JP2006339179A - Exposure method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the displacement of transfer position of a pattern image so as to realize high-accuracy exposure. <P>SOLUTION: When the movement of a wafer W with respect to the image of a reticle pattern and the transfer of the pattern to the wafer W are repeated alternately for transferring the reticle pattern to a plurality of different shot areas SA<SB>n</SB>(n=1-28) on the wafer W, the correction quantities dx<SB>n</SB>and dy<SB>n</SB>of X axis and Y axis at the position of the wafer W are calculated, on the basis of the movement distance and an exposure time for transferring the pattern image to the wafer W, prior to the movement of the wafer W, and the target position for moving the wafer W is corrected by corresponding amounts dx<SB>n</SB>and dy<SB>n</SB>. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exposure method, and more particularly, to transfer a pattern to a plurality of different regions on a photosensitive object, and to move the photosensitive object relative to the pattern image and transfer the pattern image to the photosensitive object. The present invention relates to an exposure method that alternately and repeatedly.

  Conventionally, in a lithography process for manufacturing an electronic device such as a semiconductor element (integrated circuit) or a liquid crystal display element, a pattern of a mask or a reticle (hereinafter referred to as “reticle”) held on a mask stage (reticle stage) is used. An image is held on a photosensitive substrate (hereinafter referred to as “substrate” or “wafer”) such as a wafer or a glass plate which is held on an object stage and coated with a resist (photosensitive agent) via a projection optical system. A projection exposure apparatus for transferring to each shot area is used. In this type of projection exposure apparatus, in order to transfer a pattern to a plurality of different shot areas on a wafer, the movement of a wafer stage that holds the wafer relative to the pattern image and the pattern on the reticle relative to the wafer are conventionally known. A step-and-repeat reduction projection exposure apparatus (so-called stepper) that alternately and repeatedly transfers an image is employed.

  In such a stepper, it is required to transfer the circuit pattern on the reticle onto the wafer with high accuracy, while it is also required to improve the number of wafers processed per unit time. In order to improve the number of wafers to be processed, it is necessary to reduce the exposure time for one shot area or the movement time of the wafer. From the viewpoint of exposure accuracy, the exposure is directly linked to the exposure accuracy for the wafer. Since it is difficult to shorten the exposure time due to the relationship with the amount, it is required to shorten the time other than the exposure, that is, the wafer moving time.

  In order to shorten the moving time of the wafer, it is necessary to increase the moving speed of the stage holding the wafer, but a reaction force is generated in the apparatus due to the acceleration / deceleration movement of the stage. Therefore, in the stepper, exposure is not performed until the relative vibration between the image of the circuit pattern resulting from the reaction force or the like and the wafer falls within an allowable range. In this way, the circuit pattern is transferred to the target position on the wafer with high accuracy.

  However, even if exposure is performed in a state where the relative vibration of the image of the circuit pattern has been sufficiently reduced, depending on the machine, the transfer position of the circuit pattern depending on the movement direction before exposure may be different from the wafer before the exposure. It has been found that there is a case where the position is shifted in a direction depending on the moving direction.

  According to the first aspect of the present invention, in order to transfer the pattern to a plurality of different areas on the photosensitive object, the movement of the photosensitive object relative to the pattern image and the transfer of the image of the pattern relative to the photosensitive object are alternately performed. An exposure method that is repeatedly performed based on information on a moving distance and information on an exposure time when the image of the pattern is transferred onto the photosensitive object prior to the movement of the photosensitive object. An exposure method includes a correction step of correcting a target position for movement of a photosensitive object.

  According to the knowledge obtained by the present inventor, when the movement of the photosensitive object and the transfer of the pattern image onto the photosensitive object are continuously performed, the positional deviation amount of the pattern image transfer position is And the exposure time for transferring the pattern image. Therefore, in the present invention, the target position of the movement of the photosensitive object is corrected based on the information on the movement distance and the information on the exposure time when the pattern image is transferred onto the photosensitive object. The displacement of the image transfer position can be reduced, and high-accuracy exposure is possible.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 schematically shows an overall configuration of an exposure apparatus 100 that can suitably perform an exposure method according to an embodiment of the present invention. In order to transfer the reticle pattern to a plurality of different shot areas on the wafer W, the exposure apparatus 100 alternates the movement of the wafer W with respect to the reticle pattern image and the transfer of the pattern image on the reticle R to the wafer W. This is a step-and-repeat exposure apparatus that is repeatedly performed.

  The exposure apparatus 100 includes an illumination system 10 that illuminates the reticle R with uniform illuminance by exposure illumination light (hereinafter abbreviated as “illumination light”) IL as an energy beam, and a reticle stage RST that holds the reticle R. , Projection optical system PL that projects illumination light IL emitted from reticle R onto wafer W, wafer stage WST that can hold wafer W and move freely within the XY plane, reticle stage RST, projection optical system PL, A body 50 or the like on which a wafer stage WST or the like is mounted is provided.

The illumination system 10 is connected to a light source (not shown) via a light transmission optical system (not shown). As the light source, for example, an i-line (365 nm) of an Hg lamp, a far ultraviolet light source such as an ArF excimer laser (output wavelength 193 nm), a KrF excimer laser (output wavelength 248 nm), or a vacuum such as an F ₂ laser (output wavelength 157 nm). An ultraviolet light source or the like is used.

  The illumination system 10 includes, for example, an illumination uniformity optical system including an optical integrator, a relay lens, a variable ND filter, a variable field stop (also referred to as a reticle blind or a masking blade), a dichroic mirror, and the like (all not shown). And an illumination optical system. Here, as the optical integrator, a fly-eye lens, an internal reflection type integrator (such as a rod integrator), or a diffractive optical element is used. In the illumination system 10, the reticle R on which a circuit pattern or the like is drawn is illuminated with a substantially uniform illuminance by the illumination light IL.

  The reticle stage RST is disposed above a reticle stage surface plate (not shown). The reticle stage RST holds the reticle R.

  The projection optical system PL is inserted from above into an opening (not shown) formed at the center of a lens barrel base plate 25 constituting a first column, which will be described later. A flange portion FLG is provided at a position slightly below the center in the height direction of the lens barrel portion of the projection optical system PL. This flange portion FLG is fixed to the lens barrel surface plate 25.

  As the projection optical system PL, for example, a double-sided telecentric reduction system that uses a refractive optical system composed of a plurality of lens elements having a common optical axis AX in the Z-axis direction is used. The projection magnification of the projection optical system PL is, for example, 1/4, 1/5, or 1/6. For this reason, when the illumination area IL on the reticle R is illuminated by the illumination light IL from the illumination system 10, a reduced image (inverted image) of the circuit pattern in the illumination area of the reticle R is projected via the projection optical system PL. , A slit-shaped projection area conjugate to the illumination area on the wafer W having a photoresist coated on the surface, that is, an exposure area.

  As shown in FIG. 1, wafer stage WST is disposed above wafer stage surface plate 29 disposed below lens barrel surface plate 25. Wafer stage WST moves in the XY plane while holding wafer W.

  Wafer stage WST includes an X stage TX movable in the X axis direction, a Y stage TY mounted on the X stage TX and movable in the Y axis direction, and a wafer table TB mounted on the Y stage TY. It has. A wafer holder WH is fixed on the wafer table TB by vacuum suction, and the wafer W is fixed on the wafer holder WH by vacuum suction, electrostatic suction, or the like.

  The wafer table TB can move in the XY plane by the cooperative operation of the X stage TX and the Y stage TY, and can rotate about the Z axis (the yawing direction). In addition, the three actuators disposed between the Y stage TY and the wafer table TB allow the wafer table TB to rotate about the Z axis direction, the X axis (pitching direction), and the Y axis (rolling direction). It is configured.

  The position information of the wafer table TB in the X-axis direction and the Y-axis direction is always detected by the wafer interferometer WIF with a resolution of about 0.5 to 1 nm, for example, with the fixed mirror Mw as a reference. The wafer X interferometer and wafer Y interferometer are each composed of a multi-axis interferometer having a plurality of measurement axes, and can measure rotation (yawing, pitching, rolling) in addition to the X and Y positions of the wafer table TB. It has become.

  Position information (or velocity information) of wafer stage WST measured by wafer interferometer WIF is sent to stage controller 19 and main controller 20 via this, as shown in FIG. The stage controller 19 creates a command value (target position, target speed) for the wafer stage WST based on the shot arrangement information given from the main controller 20, and the wafer interferometer WIF so as to match the target position. The movement of the wafer stage WST in the XY plane is controlled via the wafer stage drive unit WSC based on the position information (or speed information) output from the.

The main body column 50, as shown in FIG. 1, four vibration isolator 31A above the floor surface F ₁ ~31A ₄ (where vibration isolator 31A _3, 31A ₄ of depth of the page surface in FIG. 1 And a first column CL1 disposed on the base plate 21. The base plate 21 is supported horizontally via a base plate 21 (not shown).

  The first column CL1 is arranged above the base plate 21 and is supported by four support columns 23 (however, the support columns on the back side of the drawing are not shown in FIG. 1). Main frame) 25. A support member 27 is provided from the lens barrel surface plate 25 to suspend and support the wafer stage surface plate 29 horizontally.

  Further, although not shown, the exposure apparatus 100 employs an oblique incidence method for detecting the position in the Z-axis direction (optical axis AX direction) of the portion in the exposure area on the surface of the wafer W and the vicinity thereof. A multi-point focus position detection system is provided, and focus / leveling control of the wafer W is performed by the main controller 20 at the time of exposure described later.

  As described above, since the exposure apparatus 100 is provided with the above-described various vibration isolators, vibrations transmitted from the floor surface F, vibrations generated by reaction forces generated as the wafer table TB moves, and the like are Transmission of vibration components such as a portion that supports the projection optical system PL is limited.

  In the exposure apparatus 100 of the present embodiment configured as described above, the exposure operation is performed as follows. As a premise, it is assumed that reticle R has already been loaded on reticle stage RST, and preparation work including so-called reticle alignment has been completed.

First, the wafer W is loaded by a wafer loader (not shown) under the control of the main controller 20. During this loading, the wafer stage WST is moved to the loading position of the wafer W under the control of the stage controller 19 via the wafer stage drive unit WSC. Hereinafter, this load position is assumed to be (X _L , Y _L ).

  If the loaded wafer W is a wafer W on which one or more layers have already been formed, the main controller 20 uses an alignment detection system (not shown) to perform EGA (Enhanced Global Alignment). Measure alignment. In this alignment measurement, under the instruction of the main control device 20, the stage control device 19 has several alignment marks attached to the shot area formed on the wafer W within the detection visual field of the alignment detection system (not shown). In order to accommodate the above, it is performed in a state where it is appropriately moved in the XY plane.

  On the other hand, if the loaded wafer W is a wafer that has not been exposed yet, the alignment measurement is not performed and the process proceeds to the next step.

Thereafter, a step-and-scan exposure operation is performed as follows. In this exposure operation, first, wafer stage WST is moved within the XY plane so that the first shot area (first shot) on wafer W matches the pattern image on reticle R via projection optical system PL. Move with. The target position at this time is determined based on the design position coordinates of the shot area of the designed wafer W. At this time, when the wafer W has been subjected to the alignment measurement described above, the target position reflects the measurement result. This target position is assumed to be (X ₁ , Y ₁ ).

  Thus, when the transfer of the pattern image on reticle R to one shot area is completed, wafer stage WST moves stepwise in the XY plane, and exposure to the next shot area is performed. When the exposure of the shot area is completed, wafer stage WST further moves stepwise in the XY plane, and further exposure for the next shot area is performed. That is, in the exposure apparatus 100, stepping and exposure are sequentially repeated, and a pattern having the required number of shots is transferred onto the wafer W.

  FIG. 3A shows an example of an array of shot areas that are transferred and formed on the wafer W by repeating stepping and exposure in this way. In FIG. 3A, the order in which the shot areas are exposed is indicated by broken-line arrows. The main controller 20 refers to an exposure recipe that is predetermined design information for the wafer W, and acquires array information of a plurality of shot areas to be transferred and formed in FIG. In the example shown in FIG. 3A, an array of 4 × 6 shot areas SA is formed in the center area of the wafer W, and 2 shot areas SB are respectively provided at both ends in the Y-axis direction of the wafer W. It is designed to form one by one.

  In the wafer W shown in FIG. 3A, it is designated to perform exposure from the shot area SA of 4 rows and 6 columns. Here, the shot area SA closest to the −X side in the first row is set as the shot area to be exposed first, and the shot area SA adjacent to the + X side of the shot area SA is set as the shot area SA to be exposed second. . Similarly, the shot area SA in the first row is exposed sequentially from the −X side.

  When the exposure for all the shot areas SA in the first row is completed, the exposure for the shot areas SA in the second column is performed. Even in the second row, exposure is performed in order from the shot region on the most + X side. Similarly, the shot area in the next third row is exposed in order from the −X side, and the shot area in the next fourth row is exposed in order from the + X side.

  When the exposure of the 4 × 6 shot area SA is completed, the remaining 4 shot areas SA are exposed. As shown in FIG. 3B, for these four shot areas SA, the two shot areas SA at the −Y end are exposed in order from the −X side, and then the two shot areas on the + Y side SA is exposed sequentially from the -X side.

Note that the shot size of the shot area SA of 4 rows and 6 columns is different from that of the four shot areas SB formed at both ends. In this case, in the shot area SA and the shot area SB, the blind ID in the exposure recipe (the size of the exposure area provided in the illumination system 10 is limited so as to be arranged on the conjugate plane of the exposure area). The identification number for specifying the blind state) is different. In the exposure recipe, the exposure amount [mJ / cm ² ] specified for each blind ID is specified, and the exposure time of each shot area varies depending on the specified exposure amount. Therefore, exposure apparatus 100 refers to the exposure recipe prior to exposure of shot area SA, adjusts illumination system 10 (for example, a reticle blind) and exposure time for the shot area, and exposes shot area SB. Change the setting to the exposure condition.

  As described above, in exposure apparatus 100, shot regions are transferred and formed at a plurality of different positions on wafer W while stepping movement and exposure are repeated on wafer stage WST. Therefore, it is necessary that the vibration in the XY plane of wafer stage WST generated along with the step movement is sufficiently set. Therefore, exposure apparatus 100 refers to the measurement value of wafer interferometer WIF and starts exposure in a state where vibration of wafer stage WST is within an allowable value.

  However, even if exposure is performed after this vibration is sufficiently settled, there may be a case where the pattern image transfer position shifts depending on the step movement of wafer stage WST. FIG. 3B shows an example of the positional deviation. In the example shown in FIG. 3B, the first and third shot areas SA are shifted to the −X side and the + Y side, and the second and fourth shot areas are the + X side and − The position is shifted to the Y side. In addition, the same positional deviation occurs in the shot area SB. Such misregistration is different from each other in the direction of misregistration of the shot area SA, and the phenomenon that the position of the shot area is deviated is hereinafter also referred to as “line misalignment”.

Therefore, the exposure apparatus 100 has a position adjustment function for canceling the above-described positional deviation (line deviation). According to the knowledge obtained by the present inventor, the magnitude and amount of this positional deviation depend on the step movement of wafer stage WST and the exposure time. That is, it is known that the positional deviation amount increases as the direction of the positional deviation is determined by the direction of the step movement immediately before exposure, the movement distance becomes longer, and the exposure time becomes shorter. Therefore, in the present embodiment, model expressions for the positional deviation amounts dx _n and dy _n [μm] of the shot area SA _n (including the shot areas SA and SB) exposed n-th are defined by the following expressions.

ここで、ＤＸ_n、ＤＹ_nは露光前のウエハステージＷＳＴのＸ軸方向及びＹ軸方向の移動量であり、ｔは、ショット領域ＳＡ_nにおいて、露光レシピのブラインドＩＤに基づいて求められる露光時間である。また、Ａ、Ｂ，Ｃ、Ｅ、Ｆ、Ｇは係数であり、装置パラメータとして設定可能な係数である。Ｓｉｇｎ（ＤＸ_n）は、ＤＸ_nの符号に基づいて＋１か−１かいずれかの値をとる。

Here, DX _n and DY _n are the movement amounts of wafer stage WST before exposure in the X-axis direction and Y-axis direction, and t is the exposure time obtained based on the blind ID of the exposure recipe in shot area SA _n . It is. A, B, C, E, F, and G are coefficients and can be set as apparatus parameters. Sign (DX _n ) takes a value of either +1 or −1 based on the sign of DX _n .

FIG. 4A schematically shows the displacement amounts dx _n and dy _n . Wafer stage from the exposure position of the n−1th shot area (x _n−1 , y _n−1 ) exposed last time to the exposure position of the nth shot area (x _n , y _n ) exposed this time It is shown that the n-th shot area exposed this time is shifted by dx _n and dy _n as the WST moves. Further, as shown in FIG. 4B, when the moving direction of wafer stage WST is opposite, the polarities of the positional deviation amounts dx _n and dy _n are reversed.

DX _n and DY _n are defined by the following equations.

上記式（１）のｄｘ_n，ｄｙ_nは、露光時間ｔと、ウエハステージＷＳＴの移動距離ＤＸ_nを独立変数とする関数となっており、その大きさは、ウエハステージＷＳＴの移動距離ＤＸ_nの絶対値と、露光時間ｔを反転させた−ｔを独立変数とする指数関数との和によって決定される。すなわち、ｄｘ_n，ｄｙ_nは、ウエハステージＷＳＴの移動距離ＤＸ_nが長くなるにつれて大きくなり、露光時間ｔが長くなる。位置ずれ量ｄｘ_n，ｄｙ_nと、露光時間ｔ、移動距離ＤＸ_nとの関係は、本発明者の鋭意検討により導き出されたものである。

The dx _n and dy _{n in} the above equation (1) are functions having the exposure time t and the movement distance DX _n of the wafer stage WST as independent variables, and the magnitude thereof is the movement distance DX _{n of the} wafer stage WST. And an exponential function having −t as an independent variable obtained by inverting the exposure time t. That is, dx _n and dy _n increase as the moving distance DX _n of wafer stage WST increases, and the exposure time t increases. The relationship between the positional deviation amounts dx _n and dy _n , the exposure time t, and the movement distance DX _n is derived from the inventors' intensive studies.

f (DY _n ) is a function that functions as a limit of the amount of misalignment when accompanied by a large amount of movement in the Y-axis direction. For example, the function is 1 when DY _n <LY (for example, 1000 μm), and 0 when DY _n ≧ LY (for example, 1000 μm). FIG. 5A shows a model of the positional deviation amounts dx _n and dy _n when DY _n ≧ LY. As described above, wafer stage WST has a configuration in which X stage TX that moves in the X-axis direction is mounted on Y stage TY that moves in the Y-axis direction. Therefore, considering the balance between the weight of these stages and the driving force for wafer stage WST in the Y-axis direction, the movement speed is compared when the movement of wafer stage WST involves the movement in the Y-axis direction. It is regulated to become a low speed. In this case, the reaction force generated along with the acceleration / deceleration of wafer stage WST is reduced, and it is considered that displacement amounts dx _n and dy _n are substantially zero as shown in FIG.

Further, as shown in FIG. 5 (B), the moving amount DX _n in the X-axis direction, if it is exceeded LX is a DX _n to be input by the above formula (1) and LX. The reason for this is as follows.

  Here, as shown in FIG. 6A, after the exposure of a certain shot area is completed, in order to make the adjacent shot area coincide with the exposure area, as shown in FIG. When the acceleration / deceleration is moved, the influence of the reaction force generated by the acceleration at this time reaches the entire exposure apparatus 100. Thereafter, as shown in FIG. 6C, wafer stage WST starts decelerating before the exposure area reaches the adjacent shot area. The influence of the reaction force generated with this deceleration also reaches the entire exposure apparatus 100. The direction of the reaction force at this time is opposite to the direction of the reaction force shown in FIG.

As described above, the positional deviation amounts dx _n and dy _n are considered to be strongly influenced by the reaction force generated in the state shown in FIGS. 6 (B) and 6 (C). In this case, if the moving distance of wafer stage WST is long, the reaction force generated when wafer stage WST is accelerated is sufficiently reduced when the adjacent shot area is exposed, and the positional deviation amount dx _{n of the} shot area is reduced. , Dy _n are considered to be only the reaction force during deceleration. Therefore, in this embodiment, when DX _n ≧ LX, it is assumed that the positional deviation amounts dx _n and dy _n do not increase any more, and DX _n = LX, and the calculation of the above formula (1) Shall be performed.

  By the way, it is necessary to actually obtain the coefficients A to F of the above formula (1) for each unit. Therefore, in the present embodiment, exposure is actually performed, the actual positional deviation amount of the shot area is measured, and coefficients A to F are derived from the measurement result. However, since it is difficult to directly measure the amount of positional deviation from the design position, in this embodiment, the relative amount of positional deviation between adjacent shot regions is measured.

  In order to facilitate the measurement of the relative positional deviation amount between the adjacent shot areas, in the present embodiment, exposure is performed so that part of the shot areas overlap as shown by the oblique lines in FIG. . As shown in FIG. 7A, in the + Y side shot area and the −Y side shot area, the movement direction of wafer stage WST before the exposure is opposite and the movement distance is the same. And The shot size is also the same. That is, in the upper and lower shot areas, the moving direction of the stage before the exposure is only reversed, the other conditions are the same, and the stage moving distance and the exposure time are the same.

  A mark is transferred and formed on the overlapping portion so that the amount of displacement can be measured. FIG. 7B shows an example of these marks. By observing these marks, it is possible to measure the amount of relative positional deviation between adjacent shot areas. Since the movement distance before exposure and the exposure time of the upper and lower shot areas are the same, half of the relative positional deviation amount is equal to the magnitude of the positional deviation amount of the shot area at the movement distance and exposure time at this time. Can be considered. In FIG. 7B, only the mark for measuring the relative positional deviation amount in the X-axis direction is shown, but the mark for measuring the relative positional deviation amount in the Y-axis direction is also overlapped. It is formed in the part.

  Therefore, in the present embodiment, a plurality of different conditions (for example, blind IDs) are set for combinations of movement distances and exposure times of various stages, and exposure is performed so that part of the shot area overlaps for each condition. Then, the relative displacement amount at that time is measured. Then, half of the measured misregistration amount is regarded as the misregistration amount from the design transfer position of the shot area under the condition.

  Then, the amount of misregistration, the moving time and the exposure time at that time are substituted into the above equation (1), and the coefficients A to F of the equation (1) are obtained using the least square method. The obtained coefficients A to F are set as device parameters.

  After this setting, the exposure apparatus 100 starts executing the process. FIG. 8 shows a flowchart of the processing algorithm of the main controller 20 when executing the process.

  First, as shown in step 201, an exposure recipe is acquired. In this exposure recipe, design information of a shot area to be transferred onto the wafer W, for example, position coordinates of each shot area, a blind ID, and the like are set. In the next step 203, preparation processing such as loading of the reticle R onto the reticle stage RST, reticle alignment, and baseline measurement is performed.

  In the next step 205, the position coordinates (exposure position) of each shot area are determined based on the position coordinates of each shot area set in the exposure recipe and the exposure time obtained based on the blind ID of each shot area. Make corrections.

An example of a shot map set in the exposure recipe is shown in FIG. The position coordinates (start coordinates) of the stage coordinates before this exposure is started are (X ₀ , Y ₀ ). This start coordinate (X ₀ , Y ₀ ) is the wafer stage WST when the wafer alignment is completed in step 211 described later, when the wafer W is a wafer that has already been subjected to one or more exposures. If this is not the case, the position coordinates of the wafer stage when the wafer is exchanged in step 207 to be described later (that is, the aforementioned load position (X _L , Y _L )) are obtained.

In this exposure, the position coordinates on the design (X _1, Y ₁₎ in order to expose the first shot area is, wafer stage WST from _{(X 0, Y 0) (} X 1, Y 1) Then, exposure is performed by defining a necessary exposure time t obtained from the exposure amount determined based on the blind ID specified for this shot area. That is, the movement distances in the X-axis direction and the Y-axis direction of wafer stage WST before exposure of the first shot area are DX ₁ = X ₁ -X ₀ and DY ₁ = Y ₁ -Y ₀ , respectively. The exposure time t is determined by the blind ID.

Therefore, the obtained moving distances DX ₁ and DY ₁ and the exposure time t are substituted into the above equation ( ₁ ) to obtain the correction amount (dX ₁ , dY ₁ ) of the center position of the shot area. As shown in the above equation (1), when DY ₁ is greater than or equal to a predetermined distance, f (DY ₁ ) = 0 and (dX ₁ , dY ₁ ) are both 0.

Thereafter, since the blind IDs of the second to 24th shot areas are the same, their exposure times t are the same as those of the _first shot area SA _1, and the movement distance of wafer stage WST prior to each exposure. Is obtained from the design position coordinates of each shot area. That is, the movement distances of wafer stage WST in the X-axis direction and Y-axis direction are DX _n = X _n −X _n−1 and DY _n = Y _n −Y _n−1 (n = 2 to 24), respectively. The above equation (1) is calculated, and the correction amount of the position coordinate of each shot area is obtained. At this time, for example, for the movement from the sixth shot area to the seventh shot area, when the movement distance in the Y-axis direction is LY, the correction amount at that time is set to (0, 0).

Since the blind IDs of the 25th to 28th shot areas SA _n (SB) are different from the blind IDs of the 1st to 24th shot areas SA _n (SA), those shot areas are obtained from the blind IDs. The exposure time t is recalculated using the exposure amount thus obtained, and the correction amount of the position coordinate of each shot area SA _n is obtained. Then, the design position coordinates of the first to 28th shot areas are corrected based on the obtained correction amount, and the exposure position of each shot area SA _n is obtained. The corrected position coordinates in the shot area SA _n are stored in a storage device (not shown).

In the next step 207, the wafer W is loaded onto the wafer stage WST. In step 209, it is determined whether or not this wafer W has already been subjected to the first exposure. If this determination is affirmative, the wafer W is aligned such as search alignment and wafer alignment. Here, marks attached to several shot areas SA _n of the previous layer already formed on the wafer W are detected by an alignment system (not shown), and the position information is measured. Then, based on the measurement result, the position coordinates of the actual shot area of the previous layer on the wafer W are estimated. In this alignment as well, wafer stage WST is driven in order to keep the mark within the detection visual field of the alignment system. However, it is not necessary to correct the target position at that time with the correction amount expressed by the above equation (1). .

In the next step 213, each shot area SA _n is exposed while moving wafer stage WST to the exposure position corrected with the correction amount stored in the storage device (not shown).

When the exposure for all the shot areas SA _n on the wafer W is completed, the process proceeds to step 215, and it is determined whether or not the exposure for all the wafers in the lot is completed. If this determination is negative, the process returns to step 207.

  Thereafter, the processing from step 207 to step 215 is repeated until the determination in step 215 is affirmed, and exposure is performed on all the wafers W in the lot. If the determination in step 215 is affirmative, the process ends.

As described above in detail, when the movement of the wafer stage WST (wafer W) and the transfer of the reticle pattern image onto the wafer W are continuously performed, the displacement amount of the transfer position of the image of the reticle pattern. When (dx _n , dy _n ) depends on the movement of the wafer W and the exposure time t when transferring the image of the reticle pattern, the movement position of the wafer W is moved in the X-axis direction. If correction is made based on the distance DX _n and the exposure time t when the circuit pattern image is transferred onto the wafer W, it is possible to reduce the displacement of the transfer position of the reticle pattern image. Thereby, the transfer position of the image of the reticle pattern can be brought close to the target position, and high-precision exposure is possible.

Further, according to the present embodiment, in step 205, the movement distance in the X-axis direction of wafer stage WST (wafer W) and the exposure time t are set as independent variables, and the target position of movement of wafer stage WST (wafer W) is set. Using the correction function (equation (1)) having the correction amount (dx _n , dy _n ) as a dependent variable, the correction amount of the target position is calculated, and the movement of the wafer W is calculated based on the calculated correction amount. The target position is corrected.

  The correction function is determined in accordance with the direction of the movement of wafer stage WST (wafer W) in the X-axis direction, and the absolute value of the movement distance in the X-axis direction of movement of wafer stage WST (wafer W). Includes a term that increases in value as the value increases, and a term that decreases in value as the exposure time t increases. The term having the exposure time t as an independent variable is an exponential function having the exposure time t as an independent variable. Since this positional deviation amount is caused by a reaction force generated along with the movement of wafer stage WST, in consideration of the attenuation state of the influence of the reaction force, a term having exposure time t as an independent variable is an exposure time. Most preferably, it is an exponential function that decays over time. However, the present invention is not limited to this, and the term having the exposure time t as an independent variable does not have to be an exponential function, and may be a term whose magnitude attenuates as the exposure time increases. In addition, the term of the movement distance in the X-axis direction can also be expressed when the movement distance decreases depending on the sign of the parameter.

  In this embodiment, when the movement distance of the movement of the wafer W in the X-axis direction is equal to or greater than LX, the size of the term is constant. This is because the influence of the reaction force generated during acceleration out of the reaction force generated during acceleration / deceleration of wafer stage WST is reduced to a negligible level when the moving distance is greater than or equal to LX. In this way, it is possible to prevent an excessive amount of misalignment from being corrected.

  In the present embodiment, when the movement of wafer stage WST (wafer W) includes movement of LY or more in the Y-axis direction, the value of the correction function shown in the above equation (1) is set to zero. This is due to the structure of the wafer stage WST in the above embodiment in which the X stage TX is mounted on the Y stage TY. If the wafer stage WST has another structure, such a limitation is imposed. There may be a case where it is not necessary to provide it.

Further, in the present embodiment, prior to the series of the exposure operation (step 207～ step 215), collectively in step 205 has been calculated correction amount of the position coordinates of all shot areas SA _n at a time, this is The calculation of the correction amount of the position coordinate of each shot area SA _n is not limited, but before the start of the movement of the wafer stage WST for exposing the shot area SA _n , for example, at the time of exposure of the previous shot area SA _n It may be calculated as follows.

  In the above embodiment, the design exposure time obtained based on the blind ID in the exposure recipe is used for the calculation. However, when the exact exposure time is used for the calculation, the actual exposure time corresponding to the blind ID is used. The exposure time may be measured using an integrator sensor or the like provided in the illumination system 10.

In the above embodiment, the cause of the displacement of the transfer position of the shot area SA _n is between the reference mirror Mw provided in the projection optical system PL due to the reaction force and the optical axis AX of the projection optical system PL. Variation of the distance, deformation of the movable mirror 34 due to reaction force, variation of the wafer holder WH relative to the wafer stage WST when the wafer holder WH holding the wafer W is included. Since neither of these can be detected by the wafer interferometer WIF, it causes the positional deviation of the shot area. If the present invention is applied, the transfer position of the shot area SA _n can be accurately corrected regardless of these causes.

  The present invention can also be applied to an immersion type exposure apparatus disclosed in, for example, the pamphlet of International Publication No. WO99 / 49504 and the like in which a liquid (for example, pure water) is filled between the projection optical system PL and the wafer. . The exposure apparatus of the above embodiment is an exposure position where a reticle pattern is transferred via a projection optical system as disclosed in, for example, Japanese Patent Application Laid-Open No. 10-214783 and International Publication WO98 / 40791. Alternatively, a twin wafer stage type in which a wafer stage is arranged at each of the measurement positions (alignment positions) where mark detection by the wafer alignment system is performed, and the exposure operation and the measurement operation can be performed substantially in parallel. Further, the projection optical system PL may be any of a refraction system, a catadioptric system, and a reflection system, and may be any one of a reduction system, an equal magnification system, and an enlargement system.

  In the above-described embodiment, a light-transmitting mask in which a predetermined light-shielding pattern (or phase pattern / dimming pattern) is formed on a light-transmitting substrate, or a predetermined reflecting pattern is formed on a light-reflecting substrate. Although the formed light reflection type mask is used, an electronic mask that forms a transmission pattern, a reflection pattern, or a light emission pattern based on electronic data of a pattern to be exposed may be used instead of these masks. Such an electronic mask is disclosed in, for example, US Pat. No. 6,778,257. Here, this US Pat. No. 6,778,257 is incorporated by reference.

  Note that the above-described electronic mask is a concept including both a non-light-emitting image display element and a self-light-emitting image display element. Here, the non-light-emitting image display element is also called a spatial light modulator, and is an element that spatially modulates the amplitude, phase, or polarization state of light. It can be divided into a reflective spatial light modulator. The transmissive spatial light modulator includes a transmissive liquid crystal display (LCD), an electrochromic display (ECD), and the like. The reflective spatial light modulator includes a DMD (Digital Mirror Device or Digital Micro-mirror Device), a reflective mirror array, a reflective liquid crystal display element, an electrophoretic display (EPD), electronic paper (or electronic paper). Ink), and a light diffraction light valve (Grating Light Value).

  Self-luminous image display elements include CRT (Cathod Ray Tube), inorganic EL (Electro Luminescence) display, field emission display (FED), plasma display (PDP), A solid light source chip having a light emitting point, a solid light source chip array in which a plurality of chips are arranged in an array, or a solid light source array in which a plurality of light emitting points are formed on a single substrate (for example, an LED (Light Emitting Diode) display, OLED) (Organic Light Emitting Diode) display, LD (Laser Diode) display, etc.). Note that when a fluorescent material provided in each pixel of a known plasma display (PDP) is removed, a self-luminous image display element that emits light in the ultraviolet region is obtained.

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 erbium (or both erbium and ytterbium), for example, an infrared or visible single wavelength laser beam oscillated from a DFB semiconductor laser or fiber laser. Harmonics that are amplified by an amplifier and wavelength-converted to ultraviolet light using a nonlinear optical crystal may be used.

  An illumination optical system, a projection optical system, and an alignment system AS composed of a plurality of lenses are incorporated in the exposure apparatus body for optical adjustment, and a reticle stage and wafer stage comprising a large number of mechanical parts are incorporated in the exposure apparatus body. The exposure apparatus of the above-described embodiment can be manufactured by attaching and connecting wirings and pipes 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.

  The mark detection method according to the present invention is not limited to an exposure apparatus, and can be applied to any apparatus that positions a stage that holds an object.

  As described above, the exposure method of the present invention is suitable for a lithography process for manufacturing a semiconductor element, a liquid crystal display element and the like.

It is a figure which shows typically the structure of the exposure apparatus which concerns on one Embodiment of this invention. FIG. 2 is a block diagram showing a configuration of a control system of the exposure apparatus in FIG. 1. FIG. 3A is a diagram schematically illustrating an example of the wafer shot map and the exposure order of the shot regions, and FIG. 3B is a diagram illustrating the positional deviation amount of each shot region. FIG. 4A is a diagram schematically illustrating the amount of misalignment, and FIG. 4B is a diagram schematically illustrating the amount of misalignment in a reverse movement. FIG. 5 (A) is a diagram schematically showing the amount of displacement when movement in the Y-axis direction is involved, and FIG. 5 (B) is a position when movement in the X-axis direction is a predetermined distance or more. It is a figure which shows the deviation | shift amount typically. FIG. 6A is a diagram showing a state of the wafer stage when a certain shot area is exposed, and FIG. 6B shows that the wafer stage starts moving for exposure of the next shot area. FIG. 6C is a diagram illustrating a state when the movement for exposure of the next shot area is completed by the wafer stage. FIG. 6D is a diagram showing how the next shot area is exposed. FIG. 7A is a diagram schematically showing a shot area transfer method for calculating the displacement amount of the transfer position at a predetermined movement distance and a predetermined shot size, and FIG. It is a figure which shows the relationship of the mark formed in the part which the shot area | region to overlap. It is a flowchart which shows the process algorithm of the main controller 20 at the time of performing a series of exposure operation | movement which concerns on one Embodiment of this invention. It is a figure which shows an example of the information for calculating the exposure order and positional offset amount of the shot area on a wafer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Illumination system, 100 ... Exposure apparatus, PL ... Projection optical system, R ... Reticle, RST ... Reticle stage, W ... Wafer, WST ... Wafer stage.

Claims (8)

In order to transfer a pattern to a plurality of different areas on a photosensitive object, an exposure method in which the movement of the photosensitive object with respect to the pattern image and the transfer of the pattern image with respect to the photosensitive object are alternately repeated,
Prior to the movement of the photosensitive object,
An exposure method including a correction step of correcting a target position of movement of the photosensitive object based on information on the movement distance and information on an exposure time when the pattern image is transferred onto the photosensitive object. The correction step includes
The correction amount of the target position is calculated using a correction function in which the movement distance in the predetermined direction of the movement of the photosensitive object and the exposure time are independent variables and the correction amount of the target position of the movement of the photosensitive object is a dependent variable. A first sub-step;
The exposure method according to claim 1, further comprising: a second sub-step of correcting a target position of the movement of the photosensitive object based on the calculated correction amount. The correction function is
The positive / negative is determined according to the direction of the predetermined axial direction of the movement of the photosensitive object,
A first term that increases as the absolute value of the movement distance of the photosensitive object in the predetermined axial direction increases, and a second term that decreases as the exposure time increases. The exposure method according to claim 1, wherein the exposure method is included.   4. The exposure method according to claim 3, wherein when the moving distance of the photosensitive object in a predetermined axial direction is equal to or longer than a predetermined distance, the size of the first term is made constant. The second term is
5. The exposure method according to claim 3, further comprising an exponential function having the exposure time as an independent variable.   6. The value of the correction function is set to 0 when the movement of the photosensitive object includes a movement of a predetermined distance or more in an axial direction orthogonal to the predetermined axial direction. The exposure method according to one item. In the correction step,
Prior to the initial movement of the photosensitive object,
The exposure method according to claim 1, wherein target positions for all movements of the photosensitive object are corrected at a time. In the correction step,
The exposure method according to claim 1, wherein a target position for the next movement is corrected each time a pattern image is transferred to the photosensitive object.

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