Exposure apparatus and exposure method

Abstract

To perform multi-exposure according to an exposure pitch that becomes a pattern formable exposure point distribution with high definition including a pattern along a slant direction in an exposure apparatus.SOLUTION: An exposure apparatus performs a relative movement of the exposure area EA while it is inclined at a small angle α relative to the main scanning direction (X direction), and during this movement, it carries out multiple exposure operations according to a pitch determined by the following equations. P=(n + u / m)C + a (1) a=(1 / (m2-b))×(b / m)×C (2) Here, P is the pitch, C is the size (width) of a single exposure area of the optical modulation device, m is an integer greater than or equal to 2, n is an arbitrary integer, and u is an integer smaller than m. In addition, a represents a value smaller than C.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an exposure apparatus that forms a pattern using a light modulation element array, and more particularly to multiple exposure. [Background technology]

[0002] In a maskless exposure apparatus, a stage on which the substrate is mounted is moved along the scanning direction while a light modulation element array such as a DMD (Digital Micro-mirror Device) projects pattern light onto the substrate. To form a pattern with a resolution equal to or smaller than the projection size (cell size) of the micromirror, the light modulation element array is positioned so that the exposure area is slightly tilted with respect to the main scanning direction, and a multiple exposure operation is performed in which the exposure areas are repeatedly exposed while overlapping each other (see, for example, Patent Documents 1 and 2).

[0003] To improve the resolution of the pattern, it is necessary to distribute a large number of exposure points (shot center positions) as uniformly as possible within the projection area of ​​any micromirror (hereinafter referred to as a unit exposure area). For example, the pitch of the multiple exposure operation is determined based on a predetermined formula, and multiple exposure point lines are defined along the tilt angle of the exposure area relative to the main scanning direction. Then, multiple exposure is performed by sequentially switching the exposure points between the multiple exposure point lines (see Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4273290 [Patent Document 2] Patent No. 4273291 [Patent Document 3] Patent Publication No. 2021-157039 Summary of the Invention [Problem to be solved by the invention]

[0005] With regard to patterns, high resolution is required for patterns along diagonal directions, just as it is for the main scanning direction and sub-scanning direction. However, as patterns become finer, it becomes difficult to form patterns (especially patterns along diagonal directions) with high precision by simply determining an exposure pitch that scatters exposure points (shot center positions) across a unit exposure area.

[0006] Therefore, it is required to perform multiple exposure in accordance with an exposure pitch that results in an exposure spot distribution that allows formation of high-resolution patterns, including patterns along oblique directions. [Means for solving the problem]

[0007] The exposure apparatus of the present invention includes a light modulation element array in which multiple light modulation elements are arranged two-dimensionally. The exposure area, which is the projection region of the light modulation element array, is tilted at a predetermined angle with respect to the main scanning direction. For example, the arrangement of the light modulation element array may be tilted at a small angle with respect to the main scanning direction. The exposure apparatus also includes a scanning unit that moves the exposure area relative to the object in the main scanning direction. For example, the scanning unit includes a stage on which the object to be imaged, such as a substrate, is mounted, and by moving the stage on which the object to be imaged, such as a substrate, is mounted, the exposure area moves relative to the object to be imaged. The exposure apparatus also includes an exposure control unit that modulates the multiple light modulation elements at a predetermined pitch and performs a multiple exposure operation. In the present invention, the pitch is defined as a pitch that results in a distribution of exposure points that are arranged along three non-orthogonal directions and are located at the vertices of a triangle with the same geometric properties between adjacent exposure points.

[0008] Here, "geometrically equal triangles" refers to a distribution of exposure points that allows any adjacent exposure points to form triangles with geometric characteristics that are substantially congruent or close to congruent. For example, the pitch can be determined as a distribution of exposure points at the vertices of an equilateral triangle. However, "equilateral triangle" does not only refer to equilateral triangles in the strictest geometric sense, i.e., triangles with equal sides and 60° interior angles, but also to triangles that are close to equilateral triangles, with differences in side lengths and included angles within the range acceptable for an equilateral triangle.

[0009] Alternatively, the pitch can be determined as a pitch that results in a distribution of exposure spots at the vertices of an isosceles triangle. The "isosceles triangle" does not only refer to an isosceles triangle in the strict geometric sense, but also to a triangle that is close to an isosceles triangle in which the lengths of the sides and the included angle differ within an allowable range.

[0010] Considering the need to increase the resolution of the diagonal pattern, i.e., to make the exposure point distribution denser, the pitch can be determined so that the exposure points are arranged in a direction inclined relative to the boundary of the unit exposure area of ​​the light modulation element, i.e., so that the exposure points are not arranged along the boundary of the unit exposure area.

[0011] Considering that the exposure area is scanned with a slight inclination, the pitch can be determined so that multiple exposure operations are performed using micromirrors aligned in the main scanning direction.

[0012] The exposure apparatus may be provided with a pitch setting means for setting the pitch, which can set the pitch from among a plurality of pitches corresponding to a plurality of exposure spot distributions having mutually different distribution states.

[0013] The exposure method of the present invention is an exposure method in which a light modulation element array is arranged in which a plurality of light modulation elements are arranged two-dimensionally, the exposure area of ​​the light modulation element array is tilted at a predetermined angle with respect to the main scanning direction, the exposure area is moved relative to the object to be drawn in the main scanning direction, the plurality of light modulation elements are modulated at a predetermined pitch, and a multiple exposure operation is performed, the pitch being determined as a pitch that results in an exposure point distribution in which the exposure points are aligned along three directions that are not orthogonal to each other and are located at the vertices of a triangle that is geometrically equal between adjacent exposure points. [Effects of the Invention]

[0014] According to the present invention, in the exposure apparatus, multiple exposure can be performed according to an exposure pitch that results in an exposure spot distribution that allows formation of high-resolution patterns, including patterns along an oblique direction. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a block diagram of an exposure apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing the arrangement of an exposure head relative to a stage. [Figure 3] FIG. 10 is a diagram showing the distribution of exposure points within a unit exposure area. [Figure 4] FIG. 10 is a diagram showing an oblique rhombic grating defined based on the light spot distribution. [Figure 5] 10A and 10B are diagrams illustrating a process of deriving a pitch that determines an exposure point distribution. [Figure 6] FIG. 10 is a diagram showing an exposure spot distribution in which adjacent exposure spots are spaced apart by an isosceles triangle. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0017] Fig. 1 is a block diagram of an exposure apparatus according to the present embodiment, and Fig. 2 is a diagram showing the arrangement of an exposure head relative to a stage.

[0018] The exposure apparatus 10 is a maskless exposure apparatus that forms a pattern by irradiating light onto a substrate (exposure target) W that has been coated or affixed with a photosensitive material such as photoresist, and a stage 12 that carries the substrate W is installed so as to be movable along the main scanning direction. A stage driving mechanism 15 moves the stage 12 along the main scanning direction X and the sub-scanning direction Y.

[0019] The exposure apparatus 10 includes a DMD 22, an illumination optical system 23, and a projection optical system 25, and is provided with a plurality of exposure heads 18 that project pattern light (only one exposure head is shown in FIG. 1). The plurality of exposure heads 18 are arranged in a staggered pattern along the sub-scanning direction Y, as shown in FIG. 2. The light source 20 is formed of, for example, a discharge lamp (not shown), and is driven by a light source driver 21.

[0020] When CAD / CAM data composed of vector data and the like is input to exposure apparatus 10, the vector data is sent to raster conversion circuit 26, which converts the vector data into raster data. The generated raster data is temporarily stored in a buffer memory (not shown) and then sent to DMD drive circuit 24.

[0021] The DMD 22 is a light modulation element array in which minute micromirrors are arranged two-dimensionally, and each micromirror selectively switches the direction of light reflection by changing its posture. The posture of each mirror is controlled by a DMD drive circuit 24, and light corresponding to the pattern is projected (imaged) onto the surface of the substrate W via a projection optical system 25. In this way, a pattern image is formed on the substrate W. Here, the projection magnification is set to 1x.

[0022] The stage driving mechanism 15 moves the stage 12 in accordance with a control signal from the controller 30. The controller (exposure control unit) 30 controls the operation of the exposure apparatus 10, and outputs control signals to the stage driving mechanism 15 and the DMD driving circuit 24 based on stage position information sent from the position detection unit 27. For the substrate W mounted on the stage 12, an XY coordinate system is defined, with the main scanning direction being X and the sub-scanning direction being Y.

[0023] During the exposure operation, the stage 12 moves at a constant speed, and the projection area (hereinafter referred to as the exposure area) EA of the entire DMD 22 moves relatively on the substrate W in the main scanning direction X as the substrate W moves. As shown in FIG. 2, the arrangement direction of the multiple exposure heads 18 along the sub-scanning direction Y does not coincide with the sub-scanning direction Y, but is tilted by a small predetermined angle α (hereinafter referred to as the small angle). Therefore, when the stage 12 moves in the direction indicated by arrow A, the exposure area EA becomes an area tilted at the small angle α with respect to the main scanning direction X, and moves relatively in the main scanning direction X in this tilted state. Note that the small angle α is exaggerated in FIG. 2.

[0024] The controller 30 performs multiple exposure, i.e., overlapping exposure, in which the next exposure is performed at a position that overlaps a portion of the previous exposure area. The exposure operation is performed at a predetermined pitch, and the light of the pattern to be drawn is sequentially projected onto the exposure area by modulating each micromirror of the DMD 22 according to the relative position (stage position) of the exposure area. A pattern is formed over the entire substrate W by drawing the entire substrate W using multiple exposure heads 18. Note that the stage 12 may move intermittently instead of continuously. The memory 32 stores programs for controlling the controller 30, etc.

[0025] In this embodiment, multiple exposure is performed, i.e., the pitch is determined so that when the mirror center points (shot center positions, hereinafter referred to as exposure points) at the time of exposure are plotted when each micromirror is modulated at a predetermined pitch, the distribution is arranged in three directions that are not mutually orthogonal, and the distance intervals between adjacent exposure points are equal. Furthermore, it is possible to set and select the intervals between the exposure points and the direction in which the exposure points are arranged. This will be explained below.

[0026] FIG. 3 is a diagram showing the distribution of exposure points in a unit exposure area.

[0027] Here, a unit exposure area E, which is the area projected by one micromirror of the DMD 22, is a rectangular pattern with a width C according to the square-shaped micromirror. For example, C is set to 10 μm or less. The DMD 22 also has a matrix arrangement in which a predetermined number of micromirrors are arranged vertically in accordance with the sub-scanning direction Y and horizontally in accordance with the main scanning direction X (for example, 3840 × 2160).

[0028] Because the exposure area EA, which is the projection area of ​​the DMD 22, is tilted at a small angle α with respect to the main scanning direction X, the exposure point (shot center position) EP of each micromirror also moves in a direction tilted at the small angle α in line with the movement direction of the exposure area EA. Therefore, when a unit exposure area E is defined on the substrate W, while multiple exposure operations are performed at a predetermined pitch, the exposure point EP of the micromirror 22 that reaches a position where it can irradiate the unit exposure area E with a pattern shifts in the sub-scanning direction Y. Specifically, it shifts in the sub-scanning direction Y by an integer multiple of the pitch value.

[0029] Here, when the exposure points EP shift along the sub-scanning direction Y as the exposure area EA advances in the main scanning direction X, the inclination angle β of the line (here represented by the symbol L1) along which the exposure points EP are arranged is larger than the small angle α of the exposure area EA with respect to the main scanning direction X, i.e., the small angle of the unit exposure area E of each micromirror with respect to the main scanning direction X (β>α).

[0030] The exposure spots EP are also regularly distributed in the unit exposure area E, aligned along line L1, lines L2, and L3. Specifically, the distance between any three adjacent exposure spots is equal. The three exposure spots P0, P1, and P2 shown in Figure 3 are equally spaced from one another and form the vertices of an equilateral triangle. The three lines L1, L2, and L3 along which the exposure spots EP are aligned are not perpendicular to one another, nor are they parallel to the boundary lines of the unit exposure area E or the main scanning direction X or sub-scanning direction Y.

[0031] FIG. 4 is a diagram showing an oblique rhombic lattice (hexagonal lattice) defined based on the above exposure spot distribution.

[0032] A plane lattice (grid) with the exposure points EP distributed as shown in Fig. 3 as lattice points can be defined as an orthorhombic lattice G. The orthorhombic lattice G here is defined as an analogy to a lattice that forms a repeating pattern in the crystalline structure of metals, etc., and is obtained by connecting lattice points arranged along three directions that are not orthogonal to each other.

[0033] In particular, the positions of the lattice points in the orthorhombic lattice G here are determined by the distance intervals between adjacent lattice points that form equilateral triangles. Such a planar lattice will be referred to as a hexagonal lattice below. In a hexagonal lattice, figures are represented using equilateral triangles as units, and various figures can be represented by connecting the lattice points.

[0034] Similar to the hexagonal lattice structure in metal crystals, the hexagonal lattice G as a planar lattice allows for denser arrangement of lattice points than a square lattice consisting of two perpendicular lines. In particular, more lattice points can be arranged when forming a figure whose outline is a diagonal line. For example, it is possible to draw a regular hexagon PP along the arc of the circle CP shown in Figure 4.

[0035] Therefore, by performing multiple exposure based on the exposure spot distribution shown in Fig. 3, it is possible to form highly accurate patterns in the main scanning direction X, the sub-scanning direction Y, and also in oblique directions inclined relative to the main scanning direction X and the sub-scanning direction Y. The pitch that produces the exposure spot distribution shown in Fig. 3 can be calculated, for example, as follows.

[0036] FIG. 5 is a diagram showing the process of deriving the pitch that determines the exposure spot distribution.

[0037] The pitch of the multiple exposure operation is determined by the following formula, where P is the pitch, C is the size (width) of the unit exposure area of ​​the light modulation element, m is an integer equal to or greater than 2, n is an arbitrary integer, and u is an integer smaller than m. Also, a represents a value smaller than C. P=(n+u / m)C+a ············(1) In addition, a multiple exposure operation is performed using micromirrors arranged along the main scanning direction (X direction), and by performing the multiple exposure operation while continuously using some of the micromirrors according to the pitch P of the multiple exposure operation, an exposure point distribution is formed that can achieve exposure in which the exposure points are dispersed over the entire unit exposure area E.

[0038] In the exposure spot distribution ED shown in Figure 3, the lines L1, L2, and L3 along which the exposure spots EP are arranged are all inclined with respect to the boundary line of the unit exposure field E. In the above equation (1), by setting a = 0, an exposure spot distribution is determined in which the exposure spots EP are arranged along the boundary line of the unit exposure field E. In contrast, by setting a value other than 0, the direction in which the exposure spots EP are arranged is inclined with respect to the boundary line of the unit exposure field E.

[0039] Figure 5(A) shows the exposure spot distribution when n = 1, m = 8, u = 1, and a = 0 are substituted into (1) above (here, the exposure spot distribution is different from the actual exposure spot distribution, so it is represented by the symbol E0). In this case, the pitch P of the multiple exposure operation is P = 1.125C based on the above formula (1). The exposure spot distribution E0 is regularly arranged along a line (exposure spot line) L30 that runs along the boundary line of the unit exposure area E (≒ sub-scanning direction (Y direction)). The number of these exposure spot lines L30 corresponds to the value of m (= 8).

[0040] Meanwhile, through the multiple exposure operation, the exposure points EP are aligned along multiple lines (exposure point lines) while shifting in the sub-scanning direction (Y direction) at the inclination angle β in the square unit exposure area E. The number of exposure point lines L10 along the inclination angle β is equal to the number of exposure point lines L30 (=8).

[0041] When a≠0 is set, the exposure points EP are not aligned along the exposure point line L30 (≈sub-scanning direction (Y direction)), but are shifted in the main scanning direction (X direction) by the value of a each time a multiple exposure operation is performed, and this shift amount accumulates in the unit exposure area E. In Figure 5(A), the exposure points at this time are represented by the symbol EP', and the single exposure point line along which the exposure points EP' are aligned is represented by the symbol L'.

[0042] Here, considering that the inclination of the line L' along which the exposure points EP' are arranged changes depending on the value of a, and that in a square unit exposure area E, the number of exposure point lines L10 along the inclination angle β is equal to the number of exposure point lines L30 (=8), by adjusting the value of a, it is possible to realize the exposure point distribution ED shown in Figure 3, i.e., an exposure point distribution ED in which the distance intervals between three adjacent exposure points are equal and which forms an equilateral triangle.

[0043] Specifically, a perpendicular bisector is drawn through the midpoint of adjacent exposure spot lines along the sub-scanning direction (Y direction), and the intersection point of two adjacent exposure spots aligned along the tilt angle β is found. Figure 4(B) shows an enlarged view of the distribution area of ​​four exposure spots in Figure 4(A). The intersection point when the exposure spots are N1, N2, N9, and N10 is represented by the symbol p. Note that when a≠0, exposure spot N2 is offset from exposure spot line L30, but this offset is sufficiently small compared to the value of pitch P, so the value of a is found by assuming that exposure spot N2 is positioned on exposure spot line L30.

[0044] The intersection point between the line segment connecting exposure point N1 at the bottom left edge of unit exposure field E and intersection point p and the top side of unit exposure field E is defined as q, and when exposure points ED are lined up along this exposure point line (denoted by symbol LL1), the number of exposure point lines from the left side of unit exposure field E is defined as b. In Figure 5(C), b = 3.

[0045] When an exposure point line LL2 is defined that is parallel to the exposure point line LL1 and has an exposure point located at the upper right corner of the unit exposure field E, the position of the exposure point (see symbol PP) when a=0 shown in FIG. 5A becomes the last exposure shot position in the unit exposure field E. This exposure point PP is located at the position (m 2 -b) It is the second exposure point.

[0046] Here, in the exposure spot distribution E0 shown in FIG. 5(A), (m 2 -b) Since the position of the exposure point PQ following the exposure point PP is the position of the upper right end of the unit exposure area E, when the exposure point lines LL1 and LL2 are defined, d shown in (D) of Figure 5 can be expressed as (b / m) x C.

[0047] For the exposure spot N2 shown in Figure 5(B), it is shifted in the main scanning direction (X direction) by the value of a (≠0), and the shift amount in the main scanning direction (X direction) for the sequentially determined exposure spots is accumulated for the number of multiple exposure operations. Therefore, the value of a that realizes the exposure spot distribution shown in Figure 3 can be calculated using the following formula. a=(1 / (m 2 -b))×(b / m)×C (2) In FIG. 5, b=3 and m=8, so a=0.006C.

[0048] The exposure spot distribution ED obtained in accordance with the pitch P of the multiple exposure operation described above is an exposure spot distribution in which the distances between three adjacent exposure spots are substantially equal and which forms a planar lattice point in the shape of an equilateral triangle. Note that, because the pitch P is determined based on a geometric approximation as described above, in the strict sense, the exposure spot distribution obtained is not exactly the same as a planar lattice point that forms an equilateral triangle.

[0049] However, given that the exposure point distribution ED is determined to be capable of improving pattern accuracy under conditions (restrictions) such as the size of the micromirror and the number of exposure point lines being an integer, and that the pitch is derived using software implemented in the exposure tool, it can be said that an exposure point distribution with exposure points spaced at geometric distances in the shape of an "equilateral triangle" has been created, that is, an exposure point distribution similar to the hexagonal lattice in the crystal structure of a metal has been created by analogy.

[0050] The above-mentioned pitch P is used as a calculation formula for determining an exposure point distribution in which the vertices of adjacent exposure points are spaced apart in an "equilateral triangle" shape. However, the pitch P determined in Figure 5 is based on the premise that the number of exposure points located on the exposure point line when a = 0 is the same (8 in Figure 5). This means that the exposure point distribution shown in Figure 5 cannot be derived depending on the value of the small angle α of the unit exposure area E with respect to the main scanning direction X. In this case, a pitch P is calculated that achieves an exposure point distribution in which the vertices of three adjacent exposure points are spaced apart in an "isosceles triangle" shape.

[0051] FIG. 6 is a diagram showing an exposure spot distribution in which adjacent exposure spots are spaced apart by an isosceles triangle.

[0052] Here, the minute angle α of the unit exposure area E with respect to the main scanning direction (X direction) is different from that in Figure 5. More specifically, in the exposure point distribution shown in Figure 5, when multiple exposure operation is performed using 64 micromirrors (=8×8) in succession in the same row and n=1, m=8, and u=1, the minute angle α=1 / 72, whereas in Figure 6, when multiple exposure operation is performed using 48 micromirrors (=8×6) in succession in the same row and n=1, m=8, and u=1, the minute angle α=1 / 54.

[0053] The pitch P of the multiple exposure operation can be calculated in the same way as in Figure 5. However, if the number of exposure points on the exposure point line L30 when a = 0 is m' (6 in Figure 6), the (m × m - b)th exposure point will be the final exposure point, and so it can be calculated using the following formula. a=(1 / (m×m'-b))×(b / m)×C (3)

[0054] The exposure point distribution shown in FIG. 6 is not as uniform as the exposure point distribution shown in FIG. 5, but it is possible to create a pattern (especially in the diagonal direction) with higher accuracy than an exposure point distribution that is neither an equilateral triangle nor an isosceles triangle, but is simply the vertices of a triangle.

[0055] As described above, according to the exposure apparatus of this embodiment, the exposure area EA moves relatively to the main scanning direction (X direction) while being tilted at a small angle α, and during this time, multiple exposure operations are performed according to the pitch calculated by the above formula. By performing multiple exposure operations according to an exposure point distribution in which exposure points are distributed at the vertices of an equilateral triangle or an isosceles triangle, it is possible to form a pattern with high precision.

[0056] Furthermore, the exposure spot distribution may be configured so that the exposure spots are located at the vertices of triangles other than equilateral or isosceles triangles. In this case, the triangles can be considered congruent, i.e., the exposure spot distribution is configured so that the exposure spots are located at the vertices of triangles that have the same geometric properties.

[0057] 5 and 6 or other exposure point distributions may be configured so that the operator can select and set them as appropriate. For example, the controller 30 may be configured to set one of the exposure point distributions in accordance with an input operation from the operator. [Explanation of symbols]

[0058] 10 Exposure equipment 22 DMD (Digital Modulator Array) E Unit exposure area EA Exposure Area α small angle Pitch ED exposure point distribution

Claims

1. a light modulation element array in which a plurality of light modulation elements are arranged two-dimensionally; a scanning unit that moves an exposure area of ​​the light modulation element array, which is inclined at a predetermined angle with respect to the main scanning direction, relative to an object to be imaged in the main scanning direction; an exposure control unit that modulates the plurality of light modulation elements at a predetermined pitch and performs a multiple exposure operation; An exposure apparatus characterized in that the pitch is determined as a pitch that results in an exposure spot distribution in which the exposure spots are aligned along three directions that are not orthogonal to each other and are located at the vertices of a triangle that is geometrically equal between adjacent exposure spots.

2. 2. An exposure apparatus according to claim 1, wherein the pitch is determined as a pitch that results in a distribution of exposure spots at vertices of an equilateral triangle or an isosceles triangle.

3. 2. An exposure apparatus according to claim 1, wherein the pitch is determined so as to provide an exposure spot distribution in which the exposure spots are arranged in a direction inclined with respect to the boundary of the unit exposure area of ​​the light modulation element.

4. further comprising a pitch setting means for setting the pitch, 2. An exposure apparatus according to claim 1, wherein said setting means sets the pitch from among a plurality of pitches corresponding to a plurality of exposure spot distributions that are different from one another in distribution state.

5. 5. An exposure apparatus according to claim 1, wherein the pitch is determined so that multiple exposure operations are performed using micromirrors arranged in parallel along the main scanning direction.

6. A light modulation element array is arranged in which a plurality of light modulation elements are arranged two-dimensionally, tilting the exposure area of ​​the light modulation element array at a predetermined tilt angle with respect to the main scanning direction; The exposure area is moved relative to the object in a main scanning direction; An exposure method for performing a multiple exposure operation by modulating the plurality of light modulation elements at a predetermined pitch, comprising: An exposure method characterized in that the pitch is determined as a pitch that results in an exposure spot distribution in which the exposure spots are aligned along three directions that are not orthogonal to each other and are located at the vertices of a triangle that is geometrically equal between adjacent exposure spots.

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