JP3823417B2 - Exposure apparatus and exposure method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exposure apparatus and an exposure method used in a photolithography process in a manufacturing process of a semiconductor device or a liquid crystal display device.
[0002]
[Prior art]
Since a semiconductor device or a liquid crystal display device is formed by laminating a plurality of circuit patterns on a wafer, when performing projection exposure in the photolithography process, the circuit pattern formed in each shot region on the wafer, It is necessary to perform exposure after accurately aligning the image of the reticle circuit pattern projected on the upper layer. In a conventional exposure apparatus, the reticle is aligned and fixed with respect to the reference mark on the wafer stage, and then the positional relationship between the reference mark and the wafer is measured, and then the wafer stage control system is used to remove the wafer from the wafer stage position measurement system. While feeding back the wafer stage position, the wafer stage driving system was controlled to drive the wafer stage steppingly, and each shot area of the wafer was sequentially positioned at the exposure position. When the difference between the current position of the wafer stage and the target position continues for a predetermined time or longer and falls within a predetermined allowable range, the exposure light source shutter is opened to start exposure.
[0003]
The positioning operation of the wafer stage up to this exposure includes a stepping operation in which the wafer stage is moved from the pre-exposure position of the wafer to the vicinity of the next exposure position (target position), and the wafer stage is accurately targeted following the stepping operation. It is divided into a driving operation for positioning at a position. FIG. 4 shows an example of the dynamic characteristics of the wafer stage from the stepping operation to the follow-up operation. In FIG. 4, the horizontal axis represents the elapsed time, and the vertical axis represents the error amount from the wafer target position. In FIG. 4, the wafer stage approaches the target position while decelerating based on a predetermined speed profile, but once passes through the target position, and then converges in a transient response and falls within a steady position deviation. Exposure in the case of controlling the wafer stage with such dynamic characteristics is determined to start after a predetermined time from the time when the wafer stage converges within the steady position deviation. Since the position of the wafer stage is always fed back from the laser length measuring device of the wafer stage position measurement system, for example, a plurality of wafer stage positions (for example, 10 points) from the time when it is recognized that the wafer stage has converged within the steady position deviation. Data is sampled, and if they are within the steady position deviation, an exposure start command is issued.
[0004]
Accordingly, if the time from the wafer stage positioning operation until the exposure start command is issued can be shortened, that is, the time required for the wafer stage stepping operation and the follow-up operation can be shortened, the throughput of the exposure apparatus can be reduced. It can be improved.
[0005]
However, since the wafer stage system of the exposure apparatus requires extremely high positioning accuracy, the stage itself is required to have high rigidity, and the stage drive system has sufficient resolution and power in addition to minimal backlash. As a result of the requirement, the wafer stage system has to have a considerable weight, and it is difficult to realize a wafer stage control system that positions the wafer stage system at a predetermined position in a short time. After all, in the conventional exposure apparatus, since it is difficult to control to reduce the time for the follow-up operation, the throughput cannot be improved, and there is a disadvantage that the entire exposure time becomes long. In addition, even if an attempt is made to shorten the time of the positioning operation by speeding up the stepping operation, in the situation where a large inertial force is exerted by the heavy wafer stage during deceleration, it is necessary for the driving operation no matter how much the control system is adjusted. On the other hand, since the time becomes longer, the conventional control method has a limit in improving the throughput of the exposure process.
[0006]
Means for solving this problem is disclosed in JP-A-7-220998. The control method disclosed in the publication will be described with reference to FIG. FIG. 5 shows an example (solid line) of the dynamic characteristics of the wafer stage having the same waveform as that of FIG. 4 from the stepping operation to the driving operation (solid line), and the dynamic characteristics (broken line) of the reticle stage that moves following the movement of the wafer stage. ing. In FIG. 5, the horizontal axis represents the elapsed time, and the vertical axis represents the error amount from the wafer target position. In FIG. 5, first, the wafer stage approaches the target position while decelerating based on a predetermined speed profile. When the wafer stage reaches within a predetermined error amount determined in advance, the reticle stage control system uses the error amount as a tracking range, and the reticle stage drive system so that the reticle stage follows the movement characteristics of the subsequent wafer stage. To control.
[0007]
More specifically, the reticle stage control system further sets a predetermined constant in the wafer stage position error signal (constant = 1 in FIG. 5) with respect to the difference between the target position information of the reticle stage and the reticle stage position information. The reticle stage drive system is controlled based on the reticle stage position error signal obtained by calculating the difference from the value obtained by multiplying the value obtained by multiplying the value by (a).
[0008]
In this reticle stage control system, the reticle stage drive system is controlled by PI control based on a differential equation using a proportional term Kp and an integral term Ki as gain terms for the reticle stage position error signal. In order to move the reticle stage following the wafer stage that is moving in a transient response, the P (proportional) control that uses only the proportional term Kp as the gain term for the reticle stage position error signal cannot follow the throughput. Therefore, the reticle stage position error signal is integrated, and a value obtained by multiplying by the integral term Ki is added to enable stable tracking.
[0009]
In the conventional exposure apparatus, the start of exposure is made to wait until the wafer stage sufficiently converges within the steady position deviation, but according to this method, the reticle stage moves following the movement of the wafer stage. So that the wafer and the reticle can be relatively aligned even when the wafer stage does not converge within the steady position deviation and is still oscillating in a transient response. Become. Since the position of the wafer stage and the position of the reticle stage are always fed back from each laser length measuring device of the wafer stage position measurement system and the reticle stage position measurement system, the relative position error between the wafer stage and the reticle stage is, for example, FIG. From the time when it is recognized that it has converged within the same relative position deviation as the steady position deviation, as shown in Fig. 1, sample the data of the relative position error of multiple points (for example, 10 points), and they are within the relative position deviation If so, an exposure operation start command is issued.
[0010]
Since the reticle stage is sufficiently light compared to the wafer stage, control with excellent responsiveness can be easily performed. Accordingly, it is possible to reduce the time required for the follow-up operation for setting each exposure area of the wafer from the vicinity of the exposure position of the reticle pattern to the exposure position.
[0011]
[Problems to be solved by the invention]
For example, in a step-and-repeat type reduction projection exposure apparatus, consider a case where the reticle stage follows the step operation and the follow-up operation of the wafer stage based on the above-described control method. In order to move the imaging position of the circuit pattern of the reticle from the pre-exposure position of the wafer to the next exposure position, for example, when moving the wafer stage in the X-axis direction, the target position in the Y-axis control of the wafer stage is set. There is no change and ideally the wafer stage should not move in the Y-axis direction.
[0012]
However, in reality, when the X-axis stage of the wafer stage is driven by the drive system and starts to move, vibration generated in each part as the X-axis stage moves is transmitted to the Y-axis stage of the wafer stage, and the Y-axis stage It starts to vibrate slightly. Since this vibration is caused by resonance of each component in the stage mechanism, it has a relatively high frequency component. This phenomenon is hereinafter referred to as crosstalk. FIG. 6 shows how the Y-axis stage vibrates due to the crosstalk. As shown in FIG. 6, with respect to the vibration of the Y-axis stage of the wafer stage (the amplitude of the vibration is about 200 nm, for example), the reticle stage control system determines the target position information in the Y-axis direction of the reticle stage and the Y-axis direction. Based on the reticle stage position error signal in the Y-axis direction obtained by calculating the difference between the difference from the reticle stage position information and the value obtained by multiplying the wafer stage position error signal in the Y-axis direction by a predetermined constant. This reticle stage drive system is driven by PI control.
[0013]
Accordingly, the reticle stage, which originally has no change in the target position in the Y-axis direction and does not need to be moved in the Y-axis direction, starts to move following the vibration of the wafer stage in the Y direction. However, in this PI control, since the integral value of the wafer stage position error signal in the Y-axis direction including a relatively high frequency component is added, the phase with respect to the damped oscillation (solid line) of the wafer stage as shown by the broken line in FIG. The reticle stage is controlled so that it attenuates in the inverted state, and eventually the exposure operation start condition on the Y-axis side is delayed even if the exposure operation start condition in the X-axis direction of the stepped reticle stage is ready. On the contrary, there is a problem that throughput is lowered and accuracy is deteriorated.
[0014]
As described above, in the control method disclosed in Japanese Patent Laid-Open No. 7-220998, the exposure operation start condition can be adjusted in a short time by causing the reticle stage to follow the axis on which the wafer stage steps (in the above-described X axis). Reticle stage against wafer stage vibration on non-step axis, but not considering vibration of wafer stage having relatively high frequency component generated in non-stepped axis (Y-axis in the above) direction There is a problem that it is not possible to avoid a decrease in throughput based on the difficulty of following.
[0015]
SUMMARY OF THE INVENTION An object of the present invention is to provide an exposure apparatus and an exposure method in which the time required for positioning each exposure position on a substrate to the image formation position of a reticle pattern is shortened and the throughput of the exposure process is improved. is there.
[0016]
[Means for Solving the Problems]
In order to achieve the above object, the following configuration is provided.
When the wafer stage is moved only in the first axis (X-axis) direction, the first axis direction of the reticle stage is controlled by PI control using the proportional term Kp and the integral value Ki, and the second axis of the reticle stage. The (Y axis) direction is controlled by P control using only the proportional term Kp. When the wafer stage is moved only in the second axis (Y-axis) direction, the second axis direction of the reticle stage is controlled by PI control using the proportional term Kp and the integral value Ki, and the first axis of the reticle stage. The direction is controlled by P control using only the proportional term Kp. By such control, the reticle stage is prevented from following high-frequency components generated in a direction orthogonal to the moving direction of the wafer stage.
[0017]
In the exposure apparatus, the reticle stage position control system may control the reticle stage drive system by the P control if the scheduled movement amount is 0 or within a predetermined reference range. Further, the predetermined reference value may be an offset amount of the stop position of the substrate stage with respect to the previous target position.
[0018]
Moreover, in order to achieve the said objective, it has the following processes.
When positioning the wafer stage, when the wafer stage is within a predetermined range, the reticle stage is positioned by following the movement of the wafer stage, and the first is based on the position information of the wafer stage and the next target position information of the wafer stage. Of the step of calculating the planned movement amount between the axial direction and the second axial direction, and the planned movement amount between the first axial direction and the second axial direction, the axial direction within which the planned movement amount is within the reference range is only the proportional term Kp. And a step of performing control so that PI control using the proportional term Kp and the integral value Ki is performed in the axial direction where the estimated movement amount is outside the reference range.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
An exposure apparatus and exposure method according to an embodiment of the present invention will be described with reference to FIGS. The exposure apparatus in the present embodiment reduces and projects a pattern image on a reticle via a projection optical system, and sequentially reduces and exposes the pattern image to each shot area on a photosensitive substrate. Device.
FIG. 1 shows a schematic configuration of an exposure apparatus according to the present embodiment. Hereinafter, the configuration of the exposure apparatus according to the present embodiment will be described with the optical axis direction of projection optical system PL as the Z axis and the plane perpendicular to the optical axis as the XY plane.
[0020]
Illumination light IL from the illumination light source LMP for exposure is, for example, an i-line (wavelength λ = 365 nm), g-line (λ = 436 nm) or KrF excimer laser light (λ = 248 nm) that is an emission line of an ultra-high pressure mercury lamp. In addition, ultraviolet light such as ArF excimer laser light and metal vapor laser light can be used.
[0021]
Illumination light IL emitted from the illumination light source LMP is converted into a parallel light flux having a substantially uniform illuminance distribution by the illumination optical system 6 including a collimator lens, a fly-eye lens, a reticle blind, and the like via the shutter 4 to make the reticle R uniform. Illuminate with a good illuminance distribution.
In the pattern drawing area of the reticle R, a circuit pattern to be projected onto the wafer W, which is the substrate to be exposed, is drawn by an electron beam drawing apparatus or the like. The circuit pattern on the reticle R is projected and exposed onto the wafer W by irradiation with an illumination light beam from above the reticle R.
[0022]
The reticle R is fixed on the reticle stage RST by, for example, vacuum suction or the like by a reticle chuck (not shown) provided on the reticle stage RST that can move in the XY plane. Although detailed illustration is omitted, the reticle stage RST is composed of a reticle X stage that moves in the X-axis direction and a reticle Y stage that supports the reticle X stage and moves in the Y-axis direction. Each of them can be moved by a reticle stage drive mechanism having a screw and a drive motor for rotating the feed screw. FIG. 1 shows a drive system in the X direction, and shows a feed screw 10X and a drive motor 8X for driving the reticle X stage. In FIG. 1, the Y-axis side drive system is not shown, but the configuration is the same as that of the X-axis side.
[0023]
The position of the reticle stage RST in the X and Y directions is always measured by reflecting the laser beam from the laser length measuring device 14X to the reflecting mirror 12X fixed to the periphery of the reticle stage RST, and the same. The position in the Y direction is always measured by the reflecting mirror 12Y and the laser length measuring device 14Y (not shown). Position information in the X direction of the reticle stage measured by the laser length measuring device 14X is sent to a control system 24X that performs control in the X direction. The configuration of the control system 24X will be described in detail later. Based on the reticle stage position information in the X direction, the control system 24X accurately controls the X-axis drive system of the reticle stage RST to bring the reticle R to a predetermined position. It can be positioned. Similarly, the control system 24Y (not shown) can accurately control the Y-axis drive system of the reticle stage RST based on the reticle stage position information in the Y direction to position the reticle R at a predetermined position. .
[0024]
Projection optical system PL focuses a light beam that has passed through reticle R, and is a predetermined shot position of wafer W placed on a wafer holder (not shown) provided on substrate stage WST that can move in the X and Y directions. An image of the pattern of the reticle R is projected onto The wafer holder holds the wafer W by vacuum suction, moves in the Z-axis direction, adjusts the distance between the wafer W surface and the projection optical system PL, and aligns the wafer W surface with the imaging surface of the projection optical system PL. Can be done. In the present embodiment, the projection magnification β of the projection optical system PL is 1/5, and the width of the projected image is reduced to 1/5 with respect to the pattern width of the reticle R.
[0025]
Although not shown in detail, wafer stage WST includes a wafer X stage that moves in the X-axis direction and a wafer Y stage that supports the wafer X stage and moves in the Y-axis direction. Each of them can be moved by a reticle stage drive mechanism having a screw and a drive motor for rotating the feed screw. In FIG. 1, a feed screw 18X and a drive motor 16X for driving the reticle X stage are shown. Although the illustration of the drive system on the Y-axis side is omitted, the configuration is the same as that on the X-axis side.
[0026]
The position of wafer stage WST in the X direction is always measured by reflecting the laser beam from laser length measuring device 22X to reflecting mirror 20X fixed to the periphery of wafer stage WST, and in the same way in the Y direction. These positions are always measured by a reflecting mirror 20Y and a laser length measuring device 22Y (not shown). Position information in the X direction of wafer stage WST measured by laser length measuring device 22X is sent to control system 24X. Based on the wafer stage position information in the X direction, the control system 24X is placed on wafer stage WST by accurately controlling the X-axis drive system of wafer stage WST and stepping wafer stage WST in the X direction. In addition, the circuit pattern image of the reticle R can be sequentially superimposed and exposed at a plurality of predetermined shot positions on the wafer W. The Y-direction control system 24Y (not shown) has a configuration similar to that of the control system 24X and can perform the same operation.
[0027]
Note that when the pattern of the reticle R is exposed on the wafer W, it is necessary to align the reticle R and the wafer W in advance, so that alignment marks for alignment are formed on the reticle R and the wafer W. Yes. These alignment marks are observed and aligned with a reticle alignment optical system or a wafer alignment optical system, but their illustration and description are omitted here.
[0028]
Next, the configuration of the control system 24X will be described with reference to FIG. FIG. 1 shows a configuration for positioning the reticle stage RST and the wafer stage WST in the control system 24X at target positions in the X-axis direction. Since the control system for the Y-axis direction has the same configuration as the control system for the X-axis direction, illustration and description thereof are omitted. The control system 24X includes a target position setting unit 26X that sets target positions at which the wafer stage WST and the reticle stage RST should be positioned. The wafer stage target position information Xw0 output from the target position setting unit 26X is input to the addition point 28X. In addition, information on the current position in the X direction of wafer stage WST measured by laser length measuring device 22X is also input to alignment point 22X. Specifically, the addition point 28X is a subtractor, and calculates the difference between the wafer target position information Xw0 and the wafer stage position information from the laser length measuring device 22X.
[0029]
The obtained difference in wafer position information is input as a wafer stage position error (signal) to the control circuit 30X and calculated as a gain term based on a predetermined difference equation, and the result is input as a digital output value to the DA converter 32X. The In the present embodiment, control circuit 30X for wafer stage WST uses only proportional term Kp as a gain term, but is not limited to this, and other gain terms may be added. . The DA converter 32X converts the input digital value into an analog voltage and outputs it to the servo amplifier 34X. The servo amplifier 34X amplifies the input analog voltage with a predetermined amplification factor and supplies it to the drive motor 16X. As a result, the drive motor 16X rotates at a predetermined rotational speed to rotate the feed screw 18X, and the wafer stage WST moves in the X-axis direction. The amount of movement of this wafer stage WST is always measured by the laser length measuring device 22X, and the wafer stage position information is fed back to the control system 24X, and the position is always controlled while being compared with the target position to be positioned at the target position. A closed loop servo system is configured.
[0030]
Further, the wafer stage position error obtained at the addition point 28X is also input to the switch 37X. The switch 37X outputs the wafer stage position error to the multiplier 38X when the wafer stage position error enters a predetermined range (for example, 0.125 μm), and shuts off the output to the multiplier 38X when the exposure is completed. It has become. The multiplier 38X performs an operation of inverting the input wafer stage position error value and multiplying by the inverse of the projection magnification (1 / β). This calculation result is input to the addition point 40X of the reticle stage control system.
[0031]
On the other hand, reticle stage target position information Xr0 is added to target point 36X from target position setting unit 26X. Further, information on the current position in the X direction of reticle stage WST measured by laser length measuring instrument 14X is also input to addition point 36X. Specifically, the addition point 36X is a subtractor, and calculates a difference between the reticle target position information Xr0 and the reticle stage position information from the laser length measuring instrument 14X.
[0032]
The obtained difference in reticle stage position information is further input to the addition point 40X. The adding point 40X is specifically an adder, and the wafer stage position error, which has been subjected to a predetermined calculation by the multiplier 38X, and the difference between the reticle stage position information are added together to generate a reticle stage position error signal. .
The reticle stage position error signal is input to the control circuit 42X, calculated as a gain term based on a predetermined difference equation, and the result is input to the DA converter 44X as a digital output value.
[0033]
The control circuit 42X for the reticle stage WST has a proportional term Kp and an integral term Ki as gain terms, and adds them at the addition point to make PI control, or P control using only the proportional term Kp. Can also be made. In the figure, a state in which PI control is performed is shown. This switching is performed in the control switching unit 48X. Prior to the control, the control switching unit 48X calculates the expected movement amount of the wafer stage WST from the wafer stage position information and the next target position information of the wafer stage, and the proportional term Kp is calculated in the control circuit 42X based on the estimated movement amount. And switching to PI control using the integral term Ki and P control using only the proportional term Kp.
[0034]
The planned movement amount used for the switching determination is obtained as a difference between the next wafer stage target position and the current wafer stage position information. Therefore, if the next wafer stage target position does not change from the previous position, the expected movement amount is zero. If the planned movement amount is a reference value (= 0), the control switching unit 48X instructs the control circuit 42X to control the reticle stage drive system by P control, and the planned movement amount is a value other than zero. If so, an instruction is given to control the reticle stage drive system by PI control.
[0035]
Similar to the control switching unit 48X provided in the X direction control system of the reticle stage RST, the control switching unit 48Y is provided in the Y direction control system (not shown). In this configuration, for example, consider a case where the wafer stage performs a step operation of a predetermined distance (for example, 20 mm) in the X direction but does not move in the Y direction. The control switching unit 48X calculates the planned movement amount = 20, and since the planned movement amount is different from the reference value = 0, it instructs the control circuit 42X to control the reticle stage in the X direction by PI control, The control switching unit 48Y calculates the planned movement amount = 0, and since the planned movement amount is the same as the reference value = 0, instructs the control circuit 42Y to control the reticle stage in the Y direction by P control. That is, in the reticle X stage corresponding to the wafer X stage that performs the step operation, the position of the wafer stage WST in the X direction falls within a predetermined tracking range in accordance with the control method disclosed in the above-mentioned JP-A-7-220998. The wafer stage WST is driven by PI control so as to follow the movement in the X direction.
[0036]
Then, the reticle Y stage corresponding to the wafer Y stage, which should actually stop, but actually vibrates with a relatively high frequency component, is driven by P control. FIG. 2 shows an example (solid line) of the dynamic characteristics of the wafer Y stage having the same waveform as that of FIG. 6 from the stepping operation to the follow-up operation, and the dynamic characteristics of the reticle Y stage that moves following the movement of the wafer Y stage (broken line). ). In FIG. 2, the horizontal axis represents the elapsed time, and the vertical axis represents the error amount from the wafer target position. By switching the reticle Y stage to P control, the integral value of the wafer stage position error signal in the Y-axis direction including a relatively high frequency component is not added, so that the reticle Y stage is PI as shown in FIG. The phase inversion due to the follow-up delay with respect to the damped vibration of the wafer stage caused by the control does not occur, and it can be quickly converged within the relative position deviation accordingly. In the above description, the PI control is switched to the P control. However, the filter control means is provided in the control circuits 42X and 42Y, and instead of switching the PI control to the P control, the filter is switched from the PI control to the P control. You may make it switch to control.
[0037]
In the present embodiment, the reference value of the scheduled movement amount is described as 0. However, when a predetermined reference range is set in advance and the planned movement amount is within the predetermined reference range, the control circuits 42X and 42Y On the other hand, it is of course possible to instruct the reticle stage drive system to be controlled by P control, and to control the reticle stage drive system by PI control if the expected movement amount is a value outside the predetermined reference range. This predetermined reference range may be set to an offset amount of the stop position of wafer stage WST with respect to the previous target position, for example. In short, the non-step driven by P control (or filter control) is almost the same as or faster than the time when the reticle X stage driven by PI control converges within the relative positional deviation from the wafer X stage during the step operation. A predetermined reference range may be set so that the reticle Y stage in operation converges within a relative positional deviation from the wafer Y stage.
[0038]
The digital control signal output from the control circuit 42X is input to the DA converter 44X. The DA converter 44X converts the input control signal into an analog voltage and outputs it to the servo amplifier 46X. The servo amplifier 46X amplifies the input analog voltage with a predetermined amplification factor and supplies it to the drive motor 8X. As a result, the drive motor 8X rotates at a predetermined rotational speed to rotate the feed screw 10X, and the reticle stage WST moves in the X-axis direction. The amount of movement of the reticle stage WST is constantly measured by the laser length measuring device 14X, and the reticle stage position information is fed back to the control system 24X, and the position is always controlled while being compared with the target position to be positioned at the target position. A closed loop servo system is configured.
[0039]
The reticle stage position error obtained at the addition points 40X and 40Y is also input to the exposure determination circuit 50. The exposure determination circuit 50 outputs a shutter opening command to the shutter drive circuit 52 when the reticle stage position error is equal to or less than a predetermined relative deviation amount at a predetermined sampling number (for example, 10 points). When a shutter open command is input, the shutter drive circuit 52 opens the shutter 4 that has shielded the illumination light from the illumination light source LMP.
[0040]
Next, the operation of the exposure apparatus according to this embodiment will be described. In the description of the operation, the control operation in both the X and Y directions will be described at the same time in order to clearly describe the characteristics of the present embodiment. Then, the case where wafer stage WST performs a step operation in the X direction will be described.
First, in a state where the shutter 4 is closed by the shutter drive circuit 52 and the illumination light IL from the illumination light source LMP is blocked, the positional relationship of the reticle R with respect to the reference position on the wafer stage WST is detected by a reticle alignment optical system (not shown). . Next, reticle R is fixed at an initial exposure position having a predetermined positional relationship with respect to the reference position on wafer stage WST, and the measured values of laser length measuring devices 14X and 14Y are reset to 0 in this state. Thereby, the coordinates of the reticle stage RST when the reticle R is fixed at the initial exposure position, that is, the initial target position (Xr0, Yr0) becomes (0, 0).
[0041]
Next, an exposure wafer W is loaded onto wafer stage WST, and the positional relationship of wafer W with respect to a reference position on wafer stage WST is detected by a wafer alignment optical system (not shown). Thereby, the positional relationship between the position (exposure position) of the projection image of the pattern of the reticle R by the projection optical system PL and each shot area of the wafer W is known, and each shot area of the wafer W is set to the exposure position. The target position (Xw0, Yw0) of the wafer stage WST is calculated.
[0042]
Next, the target position (Xw0, Yw0) of wafer stage WST is set to target points 28X and 28Y from target position setting units 26X and 26Y, respectively, and the target position (of reticle stage RST) is set to target points 36X and 36Y. Xr0, Yr0) = (0, 0) is set. Thereafter, by driving the drive motors 16X and 16Y of the wafer stage drive system, the wafer stage WST is stepped in the X direction with a speed profile as shown in FIG. 3, and the X position of the wafer stage WST is moved to the target position Xw0. Move closer. In FIG. 3, the velocity VWX in the X direction of wafer stage WST is accelerated and decelerated in a trapezoidal shape, and gradually becomes 0 in a transient response during convergence period T when wafer stage WST approaches the target position. In the convergence period T, a driving operation for final positioning is performed.
[0043]
The wafer stage position error signal ΔXw1 from the addition point 28X of the control system 24X is input to the control circuit 30X, and the movement of the wafer stage in the X direction is controlled by P control. When the wafer stage position error ΔXw1 enters a predetermined range (for example, 0.125 μm) just before the convergence period T, the wafer stage position error ΔXw1 is output from the switch 37X to the multiplier 38X and is input to the wafer stage. Calculation is performed by inverting the value of the position error ΔXw1 and multiplying by the reciprocal of the projection magnification (1 / β = 5). As a result of this calculation, 5 · ΔXw1 is input to the addition point 40X of the reticle stage control system. A difference ΔXr1 between the reticle target position information and the reticle stage position information from the laser length measuring instrument 14X is also input to the addition point 40X, and is added to the wafer stage position error 5 · ΔXw1 to add the reticle stage position error signal VX1 = ( 5 · ΔXw1) −ΔXr1 is generated.
[0044]
Prior to the control, the control switching unit 48X calculates the expected movement amount by calculating the difference between the target position in the X direction of the wafer stage WST with respect to the wafer stage position information in the X direction from the laser length measuring device 14X. Since the scheduled amount (= 20) is different from the reference value 0, the control circuit 42X is instructed to perform control by PI control. In response to an instruction from the control switching unit 48X, the control circuit 42X calculates the input reticle stage position error signal VX1 by PI control and outputs it to the DA converter 44X.
[0045]
On the other hand, the wafer stage position error signal ΔYw1 from the addition point 28Y of the control system 24Y is input to the control circuit 30Y, and the movement of the wafer stage in the Y direction is controlled by P control. When wafer stage position error ΔYw1 enters a predetermined range (for example, 0.125 μm), wafer stage position error ΔYw1 is output from multiplier 37Y to multiplier 38Y, and the value of input wafer stage position error ΔYw1 is inverted. An operation of multiplying the reciprocal of the projection magnification (1 / β = 5) is performed. As a result of this calculation, 5 · ΔYw1 is input to the addition point 40Y of the reticle stage control system. A difference ΔYr1 between the reticle target position information and the reticle stage position information from the laser length measuring instrument 14Y is also input to the addition point 40Y, and added to the wafer stage position error 5 · ΔYw1 to add the reticle stage position error signal VY1 = ( 5 · ΔYw1) −ΔYr1 is generated.
[0046]
Prior to control, the control switching unit 48Y calculates a difference in the target position in the Y direction of the wafer stage WST with respect to the wafer stage position information in the Y direction from the laser length measuring device 14Y to obtain a planned movement amount, and this movement Since the scheduled amount (= 0) is the same value as the reference value 0, the control circuit 42Y is instructed to perform control by P control. In response to an instruction from the control switching unit 48Y, the control circuit 42Y calculates the input reticle stage position error signal VY1 by P control and outputs it to the DA converter 44Y.
[0047]
The reticle stage position errors VX1, VY1 obtained at the addition points 40X, 40Y are input to the exposure determination circuit 50, and each of the reticle stage position errors VX1, VY1 has a predetermined sampling number (for example, 10 points). If the amount is less than the predetermined relative deviation amount, a shutter opening command is output to the shutter drive circuit 52. When a shutter open command is input, the shutter drive circuit 52 opens the shutter 4 that has shielded the illumination light from the illumination light source LMP. Thereafter, the circuit pattern of the reticle R is exposed to a predetermined exposure area on the wafer W through the projection optical system PL.
[0048]
The present invention is not limited to the above embodiment, and various modifications can be made.
For example, in the above-described embodiment, the present invention is applied to a step-and-repeat type reduction projection exposure apparatus. However, the present invention can be applied to a step-and-scan type projection exposure apparatus, or the exposure apparatus using proximity exposure. It is also possible to use the invention.
[0049]
【The invention's effect】
As described above, according to the present invention, it is possible to realize an exposure apparatus that shortens the time required to position each exposure position on the substrate at the image formation position of the reticle pattern and improves the throughput of the exposure process.
[Brief description of the drawings]
FIG. 1 is a view showing the schematic arrangement of an exposure apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing movement characteristics of a wafer stage and a reticle stage on a non-step axis when a positioning operation is performed by an exposure apparatus according to an embodiment of the present invention.
FIG. 3 is a view showing a velocity profile on a step axis when a positioning operation is performed by an exposure apparatus according to an embodiment of the present invention.
FIG. 4 is a diagram showing a movement characteristic of a wafer stage when a positioning operation is performed by a conventional exposure apparatus.
FIG. 5 is a diagram showing movement characteristics of a wafer stage and a reticle stage when a positioning operation is performed by a conventional exposure apparatus.
FIG. 6 is a diagram showing movement characteristics of a wafer stage and a reticle stage on a non-step axis when a positioning operation is performed by a conventional exposure apparatus.
[Explanation of symbols]
4 Shutter
6 Illumination optics
8X, 8Y, 16X, 16Y Drive motor
10X, 10Y, 18X, 18Y Lead screw
12X, 12Y, 20X, 20Y Reflector
14X, 14Y, 22X, 22Y Laser length measuring instrument
26X, 26Y Target position setting section
28X, 28Y, 36X, 36Y, 40X, 40Y Additional points
30X, 30Y control circuit (wafer stage side)
32X, 32Y, 44X, 44Y DA converter
34X, 34Y, 46X, 46Y Servo amplifier
37X, 37Y selector
38X, 38Y multiplier
42X, 42Y Control circuit (reticle stage side)
48X, 48Y Control switching part
50 Exposure judgment circuit
52 Shutter drive circuit
LMP illumination light source
IL illumination light
PL projection optical system
R reticle
RST reticle stage
W wafer
WST wafer stage

Claims (4)

A substrate stage drive system for holding a photosensitive substrate and driving a substrate stage movable two-dimensionally;
A substrate stage position measurement system for measuring the position of the substrate stage and outputting substrate stage position information;
A substrate stage position control system that controls the substrate stage drive system based on a substrate stage position error signal that is a difference between the target position information of the substrate stage and the substrate stage position information;
A reticle stage drive system for holding a reticle on which a circuit pattern to be exposed on the photosensitive substrate is drawn and driving a reticle stage that can be moved two-dimensionally;
A reticle stage position measurement system that measures the position of the reticle stage and outputs reticle stage position information;
Based on the reticle stage position error signal obtained by calculating the difference between the difference between the target position information of the reticle stage and the reticle stage position information and a value obtained by multiplying the substrate stage position error signal by a predetermined constant. A reticle stage position control system for controlling the reticle stage drive system,
In an exposure apparatus that exposes the circuit pattern on the photosensitive substrate when the magnitude of the reticle stage position error signal becomes a predetermined value or less,
The reticle stage position control system includes a PI control unit having a proportional term Kp and an integral term Ki as gain terms, and the PI control unit prior to the control includes the substrate stage position information and the next of the substrate stage. The estimated amount of movement of the substrate stage is calculated from the target position information, and based on the estimated amount of movement, PI control using the proportional term Kp and the integral term Ki, and P using only the proportional term Kp. An exposure apparatus characterized by switching to one of the controls. The exposure apparatus according to claim 1, wherein
The exposure apparatus according to claim 1, wherein the reticle stage position control system controls the reticle stage drive system by the P control when the scheduled movement amount is 0 or within a predetermined reference range. The exposure apparatus according to claim 2, wherein
The exposure apparatus according to claim 1, wherein the predetermined reference value is an offset amount of a stop position of the substrate stage with respect to a previous target position. A substrate stage position error, which is a difference between the target position information of the substrate stage and the substrate stage position information, is measured by feeding back the substrate stage position information by measuring the position of the substrate stage that holds the photosensitive substrate and moves two-dimensionally. A first step of controlling a drive system of the substrate stage based on a signal;
The reticle stage position information is fed back by measuring the position of the reticle stage that moves two-dimensionally while holding the reticle on which the circuit pattern to be exposed on the photosensitive substrate is drawn, and the target position information of the reticle stage and the reticle stage The reticle stage drive system is controlled based on a reticle stage position error signal obtained by calculating a difference between the difference from the reticle stage position information and a value obtained by multiplying the substrate stage position error signal by a predetermined constant. 2 steps,
In the exposure method of exposing the circuit pattern on the photosensitive substrate when the magnitude of the reticle stage position error signal becomes a predetermined value or less,
The second step calculates a planned movement amount of the substrate stage from the substrate stage position information and the next target position information of the substrate stage prior to control, and based on the planned movement amount, An exposure method characterized by switching between PI control using a proportional term Kp and an integral term Ki and P control using only the proportional term Kp.

Images