Compare to the conventional twisted nematic (TN) mode TFT-LCD fabrication process, so far suggested method [1][2][3][4][5][6] for the wide viewing angle modes require extra mask-counts. Patterning of the color filter common electrode to achieve the multi-domain vertical alignment (VA) mode costs additional process step. In addition, to avoid improper disclinations, strict alignment margin is necessary. Enhanced vertical alignment (EVA) mode has been developed where the multi-domain cell is formed by the interaction between fringe fields of the pixel electrodes and protrusions on the TFTarray panel. Compared to the TN-mode, since the common electrode is not patterned, EVA mode does not require any additional mask-count. Using the combinations of multi-layer overlap patterns with gate metal, gate dielectrics, passivation nitride, and source/drain metal, protrusions can be formed during the normal TFT-array fabrication process. Viewing angle of the EVA mode can even surpass other wide viewing modes.

In order to simplify a-Si TFT array manufacturing process, advanced 4 mask process of low resistant metal and new pixel electrode with improved unit process was developed. Slit photolithography with continuous dry etching process on the basis of metal dry etching cleared chronic problems of currently adopted 4 mask process and new combination of material and etchant for wet etching process made it possible to achieve stabilized wet etching and reduce total process steps. Our final version of a-Si TFT process architecture applicable to both notebook and monitor devices, will reinforce competitive power of TFT-LCD by improved displaying performance and ultimate process simplification.

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