JP2010040632A - Measurement condition optimization method and method of creating program, and aligner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To optimize measurement conditions of an efficient EGA sample mark. <P>SOLUTION: In measurement conditions of a sample mark used by enhanced global alignment (EGA), illumination conditions important for capturing an image signal of the mark are first optimized (step 206), and other measurement conditions are optimized under the optimized illumination conditions (step 208), thus suppressing the occurrence frequency of redoing of optimization. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a measurement condition optimization method, a program creation method, and an exposure apparatus, and in particular, the measurement is performed for statistical calculation using a predetermined model function for calculating array coordinates of a plurality of partitioned regions on a substrate. A measurement condition optimization method for optimizing the measurement conditions of sample marks attached to at least some sample partition areas of a plurality of partition areas in which information is used, a method for creating a program using the method, and the measurement conditions The present invention relates to an exposure apparatus suitable for carrying out an optimization method.

  Conventionally, in the lithography process in the manufacture of microdevices (such as electronic devices) such as semiconductor elements and liquid crystal display elements, step-and-repeat projection exposure apparatuses (so-called steppers), step-and-scan projection exposure apparatuses ( A so-called scanning stepper (also called a scanner)) is used relatively frequently.

  For example, a semiconductor element is formed by superimposing multiple layers of circuit patterns on a wafer as a sensitive substrate. Therefore, when forming circuit patterns for the second and subsequent layers on a wafer, circuit patterns are already formed on the wafer. It is necessary to accurately perform alignment between each shot area and the pattern image of the reticle, that is, alignment between the wafer and the reticle. A wafer alignment method in a conventional stepper or the like is roughly as follows (see, for example, Patent Document 1).

That is, chip patterns including alignment marks (alignment marks) are formed on a number of shot areas regularly arranged based on preset arrangement coordinates on a wafer to be processed. ing. At this time, an array coordinate value (FM _Xn , FM _Yn ) obtained by actual measurement for a plurality of shot areas selected from the wafer and a predetermined model formula including design array coordinate values for the corresponding shot area. The parameters in the model formula are determined using the method of least squares so that the average deviation from the calculated array coordinate values (F _Xn , F _Yn ) obtained based on the above is minimized. Conventionally, based on the determined parameters and the design array coordinate values (D _Xn , D _Yn ), the calculated array coordinate value (F) of the position to be actually aligned using the model formula. _Xn , F _Yn ) are calculated, and each shot area of the wafer is positioned based on the calculated coordinate values. Such a wafer alignment method is called EGA (enhanced global alignment).

  Further, the remaining rotation error θ of the circuit pattern (chip pattern) on each shot area of the wafer, the orthogonality error w of the coordinate system (chip pattern) on the wafer, and linear expansion / contraction rx, ry in two directions orthogonal to the chip pattern When it is necessary to consider the above, etc., a plurality of alignment marks are formed in each shot area, and a statistical calculation similar to the above is performed using a model formula including positional information on the design of these alignment marks. A so-called in-shot multipoint EGA is performed instead of the EGA (see, for example, Patent Document 2).

  When performing EGA or the like, it is important to accurately measure the position information of the alignment mark. To that end, the measurement conditions at the time of mark detection of the mark detection system (wafer alignment system) for detecting the alignment mark are as follows: Need to optimize. Conventionally, when a process program file (hereinafter also referred to as a recipe file) that defines a wafer alignment processing procedure is created, measurement conditions are optimized by an engineer.

  However, with recent exposure systems, the required alignment accuracy has become stricter. As a result, the types and sizes of alignment marks have diversified, and engineers can optimize measurement conditions when creating process program files. In addition, it is becoming difficult to optimize the measurement conditions.

US Pat. No. 4,780,617 JP-A-6-27596

  According to the first aspect of the present invention, the predetermined model for calculating the array coordinates of the plurality of partition regions, which is performed to form a pattern superimposed on the plurality of partition regions formed on the substrate. The measurement information is used for statistical calculation using a function, and is a measurement condition optimization method for optimizing the measurement conditions of sample marks attached to at least some sample partition areas of the plurality of partition areas, A first step of optimizing an illumination condition at the time of detection of the sample mark in an image processing type mark detection system used for detection of the sample mark attached to each partition area on the substrate; And a second step of optimizing measurement conditions other than the illumination conditions under the optimized illumination conditions.

  According to this, among the measurement conditions of the sample mark, an illumination condition that is important for capturing the image signal of the sample mark is first optimized, and under the optimized illumination condition, Optimization is performed. As a result, it is possible to suppress the occurrence frequency of optimization redo.

  According to the second aspect of the present invention, the optimum condition determined by the measurement condition optimization method of the present invention is calculated using a statistical calculation using a predetermined model function for calculating the array coordinates of the plurality of partition regions. There is provided a method for creating a program including a step of determining as a corresponding condition in a program that defines a processing procedure of a series of measurements.

  According to a third aspect of the present invention, there is provided an exposure apparatus that forms a pattern on a plurality of partitioned areas on a substrate by superimposing a predetermined model function for calculating array coordinates of the plurality of partitioned areas. An image processing method in which the measurement information is used for the statistical calculation used, and a mark including a sample mark attached to at least a part of the plurality of divided areas is a detection target, and at least the illumination condition can be changed A mark detection system; and an optimization device that optimizes illumination conditions at the time of detection of the sample mark of the mark detection system, and optimizes measurement conditions other than the illumination conditions under the optimized illumination conditions; An exposure apparatus is provided.

  According to this, among the measurement conditions of the sample mark, the optimization condition that is important for capturing the image signal of the sample mark is first optimized by the optimization device, and under the optimized illumination condition, Other measurement conditions are optimized. As a result, it is possible to suppress the occurrence frequency of optimization redo.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of an exposure apparatus 100 according to an embodiment that can suitably implement the optimization condition determination method of the present invention. The exposure apparatus 100 is a step-and-scan projection exposure apparatus (so-called scanning stepper (also called a scanner)).

  The exposure apparatus 100 includes an illumination system IOP, a reticle stage RST that holds a reticle R, a projection unit PU that projects a pattern image formed on the reticle R onto a wafer W coated with a sensitive agent (resist), and a wafer W. A wafer stage WST that holds and moves in the XY plane, a drive system 22 that drives the wafer stage WST, and a control system thereof are provided. The control system is mainly composed of a main controller 28 including a microcomputer (or a workstation) that performs overall control of the entire apparatus.

  The illumination system IOP includes a light source composed of, for example, an ArF excimer laser (output wavelength 193 nm) (or KrF excimer laser (output wavelength 248 nm)), and an illumination optical system connected to the light source via a light transmission optical system. As an illumination optical system, as disclosed in, for example, US Patent Application Publication No. 2003/0025890, an illuminance uniformizing optical system including an optical integrator, a beam splitter, a reticle blind, and the like (all not shown) are used. In addition, the laser beam emitted from the light source is shaped, and this shaped laser beam (hereinafter also referred to as illumination light) IL is elongated in the X-axis direction (the direction perpendicular to the plane of FIG. 1) on the reticle R. The illumination area is illuminated with almost uniform illuminance.

  Reticle stage RST is arranged below illumination system IOP in FIG. Reticle R is placed on reticle stage RST. The reticle R is sucked and held on the reticle stage RST via a vacuum chuck or the like (not shown). Reticle stage RST can be finely driven in a horizontal plane (XY plane) by a reticle stage drive system (not shown), and is predetermined in the scanning direction (here, the Y-axis direction which is the horizontal direction in FIG. 1). Scanned in the stroke range. Position information of the reticle stage RST is measured by the laser interferometer 14 via the movable mirror 12 fixed to the end thereof, and the measurement value of the laser interferometer 14 is supplied to the main controller 28. Instead of the movable mirror 12, the end surface of the reticle stage RST may be mirror-finished to form a reflective surface (corresponding to the reflective surface of the movable mirror 12).

  Projection unit PU is arranged below reticle stage RST in FIG. The projection unit PU includes a lens barrel 40 and a projection optical system PL that includes a plurality of optical elements held in the lens barrel 40 in a predetermined positional relationship. Here, as the projection optical system PL, a bilateral telecentric reduction system is used, and a refractive optical system including a plurality of lens elements (not shown) arranged in a direction parallel to the optical axis AXp (Z-axis direction) is used. It has been.

  The projection magnification of the projection optical system PL is ¼ as an example. For this reason, when the reticle R is illuminated with uniform illumination by the illumination light IL as described above, the pattern of the reticle R in the illumination area is reduced by the projection optical system PL, and is applied onto the resist-coated wafer W. Projected, and a reduced image of the pattern is formed in a part of the exposed area (shot area) on the wafer W. At this time, the projection optical system PL forms a reduced image in a part of its field of view (that is, an exposure area that is a rectangular area conjugate with the illumination area with respect to the projection optical system PL).

  Wafer stage WST is driven with a predetermined stroke in the X-axis direction and Y-axis direction by a drive system 22 including a linear motor and the like, and also rotates in the Z-axis direction, the rotation direction around the X-axis (θx direction), and the rotation around the Y-axis. It is micro-driven in the rotational direction (θy direction) and the rotational direction around the Z axis (θz direction). Wafer W is held on wafer stage WST by vacuum suction or the like via a wafer holder (not shown).

  The position information of wafer stage WST is measured by a laser interferometer system (hereinafter abbreviated as “interferometer system”) 26 via a movable mirror 24 fixed to the end of the wafer stage WST. Is supplied to the main controller 28. Based on the measurement value of interferometer system 26, main controller 28 determines positional information (rotation information (yaw amount (rotation amount θz in θz direction), pitching amount (rotation amount in θx direction) of wafer stage WST). θx) and the amount of rolling (including the amount of rotation θy in the θy direction)). Note that the end surface of wafer stage WST may be mirror-finished to form a reflecting surface (corresponding to the reflecting surface of movable mirror 24). Further, instead of wafer stage WST, a first stage that moves in the X-axis direction, the Y-axis direction, and the θz direction, and a second stage that finely moves in the Z-axis direction, θx direction, and θy direction on the first stage. A stage may be used.

  The measurement value of the interferometer system 26 is supplied to the main controller 28, and the main controller 28 determines the position of the wafer stage WST in the XY plane (in the θz direction) via the drive system 22 based on the measurement value of the interferometer system 26. Control (including rotation).

  Further, the position and the tilt amount of the surface of the wafer W in the Z-axis direction can be determined by, for example, an oblique incidence type multi-point focal point having a light transmission system 50a and a light reception system 50b disclosed in US Pat. It is measured by a focus sensor AFS comprising a position detection system. The measurement value of the focus sensor AFS is also supplied to the main controller 28.

  On the wafer stage WST, a reference plate FP is fixed so that the surface thereof is the same height as the surface of the wafer W. On the surface of the reference plate FP, a reference mark used for so-called baseline measurement of an alignment detection system AS described later is formed.

  An alignment detection system AS that detects the alignment mark formed on the wafer W and the reference mark is provided on the side surface of the lens barrel 40 of the projection unit PU. As an example of the alignment detection system AS, a kind of image-forming type alignment sensor that measures a mark position by illuminating a mark with broadband light such as a halogen lamp and processing the mark image. The FIA (Field Image Alignment) system is used.

  The detection signal of the alignment detection system AS is supplied to the alignment control device 16, and the alignment control device 16 performs A / D conversion on the detection signal and arithmetically processes the digitized waveform signal to detect the mark position. . This result is supplied from the alignment controller 16 to the main controller 28.

  In this embodiment, an alignment detection system AS that can change at least the illumination condition and change (or switch) the focus offset (that is, alignment autofocus) is used. The illumination condition can be changed by switching at least one of an illumination band (illumination light wavelength band), an illumination stop, and an ND filter (neutral density filter). As an illumination light wavelength band, for example, four illumination bands of broad, green, orange, and red can be set. Further, it is assumed that at least three circular diaphragms and annular diaphragms having different diameters are provided so as to be switchable as illumination lamps. In addition, as a light reduction device having an ND filter, for example, a device having a three-stage rotating plate is used, and each rotating plate is provided with a plurality of ND filters having different transmittances (light reduction rates). . The transmittance can be switched and set to each% of 3, 6, 10, 15, 20, 30, 50, 100 by the dimming device. The ND filter having a transmittance of 100% is an opening formed in a filter plate to which a plurality of ND filters are attached. The illumination condition and the focus offset are changed by the alignment control device 16 based on an instruction from the main control device 28.

  Further, in the exposure apparatus 100 of this embodiment, although not shown, light having an exposure wavelength disclosed in, for example, US Pat. No. 5,646,413 is used above the reticle R. A pair of reticle alignment detection systems comprising a TTR (Through The Reticle) alignment system is provided, and detection signals of the reticle alignment detection system are supplied to the main controller 28 via the alignment controller 16.

  Next, with respect to the optimization condition determination method at the time of alignment performed prior to actual exposure by the exposure apparatus 100 according to the present embodiment configured as described above, the main controller 28 (more precisely, the internal The processing algorithm of the CPU will be described along the flowchart of FIG. As a premise, it is assumed that the flag F indicating whether or not the optimization measurement error processing described later has already been performed has been lowered (F = 0).

  First, in step 202, a wafer is loaded onto a wafer holder (not shown) mounted on wafer stage WST using a wafer loader (not shown). Here, at least one layer of reticle pattern, which is actually used for manufacturing a device, is transferred, and at that time, a wafer W on which a search alignment mark and a fine alignment mark are formed is loaded on the wafer holder. In each shot area on the wafer W (more precisely, on the scribe line around it), one X search alignment mark, Y search alignment mark, two X fine alignment marks (XEGA mark), and Y fine alignment. Marks (YEGA marks) are respectively formed. When a two-dimensional mark is used as the fine alignment mark (EGA mark), it is sufficient that two two-dimensional marks are provided in each shot area. It is assumed that a line and space pattern (multibar pattern) formed at a predetermined pitch in the X-axis direction or the Y-axis direction is used as the search alignment mark and fine alignment mark. In addition, design parameters (shape, number, position, etc.) of search alignment mark and fine alignment mark, and wafer design parameters (wafer size, layout of layout area, etc.) are determined in advance, Assume that it is stored in a memory (not shown) prior to the optimization process.

  In the next step 204, search alignment of the wafer loaded on the wafer holder is performed. Specifically, for example, two Y search alignment marks and one X search alignment mark positioned in the peripheral portion substantially symmetrically with respect to the wafer center are detected using the alignment detection system AS. Detection of these search alignment marks is performed while sequentially positioning wafer stage WST so that each search alignment mark is positioned within the detection field of alignment detection system AS. Based on the detection result of the alignment detection system AS (relative positional relationship between the index center of the alignment detection system AS and each search alignment mark) and the measurement value of the interferometer system 26 when each search alignment mark is detected, three searches are performed. The position coordinate of the alignment mark on the stage coordinate system is obtained. Thereafter, the wafer center deviation and the residual rotation error are calculated from the position coordinates of the three search alignment marks, and the wafer stage WST (or wafer holder) is slightly rotated so that at least the residual rotation error becomes substantially zero. This completes the wafer search alignment.

  After the search alignment is completed, optimization measurement of fine alignment, here, EGA (Enhanced Global Alignment) is started. Specifically, in step 206, ND optimization (optimization of illumination conditions) is performed for each illumination band. Here, the optimization of illumination conditions is specifically performed as follows. That is, the main control device 28 gives one of the above four illumination bands, changes the illuminance (ND filter) in the given illumination band, and uses the alignment detection system AS to set the initial focus position. The EGA first sample mark (first sample shot area first mark) is detected at (alignment autofocus driving position). Then, main controller 28 optimizes the illuminance (finds the optimum illuminance) by finding the illuminance at which the contrast of the obtained imaging signal is maximized. Here, if the contrast at the optimum illuminance is within the allowable range, the optimization process is successful, and if the contrast is outside the allowable range (including the case where the optimum illuminance is not determined), it is determined as failure. Similarly, the illuminance is optimized for the other illumination bands. The diaphragm may be switched to obtain the optimum illumination condition, but the diaphragm may remain fixed.

  In the next step 208, alignment AF (alignment autofocus) is performed under each illumination condition that has succeeded in ND optimization (optimum ND condition for each illumination band) to obtain a focus offset.

  In the next step 210, EGA measurement for measuring all EGA sample marks on the wafer under all determined measurement conditions is performed once.

  In the next step 212, it is determined as a result of the processing in step 210 whether or not there is a condition for one or more conditions for successful EGA measurement. Here, “successful EGA measurement” means that measurement of a predetermined number of EGA sample marks does not include a measurement error.

  If there is a condition for successful EGA measurement for one or more conditions, the process proceeds to a subroutine of the result determination process in step 214. In this result determination processing subroutine, the condition for successful EGA measurement is the result determination target.

  On the other hand, if there is no condition for successful EGA measurement, that is, if any error occurs under all conditions, the process proceeds to step 216 to determine whether or not the flag F is set (F = 1). In this case, since the flag F has been lowered (F = 0), the process proceeds to the optimization measurement error processing subroutine of step 220.

  In the optimization measurement error processing subroutine, first, the number of screens (the number of captured screens) is set to 10 in step 222 in FIG. 4, and then the process proceeds to step 224 to set a flag F (F ← 1). Thereafter, the process returns to step 210 of the main routine. Here, the number of screens is normally set to 2 screens. Increasing this to 10 screens may be caused by the signal contrast being too low as a cause of error occurrence. Because it is effective. Note that the number of screens is set to 10 because the integrated value of the signal intensity is five times as an example, and is not limited to this, and the number of screens may be optimized.

  In step 210, as described above, the above-described EGA measurement is performed once under all the illumination conditions previously determined. However, the measurement in this case is performed with 10 captured screens.

  In step 212, it is determined whether or not there is a condition for successful EGA measurement for one or more conditions. If the determination here is negative, the process proceeds to step 216. In step 216, it is determined whether or not the flag F = 1. At this time, since the flag F = 1, the determination in step 216 is affirmed, and the process proceeds to step 218 to check the coordinates and mark dimensions. After outputting the prompt message, the process proceeds to the assist process (manual assist process) in step 219.

  In the assist process, the operator notifies the operator that “the optimization process cannot be continued any more” or by voice, and displays a selection screen for “abnormal termination” and “continue”.

  When the abnormal termination is selected, the main controller 28 does not save the optimum result. If continue is selected, the data is forcibly saved regardless of whether the optimization is determined. In this case, however, the fact that the optimization has failed can be recorded as the contents of the optimization result, and a warning can be issued when an actual job is executed or a recipe file is selected.

  After the assist process, the series of processes in this routine is terminated.

  Note that a display of a “change layout” selection screen may be added as an assist process. In this case, the operator sees this message and changes the EGA shot layout, for example. In this case, the optimization operation may be redone for the changed EGA shot layout.

  On the other hand, in the result determination processing subroutine at step 214, first, at step 226 in FIG. 3, it is determined whether or not the standard mode is set. In this embodiment, two modes of “standard” and “minimum value priority” are prepared, and the operator can arbitrarily select these modes. Here, the standard mode means a mode in which a determination is made to achieve both a small value of the EGA random 3σ described later and a small absolute value of the difference between the EGA random 3σ in the X-axis direction and the Y-axis direction. The minimum value priority mode means a mode in which priority is given to the one including the minimum value of the EGA random 3σ regardless of the X-axis direction and the Y-axis direction.

  Here, when the standard mode is selected, the determination in step 226 is affirmed, and the process proceeds to step 228. In step 228, the larger value of the EGA random 3σ in the X-axis and Y-axis directions of each condition is rearranged in ascending order (sorted).

  Here, the EGA random 3σ will be briefly described.

  In the present embodiment, it is assumed that wafer alignment is performed by so-called multi-point EGA in a shot, and this will be described on the assumption. The in-shot multipoint EGA is disclosed in detail in, for example, Japanese Patent Application Laid-Open No. Hei 6-27596.

  In the shot multipoint EGA, a model formula represented by the following formula (1) is used as an example.

In Formula (1), F _NXn and F _NYn are the X coordinate and Y coordinate of the position where the Nth alignment mark of the nth shot region should actually be on the stage coordinate system (X, Y).

  Rx and Ry are linear expansion and contraction (wafer scaling) in the α and β directions in the wafer coordinate system (α, β). The α direction and the X-axis direction, and the β direction and the Y-axis direction do not exactly match, but are substantially the same direction. However, the wafer scaling Rx in the α direction is the ratio of the measured value between the two points in the α direction on the wafer W and the designed value, and the wafer scaling Ry in the β direction is the measured value and the designed value between the two points in the β direction. And expressed as a ratio.

W is an orthogonality error (orthogonality of the stage coordinate system (X, Y)), and Θ is a residual rotation error (α, β) of the wafer coordinate system (α, β) with respect to the stage coordinate system (X, Y). Wafer rotation). Further, C _Xn and C _Yn are the design X coordinate and Y coordinate of the reference point of the nth shot region.

O _X and O _Y are offset amounts (offsets of the coordinate system (α, β) on the wafer with respect to the stage coordinate system (X, Y)) in the X axis direction and the Y axis direction.

  Rx and ry are linear expansion and contraction (chip scaling) of the chip (shot area). Here, the chip scaling rx in the x direction in the coordinate system (shot coordinate system) (x, y) on the shot area is the ratio between the measured value of the distance between two points in the x direction and the design value, and the chip in the y direction. Scaling ry is represented by the ratio between the measured value of the distance between two points in the y direction and the design value.

Further, w is an angle error (chip pattern orthogonality error), and θ is a chip pattern rotation (rotation error with respect to the coordinate system (x, y) of the shot area). S _NXn and S _NYn are the designed x-coordinate and y-coordinate on the coordinate system (x, y) of the Nth alignment mark.

In EGA measurement, out of a plurality of EGA marks attached to a plurality of shot areas on the wafer W, the number of EGA marks (in the case of a one-dimensional mark) exceeding the total number of parameters of the above model formula (here, 10). The sample mark is detected by using the alignment detection system AS, the position of the sample mark in the stage coordinate system (X, Y) is obtained, and the obtained equation (1) is obtained by using the obtained position of each sample mark. ) 10 parameters (Rx, Ry, Θ, W, O _X , O _Y , rx, ry, θ, w) are obtained, and the obtained parameters are substituted into the expression (1) to obtain each sample mark. The position (calculation position) that should actually be on the stage coordinate system (X, Y) is obtained, and the difference (residual) between this position and the actually measured position is obtained for all sample marks. Number 3 times the standard deviation σ calculated for residuals (sample marks number), an EGA random 3 [sigma]. The EGA random 3σ is obtained for each condition in the X-axis direction and the Y-axis direction.

  However, it is also conceivable that the evaluation values (the larger value of the EGA random 3σ in the X-axis direction and the Y-axis direction) of the plurality of conditions become the same. In such a case, the main controller 28 determines in step 228. Thus, the absolute values of the differences between the EGA random 3σ in the X-axis direction and the Y-axis direction are rearranged (sorted).

  On the other hand, if the minimum value priority mode is selected, the determination at step 226 is negative and the routine proceeds to step 230. In step 230, the smaller value of the EGA random 3σ in the X-axis direction and Y-axis direction of each condition is rearranged in ascending order as an evaluation value. However, in this case as well, it is conceivable that the evaluation values of a plurality of conditions are the same. In such a case, the main control device 28 rearranges (sorts) the EGA random 3σ of the other axis in ascending order. ).

  Then, after step 228 or 230, in step 232, it is determined whether or not the numerical values of both axes (the values of EGA3σ in the X and Y axis directions) all coincide with each other under the uppermost multiple conditions. If this determination is affirmative, that is, if the values of EGA3σ in the X and Y axis directions are at least partly different under the uppermost multiple conditions, the routine proceeds to step 236.

On the other hand, if the determination in step 232 is negative, that is, if the values of EGA3σ in the X and Y axis directions all match with each other in the uppermost plurality of conditions, the process proceeds to step 234. In step 234, the plurality of conditions are rearranged in ascending order using the maximum reproducibility (3σ) to be determined as an evaluation value. Here, the determination target is 10 pieces of Expression (1) calculated by the least square method using the positions of each sample mark obtained as a result of the EGA measurement in the stage coordinate system (X, Y). 8 parameters (Rx, Ry, Θ, W, O _X , O _Y , rx, ry, θ, w) excluding offsets O _X and O _Y are meant.

  In this case as well, it is conceivable that the evaluation values are the same. In such a case, the evaluation values are rearranged in ascending order with the smallest reproducibility (3σ) to be determined. Thereafter, the process proceeds to step 236.

  In step 236, it is determined whether or not the evaluation value (EGA random 3σ or the above-described reproducibility of the determination target (3σ)) of the highest condition is equal to or less than each allowable value. Here, as the allowable value, one stored in a predetermined storage area is used. In the present embodiment, the allowable value is different for each evaluation mode, that is, for each route to step 236.

  For example, when the determination is performed in the above-described standard mode or minimum value priority mode, that is, in the case of steps 226 → 228 (or 230) → 232 → 236, the allowable values in the evaluation of the EGA random 3σ (by default, X, Y Both are 20 [nm]).

  For example, when the determination is performed in the EGA reproducibility evaluation mode, that is, in the case of steps 232 → 234 → 236, an allowable value in the EGA reproducibility evaluation (wafer parameters (Rx, Ry, Θ, W in the default setting) ) Is 0.03, for example, and shot parameters (rx, ry, θ, w) are each 0.3, for example).

  If the determination in step 236 is negative, the process proceeds to a sub-routine for the allowable accuracy value error process in step 240. In this subroutine, first, in step 252 of FIG. 5, after setting the number of screens (the number of captured screens) to 10 screens, in step 254, EGA measurement is performed once under the conditions, and then the process returns to step 242 of the main routine. . Here, the reason why the number of screens is increased is that it is considered that a decrease in measurement reproducibility (low contrast) and an erroneous measurement (dimension change) occur for the same reason as in the case of a measurement error.

  In step 242, it is determined whether or not the evaluation value of the condition exceeds the allowable value. If this determination is affirmative, that is, if an allowable value error occurs again, the process proceeds to step 244 to output a message for confirming the coordinates and mark dimensions, and then the assist process (manual The process proceeds to assist processing. The contents of the assist process in step 246 are the same as in step 219 described above.

  On the other hand, if the determination in step 236 is affirmed, or if the determination in step 242 is negative, the process proceeds to step 248 to save the optimization result. Thereby, at least the conditions such as the optimum illumination condition and the optimum focus offset of the alignment detection system AS at the time of the alignment of the wafer are stored.

  In this way, after the above optimization result storage or assist process is performed, the subroutine 214 is terminated and the process returns to the main routine, and then a series of processes for determining optimization conditions during alignment is terminated.

  When the optimization result is saved, the main controller 28 creates an EGA (wafer alignment) recipe file using the optimum conditions determined by the optimization. This recipe file can be created easily by preparing a recipe file in which the numerical value of the condition to be optimized is blank and applying the optimum condition determined to the blank of this recipe file. it can.

  Thus, in actual wafer processing, the main controller 28 reads out the created recipe file, and based on this recipe file, fine alignment of the wafer (here, multi-point EGA within a shot), It becomes possible to carry out reliably and accurately.

  Further, in the exposure apparatus 100 of the present embodiment, the fine alignment of the wafer can be performed with high accuracy as described above. Therefore, the pattern of the reticle R is applied on the wafer W during the exposure based on the result of the fine alignment. It is possible to accurately superimpose and transfer to each shot area.

  As described above, according to the exposure apparatus 100 of the present embodiment, the main controller 28 optimizes the illumination conditions when detecting the EGA mark of the alignment detection system AS (step 206), and then optimizes the illumination conditions. Under the illumination conditions, measurement conditions other than the illumination conditions, specifically, the focus offset in the alignment focus is optimized (step 208). As a result, it is possible to suppress the occurrence frequency of optimization redo as much as possible.

  Further, according to the exposure apparatus 100, the main controller 28 determines in advance a plurality of shot areas on the wafer W under all conditions (measurement conditions) determined by optimizing the illumination conditions and optimizing the focus offset. EGA measurement for sequentially detecting position information of EGA marks (sample marks) attached to a plurality of shot areas (sample shot areas (also referred to as alignment shot areas)) using the alignment detection system AS (step 210), It is determined whether or not the measurement has succeeded with respect to one or more of the determined conditions (step 212), and the conditions determined to have succeeded in the EGA measurement as a result of the determination are evaluated according to a predetermined evaluation standard, and the optimum Conditions are determined (step 214). Therefore, the exposure apparatus 100 can determine the optimum measurement conditions in the EGA measurement almost completely automatically without the need for manual operation by an operator (or engineer) or the like.

  Further, according to the exposure apparatus 100 of the present embodiment, the main controller 28 determines the determined optimum conditions as corresponding conditions in a process program (recipe file) that defines the processing procedure of EGA measurement. Create a recipe file for EGA measurement. This makes it possible to create an EGA measurement recipe file that includes optimum measurement conditions corresponding to the EGA mark almost completely automatically.

  In the above-described embodiment, the case where the optimization method according to the present invention is performed when creating a recipe file has been described. However, the present invention is not limited to this, and a pilot wafer or a lot is processed during actual wafer processing. The measurement conditions of the above EGA measurement may be optimized using the leading wafer or the like.

  In the above embodiment, EGA random 3σ is evaluated in step 228 or 230, and as a result, only when the evaluation values are the same for the X axis and the Y axis under a plurality of conditions and cannot be determined. Although the reproducibility evaluation (step 234) is performed, an execution / non-execution switch is provided, and when execution is selected with the switch, the EGA reproducibility evaluation is forcibly executed. It is also possible. In this case, the evaluation target is all conditions. In the case of forced execution, judgment evaluation is performed but the evaluation result is not adopted. However, it is possible to leave the result in the log and refer to it later.

  In the above embodiment, in the optimization measurement error process, the case where the number of captured screens is increased with the intention of taking measures against the signal contrast being too low has been described. It is also possible that the standard setting has changed too much. As a countermeasure in such a case, the mark parameter may be optimized.

  In the above embodiment, the illumination condition and the focus offset are targeted for optimization. However, the present invention is not limited to this, and for example, a signal processing algorithm or other measurement conditions for mark detection may be targeted for optimization.

  When optimizing measurement conditions including a signal processing algorithm, it is possible to perform optimal measurement with an optimal algorithm for any input (mark). Therefore, the operator only has to input the minimum information such as the dimension of the mark, for example, so that the apparatus automatically sets the optimum measurement conditions according to the mark and thus creates the measurement recipe file. Is also possible.

  In the above embodiment, the exposure apparatus creates an EGA recipe file and optimizes the measurement conditions. However, the present invention is not limited to this, and the measurement condition optimization method and program of the present invention are not limited thereto. It is also possible to create an EGA recipe file by using an apparatus having an image processing type alignment sensor other than the exposure apparatus, such as an overlay measuring machine. .

  In the above embodiment, for the sake of simplification of explanation, the main controller 28 performs all processes related to EGA measurement including optimization of measurement conditions, creation of a recipe file, and the like. The various processes performed by may be performed by a plurality of hardware. For example, the processing of each step shown in the flowchart of FIG. 2 described above may be performed by appropriately sharing a plurality of microcomputers.

In the above embodiment, an ultraviolet light source such as a KrF excimer laser (output wavelength 248 nm), a pulsed laser light source in the vacuum ultraviolet region such as an ArF excimer laser, or the like is used as the light source. Of course, other vacuum ultraviolet light sources such as F ₂ laser or Ar ₂ laser (output wavelength 126 nm) may be used. Further, for example, not only laser light output from each of the above light sources as vacuum ultraviolet light, but also single wavelength laser light in the infrared region or visible region oscillated from a DFB semiconductor laser or fiber laser, for example, erbium (Er) A harmonic that is amplified by a fiber amplifier doped with erbium and ytterbium (Yb) and wavelength-converted into ultraviolet light using a nonlinear optical crystal may be used.

  Further, an exposure apparatus that uses EUV light, X-rays, or charged particle beams such as an electron beam or an ion beam as illumination light IL, a projection system that does not use a projection optical system, such as a proximity type exposure apparatus, a mirror projection aligner, and The present invention may also be applied to an immersion type exposure apparatus disclosed in International Publication WO99 / 49504, etc., in which a liquid is filled between the projection optical system PL and the wafer.

  In each of the above-described embodiments, a light-transmitting mask in which a predetermined light-shielding pattern (or phase pattern / dimming pattern) is formed on a light-transmitting substrate, or a predetermined reflecting pattern on a light-reflecting substrate. However, the present invention is not limited to these. For example, instead of such a mask, an electronic mask (which is a kind of optical system) that forms a transmission pattern, a reflection pattern, or a light emission pattern based on electronic data of a pattern to be exposed may be used. Such an electronic mask is disclosed, for example, in US Pat. No. 6,778,257. Note that the above-described electronic mask is a concept including both a non-light-emitting image display element and a self-light-emitting image display element.

  Further, for example, the present invention can also be applied to an exposure apparatus that exposes a substrate with interference fringes caused by interference of a plurality of light beams, which is called two-beam interference exposure. Such an exposure method and exposure apparatus are disclosed in, for example, WO 01/35168.

  In the above embodiment, the case where the present invention is applied to a scanning exposure apparatus such as the step-and-scan method has been described. However, the present invention is not limited to this, and the step-and-repeat method or the step-and-stitch method is used. The present invention can also be suitably applied to the projection exposure apparatus.

  The present invention is not limited to an exposure apparatus for manufacturing a semiconductor, but is used for manufacturing a display including a liquid crystal display element. An exposure apparatus for transferring a device pattern onto a glass plate and a device used for manufacturing a thin film magnetic head. The present invention can also be applied to an exposure apparatus that transfers a pattern onto a ceramic wafer, and an exposure apparatus that is used for manufacturing an imaging device (CCD or the like), micromachine, organic EL, DNA chip, and the like. Further, in order to manufacture reticles or masks used in not only microdevices such as semiconductor elements but also light exposure apparatuses, EUV exposure apparatuses, X-ray exposure apparatuses, electron beam exposure apparatuses, etc., glass substrates or silicon wafers, etc. The present invention can also be applied to an exposure apparatus that transfers a circuit pattern.

  Heretofore, the exposure apparatus for forming a pattern on a substrate has been described. However, the method for forming a pattern on a substrate by a scanning operation is not limited to the exposure apparatus, for example, Japanese Patent Application Laid-Open No. 2004-130312 It can also be realized by using an element manufacturing apparatus provided with an ink jet functional liquid application device similar to the ink jet head group disclosed in the above.

  The ink jet head group disclosed in the above publication is applied to a substrate (for example, PET, glass, silicon, paper, etc.) by discharging a predetermined functional liquid (metal-containing liquid, photosensitive material, etc.) from a nozzle (discharge port). A plurality of inkjet heads. What is necessary is just to prepare a functional liquid provision apparatus like this inkjet head group, and to use it for the production | generation of a pattern. In the element manufacturing apparatus provided with this functional liquid application apparatus, the substrate may be fixed and the functional liquid application apparatus may be scanned in the scanning direction, or the substrate and the functional liquid application apparatus may be reversed. You may scan.

  For semiconductor devices, the step of designing the function and performance of the device, the step of manufacturing a reticle based on this design step, the step of manufacturing a wafer from a silicon material, and transferring the reticle pattern to the wafer by the exposure apparatus of the above-described embodiment And a device assembly step (including a dicing process, a bonding process, and a packaging process), an inspection step, and the like. Therefore, the semiconductor device can be manufactured with high productivity.

  As described above, the measurement condition optimization method of the present invention is suitable for optimizing the measurement conditions for EGA measurement. The program creation method of the present invention is suitable for creating an EGA measurement recipe. Further, the exposure apparatus of the present invention is suitable for forming a pattern by superposing it on a plurality of partitioned regions on the substrate.

It is a figure which shows schematic structure of the exposure apparatus which concerns on one Embodiment. It is a flowchart which shows roughly the processing algorithm of the main control apparatus 28 (more precisely, internal CPU) regarding the optimization condition determination method at the time of alignment. It is a flowchart which shows the detail of the subroutine of step 214 of FIG. It is a flowchart which shows the detail of the subroutine of step 220 of FIG. It is a flowchart which shows the detail of the subroutine of step 240 of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 16 ... Alignment control apparatus, 28 ... Main control apparatus, 100 ... Exposure apparatus, W ... Wafer, AS ... Alignment detection system.

Claims (15)

The measurement information is included in a statistical calculation using a predetermined model function for calculating the array coordinates of the plurality of partition areas, which is performed in order to form a pattern overlaid on the plurality of partition areas formed on the substrate. A measurement condition optimization method for optimizing measurement conditions of sample marks attached to at least some sample partition areas of the plurality of partition areas used,
A first step of optimizing an illumination condition at the time of detection of the sample mark in an image processing type mark detection system used for detection of the sample mark attached to each partition area on the substrate;
And a second step of optimizing measurement conditions other than the illumination conditions under the optimized illumination conditions after the optimization of the illumination conditions. Sample mark measurement is performed to sequentially detect the position information of the sample mark using the mark detection system under all conditions determined in the first and second steps, and the measurement is performed in the processing of the first and second steps. A third step of determining whether or not one or more conditions determined as a result of the success have been achieved;
The measurement condition optimization method according to claim 1, further comprising: a fourth step of performing an evaluation according to a predetermined evaluation criterion for a condition determined to have succeeded in the sample mark measurement in the third step, and determining an optimum condition. .   As a result of the determination in the third step, for any of the conditions determined as a result of the processing of the first and second steps, when the sample mark measurement fails, prior to starting the sample mark measurement again, The measurement condition optimization method according to claim 2, further comprising a fifth step of changing the setting so that the number of capture screens when the sample mark is detected by the mark detection system is increased. In the fourth step, depending on the mode setting,
Random is an error from the correction position of each sample mark after being corrected by the model function that minimizes the sum of errors from the design position of each sample mark calculated using the position information of the sample mark Determination that balances the small value of the error component with the small difference between the two coordinate axes of the stationary coordinate system that defines the movement position of the substrate, or includes the minimum value of the random error component regardless of the axis The measurement condition optimizing method according to claim 2 or 3, wherein a determination is made to prioritize the measurement.   In the fourth step, it is further determined whether or not the numerical values of the two coordinate axes of the random error component all coincide with each other under the uppermost plural conditions. The measurement condition optimizing method according to claim 4, wherein the determination is made such that the maximum reproducibility of the determination target is the evaluation value.   The measurement condition optimization method according to claim 4 or 5, wherein in the fourth step, it is further confirmed whether or not the evaluation value of the highest condition is within a predetermined allowable value.   The measurement condition optimization method according to claim 1, wherein the measurement condition other than the illumination condition includes a focus offset of the mark detection system.   The optimal condition determined by the measurement condition optimization method according to any one of claims 1 to 7 includes a statistical calculation using a predetermined model function for calculating array coordinates of the plurality of partition regions. A method for creating a program, including a step of determining as a corresponding condition in a program that defines a series of measurement processing procedures. An exposure apparatus for forming a pattern on a plurality of partitioned areas on a substrate by overlapping the pattern,
Sample marks attached to at least some sample partition areas of the plurality of partition areas, whose measurement information is used for statistical calculation using a predetermined model function for calculating array coordinates of the plurality of partition areas. An image processing type mark detection system that can detect at least a mark including the mark and that can change at least illumination conditions;
An exposure apparatus comprising: an optimization apparatus that optimizes illumination conditions at the time of detection of the sample mark of the mark detection system and optimizes measurement conditions other than the illumination conditions under the optimized illumination conditions. Sample mark measurement is performed to sequentially detect the position information of the sample mark on the substrate using the mark detection system under all conditions determined as a result of the processing by the optimization device, and the sample mark measurement is confirmed. A determination device for determining whether one or more conditions are successful;
The exposure apparatus according to claim 9, further comprising: an evaluation / determination device that performs an evaluation according to a predetermined evaluation criterion for a condition that the determination device determines to have succeeded in the sample mark measurement, and determines an optimum condition.   As a result of the determination by the determination device, if any of the conditions determined as a result of the processing by the optimization device fails in the sample mark measurement, prior to starting the sample mark measurement again, the mark detection is performed. The exposure apparatus according to claim 10, further comprising an error processing apparatus that changes a setting so that the number of captured screens when the sample mark is detected increases.   The evaluation / determination device is corrected by the model function that minimizes the sum of errors from the design position of each sample mark calculated using the position information of the sample mark according to the mode setting. Determination that achieves both a small value of a random error component that is an error from the correction position of each of the sample marks and a small difference between both coordinate axes of the stationary coordinate system that defines the moving position of the substrate, or The exposure apparatus according to claim 10 or 11, wherein priority is given to the one including the minimum value of the random error component regardless of the axis.   The evaluation / determination device further determines whether or not the numerical values of the two coordinate axes of the random error component all match under the highest plural conditions, and if they match, the parameters of the model function are preliminarily determined. The exposure apparatus according to claim 12, wherein a determination is made such that a maximum one of the determined reproducibility of the determination target is an evaluation value.   The exposure apparatus according to claim 12 or 13, wherein the evaluation / determination apparatus further confirms whether an evaluation value of the highest condition is within a predetermined allowable value.   The optimum condition determined by the evaluation / determination device corresponds to a program in the program that defines a series of measurement processing procedures including statistical calculation using a predetermined model function for calculating the array coordinates of the plurality of partitioned areas. The exposure apparatus according to any one of claims 10 to 14, wherein the program is created by determining as a condition.

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