Methods of forming CIGS films
Methods for forming CIGS films are provided. According to an aspect of the invention, a method of forming a CIGS film includes a precursor step, which includes simultaneously evaporating Cu, In, Ga, Se, and Sb onto a substrate. The Se is incident on the substrate at a rate of at least 20 Å/s. The method also includes a selenization step, which includes evaporating Se over the substrate after the precursor step.
1. A method of forming a CIGS film, the method comprising:
a precursor step comprising simultaneously evaporating Cu, In, Ga, Se, and Sb onto a substrate, wherein the Se is incident on the substrate at a rate of at least 20 Å/s and the Sb is incident on the substrate at a rate of at least 0.2 Å/s; and
a selenization step comprising evaporating Se over the substrate after the precursor step.
2. The method according to claim 1 , wherein the precursor step further comprises maintaining the substrate at a first temperature during a first time period.
3. The method according to claim 2 , wherein the selenization step further comprises:
maintaining the substrate at a second temperature that is higher than the first temperature during a second time period; and
subsequently maintaining the substrate at a third temperature that is higher than the second temperature during a third time period.
4. The method according to claim 2 , wherein the first temperature is below approximately 350° C.
5. The method according to claim 3 , wherein the selenization step further comprises:
after the third time period, stopping the evaporation of the Se when the temperature of the substrate falls below a fourth temperature that is lower than the second temperature.
6. The method according to claim 3 , wherein the third temperature is between approximately 400° C. and approximately 610° C.
7. The method according to claim 3 , wherein the third temperature is between approximately 470° C. and approximately 610° C.
8. The method according to claim 1 , wherein a ratio of Cu/(In+Ga) deposited onto the substrate during the precursor step is between 0.75 and 1.
9. The method according to claim 1 , wherein a ratio of Ga/(In+Ga) deposited onto the substrate during the precursor step is approximately 0.33.
10. The method according to claim 1 , wherein a ratio of Ga/(In+Ga) deposited onto the substrate during the precursor step is approximately 0.5.
11. The method according to claim 1 , wherein a ratio of Sb/(Cu+In+Ga) deposited onto the substrate during the precursor step is between 0.01 and 0.04.
12. The method according to claim 1 , wherein a ratio of Se/(Cu+In+Ga) deposited onto the substrate during the precursor step is between 0.88 and 1.8.
13. The method according to claim 1 , wherein the Se is incident on the substrate at a rate of approximately 30 Å/s during the selenization step.
14. The method according to claim 1 , wherein the precursor step further comprises stepping fluxes of the Ga and the In to produce a gradient of the Ga in the film.
15. A method of forming a CIGS film, the method comprising:
a precursor step comprising simultaneously evaporating Cu, In, Ga, Se, and Sb onto a substrate, wherein the Se is incident on the substrate at a rate of at least 20 Å/s; and
a selenization step comprising evaporating Se over the substrate after the precursor step, wherein:
the precursor step further comprises maintaining the substrate at a first temperature during a first time period, and
the selenization step further comprises:
maintaining the substrate at a second temperature that is higher than the first temperature during a second time period; and
subsequently maintaining the substrate at a third temperature that is higher than the second temperature during a third time period.
16. The method according to claim 15 , wherein the selenization step further comprises:
after the third time period, stopping the evaporation of the Se when the temperature of the substrate falls below a fourth temperature that is lower than the second temperature.
17. The method according to claim 15 , wherein the first temperature is below approximately 350° C.
18. The method according to claim 15 , wherein the third temperature is between approximately 400° C. and approximately 610° C.
19. The method according to claim 15 , wherein the third temperature is between approximately 470° C. and approximately 610° C.
20. A method of forming a CIGS film, the method comprising:
a precursor step comprising simultaneously evaporating Cu, In, Ga, Se, and Sb onto a substrate, wherein the Se is incident on the substrate at a rate of at least 20 Å/s; and
a selenization step comprising evaporating Se over the substrate after the precursor step,
wherein the precursor step further comprises stepping fluxes of the Ga and the In to produce a gradient of the Ga in the film.