Laser irradiation apparatus and method of fabricating a semiconductor device

• US 20010005606A1
• Filed: 12/21/2000
• Published: 06/28/2001
• Est. Priority Date: 12/24/1999
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Tanaka, Koichiro, Nakaya, Tomoko
• Granted Patent: US 6,573,162 B2
• Time in Patent Office: Days
• US Class Current: 438/151
• CPC Class Codes: B23K 2101/40 Semiconductor devices
• CPC Class Codes: B23K 26/0604 by a combination of beams
• CPC Class Codes: B23K 26/0608 in the same heat affected zone [HAZ] B23K26/0613, B23K26/0619 take precedence
• CPC Class Codes: B23K 26/067 Dividing the beam into multiple beams, e.g. multifocusing
• CPC Class Codes: B23K 26/0732 into a rectangular shape
• CPC Class Codes: B23K 26/0738 into a linear shape
• CPC Class Codes: G02B 19/0028 refractive and reflective surfaces, e.g. non-imaging catadioptric systems
• CPC Class Codes: G02B 19/0057 in the form of a laser diode array, e.g. laser diode bar semiconductor laser arrays with beam combining arrangement H01S5/4012
• CPC Class Codes: G02B 19/0095 for use with ultraviolet radiation
• CPC Class Codes: G02B 27/09 Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for adapting the beam shape of a laser diode G02B19/0052; adapting the beam shape of an LED G02B19/0061; coupling into light guides using intermediate optical elements G02B6/4204; beam shaping specially adapted for lasers H01S3/005
• CPC Class Codes: G02B 27/0905 Dividing and/or superposing multiple light beams
• CPC Class Codes: G02B 27/0961 Lens arrays lens arrays per se G02B3/0006
• CPC Class Codes: G02B 27/0966 Cylindrical lenses cylindrical lenses per se G02B3/06
• CPC Class Codes: H01L 21/0242 Crystalline insulating materials
• CPC Class Codes: H01L 21/02422 Non-crystalline insulating materials, e.g. glass, polymers
• CPC Class Codes: H01L 21/02488 Insulating materials
• CPC Class Codes: H01L 21/02502 consisting of two layers
• CPC Class Codes: H01L 21/02532 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/02592 amorphous
• CPC Class Codes: H01L 21/02672 using crystallisation enhancing elements
• 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 21/02686 : Pulsed laser beam
• CPC Class Codes: H01L 21/02691 : Scanning of a beam
• CPC Class Codes: H01L 21/268 : using electromagnetic radiation, e.g. laser radiation
• CPC Class Codes: H01L 27/12 : the substrate being other than a semiconductor body, e.g. an insulating body
• CPC Class Codes: H01L 27/1214 : comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs
• 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 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 29/78621 : with LDD structure or an extension or an offset region or characterised by the doping profile
• CPC Class Codes: H01L 29/78627 : with a significant overlap between the lightly doped drain and the gate electrode, e.g. GOLDD
• CPC Class Codes: H01S 3/005 : Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B
• CPC Class Codes: H01S 5/005 : Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping H01S5/026, H01S5/18388 take precedence
• CPC Class Codes: H01S 5/4025 : Array arrangements, e.g. constituted by discrete laser diodes or laser bar H01S5/42 takes precedence

Abstract

There is provided an optical system for reducing faint interference observed when laser annealing is performed to a semiconductor film. The faint interference conventionally observed can be reduced by irradiating the semiconductor film with a laser beam by the use of an optical system using a mirror of the present invention. The optical system for transforming the shape of the laser beam on an irradiation surface into a linear or rectangular shape is used. The optical system may include an optical system serving to convert the laser beam into a parallel light with respect to a traveling direction of the laser beam. When the laser beam having passed through the optical system is irradiated to the semiconductor film through the mirror of the present invention, the conventionally observed faint interference can be reduced. Besides, the optical system which has been difficult to adjust can be simplified.

Claims

1. A laser irradiation apparatus for irradiating a laser beam having a linear or rectangular shape on an irradiation surface, comprising:

a laser oscillator;

an optical system for transforming the shape of the laser beam on the irradiation surface into the linear or rectangular shape; and

a stage moving in at least one direction,

wherein the optical system includes,

in a width direction of the laser beam,

a first optical system serving to convert the laser beam into a parallel light with respect to a traveling direction of the laser beam, and

a second optical system serving to divide the laser beam of the parallel light into plural beams, to unite them to make one beam at the irradiation surface, and to unify energy of the laser beam in which the shape on the irradiation surface becomes linear or rectangular, and

in a longitudinal direction of the laser beam,

a third optical system serving to divide the laser beam into plural beams in a direction perpendicular to the traveling direction of the laser beam, and

a fourth optical system serving to unite the divided laser beams to make one beam at the irradiation surface, and to unify energy of the laser beam in which the shape on the irradiation surface becomes linear or rectangular, and

means for making differences between optical paths from outlets of the respective laser beams divided by the second optical system to the irradiation surface longer than a coherent length of the laser beam.

3. A laser irradiation apparatus according to

claim 1

, wherein said second optical system includes a combination of a plurality of mirrors.

4. A laser irradiation apparatus according to

claim 1

or

2

, wherein the longitudinal direction of the laser beam in which the shape of the laser beam on the irradiation surface becomes linear or rectangular is perpendicular to an operation direction of the stage moving in at least the one direction.

5. A laser irradiation apparatus according to

claim 1

or

2

, wherein the laser irradiation apparatus includes a load/unload chamber, a robot arm, and a laser irradiation chamber.

2. A laser irradiation apparatus for irradiating a laser beam having a linear or rectangular shape on an irradiation surface, comprising:

a laser oscillator;

an optical system for transforming the shape of the laser beam on the irradiation surface into the linear or rectangular shape; and

a stage moving in at least one direction,

wherein the optical system includes,

in a width direction of the laser beam,

a first cylindrical array lens and a first cylindrical lens serving to convert the laser beam into a parallel light with respect to a traveling direction of the laser beam, and

a mirror serving to divide the laser beam of the parallel light into plural beams, to unite them to make one beam at the irradiation surface, and to unify energy of the laser beam in which the shape on the irradiation surface becomes linear or rectangular, and

in a longitudinal direction of the laser beam,

a second cylindrical array lens serving to divide the laser beam into plural beams in a direction perpendicular to the traveling direction of the laser beam, and

a second cylindrical lens serving to unite the divided laser beams to make one beam on the irradiation surface and to unify energy of the laser beam in which the shape on the irradiation surface becomes linear or rectangular, and

means for making differences between optical paths from outlets of the respective laser beams reflected by the mirror to the irradiation surface longer than a coherent length of the laser beam.

6. A method of fabricating a semiconductor device, comprising the steps of:

forming a semiconductor film on an insulating surface;

irradiating a laser beam having a linear or rectangular shape on an irradiation surface to a surface of the semiconductor film by use of a laser as an oscillation source; and

forming a TFT including the semiconductor film irradiated with the laser beam as an active region,

wherein the shape of the laser beam on the irradiation surface is transformed into the linear or rectangular shape by an optical system including a mirror serving to unify energy of the laser beam.

7. A method of fabricating a semiconductor device according to

claim 6

, wherein the semiconductor film is one selected from the group consisting of an amorphous semiconductor film and a microcrystalline semiconductor film.

8. A method of fabricating a semiconductor device according to

claim 6

or

7

, wherein the semiconductor device is one selected from the group consisting of a liquid crystal display device and an EL display device.

9. A method of fabricating a semiconductor device according to

claim 6

or

7

, wherein the semiconductor is one selected from the group consisting of a portable telephone, a video camera, a digital camera, a projector, a goggle type display, a personal computer, a DVD player, an electronic book, and a portable information terminal.

10. A laser irradiation apparatus comprising:

a laser oscillator for producing a laser beam;

;

at least first and second mirrors to divide said laser beam into at least first and second divided laser beams wherein said first and second mirrors are so arranged that the divided laser beams are directed to a same irradiation surface of an object and united as one beam at said surface wherein a difference of optical path lengths of said first and second divided laser beams between said surface and said first and second mirrors is larger than a coherent length of said laser beam as emitted from said laser oscillator.

11. The laser irradiation apparatus according to

claim 10

further comprising a beam collimator between said laser oscillator and said first and second mirrors.

12. A laser irradiation method comprising:

emitting a laser beam from a laser oscillator;

dividing said laser beam to at least first and second divided laser beams;

directing said first and second divided laser beams to a same portion of an object to obtain one united laser beam at said object;

moving said object relative to said united laser beam,

wherein a difference of optical path lengths between said first and second divided laser beams is larger than a coherent length of said laser beam.

13. The laser irradiation method according to

claim 12

further comprising irradiating a semiconductor film with said united laser beam for crystallizing said semiconductor film.

14. The laser irradiation method according to

claim 12

further comprising making said laser beam as emitted from said laser oscillator a parallel laser beam before the step of dividing said laser beam.

15. A laser irradiation apparatus comprising.

a laser oscillator for producing a laser beam having a cross section perpendicular to a propagation direction of the laser beam;

at least one cylindrical lens array to expand the cross section of said laser beam only in a direction along a longitudinal direction of said cross section;

at least first and second mirrors to divide said laser beam into at least first and second divided laser beams in a width direction of the cross section wherein said first and second mirrors are so arranged that the divided laser beams are directed to a same portion of an object and united as one beam at said portion wherein a difference of optical path lengths of said first and second divided laser beams between said portion and said first and second mirrors is larger than a coherent length of said laser beam as emitted from said laser oscillator.

16. The laser irradiation apparatus according to

claim 15

further comprising a beam collimator between said laser oscillator and said first and second mirrors.

17. A laser irradiation method comprising:

emitting a laser beam from a laser oscillator having a cross section perpendicular to a propagation direction of the laser beam;

expanding the cross section of the laser beam only in a longitudinal direction of the cross section;

dividing the laser beam to at least first and second divided laser beams in a width direction of the cross section;

;

directing said first and second divided laser beams to a same portion of an object to obtain one united laser beam at said object;

moving said object relative to said united laser beam in a direction perpendicular to said longitudinal direction,

wherein a difference of optical path lengths between said first and second divided laser beams is larger than a coherent length of said laser beam.

18. The laser irradiation method according to

claim 17

further comprising irradiating a semiconductor film with said united laser beam for crystallizing said semiconductor film.

19. The laser irradiation method according to

claim 17

further comprising making said laser beam as emitted from said laser oscillator a parallel laser beam before the step of dividing said laser beam.

20. A method of manufacturing a semiconductor device comprising the steps of:

forming a semiconductor film over a substrate;

emitting a laser beam from a laser oscillator having a cross section perpendicular to a propagation direction of the laser beam;

expanding the cross section of the laser beam only in a longitudinal direction of the cross section;

dividing the laser beam to at least first and second divided laser beams in a width direction of the cross section;

;

directing said first and second divided laser beams to a same portion of said semiconductor film to obtain one united laser beam at said semiconductor film;

moving said substrate relative to said united laser beam in a direction perpendicular to said longitudinal direction in order to irradiate said semiconductor film with said united laser beam, thereby crystallizing said laser beam,

wherein a difference of optical path lengths between said first and second divided laser beams is larger than a coherent length of said laser beam.

21. The method according to

claim 20

wherein said semiconductor device is selected from the group consisting of a light emitting device and a liquid crystal display device.

22. The method according to

claim 20

wherein said semiconductor device is selected from the group consisting of a video camera, a digital camera, a head mount display, a wearable display, a navigation system, a personal computer, a portable information terminal, a digital camera, and a projector.