JP2004279332A - Method and instrument for measuring position, exposure method, and exposure device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a position measuring method and an exposing method capable of enhancing mark detecting ability without increasing a mark position detecting time. <P>SOLUTION: A mark SM formed on an object is image-picked up within a prescribed imaging field FV, and positional information of the mark SM is measured based on an image pick-up result therein. The imaging field FV is divided into a plurality of areas A, B, C, and the image of the mark SM is searched in order in every of the divided areas. In this exposure method, a pattern of the mask is exposed onto a substrate, after aligned using a mask mark on a mask and a substrate mark on the substrate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a position measurement method, a position measurement apparatus, and an exposure method which are preferably used when measuring the position of each shot area when sequentially transferring a pattern image of a mask to each shot area on a photosensitive substrate (such as a wafer). And an exposure apparatus.
[0002]
[Prior art]
When manufacturing a semiconductor device or a liquid crystal display device by a photolithography process, a pattern image of a photomask or a reticle (hereinafter, collectively referred to as “reticle”) is projected onto each shot area on a photosensitive substrate via a projection optical system. A projection exposure apparatus is used. In recent years, as this type of projection exposure apparatus, a photosensitive substrate is placed on a two-dimensionally movable stage, and the photosensitive substrate is step-moved by this stage, so that a reticle pattern image is shot on each of the shots on the photosensitive substrate. An exposure apparatus of a so-called step-and-repeat method, for example, an exposure apparatus (stepper) of a reduction projection type, which repeats an operation of sequentially exposing regions, is often used.
[0003]
For example, since a semiconductor device is formed as a photosensitive substrate by laminating a large number of circuit patterns on a wafer coated with a photosensitive material, when projecting and exposing the second and subsequent circuit patterns on the wafer, the wafer is exposed. It is necessary to precisely align each of the shot areas on which a circuit pattern has already been formed with the pattern image of the reticle to be exposed, that is, the alignment (alignment) between the wafer and the reticle.
[0004]
For example, as a method of aligning wafers when performing overlay exposure on one wafer on which circuit patterns (shot areas) are arranged in a matrix, a so-called enhanced technology disclosed in, for example, Patent Document 1・ Global alignment (EGA) is the mainstream. The EGA method specifies at least three regions (hereinafter referred to as EGA shots) among a plurality of shot regions formed on a wafer, and turns off the coordinate position of an alignment mark (wafer mark) attached to each shot region. Measure with an axis alignment system.
[0005]
Thereafter, error parameters (offset, scale, rotation, orthogonality) relating to the array characteristics (position information) of the shot areas on the wafer are statistically calculated and determined by the least square method or the like based on the measured values and the design values. Then, based on the determined parameter values, the design coordinate values of all shot areas on the wafer are corrected, and the wafer stage and the projection optical system are off-axis in accordance with the corrected coordinate values. In this method, a wafer is positioned by performing stepping using a baseline amount that is a distance from an alignment system. As a result, the projected image of the reticle pattern and each of the plurality of shot areas on the wafer are processing points set in the shot area (the reference points at which coordinate values are measured or calculated. 2) will be exposed in a superimposed manner.
[0006]
The wafer loaded on the wafer stage is placed in a pre-aligned state, but is not positioned at a level at which EGA measurement as fine alignment can be performed. For this reason, usually, so-called search alignment, in which the wafer is roughly adjusted so as not to hinder the EGA measurement, is performed before the EGA measurement is performed. This search alignment measures search alignment marks (search marks) in a predetermined shot area (for example, two locations, hereinafter referred to as search shots) and corrects the coordinate values of the shot area based on the measurement result. It is.
[0007]
As such a search mark, as an alignment system of this type, an LSA (irradiating a laser beam to a grid-like alignment mark formed on a wafer and measuring the position of the alignment mark based on a change in reflected light intensity) is used. There is a laser step alignment) method. Further, a coherent light beam is incident from two symmetric order directions (for example, the direction of the + 1st-order diffracted light and the direction of the -1st-order diffracted light) of the lattice-shaped alignment mark, and the two diffracted lights generated from the lattice mark in the same direction. There is an LIA (Laser Interference Alignment) method of measuring the position or displacement of the grating mark in the pitch direction by causing components to interfere. Further, the wafer stage is stopped, and illumination light such as white light from a halogen lamp is radiated onto the alignment mark of the wafer, and an image of the obtained alignment mark is captured by an image sensor within a predetermined imaging field of view. There is an FIA (Field Image Alignment) method for measuring the alignment mark position by processing.
[0008]
FIG. 9 shows an example in which a cross-shaped search mark (mark, substrate mark) SM is imaged in the camera field of view (imaging field of view) FV by the FIA type alignment sensor. As the alignment marks formed on the wafer, for example, a mark as shown in FIG. 11A is used for fine alignment, and a mark as shown in FIG. 11B is used for search alignment. In the following description, it is assumed that a cross mark is simply used.
[0009]
For the search mark SM imaged in the camera field of view FV, the image processing of a two-dimensional image increases processing time and is disadvantageous in terms of throughput. In addition, a two-dimensional image is compressed in a non-measurement direction (a direction orthogonal to the measurement direction), and mark position measurement is performed by performing image processing on the one-dimensional image.
[0010]
[Patent Document 1]
JP-A-61-44429
[0011]
[Problems to be solved by the invention]
However, as described above, the conventional position measurement method, position measurement device, exposure method, and exposure device using the FIA alignment system have the following problems.
[0012]
When the search mark is reduced in size with respect to the camera field of view, if the entire two-dimensional field of view is compressed to one dimension, the signal contrast of the search mark is reduced as shown in FIG. In such a case, a problem occurs that the detection capability is reduced. As a countermeasure to this problem, if the camera field of view is narrowed, the ratio of search marks occupied relatively increases and the contrast improves, but it is necessary to increase the pre-alignment accuracy in order to reliably image the search marks within the camera field of view. Would. Conversely, it is conceivable to increase the size of the search mark itself while maintaining the size of the field of view of the camera, but this disadvantageously affects the size of the pattern area.
[0013]
Therefore, since the image of the search mark has a high probability of being located near the center in the camera field of view in the range where the mark center can exist, conventionally, as shown in FIG. Only the band-like area B passing through is taken out, and the image of only this area B is compressed and processed. According to this method, the ratio of the image of the search mark SM occupied in the camera field of view is relatively large, and there is an advantage that a predetermined signal contrast is easily obtained. However, depending on the precision of the pre-alignment, as shown in FIG. 9, the search mark SM may be imaged at a position outside the central area B in the camera field of view FV.
[0014]
In this case, even if a search is performed on the central region B by one-dimensional image processing, there is a problem that a sufficient signal contrast cannot be obtained and accurate mark position measurement cannot be performed as shown in FIG. Was. Further, in the worst case, the search mark SM completely deviates from the center area B, and the mark itself cannot be detected. As described above, if the search mark SM is not detected in the area B, an error occurs, and the operator has to intervene, for example, separately instructing a mark detectable position, so that the throughput is reduced and the production efficiency is reduced. was there.
[0015]
The present invention has been made in view of the above points, and provides a position measurement method, a position measurement device, an exposure method, and an exposure device that improve the mark detection capability without increasing the mark position detection time. The purpose is to do.
[0016]
[Means for Solving the Problems]
In order to achieve the above object, the present invention employs the following configuration corresponding to FIGS. 1 to 7 showing the embodiment.
According to the position measurement method of the present invention, a mark (SM) formed on an object (W) is imaged within a predetermined imaging field of view (FV), and position information of the mark (SM) is measured based on the imaging result. A position measuring method, wherein an imaging field of view (FV) is divided into a plurality of regions (A, B, C), and an image of a mark (SM) is sequentially searched for each divided region. is there.
[0017]
In addition, the position measurement device of the present invention includes an imaging unit that captures an image of a mark (SM) formed on an object (W) within a predetermined imaging field of view (FV), and a mark based on a result of imaging by the imaging unit. A position measurement device (17) having a measurement unit (19) for measuring position information of (SM), wherein an imaging field of view (FV) is divided into a plurality of regions (A, B, C), and the divided region is divided. A control unit (15) for controlling the measuring unit (19) so as to sequentially search for an image of the mark (SM) for each area (A, B, C).
[0018]
Therefore, in the position measuring method and position measuring device of the present invention, first, the mark (SM) is searched for in one of the plurality of areas (B), and when the search is not possible, the other area (A) is searched. As described above, the sequentially divided areas (A, B, C) can be searched until the mark (SM) can be detected, so that the ability to detect the mark (SM) is improved. Therefore, the mark (SM) can be detected in a short time without manual intervention. Further, since the area (A, B, C) to be searched divides the imaging field of view (FV), the ratio of the mark (SM) occupied by the image is relatively large, and a predetermined contrast can be easily obtained. , It is easy to detect the mark (SM).
[0019]
In the exposure method of the present invention, the mask (R) and the substrate (W) are aligned using the mask mark on the mask (R) and the substrate mark (SM) on the substrate (W). The position measurement according to any one of claims 1 to 8, wherein in the exposure method for exposing the pattern (R) on the substrate (W), at least one of the position of the mask mark and the position of the substrate mark (SM) are measured. It is characterized in that it is measured by a method.
[0020]
Further, the exposure apparatus of the present invention aligns the mask (R) with the substrate (W) using the mask mark on the mask (R) and the substrate mark (SM) on the substrate (W), and 15. The exposure apparatus (1) for exposing the pattern of (1) to the substrate (W) as an apparatus for measuring at least one of a position of a mask mark and a position of a substrate mark (SM). The position measuring device (17) described in (1) is used.
[0021]
Therefore, in the exposure method and the exposure apparatus of the present invention, when the mask (R) and the substrate (W) are aligned, the ability to detect a mask mark or a substrate mark (SM) is improved, which can contribute to an improvement in throughput.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a first embodiment of a position measurement method, a position measurement device, an exposure method, and an exposure device according to the present invention will be described with reference to FIGS. Here, for example, a case where a circuit pattern on a reticle is exposed on a wafer for manufacturing a semiconductor device by using a step-and-repeat type exposure apparatus will be described. Further, the position measuring apparatus of the present invention will be described as being used for position measurement of an alignment mark formed on a wafer when aligning a reticle with a wafer. In these figures, the same components as those in FIGS. 9 and 10 shown as conventional examples are denoted by the same reference numerals, and description thereof will be omitted.
[0023]
FIG. 1 is a schematic configuration diagram of the exposure apparatus 1. Illumination light emitted from a light source 2 such as an ultra-high pressure mercury lamp or an excimer laser is reflected by a reflecting mirror 3 and enters a wavelength selection filter 4 that transmits only light having a wavelength required for exposure. The illumination light transmitted through the wavelength selection filter 4 is adjusted to a light flux having a uniform intensity distribution by an optical integrator (fly-eye lens or rod) 5 and reaches a reticle blind (field stop) 6. In the reticle blind 6, a plurality of blades defining the opening S are driven by a drive system 6a, respectively, and the size of the opening S is changed to set an illumination area on the reticle (mask) R by illumination light.
[0024]
The illumination light having passed through the opening S of the reticle blind 6 is reflected by the reflecting mirror 7 and enters the lens system 8. An image of the opening S of the reticle blind 6 is formed on the reticle R held on the reticle stage 20 by the lens system 8, and a desired area of the reticle R is illuminated. In FIG. 1, an illumination optical system includes the wavelength selection filter 4, the optical integrator 5, the reticle blind 6, and the lens system 8. The reticle stage 20 is two-dimensionally movable in a plane perpendicular to the optical axis of the projection optical system 9, and the position and the amount of rotation of the reticle stage 20 (reticle R) are detected by a laser interferometer (not shown). The measurement values (position information) of the laser interferometer are output to the later-described stage control system 14, main control system 15, and alignment control system 19, respectively.
[0025]
The image of the circuit pattern and / or the alignment mark existing in the illumination area of the reticle R is formed by the projection optical system 9 on the wafer (object, substrate) W coated with the resist. As a result, a pattern image and / or an alignment mark image of the reticle R is exposed on a specific area (shot area) on the wafer W mounted on the wafer stage 10.
[0026]
The wafer stage 10 has a wafer holder (not shown) for vacuum-sucking the wafer W, and is moved by a driving device 11 such as a linear motor in X and Y directions perpendicular to the optical axis of the projection optical system 9 and orthogonal to each other. You. Thereby, the wafer W is two-dimensionally moved on the image plane side with respect to the projection optical system 9, and a reticle is formed on each shot area on the wafer W by, for example, a step-and-repeat method (or a step-and-scan method). The R pattern image is transferred.
[0027]
Further, the position of the wafer stage 10 (wafer W) in the X and Y directions and the amount of rotation (the amount of yawing, the amount of pitching, and the amount of rolling) on the stage movement coordinate system (orthogonal coordinate system) XY are determined at the end of the wafer stage 10. It is detected by a laser interferometer 13 that irradiates a movable mirror (reflecting mirror) 12 provided in the unit with laser light. The measurement value (position information) of the laser interferometer 13 is output to the stage control system 14, the main control system 15, and the alignment control system 19, respectively. The stage control system 14 controls the movement of the reticle stage 20 and the wafer stage 10 via the driving device 11 and the like based on the position information from the main control system 15 and the laser interferometer 13 and the like. The main control system 15 controls the size and shape of the opening S of the reticle blind 6 via the drive system 6a, and performs EGA calculation based on the position information of the alignment mark on the wafer W output from the alignment control system 19. In addition to this, it controls the entire system.
[0028]
The exposure apparatus 1 includes, for example, a reticle alignment sensor 16 of a TTR (through-the-reticle) type and a wafer alignment sensor of an off-axis type (position measuring device) in order to align the reticle R with the wafer W. ) 17 are provided.
[0029]
The reticle alignment sensor 16 detects a reference mark on a reference mark member 18 via an alignment mark (mask mark) (not shown) formed on the reticle R and the projection optical system 9 using, for example, exposure illumination light. . In the exposure light alignment method, the positional relationship can be directly observed by displaying the alignment mark and the reference mark of the reticle R on a monitor using an image pickup device (CCD). The reference mark member 18 is fixed on the wafer stage 10 and has a reference mark formed at the same height as the surface of the wafer W.
[0030]
The reticle alignment sensor 16 outputs an image signal of the alignment mark and the reference mark of the reticle R to the alignment control system 19. The alignment control system 19 detects the amount of displacement between the two marks based on the imaging signal, and also inputs the measurement values of the laser interferometer 13 and the like for detecting the positions of the reticle stage 20 and the wafer stage 10, respectively. The respective positions of the reticle stage 20 and the wafer stage 10 when the amount of positional deviation becomes a predetermined value, for example, zero, are obtained. Thereby, the position of the reticle R on the wafer stage movement coordinate system XY is detected. In other words, the association between the reticle stage movement coordinate system and the wafer stage movement coordinate system XY (that is, detection of the relative positional relationship) is performed. The alignment control system 19 outputs the result (position information) to the main control system 15.
[0031]
The alignment sensor 16 may use any one of a single-wavelength laser beam (such as a He-Ne laser), a multi-wavelength light, a broadband light, and an exposure light as the illumination light for alignment. When other than light is used as the alignment illumination light, a known correction optical element for correcting chromatic aberration generated by the projection lens is arranged between the reticle R and the projection optical system 9 or near the pupil plane of the projection optical system 9. It is necessary to use an image sensor, an SPD, or the like as the light receiving element.
[0032]
As an alignment method of the off-axis wafer alignment sensor 17, an FIA method, an LSA method, an LIA method, or an exposure light alignment method using exposure light can be applied. As the wafer alignment sensor 17, a photoelectric conversion element such as an SPD is used in the LSA method and the LIA method, and an imaging element such as a CCD camera is used in the FIA method. Among these methods, the present embodiment employs the FIA method.
[0033]
That is, the wafer alignment sensor 17 uses an objective optical system provided separately from the projection optical system 9 to emit illumination light in a wavelength range that does not expose the resist on the wafer W, for example, broadband light having a wavelength of about 550 to 750 nm ( Broadband light) is irradiated onto the alignment mark on the wafer W, and an index mark image (not shown) is formed on the light receiving surface of an unillustrated imaging device (imaging unit) such as a CCD camera through the objective optical system. Are formed, and imaging signals (image signals) of both mark images are output to the alignment control system 19. Further, the wafer alignment sensor 17 has an AF (auto focus) function, that is, a function of detecting position information of the wafer W in a direction along the optical axis of the objective optical system described above, and based on the position information, By driving the stage 10, the alignment marks on the wafer W can be arranged on the focal plane of the objective optical system.
[0034]
The alignment control system 19 measures the amount of displacement between the two marks as a measuring unit based on the imaging signal from the wafer alignment sensor 17 and also inputs the measured value of the laser interferometer 13 to determine the amount of displacement. A value, for example, the position of the wafer stage 10 when it becomes zero is obtained as a coordinate value of the alignment mark on the wafer stage movement coordinate system XY, and the position information is output to the main control system 15.
[0035]
The main control system 15 gives a command regarding the signal processing conditions and the like to the alignment control system 19 as a control unit, and performs EGA calculation based on position information (coordinate values) of the alignment mark output from the alignment control system 19. That is, position information (coordinate values) of each shot area (a reference point, for example, a shot center) on the wafer W is calculated. Further, main control system 15 corrects the calculated coordinate values based on the baseline amount of wafer alignment sensor 17 and outputs the corrected coordinate values to stage control system 14. The stage control system 14 controls the movement of the wafer stage 10 via the driving device 11 based on the position information from the main control system 15. Thus, the pattern image of the reticle R is transferred to each shot area on the wafer W by, for example, a step-and-repeat method (or a step-and-scan method).
[0036]
Subsequently, when performing exposure processing using the exposure apparatus 1 having the above-described configuration, a procedure for performing a so-called search alignment in which the position of the search mark SM formed on the wafer W is measured by the wafer alignment sensor 17 is shown. This will be described with reference to the flowchart shown in FIG. It is assumed that the alignment with respect to reticle R has already been completed.
[0037]
When a wafer W to be subjected to exposure processing is loaded on the wafer stage 10, mark position measurement starts (step S0). First, the wafer stage 10 (wafer W) is moved via the stage control system 14 and the driving device 11 to position the search mark SM in the measurement area of the wafer alignment sensor 17 (step S1). When the movement of the wafer W is completed, the wafer alignment sensor 17 adjusts the focus of the wafer W, and then displays the image of the search mark SM illuminated with the illumination beam from the halogen lamp or the like as shown in FIG. An image is taken within a predetermined camera field of view FV using an image sensor (step S2), and an image signal is output to the alignment control system 19.
[0038]
When the image of the search mark SM is searched in the camera field of view FV using the image signal input by the alignment control system 19, the main control system 15 changes the camera field of view FV from the belt-like areas A, B, and C along the Y direction. Is instructed to search for the image of the search mark SM in the order of the areas B → A → C. Therefore, the alignment control system 19 first searches the area (first area) B in the camera field of view FV for an image of the search mark SM by one-dimensional image processing (step S3), and determines whether the search mark SM is detected. Is determined (step S4).
[0039]
In the area B, as shown in FIG. 10B, the search mark SM cannot be detected because the measured mark signal does not have a predetermined contrast. Accordingly, the alignment control system 19 subsequently searches the area (second area) A for an image of the search mark SM by one-dimensional image processing (step S5), and determines whether the search mark SM has been detected. (Step S6). When the search mark SM is detected in step S4, the process of step S7 described below is executed.
[0040]
In the area A, as shown in FIG. 4A, since the measured signal has a predetermined contrast, the search mark SM can be detected. Therefore, the alignment control system 19 terminates the subsequent search processing, measures the amount of misalignment between the search mark SM and the index mark, and also inputs the measured value of the laser interferometer 13 to determine the amount of misalignment. A value, for example, the position of the wafer stage 10 when it becomes zero is obtained as a coordinate value (position information) of the search mark SM on the wafer stage movement coordinate system XY, and the position information is output to the main control system 15 (step S7). ).
[0041]
On the other hand, if the search mark SM cannot be detected in step S6, the area C is searched in step S8 to determine whether the search mark SM has been detected (step S9). When the search mark SM is detected in step S9, the process of step S7 is executed. However, when a sufficient signal contrast cannot be obtained, or when the search mark SM does not exist in the region C, the process proceeds to FIG. As shown, when the measured signal does not have any contrast, the alignment control system 19 stops the one-dimensional image processing based on the instruction of the main control system 15, and performs the entire camera field of view FV by the two-dimensional image processing. Is searched (step S10), and it is determined whether or not the search mark SM is detected (step S11).
[0042]
Here, when the search mark SM is detected, the processing of the above-described step S7 is executed. However, when the search mark SM cannot be detected even in the two-dimensional image processing, it is determined that an error has occurred due to some kind of trouble, and the operator The call is executed (step S12), and an instruction from the operator is obtained.
[0043]
When the position measurement of the search mark SM is completed, the main control system stores the mark position, and also performs the mark position measurement for the other search marks by the alignment control system 19 in the same procedure as described above. Remember the position. Thereafter, the main control system 15 performs arithmetic processing based on the measured coordinate values of the search mark SM on the wafer stage movement coordinate system XY and the corresponding design coordinate values (step S13), and EGA The design coordinate value of the wafer mark on the wafer stage movement coordinate system XY is corrected for each shot, and the mark position measurement at the time of search alignment is completed (step S14).
[0044]
Thereafter, the stage control system 14 moves the wafer stage 10 based on the measured value of the laser interferometer 13 with the corrected coordinate value as a target value in order to execute fine alignment. Are sequentially measured by the wafer alignment sensor 17, respectively. Then, the main control system 15 performs shift, scale, rotation, and position information as position information on the arrangement characteristics of the shot areas on the wafer W by performing a statistical calculation process such as a least square method based on the obtained measurement values and design values. Error parameters such as orthogonality are calculated, and based on these error parameters, design coordinate positions are corrected for all shot areas on the wafer W.
[0045]
The imaging characteristics (projection magnification, distortion, etc.) of the projection optical system 9 are adjusted, and the wafer stage 10 is sequentially moved stepwise using the corrected (calculated) coordinate position and the baseline amount. The pattern on the reticle R is sequentially exposed on each shot area on the wafer W by a step-and-repeat method.
[0046]
In the position measurement method, the position measurement device, the exposure method, and the exposure device of the present embodiment, the camera field of view FV is divided into a plurality of regions A, B, and C, and the search mark SM is subjected to one-dimensional image processing for each divided region. Since the search is performed, the occupation ratio of the search mark SM in each area increases, the signal contrast of the mark improves, the mark detection capability and detection accuracy can be improved, and the mark can be detected in one of the areas. Even if not performed, by sequentially searching other areas, it is possible to reduce the frequency of stopping the exposure apparatus and intervening an operator, thereby preventing a decrease in production efficiency. In particular, in the present embodiment, when a mark cannot be detected by the one-dimensional image processing, the mark is searched by the two-dimensional image processing. A decrease in efficiency can be prevented more effectively.
[0047]
In the position measurement method, position measurement device, exposure method, and exposure device of the present embodiment, when a search mark SM is detected in one of the divided regions, the other region is not searched, and therefore, there is no need for extra search. The measurement time can be omitted, which can contribute to an improvement in throughput. Therefore, in the exposure method and the exposure apparatus of the present embodiment, the time required for the alignment between the reticle R and the wafer W is shortened by improving the detection capability of the mark position measurement, thereby contributing to an improvement in production efficiency. In the above embodiment, the search order of the areas is B → A → C. However, the search order is not limited to this, and the search may be started from any area.
[0048]
5 to 7 are views showing a second embodiment of the position measuring method, the position measuring device, the exposure method, and the exposure device of the present invention. In these figures, the same elements as those of the first embodiment shown in FIGS. 1 to 4 are denoted by the same reference numerals, and description thereof will be omitted. The difference between the second embodiment and the first embodiment is that the result of the first mark position measurement is reflected in the subsequent mark position measurement.
[0049]
First, a wafer used in the present embodiment will be described.
As shown in FIG. 5, a plurality of shot areas are arranged in a matrix on the wafer W, and a chip pattern is formed in each shot area by exposure and development in a previous process. In each shot area, a wafer mark and a search mark shown in FIGS. 11A and 11B are formed, respectively. FIG. 7 is a flowchart showing a procedure for measuring the positions of the two search marks SM1 and SM2 (hereinafter, appropriately referred to as SM) formed on the wafer W by the wafer alignment sensor 17 during the search alignment. This will be described with reference to FIG.
[0050]
Before measurement of the search marks SM1 and SM2 as the second marks formed on the wafer (N (N ≧ 2) th wafer) W as the second object to be measured, the wafer as the first object is measured. The main control system 15 stores the areas where the search marks SM1 and SM2 as the first marks are detected when measuring (the first wafer to the (N-1) th wafer W). FIG. 6A shows the frequency of the area where the search mark SM1 is detected, and FIG. 6B shows the frequency of the area where the search mark SM2 is detected. As shown in this figure, the area where the search marks SM1 and SM2 are detected during the search has a tendency to depend on the pre-alignment error and the offset value of the apparatus itself. Is decided to some extent. Therefore, in the present embodiment, the order in which main control system 15 searches alignment control system 19 is determined and instructed in accordance with the frequency at which each search mark is detected.
[0051]
Hereinafter, this will be described in detail with reference to FIG.
In step S2, for example, an image of the search mark SM1 is picked up by the wafer alignment sensor 17 and its image signal is output to the alignment control system 19, based on the instruction from the main control system 15, the alignment control system 19 The image of the search mark SM1 is searched by one-dimensional image processing in the area B (see FIG. 6A) where the search mark SM1 is detected most in the measured wafer (step S15).
[0052]
If it is determined in step S4 that the search mark SM1 has not been detected, the alignment control system 19 performs one-dimensional image processing on the area C of the measured wafer where the search mark SM1 is detected second most. The image of the search mark SM1 is searched (step S16). Similarly, when it is determined in step S6 that the search mark SM1 has not been detected, the alignment control system 19 performs one-dimensional image processing on the region A where the third most search mark SM1 is detected on the measured wafer. To search for the image of the search mark SM1 (step S17).
[0053]
If the search mark SM1 cannot be detected even in this area A, the sequence from step S10 for searching the entire camera field of view FV by two-dimensional image processing is executed as in the first embodiment.
[0054]
On the other hand, when measuring the search mark SM2, referring to FIG. 6B, the area B is searched in step S15, the area A is searched in step S16, and the area C is searched in step S17.
[0055]
In the position measuring method, the position measuring device, the exposure method, and the exposure device according to the present embodiment, the same operation and effect as those of the first embodiment can be obtained, and in addition, the region where the probability that the search mark exists is high. Since the search is performed first, the detection accuracy of the search mark at an early stage is increased, the time required for the search can be reduced, and a decrease in throughput can be prevented.
[0056]
In the above-described second embodiment, the description has been made assuming that the frequency of the area where the search mark is detected in the previously measured wafer is reflected. However, the present invention is not limited to this. When measuring a plurality of marks, an area in which to search for a mark may be determined according to the frequency of the area in which the mark has been detected in the previous measurement. In this case, since the measurement results in the same wafer are used, the accuracy of detecting the mark is further increased, and the time required for the search can be further reduced.
[0057]
Further, in the above-described embodiment, the description has been given assuming that the mark measurement is applied to the search alignment. However, the present invention is not limited to this, and can be applied to the fine alignment. Further, in the above embodiment, the mark is searched for each area obtained by dividing the camera field of view FV into three, but the number of divisions may be any number as long as it is two or more.
[0058]
In the above embodiment, the position measuring apparatus of the present invention is applied to the wafer alignment sensor 17. However, the present invention is not limited to this, and the position information of the alignment mark (mask mark) formed on the reticle R may be used. The present invention is also applicable to the reticle alignment sensor 16 for measuring.
[0059]
The substrate of the present embodiment is not limited to a semiconductor wafer W for a semiconductor device, but also a glass substrate for a liquid crystal display device, a ceramic wafer for a thin-film magnetic head, or an original mask or reticle used in an exposure apparatus. (Synthetic quartz, silicon wafer) and the like are applied.
[0060]
The exposure apparatus 1 includes a step-and-repeat type projection exposure apparatus (stepper) that exposes a pattern of the reticle R while the reticle R and the wafer W are stationary and sequentially moves the wafer W step by step. The present invention is also applicable to a step-and-scan type scanning exposure apparatus (scanning stepper; US Pat. No. 5,473,410) for scanning and exposing the pattern of the reticle R by synchronously moving the R and the wafer W.
[0061]
The type of the exposure apparatus 1 is not limited to an exposure apparatus for manufacturing a semiconductor element for exposing a semiconductor element pattern onto a wafer W, but may be an exposure apparatus for manufacturing a liquid crystal display element or a display, a thin-film magnetic head, an image sensor (CCD). ) Or an exposure apparatus for manufacturing a reticle or a mask.
[0062]
As the light source 2, bright lines (g-line (436 nm), h-line (404.nm), i-line (365 nm)) generated from an ultra-high pressure mercury lamp, a KrF excimer laser (248 nm), an ArF excimer laser (193 nm), F ₂ Laser (157 nm), Ar ₂ Not only a laser (126 nm) but also a charged particle beam such as an electron beam or an ion beam can be used. For example, when an electron beam is used, a thermionic emission type lanthanum hexaborite (LaB) is used as an electron gun. ₆ ) And tantalum (Ta) can be used. Further, a higher harmonic such as a YAG laser or a semiconductor laser may be used.
For example, a single-wavelength laser in the infrared or visible range oscillated from a DFB semiconductor laser or a fiber laser is amplified by a fiber amplifier doped with, for example, erbium (or both erbium and yttrium), and a nonlinear optical crystal is used. Alternatively, a harmonic converted to ultraviolet light may be used as exposure light. When the oscillation wavelength of the single-wavelength laser is in the range of 1.544 to 1.553 μm, an eighth harmonic within the range of 193 to 194 nm, that is, ultraviolet light having substantially the same wavelength as the ArF excimer laser can be obtained. If the oscillation wavelength is in the range of 1.57 to 1.58 μm, a 10th harmonic in the range of 157 to 158 nm, that is, ultraviolet light having substantially the same wavelength as the F2 laser can be obtained.
[0063]
In addition, a laser plasma light source or EUV (Extreme Ultra Violet) light having a wavelength of about 5 to 50 nm generated from the SOR and having a wavelength of about 5 to 50 nm, for example, 13.4 nm or 11.5 nm may be used as the exposure light. In the exposure apparatus, a reflection type reticle is used, and the projection optical system is a reduction system including only a plurality (for example, about 3 to 6) of reflection optical elements (mirrors). Further, hard X-rays (for example, having a wavelength of about 1 nm or less) may be used as exposure light, and a proximity method is adopted in this exposure apparatus.
[0064]
The projection optical system 9 may be not only a reduction system but also any one of an equal magnification system and an enlargement system. Further, the projection optical system 9 may be any one of a refraction system, a reflection system, and a catadioptric system. When the wavelength of the exposure light is about 200 nm or less, it is desirable to purge the optical path through which the exposure light passes with a gas that absorbs less exposure light (an inert gas such as nitrogen or helium). When an electron beam is used, an electron optical system including an electron lens and a deflector may be used as the optical system. It is needless to say that the optical path through which the electron beam passes is in a vacuum state. Further, the present invention can also be applied to a proximity exposure apparatus that exposes the pattern of the reticle R by bringing the reticle R and the wafer W close to each other without using the projection optical system 9.
[0065]
When a linear motor (see US Pat. No. 5,623,853 or US Pat. No. 5,528,118) is used for the wafer stage 10 or the reticle stage 20, an air levitation type using an air bearing and a magnetic levitation type using Lorentz force or reactance force are used. Either may be used. Further, each of the stages 10 and 20 may be of a type that moves along a guide, or may be a guideless type in which a guide is not provided.
[0066]
As a drive mechanism of each of the stages 10 and 20, a planar motor that drives each of the stages 10 and 20 by an electromagnetic force by opposing a magnet unit having a two-dimensionally arranged magnet and an armature unit having a two-dimensionally arranged coil is used. May be used. In this case, one of the magnet unit and the armature unit may be connected to the stages 10 and 20, and the other of the magnet unit and the armature unit may be provided on the moving surface side of the stages 10 and 20.
[0067]
As described in JP-A-8-166475 (US Pat. No. 5,528,118), a reaction force generated by the movement of the wafer stage 10 is not transmitted to the projection optical system 9 by using a frame member. You may escape to the floor (ground).
As described in Japanese Patent Application Laid-Open No. 8-330224 (USP 6,020,710), a reaction force generated by the movement of the reticle stage 20 is not transmitted to the projection optical system 9 by using a frame member. You may mechanically escape to the floor (ground).
[0068]
As described above, the exposure apparatus 1 according to the embodiment of the present invention controls the various subsystems including the components described in the claims of the present application so as to maintain predetermined mechanical accuracy, electrical accuracy, and optical accuracy. Manufactured by assembling. Before and after this assembly, adjustments to achieve optical accuracy for various optical systems, adjustments to achieve mechanical accuracy for various mechanical systems, and various electric systems to ensure these various accuracy Are adjusted to achieve electrical accuracy. The process of assembling the exposure apparatus from the various subsystems includes mechanical connection, wiring connection of an electric circuit, and piping connection of a pneumatic circuit among the various subsystems. It goes without saying that there is an assembling process for each subsystem before the assembling process from these various subsystems to the exposure apparatus. When the process of assembling the various subsystems into the exposure apparatus is completed, comprehensive adjustment is performed, and various precisions of the entire exposure apparatus are secured. It is desirable that the manufacture of the exposure apparatus be performed in a clean room in which the temperature, cleanliness, and the like are controlled.
[0069]
As shown in FIG. 8, in the semiconductor device, as shown in FIG. 8, a step 201 for designing the function and performance of the device, a step 202 for manufacturing a mask (reticle) based on this design step, a step 203 for manufacturing a wafer from a silicon material, The exposure apparatus 1 of the embodiment is manufactured through a wafer processing step 204 of exposing a reticle pattern to a wafer, a device assembling step (including a dicing step, a bonding step, and a packaging step) 205, an inspection step 206, and the like.
[0070]
【The invention's effect】
As described above, the position measurement method according to the first aspect is a procedure for sequentially searching for a mark image for each of a plurality of regions obtained by dividing the imaging visual field.
Accordingly, in this position measurement method, the ratio of the occupation of the mark in each area increases, and the detection capability of the mark can be improved. In addition, even if the mark is not detected in one of the areas, the other areas are sequentially detected. By performing the search, it is possible to reduce the frequency of stopping the exposure apparatus and intervening an operator, thereby preventing a reduction in production efficiency.
[0071]
The position measurement method according to claim 2 is a procedure for determining whether to search the second area based on the result of searching the first area.
Accordingly, in this position measurement method, when a mark is detected in the search of the first area, it is not necessary to search the second area, so that an unnecessary measurement time can be omitted, and the throughput can be improved. The effect that can be obtained is obtained.
[0072]
The position measuring method according to claim 3 is a procedure for terminating the measurement when the signal of the mark measured in the first area has a predetermined contrast.
Thus, in this position measurement method, the measurement is terminated when a predetermined contrast is obtained, so that an unnecessary measurement time can be omitted, and the effect of improving the throughput can be obtained.
[0073]
The position measuring method according to claim 4 is a procedure for searching for an image of a mark by one-dimensional image processing.
As a result, in this position measurement method, there is an effect that the detection accuracy of a low contrast mark can be improved.
[0074]
The position measuring method according to claim 5 has a procedure of searching for an image of a mark by two-dimensional image processing based on the result of one-dimensional image processing.
As a result, in this position measurement method, the frequency of occurrence of errors due to undetection can be significantly reduced, and the effect of reducing the production efficiency more effectively can be obtained.
[0075]
The position measuring method according to claim 6 is a procedure for determining an area for searching for the second mark in the imaging visual field based on the result of detecting the first mark when measuring a plurality of marks.
Thus, in this position measurement method, the accuracy of mark detection at an early stage is increased, and the time required for search can be shortened, so that an effect of preventing a decrease in throughput can be obtained.
[0076]
The position measuring method according to claim 7 has a procedure of first searching for an area where the first mark is detected when searching for the second mark.
As a result, in this position measurement method, the effect of increasing the accuracy of detecting the second mark at an early stage can be obtained.
[0077]
The position measuring method according to claim 8 is a procedure for determining an area in which to search for a mark of a second object based on a measurement result of a mark of the first object when measuring a plurality of objects.
Thus, in this position measurement method, the accuracy of mark detection in the early stage of the second object is increased, and the time required for the search can be shortened, so that an effect of preventing a decrease in throughput can be obtained.
[0078]
An exposure method according to a ninth aspect is a procedure for measuring at least one position of a mask mark and a substrate mark by the position measurement method according to any one of the first to eighth aspects.
As a result, in this exposure method, the time required for the alignment between the mask and the substrate is shortened, and the effect of improving the production efficiency is obtained.
[0079]
The position measuring device according to claim 10 is configured such that the control unit controls the measuring unit so as to sequentially search for a mark image for each of a plurality of regions obtained by dividing the imaging visual field.
As a result, in this position measuring device, the ratio of the occupation of the mark in each region increases, and the detection capability of the mark can be improved. In addition, even if the mark is not detected in one of the regions, the other regions are sequentially detected. By performing the search, it is possible to reduce the frequency of stopping the exposure apparatus and intervening an operator, thereby preventing a reduction in production efficiency.
[0080]
The position measuring device according to claim 11 is configured such that the control unit determines whether or not to search the second area based on a result of searching for the first area.
Thus, in the position measurement device, when a mark is detected in the search of the first area, it is not necessary to search the second area, so that an unnecessary measurement time can be omitted, and the throughput can be improved. The effect that can be obtained is obtained.
[0081]
According to a twelfth aspect of the present invention, the control unit terminates the measurement when the signal of the mark measured in the first area has a predetermined contrast.
Thus, in this position measurement device, the measurement is terminated when a predetermined contrast is obtained, so that an unnecessary measurement time can be omitted, and the effect of improving the throughput can be obtained.
[0082]
The position measuring device according to claim 13 is configured such that, when measuring a plurality of marks, the control unit determines an area for searching for the second mark in the imaging visual field based on a result of detecting the first mark. I have.
Thus, in this position measurement device, the accuracy of mark detection is increased, and the time required for search can be reduced, so that an effect of preventing a decrease in throughput can be obtained.
[0083]
The position measuring device according to claim 14 has a configuration in which, when measuring a plurality of objects, the control unit determines an area in which to search for a mark on the second object based on a measurement result of the mark on the first object. I have.
Accordingly, in this position measurement device, the accuracy of detecting the mark of the second object at an early stage is increased, and the time required for the search can be shortened, so that an effect of preventing a decrease in throughput can be obtained.
[0084]
An exposure apparatus according to a fifteenth aspect is configured such that the position measuring device according to any one of the tenth to fourteenth aspects is used as an apparatus for measuring at least one of a mask mark and a substrate mark. Has become.
As a result, in this exposure apparatus, the time required for the alignment between the mask and the substrate is shortened, and the effect of improving the production efficiency is obtained.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an exposure apparatus showing an embodiment of the present invention.
FIG. 2 is a flowchart illustrating a position measuring method according to a first embodiment of the present invention.
FIG. 3 is a plan view of a camera field of view divided into three regions.
4A is a signal waveform when a region A is searched, and FIG. 4B is a signal waveform when a region C is searched.
FIG. 5 is a plan view of the wafer on which search marks are formed.
FIG. 6 is a diagram illustrating a relationship between an area when a previous wafer is measured and a frequency at which a mark is detected.
FIG. 7 is a flowchart illustrating a position measurement method according to a second embodiment of the present invention.
FIG. 8 is a flowchart illustrating an example of a manufacturing process of a semiconductor device.
FIG. 9 is a plan view showing an example of a camera field of view according to the related art.
10A shows a signal waveform of the entire camera field of view, and FIG. 10B shows a signal waveform when a region B is searched.
11A is a plan view of a wafer mark, and FIG. 11B is a plan view of a search mark.
[Explanation of symbols]
Area A (second area)
Area B (first area)
FV camera field of view (imaging field of view)
R reticle (mask)
SM, SM1, SM2 Search mark (mark, board mark)
W wafer (object, second object, substrate)
1 Exposure equipment
15 Main control system (control unit)
19 Alignment control system (measurement unit)

Claims (15)

A position measurement method of imaging a mark formed on an object within a predetermined imaging field of view and measuring position information of the mark based on the imaging result,
Dividing the imaging field of view into a plurality of regions,
A position measuring method for sequentially searching for the image of the mark for each of the divided areas. The position measuring method according to claim 1,
A position measurement method comprising: determining whether to search for a second area based on a result of searching for a first area among the plurality of areas. The position measuring method according to claim 2,
Position measurement, wherein the measurement is terminated when a signal of the mark measured in the first area has a predetermined contrast, and the second area is searched when the signal does not have a predetermined contrast. Method. 4. The position measurement method according to claim 1, wherein the image of the mark is searched by one-dimensional image processing. In the position measuring method according to claim 4,
A position measuring method, wherein an image of the mark is searched by two-dimensional image processing based on a result of the one-dimensional image processing. The position measurement method according to claim 1, wherein when measuring a plurality of marks, the area for searching for a second mark in the imaging visual field is determined based on a result of detecting a first mark. A position measurement method characterized by determining. The position measuring method according to claim 6,
When searching for the second mark, an area in which the first mark is detected is first searched out of the plurality of areas. The position measuring method according to claim 6 or 7,
When measuring a plurality of said objects, the position measuring method characterized by determining the area where the mark of the second object is searched based on the measurement result of the mark of the first object. After aligning the mask and the substrate using a mask mark on a mask and a substrate mark on the substrate, in an exposure method of exposing the pattern of the mask to the substrate,
9. An exposure method, wherein the position of at least one of the mask mark and the substrate mark is measured by the position measurement method according to claim 1. What is claimed is: 1. A position measuring device comprising: an imaging unit that images a mark formed on an object within a predetermined imaging field of view; and a measurement unit that measures position information of the mark based on a result obtained by the imaging unit. ,
A position measuring apparatus, comprising: a control unit that divides the imaging field of view into a plurality of regions, and controls the measuring unit to sequentially search for the image of the mark for each of the divided regions. The position measuring device according to claim 10,
The position measurement device, wherein the control unit determines whether or not to search for a second area based on a result of searching for a first area among the plurality of areas. The position measuring device according to claim 11,
The control unit terminates the measurement when the signal of the mark measured in the first area has a predetermined contrast, and searches the second area when the signal does not have the predetermined contrast. Characteristic position measuring device. The position measuring device according to any one of claims 10 to 12,
The position measuring device, wherein the control unit determines the area where the second mark is searched in the imaging visual field based on a result of detecting the first mark when measuring the plurality of marks. The position measuring device according to claim 13,
The position measuring device, wherein the control unit determines the area in which to search for the mark of a second object based on a measurement result of the mark of a first object when measuring the plurality of objects. . In an exposure apparatus for aligning the mask and the substrate using a mask mark on a mask and a substrate mark on a substrate, and exposing the pattern of the mask to the substrate,
An exposure apparatus, wherein the position measurement device according to any one of claims 10 to 14 is used as an apparatus for measuring at least one of the position of the mask mark and the position of the substrate mark.

Images