18.3: Implementation of a New Wide Viewing Angle Mode for TFT‐LCDs

Abstract Compare to the conventional twisted nematic (TN) mode TFT‐LCD fabrication process, so far suggested method 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 TFT‐array 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.