Fast optical inspection of operations of large-area active-matrix backplane by gate modulation imaging

Abstract We report herein a fast optical inspection technique for the operation of large-area active-matrix (AM) backplanes by means of gate modulation (GM) imaging measurements. The technique is based on highly sensitive difference-image sensing between alternately biased gate-on and gate-off states for optical microscope images with many AM pixels. The use of a high-frame-rate complementary-metal-oxide-semiconductor image sensor and a high-speed image-subtraction module facilitates the bulk inspection of 30,000 pixels within 3 min, as is demonstrated using an all-printed and flexible AM backplane composed of one-transistor–one-capacitor cells arranged at a 150 pixel-per-inch resolution. We also demonstrate that the technique is very useful and effective not only in quickly identifying both defective transistors and capacitors by examining a zoomed-out image, but also in identifying the origin of defects within channel layers or capacitors by investigating an expanded image.