Process and system for uniformly crystallizing amorphous silicon substrate by fiber laser

Patent metadata

Field	Value
Publication number	US-RE48398-E
Application number	US-201916535316-A
Country	US
Kind code	E1
Filing date	Aug 8, 2019
Priority date	Jul 3, 2014
Publication date	Jan 19, 2021
Grant date	Jan 19, 2021

Abstract

The inventive system for crystallizing an amorphous silicon (a-Si) film is configured with a quasi-continuous wave fiber laser source operative to emit a film irradiating pulsed beam. The fiber laser source is operative to emit a plurality of non-repetitive pulses incident on the a-Si. In particular, the fiber laser is operative to emit multiple discrete packets of film irradiating light at a burst repetition rate (BRR), and a plurality of pulses within each packet emitted at a pulse repetition rate (PRR) which is higher than the BRR. The pulse energy, pulse duration of each pulse and the PRR are controlled so that each packet has a desired packet temporal power profile (W/cm2) and packet energy sufficient to provide transformation of a-Si to polysilicon (p-Si) at each location of the film which is exposed to at least one packets.

First claim

The invention claimed is:

1. A system for crystallizing an amorphous silicon (a-Si) film by sequential lateral solidification (SLS), comprising:
a quasi-continuous wave (QCW) fiber laser source operative to emit a pulsed line beam in an ultra-violet (UV) wavelength range and configured to have a master oscillator (MO) power fiber amplifier (MOPFA) optical scheme, the MO being directly modulated; and
a controller operative to control the MO so as to emit:
multiple discrete packets of light at a burst repetition rate (BRR), each packet having a duration in a nanosecond (ns) range and packet temporal power profile in a μJ/cm 2 range, and
a plurality of ns pulses within each packet emitted at a pulse repetition rate (PRR) in a ns range which is higher than the BRR, wherein a pulse energy, pulse duration and the PRR are controlled so that each packet has a desired packet temporal power profile and packet energy sufficient to provide crystalization crystallization of a-Si to polysilicon (p-Si) at each location of the film which is exposed to at least two packets.

2. The system of claim 1 , wherein the fiber laser source emits
the pulses within each packet at the PRR ranging between 100 and 200 MHz, and
the packets at the BRR varying between tens of KHz and about 1 MHz, and
the packet power profile energy varies from 50 μJ/cm 2 μJ to 200 μJ/cm 2 μJ.

3. The system of claim 1 , wherein the fiber laser controllably emits the packets having each a duration between 50 30 ns and 500 ns.

4. The system of claim 1 , wherein the MO of the QCW fiber laser source controllably emits the plurality of ns pulses within each of the packets so that a time period between consecutive pulses is at most 20 ns.

5. The system of claim 1 , wherein the MO of the QCW fiber laser source emits the light in single mode (SM) or low modes (LM) at a fundamental wavelength in a 1 μm wavelength range, the LM pump light having an M 2 value of up to 2;
the power amplifier being an ytterbium (Yb) doped fiber booster operative to amplify the light at the fundamental frequency so that a peak power of each packet is in a KW range and an average power of each packet is about half the peak power and reaches KW levels; and
a second harmonic generator located downstream from the Yb fiber booster and operative to convert the fundamental wavelength of the light from the QCW fiber laser source to a first operating wavelength of a film irradiating light in a 5xx nm wavelength range.

6. The system of claim 5 , wherein the fiber laser source further comprises a third harmonic generator located between the film and second harmonic generator and operative to convert the first operating wavelength of the film irradiating light to a second operating wavelength of the film irradiating light in a 3xx nm wavelength range.

7. The system of claim 1 further comprising a pump generating light which is coupled into the fiber booster in accordance with a side-pumping technique or end pumping technique, the pump including current-modulated MM diode lasers operatively connected to the controller.

8. The system of claim 7 , wherein the fiber booster comprises an active fiber which has a monolithic multimode (MM) core surrounded by at least one cladding, the MM core being configured to support a single fundamental mode at the fundamental wavelength and having a double bottleneck-shaped cross section.

9. The system of claim 7 , wherein the fiber booster comprises
a monolithic core which is configured with a monolithic bottleneck-shaped cross section expanding towards a distal end of the fiber boosters,
at least one cladding surrounding the core,
a reflector opposing the distal end of the fiber booster and configured to reflect the light from the pump into the core in a direction which is counter to a direction of the pump light at the fundamental wavelength.

10. The system of claim 7 further comprising a linewidth broadening system coupled between the master oscillator and fiber booster and selected from an acousto-optical modulator or electro-optical modulator.

11. The system of claim 1 further comprising a packet picker selected from a polygon, galvanometer, acousto-optical or electro-optical modulator.

12. The system of claim 7 , wherein the pump is configured to operate in a continuous regime or pulsed regime and output the light with a uniform power or controllably variable power so that the booster is operative to emit individual pulses with a uniform amplitude within each packet or non-uniform amplitude.

13. The system of claim 1 , wherein the controller operates so that the film is selectively irradiated to have opaque areas, which correspond to exposed locations of the film, and transparent areas.

14. A system for crystallizing an amorphous silicon (a-Si) film by sequential lateral solidification (SLS), comprising:
a quasi-continuous wave (QCW) fiber laser source operative to emit a pulsed line beam in an ultra-violet (UV) wavelength range and configured to have a master oscillator (MO) power fiber amplifier (MOPFA) optical scheme, the MO being directly modulated; and a controller operative to control the MO so as to emit:
multiple discrete packets of light at a burst repetition rate (BRR), each packet having a duration in a ns range and a packet energy in a microjoule (μJ) range, and
a plurality of ns pulses within each packet emitted at a pulse repetition rate (PRR) in a ns range which is higher than the BRR, wherein a pulse energy, pulse duration and the PRR are controlled so that each packet has a desired packet temporal power profile and packet energy sufficient to provide crystallization of a-Si to polysilicon (p-Si) at each location of the film which is exposed to at least one packet.

15. A system for crystallizing an amorphous silicon (a-Si) film by sequential lateral solidification (SLS), comprising:
a quasi-continuous wave (QCW) fiber laser source operative to emit a pulsed line beam in an ultra-violet (UV) wavelength range and configured to have a master oscillator (MO) power fiber amplifier (MOPFA) optical scheme, the MO being directly modulated; and a controller operative to control the MO so as to emit:
multiple discrete packets of light at a burst repetition rate (BRR), each packet having a duration in a ns range, and
a plurality of ns pulses within each packet emitted at a pulse repetition rate (PRR) in a ns range which is higher than the BRR, wherein a pulse energy, pulse duration and the PRR are controlled so that each packet has a desired packet temporal power profile and packet energy sufficient to provide crystallization of a-Si to polysilicon (p-Si) at each location of the film which is exposed to at least one packet.

Assignees

• Ipg Photonics Corp

Inventors

• Avdokhin Alexey
• Erokhin Yuri
• Leonardo Manuel
• Limanov Alexander
• Samartsev Igor
• Von Dadelszen Michael

Classifications

• H10P14/3411

  Silicon, silicon germanium or germanium · CPC title

• H10P14/3816 Primary

  Pulsed laser beam · CPC title

• H01S3/094003

  the pumped medium being a fibre · CPC title

• H01S3/1618

  ytterbium · CPC title

• H01S3/06754

  Fibre amplifiers (H01S3/06708 takes precedence) · CPC title