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

• US 20030068836A1
• Filed: 10/10/2002
• Published: 04/10/2003
• Est. Priority Date: 10/10/2001
• Status: Active Grant

• 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
• Granted Patent: US 6,943,086 B2
• Time in Patent Office: Days
• US Class Current: 438/30
• 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:

stage means that are movable in a state supporting a sample;

laser beam source means for emitting a laser beam;

modulation means for modulating in terms of time the energy of the laser beam emitted from the laser beam source means;

energy distribution adjusting means for adjusting said laser beam, emitted from the laser beam source means, to have desired spatial energy distribution;

coherency reducing means for reducing the coherency of said laser beam emitted from the laser beam source means; and

projecting optical system means for projecting onto the surface of said sample the laser beam which has passed through said modulating means, said energy distribution adjusting means, and said coherency reducing means.

5. The laser annealing apparatus according to claim 1, wherein the modulating means for modulating said laser beam in terms of time are an electro-optical modulator.

6. The laser annealing apparatus according to claim 1, wherein said energy distribution controlling means comprise a beam-homogenizer, a filter having desired transmittance distribution, and a rectangular slit.

7. The laser annealing apparatus according to claim 1, wherein said coherency reducing means are a diffuser rotating at a high speed.

8. The laser annealing apparatus according to claim 1, wherein said laser beam source means generate second harmonics of YVO₄ laser.

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

2. A laser annealing apparatus comprising:

stage means that are movable in a state supporting a sample;

laser beam source means for emitting a laser beam;

modulation means for modulating in terms of time the energy of the laser beam emitted from the laser beam source means;

shaping means for shaping the cross sectional form of said laser beam emitted from the laser beam source means;

coherency reducing means for reducing the coherency of said laser beam emitted from the laser beam source means; and

projecting optical system means for projecting onto the surface of said sample the laser beam which has passed through said modulating means, said forming means, and said coherency reducing means.

3. A laser annealing apparatus comprising:

stage means that are movable in a state supporting a sample;

laser beam source means for emitting a laser beam;

modulation means for modulating the energy of the laser beam emitted from the laser beam source means and passed through said shutter means within a time period when said shutter means are on;

energy distribution adjusting means for adjusting said laser beam emitted from the laser beam source means to have desired spatial energy distribution;

coherency reducing means for reducing the coherency of said laser beam emitted from the laser beam source means and

Projecting optical system means for projecting onto the surface of said sample the laser beam which has passed through said modulating means, said energy distribution adjusting means, and said coherency reducing means.

4. A laser annealing apparatus comprising:

stage means that are movable in a state supporting a sample;

laser beam source means for emitting a laser beam;

modulation means for modulating in terms of time the energy of the laser beam emitted from the laser beam source means and passed through said shutter means;

energy distribution adjusting means for adjusting the spatial energy distribution of said laser beam emitted from the laser beam source means; and

projecting optical system means for projecting onto the surface of said sample the laser beam which has passed through said modulating means and said energy distribution adjusting means.

10. A laser annealing method for annealing a thin film formed on the surface of a sample by:

modulating in terms of time the energy of a laser beam emitted from a laser beam source;

adjusting the energy distribution of the laser beam the energy of which has been modulated; and

radiating said laser beam the energy of which has been modulated in terms of time and said energy distribution of which has been adjusted, so as to scan the surface of the sample having the thin film formed on the surface.

13. The laser annealing method according to claim 10, wherein said laser beam is modulated in terms of time using an electro-optical modulator.

14. The laser annealing method according to claim 10, wherein said laser beam energy distribution is adjusted using a beam-homogenizer, a filter having desired transmittance distribution, and a rectangular slit.

11. A laser annealing method for annealing a desired region of a thin film on the surface of a sample by:

modulating in terms of time the energy of a laser beam emitted from a laser beam source;

shaping the cross sectional form of the laser beam the energy of which has been modulated; and

radiating said laser beam the energy of which has been modulated in terms of time and the cross sectional form of which has been shaped, so as to scan the surface of the sample having the thin film formed on the surface.

12. A laser annealing method for partially annealing a thin film on the surface of a sample by:

modulating in terms of time the energy of a laser beam emitted from a laser beam source;

adjusting the energy distribution of the laser beam the energy of which has been modulated in terms of time; and

intermittently radiating the laser beam the energy of which has been modulated in terms of time and said energy distribution of which has been adjusted, over the surface of the sample having the thin film formed on the surface.

15. A laser annealing method comprising:

converting a continuous laser beam to a pulsed laser beam having a desired waveform using time modulating means;

converting said pulsed laser beam to a laser beam having desired energy distribution using spatial modulating means;

concentrating said laser beam having the desired energy distribution; and

radiating the concentrated laser beam only over desired regions while scanning relatively over the amorphous or polycrystalline silicon film, formed on a glass substrate with an insulating film interposed therebetween.

16. A laser annealing method comprising:

converting a continuous laser beam to a pulsed laser beam having a desired waveform using time modulating means;

converting said pulsed laser beam to a laser beam having desired energy distribution using spatial modulating means;

concentrating the laser beam after reducing the coherency of said laser beam using an incoherent optical system; and

radiating the concentrated laser beam only over desired regions while scanning relatively over the amorphous or polycrystalline silicon film, formed on a glass substrate with an insulating film interposed therebetween.

17. A laser annealing method comprising:

a process for radiating an excimer laser over the entire surface of a amorphous silicon film formed on a glass substrate with an insulating film interposed therebetween, and converting said amorphous silicon film to a polycrystalline silicon film; and

a process for radiating a laser beam which has been to a rectangular or linear laser beam having a desired pulse waveform and desired energy distribution, only over the regions for forming a driving circuit.

18. A laser annealing method comprising:

a process for radiating an excimer laser over the entire surface of a amorphous silicon film formed on a glass substrate with an insulating film interposed therebetween, and converting said amorphous silicon film to a polycrystalline silicon film;

a process for radiating a laser beam at a plurality of locations on said polycrystalline silicon film and forming alignment marks; and

a process for detecting said alignment marks and, based on the position of said alignment marks, radiating a laser beam which has been to a rectangular or linear laser beam having the desired pulse waveform and desired energy distribution, only over the regions for forming a driving circuit;

wherein said alignment marks are used for positioning in at least one downstream photo-resist process.

19. A TFT device having a pixel portion and a driving circuit portion formed on a glass substrate;

wherein at least the active layer (active region) of a transistor constituting said driving circuit comprises polycrystalline silicon including crystals that do not have crystal grain boundaries which cross the direction of current flow.

20. A TFT device having a pixel portion and a driving circuit portion formed on a glass substrate;

wherein the active layer (active region) of a switching transistor forming said pixel portion comprises amorphous or polycrystalline silicon; and

the polycrystalline silicon of the active region of a transistor constituting said driving circuit has a crystal grain size greater than that of the amorphous silicon or polycrystalline silicon constituting the active layer (active region) of said switching transistor.

21. A TFT device comprising a pixel portion and a driving circuit portion, formed in the surrounding of the pixel portion, on a glass substrate having a polycrystalline silicon film formed thereon;

wherein the gate electrode, source electrode, and drain electrode of a transistor constituting said driving circuit are disposed on the same silicon crystal grain.