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 information. The results from electrical test structures for routine monitoring of key process parameters such as line width, edge-taper width, layer-to-layer alignment, and metal coverage are compared with those from traditional metrology methods. In all cases, the correlation coefficient R was near unity, R2≥ 0.97, demonstrating that electrical test structures have sufficient accuracy for process-control applications. For the structures used, the line width, edge-taper width, and layer-to-layer-alignment electrical measurements have uncertainties of less than 0.1 µm. The test structures are all compatible with typical thin-film-transistor (TFT) array processing.