Phosphorous trifluoride co-gas for carbon implants
Processes and systems for carbon ion implantation include utilizing phosphorous trifluoride (PF 3 ) as a co-gas with carbon oxide gas, and in some embodiments, in combination with the lanthanated tungsten alloy ion source components advantageously results in minimal oxidation of the cathode and cathode shield. Moreover, acceptable levels of carbon deposits on the arc chamber internal components have been observed as well as marked reductions in the halogen cycle, i.e., WF x formation.
1. A process for implanting carbon into a substrate, the process comprising:
ionizing a carbon oxide gas source and a co-gas comprising phosphorous trifluoride in an ion source chamber to produce carbon ions and phosphorous oxide;
detecting formation of phosphorous oxides based on analysis of atomic mass unit spectra;
determining a final ratio between the carbon oxide gas source and the co-gas comparing the phosphorous trifluoride when the phosphorous oxides are no longer detectable; and
implanting the carbon ions into the substrate.
2. The process of claim 1 , wherein the carbon oxide source comprises carbon suboxide, carbon monoxide, carbon dioxide, a carbon containing gas and an oxygen gas mixture or combinations thereof.
3. The process of claim 1 , wherein the ion source chamber comprises one or more components formed of or coated with lanthanum tungsten.
4. The process of claim 3 , wherein the one or more components are selected from the group consisting of a cathode, cathode shield, a repeller, a liner, an arc slit, a source chamber wall, a liner, aperture plates, extraction electrodes, and an arc chamber body.
5. The process of claim 1 , wherein the phosphorous trifluoride relative to the carbon oxide gas is at a ratio such that formation of the phosphorous oxides is at about zero.
6. The process of claim 1 , wherein the carbon oxide gas is carbon monoxide and reacts with the phosphorous trifluoride in accordance with reaction scheme I having corresponding atomic mass units shown in parenthesis:
CO+PF 3 C(12)+O(16)+F(19)+CO(28)+P(31)+CF(31)+PF(50). I.
7. The process of claim 1 , wherein the carbon oxide gas is carbon dioxide and reacts with the phosphorous trifluoride in accordance with reaction scheme II having corresponding atomic mass units shown in parenthesis:
CO 2 +PF 3 C(12)+O(16)+F(19)+CO(28)+P(31)+CF(31)+PF(50). II.
8. The process of claim 3 , wherein the lanthanated tungsten comprises lanthanum in an amount from 1 to 3% by weight.
9. A process for implanting carbon ions into a workpiece, the process comprising:
supplying a mixture of a carbon oxide gas and a phosphorous trifluoride gas to an ion source, wherein the ion source and an ion implantation system containing the ion source comprises a cathode, a cathode shield, and/or a repeller formed of or coated with lanthanum tungsten;
ionizing the carbon oxide gas and the phosphorous trifluoride gas with the ion source at a stoichiometry effective to create a feedstream of ionized carbon and a byproduct comprising phosphorous oxides, wherein the stoichiometry is in accordance with reaction scheme III having corresponding atomic mass units shown in parenthesis:
19CO+7PF 3 +4LaW 17C + +O+20F+2CO+P+PO+2La 2 O 3 +3W+WO 3 +P 4 O 6 . III.
extracting the ionized carbon within the plasma to form an ion beam; and
exposing the workpiece to the ion beam to implant the ionized carbon into the workpiece.
10. The process of claim 9 , wherein the carbon oxide gas is selected from the group of gases consisting of carbon monoxide, carbon dioxide, carbon suboxide, a carbon-containing gas and an oxygen gas mixture, and combinations thereof.
11. The process of claim 9 , further comprising evacuating the phosphorous oxides from the ion source chamber.
12. The process of claim 9 , wherein the lanthanated tungsten comprises lanthanum in an amount from 1 to 3% by weight component or the coating, respectively.