Interlayer insulation of TFT LCD device having of silicon oxide and silicon nitride

• US 6,160,600 A
• Filed: 11/18/1996
• Issued: 12/12/2000
• Est. Priority Date: 11/17/1995
• Status: Expired due to Term

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Nishi, Takeshi, Yamazaki, Shunpei
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): TON, MINH TOAN T
• Application Number:
  US08/751,365
• Time in Patent Office: 1,485 Days
• Field of Search: 349/141, 349/128, 349/42, 349/149, 349/92, 349/122, 349/138
• US Class Current: 349/138
• CPC Class Codes: G02F 1/13306 Circuit arrangements or driving methods for the control of single liquid crystal cells G02F1/132, G02F1/133382 take precedence
• CPC Class Codes: G02F 1/13363 Birefringent elements, e.g. for optical compensation
• CPC Class Codes: G02F 1/134363 for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]
• CPC Class Codes: G02F 1/13454 Drivers integrated on the active matrix substrate G02F1/136277 takes precedence
• CPC Class Codes: G02F 1/1393 the birefringence of the liquid crystal being electrically controlled, e.g. ECB-, DAP-, HAN-, PI-LC cells G02F1/1396, G02F1/141 take precedence
• CPC Class Codes: G02F 2203/02 reflective

Abstract

There is disclosed a lightweight and small liquid crystal display which achieves low power consumption and in which the optical anisotropy of the liquid crystal material is compensated for in order to enhance the viewing angle characteristics and the response speed of the liquid crystal material. Display electrodes and a common electrode are formed on one of the substrates. The orientation of the liquid crystal material is of the HAN (hybrid alignment nematic) type. This compensates for the optical anisotropy of the liquid crystal material and improves the response speed.

Claims

1. A reflective type liquid crystal display device comprising:

a first insulating substrate having transparency;

a reflecting layer;

a second insulating substrate disposed opposite to the first insulating substrate, and at least a part of said second insulating substrate covering the reflecting layer;

a liquid crystal material interposed between the first and second substrates;

a first electrode formed over the first insulating substrate;

a first conducting line for applying electrical signals to the first electrode, said first conducting line being formed over the first insulating substrate;

a first thin film transistor formed over the first insulating substrate as a switching element and electrically connected to the first electrode and the first conducting line,

said first thin film transistor comprising;

a crystalline semiconductor island formed over the first insulating substrate;

source and drain regions formed in the crystalline semiconductor island;

a gate electrode formed adjacent to the crystalline semiconductor island having a gate insulating film therebetween,

a pair of low concentration regions each being adjacent to the source and drain regions in the crystalline semiconductor island;

an interlayer insulating film covering the first thin film transistor, said interlayer insulating film being a multilayer film of silicon oxide and silicon nitride;

a second electrode formed over the first insulating substrate and electrically insulated from the first electrode and from the first conducting line; and

a second conducting line for applying electrical signals to the second electrode, said second conducting line being formed on the first insulating substrate,

wherein the liquid crystal material is operated by a parallel electric field to the first substrate, said parallel electric field being generated between the first and second electrodes,

wherein the liquid crystal material is oriented in a hybrid alignment nematic mode.

2. A liquid crystal display device according to claim 1, wherein said first and second electrodes have transparency.

3. A liquid crystal display device according to claim 2, wherein said first and second electrodes are alternately protruding lines of electrodes which are nested in each other alternately with a given spacing therebetween.

4. A device according to claim 1, wherein each of said first and second electrodes comprises ITO material.

5. A device according to claim 1, wherein each of first and second insulating substrates is one selected from the group consisting of glass, quartz and polyethylene sulfate.

10. A device according to claim 4, wherein each of first and second insulating substrate is one selected from the group consisting of glass, quartz and polyethylene sulfate.

6. A reflective type liquid crystal display device comprising:

a first insulating substrate having transparency;

a reflecting layer;

a second insulating substrate disposed opposite to the first insulating substrate, at least a part of said second insulating substrate covering the reflecting layer;

a liquid crystal material interposed between the first and second substrates;

a first electrode formed over the first insulating substrate;

a first conducting line for applying electrical signals to the first electrode, said first conducting line being formed over the first insulating substrate;

a first thin film transistor formed over the first insulating substrate as a switching element and electrically connected to the first electrode and the first conducting line;

said first thin film transistor comprising;

a crystalline semiconductor island formed over the first insulating substrate;

source and drain regions formed in the crystalline semiconductor island;

a gate electrode formed adjacent to the crystalline semiconductor island having a gate insulating film therebetween,

a pair of low concentration regions each being adjacent to the source and drain regions in the crystalline semiconductor island;

a second thin film transistor formed over the first insulating substrate for driving the first thin film transistor;

an interlayer insulating film covering each of the first and second thin film transistors, said interlayer insulating film being a multilayer film of silicon oxide and silicon nitride;

a second electrode formed over the first insulating substrate and electrically insulated from the first electrode and from the first conducting line;

a second conducting line for applying electrical signals to the second electrode, said second conducting line being formed over the first insulating substrate;

a biaxial film disposed over the first insulating substrate; and

a polarizing plate disposed on the biaxial film,

wherein the liquid crystal material is operated by a parallel electric field to the first substrate, said parallel electric field being generated between the first and second electrodes,

wherein the liquid crystal material is oriented in a hybrid alignment nematic mode.

7. A liquid crystal display device according to claim 6, wherein said first and second electrodes have transparency.

8. A liquid crystal display device according to claim 7, wherein said first and second electrodes are alternately protruding lines of electrodes which are nested in each other alternately with a given spacing therebetween.

9. A device according to claim 6, wherein each of said first and second electrodes comprises ITO.

11. A reflective type liquid crystal display device comprising:

a first insulating substrate having transparency;

a second insulating substrate disposed opposite to the first insulating substrate and having a reflecting layer thereon;

a liquid crystal material interposed between the first and second substrates;

a first electrode formed over the first insulating substrate;

a first conducting line for applying electrical signals to the first electrode, said first conducting line being formed over the first insulating substrate;

a first thin film transistor formed over the first insulating substrate as a switching element and electrically connected to the first electrode and the first conducting line;

said first thin film transistor comprising;

a crystalline semiconductor island formed over the first insulating substrate;

source and drain regions formed in the crystalline semiconductor island;

a gate electrode formed adjacent to the crystalline semiconductor island having a gate insulating film therebetween,

a pair of low concentration regions each being adjacent to the source and drain regions in the crystalline semiconductor island;

a second thin film transistor formed over the first insulating substrate for driving the first thin film transistor, said second thin film transistor including an n-channel third thin film transistor and a p-channel fourth thin film transistor being connected to each other;

an interlayer insulating film covering each of the first and second thin film transistors, said interlayer insulating film being a multilayer film of silicon oxide and silicon nitride;

a second electrode formed over the first insulating substrate and electrically insulated from the first electrode and from the first conducting line; and

a second conducting line for applying electrical signals to the second electrode, said second conducting line being formed over the first insulating substrate,

wherein the liquid crystal material is operated by a parallel electric field to the first substrate, said parallel electric field being generated between the first and second electrodes, and

wherein the liquid crystal material has a first orientation near the first insulating substrate while the liquid crystal material has a second orientation near the second insulating substrate, said second orientation being different from the first orientation.

12. A liquid crystal display device according to claim 11, wherein said first and second electrodes have transparency.

13. A liquid crystal display device according to claim 11, wherein said first and second electrodes are alternately protruding lines of electrodes which are nested in each other alternately with a given spacing therebetween.

14. A device according to claim 11, wherein each of said first and second electrodes comprises ITO material.

15. A device according to claim 11, wherein each of first and second insulating substrate is one selected from the group consisting of glass, quartz and polyethylene sulfate.

16. A reflective type liquid crystal display device comprising:

a first insulating substrate having transparency;

a second insulating substrate disposed opposite to the first insulating substrate;

a reflecting layer on the second insulating substrate;

a liquid crystal material interposed between the first and second substrates;

a first electrode formed over the first insulating substrate;

a first conducting line for applying electrical signals to the first electrode, said first conducting line being formed over the first insulating substrate;

a first thin film transistor formed over the first insulating substrate as a switching element and electrically connected to the first electrode and the first conducting line;

said first thin film transistor comprising;

a crystalline semiconductor island formed over the first insulating substrate;

source and drain regions formed in the crystalline semiconductor island;

a gate electrode formed adjacent to the crystalline semiconductor island having a gate insulating film therebetween,

a pair of low concentration regions each being adjacent to the source and drain regions in the crystalline semiconductor island;

a second thin film transistor formed over the first insulating substrate for driving the first thin film transistor;

an interlayer insulating film covering each of the first and second thin film transistors, said interlayer insulating film being a multilayer film of silicon oxide and silicon nitride;

a second electrode formed over the first insulating substrate and electrically insulated from the first electrode and from the first conducting line; and

a second conducting line for applying electrical signals to the second electrode, said second conducting line being formed over the first insulating substrate,

wherein the liquid crystal material is operated by a parallel electric field to the first substrate, said parallel electric field being generated between the first and second electrodes, and

wherein the liquid crystal material is oriented substantially horizontally to the first insulating substrate near the first insulating substrate while the liquid crystal material is oriented substantially vertically to the second insulating substrate near the second insulating substrate.

17. A liquid crystal display device according to claim 16, wherein said first and second electrodes have transparency.

18. A liquid crystal display device according to claim 16, wherein said first and second electrodes are alternately protruding lines of electrodes which are nested in each other alternately with a given spacing therebetween.

19. A device according to claim 16, wherein each of said first and second electrodes comprises ITO material.

20. A device according to claim 16, wherein each of first and second insulating substrate is one selected from the group consisting of glass, quartz and polyethylene sulfate.

21. A reflective type liquid crystal display device comprising:

a first insulating substrate having transparency;

a reflecting layer;

a second insulating substrate disposed opposite to the first insulating substrate and coupled to the reflecting layer;

a liquid crystal material interposed between the first and second substrates;

a first electrode formed over the first insulating substrate;

a first conducting line for applying electrical signals to the first electrode, said first conducting line being formed over the first insulating substrate;

a first thin film transistor formed over the first insulating substrate as a switching element and electrically connected to the first electrode and the first conducting line;

said first thin film transistor comprising;

a crystalline semiconductor island formed over the first insulating substrate;

source and drain regions formed in the crystalline semiconductor island;

a gate electrode formed adjacent to the crystalline semiconductor island having a gate insulating film therebetween,

a pair of low concentration regions each being adjacent to the source and drain regions in the crystalline semiconductor island;

a second thin film transistor formed over the first insulating substrate for driving the first thin film transistor;

an interlayer insulating film covering each of the first and second thin film transistors, said interlayer insulating film being a multilayer film of silicon oxide and silicon nitride;

a second electrode formed over the first insulating substrate and electrically insulated from the first electrode and from the first conducting line;

a second conducting line for applying electrical signals to the second electrode, said second conducting line being formed over the first insulating substrate,

wherein the liquid crystal material is operated by a parallel electric field to the first substrate, said parallel electric field being generated between the first and second electrodes, and

wherein the liquid crystal material is oriented substantially horizontally to the first substrate near the first substrate while the liquid crystal material is oriented substantially vertically to the second substrate near the second substrate.

22. A device according to claim 21, wherein each of said first and second electrodes comprises ITO material.

23. A device according to claim 21, wherein each of first and second insulating substrate is one selected from the group consisting of glass, quartz and polyethylene sulfate.

24. A method of driving a reflective type liquid crystal display device, said reflective type liquid crystal display device comprising:

a first insulating substrate having transparency,

a reflecting layer;

a second insulating substrate disposed opposite to the first insulating substrate and coupled to the reflecting layer,

a liquid crystal material interposed between the first and second substrates,

a first electrode formed over the first insulating substrate,

a first conducting line for applying electrical signals to the first electrode, said first conducting lines being formed over the first insulating substrate,

a first thin film transistor formed over the first insulating substrate as a switching element and electrically connected to the first electrode and the first conducting line,

said first thin film transistor comprising;

a crystalline semiconductor island formed over the first insulating substrate;

source and drain regions formed in the crystalline semiconductor island;

a gate electrode formed adjacent to the crystalline semiconductor island having a gate insulating film therebetween,

a pair of low concentration regions each being adjacent to the source and drain regions in the crystalline semiconductor island;

a second thin film transistor formed over the first insulating substrate for driving the first thin film transistor,

an interlayer insulating film covering each of the first and second thin film transistors, said interlayer insulating film being a multilayer film of silicon oxide and silicon nitride;

a second electrode formed over the first insulating substrate and electrically insulated from the first electrode and from the first conducting line, and

a second conducting line for applying electrical signals to the second electrode, said second conducting line being formed over the first insulating substrate,

said method comprising the step of;

producing a parallel electric field to the first insulating substrates, said parallel electric field being generated between the first and second electrodes, and

driving the liquid crystal material by the parallel electric field,

wherein the liquid crystal material is oriented substantially horizontally to the first substrate near the first substrate while the liquid crystal material is oriented substantially vertically to the second substrate near the second substrate.

25. A method according to claim 24, wherein each of said first and second electrodes comprises ITO material.

26. A method according to claim 24, wherein each of first and second insulating substrate is one selected from the group consisting of glass, quartz and polyethylene sulfate.