THIN-FILM-TRANSISTOR PROCESS-CHARACTERIZATION TEST STRUCTURES

Electrical test structures provide a method of rapid, low-cost end-of- process metrology for both materials properties and specific process i nformation. The results from electrical test structures for routine mo nitoring of key process parameters such as line width, edge-taper widt h, layer-to-layer alignment, and metal coverage are compared with thos e from traditional metrology methods. In all cases, the correlation co efficient R was near unity, R-2 greater than or equal to 0.97, demonst rating that electrical test structures have sufficient accuracy for pr ocess-control applications. For the structures used, the line width, e dge-taper width, and layer-to-layer-alignment electrical measurements have uncertainties of less than 0.1 mu m. The test structures are all compatible with typical thin-film-transistor (TFT) array processing.