JP7179420B2 - Projection exposure apparatus and shading plate used for projection exposure apparatus - Google Patents

Description

The present invention relates to a projection exposure apparatus that exposes a pattern on a wafer by step-and-repeat, and a light shielding plate used in the projection exposure apparatus.

The projection exposure apparatus is provided with a mechanism (WEM: Wafer Edge Masking) that prevents exposure of a predetermined width from the edge of the wafer when the exposure area overlaps the edge of the wafer. In a projection exposure apparatus that requires high-precision exposure results, a method of providing a WEM in the optical system is selected for reasons such as countermeasures against particles and sharpness of light-shielding boundaries.

For example, there is a prior art (Patent Document 1) in which a movable shielding plate is provided at a position conjugate to the reticle of the illumination optical system, and the wafer periphery is not exposed by moving the shielding plate according to the exposure position to shield light from a predetermined portion. ) exists. Some semiconductor wafers are provided with an orientation flat to indicate the direction of the crystal axis of the wafer. The orientation flat is, for example, a linear edge portion (hereinafter referred to as an orientation flat portion) formed by cutting out part of the wafer. The technique disclosed in Patent Document 1 cannot shield the orientation flat from light.

A technique of providing a light shielding member on a wafer is also known. Japanese Patent Application Laid-Open No. 2002-200000 (FIG. 8) describes a method of providing a light shielding member covering the entire circumference of the wafer on the wafer, in which the arc-shaped peripheral portion and the orientation flat portion of the wafer are shielded from light at the same time.

Japanese Unexamined Patent Application Publication No. 2011-233781 JP 2015-200910 A

In the WEM that shields light on the wafer, since the light shielding member is provided on the wafer, there are problems such as adhesion of particles originating from the light shielding member to the wafer and blurring of the light-shielding boundary. Further, when exposing a wafer without an orientation flat, it is necessary to replace the light shielding member with a light shielding member having no linear portion (FIG. 3 of Prior Document 2), which is a complicated operation.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a projection exposure apparatus having a WEM provided in an illumination optical system and a projection exposure apparatus capable of exposing not only an arcuate portion but also an orientation flat portion when performing peripheral non-exposure of a wafer. An object of the present invention is to provide a light shielding plate for use in an exposure apparatus.

The present invention provides an illumination optical system that uniformizes the illuminance of light emitted from a light source and irradiates a reticle with the same,
a light shielding plate provided in the illumination optical system for shielding part of the light flux of the illumination optical system ;
and a light shielding plate moving mechanism for moving the light shielding plate,
The light shielding plate moving mechanism includes a linear motion mechanism that moves the light shielding plate in and out with respect to the optical axis of the illumination optical system, a first θ axis mechanism that rotates the light shielding plate about the optical axis of the illumination optical system, and a linear motion mechanism. has a second θ axis mechanism for rotating the light shielding plate,
The light shielding plate has a continuous edge where the linear portion and the curved portion are continuous ,
This is a projection exposure apparatus in which the position of a light shielding plate is controlled by a light shielding plate moving mechanism according to the relative positional relationship between the orientation flat portion of the wafer and the projection range.
The present invention also provides a light shielding plate arranged in an illumination optical system of a projection exposure apparatus,
It is a light shielding plate having a plurality of continuous edges composed of linear portions and curved portions so as to form non-exposure areas on a wafer having an orientation flat portion.

According to at least one embodiment, not only the arcuate portion but also the orientation flat portion can be unexposed when the peripheral non-exposure of the wafer is performed. Note that the effects described herein are not necessarily limited, and may be any of the effects described herein or effects different from them.

FIG. 1 is a diagram showing the configuration of an exposure apparatus according to one embodiment of the present invention. FIG. 2 is a front view of an example of a light shielding plate in one embodiment. FIG. 3 is a front view of another example of the light shielding plate in one embodiment. FIG. 4 is a front view of still another example of the light shielding plate in one embodiment. FIG. 5 is a front view of a light shielding plate moving mechanism according to one embodiment. FIG. 6 is a cross-sectional view of a light shielding plate moving mechanism in one embodiment. FIG. 7 is a plan view used for explaining the exposure operation. FIG. 8 is a plan view showing the relationship between the wafer and the light shielding plate.

Hereinafter, embodiments of the present invention and the like will be described with reference to the drawings. The embodiments and the like described below are preferred specific examples of the present invention, and the content of the present invention is not limited to these embodiments and the like.

FIG. 1 is a schematic configuration diagram of one embodiment of the projection exposure apparatus of the present invention. Each element in FIG. 1 is shown in cross-sectional view along the main optical axis, and hatching is omitted. The projection exposure apparatus has a light source 1 and an illumination optical system 4 that uses the light emitted from the light source 1 as illumination light with uniform illuminance. Illumination light from an illumination optical system 4 is applied to a reticle (photomask) 8 which is a pattern original. An image of the reticle 8 is projected onto the wafer 13 by the projection optical system 12 .

A wafer 13 is placed on an exposure stage (work chuck) 14 . The exposure stage 14 is moved by a stage moving mechanism 15 . A stage moving mechanism 15 and an optical system (light source 1, illumination optical system 4, projection optical system 12) are supported by a pedestal 16. FIG.

The light source 1 is, for example, a UV lamp. An elliptical mirror 2 is also provided to focus the light towards the entrance of the rod lens. A rod lens 5 is supported by a rod lens supporting portion 6 . A mercury lamp, a laser, or the like may be used as the light source 1 .

The illumination optical system 4 has 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 homogenizing means. The illumination light homogenizing means is not limited to the rod lens, but may be an internal reflecting mirror (a polygonal tube in which a plurality of mirrors are glued together facing inward).

The critical illumination lens group 7 magnifies the image of the exit surface of the rod lens 5 by a predetermined magnification (for example, 2 times) and illuminates the reticle 8 . Although the critical illumination lens group 7 is omitted in the drawing by being a square, it is composed of a plurality of lenses (for example, 10 lenses). The illumination optical system 4 also includes a light shielding mechanism (WEM) 11, which will be described later.

The reticle 8 is a transmissive photomask on which a predetermined pattern is drawn. A reticle 8 is supported by a reticle stage 9 . The reticle 8 is made of quartz glass, for example, and is a transmissive photomask on which a predetermined pattern (for example, a circuit pattern) to be transferred is drawn.

The projection optical system 12 is, for example, a Dyson optical system. In one embodiment, the magnification of the projection optical system 12 is 1:1.

The wafer 13 has a circular shape and a diameter of, for example, 300 mm. Also, an orientation flat is formed. The wafer 13 is, for example, a silicon wafer having a single-crystal silicon surface coated with a photoresist (photosensitive agent). In addition to those made of single crystal silicon, they may be made of glass, sapphire, or compounds.

A photoresist is applied not only to the pattern exposure region but also to at least a part of the peripheral portion of the wafer 13 . Photoresists are photosensitive materials that are patterned using ultraviolet light. The photoresist may be either positive type or negative type. A predetermined non-exposure area is set in the peripheral portion of the wafer 13 . For example, the non-exposure area has a width of 5 mm along the entire edge of the wafer 13 . A non-exposure region is also provided in the orientation flat portion.

The exposure stage 14 holds the wafer 13 by suction. The exposure stage 14 is moved in the X, Y, and θ directions by the stage moving mechanism 15 . The surface (two-dimensional plane) of the wafer 13 is defined by the X and Y directions, and the rotation direction is defined by θ. A stage moving mechanism 15 performs movement for step exposure and fine movement for wafer alignment. A mechanism for moving in the Z direction and adjusting the tilt of the exposure stage is also provided for focusing the wafer 13 .

The projection exposure apparatus includes an exposure stage 14 and a mount 16 for installing an optical system. An alignment camera 10 is attached to a pedestal 16 .

In one embodiment, a light blocking plate 17 is installed on the conjugate plane of the wafer 13 of the illumination optical system 4 . Also, the light shielding plate 17 is positioned at the exit portion of the rod lens 5 . Specifically, the exit surface of the rod lens 5 is positioned close to the light shielding plate 17 .

FIG. 2 shows an example of a light blocking plate 17 for blocking light along the peripheral non-exposure region of the wafer 13. As shown in FIG. The light-shielding plate 17 is made of the same material as the reticle 8, such as quartz glass, and is coated with a black light-shielding agent. As will be described later, there are a linear motion mechanism that moves the light blocking plate in and out with respect to the optical axis, a first θ axis mechanism that rotates the light blocking plate around the optical axis of the illumination optical system, and a light blocking plate that rotates with respect to the linear motion mechanism. A light blocking plate moving mechanism having a second 2θ axis mechanism is provided.

The light shielding plate 17 has a semi-circular notch 18 at the central portion on the inner peripheral side, which serves as a relief for the 2θ-axis mechanism. Along the notch 18, the outer peripheral side has a chevron shape or a convex shape as a whole. The light shielding plate 17 has a first light shielding portion 19a, a second light shielding portion 19b, and a third light shielding portion 19c on the outer peripheral side. A curved edge c1 is formed from the left vertex a1 toward the right upper vertex a2 toward the drawing, and a straight edge s1 is formed from the vertex a2 toward the right upper vertex a3. A continuous edge composed of the curved edge c1 and the linear edge s1 constitutes the first light shielding portion 19a.

The vertex a3 and the vertex b3 are positioned at approximately the same height, and the curved edge c3 connecting these vertexes a3 and b3 constitutes the third light shielding portion 19c. Further, a straight edge s2 is formed from the vertex b3 toward the vertex b2 located downward to the right, and a curved edge c2 is formed from the vertex b2 toward the lower vertex b1 on the right. The curved edge c2 and the linear edge s2 constitute the second light shielding portion 19b. On the wafer 13, the length of each of the straight edges s1 and s2 is longer than the length of one exposure area in the longitudinal direction. The exposure range here means the maximum projected image that can be exposed on the wafer 13 in one exposure shot. It is represented by an enlarged (or reduced) shape according to the magnification of .

In this way, the light shielding plate 17 has a shape symmetrical with respect to a line extending vertically through the center of the semicircular cutout 18 . The first light shielding portion 19a has a function of shielding the orientation flat portion and one curved portion continuous with the straight edge portion. , and the third light shielding portion 19c has the function of shielding the portions other than the orientation flat portion. Also, the edge portion of each light shielding portion has a tapered cross section corresponding to the NA of the illumination optical system. The tapered shape is for preventing a decrease in the amount of emitted light in areas other than the non-exposure area.

FIG. 3 shows a light shielding plate 17A as a modification of the light shielding plate 17. As shown in FIG. Parts corresponding to those in FIG. 2 are given the same reference numerals. The light shielding plate 17A has a first light shielding portion 19aa and a second light shielding portion 19ab, and the third light shielding portion 19c is omitted. In the case of this light shielding plate 17A, light shielding other than the orientation flat portion is performed by the curved edge c1 of the first light shielding portion 19aa and the curved edge c2 of the second light shielding portion 19ab.

FIG. 4 shows a light shielding plate 17B as a modification of the light shielding plate 17. As shown in FIG. Unlike the light shielding plate 17, the light shielding plate 17B has an overall valley or concave shape on the outer peripheral side opposite to the notch 18. As shown in FIG. A curvilinear edge c4 is formed downward to the right from the vertex d1 on the left side of the drawing to the vertex d2. The vertex d2 reaches the vertex d3 through the orientation flat portion and the corresponding linear edge s3. Furthermore, vertex d3
A curvilinear edge c5 is formed upward to the vertex d4.

The light shielding plate 17B forms a first light shielding portion 19ba with the curved edge c4 and the straight edge s3, and forms a second light shielding portion 19bb with the curved edge c5 and the straight edge s3. These light shielding portions 19ba and 19bb shield the orientation flat portion and the curved portion continuing to the orientation flat portion. Furthermore, the curved portions other than the orientation flat portion and the curved portion continuing to the orientation flat portion are shielded by the curved edges c4 and c5.

5 and 6 are a front view and a cross-sectional side view of a light shielding plate moving mechanism that moves the light shielding plate 17, for example. As shown in FIG. 6, a light shielding plate moving mechanism is provided so as to be adjacent to the side surface of the rod lens. The light shielding plate moving mechanism has a hollow structure, and a rod lens supporting portion is installed in the hollow portion. The light shielding plate moving mechanism includes a linear motion mechanism 23 that moves the light shielding plate in and out with respect to the optical axis, a first θ axis mechanism that rotates the light shielding plate around the optical axis of the illumination optical system, and a light shielding mechanism for the linear motion mechanism 23 . A second θ axis mechanism for rotating the plate 17 is provided.

As shown in FIG. 5, the circular arc of the arc-shaped notch 18 inside the light shielding plate 17 is attached to the rotating shaft of the light shielding plate rotating motor 20 . A light shielding plate rotating motor 20 is fixed to a base plate 21 . The base plate 21 is attached to the linear motion mechanism 23 by attaching/detaching screws 22a and 22b. The light shielding plate rotating motor 20 is for rotating the light shielding plate 17 with respect to the linear motion mechanism 23, and constitutes the second .theta.-axis 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 light shielding plate rotation motor 20 . The linear motion mechanism 23 moves the edge of the light blocking plate 17 toward or away 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-exposure area.

The first .theta.-axis mechanism is a rotating mechanism that rotates the light blocking plate 17 about the optical axis of the illumination optical system. As shown in FIG. 6, a hollow motor 24 is provided and a hollow shaft 25 is rotated by the hollow motor 24 . Hollow motor 24 includes a rotating cable portion 26 such as a slip ring.

A rod lens support 6 having a rod lens 5 is installed in the hollow shaft 25 . For example, the center of the hollow shaft 25 and the optical axis of the rod lens 5 are aligned. The rod lens support portion 6 is fixed to the housing on the entrance side of the rod lens 5 and supported by a bearing 27 provided in the hollow shaft 25 on the exit side. However, a cantilever structure in which the rod lens 5 and the rod lens support portion 6 are supported only on the inlet side without supporting the outlet side of the rod lens 5 by the bearing 27 may be employed.

A rotary stage 28 is attached to the exit side of the rod lens 5 of the hollow shaft 25 . The rotation stage 28 is disc-shaped, and the tip of the hollow shaft 25 is fixed to the center position thereof. A linear motion mechanism 23 is attached to the rotation stage 28 via an attachment portion. For example, the radial direction of the rotary stage 28 and the direction of linear motion of the linear motion mechanism 23 are made to match. As described above, the linear motion mechanism 23 is attached with the 2.theta. Therefore, when the hollow shaft 25 is rotated by the hollow motor 24, the rotation stage 28, the linear motion mechanism 23, the second θ-axis mechanism and the light shielding plate 17 rotate integrally around the optical axis of the illumination optical system.

In this embodiment, a rod lens is used as the illumination light homogenizing means, but a fly-eye lens may be used. In that case, it is preferable to provide an imaging optical system behind the fly-eye lens, and to provide a light-shielding plate moving mechanism so that the light-shielding plate comes to the imaging plane.

Next, the light shielding operation of one embodiment of the present invention will be described. FIG. 7 is a diagram showing the step-and-repeat exposure operation for the wafer 13. As shown in FIG. In the example of FIG. 7, 41 exposures are performed. The rectangle represents the range of one exposure, and the cross represents the center of exposure (the position of the optical axis).

A non-exposure area MA is set along the outer circumference of the wafer 13 . An example of light shielding by WEM is shown in the upper left. During the exposure operation at a position where the exposure area does not overlap the non-exposure area MA, the light blocking plate 17 is retracted to a position retracted from the rod lens 5 .

The light-shielding plate moving mechanism performs different operations for light-shielding the orientation flat portion and light-shielding portions other than the orientation flat portion. First, the operation of shielding the non-exposure area other than the orientation flat portion from light will be described. In this case, the 2θ-axis mechanism (light-shielding plate rotating motor 20) rotates so that the third light-shielding portion 19c of the light-shielding plate 17 is centered on the movement axis of the linear motion mechanism 23, and thereafter maintains this state. maintain.

At the position (exposure areas EA1, EA2) where the exposure area overlaps the non-exposure area MA, the light shielding plate 17 advances toward the rod lens 5 by the amount that shields the non-exposure area MA, thereby shielding part of the illumination light. . Also, the first θ-axis mechanism rotates according to the angle of the non-exposure area MA in EA1 and EA2. As a result, the light shielding area SA is positioned according to the exposure position (exposure areas EA1, EA2, . . . ) and the non-exposure area MA.

Next, the light shielding operation of the orientation flat portion will be described. FIG. 8 is a diagram showing an image of the WEM (light shielding plate 17) shielding the non-exposed area MA of the orientation flat. The light shielding plate 17 shown in FIG. 8 represents an image magnified by the magnification of the illumination optical system and the projection optical system.

As shown in FIG. 7, the second light shielding portion 19b of the light shielding plate 17 is used when exposing the exposure range EA3 including the right end portion of the orientation flat portion. That is, both the linear edge s2 and the curved edge c2 are used to shield both the arcuate portion and the linear portion at the same time.

In order to shield the non-exposure area of the exposure range EA3, the 2.theta. At this time, the angle .theta.1 of the first .theta.-axis mechanism, the distance R of the direct acting mechanism 23, and the angle .theta.2 of the second .theta. , the light shielding plate 17 is moved.

Similarly, when exposing the exposure range EA5, the light shielding plate 17 is moved so that the first light shielding portion 19a of the light shielding plate 17 is appropriately positioned on the orientation flat portion. Furthermore, when exposing the exposure range EA4, light is shielded using the first light shielding portion 19a or the second light shielding portion 19b. Therefore, the linear edge s1 of the first light shielding portion 19a and the linear edge s2 of the second light shielding portion 19b are longer than the length of the long side of the exposure range EA4.

An embodiment of the present technology has been specifically described above, but the present invention is not limited to the above-described embodiment, and various modifications are possible based on the technical idea of the present invention. . In addition, the configurations, methods, processes, shapes, materials, numerical values, etc., given in the above-described embodiments are merely examples, and if necessary, different configurations, methods, processes, shapes, materials, numerical values, etc. may be used. good too.

1 light source, 4 illumination optical system, 5 rod lens,
8... Reticle, 10... Alignment camera, 11... Light blocking mechanism,
12... projection optical system, 13... wafer, 14... exposure stage,
17... light shielding plate, 19a... first light shielding part, 19b... second light shielding part,
19c... Third light shielding part, 20... Light shielding plate rotating motor, 23... Linear motion mechanism,
24... hollow motor, 28... rotary stage,
c1, c2, c3... curved edges, s1, s2... linear edges

Claims (5)

an illumination optical system that uniformizes the illuminance of light emitted from a light source and illuminates the reticle;
a light shielding plate provided in the illumination optical system for shielding part of the light flux of the illumination optical system ;
A light shielding plate moving mechanism for moving the light shielding plate,
The light shielding plate moving mechanism includes a linear motion mechanism that moves the light shielding plate in and out with respect to the optical axis of the illumination optical system, a first θ axis mechanism that rotates the light shielding plate about the optical axis of the illumination optical system, a second θ-axis mechanism for rotating the light shielding plate with respect to the linear motion mechanism;
The light shielding plate has a continuous edge where a straight line portion and a curved line portion are continuous ,
A projection exposure apparatus in which the position of the light shielding plate is controlled by the light shielding plate moving mechanism according to the relative positional relationship between the orientation flat portion of the wafer and the projection range. 2. A projection exposure apparatus according to claim 1, wherein the length of said straight portion on said wafer is longer than the length of said projection range in the longitudinal direction. 3. The projection exposure apparatus according to claim 1, wherein the two continuous edges are provided symmetrically about the center line of the light blocking plate. 4. A projection exposure apparatus according to any one of claims 1 to 3, wherein said douser has a curved edge different from said continuous edge. A light shielding plate arranged in an illumination optical system of a projection exposure apparatus,
A light shielding plate having a plurality of continuous edges composed of linear portions and curved portions so as to form non-exposure areas on a wafer having an orientation flat portion.

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