Flexible display with bent edge regions
An electronic device may have a flexible display with portions that are bent along a bend axis. The display may have display circuitry such as an array of display pixels in an active area. Contact pads may be formed in an inactive area of the display. Signal lines may couple the display pixels to the contact pads. The signal lines may overlap the bend axis in the inactive area of the display. During fabrication, an etch stop may be formed on the display that overlaps the bend axis. The etch stop may prevent over etching of dielectric such as a buffer layer on a polymer flexible display substrate. A layer of polymer that serves as a neutral stress plane adjustment layer may be formed over the signal lines in the inactive area of the display. Upon bending, the neutral stress plane adjustment layer helps prevent stress in the signal lines.
1. A method of forming a display having an active area and an inactive area, the method comprising:
depositing a buffer layer on a polymer substrate;
depositing semiconductor transistor structures on the buffer layer;
forming an etch stop layer directly on the buffer layer;
depositing interlayer dielectric on the etch stop layer over a bend axis in the inactive region of the display;
removing the interlayer dielectric over the bend axis; and
bending the display along the bend axis after removing the interlayer dielectric over the bend axis.
2. The method defined in claim 1 wherein depositing the semiconductor transistor structures comprises depositing the semiconductor transistor structures in the active area.
3. The method defined in claim 2 wherein bending the display comprises bending the display at a right angle.
4. The method defined in claim 2 wherein forming the etch stop layer comprises depositing a layer of material, the method further comprising patterning the layer of material to form the etch stop layer and to form structures in the active area.
5. The method defined in claim 4 wherein depositing the layer of material comprises depositing a layer of metal.
6. A method of forming a display having an active area and an inactive area, comprising:
depositing a buffer layer on a polymer substrate;
depositing semiconductor transistor structures on the buffer layer in the active area;
depositing a layer of metal on the buffer layer;
patterning the layer of metal to form an etch stop layer on the buffer layer and to form structures in the active area;
depositing interlayer dielectric over the etch stop layer;
removing the interlayer dielectric over the etch stop layer;
removing the etch stop layer; and
bending the display along a bend axis after removing the etch stop layer.
7. The method defined in claim 6 wherein removing the etch stop layer comprises wet etching.
8. The method defined in claim 6 further comprising forming metal traces after removing the etch stop layer.
9. The method defined in claim 8 further comprising depositing a polymer neutral stress plane adjustment layer over the metal traces overlapping the bend axis before bending the display.
10. A method of forming a display with an active area and an inactive area, comprising:
depositing an etch stop that prevents over etching of a dielectric layer in the inactive area while etching an interlayer dielectric; and
removing the etch stop over a bend axis after etching the interlayer dielectric; and
bending the display along the bend axis.
11. The method defined in claim 10 further comprising coupling display pixels in the active area to contacts in the inactive area using metal traces that overlap the bend axis.
12. The method defined in claim 11 wherein the display includes a flexible polymer substrate having a surface, wherein the dielectric layer is a buffer layer on the surface of the flexible polymer substrate, and wherein coupling the display pixels comprises forming the metal traces on the buffer layer.
13. The method defined in claim 12 further comprising depositing a neutral stress plane adjustment layer on the metal traces before bending the display along the bend axis.
14. The method defined in claim 10 wherein depositing the etch stop comprises depositing a metal layer.
15. The method defined in claim 10 wherein depositing the etch stop comprises depositing a layer containing indium.
16. The method defined in claim 10 wherein depositing the etch stop comprises depositing an oxide layer that contains indium.