Method of fabricating CIGS by selenization at high temperature

A method for processing a substrate in a combinatorial manner comprising:

• forming a plurality of Cu—In—Ga precursor films on site isolated regions of the substrate, wherein a composition of the Cu—In—Ga precursor films is varied in a combinatorial manner among the site isolated regions;
• heating the substrate to a first temperature between about 350° C. and about 450° C. in an atmosphere comprising a Se-containing gas for a first period of time sufficient to partially selenize the precursor film;
• thereafter heating the substrate to a second temperature at 625° C. in an atmosphere comprising a Se-containing gas for a second period of time sufficient to further selenize the precursor film;
• thereafter removing the Se-containing gas from the heating atmosphere;
• and
• continuing the heating the substrate at the second temperature for a third period of time sufficient to allow Ga migration in the selenized film to influence the Ga distribution through the depth of the film,
• wherein the Se-containing gas is H2Se;
• wherein the Cu concentration in the Cu—In—Ga precursor film is between about 0.8 and 1.0 and is calculated as (Cu/(In +Ga));
• wherein the removing the Se-containing gas prevents formation of a thick MoSe2 layer at a contact layer comprising Mo, the contact layer disposed in contact with the precursor film;
• and
• wherein the partial selenization of the precursor film secures the In in a selenized state and prevents agglomeration of In.