JP2006294993A - Method, system and program for measuring position - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a mark position without causing a measurement error even if the actual profile of a mark is different from a design value, or the actual characteristics of a mark detector are shifted. <P>SOLUTION: Mark positions of wafer alignment marks (e.g. Y mark SYM and θ mark SθM) formed on a wafer W are determined by performing predetermined image processing on an image signal obtained by imaging these marks. When the image processing is performed, information indicative of the width of line patterns SML1-SML4 and information indicative of the interval are altered, degree of aptitude of alteration is calculated, and a mark position is determined using a degree of aptitude satisfying predetermined criterion. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a position measurement method, a position measurement system, and a position measurement program for detecting the position of a mark formed on an object.

  When manufacturing a semiconductor element, a liquid crystal display element, a thin film magnetic head, or other devices, a reticle or a mask (hereinafter, these are collectively referred to as a reticle) is irradiated with illumination light, and light through the reticle is projected into an optical projection system. An exposure apparatus is used that projects a pattern formed on a reticle onto a substrate such as a wafer or glass plate coated with a photoresist (hereinafter referred to as “substrate” or “wafer”). As the exposure apparatus, a batch exposure type (stationary exposure type) exposure apparatus such as a stepper or a scanning exposure type exposure apparatus (scanning type exposure apparatus) such as a scanning stepper is used. In such an exposure apparatus, it is necessary to perform alignment (alignment) between the reticle and the wafer with high accuracy prior to exposure.

  Therefore, it is necessary to detect the position of the reticle and the position of the wafer with high accuracy. In such position detection, reticle alignment generally uses exposure light, and the reticle alignment mark image data captured by a CCD camera or the like is irradiated with the exposure light onto the reticle alignment mark drawn on the reticle. A VRA (Visual Reticle Alignment) method or the like that measures the mark position by image processing is employed. In wafer alignment, an LSA (Laser Step Alignment) method, an FIA (Field Image Alignment) method, an LIA (Laser Interferometric Alignment) method, or the like is employed.

  The LSA method is a method of irradiating a wafer alignment mark formed on a wafer with a laser beam and measuring the mark position using diffracted / scattered light. The FIA method is a method in which a wafer alignment mark is illuminated using a light source having a wide wavelength bandwidth such as a halogen lamp, and the mark position is measured by performing image processing on image data obtained by imaging the wafer alignment mark. is there. In the LIA method, a diffraction grating-shaped wafer alignment mark formed on the wafer surface is irradiated with laser beams having slightly different wavelengths from two directions, and the resulting two diffracted beams interfere with each other. This is a method of measuring the mark position from the phase.

  The waveform signal obtained as a measurement result by each of the above methods is in accordance with the shape of the alignment mark that is the observation target, but particularly when measuring the wafer alignment mark formed on the wafer, The waveform signal may change depending on the surface condition of the wafer. For this reason, various algorithms for processing the waveform signal that can measure the mark position with high accuracy even when the waveform signal changes in accordance with the surface state of the wafer are considered. Patent Documents 1 and 2 below disclose examples of algorithms used for measuring the mark position.

  By the way, for example, when measuring a wafer alignment mark formed on a wafer, as described above, the mark position is measured by performing processing such as image processing on the waveform signal obtained as a measurement result. In this process, the mark position is obtained using shape information (design value) relating to the shape of the wafer alignment mark. Here, the shape information relating to the shape of the wafer alignment mark is, for example, the width and pitch of the mark elements constituting the wafer alignment mark when the wafer alignment mark is a line and space pattern. Further, magnification information indicating the magnification of the optical system provided in the alignment sensor for observing the wafer alignment mark is also used for obtaining the mark position.

  The wafer alignment mark is formed on the wafer together with the pattern, but may be formed differently from the design value depending on the process. For example, the width of the mark element may be formed narrower than the design value, or the pitch of the mark element may be formed narrower than the design value. Further, the magnification of the optical system provided in the alignment sensor is measured in advance prior to the exposure process, and this measurement result is used as magnification information for obtaining the mark position. A value different from the actual magnification may be used as magnification information due to an input error or the like.

  When obtaining the mark position from the waveform signal obtained by observing the wafer alignment mark, the actual alignment mark is formed deviating from the shape indicated by the shape information above, or the actual magnification of the alignment sensor is If the magnification information is different, the mark position cannot be obtained and a measurement error may occur. When this measurement error occurs, re-measurement by an operator's instruction is required. However, if re-measurement is frequently required for each wafer alignment mark, the throughput (the number of wafers that can be exposed per unit time) is greatly increased. There is a problem that it falls.

The present invention has been made in view of such problems of the prior art, and when measuring the mark position using at least one of the mark information related to the mark shape and the device information related to the detection characteristics of the mark detection device, Detect the mark position without causing a measurement error even if the actual mark shape deviates from the shape indicated by the mark information, or the actual mark detector characteristics differ from the characteristics indicated by the device information. It is an object to provide a position measurement method, a position measurement system, and a position measurement program.
JP 2001-126981 A International Publication WO2002 / 033351 Pamphlet

  Hereinafter, in the description shown in this section, the present invention will be described in association with the member codes shown in the drawings representing the embodiments. However, each constituent element of the present invention is limited to the members shown in the drawings attached with these member codes. Is not to be done.

  According to the first aspect of the present invention, in the position measurement method for measuring the position of the mark (SYM, SθM) formed on the object (W), the detection is performed by using the mark detection device (AS) to detect the mark. Step (S14), including at least one of mark information relating to the shape of the mark and device information relating to the detection characteristics of the mark detection device, and using parameter information whose set value is automatically variable according to a predetermined rule Then, a calculation step (S17) for calculating the suitability degree of the parameter information based on the detection result in the detection step, and a determination for judging whether or not the suitability degree obtained in the calculation step satisfies a predetermined standard. Using the parameter information in step (S18) and when it is determined in the determination step that the predetermined criterion is satisfied, Position measuring method and a position calculation step (S25) of calculating a position of the mark based on the detection result of the serial detection step is provided.

  According to a second aspect of the present invention, in a position measurement system (100) that measures the position of a mark (SYM, SθM) formed on an object (W), a detection unit (AS) that detects the mark; A storage unit (42) in which parameter information including at least one of mark information related to the shape of the mark and information related to the detection characteristics of the detection unit is stored in advance, and parameter information stored in the storage unit is determined according to a predetermined rule. Obtained by the calculation unit, the parameter information changing unit (34) that changes according to the parameter information, the calculation unit (35) that calculates the appropriateness of the parameter information based on the parameter information and the detection result by the detection unit A determination unit (36) for determining whether or not the suitability satisfies a predetermined criterion; and the determination A position measurement system having a position calculation unit (37) for calculating the position of the mark based on the parameter information when it is determined that the predetermined criterion is satisfied by knit and the detection result by the detection unit is provided. Is done.

  According to a third aspect of the present invention, in a position measurement program applied to a position measurement device that measures the position of a mark (SYM, SθM) formed on an object (W), the mark is detected by a mark detection device. A parameter that includes at least one of the first step (S14) to be displayed and the mark information related to the shape of the mark and the device information related to the detection characteristics of the mark detection device, and the set value is automatically variable according to a predetermined rule A second step (S17) for calculating suitability of the parameter information based on the detection result in the first step using information, and whether the suitability obtained in the second step satisfies a predetermined standard Using the parameter information in the third step (S18) for determining whether or not the predetermined criterion is determined to be satisfied in the third step, The fourth step (S25) and position measurement program comprising calculating the position of the mark based on the detection result of the output step is provided.

  In the inventions according to the first to third aspects, the position of the mark is calculated using the parameter information having a high degree of aptitude, so that the occurrence of a measurement error is reduced.

  According to the present invention, the mark position can be detected without causing a measurement error even if the shape of the mark is deviated from the shape indicated by the design value or the detection characteristics of the mark detection device are different from the actual one. Therefore, there is an effect that the measurement process can be highly efficient.

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

[First Embodiment]
FIG. 1 is a view showing the schematic arrangement of an exposure apparatus according to the first embodiment of the present invention. The exposure apparatus shown in FIG. 1 moves the pattern formed on the reticle R on the wafer W while relatively moving the reticle R as a mask and the wafer W as a substrate with respect to the projection optical system PL in FIG. Is a step-and-scan type scanning type exposure apparatus that sequentially transfers the light. In the following description, an XYZ orthogonal coordinate system is set in the drawing, and the positional relationship of each member will be described with reference to this XYZ orthogonal coordinate system. In the XYZ orthogonal coordinate system shown in FIG. 1, the XY plane is set to a plane parallel to the horizontal plane, and the Z axis is set to the vertically upward direction. In this embodiment, the direction (scanning direction) in which the reticle R and the wafer W are moved synchronously is set to the Y direction.

  The exposure apparatus 100 includes an illumination system 10, a reticle stage RST that holds a reticle R as a mask, a projection optical system PL, a wafer stage WST on which a wafer W as a substrate (object) is mounted, a mark detection device or a detection unit. The configuration includes an alignment microscope AS and a main control system 20 that controls the entire apparatus.

The illumination system 10 includes a light source such as an ArF excimer laser light source (wavelength 193 nm), an illuminance uniformity optical system including a fly-eye lens, a relay lens, a variable ND filter, a reticle blind, a dichroic mirror, and the like (all not shown). It is configured to include. The configuration of such an illumination system is disclosed in, for example, Japanese Patent Laid-Open No. 10-112433. The illumination system 10 illuminates the slit-shaped illumination area defined by the reticle blind on the reticle R on which the pattern is drawn with the illumination light IL with a substantially uniform illuminance. In addition to the ArF excimer laser light source, KrF excimer laser (wavelength 248 nm), F ₂ laser (wavelength 157 nm), Kr ₂ laser (wavelength 146 nm), g-line (wavelength 436 nm), i-line (wavelength 365 nm) are used as the light source. An ultra-high pressure mercury lamp that emits light, a high-frequency generator of a YAG laser, or a high-frequency generator of a semiconductor laser can be used.

  On reticle stage RST, reticle R is fixed, for example, by vacuum suction. Here, the reticle stage RST is configured such that an optical axis of the illumination system 10 (an optical axis of a projection optical system PL described later) is used for positioning the reticle R by a reticle stage driving unit (not shown) composed of a magnetically levitated two-dimensional linear actuator. It can be driven minutely in the XY plane perpendicular to AX) and can be driven at a scanning speed designated in the scanning direction. Further, in the present embodiment, the magnetically levitated two-dimensional linear actuator includes a Z driving coil in addition to the X driving coil and the Y driving coil, and therefore can be finely driven in the Z 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 through the moving mirror 15 with a predetermined resolution. The position information of reticle stage RST from reticle interferometer 16 is sent to stage control system 19, and stage control system 19 controls reticle stage RST via a reticle stage drive unit (not shown) based on the position information of reticle stage RST. To drive.

  A reticle alignment system 22 is disposed above the reticle R. Although not shown in FIG. 1, the reticle alignment system 22 includes an epi-illumination system for illuminating a detection target mark with illumination light having the same wavelength as the exposure light, and an image of the detection target mark. And an alignment microscope for imaging. The alignment microscope includes an imaging optical system and an imaging device, and the imaging result of the alignment microscope is supplied to the main control system 20. Above the reticle stage RST (+ Z direction), a deflection mirror (not shown) for guiding the detection light from the reticle R to the reticle alignment system 22 is movably arranged. When the exposure sequence is started, the main control is performed. In response to a command from the system 20, the deflecting mirror is retracted out of the optical path of the exposure light IL integrally with the reticle alignment system 22 by a driving device (not shown). Note that a pair of reticle alignment systems 22 is arranged above the reticle. In FIG. 1, only one reticle alignment system 22 is shown.

  Projection optical system PL is arranged below reticle stage RST (−Z direction), and its optical axis AX is set parallel to the Z axis. As the projection optical system PL, a birefringent optical system having a predetermined reduction magnification (for example, 1/5 or 1/4) is used. For this reason, when the illumination area of the reticle R is illuminated by the exposure light IL from the illumination optical system, a reduced image (partial inverted image) of the pattern of the reticle R in the illumination area is resisted (photosensitized) on the surface by the projection optical system PL. (Agent) is projected onto the coated wafer W.

  Wafer stage WST is arranged on a base (not shown) provided below projection optical system PL (in the −Z direction). Wafer holder 25 is mounted on wafer stage WST, and wafer W is fixed on wafer holder 25 by, for example, vacuum suction. The wafer holder 25 can be tilted in an arbitrary direction with respect to a plane orthogonal to the optical axis AX of the projection optical system PL by a drive unit (not shown) and can be finely moved in the optical axis AX direction (Z direction) of the projection optical system PL. Has been. Further, the wafer holder 25 can also perform a minute rotation around the optical axis AX.

  Wafer stage WST is not only moved in the scanning direction (Y direction), but also in a direction perpendicular to the scanning direction so that a plurality of shot areas on wafer W can be positioned in an exposure area optically conjugate with the illumination area. It is also configured to be movable in the (X direction). This makes it possible to perform a step-and-scan operation that repeats an operation of scanning (scanning) exposing each shot area on the wafer W and an operation of moving to the exposure start position of the next shot area. Wafer stage WST is driven in the XY two-dimensional direction by wafer stage drive unit 24 including a motor and the like.

  The position of wafer stage WST in the XY plane is constantly detected by wafer laser interferometer (hereinafter referred to as wafer interferometer) 18 through movable mirror 17 with a predetermined resolution. Position information (or speed information) WPV of wafer stage WST is sent to main control system 20 via stage control system 19, and main control system 20 is based on this position information (or speed information) WPV and stage control system 19 Further, drive control of wafer stage WST is performed via wafer stage drive unit 24.

  A reference mark plate FM is fixed in the vicinity of wafer W on wafer stage WST. The surface of the reference mark plate FM is set to the same height as the surface of the wafer W, and a reference mark for alignment is formed on the surface. The reference mark plate FM is used to measure the relative positional relationship between the reticle R on the reticle stage RST and the wafer stage WST, and the baseline amount (the projection center of the projection optical system PL and the measurement center of the alignment microscope AS). Used to measure the distance).

  The alignment microscope AS is an off-axis type alignment sensor arranged on the side surface of the projection optical system PL. This alignment microscope AS is provided with an image sensor such as a CCD, for example, and outputs an image signal obtained by imaging a wafer alignment mark formed on the wafer W to the main control system 20. The wafer alignment mark includes a search alignment mark for measuring a rough position of the wafer W and a fine alignment mark for measuring the position of the wafer W with high accuracy.

  Next, the main control system 20 that performs overall control of the entire apparatus will be described. FIG. 2 is a block diagram showing a main configuration of the main control system 20. In FIG. 2, the data flow is indicated by solid arrows, and the control flow is indicated by dotted arrows. As shown in FIG. 2, the main control system 20 includes a main control device 30 and a storage device 40. The main control device 30 includes a control unit 31, an imaging data collection unit 32, and a mark detection unit 33.

  The control unit 31 controls the imaging data collection unit 32 and the mark detection unit 33 to obtain the mark position of the wafer alignment mark formed on the wafer W. Further, stage control data SCD for controlling wafer stage WST is generated based on position information (or velocity information) WPV from wafer interferometer 18 and the obtained mark position, and a stage control system for this stage control data SCD. 19 is controlled to control the operation of the exposure apparatus 100. The imaging data collection unit 32 collects imaging data IMD output from the alignment microscope AS. The mark detection unit 33 obtains the mark position of the wafer alignment mark from the collected imaging data IMD.

  The mark detection unit 33 includes a parameter information change unit 34, an aptitude level calculation unit 35, an aptitude level determination unit 36, a mark position calculation unit 37, and a feature information extraction unit 38. The parameter information updating unit 34 sets parameter information used when obtaining the mark position from the imaging data IMD obtained by observing the wafer alignment mark on the wafer W with the alignment microscope AS according to a predetermined rule (details will be described later). change. Here, the parameter information includes information on the shape (design value) of the wafer alignment mark (mark information) and information on the magnification of an optical system (not shown) provided in the alignment microscope AS (device information). At least one is included.

  The aptitude degree calculation unit 35 calculates the aptitude degree when the mark position of the wafer alignment mark is obtained using the changed parameter information based on the parameter information changed by the parameter information change unit 34 and the imaging data IMD. To do. The aptitude level determination unit 36 determines whether the aptitude level calculated by the aptitude level calculation unit 35 is equal to or greater than a preset threshold (predetermined standard). The mark position calculation unit 37 calculates the mark position of the wafer alignment mark based on the parameter information and the imaging data IMD when the aptitude degree determination unit 36 determines that the mark position is appropriate. The feature information extraction unit 38 performs image processing on the imaging data IMD, and extracts feature information indicating a characteristic shape in the vicinity of the wafer alignment mark.

  The storage unit 40 includes an imaging data storage area 41, a parameter information storage area 42, an aptitude degree storage area 43, an aptitude degree determination result storage area 44, and a mark position storage area 45. The imaging data storage area 41 stores imaging data IMD collected by the imaging data collection unit 32. The parameter information storage area 42 stores the parameter information (design value) described above and the parameter information changed by the parameter information changing unit 34, and the feature information extracted by the feature information extracting unit 38 is used as the mark position of the wafer alignment mark. Is stored together with the parameter information used in the mark position calculation unit 37. The aptitude degree storage area 43 stores the aptitude degree calculated by the aptitude degree calculation section 35, the aptitude degree judgment result storage area 44 stores the aptitude degree judgment result of the aptitude degree judgment section 36, and the mark position storage area 45 is a mark. The mark position of the wafer alignment mark obtained by the position calculation unit 37 is stored.

  In FIG. 2, the case where each block is configured in hardware and the main controller 30 is configured by combining these is illustrated as an example. However, in terms of hardware, the main control device 30 can be configured as a computer system, and the functions of the blocks constituting the main control device 30 can be realized by a program built in the main control system 20. When the main control device 30 is configured as a computer system, it is not always necessary to incorporate all the programs for realizing the functions of the respective blocks constituting the main control device 30 in the main control device 30 in advance. .

  For example, as shown by a dotted line in FIG. 1, a recording medium 28 storing a program for realizing the function of each of the above blocks is prepared, and the program contents can be read from the recording medium 28. 28 is connected to the main control system 20, and the main control system 20 reads the program content necessary for realizing the function from the recording medium 28 loaded in the reading device 27, and executes the read program. Can be configured to. Further, the main control system 20 can read the program contents from the recording medium 28 loaded in the reading device 27 and install it inside. Furthermore, it is also possible to adopt a configuration in which the program content necessary for realizing the function is installed in the main control system 20 via the communication network using the Internet or the like.

  As the recording medium 28, a magnetic recording medium (magnetic disk, magnetic tape, etc.), an electrical recording medium (PROM, RAM with battery backup, EEPROM, other semiconductor memory, etc.), magneto-optical Recording on a disc (magneto-optical disc, etc.), recording on an electromagnetic recording (digital audio tape (DAT), etc.), optical recording (compact disc (CD), DVD (registered trademark)), etc. What records in various recording forms is employable. As described above, it is possible to use a recording medium that records the program contents for realizing the functions and to install the program, so that the program contents can be modified later and the performance can be improved. Can be easily upgraded.

  Further, as shown in FIG. 1, in the exposure apparatus of the present embodiment, a display device 26 that displays the processing results of various processes performed in the main control system 20 and the apparatus status of the exposure apparatus 100 is connected to the main control system 20. Has been. Further, although not shown in FIG. 1, the exposure apparatus 100 transmits an imaging light beam for forming a plurality of slit images toward the best imaging surface of the projection optical system PL in the optical axis AX direction. An oblique incidence type multi-point comprising an irradiation optical system that is supplied obliquely with respect to the surface and a light receiving optical system that receives each reflected light beam of the imaging light beam on the surface of the wafer W through a slit. The focus detection system is fixed to a support portion (not shown) that supports the projection optical system PL. As this multipoint focus detection system, for example, one having the same configuration as that disclosed in Japanese Patent Laid-Open No. 5-190423 is used, and the stage control system 19 is based on the wafer position information from this multipoint focus detection system. Then, the wafer holder 25 is driven in the Z direction and the tilt direction.

  Next, the operation at the time of performing exposure processing of the second layer (second layer) and subsequent layers on the wafer W using the exposure apparatus 100 having the above configuration will be described. First, reticle R is loaded onto reticle stage RST by a reticle loader (not shown), and reticle alignment and baseline measurement are performed. Specifically, main control system 20 moves wafer stage WST via wafer stage drive unit 24 to position reference mark plate FM on wafer stage WST directly below projection optical system PL.

  Then, after detecting the relative position between the reticle alignment mark on the reticle R and the reference mark on the reference mark plate FM using the reticle alignment system 22, the wafer stage WST is moved to a predetermined amount, for example, a design value of the baseline amount XY. The reference mark on the reference mark plate FM is detected using the alignment microscope AS. At this time, the main control system 20 relates to the relative position relationship between the detection center of the alignment microscope AS and the reference mark, and the relative position between the reticle alignment mark and the reference mark on the reference mark plate FM measured in advance. The baseline amount is measured based on the measurement value of the interferometer 18.

When the above preparatory work is completed, the process of measuring the mark position of the alignment mark is performed according to the flowchart shown in FIG. Note that the flowchart shown in FIG. 3 is a flowchart showing a process when measuring a search alignment mark or a fine alignment mark formed on the wafer W. First, the number N _{w of} changing the width of the mark element constituting the search alignment mark, the variable amount S _{w of} the mark element width once, and the number of times of changing the magnification (scale) of the imaging data IMD obtained from the alignment microscope AS N _p, and variable amounts _{S p} of once magnification of the imaging data IMD is set by the operator (step S11).

Note that this step may be performed as one of the above-described preparation operations, and an initial value (default value) input in advance by the operator after the above preparation operation is completed is read and set. Also good. For example, set the magnification of the number N _w and imaging data IMD varying the width of the mark elements as the number of times N _p for varying values of "3", respectively, the value "1 as a variable amount S _w of once the width of the mark element .0 "is set, the value" 0.005 "is set as a variable quantity _{S p} of once magnification of the imaging data IMD.

  Next, the main control system 20 outputs a control signal to a wafer loader control system (not shown) to instruct loading of the wafer W. Thereby, wafer W is loaded onto wafer holder 25 on wafer stage WST by the wafer loader (step S12). Next, a process of imaging the Y mark SYM (see FIG. 4A), which is one of the search alignment marks formed on the wafer W, is performed.

  FIG. 4 is a plan view showing an example of the search alignment mark. As shown in FIG. 4, the search alignment mark includes a Y mark SYM and a θ mark SθM. As a premise, the search alignment mark including these is placed on the wafer W together with the reticle pattern during exposure to the previous layer. It is assumed that a transfer is formed. Although the search alignment mark is attached and transferred for each shot area SA shown in FIG. 4A, in the present embodiment, the rotation of the wafer W (with high accuracy by detecting few mark positions). In order to calculate the wafer rotation and the center position of the wafer W, as shown in FIG. 4A, two search alignments in which the distance in the X direction is long and the distance in the Y direction from the center position of the wafer W is long. Marks are employed as the Y mark SYM and the θ mark SθM.

  Further, in the present embodiment, as shown in FIG. 4B, line patterns SML1, SML2, SML3, and SML4 extending in the X direction as mark elements are used as search alignment marks, that is, Y marks SYM and θ marks SθM. It is assumed that line and space marks arranged in the direction are used. As shown in FIG. 4B, the Y mark SYM and the θ mark SθM have the same line width DLW as the line patterns SML1, SML2, SML3, and SML4 as shown in FIG. The intervals of SML2, SML3 and SML4 are the same interval DLD. Furthermore, in design, the boundary part (edge part) with the space part of each line pattern SML1, SML2, SML3, SML4 has the same shape. In this embodiment, a line and space mark having four line patterns is exemplified as a search alignment mark, but the number of lines in the line and space mark employed as a search alignment mark is as follows. The number is not limited to four and may be other numbers.

  When imaging the Y mark SYM, the main control system 20 sets the magnification of the alignment microscope AS to a low magnification, and in this state, the measurement of the wafer interferometer 18 is performed such that the Y mark SYM is positioned below the alignment microscope AS. While monitoring the value, wafer stage WST is moved via wafer stage drive unit 24 (step S13). And according to the instruction | indication from the control part 31 of the main control system 20, Y mark SYM is imaged with alignment microscope AS (step S14). Thus, the imaging data IMD is collected when the imaging data collection unit 32 stores the imaging data IMD within the observation field captured by the alignment microscope AS in the imaging data storage area 41 in accordance with an instruction from the control unit 31. The

  Next, the control unit 31 initializes variables s and t used in the subsequent processing (assigns a value “0” to each of s and t). Here, the variable s is a variable in which the number of times of changing the width of each line pattern SML1, SML2, SML3, SML4 constituting the Y mark SYM is set, and the variable t is each line pattern SML1, SML2, SML3, SML4. This is a variable in which the number of times the interval (pitch) is changed is set.

When the above initialization is completed, the parameter information changing unit 34 changes the width w _s and the interval p _t of the line patterns SML1, SML2, SML3, and SML4 using the following equations (1) and (2). Process.
w _s = w ₀ + (int) ((s + 1) / 2) · (−1) ^{((s + 1)% 2)} · S _w (1)
p _t = p ₀ + (int) ((t + 1) / 2) · (−1) ^{((t + 1)% 2)} · S _p (2)
Here, the operator (int) in the above expressions (1) and (2) is an operator for truncating the decimal point, and the operator “%” is a remainder operator. Also, _{w 0} is the line pattern SML1, SML2, SML3, initial width _{w s} of SML4 (here, the design value) is, _{p 0} is the line pattern SML1, SML2, SML3, the initial value of the distance _{p t} of SML4 (Design values here), which are stored in the parameter information storage area 42 in advance.

Here, since the values of the variables s and t are both set to “0” by the step S15, the right sides of the expressions (1) and (2) are w ₀ and p ₀ , respectively. When the parameter information change unit 34 by line pattern SML1, SML2, SML3, SML4 width _{w s} and spacing _{p t} of sought was determined value is stored in the parameter information storage area 42. Next, the aptitude degree of the width w _s and the interval p _t obtained in step S16 for calculating the mark position of the Y mark SYM is calculated by the aptitude degree calculation unit 35 (step S17).

The aptitude degree calculation unit 35 calculates the aptitude degree of the width w _s and the interval p _t obtained in step S16 based on the imaging data IMD stored in the imaging data storage area 41. FIG. 5 is a diagram illustrating an example of a signal waveform extracted by performing predetermined processing on the imaging data IMD. The signal waveform IP (YP) shown in FIG. 5 obtains the average of the intensity distribution on a plurality of (for example, 50) Y direction scanning lines near the center in the XP direction conjugate with the X direction on the wafer W in the imaging region. It is obtained by canceling white noise, obtaining an average signal intensity distribution in the YP direction, and further performing a smoothing process.

  As shown in FIG. 5, the signal waveform IP (YP) has four peaks PPKm corresponding to each of the line patterns SMLm (m = 1 to 4) shown in FIG. Here, the peaks PPKm have the same peak width WP. Further, the distance between the center position YP1 of the peak PPK1 in the YP direction and the center position YP2 of the peak PPK2 in the YP direction, and the distance between the center position YP2 of the peak PPK2 in the YP direction and the center position YP3 of the peak PPK3 in the YP direction. The distance and the distance between the center position YP3 of the peak PPK3 in the YP direction and the center position YP4 of the peak PPK4 in the YP direction are PW.

  Each peak PPKm has a mirror-symmetric shape with respect to its center position YPm. As a result, the shape of the peak PPK1 and the shape of the peak PPK2, the shape of the peak PPK2 and the shape of the peak PPK3, and the shape of the peak PPK3 and the shape of the peak PPK4 have translational symmetry with respect to the YP direction of the moving distance PW. Yes. In addition, the shape of the peak PPK1 and the shape of the peak PPK3, and the shape of the peak PPK2 and the shape of the peak PPK4 have translational symmetry with respect to the YP direction of the movement distance (2 × PW). Further, the shape of the peak PPK1 and the shape of the peak PPK4 have translational symmetry with respect to the YP direction of the movement distance (3 × PW).

  The shape of peak PPK1 is mirror-symmetric with respect to position YP1, the shape of peak PPK2 with respect to position YP2, the shape of peak PPK3 with respect to position YP3, and the shape of peak PPK4 with respect to position YP4. have. Further, the shape of the peak PPK1 and the shape of the peak PPK2 have mirror symmetry with respect to the midpoint position of the position YP1 and the position YP2, and the shape of the peak PPK2 and the shape of the peak PPK3 are the position YP2. It has mirror symmetry with respect to the midpoint position with respect to position YP3, and the shape of peak PPK3 and the shape of peak PPK4 have mirror symmetry with respect to the midpoint position between position YP3 and position YP4. is doing. Further, the shape of the peak PPK1 and the shape of the peak PPK3 have mirror symmetry with respect to the position YP2, and the shape of the peak PPK2 and the shape of the peak PPK4 have mirror symmetry with respect to the position YP3. In addition, the shape of the peak PPK1 and the shape of the peak PPK4 have mirror symmetry with respect to the midpoint position between the position YP2 and the position YP3.

In order to obtain the mark position of the Y mark SYM using the signal waveform IP (YP) having the above characteristics, the width w _s obtained in step S16 and the peak width WP of each peak PPKm of the signal waveform IP (YP) there coincident with the spacing of the center position YPm peak PPKm adjacent the spacing p _t determined in step S16 must match. Therefore, the aptitude degree calculation unit 35 determines the degree of coincidence between the width w _s obtained in step S16 and the peak width WP of each peak PPKm of the signal waveform IP (YP), and the interval p _t obtained in step S16. The degree of coincidence with the interval between the center positions YPm of the adjacent peaks PPKm is calculated, and this is calculated as the suitability. The calculated aptitude degree is stored in the aptitude degree storage area 43.

  Next, the aptitude degree determination unit 36 reads out the aptitude degree stored in the aptitude degree storage area 43, and determines whether or not the calculated aptitude degree exceeds a predetermined reference by determining whether or not it is equal to or greater than a preset threshold value. It is determined whether or not the condition is satisfied (step S18). When the determination result is “YES”, the aptitude degree determination unit 36 stores the aptitude degree used for the determination together with the determination result in the aptitude degree determination result storage area 44 (step S19). On the other hand, if the determination result in step S18 is “NO”, the aptitude degree determination result storage area 44 is not stored.

Next, the control unit 31, the value of the variable s is determined whether the equal _{N w} set in step S11 (step S20). If the determination result is “NO”, the value of the variable s is incremented (step S21). Then, the parameter information changing unit 34 uses the aforementioned (1) and (2), the line pattern SML1, SML2, SML3, performs a process of changing the width _{w s} and spacing _{p t} of SML4 (step S16). At this time, since the value of the variable s is “1” and the value of the variable t is set to “0”, the right side of the above expression (1) becomes (w ₀ + S _w ), and the expression (2) the right-hand side is the _{p 0} of. Then, similarly, w _s, adequacy of p _t is calculated (step S17), the calculated suitability whether satisfies a predetermined criterion is determined (step S18), and the determination result is "YES" In this case, the aptitude level used for the determination is stored in the aptitude level determination result storage area 44 together with the determination result (step S19).

When the value of the variable s by repeating the above process is equal to N _w, becomes "YES" determination result of the control unit 31 in step S20, the variable s value "0" is initialized is substituted (step S22 ). Next, the control unit 31 determines whether or not the value of the variable t is equal to _{N p} set in the step S11 (step S23). If the determination result is “NO”, the value of the variable t is incremented (step S24), and the processing from step S16 to step S22 is repeated in the same manner. When the value of the variable t is equal to N _p by repeating the above process, the determination result of the control unit 31 in step S23 becomes "YES".

By the processing described above, the variables s and t change as follows, and the right side of the above-described expressions (1) and (2) changes as follows in each combination of the variables s and t.
s = 0, t = 0: w ₀ , p ₀
s = 1, t = 0: w ₀ + S _w , p ₀
s = 2, t = 0: w ₀ −S _w , p ₀
s = 3, t = 0: w ₀ + 2 · S _w , p ₀
s = 0, t = 1: w ₀ , p ₀ + S _p
s = 1, t = 1: w ₀ + S _w , p ₀ + S _p
s = 2, t = 1: w ₀ −S _w , p ₀ + S _p
s = 3, t = 1: w ₀ + 2 · S _w , p ₀ + S _p
s = 0, t = 2: w ₀ , p ₀ −S _p
s = 1, t = 2: w ₀ + S _w , p ₀ −S _p
s = 2, t = 2: w ₀ −S _w , p ₀ −S _p
s = 3, t = 2: w ₀ + 2 · S _w , p ₀ −S _p
s = 0, t = 3: w ₀ , p ₀ + 2 · S _p
s = 1, t = 3: w ₀ + S _w , p ₀ + 2 · S _p
s = 2, t = 3: w ₀ −S _w , p ₀ + 2 · S _p
s = 3, t = 3: w ₀ + 2 · S _w , p ₀ + 2 · S _p
That is, the value of the width _{w s} of _(w 0 -S w) and the value was changed by _{S w} in the range up to _{(w 0 +2 · S w)} , the value of the distance _{p s (p} 0 _{-S p)} in combination with the value was changed by _{S p} in the range of up to _(p 0 +2 · _S p) from a width _{w s} used in order to calculate a mark position Y mark SYM, the adequacy of the interval _{p s} is calculated It is determined whether or not the suitability satisfies a predetermined standard.

When the determination result of the control unit 31 is “YES” in step S23, the mark position calculation unit 37 has the maximum aptitude stored in the aptitude determination result storage area 44 (signal waveform IP (YP) shown in FIG. 5). The mark position of the Y mark SYM is calculated using the width w _s closest to the peak width WP of each peak PPKm and the distance p _t closest to the distance between the center positions YPm of the adjacent peaks PPKm (step S25). .

  In order to obtain the mark position of the Y mark SYM, first, the signal waveform IP (YP) shown in FIG. 5 is obtained. Here, a case where the mark position calculation unit 37 extracts the signal waveform IP (YP) shown in FIG. 5 will be described as an example. However, in order to shorten the time required for the mark position calculation, an aptitude degree calculation unit is used. The signal waveform IP (YP) extracted at 35 may be temporarily stored and transferred to the mark position calculation unit 37. Next, the mark position calculation unit 37 defines four one-dimensional regions PFD1, PFD2, PFD3, and PFD4 that are sequentially arranged in the Y direction shown in FIG. FIG. 6 is a diagram showing a one-dimensional region used for obtaining the mark position.

The region PFDm (m = 1 to 4) shown in FIG. 6 has the same YP direction width PW (> WP), and in this embodiment, the center position YPP1 in the Y direction of the region PFD1 is a variable parameter. (Note that the variable parameters are not limited to the center position YPP1 in the Y direction of the area PFD1, and the center positions YPP2, YPP3, and YPP4 of the other areas PFD2, PFD3, and PFD4 may be used as variable parameters). Further, the distance between the center position YPP1 of the region PFD1 and the center position YPP2 of the region PFD2, the distance between the center position YPP2 of the region PFD2 and the center position YPP3 of the region PFD3, and the distance between the center position YPP3 of the region PFD3 and the center position YPP4 of the region PFD4 Are respectively set to PW1. YP width PW and the distance between adjacent regions PFDm (m = 1~4) region PFDm (m = 1~4) each with a width _{w s} and interval _{p t} suitability mentioned above is maximized Is set.

  Next, the mark position calculation unit 37 determines an initial position and an end position of scanning of the area PFDm, and sets the area PFDm as an initial position. In setting the initial position of the region PFDm, the initial parameter value YPP can be made sufficiently small. However, the initial parameter value YPP is expected to be a peak expected in design in a state immediately before imaging of the mark SYM. A value slightly smaller than the minimum value in the range of the peak position YP1 of PPK1 is desirable from the viewpoint of quick detection of the Y position of the mark SYM. In setting the scanning end position, the final parameter value YPP may be set to a sufficiently large value. However, the final parameter value YPP is set to the peak of the peak PPK1 that is expected in design in the state immediately before imaging of the mark SYM. A value slightly larger than the maximum value in the range of the position YP1 is desirable from the viewpoint of quick detection of the Y position of the mark SYM.

  Next, the region PFDm is scanned, and the positional relationship of the signal waveform IPm (YP) with respect to the region PFDm is changed as shown in FIG. FIG. 7 is a diagram illustrating a mark position detection method. As shown in FIGS. 7A to 7C, when the region PFDm is scanned, the position of the region PFDm with respect to the signal waveform IPm (YP) changes. In the present embodiment, while scanning the region PFDm, the mirror image conversion symmetry between the signal waveforms IPm (YP) is examined, and a plurality of translational symmetries and mirror symmetries are examined, thereby obtaining an image of the mark SYM. The YP position is detected. The details of this process are disclosed in the pamphlet of International Publication No. WO2002 / 033351.

  When the mark position of the Y mark SYM is measured, it is determined in the control unit 31 whether or not the mark measurement is completed (step S26). Here, since the case where the mark positions of the Y mark SYM and the θ mark SθM are measured is considered, the determination result is “NO” here. Next, the main control system 20 moves the wafer stage WST via the wafer stage driving unit 24 while monitoring the measurement value of the wafer interferometer 18 so that the θ mark SθM is positioned below the alignment microscope AS. In step S13, the θ mark SθM is imaged by the alignment microscope AS in accordance with an instruction from the control unit 31 (step S14). Thus, the imaging data IMD is collected when the imaging data collection unit 32 stores the imaging data IMD within the observation field captured by the alignment microscope AS in the imaging data storage area 41 in accordance with an instruction from the control unit 31. The Then, a process similar to the process of measuring the mark position of the Y mark SYM is performed to obtain the mark position of the mark SθM, and the series of processes shown in FIG. 3 ends.

  When the above processing is completed, the main control system 20 calculates the wafer rotation θs based on the position detection results of the Y mark SYM and the θ mark SθM, and then sets the magnification of the alignment microscope AS to a high magnification. Using the wafer rotation θs in the state, the wafer stage WST is sequentially moved via the wafer driving device 24 while monitoring the measurement value of the wafer interferometer 18 at a position where each fine alignment mark is directly below the alignment microscope AS. While positioning, each fine alignment mark is imaged using alignment microscope AS, and a mark position is measured from the imaging data. Even when this fine alignment mark is measured, it is preferable to perform the same processing as the processing in steps S13 to S26 shown in FIG.

  When the measurement of the fine alignment mark is completed, the main control system 20 uses a least square method as disclosed in, for example, Japanese Patent Application Laid-Open No. 61-44429 and US Pat. No. 4,780,617 corresponding thereto. Statistical calculation is performed to calculate six parameters of rotation θ, scaling in the X and Y directions SX and SY, orthogonality ORT, and offsets OX and OY in the X and Y directions related to the arrangement of each shot area on the wafer W. Next, the main control system 20 substitutes the above six parameters into a predetermined arithmetic expression to calculate the array coordinates of each shot area on the wafer W, that is, the overlay correction position.

  Thereafter, the main control system 20 sequentially steps the wafer W to the scanning start position for exposure of each shot area on the wafer W based on the obtained array coordinates of each shot area and the baseline amount measured in advance. Then, an operation of transferring the reticle pattern onto the wafer while the reticle stage RST and the wafer stage WST are synchronously moved in the scanning direction is repeated to perform an exposure operation by a step-and-scan method. Thereby, the exposure process for the wafer W is completed.

As described above, according to the present embodiment, the line patterns SML1, SML2, and SML3 are measured when measuring the mark positions of the wafer alignment marks (search alignment marks and further fine alignment marks) formed on the wafer W. mark using what is variable width w _s and spacing p _t of SML4, the suitability of the width was variable w _s and interval p _t is calculated based on the imaging data of the wafer alignment mark, suitability is maximum Position measurement is performed. For this reason, even if the shape of the wafer alignment mark formed on the wafer W is deviated from the shape indicated by the design value, or the actual magnification of the alignment microscope AS is different from the measurement value measured in advance, a measurement error is generated. The mark position can be detected without occurring.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. The configuration of the position measurement system of this embodiment is substantially the same as that of the first embodiment described above. In the first embodiment described above, were each wafer alignment mark formed on the wafer W line pattern SML1, SML2, SML3, the width _{w s} and spacing _{p t} of SML4 is varied. However, in the present embodiment, for example, in the wafer W at the head of the lot, as in the first embodiment, the line pattern width w _s and the interval _pt are changed for each wafer alignment mark formed on the wafer. Although the position is measured, in the second wafer W, basically, the mark position is measured by using the parameters (line pattern width w _s and interval p _t ) used for the mark position measurement on the wafer W at the head of the lot. The mark position is measured by changing the parameter only when a measurement error occurs.

  In the first embodiment described above, an algorithm for examining the mirror image conversion symmetry between the signal waveforms IPm (YP) is used as an algorithm for measuring the position of the wafer alignment mark. However, in this embodiment, the wafer alignment mark is used. Another difference is that an algorithm for measuring the position of the mark by checking the edge position of the line pattern as the mark element constituting the mark is used.

Hereinafter, an operation when performing exposure processing of the second layer (second layer) and subsequent layers on one lot of wafers W will be described. First, as in the first embodiment, preparatory work such as reticle alignment and baseline measurement is performed. The number N _{w of} changing the width of the mark element constituting the search alignment mark, the variable amount S _{w of} the mark element width once, and the number of times of changing the enlargement ratio (scale) of the imaging data IMD obtained from the alignment microscope AS. N _p, and variable amounts S _p of once magnification of the imaging data IMD is assumed to be preset.

  When the above preparatory work is completed, the process of measuring the mark position of the alignment mark is performed according to the flowchart shown in FIG. Note that the flowchart shown in FIG. 8 is a flowchart showing processing when measuring a wafer alignment mark formed on one wafer W. First, the main control system 20 outputs a control signal to a wafer loader control system (not shown) to instruct loading of the wafer W. Thus, the wafer loader loads the wafer W onto the wafer holder 25 on the wafer stage WST, and images a Y mark SYM (see FIG. 4A) that is one of the search alignment marks formed on the wafer W. Processing is performed (step S31).

  In this process, the main control system 20 sets the magnification of the alignment microscope AS to a low magnification, and in this state, the measurement value of the wafer interferometer 18 is set so that the Y mark SYM is positioned below the alignment microscope AS. While monitoring, wafer stage WST is moved via wafer stage drive unit 24. And according to the instruction | indication from the control part 31 of the main control system 20, the Y mark SYM is imaged with the alignment microscope AS. In this way, the imaging data collection unit 32 stores the imaging data IMD in the observation field captured by the alignment microscope AS in the imaging data storage area 41 in accordance with an instruction from the control unit 31, thereby collecting the imaging data IMD. Is done.

  Next, the control unit 31 determines whether or not the wafer W loaded on the wafer holder 25 is the first wafer in the lot (step S32). If the determination result is “YES”, variables s and t used in the subsequent processing are initialized (value “0” is substituted for each of s and t) (step S33). Here, as in the first embodiment, the variable s is a variable in which the number of times of changing the width of each line pattern SML1, SML2, SML3, SML4 constituting the Y mark SYM is set, and the variable t is each line. This is a variable in which the number of times the intervals (pitch) of the patterns SML1, SML2, SML3, and SML4 are changed is set.

When the above initialization is completed, the parameter information changing unit 34 changes the width w _s and the interval p _t of the line patterns SML1, SML2, SML3, and SML4 using the expressions (1) and (2) described above. Processing is performed (step S34). Here, since the values of the variables s and t are both set to “0” by the step S33, the right sides of the expressions (1) and (2) are w ₀ and p ₀ , respectively. When the parameter information change unit 34 by line pattern SML1, SML2, SML3, SML4 width _{w s} and spacing _{p t} of sought was determined value is stored in the parameter information storage area 42. Next, as in the first embodiment, the suitability degree of the width w _s and the interval p _t changed in step S 34 is calculated by the suitability degree calculation unit 35 and stored in the suitability degree storage area 43. Thereafter, the suitability degree determination unit 36 determines whether or not the suitability degree is equal to or greater than a preset threshold value. When the determination result is “YES”, the aptitude level used for the determination is stored in the aptitude level determination result storage area 44 together with the determination result.

  On the other hand, when the determination result is “NO”, the aptitude degree determination result storage area 44 is not stored. Then, the mark position calculation unit 37 calculates the mark position of the Y mark SYM based on the above determination result (step S35). Here, in the present embodiment, the mark position is obtained using the algorithm disclosed in Japanese Patent Laid-Open No. 2001-126981. This algorithm is to measure the mark position by checking the edge position of the line pattern as the mark element constituting the wafer alignment mark, and since it is already known, detailed description thereof is omitted here.

Next, it is determined whether or not a measurement error has occurred when the control unit 31 calculates the mark position (step S36). If the determination result is “NO”, the values of the variables s and t are substituted into the variables s _b and t _b , respectively (step S37). Here, the variables s _b and t _b are variables for storing the values of the variables s and t when the mark position is normally measured when measuring the mark position of the previous wafer alignment mark. is there. When the above processing is completed, the control unit 31 determines whether or not the mark measurement for one lot of wafers W has been completed (step S38). If this determination is “NO”, the process returns to step S31 to image another wafer alignment mark (for example, the θ mark SθM).

If a measurement error does not occur when measuring the wafer alignment mark formed on the wafer W at the head of the lot, the processes in steps S31 to S38 are performed in order. On the other hand, if a measurement error occurs during measurement of the wafer alignment mark formed on the wafer W at the head of the lot, the determination result in step S36 is “YES”, and values are set for the variables s and t. "0" is substituted and initialized (step S39). Next, the control unit 31 determines whether the variable s and the variable s _b are not equal, or whether the variable t and the variable t _b are not equal (step S40).

In the comparison between the variable s and the variable s _b and the comparison between the variable t and the variable t _b , if either or both are not equal, the determination result in step S40 is “YES”, and the above-described equation (1) and (2) using the formula, the line pattern SML1, SML2, SML3, processing for changing the width _{w s} and spacing _{p t} of SML4 is performed (step S41). On the other hand, if the determination result in step S40 is “NO”, a measurement error has already occurred in step S36, and the process of calculating the mark position is not performed (steps S41, S42, and S43 are omitted). Proceed to step S44.

When the determination result in step S40 is “YES” and the width w _s and the interval p _{t of the} line patterns SML1, SML2, SML3, SML4 are obtained by the parameter information changing unit 34 in step S41, the obtained values are stored in the parameter information. Whether the suitability degree of the width w _s and the interval p _t stored in the region 42 and changed in step S41 is calculated by the suitability degree calculation unit 35, and whether the suitability degree is _equal to or more than a preset threshold value by the suitability degree determination unit 36 It is determined whether or not. Next, when the determination result is “YES”, the aptitude degree used for the determination is stored in the aptitude degree determination result storage area 44 together with the determination result. On the other hand, when the determination result is “NO”, the aptitude degree determination result storage area 44 is not stored. Then, the mark position calculation unit 37 calculates the mark position of the Y mark SYM based on the above determination result (step S42).

Next, it is determined whether or not a measurement error has occurred when calculating the mark position by the control unit 31 (step S43). If the determination result is “NO”, the values of the variables s and t are assigned to the variables s _b and t _b , respectively (step S37), and whether or not the mark measurement of the wafer W for one lot is completed. Is determined by the control unit 31 (step S38). If this determination is “NO”, the flow returns to step S31 to image another wafer alignment mark (for example, the θ mark SθM).

On the other hand, the judgment result at Step S43 is "YES", the control unit 31 determines whether or not the value of the variable s is equal to the preset N _w (step S44). If this determination result is “NO”, the value of the variable s is incremented (step S45), the process returns to the process of step S40, and the line pattern is again used using the above-described expressions (1) and (2). A process of changing the width w _s and the interval p _t of SML1, SML2, SML3, and SML4 is performed (step S41). When the value of the variable s by repeating the above process is equal to N _w, becomes "YES" determination result of the control unit 31 in step S44, the variable s value "0" is initialized is substituted (step S46 ).

Next, the control unit 31 determines whether or not equal to N _p the value of the variable t is set in advance (step S47). If the determination result is “NO”, the value of the variable t is incremented (step S48), and the processing from step S40 to step S46 is repeated in the same manner. When the value of the variable t by repeating the above process is equal to N _p, it becomes "YES" determination result of the control unit 31 in step S23, the error end.

  If the measurement of all wafer alignment marks is completed for the wafer W at the head of the lot without completing the error, the determination result in step S38 is “YES”. In FIG. 8, the case where the search alignment mark is measured and the case where the fine alignment mark is measured are not shown separately. However, when the measurement of the search alignment mark is completed, the Y mark SYM and the θ mark are measured. Wafer rotation θs is calculated based on the position detection result of SθM, and the magnification of alignment microscope AS is set to a high magnification. In this state, the wafer rotation θs is used to position each fine alignment mark directly below the alignment microscope AS while monitoring the measurement value of the wafer interferometer 18 through the wafer driving device 24 and the wafer stage. The WSTs are sequentially positioned, each fine alignment mark is imaged using the alignment microscope AS, and processing according to the flowchart of FIG. 8 is performed from the imaged data to measure the mark position.

  When the measurement of the fine alignment mark is completed, as in the first embodiment, the main control system 20 is disclosed in, for example, Japanese Patent Application Laid-Open No. 61-44429 and US Pat. No. 4,780,617 corresponding thereto. Statistical calculation using the least square method is performed to calculate the array coordinates of each shot area on the wafer W. Thereafter, the main control system 20 sequentially steps the wafer W to the scanning start position for exposure of each shot area on the wafer W based on the obtained array coordinates of each shot area and the baseline amount measured in advance. Then, an operation of transferring the reticle pattern onto the wafer while the reticle stage RST and the wafer stage WST are synchronously moved in the scanning direction is repeated to perform an exposure operation by a step-and-scan method. Thereby, the exposure process for the wafer W is completed.

When the exposure process for the wafer W held on the wafer holder 25 is completed, the wafer W is unloaded and the next wafer W is loaded on the wafer holder 25. And the process according to the flowchart shown in FIG. 8 is performed, and the mark position is measured. However, since this wafer W is not the wafer at the beginning of the lot, the determination result in step S32 is “NO”, the value of variable s _b is substituted for variable s, and the value of variable t _b is substituted for variable t. (Step S49). Then, using the previously described in Step S34 (1) below and (2), the line pattern SML1, SML2, SML3, processing for changing the width _{w s} and spacing _{p t} of SML4 is performed.

That is, where at the time of measurement of the previous wafer alignment mark, is changed to a width w _s and spacing p _t when the measurement of the normal mark position is performed, step S35 by using the width w _s and spacing p _t To calculate the mark position. If no measurement error occurs in this process, the determination result in step S36 is “NO”, and the processes in steps S37 and S38 are performed in order. On the other hand, if a measurement error occurs, the determination result in step S36 is “NO”, and the processes in steps S39 to S48 are performed. When the measurement of the alignment mark formed on the wafer W is completed, the determination result in step S38 is “YES”, and the same exposure process as that for the wafer W at the head of the lot is performed.

As described above, in this embodiment, like the first embodiment, the width w _s and spacing p _t of the line pattern is varied, the wafer alignment the adequacy of the width was variable w _s and spacing p _t The mark position is measured using the mark with the maximum appropriateness, calculated based on the mark imaging data. For this reason, even if the shape of the wafer alignment mark formed on the wafer W is deviated from the shape indicated by the design value, or the actual magnification of the alignment microscope AS is different from the measurement value measured in advance, a measurement error is generated. The mark position can be detected without occurring. As a result, the throughput can be improved.

In the present embodiment, for the wafers W of the lot top as in the first embodiment, while varying the width w _s and spacing p _t of the line pattern for each wafer alignment mark formed on the wafer The mark position is measured. In the second and subsequent wafers W, the mark position is measured using the parameters (line pattern width w _s and interval p _t ) used at the time of mark position measurement on the first wafer W. The mark position is measured by changing the parameter only when a measurement error occurs. For this reason, the throughput can be further improved.

In the embodiment described above, the line pattern SML1, SML2, SML3, the width _{w s} and spacing _{p t} of SML4 is varied, the suitability of the width was variable _{w s} and interval _{p t} in the imaging data of the wafer alignment marks Based on this, the mark position measurement was performed using the one with the highest degree of appropriateness among these, but when the predetermined standard was met, the degree of suitability that met the standard You may make it perform mark position measurement using parameter information. Specifically, for example, in the first embodiment, when the suitability satisfies a predetermined standard (in the case of YES) in step S18 of FIG. 3, the process proceeds to step S20 after performing step S19. Instead, the process proceeds to step S25, and in step S25, the mark position is calculated using the parameter information related to the appropriateness degree that satisfies a predetermined criterion. In this way, the calculation process can be simplified and the efficiency of the process can be improved as compared to calculating the aptitude degree brute force.

As described above, when the wafer alignment mark is measured in the case where the parameter information relating to the suitability is used if the suitability is not brute force but a certain level or more is obtained, FIG. The feature information extraction unit 38 extracts feature information indicating a characteristic shape near the wafer alignment mark, and associates the extracted information with the width w _s and the interval p _t when the mark position is measured. When sequentially storing in the parameter information storage area 42 and measuring other wafer alignment marks, a shape that matches or is similar to the shape indicated by the feature information exists in the vicinity of the wafer alignment mark. The mark position can be measured using parameter information associated with the feature information. Specifically, for example, in the first embodiment, the width w associated with the feature information in the initial values (w ₀ , p ₀ ) in the expressions (1) and (2) in step S16 in FIG. _s, to perform the processing by substituting each interval p _t. In this way, the probability of finding parameter information that satisfies the predetermined criteria at an earlier stage in step S18 in FIG. 3 is increased, and the processing efficiency can be improved.

Further, in this case, as described above, the width w _s associated with the feature information in the initial values (w ₀ , p ₀ ) in the equations (1) and (2) in step S16 in FIG. instead of performing a process of substituting the spacing p _t respectively automatically be displayed on the display device 26 the information to alert the parameter information or the operator according to its characteristic information, the operator from the display result However, when measuring the next wafer alignment mark, it may be possible to select whether or not to use the value.

  A semiconductor element as a device is obtained by performing a function / performance design step of the device, a step of manufacturing a reticle based on the design step, a step of manufacturing a wafer from a silicon material, the exposure apparatus of the above-described embodiment, and the like. It is manufactured through a step of exposing and transferring a reticle pattern to a wafer, a device assembly step (including a dicing process, a bonding process, and a package process), an inspection step, and the like.

  The embodiment described above is described for facilitating understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention. For example, in the first embodiment described above, the mark position is measured using the one having the maximum appropriateness. However, the distribution of the appropriateness is obtained by performing statistical processing or the like, and the mark position is measured based on the result. You may make it do. In the above embodiment, the exposure apparatus 100 including the alignment microscope AS has been described as an example. However, the present invention can be applied to a position measurement apparatus or position measurement system including a detection unit similar to the alignment microscope AS. .

  In the above-described embodiment, the step-and-scan type exposure apparatus has been described as an example of the exposure apparatus, but the present invention can also be applied to a step-and-repeat type exposure apparatus. Also, not only exposure apparatuses used for manufacturing semiconductor elements and liquid crystal display elements, but also exposure apparatuses, reticles, and masks used for manufacturing plasma displays, thin film magnetic heads, and image sensors (CCD, etc.) are manufactured. Therefore, the present invention can also be applied to an exposure apparatus that transfers a circuit pattern to a glass substrate or a silicon wafer. In other words, the present invention can be applied regardless of the exposure method and application of the exposure apparatus.

  Furthermore, the present invention is also applicable to an immersion type exposure apparatus that fills the space between the projection optical system PL and the wafer W with a liquid. For example, as disclosed in JP-A-6-124873, an immersion exposure apparatus that moves a stage holding a substrate to be exposed in a liquid tank, or JP-A-10-303114 discloses. An immersion exposure apparatus that forms a liquid bath of a predetermined depth on such a stage and holds the substrate therein, and further an immersion exposure apparatus that locally fills the space between the projection optical system PL and the wafer W with the liquid. The present invention is also applicable to the present invention. Further, as disclosed in JP-A-10-163099, JP-A-10-214783, JP 2000-505958, etc., the present invention The present invention can also be applied to a twin-stage type exposure apparatus that includes two stages that can be separately moved in the XY directions by separately placing the substrates to be processed.

1 is a view showing a schematic configuration of an exposure apparatus according to a first embodiment of the present invention. It is a block diagram which shows the principal part structure of a main control system. It is a flowchart which shows the process in 1st Embodiment of this invention. It is a top view which shows an example of a search alignment mark. It is a figure which shows an example of the signal waveform extracted by performing a predetermined process with respect to imaging data. It is a figure which shows the one-dimensional area | region used in order to obtain | require a mark position. It is a figure which shows the detection method of a mark position. It is a flowchart which shows the process in 2nd Embodiment of this invention.

Explanation of symbols

34 ... Parameter information changing unit 35 ... Aptitude degree calculating unit 36 ... Aptitude degree determining unit 37 ... Mark position calculating unit 42 ... Parameter information storage area 100 ... Exposure apparatus AS ... Alignment microscope SYM ... Y mark S [theta] M ... [theta] mark W ... Wafer

Claims (8)

In a position measurement method for measuring the position of a mark formed on an object,
A detection step of detecting the mark using a mark detection device;
Including at least one of mark information relating to the shape of the mark and device information relating to the detection characteristics of the mark detection device, and using the parameter information whose setting value is automatically variable according to a predetermined rule, A calculation step of calculating the suitability of the parameter information based on the detection result of
A determination step of determining whether or not the suitability obtained in the calculation step satisfies a predetermined criterion;
A position calculation step of calculating the position of the mark based on the detection result in the detection step using the parameter information when it is determined that the predetermined criterion is satisfied in the determination step;
A position measurement method characterized by comprising: In the calculating step, the suitability is calculated for each case where the parameter information is changed according to the predetermined rule,
In the determining step, it is determined whether or not the degree of suitability for a predetermined processing algorithm used when calculating the mark position in the position calculating step satisfies the predetermined criterion,
The mark position is calculated using the parameter information in which the suitability is the highest value among the parameter information that satisfies the predetermined criterion in the position calculating step. Position measurement method.   The calculation step and the determination step are repeated while changing the parameter information in accordance with the predetermined rule until parameter information is determined in which the degree of suitability is determined to satisfy the predetermined criterion in the determination step. The position measuring method according to claim 1. A storage step of storing the parameter information used when calculating the mark position in the position calculation step together with the feature information of the object;
When a new object having the same feature information as the saved feature information is used for the mark position measurement, based on the saved parameter information, information about the saved parameter information is displayed, Alternatively, the stored parameter information is set as an initial value of the parameter information when the mark position on the new object is calculated. The position measuring method according to any one of claims 1 to 3. The mark is composed of a plurality of arrayed patterns,
The position measurement method according to claim 1, wherein the mark information includes at least one of a width and an arrangement pitch of the pattern. In a position measurement system that measures the position of a mark formed on an object,
A detection unit for detecting the mark;
A storage unit in which parameter information including at least one of mark information related to the shape of the mark and information related to detection characteristics of the detection unit is stored;
A parameter information changing unit for changing the parameter information stored in the storage unit according to a predetermined rule;
Based on the parameter information and the detection result by the detection unit, a calculation unit that calculates the appropriateness of the parameter information;
A determination unit that determines whether or not the suitability obtained by the calculation unit satisfies a predetermined criterion;
A position calculation unit that calculates the position of the mark based on the parameter information when the determination unit determines that the predetermined criterion is satisfied, and a detection result by the detection unit;
A position measurement system comprising: A storage unit for storing the parameter information used when calculating the mark position in the position calculation unit together with the feature information of the object;
When a new object having the same feature information as the saved feature information is used for the mark position measurement, an information display related to the saved parameter information is displayed on the display unit based on the saved parameter information. Or a control unit for setting the stored parameter information as an initial value of the parameter information at the time of calculating the mark position on the new object,
The position measurement system according to claim 6, further comprising: In a position measurement program applied to a position measurement device that measures the position of a mark formed on an object,
A first step of causing the mark detection device to detect the mark;
Using the parameter information that includes at least one of mark information related to the shape of the mark and device information related to the detection characteristics of the mark detection device, and whose set value is automatically variable according to a predetermined rule, A second step of calculating the suitability of the parameter information based on the detection result at
A third step of determining whether or not the suitability obtained in the second step satisfies a predetermined standard;
A fourth step of calculating the position of the mark based on the detection result in the detection step using the parameter information in the case where it is determined that the predetermined criterion is satisfied in the third step;
A position measurement program comprising:

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