Improving pattern precision of chromium based black matrix by annealing

Black matrix is a major component of color filter used for blocking light in flat panel industry. Films made of chromium (Cr) and its two oxide/nitride combination layers are commonly used in black matrix for its high optical density and material stability. Each single Cr based layer film of the three multilayer combinations was produced on glass and then annealed in low pressure hydrogen environment. Etching, transmittance of visible light, and microstructure of these films without and with annealing were compared. It was found that annealing can mend the interference between the incident and reflected light for Cr based black matrix. Annealing can also improve the undercut defect and thus pattern precision. The lateral etching rates of Cr based films were found to be much lower and close to one another after annealing. It can be explained the film density and adhesion increase caused by the annealing process. This article provides a potential method in color filter fabrication to improve contrast and color interference issues if Cr based black matrix is used in display application.