TWI632611B - Laser, annealing apparatus and method - Google Patents

Abstract

The invention relates to a laser annealing device that irradiates laser light to an amorphous silicon film for annealing treatment, and includes: a first pulse laser capable of generating first laser light with a fixed pulse width and a fixed wavelength; A second pulsed laser of a second laser light having a longer wave width and wavelength than the first laser light; a combining mechanism for combining the first laser light and the second laser light into the same optical axis; and A control mechanism that controls the timing of generating the first and second laser light by the action of a pulse laser and a second pulse laser; wherein the control mechanism controls the first pulse laser so that the first laser light is in the first 2 A predetermined timing within the pulse width of the laser light is generated.

Description

Laser annealing device and laser annealing method

The invention relates to a laser annealing device that irradiates laser light to an amorphous silicon film for annealing treatment, and particularly relates to a laser annealing device and a laser annealing device that improve the utilization efficiency of laser energy and can perform a good efficiency. Shot annealing method.

The conventional laser annealing device irradiates intermittently moving laser light to a plurality of island-shaped annealed films formed on the main surface of the substrate to perform annealing, so that the plurality of annealed films become films having desired characteristics. The annealed film is annealed by repeatedly irradiating the spot laser light to the annealed film a plurality of times (for example, refer to Japanese Patent Laid-Open No. 9-45632).

However, in the conventional annealing device, since the irradiated laser light is a single-wavelength ultraviolet laser light, when the amorphous silicon film is melted by the irradiation of the laser light, there is a problem that the absorption rate of the ultraviolet laser light decreases. . Therefore, it cannot be fully melted to the deep part of the amorphous silicon film, and it cannot be fully polysilicated.

In addition, in the case where it is desired to generate a plurality of dot-shaped laser lights from one laser light generated by a light source device and simultaneously anneal a plurality of positions of the annealed film, the laser light needs to be irradiated with reduced energy, so that a laser is required Large energy source devices with greater energy have the problem of increasing the manufacturing cost of the annealing device.

Regarding the aforementioned problems, although annealing the film to be annealed with a plurality of shots of laser light may be considered, the annealing treatment efficiency will be reduced, and the production cycle of the annealing treatment process becomes long.

Herein, in response to the foregoing problems, an object of the present invention is to provide a laser annealing device and a laser annealing method which can improve the utilization efficiency of laser energy and perform an efficient annealing process. law.

In order to achieve the above object, the laser annealing device of the present invention is a person who irradiates laser light to an amorphous silicon film for annealing treatment, and is characterized in that it includes a first pulse laser that generates a fixed pulse width and a fixed wavelength. The first laser light; the second pulse laser generates a second laser light with a pulse wave width and a longer wavelength than the first laser light; the synthesizing mechanism synthesizes the first laser light with the second laser light Are the same optical axis; and a control mechanism that controls the timing of generation of the first and second laser light by acting on the first and second pulse lasers; the control mechanism controls the first pulse laser so that the first 1 laser light is generated at a predetermined timing within the pulse width of the second laser light.

Through the foregoing configuration, the control mechanism is used to control the first pulse laser to generate the first laser light with a fixed pulse width and a fixed wavelength, and to control the second pulse laser to generate a pulse width and wavelength that are more than the first laser light. The second long laser light is combined with the first laser light and the second laser light into the same optical axis by using a combining mechanism, and the first and second laser lights are irradiated to the amorphous silicon film for annealing treatment. At this time, the control means controls the first pulse laser so that the first laser light is generated at a predetermined timing within the pulse wave width of the second laser light.

Preferably, the control mechanism is capable of controlling the first pulse laser to adjust the generation timing of the first laser light within the pulse wave width of the second laser light.

More preferably, the first pulsed laser system generates the first laser light with a wavelength of 355 nm or 532 nm; and the second pulsed laser system generates the second laser light with a wavelength of 1064 nm.

In addition, the laser annealing method of the present invention combines a first laser light having a fixed pulse width and a fixed wavelength with a second laser light having a pulse width and a longer wavelength than the first laser light, and synthesizing them into the same optical axis. The amorphous silicon film is irradiated for annealing treatment, wherein the following steps are performed: a phase in which the second laser light is generated and the amorphous silicon film is irradiated; and a predetermined timing within a pulse width of the second laser light is generated. A stage in which the first laser light irradiates the amorphous silicon film.

Preferably, the wavelength of the first laser light is 355 nm or 532 nm; and the wavelength of the second laser light is 1064 nm.

1‧‧‧light source device

2‧‧‧lighting device

3‧‧‧ Control agency

4‧‧‧ substrate

5‧‧‧amorphous silicon film

6‧‧‧ 1st pulse laser

7‧‧‧ 2nd pulse laser

8‧‧‧ Synthesis Agency

9‧‧‧ Resonator

10‧‧‧ Optical Amplifier

11‧‧‧laser attenuator

12‧‧‧ Front mirror department

13‧‧‧ rear mirror department

14‧‧‧ND: YAG Rod

15‧‧‧ polarizing beam splitter

16‧‧‧λ / 4 wave plate

17‧‧‧Pokes element

18‧‧‧Q switch

19A‧‧‧The first polarizing beam splitter

19B‧‧‧ 2nd polarizing beam splitter

20‧‧‧Pox

20A‧‧‧1st Pox element

20B‧‧‧ 2nd Pox element

21‧‧‧Control Department

22‧‧‧Polarizing beam splitter

23‧‧‧Beam Expander

24‧‧‧Reflector

25‧‧‧The first fly-eye lens

26‧‧‧ 1st condenser lens

27‧‧‧ 2nd fly-eye lens

28‧‧‧ Beam Scanner

29‧‧‧ 2nd condenser lens

30‧‧‧The first electro-optic crystal element

31‧‧‧The second electro-optic crystal element

32‧‧‧λ / 2 wave plate

33A‧‧‧electrode

33B‧‧‧electrode

L ₁ ‧‧‧ 1st laser light

L ₂ ‧‧‧ 2nd laser light

FIG. 1 is a front view showing an embodiment of a laser annealing apparatus according to the present invention.

Fig. 2 is a plan view showing a configuration example of a second pulse laser used in the embodiment.

Fig. 3 is an explanatory diagram showing a long pulse second laser light generated by applying a voltage applied to a Pockels cell that controls the Q switch in the above-mentioned second pulse laser, and Fig. 3 (a) is a diagram showing Graph, FIG. 3 (b) is a graph showing that the applied voltage gradually decreases.

FIG. 4 is a graph showing a laser pulse generated when the applied voltage is controlled so that the gradient of the applied voltage is gradually reduced to generate a primary inflection point in FIG. 3 (b).

FIG. 5 is a plan view showing a configuration example of a laser attenuator used in the second pulse laser.

FIG. 6 is an explanatory diagram showing a state in which the energy of a specific time is selectively reduced in one pulse of laser light by the above-mentioned laser attenuator. FIG. 6 (a) shows a state before the reduction, and FIG. 6 (b) shows a state State after reduction.

FIG. 7 is an explanatory diagram showing an example of the pulse waveforms of the first and second laser light used in the above embodiment. FIG. 7 (a) shows the first laser light, and FIG. 7 (b) shows the second laser light.

FIG. 8 is a graph showing the relationship between the wavelength and the light absorption coefficient of various inorganic materials.

FIG. 9 is an explanatory diagram showing laser energy effectively used for annealing treatment in the laser annealing method of the present invention, and FIG. 9 (a) is a diagram showing a pulse width of a first laser light in a second laser light Fig. 9 (b) shows a case where the first and second laser light are generated at the same time within a predetermined timing.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a front view showing an embodiment of a laser annealing apparatus according to the present invention. This laser annealing device irradiates laser light to an amorphous silicon film for annealing treatment, and includes a light source device 1, a lighting device 2, and a control mechanism 3.

The light source device 1 generates laser light for annealing the amorphous silicon film 5 formed on the substrate 4 and includes a first pulse laser 6, a second pulse laser 7, and a combining mechanism 8.

Here, the first pulsed laser 6 generates, for example, the first laser light L ₁ having a pulse wave width W ₁ of 20 nsec and a wavelength λ ₁ of 355 nm or 532 nm, which is performed using a non-linear optical crystal from a fundamental wave having a wavelength of 1064 nm, for example. A conventional YAG laser generated by wavelength conversion. In the following description, the case where the first laser light L ₁ is a laser light of λ ₁ = 355 nm will be described. The first pulse laser 6 is not limited to a YAG laser, and may be, for example, an excimer laser as long as it can generate short-wavelength laser light, but the case of the YAG laser will be described here.

The second pulsed laser 7 can generate a second laser light L _{2 having} a pulse wave width and a longer wavelength than the first laser light L ₁ , and generates laser light having a pulse wave width W ₂ of 350 nsec and a wavelength λ ₂ of 1064 nm, for example. YAG laser. In addition, the second pulse laser 7 is not limited to the YAG laser, and may be, for example, a CO ₂ laser, as long as it can generate long-wavelength laser light, but the case of the YAG laser will be described here.

In more detail, as shown in FIG. 2, the second pulsed laser 7 includes a resonator 9, an optical amplifier 10, and a laser attenuator 11. The second pulsed laser 7 depends on the direction of the second laser light L ₂ from upstream to downstream. Configure in the above order.

The resonator 9 generates a standing wave by turning the laser light back and forth. Between the front mirror portion 12 and the rear mirror portion 13 serving as a resonator mirror, there is provided a laser light which is excited by a flash lamp (not shown) to generate laser light. For example, an ND: YAG rod 14 and a Q formed by a polarizing beam splitter 15, a λ / 4 wave plate 16, and a Polkes element 17 are arranged behind the ND: YAG rod 14. Switch 18.

In this case, the control unit that is omitted from the design of the design is controlled so that the voltage applied to the Bokehs element 17 is gradually reduced to increase the pulse wave width of the second laser light L ₂ .

In describing this case, in contrast to a general control method in which the applied voltage to the Bokehs element 17 is rapidly reduced as shown in FIG. 3 (a), the application to the Bokehs element 17 is performed as shown in FIG. 3 (b). When the voltage is controlled gradually, the pulse width is increased from, for example, 10 ns to 70 ns. That is, during the oscillation in the resonator 9, the output energy returned from the Q switch 18 will slowly increase along the time axis and be lower than the normal energy, so the extraction of the energy in the ND: YAG rod 14 will also become slower, extending Q The pulse oscillation time in the switch 18 becomes longer.

In addition, as shown in FIG. 4, at a gradient where the applied voltage to the Pox element is gradually reduced, if the applied voltage is controlled to generate at least one inflection point, the pulse width can be further increased. Thus, by controlling the voltage applied to element 17 of Boke Si, may be generated as the pulse width W ₂ of the second laser beam 350nsec L _2.

An optical amplifier 10 is provided downstream of the resonator 9. The optical amplifier 10 amplifies and outputs the pulse energy of the laser light. For example, an ND: YAG rod can be used.

In addition, a laser attenuator 11 is provided downstream of the optical amplifier 10. The laser attenuator 11 reduces the energy of the second laser light L ₂ , and as shown in FIG. 5, the laser attenuator 11 includes a crossed Nichol prism arranged on the optical path of the second laser light L ₂ . The first and second polarizing beam splitters 19A and 19B as polarizing elements are located between the first and second polarizing beam splitters 19A and 19B, and the optical axis is 45 ° with respect to the incident linearly polarized light (for example, P polarized light). The general arrangement is to apply a voltage to rotate the polarizing surface of the laser light passing through the inside, and to use the Pox element 20 as a photoelectric element; and a control unit 21 that controls the voltage value and timing of applying the Pox element 20.

An example of the Bokehs element 20 used in this embodiment is to obtain the effect of a λ / 4 wave plate by applying a voltage of a maximum of -3.6 kV, and the first and second Bokehs elements 20A and 20B In series configuration, parallel control is performed with a maximum applied voltage of -3.6kV, and the effects of a λ / 2 wave plate are obtained by combining the first and second Bokehs elements 20A and 20B. In this case, when the applied voltages of the first and second Bokes elements 20A and 20B are changed, for example, between 0 kV and -3.6 kV, the light transmittance of the laser attenuator 11 is between 0% and 100%. Variety.

In addition, the laser attenuator 11 controls the applied voltage of the Pox element 20 by time to flatten the envelope of one pulse of laser light so that the laser energy becomes uniform along the time axis. For example, when the laser attenuator 11 inputs a long pulse second laser light L ₂ that releases excessive pulse energy within the time t _n as shown in FIG. 6 (a), for example, if the pulse energy is to be reduced by 50%, the system is applied toward the time t _n of the first and second Boke Si elements 20A, 20B of the voltage is -1.8kV, the elapsed time t _n is controlled to -3.6kV.

Thereby, the transmittance of the second laser light L ₂ that penetrates the laser attenuator 11 within the initial time t _n will be reduced to 50%, and after the time t _n , the transmittance will be 100%. Therefore, the laser intensity of the long pulse second laser light L ₂ shown in FIG. 6 (a) during the initial time t _n is reduced by 50%, and the laser intensity after the time t _n is maintained at the original intensity. As a result, as shown in FIG. 6 (b), the laser intensity within one pulse is almost constant across the full width.

In addition, in FIG. 2, reference numeral 22 denotes a polarizing beam splitter, reference numeral 23 denotes a beam expander for expanding a laser beam path, and reference numeral 24 denotes a reflecting mirror.

A synthesizing mechanism 8 is provided at an intersection of the optical path of the first pulse laser 6 and the optical path of the second pulse laser 7. The synthesizing mechanism 8 combines the first laser light L ₁ and the second laser light L ₂ into the same optical axis, for example, it penetrates the first laser light L _{1 at} λ ₁ = 355 nm and reflects the _second laser light λ _{2 at} 1064 nm. Beamsplitter of laser light L ₂ .

A lighting device 2 is provided downstream of the light source device 1. The lighting device The 2 series irradiates laser light onto a predetermined annealing area of the amorphous silicon film 5 on the substrate 4 and includes a first fly-eye lens 25, a first condenser lens 26, and a second fly-eye lens in this order from the laser light traveling direction upstream to the downstream. 27. A beam scanner 28 and a second condenser lens 29.

The first fly-eye lens 25 is provided with a plurality of convex lenses arranged in the same plane to make the intensity distribution in the cross section of the laser light uniform, and has the function of a beam expander that increases the laser light beam.

On the optical axis, a first condenser lens 26 is provided as if the front focus was aligned behind the first fly-eye lens 25. The first condensing lens 26 is used to condense the laser light beam emitted after the first fly-eye lens 25 is emitted and diverged into a second fly-eye lens 27 described later.

In order to make the intensity distribution in the cross section of the laser light uniform, the second fly-eye lens 27 is a pair of lens arrays having a plurality of convex lenses arranged in the same plane so that the corresponding convex lens central axes are aligned向 Configure.

The beam scanner 28 is provided with first and second electro-optic crystal elements 30 and 31 in a square column shape which are biased in a direction perpendicular to each other, and laser light is provided between the first and second electro-optic crystal elements 30 and 31. The λ / 2 wave plate 32 of which the polarizing plane is rotated by 90 ° and aligned with the crystal axis of the second electro-optical crystal element 31, and the optical axes of the first and second electro-optic crystal elements 30 and 31 are respectively provided at parallel facing surfaces One pair of electrodes 33A and 33B. In this case, the mounting positions of the pair of electrodes 33A of the first electro-optic crystal element 30 and the pair of electrodes 33B of the second electro-optic crystal element 31 are offset from each other by 90 degrees with the optical axis as the center.

The second condensing lens 29 is set to align the front focus to the rear focus position on the optical axis of the second fly-eye lens 27 so as to have the function of making the laser light irradiated on the substrate 4 to be parallel rays.

A control mechanism 3 is provided that is electrically connected to the first pulse laser 6 and the second pulse laser 7 of the light source device 1. The control mechanism 3 controls the timing of generation of the first and second laser beams L ₁ and L ₂ by acting on the first and second pulse lasers 6 and 7. Specifically, the control mechanism 3 controls the first pulse laser 6 such that The first laser light L _{1 is} generated at a predetermined timing within the pulse wave width W ₂ of the second laser light L ₂ .

More specifically, the control means may control the 3 lines 6 of the first laser pulse to produce a first laser beam L ₁ of the timing adjustment to the second laser light L ₂ of the _two pulse wave width W. Thereby, the irradiation energy of the laser light irradiated to the amorphous silicon film 5 can be adjusted appropriately.

Next, the operation of the laser annealing apparatus configured as described above will be described.

First, the substrate 4 on which the amorphous silicon film 5 is formed on the surface is placed on a stage (not shown) on the upper surface in a two-dimensional direction in a parallel plane on the upper surface, and the substrate 4 is annealed. The center of the area coincides with the optical axis of the lighting device 2.

Next, a control section (not shown) is used to control the gradient of the gradually decreasing voltage applied to the second pulse laser 7 and the Box element 17 to be gradually reduced as predetermined to generate, for example, a pulse width W ₂ = 350 nsec. Long pulse second laser light L _{2 having a} wavelength λ ₂ = 1064 nm.

After the second laser light L ₂ is amplified to a fixed level by the optical amplifier 10 to be described later, the applied voltages of the first and second Bokeh elements 20A and 20B of the laser attenuator 11 are reduced by parallel control to a previous experiment. The required energy intensity was sufficient in the confirmed annealing treatment. At the same time, as shown in FIG. 7 (b), the laser intensity within one pulse is almost constant across the full width. Next, the second laser light L ₂ is reflected by the beam splitter of the combining mechanism 8 and is incident on the illumination device 2 in the subsequent stage.

On the other hand, under the control of the control mechanism 3, the first pulse laser 6 is driven after the second pulse laser 7 is driven with a fixed time delay and then driven again to generate, for example, a pulse width W ₁ = 20 nsec, and a wavelength λ ₁ = For example, the short-pulse first laser light L _{1 at} 355 nm is shown in FIG. 7 (a). Next, the first laser light L ₁ passes through the beam splitter of the combining mechanism 8 and is combined with the second laser light L ₂ into the same optical axis to be incident on the lighting device 2.

The first and second laser beams L ₁ and L ₂ synthesized as described above are enlarged by the illumination device 2 to make the intensity distribution uniform, and then the substrate 4 is transmitted through the beam scanner 28 in a two-dimensional direction on the surface. Deflection to adjust the irradiation position. Accordingly, the first and second laser lights L ₁ and L ₂ can be prevented from interfering with each other, and the laser light with a uniform intensity distribution can be irradiated onto the substrate 4. As a result, the amorphous silicon film 5 in the annealed region was melted and recrystallized and changed into a polycrystalline silicon phase.

Here, the annealing treatment performed with the first and second laser lights L ₁ and L ₂ will be described in more detail.

As shown in FIG. 8, in general, it is known that when silicon (Si) has a longer wavelength of laser light, the light absorption rate decreases. Therefore, in general, in the case where the amorphous silicon film 5 is annealed, laser light having a high light absorption rate, for example, ultraviolet rays having a wavelength of 355 nm, is used.

On the other hand, it is also known that the absorption rate of ultraviolet rays by molten silicon is low. Therefore, in the case where the irradiation energy of the ultraviolet laser light is not high enough, the non- When the surface of the crystalline silicon film 5 is melted, the absorptivity of the ultraviolet laser light may be lowered and it may not be sufficiently melted to the deep part of the amorphous silicon film 5. As a result, a situation in which the amorphous silicon film 5 cannot be sufficiently polysiliconized to a deep portion is also caused.

In this regard, as shown in FIG. 8, since long-wavelength laser light such as 1064 nm is difficult to be absorbed by silicon, it is generally not used in laser annealing. However, it is also known that long-wavelength laser light is more easily absorbed by fused silicon.

Here, in the present invention, first, after the amorphous silicon film 5 is melted by the first laser light L ₁ having a short wavelength, the amorphous silicon film 5 is melted by the second laser light L ₂ having a long wavelength to Deep.

Specifically, as shown in FIG. 9 (a), after the second laser light L _{2 is} generated and irradiated to the amorphous silicon film 5, the fixed timing within the pulse width W ₂ of the second laser light L ₂ is, for example, The time after t = 100nsec has elapsed from the generation time (pulse rising time) of the second laser light L ₂ , and the first laser light L _{1 is} generated. In this case, since the amorphous silicon film 5 does not absorb the second laser light L ₂ before the first laser light L _{1 is} irradiated, the amorphous silicon film 5 does not melt. However, by the irradiation light L ₁ of the first laser, so that when the amorphous silicon film 5 is once molten, and thereafter, the amorphous silicon film 5 is absorbed by the second laser beam L ₂ to melt and deeper. In this case, the energy suitable for the annealing treatment of the amorphous silicon film 5 with respect to the first and second laser lights L ₁ and L ₂ is the energy plotted in the hatched area in FIG. 9 (a).

Accordingly, even when light L by irradiation of _a laser so that the first molten amorphous silicon film 5 of the first reducing absorption of the laser beam L ₁ ratio, but the absorption wavelength than the first laser light L ₁ is longer the second Ray The amorphous silicon film 5 is irradiated with light L ₂ and the amorphous silicon film 5 can be annealed to a deep portion. Therefore, compared with the case of using only the laser light of ultraviolet rays in the conventional technology, the utilization efficiency of laser energy can be further improved to perform the annealing treatment with better efficiency.

In the present invention, the generation timing of the first laser light L ₁ is appropriately adjusted within the pulse width W ₂ of the second laser light L _{2 to} adjust the irradiation energy of the laser light. For example, as shown in FIG. 9 (b), in the case where the second laser light L ₂ is generated and the first laser light L ₁ is also generated, the energy suitable for the annealing treatment of the amorphous silicon film 5 is shown in FIG. 9 (b). Compared with the energy shown in Figure 9 (a), the energy of the oblique line region can be increased. Of course, vice versa.

In addition, in the embodiment described above, the case where the annealing process is performed on the annealed region at one position on the amorphous silicon film 5 is described. However, the present invention is not limited to this, and may be, for example, the second polymerization of the lighting device 2. The light exit side of the optical lens 29 is disposed corresponding to a plurality of annealing regions. A microlens array having a plurality of microlenses is arranged, and a plurality of synthetic laser lights are generated from one synthetic laser light, and the plurality of annealed areas are simultaneously annealed. In this case, since the utilization efficiency of laser energy is higher than that of the conventional technique, the pulsed laser power used can be smaller than that of the conventional technique.

In addition, the substrate 4 may be transported at a fixed speed in the vertical direction of the arrangement direction of the microlenses, photographed by a photographing device in advance, and a plurality of annealed regions may be detected, and the substrate 4 may be detected after the annealed regions are detected. moving a fixed distance, when the plurality of receiving a plurality of the annealing region reaches immediately below the microlens of the microlens array, the control first and second pulsed lasers 6,7 to produce the first and second laser beam L _1, L ₂ . Thereby, a plurality of annealed areas in a row in the vertical direction of the substrate 4 in the conveying direction can be annealed together, and the annealing can be repeatedly performed in the substrate conveying direction, and the entire surface of the substrate 4 can be annealed.

Claims (4)

A laser annealing device is for irradiating laser light to an amorphous silicon film for annealing treatment, and is characterized in that: a first pulse laser is used to generate the first laser light; a second pulse laser is used to generate a pulse wave A second laser light having a longer width and wavelength than the first laser light; a synthesizing mechanism for synthesizing the first laser light and the second laser light into the same optical axis; and a control mechanism for the first and the second laser light 2 pulse laser action to control the generation timing of the first and second laser light; the control mechanism can adjust the generation timing of the first laser light to within the pulse wave width of the second laser light to adjust It is suitable for the irradiation energy of the laser light for annealing treatment, and after the surface of the amorphous silicon film is melted by the first laser light, the amorphous silicon film is melted to a deep part by the second laser light. For example, the laser annealing device of the first scope of the patent application, wherein the first pulsed laser system generates the first laser light with a wavelength of 355 nm or 532 nm; and the second pulsed laser system generates the second laser with a wavelength of 1064 nm. Shoot light. A laser annealing method is to synthesize a first laser light and a second laser light having a pulse width and a wavelength longer than the first laser light into the same optical axis and irradiate the amorphous silicon film to perform an annealing treatment. It is characterized in that the following steps are performed: a step of generating the second laser light and irradiating the amorphous silicon film; and adjusting the timing of generating the first laser light to within the pulse width of the second laser light to adjust for The amorphous silicon film is irradiated with the irradiation energy of the annealing laser light, and the surface of the amorphous silicon film is melted by the first laser light, and then the amorphous silicon film is melted by the second laser light to Deep stages. For example, the laser annealing method for item 3 of the patent application scope, wherein the wavelength of the first laser light is 355 nm or 532 nm; and the wavelength of the second laser light is 1064 nm.