Laser annealing apparatus, TFT device and annealing method of the same

• US 6,943,086 B2
• Filed: 10/10/2002
• Issued: 09/13/2005
• Est. Priority Date: 10/10/2001
• Status: Expired due to Term

• Current Assignee: Panasonic Liquid Crystal Display Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Hitachi, Ltd.
• Inventors: Uto, Sachio, Hatano, Mutsuko, Nakata, Toshihiko, Yamaguchi, Shinya, Hongo, Mikio, Nomoto, Mineo, Ohkura, Makoto
• Primary Examiner(s): Nelms, David
• Assistant Examiner(s): Lee, Calvin
• Application Number:
  US10/267,680
• Publication Number:
  US 20030068836A1
• Time in Patent Office: 1,069 Days
• Field of Search: 359273-287, 372 12- 16, 372 26- 29, 372 92-103, 372/29.02, 372/98, 372/101, 372/107, 438/308, 438/660, 438/148, 438/384, 2191216-1218, 21912173- 77, 21912182-12185
• US Class Current: 438/308
• CPC Class Codes: B23K 26/0622 by shaping pulses
• CPC Class Codes: B23K 26/064 by means of optical elements, e.g. lenses, mirrors or prisms
• CPC Class Codes: B23K 26/0648 comprising lenses
• CPC Class Codes: B23K 26/066 by using masks
• CPC Class Codes: B23K 26/0665 by beam condensation on the workpiece, e.g. for focusing
• CPC Class Codes: B23K 26/0732 into a rectangular shape
• CPC Class Codes: H01L 21/02422 Non-crystalline insulating materials, e.g. glass, polymers
• CPC Class Codes: H01L 21/02532 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/02678 Beam shaping, e.g. using a mask
• CPC Class Codes: H01L 21/02683 Continuous wave laser beam
• CPC Class Codes: H01L 21/268 using electromagnetic radiation, e.g. laser radiation
• CPC Class Codes: H01L 27/1285 using control of the annealing or irradiation parameters, e.g. using different scanning direction or intensity for different transistors
• CPC Class Codes: H01L 27/1296 adapted to increase the uniformity of device parameters
• CPC Class Codes: H01L 29/04 characterised by their crystalline structure, e.g. polycrystalline, cubic or particular orientation of crystalline planes characterised by physical imperfections H01L29/30
• CPC Class Codes: H01L 29/66757 Lateral single gate single channel transistors with non-inverted structure, i.e. the channel layer is formed before the gate
• CPC Class Codes: H01L 29/78675 with normal-type structure, e.g. with top gate

Abstract

A laser beam is concentrated using an objective lens and radiated on a amorphous silicon film or polycrystalline silicon film having a grain size of one micron or less, the laser beam being processed from a continuous wave laser beam (1) to be pulsed using an EO modulator and to have arbitrary temporal energy change while pulsing ; (2) to have an arbitrary spatial energy distribution using a beam-homogenizer, filter having an arbitrary transmittance distribution, and rectangular slit; and (3) to eliminate coherency thereof using a high-speed rotating diffuser. In this manner, it is possible to realize a liquid crystal display device in which a driving circuit comprising a polycrystalline silicon film having substantially the same properties as a single crystal is incorporated in a TFT panel device.

Claims

1. A laser annealing apparatus comprising:

a laser beam source to emit a laser beam;

a variable transmittance filter passing the laser beam therethrough and variably adjusting a transmittance thereof to a desired value;

a modulation device modulating an amplitude of the laser beam in terms of time;

a energy distribution adjuster device adjusting an energy distribution in a cross-section of the laser beam; and

a projecting optical system projecting the laser beam which has passed through the variable transmittance filter, the modulation device and the energy distribution adjuster device onto a surface of a sample.

2. The laser annealing apparatus according to claim 1, wherein the modulation device to modulate the amplitude of the laser beam in terms of time is a combination of an electro-optical modulator and a polarized beam splitter.

3. The laser annealing apparatus according to claim 1, wherein the energy distribution adjuster device comprises a beam-homogenizer and a rectangular slit.

4. The laser annealing apparatus according to claim 1, wherein the laser beam source generates second harmonics of a continuous wave YAG laser or a continuous wave YVO₄ laser.

5. The laser annealing apparatus according to claim 1, comprising an auto focusing mechanism for controlling a relationship between focal positions of the projecting optical system and the sample surface.

6. The laser annealing apparatus according to claim 1, comprising:

a stage that is movable in a state supporting the sample; and

a coherency reducing device to reduce a coherency of the laser beam emitted from the laser beam source;

wherein the projecting optical system is to effect projection of the laser beam onto the surface of the sample by projecting the laser beam which has passed through the modulation device and the energy distribution adjuster device.

7. The laser annealing apparatus according to claim 1, comprising a stage that is moveable in a state supporting a sample.

8. The laser annealing apparatus according to claim 1, wherein a cross-sectional form of the laser beam projected onto the surface of the sample has a rectangular shape or a linear shape, a lengthwise direction of which is defined as a first direction, and the surface of the sample is scanned with the rectangular or linear cross-sectional form of the laser beam in a second direction perpendicular to the first direction.

9. The laser annealing apparatus according to claim 8, wherein the energy distribution adjuster device adjusts an energy distribution of the cross-sectional form of the laser beam projected onto the surface of the sample to be uniform in the first direction and to vary in the second direction.

10. The laser annealing apparatus according to claim 9, wherein the laser beam source emits the laser beam having the Gaussian energy distribution in its cross-section, and the energy distribution adjuster device outputs the laser beam to have the Gaussian energy distribution in the second direction in the cross-sectional form thereof projected onto the surface of the sample.

11. The laser annealing apparatus according to claim 1, wherein the variable transmittance filter is a continuously variable transmittance filter passing the laser beam therethrough and continuously variably adjusting a transmittance thereof in real-time.

14. The laser annealing apparatus according to claim 2, wherein the modulation device to modulate the amplitude of the laser beam in terms of time is a combination of an electro-optical modulator and a polarized beam splitter.

12. A laser annealing apparatus comprising:

a stage that is movable in a state supporting a sample;

a laser beam source emitting a laser beam;

a variable transmittance filter passing the laser beam therethrough and adjusting a transmittance thereof to a desired value;

a modulation device modulating an amplitude of the laser beam in terms of time;

a shaping device to shape a cross-sectional form of the laser beam;

a coherency reducing device to reduce a coherency of the laser beam; and

a projecting optical system projecting the laser beam which has passed through the variable transmittance filter, the modulation device, the shaping device and the coherency reducing device onto a surface of the sample.

13. The laser annealing apparatus according to claim 12, wherein the coherency reducing device is a diffuser rotating at a high speed.

15. The laser annealing apparatus according to claim 12, comprising a beam-homogenizer adjusting an energy distribution of the laser beam in the cross-section form thereof.

16. The laser annealing apparatus according to claim 12, wherein the laser beam source generates second harmonics of a continuous wave YAG laser or a continuous wave YVO₄ laser.

17. The laser annealing apparatus according to claim 12, wherein a cross-sectional form of the laser beam projected onto the surface of the sample has a rectangular shape or a linear shape, a lengthwise direction of which is defined as a first direction, and the surface of the sample is scanned with the rectangular or linear cross-sectional form of the laser beam in a second direction perpendicular to the first direction.

18. The laser annealing apparatus according to claim 12, wherein the variable transmittance filter is a continuously variable transmittance filter passing the laser beam therethrough and continuously variably adjusting a transmittance thereof in real-time.

19. A laser annealing apparatus comprising:

a stage that is movable in a state supporting a sample;

a laser beam source emitting a laser beam;

a variable transmittance filter passing the laser beam therethrough and adjusting a transmittance thereof to a desired value;

a shutter selectively passing the laser beam emitted through the variable transmittance filter;

a modulation device modulating in terms of time an amplitude of the laser beam which has passed through the shutter within a time period when the shutter is open;

an energy distribution adjuster device adjusting the laser beam to have a desired spatial energy distribution;

a coherency reducing device to reduce a coherency of the laser beam; and

a projecting optical system to effect projection of the laser beam which has passed through the variable transmittance filter, the shutter, the modulation device, the energy distribution adjuster device and the coherency reducing device onto a surface of the sample.

20. The laser annealing apparatus according to claim 19, wherein the modulation device to modulate the amplitude of the laser beam in terms of time is a combination of an electro-optical modulator and a polarized beam splitter.

21. The laser annealing apparatus according to claim 19, wherein the energy distribution adjuster device comprises a beam-homogenizer and a rectangular slit.

22. The laser annealing apparatus according to claim 19, wherein the laser beam source generates second harmonics of a continuous wave YAG laser or a continuous wave YVO₄ laser.

23. The laser annealing apparatus according to claim 19, wherein a cross-sectional form of the laser beam projected onto the surface of the sample has a rectangular shape or a linear shape, a lengthwise direction of which is defined as a first direction, and the surface of the sample is scanned with the rectangular or linear cross-sectional form of the laser beam in a second direction perpendicular to the first direction.

24. The laser annealing apparatus according to claim 23, wherein the energy distribution adjuster device adjusts an energy distribution of the cross-sectional form of the laser beam projected onto the surface of the sample to be uniform in the first direction and to vary in the second direction.

25. The laser annealing apparatus according to claim 19, wherein the variable transmittance filter is a continuously variable transmittance filter passing the laser beam therethrough and continuously variably adjusting a transmittance thereof in real-time.

26. A laser annealing apparatus comprising:

a stage that is movable in a state supporting a sample;

a laser beam source emitting a laser beam;

a variable transmittance filter passing the laser beam therethrough and adjusting a transmittance thereof to a desired value;

a shutter selectively passing the laser beam emitted through the variable transmittance;

a modulation device to modulating an amplitude of the laser beam which has passed through the shutter in terms of time;

an energy distribution adjuster device adjusting a spatial energy distribution of the laser beam; and

a projecting optical system to effect projection of the laser beam which has passed through the variable transmittance filter, the shutter, the modulation device and the energy distribution adjuster device onto a surface of the sample.

27. The laser annealing apparatus according to claim 26, wherein the modulation device to modulate the amplitude of the laser beam in terms of time is a combination of an electro-optical modulator and a polarized beam-splitter.

28. The laser annealing apparatus according to claim 26, wherein the energy distribution adjuster device comprises a beam-homogenizer and a rectangular slit.

29. The laser annealing apparatus according to claim 26, wherein the laser beam source generates second harmonics of a continuous wave YAG laser or a continuous wave YVO₄ laser.

30. The laser annealing apparatus according to claim 26, wherein a cross-sectional form of the laser beam projected onto the surface of the sample has a rectangular shape or a linear shape, a lengthwise direction of which is defined as a first direction, and the surface of the sample is scanned with the rectangular or linear cross-sectional form of the laser beam in a second direction perpendicular to the first direction.

31. The laser annealing apparatus according to claim 30, wherein the energy distribution adjuster device adjusts an energy distribution of the cross-sectional form of the laser beam projected onto the surface of the sample to be uniform in the first direction and to vary in the second direction.

32. The laser annealing apparatus according to claim 26, wherein the variable transmittance filter is a continuously variable transmittance filter passing the laser beam therethrough and continuously variably adjusting a transmittance thereof in real-time.