JP2004356155A - Method for aligning mask and wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize alignment of a mask and a wafer with high accuracy. <P>SOLUTION: The method for aligning a mask and a wafer comprises a step for imaging a first mark put on any one of a wafer or a pallet for mounting a mask or the wafer and a second mark put on the other, a step for measuring relative positional shift of the first and second marks based on the image signals of the first and second marks thus imaged, and a step for aligning the mask and the wafer relatively based on the positional shift thus measured. The first mark consists of first and second X marks for detecting the position in the X direction, and a first Y mark for detecting the position in the Y direction wherein the first and second X marks are provided oppositely while being spaced apart by a specified distance in the Y direction. The second mark consists of third X mark for detecting the position in the X direction, and a second Y mark for detecting the position in the Y direction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of aligning a mask with a wafer, and more particularly, to a method of aligning a mask with a wafer in an exposure apparatus that transfers a mask pattern of a mask arranged in close proximity to a semiconductor wafer onto a resist layer on the wafer at an equal magnification.
[0002]
[Prior art]
As a conventional exposure apparatus of this type, an electron beam proximity exposure apparatus has been proposed (see Patent Document 1).
[0003]
FIG. 16 is a diagram showing a basic configuration of the electron beam proximity exposure apparatus. The electron beam proximity exposure apparatus 10 mainly includes an electron beam source 14 for generating an electron beam 15, an electron gun 12 including a lens 16 and a shaping aperture 18 for converting the electron beam 15 into a parallel beam, a main deflector 22, 24, The scanning unit 20 includes deflectors 26 and 28 and scans the electron beam in parallel with the optical axis, and the mask 30.
[0004]
The mask 30 is arranged so as to be close to the wafer 40 on the surface of which the resist layer 42 is formed (so that the gap between the mask 30 and the wafer 40 is, for example, 50 μm). When the mask 30 is irradiated with an electron beam in this state, the electron beam passing through the mask pattern of the mask 30 is irradiated on the resist layer 42 on the wafer 40.
[0005]
The scanning unit 20 controls the deflection of the electron beam so that the electron beam 15 scans the entire surface of the mask 30 as shown in FIG. Thus, the mask pattern of the mask 30 is transferred to the resist layer 42 on the wafer 40 at the same magnification.
[0006]
The electron beam proximity exposure apparatus 10 is provided in a vacuum chamber 50 as shown in FIG. In the vacuum chamber 50, an electrostatic chuck 60 for sucking the wafer 40 and the wafer 40 sucked by the electrostatic chuck 60 are moved in two horizontal orthogonal directions (X direction and Y direction). In addition, a wafer stage 70 for rotating in a horizontal plane is provided. The wafer stage 70 moves the wafer 40 by a predetermined amount every time the equal-size transfer of the mask pattern is completed, so that a plurality of mask patterns can be transferred to one wafer 40.
[0007]
In FIG. 18, a mask stage 80 capable of moving the mask 30 in the X direction and the Y direction is provided, and conduction pins 81 pressed against the upper surface of the wafer 40 are provided in order to establish conduction of the wafer 40. Provided.
[0008]
Incidentally, the wafer is exposed a plurality of times using a plurality of masks having different mask patterns, thereby forming an integrated circuit. When exposing each mask pattern, it is necessary to relatively align the mask and the wafer such that the mask pattern to be exposed has a predetermined positional relationship with the already exposed mask pattern.
[0009]
On the other hand, as a conventional method of aligning a mask and a wafer, an oblique detection method is known (see Patent Document 2).
[0010]
In the oblique detection method, an optical system is arranged so that a photographing optical axis is oblique to a mask surface arranged close to a wafer, and a wafer mark for alignment provided on the wafer and a mask provided on the mask are provided. A mask mark for alignment is simultaneously imaged, a positional shift between the marks is detected from the captured image, and the mask and the wafer are aligned so that the positional shift becomes zero.
[0011]
This oblique detection method has an advantage that the microscope imaging device can be arranged so as not to block the exposure, and it is not necessary to retract the optical system during the exposure, and each mark can be imaged even during the exposure.
[0012]
Further, as a method of further improving the oblique detection method, a method and an apparatus for aligning a mask and a wafer described later have been made by the present applicant (see Patent Document 3). In this method, the alignment mark provided on the mask and the alignment mark provided on the pallet or wafer on which the wafer is mounted are simultaneously imaged from a direction orthogonal to the surface on which each mark is provided. A microscope imaging device has been proposed, and a mark as shown in FIG. 19 has been proposed.
[0013]
The figure shows a case where a mask mark M and a pallet mark WP are put in a visual field V of a microscope imaging device. The mask mark M is composed of 5 × 2 openings for detecting the position of the mask in the X direction. _X And a mask mark M composed of 5 × 2 openings for detecting the position of the mask in the Y direction _Y The pallet mark WP is composed of five convex portions (or concave portions) for detecting the position of the wafer pallet in the X direction. _X And a pallet mark WP composed of five convex portions (or concave portions) for detecting the position of the wafer pallet in the Y direction. _Y It is composed of
[0014]
Further, an L-shaped opening 33 for observing the pallet mark WP located below the mask 32 is formed in the mask 32.
[0015]
[Patent Document 1]
US Patent No. 5,831,272 (corresponding to Japanese Patent No. 2951947)
[0016]
[Patent Document 2]
JP-A-11-243048
[0017]
[Patent Document 3]
JP-A-2003-37036
[0018]
[Problems to be solved by the invention]
However, even with the above-described conventional alignment method, the alignment accuracy is limited, and further improvement in the accuracy is expected. That is, the CCD as an image sensor has, for example, one pitch of 6 μm, and cannot detect a wafer or a mask of 60 nm or less even if it is enlarged 100 times in a microscope image pickup device. In addition, there is a problem that a rotation error occurs if the alignment mark and the measurement line direction of the CCD as the image sensor are not perfectly parallel, and an error occurs in the alignment accuracy depending on the focus state of the microscope imaging device. It has also been confirmed.
[0019]
The present invention has been made in view of such circumstances, and a position of a mask and a wafer can be realized with a single microscope imaging device with higher accuracy than a conventional one. The purpose is to provide a matching method.
[0020]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 of the present application provides a mask and a wafer in an exposure apparatus that disposes a mask on a wafer and transfers a mask pattern formed on the mask to a resist layer on the wafer. In the alignment method, a first mark for alignment provided on one of the pallet or the wafer on which the mask or the wafer is mounted and a position provided on the other of the mask or the pallet or the wafer Imaging a second mark for alignment by an image sensor; and determining a position of the first mark and the second mark based on an image signal of the captured first mark and the second mark. Measuring a relative displacement amount; and relatively positioning the mask and the wafer based on the measured displacement amount. And wherein the first mark comprises a first X mark and a second X mark for detecting a position in the X direction, and a first Y mark for detecting a position in the Y direction. Wherein each of the first X mark and the second X mark is a plurality of line patterns whose longitudinal direction is oriented in the Y direction and parallel to the X direction, and the first X mark And the second X mark are provided facing each other at a predetermined distance in the Y direction, and the first Y mark is a plurality of line patterns whose longitudinal directions are oriented in the X direction and arranged in parallel with the Y direction. The second mark includes a third X mark for detecting a position in the X direction and a second Y mark for detecting a position in the Y direction, and the third X mark is , A plurality of line patterns whose longitudinal direction is oriented in the Y direction and arranged in parallel with the X direction , And the second Y mark is characterized in that a plurality of line patterns in the longitudinal direction is disposed in parallel with the direction and Y direction in the X direction.
[0021]
That is, the microscope imaging apparatus can simultaneously capture images of the respective marks from a direction orthogonal to the surface on which the first mark and the second mark are provided, and obtain an image signal in which each mark is focused. be able to. Then, based on the image signals of the first mark and the second mark simultaneously obtained from the microscope image pickup device, the relative displacement between the first mark and the second mark is measured. That is, by taking an image of each mark from a direction orthogonal to the surface on which each mark is provided, measuring the two-dimensional displacement amount between the first mark and the second mark by one microscope imaging device. Can be.
[0022]
Further, the positions of the first mark and the second mark are not measured with reference to a reference position (for example, a cross mark of the microscope) of the microscope imaging device, and the first mark and the first mark simultaneously obtained from the microscope imaging device are not measured. Since the relative displacement between the marks is measured based on the image signal with the second mark, the displacement can be measured without being affected by the fluctuation of the reference position of the microscope imaging device.
[0023]
Further, the first mark includes a first X mark and a second X mark for detecting a position in the X direction, and the first X mark and the second X mark are predetermined in the Y direction. They are provided facing each other at a distance. Therefore, it is possible to effectively cope with the problem that a rotation error occurs unless the alignment mark and the measurement line direction of the CCD as the image sensor are completely positioned in parallel, and highly accurate alignment between the mask and the wafer can be realized. .
[0024]
Note that the X direction and the Y direction refer to a horizontal orthogonal two-axis direction as generally considered. Therefore, in each of the plan views in this specification, unless otherwise specified, the X direction indicates the left-right direction of the paper surface, and the Y direction indicates the up-down direction of the paper surface.
[0025]
As shown in claim 2 of the present application, when the first mark and the second mark are in the field of view of the microscope imaging device having the imaging element, the third X mark is the first X mark. And the second Y mark is arranged at a position opposed to the first Y mark.
[0026]
That is, by adopting such a configuration, the first mark and the second mark can be aligned with high accuracy in the X direction and the Y direction.
[0027]
As described in claim 3 of the present application, in the step of imaging the first mark and the second mark with an image sensor, the first mark and the second mark can be respectively focused. It is characterized in that images are taken almost simultaneously by a microscope image pickup device having a set of image forming optical systems.
[0028]
That is, since the first mark and the second mark are imaged at the same time, there is no occurrence of inaccuracy caused by the movement of the microscope imaging device or the like and inaccuracies over time (thermal expansion / shrinkage of the wafer or mask). .
[0029]
As described in claim 4 of the present application, the mask is characterized in that an opening for imaging a first mark or a second mark provided on the pallet or the wafer is formed.
[0030]
That is, if the mask has a small thickness, the second mark (or the first mark) can be imaged through the mask, but if the mask has an opening, the second mark (or the first mark) can be formed. The mark) can be more reliably imaged.
[0031]
As shown in claim 5 of the present application, in the step of measuring a relative displacement amount between the first mark and the second mark, the first mark and / or the second A horizontal tilt angle between a mark and the image sensor is calculated, and image data captured so that the horizontal tilt angle becomes zero is converted from the calculation result, and then the first mark and the second mark are converted. Is characterized by measuring a relative positional shift amount with respect to the mark of (1).
[0032]
In other words, if there is an error in the horizontal tilt angle (the amount of rotation) between the first mark or the second mark and the image sensor, the measurement error of the relative displacement amount between the first mark and the second mark is made. Will occur. If the amount of rotation between the mark and the image sensor is obtained at the time of measurement, the coordinate of image data captured so that the amount of rotation becomes zero can be converted. Thereby, the measurement error of the relative displacement between the first mark and the second mark can be minimized.
[0033]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of a method for aligning a mask and a wafer according to the present invention will be described with reference to the accompanying drawings.
[0034]
FIG. 1 is a vertical sectional view of a main part of an electron beam proximity exposure apparatus including an alignment mechanism system used in a first embodiment of a method for aligning a mask and a wafer according to the present invention, and FIG. It is a principal part top view of the shown electron beam proximity exposure apparatus. The main configuration of the electron beam proximity exposure apparatus is the same as that shown in FIGS. 16 to 18, and a detailed description thereof will be omitted.
[0035]
As shown in FIGS. 1 and 2, in this electron beam proximity exposure apparatus, one alignment unit (microscope imaging apparatus) 100 is fixed to a frame 52 in a vacuum chamber 50. The microscope imaging apparatus 100 is fixed outside an exposure area that does not interfere with transfer by the electron beam proximity exposure apparatus. In FIGS. 1 and 2, reference numeral 102 denotes an electron optical column.
[0036]
The lamp house 110 constituting the illumination means of the microscope imaging apparatus 100 is disposed outside the vacuum chamber 50, and the illumination light emitted from the lamp house 110 includes an optical fiber 111, an illumination optical system 112, and a vacuum. The light is guided into the microscope imaging device 100 through a window 54 provided on a top plate of the chamber 50.
[0037]
The mask stage 80 to which the mask 32 is attached can move in the X direction and the Y direction.
[0038]
FIG. 3 is a plan view of the mask 32. The mask 32 is an 8-inch mask, on which four types of mask patterns P1 to P4 are formed. In addition, mask marks M (first marks) for alignment are formed at left and right positions of each mask pattern, and each mask pattern and the mask mark M are formed in a fixed relationship. In FIG. 3, M1 and M2 indicate mask marks formed at left and right positions of the mask pattern P1.
[0039]
When observing the mask mark M1 with the microscope imaging device 100, the mask stage 80 is moved so that the mask mark M1 enters the visual field V of the microscope imaging device 100. The position (x, y) of the mask stage 80 is determined by the laser interferometer L _XM , L _YM (See FIG. 8).
[0040]
On the other hand, the wafer 40 is attracted and fixed on the wafer pallet 44 by an electromagnetic chuck (not shown) as shown in FIG. The wafer pallet 44 is mounted and fixed on the electromagnetic chuck 60 of the wafer stage 70 shown in FIG. FIG. 18 shows a case where the wafer 40 is directly mounted on the electromagnetic chuck 60 without using the wafer pallet 44.
[0041]
The wafer pallet 44 is provided with pallet marks WP1, WP2 (second marks) as shown in FIG. These pallet marks WP1, WP2 are formed at positions flush with the upper surface of the wafer 40.
[0042]
Further, a plurality of dies D are formed on the wafer 40 by transferring various mask patterns, and a die mark DM (second mark) for positioning these dies D is formed on the wafer 40. I have. Note that the positional relationship between the pallet marks WP1 and WP2 and each of the die marks DM is separately measured after the wafer 40 is mounted on the wafer pallet 44 and stored as data. Therefore, if the positions of the pallet marks WP1 and WP2 on the wafer stage 70 can be detected, the positions of the respective die marks DM can be calculated from the positional relationship between the pallet marks WP1 and WP2 and the respective die marks DM. The position (X, Y) of wafer stage 70 is determined by laser interferometer L _XW , L _YW (See FIG. 8).
[0043]
The microscope imaging apparatus 100 shown in FIGS. 1 and 2 simultaneously observes the mask mark M1 or M2 of the mask 32 and the die mark DM1 or DM2 or the pallet mark WP1 or WP2, and furthermore, the mask mark M2 of the mask 32 and the die mark DM2. Alternatively, the pallet mark WP2 and the pallet mark WP2 are observed at the same time, and the amount of displacement between the marks is measured. ) Have two sets of imaging optical systems that can simultaneously focus on different marks.
[0044]
FIG. 5 is an optical component arrangement diagram showing details of the microscope imaging apparatus 100. As shown in the figure, the imaging optical system of the microscope imaging apparatus 100 is divided into three optical paths with the objective lens 120 in common. That is, the microscope imaging apparatus 100 includes a mask mark imaging optical system that forms an image of the mask mark M on the solid-state imaging device (CCD) 130, a die mark imaging optical system that forms the die mark DM or the pallet mark WP on the CCD 131, An auto-focusing optical system for forming an image of the mask mark M on the CCD 132.
[0045]
The mask mark imaging optical system includes an objective lens 120, half mirrors 121 and 122, and a mask mark imaging objective lens 123, and the die mark imaging optical system includes an objective lens 120, half mirrors 121, 122, and 124. The auto-focusing optical system includes an objective lens 120, half mirrors 121, 122, and 124, and a focusing lens 126.
[0046]
Further, the microscope imaging apparatus 100 includes an illumination optical system including an objective lens 120, a half mirror 121, a total reflection mirror 127, a lens 128, an optical system 112, and an optical fiber 111, and illumination light via the illumination optical system. And a lamp house 110 that emits light. The optical system 112 in the illumination optical system includes an NA variable stop 112A, a lens 112B, and a field-of-view variable stop 112C.
[0047]
Further, the objective lens 120 and the die mark imaging objective lens 125 can be moved by a small amount in the optical axis direction, and the mask mark M is formed on the CCD 130 by moving the objective lens 120 by, for example, a piezo element. The focus adjustment is performed so that the die mark DM or the pallet mark WP forms an image on the CCD 131 by moving the die mark imaging objective lens 125.
[0048]
That is, the position of the objective lens 120 is automatically controlled so that the contrast of the output signal of the CCD 132 that captures the mask mark M via the autofocus optical system is maximized. Here, the optical system for autofocus and the optical system for imaging a mask mark are adjusted in advance so that when the mask mark M is formed on the CCD 132, the image is formed also on the CCD. Therefore, by moving the objective lens 120 such that the mask mark M forms an image on the CCD 132, the mask mark M can be formed on the CCD 130. Note that the autofocus optical system has a lower photographing magnification than the mask mark imaging optical system so that focus adjustment can be easily performed.
[0049]
In the CCD 131, the position of the die mark imaging objective lens 125 is adjusted so that the wafer 40 (palette) arranged, for example, 50 μm below the mask 32 forms an image. In order to form an image of the die mark DM or the pallet mark WP even when the gap is changed, the die mark imaging objective lens 125 can be moved by a small amount in the optical axis direction by, for example, an ultrasonic motor or the like.
[0050]
In this embodiment, the objective lens 120 and the die mark imaging objective lens 125 can be moved in the optical axis direction for focus adjustment. However, the present invention is not limited to this. If at least two of the imaging objective lens 123 and the die mark imaging objective lens 125 are configured to be movable in the optical axis direction, the mask mark M and the dimark DM or the pallet mark WP can be respectively focused. .
[0051]
In addition, the microscope imaging apparatus 100 is configured such that a phase difference plate (not shown) can be attached to and detached from the pupil position, and has a function as a phase difference microscope. Further, the illumination unit applied to the microscope imaging apparatus 100 is configured to be manually switched to epi-illumination or critical illumination.
[0052]
Further, in this embodiment, two CCDs (CCDs 130, 131) for forming an image of the mask mark M and the die mark DM or the pallet mark WP are provided, but the optical paths of the two sets of image forming optical systems are provided. May be merged via a mirror or a half mirror to form an image of the mask mark M and the die mark DM or the pallet mark WP on one CCD.
[0053]
FIG. 6 is an optical component arrangement diagram of the microscope imaging apparatus 100 'for forming an image of the mask mark M and the die mark DM or the pallet mark WP on one CCD. The same parts as those in FIG. 5 are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0054]
As shown in FIG. 6, the optical system for imaging a mask mark of the microscope imaging apparatus 100 ′ includes an objective lens 120, half mirrors 140 and 141, a reflection mirror 143, an objective lens 123 for forming a mask mark, and a half mirror 144. And the optical system for imaging the dimark includes the objective lens 120, the half mirrors 140 and 141, the objective lens 125 for forming the dimark, the half mirrors 142 and 144. The optical system for auto-focusing includes an objective lens 120, half mirrors 140 and 141, an objective lens 125 for forming a dimark, a half mirror 142, and a focusing lens 126.
[0055]
The mask mark imaging optical system and the die mark imaging optical system configured as described above can simultaneously form the mask mark M and the die mark DM or the pallet mark WP on the same alignment CCD 145.
[0056]
Next, a method for detecting the amount of displacement between the mask mark M and the die mark DM or the pallet mark WP will be described.
[0057]
FIG. 7 shows a case where a mask mark M and a die mark DM are placed in the visual field V of the microscope imaging apparatuses 100 and 100 ′. The mask marks M are first X marks M arranged at two positions for detecting the position of the mask in the X direction. _X1 And the second X mark M _X2 And a first Y mark M for detecting the position of the mask in the Y direction. _Y Consists of
[0058]
Among them, the first X mark M _X1 And the second X mark M _X2 Are formed of five parallel line pattern openings all oriented in the Y direction, and the first X mark M _X1 And the second X mark M _X2 Are provided facing each other at a predetermined distance in the Y direction. First Y mark M _Y Are composed of five parallel line pattern openings oriented in the X direction. First Y mark M _Y Of the first X mark M _X1 And the second X mark M _X2 , And the arrangement position in the Y direction is the first X mark M _X1 And the second X mark M _X2 Is an intermediate position.
[0059]
The die mark DM is a third X mark for detecting the position of the wafer in the X direction. _X And a die mark DM as a second Y mark for detecting the position of the wafer in the Y direction. _Y Consists of Of these, Daimark DM _X Is composed of five parallel line pattern convex portions (or concave portions) oriented in the Y direction. _Y Is composed of five parallel line pattern convex portions (or concave portions) oriented in the X direction.
[0060]
These Diemark DM _X And Diemark DM _Y Is the first X mark M when the mask mark M and the dimark DM are in the visual field V of the microscope imaging devices 100 and 100 '. _X1 And the second X mark M _X2 Diemark DM at a position opposite to _X And the first Y mark M _Y Diemark DM at a position opposite to _Y Is provided at a position where is disposed.
[0061]
That is, in FIG. _X Is the first X mark M _X1 And the second X mark M _X2 And the die mark DM _Y Is Diemark DM _X With the first Y mark M sandwiched in the middle of the X direction. _Y Is arranged at a position opposed to.
[0062]
Further, the mask 32 has a rectangular opening 33 for observing the die mark DM or the pallet mark WP located below the mask 32. With this opening 33, the image due to the scattered light at the die mark DM is captured without being attenuated by the mask 32, so that the contrast between the image of the die mark DM and the background does not decrease.
[0063]
In order to determine the amount of displacement between the mask mark M and the die mark DM, an image signal obtained from the CCD 130 on which the mask mark M is formed is subjected to signal processing, and the first X mark M _X1 And the second X mark M _X2 Center position and mask mark M _Y Find the center position of each. Similarly, the image signal obtained from the CCD 131 on which the dimark DM is formed is signal-processed, _X Center position and die mark DM _Y Find the center position of each.
[0064]
Based on the difference between the pixel position on the CCD 130 indicating the center position of the mask mark M obtained as described above and the pixel position on the CCD 131 indicating the center position of the die mark DM, the mask mark M and the dimark DM are determined. Is measured. Then, the wafer stage 70 or the mask stage 80 is moved so that the measured positional shift amount becomes zero, and the position indicated by the mask mark M and the position indicated by the die mark DM match.
[0065]
FIG. 7 shows a case where the position indicated by the mask mark M and the position indicated by the die mark DM match. When the objective lens 120 of each of the microscope imaging devices 100 and 100 ′ moves by a small amount, the imaging magnification changes. However, the position indicated by the mask mark M and the position indicated by the die mark DM having the shape shown in FIG. Even if the photographing magnification of 100 or 100 'fluctuates, the amount of change is extremely small.
[0066]
Next, a description will be given of the principle of generating a rotation error if the mask mark M, the die mark DM or the pallet mark WP and the measurement line of the CCD of the microscope imaging device 100, 100 'are not perfectly parallel, and the means for correcting this error. I do.
[0067]
FIG. 19 and FIG. 20 are views for explaining a method of detecting a positional shift amount between a mask and a wafer in a conventional example. Note that FIG. 19 described above shows a case where the position indicated by the mask mark M matches the position indicated by the pallet mark WP.
[0068]
In FIG. 20, the center position by the mask mark M is the mask mark M at the center in the X direction. _X Center line CMX and the mask mark M at the center in the Y direction _Y O1 which is the intersection with the center line CMY of. On the other hand, as shown in the figure, the microscope is rotated with respect to the mask mark M, that is, the mask mark M and the CCD (imaging element) of the microscope imaging device 100 have a predetermined horizontal tilt angle. In the state, the center position of the CCD is O3 which is the intersection of the center line CX in the X direction and the center line CY in the Y direction. Therefore, O1 and O3 do not match, which results in an error.
[0069]
In order to correct such an error, the first X mark (M in FIG. 7) proposed in the present invention is used. _X1 ) And the second X mark (M in FIG. 7) _X2 ) Is effective. That is, the first X mark M _X1 And the second X mark M _X2 The center lines of these marks can be easily obtained by providing them at a distance from each other. Thus, even if the center line of these marks and the CCD (image pickup device) have a predetermined tilt angle in the horizontal direction, the tilt angle can be easily eliminated.
[0070]
FIG. 8 is a block diagram showing an embodiment of the control unit of the electron beam proximity exposure apparatus. In FIG. 1, a central processing unit (CPU) 200 controls the entire apparatus, and performs processing when aligning a mask with a wafer, electron beam deflection control during exposure, and the like. Each image signal indicating the mask mark M and the dimark DM obtained by imaging with the microscope imaging device 100 and the microscope imaging device 100 ′ is applied to the signal processing circuit 202. The signal processing circuit 202 calculates the amount of displacement between the mask mark M and the die mark DM based on the input image signals.
[0071]
The CPU 200 moves the wafer stage 70 via the stage driving circuit 204 or moves the mask stage 80 via the stage driving circuit 206 so that the positional shift amount input from the signal processing circuit 202 becomes zero.
[0072]
Further, the CPU 200 determines the position (X, Y) of the wafer stage 70 in the X and Y directions when the mask mark M and the die mark DM coincide with each other by using the laser interferometer L. _XW , L _YW And the positions (x, y) of the mask stage 80 in the X direction and the Y direction are similarly set by the laser interferometer L. _XM , L _YM And stores it in the memory 203. Further, the memory 203 stores data indicating the positional relationship between the pallet marks WP1 and WP2 and each die mark DM as described with reference to FIG. The details of the control of the alignment between the mask and the wafer based on the positions of the wafer stage 70 and the mask stage 80 stored in the memory 203 will be described later.
[0073]
Further, the CPU 200 supplies correction data corresponding to the distortion of the mask together with the deflection amount data when scanning the mask to the digital arithmetic circuit 205, and the digital arithmetic circuit 205 performs digital scanning for scanning the mask based on the deflection amount data. A signal is output to the main DAC / AMP 208, and a digital signal for correcting mask distortion based on the correction data is output to the sub DAC / AMP 210.
[0074]
The main DAC / AMP 208 converts the input digital signal into an analog signal, amplifies the signal, and outputs the amplified signal to the main deflectors 22 and 24 shown in FIG. As a result, the electron beam 15 is deflected so as to scan the entire surface of the mask as shown in FIG. 17 while maintaining the state parallel to the optical axis. The sub DAC / AMP 210 converts the input digital signal into an analog signal and then amplifies the signal, and outputs the amplified signal to the sub deflectors 26 and 28 shown in FIG. Thus, the incident angle of the electron beam 15 on the mask is controlled so that the mask pattern can be transferred to a regular position even if the mask is distorted.
[0075]
FIG. 9 is a flowchart showing an operation procedure of an electron beam proximity exposure method including a mask and wafer alignment method according to the present invention.
[0076]
First, the mask 32 is loaded on the mask stage 80, and the mask stage 80 is moved so that the mask mark M1 is within the field of view of the microscope imaging device 100 (Step S10). Similarly, the wafer pallet 44 is loaded on the wafer stage 70, and the wafer stage 70 is moved so that the die mark DM1 enters the field of view of the microscope imaging device 100 (step S12).
[0077]
The microscope imaging apparatus 100 moves the objective lens 120 and the die mark imaging objective lens 125 as described with reference to FIG. 5 so that the mask mark M1 and the dimark DM1 in the field of view are respectively focused (step S14).
[0078]
Subsequently, the mask marks M1 and M2 are measured based on the die mark DM1, and the rotation amount θ of the mask 32 is determined based on the measurement result. _M Is calculated (step S16).
[0079]
FIG. 10 is a flowchart showing the details of step S16. As shown in the figure, the amount of displacement between the die mark DM1 and the mask mark M1 in the field of view of the microscope imaging device 100 is measured by processing an image signal obtained from the microscope imaging device 100 (step S16A). It is determined whether or not the measured displacement amount is zero (step S16B). If the displacement amount is not equal to zero, the mask stage 80 is moved in a direction in which the displacement amount approaches zero (step S16C). In S16A, the amount of displacement between the die mark DM1 and the mask mark M1 is measured again. Then, the processes of steps S16A, S16B, and S16C are repeated until the displacement becomes zero.
[0080]
If it is determined in step S16B that the displacement amount is equal to zero, the movement position (x ₁ , Y ₁ ) The laser interferometer L _XM , L _YM From the moving position of the wafer stage 70 (X ₁ , Y ₁ ) The laser interferometer L _XW , L _YW And stores it in the memory 203 (step S16D).
[0081]
Next, the mask stage 80 is moved so that the mask mark M2 of the mask 32 enters the field of view of the microscope imaging apparatus 100, and the mask is moved in the same manner as described above so that the displacement between the die mark DM1 and the mask mark M2 becomes zero. The stage 80 is moved (Steps S16E, S16F, S16G). Then, the moving position (x) of the mask stage 80 when it is determined in step S16F that the positional deviation amount = 0. ₂ , Y ₂ ) The laser interferometer L _XM , L _YM And stores it in the memory 203 (step S16H).
[0082]
The position of the mask stage 80 when the mask marks M1 and M2 measured as described above respectively match the die mark DM1 (x ₁ , Y ₁ ), (X ₂ , Y ₂ ) To the rotation amount θ of the mask 32 _M Is calculated (step S16I).
[0083]
Returning to FIG. 9, in step S18, the dimarks DM1 and DM2 are measured based on the mask mark M2, and the rotation amount θ of the wafer pallet 44 is determined based on the measurement result. _P Is calculated.
[0084]
FIG. 11 is a flowchart showing the details of step S18.
[0085]
At the point in time when the processing in step S16 is completed, the die mark DM1 and the mask mark M2 are in a state of coincidence, and the position (X ₁ , Y ₁ ) And the position of the mask stage 80 (x ₂ , Y ₂ ) Has been measured.
[0086]
In step S18A of FIG. 11, the wafer stage 70 is moved so that the die mark DM2 of the wafer pallet 44 enters the field of view of the microscope imaging apparatus 100, and the positional shift amount between the mask mark M2 and the die mark DM2 within the field of view of the microscope imaging apparatus 100. Is measured by processing an image signal obtained from the microscope imaging apparatus 100. It is determined whether the measured displacement amount is zero (step S18B). If the displacement amount is not equal to zero, the wafer stage 70 is moved in a direction in which the displacement amount approaches zero (step S18C). In S18A, the amount of displacement between the mask mark M2 and the die mark DM2 is measured again. Then, the processing of steps S18A, S18B, and S18C is repeated until the displacement becomes zero.
[0087]
If it is determined in step S18B that the displacement amount is 0, the movement position (X ₂ , X ₂ ) The laser interferometer L _XM , L _YM And stores it in the memory 203 (step S18D).
[0088]
The position (X) of the wafer stage 70 when the die marks DM1 and DM2 measured as described above match the mask mark M2, respectively. ₁ , Y ₁ ), (X ₂ , Y ₂ ) To the rotation amount θ of the wafer pallet 44 _P Is calculated (step S18E). The position of the wafer stage 70 (X ₁ , Y ₁ ) Have already been measured in step S16D of FIG.
[0089]
Returning to FIG. 9, in step S20, the mask stage 80 is driven to move the mask 32 to the transfer position, and the position (x ₀ , Y ₀ ) The laser interferometer L _XM , L _YM (Step S20).
[0090]
Next, the position of each die D for aligning each die D of the wafer 40 with respect to the mask 32 moved to the transfer position (the position (X, Y) of the wafer stage 70 and the rotation amount θ of the wafer stage 70) Is calculated (step S22).
[0091]
For example, the movement position (X, Y) of the wafer stage 70 for matching the die mark DM1 with the mask mark M1 of the mask 32 at the transfer position is represented by the following equation:
[0092]
(Equation 1)
X = X ₁ + (X ₀ -X ₁ )
Y = Y ₁ + (Y ₀ -Y ₁ …… (1)
Can be represented by
[0093]
However, since it is necessary to align each die D of the wafer 40 with respect to the mask 32 at the transfer position, data indicating the positional relationship between the die mark DM1 and each die mark DM measured in advance as described with reference to FIG. The position (X, Y) of the wafer stage 70 for aligning each die D of the wafer 40 with respect to the mask 32 at the transfer position is obtained based on the position data obtained by the above equation (1).
[0094]
Also, the rotation amount θ of the mask 32 _M And the rotation amount θ of the wafer pallet 44 _P Are zero, the dies D of the wafer 40 can be aligned using the position (X, Y) of the wafer stage 70 obtained as described above. In the case where 44 is rotated and attached to each stage, the rotation amount θ of the mask 32 obtained in step S16 _M , And the rotation amount θ of the wafer pallet 44 obtained in step S18 _P The wafer stage 70 is rotated based on.
[0095]
Assuming that the rotation amount of the wafer stage 70 at this time is θ, the rotation amount θ is represented by the following equation:
[0096]
(Equation 2)
θ = θ _M −θ _P … (2)
Can be represented by
[0097]
Also, the rotation amount θ of the wafer pallet 44 _P And the rotation amount θ of the wafer stage 70, the rotation amount of the wafer pallet 44 on the XY plane can be obtained. The displacement of the die mark DM of each die D of the wafer 40 based on the rotation amount of the wafer pallet 44 on the XY plane and the rotation center of the wafer stage 70 (the case where the wafer pallet 44 is not rotating on the XY plane). Then, the position (X, Y) of the wafer stage 70 for aligning the dies D of the wafer 40 is corrected based on the displacement.
[0098]
The position of each die D for aligning each die D of the wafer 40 with respect to the mask 32 moved to the transfer position calculated as described above (the position (X, Y) of the wafer stage 70 and the position of the wafer stage 70) The wafer stage 70 is moved based on the rotation amount θ), and the wafer stage 70 is rotated (step S24).
[0099]
Next, the mask pattern formed on the mask 32 is transferred to the wafer by the electron beam (Step S26). Subsequently, it is determined whether or not the transfer of all the dies has been completed (step S28). If the transfer has not been completed, the process returns to step S24 to perform the alignment of the other dies and transfer the mask pattern again. . When the transfer of all the dies is completed in this way, the wafer is unloaded and the process ends.
[0100]
FIG. 12 is a vertical sectional view of a main part of an electron beam proximity exposure apparatus including an alignment mechanism system according to a second embodiment of the mask and wafer alignment apparatus according to the present invention, and FIG. It is a principal part top view of a beam proximity exposure apparatus. Parts common to those in the first embodiment shown in FIGS. 1 and 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0101]
In the first embodiment, the mask 32 can be moved so that the mask mark M enters the field of view of the microscope imaging device 100 fixed outside the exposure area, whereas the second embodiment In this configuration, the mask 32 attached to the mask stage 82 does not move, and the microscope imaging device 150 can be moved in the X direction and the Y direction by the microscope stage 84.
[0102]
The illumination light is guided from the lamp house 110 to the microscope imaging device 150 via the optical fiber 111, the optical system 112, the window 54 provided on the top plate of the vacuum chamber 50, and the optical fiber 113. ing. The microscope imaging device 150 is configured so that an objective lens or the like at the tip of the microscope can be inserted between the electron optical barrel 102 and the mask 32, but the other internal configuration is the same as the microscope illustrated in FIG. Since the configuration is similar to that of the imaging apparatus 100, a detailed description thereof is omitted.
[0103]
FIG. 14 is a flowchart showing an operation procedure of an electron beam proximity exposure method including a mask and wafer alignment method using the alignment mechanism system according to the second embodiment.
[0104]
First, the mask 32 is loaded on the mask stage 82 (Step S100), and then the microscope stage 84 is moved so that the mask mark M1 is in the field of view of the microscope imaging device 150 (Step S102). Further, the wafer pallet 44 is loaded on the wafer stage 70, and the wafer stage 70 is moved so that the dimark DM1 is in the field of view of the microscope imaging device 150 (step S104).
[0105]
The microscope imaging device 150 moves the objective lens 120 and the pallet mark imaging objective lens 125 so that the mask mark M1 and the die mark DM1 in the field of view are respectively focused (step S106).
[0106]
Next, the mask marks M1 and M2 are measured based on the die mark DM1, and the rotation amount θ of the mask 32 is determined based on the measurement result. _M Is calculated (step S108).
[0107]
FIG. 15 is a flowchart showing the details of step S108.
[0108]
As shown in the figure, the amount of displacement between the mask mark M1 and the die mark DM1 in the field of view of the microscope imaging device 150 is measured by processing an image signal obtained from the microscope imaging device 150 (step S108A). It is determined whether or not the measured displacement amount is zero (step S108B). If the displacement amount ≠ 0, the wafer stage 70 is moved in a direction in which the displacement amount approaches zero (step S108C). In S108A, the amount of displacement between the mask mark M1 and the die mark DM1 is measured again. Then, the processing of steps S108A, S108B, and S108C is repeated until the displacement becomes zero.
[0109]
If it is determined in step S108B that the displacement amount is equal to zero, the movement position (X ₁ , Y ₁ ) The laser interferometer L _XW , L _YW And stores it in the memory 203 (step S108D).
[0110]
Next, the microscope stage 84 is moved so that the mask mark M2 of the mask 32 enters the field of view of the microscope imaging device 150 (Step S108E). Since the gap between the electron optical lens barrel 102 and the mask 32 is narrow, the microscope imaging device 150 may not be able to be moved so that the mask mark M2 is in the field of view. It is necessary to provide another microscope imaging device for observation.
[0111]
Thereafter, the wafer stage 70 is moved such that the amount of displacement between the mask mark M2 and the die mark DM1 becomes zero in the same manner as described above (Steps S108F, S108G, S108H). Then, in step S10G, when the displacement amount is determined to be 0, the moving position (X ₂ , Y ₂ ) The laser interferometer L _XW , L _YW And stores it in the memory 203 (step S108I).
[0112]
The position (X) of the wafer stage 70 when the mask marks M1 and M2 measured as described above match the die mark DM1, respectively. ₁ , Y ₁ ), (X ₂ , Y ₂ ) To the rotation amount θ of the mask 32 _M Is calculated (step S108J).
[0113]
Returning to FIG. 14, in step S110, the die marks DM1 and DM2 are measured based on the mask mark M2, and the rotation amount θ of the wafer pallet 44 is determined based on the measurement result. _P Is calculated (see the flowchart of FIG. 11).
[0114]
Next, the microscope stage 84 is driven to retract the microscope imaging device 150 from the transfer area (step S112).
[0115]
Subsequently, the position of each die D (the position (X, Y) of the wafer stage 70 and the rotation amount θ of the wafer stage 70) for aligning each die D of the wafer 40 with respect to the mask 32 is calculated (step). S114). Note that the calculation can be performed in the same manner as in step S22 of FIG. 9, but the calculation shown in Expression (1) is unnecessary because the mask 32 is not moved in the alignment mechanism system of the second embodiment.
[0116]
The wafer stage 70 is moved and the wafer stage 70 is rotated based on the position of each die D calculated as described above (the position (X, Y) of the wafer stage 70 and the rotation amount θ of the wafer stage 70) ( Step S116).
[0117]
Next, the mask pattern formed on the mask 32 is transferred to the wafer by the electron beam (Step S118). Subsequently, it is determined whether or not the transfer of all the dies has been completed (step S120). If the transfer has not been completed, the process returns to step S116 to perform the alignment of the other dies and transfer the mask pattern again. . When the transfer of all the dies is completed in this way, the wafer is unloaded and the process ends.
[0118]
As described above, the example of the embodiment of the method for aligning the mask and the wafer according to the present invention has been described. However, the present invention is not limited to the example of the above-described embodiment, and may adopt various aspects.
[0119]
For example, in the present embodiment, the mask stage or the wafer stage is moved so that the amount of displacement between the mask mark M and the die mark D becomes zero, and the movement positions of the max stage and the wafer stage at that time are measured. However, the present invention is not limited to this. In addition to measuring the amount of positional shift between the mask mark M and the die mark D from the amount of positional shift on the screen of the microscope imaging device, the moving positions of the max stage and the wafer stage during this measurement are measured. Based on these measurement results, the movement positions of the mask stage and the wafer stage when the amount of displacement between the mask mark M and the die mark D becomes zero may be calculated.
[0120]
Further, in the present embodiment, an example has been described in which wafer 40 is mounted on wafer pallet 44 and wafer pallet 44 is further mounted on wafer stage 70 (electromagnetic chuck 60 of wafer stage 70). The present invention can be applied to a case where the wafer 40 is directly attracted to the electromagnetic chuck 60 on the wafer stage 70.
[0121]
Further, in the present embodiment, the amount of misalignment between the mask mark M of the mask 32 and the die mark D of the wafer 40 is measured. A mode in which the positions of the two pallet marks WP are measured may be used. In this case, as described with reference to FIG. 4, the alignment is performed based on the data indicating the positional relationship between the pallet mark WP and each die mark DM measured in advance and the position data obtained by the equation (1). Just do it.
[0122]
【The invention's effect】
As described above, according to the present invention, the microscope imaging apparatus can simultaneously image each mark from a direction orthogonal to the plane on which the first mark and the second mark are provided, and And an image signal that is in focus with each other can be obtained. Then, based on the image signals of the first mark and the second mark simultaneously obtained from the microscope image pickup device, the relative displacement between the first mark and the second mark is measured. That is, by taking an image of each mark from a direction orthogonal to the surface on which each mark is provided, measuring the two-dimensional displacement amount between the first mark and the second mark by one microscope imaging device. Can be.
[0123]
Further, the positions of the first mark and the second mark are not measured with reference to a reference position (for example, a cross mark of the microscope) of the microscope imaging device, and the first mark and the first mark simultaneously obtained from the microscope imaging device are not measured. Since the relative displacement between the marks is measured based on the image signal with the second mark, the displacement can be measured without being affected by the fluctuation of the reference position of the microscope imaging device.
[0124]
Further, the first mark includes a first X mark and a second X mark for detecting a position in the X direction, and the first X mark and the second X mark are predetermined in the Y direction. They are provided facing each other at a distance. Therefore, it is possible to effectively cope with the problem that a rotation error occurs unless the alignment mark and the measurement line direction of the CCD as the image sensor are completely positioned in parallel, and highly accurate alignment between the mask and the wafer can be realized. .
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a main part of an electron beam proximity exposure apparatus including an alignment mechanism system used in a first embodiment of a method for aligning a mask and a wafer according to the present invention.
FIG. 2 is a top view of a main part of the electron beam proximity exposure apparatus shown in FIG.
FIG. 3 is a plan view of a mask used in the electron beam proximity exposure apparatus shown in FIG.
FIG. 4 is a plan view of a wafer pallet on which wafers are mounted.
FIG. 5 is an optical component layout diagram showing details of a microscope imaging apparatus applied to the present invention.
FIG. 6 is an optical component arrangement diagram showing another embodiment of the microscope imaging apparatus applied to the present invention.
FIG. 7 is a diagram used to explain a method of detecting a positional shift amount between a mask mark and a die mark by using a microscope imaging device.
FIG. 8 is a block diagram illustrating an embodiment of a control unit of the electron beam proximity exposure apparatus.
FIG. 9 is a flowchart showing an operation procedure of an electron beam proximity exposure method including a method of aligning a mask and a wafer according to the present invention.
FIG. 10 is a flowchart showing a detailed processing procedure of a part of the flowchart shown in FIG. 9;
FIG. 11 is a flowchart showing a detailed processing procedure of another part of the flowchart shown in FIG. 9;
FIG. 12 is a vertical sectional view of a main part of an electron beam proximity exposure apparatus including an alignment mechanism used in a second embodiment of the method for aligning a mask and a wafer according to the present invention;
13 is a top view of a main part of the electron beam proximity exposure apparatus shown in FIG.
FIG. 14 is a flowchart showing an operation procedure of another embodiment of an electron beam proximity exposure method including a mask and wafer alignment method according to the present invention.
FIG. 15 is a flowchart showing a detailed processing procedure of a part of the flowchart shown in FIG. 14;
FIG. 16 is a diagram showing a basic configuration of an electron beam proximity exposure apparatus.
FIG. 17 is a view used to explain mask scanning by an electron beam.
FIG. 18 is an overall configuration diagram of an electron beam proximity exposure apparatus.
FIG. 19 is a diagram used to describe a method of detecting a positional shift amount between a mask and a wafer using a mask mark and a pallet mark in a conventional example.
FIG. 20 is a diagram used to explain a method of detecting a positional shift amount between a mask and a wafer using a mask mark and a pallet mark in a conventional example.
[Explanation of symbols]
15 electron beam, 22, 24 main deflector, 26, 28 sub deflector, 32 mask, 40 wafer, 44 wafer pallet, 70 wafer stage, 80 mask stage, 84 microscope stage, 100 Reference numeral 150, microscope imaging device, 110, lamp house, 120, objective lens, 123, mask mark imaging objective lens, 125, die mark imaging objective lens, 130, 131, 145, CCD, 200, CPU, 203 Memory, 204, 206 ... stage drive circuit, L _XM , L _YM , L _XW , L _YW ... Laser interferometer, M ... Mask mark, WP ... Pallet mark, D ... Die, DM ... Die mark

Claims (5)

In a method of aligning a mask and a wafer in an exposure apparatus for disposing a mask close to a wafer and transferring a mask pattern formed on the mask to a resist layer on the wafer,
A first mark for alignment provided on one of the pallet or the wafer on which the mask or the wafer is mounted, and a second mark for alignment provided on the other of the mask or the pallet or the wafer Imaging the mark with the image sensor;
Measuring a relative displacement amount between the first mark and the second mark based on an image signal of the captured first mark and the second mark;
Relative positioning the mask and the wafer based on the measured displacement amount,
The first mark includes a first X mark and a second X mark for detecting a position in the X direction, and a first Y mark for detecting a position in the Y direction. The X mark and the second X mark are each a plurality of line patterns whose longitudinal directions are oriented in the Y direction and are parallel to the X direction, and the first X mark and the second X mark The marks are provided facing each other at a predetermined distance in the Y direction, and the first Y mark is a plurality of line patterns whose longitudinal directions are oriented in the X direction and arranged in parallel with the Y direction.
The second mark is composed of a third X mark for detecting a position in the X direction and a second Y mark for detecting a position in the Y direction. A plurality of line patterns whose directions are oriented in the Y direction and are arranged in parallel with the X direction, wherein the second Y mark is formed of a plurality of line patterns whose longitudinal directions are oriented in the X direction and arranged in parallel with the Y direction. A method of aligning a mask and a wafer, wherein the method is a line pattern. When the first mark and the second mark are in the field of view of the microscope imaging device having the imaging element, the third X mark is the first X mark and the second X mark 2. The method of claim 1, wherein the second Y mark is arranged at a position facing the first Y mark, and the second Y mark is arranged at a position facing the first Y mark. 3. In the step of imaging the first mark and the second mark with an image sensor, microscope imaging having two sets of imaging optical systems capable of focusing on the first mark and the second mark, respectively. 3. The method according to claim 1, wherein images are taken at substantially the same time by an apparatus. 4. The mask according to claim 1, wherein an opening for imaging a first mark or a second mark provided on the pallet or the wafer is formed in the mask. Item 3. The method for aligning a mask with a wafer according to item 3. In the step of measuring a relative displacement amount between the first mark and the second mark, a tilt in a horizontal direction between the imaged first mark and / or the second mark and the image sensor is taken. An angle is calculated, and image data taken so that the horizontal tilt angle is zero is converted from the calculation result, and then a relative displacement amount between the first mark and the second mark is calculated. 5. The method for aligning a mask and a wafer according to claim 1, wherein

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