JP6381210B2 - Optical element unit, method for adjusting relative position in rotation direction, exposure apparatus, and method for manufacturing article - Google Patents

Description

  The present invention relates to an optical element unit, a method for adjusting a relative position in a rotational direction, an exposure apparatus, and a method for manufacturing an article.

  In an optical apparatus having a plurality of lens and mirror optical element units, it is important to reduce the influence of aberration on the irradiated surface by devising the selection and arrangement of optical elements to be used.

  In Patent Document 1, two aspherical lenses having different cross-sectional shapes passing through the optical axis and having a complementary relationship with each other are arranged to face each other. A projection optical system that corrects distortion by driving and controlling the relative positions of these lenses in the translation direction is described.

JP 2010-166007 A

  However, the light passing through a pair of lenses such as the lens described in Patent Document 1 has a rotational direction as compared with light passing through a pair of lenses processed so that all cross-sectional shapes passing through the optical axis are equal. The optical path is likely to be shifted due to a minute positioning error between the lenses. Therefore, at the time of assembly, it is necessary to position in the rotational direction with higher accuracy than when handling a set of lenses processed so that all cross-sectional shapes passing through the optical axis are equal.

  Accordingly, an object of the present invention is to provide an optical element unit capable of positioning in the rotational direction with higher accuracy than in the past.

The adjustment method for adjusting the relative position of the set of optical elements according to the present invention is a method for adjusting the relative position in the rotation direction of the set of optical elements , and the thickness of each optical element of the set of optical elements. Using a plane parallel to the vertical direction or a plane parallel to the direction inclined with respect to the thickness direction, an acquisition step of acquiring angle information about the plane, and adjusting the relative position in the rotation direction using the angle information And an adjusting step.

  According to the present invention, it is possible to provide an optical element unit capable of positioning in the rotational direction with higher accuracy than in the past.

The figure which shows the structure of the optical element unit which concerns on 1st Embodiment. The figure which shows the shape of an optical element. The figure which shows the adjustment method of the rotation position of the optical element unit which concerns on 1st Embodiment. The figure which shows the structure of the optical element unit which concerns on 2nd Embodiment. The figure which shows the structure of the optical element unit which concerns on 3rd Embodiment. The figure which shows the example of application of the optical element unit to exposure apparatus. The figure explaining the distortion correction by an optical element unit.

[First Embodiment]
(Configuration of optical element unit)
FIG. 1A is a diagram showing a configuration of the optical element unit 100 according to the first embodiment, and FIG. 1B is a cross-sectional view taken along a line AA ′ in the Y-axis direction shown in FIG. FIG.

  The optical element unit 100 includes a lens 10 that is a first optical element, a holding member 20 that is a first holding member that holds the lens 10, a lens 30 that is a second optical element, and a second that holds the lens 30. It has the holding member 40 which is a holding member. At the ends of the lenses 10 and 30 and the holding members 20 and 40, a step is formed by a cross section (plane) in the Z-axis direction (thickness direction) and a D-shaped surface in a direction perpendicular to the Z-axis.

  The cross sections of the lenses 10 and 30 are cross sections 12 and 32, and the cross sections of the holding members 20 and 40 are cross sections 22 and 42, respectively. Let L be the length in the X-axis direction of the cross-sections 12, 22, 32, and 42 (the length of the plane in the plane). The outer peripheral surfaces of the lenses 10 and 30 are outer diameter surfaces 14 and 34, and the outer peripheral surfaces of the holding members 20 and 40 are outer diameter surfaces 24 and 44.

  The lens 10 and the lens 30 have aspherical lens surfaces 13 and 33 having different cross-sectional shapes passing through the optical axis and complementary to each other, and the lens surfaces 13 and 33 are assembled so as to face each other. ing.

  FIG. 2 shows an example of the shape of the lens surfaces 13 and 33 of the lens 10 and the lens 30. If the three-dimensional shape in the θ = 0 ° direction shown in FIG. 2 (a) and the three-dimensional shape in the θ = 45 ° direction shown in FIG. 2 (b) are combined, the shape is shown in FIG. 2 (c). Such a three-dimensional lens having an aspheric surface and a surface whose cross section is non-rotationally symmetric. At this time, the shape of the lens surfaces 13 and 33 is expressed by the equation (1).

  The optical path of the light transmitted through the lens 10 and the lens 30 (one set of optical elements) having such a shape changes greatly due to a slight error in relative alignment in the rotation direction. Therefore, when assembling the optical element unit 100, it is necessary to accurately align the relative positions in the rotation direction.

(Optical element unit alignment method)
A method of accurately adjusting the position in the rotational direction when assembling the optical element unit 100 using each of the cross sections 12, 22, 32, and 42 will be described.

  In assembling the optical element unit 100, first, an operation for matching the optical axes of the lens 10 and the holding member 20 (hereinafter referred to as centering operation) is performed. Centering work means that the distance from the reference position to the tip of the contact member is the same length at any position on the outer diameter surface of the centering object while the contact member is in contact with the rotating object. It is the work to become. As a result, the optical axes between the elements are matched with an accuracy of 1 μm or less.

  The lens 10 is placed on the holding member 20, and the centering operation is performed while adjusting the deviation in the in-plane direction in the XY plane using the outer diameter surface 14 and the outer diameter surface 24. The centering operation between the lens 30 and the holding member 40 is similarly performed using the outer diameter surface 34 and the outer diameter surface 44.

  Next, position adjustment in the rotation direction of the lens 10 and the holding member 20 will be described with reference to FIG. In FIG. 3, the cross-section 12 (straight line A′-B ′) of the lens 10 indicated by a broken line on the adjustment surface is minute compared to the cross-section 22 (straight line AB) of the holding member 20 indicated by a solid line as a reference surface. A state in which the angle ΔωZ is inclined is shown.

  Angle information about the cross section 12 and the cross section 22 is obtained (obtained) using a length measuring device (not shown) such as a non-contact type such as an optical type or a contact type. The angle information refers to the parallelism ΔY of the cross-section 12 with respect to the reference plane when the cross-section 22 is used as a reference plane, and the positional deviation ΔωZ in the rotational direction obtained using the parallelism ΔY and the length L of the cross-section. . The deviation of the small angle ΔωZ is minimized by manually adjusting the rotation of the lens 10 together with the holding member 20 so that this value is minimum from the measurement result of the parallelism ΔY, that is, equal to the measurement accuracy of the length measuring device. Suppress. Using a similar method, adjustment is made so that the parallelism between the lens 30 and the holding member 40 is also reduced.

  When the optical element unit 100 is assembled, the relative rotational position is adjusted so that the parallelism of the cross section 42 with respect to the cross section 22 is reduced. By adjusting the relative position of the holding member 20 and the holding member 40 in the rotational direction, the relative position of the lens 10 and the lens 30 in the rotational direction can be indirectly adjusted. Or you may adjust the relative position of the rotation direction of the lens 10 and the lens 30 by the parallelism measurement of the cross section 12 and the cross section 42. FIG.

  The reference surface does not necessarily have to be a cross section of the lenses 10 and 30 and the holding members 20 and 40. For example, a reference surface serving as another reference is provided, and the position in the rotation direction is calculated while calculating the parallelism with respect to the reference surface. You can adjust it.

  By using the above method, it becomes possible to adjust the relative rotation error between the two members within 10 seconds (second is a unit in the case of showing a minute angle, and 1 second is 1/3600). .

  Note that the rotational position measurement error includes the flatness of the cross sections 12, 22, 32, and 42 as an error factor in addition to the measurement accuracy of the length measuring device. Flatness is a value indicating the width of unevenness of each cross section, that is, smoothness. The flatness of each of the cross sections 12, 22, 32, and 42 is preferably set to be equal to or less than the parallelism. Thereby, it becomes possible to ensure the measurement accuracy of parallelism.

  For example, when the length L of the cross section 22 that is the adjustment surface is 50 mm and the position of the cross section 22 and the cross section 24 is to be adjusted with an accuracy of 10 seconds or more and 20 seconds or less, the allowable displacement component ΔY is 2.4 μm or more. 4.8 μm or less. Therefore, when L = 50 mm, it is preferable to process the cross sections 22 and 42 so that the flatness thereof is 3.2 μm or less.

  Here, when measuring parallelism, it is preferable to measure the number of cross-sections. Thereby, the influence of flatness can be reduced as much as possible. Further, in order to reduce the measurement error of the parallelism, it is preferable that the length L of the cross section to be measured is long. However, if the length L is increased to the vicinity of the lens diameter, the area through which light can be transmitted is excessively reduced. Therefore, it is desirable to design the cross-sectional length L in consideration of the parallelism measurement accuracy and the light transmission region. For example, the length L of the cross section is preferably ¼ or more and 3/5 or less, more preferably 2/5 or more and 3/5 or less, of the diameter of the lens to be subjected to cross section processing.

  The relative position of the lens 30 and the holding member 40 in the rotational direction is also adjusted, and the lens 10 and the holding member 20 and the lens 30 and the holding member 40 are fixed by applying an adhesive, a curing agent, or the like (not shown) to each gap. Or you may fix with a volt | bolt, a holding ring, a leaf | plate spring press, etc. which are not shown in figure.

  In this way, a cross section processed so that the flatness is very small is formed with respect to the lenses 10 and 30 and the holding members 20 and 40, and the relative position in the rotation direction of the lens 10 and the lens 30 is determined using the cross section. It becomes possible to adjust with high accuracy. Furthermore, there is an effect that the adjustment can be easily performed without using a driving mechanism for driving the object in the rotation direction.

[Second Embodiment]
A modification of the first embodiment is shown in FIG. The optical element unit 200 of FIG. 4 differs from the optical element unit 100 in the first embodiment in that a plurality of blocks 60 are provided along the outer diameter surfaces 24 and 44 of the holding members 20 and 40.

  When adjusting the position in the rotational direction of the cross-sections 12, 22, 32, and 42, translational movement within the XY plane between the members to be adjusted can be limited. When the optical element unit 200 is used, the block 60 is removed after adjusting the position in the rotational direction so that the lens 10 and the lens 30 can be translated in the XY plane.

  FIG. 4 shows an example in which three blocks 60 are arranged at intervals of 120 ° with the optical axis 50 as the center. However, two blocks 60 may be arranged at intervals of 90 °. The position of the block 60 may be an arrangement that prevents displacement in at least two directions in the XY plane during position adjustment in the rotational direction.

[Third Embodiment]
An optical element unit 300 according to the third embodiment is shown in FIG. The optical element unit 300 is not provided with the cross-section 22 shown in FIGS. 1A and 1B with respect to the holding member 20, and is provided with a mark 70 with respect to the holding member 20 instead. Different from the first and second embodiments.

  In the present embodiment, the centering operation of the lens 30 and the holding member 40 and the method for adjusting the rotational position are the same as those in the first embodiment, and thus description thereof is omitted.

  Alignment of the lens 10 and the holding member 20 in the rotational direction is roughly adjusted so that the position of the mark 70 and the cross section 12 is aligned, and the lens 10 is fixed to the holding member by an arbitrary fixing means such as an adhesive. Subsequently, using the cross section 12 of the lens 10 and the cross section 42 of the holding member 40, alignment in the rotational direction is performed in the same manner as in the first embodiment. By the above method, the lens 10 and the holding member 40 are aligned, and the positions of the lens 10 and the lens 30 in the rotational direction are adjusted indirectly.

  In this manner, even if the position of the lens 10 and the lens 30 in the rotational direction cannot be directly adjusted by the length measuring device due to the narrowness of the gap between the lens surfaces 13 and 33, the holding member 40 is used. The positions of the lens 10 and the lens 30 can be adjusted.

  The mark 70 is provided to adjust the position of the holding member 40 relative to the lens 10 to some extent in advance. Thereby, it is possible to prevent the lens surface 13 and the lens surface 33 from coming into contact with each other and being damaged when the holding member 20 and the holding member 40 are opposed to each other while being largely displaced in the rotation direction. Further, when using a length measuring instrument that causes a measurement error at a certain rate in accordance with the measurement range during parallelism measurement, it is possible to reduce the measurement error by reducing the initial measurement value.

  According to the present embodiment, it is possible to reduce labor and processing cost for forming the cross section 22 with respect to the holding member 20.

[Fourth Embodiment]
As a fourth embodiment, a case where the optical element unit 100 according to the first embodiment is applied to the exposure apparatus 600 shown in FIG. 6 will be described.

  The light source 601 emits exposure light. Examples of the light source for exposure light include a mercury lamp, an ArF excimer laser, a KrF excimer laser, and the like. The illumination optical system 602 shapes light emitted from the light source 601 into a predetermined shape and irradiates the reticle (original) 603. A circuit pattern is formed on the reticle 603. A reticle for one shot region on a substrate 605 via a projection optical system 620 having a lens barrel 604 containing an optical element unit 100 and a plurality of lenses 607 (only representative lenses are shown). The circuit pattern on 603 is reduced and projected.

  The driving device 606 moves the plurality of lenses 607 in a direction along the optical axis of the projection optical system 620. As a result, the distortion of the circuit pattern to be projected is reduced while the influence of the aberration caused by the projection optical system 620 is reduced. The control unit 608 for the projection lens receives an instruction from the main control unit 609 and instructs the driving device 606 about the driving amount of the lens 607 and the like.

  The substrate 605 is held by the stage 610. The stage 610 is movable in the X, Y, and Z axis directions. A movable mirror 611 and a reference mark 612 are installed on the stage 610. Interferometer 612 emits laser light toward moving mirror 611, and the position of stage 610 is detected using the laser light reflected by moving mirror 611. Based on the detection result, the stage control unit 613 instructs the drive unit 614 that drives the stage 610 about the drive amount.

  By measuring the position of the reference mark 612 via the off-axis alignment optical system 615 and the projection optical system 620, the distance between the optical axis of the projection optical system 620 and the alignment optical system 615, that is, the baseline is measured. . The alignment optical system 615 measures the position of an alignment mark (not shown) formed on the substrate 605, and measures the distortion correction amount for the layer to be formed next.

  Using the light projecting system 616 and the light receiving system 617, the reference mark 612 is aligned in the Z-axis direction. The light projecting system 616 irradiates the resist on the substrate 605 with a plurality of light beams of non-exposure light, and the light reflected by the reference mark 612 is collected by the light receiving system 617. Similarly, the position of the Z-axis at each position of the substrate 605 is measured, the height deviation of the substrate 605 with respect to the reference mark 612 is obtained, and used as a focus correction value when the substrate 605 is exposed.

  The exposure apparatus is disposed in an exposure chamber (not shown), and the atmosphere in the section in the exposure chamber is in an environment in which the temperature and humidity are controlled by an atmosphere maintaining unit (not shown).

  Between the reticle 603 and the lens barrel 604, the optical element unit 100 of the first embodiment is disposed. The light exposure apparatus 600 includes a drive unit 618 that moves at least one of the lens 10 and the lens 30 in the X-axis and Y-axis directions, and a control unit 619 that instructs the drive unit 618 to specify the drive amount.

  The optical element unit 100 may be configured inside the lens barrel 604, or may be configured as an independent unit outside the lens barrel 604 as shown in FIG. Further, it may be configured integrally with a reticle holder (not shown) holding the reticle 603 or a reticle stage mechanism (not shown).

  In consideration of the fact that the light transmitted through the reticle 603 is also transmitted through the optical element unit 100, one side of the reticle 603, which is usually rectangular, is a cross section of the optical element unit 100 (any one of the cross sections 12, 22, 32, and 42). It is preferable to arrange in the direction along More preferably, the reticle 603 is preferably arranged so that one side thereof is parallel to the cross section of the optical element unit 100 (any one of the cross sections 12, 22, 32, and 42).

  This is because it is possible to make the optical element unit 100 as small as possible while preventing the projection area of the circuit pattern on the optical element unit 100 from overlapping the area where the cross section is processed. By reducing the size of the optical element unit 100, the manufacturing cost of the optical element unit 100 can be reduced.

  The main control unit 609 is connected to the light source 601, the control unit 608, the control unit 613, and the control unit 619, and comprehensively controls them.

  The optical element unit 100 mounted in the present embodiment translates the lens 30 with respect to the lens 10 in a direction that forms 135 ° from the X-axis, for example, so that the vertical and horizontal directions shown in FIGS. Magnification difference distortion occurs. Alternatively, when the relative positions of the lens 10 and the lens 30 are translationally driven in the Y-axis direction, a parallelogram-shaped distortion as shown in FIGS. 7C and 7D is generated. In this way, by correcting the relative position of the lens 10 and the lens 30 in an arbitrary direction within the XY plane, it is possible to perform distortion correction having a two-fold rotational symmetry.

  If the alignment in the rotational direction is performed with high accuracy using the cross section formed in the optical element unit 100 as described above, the above-described distortion correction can be performed with high accuracy. If the above properties are used, even if the shot pattern previously formed on the substrate 605 is distorted, advanced overlay can be performed by appropriately correcting the distortion to be formed next. Accuracy can be realized.

[Other Embodiments]
Another step structure will be described using the cross section 12 as an example. In addition, since the following description is applied similarly about the cross sections 22, 32, and 42, description is abbreviate | omitted.

  If the parallelism by the cross section 12 can be measured, the step structure does not necessarily have to have a D-shaped surface in the XY plane. Processing is easier if the lower surface of the step is formed to the outer periphery of the lens 10, but the flatness of the cross section 12 is within an allowable range, and there is a space that can be measured in a direction orthogonal to the length L of the cross section 12. If there is, it may be a groove shape.

  The D-shaped surface does not necessarily have to be the XY plane orthogonal to the Z axis and intersects the Z axis direction as long as there is no hindrance to the processing for reducing the flatness of the cross section 12 and the measurement of parallelism. You may form in the surface of the direction to do. Further, the flatness of the D-shaped surface may be larger than the flatness of the cross section 12. Furthermore, the length L of the cross section may be such that both ends of the cross section 12 do not reach the outer diameter surface of the lens 10 as long as there is a length necessary for measuring the parallelism.

  In each of the above-described embodiments, only the example in which the cross section 12 is formed in the Z-axis direction that is the thickness direction of the lens 10 is shown, but the cross section 12 is a slope having flatness within an allowable range when measuring parallelism. It does not matter. That is, it may be an oblique plane formed in a direction inclined with respect to the Z-axis direction.

  Moreover, even if the cross section 12 is formed as in each of the above-described embodiments, the outer diameter surface 14 of the lens 10 is preferably formed over the entire circumference of the lens 10. This is because, if one end of the lens 10 is completely cut off to form the cross section 12, the contact surface of the contact member disappears during the centering operation.

  If the centering operation can be performed by another method, the cross section 12 may be completely cut off. This makes it possible to reduce the processing cost required for forming a cross section necessary for measuring the parallelism.

  If the shape of the surfaces of the lens 10 and the lens 30 is such that alignment in the rotation direction is important, the application of this embodiment is necessary. As the lenses that are not axially symmetric around the optical axis are used in combination, it is necessary to provide a plane in the thickness direction of each lens and adjust the position in the rotational direction with high accuracy. In particular, it is suitable for a lens having an aspherical shape and different cross-sectional shapes around the optical axis as in the above-described embodiments.

  The optical element unit is not only a combination of two lenses and two holding members as shown in the above-described embodiments, but also a unit constituted by two or more lenses, or two or more pieces by one holding member. A unit capable of holding the lens is referred to.

  In addition, when it is necessary to adjust the relative position in the Z-axis direction between the lens 10 and the lens 30 at the time of assembly, a configuration in which the adjustment is performed in advance by interposing a spacer (not shown) may be adopted. Furthermore, in each embodiment, only the case where the lenses 10 and 30 are opposed to each other is shown, but the other lenses are disposed between the respective lenses, and the rotation directions of the lenses 10 and 30 are also illustrated. It is also applicable when adjusting the relative position of.

[Product Manufacturing Method]
In the manufacturing method of the article of the present invention (semiconductor integrated circuit element, liquid crystal display element, CD-RW, mask for light exposure apparatus, etc.), a pattern is exposed on a substrate such as a Si substrate or glass by using the above drawing apparatus. And a step of developing the substrate on which the pattern is exposed. Furthermore, other known processes (oxidation, film formation, vapor deposition, doping, planarization, etching, resist peeling, dicing, bonding, packaging, etc.) may be included.

10, 30 Lens (optical element)
20, 40 Holding member 12, 22, 32, 42 Cross section (thickness direction or plane in a direction inclined with respect to the thickness direction)
14, 24, 34, 44 Outer surface 100 Optical element unit 600 Exposure apparatus 603 Reticle (original)
605 substrate 620 projection optical system

Claims (6)

A method of adjusting the relative position in the rotational direction of a set of optical elements,
Using the plane parallel to the thickness direction of each optical element of the set of optical elements or the plane parallel to the direction inclined with respect to the thickness direction to obtain angle information about the plane;
An adjustment step of adjusting a relative position in the rotation direction using the angle information.   The adjustment method according to claim 1, wherein the angle information is obtained by measuring a distance from a reference surface serving as a reference of the angle information to the plane.   The adjustment method according to claim 2, wherein the reference surface is provided on a holding member that holds the optical element. A set of optical elements whose relative positions are adjusted by the adjustment method according to any one of claims 1 to 3 ,
An optical element unit comprising a holding member for holding the set of optical elements. An exposure apparatus comprising a projection optical system including the optical element unit according to claim 4 and irradiating a substrate with a pattern of an original through the projection optical system. An exposure step of exposing the substrate using the exposure apparatus according to claim 5 ;
A method for producing an article comprising the step of developing the substrate exposed in the exposure step.