JPH0815512A - Apparatus for producing zone plate - Google Patents

Abstract

PURPOSE:To make it possible to shorten working time without degrading performance by making adjustment in such a manner that the diameter of a condensed luminous flux is small near the end in the radial direction of rotation and is larger than the diameter in other parts. CONSTITUTION:The condensing position is adjusted in such a manner that the position comes on the working start position of a region meeting the transmission ring band on the extreme central side by controlling a driving mechanism 2 according to a design value and moving a condensing optical system on the X-axis of a coordinate system including a working origin 0. The light spot of the smallest diameter is formed on a resist by adjusting the width of a variable slit 4 and the magnification of an objective lens 6 after the end of the position adjustment. The circular region to be exposed of the min. line width is formed by rotation of a zone plate substrate 1 according to rotation of a turn table. The diameter of the condensed luminous flux is then increased by adjusting the width of the variable slit 4 and the objective lens 6 while controlling the movement of the condensing optical system in a radial direction. As a result, the large light spot is formed on the resist.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for manufacturing a zone plate as a diffractive optical element having a concentric circular pattern.

[0002]

2. Description of the Related Art Among diffractive optical elements, an element having a concentric circular pattern (hereinafter referred to as a zone plate) has an annular pattern having a predetermined radius and width (radial width) from a central portion on a substrate. Has been formed. As an example,
Fresnel zone plates and the like are known, but in the case of a transmissive type, it is generally one in which light-transmissive annular zones and non-transmissive annular zones are alternately formed on a light-transmissive substrate. Target. In addition, the pattern of the transmissive zone plate has a mutual light transmissivity (refractive index or transmission distance, etc.).
It is also known that different parts are provided concentrically.

When manufacturing such a zone plate, exposure transfer is performed from a mask having the same pattern on a photoreactive substrate to be processed, or the substrate is directly cut according to the pattern shape. There is known a method for directly performing electron beam drawing of a pattern shape or the like.

Further, in recent years, a photoreactive substrate is used, and while the substrate is rotated, a part of the light is focused and irradiated to form an annular processing region, and the irradiation region is provided along the radius of rotation. There is known a method in which a plurality of annular processing regions are formed by moving the substrate, and thereby a concentric processing process is performed on the substrate.

In drawing such a zone plate, in order to equalize the light processing state for each annular pattern, that is, to equalize the irradiation light amount, the unit irradiation light amount determined by the light source light amount and the condensing diameter, Irradiation time (substrate rotation speed,
The peripheral velocity or the angular velocity) is controlled.

[0006]

The pattern accuracy of the zone plate is determined by the position and contour shape of the radial end (edge) of each annular pattern. In other words, if the zone plate is incorporated in a lens optical system or an optical device and used, a desired diffracted light cannot be obtained unless a sharp edge is formed at the designed position. The shape of the edge, which directly affects the performance of the zone plate, depends on the state of the luminous flux irradiated during processing (drawing). For example, if the position of the condensed light beam is deviated from the design value or the light spot formed on the workpiece by the condensed light beam is blurred, the position of the edge and the contour shape cannot be formed as designed.

However, usually the zone plate is
Each annular pattern has a different width. Therefore, when processing a relatively wide annular region, it is conceivable to change the magnification of the focusing optical system to increase the diameter of the focused light flux on the workpiece. But,
At this time, the light spot formed on the workpiece has a blurred outline, and processing (drawing) is performed with such a blurred light beam.
However, as described above, the edge portion of the pattern does not have an accurate shape.

On the other hand, an accurate edge can be obtained by reducing the light-collecting diameter. In the conventional technique, however, the edge portion of the pattern and the other portion (between both edges in the radial direction) are distinguished from each other. Therefore, in order to process the necessary width area, while processing, keep the constant small condensing diameter and gradually move the condensing position on the work piece gradually in the radial direction to fill gradually. I had to illuminate and go. In such a drawing method, there is a problem that the processing time becomes long and the throughput decreases.

In view of the above problems, it is an object of the present invention to provide a zone plate manufacturing apparatus capable of shortening the processing (drawing) time as compared with the prior art without degrading the performance of the zone plate.

[0010]

In order to achieve the above object, in the zone plate manufacturing apparatus according to the invention of claim 1, an annular processing area is provided by processing a rotating workpiece. A zone plate manufacturing apparatus for forming a concentric pattern on a workpiece by moving a machining position on the workpiece and performing the processing at different positions together with forming the workpiece. A rotary table on which is mounted, a condensing means for condensing a predetermined luminous flux on the surface of the workpiece, and a condensing position by the condensing means is at least orthogonal to the central axis of rotation of the rotary table. A moving means for moving in the direction, and an adjusting means for variably adjusting the diameter of the condensed light flux on the workpiece by the light collecting means, wherein the adjusting means is any one of the annular processing. Within the region, the diameter of the condensed light flux is adjusted so that the diameter of the condensed light flux is reduced near the radial end of the rotation, and the diameter of the condensed light flux is increased in other portions. .

Further, in the zone plate manufacturing apparatus according to the second aspect of the invention, in the zone plate manufacturing apparatus according to the first aspect, individual design conditions of the concentric pattern forming the desired zone plate are input. The moving means positions the light collecting position at a position corresponding to a concentric circular pattern based on the input information, and moves the light collecting position in the rotation radius direction to form an annular shape. Is formed, and the adjusting means adjusts the diameter of the condensed light flux based on the positional information in the annular processing area by the moving means.

Further, in a zone plate manufacturing apparatus according to a third aspect of the invention, in the zone plate manufacturing apparatus according to the first or second aspect, the condensing means is a plurality of condensing luminous flux diameters. The adjusting means includes a switching means for selectively switching the plurality of light collecting means.

[0013]

In the zone plate manufacturing apparatus of the present invention, the workpiece is placed on the rotary table, and while rotating the workpiece, the light collecting means collects a predetermined light beam on the surface of the workpiece, By moving the light collecting position of the light collecting means by the moving means at least in the direction orthogonal to the rotation center axis of the rotary table and performing the processing at different positions, a plurality of annular processing target areas are formed on the workpiece. In order to form a concentric circular pattern consisting of, by the adjusting means for variably adjusting the diameter of the condensed light flux on the workpiece by the light condensing means, in any one of the annular processing regions,
The diameter of the condensed light beam is reduced in the vicinity of the radial end of the rotation, and the diameter of the condensed light beam is adjusted to be larger in other portions.

According to such a zone plate manufacturing apparatus, when processing an annular pattern having a relatively large width, it is possible to draw with a small condensed light beam diameter at the end portion in the radial direction (edge portion of the pattern). A light spot having no blur on the contour is formed on the portion to be processed, whereby the edge portion can be machined as designed without displacement or contour blur. At the same time, processing can be performed with a large focused beam diameter from the edge portion on the center side to the next edge portion on the outer peripheral side, so that the processing time can be short even in a wide processing region. This time,
When the diameter of the focused light beam is increased by adjusting the focusing optical system, the contour of the light spot formed on the workpiece may be blurred, but the processing area is between the edges. , Does not affect the pattern processing accuracy. As a means for adjusting the diameter of the condensed light beam, there is a method of adjusting the objective lens in the light condensing optical system to change the magnification. In addition to changing the magnification, a variable slit is provided in the optical path to adjust the diameter of the condensed light flux. You may use the method of adjusting.

Further, as described in claim 2, if the zone plate manufacturing apparatus further comprises an input means for inputting individual design conditions of the concentric pattern forming the desired zone plate, the moving means is: Based on the design condition of the input means, the condensing position is sequentially located at a position corresponding to each concentric pattern, and the condensing position is moved in the radial direction of rotation to form an annular processing region. You can In addition, the adjusting means adjusts the diameter of the focused light flux based on the position information in the annular processing region by the moving means, so that the focusing position moves in the radial direction from the rotation center. When the pattern edge portion is reached, the diameter of the condensed light beam is reduced, and the diameter of the condensed light beam is increased between the center side edge and the outer peripheral side edge in the processing area.

Further, as described in claim 3, if a plurality of condensing means having different condensing light flux diameters are provided and the switching means in the adjusting means is configured to selectively switch the plurality of condensing means. As the focus position moves in the radial direction from the center of rotation, the focused beam diameter is small at the pattern edge portion, and the focused beam diameter is large between the center side edge and the outer side edge in the processing area. Since it can be switched to a different one, it takes only a short time to change the size of the condensed light beam diameter, and it is more processed than when adjusting the objective lens etc. of the condensing optical system one by one to change the condensed light beam diameter. Can be done more efficiently.

When the objective lens of the condensing optical system is adjusted to increase the diameter of the condensed light flux, if the light amount of the light source is uniform, the light amount per unit area decreases. Therefore, the amount of irradiation light required on the workpiece (for example, the amount of exposure to the photosensitive substrate)
If any one of the rotation speed, the angular speed, and the peripheral speed is adjusted so as to obtain, the processing state can be made uniform in each part of the pattern on the workpiece as a result. Further, a light amount adjusting means such as an ND filter may be provided on the light source side and a method of increasing the light amount may be used when increasing the diameter of the condensed light flux.

Further, the zone plate in the present invention is a diffractive optical element having a plurality of concentric circular patterns and is not limited to a Fresnel zone plate composed of a transmission ring zone and a light blocking zone, but is formed of a transmission area. Concentric circles with different areas of transmittance, refractive index, etc., condensing or diverging, correcting, so-called binary optical element (BOE) with step structure, refractive index distribution by interference fringes With holograms, etc. are included.

[0019]

EXAMPLES The present invention will be described below with reference to examples.
In this embodiment, the manufacturing apparatus shown in FIG. 1 is used to draw and expose a concentric circular pattern by laser light (processing means) to form a concentric quartz transmission ring zone and a chrome light blocking zone as shown in FIG. The case where a zone plate in which is alternately arranged is manufactured is shown.

The apparatus shown in FIG. 1 comprises a condensing optical system for condensing laser light from an illumination optical system onto a workpiece placed on a rotary table, and a laser light converging system by the condensing optical system. A drive mechanism (moving means) 2 for moving the light position in a direction orthogonal to the central axis of rotation of the rotary table is provided. The drive mechanism 2 is designed under the design condition of a concentric pattern input to the control device (see FIG. According to the position information according to 2), the condensing optical system is controlled to move within a unique machining plane coordinate system.

The laser light from the light source 3 becomes parallel light having an appropriate beam diameter by the beam expander and enters the condensing optical system. A variable slit 4 is provided as an adjusting means for adjusting the diameter based on the position information. Since the objective lens 6 in the condensing optical system forms a light spot by forming the aperture image of the variable slit 4 on the workpiece, the light spot diameter changes according to the aperture change of the variable slit 4.
Further, the objective lens 6 itself is also provided so as to be adjustable, and the size of the light spot corresponding to the opening of the variable slit 4 formed on the workpiece can be further changed.

In such an apparatus, first, on the machining plane coordinate system, the machining reference origin 0 is matched with the rotation center position of the rotary table which is the optical axis of the zone plate. Then, the zone plate substrate 1 is placed on the rotary table. Here, the zone plate substrate 1 is the quartz plate 1
1 has a chrome layer 12 formed on it, and a positive resist is applied to the surface thereof.

After the zone plate substrate 1 coated with the resist is placed and the rotary table is rotated at a predetermined angular velocity, the control device first controls the drive mechanism 2 in accordance with the previously input design value. Then, the condensing optical system is moved on the X axis of the coordinate system including the machining origin 0, and the condensing position is on the machining start position (radius r1 = 193.56 μm) in the region corresponding to the transmission ring zone on the most center side. Adjust the position so that it fits. After the position adjustment is completed, the width of the variable slit 4 and the magnification of the objective lens 6 are adjusted to adjust the minimum diameter (here, 0.2 μm).
Light spot) is formed on the resist. By the rotation of the zone plate substrate 1 accompanying the rotation of the rotary table, a circular exposed area having a minimum line width by this apparatus is formed.

Then, the variable slit 4 width and the objective lens 6 are adjusted while controlling the movement of the focusing optical system in the radial direction to increase the diameter of the focused light flux. As a result, a large light spot is formed on the resist, and the annular exposed portion is expanded so that the width of the previous circular exposed region expands as the substrate 1 rotates and the focus position moves in the radial direction. Is formed. At this time, since the irradiation light amount per unit area is reduced, the light amount adjustment mechanism F on the light source 3 side is adjusted so that the irradiation light amount required for exposure is obtained.
Thereby increasing the intensity of light incident on the condensing optical system.

Then, based on the position information from the driving mechanism 2, the outer peripheral portion of the exposed region approaches the position (radius r2 = 273.73 μm) corresponding to the outer peripheral side end portion of the first transmission ring zone. At this point, the width of the variable slit 4 and the objective lens 6
When the light spot diameter is minimized again and the minimum light spot is focused on the position corresponding to the outer peripheral side end of the first transmission ring zone to form a circular exposed region having the minimum line width. so,
The exposure of the area corresponding to the first transparent ring zone is completed. By the above operation, an annular exposed region having a width r2-r1 = 80.17 .mu.m having sharp edges at the center side edge and the outer peripheral side edge was formed.

Further, the drive mechanism 2 is controlled based on the position information from the control device to move the condensing position in the radial direction, and the center side end of the second transmission ring zone (radius r3 = 387.
12 μm) as the second machining start position,
Similarly to the first case, while adjusting the width of the slit 4, the objective lens 6 and the light amount on the light source 1 side according to the position information, first, a light spot having a small diameter is formed at the end portion, and then the outer peripheral side end portion. Exposure is performed with a large-diameter light spot to the vicinity and again with a small-diameter light spot at the outer peripheral side end.
As a result, the width r4-r3 = 5 having a sharp edge
An annular exposed area corresponding to a second transparent ring zone of 1.87 μm was formed.

After this, similarly, the third, fourth to 545th
An annular exposed area corresponding to the transmission ring zone 37 is formed. The width of the exposed area corresponding to the outermost transparent ring is r54.
538−r54537 = 0.5 μm. Since the width of the region to be exposed is extremely small in the vicinity of the outermost circumference, the diameter of the converged light beam between the center-side end and the outer-side end may remain the minimum diameter on the end.

However, when the rotation by the rotary table is constant in angular velocity, the peripheral velocity becomes higher as the outer periphery becomes closer, and the exposure amount per unit becomes smaller. Therefore, in this embodiment, the rotation angular velocity of the rotary table was adjusted according to the movement of the focusing position so that the exposure amount per unit was uniform as a whole.

By the above operation, the resist layer on the zone plate substrate 1 is exposed in the region corresponding to the entire transmission ring zone. Thus, after the exposure was completed, the zone plate substrate 1 was removed from the rotary stage, and the resist in which the exposed region was denatured was dissolved and removed by the developing solution.
As a result, the resist in the region corresponding to the concentric light-shielding ring zone remains, and the chromium layer is exposed between the resist ring zones.
This resist pattern has a sharp edge for each annular pattern.

After the chromium layer was removed by etching using this resist pattern as a mask, all the remaining resist was removed. The chrome light-shielding zonal zones thus obtained all have sharp edges, and by the above steps, a zone plate in which the design values shown in FIG. 2 were reproduced with high precision was obtained.

In the above embodiment, the exposure in the corresponding region of each transmission ring zone by the apparatus of FIG. 1 was continuously performed from the processing reference origin side toward the outer circumference of the radius.
The present invention is not limited to this. For example, after exposing the center side edge of the area with a light spot with a small diameter, the focus position is moved to the outer side edge and the area is exposed with the same spot. A method of controlling the movement of the condensing optical system by the drive mechanism by returning the condensing position to the vicinity of the end and increasing the light spot diameter at this time to expose between both ends may be used. As a result, in consideration of the adjustment of the light quantity, the adjustment of the rotation speed, the adjustment of the diameter of the condensed light beam, etc., the procedure that provides the highest efficiency in terms of time may be set as appropriate.

The adjustment of the rotation speed of the turntable (adjustment of the exposure time) and the adjustment of the amount of light are appropriately set according to the photosensitive material and the light source used.

[0033]

As described above, according to the present invention,
The end of each pattern can be processed as designed with a small converging light beam in both the converging position and the shape, and the processing between the ends can be done by increasing the diameter of the converging light beam, so the design is reproduced with high accuracy. The zone plate can be efficiently manufactured in a short time.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a zone plate manufacturing apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic view of a zone plate manufactured by the apparatus shown in FIG.

[Explanation of symbols]

 1: Zone plate substrate 2: Driving mechanism 3: Laser light source 4: Variable slit 5: Mirror 6: Objective lens 11: Quartz plate 12: Chromium (Cr) layer

Claims (3)

[Claims] 1. An annular processing area is formed by processing a rotating workpiece, and a processing position on the workpiece is moved to perform the processing at different positions. A zone plate manufacturing apparatus for forming a concentric circular pattern on a workpiece, a rotary table on which the workpiece is placed, and a condenser for condensing a predetermined light beam on the surface of the workpiece Means, moving means for moving the light collecting position by the light collecting means at least in a direction orthogonal to the central axis of rotation of the rotary table, and variable the diameter of the light beam condensed by the light collecting means on the workpiece. Adjusting means for adjusting, wherein the adjusting means reduces the focused light beam diameter in the vicinity of the radial end of the rotation in any one of the annular processing regions, and collects it in other portions. As the light beam diameter is larger, the zone plate manufacturing apparatus characterized in that adjusting of the focusing beam diameter. 2. An input means for inputting individual design conditions of a concentric pattern forming a desired zone plate, wherein the moving means is located at a position corresponding to the concentric pattern based on the input information. The focusing position is located, and the focusing position is moved in the radial direction of rotation to form an annular processing region, wherein the adjusting unit is the annular processing region by the moving unit. The zone plate manufacturing apparatus according to claim 1, wherein the focused light flux diameter is adjusted based on position information inside the zone plate. 3. The condensing means includes a plurality of condensing means having different condensing light flux diameters, and the adjusting means includes a switching means for selectively switching the plurality of condensing means. The zone plate manufacturing apparatus according to claim 1 or 2, which is characterized.