JPS59121913A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enable to form a large SOI single crystal by a method wherein a laser beam radiated from a laser oscillator is converged and irradiated from the slant direction to form an elliptic spot, and scanning is performed in parallel with the direction of the minor axis of said elliptic spot. CONSTITUTION:A laser beam 1 of 2mm. diameter generated from a 20W laser oscillator, for example, is irradiated from the aslant upper side to a loading base 7 loading a wafer 8, a convergent lens 2 is provided at the middle to converge the beam up to the prescribed size, and a spot is formed to perform scanning. Namely, the laser spot is converged up to have intensity sufficient to melt polycrystalline silicon and to convert into a single crystal, an elliptic spot 10 is formed on the concerned wafer 8, and scanning is performed in the direction in parallel with the minor axis. At the scanning method thereof, to perform scanning in the direction in parallel with the minor axis of the elliptic spot 10 formed on the wafer 8, scanning is performed along the direction of the minor axis making the prescribed width of the major axis, the degree of 50mum, for example, as scanning width. Accordingly, scanning having the broad width can be attained, and a large single crystal construction can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device using Sol technology using a laser beam.

(2) Technical background Since the emergence of the ruby laser by Mehman in 1960, laser research and development has been remarkable, and its application fields include, for example, high irradiation intensity achieved by using a focusing lens by utilizing the spatial coherence of laser beams. Various laser processing methods have been proposed in which microscopic areas are processed by irradiating the sample with laser beams.

For example, laser is used in a wide range of technologies in electronics, such as laser annealing of semiconductor devices, laser markers for probe inspection, redundant circuit cutting of semiconductor memories, and trimming of thick film resistive elements.

(3) Conventional technology and problems S OI (Silcon on
A method has already been developed in which polysilicon is attached on an insulator and a laser beam is irradiated onto the polysilicon to form a single crystal. However, the size of the spot width of the laser beam is a major factor in forming a single crystal over a wide range.In other words, the larger the spot width created by the laser beam, the larger the area to be single crystallized. This is because by spot irradiation with a laser beam, a region of the melted polysilicon except for a part of the periphery is turned into a single crystal.

Therefore, if the spot width of the laser beam irradiated onto polysilicon is increased, the area of single crystallization will also become larger, but there is also a minimum standard for the irradiation intensity per unit area in the irradiated area. In other words, it is impossible to melt polysilicon unless the laser beam has a certain amount of power. Therefore, if a laser beam is spread across a car, the irradiation intensity per unit area decreases, resulting in the inconvenience that good single crystal silicon cannot be formed.

FIGS. 1(a) and 1b) are optical path diagrams for forming a circular spot of a laser beam using a condensing lens in a conventional method, respectively;
FIG. 3 is a schematic perspective view showing the scanning of a circular spot;

For example, as shown in Figure 1 (al.
When a circular spot 3 is formed by narrowing a laser beam 1 of approximately 20 μm with a focused laser 2 to a diameter of approximately 20 μm, the diameter of the laser beam is i o −' In addition, since the illumination intensity at a circular spot is generally inversely proportional to the square of the diameter (or radius), the laser beam 1 at the circular spot 3
The illuminance is about 10 degrees higher than that of the previous year. In this way, the laser beam 1 is focused to ensure a predetermined required amount of irradiation intensity at the spot 3 on the wafer 8 to perform single crystallization. That is, conventionally, as shown in FIG. 2(b), a circular spot 3 with a width of approximately 20 μm is formed using a laser beam 1 and a focusing lens (schematic diagram), and scanning 4 is performed in a certain direction while securing an irradiation intensity of more than a certain required amount. However, if the spot width is made too large, a laser oscillator with an output of about several tens of watts will not be able to obtain the desired irradiation intensity, making it impossible to obtain good single crystal silicon.

Furthermore, it has become possible to obtain large single crystal silicon without weakening the irradiation intensity using a special lens.

That is, taking advantage of the fact that generally the irradiation intensity does not change when the irradiation area is constant, for example, a circular spot is changed to an elliptical spot with the same area, and the irradiation intensity is parallel to the short axis direction of the elliptical spot. By scanning, it is possible to form larger single crystal silicon than that produced by a circular spot. Figure S2 is a schematic diagram of an optical device that converts a circular laser beam into an elliptical laser beam. For example, using a device as shown in FIG. 2, a laser beam 1 is focused by a focusing lens 2, and two special lenses, that is, a lens 5 whose cross section forms part of a parabola (hereinafter referred to as , a circular laser beam can be taken out to an elliptical lens by transmitting it through a lens (referred to as a kamaboko lens), so by scanning parallel to the short axis direction, the laser beam can be scanned in the width of the long axis. It is possible to obtain. However, in this case, the above 2
It is difficult to properly combine the individual kamaboko lenses, and the combined lens system itself does not have very stable characteristics, making it extremely delicate to make adjustments to form an elliptical spot. It has the disadvantage that it is not very suitable for practical use because the adjustment may deviate with use due to vibrations transmitted from the X-Y stage.

(4) Purpose of the Invention The purpose of the present invention is to focus a laser beam from a laser oscillator and irradiate it from an oblique direction to form an elliptical spot, and to scan parallel to the short axis direction of the elliptical spot. An object of the present invention is to provide a semiconductor manufacturing apparatus that forms a large Solff1 crystal by using the following method.

(5) Structure of the present invention The feature of the present invention is that a laser beam generated from a laser oscillator is irradiated obliquely to the irradiation surface, and is focused by a focusing lens to form an elliptical spot light on the irradiation surface. This is achieved by providing a method for manufacturing a semiconductor device characterized by the following.

(6) Embodiment of the Invention An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 3(a) and 3(b) are a three-dimensional diagram for explaining the present invention and an explanatory diagram of an embodiment using the present invention, respectively.

Generally, for example, in a right circular cone-shaped solid 6 as shown in FIG. 3 <a>, the cut A when the solid is cut parallel to the bottom surface.
It is well known that the cut B has a circular shape similar to the bottom surface, and that the cut B when cutting at an arbitrary plane that is not parallel to the bottom surface forms an elliptical shape. Furthermore, it is well known that the elliptical shape of such a cut surface is an ellipse that is long in the long axis direction of the culm and is cut deeply three-dimensionally.

In the same figure (b), laser beam 1 from the laser oscillator
is configured to irradiate the wafer 8 mounted on the mounting table 7 obliquely from above, focus it with the focusing lens 2, and scan it.

For example, a laser beam 1 of two diameters generated from a 20W laser oscillator is irradiated obliquely from above onto the mounting table 7 on which the wafer 8 is mounted, and a focusing lens 2 is provided midway to form an aperture spot to a predetermined size for scanning. conduct. That is, the laser spot is focused to an intensity sufficient to melt the polysilicon and form a single crystal, forming an elliptical spot 10 on the wafer 8 and scanning in a direction parallel to the short axis.

In this scanning method, the elliptical spot 10 formed on the wafer 8 is scanned in a direction parallel to the short axis thereof, that is, a predetermined long axis width, for example, about 50 μm is used as the scanning width, and scanning is performed along the short axis direction. This makes it possible to perform scanning over a wider width than in the past, and to obtain a large single crystal structure.

FIG. 4 is a schematic cross-sectional view showing the irradiation of a laser beam onto a wafer by a laser oscillator from diagonally above in a semiconductor manufacturing apparatus using the present invention.

In the figure, components other than the wafer 8, which is irradiated with the laser beam of the semiconductor manufacturing apparatus, are omitted to simplify the explanation.

For example, in the case of a laser oscillator 9 using an argon laser,
Mainly an optical resonator (circuit) with reflecting mirrors at both ends and a laser tube (circuit) between which photons are generated by stimulated emission.
It consists of

A high voltage charge discharge occurs through the laser tube, generating high energy and colliding with gas molecules to create argon ions Ar.
+ is excited from the ground state to produce population inversion, which is amplified within the optical resonator and oscillates in a predetermined direction.

Here, the laser beam generated from the laser oscillator 9 is irradiated onto the wafer 8 obliquely from above, and after being reflected on the elliptical spot 10 of the wafer 8, the reflected beam travels in the opposite direction to the incident direction. It is possible to construct an efficient and stable laser beam in which the reflected beam is prevented from entering the laser oscillator 9 again.

FIG. 5 is a cross-sectional view illustrating the formation of an elliptical spot by oblique laser irradiation using the present invention.

In the figure, a laser beam 1 is irradiated onto a wafer 8 mounted on a mounting table 7 from diagonally above and focused to a predetermined size by a focused laser 2 to form an elliptical spot 10.

For example, in order to single-crystallize polysilicon provided on the wafer 8 to form a semiconductor substrate, an Alcon laser oscillator with an output of 50 W, for example, is placed on the wafer 8 diagonally from above.
A laser beam 1 is formed and irradiated by a circuit (circuit). Then, in order to obtain the irradiation intensity necessary for focusing the formed laser beam 1 of 2 mII and crystallizing it on the wafer 8, a convex lens with a focal length of 24 mm, for example, is used as the focusing lens 2.
An elliptical spot is formed on the wafer 8 by placing it at a position 23.5'bm obliquely above the spot center point of the wafer 1 on the same axis as the laser beam 1 with an incident angle θ of 63.43', for example. There is. In this case, the length of the major axis, that is, α
An elliptical spot with a short axis length of 78.6 μm and a short axis length of 35.7 μm is formed, and since scanning is performed along the short axis direction, it is possible to perform scanning with a width of 78.6 μm.

(7) Effects of the invention As described above, when the present invention is used, the output of the laser oscillator can be increased (but the irradiation intensity is high (and a wide range of irradiation can be realized), so a large SOI single crystal can be used. It has the effect that can be obtained.

Furthermore, although the above explanation has been made using single crystallization by laser irradiation as an example, the present invention can be applied to other purposes such as lowering the resistance of polysilicon and activating an ion-implanted layer for manufacturing semiconductor devices. Of course, you can also use In addition to laser beam J., conical electron beams, ion beam lamps, etc. Fig. 1, 2M, 3, 4

Claims (1)

[Claims] 1. A method for manufacturing a semiconductor device, which comprises irradiating a laser beam generated from a laser oscillator obliquely onto an irradiated surface and focusing the laser beam using a focusing lens to form an elliptical spot light on the irradiated surface.