TFT matrix liquid crystal device having data source lines and drain means of etched and doped single crystal silicon

• US 5,546,204 A
• Filed: 05/26/1994
• Issued: 08/13/1996
• Est. Priority Date: 05/26/1994
• Status: Expired due to Term

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: Ellis, Roger K.
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): Ton, Toan
• Application Number:
  US08/249,408
• Time in Patent Office: 810 Days
• Field of Search: 359/59, 257/59, 257/249
• US Class Current: 349/46
• CPC Class Codes: G02F 1/134345 Subdivided pixels, e.g. for grey scale or redundancy
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G02F 2202/105 single crystal Si

Abstract

An active matrix array for liquid crystal displays which provides for a large aperture ratio. A layer of single crystal silicon is disposed over a glass substrate and etched and doped to form multiple source and drain regions for an array of thin film transistors (TFTs). Multiple gate buses are laid across the source and drain regions to form the TFTs. The drain regions each electrically contact a transparent electrode used in switching an individual pixel in a liquid crystal display. The TFTs formed do not encroach significantly into the pixel aperture and the conduction lines are constructed at minimal photolithographical requirements.

Claims

1. An active matrix for a liquid crystal display comprising:

a substrate;

a plurality of parallel data source lines disposed on said substrate;

a plurality of drain means disposed proximate to said data source lines, wherein the plurality of data source lines and drain means are formed from a layer of single crystal silicon which has been etched and selectively doped;

a transparent insulating layer disposed over said data source lines, said substrate and a portion of said drain means;

a plurality of parallel gate lines disposed over the insulating layer so as to intersect said data source lines and said drain means to form a plurality of contactless thin film transistors (TFT'"'"'s); and

a plurality of transparent electrodes disposed over the insulating layer, each of the transparent electrodes in electrical contact with one of the plurality of drain means.

2. The active matrix for a liquid crystal display of claim 1 wherein each of the drain means is located proximate to an intersection of the gate line and the data source line.

3. The active matrix for a liquid crystal display of claim 1 wherein four of the drain means are located proximate to an intersection of the gate lines and the data source lines so as create four of the TFTs, each of the drain means is in electrical contact with one of the plurality of transparent electrodes so as to provide a half tone configuration for the liquid crystal display.

4. The active matrix for a liquid crystal display of claim 3 wherein a switching voltage for each of the TFT'"'"'s is determined by adjusting width to length ratios of the TFT'"'"'s.

5. The active matrix for a liquid crystal display of claim 1 wherein each of the data source lines runs parallel to a metallic conductor strip, electrical contacts are provided between the metallic conductor strips and the plurality of data source lines at predetermined intervals.

6. The active matrix for a liquid crystal display of claim 5 wherein four of the drain means are located proximate to an intersection of the gate lines and the data source lines so as create four of the TFTs, each of the drain means is in electrical contact with one of the plurality of transparent electrodes so as to provide a half tone configuration for the liquid crystal display.

7. The active matrix for a liquid crystal display of claim 6 wherein a switching voltage for each of the TFT'"'"'s is determined by adjusting width to length ratios of the drains.

8. The active matrix for a liquid crystal display of claim 1 wherein the plurality gate lines are comprised of indium tin oxide (ITO).

9. The active matrix for a liquid crystal display of claim 1 wherein the plurality gate lines are comprised of polysilicon.

10. The active matrix for a liquid crystal display of claim 1 wherein the plurality gate lines are comprised of a refractory metal silicide.

11. An active matrix for a liquid crystal display comprising:

a transparent substrate;

a first layer disposed on said transparent substrate and formed into a plurality of parallel data source lines and drain regions for a plurality of thin film transistors (TFT), wherein the plurality of data source lines and drain means are formed from a layer of single crystal silicon which has been etched and selectively doped;

an oxide layer disposed over the data source lines, said transparent substrate and a portion of each of the drain regions of the first silicon layer;

a plurality of gate lines disposed over the oxide layer which intersects the source and drains so as to form plurality of TFT'"'"'s; and

a plurality of transparent electrodes laid out in an array, each of said transparent electrodes is in electrical contact with one of the plurality of drain regions.

12. The active matrix for a liquid crystal display of claim 11 wherein each of the drains is located proximate to an intersection of the gate lines and the data source lines.

13. The active matrix for a liquid crystal display of claim 11 wherein four of the drains are located proximate to an intersection of the gate lines and the data source lines so as create four of the TFTs, each of the drains is in electrical contact with one of the plurality of transparent electrodes so as to provide a half tone configuration for the liquid crystal display.

14. The active matrix for a liquid crystal display of claim 13 wherein a switching voltage for each of the TFT'"'"'s is determined by adjusting width to length ratios of the TFT'"'"'s.

15. The active matrix for a liquid crystal display of claim 11 wherein each of the data source lines runs parallel to a metallic conductor strip, electrical contacts are provided between the metallic conductor strips and the plurality of data source lines at predetermined intervals.

16. The active matrix for a liquid crystal display of claim 15 wherein four of the drains are located proximate to an intersection of the gate lines and the data source lines so as create four of the TFTs, each of the drains is in electrical contact with one of the plurality of transparent electrodes so as to provide a half tone configuration for the liquid crystal display.

17. The active matrix for a liquid crystal display of claim 16 wherein a switching voltage for each of the TFT'"'"'s is determined by adjusting width to length ratios of the drains.

18. The active matrix for a liquid crystal display of claim 11 wherein the plurality gate lines are comprised of indium tin oxide (ITO).

19. The active matrix for a liquid crystal display of claim 11 wherein the plurality gate lines are comprised of polysilicon.

20. The active matrix for a liquid crystal display of claim 11 wherein the plurality gate lines are comprised of a refractory metal silicide.