JPH0262940B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an exposure apparatus using a laser, particularly an excimer laser, as a light source.

[Prior Art] Exposure apparatuses that use a laser light source such as a high-luminance excimer laser are conventionally known.

However, since laser light has coherency, when a mask or wafer is illuminated with laser light, interference fringes are generated on the mask or wafer, resulting in uneven exposure.

In order to suppress this kind of interference fringes, for example,
The exposure apparatus needs to be equipped with an optical system that splits the laser beam into a plurality of light beams using a light splitter and provides an optical path length difference between the plurality of light beams that is greater than the coherence length of the laser beams.

[Summary of the Invention] An object of the present invention is to provide an exposure apparatus that effectively arranges an optical system that splits a laser beam into a plurality of light beams and a light amount adjustment means that adjusts the amount of light by narrowing down the laser beam with an aperture. It's about doing.

To achieve this object, the exposure apparatus of the present invention is provided with a laser light source, a lens array, and between the laser light source and the lens array. It has a light splitting system that divides the plurality of light beams into light beams and makes the plurality of light beams enter the lens array, and an irradiation optical system that irradiates the mask with the light beams emitted from each lens of the lens array. The exposure apparatus transfers the pattern of the mask onto the wafer using the irradiated light beam, and includes a light amount adjusting means that adjusts the light amount of the light beam by narrowing the light beam from the laser light source through a predetermined aperture. It is characterized by being placed between multiple semi-transparent mirrors.

[Example] Hereinafter, an example of the present exposure apparatus will be described with reference to the drawings.

FIG. 1 shows a rotary shutter, which is an example of a light amount adjustment means used in this exposure apparatus.
has. The area ratio of the openings 2, 3, and 4 is 1:
The ratio is 1/2:1/1:4. FIG. 2 is a diagram showing a mechanism for controlling the rotation of the shutter 1 so that the pulsed laser beam 5 emitted from the excimer laser enters a predetermined opening among the openings 2, 3, and 4 of the shutter 1. be. In the figure, 6 is a light emitting diode, 8 is a light receiving element that detects light 7 from the light emitting diode 6 through the openings 2, 3, and 4, and 9 is an output signal from the light receiving element 8 as shown in FIG. This is a control device that detects the output signal and controls the rotation of the rotation shaft 10 of the shutter 1 so that the laser beam 5 irradiates a predetermined opening among the openings 2, 3, and 4 based on this output signal. Here, FIG. 3 shows the opening 2,
2 is a diagram showing a signal corresponding to the amount of light 7 from the light emitting diode 6 received by the light receiving element 8 via the light emitting diode 6 via the pulses 2', 3', 4',
are output signals from the light receiving element 8 when light is received through the apertures 2, 3, and 4, respectively. Control device 9
detects the positions and speeds of the openings 2, 3, and 4 based on this output signal.

FIG. 4 is a schematic diagram of the present exposure apparatus that performs lithography using excimer laser light.

In the figure, 11 is an excimer laser light source;
Reference numeral 1 is a light amount adjusting means, which is a rotary shutter shown in FIGS. 1 and 2; 12 is a semi-transparent mirror array, which is a splitting optical system that splits the laser beam from the excimer laser light source 1; and 13 is a semi-transparent mirror array. A fly's eye lens (lens array) 14 focuses the divided lights to form an effective light source in which a plurality of secondary light sources are distributed, and 14 focuses the light from the fly's eye lens 13 and overlaps each other. A collimator lens is a collimated irradiation optical system, 15 is a mask, and 16 is a wafer.

In this exposure apparatus, not only can the light intensity of the laser beam be easily adjusted using the shutter 1, but also a semi-transparent mirror array 12 is arranged between the shutter 1 and the fly's eye lens 13 to divide the laser beam into a plurality of beams. Therefore, the shutter 1 sends the undivided laser beam, which has a relatively small luminous flux diameter, to the aperture 2,
It suffices to narrow down the aperture by 3 or 4, and the shutter 1 can be made smaller.

In addition, in this exposure apparatus, the laser beam is focused through the apertures 2, 3, and 4 at a position away from the fly's eye lens 13 through the semi-transparent mirror array 12, so that the laser beam formed by the fly's eye lens 13 is focused. The size of the effective light source does not change much. Therefore, even though the laser beam is narrowed down by the apertures 2, 3, and 4,
The angle of incidence of the illumination light on the mask 15 can be made substantially constant, and the resolution when transferring the pattern of the mask 15 onto the wafer 16 can be stabilized. The diameter of rotary shutter 1 of this exposure device is 254
mm, rotation speed is 30 times/min, and the openings 2, 3, and 4 are provided at an average position of 100mm from the center of the shutter 1, the speed of the openings 2, 3, and 4 is 314.16mm/min.
sec. On the other hand, the luminous flux diameter is 30 mm, and the emission time is 50 nsec.
When a laser beam is emitted from the excimer laser light source 11, the position of the opening of the shutter 1 moves only 0.0157 μm during this emission time, and it can be considered that the shutter 1 is substantially stopped. Under such a premise, by synchronizing the rotation of the shutter 1 and the emission timing of the pulsed laser light, the amount of laser light can be easily adjusted by a predetermined opening of the shutter 1.

In FIG. 4, a pulsed laser beam emitted from an excimer laser light source 11 passes through a predetermined opening of a shutter 1 rotating at a constant speed, a semitransparent mirror array 12, a fly's eye lens 13, and a collimator lens 14. , enters the mask 15 and the wafer 16. Here, when the emission timing of the excimer laser light source 11 and the rotation of the shutter 1 are synchronized so that the laser beam passes through the aperture 2 of the shutter 1, the amount of laser light that has passed through the aperture 2 is too large. In this case, the control device 9
While monitoring the rotational speed of the shutter 1 based on the output signal from the light receiving element 8 shown in FIG. The rotational speed of the shutter 1 is modulated so that the As a result, the amount of exposure light is optimized.

Although three types of openings were provided in this example,
It is also possible to provide more than that. FIG. 5 shows a shutter according to another embodiment, in which numeral 17 is a wedge-shaped opening. When using this shutter, the amount of light can be continuously adjusted by changing the rotation timing.

[Effects of the Invention] As explained above, in the present invention, the light intensity of the laser beam can be easily adjusted, and even if the laser beam is narrowed down by the aperture for adjusting the light intensity, the size of the effective light source formed by the lens array can be reduced. does not change much, so the resolution when transferring the mask pattern to the wafer is stable. Therefore, it is possible to provide a highly reliable exposure apparatus.

[Brief explanation of drawings]

1 is a diagram showing an example of the light amount adjusting means used in the exposure apparatus of the present invention, FIG. 2 is a diagram showing a mechanism for controlling the light amount adjusting means shown in FIG. 1, and FIG. 3 is a diagram showing the light amount shown in FIG. 1. A diagram showing a signal corresponding to the amount of light detected by the light receiving element through the opening of the adjustment means, FIG. 4 is a schematic configuration diagram showing an example of the exposure apparatus of the present invention, and FIG. 5 is a diagram showing the light amount adjustment means. It is a figure which shows another Example. 1... Shutter, 2, 3, 4, 17... Opening, 5... Laser light, 6... Light emitting diode,
7... Light from light emitting diode, 8... Light receiving element, 9... Control device, 10... Rotating shaft, 11...
Laser light source, 12... Semi-transparent mirror array, 13...
Fly's eye lens, 14...Collimator lens,
15...Mask, 16...Wafer.

Claims (1)

[Claims] 1. A laser light source, a lens array, and a light beam provided between the laser light source and the lens array, which divides the light beam from the laser light source into a plurality of light beams with a semi-transparent mirror array, and transmits the plurality of light beams to the lens array. It has a light splitting system that makes the light incident on the mask, and an irradiation optical system that irradiates the mask with the light flux emitted from each lens of the lens array, and the pattern of the mask is transferred onto the wafer with the light flux irradiated by the irradiation optical system. The exposure apparatus is characterized in that a light amount adjusting means for adjusting the amount of light from the laser light source by narrowing the light beam through a predetermined aperture is disposed between the laser light source and the plurality of semi-transparent mirrors. exposure equipment.