JP2016051719A - Photomask and projection exposure device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly precisely align a mask pattern to a shot region of a substrate to be transferred, in a projection exposure device.SOLUTION: In the present embodiment, a mask pattern corresponding to deformations of a plurality of shot regions is formed to a reticle; the mask pattern is transferred to a substrate where the plurality of shot regions are formed, according to a step & repeat method; the positional coordinates of an alignment mark of a sample are measured according to a global alignment method; a shape error of each shot region is detected from a shape error of a global alignment region; and a mask pattern corresponding to the shape error, or having a field shape that has the same tendency in a deformation condition is selected.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a projection exposure apparatus that transfers a pattern formed on a photomask such as a reticle onto a substrate, and more particularly to alignment (positioning) with respect to a deformed substrate.

  Many devices such as a semiconductor element, a liquid crystal display element, and a package substrate manufactured using a projection exposure apparatus have a multilayer structure, and a substrate is manufactured by transferring a pattern in an overlapping manner. When the second and subsequent patterns are transferred to the substrate, it is necessary to accurately align the shot area previously formed on the substrate and the pattern image on the mask, that is, the alignment between the photomask and the substrate.

  As an alignment method, a global alignment (GA) method is known. There, a plurality of shot areas are defined along a grid on the substrate, and alignment marks are formed on the grid so as to define each shot area. Then, a global alignment area including a plurality of shot areas is defined, and the position coordinates of the sample alignment mark defining the area are detected.

  When the second and subsequent layers are transferred, an alignment error between shots is generated due to an alignment accuracy error of the stage, expansion / contraction of the substrate, and the like. Therefore, an alignment error between shots is calculated from the difference between the measured position coordinates of the sample alignment mark and the designed position coordinates of the sample alignment mark, and alignment is performed by offset correction, scaling correction, or the like (for example, , See Patent Document 1). On the other hand, with respect to scaling correction corresponding to the expansion / contraction of the substrate, the projection image of the mask pattern can be corrected for enlargement / reduction by adjusting the position of the zoom lens of the projection optical system (see Patent Document 2).

  The deformation of the substrate is not limited to vertical and horizontal linear expansion and contraction along the coordinate axis, but also includes expansion and contraction in a diagonal direction and other directions, and may be deformed into a rhombus or a trapezoid. Such deformation is difficult to correct with scaling correction. Therefore, a method is known in which a plate deformed in the same manner as the work substrate is provided on the optical path between the mask substrate and the work substrate, and a mask pattern image corresponding to the deformation is transferred (see Patent Document 3).

JP 2006-269562 A JP 2004-29546 A JP 2011-248260 A

  The deformation of the substrate is not uniform, and various distortions are generated in the substrate. In particular, in the case of a ceramic or resin substrate, the substrate deforms with complicated distortion. When the shape of the shot area is actually different from the shape determined by design due to such distortion of the substrate or device characteristics, scaling correction based on the extension and contraction along the coordinate axis direction cannot cope with it.

  The projection exposure apparatus is an exposure apparatus that is used for pattern formation with high accuracy and high resolution, and a silicon wafer is often used as a substrate in accordance with applications such as a semiconductor chip. In the case of a silicon wafer, the deformation of the shot region does not appear remarkably due to its material.

  However, it is necessary to use a projection exposure apparatus to form a high-resolution pattern even on a substrate (for example, an interposer substrate) formed of ceramic or resin. In this case, even if the alignment is performed so as to correct the arrangement error of the shot area by the GA method, the complex deformation of the shot area itself cannot be dealt with. As a result, the position of the through hole may be displaced between the respective layers, and the pattern overlay accuracy deteriorates.

  Accordingly, it is required to perform alignment with high accuracy even when various shot areas are deformed.

  The photomask for a projection exposure apparatus of the present invention is a photomask used in a projection exposure apparatus that transfers a mask pattern to a substrate according to a step-and-repeat method (reduction, equal magnification, etc.). Can be manufactured.

  For example, in a projection exposure apparatus, a projection area of a mask pattern formed on a photomask on a substrate on which a plurality of two-dimensionally arranged shot areas and a plurality of alignment marks provided along the arrangement of the plurality of shot areas are formed. Are provided with a scanning unit that is relatively moved relative to each other, and an exposure control unit that transfers the mask pattern to a plurality of shot areas in accordance with a step & repeat method.

  The photomask of the present invention includes a plurality of mask patterns corresponding to a plurality of shot regions each having a different two-dimensional shape error when the design shot region is used as a reference.

  Due to the deformation of the substrate, the shape and area position of the shot area that is actually measured deviates from the reference design shot area shape (for example, rectangular shape) and area position. Measure and detect. Here, the “two-dimensional shape error” represents the deformation of the shot area resulting from the deformation and variation of the shot area in a direction different from the coordinate axis defined on the substrate. Shape errors other than scaling (enlargement / reduction) along one axis or two axes) are included.

  In addition, when the shot area in the design is rectangular, it is different from the design when it is deformed into a non-rectangular shape such as a rhombus, parallelogram, trapezoid, barrel, pincushion, fan, or rotational deviation. The difference between the position of the entire area and the design area position is also included in the two-dimensional shape error. Such a two-dimensional shape error of the shot area is caused by distortion along a direction different from the coordinate axis of the substrate, characteristics of the apparatus, and the like. On the other hand, “difference in shape error” includes deformations such as parallelograms, trapezoids, etc., when the shape type of the shot region is different, or the amount of orthogonality deviation, that is, the difference in the angle with respect to the coordinate axis. When the amounts are different, a difference in the variation amount of the shot region position variation is also included.

  By using such a photomask in a projection exposure apparatus, by selecting a mask pattern having a field (area) corresponding to a two-dimensional shape error of a measured shot region from a plurality of mask patterns, The mask pattern can be superimposed on the shot area without deviation. For example, a mask pattern having a field with the same shape of the deformed shot area, a mask pattern having a field with the same deformation amount such as a deviation amount of orthogonality, a mask pattern having a field with the same variation position of the shot area, etc. With respect to the shape error, it is possible to select a mask pattern in which the type of area deformation, the deformation amount, and the area variation amount tend to be the same.

  For example, the plurality of mask patterns have a field shape of any one of a parallelogram, rhombus, trapezoid, barrel, and pincushion. Considering that the shot area may be the same shape as the design shot area without substantially deforming the shot area, the photomask is provided with a mask pattern having a field equal to the shape of the design shot area. Is good.

  According to the present invention, in a projection exposure apparatus, a mask pattern can be accurately transferred to a shot area of a substrate.

It is a schematic block diagram of the projection exposure apparatus which is 1st Embodiment. It is the figure which showed the board | substrate with which the shot area | region was arranged. It is the figure which showed the reticle in which the some mask pattern was formed. It is the figure which showed the shape error of the shot area | region resulting from a deformation | transformation of a board | substrate. It is the figure which showed the process of the exposure operation | movement based on a step & repeat system. It is the figure which showed an example of the deformation | transformation shape of a global alignment area | region. It is the figure which showed the shape error of the global alignment area | region and the shape error of a shot area | region in 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic block diagram of a projection exposure apparatus according to the first embodiment. The following description is based on an exposure process in which a first layer pattern is formed on a substrate, and a mask pattern is superimposed on a shot region of the substrate after the second layer.

  The projection exposure apparatus 10 is an exposure apparatus that transfers a mask pattern formed on a reticle (photomask) R to a substrate (work substrate) W according to a step & repeat method. The projection exposure apparatus 10 includes a light source 20 such as a discharge lamp and a projection optical system 34. It has. The reticle R is made of a quartz material or the like, and a mask pattern having a light shielding region is formed. Here, a substrate made of silicon, ceramics, glass or resin (for example, an interposer substrate) is used as the substrate W.

  The illumination light emitted from the light source 20 enters the integrator 24 via the mirror 22, and the amount of illumination light becomes uniform. The uniform illumination light enters the collimator lens 28 through the mirror 26. Thereby, parallel light is incident on the reticle R. The light source 20 is driven and controlled by the lamp driving unit 21.

  A mask pattern is formed on the reticle R, and the reticle R is mounted on the reticle stage 30 so that the mask pattern is at the light source side focal position of the projection optical system 34. An aperture (not shown) is provided in front of the reticle R (on the light source side), and illumination light enters only a part of the mask pattern.

  An XYZ triaxial coordinate system orthogonal to each other is defined for the stage 30 on which the reticle R is mounted and the stage 40 on which the substrate W is mounted. The stage 30 is movable in the XY directions so as to move the reticle R along the focal plane, and is driven by a stage drive unit 32. The stage 30 can also rotate on the XY coordinate plane. Here, the position coordinates of the stage 30 are measured by a laser interferometer or a linear encoder (not shown).

  The light transmitted through the field (area) of the mask pattern of the reticle R is projected as pattern light onto the substrate W by the projection optical system 34. The substrate W is mounted on the substrate stage 40 so that the exposure surface thereof coincides with the image side focal position of the projection optical system 34.

  The stage 40 is movable in the XY directions so as to move the substrate W along the focal plane, and is driven by the stage driving unit 42. The stage 40 can move in the Z-axis direction (the optical axis direction of the projection optical system 34) perpendicular to the focal plane (XY direction), and can also rotate on the XY coordinate plane. The position coordinates of the stage 40 are measured by a laser interferometer or a linear encoder (not shown).

  The control unit 50 controls the stage driving units 32 and 42 to position the reticle R and the substrate W, and controls the lamp driving unit 21. Then, an exposure operation based on the step & repeat method is executed. A memory (not shown) provided in the control unit 50 stores a mask pattern position coordinate of the reticle R, a design position coordinate of a shot area formed on the substrate W, a step movement amount, and the like.

  An alignment mark imaging unit 36 disposed beside the projection optical system 34 is a camera (or a microscope) that images the alignment mark formed on the substrate W, and images the alignment mark before shot exposure. The image processing unit 38 detects the position coordinates of the alignment mark based on the image signal sent from the alignment mark imaging unit 36. Note that the alignment mark may be detected by a TTL method.

  In accordance with the step & repeat method, the control unit 50 sequentially transfers the mask pattern of the reticle R to each shot region formed on the substrate W. That is, the controller 50 intermittently moves the stage 40 according to the shot area interval, and when the shot area to be exposed is positioned at the projection position of the mask pattern, the control unit 50 drives the light source 20 to bring the pattern light into the shot area. Project.

  Prior to the transfer of the mask pattern, the control unit 50 detects an arrangement error of the shot area according to the global alignment method, and aligns the shot area of the substrate W with the projection area of the mask pattern. Furthermore, in the present embodiment, the shot region and the pattern projection area are aligned by detecting the shape error of the shot region caused by the deformation of the substrate and projecting a mask pattern suitable for the shape error. At this time, a shape error in the global alignment region is detected, and the error is regarded as a shape error in the shot region.

  FIG. 2 is a diagram showing a substrate on which shot areas are arranged. FIG. 3 is a diagram showing a reticle on which a plurality of mask patterns are formed. FIG. 4 is a diagram showing the shape error of the shot area due to the deformation of the substrate. The shape error of the shot area will be described with reference to FIGS.

  As shown in FIG. 2, the substrate W is formed with shot areas SA arranged in a matrix at regular intervals according to an XY coordinate system. Then, alignment marks AM for alignment are formed at the four corners of each shot area along the arrangement of the shot areas SA.

  In the global alignment method, a global alignment area including a predetermined number (one or more) of shot areas is defined, and an arrangement error and a correction value of the shot areas are calculated by statistical calculation. Here, a sample (measurement) alignment mark SM is defined for each of four adjacent shot areas SA, and a global alignment area ARM is defined. Other global alignment regions (not shown here) are defined on the substrate W, and as an example, shot regions are formed in the same arrangement in each of a total of four global alignment regions here.

  Due to the difference between the position coordinates of the designed sample alignment mark SM and the actually measured position coordinates of the sample alignment mark SM, the deviation of the straightness of the shot area in the global alignment area ARM, the rotation error, and the linear expansion / contraction of the substrate W A scaling error due to is detected. Based on the detected statistical error, the control unit 50 calculates an offset value, a scaling value, and a rotation amount correction value for each shot area, and moves the stage 40 along the XY coordinate axes, or XY. Rotate along the coordinate plane.

  Of the shot region arrangement errors, the scaling error is an error caused by substrate deformation and can be corrected by the scaling correction value. However, a correction value cannot be obtained for the deformation of the shot area itself along a direction different from the X direction or the Y direction. The shot area arrangement error presupposes that the rectangular shape of the shot area SA having the orthogonality (90 °) between the side along the X axis and the side along the Y axis is maintained.

  However, complicated deformation has occurred on the resin substrate W due to heat shrinkage or the like, and the rectangular shape of the shot region is deformed into a shape in which the orthogonality is not maintained (herein referred to as a non-rectangular shape). When the orthogonality shift occurs, the rectangular shape changes to a parallelogram (diamond), a trapezoid, or the like. The non-rectangular shape also changes depending on the difference in the degree of orthogonality deviation.

  FIG. 4 shows how the shot area is deformed. The shot area VP1 is a rectangular shot area shape that is maintained in a rectangular shape without any substrate deformation. When linear expansion and contraction occurs in the substrate W, the reference shot region VP1 maintains a rectangular shape, and only the dimensions change. The shot areas VP2 and VP3 indicate the shape of linear deformation.

  On the other hand, when the same degree of orthogonality deviation occurs with respect to the sides facing in the +/− direction with respect to the X direction / Y direction, the shot region changes to a parallelogram shape. The shot region VP4 has a parallelogram (rhombus) shape in which the orthogonality shift occurs in the −X direction, and the shot region VP6 has the orthogonality shift in the −Y direction. In addition, the shot areas VP5 and VP7 have non-rectangular shapes in which the deviation in orthogonality is larger. Note that the orthogonality deviation may occur in the + X direction and the + Y direction.

  Further, as shown by the shot area VP ′, the reference shot area VP1 may be deformed like a trapezoidal shot area VP ′ due to a shift in orthogonality so that opposite sides approach each other. As described above, the deformation of the shot area from the rectangular shape to the non-rectangular shape due to the distortion of the substrate W is various.

  In this embodiment, a plurality of mask patterns (deformed mask patterns) are formed on the reticle R in accordance with shot regions deformed into various non-rectangular shapes in the same pattern forming layer (here, the second layer) of the substrate. Yes. As shown in FIG. 3, here, eight mask patterns are formed on the reticle R, and the field shape (pattern area shape) of each mask pattern corresponds to the deformed shape of the shot region.

  Here, the mask pattern P1 has a field shape corresponding to the reference shot region VP1. Mask patterns P2 to P7 have field shapes corresponding to shot regions VP2 to VP7. In this case, the mask pattern is formed in accordance with the field shape. For example, in the case of the shot region VP4, the linear wiring line is inclined along the orthogonality deviation (θ).

  Therefore, by measuring the deformed shot region shape and selecting a mask pattern corresponding to the deformed non-rectangular shape (that is, the degree of deformation and the characteristics of the deformation tend to be the same), the projected image of the mask pattern is It is possible to accurately overlay the deformed shot area. Note that the shot area can be determined to be other than a rectangular shape (for example, a rectangle having a partially cut portion). For such a shot area, a mask pattern can be prepared in accordance with the shape error. Good.

  For the shot areas VP2 and VP3 having only the scaling error, scaling correction may be performed by adjusting the projection optical system, and only the mask pattern corresponding to the shape error that cannot be handled by the scaling correction may be formed on the reticle R. It is also possible to select a mask pattern corresponding to the distortion of the pattern image resulting from the adjustment of the projection optical system.

  FIG. 5 is a diagram showing an exposure operation process based on the step & repeat method. FIG. 6 is a diagram illustrating an example of a deformed shape of the global alignment region.

  As described above, four global alignment regions ARO, ARP, ARN, and ARM are defined on the substrate W, and an arrangement error and a shape error of the shot region are measured for each global alignment region (S101). Since the shape error of the shot area uses the shape error of the global alignment area as it is, the position coordinates of the sample alignment mark SM are measured, and the shape error of the shot area is calculated from the deviation in the orthogonality of the global alignment area and the scaling error. calculate.

  FIG. 6 shows a shift in the orthogonality of the global alignment region ARM due to the substrate deformation. When the global alignment area ARM is measured for deformation into a rhombus or parallelogram shape by statistical calculation, the shot area SA in the global alignment area ARM is regarded as having the same rectangular shape.

  Then, correction values such as a scaling value, an offset amount, and a rotation amount are calculated based on the shot region arrangement error, and a mask pattern having a field shape corresponding to the shape of the shot region is selected (S102). Then, the movement of the stage 30 positions the reticle R so that the illumination light passes through the selected mask pattern, and exposure by the step-and-repeat method so that the shot area to be exposed coincides with the pattern projection area. (S103). When the exposure for one global alignment region is completed, the same exposure operation is performed for the other global alignment regions (S104). By performing such an exposure operation on the substrate in a multilayer manner, the substrate is manufactured.

  As described above, according to the present embodiment, a plurality of mask patterns corresponding to deformation of a shot region formed in a predetermined pattern formation layer of the substrate are formed on the reticle R, and a plurality of shots are performed according to the step & repeat method. The mask pattern is transferred to the substrate on which the region is formed. The position coordinates of the sample alignment mark are measured according to the global alignment method, and the shape error of the shot area is detected from the shape error of the global alignment area. Then, a mask pattern having a field shape corresponding to the shape error, that is, having the same tendency of deformation is selected.

  Next, a projection exposure apparatus according to the second embodiment will be described with reference to FIG. In the second embodiment, the shape error of the shot area is measured independently of the global alignment.

  FIG. 7 is a diagram showing the shape error of the global alignment region and the shape error of the shot region in the second embodiment.

  In the second embodiment, the alignment error of the shot area is measured based on the sample alignment mark SM in the global alignment area ARM, while the alignment mark AM defined at the four corners of each shot area SA is detected by the alignment mark imaging unit 36. The shape error of the shot area SA is calculated by imaging and calculating a statistical value such as the average value of the position coordinates of each shot area.

  Here, while the shot area SA is deformed into a trapezoidal shape, a rotational deviation (rotation of the entire shot area with respect to the X axis or the Y axis) occurs, and the amount of rotational deviation varies depending on the position of the shot area. This makes it possible to accurately measure the shape error for each shot area. Note that in the case of the global alignment method of the first embodiment, the rotational deviation of the global alignment region may be measured, and this may be regarded as the rotational deviation of the shot region.

  Note that the individual shape errors may be calculated without obtaining the average value of the shape errors. Alternatively, the shape error of the shot area at a specific position in the global alignment area may be calculated, and the other shape areas may be estimated as the same shape error.

  In the first and second embodiments, a mask pattern is prepared in consideration of the orthogonality deviation according to the distortion of the substrate along a direction different from the XY coordinate axis. Corresponding mask patterns can be prepared. For example, it is possible to form a mask pattern such as a pincushion type, a barrel type, a fan shape, or a kamaboko type.

  Further, a mask pattern may be prepared in accordance with the shape error (deformation) of the shot region due to a cause other than the distortion of the substrate. For example, a mask pattern for correcting distortion of the projection optical system may be formed, or a mask pattern corresponding to the shape deformation of the shot region caused by the unevenness of the substrate may be prepared.

  The alignment mark only needs to be an index such as a hole. The number of photomasks is not limited to one, and a plurality of reticles may be prepared and one or a plurality of mask patterns may be formed on each reticle. In this case, positioning control of a plurality of reticles is performed.

10 Projection Exposure Device 36 Alignment Mark Imaging Unit (Shape Error Measuring Unit)
38 Image processing unit (shape error measurement unit)
40 Stage 42 Stage drive unit (scanning unit)
50 Control unit (operation unit, exposure control unit)
W Substrate P2 to P8 Deformed mask pattern SA Shot area SM Alignment mark AM for sample Alignment mark ARM Global alignment area R Reticle (photomask)

Claims (6)

  A projection exposure apparatus photomask comprising a plurality of mask patterns corresponding to a plurality of shot areas each having a different two-dimensional shape error when a design shot area is used as a reference.   2. The projection exposure apparatus according to claim 1, wherein the plurality of modified mask patterns have a mask pattern corresponding to a shot area in which an orthogonality deviation or a rotational deviation occurs with respect to a designed shot area. Photomask.   2. The photomask for projection exposure apparatus according to claim 1, wherein the plurality of mask patterns have a field shape of any one of a parallelogram, a rhombus, a trapezoid, a barrel, and a pincushion.   4. The photomask for a projection exposure apparatus according to claim 1, wherein the photomask further has a mask pattern having a field equal to a shape of a designed shot area.   A projection exposure apparatus comprising the photomask for a projection exposure apparatus according to claim 1. 5. A substrate manufacturing method for manufacturing a substrate using the projection exposure photomask according to claim 1 in a projection exposure apparatus.

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