which corresponds to a loci on and outside of one or more curves of FIG. 3, said curves corresponding to concentrations of silane homologs which are greater than and equal to the concentration of silane homologs in step (b) and (e) pyrolyzing the feedstock of step (c) at said pyrolysis temperature. 15. A process as in claim 14 wherein the pyrolysis temperature is additionally limited to values corresponding to loci on a curve selected from FIG. 3, the selected curve corresponding to the lowest SiH 4 concentration which is greater than or equal to the concentration of silane in step (b). 16. A method of reducing the homogeneous nucleation of particulate solid and liquid silicon in the gaseous phase to 1 silicon nucleus/cm 3 /sec and less when pyrolyzing silane homologs comprising (a) selecting silane homologs from the group consisting of SiH 4, SiH 3 Cl, SiH 2 Cl 2, SiH 2 F 2, SiH 3 F and mixtures thereof, (b) diluting the silane homologs of step (a) with hydrogen to provide a gaseous feedstock having a concentration of silane homologs in the range of about 0.001 to 5 mole percent; (c) adding a silane homolog selected from the group consisting of SiCl 4 to said feedstock in a concentration within the range of about 0.001 to 30 mole percent of said feedstock; (d) selecting a pyrolysis temperature from the group of values within the range of 800 to 3000 K. which correspond to loci on and outside of the 0.01 SiH 4 curve of FIG. 5 for concentrations of silane homologs less than or equal to 0.01 mole percent of feedstock, loci on or outside of the 1.0 SiH 4 curve of FIG. 5 for concentrations of silane homologs less than or equal to 1 mole percent of feedstock; loci on and outside of the 2.0 SiH 4 curve of FIG. 5 for concentrations of silane homologs less than or equal to 2 mole percent of the feedstock; loci on and outside of the 2.5 SiH 4 curve of FIG. 5 for concentrations of silane homologs less than or equal to 2.5 mole percent of the feedstock and loci on and outside of the 5.0 SiH 4 curve of FIG. 5 for concentrations of silane homologs less than or equal to 5 mole percent of the feedstock; and (e) pyrolyzing the feedstock of step (c) at said pyrolyzing temperature. 17. A method as in claim 16 wherein the pyrolysis temperature is additionally limited to values corresponding to the loci on the 0.01 SiH 4, 1.0 SiH 4, 2.0 SiH 4, 2.5 SiH 4, and 5.0 SiH 4 curves of FIG. 5. 18. A method of reducing the homogeneous nucleation of particulate solid and liquid silicon in the gaseous phase to 1 silicon nucleus/cm 3 /sec and less when pyrolyzing silane homologs comprising (a) selecting silane homologs from the group consisting of SiH 4, SiH 3 Cl, SiH 2 Cl 2, SiH 3 F, SiH 2 F 2 and mixtures thereof, (b) diluting the silane homologs of step (a) with hydrogen to provide a gaseous feedstock having a concentration of silane homologs in the range of about 0.01 to about 10 mole percent of feedstock; (c) adding a silane homolog selected from the group consisting of SiHCl 3 and SiHF 3 to said feedstock in a concentration within the range of about 0.001 to 50 mole percent of said feedstock; (d) selecting a pyrolysis temperature from the group of values within the range of 800 to 3000 K. which correspond to loci on or outside of the 0.01 SiH 4 curve of FIG. 6 for concentrations of silane homologs less than or equal to 0.01 mole percent of the feedstock; loci on or outside of the 1.0 SiH 4 curve of FIG. 6 for concentrations of silane homologs less than or equal to 1 mole percent of feedstock; loci on or outside of the 5.0 SiH 4 curves of FIG. 6 for concentrations of silane homologs less than or equal to 5 mole percent of feedstock and loci on or outside of the 10.0 SiH 4 curves of FIG. 6 for concentration of silane homologs less than or equal to 10 mole percent of feedstock, and (e) pyrolyzing the feedstock of step (c) at said pyrolysis temperature. 19. A method as in claim 18 wherein the pyrolysis temperature is additionally limited to values corresponding to the loci on the 0.01 SiH 4, 1.0 SiH 4, SiOSiH 4, and 10.0 SiH 4 curves of FIG. 6. 20. A method of reducing the homogeneous nucleation of particulate solid and liquid silicon in the gaseous phase of 1 silicon nucleus/cm 3 /sec and less when pyrolyzing SiH 4, said method comprising (a) diluting SiH 4 with hydrogen to provide a gaseous feedstock having a concentration of about 1 mole percent silane; (b) adding Cl 2 and SiHCl 3 to said feedstock in a concentration within the range of 0.1 to 5 mole percent of said feedstock for both Cl 2 and SiHCl 3 (c) selecting a pyrolysis temperature from a group of values within the range of 800 to 3000 K. which correspond to loci on and outside of the curve of FIG. 8 and (d) pyrolyzing the feedstock of step (b) at said pyrolysis temperature. 21. A method of reducing the homogeneous nucleation of particulate solid and liquid silicon in the gaseous phase to 1 silicon nucleus/cm 3 /sec and less when pyrolyzing SiH 2 Cl 2, said method comprising (a) diluting SiH 2 Cl 2 with hydrogen gas to provide a gaseous feedstock having a concentration of about 10 mole percent SiH 2 Cl 2 ; (b) adding halogen to the feedstock in the form of a mixture selected from the group consisting of HCl plus Cl 2, SiHCl 3 plus SiCl 4, and Cl 2 in a concentration within the range of 0.1 to 5 mole percent of said feedstock for each constituent of said mixture; (c) selecting a pyrolysis temperature from a group of values within the range of 800 to 3000 K. which correspond to loci on and outside of the curve of FIG. 8 for additions of HCl plus Cl 2, loci on and outside of the curve of FIG. 9 for the addition of Cl 2 and loci on and outside the curve of FIG. 10 for additions of SiHCl 3 plus SiCl 4 and (d) pyrolyzing the feedstock of step (b) at said pyrolysis temperature. 22. A method as in claim 21 where the pyrolysis temperatures are additionally limited to values corresponding to loci on the curves of FIGS. 8 through 10.