WO2006103836A1

WO2006103836A1 - Method and device of crystallizing thin film material

Info

Publication number: WO2006103836A1
Application number: PCT/JP2006/302459
Authority: WO
Inventors: Osamu Kato; Toshio Inami; Junichi Shida; Suk-Hwan Chung; Miki Sawai; Akinori Koyano; Naoyuki Kobayashi
Original assignee: The Japan Steel Works, Ltd.
Priority date: 2005-03-29
Filing date: 2006-02-13
Publication date: 2006-10-05
Also published as: JP2006278746A; KR20070112485A; TWI301293B; TW200717608A; JP3977379B2; KR100930855B1

Abstract

When crystal particle size cannot be uniformed, it is impossible to reduce variations in TFT characteristics over the entire panel. A method of crystallizing a thin film material comprising the step of splitting a pulse-form laser into a plurality of split lasers and delaying them and irradiating a material (12, 112) with them when the thin-film-form silicon material (12, 112) is irradiated with a pulse-form laser several times to form crystals, wherein the pulse waveform (2) of one pulse-form laser formed by a plurality of superimposed split lasers has a maximum peak (23) having the maximum intensity I, at least one maximum peak (22) having an intensity exceeding I/2, and at least one minimum point (21) positioned between adjacent maximum peaks (22, 23) and having an intensity lower than I/2.

Description

Specification

Method and apparatus for crystallizing thin film material

Technical field

TECHNICAL FIELD [0001] The present invention relates to a thin film material crystallization method and an apparatus therefor, and in particular, it is used mainly for a flat panel by irradiating a thin film silicon material with a pulsed laser to crystallize the material. The present invention relates to a method and apparatus for crystallizing a thin film material used for producing crystallized silicon for forming a thin film transistor.

Background art

[0002] When forming a crystal grain by irradiating a thin-film silicon material with a pulsed laser multiple times, a single pulsed laser is divided into a plurality of divided lasers, and these divided lasers are divided. Patent Documents 1 and 2 describe a method or apparatus for irradiating a laser as a superimposed laser. In this pulsed laser, the time width of the pulse is widened by overlapping a plurality of divided lasers. As a result, after the material is melted by one pulsed laser irradiation, the crystallization progress time is lengthened, and the crystal size can be increased. By increasing the crystal grains, the number of grain boundaries between the source and drain of a thin film transistor (hereinafter referred to as “TFT”) can be reduced, so that the operating speed of the TFT can be increased.

Patent Document 1: Japanese Patent Laid-Open No. 8-148423

Patent Document 2: JP-A-6-5537

Disclosure of the invention

Problems to be solved by the invention

[0003] When a flat panel is made of a thin-film silicon material crystallized by laser irradiation, it is important that the TFT operating speed is fast. More importantly, the _TFT characteristics of the entire panel Small variation is required. For this purpose, the crystal grains must be uniform in size.

However, Patent Documents 1 and 2 lack consideration of this point. Of course, when producing a flat panel, it is also desired to have excellent throughput. [0005] In order to make the crystal grain size uniform, a square (space) line beam consisting of a pulsed (time) laser is applied several times, especially 10-20 times, at the optimum irradiation energy density. It is necessary to produce by irradiation. At this time, since the repetition frequency of the laser is several hundred Hz, the pulsed laser is irradiated at intervals of several ms. Therefore, after one pulse of irradiation, the silicon is melted and crystallized and then cooled to the temperature before irradiation, and pulsed lasers after the second pulse are irradiated one after another.

That is, a pulse (time) excimer laser is shaped into a square (space) line beam by a homogenizer, and with an energy density optimal for a-Si in a thin film at a feed pitch of 5 to 10%, Irradiate 10 to 20 times per spot to form a crystal with a uniform V and grain size that is approximately equal to the wavelength of the laser.

[0007] As described in JP-A-10-256152, the reason why crystal grains having the same size as the wavelength of the laser beam are obtained is that after the semiconductor film is melted and recrystallized by laser beam irradiation. It is thought that the resulting surface roughness is the starting point of light scattering (light splitting). This surface roughness is basically caused by the density change in the solid-liquid state, and unevenness is formed at the solidification end point (grain boundary part) when the solidification progresses laterally and the crystal grains grow. It is understood qualitatively as a phenomenon. Then, when the rough surface of the semiconductor film is irradiated again with laser light, the scattered light scattered by the concavo-convex portions interfere with each other and form a standing wave on the film surface. Therefore, in the multiple irradiation, an uneven pattern with a specific period is finally formed on the surface of the semiconductor film by repeating this process (J. Sipe J. F. Young, JSPerston, and HM van Driel, Phys Rev. B27, 1141, 1155, 2001 (1983).

[0008] Then, when the material is irradiated with a pulsed laser, the incident angle of the laser to the material is set to a vertical line.

By making the angle 1 ° or more from the (normal) line, the size of the crystal grains can be increased (for example, Patent Publication 2004-172424). The crystal grains produced in this way are characterized in that they can be made uniform with almost the same size as the wavelength of the irradiated laser.

[0009] Therefore, in these methods, it is necessary to slow down the line beam feed rate (feed rate = line beam width Z number of times X laser repetition frequency) in order to set the number of times of irradiation to 10 to 20 times. Therefore, there was a technical problem that the production efficiency was lowered.

[0010] In the prior art, this is a pulse wave of one pulsed laser that irradiates a material. This is due to the fact that it only functions as a single pulse laser for melting and solidifying the material, so that the effect of reducing the number of irradiations cannot be achieved.

[0011] When the excimer laser oscillator is operated for a long time, the average value of the pulse energy may change by several% or more. Due to this change, when the range of the optimum energy value is narrow, the energy density to be irradiated may deviate from the optimum value power, so it becomes necessary to frequently measure and adjust the laser, and therefore stop production. However, there was a problem that productivity was lowered.

That is, the crystallinity of the material (p-Si film) greatly depends on the energy density of the laser beam, and cannot be obtained satisfactorily if the energy density is too low or too high. When manufactured at the optimum energy density, crystal grains having a size approximately equal to the wavelength of the laser beam 2 (λ = 308 nm) can be obtained.

[0013] The width of the optimum irradiation energy density at which a crystal grain size approximately equal to the laser wavelength is obtained is hereinafter referred to as "process margin". By the way, in a general conventional method that does not use a split laser, a process margin of 20 mjZcm2 is a typical value when the number of irradiations is 20, and the process margin is zero when the number of irradiations is 10 times or less.

Means for solving the problem

[0014] The invention of claim 1 is a material in which a pulsed laser is divided into a plurality of divided lasers and delayed when a thin film silicon material is irradiated with a pulsed laser a plurality of times to form crystal grains. In the crystallization method of the thin film material irradiated to the material, the pulse waveform force of one pulsed laser formed by the superposition of a plurality of divided lasers The maximum peak of intensity I and at least one of the intensity exceeding \ / 2 A thin film material crystallization method characterized by having a maximum peak and a minimum point located between at least one adjacent maximum peak and decreasing in intensity below IZ2.

In the invention of claim 2, when forming crystal grains by irradiating a thin silicon material with a pulsed laser multiple times, the pulsed laser is divided into a plurality of divided lasers and delayed to irradiate the material. In the thin film material crystallization method, the pulse waveform force of one pulsed laser formed by the superposition of a plurality of divided lasers has at least two maximum peaks with a predetermined intensity IA or more, and a maximum peak that causes melting of the material Strength decreases to the minimum point Then, after the material is crystallized, the material has a maximum peak that causes the material to melt.

The invention according to claim 3 is the method for crystallizing a thin film material according to claim 1, wherein the strength of the minimum point is I Z10 or more.

In the invention of claim 4, when forming crystal grains by irradiating a thin silicon material with a pulsed laser multiple times, the pulsed laser is divided into a plurality of divided lasers and delayed to irradiate the material. In the thin film material crystallization method, the pulse waveform of one pulsed laser formed by the superposition of a plurality of divided lasers is

It has a maximum peak of maximum intensity I, one or more minimum points with an intensity of I Z10 or more and IZ2 or less, and before and after the minimum point, the maximum peaks of I and IA exceeding IZ2 are 1 It is a method for crystallizing a thin film material characterized by existing one by one.

According to the invention of claim 5, when forming crystal grains by irradiating a thin silicon material with a pulsed laser a plurality of times, the pulsed laser is divided into a plurality of divided lasers and delayed to irradiate the material. In the thin film material crystallization method, the pulse waveform force of one pulsed laser formed by the superposition of a plurality of divided lasers, the first maximum peak between the irradiation start point and the first minimum point, and the first minimum point The second maximum peak between the second minimum points, the Nth maximum peak between the (N-1) minimum point and the Nth minimum point, and the (N + 1) maximum between the Nth minimum point and the end point of irradiation. It has a total of N minimum points that cause crystallization in a material consisting of large peaks and (N + 1) maximum peaks that cause melting in the material, N is an integer of 3 or more, and the nth minimum point The intensity is the intensity of In nZlO and I nZ2 or less with respect to the intensity n of the previous nth maximum peak, and n is in the range of 1 to N It is a thin film material crystallization method characterized by being an integer.

The invention of claim 6 is characterized in that the intensity of the nth minimum point is an intensity of InZlO or more and InZ2 or less with respect to the intensity In of the immediately following n + 1 maximum peak. This is a method for crystallizing a thin film material.

The invention according to claim 7 is characterized in that the number of times of irradiation of the pulsed laser per place of the material is 10 times or less, and the crystallization of the thin film material according to claim 1, 2, 3, 4, 5 or 6 It is a method.

The invention of claim 8 is a laser in which the pulsed laser is not linearly polarized light, 8. The method of crystallizing a thin film material according to claim 1, wherein the incident angle of the incident light with respect to the normal line is 1 ° or more.

The invention of claim 9 divides and delays the pulsed laser into a plurality of divided lasers when a thin film silicon material is irradiated with a pulsed laser from a laser oscillator a plurality of times to form crystal grains. Then, a thin-film material crystallization apparatus that irradiates the material with a dividing device that divides the pulsed laser by delaying it into a plurality of divided lasers, and shapes the intensity distribution of the plurality of divided lasers and superimposes them on the material. The pulse waveform force of one pulsed laser formed by the superposition of a plurality of divided lasers has a maximum peak of I, and an intensity of IZ10 or more and IZ2 or less This thin film material crystallization apparatus is characterized in that there are one or more minimum points, and there are one maximum peak of intensities I and IA exceeding IZ2 before and after the minimum point.

The invention's effect

[0015] According to the independent claims 1, 4, 5 and 9, when forming crystal grains by irradiating a thin silicon material with a pulsed laser a plurality of times (multiple pulses), the material is irradiated. The pulse waveform force S of a single pulsed laser formed by the superposition of split lasers, and at least two maximum peaks, and at least two minimum points where the intensity decreases from the maximum peak of maximum intensity I to IZ2 or lower Between two maximum peaks. This can cause the material to melt at the maximum peak of maximum intensity I or other maximum peak and to crystallize the material at the minimum point between the two maximum peaks.

[0016] Since irradiation of such a split laser of one Norse-shaped laser, after melting and crystallization of the material, it is melted again immediately after crystallization without being cooled to the temperature before irradiation. By reducing the number of pulsed laser irradiations, crystallization can be performed quickly with uniform-sized crystal grains. As a result, the variation in TFT characteristics across the panel is reduced.

[0017] When the delay time of the divided laser is set appropriately and the intensity of the minimum point is set to IZ2 or less, process conditions that give an appropriate process margin can be obtained, and the material can be crystallized satisfactorily.

[0018] Further, if the intensity of the minimum point is IZ10 or more as in claims 3, 4, 5, 6, and 9, the pulse An increase in the optimum crystallization energy of the laser can be avoided.

[0019] According to the independent claim 2, when a crystal grain is formed by irradiating a thin film silicon material with a pulsed laser a plurality of times, it is formed by superposition of divided lasers that irradiate the material. Pulse waveform force of two pulsed lasers After at least two maximum peaks with a predetermined intensity of IA or more, maximum peak force that causes melting in the material After the intensity decreases to the minimum point and the material is crystallized The material has a maximum peak that causes the material to melt.

[0020] With this, by the irradiation of one pulsed laser split laser, the material is melted and crystallized, and then melted again immediately after crystallization without being cooled to the temperature before irradiation. As a result, the number of times of irradiation with the pulsed laser can be reduced, and crystallization with crystal grains of uniform size can be performed quickly.

[0021] As described in claim 7, the number of times of irradiation with the pulsed laser can be 10 times or less per part of the material.

[0022] According to claim 8, since the pulsed laser applied to the material is a laser that is not linearly polarized light and the incident angle of the incident light with respect to the normal of the material is 1 ° or more, a polarizing plate is used. The size of the crystal grains can be increased without reducing the output.

Brief Description of Drawings

FIG. 1 is a schematic view showing an apparatus for crystallizing a thin film material according to one embodiment of the present invention.

[Fig. 2] Similarly, a split laser with time on the horizontal axis and intensity on the vertical axis is shown, Fig. 2 (a) is a diagram showing the split laser individually, and Fig. 2 (b) is the superposition state of the split laser. Diagram shown.

[Fig. 3] Diagram showing the superimposed state of split lasers with time on the horizontal axis and intensity on the vertical axis

[Fig.4] Diagram showing delay time process margin characteristics.

[Fig. 5] Diagram showing the optimum crystallization energy characteristics for delay time.

[Fig. 6] A diagram showing the process margin characteristics of the maximum number of peaks.

FIG. 7 shows a crystallization apparatus for a thin film material similarly used in one example, FIG. 7 (A) is a schematic diagram showing a laser oscillator and a dividing means, FIG. 7 (B) omits a short axis homogenizer, Fig. 7 (C) is a schematic diagram showing the material from the long axis homogenizer to the material. Fig. 7 (C) is a schematic diagram showing the material from the short axis homogenizer to the material. BEST MODE FOR CARRYING OUT THE INVENTION

1 to 7 show an embodiment of a thin-film material crystallization apparatus according to the present invention. In FIG. 1, reference numeral 1 denotes a laser oscillator. Specifically, an excimer laser (wavelength 308 nm), which is an ultraviolet laser that is not linearly polarized, is emitted. The pulsed laser 20 emitted from the laser oscillator 1 is divided into two by a semi-transmissive mirror 221 having a transmittance of 50%, and the first divided laser 20a reflected by the semi-transmissive mirror 221 is incident on the homogenizer 224. The second split laser 20b that has passed through the semi-transmissive mirror 221 passes through the delay circuit 223, and then enters the homogenizer 224 through the total reflection mirror 222. The semi-transmission mirror 221, the total reflection mirror 222, and the delay circuit 223 make up a splitting device that splits one pulsed laser into a plurality of split lasers while being mutually delayed.

[0025] The homogenizer 224 and the subsequent steps are the same as the general conventional method. The first and second divided lasers 2 Oa and 20b are formed into line beams, and the delay time is reduced to the thin-film silicon material 12. Is crystallized by superimposing the first and second divided lasers 20a and 20b, which become a plurality of pulses exceeding 0 ns and not exceeding 100 ns.

[0026] When the first and second divided lasers 20a and 20b functioning as the two pulses shown in Fig. 2 (a) are irradiated while being superimposed with an appropriate delay time T, the first and second divided lasers are used. As shown in Fig. 2 (b), the pulse waveform 2 with 20a and 20b superimposed is a local minimum point where the intensity of the maximum peak 23 is I and the intensity decreases from the maximum peak 23 to IZ10 or more and to IZ2 or less. One maximal peak 22 of intensity IA having 21 and exceeding IZ2 is formed. This maximum peak 23 occurs after the minimum point 21 as the material 12 can be melted by the superposition of the first and second divided lasers 20a and 20b. In addition, this waveform 2 shows that the material 12 can be crystallized when the intensity of the maximum peak 23 is I, and a minimum point 21 having an intensity of IZ10 or more and IZ2 or less is formed. It can be said that before and after point 21, one maximum point 22, 23 of strength exceeding IZ2 capable of melting material 12 is formed. The number of maximum points 22, 23 and minimum point 21 varies depending on the number of divisions of the divided lasers 20a and 20b. There are a plurality of local maximum points 22, 23 and local minimum points 21, and at least one local minimum point 21 that can be crystallized with an intensity of 10 Z or more and IZ 2 or less. It is sufficient that 22 and 23 are formed one by one. [0027] One pulsed laser 20 emitted from the laser oscillator 1 is divided into a plurality of pieces, such as first and second divided lasers 20a and 20b, and delayed (delay time: T = 0 to: LOOns). We tried to make the crystal size uniform by reducing the number of times of irradiation with the pulsed laser 20 by irradiating the material 12 with the laser with the pulse waveform 2 superimposed after the pulse. Even if the number of irradiations is reduced, uniform and large crystals can be obtained only when specific conditions are given to the divided lasers 20a and 20b shown in Fig. 2 (a). It turns out that it is obtained.

In other words, in order to reduce the number of times of irradiation and make the size of crystal grains uniform, one pulsed laser 20 is divided into a plurality of parts, delayed, and then superimposed to irradiate the material 12 with the laser. When the pulse waveform 2 of the laser melts the material 12, the maximum peak 23 of the intensity I that can melt the material 12, and at least one minimum point 21 that decreases in intensity to IZ2 or less that can crystallize the material 12 There must be at least one maximal peak 22 with an intensity exceeding IZ2 to obtain. That is, there is one or more pulse waveforms 2 in which the minimum point 21 is located between at least one adjacent maximum peak 22, 23, and the maximum peak 22 causing melting of the material 12 before and after the minimum point 21 There must be one 23 each. However, since the maximum peak 23 is a type of maximum peak and is the maximum peak of the maximum intensity I, the pulse waveform 2 of one pulsed laser that irradiates the material 12 has an intensity IA or more that can melt the material 12. The material 12 is crystallized from the maximum peak 22 that melts in the material 12, with at least two local maximum peaks 2 2 and 23, and a minimum point 21 located between the two adjacent maximum peaks 22 and 23. There will be a maximum peak 23 that will cause the material 12 to crystallize after the strength has decreased to the minimum point of 21 to be crystallized and then melted again in the material 12! /.

[0029] That is, when the material 12 is irradiated with a laser that is superposed after being divided and delayed into a plurality of one laser-like lasers 20, when the intensity of the maximum pulse 23 is I, After a maximum peak 22 having an intensity exceeding IZ2 is obtained, a minimum point 21 where the intensity decreases below IZ2 is generated, and then a maximum peak 23 (maximum peak 23) is generated. A pulse waveform 2 of a laser having a maximum peak 22 with an intensity exceeding IZ2, a minimum point 21 where the intensity decreases below IZ2, and a maximum peak 23 (maximum peak 23 with an intensity exceeding IZ2) is sequentially obtained. Set to 1 pulse waveform. [0030] Therefore, in a method of forming crystal grains by irradiating a thin-film silicon material 12 with a Norlas laser 20 multiple times (multiple pulse irradiation), a laser having a first pulse waveform is used as a material. If the thin film material 12 is crystallized by irradiating 12, a large and uniform crystal can be obtained even if the number of pulsed lasers 20 emitted from the laser oscillator 1 and irradiated is reduced. As a result, the variation in crystal grain size is reduced, and the variation in TFT characteristics across the panel is reduced.

[0031] The crystal growth process will be described. The crystal growth is thought to increase due to the combination of the grain strength generated by the first irradiation and subsequent irradiation. In order to grow this crystal, it is necessary to re-irradiate the laser so that the solidified state of the material 12, that is, the state force of crystallization, rises to near the melting temperature, and to provide melting and recrystallization. . If the energy density of the laser is optimal, crystal grains will grow and will be approximately at the wavelength of the laser.

It is possible to obtain crystal grains of LV and size.

[0032] The optimum energy density for melting and recrystallization of the material 12 is not only when the single pulsed laser 20 has, but also when the waveform 2 has the first waveform. Can be obtained.

[0033] When Norse waveform 2 has the first Nors waveform, the material 12 made of silicon melts near the first peak 22, and the material near the minimum point 21 where the strength decreases to IZ2 or less. 12 begins to crystallize, after which the second peak 23 is incident and the material 12 melts and crystallizes again. In this way, by inputting heat with the split laser after the crystallization of the material 12 is started, a pulsed laser having a Norse waveform composed of only one conventional peak that is not a split laser is placed for a sufficient time. Thus, the same effect as when irradiated twice is considered.

In order to confirm this effect, one pulsed laser 20 having a half width W = 25 ns is divided into two as shown in FIG. 2 (a), and the first and second divided lasers 20a, 20a, 20b is obtained, formed into a line beam, and superimposed on the thin-film silicon material 12 as the first and second split lasers 20a and 20b with two delay times: T = 0 ~: LOOns And crystallized upon irradiation. As shown in FIG. 2 (a), the half widths of the first and second divided lasers 20a and 20b with the delay time T are W. [0035] As shown in Fig. 2 (b), the Norse waveform 2 in which the first and second divided lasers 20a and 20b are superimposed has a maximum peak 23 intensity of I, and from the maximum peak 23 to I Z10 or more There is a minimum point 21 where the intensity decreases below IZ2, and there is one maximum peak 22 of intensity IA exceeding IZ2. This maximum peak 23 occurs after the minimum point 21 due to the superposition of the first and second divided lasers 20a and 20b.

[0036] The first and second divided lasers 20a, 20b (pulse waveform 2) force The pulsed laser 20 having a force 20 The number of times of irradiation of the material 12, the process margin at 10 and 20, and the two divided lasers 2 Oa, The optimum crystallization energy density when adding 20b was measured, and the results shown in Figs. 4 and 5 were obtained. The minimum point 21 is reduced when the delay time T is increased, and is で at 1/2, T = 5 Ons when T = 30 ns. Therefore, as described later, it is desirable to set the half-value width W = 25 ns to the delay time T and the delay time T = 30 to 50 ns. The pulse energy of the laser 20 is 670 mJ and the repetition frequency is 300 Hz. The number of irradiations (10 times, 20 times) in Fig. 4 is the number of times the laser 20 is irradiated.

[0037] From Fig. 4 and Fig. 5, in the general conventional method (delay time T = 0ns), there were no process conditions after 10 irradiations (the process margin was zero). If the delay time T of the split lasers 20a and 20b is increased, a positive process margin will start to occur for delay time T = 20 ns or more, and it is appropriate to set delay time T = 30 ns or more (minimum point intensity IZ2 or less). Process conditions (appropriate process margin) were obtained. Therefore, the intensity of the minimum point 21, that is, the minimum value is set to IZ2 or less. However, as shown in Fig. 5, since the optimum crystallization energy started to increase rapidly with a delay time of T = 50 ns or more (minimum point intensity I Z10 or less), the intensity at minimum point 21 is set to IZ10 or more.

[0038] The process margin below the minimum value IZ2 shown in Fig. 4 (approximately 20mJ Zcm2 with 10 irradiations and approximately 40mjZcm2 with 20 irradiations) is a process in the conventional method that does not use the above-mentioned split laser. Compared to the margin (zero at 10 exposures, approximately 20 miZcm2 at 20 exposures).

[0039] The silicon thin film material 12 crystallized with 10 irradiations shown in Fig. 4 is observed by SEM (scanning electron microscope), and the size of the crystal grains in one field of view is measured. 90% or more of the laser beam size is 308nm ± 30nm. We observed the allowable range (process margin) of the irradiation energy density at which the process conditions were obtained. As a result, the process margin (about 20mjZcm2) when the number of irradiations is 10 times is almost the same as that of a material crystallized after 20 times of irradiation with a general conventional method that does not use a split laser. The crystal grains were obtained satisfactorily.

[0040] In this way, it was found that the number of irradiations can be reduced by setting the intensity value of the local minimum point to IZ2 or less. Next, with integer N≥3, N + 1 peaks and IZ2 ~ N minimum points satisfying IZ10 were created and the effect was confirmed by tests.

[0041] As shown in FIG. 3, the pulse waveform 3 of one pulsed laser formed by superimposing the N + 1 divided lasers is a first waveform between the irradiation start point 30 and the first minimum point 31. Maximum peak 41, second maximum peak 42 between first minimum point 31 and second minimum point 32, Nth maximum peak 48 between (N-1) minimum point 37 and Nth minimum point 38, Nth minimum point (N + 1) maxima peak 49 between irradiation and end point 50 of irradiation, for example, a total of N minima that cause crystallization in material 112 and (N + 1) maxima that cause melting in material 1 12 And have. Then, the intensity of the nth minimum point is an intensity of InZlO or more and InZ2 or less with respect to the intensity In of the immediately preceding nth maximum peak, or the intensity of the nth minimum point is For the intensity of the n + 1st peak, In + 1, the crystallization method has an intensity in the range of I nZlO or more and I nZ2 or less, and the material 112 is at least melted, crystallized, melted by one pulsed laser If crystallization is applied sequentially, the number of irradiations can be reduced. However, n is an integer in the range of 1 to N.

[0042] As a test apparatus for this purpose, a plurality of (three in the figure) semi-transparent mirrors 103, 104, 105 and one total reflection as shown in FIGS. 7 (A), (B), (C) Using a mirror 106, one pulsed laser 102 emitted from an oscillator 101 is divided, and multiple adjacent lasers 120a, 120b, 120c, 120d that are close in time (four in the figure) are delayed by T = It was formed as 30 ns (minimum point intensity value IZ2), and all the split lasers 120a, 120b, 120c, and 120d were made incident on the common homogenizer 110. For this reason, the delay circuits 107, 108, and 109 are arranged between the semi-transparent mirrors 103 to 105 and the total reflection mirror 106. This produced a pulse waveform with N + 1 maximum peaks and N minimum points as shown in Fig. 3. The semi-transmissive mirrors 103 to 105, the total reflection mirror 106, and the delay circuits 107 to 109 allow a plurality of pulsed lasers 102 to be used. The splitting means for splitting the split lasers 120a, 120b, 120c, and 120d with mutual delay is configured. Intensity of two adjacent maximum peaks of pulse waveform 3 shown in Fig. 3 In n, I n + 1 is the intensity of the minimum point between them Intensities of multiple values that exceed the intensity of InZ2 and melt material 112 The maximum peak of the maximum intensity exists in the maximum peak of In.

[0043] Actually, the number of transflective mirrors 103 to 105 and delay circuits 107 to 109 is changed, and a pulse waveform with the number of maximum peaks of 1 to 7 is irradiated to the thin-film silicon material 12 to generate pulses. We measured the relationship between the number of maximum peaks and the process margin at 5, 10, 15 and 20 times. The result is shown in Fig. 6. As shown in Fig. 6, as the number of maximum peaks (and the number of minimum points) increases, the process margin increases, and even if the number of irradiations is 5, the split laser with the maximum peak number of 3 or more provides good process conditions. I found out. The number of irradiations is the number of pulsed lasers 102. The number of times of irradiation of the pulsed laser per part of the material 12 is 10 or less.

Example

One embodiment will be specifically described with reference to FIG.

XeCl excimer laser oscillator 101 pulse energy: 670mJ, repetition frequency: 300Hz, pulsed laser 102 with a pulse waveform emitted by four mirrors 103, 104, 105, 106 with reflectivity Rl, R2, R3, R4 Dividing and changing the direction, the delay circuits 107, 108, 109 provided between the mirrors 103, 104, 105, 106 delay the adjacent ij lasers 120 a to 120 d with each other, and successively pass to the long axis homogenizer 110. The a-Si film 112 having a film thickness of 50 nm on the glass, which is the material 12, was irradiated with a rectangular wave having a long axis of 200 mm. The reflectivity of the mirror 103 is Rl, the reflectivity of the mirror 104 is R2, the reflectivity of the mirror 105 is R3, and the reflectivity of the total reflection mirror 106 is R4 = 100%.

[0045] At this time, the reflectance is set to R1 = 25%, R2 = 33.3%, R3 = 50% so that the waveform shown in Fig. 3 can be obtained in which the maximum peak intensity is four with a period of 30ns. , R4 = 100%.

The excimer laser emits light that is not linearly polarized in the ultraviolet region and has high absorption power to the a-Si film 112, and high-power pulsed light (wavelength 308 nm) is obtained. [0047] Each delay circuit 107, 108, 109 includes a plurality of total reflection mirrors for generating an optical path difference, and these total reflection mirrors provide time differences to the divided lasers 120a to 120d. Delay time: A 9m optical path was provided to delay 30ns.

[0048] A short-axis homogenizer 111 shown in Fig. 7 (C) is provided in the direction perpendicular to the long axis of the pulsed laser 102, and the short-axis width is shaped into a rectangular wave spatial intensity distribution of 0.4 mm. 112 was irradiated with an incident angle α = 5 ° of the incident light with respect to the normal of the material 112. The a-Si film 112 on the glass is not shown in the figure! It was placed on the stage and scanned in the minor axis direction at a speed of V (mm / s). Then, the number of times of irradiation of one location of the a-Si film 112: V = 24, 12, 8, 6mm / with V = 0.4-300 / Z so that Z = 5, 10, 15, 20 s. The homogenizers 110 and 111 constitute shaping means for shaping the intensity distribution of a plurality of divided lasers and superimposing them on the material 112 for irradiation.

[0049] The material 112 made of a crystallized silicon thin film after irradiation with the pulsed laser 102 is observed with a SEM (scanning electron microscope), and the size of the crystal grain in one field of view is measured. With 90% or more of the laser wavelength size being 308nm ± 30nm as the process condition, the allowable width (process margin) of the irradiation energy density at which the process condition was obtained was measured. As a result, when the number of irradiations was 5, 10, 15, 20 times, the process margin was about 20, 40, 60, 100mjZcm2, as shown in Fig. 6 as the maximum number of peaks 4. Number of times: Processable conditions were obtained even under 5 times.

[0050] By making the incident angle α of the pulsed laser 102 (split laser 120a to 120d) to the material 112 1 ° or more with respect to the vertical line (normal line), the crystal grains can be made larger than the wavelength of the laser 102. It is known. Therefore, the incident angle of the incident light with respect to the normal of the material 112 is set to 1 ° or more. Further, since the repetition frequency of the laser is several hundred Hz, the pulsed laser 102 is irradiated at intervals of several ms. Therefore, silicon (material 112) is repeatedly melted and cooled and crystallized by irradiation with a plurality of pulsed lasers, and becomes uniform at a size approximately equal to or greater than the wavelength of the laser to be irradiated. The variation in thickness can be reduced. If one pulsed laser 102 is irradiated as a plurality of divided lasers 120a to 120d, the effect equivalent to irradiating a pulsed laser with multiple pulses according to the number of divisions by one pulsed laser 102 can be obtained. It is done. Further, as described in JP-A-2004-172424, if the pulsed laser 102 irradiated to the material 112 is a laser that is not linearly polarized light, crystal grains can be grown without reducing the output using a polarizing plate. If the incident angle of the incident light with respect to the normal of the material is 1 ° or more, the crystal grains can be made equal to the wavelength of the laser 102 or larger than the wavelength of the laser by repeated irradiation of the pulsed laser 102. An excimer laser is a random polarization without a specific polarization. Large crystal grains are obtained when the incident angle of the incident light with respect to the normal of the material is 1 ° or more.

Claims

The scope of the claims

[1] When a thin film of silicon material (12, 112) is irradiated with a pulsed laser multiple times to form crystal grains, the pulsed laser is divided into a plurality of divided lasers and delayed (material (12 , 1 12), the pulse waveform (2) of one pulsed laser formed by the superposition of a plurality of divided lasers has a maximum peak of maximum intensity I (23 ) And at least one maximum peak (22) with an intensity exceeding IZ2 and at least one adjacent maximum peak (22, 23) and a minimum point (21) where the intensity drops below IZ2 A method for crystallizing a thin film material, comprising:

[2] When forming crystal grains by irradiating a thin-film silicon material (12, 112) with a pulsed laser multiple times, the pulsed laser is divided into a plurality of divided lasers and delayed (the material (12 , 1 12), the pulse waveform (2) of one pulsed laser formed by the superposition of a plurality of divided lasers is a pole having a predetermined intensity (IA) or higher. Maximum peak that has at least two large peaks (22, 23) and causes melting in the material (12, 112)

It has a maximum peak (23) that causes the material (12, 112) to melt after the strength decreases from (22) to the minimum point (21) and crystallization occurs in the material (12, 112). A thin film material crystallization method.

[3] The method for crystallizing a thin film material according to claim 1, wherein the strength of the minimum point (21) is I Z10 or more.

[4] When a thin film silicon material (12, 112) is irradiated with a pulsed laser multiple times to form crystal grains, the pulsed laser is divided into a plurality of divided lasers and delayed (the material (12 , 1 12) In the method of crystallizing thin film materials irradiated to 12), the pulse waveform (2) of one pulsed laser formed by the superposition of a plurality of divided lasers has a maximum peak of maximum intensity I.

There are one or more minimum points (21) that have (23) and have an intensity greater than or equal to I Z10 and less than or equal to IZ2, and before and after the minimum point (21), the maximum peaks of intensities I and IA exceeding IZ2 ( A thin film material crystallization method characterized in that there is one each of 22, 23).

[5] When forming a crystal grain by irradiating a thin film of silicon material (12, 112) with a pulsed laser multiple times, the pulsed laser is divided into a plurality of divided lasers and delayed (material (12 , 1 12) in the method of crystallizing thin film materials, The pulse waveform (3) of a single pulsed laser formed in this way shows the first maximum peak (41) between the irradiation start point (30) and the first minimum point (31), and the first minimum point (31) And the second maximum peak (42) between the second minimum point (32), the Nth maximum peak (48) between the (N-1) minimum point (37) and the Nth minimum point (38), A total of N local minimum points and materials (12, 112) that cause crystallization in the material (12, 112) consisting of the N minimum point and the (N + 1) maximum peak (49) between the end point of irradiation (50) (N + 1) maximum peaks that cause melting, N is an integer of 3 or more, and the intensity of the nth minimum point is I nZlO relative to the intensity In of the immediately preceding nth maximum peak. A method for crystallizing a thin film material, characterized in that the strength is not more than InZ2 and n is an integer in the range of 1 to N.

[6] The intensity of the n-th local minimum point is I nZlO or more with respect to the intensity In of the next n + 1 local maximum peak.

6. The method for crystallizing a thin film material according to claim 5, wherein the strength is nZ2 or less.

[7] The thin film material according to claim 1, 2, 3, 4, 5 or 6, wherein the number of times of irradiation of the pulsed laser per part of the material (12, 112) is 10 times or less. Crystallization method.

8. The pulsed laser is a laser that is not linearly polarized light, and an incident angle of incident light with respect to the normal of the material (12, 112) is 1 ° or more. , 3, 4, 5, 6 or 7 thin film material crystallization method.

[9] When forming a crystal grain by irradiating the thin silicon material (12, 112) with the pulsed laser (20, 102) from the laser oscillator (1, 101) multiple times In a thin film material crystallization apparatus that divides and delays a laser beam into a plurality of split lasers and irradiates the material (12, 112), a splitting means for delaying and splitting the pulse laser into a plurality of split lasers; And shaping means (110, 111) for shaping the intensity distribution of a plurality of divided lasers and superimposing them on the material (12, 112), and forming one pulse formed by superposing a plurality of divided lasers. The pulse waveform of the laser beam (2) force The maximum intensity I has a maximum peak (23), and there is at least one minimum point (21) that is greater than I Z10 and less than IZ2, and the minimum point ( Before and after 21), there is one maximum peak (22, 23) of intensities I and IA exceeding IZ2. Crystallizer.