Flexible active matrix display
View Patent ↗High resolution active matrix structures are fabricated using techniques applicable to flexible substrates. A backplane layer including active semiconductor devices is formed using a semiconductor-on-insulator substrate. The substrate is thinned using a layer transfer technique or chemical/mechanical processing. Driver transistors are formed on the semiconductor layer of the substrate along with additional circuits that provide other functions such as computing or sensing. Contacts to passive devices such as organic light emitting diodes may be provided by heavily doped regions formed in the handle layer of the substrate and then isolated. A gate dielectric layer may be formed on the semiconductor layer, which functions as a channel layer, or the insulator layer of the substrate may be employed as a gate dielectric layer.
1. An active matrix structure comprising:
a crystalline semiconductor layer adjoining a buried insulator layer;
a backplane layer on a top side of the buried insulator layer, the backplane layer including an array of electrically isolated, active semiconductor devices, the crystalline semiconductor layer being incorporated within the active semiconductor devices, a dielectric layer encapsulating the active semiconductor devices, and electrical conductors extending within the dielectric layer and electrically connected to the active semiconductor devices;
a frontplane formed on a bottom side of the buried insulator layer and including a plurality of passive devices, a plurality of first highly doped contact regions adjoining the bottom side of the buried insulator layer and electrically connected to the active semiconductor devices, a plurality of second highly doped contact regions adjoining the bottom side of the buried insulator layer and electrically connected to the electrical conductors within the dielectric layer, a plurality of first electrodes electrically coupled to the first highly doped contact regions and to the passive devices, a plurality of second electrodes electrically coupled to the second highly doped contact regions and to the passive devices, and an encapsulation layer encapsulating the passive devices, the first and second highly doped contact regions, and the first and second electrodes.
2. The active matrix structure of claim 1 , wherein the semiconductor layer includes a plurality of electrically isolated crystalline silicon layers adjoining the buried insulator layer, the active semiconductor devices including source/drain regions and gate structures adjoining the electrically isolated crystalline silicon layers, and the passive devices include organic light emitting diodes.
3. The active matrix structure of claim 2 , wherein the first and second highly doped contact regions are comprised of highly doped silicon.
4. The active matrix structure of claim 2 , wherein the encapsulation layer is optically transparent.
5. The active matrix structure of claim 4 , wherein one or more of the first and second electrodes include a reflective surface for reflecting light emitted by the organic light emitting diodes through the transparent encapsulation layer.
6. The active matrix structure of claim 4 , wherein the buried insulator layer includes a buried oxide layer.