Laser annealing apparatus

Abstract

To increase a crystal grain size of a polysilicon film formed by annealing an amorphous silicon film.SOLUTION: A layer annealing apparatus 1 includes: a first laser light source 2 that emits a first laser beam A; a second laser light source 3 that emits a second laser beam B; an irradiation unit 10 that irradiates an amorphous silicon film W1 with a combination of the first laser beam and the second laser beam; a stage 8 on which a base material W provided with the amorphous silicon film W1 is placed; and a scanning mechanism that scans at least one of the irradiation unit 10 and the stage 8 so that the irradiation unit 10 relatively scans along the amorphous silicon film W1. A wavelength of the first laser beam is longer than that of the second laser beam. Assuming that a scanning direction of an irradiation head with respect to the amorphous silicon film is a front X1, when the irradiation head irradiates the amorphous silicon film with the first laser beam and the second laser beam to perform an annealing process, a first rearmost portion Ar of the first laser beam is located behind X2 a second rearmost portion Br of the second laser beam.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a laser annealing apparatus. [Background technology]

[0002] A laser annealing apparatus forms a polysilicon film by irradiating an amorphous silicon film with laser light to perform an annealing process. For example, the laser annealing apparatus disclosed in Patent Document 1 includes a laser light source configured to generate a plurality of light-emitting points that emit laser beams with wavelengths of 350 to 450 nm using GaN-based semiconductor laser elements, a spatial light modulation element on a substrate on which a number of pixel units, each of which changes its optical modulation state in response to a control signal, are arranged and which modulates the laser beam emitted from the laser light source, and a scanning means for scanning an annealing surface with the laser beam modulated by each pixel unit.

[0003] Furthermore, Non-Patent Document 1 discloses a technique for increasing the grain size of a polysilicon film by slowing down the cooling rate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-064066 [Non-Patent Document 1] T. Okada, JDD Mugiraneza, K. Shirai, T. Suzuki, T. Noguchi, H. Matsushima1, T. Hashimoto1, Y. Ogino, and E. Sahota, J. Appl. Phys. 51 (2012) 03CA02. Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, a polysilicon film is formed by irradiating an amorphous silicon film with laser light and performing an annealing process. However, there is a demand for a larger crystal grain size in the polysilicon film. While slowing the cooling rate is an effective way to increase the grain size of the polysilicon film, controlling the cooling rate to a slow rate is not easy.

[0006] The present disclosure has been made in view of the above points, and aims to increase the crystal grain size of a polysilicon film formed by annealing an amorphous silicon film. [Means for solving the problem]

[0007] The laser annealing device according to the present disclosure includes a first laser light source that emits a first laser beam, a second laser light source that emits a second laser beam, an irradiation unit that combines the first laser beam and the second laser beam and irradiates the combined first laser beam and the second laser beam onto an amorphous silicon film, a stage on which a substrate having the amorphous silicon film is placed, and a scanning mechanism that scans at least one of the irradiation unit and the stage so that the irradiation unit relatively scans along the amorphous silicon film, wherein the first laser beam has a longer wavelength than the second laser beam, and when the relative scanning direction of the irradiation unit with respect to the amorphous silicon film is set to forward, when the irradiation head irradiates the amorphous silicon film with the first laser beam and the second laser beam to perform an annealing process, a first rear end of the first laser beam is located behind a second rear end of the second laser beam. [Effects of the Invention]

[0008] According to the present disclosure, the crystal grain size of the polysilicon film formed by annealing the amorphous silicon film can be increased. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of a laser annealing apparatus according to the first embodiment. [Figure 2]FIG. 2 is a schematic diagram showing the internal structure of the irradiation head according to the first embodiment. [Figure 3] FIG. 3 shows how the first laser beam and the second laser beam are irradiated onto the amorphous silicon film according to the first embodiment. [Figure 4] FIG. 4 shows how the first laser beam and the second laser beam are irradiated onto the amorphous silicon film according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the present disclosure, its applications, or its uses.

[0011] First Embodiment A first embodiment will be described.

[0012] (Laser annealing equipment) 1 is a schematic diagram of a laser annealing apparatus 1. The laser annealing apparatus 1 forms a polysilicon film (crystallized film) by irradiating an amorphous silicon film W1 deposited (provided) on the surface of a substrate W serving as a base material with laser light to perform an annealing process.

[0013] The laser annealing apparatus 1 includes an irradiation head 10 as an irradiation unit, a first laser oscillator 2 as a first laser light source, a second laser oscillator 3 as a second laser light source, a first optical fiber 4, a second optical fiber 5, a manipulator 6 as a scanning mechanism, a control device 7, and a stage 8.

[0014] The first laser oscillator 2 emits (oscillates) a first laser light A. The second laser oscillator 3 emits (oscillates) a second laser light B. The first laser light A and the second laser light B have different wavelengths. The first laser light A has a longer wavelength than the second laser light B. The second laser light B has a shorter wavelength than the first laser light A.

[0015] The first laser light A is infrared light (preferably near-infrared light) and has a wavelength of, for example, about 900 nm to 1200 nm. The second laser light B is blue light and has a wavelength of, for example, about 400 nm to 450 nm.

[0016] The first optical fiber 4 transmits the first laser light A from the first laser oscillator 2 to the irradiation head 10. The second optical fiber 5 transmits the second laser light B from the second laser oscillator 3 to the irradiation head 10.

[0017] The irradiation head 10 combines the first laser beam A and the second laser beam B and irradiates the amorphous silicon film W1 on the surface of the substrate W with the combined laser beam.

[0018] The manipulator 6 has an irradiation head 10 attached to its tip, and moves the irradiation head 10. The control device 7 controls the operation of the manipulator 6 and the oscillation of the laser beams A and B by the laser oscillators 2 and 3. The control device 7 may also control the operation of an actuator (described later) inside the irradiation head 10.

[0019] (Irradiation head) Fig. 2 shows a schematic diagram of the internal structure of the irradiation head 10. Note that X, Y, and Z in Fig. 2 indicate directions in a Cartesian coordinate system, with X being the front-to-back direction, Y being the left-to-right direction, and Z being the up-down direction (vertical direction).

[0020] The manipulator 6 causes the irradiation head 10 to scan relatively in the forward direction X1 in the forward-backward direction X with respect to the amorphous silicon film W1 on the surface of the substrate W. The substrate W is placed on a fixed stage 8. The irradiation head 10 is movable and scans in the forward direction X1 in the forward-backward direction X with respect to the fixed stage 8. The forward direction X1 in the forward-backward direction X is the scanning direction of the irradiation head 10 with respect to the amorphous silicon film W1.

[0021] The irradiation head 10 uses a focusing optical system provided inside a housing 11 to focus each of the first laser beam A and the second laser beam B and irradiate the beam onto an amorphous silicon film W1 on the surface of the substrate W. The irradiation head 10 includes, as the focusing optical system, a first collimating lens 20, a second collimating lens 21, a bend mirror 30, a dichroic mirror 40, a substrate-side focusing lens 50, an image sensor 60, a detection-side focusing lens 70, an aperture 71, a mirror-side actuator 80, a first lens-side actuator 81, and a second lens-side actuator 82.

[0022] The first laser light A from the first optical fiber 4 and the second laser light B from the second optical fiber 5 are incident on the incident portion 12 in the housing 11 in the vertical direction Z, parallel to each other. In the incident portion 12, the first laser light A and the second laser light B travel straight in the vertical direction Z, parallel to each other.

[0023] The first collimating lens 20 collimates (parallelizes) the first laser light A. The second collimating lens 21 collimates (parallelizes) the second laser light B. The laser lights A and B are each made into approximately parallel light by the collimating lenses 20 and 21.

[0024] The bend mirror 30 bends the second laser light B, which is parallel to the first laser light A, in a direction intersecting the first laser light A, specifically in a direction perpendicular to the first laser light A (front-rear direction X).

[0025] The dichroic mirror 40 is a mirror that transmits most of the light in a specific wavelength region and reflects most of the light in other wavelength regions. The dichroic mirror 40 transmits most of the first laser light A incident from the back surface 41 side substantially straight toward the front surface 42 side, and reflects most of the second laser light B incident from the front surface 42 side substantially perpendicularly toward the front surface 42 side. On the other hand, the dichroic mirror 40 reflects the remainder of the first laser light A incident from the back surface 41 side substantially perpendicularly toward the back surface 41 side, and transmits the remainder of the second laser light B incident from the front surface 42 side substantially straight toward the back surface 41 side.

[0026] The substrate W is disposed on the traveling side of most of the first laser light A transmitted through the dichroic mirror 40 and most of the second laser light B reflected by the dichroic mirror 40, via the irradiation port 13 of the irradiation head 10. That is, the dichroic mirror 40 transmits most of the first laser light A toward the substrate W, and reflects most of the second laser light B toward the substrate W.

[0027] The majority of the laser beams A and B is, for example, in terms of energy, approximately 95% to 99.9% of the laser beams A and B before they are incident on the dichroic mirror 40. The remainder of the laser beams A and B is, for example, in terms of energy, approximately 0.1% to 5% of the laser beams A and B before they are incident on the dichroic mirror 40.

[0028] The substrate-side collecting lens 50 is disposed between the dichroic mirror 40 and the substrate W. The substrate-side collecting lens 50 collects each of the first laser beam A and the second laser beam B. The substrate-side collecting lens 50 then irradiates the collected first laser beam A and second laser beam B onto the amorphous silicon film W1 on the surface of the substrate W via the irradiation port 13. The laser beams A and B irradiated by the substrate-side collecting lens 50 travel in the vertical direction Z.

[0029] The image sensor 60 is disposed on the rear surface 41 side of the dichroic mirror 40. The image sensor 60 receives, on a light-receiving surface 61, the remaining part of the first laser light A reflected by the dichroic mirror 40 and the remaining part of the second laser light B transmitted through the dichroic mirror 40.

[0030] The detection-side condenser lens 70 and the aperture 71 are disposed between the dichroic mirror 40 and the image sensor 60 .

[0031] The mirror-side actuator 80 changes the tilt of the bend mirror 30. The mirror-side actuator 80 is configured with, for example, a motor or a piezoelectric element. As the mirror-side actuator 80 changes the tilt of the bend mirror 30, the direction of the second laser light B bent by the bend mirror 30 changes.

[0032] The first lens-side actuator 81 moves the first collimator lens 20 in the vertical direction Z. The first lens-side actuator 81 is configured with, for example, a motor, a piezoelectric element, etc. The second lens-side actuator 82 moves the second collimator lens 21 in the vertical direction Z. The second lens-side actuator 82 is configured with, for example, a motor, a piezoelectric element, etc. The movement of the collimator lenses 20, 21 in the vertical direction Z by the lens-side actuators 81, 82 changes the size diameter of the laser beams A, B.

[0033] (cooling rate) A polysilicon film is formed by annealing an amorphous silicon film W1 on the surface of a substrate W by irradiating it with laser beams A and B. Here, there is a demand for increasing the crystal grain size of the polysilicon film.

[0034] In order to increase the crystal grain size of the polysilicon film, it is effective to slow down the cooling rate of the substrate W after annealing, but it is not easy to control the cooling rate of the substrate W to be slow. The inventors of the present application have succeeded in controlling the cooling rate of the substrate W after annealing to be slow by the method described below, thereby achieving an increase in the crystal grain size of the polysilicon film.

[0035] 3 shows how the first laser beam A and the second laser beam B are irradiated onto the amorphous silicon film W1 on the surface of the substrate W. The first laser beam A and the second laser beam B are irradiated downward in the up-down direction Z toward the amorphous silicon film W1 on the surface of the substrate W. The first laser beam A and the second laser beam B extend linearly in the left-right direction Y.

[0036] The manipulator 6 causes the irradiation head 10 to scan forward in the forward and backward direction X1 so that the irradiation head 10 scans relatively along the amorphous silicon film W1 on the surface of the substrate W.

[0037] When the relative scanning direction of the irradiation head 10 with respect to the amorphous silicon film W1 on the surface of the substrate W is set to the forward direction X1 in the front-rear direction X, when the irradiation head 10 irradiates the first laser light A and the second laser light B onto the amorphous silicon film W1 on the surface of the substrate W to perform an annealing process, the first rear end Ar of the first laser light A is located rearward X2 in the front-rear direction X from the second rear end Br of the second laser light B.

[0038] The first foremost portion Af of the first laser beam A is located forward X1 in the front-to-back direction X from the second rearmost portion Br of the second laser beam B. Conversely, the second rearmost portion Br of the second laser beam B is located rearward X2 in the front-to-back direction X from the first foremost portion Af of the first laser beam A.

[0039] The mirror-side actuator 80 changes the tilt of the bend mirror 30. As the mirror-side actuator 80 changes the tilt of the bend mirror 30, the direction of the second laser light B bent by the bend mirror 30 changes.

[0040] The mirror-side actuator 80 changes the tilt of the bend mirror 30, so that the second rearmost portion Br of the second laser beam B is positioned at a position X1 in front of the first rearmost portion Ar of the first laser beam A in the front-to-rear direction X. Conversely, the mirror-side actuator 80 changes the tilt of the bend mirror 30, so that the first rearmost portion Ar of the first laser beam A is positioned at a position X2 behind the second rearmost portion Br of the second laser beam B in the front-to-rear direction X.

[0041] The rearmost portions Ar and Br are the rearmost portions X2 of the laser beams A and B. The first frontmost portion Af is the frontmost portion X1 of the first laser beam A.

[0042] (Action and effect) When the scanning direction of the irradiation head 10 with respect to the amorphous silicon film W1 on the surface of the substrate W is set to the forward X1 in the front-rear direction X, the first rear end Ar of the first laser light A having a longer wavelength is located behind the second rear end Br of the second laser light B having a shorter wavelength in the front-rear direction X2. When the irradiation head 10 irradiates the amorphous silicon film W1 on the surface of the substrate W with the first laser light A and the second laser light B to perform the annealing treatment, the first laser light A having a longer wavelength chases the second laser light B having a shorter wavelength. After the second laser light B having a shorter wavelength anneals the amorphous silicon film W1 on the surface of the substrate W, the first laser light A having a longer wavelength heats the substrate W.

[0043] This allows the cooling rate of the substrate W after the annealing treatment to be controlled to be slow, and the crystal grain size of the polysilicon film formed by annealing the amorphous silicon film W1 on the surface of the substrate W can be increased.

[0044] By using infrared light as the first laser light A and blue light as the second laser light B, it is possible to effectively achieve both annealing of the amorphous silicon film W1 on the surface of the substrate W and suppression of the cooling rate of the substrate W after the annealing.

[0045] By changing the inclination of the bend mirror 30, the first rearmost portion Ar of the first laser beam A can be easily positioned rearward X2 in the front-rear direction X from the second rearmost portion Br of the second laser beam B.

[0046] By positioning the first front part Af of the first laser light A at a position X1 in front of the second rear part Br of the second laser light B, the cooling rate suppression by the first laser light A can be performed immediately after the annealing process by the second laser light B.

[0047] Second Embodiment A second embodiment will be described. In the following description, the same components as those in the above embodiment will be denoted by the same reference numerals, and detailed description thereof may be omitted. Fig. 4 shows the irradiation of a first laser beam A and a second laser beam B onto an amorphous silicon film W1 on the surface of a substrate W.

[0048] By moving the first collimator lens 20 in the vertical direction Z using the first lens side actuator 81 or by moving the second collimator lens 21 in the vertical direction Z using the second lens side actuator 82, the first size Da of the first laser light A is made larger than the second size Db of the second laser light B.

[0049] Alternatively, by changing the distance L (in the vertical direction Z) between the irradiation head 10 and the amorphous silicon film W1 on the surface of the substrate W, the first size diameter Da of the first laser beam A is made larger than the second size diameter Db of the second laser beam B. At this time, the irradiation head 10 may be moved in the vertical direction Z by the manipulator 6 (or manually).

[0050] In this example, the diameters Da and Db indicate the dimensions of the laser beams A and B in the forward and backward direction X.

[0051] Even in the above case, the first rearmost portion Ar of the first laser beam A is located rearward X2 from the second rearmost portion Br of the second laser beam B in the front-rear direction X.

[0052] Other configurations are the same as those of the first embodiment. According to this embodiment, the same effects as those of the first embodiment can be obtained.

[0053] <Other embodiments> The bend mirror may bend the first laser light A. That is, the bend mirror may bend at least one of the first laser light A and the second laser light B. Furthermore, the bend mirror may not be necessary.

[0054] The collimating lens only needs to collimate at least one of the first laser light A and the second laser light B. Furthermore, the collimating lens may not be necessary.

[0055] The first laser light A does not have to be infrared light. It is sufficient that the first laser light A has a longer wavelength than the second laser light B. The second laser light B does not have to be blue light. The second laser light B may be, for example, green light. It is sufficient that the second laser light B has a shorter wavelength than the first laser light A.

[0056] A mechanism (such as an actuator) that scans a movable stage 8 (on which the substrate W is placed) may be used as the scanning mechanism. In this case, the irradiation head 10 may be fixed. In this case, the scanning mechanism scans the movable stage 8 (on which the substrate W is placed) so that the irradiation head 10 relatively scans along the amorphous silicon film W1 on the surface of the substrate W.

[0057] The laser beams A and B do not have to extend in a straight line, but may be circular (point-shaped), for example.

[0058] The first front portion Af of the first laser beam A may be located rearward X2 in the front-rear direction X from the second rearward portion Br of the second laser beam B. In other words, there may be a gap between the first laser beam A and the second laser beam B.

[0059] The irradiation unit is not limited to an irradiation head, and may be, for example, a galvanometer mirror.

[0060] The substrate does not have to be a substrate (it may be plate-shaped).

[0061] The laser annealing apparatus may be configured with a diffraction grating. That is, the laser annealing apparatus includes a plurality of laser oscillators that emit laser beams having different wavelengths, and a diffraction grating that diffracts the laser beams emitted from the laser oscillators. In this case, the first laser beam having a longer wavelength is positioned behind the second laser beam having a shorter wavelength in the scanning direction. [Industrial Applicability]

[0062] The present disclosure is applicable to laser annealing apparatuses and is therefore extremely useful and has high industrial applicability. [Explanation of symbols]

[0063] X Anteroposterior direction X1 Front (scanning direction) X2 rear W substrate (base material) W1 amorphous silicon film A First laser beam B Second laser beam Ar 1st rear end Af 1st Front Br 2nd rear end Da First size diameter Db Second size diameter L distance 1. Laser annealing equipment 2. First laser oscillator (first laser light source) 3 Second laser oscillator (second laser light source) 6 Manipulator (scanning mechanism) 8 Stages 10 Irradiation head (irradiation unit) 20 First collimating lens 21 Second collimating lens 30 Bend Mirror

Claims

1. a first laser light source that emits a first laser beam; a second laser light source that emits a second laser light; an irradiation unit that irradiates an amorphous silicon film with a combination of the first laser light and the second laser light; a stage on which the substrate provided with the amorphous silicon film is placed; a scanning mechanism that scans at least one of the irradiation unit and the stage so that the irradiation unit scans relatively along the amorphous silicon film, the first laser light has a longer wavelength than the second laser light, a laser annealing device, wherein when the relative scanning direction of the irradiation unit with respect to the amorphous silicon film is forward, when the irradiation head irradiates the amorphous silicon film with the first laser light and the second laser light to perform an annealing process, a first rear end of the first laser light is located behind a second rear end of the second laser light.

2. the first laser light is infrared light, The laser annealing apparatus according to claim 1 , wherein the second laser light is blue light or green light.

3. the irradiation unit includes a bend mirror that bends at least one of the first laser beam and the second laser beam, 3. The laser annealing apparatus according to claim 1, wherein the first rearmost portion of the first laser beam is positioned rearward of the second rearmost portion of the second laser beam by changing the tilt of the bend mirror.

4. the irradiation unit includes a collimating lens that collimates at least one of the first laser light and the second laser light, 3. The laser annealing apparatus according to claim 1, wherein the first size of the first laser beam is made larger than the second size of the second laser beam by moving the collimator lens.

5. 3. The laser annealing apparatus according to claim 1, wherein the first size of the first laser beam is made larger than the second size of the second laser beam by changing the distance between the irradiation head and the amorphous silicon film.

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