JPS6281710A - Laser scanning optical system device - Google Patents

Abstract

PURPOSE:To realize the temperature distribution controlled two-dimentionally on an irradiated plane efficiently and stably by irradiating with laser beam a diffusion plate on which a predetermined phase series is arranged through a collimate optical system, followed by converging and then scanning a non- crystal layer or a polycrystalline layer on a substrate with the beams of two- peak light intensity distribution. CONSTITUTION:A laser scanning optical system device is composed of a laser beam oscillator 5 as a beam source, a beam expander 6, a collimate lens 7 composing a collimate optical system together with said beam expander 6, a phase plate 9 into which a laser beam 1 which has passed through the collimate system enters, and a converging lens 8 composed of a Fourier transform lens arranged behind the phase plate 9. The laser beam 1 emitted from the laser beam oscillator 5 enters into the phase plate 9 through the beam expander 6 and collimate lens 7. After being diffracted as predetermined in the phase plate 9, the beam is refracted by the converging lens 8 to produce a predetermined two-peak distribution of beam intensity, namely a temperature distribution 13 on an X-Y plane.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a laser scanning optical system device that uses recrystallization technology to produce semiconductor crystals on an insulating film to construct an integrated circuit.

Conventional technology As a new means of improving the performance or increasing the degree of integration of integrated circuits, three-dimensional (3D)
/i: Laminated technology has recently been attracting attention. Establishment of active layer stacking technology is essential for multilayering including semiconductor single crystal layers, and in recent years, SOI using lasers has been developed.
With the development of 5 silicon on insulator technology, it has been shown that a single crystal layer can be formed relatively easily on an insulating film, and efforts are being made to put three-dimensional devices into practical use. On the other hand, in addition to three-dimensional devices, SOI technology is also an effective means of realizing two-dimensional integrated circuits on large-sized bonded substrates. This makes it possible to arrange it on a substrate.

Formation of a semiconductor layer using S○ technology has been attempted using various methods belonging to (1) deposited layer recrystallization method, (2) epitaxial deposition method, and (3) single crystal separation method. depositing an amorphous or micro-polycrystalline semiconductor;
The method (1) above, in which recrystallization is achieved through heating and melting and cooling processes, is considered to be highly versatile and economical, and is currently being studied most extensively. In addition to laser beams, methods using electron beams, heaters, and lamps are being considered as heating and melting methods, but the laser beam method is effective because it requires only a short heating time and does not require a vacuum.

In order to obtain a good crystal using this laser beam method, it is necessary to control the shape of the (2L) beam, and (1)
) It is necessary to realize an appropriate temperature distribution so that recrystallization starts from the center of the molten zone by controlling the structure of the irradiated object. The one that is less affected by the structure of the irradiated object is (a
) is a method based on beam shape control, and as a conventional example for implementing this method, an optical system device as shown in FIG. 5B has been proposed. This optical system device includes a laser light source 1a, an insulating substrate 2, and a GVD polysilicon layer 3.
Consists of spikes. A continuous wave gas laser such as an argon ion laser is used as the laser light source 1a, and the oscillation spectrum (λ
= 542 nm) f, (has. An SiO2 plate or 5io2 film with excellent heat resistance is used as the insulating substrate 2. Then, the laser beam 1 is focused in a bimodal shape and irradiated, and the polysilicon is The entire layer melts.The laser beam 1 irradiated from the laser light source 11L has a Gaussian distribution intensity characteristic with optical axis symmetry, and even if it is focused on the sample surface as it is, the Gaussian distribution light intensity is maintained and the irradiated surface is Recrystallization control is difficult because a Gaussian temperature distribution occurs.Therefore, in order to obtain a beam shape convenient for temperature distribution control, a crystal birefringence plate 4 is used to transform the two beams at 10°11. A total of 12 combined beams are formed.

At this time, the laser beam 1 is scanned by moving relative to the irradiated surface in the Y direction, and the spatial distribution 13 (T-X) or the spatial distribution 130 (T-
Figure 6 explains the relationship between crystal formation on the irradiated surface of the polysilicon layer 3 and the laser beam intensity distribution. Melted region 30, liquid phase-solid phase boundary 3oO when the polysilicon film is scanned in the Y direction with a distributed beam
1 Polycrystalline region 31° Single crystalline region 32 and crystal growth direction 32
It shows 0. The right side shows the progress of recrystallization obtained when irradiating with two mutually parallel Gaussian distribution laser beams as shown in Figure 6. As shown in Figure 2, differences in temperature distribution cause large differences in the recrystallization process. Figures 6c and d compare the temperature distribution shapes in the X direction between the above two series of laser beam irradiations. As a result, single crystal growth that inherited that crystallinity has progressed over a wide range of areas. In addition to using a birefringent plate and controlling the laser oscillation mode, methods for forming a bimodal beam as described above include using a beam splitter,
A method is known in which independent laser beams are combined into two closely spaced Gaussian beams. However, this method of laser oscillation mode control and independent laser oscillation beam synthesis is difficult to maintain stability over a long period of time, and the use of birefringent plates and beam spreaders also results in a symmetrical bimodal beam shape. Light intensity loss occurs when shaping into a mold,
Another problem is that it is not possible to have a large degree of freedom in temperature distribution control.

The present invention was developed in view of these conventional problems, and its purpose is to use a Gaussian distribution laser beam with a stable oscillation mode to condense a predetermined bimodal beam without causing any loss in light intensity. An object of the present invention is to provide a laser scanning optical system device that makes it possible.

Means for Solving the Problems In order to achieve the above object, the present invention uses an oscillator that emits a laser beam, a collimating optical system, a beam diffusing means, and a beam concentrating means, to form a predetermined bimodal beam. A laser scanning optical system that performs shaping uses an information processing system using a coherent optical system, in particular an information diffusion plate mechanism that enables high-quality, high-density image recording in the holography system.

A coherent beam emitted from a working laser oscillator and typically having a Gaussian distribution of intensity that ′=! Even when the light is focused, there are even trenches that retain all the similar shapes, but in the laser scanning optical system device of the present invention, the beam, which has been expanded by the collimating optical system, is made incident on a diffuser plate (phase plate) K having a fine structure.
To diffuse light by a predetermined width in the X-12 direction without suffering loss of light quantity.

Moreover, the fine structure of the phase plate is realized by uneven regions corresponding to a predetermined phase sequence so that the Fourier transform of its amplitude transmittance has a bimodal distribution. In this case, the above-mentioned predetermined phase series means that the phase plate is formed of, for example, a matrix-like rectangular region, and the amplitude transmittance of each row or column is 0. -π or -π, and the phase difference between adjacent terms in the matrix direction is 10-pi or -1-pi, and the Fourier transform surface, that is, the beam condensing surface, has two peaks. A stable laser beam distribution is achieved.

Embodiment FIGS. 1 to 4 are diagrams showing an embodiment of the laser scanning optical system device of the present invention and its operating status.

The laser scanning optical system device according to this embodiment includes a laser beam oscillator 6 serving as a light source, a beam expander 6, a collimating lens 7 that constitutes a collimating optical system together with the beam expander 6, and a laser beam passing through the collimating optical system. It consists of a phase plate 9 into which the laser beam 1 is incident, and a condensing lens 8 formed from a Fourier transform lens provided behind the phase plate 9. A laser beam 1 emitted from a laser beam oscillator 5 enters a phase plate 9 via a beam expander 6 and a collimating lens 7, undergoes a predetermined diffraction at the phase plate 9, and is then refracted by a condenser lens 8. A predetermined bimodal beam intensity distribution, ie, temperature distribution 13, is produced in the XY plane. In its first embodiment, the phase plate 9 has rectangular areas 91, 92, 93, . . . , as shown in FIG.
..., and with respect to the speed of light of a predetermined wavelength λ passing through each region, the phase difference is -π, O9-π...There are uneven steps like gold, and the amplitude transmission The rate can be expressed as in the X direction. Here, φ again. is the amount of phase displacement given to the light wave passing through the n-th sample region, and the phase sequence (φ.) is determined to be as follows.

The probability of occurrence is set to be equally lower when the number N of sample regions is sufficiently large.

For convenience, the power spectrum of the above amplitude transmittance on the condensing surface (ξX, ξ,) is found in the ξX direction as follows: (4) where λ: light wavelength f: focal length of the condensing lens Figure 2 shows pitches PK that differ in the two axis directions, X and Y.

A phase plate 9 consisting of a matrix of rectangular regions of PY and its light condensing surface (
ξ-k, ξ-k) shows the condensing state. The size of the main part of the bimodal power spectrum is as follows.

As an example, if PX = 2571m, λ = 4881m (nanometers), and 7 = 1401ff shoulder, then Dx-2
It's my friend.

Also, PY=100μm, λ=asanm, f=1
If we assume 4o tomo, we will get D a of 0.6 tomo.

FIG. 3 shows a one-dimensional model configuration of a phase plate 9N used as a second embodiment of the present invention. In this configuration example, the sample areas of the phase plate 9a alternately have two widths LTn and L.
s (where Lm>Ls), and the pitch between sample areas is PK.

The extension to the 02-dimensional model in which the main sequence phase level (φ2n) and the sub-sequence phase level (φ2n-N) are assigned to the sample regions of the above two types of widths Lm and Ls(L,n)Ls) is as follows: , -dimensional diffusion plates may be simply superimposed so that they are perpendicular to each other. That is, if the amplitude transmittance distribution of each diffuser plate is '(ri '' (Y)), then the orthogonally arranged diffuser plates are g(X, Y) ``g(X)'' (Y)
""" (7) Actually... (8) Here, the pitch P and the modulation degree J"i, are. If the phase difference between adjacent phase terms in the main sequence (φ2n) is φ −φ, then with equal probability - π or 21
It takes the value of 2n±22 π(--T). Overall, including subseries,
The phase difference φ2n−φ2n++ between adjacent phase terms takes a value of − or −(=−−y) with equal probability of 7.

The beam intensity obtained at the focusing surface (ξ, ξ1) through diffusion with a transmittance as expressed by the above equation 8 is calculated from the power spectrum of the transmittance distribution generated on the focusing surface, and is calculated as follows. It becomes like the expression.

ξ +li(1-M)slnc ((1-M)P-)λf
.

h −π) cos(aπKPξ) ξ X(1+J2sinc2((1+M)P)λf h (-π):)cos(aπKPξ) ξ X(1-M)slnc ((1-M)P-)λf h=.

2h+1 (□2π)] ε M2sinc2 (MP-Month) ・・・−−−(
11) λf Here, the phase difference between the phase terms of the main sequence and between the phase terms of the main sequence and the sub-sequence, φ2n - φ2n force. and φ2 n +
+-φ2n±, ±7 or 7J (J=0.1.2-...
...6) is expressed as Pr (J, α), and the phase difference between the phase terms of the subsequences φ2n+, -φ2n+1±a is expressed as Pr' (J, α], using the following recurrence formula. I can do it.

Pr(2h, 2K)"7(Pr(2h-2,-2 to 2)
+Pr (2h+2°2 to -2), l ・
...(12)Pr(-1 to 2h+1.2)=,(
Pr (2h, -2 to 2) + Pr (2h + 2゜ -2 to 2)
)) ......(13)Pr' (2h
, 2x)=, (pr(2h −1, 2 to −1)+Pr(
2h+1゜2-1)) ・・・・・・
(14) However, h is a natural number less than or equal to S/2-1,
Also, the initial condition is .

The ・(Worth vector of a width modulation diffuser plate with an arbitrary modulation degree can be obtained using Equation 11, and M=O, 0,
Figure 6 shows design examples for cases 5, 1, and ○. The horizontal axis is P==25 μm, λ=assnm.

, 7' = 70 The main part of the bimodal beam is about 1.
It becomes clear that energy is focused within a width of ○π.

The optimum value of the modulation degree M can be arbitrarily selected depending on the material to be irradiated, the laser wavelength, the scanning speed, etc.

As described in detail, according to the present invention, a laser in a stable mode, which is usually used most widely, is irradiated onto a diffuser plate arranged with a predetermined phase sequence through a fully collimated optical system, and then focused on a substrate. Since the upper amorphous layer or polycrystalline layer is scanned with a beam with a bimodal light intensity distribution, there are two
Dimensionally controlled □? It is possible to efficiently and stably achieve the desired temperature, and it is possible to grow high-quality crystals over a large area with good reproducibility.

In addition, in the collimated element system device of the present invention, the beam itself that irradiates the diffuser plate has an intensity distribution close to a Gaussian distribution (
truncated Gaussian)
Since it can be used as long as the influence on the light intensity distribution on the beam condensing surface is not a practical problem, it is effective in terms of effective use of the amount of light.

Furthermore, in the present invention, the temperature of the irradiated surface is controlled by the intensity distribution based on the phase distribution (power spectrum) of the diffuser plate, without directly using the entire intensity distribution of the beam due to the laser oscillation mode. It is possible to reliably maintain long-term reproducibility without depending on the stability of Furthermore, the beam intensity in two axial directions of the irradiated surface can be designed and controlled independently.

[Brief explanation of drawings]

FIG. 1 shows the configuration of a laser scanning optical system device according to an embodiment of the present invention, where a is a configuration diagram of the laser scanning optical system device, and b is a phase series of a phase plate used in this laser scanning optical system device. Fig. 2 is an enlarged view of the focusing state of the laser beam in the laser scanning optical system shown in Fig. 1, and Fig. 3 shows the phase series of the phase plate used in the laser scanning optical system shown in Fig. 1. Another configuration diagram, Figure 4, is an intensity distribution diagram of a laser beam shaped into a bimodal shape by various modulation degrees,
Fig. 6 shows a conventional example of a laser scanning optical system device using beam shape control;
is a spatial distribution diagram of the temperature T on the condensing surface when two laser beam irradiations are performed with the optical system device, and Fig. 6 shows the relationship between crystal formation by laser beam irradiation and the laser beam intensity distribution in the crystal generation part. 2. , b is a distribution diagram of the crystal formation state, and C,' is a distribution diagram of the laser beam intensity. DESCRIPTION OF SYMBOLS 1... Laser beam, 2... Insulating substrate, 3... Polysilicon layer, 4... Birefringent plate, 6... Laser Emitter (light source), 6...
... Beam expander, 7 ... Collimating lens, 8 ... Condensing lens, 9 ... Phase plate. Name of agent: Patent attorney Toshio Nakao and 1 other person Figure 3 Figure 4 'E, (4r+m Figure 5 (CL) Figure 6 (α) (C) (d)

Claims (3)

[Claims] (1) A laser scanning optical system is configured by a laser light source, a collimating optical system, a phase plate composed of an uneven region corresponding to a predetermined phase sequence {φi, j}, and a means for focusing the laser beam. and the phase plate has at least {O,2
/3π, 4/3π} phase series with approximately equal probability of occurrence, and this phase plate shapes the intensity of the light beam emitted from the laser light source into a bimodal shape and transfers it onto the insulating substrate. A laser scanning optical system device characterized in that it scans over a deposited amorphous layer or polycrystalline layer. (2) The phase plate is composed of rectangular uneven regions arranged in a matrix, and the pitch P_Y of the rectangular region array with respect to the laser scanning direction is P_ with respect to the pitch P_X in the direction perpendicular to the scanning direction.
2. The laser scanning optical system device according to claim 1, wherein X<P_Y. (3) The phase plate has two widths L_m and L_s(
It has a configuration in which sample regions of L_m>L_s) are arranged alternately, and a width modulation composite type pseudo-random phase sequence with a pitch P = (L_m + L_s)/2 and a modulation degree M = (L_m - L_s)/2P is used. The main sequence (φ_2n) of the amplitude transmittance g(x) is (O, 2/3π, 4/3π, and the subsequence {φ_2n+1} is {π/3, π, 5/3π} with substantially equal probability of occurrence. The laser scanning optical system device according to claim 1.