JP2005166951A - Exposure method, exposure apparatus, and lithography system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure method capable of accurately transferring a pattern on a reticule onto a wafer. <P>SOLUTION: A correction function with respect to a dynamic characteristic of a reticule stage RST during relative scanning is generated from the baking result of a measurement mark to a reference wafer W<SB>T</SB>, and the position of the reticule stage RST during scanning exposure is controlled by using correction maps (R<SB>x</SB>(Y'<SB>i</SB>), R<SB>YL</SB>(Y'<SB>i</SB>), R<SB>YR</SB>(Y'<SB>i</SB>)) to correct shot distortion of its own apparatus. Further, an overlapping error of two different exposure apparatuses is detected by a result of actual overlapping baking to generate a function of correcting a positional deviation due to the detected overlapping error, and the correction maps on the basis of the function are used to control the position of the reticule stage RST during the scanning exposure, thereby correcting the overlapping error. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exposure method, an exposure apparatus, and a lithography system, and more specifically, a pattern formed on the mask by synchronous scanning in a predetermined direction of the mask and the object with respect to illumination light via the projection optical system. The present invention relates to an exposure method and an exposure apparatus that perform scanning exposure to be transferred thereon, and a lithography system including at least one exposure apparatus.

  Conventionally, when a semiconductor element or a liquid crystal display element or the like is manufactured by a photolithography process, a pattern of a photomask or a reticle (hereinafter, collectively referred to as “reticle”) is formed on a surface with a photoresist or the like via a projection optical system. In addition to an exposure apparatus that transfers onto a substrate such as a wafer or glass plate coated with a photosensitive agent, for example, a step-and-repeat reduction projection exposure apparatus (so-called stepper), step-and-scan scanning projection An exposure apparatus (so-called scanning stepper) or the like is used.

  The scanning stepper performs exposure (so-called scanning exposure) while synchronously scanning the reticle stage holding the reticle and the wafer stage holding the wafer in the scanning direction. Scanning exposure has the advantages of reducing the influence of the aberration of the projection optical system and forming a shot area with a large area, and recently, the control technology for both stages has been greatly improved. Today, scanning steppers are becoming more popular than steppers.

  On the other hand, the most important requirement for the performance of such an exposure apparatus is to accurately transfer the pattern on the reticle onto the wafer. Factors that hinder this accurate transfer include shot distortion that depends on the imaging characteristics of the projection optical system and a decrease in control accuracy in the stage control technique.

  According to the first aspect of the present invention, the pattern formed on the mask is transferred to the object via the projection optical system by the synchronous movement of the mask and the object in a predetermined direction with respect to the illumination light. An exposure method for performing a scanning exposure to be transferred on, wherein a first step of transferring a plurality of measurement marks arranged on a mask onto a predetermined object by the scanning exposure; and transferring the plurality of measurement marks A second step of detecting, from the result, information relating to a positional shift of the transfer position of each measurement mark on the predetermined object in a two-dimensional plane orthogonal to the optical axis of the projection optical system; The dynamic characteristics of the mask and the object during the scanning exposure in the two-dimensional plane, where the position of either the object or the mask with respect to the predetermined direction is an independent variable A third step of creating at least one function; when the scanning exposure is performed and the pattern is transferred onto the object, the function is used to either one of the object and the mask in the predetermined direction. A fourth step of controlling the position; and an exposure method.

  According to this, the position of either the object during scanning exposure or the mask is accurately controlled using a function relating to the dynamic characteristics during relative scanning between the mask and the object, which is obtained from the transfer result of actual scanning exposure. can do.

  In this case, in the third step, as the function, the position of either the object or the mask in the predetermined direction is set as an independent variable, and the position of the object or the mask in the predetermined direction is set as the function. At least one correction function for correction may be created.

  According to a second aspect of the present invention, scanning exposure is performed in which a pattern formed on the mask is transferred onto the object via a projection optical system by synchronous movement of the mask and the object in a predetermined direction with respect to illumination light. An exposure apparatus for performing a transfer apparatus that transfers a plurality of measurement marks arranged on a mask onto a predetermined object by the scanning exposure; and the predetermined direction obtained from a transfer result of the plurality of measurement marks. A function creation device for creating at least one function relating to the dynamic characteristics of the mask and the object in the two-dimensional plane during the scanning exposure, wherein the position of one of the object and the mask is an independent variable; When the scanning exposure is performed and the pattern is transferred onto the object, any one of the object and the mask related to the predetermined direction is used using the function. It is an exposure apparatus comprising a; controller and for controlling the position.

  According to this, the position of one of the object and the mask during the scanning exposure can be controlled using the function relating to the dynamic characteristics during the relative scanning between the mask and the object.

  According to the third aspect of the present invention, at least one of the mask and the pattern formed on the mask is synchronized with the illumination light in a predetermined direction on the object via the projection optical system. A plurality of exposure apparatuses which are scanning exposure apparatuses to be transferred; at least one of the plurality of exposure apparatuses is arranged on a mask by exposure with each of two exposure apparatuses which are scanning exposure apparatuses A detection device that detects information on a positional deviation of the measurement marks in a two-dimensional plane orthogonal to the optical axis of the projection optical system of the two exposure devices based on a result of overlay transfer of the plurality of measurement marks. And, based on the detection result, the position of either the object or the mask with respect to the predetermined direction as an independent variable, between the two exposure apparatuses. A function creation device that creates a function for correcting misalignment misalignment, and at least one of the two exposure devices scans the pattern onto the object, The lithography system uses the function to control the position of one of the object and the mask.

  According to this, an overlay error of two different exposure apparatuses is detected from an actual transfer result, a function for correcting a positional deviation due to the detected overlay error is created, and scanning is performed using the function. The position of either the object being exposed or the mask can be controlled with high accuracy.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to FIGS.

FIG. 1 schematically shows the configuration of a lithography system 100 according to an embodiment to which the exposure method of the present invention is applied. The lithography system 100 includes N projection exposure apparatuses 110 _{1 to} 110 _N , a storage device 140, a terminal server 150, a host computer 160, and a measurement apparatus 190. Among these, the exposure apparatus 110 _k (k = 1, 2,..., N), the terminal server 150, and the measurement apparatus 190 are connected to a local area network (LAN) 170. In addition, the storage device 140 is connected to the host computer 160 via a communication path 180 such as a skazy (SCSI). The host computer 160 is connected to the LAN 170 via the terminal server 150. That is, on the hardware configuration, a communication path among the exposure apparatus 110 _k , the terminal server 150, the host computer 160 and the measurement apparatus 190 is secured. Note that communication between actual components in this system will be described later.

As the measuring device 190, for example, an image processing type measuring device that images a plurality of marks formed on a wafer and measures a relative positional relationship (amount of positional deviation) between the marks is used. The exposure apparatus 110 _p as shown in Figure 1, the above apparatus is an exposure apparatus that is not the LAN connection, in this embodiment, intended to be used to create a reference wafer W _T to be described later is there.

Each of the exposure apparatuses 110 _{1 to} 110 _N may be a step-and-repeat type projection exposure apparatus, that is, a so-called stepper (hereinafter referred to as “static exposure apparatus”), or a step-and-scan system. Or a scanning stepper (hereinafter referred to as a “scanning exposure apparatus”). However, at least one of the exposure apparatuses 110 _{1 to} 110 _N needs to be a scanning exposure apparatus. In the following, it described as an exposure apparatus 110 ₁ is at least the scanning type exposure apparatus.

  The host computer (hereinafter abbreviated as “host”) 160 is a computer that comprehensively manages this lithography process. The host 160 may be a computer that comprehensively manages a production line for semiconductor elements and the like including this lithography process.

The host 160 as a function creation device also has a function of creating a correction function to be described later for canceling an overlay error between two exposure devices among the exposure devices 110 _{1 to} 110 _N. Information about correction function created by the host 160, is managed by being stored in the storage device 140 by the host 160, when instructing the overlay exposure to the exposure apparatus 110 _k is the information about the correction function, storage The data is read from the apparatus 140 and sent to the exposure apparatus 110 _k .

  The LAN 170 can be either a bus type LAN or a ring type LAN. In this embodiment, a carrier type medium access / contention detection (CSMA / CD) type bus type LAN of IEEE802 standard is adopted. ing.

The measuring device 190 is provided with an image pickup device such as a CCD, and picks up an image of the wafer conveyed from the exposure device 110 _{k and the} like, and performs predetermined image processing on the image pickup result, thereby performing later-described processing on the wafer. The transfer position of the measurement mark image to be measured is measured, and the amount of displacement from the designed transfer position is detected. The amount of positional deviation detection result of the measuring device 190 is sent to the exposure device 110 _k or the host 160, it becomes to be managed by the exposure apparatus 110 _k or the host 160.

Figure 2 is an example of a schematic configuration of an exposure apparatus 110 ₁ as a representative of the scanning exposure apparatus is illustrated. The exposure apparatus 110 ₁ includes an illumination system 10, a reticle stage RST on which a reticle R as a mask is placed, a projection optical system PL, a wafer stage WST on which a wafer W as an object is held, an alignment detection system AS, and an apparatus A main controller 20 and the like for overall control are provided.

  The illumination system 10 includes, for example, a light source, an illuminance uniformizing optical system including an optical integrator, a relay lens, a variable ND filter, a variable field stop (reticle blind or masking) as disclosed in Japanese Patent Laid-Open No. 6-349701. (Also referred to as a blade) and a dichroic mirror or the like (both not shown). As the optical integrator, a fly-eye lens, a rod integrator (an internal reflection type integrator), a diffractive optical element, or the like is used.

In this illumination system 10, on a reticle R on which a circuit pattern or the like is drawn, a slit-shaped illumination area (a rectangular illumination area elongated in the X-axis direction) defined by the reticle blind is illuminated with light (exposure light) IL. Illuminates with almost uniform illuminance. Here, as the illumination light IL, far ultraviolet light such as KrF excimer laser light (wavelength 248 nm), ArF excimer laser light (wavelength 193 nm), vacuum ultraviolet light such as F ₂ laser light (wavelength 157 nm), or the like is used. . As the illumination light IL, it is also possible to use an ultraviolet bright line (g-line, i-line, etc.) from an ultra-high pressure mercury lamp.

  On reticle stage RST, reticle R is fixed, for example, by vacuum suction. Reticle stage RST is XY perpendicular to the optical axis of illumination system 10 (corresponding to optical axis AX of projection optical system PL described later) by a reticle stage drive unit (not shown) using a linear motor, a voice coil motor or the like as a drive source. It can be driven minutely in a plane and can be driven (scanning operation) in a predetermined direction (here, the Y-axis direction which is the left-right direction in FIG. 2) at a set scanning speed.

  The reticle stage RST is formed with a reflecting surface made of, for example, a moving mirror that faces the X-axis direction and the Y-axis direction for reflecting the laser light. The position of the reticle stage RST within the stage moving surface is on the reflecting surface. It is always measured by a reticle laser interferometer (hereinafter referred to as “reticle interferometer”) 16 that emits laser light with a resolution of, for example, about 0.5 to 1 nm.

Here, in practice, as shown in the plan view of FIG. 3, an X-axis moving mirror 38X extending in the Y-axis direction is fixed to one end (+ X side) of the reticle stage RST in the X-axis direction. Two Y-axis moving mirrors 38Y _L and 38Y _R made of a retroreflector are fixed to the + Y side end. Correspondingly, a reticle X-axis interferometer 16X constituting the reticle interferometer 16 of FIG. 2 is provided at a position facing the X-axis movable mirror 38X, and each of the Y-axis movable mirrors 38Y _L and 38Y _R is provided. A pair of reticle Y-axis interferometers 16Y _L and 16Y _R are provided at the opposing positions, respectively. From the reticle X-axis interferometer 16X, the laser beam LR _X is irradiated in parallel to the X-axis toward the X-axis moving mirror 38X. From each of the reticle Y-axis interferometers 16Y _L and 16Y _R , the Y-axis moving mirror is irradiated. Laser beams LR _L and LR _R are irradiated toward 38Y _L and 38Y _R in parallel with the Y axis, respectively.

In this case, the laser beams LR _L and LR _R reflected by the movable mirrors (retro-reflectors) 38Y _L and 38Y _R in the Y-axis direction that is the scanning direction are reflected by the reflective mirrors 39A and 39B, respectively, and again the movable mirror 38Y _L , 38Y _R and reflected back to the reticle Y-axis interferometers 16Y _L , 16Y _R. Note that the end surface of reticle stage RST may be mirror-finished to form a reflecting surface, and this reflecting surface may be used instead of the movable mirror.

As shown in FIG. 2, the output of the three-axis reticle interferometer is supplied to the main controller 20 via the stage controller 19, and the main controller 20 measures the length of the laser beam LR _X. The X position of reticle stage RST is measured based on the output of interferometer 16X as an axis, and the output of each of two Y-axis interferometers 16Y _L and 16Y _{R using} laser beams LR _L and LR _R as measurement axes, respectively. Based on this, the Y position of the reticle stage RST is measured with respect to the X position on the respective measurement axes of the Y axis interferometers 16Y _L and 16Y _R. Also, the interferometer 16Y _L, and the difference between the output of 16Y _R, based on the laser beam LR _L, the interval L and LR _R, a straight line parallel to the Y axis passing through the origin position of the reticle stage RST, reticle stage The rotation angle of the RST in the XY plane is calculated.

  Position information (including rotation information such as yawing amount) of reticle stage RST from reticle interferometer 16 is supplied to stage controller 19 and main controller 20 via this. In response to an instruction from main controller 20, stage controller 19 controls driving of reticle stage RST via a reticle stage drive unit (not shown) based on the position information of reticle stage RST, and holds it on reticle stage RST. The position of the reticle R is controlled.

  Above the reticle R, a pair of reticle alignment detection systems 22 (however, in FIG. 2, the reticle alignment detection system 22 on the back side of the drawing is not shown) are arranged at a predetermined distance in the X-axis direction. Although not shown here, each reticle alignment detection system 22 includes an epi-illumination system for illuminating the detection target mark with illumination light having the same wavelength as the illumination light IL, and the detection target mark. And a detection system for capturing an image. The detection system includes an imaging optical system and an image sensor, and an imaging result (that is, a mark detection result by the reticle alignment detection system 22) by this detection system is supplied to the main controller 20. In this case, a mirror (not shown) for guiding the illumination light emitted from the epi-illumination system onto the reticle R and guiding the detection light generated from the reticle R by the illumination to the detection system of the reticle alignment detection system 22 Mirror) is detachably disposed on the optical path of the illumination light IL, and when the exposure sequence is started, before irradiation of the illumination light IL for transferring the pattern on the reticle R onto the wafer W, On the basis of a command from the main controller 20, the incident mirror is retracted out of the optical path of the illumination light IL by a driving device (not shown).

  The projection optical system PL is disposed below the reticle stage RST in FIG. 2, and the direction of the optical axis AX is the Z-axis direction. As projection optical system PL, a birefringent optical system having a predetermined reduction magnification 1 / M (M is 4 or 5, for example) is used. Therefore, when the illumination area of the reticle R is illuminated by the illumination light IL from the illumination system 10, a reduced image (partial inverted image) of the illumination area portion of the circuit pattern of the reticle R is passed through the projection optical system PL through the wafer W. The light is projected onto the projection area in the field of view of the projection optical system PL conjugate to the illumination area above, and transferred to the resist layer on the surface of the wafer W.

  Wafer stage WST is arranged on a base (not shown) below projection optical system PL in FIG. Wafer holder 25 is placed on wafer stage WST. A wafer W is fixed on the wafer holder 25 by, for example, vacuum suction.

  Wafer stage WST is rotated by X, Y, Z, θz (rotation direction around Z axis), θx (rotation direction around X axis), and θy (rotation direction around Y axis) by wafer stage drive unit 24 in FIG. ) In a single stage that can be driven in the direction of 6 degrees of freedom.

  Wafer stage WST is formed with a reflecting surface composed of a moving mirror or the like facing the X-axis direction and Y-axis direction that reflects the laser beam. The position of wafer stage WST is irradiated with the laser beam. The wafer laser interferometer (hereinafter referred to as “wafer interferometer”) 18 disposed outside is constantly measured with a resolution of about 0.5 to 1 nm, for example. In practice, an interferometer having a length measuring axis in the X-axis direction and an interferometer having a length measuring axis in the Y-axis direction are provided, but these are typically shown as a wafer interferometer 18 in FIG. Has been. These interferometers are composed of multi-axis interferometers having a plurality of measurement axes, and in addition to the X and Y positions of wafer stage WST, rotation (yawing (θz rotation that is rotation around the Z axis)), pitching (X axis) Rotation around (θx rotation) and rolling (θy rotation around Y axis)) can also be measured. In response to an instruction from main controller 20, stage controller 19 drives and controls wafer stage WST via wafer stage driver 24 based on the position information of wafer stage WST, and is held on wafer stage WST. The position of the wafer W is controlled.

  A reference mark plate FM is fixed in the vicinity of wafer W on wafer stage WST. The surface of the reference mark plate FM is set to substantially the same height as the surface of the wafer W, and at least a pair of reticle alignment reference marks, a reference mark for baseline measurement of the alignment detection system AS, and the like are provided on this surface. Is formed.

  The alignment detection system AS is an off-axis alignment sensor disposed on the side surface of the projection optical system PL. As this alignment detection system AS, for example, a broadband detection light beam that does not sensitize a resist on a wafer is irradiated onto a target mark, and an image of the target mark formed on a light receiving surface by reflected light from the target mark is not shown. An image processing system FIA (Field Image Alignment) that captures an image of an index (an index pattern on an index plate provided in the alignment detection system AS) using an imaging device (CCD) or the like and outputs the imaged signals. ) System sensors are used. The alignment sensor of the alignment detection system AS is not limited to the FIA system, and the target mark is irradiated with coherent detection light to detect scattered light or diffracted light generated from the target mark, or generated from the target mark. Of course, it is possible to use an alignment sensor that detects and interferes with two diffracted lights (for example, diffracted lights of the same order or diffracted in the same direction) alone or in appropriate combination. The imaging result of the alignment detection system AS is output to the main controller 20.

In FIG. 2, the control system is mainly configured by a main controller 20 and a stage controller 19 subordinate thereto. The main control device 20 includes a so-called microcomputer (or workstation) including a CPU (central processing unit), a main memory, and the like, and controls the entire device. Further, in the present embodiment, the main controller 20, coater developer (not shown) which are parallel in the exposure apparatus 110 ₁ (hereinafter, referred to as "C / D") is also controlled.

  The main controller 20 includes, for example, a storage device including a hard disk, an input device including a pointing device such as a keyboard and a mouse, and a display device such as a CRT display (or a liquid crystal display) (all not shown). Connected externally.

In FIG. 1, the exposure apparatus 110 _k is illustrated as being connected to the LAN 170, but actually, the main control apparatus 20 is connected to the LAN 170 and is connected to the host 160 and the like via the LAN 170. We are communicating.

  For example, when performing scanning exposure, the main control device 20 instructs the stage control device 19 to perform the operation and transmits information necessary for the operation to the stage control device 19. The stage controller 19 includes a position feedback control system as a feedback control system for controlling the position of the reticle stage RST and a position feedback control system as a feedback control system for controlling the position of the wafer stage WST. Has been.

  Upon receiving the instruction and information, the stage control device 19 creates a position command per unit time for the position feedback control system of both stages RST and WST based on the information. Then, the position feedback control system of both stages RST and WST calculates target drive amounts of reticle stage RST and wafer stage WST corresponding to the position command. The stage control device 19 performs, for example, synchronous scanning of the reticle R and the wafer W during scanning exposure or movement of the wafer W via the reticle stage driving unit and the wafer stage driving unit 24 according to the calculated target driving amount. (Stepping) etc. are performed.

  In order to realize synchronous scanning of both stages RST and WST, one of the position feedback control systems of both stages RST and WST may be in a primary relationship and one in a secondary relationship. For example, a position command for the control system of wafer stage WST may be created based on the feedback control amount of the control system of reticle stage RST, or vice versa.

  In addition, the position feedback control system of both stages WST and RST may have a speed feedback control system built inside the control loop.

  More specifically, the stage control device 19 is configured so that, for example, during scanning exposure, the reticle R passes through the reticle stage RST at a scan speed set in the + Y direction or the −Y direction based on the set scan direction. Synchronously with the scanning, the wafer W is moved through the wafer stage WST with respect to the projection area conjugate to the illumination area, and the speed of the reticle R is opposite to the movement direction of the reticle stage RST (scanning direction). A command value during scanning exposure for the feedback control system is created so that scanning is performed at a speed of (1 / M) times. When the position command value is input to the feedback control system, the feedback control system calculates a deviation between the position command value and the feedback amount based on the measurement values of the reticle interferometer 16 and the wafer interferometer 18. The positions of the reticle stage RST and wafer stage WST are controlled via a reticle stage driving unit and a wafer stage driving unit 24 (not shown) so that the deviation is canceled.

  Further, at the time of stepping, the stage control device 19 creates a position command value at the time of step movement based on the set step speed, inputs the created position command value to the feedback control system, and feeds back the position command value. In the control system, the position of wafer stage WST is controlled via wafer stage drive unit 24 based on the deviation between the command value and the feedback amount based on the measurement value of wafer interferometer 18.

Non Furthermore, the exposure apparatus 110 ₁ of this embodiment, supplies from an oblique direction the imaging light beam for forming a plurality of slit images toward the best imaging plane of the projection optical system PL with respect to the optical axis AX direction An oblique incidence type multi-point focus detection system comprising an irradiation system shown in the drawing and a light receiving system (not shown) that receives each reflected light beam of the imaging light beam on the surface of the wafer W through a slit is provided. . As this multipoint focus detection system, for example, one having the same configuration as that disclosed in Japanese Patent Application Laid-Open No. 6-283403 (corresponding US Pat. No. 5,448,332) is used, and this multipoint focus detection system is used. Is supplied to the main controller 20. In response to an instruction from the main controller 20, the stage controller 19 moves the wafer stage WST in the Z direction via the stage controller 19 and the wafer stage drive unit 24 based on the wafer position information from the multipoint focus detection system. And drive in the tilt direction.

The basic configuration of a scanning type exposure apparatus of the exposure apparatus 110 _k in this lithography system is assumed to be substantially identical to the configuration of the exposure apparatus 110 _1.

Next, is performed by the lithography system and exposure apparatus 110 ₁ has the above configuration, a description will be given of an exposure method of the present embodiment. In the exposure apparatus 110 _1, as described above, the Y-axis direction of the synchronous scanning of the reticle stage RST (reticle R) and the wafer stage WST (wafer W), the scanning exposure to transfer the pattern on the reticle R onto the wafer W Do. In such scanning exposure, the pattern transfer accuracy on the reticle R greatly depends on the dynamic characteristics of the reticle stage RST and wafer stage WST during relative scanning. For example, based on the measurement value of the wafer interferometer 18, the relative positional relationship between both stages RST and WST gradually shifts in the X-axis direction during the relative movement of both stages RST and WST in the Y-axis direction. If it has the characteristics, the pattern image transferred onto the wafer W is distorted with respect to the pattern on the reticle R. Such distortion becomes a shot distortion component in the shot area and appears in the exposure result.

To cope with such shot distortion problem, in exposure apparatus 110 ₁ of the present embodiment corrects the position command with respect to the reticle stage RST during scanning exposure. For example, when the reticle stage RST gradually shifts in the + X direction during synchronous scanning in the Y-axis direction, if the position command for the reticle stage RST is corrected in the −X direction, the reticle stage RST is consequently obtained. Does not shift to the + X side, that is, relative scanning between the wafer stage WST and the reticle stage RST is performed without causing a shift in the X-axis direction.

Therefore, in the present embodiment, before performing actual scanning exposure, first, a predetermined reticle (measurement reticle R _T described later) is loaded on the reticle stage RST in place of the reticle R in FIG. And the exposure result (printing result) transferred onto the wafer is measured by the scanning exposure to detect a distortion component of the shot area, and based on the detected distortion component, the reticle stage RST during the scanning exposure is detected. A correction function that gives a correction value for the position command is created, and during the scanning exposure, the position command for the position feedback control system of the reticle stage RST is corrected using the correction function.

  For example, as in the above example, when the reticle stage RST gradually shifts in the + X direction during synchronous scanning in the Y-axis direction, the distortion of the shot area shifts in the −X direction with respect to the scanning direction. It will be like distortion. Therefore, if a correction that shifts to the −X side is added to the position command of the reticle stage RST, distortion of the shot region in the −X direction is reduced.

Further, in the lithography process, different circuit patterns are stacked and formed on the wafer in several layers. In the lithography system of this embodiment, the circuit pattern of each layer (layer) of the same wafer is increased in order to increase the throughput. Therefore, process management is performed such that transfer formation is performed using different exposure apparatuses. For example, the second layer of the shot area on the wafer was exposed for the first layer in the exposure apparatus 110 _2, also be transferred and formed in the exposure apparatus 110 _1. The issue in the process management for overlaying between units is the overlay accuracy of shot areas between layers, and the biggest factor that reduces this overlay accuracy is the distortion error of the transferred image between units. (Overlay error). In the following, in overlay exposure, an exposed layer that is a reference for overlay is referred to as an original process layer, or simply an original process, and a layer formed by superposition is referred to as an existing process layer or simply an existing process. Shall be called.

  Therefore, in the present embodiment, an overlay error between the units is detected in advance, and a correction function that cancels the detected overlay error is created. During the scanning exposure, the correction function is used. The position command for the reticle stage RST is corrected.

That is, in this embodiment, to create a correction function to an exposure apparatus 110 ₁ of the scanning exposure as shown below.
(A) Correction function for canceling shot distortion component in own machine (B) Correction function for correcting overlay error between machines Since these two correction functions are different in creation method and application method, Now, a method for creating each correction function will be described individually. In the present embodiment, among the above two correction functions, first, a correction function (A) is created, and scanning exposure is performed with the position command for the reticle stage RST corrected by the correction function (A). , Exposure is performed to create the correction function (B), and the correction function (B) is created based on the result. In this way, since the overlay error can be detected in a state where the shot distortion of the own machine is corrected, the shot distortion component and the overlay error component of the own machine are independent without overlapping each other. Can be separated and extracted.

In order to simplify the description, in the present embodiment, of the exposure apparatuses 110 _{1 to} 110 _N , the scanning exposure apparatus (exposure apparatus 110 ₁ or the like) is usually the both stages RST when performing exposure. , It is assumed that the WST scanning speeds are all the same.

  First, an example of a measurement reticle used for creating a correction function according to this embodiment will be described.

FIG. 4 shows an example of the measurement reticle _RT . FIG. 4 is a plan view of the measurement reticle _RT as viewed from the pattern surface side (the lower surface side in FIG. 2).

In this measurement reticle _RT , a pattern area PA composed of a light-shielding band indicated by oblique lines is formed on one surface (pattern surface) of a substantially rectangular glass substrate 42, and a predetermined measurement mark is formed in the pattern area PA. M _p is arranged in a matrix at predetermined intervals. In FIG. 4, only a total of 15 (M _{1 to} M ₁₅ ) predetermined measurement marks M _p (3 rows and 5 columns (rows in the Y-axis direction)) are illustrated. Are formed in the pattern area PA.

A pair of reticle alignment marks RM1 and RM2 are formed on both sides in the X-axis direction of the pattern area PA passing through the center of the pattern area PA, that is, the center of the measurement reticle _RT (reticle center). A plurality of reticle alignment marks are formed along the Y-axis direction with the same positional relationship in the X-axis direction as these reticle alignment marks RM1 and RM2. Although not shown in FIG. 4, a wafer mark (alignment mark) having a known positional relationship with the center of the pattern area PA is also arranged on the measurement reticle _RT . This wafer mark is transferred onto the wafer W together with the measurement mark M _{p at} the time of scanning exposure, and used for wafer alignment processing described later.

FIG. 5 shows an example of a predetermined measurement mark M _p is shown. As shown in FIG. 5, L / S patterns MX ₁ and MX ₂ extending in the X-axis direction and L / S patterns MY ₁ and MY ₂ extending in the Y-axis direction are formed on the measurement mark M _p. Yes. In FIG. 5, the chrome part in the measurement mark M _p is indicated by oblique lines, and the light transmission part is indicated by a solid color. As shown in FIG. 5, in the L / S patterns MX ₁ , MX ₂ , MY ₁ , MY ₂ , the lines are light transmission portions and the spaces are chrome portions. The L / S patterns MX ₁ and MY ₁ have three line patterns formed at both ends in the arrangement direction, and have a space (chrome portion) having a region that can contain the L / S patterns MX ₂ and MY ₂ near the center. ) Is formed. The L / S patterns MX ₁ and MY ₁ are provided apart from the L / S patterns MX ₂ and MY ₂ by the distance M × w in the X-axis direction and the Y-axis direction on the measurement reticle _RT , respectively. Yes.

Next, the operation of the lithography system when creating the correction function (A) will be described. Here, the operation will be described for creating in the exposure apparatus 110 ₁ as a representative of the scanning exposure apparatus a correction function of (A).

First, the operator, via the input device (not shown), the imaging condition, for example, the illumination conditions are set, to the main controller 20 of exposure apparatus 110 _1, an instruction for exposure is made, the main controller 20 Under the control of, the measurement reticle _RT is transported by a reticle transport system (not shown) and is sucked and held on the reticle stage RST in the loading position. This completes the loading of the measurement reticle _RT .

Next, preparatory work such as alignment of the measurement reticle _RT is performed. Specifically, main controller 20 moves wafer stage WST via stage controller 19 and wafer stage drive unit 24, and moves reference mark plate FM to a predetermined position directly below projection optical system PL (hereinafter, for convenience, “ (Referred to as “reference position”). Subsequently, the relative position between the pair of first reference marks on the reference mark plate FM and the pair of reticle alignment marks RM1 and RM2 on the measurement reticle _RT corresponding to the first reference mark is detected by the pair of reticle alignment detection described above. Detection is performed using system 22. Then, main controller 20 stores the detection result of reticle alignment detection system 22 and the measurement values of reticle interferometer 16 and wafer interferometer 18 at the time of detection in main memory.

Next, main controller 20 moves wafer stage WST and reticle stage RST in the opposite directions along the Y-axis direction by a predetermined distance, respectively, to generate another pair of first reference marks on reference mark plate FM. And the relative position of the pair of reticle alignment marks on the measurement reticle _RT corresponding to the first reference mark using the pair of reticle alignment detection systems 22 described above. Then, main controller 20 stores the detection result of reticle alignment detection system 22 and the measurement values of interferometers 16 and 18 at the time of detection in main memory. Next, in the same manner as described above, the relative positional relationship between another pair of first reference marks on the reference mark plate FM and the reticle alignment mark corresponding to the first reference mark is further measured.

  Then, main controller 20 obtains information on the relative positional relationship between the plurality of first reference marks thus obtained and the corresponding reticle alignment marks, and the measured values of interferometers 16 and 18 at the time of each measurement. Is used to determine the relative positional relationship between the reticle stage coordinate system defined by the measurement axis of the interferometer 16 and the wafer stage coordinate system defined by the measurement axis of the interferometer 18. Thereby, reticle alignment is completed. In the following scanning exposure, scanning exposure is performed by synchronously scanning the reticle stage RST and the wafer stage WST in the Y-axis direction of the wafer stage coordinate system. In this case, the reticle stage coordinate system and the wafer stage coordinate system are used. Based on the relative positional relationship, the reticle stage RST is scanned.

  Next, main controller 20 performs baseline measurement. Specifically, wafer stage WST is returned to the above-mentioned reference position, moved from the reference position by a predetermined amount, for example, the design value of the baseline, in the XY plane, and then moved onto reference mark plate FM using alignment detection system AS. The second reference mark is detected (the measured value of the wafer interferometer 18 is stored in the main memory). Main controller 20 obtains information on the relative positional relationship between the detection center of alignment detection system AS and the second reference mark obtained at this time, and a pair of first reference values measured when wafer stage WST is first positioned at the reference position. Information on the relative positional relationship between the mark and the pair of reticle alignment marks corresponding to the first reference mark, the measurement value of the wafer interferometer 18 at the time of each measurement, the design value of the baseline, and a known first value Based on the positional relationship between the first reference mark and the second reference mark (design positional relationship information between the two reference marks on the reference mark plate FM), the baseline of the alignment detection system AS, that is, the projection center of the reticle pattern And a distance (positional relationship) between the detection center (index center) of the alignment detection system AS. If this baseline is calculated, the wafer stage WST can be accurately positioned at the exposure position of each shot area during exposure after wafer alignment described later by measurement of the alignment detection system AS.

Then, under the control of the main controller 20, the reference wafer W _T is loaded on the wafer stage WST. The reference wafer W _T is subjected to pattern transfer of the measurement reticle _RT to a plurality of shot areas by exposure, and an image of a measurement mark M _p (for example, a resist image or an etching image) is formed in each shot area. It is assumed that the wafer has a negative photoresist coated on its surface by C / D (not shown). The reference wafer WT _{serves as} a sample for creating the correction function (A), and the misregistration in which the already formed resist image of the measurement mark M _p is measured to create the correction function. It becomes the standard of quantity.

Note that the amount of positional deviation (dx ′ _p , dy ′ _p ) from the design formation position of the image of the measurement mark M _{p on} the reference wafer W _T is obtained in advance using, for example, a light wave measuring device, and is stored in the storage device. 140 is stored.

Next, main controller 20, with respect to the reference wafer W _T that has been loaded, executing a wafer alignment such as EGA (Enhanced Global Alignment). That is, the main controller 20, the reference wafer W _T already wafer such as to sequentially position the wafer marks arranged in a plurality of shot areas (sample shots) formed within the detection field of the alignment detection system AS on The target position of the stage WST is given to the stage controller 19. The stage controller 19 sequentially positions the wafer stage WST via the wafer stage drive unit 24 in accordance with the target position. Each time this positioning is performed, main controller 20 detects the position information of the wafer mark by alignment detection system AS.

Next, main controller 20 determines the position of each wafer mark on the stage coordinate system based on the position of the wafer mark relative to the center of the index, which is the detection result of the wafer mark, and the measured value of wafer interferometer 18 at that time. Calculate the coordinates. Then, main controller 20 uses the least square method disclosed in, for example, Japanese Patent Application Laid-Open No. 61-44429 (corresponding US Pat. No. 4,780,617) using the calculated position coordinates of the wafer mark. perform had statistical calculation, the rotational component of the array coordinate system and the stage coordinate system of each shot area of the reference wafer W _T, scaling component, the offset component, given such orthogonality component in the X-axis and Y-axis of the stage coordinate system calculating the parameters of the regression model, by substituting the parameters in the regression model, calculates array coordinates of each shot area on the reference wafer W _T, i.e. the overlay position.

  Thus, the wafer alignment is completed, and then main controller 20 performs a step-and-scan exposure operation as follows.

In this exposure operation, main controller 20 instructs stage controller 19 to move wafer stage WST based on the wafer alignment result and the baseline measurement result. Response to this instruction, the stage controller 19, while monitoring the measurement values of wafer interferometer 18, the scan start position (acceleration starting position for exposure of the first shot of the reference wafer W _T (1st shot area) ) To move wafer stage WST.

  This scan start position (acceleration start position) is transferred and formed by the current scan exposure with respect to the center position coordinate of the first shot (that is, the first shot area of the original process) obtained by the wafer alignment. The center position coordinates of the shot area are set so as to be shifted by w with respect to the X-axis direction and the Y-axis direction, respectively.

The stage controller 19 starts scanning the reticle stage RST and the wafer stage WST in the Y-axis direction via the reticle stage driving unit and the wafer stage driving unit 24, and both stages RST and WST have their respective target scanning speeds. , The pattern area of the measurement reticle _RT starts to be illuminated by the illumination light IL, and scanning exposure is started.

  That is, in the stage controller 19, the movement speed Vr of the reticle stage RST in the Y-axis direction and the movement speed Vw of the wafer stage WST in the Y-axis direction are set to the projection magnification 1 / M of the projection optical system PL, particularly during the above-described scanning exposure. The reticle stage RST and wafer stage WST are synchronously controlled so that the corresponding speed ratio is maintained.

Then, different areas of the pattern area of the measurement reticle _RT are sequentially illuminated with the illumination light IL, and the illumination of the entire pattern area is completed, whereby the first shot scanning exposure on the reference wafer W _T is completed. As a result, the circuit pattern of the measurement reticle _RT is reduced and transferred to the first shot via the projection optical system PL.

  In this way, when the first shot scanning exposure is completed, main controller 20 gives an instruction to stage controller 19 to move wafer stage WST stepwise in the X and Y axis directions, and to perform a second shot (second shot). It is moved to the scanning start position (acceleration start position) for exposure of the shot area. In this case as well, as in the first shot, the scanning start position of the shot area transferred and formed by the current scanning exposure is relative to the center position coordinates of the second shot of the original process obtained by the wafer alignment. A position where the center position coordinates are shifted from each other by an interval w with respect to the X-axis direction and the Y-axis direction.

  Then, main controller 20 performs scanning exposure similar to the above-described operation on the second shot.

Thus, the reference m-th on wafer W _T (m is a natural number) are stepping operation and is repeatedly performed for the exposure of scanning exposure and m + 1-th shot area of shot areas, all on the reference wafer W _T The pattern of the measurement reticle _RT is sequentially transferred to the exposure target shot area.

Then, the reference wafer W _T on wafer holder 25 using the wafer transfer system (not shown) is unloaded and conveyed to a C / D (not shown) by the main controller 20. Then, this C / D development of the reference wafer W _T is performed, after its development, on the reference wafer W _T, the resist images of the plurality of measurement marks M _p of measurement reticle R _T, i.e., the present process A resist image of the measurement mark M _p is formed.

In FIG. 6 (A), exposure result on reference wafer W _T in the case where the scanning exposure is performed as designed (transfer results) are shown schematically. As shown in FIG. 6A, each measurement mark M formed on the measurement reticle _RT is obtained by performing scanning exposure by shifting the wafer stage WST by the interval w in the −X direction and the −Y direction. and the resist image of the original process in _p, the superposition image MP _p is the + X direction and the + Y direction between the resist image of the present process, (a projection magnification, and has a 1 / M times on the reticle R _T) w only It is shifted and superimposed and transferred.

In FIG. 6 (B), an example of a transfer result of each mark M _P in the scanning exposure is shown enlarged. As shown in FIG. 6B, as a result of the overlapping scanning exposure, the L / S pattern MX ₁ and the L / S pattern MX ₂ are transferred so as to overlap, and the L / S pattern MY ₁ and L / S pattern MY ₂ is transferred so as to overlap. As a result, an L / S pattern image MXP _P is formed by the image of the L / S pattern MX _{1 and} the image of the L / S pattern MX ₂ , and the image of the L / S pattern MY ₁ and the L / S pattern MY ₂ in the image, so that the L / S pattern images MYP _p is formed.

FIG. 7A shows an enlarged L / S pattern image MXP _p when the measurement mark M _p is transferred as designed by the scanning exposure. As shown in FIG. 7A, when each measurement mark M _p is accurately transferred in the superposed scanning exposure, the center of the image MX ₁ ′ of the L / S pattern MX ₁ and the L / S pattern MX ₂ of the image MX ₂ 'with the center of being adapted to match, L / S pattern image MX _1' and the center of the image of each L / S pattern at both ends of, the L / S pattern image MX ₂ 'of The distances from the center are predetermined distances L1 and L2, respectively. As for the distance between the L / S pattern MY ₁ and the L / S pattern MY ₂ , the center of the transferred image is the same as the relationship between the L / S pattern MX ₁ and the L / S pattern MX ₂ described above. It is assumed that the positional relationship between the images of the patterns when they are matched and overlaid is known.

However, as shown in FIG. 7B, the resist image of the measurement mark M _p formed by the scanning exposure in the current process is different from the image of the measurement mark M _p formed by the scanning exposure in the original process. When the position is displaced with respect to the X-axis direction, the distance between the pattern image MX ₂ ′ and the L / S pattern at both ends of the pattern image MX ₁ ′ is different from L1 and L2, and FIG. ) positional deviation amount dx _p, as shown in results. Similarly, a positional deviation amount dy _{p in the} Y-axis direction also occurs between the L / S pattern image MY ₁ ′ and the L / S pattern image MY ₂ ′ related to the mark image MYP _p .

In FIGS. 7A and 7B, the L / S pattern image MX ₁ ′ and the L / S pattern image MX ₂ ′ integrally form an L / S pattern with a duty ratio of 50%. Although shown as such, it is not necessary. Rather, even if the center of the image MX ₁ ′ of the L / S pattern MX ₁ and the center of the image MX ₂ ′ of the L / S pattern MX ₂ are slightly shifted, the line pattern image of the L / S pattern MX ₁ and L / S pattern as MX ₂ of the line pattern image not overlapping, it is desirable to take a sufficiently wide central chromium portion of the L / S pattern MX _2. This is because, in the process described later, the L / S pattern MX ₁ and the L / S pattern MX ₂ formed on the measurement reticle _RT are represented as shown in FIGS. 7A and 7B. The distance between the L / S pattern MX ₁ image MX ₁ ′ and the L / S pattern MX ₂ image MX ₂ ′ in the transfer result of the overlay is it is necessary to detect whether the shift how much from each L1, L2, to accurately calculate the deviation, it is necessary to each line pattern is almost completely reproduced on the reference wafer W _T.

To measure the positional displacement amount (dx _p, dy _p), the reference wafer W _T is unloaded from the wafer stage WST, the conveying system (not shown) is conveyed to the measuring apparatus 190. The measuring device 190 measures the amount of misalignment (dx _p , dy _p ) corresponding to the measurement mark M _p in all shot areas, and the measured amount of misalignment (dx _p , dy _p ) is sent to the main controller 20. send.

When the measured misregistration amounts (dx _p , dy _p ) are sent, the main controller 20 calculates an average value of misregistration amounts for all measurement marks in all or at least a part of the shot area, The average value of the calculated displacement amounts is regarded as the displacement amount (dx _p , dy _p ) of the measurement mark M _p . Then, main controller 20 inquires host 160 about the amount of positional deviation (dx ′ _p , dy ′ _p ) from the design transfer position of measurement mark M _p in the original process. When the host 160 receives the inquiry, the host 160 reads out the misregistration amounts (dx ′ _p , dy ′ _p ) stored in the storage device 140 and sends them to the main control device 20 of the exposure apparatus 110 ₁ .

Incidentally, instead of the above average value, positional deviation amount of each measurement mark M _p in any one shot area on the wafer W (dx _p, dy _p) as it is positional deviation amount of the current measurement marks M _p (dx _p , Dy _p ).

When the main control device 20 receives the above-described positional deviation amounts (dx ′ _p , dy ′ _p ), the main control device 20 converts the positional deviation amounts (dx _p , dy _p ) corresponding to the respective measurement marks M _p into the positional deviation amounts (dx ′ _p , dy ′ _p ) is corrected. In this way, if the positional deviation amount (dx ′ _p , dy ′ _p ) of the measurement mark M _p in the original process is corrected, an error component (for example, a measurement reticle) other than the component related to the dynamic characteristics of both stages RST and WST. (Component due to reticle manufacturing error in _RT ) can be canceled. Note that such an error component, the error components caused by the replacement of the reference wafer W _T, for example, the EGA based on wafer marks arranged in the shot area deformation component and the EGA by the original process of the reference wafer W _T You may make it include the component which originates in performing and originates in the position shift | offset | difference from the ideal lattice of the shot area | region of the present process.

Next, main controller 20 calculates the correction function (A). Specifically, the positional deviation amount _{(dx 'p, dy' p} ) positional deviation amount is canceled (dx _p, dy _p) and, mark measurement in shot coordinate system with its origin at the center point of the shot area Regarding the design position coordinates (x _p , y _p ) of M _p , a relational expression as shown in the following expression is set, and coefficients k _{0 to} k ₁₆ of the expression are obtained by least square approximation.

なお、上記式（１）における、ｄｘ_pの関係式は、計測マークＭ_pの像の設計上の位置座標ｙ_pのべき乗の関数となっており、ｄｙ_pの関係式は、マークＭ_pの像の設計上の位置座標ｙ_pのべき乗の項と、マークＭ_pの像の設計上の位置座標ｙ_pのべき乗と位置座標ｘ_p（１次）との積の項とを含む式となっている。

Incidentally, in the formula (1), the relational expression of dx _p is a power of a function of the position coordinates y _p of the design of the image of the measuring mark M _p, relational expression dy _p is the mark M _p is a power of terms of position coordinates y _p of the design of the image, the expression including a term of the product of the power of the position coordinates y _p of the design of the image of the mark M _p and the position coordinate x _p (1-order) ing.

When the coefficients k _{0 to} k ₁₆ are obtained by the least square approximation, the main controller 20 sets the values of the obtained coefficients k _{0 to} k ₁₆ as device parameters. Thereby, the determination process of the value of each coefficient of the correction function (A) is completed.

The correction function created in the present embodiment is a function for correcting the position command of reticle stage RST as described above. Therefore, the independent variable in this correction function is the Y position of the reticle stage in terms of the in-shot coordinate system. From the measurement value Y _p of the reticle interferometer 16, the origin Y ₀ of the reticle stage RST, and the projection magnification (1 / M), the Y position Y ′ _p of the reticle stage RST converted to the in-shot coordinate system is expressed by the following equation: It is expressed as

したがって、上記レチクルステージＲＳＴのＹ位置Ｙ’_pを独立変数とするＸ軸方向、Ｙ軸方向に関する補正関数は次式で表される。なお、実際には、レチクルステージの軌道上の、露光スリット幅長（例えば８ｍｍ）の移動平均が焼き付け（パターン転写）結果となる。ここで、露光スリットとは、前述のレチクルブラインドで規定されるスリット状の照明領域の規定部分であり、パターン転写時はレチクルＲ上において、この露光スリットで規定されたスリット状の照明領域部分が照明光で照明されることになる。また、露光スリット幅長とは、露光スリットの、走査方向（Ｙ軸方向）の幅（長さ）のことである。

Therefore, the correction functions related to the X-axis direction and the Y-axis direction with the Y position Y ′ _p of the reticle stage RST as an independent variable are expressed by the following equations. In practice, the moving average of the exposure slit width (for example, 8 mm) on the trajectory of the reticle stage is the result of printing (pattern transfer). Here, the exposure slit is a defined portion of the slit-shaped illumination area defined by the above-described reticle blind. At the time of pattern transfer, the slit-shaped illumination area defined by the exposure slit is on the reticle R. It will be illuminated with illumination light. The exposure slit width length is the width (length) of the exposure slit in the scanning direction (Y-axis direction).

  Therefore, the printing (pattern transfer) result at the time of scanning exposure is a convolution result of the exposure slit width and reticle stage trajectory. For this reason, it is desirable to obtain the following equation (3) after performing the deconvolution calculation processing on the above equation (1) calculated from the printing result based on the slit width length.

すなわち、本実施形態においては、Ｘ軸方向に関する補正関数を、ショット内座標系のスキャン方向に関する設計上の位置座標Ｙ’_pを独立変数とする関数Ｈ_X（Ｙ’_p）とする。そして、Ｙ軸方向に関する補正関数を、ショット内座標系のスキャン方向に関する設計上の位置座標Ｙ’_pを独立変数とし、さらに設計上の位置座標Ｘ’_pの１次の項を含む関数Ｈ_Y（Ｘ’_p，Ｙ’_p）として表すことができる。なお、Ｙ’_pを独立変数とする関数ｆ_x（Ｙ’_p）、ｆ_y（Ｙ’_p）、ｐ_y（Ｙ’_p）を位置項と呼ぶ。ｏ_x、ｏ_yはオフセットである。最小二乗近似に用いられる式が上記式（１）である場合には、上記式（３）の補正関数におけるｆ_x（Ｙ’_p）、ｆ_y（Ｙ’_p）、ｐ_y（Ｙ’_p）は、Ｙ’_pのべき乗の項となる。

That is, in the present embodiment, the correction function related to the X-axis direction is a function H _X (Y ′ _p ) having the designed position coordinate Y ′ _p related to the scan direction of the in-shot coordinate system as an independent variable. The correction function related to the Y-axis direction is a function H _Y including the design position coordinate Y ′ _p related to the scan direction of the in-shot coordinate system as an independent variable and further including a first-order term of the design position coordinate X ′ _p. It can be expressed as (X ′ _p , Y ′ _p ). The functions f _x (Y ′ _p ), f _y (Y ′ _p ), and p _y (Y ′ _p ) having Y ′ _p as an independent variable are referred to as position terms. o _x and o _y are offsets. When the equation used for the least square approximation is the above equation (1), f _x (Y ′ _p ), f _y (Y ′ _p ), p _y (Y ′ _p ) in the correction function of the above equation (3). ) Is a power term of Y ′ _p .

Next, a method for applying the correction function (A) at the time of scanning exposure in the exposure apparatus 110 ₁ will be described. As a premise, on reticle stage RST, reticle R on which a circuit pattern to be transferred is formed is exchanged and loaded with measurement reticle _RT, and reticle alignment and baseline measurement for reticle R are performed. , in addition, the wafer stage WST of the exposure apparatus 110 _1, the wafer W is loaded already one or more layers of the exposure is completed, the wafer alignment by the EGA is performed on the wafer W, each shot on the wafer W It is assumed that the position coordinates of the area are obtained.

First, main controller 20 creates a correction map for correcting the shot distortion component of its own machine based on the created correction function (A). This correction map is obtained by correcting the correction function H _x (Y ′ _p ) at the position Y ′ _i (i = 1 to q) in the Y-axis direction of the reticle stage RST shown in the following equations (4) to (6). This is a map of the value R _X (Y ′ _i ) and the value R _YL (Y ′ _i ), R _YR (Y ′ _i ) of the correction function H _y (X ′ _p , Y ′ _p ). Thus, there are two Y interferometers 16Y _L and 16Y _R in the Y-axis direction, and the reticle stage RST is controlled based on the measurement axis of each interferometer. Two correction maps (R _YL (Y ′ _i ) and R _YR (Y ′ _i ) maps) corresponding to the measurement axes of 16Y _L and 16Y _R are created. Further, in the following R _YL (Y ′ _i ) and R _YR (Y ′ _i ), the X position X ′ _i of the reticle stage RST converted to the in-shot coordinate system is the X axis direction of the measurement axis of each Y interferometer. Is replaced with the position (± L / M).

作成された自号機のショット歪み補正マップは、主制御装置２０の記憶装置に格納される。

The created shot distortion correction map of the own machine is stored in the storage device of the main controller 20.

  Next, a method for applying this correction map will be described. First, main controller 20 instructs stage controller 19 to move wafer stage WST based on the wafer alignment result and the baseline measurement result.

At this time, main controller 20 also instructs stage controller 19 to create position commands for wafer stage WST and reticle stage RST during first-shot scanning exposure. At this time, the correction maps (R _X (Y ′ _i ), R _YL (Y ′ _i ), R _YR (Y ′ _i )) stored in a storage device (not shown) are read out, and the stage control device is read out. Send to 19.

The stage controller 19 creates a position command profile for the wafer stage WST and the reticle stage RST according to the scan speed based on the set scan speed. That is, the stage control device 19 creates a position command profile for scanning the reticle stage RST at a constant scan speed based on the set scan speed, and for the position command Y _i per unit time in the profile, The correction amounts expressed by the correction maps R _X (Y ′ _i ), R _YL (Y ′ _i ), R _YR (Y ′ _i ) are added, and the addition result is used as the final position command profile. The position command Y _i and, 'when there is a shift in the _i, the Y position Y _i two in the vicinity of the reticle Y position Y' reticle Y position Y shot coordinate system converted correction map R in _i The interpolation values of _X (Y ′ _i ), R _YL (Y ′ _i ), and R _YR (Y ′ _i ) (linear interpolation or any other interpolation value) may be added as the correction amount.

  After completion of the correction of the position command profile, the stage control device 19 monitors the measurement value of the wafer interferometer 18 while scanning the start position (acceleration start) for exposure of the first shot (first shot area) of the wafer W. The wafer stage WST is moved to (position), and the reticle stage RST is moved to the acceleration start position while monitoring the measurement value of the reticle interferometer 16.

  Then, when it is confirmed from the measured values of the interferometers 16 and 18 that the wafer stage WST and the reticle stage RST have reached the acceleration start position, the stage control device 19 detects the unit time from the corrected position command profile. Is input to the position feedback control system of reticle stage RST, and the position command value is also input to the position feedback control system of wafer stage WST. Then, both stages WST and RST are synchronously moved in the scan direction in consideration of the shot distortion expressed by the correction function, and the circuit pattern on the reticle R is transferred onto the wafer W.

In the perspective view of FIG. 8A, an example of correction of the position of reticle stage RST in the X-axis direction by the value R _X (Y ′ _i ) of the position command correction map in the X-axis direction is schematically shown. The perspective view of FIG. 8B shows the correction of the position of the reticle stage RST in the Y-axis direction by the values R _YL (Y ′ _i ) and R _YR (Y ′ _i ) of the position command correction map in the Y-axis direction. An example is shown schematically. An arrow indicated by an alternate long and short dash line in FIG. 8A indicates the traveling direction of reticle stage RST during scanning exposure. Arrow thick line attached to the arrows shown in this one-dot chain line represents the Y 'correction map for the X-axis direction with respect to the reticle stage RST in the Y position corresponding to _{i R X (Y' i)} . That is, according to this example, when the position command for the reticle stage RST is corrected by the correction map R _X (Y ′ _i ) as shown by the thick line in FIG. 8A, the reticle stage RST during the scanning exposure is corrected. The locus is convex in the + X axis direction. This correction map R _X (Y ′ _i ) is calculated from the distortion of the shot area in the X-axis direction indicated by the dotted line on the wafer W in FIG. Therefore, if the position command for the reticle stage RST is corrected by the correction map R _X (Y ′ _i ) as described above, a shot area without distortion can be obtained on the wafer W as indicated by the solid line.

On the other hand, also in FIG. 8B, a thick arrow attached to an arrow indicated by a one-dot chain line indicating a traveling direction of reticle stage RST during scanning exposure is a correction map R _YL for the Y axis direction with respect to reticle stage RST. (Y ′ _i ), R _YR (Y ′ _i ). That is, when the position command in the Y-axis direction for the reticle stage RST is corrected by the correction maps R _YL (Y ′ _i ) and R _YR (Y ′ _i ) as shown by the thick lines in FIG. The scanning speed and direction of reticle stage RST inside changes according to the Y position. The correction maps R _YL (Y ′ _i ) and R _YR (Y ′ _i ) are calculated from the distortion of the shot area in the Y-axis direction as indicated by the dotted line on the wafer W in FIG. 8B. is there. Therefore, if the position command for the reticle stage RST is corrected by the correction maps R _YL (Y ′ _i ) and R _YR (Y ′ _i ) as described above, as shown by the solid line on the wafer W, a shot without distortion. An area will be obtained.

In the exposure apparatus 110 _1, since the pattern on the reticle R, and the pattern image on the wafer W are in a relationship of the inverted, and correcting the direction, the direction of the shot distortion is modified, FIG. 8 (A), the As shown in FIG. 8B, the directions are reversed, but when these relationships are upright, the directions are the same, so care is required.

Next, the operation of the lithography system when creating the correction function (B) for canceling the overlay error between the units will be described. Given, in the exposure apparatus 110 ₁ except the exposure apparatus 110 _k (i.e. exposure apparatus 110 ₂ to 110 _N), it is carried out exposure using measurement reticle R _T, exposure apparatus 110 ₂ to 110 _N for measurement at each shall have the reference wafer W _T to the original process layer is formed by transfer of the reticle R _T, after the creation of the reference wafer W _T, measurement reticle R _T, loaded on the wafer stage WST of the exposure apparatus 110 ₁ It shall be.

The main controller 20, in the exposure apparatus 110 ₂ to 110 _N, respectively exposed has completed (N-1) pieces of reference wafer W _T are sequentially loaded on the wafer stage WST of the exposure apparatus 110 _1, performs EGA process Thus, the scanning exposure is performed at the set scanning speed in a state where the shot area of the original process is shifted by the interval w in the X-axis direction and the Y-axis direction. Incidentally, during the scanning exposure of this time, the position command based on (a correction function of the which had been determined in advance the aforementioned method in the exposure apparatus 110 ₁ (A)) The above correction functions (A), the exposure apparatus 110 ₁ Suppose that the reticle stage RST is controlled.

Reference wafer W _T that exposure is completed is sent to the measuring apparatus 190, the measuring apparatus 190, similarly to when creating the correction function of the (A), for each reference wafer W _T, positional displacement amount (dx _{p , k} , dy _{p, k} ) are measured.

This positional deviation amount (dx _{p, k} , dy _{p, k} ) is sent to the host 160 via the LAN 170. The host 160 stores, in the storage device 140, the average value of the positional deviation amounts (dx _{p, k} , dy _{p, k} ) of the measurement marks M _p of each shot area transferred and formed by exposure by the exposure device 110 _k .

Then, the host 160 executes the calculation of the correction function (B) based on the positional deviation amount (dx _{p, k} , dy _{p, k} ). Specifically, with respect to the positional deviation amount (dx _{p, k} , dy _{p, k} ) and the design position coordinates (x _p , y _p ) of the resist image of the mark M _{p in} the in-shot coordinate system, Is set, and coefficients k ′ _{0 to} k ′ ₁₀ of the following expressions are obtained by least square approximation.

上記式（１）と同様に、上記式（７）における、ｄｘ_p,kに関するモデル式は、計測マークＭ_pのレジスト像の設計上の位置座標ｙ_pのべき乗の関数となっており、ｄｙ_p,kに関するモデル式は、計測マークＭ_pのレジスト像の設計上の位置座標ｙ_pのべき乗の項と、マークＭ_pのレジスト像の設計上の位置座標ｙ_pのべき乗と位置座標ｘ_pとの積の項とを含む式となっている。

Similar to the above formula (1) in (7), the model equation for dx p, _k is a power function of the position coordinates y _p of the design of the resist image of the measuring mark M _p, dy _p, the model equation for _k, the measurement marks M and power sections coordinates y _p of the design of the resist image of _p, the mark M _p resist image power and position coordinates x _p coordinates y _p of the design of the And the product term.

When the coefficients k ′ _{0 to} k ′ ₁₀ are obtained by the least square approximation, the host 160 determines the values of the obtained coefficients k ′ _{0 to} k ′ ₁₀ as the exposure apparatus 110 _k and (k = 2 to N). The value is stored in the storage device 140 as a coefficient value of a correction function for overlay with the exposure apparatus 110 ₁ . Thereby, calculation of the value of the coefficient of the correction function (B) for correcting the overlay between the exposure apparatus 110 _k and the exposure apparatus 110 ₁ is completed.

  Note that the correction function (B) is a function for correcting the position command of the reticle stage RST represented by the following equation, similarly to the correction function (A). That is, the independent variable in this correction function is the Y position of reticle stage RST.

すなわち、本実施形態においては、Ｘ軸方向に関する補正関数を、スキャン方向に関する位置座標Ｙ’_pを独立変数とする関数Ｈ’_x（Ｙ’_p）とし、Ｙ軸方向に関する補正関数を、スキャン方向に関する位置座標Ｙ’_pを独立関数とし、Ｘ軸方向に関する位置座標Ｘ’_pの１次の項を含む関数Ｈ’_Y（Ｘ’_p，Ｙ’_p）として表すことができる。なお、ｆ’_x（Ｙ’_p）、ｆ’_y（Ｙ’_p）、ｐ’_y（Ｙ’_p）を位置項と呼ぶ。ｏ’_x、ｏ’_yはオフセットである。最小二乗近似に用いられる式が上記式（７）である場合には、上記式（８）の補正関数におけるｆ’_x（Ｙ’_p）、ｆ’_y（Ｙ’_p）、ｐ’_y（Ｙ’_p）は、Ｙ’_pのべき乗の項となる。

That is, in the present embodiment, the correction function related to the X-axis direction is a function H ′ _x (Y ′ _p ) with the position coordinate Y ′ _p related to the scan direction as an independent variable, and the correction function related to the Y-axis direction is set to the scan direction. 'and _p independent function, the position coordinates X in the X-axis direction' coordinates Y about functions H _'Y (X' _p, Y _'p) comprising a first-order term of _p can be expressed as. Note that f ′ _x (Y ′ _p ), f ′ _y (Y ′ _p ), and p ′ _y (Y ′ _p ) are referred to as position terms. o ′ _x and o ′ _y are offsets. When the equation used for the least square approximation is the above equation (7), f ′ _x (Y ′ _p ), f ′ _y (Y ′ _p ), p ′ _y ( Y ′ _p ) is a power term of Y ′ _p .

Thereafter, similarly, the wafer W on which the original process shot area is formed by each of the exposure apparatuses 110 _{3 to} 110 _N is further subjected to scanning exposure by the exposure apparatus 110 ₁ , so that the measurement mark M _p in the overlay exposure can be measured. The value of the coefficient of the correction function is calculated based on the measurement result of the positional deviation amount, stored in the storage device 140, and managed by the host 160.

In the above-described embodiment, when the correction function (B) (correction function for correcting the overlay error between units) is created, the reference in which the original process layer is formed by transferring the measurement reticle _RT is used. the wafer W _T, assumes that you make in each of all the exposure apparatus 110 _k other than the exposure apparatus _{110 1 (110 2 ~110 N)} . However, the present invention is not limited to this. For example, the measurement reticle R _T is set in a certain machine (the exposure apparatus 110 _p not connected to the LAN 170 shown in FIG. 1 or any _{one of the} exposure apparatuses 110 _{1 to} 110 _N connected to the LAN). load the above (B) of the correction function (hereinafter the correction function B and may be referred to) a number (the number of at least No.) required between desired Unit that determined previously by creating a reference wafer W _T, the while using each reference wafer W _T may be using the correction function B.

In the following, for this method, for example, a case where the correction function B between each of the _three exposure apparatuses 110 _{1 to} 110 ₃ is obtained (and the reference wafer W _T creation number machine is assumed to be the exposure apparatus 110 _p ). It is assumed and described concretely.

First, three of the reference wafer W _T (respectively referenced wafer 1-3) using the exposure apparatus 110 _p create.

Next, the design formation position (referred to as an ideal lattice for convenience) of the image of the measurement mark M _p formed on the reference wafer W _T and the actual formation position of the measurement mark M _p image on the wafer (for convenience) For convenience, the amount of misalignment between the three reference wafers W _T (reference wafers 1 to 3) is measured using a measuring device such as a light wave measuring device.

Then, load the measurement reticle R _T and the reference wafer 1 to the exposure apparatus 110 _1, similarly to the embodiment described above on the reference wafer 1, baking superimposed reticle pattern of the measurement reticle R _T. Similarly, the reference wafer 2 is loaded on the exposure apparatus 110 ₂ , and the reference wafer 3 is loaded on the exposure apparatus 110 _3, and the reticle patterns of the measurement reticle _RT are overprinted.

Thereafter, as in the above-described embodiment, the overlay transfer results of the three reference wafers W _T (reference wafers 1 to 3) overprinted by the exposure apparatuses 110 _{1 to} 110 ₃ are used to measure the overlay transfer results. To measure. Then, using the transfer result and the amount of positional deviation from the ideal lattice measured for each reference wafer W _T (reference wafers 1 to 3) by the light wave measuring device or the like before the overlay exposure, the above-described implementation is performed. The correction function B is created by the same method as the embodiment. The relative deviation in the reference wafer 1-3 each formed lattice inter Because the ideal lattice can relatively calculated based, is not a problem reference wafer W _T to be used are different in each exposure apparatus . Since the printing position deviation amount between the exposure apparatuses 110 _{1 to} 110 ₃ can be calculated via the reference wafer W _T , the expression (7) is used in the same manner as in the above embodiment based on the calculated positional deviation amount. The correction function B may be calculated by the equation (8).

Next, a method for applying the correction function (B) at the time of scanning exposure in the exposure apparatus 110 ₁ will be described.

First, the host 160, for example, the exposure apparatus 110 ₁ instructs the exposure of the wafer W of the lot A. This instruction includes the transfer of a data file for determining exposure conditions called a process program used for exposure of the wafer of lot A. This process program also includes the value of the coefficient of the overlay correction function.

The main controller 20 reads the value of the coefficient of the overlay correction function from this process program. Then, based on the value of the coefficient of the correction function, a correction map which is a correction amount map for the position command of reticle stage RST is created. This correction map is a correction function H ′ _x (Y ′ _p ) at the position Y ′ _i (i = 1 to q) of the reticle stage RST in the Y-axis direction shown in the following equations (9) to (11). R ′ _X (Y ′ _i ) and correction function H _y (X ′ _p , Y ′ _p ) values R ′ _YL (Y ′ _i ) and R ′ _YR (Y ′ _i ). For the Y-axis direction, since the two Y interferometer 16Y _L, is 16Y _R exists, each interferometer 16Y _L, corresponding to the measurement axis of 16Y _R, two correction maps _{(R 'YL (Y' i} ) , R ′ _YR (Y ′ _i ) map). The created map is stored in the storage device of the main controller 20. For R ′ _YL (Y ′ _i ) and R ′ _YR (Y ′ _i ), X ′ _i is replaced with the position (± L / M) in the X-axis direction of the measurement axis of each interferometer. Yes.

Here, it is assumed that reticle R on which a circuit pattern to be transferred is formed is replaced with measurement reticle _RT on reticle stage RST. Then, the reticle alignment and base line measurement is performed for the reticle R, further, the wafer stage WST of the exposure apparatus 110 _1, the wafer W is loaded already one or more layers of the exposure is completed, for the wafer W It is assumed that the wafer alignment by the EGA is performed and the position coordinates of each shot area on the wafer W are obtained.

  Next, main controller 20 instructs stage controller 19 to move wafer stage WST based on the wafer alignment result and the baseline measurement result.

  At this time, main controller 20 also instructs stage controller 19 to create position commands for wafer stage WST and reticle stage RST during first-shot scanning exposure. At this time, a correction map stored in a storage device (not shown) is also sent to the stage control device 19.

  The stage controller 19 creates a position command profile for the wafer stage WST and the reticle stage RST according to the scan speed based on the set scan speed.

Here, the position command profile for the reticle stage RST takes the above correction function into consideration. That is, first, a position command profile for scanning the reticle stage RST at a constant scan speed is created based on the set scan speed, and the position commands X _i and Y _{i are obtained} from the correction function (A). Correction map values R _X (Y ′ _i ), R _YL (Y ′ _i ), R _YR (Y ′ _i ) to be created and a correction map value R ′ _X ( Y ′ _i ), R ′ _YL (Y ′ _i ), and R ′ _YR (Y ′ _i ) are added. In this case, the position command Y _i, reticle Y position Y shot coordinate system converted 'if there is a deviation in the _i, the Y position Y _i 2 both in the vicinity of the reticle Y position Y' correction at _i Maps R _X (Y ′ _i ), R _YL (Y ′ _i ), R _YR (Y ′ _i ), R ′ _X (Y ′ _i ), R ′ _YL (Y ′ _i ), R ′ _YR (Y ′ _i) ) Interpolation value (linear interpolation or any other interpolation value) may be added as a correction amount.

  Then, the stage control device 19 monitors the measurement value of the wafer interferometer 18 and moves the wafer stage WST to the scanning start position (acceleration start position) for exposure of the first shot (first shot area) of the wafer W. And the reticle stage RST is moved to the acceleration start position while monitoring the measurement value of the reticle interferometer 16.

  Then, when it is confirmed from the measured values of the interferometers 16 and 18 that the wafer stage WST and the reticle stage RST have reached the acceleration start position, the stage control device 19 performs unit time based on the created position command profile. Are input to the position feedback control system of reticle stage RST. Then, both stages WST and RST are synchronously moved in the scan direction in consideration of the shot distortion expressed by the correction function, and the circuit pattern on the reticle R is transferred onto the wafer W.

  The operations of the correction function and correction map calculation method described above are summarized in the flowcharts shown in FIGS. The flowchart of FIG. 9 is a flowchart showing an operation flow of the lithography system 10 when calculating the correction function A, and FIG. 10 shows an operation flow of the lithography system 10 when calculating the correction function B. It is a flowchart.

  That is, in the present embodiment, (A) a correction map based on a correction function for correcting shot distortion of the own machine, and (B) a correction map based on a correction function for correcting shot distortion between the cars. Thus, by correcting the position command for the reticle stage RST, the shape of the shot area of the current process can be accurately superimposed on the shot area of the original process.

It should be noted that the scanning exposure apparatus other than the exposure apparatus 110 ₁ can similarly create the correction function (A) and the correction function (B) and apply them during scanning exposure.

In the present embodiment, the correction function is a power function of the Y position Y ′ _p of the reticle stage RST corresponding to the in-shot coordinate system, but is not limited thereto. For example, the correction function may be a trigonometric function corresponding to the Y position Y ′ _p as shown by the following equation, for example.

ここで、Ｈ_y（Ｙ’_p）は、Ｙ軸方向に関する補正量を与える補正関数であり、Ｌ_Sは、ショット領域のＹ軸方向（スキャン方向）に関する長さ、すなわちスキャン長である。そして、ａ_n、ｂ_nは、それぞれ正弦関数、余弦関数の係数である。

Here, H _y (Y ′ _p ) is a correction function that gives a correction amount in the Y-axis direction, and L _S is the length of the shot region in the Y-axis direction (scan direction), that is, the scan length. A _n and b _n are coefficients of a sine function and a cosine function, respectively.

Further, the measurement mark used in the above embodiment is not limited to the measurement mark M _p as shown in FIG. For example, the L / S patterns MX ₁ and MY ₁ may be just one L / S pattern. Further, in addition to the L / S patterns MX ₁ , MX ₂ , MY ₁ , MY ₂ shown in FIG. 5, marks including other L / S patterns and patterns that become box-in-box patterns are included. It may be used. Even in such a pattern, it is possible to detect a misalignment between the outer pattern and the inner pattern as a positional deviation amount in the X-axis direction and the Y-axis direction. In addition, when a plurality of misregistration measurement patterns are provided in one mark as described above, a plurality of misregistration amounts can be detected for each mark in each axial direction. Therefore, it is possible to improve the detection accuracy of the positional deviation amount by using the average value of the detected positional deviation amounts as the positional deviation amount at the mark.

In addition, the arrangement of the measurement marks M _{p on} the measurement reticle _RT may not be uniform as shown in FIG.

In the above embodiment, when obtaining the coefficient of the correction function related to the Y-axis direction, the least-square approximation is performed using the positional deviation amounts in all the measurement marks M _p without specifying the value of X ′ _i. ,
When obtaining a correction function for the Y-axis direction, X ′ _i = (± L / M) is substituted into the above formula (1) or (7), and then the lengths of the Y interferometers 16Y _L and 16Y _R are measured. The least square approximation may be performed using only the positional deviation amount of the mark M _p corresponding to the axis. In this way, the calculation amount in the least square approximation can be reduced, and the calculation time can be shortened.

  In the above embodiment, the coefficient of each term of the correction function is obtained by applying the least square method. However, when the nonlinearity of the function model with respect to the parameter to be obtained is high, the coefficient of the correction function may be obtained by applying a nonlinear least square method such as the steepest descent method.

Moreover, information on the coefficient of the correction function (B) for correcting the registration error of inter In the above embodiments, Unit are intended to be included in the process program, and those sent from the host 160 to the exposure apparatus 110 ₁ but was, this is not limited to an exposure apparatus 110 ₁ itself (main controller 20) may be managed coefficients of the correction function for correcting the overlay error between themselves and other unit. On the other hand, the information about each coefficient of the correction function (A) for correcting shot distortion of the own machine is managed by the exposure apparatus 110 ₁ itself (main control apparatus 20). You may make it manage with.

As is apparent from the above description, in the present embodiment, the main control device 20 corresponds to the transfer device and function creation device of the exposure apparatus of the present invention, and the stage control device 19 corresponds to the control device. ing. In the present embodiment, the exposure apparatus 110 _k corresponds to the exposure apparatus of the lithography system of the present invention, and the exposure apparatus 110 ₁ is a scanning exposure apparatus. The measurement device 190 corresponds to the detection device, and the host 160 corresponds to the function creation device.

As described in detail above, according to exposure apparatus 110 ₁ of the present embodiment, the correction function for the dynamic characteristics of the reticle stage RST in the relative scanning, made from baked results of measurement marks M _p to the reference wafer W _T Since the position of reticle stage RST (resulting reticle R) during scanning exposure can be controlled using the correction function, high-precision exposure is realized by correcting shot distortion of the own machine. be able to.

Further, according to the lithography system 100 of the present embodiment, a function for detecting an overlay error between the exposure apparatuses 110 _{2 to} 110 _N and the exposure apparatus 110 ₁ and correcting a positional shift due to the detected overlay error. (Correction functions H _x (Y ′ _i ), H _y (X ′ _i , Y ′ _i )) are created and the position of the reticle stage RST (reticle R) during scanning exposure is controlled using the functions. Therefore, it is possible to correct the overlay error and realize high-precision exposure.

  In the above embodiment, a correction function that provides a correction amount for a position command for reticle stage RST is created. However, the present invention is not limited to this, and a correction function that provides a correction amount for a position command for wafer stage WST is created. In this case, both stages WST and RST may be corrected simultaneously. In addition, when two wafer stages that are independently movable are provided, a correction function may be provided for each stage.

  In the above embodiment, the stage control device 19 corrects the position command for the reticle stage RST based on the correction map based on the correction function. However, the present invention is not limited to this, and the stage control device 19 uses the main control device. 20, each coefficient of the correction function is received, and the position command in the Y direction of reticle stage RST at each sampling time is substituted into the correction function to obtain the value, and that value is used as the correction amount of the position command. good.

  In the above embodiment, the correction error is created by correcting the overlay error while correcting the shot distortion of the own machine, but it is not always necessary to correct the shot distortion of the own machine. This is because even if this correction is not required, it is possible to realize highly accurate exposure by canceling the overlay error. However, in the exposure of the first layer on the wafer, it is desirable to correct the shot distortion of the own machine. In this way, even when the second and subsequent layers are exposed so as to be faithfully superimposed on the first layer shot area, the shape of the second and subsequent shot areas can be brought close to the ideal lattice. Because.

In the above embodiment, the correction function for correcting the shot distortion component of the own machine in (A) is a fifth order function, and the correction function for correcting the overlay error between the machines in (B) is 3. Although the following functions are used, the present invention is not limited to this, and both functions may be functions. However, it goes without saying that the term including the X position X ′ _i is limited to the first-order or higher term due to the stage structure.

  In the above embodiment, the correction is performed using a correction function that gives a correction amount for the position command with respect to the reticle stage RST. However, the present invention is not limited to this, and the measurement function of the reticle interferometer 16 is used as the generated correction function. You may make it correct | amend using.

In the above embodiment, the scanning speed when transferring the measurement reticle _RT is a constant scanning speed, but the present invention is not limited to this. If the function to correct shot distortion according to scanning conditions such as scanning speed is always enabled, shot distortion depending on scanning conditions will be constant, and the above-mentioned shot distortion correction and overlay error between units will be Measurement can be performed in the same manner as in the embodiment. However, when the exposure apparatus 110 _k does not have such a correction function, the measurement reticle _RT is burned under the same scan conditions (scan speed, scan length, etc.) as in the above embodiment. It is desirable to use one.

  As described above, the correction function based on the correction function in the above embodiment can be applied in addition to various other correction functions used for stage control. Such functions include, for example, a movable mirror bending correction and a biased load correction function, in addition to the above-described shot distortion correction function according to the scanning conditions.

For example, in the correction of motion curvature mirror, a reticle stage RST, while positioning the same X position, while sequentially positioned in a plurality of different Y positions on the reticle stage RST reticle example measured is held on the R _T reticle The alignment marks RM1 and RM2 are detected by the reticle alignment detection system 22, and the degree of bending of the movable mirror 38X is measured by measuring the displacement of the measurement values of the X positions of the reticle alignment marks RM1 and RM2. In the actual scanning exposure, based on the measurement result, the position command of the reticle stage RST during the scanning exposure or the reticle X interferometer 16X so that the actual position of the reticle stage RST is not influenced by the bending of the movable mirror. Correct the measured value.

Further, in the correction of the offset load, the reticle stage RST is sequentially positioned at a plurality of different Y positions Y _i, and the position of the reticle stage RST from the center of gravity of the entire stage at the Y position is generated due to the offset load. A measurement error of the reticle interferometer 16 that occurs in response to a change in the attitude of the reticle stage RST is detected by a sensor (not shown). In actual scanning exposure, based on the detection result, the position command of reticle stage RST during scanning exposure or measurement by reticle X interferometer 16X is performed so that the actual position of reticle stage RST is not affected by this offset load. Correct the value.

  It should be noted that such moving mirror bending and offset load are not considered as dynamic characteristics of the stage, but as static characteristics, as is apparent from the above measurement method. Therefore, it can be said that such a correction function is not a correction function related to the dynamic characteristics of the stage.

  Therefore, the correction function based on the correction function in the above-described embodiment is a correction function related to the dynamic characteristics of the stage, and can be simultaneously executed during scanning exposure along with this movable mirror bending correction and offset load correction.

In the above embodiment, in the L / S pattern of the measurement mark M _p , the line portion is a light transmission portion and the space portion is a light shielding portion. However, the present invention is not limited to this, and the line portion is a light shielding portion, and the space portion is A light transmission part may be used. In this case, not the negative photoresist but the positive photoresist is applied on the wafer.

In the above embodiment, in the exposure apparatuses 110 _{1 to} 110 _N , two reticles can be simultaneously mounted on the reticle stage RST, and the patterns on the two reticles are applied to the same region on the wafer. In some cases, a scanning type exposure apparatus capable of performing so-called double exposure, in which the images are transferred so as to overlap each other, may be included. When double exposure is performed with such an exposure apparatus, the difference in manufacturing error between the two reticles mounted on the reticle stage RST hinders improvement in exposure accuracy. Therefore, the reticle manufacturing error of the two reticles is detected by some method (for example, a method of measuring the mark on the reticle using an optical wave measuring device), and the above correction is made for each of the two reticles according to the detected reticle manufacturing error. The position command of the reticle stage RST may be corrected for each reticle so that the function is provided separately (that is, the coefficient of the correction function is provided for each reticle). In this way, it is possible to eliminate an overlay error due to a reticle manufacturing error between two reticles in double exposure due to the difference in the correction function for each reticle. The same applies to multiple exposures of triple exposure or more.

  In this way, exposure using different reticles (double exposure or overlap exposure) is, in other words, performing exposure under different exposure conditions (process / step). In the above description, each reticle (process) has a correction function. However, the present invention is not limited to this, and a correction function may be obtained for each exposure condition (process / process) other than the reticle used.

In the following, such a correction function is
(C) A correction function for correcting an overlay error between processes, and a method for obtaining the correction function (C) will be described below.

  The “process” referred to here is not limited to the above-described reticle differences. For example, illumination conditions (normal illumination / tilted illumination / illumination aperture value, etc.) and exposure conditions (NA and σ of the projection lens, Various exposure conditions such as exposure amount, etc., development / coating conditions (resist type, resist film thickness and other resist-related conditions, and development conditions such as heating temperature and heating time during development) are included.

≪ (C) Correction function creation method≫
The original process will be described as process 1, and the current process will be described as process 2. Note that the difference between the process 1 and the process 2 is a difference in “process” as described above, such as a difference in reticle used, a difference in resist, and the like.

The exposure in the original process is performed by the exposure apparatus 110 _k (k = 1 to N), and the exposure in the current process is performed by the exposure apparatus 110 ₁ . Note that 1 is included in k here even in the overlap exposure of the own machine (performing the exposure of the original process and the exposure of the current process with the same exposure apparatus) (for example, use This is because the distortion may change due to differences in reticles and illumination conditions.

  In the following, the correction function of C (hereinafter sometimes referred to as the correction function C) is determined separately when the factor (cause) of the distortion change between processes (steps) is clear and when it is not. I will describe how.

<Method A: When the cause is not clear>
Similar to the calculation method of the correction function B, is first prepared reference wafer W _T, the reticle pattern of the reference to the wafer W _T, process 1 as (former step), measurement reticle R _T in exposure apparatus 110 _k Bake over.

Then, in the same way as the calculation method of the correction function B, and using the measurement apparatus 190, the reference wafer W _T is measured to obtain the position displacement amount (dx, dy), then based on the positional deviation amount The above formulas (7) and (8) are created. Thereby, the correction function C in the process 1 (original process) is obtained. For the process 2 (current process), the correction function C is obtained by the same method as the process 1 (however, the exposure apparatus used is the exposure apparatus 110 ₁ ).

<Method B: When the cause is clear>
Here, a case where it is clear that the printing error is caused by the reticle will be described.

  First, the reticle itself (mark formed on the reticle) used in the original process (process 1) is measured using a light wave measuring instrument or the like.

  The error obtained from the reticle measurement result (the amount of misalignment between the actually measured value of the reticle mark actually formed on the reticle and the design value of the reticle mark on the reticle) is calculated by the method A. Fitting is performed by the above equation (8) (target value function of the reticle stage RST) obtained with respect to the process 1 (original process), thereby obtaining the correction function C.

  Similarly to the above, the reticle mark error (positional deviation amount) of the reticle used in the process 2 is also fitted to the current process by the equation (8) obtained with respect to the process 2 (current process) by the method A. A correction function C is obtained.

  Next, a method for applying the correction function C will be described. There are two possible application methods. One is application method A when correction is possible in the original process, and the other is application method B when correction is not possible in the original process.

Here, the correction function C of the original process (process 1, exposure apparatus 110 _k ) is the correction formula (A), and the correction function C of the current process (process 2, exposure apparatus 110 ₁ ) is the correction formula (B). The correction equations (A) and (B) are obtained by converting the correction function C (Equation (8)) obtained above into the above equations (9) to (11) indicating the correction map as described above. And

<Apply method A: Can be corrected in the original process>
First, in the original process, correction is performed using the correction formula (A), and in the next current process, correction is performed using the correction formula (B).

<Apply method B: Uncorrectable in the original process>
First, the following correction formula (C) is created using the correction formulas (A) and (B).
Correction formula (C) =-Correction formula (A) + Correction formula (B)
In the current process, the reticle stage position is controlled using a “reticle stage target trajectory” expressed by the following equation.
Reticle stage target trajectory = target trajectory-correction formula (c)

  By the way, in the said embodiment, although the type | formula employ | adopted in the case of the least square approximation was said Formula (1) or said Formula (7), it is good also as following Formula.

ｇ₁〜ｇ₆は、レチクルステージＲＳＴのＸ位置Ｘ_pのべき乗を含む項の係数である。すなわち、最小二乗近似を求める際には、レチクルステージＲＳＴのＸ位置Ｘ_pのべき乗の項も考慮した上で、補正関数の各係数を求めることができる。なお、露光装置１１０₁の投影光学系ＰＬが像歪み補正能力を有している場合には、レチクルステージＲＳＴのＸ位置Ｘ_pのべき乗の項の成分に関しては、投影光学系ＰＬの像歪み補正により対応することが可能である。

g _{1 to} g ₆ are coefficients of a term including a power of the X position X _p of the reticle stage RST. That is, when obtaining the least squares approximation, exponential terms of X-position X _p of the reticle stage RST also in consideration, it is possible to determine the coefficients of the correction function. When the projection optical system PL of the exposure apparatus 110 ₁ has an image distortion correction capability, the image distortion correction of the projection optical system PL is performed with respect to the component of the power term of the X position X _p of the reticle stage RST. It is possible to cope with this.

Further, in the above embodiment, when the original process is performed by any one of the exposure apparatuses 110 _{2 to} 110 _N and the current process is performed by the exposure apparatus 110 ₁ , the scanning exposure by the exposure apparatus 110 ₁ is performed. Although the correction function is applied, the host 160 determines that the original process of a wafer is performed by the exposure apparatus 110 ₁ and the current process is performed by any of the exposure apparatuses 110 _{2 to} 110 _N. , when the scanning exposure of the exposure apparatus 110 ₁ in its original step, may be applied the correction function. That is, the correction function may be applied not when the current process layer is formed but when the original process layer is formed.

In the above embodiment, the measurement device 190 measures the amount of misalignment in the transfer result of the measurement reticle _RT . However, the present invention is not limited to this, and the misalignment amount is measured by the alignment detection system AS of the exposure device 110 _k. You may make it measure.

  In the above embodiment, the FIA type alignment sensor is used as the alignment detection system AS. However, as described above, the laser beam is irradiated to the alignment mark in the form of a dot on the wafer W and is diffracted by the mark. The present invention can also be applied to an LSA (Laser Step Alignment) type alignment sensor that detects a mark position using scattered light, or an alignment sensor that appropriately combines the alignment sensor and the FIA method. . Further, for example, an alignment sensor that irradiates a mark on the surface to be measured with a coherent detection light and causes two diffracted lights (for example, the same order) generated from the mark to interfere with each other may be used alone, or the FIA method, the LSA. Of course, the present invention can be applied to an alignment sensor appropriately combined with a method or the like.

  The alignment detection system may be an on-axis method (for example, a TTL (Through The Lens) method). In addition, the alignment detection system is not limited to the one that detects the alignment mark in a state where the alignment mark is almost stationary in the detection visual field of the alignment detection system. Relative movement may be used (for example, the aforementioned LSA system or homodyne LIA system). In the case where the detection light and the alignment mark are moved relative to each other, it is desirable that the relative movement direction is the same as the movement direction of the wafer stage WST when detecting each of the alignment marks.

  Further, the projection optical system PL may be any of a refraction system, a catadioptric system, and a reflection system, and may be any of a reduction system, an equal magnification system, and an enlargement system.

Further, although the light source of the exposure apparatus to which the present invention is applied is a KrF excimer laser, an ArF excimer laser, or an F ₂ laser, other pulse laser light sources in the vacuum ultraviolet region may be used. In addition, as the illumination light for exposure, for example, a fiber doped with, for example, erbium (or both erbium and ytterbium) with a single wavelength laser beam oscillated from a DFB semiconductor laser or a fiber laser. Harmonics that are amplified by an amplifier and wavelength-converted to ultraviolet light using a nonlinear optical crystal may be used.

  In addition, the present invention may be applied to, for example, an immersion type exposure apparatus disclosed in International Publication WO99 / 49504 or the like in which a liquid is filled between the projection optical system PL and the wafer.

  An illumination optical system, a projection optical system, and an alignment detection system AS composed of a plurality of lenses are incorporated in the exposure apparatus main body, optically adjusted, and a reticle stage and wafer stage made up of a large number of mechanical parts are arranged in the exposure apparatus main body. The exposure apparatus of the above-described embodiment can be manufactured by connecting the wiring and pipes to each other and further performing general adjustment (electrical adjustment, operation check, etc.). The exposure apparatus is preferably manufactured in a clean room where the temperature, cleanliness, etc. are controlled.

  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, an exposure apparatus used for manufacturing an image sensor (CCD, etc.), an organic EL, a micromachine, and a DNA chip. 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. Here, in an exposure apparatus using DUV (far ultraviolet) light, VUV (vacuum ultraviolet) light, or the like, a transmission type reticle is generally used. As a reticle substrate, quartz glass, fluorine-doped quartz glass, fluorite, Magnesium fluoride or quartz is used. Further, in a proximity type X-ray exposure apparatus or an electron beam exposure apparatus, a transmission mask (stencil mask, membrane mask) is used, and a silicon wafer or the like is used as a mask substrate.

  In addition, the present invention is not limited to an exposure apparatus, and an apparatus that mounts an object on a stage that can move in a two-dimensional plane, and that processes the object while moving the stage in a predetermined direction in the two-dimensional plane. If so, it can be applied.

  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.

  As described above, the exposure apparatus, exposure method, and lithography system of the present invention are suitable for lithography processes for manufacturing semiconductor elements, liquid crystal display elements, and the like.

1 is a diagram schematically showing a configuration of a lithography system according to an embodiment of the present invention. FIG. It is a diagram showing a schematic configuration of a scanning exposure apparatus exposure apparatus 110 _1. It is a top view including a reticle stage and a reticle interferometer. It is a figure which shows an example of the reticle for measurement. It is a figure which shows an example of the measurement mark formed in the measurement reticle. FIG. 6A is a diagram schematically showing an exposure result of overlay exposure on a reference wafer for creating a correction function for correcting shot distortion of the own machine, and FIG. It is an enlarged view of a mark transfer result. FIG. 7A is an enlarged view of an L / S pattern image formed as a result of overlaying measurement marks, and FIG. 7B is an overlay of measurement marks showing the amount of positional deviation in the X-axis direction. It is an enlarged view of the L / S pattern image formed as a result. FIG. 8A is a diagram showing the relationship between the distortion component of the shot area in the X-axis direction and the correction map, and FIG. 8B shows the distortion component of the shot area in the Y-axis direction and the correction map. It is a figure which shows the relationship. It is a flowchart which shows the flow of operation | movement at the time of calculating | requiring the correction function A for canceling the shot distortion component in the own machine. It is a flowchart which shows the flow of operation | movement at the time of calculating | requiring the correction function B for correct | amending the overlay error between machines.

Explanation of symbols

19 ... stage controller (control device), 20 ... main control unit (transfer device, function generating device), 110 ₁ to 110 _N ... exposure apparatus, 160 ... host computer, 190 ... measuring device, R ... reticle (mask), R _T ... reticle for measurement, RST ... reticle stage, W ... wafer (object), W _T ... reference wafer, WST ... wafer stage.

Claims (17)

An exposure method for performing scanning exposure in which a pattern formed on the mask is transferred onto the object via a projection optical system by synchronous movement of the mask and the object with respect to illumination light in a predetermined direction,
A first step of transferring a plurality of measurement marks arranged on a mask onto a predetermined object by the scanning exposure;
A second step of detecting, from a transfer result of the plurality of measurement marks, information relating to a displacement of a transfer position of each measurement mark on the predetermined object in a two-dimensional plane orthogonal to the optical axis of the projection optical system; ;
Based on the detection result, at least one of the dynamic characteristics of the mask and the object during the scanning exposure in the two-dimensional plane, with the position of either the object or the mask in the predetermined direction as an independent variable. A third step of creating two functions;
A fourth step of controlling the position of either the object or the mask with respect to the predetermined direction using the function when the scanning exposure is performed to transfer the pattern onto the object. . In the third step,
As the function, at least one correction function for correcting the position of either the object or the mask with respect to the predetermined direction, with the position of either the object or the mask with respect to the predetermined direction as an independent variable. The exposure method according to claim 1, wherein the exposure method is created. In the third step,
As the function, a correction function for correcting the position of either the object or the mask in the orthogonal direction of the predetermined direction with the position of either the object or the mask in the predetermined direction as an independent variable. The exposure method according to claim 2, further comprising creating the exposure method. In the third step,
As correction functions for correcting the position of one of the object and the mask with respect to the predetermined direction, two correction functions respectively used for position control at two positions that are orthogonal to the predetermined direction are separated from each other. The exposure method according to claim 2, wherein the exposure method is created.   The correction function for correcting the position of one of the object and the mask with respect to the predetermined direction includes a first-order term of the position of either the object or the mask with respect to a direction orthogonal to the predetermined direction. The exposure method according to claim 4. The predetermined object is an object on which images of the plurality of measurement marks are previously transferred and formed by the scanning exposure,
6. The information on positional deviation of the transfer position of each measurement mark is information on positional deviation based on a formation position of a measurement mark image formed in advance. An exposure method according to 1. The predetermined object is an object on which images of the plurality of measurement marks are transferred and formed in advance by exposure with another exposure apparatus,
The information on the positional deviation of the transfer position of each measurement mark is information based on the formation position of a measurement mark image formed in advance. Exposure method.   8. The exposure method according to claim 6, wherein a scanning condition of scanning exposure at the time of transfer formation of the plurality of measurement mark images coincides with a scanning condition of scanning exposure in the first step. .   Each term of the function is at least one of a power function and a sine function in which the position of one of the object and the mask with respect to the predetermined direction is an independent variable. The exposure method according to claim 1. An exposure apparatus that performs scanning exposure for transferring a pattern formed on the mask onto the object via a projection optical system by synchronous movement of the mask and the object in a predetermined direction with respect to illumination light,
A transfer device for transferring a plurality of measurement marks arranged on a mask onto a predetermined object by the scanning exposure;
In the two-dimensional plane of the mask and the object during the scanning exposure, the position of one of the object and the mask in the predetermined direction obtained from the transfer result of the plurality of measurement marks is an independent variable. A function creation device for creating at least one function relating to dynamic characteristics;
An exposure apparatus comprising: a controller that controls the position of one of the object and the mask with respect to the predetermined direction by using the function when the pattern is transferred onto the object by performing the scanning exposure. . The function creation device includes:
As the function, at least one correction function for correcting the position of either the object or the mask with respect to the predetermined direction, with the position of either the object or the mask with respect to the predetermined direction as an independent variable. The exposure apparatus according to claim 10, which is created.   The detection device according to claim 10, further comprising: a detection device configured to detect information related to a displacement of a transfer position of each measurement mark on the predetermined object based on a transfer result of the plurality of measurement marks. Exposure equipment. At least one of the plurality of exposures is a scanning type exposure apparatus that transfers a pattern formed on the mask onto the object via a projection optical system by synchronous movement of the mask and the object in a predetermined direction with respect to illumination light. With the device;
Based on a result of overlay transfer of a plurality of measurement marks arranged on a mask by exposure in each of two exposure apparatuses in which at least one of the plurality of exposure apparatuses is a scanning exposure apparatus, A detection device for detecting information relating to the positional deviation of the overlay of each measurement mark in a two-dimensional plane perpendicular to the optical axis of the projection optical system of the two exposure devices;
Based on the detection result, a function for correcting the misalignment of the superposition between the two exposure apparatuses is created with the position of either the object or the mask in the predetermined direction as an independent variable. A function creation device;
At least one scanning exposure apparatus of the two exposure apparatuses uses the function to control the position of either the object or the mask when transferring the pattern onto the object. . The function creation device includes:
The lithography system according to claim 13, wherein a correction function that corrects a position of one of the object and the mask with respect to the predetermined direction is created as the function.   In the third step, the detection result is deconvolved based on a slit width that is a length in the predetermined direction of a slit that defines an illumination area of the mask when the mask pattern is transferred onto the object. The exposure method according to claim 1, wherein the correction function is created.   The function creation device transfers the plurality of measurement marks based on a slit width that is a length in the predetermined direction of a slit that defines an illumination area of the mask when the mask pattern is transferred onto the object. The exposure apparatus according to any one of claims 10 to 12, wherein the correction function is created by deconvolution processing a result. The function creation device performs a deconvolution process on the detection result based on a slit width that is a length in a predetermined direction of a slit that defines an illumination area of the mask when the mask pattern is transferred onto the object. The lithography system according to claim 13, wherein the correction function is created.

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