JP2005322843A - Alignment equipment and alignment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide alignment equipment which can perform alignment with high precision, even when observation of wafer marks through a mask membrane is difficult. <P>SOLUTION: A rough movement stage moves a rough movement top table in a direction parallel to an XY plane. A jogging stage displaces a jogging top table which holds a wafer in the direction, which is parallel to the XY plane with respect to the rough movement top table. A reference mark is attached on the fine-adjustment top table. A mask stage holds a mask by having a certain spacing from the wafer. A mask alignment sensor attached on the fine-adjustment top table observes a mask mark and the reference mark simultaneously. A wafer alignment sensor is attached on a references base. The reference mark is arranged in an observation-enabled region of the wafer alignment sensor by moving the jogging top table. A position sensor measures the position of the fine-adjustment top table. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an alignment apparatus and an alignment method, and more particularly to an alignment apparatus and an alignment method for aligning a mask and a wafer by off-axis alignment.

  Patent Document 1 discloses a low energy electron beam lithography (LEEEPL) technique. In LEEPL, exposure is performed by placing a wafer and a mask close to each other and irradiating the wafer with a low energy electron beam through the mask. A finer pattern can be formed as compared with lithography using conventional light.

  In LEEPL, a mask in which a mask pattern is formed in an opening through which an electron beam can pass through a mask membrane such as a thin SiC film or SiN film that shields the electron beam is used. The mask membrane is designed in terms of area, thickness, etc. so that the mask pattern can be maintained with high accuracy. As the membrane thickness increases, light transmission decreases. For example, when the membrane is formed of a SiC film, it becomes opaque to visible light when the thickness is about 10 μm.

  In LEEPL, when performing die-by-die alignment between a mask and a wafer, an alignment mark (hereinafter referred to as a wafer mark) on the wafer is observed through the mask membrane. When the light transmittance of the mask membrane is poor, the image of the wafer mark becomes darker than the image of the alignment mark (hereinafter referred to as mask mark) on the mask, making it difficult to detect the position of the wafer mark. Become.

  Patent Document 2 discloses a reduction projection exposure apparatus to which an off-axis alignment technique is applied. According to this off-axis alignment technique, first, a reference mark provided on a wafer stage is placed at an exposure position, and the reference mark is observed with a through-the-reticle type alignment microscope. Next, the stage is moved to place the reference mark at the non-exposure position, and the reference mark is observed by the wafer alignment sensor. The baseline is determined based on the observation result of the reference mark at the exposure position and the non-exposure position.

  In the upper right column on page 18 of Patent Document 2, it is suggested that this off-axis alignment technique can be applied to a proximity exposure apparatus such as an X-ray exposure apparatus. When the off-axis alignment technique disclosed in Patent Document 2 is applied to LEEPL, the reference mark is arranged at the exposure position, and the position of the reference mark is measured through the mask membrane. Therefore, when the light transmittance of the mask membrane is low, it is difficult to detect the position of the reference mark.

US Pat. No. 5,831,272 JP-A-4-65603

  When die-by-by alignment is applied to LEEPL, it becomes difficult to detect the position of the wafer mark through the mask membrane when the light transmittance of the mask membrane is low. Even if the off-axis alignment disclosed in Patent Document 2 is applied, it is difficult to detect the position of the reference mark through the mask membrane.

  An object of the present invention is to provide an alignment apparatus capable of performing alignment with high accuracy even when the light transmittance of a mask membrane is low and it is difficult to observe a wafer mark or a reference mark through the mask membrane. It is to provide an alignment method.

  According to one aspect of the present invention, a reference base that defines an XYZ rectangular coordinate system, a coarse movement stage that is attached to the reference base and moves a coarse movement top table in a direction parallel to the XY plane, and a wafer to be processed A fine movement stage for displacing a fine movement top table held parallel to the XY plane in a direction parallel to the XY plane with respect to the coarse movement top table, a reference mark attached to the fine movement top table, and the fine movement top table A mask stage that holds the mask so that the relative position with respect to the reference base is constrained from the held wafer at a certain interval in the Z direction, and is attached to the fine movement top table and held on the mask stage. Mask alignment sensor capable of simultaneously observing a mask mark on the mask and the reference mark A wafer alignment sensor attached to the reference base, wherein the reference mark can be arranged in an observable region of the wafer alignment sensor by moving the coarse movement top table and the fine movement top table. There is provided an alignment apparatus having an attached wafer alignment sensor and a position sensor for measuring a position in the XY plane of the fine movement top table.

  According to another aspect of the present invention, there is provided a method for performing alignment using the alignment apparatus described above, wherein: (a) the coarse movement stage or the coarse movement stage is arranged so that the reference mark can be observed by the wafer alignment sensor. First information indicating the position of the fine movement top table measured by the position sensor and the position of the reference mark observed by the wafer alignment sensor are driven by both the movement stage and the fine movement stage. 2, (b) a step of holding a mask on which the mask mark observable by the mask alignment sensor is formed on the mask stage, and (c) the reference by the mask alignment sensor. The coarse movement stage or the coarse movement stage and the fine movement stage so that the mark and the mask mark can be observed simultaneously. Based on the information indicating the position of the fine movement top table measured by the position sensor and the information indicating the relative position of the reference mark and the mask mark measured by the mask alignment sensor, Obtaining a third information indicating the position of the mask; (d) holding a wafer on which a wafer mark observable by the wafer alignment sensor is formed on the fine movement top table; Information indicating the position of the fine movement top table measured by the position sensor by driving the coarse movement stage or both the coarse movement stage and the fine movement stage so that the wafer mark can be observed by the wafer alignment sensor. And information indicating the position of the wafer mark measured by the wafer alignment sensor, A step of obtaining fourth information indicating the position of the wafer; (f) fifth information indicating a design position of each of a plurality of shot regions defined on the surface of the wafer; and the fourth information. And (g) aligning the wafer based on the first, second, third, and sixth information, and obtaining sixth information indicating each position of the shot area based on There is provided an alignment method including a step of driving the coarse movement stage and the fine movement stage so that a position of a shot region to be matched with a position of the mask.

  Since the wafer mark is observed by the wafer alignment sensor without passing through the mask, the wafer mark can be accurately observed even when the light transmittance of the mask is low. A mask alignment sensor is attached to the fine movement top table. The position and orientation of the fine movement top table can be measured with high accuracy by a position sensor. For this reason, the position and posture of the mask alignment sensor can be maintained constant.

  FIG. 1 shows a schematic view of an exposure apparatus that employs an alignment apparatus according to an embodiment of the present invention. The reference base 1 is constituted by the lower reference base 1A and the upper reference base 1B. The reference base 1 defines an XYZ orthogonal coordinate system that serves as a reference for the positions of other components. A coarse movement stage 2 is mounted on the lower reference base 1A. The coarse movement stage 2 includes a coarse movement mechanism 2A and a coarse movement top table 2B. The coarse movement mechanism 2A moves the coarse movement top table 2B in a direction parallel to the XY plane.

  The fine movement stage 3 is attached to the coarse movement top table 2B. The fine movement stage 3 includes a fine movement mechanism 3A and a fine movement top table 3B. The fine movement mechanism 3A moves the fine movement top table 3B with respect to the coarse movement top table 2B in a two-dimensional direction parallel to the XY plane and in the Z direction, and a rotation direction (θz centered on the axis parallel to the Z axis). Direction). Further, the fine movement mechanism 3A can adjust the inclination of the fine movement top table 3B with respect to the XY plane. In other words, it can be displaced by a minute angle in the rotation direction (θx direction and θy direction) around an axis parallel to the X axis and the Y axis.

  A wafer chuck is fixed to the upper surface of fine movement top table 3B, and wafer 20 to be processed is held on the wafer chuck. The surface of the wafer 20 is substantially parallel to the XY plane.

  The reference mask 4 is fixed to the fine movement top table 3B. The reference mask 4 includes a membrane that transmits visible light, and a reference mark 4M formed on the membrane. A mask alignment sensor 6 is disposed below the reference mask 4. Mask alignment sensor 6 is fixed to fine movement top table 3B.

  A mask stage 10 is attached to the upper reference base 1 </ b> B via a rotation mechanism 11. The mask stage 10 holds the mask 21 on its lower surface. The held mask 21 is arranged at a minute interval (proximity gap) in the Z direction from the wafer 20 and faces the wafer 20. The rotation mechanism 11 holds the mask stage 10 so as to be rotatable about an axis parallel to the Z axis. When the mask 21 is held on the mask stage 10, the relative position and posture of the mask 21 with respect to the reference base 1 are constrained.

  A mask mark formed on the mask 21 is observed by the mask alignment sensor 6 through the reference mask 4. The mask alignment sensor 6 can simultaneously observe the reference mark 4M formed on the reference mask 4 and the mask mark formed on the mask 21.

  A wafer alignment sensor 12 is attached to the upper reference base 1B so as to face the fine movement stage 3 side. The wafer alignment sensor 12 measures the position of the reference mark 4M and the wafer mark formed on the wafer 20.

  A position sensor 7 is attached to the upper reference base 1B. The position sensor 7 measures the positions of the fine movement top table 3B in the X-axis direction and the Y-axis direction, and the positions in the θx, θy, and θz directions. As the position sensor 7, for example, a laser interferometer can be used. In this case, a length measuring mirror parallel to the YZ plane and a length measuring mirror parallel to the ZX plane may be attached to the side surface of the fine movement top table 3B, and a reference mirror corresponding to each length measuring mirror may be attached to the mask stage 10. For example, the displacement amount in the θz direction can be detected by measuring two points with different Y coordinates, and the displacement amount in the θx and θy directions can be detected by measuring two points with different Z coordinates. .

  An electron beam source 15 is disposed above the mask stage 10. A low energy electron beam emitted from the electron beam source 15 is irradiated onto the wafer 20 through the mask 21.

  FIG. 2A shows a plan view of fine movement top table 3B. The shape of the fine movement top table 3B is a square or a rectangle having sides parallel to the X axis and the Y axis when viewed with a line of sight parallel to the Z axis. A Y-side long mirror 7Y constituting a part of the laser interferometer is attached to a side surface orthogonal to the Y-axis, and an X-side long mirror 7X is attached to a side surface orthogonal to the X-axis. Wafer chuck 3U is arranged at substantially the center of fine movement top table 3B.

A reference mask 4 is attached between the wafer chuck 3U and one vertex. A reference mark 4M is formed in the reference mask 4. Reference mark 4M has a reference mark 4M _X for X, composed of the Y reference mark 4M _Y.

  The mask alignment sensor 6 includes an X mask alignment microscope 6X and a Y mask alignment microscope 6Y. Each of the X mask alignment microscope 6X and the Y mask alignment microscope 6Y is configured by a metal microscope that observes the surface of an object by reflected illumination. The optical axis of the objective lens of the X mask alignment microscope 6X is inclined in the Y direction from the normal direction of the XY plane. The optical axis of the objective lens of the Y mask alignment microscope 6Y is inclined in the X direction from the normal direction of the XY plane.

Mask alignment microscope 6X for X is, irradiates the illumination light in the X reference mark 4M _X, generates an image signal of an image due to scattered light from the X reference mark 4M _X. Mask alignment microscope 6Y for Y is, irradiates the illumination light in the Y reference mark 4M _Y, it generates an image signal of an image due to scattered light from the Y reference mark 4M _Y.

FIG. 2B shows a plan view of the reference mark 4. As described above, the reference mark 4M is composed of an X reference mark 4M _X and Y reference mark 4M _Y. The X reference mark 4M _X has a symmetrical pattern with respect to the center line 4C _X parallel to the Y axis. No pattern is arranged in the region of width W centered on the center line 4C _X , and square patterns are distributed in a matrix form in the regions on both sides thereof. FIG. 2B shows a case where three square patterns are distributed in the X direction and ten square patterns are distributed in the Y direction. The edge of each square pattern becomes a scattering source that scatters illumination light. Since the optical axis of the X mask alignment microscope 6X is tilted in the Y direction from the normal direction of the XY plane, all square patterns constituting the _X reference mark 4MX are not in focus, and the X direction is not covered in the Y direction. Only the square pattern located within the depth of field is in focus.

The Y reference mark 4M _Y has the same pattern as that obtained by rotating the _X reference mark 4M _X by 90 °, and is symmetric with respect to the center line 4C _Y parallel to the X axis. With respect to the X direction, a square pattern positioned within the depth of field of the Y mask alignment microscope 6Y is focused.

Observation of X reference mark 4M _X by X mask alignment microscope 6X, and to allow Y reference mark 4M _Y observations simultaneously by Y mask alignment microscope 6Y, positions of these marks and the microscope is adjusted .

FIG. 3A shows the arrangement of mask marks formed on the mask 21. Mask marks 21M _{1 to} 21M ₃ are arranged in the scribe line areas near the three apexes of the square area 21A where the circuit pattern to be transferred is formed.

FIG. 3B shows a plan view of _one mask mark 21M1. Other mask mark 21M ₂ and 21M ₃ also has the same pattern as the mask mark 21M _1. Mask mark 21M ₁ is composed of an X mask mark _{21M 1X} and Y mask mark _{21M 1Y.} The X mask mark 21M _1X is composed of square openings arranged in a matrix of three in the X direction and ten in the Y direction. The Y mask mark 21M _1Y has a pattern obtained by rotating the X mask mark 21M _1X by 90 °.

Referring to FIG. 4 (A), the mask alignment microscope 6X and 6Y, describes a method of observing the reference mark 4M and mask marks 21M _1. In a state where the alignment was carried out between the reference mark 21M ₁ and the mask mark 4M drives the coarse movement stage 2 and the fine motion stage 3, when viewed in parallel line of sight Z-axis, the mask mark 21M _1X is for X, X With respect to the axial direction, the reference mark 4MX for _X is arranged substantially at the center. Similarly, Y mask mark _{21M 1Y} are arranged substantially in the center of the Y-axis direction with respect to the Y reference mark 4M _Y.

In FIG. 4 (B), shows the arrangement of X mask mark _{21M 1X,} and X reference mark 4M _X when viewed in a parallel line of sight to the X-axis. The reference mask 4 and the mask 21 are arranged substantially in parallel with a minute interval. On the surface of the membrane of the reference mask 4, X reference mark 4M _X is formed, the mask membrane mask 21, X mask mark 21M _1X comprising a plurality of openings are formed.

The optical axis 30 of the X mask alignment microscope 6X is inclined in the Y direction from the normal direction of the XY plane. Object plane 32 on the image receiving surface 31 and the conjugate relationship of the X mask alignment microscope 6X intersects the X reference mark 4M _X and X mask mark _{21M 1X.} The pattern arranged at the position intersecting the object surface 32 is in focus. At the same time as focus is on both the X reference mark 4M _X and X mask mark _{21M 1X,} reference marks 4M _X and X mask mark _{21M 1X} for X are arranged offset to each other in the Y direction. Similarly, as shown in FIG. 4 (A), Y reference mark 4M _Y and Y mask mark _{21M 1Y} are arranged offset to each other in the X direction.

In the mask alignment microscope 6X for X, by observing the X reference mark 4M _X and X mask mark 21M _1X simultaneously, information indicating a relative position in the X-axis direction of both is obtained. Similarly, the mask alignment microscope 6Y for Y, by observing the Y reference mark 4M _Y and Y mask mark 21M _1Y simultaneously, information indicating the relative position both the Y-axis direction is obtained.

  The mask alignment sensor 6 is fixed to the fine movement top table 3B, and the position and orientation of the fine movement top table 3B are controlled with high accuracy by the position sensor 7 and the fine movement mechanism 3A. For this reason, the position and orientation of the mask alignment sensor 6 are also controlled with high accuracy, and the position and orientation can be maintained constant. Thereby, the measurement accuracy of the position of the mask mark 21M and the reference mark 4M can be improved.

  FIG. 5 shows a plan view of the wafer alignment sensor 12. An X wafer alignment microscope 12X and a Y wafer alignment microscope 12Y are fixed to the intermediate member 12A. The X wafer alignment microscope 12X and the Y wafer alignment microscope 12Y are composed of metal microscopes. The intermediate member 12A is fixed to the upper reference base 1B shown in FIG.

The optical axis of the objective lens of the X wafer alignment microscope 12X is tilted in the Y direction from the normal direction of the XY plane, and the optical axis of the objective lens of the Y wafer alignment microscope 12Y is in the X direction from the normal direction of the XY plane. Tilted. By moving the reference mask 4, it is possible to observe the X reference mark 4M _X in wafer alignment microscope 12X for X, to observe the Y reference mark 4M _Y in Y wafer alignment microscope 12Y. The observation of the X reference mark 4M _X, and observation of the Y reference mark 4M _Y, so as to perform simultaneously a reference mask 4 in a stationary state, the wafer alignment microscope 12X and Y wafer alignment microscope X 12Y is arranged.

  By observing the reference mark 4M with the wafer alignment sensor 12, information indicating the position of the reference mark 4M can be obtained.

  FIG. 6 shows a plan view of the wafer 20 to be exposed. A plurality of shot areas 35 arranged in a matrix are defined on the surface of the wafer 20. The shot area 35 is a unit for alignment with the mask 21 and is also a unit that is exposed by the step-and-repeat method.

Four wafer marks 20M _{1 to} 20M ₄ are formed in the scribe line of the wafer 20. At least three sets of wafer marks 20M _{1 to} 20M ₃ are arranged so as not to be positioned on a straight line. The wafer mark 20M ₃ and 20M _4, are simultaneously transferred when transferring a circuit pattern on one shot area 35a. Each of the wafer marks 20M _{1 to} 20M ₄ has the same pattern as the reference mark 4M shown in FIG. 2B and can be observed by the wafer alignment sensor 12.

A local coordinate system is defined in the surface of the wafer 20. In this local coordinate system, the wafer center coordinates, the design coordinates of the reference point (for example, the center) of each shot area 35, and the wafer marks 20M _{1 to} 20M ₄ are displayed. Design coordinates are predetermined.

  Next, a method for aligning a mask and a wafer using the exposure apparatus will be described with reference to FIGS.

  FIG. 7 shows an XY coordinate system fixed to the reference base 1, a UV coordinate system fixed to the fine movement stage 3 </ b> A, and a local PQ coordinate system defined on the wafer 20. The X axis and the U axis are parallel. When the fine movement top table 3B is moved in the X axis direction and the Y axis direction, the UV coordinate system moves in translation with respect to the XY coordinate system. Ideally, the wafer 20 is held on the fine movement top table 3B so that the P-axis is parallel to the U-axis. Actually, the P-axis and the U-axis are not strictly parallel due to the limit of mechanical accuracy when holding the wafer 20.

  The center position C of the observable area of the wafer alignment sensor 12 is set as the origin of the XY coordinate system. Let R be the position of the reference point (for example, the center) of the mask 21. By aligning the reference point S defined in the shot area 35 of the wafer 21 with the reference point R of the mask 21, the mask 21 and the wafer 20 can be aligned.

The center point F of the reference mark 4M of the reference mask 4 fixed to the fine movement top table 3B (the point where the center lines 4Cx and 4Cy shown in FIG. 2B intersect) is set as the origin of the UV coordinate system. The wafer 20 is fixed to the UV coordinate system. Let the origin of the PQ coordinate system defined on the surface of the wafer 20 be G. The coordinates of the reference point S of each shot area 35 in the PQ coordinate system are determined at the time of design. The coordinates at the time of design are assumed to be ( _SP , _SQ ).

  As shown in FIG. 8A, the mask 21 is held on the mask stage 10 and the wafer 20 is held on the fine movement top table 3B.

  The coarse movement stage 2 and the fine movement stage 3 are driven so that the reference mark 4M is arranged in the observable region of the wafer alignment sensor 12. Note that only the coarse movement stage 2 may be driven. However, when the coarse movement stage 2 is driven, pitching, rolling, and yawing of the coarse movement top table 2B occurs. When the posture of fine movement top table 3B changes beyond the allowable range due to pitching, rolling, and yawing, it is preferable to drive fine movement stage 3 to correct the posture of fine movement top table 3B.

The position of the reference mark 4M is observed by the wafer alignment sensor 12, and information indicating the position of the reference mark is acquired. Specifically, in a stationary state of the fine movement top table 3B, the observation of the X reference mark 4M _X by X for wafer alignment microscope 12X shown in FIG. 5, and by the wafer alignment microscope 12Y for Y Y reference mark 4M _Y is observed simultaneously. Further, the position of the fine movement top table 3B is measured by the position sensor 7, and information indicating the position of the fine movement top table 3B at this time is acquired. Information relating the relative positions of the XY coordinate system and the UV coordinate system can be obtained from the two pieces of position information. In the XY coordinate system, given target coordinates (vector CF, that is, XY coordinates (F _X , F _Y ) of the point F) to which the center point F of the reference mark 4M is to be moved, based on information relating the two coordinate systems. Thus, the fine movement top table 3B can be moved and the reference mark 4M can be arranged at the target position.

As shown in FIG. 8B, the fine movement top table 3B is moved to a position where the reference mark 4M and the mask mark 21M can be simultaneously observed by the mask alignment sensor 6. Observing Figure 3 of three as shown in (A) the mask marks _21M 1 _{~21M 3,} to obtain the XY coordinates of each mask marks _21M 1 _{~21M 3.} The period of observing one mask marks 21M _1, are kept stationary during fine movement top table 3B, the reference mark 4M _X and X mask mark X by X mask alignment microscope 6X that shown in FIG. 4 (A) observation with 21M _1X, and simultaneously observed with the Y reference mark 4M _Y and Y mask mark _{21M 1Y} by the Y mask alignment microscope 6Y.

  Immediately before observing the mask mark 21M, the illumination light sources of the X mask alignment microscope 6X and the Y mask alignment microscope 6Y are turned on. When the observation of all the mask marks 21M is completed, the illumination is performed before proceeding to the next step. Turn off the light source. Thereby, the heat generation from the mask alignment sensor 6 can be suppressed.

From these three coordinates, the XY coordinates (R _X , R _Y ) of the reference point R of the mask 21 can be obtained. The vector CR is generally called a baseline. In this step, information indicating the position of the mask 21 in the XY coordinate system is obtained.

As shown in FIG. 8C, the wafer mark 20M of the wafer 20 is moved into the observable area of the wafer alignment sensor 12, and the wafer mark 20M is observed. For example, to observe at least three wafer marks are not arranged on a straight line _20M 1 to 20 m ₃ shown in FIG. Period for observing one wafer marks 20M ₁ is in a stationary state of the fine movement top table 3B, the observation of X for the wafer mark by X for wafer alignment microscope 12X shown in FIG. 5, according to the wafer alignment microscope 12Y for Y The Y wafer mark is observed simultaneously.

  Immediately before the wafer mark 20 is observed, the illumination light sources of the X wafer alignment microscope 12X and the Y wafer alignment microscope 12Y are turned on. When the observation of all the wafer marks 20M is completed, the illumination light source is turned off before proceeding to the next step. Thereby, the heat generation from the wafer alignment sensor 12 can be suppressed, and further, the temperature rise of the wafer 20 due to irradiation with illumination light can be suppressed.

Information indicating the position and orientation of the wafer 20 is obtained from information indicating the position of the fine movement top table 3B measured by the position sensor 7 and information indicating the positions of the three wafer marks observed by the wafer alignment sensor 12. The information indicating the position and orientation of the wafer 20 includes, for example, the wafer expansion / contraction amount (r _P , r _Q ), the wafer residue rotation amount θ _U , the wafer orthogonality ω _U , and the UV coordinate (Q _U of the origin G of the local coordinate of the wafer 21. , Q _V ). Here, the wafer expansion amount r _P is a measure of the P-axis direction of the length from the shot area on the wafer 20 to the other shot areas, is a value obtained by dividing the design value of its length. Wafer expansion amount r _Q is the Q-axis direction from the shot area on the wafer 20 to another shot region length measurement of a value obtained by dividing the design value of its length.

Wafer residue amount of rotation theta _U is the angle between the P axis and the U axis. The wafer orthogonality ω _U is an angle in which the Q-axis direction calculated from the measurement result of the wafer mark position is shifted from the direction orthogonal to the P-axis, and is 0 ° when both are orthogonal. Based on the position information of the wafer 20, the PQ coordinate system and the UV coordinate system can be associated with each other.

If the design coordinates of the reference point S of one shot area in the local PQ coordinate system is (S _P , S _Q ) and the UV coordinates of the origin G of the PQ coordinate system are (G _U , G _V ), The UV coordinates (S _U , S _V ) are expressed by the following formula.

  As shown in Expression (1), UV coordinates (shot region arrangement information) of the reference point of the shot region 35 are obtained from information indicating the position and orientation of the wafer 20 and the design coordinates of the reference point S of each shot region 35. Calculated.

  As shown in FIG. 8D, based on the information obtained in the steps of FIGS. 8A to 8C, the shot area to be exposed on the wafer 20 and the mask 21 are aligned. Hereinafter, this positioning method will be described.

  In FIG. 7, if the fine movement top table 3B is moved so that the combined vector obtained by adding the vector FS to the vector CF is equal to the vector CR, the reference point S of the shot area 35 coincides with the reference point R of the mask 21. . From this condition, the following equation is obtained.

The coordinates (R _X , R _Y ) are measured in the process shown in FIG. The coordinates (S _U , S _V ) are calculated by the above equation (1). Accordingly, the coordinates (F _X , F _Y ) to move the point F defined by the reference mark 4M are obtained. Based on the information relating the XY coordinate system and the UV coordinate system obtained in the process of FIG. 8A, the coarse movement stage 2 and the fine movement stage are arranged so that the point F is arranged at the coordinates (F _X , F _Y ). 3 is driven.

  In the method according to the above embodiment, the control information of the coarse movement stage 2 and the fine movement stage 3 for aligning the shot area 35 and the mask 21 is obtained for each shot area 35 by the equation (2). After this control information is obtained, alignment is performed only by controlling the coarse movement stage 2 and the fine movement stage 3 without observing the mask mark or wafer mark. For this reason, compared with the case where die-by-die alignment is performed, the time required for alignment can be shortened. Thereby, the throughput can be increased. In addition, as described in Japanese Patent Application No. 2004-98571 already filed by the present inventors, a plurality of fine movement stages are attached to one coarse movement top table 2B, and an electron beam source is provided for each fine movement stage. By arranging this, it is possible to further increase the throughput.

  In the above embodiment, the wafer mark 20M is observed by the wafer alignment sensor 12 in the process shown in FIG. At this time, the wafer mark 20M is directly observed without passing through the membrane of the mask 21. For this reason, even when the light transmittance of the mask membrane is not sufficient, the position of the wafer mark can be detected with high accuracy.

  Further, in the above embodiment, a plurality of mask marks 21M are observed by moving one mask alignment sensor 6 in the XY plane direction in the step shown in FIG. 8B. Similarly, in the process shown in FIG. 8C, the wafer 20 is moved in the XY plane direction, and a plurality of wafer marks 20M are observed by one wafer alignment sensor 12. On the other hand, when performing die-by-die alignment, it is necessary to fix a mask and a wafer and observe a plurality of marks, so an alignment sensor corresponding to the number of marks must be prepared. Furthermore, since the position of the mask mark changes depending on the mask, it is necessary to attach a movement mechanism in the X direction and the Y direction to the alignment sensor. In the apparatus of the above embodiment, the number of alignment sensors can be reduced as compared with an apparatus that performs die-by-die alignment. Further, since the alignment sensor moving mechanism is unnecessary, the cost of the apparatus can be reduced.

  In the above embodiment, the mask 21 and the wafer 20 are held on the mask stage 10 and fine movement top table 3B, respectively, before the reference mark 4M observation step shown in FIG. 8A. The mask 21 may be held on the mask stage 10 after the observation process of the reference mark 4M shown in FIG. Further, the wafer 20 may be held on the fine movement top table 3B after the observation step of the mask mark 21M shown in FIG. When the processing of one wafer 20 is completed, the wafer to be processed next is held on the fine movement top table 3B, the wafer mark observation step shown in FIG. 8C, and the position shown in FIG. 8D. What is necessary is just to perform a matching process and an exposure process.

  In the above embodiment, the position of the reference point of the mask 21 is calculated in the step shown in FIG. 8B, but information other than the position of the reference point can also be obtained. Next, a method for obtaining the rotation residue and linear expansion / contraction amount of the mask 21 will be described.

In FIG. 3, the measurement results of the XY coordinates of the mask marks 21M _{1 to} 21M ₃ are respectively (x ₁ , y ₁ ), (x ₂ , y ₂ ), and (x ₃ , y ₃ ). The mask mark 21M ₁ and 21M _2, Y coordinates of the design is the same, the mask mark 21M ₁ and 21M _3, X coordinate of the design are the same. The rotational residue θ _M of the mask 21 is

(Equation 3)
θ _M = (y ₁ −y ₂ ) / (x ₁ −x ₂ )
It is expressed. The linear expansion and contraction amounts M _MX and M _MY in the X direction and the Y direction are

(Equation 4)
M _MX = (x ₁ −x ₂ ) / A
M _MY = (y ₁ -y ₃ ) / B
It is expressed. Here, A is represents the distance between the X-axis direction on the design of the mask mark 21M ₁ and 21M _2, B represents the distance between the Y-axis direction on the design of the mask mark 21M ₁ and 21M _3.

  Further, in the above embodiment, the position information of the wafer 20 is acquired in the process shown in FIG. 8C. However, the displacement amount (rotation amount) in the rotation direction of the pattern transferred in the shot area is linear and linear. It is also possible to measure the amount of expansion and contraction. Measurement for obtaining such information of the transferred pattern is called intra-field measurement. Next, the method of intrafield measurement will be described.

6, around the shot area 35a for intra field measurement, two wafer marks 20M ₃ and 20M ₄ are formed. The wafer mark 20M ₃ and 20M _4, upon the transfer of a circuit pattern in the shot area 35a for intra field measurement, is one which is simultaneously transferred to the circuit pattern.

By measuring the position of the two wafer marks 20M ₃ and 20M _4, it can be determined rotation amount theta _C, and the amount of expansion or contraction _{r C.} In addition, a plurality of shot areas for intrafield measurement may be prepared, and the rotation amount and the expansion / contraction amount calculated for each shot area may be averaged. The rotation amount θ _C calculated here is the sum of the wafer rotation amount θ _U and the intra-field rotation amount θ _S shown in Equation (1). Therefore, the rotation amount θ _S of the pattern in the shot area 35a is

(Equation 5)
θ _S = θ _C −θ _U
It becomes. The expansion / contraction amount r _C is a combination of the wafer expansion / contraction amounts r _X and r _Y shown in the equation (1) and the intra-field expansion / contraction amount r _S. Intrafield expansion / contraction amount r _S is

(Equation 6)
r _S = r _C / ((r _X + r _Y ) / 2)
It becomes.

Next, a method for aligning in consideration of the mask rotation residue θ _M and the intra-field rotation amount θ _S will be described. After the wafer mark observation step shown in FIG. 8 (C), the intra-field rotation amount, so as to match the mask rotation residue theta _M, to rotate the wafer 20 by an angle theta _J. Thereafter, the reference point of the mask 21 and the reference point of each shot area 35 are aligned while the fine movement top table 3B is translated in the X and Y directions. Here, the angle θ _J to rotate the wafer 20 is:

(Equation 7)
θ _J = θ _M −θ _C
It is expressed.

The wafer 20 instead of rotating may rotate the mask 21 by an angle theta _J. Alternatively, the electron beam for exposure may be deflected so as to correct the positional shift in the rotation direction between the mask 21 and the circuit pattern in the shot area 35.

Further, when the mask expansion / contraction amounts M _MX and M _MY and the expansion / contraction amount r _C of the shot area 35 are different, the positional deviation between the mask pattern and the pattern on the wafer due to the difference in the expansion / contraction amount is corrected. Further, it is preferable to deflect the electron beam.

FIG. 9 shows another configuration example of the reference mask 4. 2A and 2B, one reference mark 4M is formed in the reference mask 4. In the configuration example shown in FIG. 9, three reference marks 4M _{1 to} 4M ₃ are formed in the reference mask 4. Each of the reference marks 4M _{1 to} 4M ₃ has the same shape as the reference mark 4M shown in FIG. For example, at the beginning of the device assembly, the reference mark 4M ₁ is used, and the reference marks 4M ₂ and 4M ₃ become spare reference marks. For some reason the reference mark 4M ₁ is, for example, adhesion of particles, the shape defects of the reference marks, when it becomes unusable by a membrane such as breakage of the reference mask 4, by shifting the position of the reference mask 4, the reference mark of the pre 4M ₂ or 4M ₃ can be used.

  Usually, even if the number of reference marks increases, the manufacturing cost of the reference mask 4 hardly changes. For this reason, by forming a plurality of reference marks on the reference mask 4, the manufacturing cost per reference mark can be reduced.

  With reference to FIG. 10, another effect of the mask alignment microscope will be described. FIG. 10 shows a schematic diagram of fine movement stage 3, mask stage 10, and components attached thereto. Description of the components described with reference to FIG. 1 is omitted here. A leveling sensor 40 is attached to the fine movement top table 3B so as to face the mask stage 10 side. A leveling sensor 41 is attached to the mask stage 10 so as to face the fine movement top table 3B side. These leveling sensors 40 and 41 are constituted by electrostatic capacitance sensors, for example.

  By moving the fine movement top table 3B to a position where the leveling sensor 40 faces the mask 21, the position (height) of the mask 21 in the Z direction can be measured. By measuring the height of at least three points on the mask 21, the inclination of the mask 21 with respect to the XY plane can be detected. The mask stage 10 has a fine adjustment mechanism that finely adjusts the inclination of the mask 21, and can perform leveling of the mask 21.

  Further, by moving the fine movement top table 3B to a position where the leveling sensor 41 faces the wafer 20, the position (height) in the Z direction of the surface of the wafer 20 can be measured. By measuring the height of at least three points on the wafer 20, the wafer 20 can be leveled. Further, the distance between the mask 21 and the wafer 20 can be obtained.

  The wafer thickness varies from wafer to wafer. In order to set the distance between the mask 21 and the wafer 20 to a predetermined value, the fine movement top table 3B is moved in the Z direction. When the fine movement top table 3B is moved in the Z direction, the distance from the mask 21 to the mask alignment sensor 6 also varies.

As described with reference to FIG. 4B, the optical axis 30 of the X mask alignment microscope 6X constituting the mask alignment sensor 6 is inclined with respect to the XY plane. When the distance from the mask 21 to the X mask alignment microscope 6X changes, the position where the object surface 32 and the mask 21 intersect moves in the Y direction. If this intersection is accommodated in the mask mark 21M in _1X for X, it is possible to detect the position in the X-axis direction of the X mask mark 21M _1X. As described above, the mask mark 21M can be observed by the mask alignment sensor 6 even if the fine movement top stage 3B is moved in the Z direction due to the variation in the thickness of the wafer 20.

  Further, even when exposure is performed by changing the distance between the mask and the wafer, it is possible to respond flexibly without adjusting the position of the mask alignment sensor 6.

  FIG. 11A is a perspective view of a portion where a circuit pattern of a mask used in LEEPL is formed. In order to maintain the mechanical strength of the mask membrane 21A, beams 21B are provided in a lattice shape. A circuit pattern to be transferred is arranged in an area where the beam 21B is not provided in the mask membrane 21A.

  When performing die-by-die alignment, the mask mark formed on the mask membrane 21A is observed, and simultaneously the wafer mark on the wafer is observed through the mask membrane 21A. For this reason, the mask mark must be arranged in a region where the beam 21B is not provided. On the other hand, in the case of this embodiment, the mask mark 21M is observed from the surface facing the wafer 20 as shown in FIGS. 8B and 11B. For this reason, the mask mark 21M can be arranged in the region where the beam 21B is provided.

  The mask membrane 21A is fixed to a support member that supports the mask membrane 21A around the area where the circuit pattern is disposed. It is also possible to arrange a mask mark in a region fixed to the support member.

  FIG. 5 shows a configuration example of the wafer alignment sensor 12. Next, another configuration example of the wafer alignment sensor 12 will be described.

  FIGS. 12A and 12B are a plan view and a side view of a wafer alignment sensor 12 according to another configuration example, respectively. Three objective lenses 44X, 44Y and 44Z are attached to the tip of the lens barrel 12B. Three receivers 45X, 45Y, and 45Z are attached to the other end of the lens barrel 12B. The objective lens 44X and the receiver 45X constitute the X wafer alignment microscope 12X, the objective lens 44Y and the receiver 45Y constitute the Y wafer alignment microscope 12Y, and the objective lens 44Z and the receiver 45Z are used for vertical observation. A wafer alignment microscope 12Z is configured. The X wafer alignment microscope 12X and the Y wafer alignment microscope 12Y correspond to the X wafer alignment microscope 12X and the Y wafer alignment microscope 12Y shown in FIG. 5, respectively.

  The optical axis of the objective lens 44X is inclined in the Y direction from the normal direction of the XY plane, and the optical axis of the objective lens 44Y is inclined in the X direction from the normal direction of the XY plane. The optical axis of the objective lens 44Z is parallel to the normal line of the XY plane.

  FIG. 13 is a plan view of a portion where the wafer alignment sensor 12 is attached to the reference base 1B. The wafer alignment sensor 12 is attached to the reference base 1B via a low thermal expansion member 47. The low thermal expansion member 47 has a shape obtained by cutting out a substantially semicircular portion of the ring. The low thermal expansion member 47 is fixed to the reference base 1B by fixing screws 46a and 46b at both ends thereof. The position fixed by the fixing screws 46a and 46b is the same as the position of the rotation center of the mask 21 in the X-axis direction. Further, the midpoint of the line segment connecting the positions fixed by the fixing screws 46 a and 46 b coincides with the rotation center of the mask 21.

  The low thermal expansion member 47 has a protruding portion 47a protruding in the Y direction from a part of its inner periphery. The wafer alignment sensor 12 is fixed to the tip of the protruding portion 47a by a fixing screw 48. With respect to the X-axis direction, the fixing position by the fixing screw 48 coincides with the position of the optical axis of the objective lens 44X. With respect to the Y-axis direction, the position of the optical axis of the objective lens 44Y coincides with the position of the rotation center of the mask 21.

  The low thermal expansion member 47 is formed of a material having a thermal expansion coefficient smaller than that of the reference base 1 </ b> B or the lens barrel of the wafer alignment sensor 12. As a material of the low thermal expansion member 47, for example, ZFP (trade name) manufactured by Nippon Ceratech Co., Ltd. can be used.

  Assume that the reference base 1B and the lens barrel of the wafer alignment sensor 12 are thermally expanded in the X direction and the Y direction. At this time, it is assumed that the low thermal expansion member 47 hardly expands. Since the rotation center of the mask 21 coincides with the midpoint connecting the positions where the low thermal expansion member 47 is fixed by the fixing screws 46a and 46b, the low thermal expansion member 47 is in the X direction and the Y direction with respect to the mask 21. Almost no displacement.

  Since the position of the optical axis of the objective lens 44X coincides with the position of the fixing screw 48 with respect to the X-axis direction, the optical axis of the objective lens 44X is hardly displaced in the X direction even when the lens barrel is expanded. Further, with respect to the Y-axis direction, the displacement of the optical axis of the objective lens 44Y in the Y direction can be reduced by bringing the position of the optical axis of the objective lens 44Y closer to the position of the fixing screw 48.

  As described above, by attaching the wafer alignment sensor 12 to the reference base 1B via the low thermal expansion member 47, it is possible to suppress the deviation of the optical axis due to the thermal expansion of the reference base 1B or the lens barrel of the wafer alignment sensor 12. .

  In FIG. 13, the midpoint of the line connecting the fixing screws 46a and 46b is made to coincide with the rotation center of the mask 21, but it is not always necessary to coincide with the midpoint. Even if the fixing screws 46a and 46b are arranged on both sides of the mask stage with respect to the Y direction, the positions of the optical axes of the objective lenses 44X and 44Y are hardly affected by the thermal expansion of the reference base 1B. . In addition, the optical axis of the objective lens 44Y and the rotation center of the mask 21 are configured to coincide with each other in the Y direction. If the wafer alignment sensor 12 is arranged at a position overlapping the mask stage in the Y-axis direction, the influence of thermal expansion is mitigated.

  In the above embodiment, the alignment method using the X wafer alignment microscope 12X and the Y wafer alignment microscope 12Y has been described. Next, a method of performing alignment using the vertical observation wafer alignment microscope 12Z shown in FIGS. 12A and 12B will be described.

In the step shown in FIG. 8 (A), to observe the X reference mark 4M _X and Y reference mark 4M _Y shown in vertical observation wafer alignment sensor 12Z in FIG 2 (B). X-direction position of the reference mark 4M from the center line 4C _X of X reference mark 4M _X is calculated, the position of the Y direction of the reference mark 4M is calculated from the center line 4C _Y of Y reference mark 4M _Y.

  The mask mark observation process shown in FIG. 8B is the same as the method of the above embodiment.

  In the step shown in FIG. 8C, the wafer mark 20M is observed by the vertical observation wafer alignment sensor 12Z. In this case, as the wafer mark 20M, for example, an FIA mark proposed by Nikon Corporation or a He-Ne multimark proposed by Canon Inc. can be used.

  Through the steps so far, the same position information as in the case of the above embodiment can be obtained. The alignment and exposure process shown in FIG. 8D is the same as the method of the above embodiment.

  12 and 13, the X wafer alignment microscope 12X, the Y wafer alignment microscope 12Y, and the vertical observation wafer alignment microscope 12Z are attached to one lens barrel 12B, and the lens barrel 12B is fixed to the upper reference base 1B. However, other configurations may be used. For example, the X wafer alignment microscope 12X and the Y wafer alignment microscope 12Y shown in FIG. 5 are attached to the upper reference base 1B via the intermediate member 12A, and the vertical observation wafer alignment microscope is individually connected to the upper reference base 1B. You may attach to.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

1 is a schematic view of an alignment apparatus according to an embodiment of the present invention. (A) is a plan view of a fine movement top table, and (B) is a plan view of a reference mark. (A) is a plan view of the mask, and (B) is a plan view of the mask mark. It is the schematic which shows the positional relationship of a mask mark, a reference mark, and a mask alignment sensor. It is a top view of a wafer alignment sensor. It is a top view of a wafer. It is a diagram which shows the relationship of a coordinate system. It is process drawing for demonstrating the alignment method by an Example. It is a top view which shows the other structural example of a reference | standard mask. It is the schematic which shows a fine movement top table, a mask stage, and the component attached to these. (A) is a perspective view of a portion where a circuit pattern of a mask is formed, and (B) is a sectional view thereof. (A) is a top view of the other structural example of a wafer alignment sensor, (B) is the side view. It is a top view of a low thermal expansion member and a wafer alignment sensor.

Explanation of symbols

1 reference base 2 coarse movement stage 2A coarse movement mechanism 2B coarse movement top table 3 fine movement stage 3A fine movement mechanism 3B fine movement top table 4 reference mask 4M reference mark 6 mask alignment sensor 7 position sensor 7X, 7Y measuring mirror 10 mask stage 11 rotation Mechanism 12 Wafer alignment sensor 15 Electron beam source 20 Wafers 20M _{1 to} 20M ₄ Wafer mark 21 Mask 21M _{1 to} 21M ₃ Mask mark 30 Optical axis 31 Image receiving surface 32 Object surface 35 Shot area 40, 41 Leveling sensors 44X, 44Y, 44Z Objective Lenses 45X, 45Y, 45Z Image receiving devices 46a, 46b, 48 Fixing screw 47 Low thermal expansion member

Claims (26)

A reference base defining an XYZ Cartesian coordinate system;
A coarse movement stage attached to the reference base and moving the coarse movement top table in a direction parallel to the XY plane;
A fine movement stage that displaces a fine movement top table that holds a wafer to be processed parallel to the XY plane in a direction parallel to the XY plane with respect to the coarse movement top table;
A reference mark attached to the fine movement top table;
A mask stage that holds the mask so that the relative position with respect to the reference base is constrained from the wafer held on the fine movement top table at a certain interval in the Z direction;
A mask alignment sensor attached to the fine movement top table and capable of simultaneously observing a mask mark on the mask held on the mask stage and the reference mark;
A wafer alignment sensor attached to the reference base, wherein the reference mark can be arranged in an observable region of the wafer alignment sensor by moving the coarse top table and the fine top table. A wafer alignment sensor,
And a position sensor for measuring a position of the fine movement top table in the XY plane. The position sensor can detect the position of the fine movement top table with respect to the amount of inclination from the XY plane and the rotation direction about an axis parallel to the Z axis,
The fine movement stage is capable of adjusting the amount of inclination of the fine movement top table from the XY plane and displacing the fine movement top table in a rotation direction about an axis parallel to the Z axis. The alignment apparatus as described. The mask alignment sensor is
A mask alignment microscope for X having an optical axis inclined in the Y direction from the normal direction of the XY plane;
A Y mask alignment microscope having an optical axis inclined in the X direction from the normal direction of the XY plane,
The alignment apparatus according to claim 1, wherein the reference mark includes an X reference mark observed with the X mask alignment microscope and a Y reference mark observed with the Y mask alignment microscope. The X mask alignment microscope, the Y mask alignment microscope, so that the observation of the X reference mark by the X mask alignment microscope and the observation of the Y reference mark by the Y mask alignment microscope can be performed simultaneously, The alignment apparatus according to claim 3, wherein the X reference mark and the Y reference mark are arranged. The reference mark includes a plurality of scattering sources formed on a transmissive member that transmits illumination light for observation,
The alignment apparatus according to claim 4, wherein a preliminary reference mark having the same shape as the reference mark is formed on the transmitting member at a position different from the reference mark. The wafer alignment sensor is
A wafer alignment microscope for X having an optical axis inclined in the Y direction from the normal direction of the XY plane;
The alignment apparatus according to claim 4, further comprising a Y wafer alignment microscope having an optical axis inclined in the X direction from a normal direction of the XY plane. Observation of the X reference mark by the X wafer alignment microscope and observation of the Y reference mark by the Y wafer alignment microscope can be performed simultaneously with the coarse movement top table and the fine movement top table stationary. The alignment apparatus according to claim 6, wherein the X wafer alignment microscope and the Y wafer alignment microscope are arranged. Furthermore, a low thermal expansion member attached to the reference base so as to be fixed to the reference base on both sides of the mask stage with respect to the Y-axis direction and formed of a material having a smaller thermal expansion coefficient than the material of the reference base. Have
The alignment apparatus according to claim 7, wherein the wafer alignment sensor is disposed at a position overlapping with the mask stage in the Y-axis direction, and is attached to the reference base via the low thermal expansion member. The alignment apparatus according to claim 8, wherein the wafer alignment sensor is fixed to the low thermal expansion member at the same position as the optical axis of the X wafer alignment microscope in the X-axis direction. The wafer alignment sensor includes a vertical observation wafer alignment microscope having an optical axis parallel to the Z axis, and the vertical observation wafer alignment microscope is capable of observing the reference mark. The alignment apparatus of crab. A reference base defining an XYZ Cartesian coordinate system;
A coarse movement stage attached to the reference base and moving the coarse movement top table in a direction parallel to the XY plane;
A fine movement stage that displaces a fine movement top table that holds a wafer to be processed parallel to the XY plane in a direction parallel to the XY plane with respect to the coarse movement top table;
A reference mark attached to the fine movement top table;
A mask stage that holds the mask so that the relative position with respect to the reference base is constrained from the wafer held on the fine movement top table at a certain interval in the Z direction;
A mask alignment sensor attached to the fine movement top table and capable of simultaneously observing a mask mark on the mask held on the mask stage and the reference mark;
A wafer alignment sensor attached to the reference base, wherein the reference mark can be arranged in an observable region of the wafer alignment sensor by moving the coarse movement top table and the fine movement top table. When,
A method of performing alignment using an alignment device having a position sensor that measures a position in the XY plane of the fine movement top table,
(A) The coarse movement stage or both the coarse movement stage and the fine movement stage are driven so that the reference mark can be observed by the wafer alignment sensor, and the position of the fine movement top table measured by the position sensor Obtaining the first information indicating the position and the second information indicating the position of the reference mark observed by the wafer alignment sensor;
(B) holding a mask on which mask marks observable by the mask alignment sensor are formed on the mask stage;
(C) The mask alignment sensor drives the coarse movement stage or both the coarse movement stage and the fine movement stage so that the reference mark and the mask mark can be observed at the same time, and is measured by the position sensor. Third information indicating the position of the mask is acquired based on information indicating the position of the fine movement top table and information indicating a relative position between the reference mark and the mask mark measured by the mask alignment sensor. And a process of
(D) holding the wafer on which the wafer mark observable by the wafer alignment sensor is formed on the fine movement top table;
(E) The coarse movement stage or both the coarse movement stage and the fine movement stage are driven so that the wafer mark can be observed by the wafer alignment sensor, and the fine movement top table measured by the position sensor is used. Obtaining fourth information indicating the position of the wafer based on information indicating the position and information indicating the position of the wafer mark measured by the wafer alignment sensor;
(F) A sixth information indicating the position of each shot area based on the fifth information indicating the design position of each of the plurality of shot areas defined on the surface of the wafer and the fourth information. Obtaining information on
(G) based on the first, second, third, and sixth information, the coarse movement stage and the mask so that the position of the shot region to be aligned with the position of the mask matches And a step of driving the fine movement stage. In step e, the positions of at least three wafer marks that are not on a straight line of the wafer are measured, and the fourth information is a position in the XY plane direction, an expansion / contraction amount in the XY plane direction, and parallel to the Z axis. The alignment method according to claim 11, comprising information indicating a position in a rotation direction about a simple axis and an orthogonality of an arrangement of a plurality of shot areas. 13. In the step c, the illumination light source is turned on before observing the reference mark and mask mark with the mask alignment sensor, and the illumination light source is turned off when the observation is completed. Alignment method. The mask alignment sensor is
A mask alignment microscope for X having an optical axis inclined in the Y direction from the normal direction of the XY plane;
A Y mask alignment microscope having an optical axis inclined in the X direction from the normal direction of the XY plane,
The reference mark includes an X reference mark observed with the X mask alignment microscope, and a Y reference mark observed with the Y mask alignment microscope,
The mask mark includes an X mask mark observed with the X mask alignment microscope, and a Y mask mark observed with the Y mask alignment microscope,
The observation of the X reference mark and the X mask mark by the X mask alignment microscope, and the observation of the Y reference mark and the Y mask mark by the Y mask alignment microscope can be performed simultaneously. The X mask alignment microscope, the Y mask alignment microscope, the X reference mark, the Y reference mark, the X mask mark, and the Y mask mark are arranged,
In the step c, the X reference mark, the X mask mark, the Y reference mark, and the Y mask mark are observed in a state where the coarse movement top table and the fine movement top table are stationary. Item 14. The alignment method according to any one of Items 11 to 13. The wafer alignment sensor is
A wafer alignment microscope for X having an optical axis inclined in the Y direction from the normal direction of the XY plane;
A Y wafer alignment microscope having an optical axis inclined in the X direction from the normal direction of the XY plane,
The wafer alignment microscope for X and the wafer alignment microscope for Y so that the observation of the reference mark for X with the wafer alignment microscope for X and the observation of the reference mark for Y with the wafer alignment microscope for Y can be performed simultaneously. Is placed,
The position according to any one of claims 11 to 14, wherein in the step a, both the X reference mark and the Y reference mark are observed in a state where the coarse movement top table and the fine movement top table are stationary. How to match. The wafer mark includes an X wafer mark observed with the X wafer alignment microscope, and a Y wafer mark observed with the Y wafer alignment microscope,
The X wafer mark and the Y wafer mark are arranged so that observation of the X wafer mark by the X wafer alignment microscope and observation of the Y wafer mark by the Y wafer alignment microscope can be performed simultaneously. And
The alignment method according to claim 15, wherein in the step e, both the X wafer mark and the Y wafer mark are observed while the top table and the fine movement top table are stationary. The wafer alignment sensor includes a vertical observation wafer alignment microscope having an optical axis parallel to the Z-axis. In the step a, the vertical reference wafer alignment microscope uses the X reference mark and the Y reference mark. The alignment method according to claim 14, wherein observation is performed simultaneously. 18. The wafer mark is a mark for observation with a microscope having an optical axis perpendicular to the wafer surface, and the wafer mark is observed with the vertical observation wafer alignment microscope in the step e. Alignment method. The light source for illuminating the wafer mark is turned on before observing the wafer mark in the step e, and the light source is turned off when observation of all the wafer marks is completed. The alignment method according to any one of the above. A mask reference point is defined in the mask, and a shot reference point to be aligned with the reference point of the mask is defined in each shot area of the wafer,
In the step a, information associating the XY coordinate system fixed to the reference base and the UV coordinate system fixed to the fine movement top table is acquired,
In the step c, the coordinates of the reference point of the mask in the XY coordinate system are acquired,
In the step e, information that associates the design coordinates fixed on the wafer with the UV coordinates is acquired,
In the step f, the coordinates of the shot reference point of each shot area in the UV coordinate system are acquired,
In the step g, in order to make the shot reference point of the shot region to be aligned coincide with the mask reference point, the distance to move the UV coordinate system in the X axis direction and the Y axis direction with respect to the XY coordinate system is set. The positioning method according to claim 11, wherein the coarse movement stage and the fine movement stage are driven so that the fine movement top table moves by the obtained distance. In the step c, the positions of at least three mask marks that are not on a straight line on the mask are measured, and the third information is a position in the X-axis and Y-axis directions of the mask, an axis parallel to the Z-axis. The alignment method according to any one of claims 11 to 20, including information indicating a position related to a rotation direction centered on the axis and an amount of expansion and contraction related to the X-axis and Y-axis directions. After step g,
Based on the position in the rotational direction of the mask and the amount of expansion / contraction obtained in the step c, the electron beam is deflected so as to compensate for the positional deviation in the rotational direction of the mask and the positional displacement due to the expansion / contraction, and passed through the mask. The alignment method according to claim 21, further comprising a step of transferring a pattern on a mask to a shot region of the wafer. At least one of the plurality of shot areas of the wafer is an intra-field measurement shot area, and at least two wafer marks are formed in the intra-field measurement shot area;
The step e measures the positions of at least two wafer marks provided in the intra-field measurement shot area, and, based on the measurement result, the shot area with respect to the rotation direction about an axis parallel to the Z-axis. The alignment method according to any one of claims 11 to 21, further comprising a step of obtaining information indicating a rotation amount of a pattern formed therein. 24. The alignment method according to claim 23, wherein in the step e, information indicating a pattern expansion / contraction amount in the shot area is obtained based on a wafer mark position measurement result in the intra-field measurement shot area. After step g,
Based on the rotation amount and expansion / contraction amount of the pattern in the shot area obtained in the step e, the electron is compensated for the positional deviation due to the rotation amount of the pattern in the shot region and the positional deviation due to the expansion / contraction amount. The alignment method according to claim 24, further comprising a step of transferring a pattern on the mask to the shot region of the wafer through the mask by deflecting a beam. After the item step g,
The alignment method according to claim 23 or 24, further comprising a step of rotating the mask so as to compensate for a positional shift caused by a rotation amount of the pattern in the shot region obtained in the step e.

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