JP2006278799A - Positioning method and device manufacturing method employing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positioning method and the like capable of improving alignment measuring accuracy or throughput. <P>SOLUTION: If search alignment is performed in an AIS sensor 60, fine alignment to be performed successively is also performed in the same AIS sensor 60. If measuring error occurs during the execution of alignment, a positioning operation is temporarily stopped. A reticle stage RST or wafer stage WST is then manually moved while watching an image of an imaging element 55 imaging a reference mark FM2 for assist operation by a VRA sensor 50, and the assist operation is performed for adjusting a relative position relation between a reticle R and the reference mark plate FM, thereby adjusting the relative position relation between a projecting position of an alignment mark and a reference opening mark 61. After the adjustment, alignment is successively executed by the AIS sensor 60. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a position measurement method for improving measurement accuracy and throughput, and a device manufacturing method using this position measurement method.

  In general, in a manufacturing process for manufacturing a semiconductor element, a step-and-repeat method or a step-and-scan is an apparatus for transferring a circuit pattern formed on a mask (reticle) onto a wafer as a substrate. An exposure apparatus such as a system, a wafer prober, a laser repair apparatus or the like is used. In the exposure process of semiconductor devices using these devices, circuit patterns of 10 layers or more are sequentially superimposed and transferred on the wafer, and if the overlay accuracy between each layer is low, the formed circuit has the desired characteristics. In the worst case, it becomes a defective product and the yield is lowered as a whole. To avoid this, when a circuit pattern is exposed and transferred onto the wafer, the circuit pattern on the reticle on which a new circuit pattern to be exposed is formed and each shot on the wafer on which the circuit pattern has already been formed. Alignment with the region is performed with high accuracy. This alignment includes a reticle alignment for aligning the reticle with respect to the wafer and a wafer alignment for detecting positional information of each shot area on the wafer.

  In reticle alignment, an alignment method using a VRA (Video Reticule Alignment) sensor is known (see, for example, Patent Document 1). According to this, the alignment mark formed on the reticle using the exposure light and the predetermined reference mark on the reference mark plate arranged on the wafer stage are illuminated, and the reflected image from the alignment mark and the reference mark are illuminated. The image is reflected with a CCD camera, and the alignment is performed by detecting the amount of positional deviation of the alignment mark with respect to the reference mark.

  Another alignment method using an AIS (Aerial Image Sensor) sensor is also known (see, for example, Patent Documents 2 and 3). According to this, exposure light is irradiated to the alignment mark portion formed on the reticle, and an image of the alignment mark is formed on the reference mark plate on the wafer stage via the projection optical system (slit). ), While moving the reticle stage or wafer stage relatively, the projected image of the alignment mark is received by the photoelectric sensor through the reference aperture mark, and the position of the alignment mark relative to the reference aperture mark is detected and aligned. It is carried out.

  In the former method, an exposure amount control mirror (ND filter), a reticle alignment microscope mirror, etc. are arranged in the optical path between the illumination optical system and the reticle stage during alignment, and the exposure amount control mirror has different transmittance at the end of alignment. In addition, the reticle alignment microscope needs to be retracted from the optical path, and there is a problem in terms of alignment throughput.

  On the other hand, in the latter method, the alignment mark is arranged in the vicinity of the circuit pattern on the reticle as compared with the former method, and the telecentricity is good, and a mirror or the like enters and retracts in the optical path during alignment. However, there is a problem in that it takes a long time to recover when a measurement error occurs during measurement.

Japanese Patent Laid-Open No. 7-176468 Japanese Patent Laid-Open No. 10-144593 JP 2002-14005 A

  Therefore, it has been studied to equip a VRA sensor and an AIS sensor and select either the former or the latter sensor at the time of reticle alignment so that the advantages of both can be utilized.

  However, in any of the alignment methods using any of the above-described sensors, position measurement is performed at a predetermined measurement magnification to perform rough position measurement and alignment, and more precise than search alignment (for example, from a predetermined measurement magnification) (Fine Magnification and High Accuracy) must be executed, and the alignment measurement accuracy and throughput differ depending on which sensor is selected for search alignment and which sensor is selected for fine alignment. Has a problem.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a position measurement method capable of improving alignment measurement accuracy and throughput and a device manufacturing method using the position measurement method. And

  The position measuring method according to claim 1 of the present invention that achieves the above object, before transferring a pattern on a first object (for example, a reticle as a mask) onto a second object (for example, a wafer as a substrate). A measurement method for measuring a relative positional relationship between a reference member (for example, a reference mark plate) provided on a stage on which the second object is placed and the first object. A first position measurement step (for example, the step in FIG. 1) that measures a predetermined area on the object (for example, refer to the alignment mark FM2 for search measurement in FIG. 4 or the like) with a predetermined precision to obtain position information of the object. Measure the AIS-RA search measurement process in S103) and a predetermined area on the first object (see, for example, the alignment mark FM3 for fine measurement in FIG. 4 and the like) with further precision than the precision. The A second measurement step for obtaining body position information (see, for example, the AIS-RA fine measurement step in step S107 in FIG. 1), and a plurality of measurement sensors having different measurement principles (VRA sensors in FIG. 2) 50 and the AIS sensor 60 in FIG. 3), and the same measurement sensor as the measurement sensor used in any one of the first and second position measurement steps is used. Then, the position measurement in the other position measurement step is performed.

  The plurality of measurement sensors, for example, use a projected image projected on the reference member of a mark (see an alignment mark AM2 in FIG. 4) formed on a predetermined region on the first object. First sensor (AIS sensor 60: reference aperture mark 61 in FIG. 3, light transmission system 62, photomultiplier tube 63) that performs photoelectric detection through a slit (see reference aperture mark 61 in FIG. 3) provided on the member. ), A reflection image of a mark (see alignment mark AM1 in FIG. 4) formed on a predetermined area on the first object, and a mark (in FIG. 5) formed on the reference member. A second sensor (see VRA sensor 50 in FIG. 2) that simultaneously captures the reflected image of the reference mark FM1, and a projected image of the mark formed on a predetermined area on the first object Is detected by the first sensor If not, the relative positional relationship between the first object and the reference member is adjusted based on the imaging result of the predetermined location on the reference member by the second sensor, and then the first sensor is used. It is preferable to perform a redetection operation of the projection image.

  Further, at the predetermined location, for example, an assist mark (assist in FIG. 5) that is a measurement target only when the positional relationship with the slit is known and the projection image cannot be detected by the first sensor. Preferably, an operation reference mark FM2 is formed (claim 3).

  In addition, the first mark measured in the first position measuring step and the second mark measured in the second measuring step are, for example, marks having different shapes and the mutual positional relationship is known. Preferably, the mark is a mark (see the alignment mark AM2 for search alignment and the alignment mark AM3 for fine alignment in FIG. 4).

  Further, in the first position measurement step, a projection image of the mark formed on the predetermined area on the first object and projected on the reference member is passed through a slit provided on the reference member. In the case of using a first sensor that performs photoelectric detection while relatively scanning the projection image and the slit, the first mark is, for example, parallel to the pattern formation surface on the first object. A first linear pattern extending in the first direction in the plane, and a second linear pattern that obliquely intersects the first linear pattern in the plane (for example, alignment mark AM2 in FIG. 6A) In the first position measurement step, it is preferable to relatively scan the projected image of the first mark and the slit in a direction perpendicular to the first direction in the plane (for example, FIG. 7). See: Claims ).

  Further, in the first position measurement step, a projection image of the mark formed on the predetermined area on the first object and projected on the reference member is passed through a slit provided on the reference member. In the case of using a first sensor that performs photoelectric detection while relatively scanning the projection image and the slit, the first mark is, for example, parallel to the pattern formation surface on the first object. Including a first linear pattern and a second linear pattern extending in a first direction and a second direction orthogonal to each other in a plane (see, for example, the alignment mark AM2 ′ in FIG. 9), and the first position measuring step Then, it is preferable to relatively scan the projected image of the first mark and the slit in a direction intersecting the first and second directions in the plane (see, for example, an arrow P in FIG. 10: Contract Section 6).

  The second linear pattern preferably includes, for example, a plurality of linear patterns having different line widths in the first direction and spaced apart from each other in the first direction (for example, the alignment mark AM2 ″ in FIG. 12). See claim 7).

  In the second position measurement step, a projection image of a mark formed on a predetermined region on the first object and projected onto the reference member is converted into a slit (for example, FIG. In the case of using a first sensor that performs photoelectric detection while relatively scanning the projection image and the slit via the reference aperture mark 61 of B), the second mark is, for example, In a plane parallel to the pattern forming surface on the first object, a plurality of pieces extending in the first direction while shifting their start points in a third direction intersecting each other with respect to the first and second directions orthogonal to each other A first linear pattern and a plurality of second linear patterns extending in the second direction while shifting the starting point in the third direction, and each starting point of the plurality of first linear patterns and the plurality of the second linear patterns Each starting point of the second linear pattern Are sequentially arranged in the third direction (see, for example, FIG. 15A, alignment mark AM3 in FIG. 18), and in the second position measurement step, the second direction in the third direction in the plane. It is preferable to relatively scan the projected image of two marks and the slit (see, for example, the arrow P in FIG. 16: claim 8).

  The device manufacturing method according to claim 9 of the present invention that achieves the above object is a process of preparing a mask on which a device pattern is formed and a substrate having a plurality of partition regions to which the device pattern is to be transferred. And a projection position of the pattern image of the mask and each of the plurality of partitioned areas on the substrate based on position information measured using the position measurement method according to any one of claims 1 to 8. And sequentially transferring the device pattern onto each of the aligned partitioned regions (see, for example, FIG. 23).

  According to the position measurement method of the present invention, the first position measurement step and the subsequent second position measurement step are performed using measurement sensors having the same measurement principle, so that alignment accuracy and throughput are improved. It becomes possible.

  Further, when the projected image of the mark cannot be detected using the first sensor (AIS sensor), the relative positional relationship between the first object and the reference member is adjusted using the second sensor (VRA sensor). In such a case, the measurement error recovery by the first sensor can be completed in a short time.

  If the present invention is applied to a device manufacturing method, alignment can be performed with high accuracy. For example, when transferring a plurality of device patterns on each partition area, there are few overlay errors, resulting in improved product yield. Is possible.

  Embodiments of a position measuring method and a device manufacturing method using the position measuring method of the present invention will be described below with reference to FIGS.

  FIG. 2 is an overall configuration diagram showing an outline of an exposure apparatus for carrying out the position measuring method and the device manufacturing method of the present invention.

  First, an outline of the entire exposure apparatus will be described with reference to FIG. The exposure apparatus 10 uses, for example, a circuit pattern or the like formed on a mask (reticle R) as a first object by a step-and-scan method as a substrate (wafer) as a second object via the projection optical system PL. W) a scanning type exposure apparatus that performs exposure transfer on each shot area.

  The exposure apparatus 10 includes an illumination optical system 11, a reticle stage RST that holds the reticle R movably in an XY axis plane (horizontal plane), a projection optical system PL, and a wafer W in an XY axis plane (horizontal plane) and Wafer stage WST mounted movably in the Z-axis direction (vertical direction orthogonal to the horizontal plane which is the XY-axis plane), wafer alignment system AS, VRA sensor 50, AIS sensor 60, and the main control system for overall control of the apparatus 40 is equipped.

  The illumination system 11 includes a light source, a fly-eye lens as an optical integrator, a rod integrator (internal reflection type integrator), or the like, as disclosed in, for example, Japanese Patent Application Laid-Open Nos. 10-112433 and 6-349701. An illuminance uniforming optical system, a relay lens, a variable ND filter, a reticle blind, a dichroic mirror, and the like (all not shown) are included. The illumination system 11 illuminates a slit-shaped illumination area defined by a reticle blind on a reticle R on which a circuit pattern or the like is drawn with a substantially uniform illuminance with illumination light IL.

As illumination light IL, far ultraviolet light such as KrF excimer laser light (wavelength 248 nm), vacuum ultraviolet light such as ArF excimer laser (wavelength 193 nm), F ₂ laser light (wavelength 157 nm), or ultraviolet region from an ultrahigh pressure mercury lamp Bright lines (g-line, i-line, etc.) are used.

  On reticle stage RST, reticle R is fixed, for example, by vacuum suction. This reticle stage RST coincides with the optical axis of the illumination system 11 (to be described later, the optical axis AX of the projection optical system PL) for positioning the reticle R by the reticle stage drive unit 12 made of, for example, a magnetically levitated two-dimensional linear actuator. And can be driven at a scanning speed set in a predetermined scanning (scanning) direction (for example, the Y-axis direction). The two-dimensional linear actuator includes a Z-axis drive coil in addition to the X-axis drive coil and the Y-axis drive coil, and can finely drive the reticle stage RST in the Z-axis direction.

  The position of the reticle stage RST in the stage moving surface is always detected by a reticle laser interferometer (hereinafter referred to as a reticle interferometer) 16 via a moving mirror 15 with a resolution of about 0.5 nm to 1 nm, for example. Position information of reticle stage RST from reticle interferometer 16 is supplied to control unit 43 via position calculation unit 41 and stage control system 42. The position calculation unit 41 performs calculation processing based on the position information from the reticle interferometer 16 and sends the calculation result to the control unit 43. The stage control system 42 drives and controls the reticle stage RST via the reticle stage drive unit 12 based on the position information of the reticle stage RST in response to an instruction from the control unit 43.

  As shown in FIG. 4, the reticle R has a pattern formation surface PA (a hatched portion shown in FIG. 4 and a side extending in the X-axis direction and a Y-axis direction (scanning) as shown in FIG. A surface surrounded by a side extending in the direction), and a peripheral portion of the pattern formation surface PA, and a plurality of locations (a total of six locations in FIG. 4) away from the pattern formation surface PA. Each of the alignment marks AM1 is formed, and a plurality of locations (a total of 8 locations in FIG. 4) parallel to the pattern formation surface PA located adjacent to the pattern formation surface PA are mutually shaped for the AIS sensor 60. Are formed, and alignment marks AM2 and AM3 having a known positional relationship are formed.

  Projection optical system PL is arranged below reticle stage RST, and the direction of optical axis AX is along the Z-axis direction. As the projection optical system PL, for example, a double-sided telecentric reduction system is used. The projection magnification of the projection optical system PL is, for example, 1/4, 1/5, or 1/6. When the illumination area of the reticle R is illuminated by the illumination light IL from the illumination system 110, a reduced image of the circuit pattern on the reticle R in the illumination area is projected via the projection optical system PL by the illumination light that has passed through the reticle R. It is formed on a wafer W whose surface is coated with a photoresist.

  An off-axis wafer alignment system AS is provided on the side surface of the projection optical system PL. As this alignment system AS, an FIA (Field Image Alignment) sensor is used, and illumination light (for example, white light) having a predetermined wavelength width is irradiated on the wafer W, and an image of the alignment mark on the wafer W and the wafer W are irradiated. An image of an index mark on an index plate arranged in a conjugate plane is imaged and detected on a light receiving surface of an image sensor (CCD camera or the like) by an objective lens or the like. The wafer alignment system AS outputs to the main control system 40 an imaging signal that is an imaging result of a reference mark (not shown) on the alignment mark and the wafer fidelity mark plate (reference mark plate) FM.

  Wafer stage WST is arranged on a base (not shown) below projection optical system PL. A wafer holder (not shown) is placed on wafer stage WST, and wafer W is fixed on this wafer holder by, for example, vacuum suction.

  The wafer holder can be tilted in an arbitrary direction with respect to a plane perpendicular to the optical axis AX of the projection optical system PL by a drive unit (not shown), and also in the optical axis AX direction (Z-axis direction) of the projection optical system PL. It is configured to be finely movable. Further, the wafer holder can also be rotated minutely around the optical axis AX.

  Wafer stage WST not only moves in the scanning direction (eg, the Y-axis direction), but also non-scanning orthogonal to the scanning direction so that a plurality of shot areas of wafer W can be positioned in an exposure area conjugate with the illumination area. It is configured to be movable in the direction (for example, the X-axis direction), and an operation for scanning (scanning) exposing each shot area on the wafer W and an operation for moving to an acceleration start position for exposure of the next shot area Step and scan operation is repeated. Wafer stage WST is driven in the XY two-dimensional direction by a wafer stage drive system 20 including, for example, a linear motor.

  The position of wafer stage WST in the XY plane is a moving mirror system provided on the upper surface (Y moving mirror 21 having a reflecting surface orthogonal to the Y axis direction that is the scanning direction) and the X axis direction that is the non-scanning direction. A wafer laser interferometer system (including a Y interferometer that irradiates an interferometer beam perpendicular to the Y moving mirror 21) and an interferometer beam perpendicular to the X movable mirror. X is always detected with a resolution of, for example, about 0.5 nm to 1 nm.

  A stationary coordinate system (orthogonal coordinate system or stage coordinate system) for determining the movement position of wafer stage WST is determined by the measurement axes of the Y interferometer and X interferometer of wafer interferometer 22. Position information (or speed information) of wafer stage WST on the stage coordinate system is supplied to control unit 43 via position calculation unit 41 and stage control system 42. The position calculation unit 41 performs calculation processing based on the position information from the wafer interferometer 22 and sends the calculation result to the control unit 43. In response to an instruction from control unit 43, stage control system 42 drives and controls wafer stage WST via wafer stage drive system 20 based on position information of wafer stage WST.

  A wafer fiducial mark plate (reference mark plate) FM is disposed in the vicinity of wafer W on wafer stage WST. The surface of the fiducial mark plate FM is set to the same height as the surface of the wafer W. On this surface, as shown in FIG. 5, the wafer fiducial mark (reference mark) FM1 of the VRA sensor 50 and the AIS sensor 60 are arranged. The reference opening mark 61 (shown in FIGS. 3, 6B, and 15B) is formed.

  Next, the VRA sensor 50 will be described.

  The VRA sensor 50 is disposed between the reticle stage RST and the illumination optical system 11 at a predetermined position on the X-axis direction side and a predetermined position on the opposite side across the optical axis AX. The VRA sensor 50 includes an alignment mark AM1 (see FIG. 4) formed on the reticle R, which is an object to be measured with illumination light having the same wavelength as the illumination light IL, and the above-described reference mark formed on the reference mark plate FM. An epi-illumination system 51 for illuminating FM1 (see FIG. 5) and an alignment microscope 52 that captures reflected images of the alignment mark AM1 and reference mark FM1 to be measured are provided. The epi-illumination system 51 includes an optical system including an epi-illumination mirror 53 that guides the illumination light IL from the illumination optical system 11 to the reticle R as measurement light, and a drive that drives the epi-illumination mirror 53 during alignment or an exposure sequence. A system (not shown). The alignment microscope 52 includes an image pickup device 55 that is a CCD camera that picks up reflected images of the alignment mark AM1 and the reference mark FM1, and an imaging optical system 54 that forms these reflected images on the image pickup surface of the image pickup device 55.

  At the time of alignment, an optical path switching operation, an ND switching operation, and an epi-illumination illumination system 51 for guiding illumination light (exposure light) IL from an exposure light source (not shown) as measurement light onto an illumination system (not shown) in the VRA sensor 50. Perform moving operations. In the moving operation of the epi-illumination system 51, the epi-illumination mirror 53 of the epi-illumination system 51 is caused to enter between the illumination optical system 11 and the reticle stage RST by a drive system (not shown). Thus, the incident light mirror 53 guides the measurement light to the peripheral portion of the reticle R to illuminate the alignment mark AM1, while the reflected light from the alignment mark AM1 passes through the incident light mirror 53 and the imaging optical system 54. Then, the light is guided onto the image sensor 55 and formed on the image pickup surface of the image sensor 55. Of the illumination light (measurement light) guided to the peripheral portion of the reticle R, the illumination light transmitted through the reticle R is guided to the reference mark FM1 on the reference mark plate FM via the projection optical system PL, and this reference While illuminating the mark FM1, the reflected light from the reference mark FM1 is guided onto the image sensor 55 via the projection optical system PL, the reticle R, the epi-illumination mirror 53, and the imaging optical system 54, and the imaging surface of the image sensor 55 To form an image. The reflected image from the alignment mark AM1 and the reflected image from the reference mark FM1 are imaged on the imaging surface of the imaging element 55, photoelectrically converted, and supplied to the main control system 40 (position calculating unit 41) as an imaging signal. . Although not shown, the imaging optical system 54 includes a low-magnification optical system having a predetermined magnification and a high-magnification optical system having a higher magnification than the predetermined magnification. In addition, an imaging element that receives reflected light through the low-magnification optical system and an imaging element that receives reflected light through the high-magnification optical system are included. In the VRA sensor 50, when the search measurement is performed, the alignment mark AM1 and the reference mark FM1 are imaged through the low magnification optical system, and when the fine measurement is performed, the marks AM1 and FM1 are captured using the high magnification optical system. To image through. In the main control system 40, the position calculation unit 41 performs calculation processing on the image pickup signal, obtains a positional shift amount of the alignment mark AM1 with respect to the reference mark FM1, and aligns the reticle R with the wafer stage WST (reticle alignment). A command is output from the control unit 43 to the stage control system 42. During the exposure sequence, the optical path switching operation and the ND switching operation are performed to return to the exposure sequence state, and the epi-illumination mirror 53 is retracted from between the illumination optical system 11 and the reticle stage RST by a drive system (not shown).

  As described above, the VRA sensor 50 requires operations such as making the epi-illumination system 51 enter between the illumination optical system 11 and the reticle stage RST at the time of alignment, and the epi-illumination system 51 at the time of the exposure sequence. Therefore, operations such as evacuation are required, and these operations require a certain amount of time, and in this respect, there is a problem in alignment throughput.

  In this regard, the AIS (aerial image) sensor 60 does not require an operation such as moving the epi-illumination mirror 53 as described above at the time of alignment or exposure sequence, and has higher throughput than the VRA sensor 50. Yes.

  Further, as described above, the AIS sensor 60 uses the alignment marks AM2 and AM3 formed in a plane parallel to the pattern formation surface located adjacent to the pattern formation surface of the reticle R. Therefore, these alignment marks AM2 The optical path of the illumination light IL that irradiates AM3 is more parallel to the optical axis AX and has a smaller reticle telecentricity than the optical path of the measurement light IL that irradiates the alignment mark AM1 used in the VRA sensor 50. Measurement errors can be reduced by measuring at locations (high-precision measurement can be expected). In addition, measurement errors due to magnification fluctuations are reduced. In other words, measurement errors can be reduced by performing measurement under conditions close to the actual exposure state.

  The AIS sensor 60 includes the above-described reference opening mark 61 (see FIGS. 3, 6A, and 15A), and a mirror and relay disposed inside the wafer stage WST below the reference opening mark 61. A light transmission system 62 including a lens, an optical fiber, and the like, and a photomultiplier tube 63 as a photoelectric conversion element are included.

  The reference opening mark 61 is configured, for example, by fitting a light receiving glass into an opening formed in the reference mark plate FM, and forming a reflective film that also serves as a light shielding film having a slit on the surface of the light receiving glass. As the light receiving glass, for example, synthetic quartz or fluorite having good transparency such as KrF excimer laser light, ArF excimer laser or the like is used. FIGS. 6B and 15B are plan views of the reference opening mark 61, which have a mark portion 61a extending in the X-axis direction and a mark portion 61b extending in the Y-axis direction, which are orthogonal to each other.

  At the time of alignment, alignment mark AM2 (refer to FIG. 4, FIG. 6, FIG. 9, FIG. 12: search alignment mark) or AM3 (FIG. 4, FIG. 4) by illumination light IL from illumination optical system 11 via a reticle blind (not shown). Referring to FIG. 15, the peripheral portion of the reticle R on which the fine alignment mark) is formed is illuminated, and the image of the alignment mark AM2 or AM3 is projected on the reference aperture mark 61 of the reference mark plate FM via the projection optical system PL. , The projected image is sent to the photomultiplier tube 63 via the reference aperture mark 61 and the light transmission system 62 and subjected to photoelectric conversion, and a signal (light quantity signal) corresponding to the light quantity from the photomultiplier tube 63 is mainly controlled. It is output to the system 40. Since the photomultiplier tube 63 is of a light quantity detection type, in order to detect the positional relationship of the alignment marks AM2 and AM3 with respect to the reference aperture mark 61, the reticle stage RST or wafer stage WST is driven to make the two relative to each other. However, the time required for this scanning is equivalent to the time measured by the VRA sensor 50 described above, and is shorter by the amount of unnecessary optical path switching operation, ND switching operation, and epi-illumination mirror 53 movement operation. I'll do it. As shown in FIG. 4, the fine alignment mark AM3 formed on the reticle R, which is measured by AIS-RA measurement, is generally smaller than the search alignment mark AM2, and the width of each line is also large. It is thin and the pitch between lines is also fine. For this reason, the AIS-RA measurement with the fine alignment mark AM3 can be performed more accurately than the AIS-RA measurement with the search alignment mark AM2.

  FIG. 6A shows an example of an alignment mark (AIS search mark) AM2 used for search alignment. The alignment marks AM2 are respectively arranged at four positions in a plane parallel to the pattern formation surface PA adjacent to the pattern formation surface PA (shaded portion in FIG. 4) on which the circuit pattern of the reticle R is formed (see FIG. 4). 4). Each alignment mark AM2 includes a pair of first linear patterns AM2a extending in the X-axis direction parallel to the side along the X-axis direction of the pattern formation surface, and the side and the first linear shape along the X-axis direction of the pattern formation surface. One third linear pattern AM2c that intersects the pattern AM2a at an angle θ, and a pair of second linear patterns AM2b that extend in the Y-axis direction parallel to the other sides along the Y-axis direction of the pattern formation surface. In addition, the third linear pattern AM2c is formed on a diagonal line in a rectangular frame constituted by a pair of the first linear pattern AM2a and the second linear pattern AM2b. The aspect ratio (the ratio of the length of the first linear pattern AM2a to the length of the second linear pattern AM2b) of the alignment mark AM2 is set to 5: 1, for example. The reason for this setting is that, as shown in FIG. 4, the margin area of the peripheral portion of the reticle R has a relatively large margin in the X-axis direction than in the Y-axis direction.

  At the time of alignment, the illumination light IL is irradiated onto the portion of the reticle R where the alignment mark AM2 is formed, and an image of the alignment mark AM2 is projected onto the reference mark plate FM, for example, as shown in FIG. Is moved at a constant speed in the arrow direction (Y-axis direction) orthogonal to the X-axis direction, the reference aperture mark 61 is scanned (scanned) in the arrow direction (Y-axis direction) with respect to the projected image of the alignment mark AM2. . During this scan, from the mark portion 61a and the mark portion 61b (see FIG. 6B) of the reference opening mark 61, the first linear pattern portion AM2a, the second linear pattern portion AM2b, and the third linear pattern portion AM2c. A projected image enters. These incident projection images are sent to the photomultiplier tube 63 through the light transmission system 62, and are photoelectrically converted by the photomultiplier tube 63, so that a high peak value waveform and a low peak value waveform as shown in FIG. A signal waveform in which appears alternately. In the main control system 40, the arithmetic processing unit 41 performs arithmetic processing based on the signal from the photomultiplier tube 63 (based on intervals L0, L1, L2, and L3 between the peaks of the signal waveform shown in FIG. 8). That is, by substituting the intervals L0, L1, L2, L3 between the peaks of the signal waveform and the inclination θ of the third linear pattern AM2c into the following equation, the X position in the X-axis direction with respect to the reference aperture mark 61 of the alignment mark AM2 The Y position in the Y axis direction is obtained.

X position = (L2-L1) × (1/2) × (1 / tan θ)
Y position = (L3-L0) × (1/2)
In this way, during alignment, the wafer stage WST is moved once in the Y-axis direction (the reference aperture mark 61 is scanned once in the Y-axis direction with respect to the projection image projected on the reference mark plate FM. Thus, the position in the X axis direction (X position) with respect to the reference opening mark 61 of the alignment mark AM2 and the position in the Y axis direction (Y position) can be measured simultaneously.

  FIG. 9 shows another embodiment of the alignment mark AM2 used for search alignment. The alignment mark AM2 ′ is arranged at the first linear shape at the central position (the central position in the X-axis direction) within a rectangular frame constituted by the pair of first linear pattern AM2a and second linear pattern AM2b. A pattern AM2a and a second linear pattern AM2b are different in line width (thickening the line width), and a fourth linear pattern AM2d is arranged in parallel with the second linear pattern AM2b.

  At the time of alignment, as shown in FIG. 10, for example, wafer stage WST is moved at a constant speed in a direction intersecting at an angle of 45 ° with respect to the X-axis direction and the Y-axis direction (direction of 45 ° obliquely: arrow P direction). As a result, the reference aperture mark 61 is scanned in an oblique 45 ° direction with respect to the projected image of the alignment mark AM2 ′. During this scanning, as in the case described above, the first linear pattern portion AM2a, the second linear pattern portion AM2b, the fourth linear shape from the mark portion 61a and the mark portion 61b (see FIG. 10) of the reference opening mark 61. The projection image of the pattern portion AM2d enters. These incident projection images are photoelectrically converted by the photomultiplier tube 63 to obtain a signal waveform in which a plurality of waveforms having different widths and heights as shown in FIG. 11 appear alternately. In the main control system 40, the arithmetic processing unit 41 performs arithmetic processing based on the signal from the photomultiplier tube 63, and the position (X position) of the alignment mark AM2 ′ with respect to the reference opening mark 61 (X position) and the Y axis direction. The position (Y position) with respect to is simultaneously obtained (measured).

  In this way, in the first linear pattern AM2a, the second linear pattern AM2b, and the fourth linear pattern AM2d constituting the alignment mark AM2 ′, the line width of the fourth linear pattern AM2d is set to the other first line. As shown in FIG. 11, the peaks (waveforms) representing the X position and the Y position can be clearly distinguished from each other by configuring the pattern pattern AM2a and the second line pattern AM2b wider, and the reference of the alignment mark AM2 The position in the X axis direction (X position) with respect to the opening mark 61 and the position in the Y axis direction (Y position) can be measured with high accuracy.

  Even if the third linear pattern AM2c extending obliquely is not arranged, the alignment mark AM2 ′ is scanned once in the direction of 45 ° obliquely with respect to the projected image of the alignment mark AM2 ′. X position and Y position with respect to the reference opening mark 61 can be obtained simultaneously.

  FIG. 12 shows a modification of the alignment mark AM2 ′ shown in FIG. The alignment mark AM2 ″ of this modified example has a first frame instead of the fourth linear pattern AM2d in a square frame constituted by a pair of first linear pattern AM2a and second linear pattern AM2b. Three fifth linear patterns AM2e, AM2f, and AM2g that are different in line width from the linear pattern AM2a and the second linear pattern AM2b and that have different line widths (in the X-axis direction) from each other are substantially aligned along the X-axis direction. Arranged at equal intervals.

  At the time of alignment, similarly to the case shown in FIG. 10, wafer stage WST is moved at a constant speed in a direction intersecting at an angle of 45 ° with respect to the X axis direction and the Y axis direction (oblique direction: arrow P direction in FIG. 13). As a result, the reference aperture mark 61 is scanned obliquely at an angle of 45 ° with respect to the projected image of the alignment mark AM2 ″. Thereby, a signal waveform as shown in FIG. 14 is obtained from the output of the photomultiplier tube 63.

  Even when this alignment mark AM2 ″ is used, as in the case of using the alignment mark AM2 ′ shown in FIG. 9, the peaks (waveforms) representing the X position and the Y position can be clearly distinguished, and the alignment mark AM2 The position in the X-axis direction (X position) and the position in the Y-axis direction (Y position) with respect to the reference aperture mark 61 can be obtained with high precision. By scanning once in an oblique 45 ° direction, the X position and the Y position of the alignment mark AM2 ″ with respect to the reference opening mark 61 can be obtained simultaneously.

  As a modification of the AIS search mark (alignment mark AM2 used for search alignment by the AIS sensor 60) shown in FIG. 6A, the modification shown in FIG. 24A may be used.

  In the mark shown in FIG. 24A, a plurality of oblique lines (three in the modified example shown in FIG. 24) that are inclined at 45 ° are arranged apart from each other in the X direction. Further, the line widths (thicknesses in the X direction) of the diagonal lines are different from each other.

  When the mark in FIG. 24A is measured by the same method as the measurement method already described in FIG. 7 as shown in FIG. 24B, a signal waveform in FIG. 24C is obtained. Mark position measurement is performed by applying the measurement processing described above with reference to FIG. 8 to the signal waveform. Since the measurement method and the measurement process are the same as those shown in FIGS. 7 and 8, the description thereof is omitted here.

  In the mark of FIG. 24A, three 45 ° lines are provided. However, since the line widths are different from each other as described above, the AIS slit (reference opening mark) 61 is formed on the diagonal line. It is possible to determine which diagonal line is measured based on the signal waveform (the length of the TOP portion of the signal) obtained when crossing.

  FIG. 15A shows an example of an alignment mark AM3 used for fine alignment. This alignment mark AM3 is different in shape from the alignment marks AM2, AM2 ′, AM2 ″ and has a pattern formation surface adjacent to the pattern formation surface (shaded portion in FIG. 4) on which the circuit pattern of the reticle R is formed. It is arranged adjacent to each alignment mark AM2, AM2 ′, AM2 ″ in a parallel plane (with a predetermined interval: in a known positional relationship) (see FIG. 4). Each alignment mark AM3 includes a plurality of parallel first linear patterns AM3a extending along the X-axis direction and a plurality of parallel second linear patterns AM3b extending along the Y-axis direction. A direction in which the start point of each first linear pattern AM3a and the start point of each second linear pattern AM3b intersect with each other with respect to the X-axis direction and the Y-axis direction (inclination of 45 °: direction of arrow P in FIG. 16) And the starting point of each first linear pattern AM3a and the starting point of each second linear pattern AM3b are arranged sequentially in an oblique direction (staggered arrangement: see FIG. 18). In FIG. 15A, the leftmost patterns AM3a ′ and AM3b ′ are used for focus calibration.

  At the time of alignment, the illumination light IL is irradiated onto the portion of the reticle R where the alignment mark AM3 is formed, and an image of the alignment mark AM3 is projected onto the reference mark plate FM, for example, as shown in FIG. Is projected at a constant speed in the direction of an arrow that intersects the line extending in the X-axis direction and the line extending in the Y-axis direction at an angle of 45 ° (in the direction of 45 ° obliquely: the direction of the arrow P), thereby projecting the alignment mark AM3 The reference aperture mark 61 is scanned (scanned) in an oblique 45 ° direction with respect to the image. During this scan, the projected image of the first linear pattern portion AM3a and the projected image of the second linear pattern portion AM3b are alternately incident from the mark portion 61a and the mark portion 61b of the reference aperture mark 61. These incident projected images are photoelectrically converted by the photomultiplier tube 63 to obtain a signal waveform in which a waveform for Y position measurement and a waveform for X axis measurement alternately appear as shown in FIG. In the main control system 40, the arithmetic processing unit 41 performs arithmetic processing based on the signal from the photomultiplier tube 63, and the position of the alignment mark AM3 in the X-axis direction (X position) relative to the reference opening mark 61 and the Y-axis direction. The position (Y position) is simultaneously obtained (measured) with high accuracy.

  As described above, the X position and the Y position of the alignment mark AM3 with respect to the reference opening mark 61 can be simultaneously obtained by scanning the reference opening mark 61 once in the oblique 45 ° direction with respect to the projection image of the alignment mark AM3. I can do it.

  Next, an embodiment of the position measuring method of the present invention will be described.

  As described above, reticle alignment includes search alignment for rough position measurement and alignment, and fine alignment for more precise position measurement. In this reticle alignment, search alignment is executed by the VRA sensor 50. Then, when the fine alignment is executed by the AIS sensor 60 or the search alignment is executed by the AIS sensor 60, and then the fine alignment is executed by the VRA sensor 50, the incident illumination is used. An operation for moving the system 51 between the illumination optical system 11 and the reticle stage RST is required, and the alignment throughput cannot be improved.

  Therefore, when search alignment is performed by the AIS sensor 60, it is possible to improve alignment throughput by performing the same fine AIS sensor 60 even if fine alignment is performed subsequently.

  However, when a measurement error occurs during alignment by the AIS sensor 60, for example, the images of the alignment marks AM2 and AM3 projected on the reference mark plate FM cannot be sufficiently captured by the reference aperture mark 61, and the photomultiplier tube is used. If an output exceeding a predetermined level required for the arithmetic processing is not obtained from 63, the position measurement operation is temporarily stopped, the wafer stage WST or the reticle stage RST is moved to each other, and the alignment mark AM2 is moved. , It is necessary to perform an operation of adjusting the relative positional relationship between the projection position of AM3 and the reference aperture mark 61. However, this operation is very laborious and time consuming, lowers the throughput, and the advantage of performing both search alignment and fine alignment with the AIS sensor 60 cannot be utilized.

  In this embodiment, when a measurement error occurs during execution of alignment by the AIS sensor 60, the VRA sensor 50 is used as a recovery measure, and the reticle stage is viewed while viewing the image of the image sensor 55 that has captured the reference mark FM1. By manually moving the RST or the wafer stage WST to adjust the relative positional relationship between the reticle R and the reference mark plate FM, an assist operation is performed, whereby the projection positions of the alignment marks AM2 and AM3 and the reference opening mark 61 Adjust the relative positional relationship between.

  Thereby, even if a measurement error occurs during execution of alignment by the AIS sensor 60, it can be recovered immediately and the alignment can be continued by the AIS sensor 60. However, in this assist operation, the illumination light (exposure light) is irradiated to the reference mark FM1 for a long time. Therefore, depending on the material of the reference mark FM1, the VRA deteriorates, the reflectance decreases, and the measurement accuracy deteriorates. There arises a new problem such as the possibility that the alignment by the sensor 50 may be hindered.

  Therefore, in this embodiment, as shown in FIG. 5, a reference mark FM2 dedicated to assist operation is formed on the reference mark plate FM in a predetermined (known) positional relationship with the reference opening mark 61, and this reference mark FM2 is formed. Only when the assist operation is performed using the mark FM2 and alignment is performed by the VRA sensor 50, the reference mark FM1 is used. The reference mark FM2 dedicated to the assist operation can also be used when the measurement operation for imaging the reference mark FM1 by the VRA sensor 50 fails.

  Next, the above-described alignment (position measurement) operation will be described with reference to the flowchart of FIG.

  First, in step S100, a position measurement method for alignment is selected. It is selected whether the alignment is executed by the VRA sensor 50 (VRA measurement method) or the AIS sensor 60 (AIS-RA measurement method).

  If it is not selected in step S101 to perform alignment by the AIS sensor 60 (AIS-RA measurement method), the process proceeds to step S102, search alignment is performed by the VRA sensor 50 (VRA measurement method), and then Perform fine alignment. Thereafter, the process proceeds to step S111. On the other hand, if selected, the process proceeds to step 103, and search alignment is executed by the AIS sensor 60 (AIS-RA measurement method).

  In the search alignment by the AIS sensor 60 (AIS-RA measurement method) in step S103, for example, as described with reference to FIGS. 6 to 8, 9 to 11, or 12 to 14, the projected image of the alignment mark AM2. The reference aperture mark 61 is scanned in a predetermined direction, and during this scanning, the projection image of the alignment mark AM2 incident from the reference aperture mark 61 is sent to the photomultiplier tube 63, subjected to photoelectric conversion, and the main control system 40 Send to. In the main control system, the arithmetic processing unit 41 performs arithmetic processing based on the signal from the photomultiplier tube 63 to obtain the X position in the X axis direction and the Y position in the Y axis direction with respect to the reference opening mark 61 of the alignment mark AM2. .

  During execution of the search alignment described above in step S104, it is determined whether or not the measurement is successful (whether or not a measurement error has occurred). If the measurement fails, the process proceeds to step S105, and the VRA sensor 50 and the assist operation are performed. Using the dedicated reference mark FM2, the reticle stage RST or the wafer stage WST is manually moved while visually observing the image of the image sensor 55 that has captured the reference mark FM2 dedicated to the assist operation, and the reticle R and the reference mark plate By performing an assist operation for adjusting the relative positional relationship with the FM, the relative positional relationship between the projection position of the alignment mark AM2 and the reference opening mark 61 is adjusted, and then the search alignment is executed again. If the search alignment measurement is successful, the process proceeds to step S106.

  In step S106, the wafer stage WST is moved to the fine alignment measurement start position while correcting the position of the reticle stage RST based on the search alignment measurement result. After the movement is completed, the process proceeds to step S107.

  In step S107, fine alignment is executed. In this fine alignment, for example, as described with reference to FIGS. 15 to 17, the reference aperture mark 61 is scanned in an oblique 45 ° direction with respect to the projection image of the alignment mark AM3, and the reference aperture mark 61 is incident during this scanning. The projected image of the alignment mark AM3 is sent to the photomultiplier tube 63, subjected to photoelectric conversion, and sent to the main control system 40. In the main control system, the arithmetic processing unit 41 performs arithmetic processing based on the signal from the photomultiplier tube 63 to increase the X position in the X-axis direction and the Y position in the Y-axis direction with respect to the reference opening mark 61 of the alignment mark AM3. Measure accurately.

  During the fine alignment described above in step S108, it is determined whether or not the measurement has succeeded (whether or not a measurement error has occurred). If the measurement has failed, the process proceeds to step S109, which is the same as in step S105. By moving the reticle stage RST or wafer stage WST manually while visually observing the image of the image sensor 55 and performing an assist operation, the relative positional relationship between the projection position of the alignment mark AM2 and the reference aperture mark 61 is obtained. After this, fine alignment is performed again.

  If the fine alignment measurement is successful, the process proceeds to step S110, and the fine alignment measurement result is stored in the memory.

  When reticle alignment is completed as described above, the process proceeds to step S111. In step S111, the main control system 40 moves the wafer stage WST so that the AIS sensor 60 is positioned directly below the wafer alignment system AS, and the wafer alignment system AS sets a reference opening mark 61 that serves as a position reference for the AIS sensor 60. To detect. In the main control system 40, the detection signal of the wafer alignment system AS, the measurement value of the wafer interferometer 22 at that time, and the position of the alignment mark AM1 in the X-axis direction (X position) with respect to the reference mark FM1 (the position in the Y-axis direction ( The position of the reticle R obtained from the pattern projection position of the reticle R obtained from the (Y position) or the position (X position) in the X-axis direction with respect to the reference aperture mark 61 of the alignment marks AM2 and AM3 and the position (Y position) in the Y-axis direction. Based on the pattern projection position, the relative position between the projection position of the pattern on the reticle R and the wafer alignment system AS, that is, the baseline amount of the wafer alignment system AS is obtained, and the main control system 40, for example, Japanese Patent Laid-Open No. 61-44429. EGA (Enhanced Global Alignment) Ha alignment performed using the wafer alignment system AS, determining the position of all the shot areas on the wafer W.

  In step S112, based on the fine alignment measurement result (S110), the EGA measurement result (S111), and the baseline amount, the position correction calculation of the reticle stage RST and wafer stage WST is executed.

  In step S113, position information from reticle interferometer 16 and wafer interferometer 22 is monitored based on the position correction calculation amounts of reticle stage RST and wafer stage WST, and wafer stage WST is positioned at the scanning start position of the first shot area. The reticle stage RST is positioned at the scanning start position.

  In step S114, scanning exposure of the first shot area is executed.

  When the scanning exposure of the first shot area is completed in this way, a stepping operation between shots for moving the wafer stage WST to the scanning start position of the second shot area is performed, and then the scanning exposure of the second shot area is described above. Perform as in the case. The same operation is repeated for the third shot area and thereafter. As a result, the pattern of the reticle R is transferred to all shot areas on the wafer W.

  In the above-described VRA sensor 50, since the exposure light is used as the illumination light for measurement, the reflectance is changed (decreased) by oxidation of chromium (Cr) constituting the wafer fiducial mark (reference mark) FM1. It has been pointed out that This decrease in reflectivity results in a decrease in signal contrast, leading to deterioration in measurement accuracy.

  Therefore, as shown in FIG. 19 to FIG. 22, when the signal intensity of the reference mark FM1 is periodically measured by the VRA sensor 50 to measure the change in reflectance, and when the reflectance decreases beyond a certain threshold, By automatically changing to another wafer fiducial mark (reference mark) FM1a, FM1b, FM1c (see FIG. 21), deterioration in measurement accuracy due to a decrease in reflectance is avoided in advance. It is desirable to select another reference mark FM1a, FM1b, FM1c that is not included in the illumination field of the reference mark FM1 used previously (portion surrounded by a two-dot chain line in FIG. 21).

  FIG. 19A is a signal waveform diagram of a reflection image from the alignment mark AM1 and the reference mark FM1, and the signal waveform of the reference mark FM1 appears on both sides, and the signal waveform of the alignment mark AM1 appears at the center position. FIG. 5B shows a signal waveform of the reference mark FM1 before being oxidized by irradiation with exposure light as measurement illumination light, and FIG. 5C shows a reference mark FM3 for reflectance reference (FIG. 21). Signal waveform).

  Before oxidation by irradiation with exposure light as measurement illumination light, as shown in FIGS. 19B and 19C, the signal intensity of the reference mark FM1 and the signal intensity of the reference mark FM3 are the same. .

However, the exposure apparatus 10 is used to repeatedly irradiate the reference mark FM1 with exposure light, and as a result of irradiating exposure light of a certain amount or more, the reference mark FM1 is oxidized as shown in FIG. The reflectance decreases, and the signal intensity (I ₂ ) of the reflected image of the reference mark FM1 decreases. This decrease in signal intensity includes fluctuations in the amount of illumination light (exposure light) in addition to a decrease in reflectance.

Therefore, as shown in FIG. 4B, the signal intensity (I ₁ ) of the reference mark FM3 for reflectance reference is measured to determine the change in reflectance. This change in reflectance can be obtained by ΔR = | I ₂ −I ₁ | / I ₁ .

  FIG. 21 shows another embodiment of the wafer fiducial mark plate (reference mark plate) FM. On the surface of the reference mark plate FM, in addition to the wafer fidelity mark (reference mark) FM1 for VRA measurement, wafer fiducial marks (reference marks) FM1a, FM1b, FM1c for VRA measurement are formed. Further, a reference mark FM3 for reflectance reference is formed. If the reflectance of the reference mark FM1 decreases beyond a certain threshold, another reference mark FM1a, FM1b, or FM1c is selected. At this time, other fiducial marks FM1a, FM1b, FM1c that are out of the illumination field of the fiducial mark FM1 and not yet irradiated with the exposure light are selected. In FIG. 21, the reference mark FM2 dedicated to the assist operation is omitted.

  FIG. 22 shows a flowchart in the case where alignment is performed by selecting another fiducial mark FM1a, FM1b, FM1c when the reflectance is lowered.

  In step S200, the baseline amount is measured (baseline check) for the first wafer W of the lot (for example, the first wafer W when 25 wafers are processed in one lot) by the above-described method. To start. In this baseline check, first, the reflectance of the fiducial mark FM1 is measured to confirm whether or not the reflectance has decreased.

  In step S201, measurement of the reflectance of the reference mark FM1 is started. In this reflectance measurement, the VRA sensor 50 irradiates the reference mark FM1 with exposure light as measurement illumination light, and measures the signal intensity. Further, the signal intensity is measured by irradiating the reference mark FM3 for reflectance reference with exposure light. Then, the reflectance is obtained by the method described above.

  In step S202, it is determined whether or not the reflectance of the reference mark FM1 is higher than the threshold value. If it is determined that the reflectance is low, the process proceeds to step S203 to check the reflectance of another reference mark FM1a, FM1b, FM1c. A reference mark having a reflectance higher than the threshold is selected from the marks FM1a, FM1b, and FM1c, and the process proceeds to step S204.

  In step S204, baseline check measurement is performed using the mark selected in step S203. In step S205, it is determined whether or not the baseline check measurement is completed. If completed, the process proceeds to step S206, alignment is performed by the method described above, and then an exposure operation is performed in step S207.

  If the reflectivity is reduced in this way, it is changed to a pair of marks of another reference mark FM1a, FM1b, FM1c, thereby avoiding a measurement error, improving alignment throughput, and improving the exposure apparatus 10 It is possible to reduce the influence on the operation rate.

  In addition, by preparing the reference mark FM3 for reference of reflectance, it is possible to perform reflectance measurement that is not affected by fluctuations in the amount of illumination light irradiated.

  FIG. 23 shows an embodiment of the device manufacturing method of the present invention. In this embodiment, since reticle alignment is performed by the position measurement method shown in FIG. 1, the throughput is excellent and high-precision exposure can be performed.

  In step S300, device function / performance design such as electronic device circuit design is performed, and pattern design for realizing the function is performed. In step S301, a reticle R on which the designed circuit pattern is formed is manufactured. In step S302, a wafer (silicon substrate) W is manufactured using a material such as silicon.

  In step S303, wafer processing is performed by using the reticle R manufactured in step S301 and the wafer W manufactured in step S302 to form a circuit or the like on the wafer W by lithography or the like. In this wafer processing, first, the position is measured by the method shown in FIG. 1, and the projection position of the image of the device pattern on the reticle R and each shot area on the wafer W are sequentially aligned based on this position information. Then, the device pattern formed on the reticle R is sequentially exposed and transferred to each positioned shot area. When the exposure is completed, the wafer W is unloaded from the wafer stage WST, and processes such as development, etching, and cleaning processes are repeated to form a circuit and the like on the wafer W.

  In step S304, device assembly is performed. In this device assembly, a wafer W on which a circuit or the like is formed is diced and divided into individual chips, each chip is mounted on a lead frame or a package and bonding is performed to connect electrodes, and packaging such as resin sealing is performed. Process.

  In step S305, an inspection is performed. In this inspection, the assembled devices are tested for operation and durability, and the accepted products are shipped.

  The present invention is not limited to the one described in the above embodiment, and various modifications can be made within the scope of the present invention.

  As alignment marks AM2, AM2 ′, AM2 ″, and AM3 used in the measurement of the AIS sensor 60, for example, those shown in FIGS. 6A, 9, 12, 15A, and 24A are used. However, the present invention is not limited to these examples, but an alignment mark that can obtain a signal waveform capable of high-precision measurement in one scan from the viewpoint of throughput and measurement accuracy. If it is.

  Further, the scanning direction of the reference aperture mark 61 with respect to the projected images of the alignment marks AM2, AM2 ′, AM2 ″ and AM3 is the Y-axis direction as shown in FIG. 7, and obliquely as shown in FIGS. 10, 13, and 16. Although the case where the direction is 45 ° is shown, it is not limited thereto.

  In addition, by preparing a plurality of reference marks FM2 dedicated to assist operations and reference marks FM1 for normal measurement and using them alternately, it is possible to delay the decrease in reflectance, and as a result, it is possible to extend the life of the apparatus. Become.

It is a flowchart which shows one embodiment of the position measuring method of this invention. It is a schematic block diagram of the exposure apparatus which performs the position measuring method of this invention shown in FIG. FIG. 3 is a schematic configuration diagram in which an AIS sensor 60 provided in the exposure apparatus shown in FIG. 2 is partially cut away. FIG. 3 is a schematic plan view showing one embodiment of a reticle used in the exposure apparatus of FIG. 2. FIG. 3 is a schematic plan view showing one embodiment of a wafer fidelity mark plate (reference mark plate) used in the exposure apparatus of FIG. 2. FIG. 6A is a plan view showing an embodiment of an alignment mark for search alignment, and FIG. 6B is a plan view showing an embodiment of a reference opening mark. It is explanatory drawing of the scanning method of the reference | standard opening mark 61 with respect to the projection image of the alignment mark shown to FIG. 6 (A). FIG. 8 is a signal waveform diagram obtained as a result of scanning the alignment mark shown in FIG. 6A by the method shown in FIG. 7. It is a top view which shows another embodiment of the alignment mark for search alignment. It is explanatory drawing of the scanning (scanning) method of the reference | standard opening mark 61 with respect to the projection image of the alignment mark shown in FIG. FIG. 11 is a signal waveform diagram obtained as a result of scanning the alignment mark shown in FIG. 9 by the method shown in FIG. 10. It is a top view which shows the modification of the alignment mark shown in FIG. FIG. 13 is an explanatory diagram of a scanning method of the reference aperture mark 61 with respect to the projected image of the alignment mark shown in FIG. FIG. 14 is a signal waveform diagram obtained as a result of scanning the alignment mark shown in FIG. 12 by the method shown in FIG. 13. FIG. 15A is a plan view showing one embodiment of an alignment mark for fine alignment, and FIG. 15B is a plan view showing one embodiment of a reference opening mark. FIG. 16A is an explanatory diagram of a reference aperture mark scanning method for the projection image of the alignment mark FM3 shown in FIG. FIG. 17 is a signal waveform diagram obtained as a result of scanning the alignment mark shown in FIG. 15A by the method shown in FIG. 16. FIG. 16 is an enlarged plan view for explaining that the X position measurement pattern and the Y position measurement pattern of the alignment mark shown in FIG. 19A is a signal waveform diagram of an alignment mark and a wafer fidelity mark (reference mark) measured by the VRA sensor, and FIG. 19B is a signal waveform diagram of an unoxidized fiducial mark. FIG. 19C is a signal waveform diagram of a wafer fiducial mark for reflectance reference. FIG. 20A is a signal waveform diagram of a fiducial mark that has been oxidized by exposure light irradiation and has a decreased reflectance, and FIG. 20B is a reference waveform for reflectance that is not oxidized and has a decreased reflectance. It is a signal waveform diagram of a wafer fiducial mark. It is a top view which shows another embodiment of a wafer fiducial mark board (reference | standard mark board). It is a flowchart in the case of performing alignment by selecting another reference mark when the reflectance decreases. It is a flowchart which shows one embodiment of the device manufacturing method of this invention. FIG. 24A is a diagram showing a modification of the mark for search alignment in the AIS sensor, and FIG. 24B is a scanning method of the reference aperture mark 61 for the projected image of the alignment mark shown in FIG. FIG. 24C is a signal waveform diagram obtained as a result of scanning the alignment mark of FIG. 24A by the method shown in FIG. 24B.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Exposure apparatus 11 Illumination system 40 Main control system 50 VRA sensor 60 AIS sensor 61 Reference aperture mark 62 Light transmission system 63 Photomultiplier tube PL Projection optical system AS Alignment system AX Optical axis R Reticle RST Reticle stage W Wafer WST Wafer stage AM2 Alignment Mark (for search measurement)
AM3 alignment mark (for fine measurement)
FM1 fiducial mark (wafer fiducial mark)
Reference mark for FM2 assist operation

Claims (9)

Before transferring the pattern on the first object onto the second object, the relative positional relationship between the reference member provided on the stage on which the second object is placed and the first object is determined. A measurement method for measuring,
A first position measuring step of measuring a predetermined area on the first object with a predetermined precision to obtain position information of the object;
A second measurement step of measuring a predetermined area on the first object with a further precision than the predetermined precision to obtain position information of the object,
Using the same measurement sensor as the measurement sensor selected from a plurality of measurement sensors having different measurement principles and used in any one of the first and second position measurement steps, A position measurement method comprising performing position measurement in one of the other position measurement steps. The position measurement method according to claim 1,
The plurality of measurement sensors are:
A first sensor that photoelectrically detects a projected image of a mark formed on a predetermined region on the first object and projected on the reference member through a slit provided on the reference member;
A second sensor that simultaneously captures a reflected image of a mark formed on a predetermined region on the first object and a reflected image of a mark formed on the reference member;
If the projected image of the mark on the first object cannot be detected by the first sensor, the first object and the reference member based on the imaging result of the predetermined location on the reference member by the second sensor The positional measurement method is characterized by adjusting the relative positional relationship between the projected image and the re-detection operation of the projected image using the first sensor. In the position measuring method according to claim 2,
An assist mark that is a measurement target is formed at the predetermined location only when the positional relationship with the slit is known and the projection image cannot be detected by the first sensor. Position measurement method. In the position measuring method according to any one of claims 1 to 3,
The first mark measured in the first position measuring step and the second mark measured in the second measuring step are marks having different shapes from each other and having a known positional relationship with each other. Characteristic position measurement method. The position measurement method according to claim 4,
In the first position measurement step, a projected image of the mark on the first object projected onto the reference member is passed through the slit provided on the reference member, and the projected image and the slit In the case of using the first sensor that performs photoelectric detection while relatively scanning,
The first mark is
A first linear pattern extending in a first direction in a plane parallel to the pattern formation surface on the first object; and a second linear pattern that intersects the first linear pattern obliquely in the plane Including
In the first position measuring step, the projected image of the first mark and the slit are relatively scanned in a direction orthogonal to the first direction in the plane. The position measurement method according to claim 4,
In the first position measurement step, a projected image of the mark on the first object projected onto the reference member is passed through the slit provided on the reference member, and the projected image and the slit In the case of using the first sensor that performs photoelectric detection while relatively scanning,
The first mark is
A first linear pattern and a second linear pattern respectively extending in a first direction and a second direction orthogonal to each other in a plane parallel to a formation surface of the pattern on the first object;
In the first position measuring step, the projected image of the first mark and the slit are relatively scanned in a direction intersecting with the first and second directions in the plane. Method. The position measurement method according to claim 6,
The position measuring method, wherein the second linear pattern includes a plurality of linear patterns having different line widths in the first direction and spaced apart from each other in the first direction. The position measurement method according to claim 4,
In the second position measurement step, a projected image of the mark on the first object projected onto the reference member is passed through the slit provided on the reference member, and the projected image and the slit In the case of using the first sensor that performs photoelectric detection while relatively scanning,
The second mark is
A plurality of elements extending in the first direction while shifting their start points in a third direction intersecting each other with respect to the first and second directions orthogonal to each other in a plane parallel to the pattern forming surface on the first object. A first linear pattern and a plurality of second linear patterns extending in the second direction while shifting the starting point in the third direction, and each starting point of the plurality of first linear patterns and the plurality of the second linear patterns Are arranged in order in the third direction with respect to the starting points of the second linear pattern,
In the second position measurement step, the position measurement device relatively scans the projected image of the second mark and the slit in the third direction in the plane. Providing a mask on which a device pattern is formed and a substrate having a plurality of partition regions to which the device pattern is to be transferred;
A projection position of the pattern image of the mask and each of the plurality of partition areas on the substrate are determined based on position information measured using the position measurement method according to any one of claims 1 to 8. A step of sequentially aligning;
And sequentially transferring the device pattern onto each of the aligned partitioned regions.

Images