KR20190103000A - Projection exposure apparatus - Google Patents

Abstract

The present invention relates to a projection exposure apparatus which prevents the degradation of the light quantity by installing a relay optical system. The projection exposure apparatus comprises: an illumination optical system in which the emitted light of a light source is incident on an illumination light uniforming means, and the emitted light of the illumination light uniforming means illuminates reticle; a light shielding means, which is installed on an exit part of the illumination light uniforming means, and capable of displacing a light shielding area by blocking a part of the luminous flux of the emitted light.

Description

Projection exposure apparatus {PROJECTION EXPOSURE APPARATUS}

TECHNICAL FIELD This invention relates to the projection exposure apparatus which exposes a pattern to a wafer by step-and-repeat.

In a lithography process included in a manufacturing process such as a semiconductor device or a liquid crystal display, a projection exposure apparatus uses a pattern of a reticle as an original as a photosensitive substrate (a resist layer is formed on a surface thereof) through a projection optical system. Wafer). In the step and repeat method of moving a wafer to expose a sequential pattern, step movement and exposure of the wafer are alternately repeated. When the exposure position comes to the wafer edge (peripheral portion), there is a function of not exposing a predetermined range from the edge end. This wafer peripheral non-exposure function is referred to as WEM (wafer edge masking).

For example, in the case of a negative photoresist, the WEM does not expose the peripheral portion, thereby removing excess photoresist at the wafer edge during development. Alternatively, in the case of a positive photoresist, a WEM is used to prevent exposure spots (partial double exposure by the projection exposure apparatus and the peripheral exposure apparatus) of the wafer edge when the wafer edge is exposed using a separate peripheral exposure apparatus. Used.

As a technique of WEM, the mechanism which installs a light shielding plate on a wafer, and the mechanism which provides a light shielding plate in a reticle conjugate space position are known. For example, Patent Document 1 describes a mechanism for carrying in and carrying out a ring-shaped light shielding plate on a work chuck. In addition, Patent Document 2 describes that a light shielding band is provided above the wafer. Patent Document 2 describes that the light shielding band has a plurality of curvatures and rotates and moves the light shielding band. In addition, Patent Document 3 describes a mechanism for providing a light shielding plate at a reticle airspace position.

WEMs shielding on wafers are relatively simple in structure and do not require complex control. On the other hand, attention should be paid to the selection of parts, maintenance, and the like, for wafer contamination caused by particles from the movable portion for moving the light shielding body or wafer damage due to contact between the light shielding portion and the wafer. Moreover, since the light shielding plate is provided apart from the wafer, there is a problem that blur occurs at the light shielding boundary.

The WEM shielding at the reticle conjugate position has a problem that the amount of light decreases as the optical elements such as the relay lens increase, and the movement mechanism and control of the light shielding plate are complicated. On the other hand, there is no worry of contamination or damage of the wafer, and there is little advantage in blurring of the light shielding boundary. In consideration of the features of these two systems, the merits of adopting the WEM at the reticle conjugate position are large as it becomes a projection exposure apparatus requiring high-precision exposure.

Japanese Patent Publication No. 2005-505147 Japanese Laid-Open Patent Publication No. 2005-045160 Japanese Unexamined Patent Application Publication No. 2011-233781

In order to increase the size of one exposure range (exposure area), it is conceivable to improve the illuminance distribution by using, for example, a rod lens as the illumination light uniforming means in the illumination optical system. When the rod lens and the relay optical system are provided in the illumination optical system, a decrease in the amount of light becomes a problem. In order to solve this problem, in order to realize WEM to the reticle conjugate plane without providing the relay optical system, it is conceivable to install a WEM mechanism next to the rod lens exit surface.

In the optical design, it is ideal that the light shield plate and the rod lens exit are provided at the reticle conjugate position. However, in order to avoid interference of the movable part, it is necessary to provide a gap between them. When this gap is widened, the following disadvantages arise.

The farther the rod lens exit is from the reticle conjugate position, the worse the illuminance distribution of the light irradiating the reticle.

As the light shielding plate moves away from the reticle airspace position, blur occurs at the edge portion of the projected image of the light shielding plate, and when developed, the cross section of the photoresist becomes inclined at the blur.

On the other hand, when the light blocking plate contacts and scratches the rod lens exit surface, the defect is projected onto the wafer as it is, so high rigidity, reliable operation, and easy maintenance are necessary to narrow the gap. In addition, the space between the rod lens exit surface and the next lens (critical illumination lens group) is narrow, and it is necessary to provide a WEM mechanism in this space. In Patent Document 2, there is no disclosure about a mechanism for rotating and moving the light shielding band, and there is no consideration about providing the light shielding band in a narrow space.

It is therefore an object of the present invention to provide a projection exposure apparatus having variable light shielding means having a space-saving configuration that can be disposed close to the exit of the illumination light uniforming means.

According to the present invention, the light emitted from the light source is incident on the illumination light uniforming means, and the light emitted from the illumination light uniforming means is provided with an illumination optical system for illuminating the reticle, and an exit portion of the illumination light uniforming means to shield a part of the luminous flux of the emitted light. It is a projection exposure apparatus provided with the light shielding means which can displace a light shielding area | region.

According to at least one embodiment, the variable light-shielding means which forms a desired non-exposed area can be made space-saving. Therefore, it is possible to provide the variable light shielding means at the exit of the illumination light uniforming means, and to prevent the decrease in the amount of light. In addition, the effect described here is not necessarily limited, Any effect described in this invention, or the effect of heterogeneity may be sufficient.

1 is a diagram illustrating a configuration of an exposure apparatus according to an embodiment of the present invention.
FIG. 2 is a front view, a plan view, and a side view of a light shielding plate in one embodiment. FIG.
3 is a cross-sectional view of the light shielding mechanism in one embodiment.
FIG. 4 is a diagram illustrating the light shielding plate moving mechanism in the embodiment. FIG.
FIG. 5 is a plan view of a wafer used for describing the exposure operation. FIG.
FIG. 6 is a front view of another example of a light shielding plate. FIG.
FIG. 7: is a figure which shows the other structural example of a light shielding plate movement mechanism.
FIG. 8 is a diagram showing still another configuration example of the light shielding plate moving mechanism.

EMBODIMENT OF THE INVENTION Hereinafter, it demonstrates, referring drawings for embodiment of this invention. In addition, description is given in the following procedure.

<1. Embodiment of work>

<2. Variation>

Embodiments described below are very suitable specific examples of the present invention, and the content of the present invention is not limited to these embodiments and the like.

<1. Embodiment of work>

`` Device configuration ''

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram of one Embodiment of the projection exposure apparatus of this invention. The projection exposure apparatus has the light source 1 and the illumination optical system 4 which makes the emission light of the light source 1 into illumination light of uniform illuminance. Illumination light from the illumination optical system 4 is irradiated to a reticle (photomask) 8 which is a disc of a pattern. The image of the reticle 8 is projected onto the wafer 13 by the projection optical system 12.

The wafer 13 is mounted on the exposure stage (work chuck) 14. The exposure stage 14 is moved by the stage moving mechanism 15. The stage moving mechanism 15 and the optical system (light source 1, illumination optical system 4, projection optical system 12) are supported by the scaffold 16. As shown in FIG. In addition, in FIG. 1, each element is represented by sectional drawing along the main optical axis, and hatching at that time is abbreviate | omitted.

The light source 1 is a UV lamp which emits light which is a broadband including g, h and i lines. Moreover, the elliptical mirror 2 is provided as a condensing mirror. The light of the light source 1 is reflected by the mirror 3 and condenses toward the entrance of the rod lens 5 of the illumination optical system 4. The rod lens 5 is supported by the rod lens support part 6. As a light source 1, a mercury lamp, a laser, etc. may be used.

The illumination optical system 4 includes a rod lens 5 and a critical illumination lens group 7. The rod lens 5 is a transparent body having a polygonal cross section and functions as illumination light uniforming means by internal surface reflection. As illumination light uniforming means, you may use not only a rod lens but an inner surface reflector (polygon cylinder which bonded several mirrors inwardly). Moreover, the illumination optical system 4 is equipped with the light shielding mechanism (WEM mechanism) 11 mentioned later.

In addition to the pattern exposure region, photoresist is applied to at least a portion of the periphery of the wafer 13. A photoresist is a photosensitive material which forms a pattern using ultraviolet rays. As photoresist, any of a positive type and a negative type may be sufficient. A predetermined non-exposed area is set at the periphery of the wafer 13. For example, a width of 5 mm becomes a non-exposed area over the entire edge of the edge of the wafer 13. In the periphery of the wafer 13, a notch or orientation flat for angular alignment of the wafer may be provided.

In one embodiment, the light shielding plate 17 is provided on the conjugate plane of the wafer 13 of the illumination optical system 4. In addition, the light shielding plate 17 is located at the exit of the rod lens 5. Specifically, the exit surface of the rod lens 5 is positioned at a position close to the light shielding plate 17. In this way, the position from the exit surface of the rod lens 5 to the position slightly apart is called the exit portion of the rod lens 5. As for the separation distance, the exit surface of the rod lens 5 is located at an interval of 3 mm with respect to the light shielding plate 17, for example. Moreover, although intervals other than 3 mm may be sufficient, the interval as narrow as possible is preferable. In addition, the exit surface of the rod lens 5 may coincide with the conjugate surface. FIG. 2 shows a front view, a plan view, and a side view of an example of a light shielding plate 17 for shielding light along a peripheral non-exposed area of the wafer 13, and FIG. 3 shows an enlarged view of the light shielding mechanism 11. 4 shows the light shielding mechanism 11 seen from the emission surface.

The light shielding plate 17 is obtained by depositing a black light shielding agent on the same material as the reticle 8, for example, a plate of quartz glass. The light shielding plate 17 has four arc-shaped edges R1, R2, R3, and R4 having an arc-shaped notch R0 on the inner circumferential side and having a radius (i.e., different curvature) on the outer circumferential side. It has a shape. Moreover, mounting blood 18a, 18b, and 18c are formed, and ring-shaped holder 19 is attached by mounting blood 18a, 18b, and 18c as shown in FIG. The ring holder 19 is made of metal, for example, and the light shielding plate 17 is reinforced.

In addition, the edge part of the circular arc shape of the light shielding plate 17 has a tapered cross section corresponding to NA (opening ratio) of an illumination optical system. The tapered shape is for preventing a decrease in the amount of light emitted from the non-exposed areas. Moreover, although there are four edges on the circular arc of the light shielding plate in an Example, it is not necessary to limit to this. For example, it may be a light shielding plate having two circular arc edges. Since the light shielding plate 17 has edges of different curvature, it is possible to correspond to the non-exposed areas of the wafer 13 of different radii, and the light shielding plate 17 can be replaced according to the radius of the non-exposed areas of the wafer 13. There is an advantage that does not need to.

`` Light shield plate moving mechanism ''

The position of the light shielding plate 17 is displaced by the light shielding plate moving mechanism. The light shielding plate moving mechanism includes a linear motion mechanism 23, a first θ axis mechanism and a second θ axis mechanism. And the variable light shielding means is comprised by the light shielding plate 17 and the light shielding plate moving mechanism. As shown in FIG. 4, the circular arc notch R0 inside the light shielding plate 17 or the circular arc inside the ring holder 19 is attached to the rotating shaft of the arc switching motor 20. The arc switching motor 20 is fixed to the base plate 21. The base plate 21 is attached to the linear motion mechanism 23 by the detachable screws 22a and 22b. That is, the base plate 21 to which the light shielding plate 17 and the circular arc switching motor 20 are previously attached is made detachable with respect to the linear motion mechanism 23. Therefore, the light shielding plate 17 is exchanged integrally with the arc switching motor 20 and the base plate 21. In addition, the mechanism for rotating the light shielding plate 17 by the arc switching motor 20 is called a 2θ shaft mechanism.

The linear motion mechanism 23 is a single axis actuator such as a ball screw, and is a mechanism for linearly displacing the light shielding plate 17 and the arc switching motor 20. By the linear motion mechanism 23, the edge of the light shielding plate 17 approaches or is spaced apart from the optical axis of the illumination optical system 4. The linear motion mechanism 23 sets the position of the edge of the light shielding plate 17 corresponding to the width of the non-exposed area.

The 1θ axis mechanism is a rotation mechanism that rotates the light shielding plate 17 around the optical axis of the illumination optical system. As shown in FIG. 3, the hollow motor 24 is provided and the hollow shaft 25 is rotated by the hollow motor 24. As shown in FIG. The hollow motor 24 is equipped with rotary cable parts 26, such as a slip ring. The rod lens support part 6 which has the rod lens 5 is provided in the hollow shaft 25, and the center of the hollow shaft 25 and the optical axis of the rod lens 5 will correspond.

The rotating stage 28 (rotating body) is attached to the exit side of the rod lens 5 of the hollow shaft 25. As for the rotation stage 28, the front-end | tip of the hollow shaft 25 is fixed to the center position in the disk shape. The linear motion mechanism 23 is attached to the rotating stage 28 via a mounting portion. For example, the radial direction of the rotating stage 28 and the direction of the linear motion of the linear motion mechanism 23 are made to correspond. As described above, the second θ shaft mechanism having the light shielding plate 17 and the arc switching motor 20 is attached to the linear motion mechanism 23. Therefore, when the hollow shaft 25 is rotated by the hollow motor 24, the rotation stage 28, the linear motion mechanism 23, and the 2θ shaft mechanism rotate integrally.

In addition, the position detection sensor 29 of the light shielding plate 17 is provided in the light shielding plate moving mechanism at a position facing the light shielding plate 17 with the optical axis therebetween. The position detection sensor 29 is attached to the rotation stage 28 so as to rotate together with the light shielding plate 17, and always holds a position facing the light shielding plate 17, and the light shielding plate 17 is directed to a target position. It is confirmed by the position detection sensor 29 every time whether it is in the correct position (for example, whether the amount of protrusion of the light shielding plate 17 is according to a set value). As the position detection sensor 29, the position measurement sensor using a laser, the image recognition sensor using a camera, etc. are used.

`` Blocking behavior ''

5 is a diagram illustrating a step and repeat exposure operation on the wafer 13. In the example of FIG. 5, 41 exposures are performed. One exposure range (hereinafter referred to as a shot suitably) is represented by a rectangle, and the cross represents the center of the shot (position of the optical axis). The rectangle of one shot is basically determined by the reticle 8. A blind or the like for defining the shot may be provided.

The non-exposed area MA of a predetermined width from the outer circumference of the wafer 13 to the inner boundary is set. Light is not incident on the non-exposed area MA by the light blocking plate 17. The light is shielded from the surrounding shot including the non-exposed area MA. In the exposure operation of the position where the shot does not catch the non-exposed area MA, the light shielding plate 17 is retracted to the position to retract from the rod lens 5.

In FIG. 5, the light shielding area by the light shielding plate 17 is represented by SA and the shots on which the non-exposed area MA is applied are shown by EA1 and EA2 in the example of the upper left portion of the wafer 13. In shots EA1 and EA2 in which the exposure area is exposed to the non-exposed area MA, the light shielding plate 17 approaches the optical axis of the rod lens 5 as much as the light-shielding plate 17 shields the non-exposed area MA, and a part of the illumination light is applied. Shading. Moreover, according to the angle of the non-exposure area | region MA in shot EA1, EA2, a 1 (theta) shaft mechanism (having hollow motor 24 and rotation stage 28) rotates. That is, the edge of the light shielding plate 17 coincides with the arc of the inner boundary defining the non-exposed area MA. As a result, the light shielding area SA is positioned according to the exposure areas EA1 and EA2 and the non-exposure area MA.

When the width of the non-exposed area MA of the wafer 13 is changed, or when the wafer 13 is replaced with one of a different radius without changing the width of the non-exposed area MA, There is a need to change the curvature. In this case, by responding by rotating the light shielding plate 17 by the 2θ shaft mechanism having the arc switching motor 20 (having the arc switching motor 20) and changing the arcuate edge of the light shielding plate 17, It is possible. By having the edges of a some curvature, the light shielding plate 17 can change the curvature of the boundary which defines a non-exposed area | region without replacing the light shielding plate 17. FIG.

`` Another example of the shape of the light shield plate ''

As shown in FIG. 6, you may use the light shielding plate 17 'which has the edge of two curvatures R5 and R6, and has circular arc notch R0 inside. That is, the light shielding plate needs to have an edge of two or more different curvatures.

`` Another example of linear mechanism ''

As shown in FIG. 7, the linear motion mechanism may be arranged obliquely so as not to intersect the axis (displacement direction) of the linear motion mechanism perpendicularly to the optical axis. The same reference numerals as in FIG. 4 showing the aforementioned linear motion mechanism are issued and shown. By such arrangement, the height of the light shielding plate moving mechanism can be reduced.

`` Another example of linear mechanism ''

As shown in FIG. 8, the light shielding plate 17, the ring-shaped holder 19, and the arc switching motor 20 are attached to one end side of the arm 30, and the other end side of the arm 30 is attached to the linear motion mechanism 31. As shown in FIG. do. The extending direction of the arm 30 and the axial direction (displacement direction) of the linear motion mechanism 31 become orthogonal. By such a configuration, the shapes of the linear motion mechanism and the 2θ shaft mechanism can be miniaturized.

<2. Variation>

As mentioned above, although one Embodiment of this technology was described concretely, this invention is not limited to one embodiment mentioned above, Various deformation | transformation based on the technical idea of this invention is possible. In addition, the structure, the method, the process, the shape, the material, the numerical value, etc. which were mentioned about embodiment mentioned above are only examples, and if necessary, the structure, method, process, shape, material, numerical value, etc. which differ from this may be used. good.

As mentioned above, according to this invention, the variable light-shielding means which forms a desired non-exposed area | region can be set as a space saving structure. Therefore, it is possible to provide the variable light shielding means at the exit of the illumination light uniforming means, and to prevent the decrease in the amount of light.

According to the present invention, the light shielding plate can be replaced in units of units including the edge switching unit, whereby the replacement operation can be easily performed, and damage to optical elements such as rod lenses can be prevented, and installation accuracy can be improved.

1 light source, 4 illumination optical system, 5 rod lens,
6 rod lens support, 8 reticles, 10 alignment cameras,
11 shading mechanism, 12 projection optical system, 13 wafer,
14 exposure stage, 15 stage moving mechanisms, 17 shading plates,
19 ... ring holder, 20 arc switching motor, 23 direct mechanism,
24 hollow motors, 25 hollow shafts, 28 rotating stages

Claims (13)

An illumination optical system in which the emitted light of the light source is incident on the illumination light uniforming means, and the emission light of the illumination light uniforming means illuminates the reticle;
Light shielding means which is provided in the exit part of the said illumination light equalization means, can block a part of the luminous flux of the said exit light, and can displace the light shielding area.
Projection exposure apparatus provided with.
The method of claim 1,
And the light shielding means is disposed at the conjugate position with the reticle.
The method of claim 1,
The illumination light uniforming means is constituted by a rod lens,
A rotation drive unit in which a length direction of the rod lens penetrates a central portion thereof is provided,
And the light shielding means is displaced in a rotational direction about an optical axis passing through the rod lens by the rotation driving unit.
The method of claim 3,
The projection exposure apparatus provided with the said light shielding means in the mounting surface of the rotating body rotated by the said rotation drive part.
The method of claim 4, wherein
And a linear motion mechanism for linearly displacing the light blocking means so as to approach or be separated from the optical axis of the rod lens on the mounting surface of the rotating body.
The method of claim 5,
The light shielding means has a plurality of light shielding portions having different curvatures,
The projection exposure apparatus attached to the rotating part provided with respect to the said linear motion mechanism in the state rotatable.
The method according to any one of claims 1 to 6,
And said light shielding means is a light shielding plate having an arc-shaped edge overlapping an inner boundary line by a predetermined width from an outer circumference of said wafer, and blocking light so that light does not enter an area outside said boundary line.
The method of claim 1,
The light shielding means has a light shielding plate having a plurality of edges having different curvatures for shielding a part of the luminous flux of the emitted light,
A rotation drive unit having a rotating body rotating about an optical axis of the illumination optical system;
A linear actuating mechanism mounted on a rotating body of the rotation driving unit to linearly displace the light shielding plate so as to approach or be separated from the optical axis of the illumination optical system;
And a rotating part attached to the linear motion mechanism to rotate the light blocking plate on a plane perpendicular to the optical axis of the illumination optical system.
The method of claim 8,
The said light shielding plate has the said edge on the outer peripheral side, and the projection exposure apparatus in which the arc-shaped notch was formed in the inner peripheral side.
The method of claim 9,
At least three edges are provided in the outer peripheral side of the said light shielding plate.
The method of claim 9,
The rotation exposure actuator of the said rotation part is located inside the said arc-shaped notch.
The method according to any one of claims 8 to 11,
The said light shielding plate and the said rotation part were the projection exposure apparatuses which consisted of the structure of a detachable material integrally with respect to the said linear motion mechanism.
The method according to any one of claims 8 to 11,
Projection exposure apparatus mounted to the said rotating body and provided with the measuring means which measures the position of the said light shielding plate with respect to the said rotating body.

Images