JP5288838B2 - Exposure equipment - Google Patents

Description

The present invention relates to an exposure apparatus.

  A projection exposure apparatus used for manufacturing a semiconductor device transfers a pattern formed on a reticle as an original to a photoresist layer on a wafer or a glass plate as a substrate with high overlay accuracy. Therefore, it is required to align the reticle and the wafer with high accuracy. In addition, process miniaturization has accelerated and the level allowed for the apparatus has become strict.

  On the other hand, it is known that a coating material such as chromium for coating a reticle absorbs laser light during exposure and expands thermally. When this thermal expansion occurs, a transfer error occurs because the pattern on the reticle is transferred onto the wafer in a distorted state. Therefore, in manufacturing the device, it is required to reduce this error.

  In reticles used in device manufacturing, a plurality of alignment measurement marks are arranged outside an area where an exposure pattern is drawn, and the arrangement is often fixed regardless of the type of exposure pattern. This is because if the mark arrangement is optimized according to the type of the exposure pattern, it takes time for verification and the like.

  However, in practice, the deformation of the entire reticle differs depending on the position, area, and pattern distribution of the exposure region. In order to minimize the transfer error resulting from this deformation, this deformation is performed prior to the exposure operation. It is necessary to grasp accurately.

  In particular, device manufacturers use an exposure method in which the entire reticle surface is divided into exposure regions and used in a plurality of layers for a single reticle in order to effectively utilize reticle resources. In this case, since the position of the exposure region varies greatly depending on the layer, the change in the shape of the entire reticle also varies greatly.

As a method for measuring and adjusting the surface shape of the reticle placed on the reticle stage, the present applicant measures a mark near the exposure area of the reticle and adjusts the shot magnification based on the measurement result. (Patent Document 1).
JP-A-11-354401

  As described above, the shape change of the entire reticle varies depending on the situation. In order to accurately measure and adjust such a change in shape depending on the situation, it is necessary to calculate a measurement value that represents the overall deformation of the exposure area of the reticle. For this purpose, the optimum mark position is determined based on the exposure conditions in the layer, such as the position of the exposure area and the characteristics of the pattern change, from among the plurality of alignment measurement marks arranged outside the pattern area described above. Must be selected by the user each time.

  However, this method has a problem that it takes a burden on the user because it takes a set time and a setting error may occur.

  An object of the present invention is to provide a method for reducing a transfer error due to a pattern change without imposing a burden on a user in an exposure apparatus.

An exposure apparatus according to one aspect of the present invention includes a projection optical system that projects a pattern of an original on a substrate using light from a light source, an original reference plate having an original reference mark, and an original stage that holds the original, An exposure apparatus having a substrate reference plate having a substrate reference mark and a substrate stage for holding the substrate, a defining part for defining an exposure area in the original, and a plurality formed on the original or the original reference plate position information, the information of the exposure region in which the Ru is defined by defining portion of the mark, and an input unit for adjusting items related transfer error when transferring the pattern of the original onto the substrate is input, the plurality of marks position information of the selection information of the exposure area, and, on the basis of the adjustment items, the measurement marks to be used for measurement from said plurality of marks And that the selection unit, a measuring unit for measuring the substrate reference mark and the meter hakama over click, based on the measurement result by the measuring unit, positional deviation of the substrate reference mark and the meter hakama over click decreases As described above, an adjustment unit that performs at least one of driving of the original stage, driving of the substrate stage, driving of the lens of the projection optical system, and wavelength switching of the light source is provided.

  According to the method of the present invention, it is possible to reduce a transfer error due to a pattern change without imposing a burden on the user.

Embodiments according to the present invention will be described below in detail with reference to the accompanying drawings.
[First Embodiment]
First, a first embodiment of the present invention will be described.

  FIG. 1 is a block diagram illustrating the configuration of an exposure apparatus 100 in the present embodiment.

  In FIG. 1, reference numeral 1 denotes an illumination optical system that constitutes a light source for exposure such as a lamp, a laser, and an EUV light source, and has a movable blind (so-called masking blade) (not shown) that defines an exposure area. The range of the exposure area is appropriately selected according to the position, size, and shape of the circuit pattern drawn on the reticle surface, for example. When the circuit pattern drawn on the reticle is transferred and exposed onto a wafer (exposed body), a command from the exposure apparatus control system 70 is transmitted to the illumination optical system control system 30, and the command from the illumination optical system control system 30 is used. The operation of the illumination optical system 1 is controlled.

  Reference numeral 2 denotes a quartz glass reticle (original plate) having an actual element pattern region formed by chromium coating on the lower surface, and is held on the reticle stage 4. The reticle 2 may be a binary reticle or a halftone reticle. The reticle 2 is provided with a plurality of reticle marks, and the coordinates of these reticle marks are stored in a storage unit 74 described later in association with the management ID of the reticle.

  In the present embodiment, the reticle mark includes a first reticle mark 43 and second reticle marks 44a to 44z shown in FIG.

  Reference numeral 3 denotes a reticle reference plate (original reference plate), which is held on the reticle stage 4 in FIG. 1 but may be optically fixed to another position equivalent to the reticle.

  In the scanning exposure apparatus, the reticle stage (original stage) 4 can be driven in a direction (Y direction) perpendicular to the front and rear with respect to the optical axis direction (Z direction) of the projection optical system 5. In the drive control of the reticle stage 4, a command from the exposure apparatus control system 70 is transmitted to the reticle stage control system 40, and the reticle stage 4 is driven and controlled by a command from the reticle stage control system 40. The exposure apparatus control system 70 includes a control unit 72, an arithmetic processing unit 73, a storage unit 74, a display unit 76, an input unit 75, a selection unit 77, and an adjustment unit 78. In the input unit 75, the range of the exposure area and adjustment items described later are input. The selection unit 77 selects a mark used for measurement by a method described later. The adjustment unit 78 performs reticle stage drive, wafer stage drive, projection optical system lens drive, and light source wavelength switching in order to reduce transfer errors. The exposure apparatus control system 70 may be built in the exposure apparatus, or may be configured outside the exposure apparatus and connected by a network or the like. The calculation performed by the calculation processing unit 73 is realized by executing a program executable by a computer. A program required for the calculation is stored in the storage unit 74, and the calculation processing unit 73 can perform a calculation described later by reading and executing the program stored in the storage unit 74. The program is also stored in the storage unit 74 by installing a program recorded on a computer-readable recording medium.

  A reticle reference mark (original reference mark) (not shown) is provided on the reticle stage 4. At a plurality of locations in the surface of the reticle 2, the relative displacement amount of the first reticle mark 43 with respect to the reticle reference mark on the reticle stage 4 is measured by an alignment scope (not shown). Based on these measured deviation amounts, the relative deviation amount of the reticle 2 with respect to the reticle stage 4 is measured, and the wafer stage 10 is driven in a direction opposite to the deviation amount in consideration of the projection magnification. To cancel the transfer error due to the deviation.

  The second reticle mark 44 of the reticle 2 is used to detect the amount of deviation from a reference mark (substrate reference mark) 11a provided on a wafer reference plate 9 described later.

  The projection optical system 5 is composed of a plurality of lenses, and at the time of exposure, a circuit pattern drawn on the reticle 2 is imaged on a wafer (substrate) 8 at a magnification corresponding to the reduction magnification of the projection optical system 5. Reference numeral 50 denotes a projection optical system control system.

  A wafer reference plate (substrate reference plate) 9 and a wafer chuck 7 are fixed on a wafer stage (substrate stage) 10, and the wafer 8 is held by vacuum chucking of the wafer chuck 7. The wafer stage 10 is movable in the optical axis direction (Z direction) of the projection optical system 5 and in the direction (X, Y direction) perpendicular to the optical axis direction, and can be rotated with respect to the optical axis. . In the drive control of the wafer stage 10, a command from the exposure apparatus control system 70 is transmitted to the wafer stage control system 60, and the wafer stage 10 is driven and controlled by a command from the wafer stage control system 60.

  An off-axis scope 12 is fixed around the bottom of the projection optical system 5. When performing overlay exposure, the wafer is aligned so that the exposure position on the wafer 8 is on the optical axis of the projection optical system 5 after alignment with the off-axis scope 12 by measuring a mark (not shown) on the wafer 8. The stage 10 is driven.

  The TTR observation optical system (measurement unit) 20 includes a fiber 21, a half mirror 22, a relay lens 23 that changes a focal position with respect to the observation surface, a mirror 24, an objective lens 25, and an image sensor 26. The illumination light beam emitted from the fiber 21 passes through the half mirror 22 and is condensed on the reticle 2 via the relay lens 23, the mirror 24, and the objective lens 25. The illumination light beam condensed on the reticle 2 is condensed on the wafer reference plate 9 via the projection optical system 5. Reflected light from the wafer reference plate 9 returns to the original optical path, and is reflected by the half mirror 22 via the projection optical system 5, reticle 2, objective lens 25, mirror 24, and relay lens 23 in order, and enters the image sensor 26. . Although not shown, the TTR observation optical system 20 is arranged on the left and right (X direction) with respect to the scanning direction (Y direction) of the reticle stage 4, and the two TTR observation optical systems 20 are both X It can be driven in the direction.

  Measurement of the shape of the reticle 2 placed on the reticle stage 4 and the relative positional relationship between the reticle 2 and the wafer stage 10 will be described. FIG. 2 is a plan view showing the relationship between reticle 2 on reticle stage 4, reticle suction pad 42, and reticle marks 44a to 44t. The 20 reticle marks 44a to 44t are marks shown as the reticle mark 44 in FIG. The reticle marks 44a to 44i and 44j to 44r are arranged at equal intervals and symmetrically. Reticle marks 44a to 44i are arranged in the reticle scanning direction (Y direction). The same applies to the reticle marks 44j to 44r. Also, 44a, 44s, 44j and 44i, 44t, 44r are also arranged at equal intervals and vertically symmetrically.

  The reticle marks 44a to 44t of the present embodiment are not arranged in the actual element pattern area, but can be arranged in the actual element pattern area.

  Hereinafter, measurement of relative deviation (X, Y, Z) between the reticle mark 44 and the reference mark 11a will be described with reference to FIGS.

  FIG. 3 is a measurement sequence flow for measuring the relative deviation (X, Y, Z) between the reticle mark 44 and the reference mark 11a. The flowchart shown in FIG. 3 is stored in the storage unit 74 in the control system 70, for example.

  First, in step S0, the TTR observation optical system 20 is driven to the X coordinate of the mark measurable position.

  Next, in step S1, the wafer stage 10 is driven in the X and Y directions so that the reference mark 11a on the wafer reference plate 9 is on the optical axis of the measurement optical system.

  Next, in step S2, the reticle stage 4 is driven in the Y direction so that the reticle mark 44 to be measured on the reticle 2 is on the optical axis of the measurement optical system.

  A method for selecting the reticle mark 44 to be measured will be described later.

  Next, in step S3, the relay lens 23 is driven in the optical axis direction to focus on the mark of the reticle 2, and the position (height) of the reticle mark 44 in the Z direction is calculated based on the focal position of the relay lens 23. ,Remember.

  Next, in step S4, the wafer stage 10 is driven in the optical axis direction to focus on the reference mark 11a on the wafer reference plate 9, and the in-focus position of the wafer stage 10 is stored.

  Next, in step S5, the relative displacement in the X and Y directions between the reticle mark 44 and the reference mark 11a is measured and stored by the TTR observation optical system 20.

  Next, in step S6, it is determined whether measurement of all the reticle marks 44 to be measured has been completed.

  If the measurement of all the reticle marks 44 to be measured has not been completed, the reticle stage 4 is driven in the Y direction so that the reticle mark 44 to be measured next is on the optical axis of the measurement system in step S7. Step S5 is performed. In step S7, in the case of a stepper (step-and-repeat type projection exposure apparatus) in which the movable range of the reticle stage 4 is narrow, the TTR observation optical system 20 that can be driven in the XY directions may be driven to the mark observation position.

  Steps S0 to S7 are repeated until the measurement of all the reticle marks 44 to be measured is completed, and the measurement sequence is completed.

  Next, adjustment value calculation and the number of necessary marks will be described. FIG. 4 shows the adjustment item and the minimum number of marks necessary for obtaining the adjustment value of the adjustment item. The adjustment value calculation described below is performed by the arithmetic processing unit 73, for example.

  One or more baselines in the X direction and one or more baselines in the Y direction, that is, only one mark may be provided.

  Here, the baseline means the relative position of the exposure area center of the reticle 2 with respect to the off-axis scope 12. Since the relative position of the reticle 2 with respect to the reticle stage 4 has already been adjusted as described above, the adjustment value may be set based on the relative position of the reticle 2 with respect to the off-axis scope 12.

Therefore, regarding the calculation of the adjustment value, for example, when the relative position of the wafer stage 10 with respect to the reticle 2 is V1, the relative position of the reticle with respect to the reticle stage 4 is V2, and the relative position of the wafer stage 10 with respect to the off-axis scope 12 is V3.
BL = V1 + V2-V3
Based on the value of.

  When using one mark, the relative positional relationship between the reticle 2 and the wafer stage 10 is based on the measured value of the mark. When measuring multiple marks, it may be based on the average value of the measured values of all the marks to be measured, may be based on the average value of the measured values of any number of measurement marks, or the mark design An approximate line may be obtained with respect to the measured values for the coordinates and may be based on the intercept of the approximate line.

  The method for calculating the relative positional relationship between the reticle stage 4 and the reticle 2 is as described above. The relative positional relationship between the off-axis scope 12 and the wafer stage 10 is such that after the wafer stage 10 is driven so that the off-axis observation reference mark 11b on the wafer reference plate 9 is below the off-axis scope 12, the off-axis scope 12 Measure with The relative positional relationship between the off-axis scope 12 and the wafer stage 10 is based on this measurement value.

Since the magnification X (primary magnification) is a deviation in the X direction with respect to the span in the X direction of the mark, it is sufficient that there are two or more marks in the X direction and one or more marks in the Y direction. Regarding the calculation of the adjustment value, for example, under the above-mentioned conditions for the minimum number of marks, the design coordinates of the marks M1 and M2 are M1X, M2X, and the measurement values in the X direction are M1x and M2x, respectively. The adjustment value is a value obtained by dividing the mark measurement value difference (M2x-M1x) by the design value difference (M2X-M1X). ScaleX = (M2x-M1x) / (M2X-M1X)
Is calculated based on When measuring three or more marks, an approximate line is obtained for the measured values for the design coordinates of the mark from the measured values of any two or more marks arranged in the X direction, and the linear coefficient of the function representing the approximate line Based on (slope) value.

  For the magnification Y, the same idea as that for the magnification X may be used.

Since the rotation X is a deviation in the Y direction with respect to the span in the X direction of the mark, it is sufficient that there are two or more marks in the X direction and one or more marks in the Y direction. Regarding the calculation of the adjustment value, for example, under the above-described conditions for the minimum number of marks, the design coordinates of the marks M1 and M2 are M1X, M2X, and the measurement values in the Y direction are M1y and M2y, respectively. The adjustment value is a value obtained by dividing the mark measurement value difference (M2y-M1y) by the design value difference (M2X-M1X). X = (M2y-M1y) / (M2X-M1X)
Is calculated based on When measuring three or more marks, an approximate line is obtained for the measured values for the design coordinates of the mark from the measured values of any two or more marks arranged in the X direction, and the linear coefficient of the function representing the approximate line Based on (slope) value.

  Regarding the rotation Y, the same idea as that for the rotation X may be used.

  The focus may be one or more in the X direction and one or more in the Y direction. Regarding the calculation of the adjustment value, for example, when one mark is used, it is based on the measured value of the mark in the Z direction. When measuring a plurality of marks, it may be based on the average value of the measured values in the Z direction of all the marks to be measured, or may be based on the average value of the measured values in the Z direction of any of a plurality of measured marks. Alternatively, an approximate line may be obtained with respect to the measurement value with respect to the design coordinates of the mark and based on the intercept of the approximate line. Alternatively, an approximate surface may be obtained with respect to the measurement value with respect to the design coordinates of the mark, and may be based on the value on the approximate surface at the exposure center.

Since the tilt X is a Z-direction shift with respect to the X-direction span of the mark, it is sufficient if there are two or more marks in the X-direction and one or more marks in the Y-direction. Regarding the calculation of the adjustment value, for example, in the condition of the minimum number of marks, the design coordinates of the marks M1 and M2 are M1X, M2X, and the measured values in the Z direction are M1z and M2z, respectively. The adjustment value is a value obtained by dividing the mark measurement value difference (M2z-M1z) by the design value difference (M2X-M1X) (M2z-M1z) / (M2X-M1X).
Is calculated based on When measuring three or more marks, an approximate line is obtained for the measured values for the design coordinates of the mark from the measured values of any two or more marks arranged in the X direction, and the linear coefficient of the function representing the approximate line Based on (slope) value.

  Regarding the tilt Y, the same idea as that for the tilt X may be used.

  Since the tertiary magnification X is equivalent to a third-order coefficient of X-direction deviation with respect to the X-direction span of the mark, it is sufficient that there are four or more marks in the X direction and one or more marks in the Y direction. Regarding the calculation of the adjustment value, for example, a cubic or higher-order approximation curve is obtained with respect to the measurement values for the design coordinates of all the marks or any four or more marks arranged in the X direction, and a cubic of a function representing this approximation curve is obtained. Based on the value of the coefficient.

  Since the field curvature is equivalent to a second-order coefficient of Z-direction deviation with respect to the X-direction span of the mark, it is sufficient that there are three or more marks in the X-direction and one or more marks in the Y-direction. Regarding the calculation of the adjustment value, for example, a quadratic or higher-order approximation curve is obtained with respect to the measurement values for the design coordinates of any three or more marks arranged in the X direction, and based on the value of the quadratic coefficient of the function representing this approximation curve. .

  In these adjustment items, especially at the magnification X and magnification Y, the location of the measurement mark and the location of the actual exposure region are different, so the magnification obtained based on the change in the measurement mark interval and the actual exposure region There may be a discrepancy with respect to the expansion ratio. It is desirable to place the measurement mark on the outer periphery of the exposure area, but if that does not happen, set a coefficient to compensate for this deviation and set this coefficient to the magnification obtained from the measurement result of the mark measurement. By multiplying, it is possible to measure with higher accuracy.

  Note that the number of marks in the “X direction” shown in FIG. 4 is not necessarily the same as the Y coordinate as long as the X coordinate is different. For example, when simultaneous measurement on the left and right is possible, there is no reduction in throughput due to the simultaneous measurement, so the number of marks in the “X direction” such as the baseline and the magnification Y may be “2” instead of “1”.

A method for determining the number and position of marks used for measurement will be described with reference to FIG. 6 based on mark position information, adjustment items, exposure area position information, and reticle deformation model. The determination of the number and position of the marks described below is performed by the arithmetic processing unit 73, for example.
First, in step S22, whether to adjust each of the baseline, magnification X, magnification Y, rotation X, rotation Y, focus, tilt X, tilt Y, tertiary magnification X, and field curvature is selected (adjustment item selection step). ).

  The item to be set to “with adjustment” is set after confirming that the mark 44 satisfying the mark arrangement condition shown in FIG. 4 is arranged on the reticle 2. If you want to omit this check, provide a mark placement discriminator (not shown), and if it is determined that the number of marks required for the adjustment item is not placed on the reticle, "And it is sufficient.

  Next, in step S24, for the item “with adjustment” selected in step S22, the minimum number of marks and their arrangement are determined based on the table of FIG.

  As an example, in this embodiment, three items of a baseline, a magnification X, and a rotation Y are set as “with adjustment”. At this time, the required number of marks is two in the X direction and two in the Y direction, and two marks as a whole may be measured as shown in FIG. However, here, if the Y coordinate is the same, it is assumed that the left and right simultaneous measurement is possible, and four marks are measured as shown in FIG. 5B. In this case, compared with FIG. 5A, the mark selection of FIG. 5B does not decrease the throughput, and an averaging effect can be expected in the measurement accuracy.

  Next, in step S26, the number of combinations selected from the mark arrangements stored in the storage unit 74 for the measurement mark arrangements determined in step S24 is determined.

  If the number is 1, the measurement mark is determined in step S29, and the process proceeds to the determination of span tolerance in step S30 described later.

  If the number is two or more, the measurement mark is determined based on the reticle deformation model described later so that the highest measurement accuracy can be obtained for one adjustment item in step S28, and the span tolerance determination in step S30 described later is performed. Proceed to

  In this embodiment, it is assumed that the reticle causes thermal expansion by absorbing exposure heat, and the mark is selected so that the measurement accuracy with the highest adjustment value of the magnification X variation caused by the thermal expansion can be obtained. As for the adjustment value calculation other than the magnification X, measurement is performed using a mark selected from the viewpoint of adjusting the magnification X variation, and the adjustment value is calculated based on the measurement value.

  Here, as shown in FIG. 5B, the four measurement marks are selected to form a rectangular vertex. In this case, there are two combinations when 44s and 44t are used, and since two Y coordinates are selected from nine Y coordinates when not used, 9C2 = (9 × 8) / (2 × 1) = There are 36 ways.

  For magnification measurement, a longer span between two marks that are divisors is advantageous in accuracy. Therefore, in order to perform the magnification X measurement, it is preferable to select all the marks from the left and right sides of the reticle without including 44s and 44t in the four measurement marks.

  Next, FIGS. 7 and 8 show a reticle thermal deformation model (prediction information). It is known that the thermal deformation of the pattern in the exposure area does not deform in a similar shape when the chrome coated on the reticle absorbs the exposure heat, but becomes a curved curve with the center swelled as shown in FIG. For example, the patent publication WO 99/31716 introduces it as background art.

  In this case, the magnification X with respect to the Y coordinate is a curve as shown in FIG. At this time, an average value of the magnification X is obtained for the Y coordinate range in which the actual element pattern region is located, and this value is defined as P1.

  Assuming that Y coordinates where the magnification X is P1 are Y1 and Y2, the four marks closest to Y1 and Y2 are 44c, 44g, 44l and 44p, and these four marks are selected.

  Note that the reticle deformation model may use simulation by a finite element method, or may be obtained from an experiment by performing exposure in advance.

  When calculating the deformation amount by simulation, such as a simulation, a relatively simple model in which the exposure area of the reticle is entirely covered with chrome may be used, or more based on chrome pattern distribution information. An advanced model may be used. The chromium pattern distribution information may be measured by a measuring instrument inside or outside the exposure apparatus, or may be obtained from a reticle design drawing.

  Further, the curves shown in FIGS. 7 and 8 may be continuous curves represented by one function, or may be broken lines obtained by dividing the exposure area in a lattice pattern and calculating the amount of variation of the lattice points. Good. The average value P1 may be obtained by integrating a function representing the magnification X with respect to the Y coordinate in the exposure area and dividing the function by the width of the exposure area in the Y direction. It may be obtained from the value.

  In consideration of the thermal expansion of the reticle, the curve representing the magnification X with respect to the Y coordinate changes with time (the magnification X increases). For this reason, when the selected mark differs depending on the elapsed time, it may be considered with a model after the elapse of an infinite time, may be considered with a model after an elapse of an arbitrary fixed time, or a model with a plurality of elapsed times may be considered. A value obtained by averaging may be used. Alternatively, as in an embodiment described later, a simple model in which thermal expansion occurs only in the exposure area and the expansion amount is constant may be used.

  In addition to thermal expansion, there are mechanical deformations caused by the pressure of the suction and deformation of the reticle itself when the reticle is sucked and fixed, as a deformation factor of the reticle, and a mechanical deformation model may be used.

  Up to this point, the mark selection method when the adjustment of the magnification X variation is given top priority has been described, but the baseline, magnification Y, rotation X, rotation Y, focus, tilt X, tilt Y, tertiary magnification X, and image plane An example of the mark selection method when the curvature adjustment is given the highest priority is as follows. In this case, the deformation of the reticle is not a barrel shape as shown in FIG. 7, but is a deformation model represented by the following respective curves.

  The baseline mark selection method is selected in the same manner as described above with the vertical axis as the baseline in FIG.

  In the mark selection method for rotation X, 44c, 44g, 44l, and 44p are selected in the same manner as described above with the vertical axis as rotation X in FIG.

  In the focus mark selection method, 44c, 44g, 44l, and 44p are selected in the same manner as described above with the vertical axis as the focus in FIG.

  In the mark selection method for tilt X, 44c, 44g, 44l, and 44p are selected in the same manner as described above, with the vertical axis as tilt X in FIG.

  As the mark selection method for the tertiary magnification X, the vertical axis is the tertiary magnification X in FIG. 8, and 44c, 44g, 44l, and 44p are selected by the same method as described above.

  In the field curvature mark selection method, the vertical axis is the field curvature in FIG. 8, and 44c, 44g, 44l, and 44p are selected by the same method as described above.

  Further, since the magnification Y, rotation Y, and tilt Y are changes with respect to the span in the Y direction, they cannot be considered as changes with respect to the Y coordinate as shown in FIG. Therefore, when the mark is selected with the highest priority on the adjustment of these items, as shown in FIG. 16, the mark is selected from a group of marks arranged in the X direction.

  As a mark selection method for the magnification Y, 44v, 44y, 44γ, and 44ε are selected in the same manner as described above in FIG.

  As for the mark selection method for rotation Y, 44v, 44y, 44γ, and 44ε are selected in the same manner as described above with the vertical axis as the rotation Y in FIG.

  The mark selection method for tilt Y is 44v, 44y, 44γ, 44ε in the same manner as described above, with the vertical axis being tilt Y in FIG.

  Next, in step S30, when adjusting at least one of magnification X, magnification Y, rotation X, rotation Y, tilt X, tilt magnification Y, tertiary magnification X, and field curvature, the mark interval and exposure area are adjusted. Perform a tolerance check on the width of the

  The tolerance check for the mark interval is to prevent the measurement accuracy from deteriorating by dividing by a small mark interval. Further, the tolerance check regarding the width of the exposure area is because the merit of the adjustment is small when the width of the exposure area is small, and thus the throughput is more important than the error reduction by the adjustment.

  In the tolerance check of the mark interval with respect to the magnification X, rotation X, and tilt X, at least one adjustment item is used to calculate two measured values (the outermost two in the case of three or more) in the X direction. If the interval is smaller than the predetermined value, it will be rejected. Then, “no adjustment” is set for the adjustment item, and the process returns to step S24.

  Similarly, in the tolerance check of the mark interval with respect to the magnification Y, rotation Y, and tilt Y, at least one or more adjustment items are used for calculation of measurement values (the outermost two in the case of three or more). If the interval in the Y direction is smaller than the predetermined value, it will be rejected. Then, “no adjustment” is set for the adjustment item, and the process returns to step S24.

  The tolerance check of the mark interval related to the third-order magnification X and the field curvature is not performed when the closest two X-direction intervals used for calculation of measurement values are smaller than a predetermined value for at least one adjustment item. Pass. Then, “no adjustment” is set for the adjustment item, and the process returns to step S24.

  In the tolerance check of the width of the exposure area with respect to the magnification X, rotation X, tilt X, third-order magnification X, and field curvature, when the width in the X direction of the exposure area is smaller than a predetermined value for at least one adjustment item, It will be rejected. Then, “no adjustment” is set for the adjustment item, and the process returns to step 24. The same applies to the magnification Y, rotation Y, and tilt Y.

  If the tolerance check is not rejected for any of the adjustment items regarding the mark interval and the exposure area width, the process proceeds to step S 32, and the coordinates of the selected measurement mark are transmitted to the exposure control unit 72.

  Note that the value of the predetermined value (threshold value) that serves as a criterion for each tolerance check may be set for each tolerance check item, or may be defined as a uniform value.

After selecting the measurement mark, measurement and adjustment value calculation are performed by the method described above. For the adjustment method,
• Wafer stage adjustment drive • Reticle stage adjustment drive • Projection lens adjustment drive • Select one of the exposure light source wavelength switching methods.

Specifically, when performing magnification X adjustment, magnification Y adjustment, tertiary magnification X adjustment, focus adjustment, and field curvature adjustment,
• Wafer stage adjustment drive • Reticle stage adjustment drive • Projection lens adjustment drive • Select one of the exposure light source wavelength switching methods.

When performing baseline adjustment, rotation X adjustment, rotation Y adjustment, tilt X adjustment, tilt Y adjustment,
• Select either wafer stage adjustment drive or reticle stage adjustment drive.

As described above, according to the present embodiment, it is possible to reduce a transfer error due to a pattern change without imposing a burden on the user.
[Second Embodiment]
Hereinafter, the second embodiment will be described.

  The second embodiment is a case where a more simplified reticle deformation model is used in the first embodiment.

  In the present embodiment, only the step S28 in the first embodiment is performed as follows, and the other portions are the same as those already described in the first embodiment, so that the description thereof is omitted.

  9 and 10 show a reticle deformation model. This embodiment is a case where the exposure area is biased upward in the reticle Y direction. In FIG. 8, the same amount of thermal deformation occurs at any point in the exposure area, and thermal deformation does not occur outside the exposure area. It is a model to think about. This is effective when there is no characteristic deformation model by simulation or experiment.

  This deformation model may be applied when an exposure area is set on almost the entire surface of the reticle as in the first embodiment. Conversely, when the exposure area is biased in one direction, a curved line as shown in FIG. A model that causes general deformation may be applied.

FIG. 10 shows the relationship of the magnification X to the Y coordinate. Within the exposure area, the magnification X = P2 at any Y coordinate. There are three Y coordinates where marks indicating this value exist, but from the viewpoint of measurement accuracy of the rotation Y, the four marks are combinations of the outermost Y coordinates in the exposure region, 44b, 44e, 44k. , 44n.
[Third Embodiment]
Hereinafter, a third embodiment will be described.

  The third embodiment is a case where a measurement system using a line mark and a light amount sensor is used instead of the TTR observation optical system 20 in the first or second example. Since points other than the means for obtaining the relative relationship between the reticle 2 and the wafer stage 10 are the same as those in the first or second embodiment, the description thereof is omitted.

  FIG. 11 shows the configuration of the exposure apparatus 100A used. In this configuration, the TTR observation optical system 20 is deleted from FIG. 1, the line mark 45 is disposed on the reticle 2, the line mark 11c is formed on the reference plate 9, and the light quantity sensor 14 is formed below the line mark 11c.

  Line mark 45 and line mark 11c are patterns produced by coating quartz glass with chromium as shown in FIG. 12, and are shown in FIG. 12 (a) and the X measurement mark and FIG. 12 (b). It consists of Y measurement marks. Both shapes are optically equivalent via the projection optical system 5.

  Hereinafter, the principle of the light quantity sensor measurement system will be described.

  The exposure light emitted from the illumination optical system 1 enters the line mark 45, and the exposure light is transmitted only through the slit portion not covered with chromium. The transmitted exposure light enters the line mark 11 c of the wafer reference plate 9 via the projection optical system 5. The exposure light incident on the chrome portion of the line mark 11c is shielded, and only the exposure light transmitted from the glass portion enters the light amount sensor 14 below. The light amount sensor 14 measures the amount of incident exposure light.

  Here, when the wafer stage 10 is driven in the X direction, the light amount of the exposure light incident on the light amount sensor 14 increases or decreases depending on the overlapping state of the line mark 45 and the line mark 11c. FIG. 13A shows the relationship between the X coordinate of the wafer stage 10 and the light amount measured by the light amount sensor 14. The relative relationship between the line mark 45 and the line mark 11c in the X direction is calculated based on the stage X coordinate X0 indicating the maximum light amount IX0.

  The same applies to the Y direction.

  Regarding the Z direction, when the wafer stage 10 is driven in the Z direction as shown in FIG. 13B, the amount of light measured by the light amount sensor increases or decreases. Based on the stage Z coordinate Z0 where the light quantity indicates the maximum value IZ0, the relative relationship between the line mark 45 and the line mark 11c in the Z direction is calculated.

By measuring in the X, Y, and Z directions with respect to the plurality of line marks 45, the relative relationship between the reticle 2 and the wafer stage 10 can be obtained.
[Fourth Embodiment]
Hereinafter, a fourth embodiment will be described.

  The fourth embodiment is a case where measurement is performed using the mark on the reticle reference plate 3 instead of the mark on the reticle 2 in the first, second, or third example. Since the embodiment after the selection of the mark is the same as the first, second, or third embodiment, the description thereof is omitted.

  Since the reticle reference plate 3 is hardly exposed to the exposure light, the energy absorption of the exposure light is extremely small. Further, since it is not exchanged like a reticle, the shape of mechanical deformation due to attachment does not change. Therefore, it may be considered that the shape of the reticle reference plate is always constant.

  Therefore, the reticle stage 4 is driven in the Y direction so that the mark of the reticle reference plate 3 coincides with the optical axis and the Y coordinate, and the mark of the reticle reference plate 3 is measured, whereby the lenses constituting the projection optical system 5 are measured. The effect of thermal deformation can be measured.

  In particular, when exposure is performed with a reticle having low transmittance, the amount of thermal deformation of the reticle is small and the amount of thermal deformation of the lens is large. Therefore, reducing the influence of thermal deformation of the lens reduces transfer errors. It is effective.

  In the measurement using the reticle reference plate 3, the baseline, magnification X, rotation X, focus, tilt X, tertiary magnification X, and field curvature due to thermal deformation of the lens can be measured. The method of obtaining the adjustment values for the magnification X, rotation X, focus, tilt X, tertiary magnification X, and field curvature is as described in the first embodiment.

  Here, the baseline means a relative position of the reticle reference plate 3 with respect to the off-axis scope 12.

Therefore, regarding the calculation of the adjustment value, if the relative position of the wafer stage 10 with respect to the reticle reference plate 3 is V4, and the relative position of the wafer stage 10 with respect to the off-axis scope 12 is V3,
BL = V4-V3
Based on the value of.

  The method for obtaining the relative positional relationship between the reticle reference plate 3 and the wafer stage 10 is the same as the method for obtaining the relative positional relationship between the reticle 2 and the wafer stage 10 in the first embodiment.

  Hereinafter, in this embodiment, description will be made assuming that the magnification X is adjusted.

  As shown in FIG. 14, reticle marks 46 a to 46 g are arranged on the same Y coordinate on the reticle reference plate 3, and these coordinates are stored in the storage unit 74.

  Between the lines 46a and 46b and between the lines 46f and 46g, there are extended lines on the left and right sides of the exposure area, respectively.

FIG. 15 shows a model (prediction information) of thermal deformation of the lens in this case. The error in the X direction from the ideal transfer position with respect to the X coordinate of an arbitrary point in the transferred shot is shown in the curve shown in FIG.
The magnification X is obtained from the slope P3 of the approximate straight line of the curve in the exposure area.

  Here, in order to select the two measurement marks whose magnification X is closest to P3, the X coordinate of the intersection of the curve and the straight line in FIG. 15 and the two marks whose X coordinates are close to X1 and X2 are selected. Just choose. As a result, the marks 46b and 46f are selected.

  Hereinafter, a method of manufacturing a device (semiconductor IC element, liquid crystal display element, etc.) using the above-described exposure apparatus will be described. The device includes a step of exposing a substrate (wafer, glass substrate, etc.) coated with a photosensitive agent using the above-described exposure apparatus, a step of developing the substrate (photosensitive agent), and other known steps. It is manufactured by going through. According to this device manufacturing method, it is possible to manufacture a higher quality device than before. Thus, the device manufacturing method using such an exposure apparatus and the resulting device also function as one aspect of the present invention.

Block diagram of exposure equipment Reticle top view Diagram showing measurement sequence flow of TTR observation optical system Table for number of required marks for each adjustment item Reticle mark arrangement concept Diagram showing measurement mark determination sequence flow Conceptual diagram of thermal deformation of reticle Conceptual graph of magnification X with respect to the Y coordinate of the reticle when thermal deformation occurs in the reticle Conceptual diagram of thermal deformation of reticle Conceptual graph of magnification X with respect to the Y coordinate of the reticle when thermal deformation occurs in the reticle Block diagram of exposure equipment Conceptual diagram of line mark Conceptual graph showing the amount of light with respect to X or Z coordinates Plane view of reticle reference plate Conceptual graph showing transfer error in X direction with respect to X coordinate in shot due to thermal deformation of lens Plan view of a reticle with a group of marks in the X direction Conceptual graph of magnification X with respect to the X coordinate of the reticle when thermal deformation occurs in the reticle

Explanation of symbols

1: illumination optical system 2: reticle 3: reticle reference plate 4: reticle stage 5: projection optical system 7: wafer chuck 8: wafer 9: wafer reference plate 10: wafer stage 11: mark 12 on wafer reference plate: off-axis Scope 14: Light quantity sensor 20: TTR observation optical system 21: Fiber 22: Half mirror 23: Relay lens 24: Mirror 25: Objective lens 26: Imaging element 30: Illumination optical system control system 40: Reticle stage control system 42: Reticle adsorption Pad 43: First reticle mark 44: Second reticle mark 45: Reticle line mark 46: Reticle reference plate mark 50: Projection optical system control system 60: Wafer stage control system 70: Exposure apparatus control system 72: Control Unit 73: Calculation processing unit 74: Storage unit 76: Display unit

Claims (7)

Projection optical system for projecting a pattern of an original on a substrate using light from a light source, an original reference plate having an original reference mark, an original stage holding the original, a substrate reference plate having a substrate reference mark, and the substrate An exposure apparatus having a substrate stage for holding
A defining part for defining an exposure area in the original plate;
Adjustment items relating to position information of a plurality of marks formed on the original plate or the original reference plate, information on the exposure area defined by the defining unit, and transfer error when transferring the pattern of the original plate to the substrate An input section where
Based on the position information of the plurality of marks, the information on the exposure area, and the adjustment item, a selection unit that selects a measurement mark to be used for measurement from the plurality of marks,
A measurement unit for measuring the measurement mark and the substrate reference mark;
Based on the measurement result of the measurement unit, the original stage drive, the substrate stage drive, the projection optical system lens drive, and the light source so that the positional deviation between the measurement mark and the substrate reference mark is reduced. And an adjusting unit that performs at least one of the wavelength switching. The selection unit includes:
Determine the number of measurement marks based on the adjustment item,
Based on the information of the exposure region, the so highest measuring accuracy for one adjustment item out of the adjustment items is obtained, selecting the position of the measuring mark of the determined number to claim 1, wherein The exposure apparatus described .   The exposure apparatus according to claim 2, wherein the selection unit selects four measurement marks as the measurement marks so as to form rectangular vertices.   The selection unit selects a mark to be used for the measurement from the plurality of marks based on at least one of pattern distribution information of the original plate or prediction information related to a transfer error. 4. The exposure apparatus according to any one of 3. The adjustment items include at least one of baseline, primary magnification, tertiary magnification, rotation, focus, tilt, and field curvature,
5. The exposure apparatus according to claim 1, wherein presence / absence of adjustment relating to the adjustment item is input to the input unit. 6.   6. The adjustment according to any one of claims 1 to 5, wherein when the width of the mark used for the measurement or the width of the exposure area is smaller than a threshold value, the adjustment according to the adjustment item is not performed. The exposure apparatus described in 1. Exposing the substrate using the exposure apparatus according to any one of claims 1 to 6;
And developing the exposed substrate. A device manufacturing method comprising: