Display with shallow contact holes and reduced metal residue at planarization layer steps

Abstract

Thin-film transistor circuitry for a display may include conductive layers such as transparent conductive layers and metal layers and may include dielectric layers. The dielectric layers may include buffer layers, interlayer dielectric, gate insulator, and organic planarization layers. The organic planarization layers may be patterned photolithographically to form vias, trenches, and other structures. Trenches may be formed by removing the planarization layer in a strip. When planarization material is removed for forming a trench or other structure, a step is formed in the planarization material. Metal lines such as data lines and other signal lines may cross steps in the planarization material. To prevent shorts between lines, a step may have protrusions that help eliminate metal etch residue. Vias may be reduced in depth by forming metal bumps and dielectric bumps under the vias and by forming other via structures.