JPH09115814A - Exposure method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To expose all shot regions while focusing the pattern even on the peripheral shot regions in the wafer scanning direction with high precision, without decreasing the throughput. SOLUTION: In a scanning projection exposure apparatus, the exposure order is obtained so as to provide the shortest scanning path and shortest moving path for exposing all shot regions S1.1 through S6.4 on a wafer W. Thereafter, on conditions that the entire exposure time is little changed, the exposure order is changed as indicated by arrows B1, B2 to B32. A slit-like field is scanned on a coordinate system wherein the wafer is at rest from inside and outside of the wafer W to the periphery thereof in the peripheral shot regions S1.1 , S1.2 , S1.3 and the like. Autofocus is conducted based on the focal point detected near the field 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus used in a photolithography process for manufacturing a semiconductor device, a liquid crystal display device, an image pickup device (CCD, etc.), a thin film magnetic head, etc. More specifically, the present invention relates to an exposure method for exposing a pattern to a plurality of shot areas on a photosensitive substrate, and particularly, by scanning the mask and the photosensitive substrate in synchronization with a projection optical system, It is suitable for application to a scanning exposure type projection exposure apparatus such as a so-called step-and-scan method, which sequentially exposes each shot area on a substrate.

[0002]

2. Description of the Related Art Conventionally, when a semiconductor device or the like is manufactured by using a photolithography technique, an image of a pattern of a reticle (or a photomask or the like) is applied to a wafer coated with a photoresist (via a projection optical system). Alternatively, a projection exposure apparatus such as a stepper that collectively exposes each shot area on a glass plate) has been widely used. On the other hand, recently, the chip of the semiconductor element tends to be large, and it is necessary to expose a pattern of a larger area on the wafer,
By scanning the reticle and the wafer in synchronization with the projection optical system, it is possible to expose a wider area than the effective illumination field of the projection optical system. Projection exposure apparatuses are receiving attention.

In these projection exposure apparatuses, generally, a focusing operation (autofocus mechanism) for focusing the surface of the wafer (wafer surface) within the range of the depth of focus with respect to the image plane of the projection optical system. There is a focusing mechanism for performing.
This focusing mechanism includes a focus and leveling detection system that detects the height (focus position) and tilt of the wafer surface in the optical axis direction of the projection optical system, and the position and position of the wafer surface based on the detected height and tilt. And a stage mechanism for adjusting the inclination angle.

By the way, in the scanning exposure type projection exposure apparatus, in order to expose a certain shot area on the wafer,
It is necessary to scan the reticle at a speed ratio that is the reciprocal of the projection magnification in synchronism with scanning the shot area at a constant speed determined by the target exposure amount. Therefore, when performing exposure, the stage on which the wafer is placed starts the run before the shot area to be exposed and is synchronized with the stage on which the reticle is placed during the run, and then that shot area When the slit-shaped illumination field of the projection optical system is reached, the exposure light is emitted, and the sequence of performing the exposure is repeated. In this case, the focusing mechanism described above detects the focus position of the wafer surface at the start of running and moves the wafer surface to the focusing position, and the focusing operation continues in a manner to follow the moving wafer surface. It had been.

[0005]

In the conventional scanning exposure type projection exposure apparatus as described above, in order to increase the throughput (productivity), a method of reversing the scanning direction of the wafer every exposure operation is adopted. Was there. This is because the reticle can be alternately scanned in the opposite direction during the exposure operation for one shot area, and reticle idle return (non-exposure scanning) can be eliminated. At this time, in the shot area at the peripheral portion of the wafer, if the wafer scanning direction is from the outer side to the inner side of the wafer, the wafer surface cannot be detected by the focus and leveling detection system at the run-up start position. The focus position and tilt angle cannot be detected. For this reason, conventionally, when the scanning direction goes from the outer side to the inner side at the peripheral edge of the wafer, the focus position is not detected, and the height of the wafer surface in the shot area that can detect the focus position in the vicinity is used as a guide. The adjustment mechanism is controlled to perform exposure, or the scanning direction is changed to scan the wafer from the outside to the inside.

However, for example, in the former method of adjusting the focus position based on the position of the wafer surface in the area where the focus position can be detected, the focus area with the near shot area may be adjusted depending on the unevenness of the wafer surface. There is an inconvenience that the position difference may remain and precise focusing may not be possible. In the latter method of changing the scanning direction, it is not possible to scan and expose the wafer continuously in the same direction without performing the reticle idle return because of the limitation of the stage mechanism. However, there is a problem in that the reticle of FIG.

In view of the above problems, an object of the present invention is to provide an exposure method capable of exposing a reticle pattern onto a shot area at the peripheral edge of a wafer while accurately performing focusing with almost no reduction in throughput. .

[0008]

An exposure method according to the present invention scans a photosensitive substrate (W) in synchronism with alternately scanning a mask (R) on which a transfer pattern is formed in the opposite direction. By doing so, in the exposure method of sequentially exposing the plurality of shot areas (S _{1,1 to} S _6,4 ) on the substrate (W) with the image of the transfer pattern, all the shot areas at the peripheral edge of the substrate So that the scanning at the time of exposure of the substrate (W) is performed from the inside to the outside of the substrate (W) based on the distance that the substrate (W) can move within the reversal time of the mask (R). The exposure order of S _{1,1 to} S _6,4 ) is set.

According to such an exposure method of the present invention, for the shot area at the peripheral edge of the substrate (W), the exposure area on the slit is moved from the inside of the substrate (W) to the outside on the coordinate system in which the substrate is fixed. Since the exposure is performed by scanning toward, the heights of those peripheral portions can be detected with high accuracy. Therefore, the pattern of the mask (R) is transferred to the shot area in the peripheral portion with high accuracy while performing the focusing accurately. In this case, an area that can be moved within the time when the mask (R) is reversed is selected as the shot area to be exposed next. Generally, the time required for reversing the scanning direction of the mask (R) is longer than the stepping time of the stage on the substrate side, and in the present invention, there is no change in the exposure time due to the change in the exposure sequence, and the throughput decreases. There is no such thing.

In this case, the exposure order is set so that the amount of movement of the substrate (W) in the non-scanning direction (X direction) when sequentially exposing all shot areas on the substrate (W) is minimized. Preferably. As a result, the time for moving the substrate in the non-scanning direction is shortened, and the overall exposure time is shortened. The exposure order is preferably set by selecting the next shot area from the eight shot areas adjacent to the shot area.
Thereby, the exposure order is easily set.

Further, the exposure order is the mask (R).
It is preferable to set without the non-exposure scanning (scanning of the sky without exposure). This eliminates unnecessary movement of the mask (R) and further shortens the entire exposure time.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In this example, the pattern on the reticle is sequentially exposed to each shot area on the wafer by scanning the reticle and the wafer in synchronization, and the exposure is performed by a step-and-scan projection exposure apparatus. Is applied.

FIG. 1 shows a schematic configuration of the projection exposure apparatus of this example. In FIG. 1, the exposure illumination light IL from the exposure illumination system LE at the time of exposure covers the illumination area 1 on the slit on the reticle R. Illuminates with a uniform illuminance distribution and its illumination light IL
The pattern in the illumination area 1 under the projection optical system PL
Via the projection magnification β (β is, for example, ¼), and transferred onto the illumination field 6 on the wafer W coated with the photoresist. In the following description, the Z axis is taken parallel to the optical axis AX of the projection optical system PL, the X axis is taken perpendicular to the plane of FIG. 1 and the Y axis is taken parallel to the plane of FIG. .

The reticle R is placed on the reticle stage 3 via the reticle holder 2. The reticle stage 3 finely moves two-dimensionally in a plane (XY plane) perpendicular to the optical axis AX to position the reticle R. Further, the reticle stage 3 is movable along the guide surface of the reticle stage guide 4 in the scanning direction (Y direction) at a predetermined scanning speed. The reticle stage 3 has a stroke in the Y direction that allows the entire surface of the reticle R to cross at least the optical axis AX. At the end of the -Y direction of the reticle stage 3, the laser beam moving mirror 5 for reflecting the LB _R is fixed, the position of the reticle stage 3 from an external reticle interferometer 13, the movable mirror 5 and reticle interferometer It is constantly monitored by a total of 13. The position information of the reticle stage 3 from the reticle interferometer 13 is sent to the main control system 20, and the main control system 20 controls the position and speed of the reticle stage 3 via the reticle stage drive unit 14 based on the information. There is.

On the other hand, the wafer W is vacuum-sucked on the wafer holder 8, and the wafer holder 8 is placed on the Z tilt stage 10. The Z tilt stage 10 is configured to be movable in a direction parallel to the optical axis AX and tiltable with respect to the XY plane by an internal drive system, and the wafer holder 8 is also configured to be rotatable around the optical axis AX. ing.
The Z tilt stage 10 is mounted on the X stage 11X which is driven in the X direction by the wafer stage drive unit 16,
The X stage 11X is mounted on the Y stage 11Y driven in the scanning direction (Y direction) by the wafer stage driving unit 16. X stage 11X and Y stage 11
A step-and-scan operation is performed in which the operation of scanning and exposing each shot area on the wafer W with Y and the operation of stepping to the next exposure start position are repeated. A movable mirror 12 that reflects a laser beam LB _W from an external wafer interferometer 15 is fixed to an end portion of the Z tilt stage 10, and the position of the Z tilt stage 10 (wafer W) is moved relative to the wafer interferometer 15 and the movement. With the mirror 12,
It is constantly monitored with a resolution of 0.01 μm, for example.
The position information of the Z tilt stage 10 from the wafer interferometer 15 is sent to the main control system 20, and the main control system 20 controls the position and speed of the wafer W via the wafer stage drive unit 16 based on the position information. ing. In addition, the main control system 20
Is provided with an input / output device 18, and various information is input and output via the input / output device 18.

[0016] Incidentally, the speed on the reticle R in the scanning exposure in the present example is the + Y direction (or the -Y direction) to the example in synchronism with the scanning at a velocity V _R, the wafer W is -Y direction (or the + Y direction) Scan at V _W. The ratio (V _W / V _R ) between the scanning speed V _R and the scanning speed V _W exactly matches the projection magnification β of the projection optical system PL, so that the pattern on the reticle R becomes the wafer W. It is accurately transferred to each shot area.

Further, the apparatus of FIG. 1 is provided with an oblique incidence type multi-point focus position detection system for detecting the focus position and tilt angle of the wafer W. The oblique incidence type multi-point focus position detection system includes an irradiation optical system 7a that supplies detection light AL for forming a plurality of slit images toward the surface of the wafer in an oblique direction with respect to the optical axis AX. The detection light A
It is composed of a light receiving optical system 7b which re-images a slit image corresponding to a plurality of oscillating slits from the light beam reflected by the surface of the wafer W of L and receives the light beam passing through the oscillating slits. A plurality of focus signals obtained by synchronously rectifying the photoelectric conversion signal of the light flux received through the vibrating slits with the drive signal of the corresponding vibrating slits are output. The multi-point focus position detection system is hereinafter referred to as "focus position detection system 7a, 7b".

The focus position detection systems 7a and 7b detect the deviation of the position (focus position) in the Z direction and the deviation of the tilt angle with respect to the image plane of the projection optical system PL on the surface of the wafer W,
It is used to drive the Z tilt stage 10 so that the surface of the wafer W and the image plane of the projection optical system PL are kept in a matched state. The wafer position information from the focus position detection systems 7a and 7b is sent to the main control system 20, and the main control system 20 sets the focus position and tilt angle of the Z tilt stage 10 based on this wafer position information. In this example, each focus signal is calibrated so that the image plane becomes the zero-point reference, and the autofocus and autoleveling operations are performed so that the plurality of focus signals from the light receiving optical system 7b become zero. Done.

Here, the structure and operation of the multi-point focus position detection system will be briefly described. FIG. 5A is a schematic diagram for explaining the operation at one measurement point of the focus position detection system. In FIG. 5A, the state in which the surface of the wafer W matches the image plane Then, a slit image is projected from the irradiation optical system 7a to a position P ₁ on the wafer W, and the position P ₁
The reflected light from _{1 is transferred} to the objective lens 24 in the light receiving optical system 7b.
It is assumed that the slit image is re-formed on the vibration center Q ₁ of the vibration slit 24b by a. When the surface of the wafer W is displaced downward by ΔZ from that state, the position of the slit image re-formed in the light receiving optical system 7b is shifted by ΔF. The displacement amount ΔZ of the wafer W in the Z direction is proportional to the shift amount ΔF of the re-imaging position on the diaphragm slit 24b, and the displacement amount ΔZ of the wafer W in the Z direction is measured by measuring the shift amount ΔF. To be detected.

FIG. 5B shows the relationship between the focus signal I from the light receiving optical system 7b and the change amount ΔZ of the position of the wafer W in the Z direction, and the horizontal axis represents the change amount of the position of the wafer W in the Z direction. ΔZ, the vertical axis represents the focus signal I from the light receiving optical system 7b. As shown in FIG. 5B, the focus signal I
Changes substantially linearly with the change amount ΔZ within a predetermined range, so that the change amount ΔZ, that is, the shift amount of the focus position with respect to the image plane can be detected from the focus signal I.

FIG. 6A shows the arrangement of multiple measurement points of the focus position detection systems 7a and 7b in this example.
As shown in (a), a slit image is projected on each of _nine measurement points f _{1 to} f ₉ in 3 rows × 3 columns on the slit-shaped illumination field 6 on the wafer W. Measurement points f _{1 to} f
₉ are arranged at equal intervals in triplicate respectively parallel to the X-axis and Y-axis around the optical axis AX of the projection optical system PL. In the present example, thus the focus position detection system 7a, place the measuring point f ₁ ~f ₉ two-dimensionally by 7b, the measurement points f ₁ ~
By approximating the shift amount of each focus position detected at f ₉ using the least square method in a plane approximation, the shift amount of the focus position of the average surface of the illumination field 6 and the tilt angle around the X-axis , And the tilt angle around the Y axis is detected. That is, the illumination field 6 is a focus position detection area. However, the illumination light for exposure is applied to the illumination field 6 only during the period in which the illumination field 6 covers the shot area to be exposed. The main control system 20 controls the Z tilt stage 10 using the measurement values of the focus position detection systems 7a and 7b so that the surface of the wafer W coincides with the image plane of the projection optical system.

Next, a method of determining the exposure order of each shot area in the exposure method of this example will be described. In this example, generally, the driving characteristics of the stages of the exposure apparatus, that is, the reticle stage 3, the X stage 11X on the wafer side, and the Y stage 11Y are utilized to reduce the throughput and reduce the peripheral portion of the wafer W. The exposure is performed by accurately focusing the shot area. In this case, the main control system 20 determines the exposure order of each shot area before exposing the wafer W. In determining the exposure order, first, the exposure order with the shortest movement path is obtained.
Next, based on this exposure order, the exposure order is obtained under the condition that the processing time required for exposing all the shot areas does not increase. However, when the solution cannot be obtained under the condition that the processing time does not increase, the exposure order is changed under the limitation that the increase in the processing time is minimized.

Here, in this example, a basic concept for determining the exposure order of the shot areas will be described. 2A to 2C show the relationship between the speed and time of the reticle stage 3, the Y stage 11Y, and the X stage 11X, respectively, and in each of these figures, the horizontal axis represents time t and the vertical axis represents. The speed V is shown. 2 (a) to 2 (c), the acceleration at the time of acceleration / deceleration of each stage is set to be constant at a time t with reference to the time T _{iE at} which exposure of a certain shot area is completed. On the other hand, it is set to change into a trapezoid. In this case, the reticle stage 3 is mechanically required to repeat the reversal of the scanning direction every exposure of one shot area.
The Y stage 11Y, which is the scanning stage on the wafer side, is also 1
The scanning direction is reversed each time the shot area is exposed. This figure 2
(A), the reticle stage 3 is controlled at a constant speed V _R in the exposure (or -V _R). As shown by the polygonal line 21, when the exposure of a certain shot area ends at the time point T _iE , the vehicle runs for the settling time t _d at the same speed V _R , then starts deceleration from the time point T _R1, and after the time t _a1 . acceleration starts in the reverse direction when the speed becomes zero at time T _R2, speed -V _R
Accelerate until. When time t _a1 has further elapsed T _R3
When the acceleration is completed at, Y during the settling time t _d1 (≈t _d ).
After the synchronization with the stage 11Y is realized, the exposure of the next shot area _starts from time T _jS . In this case, the driving time T ₁ of the reticle stage 3 from the time T _iE at which a certain exposure ends to the settling start time T _R3 for the exposure of the next shot area is calculated by the following equation.

T ₁ = t _d + 2 · t _a1 (1) On the other hand, as shown by the broken line 23 in FIG. 2C, the X stage 11X immediately _moves from the exposure end time T _iE of a shot area to the next shot area. Start moving. During the time t _a2 from time T _iE to time T _X1, after reaching the maximum speed V _m2 accelerating from zero velocity, the constant maximum speed V _m2 for a time t _b2 from time T _X1 to time T _X2 It is driven at high speed, decelerates from the time point T _X2 , and reaches the approach start position of the next shot area at the time point T _X3 after the time t _a2 . Then, the speed of the X stage 11X becomes almost 0, and the X stage 11X completely stops while repeating fine movement during the settling time t _d2 from the time T _X3 when the alignment is started to the time T _jS when the scanning is started. In this case, the X stage 11X from a time T _iE at which a certain exposure is finished to a time T _X3 at which the approaching position for exposure of the next shot area is reached.
The driving time T _{2 of} is given by the following equation.

T ₂ = 2 · t _a2 + t _b2 (2) On the other hand, the Y stage 11Y is scanned at a constant speed V _W (or −V _W ) during exposure. As mentioned above, the Y stage 1
The relationship of V _W = βV _R is established between the scanning speed V _{W of} 1 × and the scanning speed V _R of the reticle stage 3.
However, β is the projection magnification of the projection optical system PL. FIG.
As shown by the polygonal line 22 in (b), the Y stage 11Y
Is scanned at a scanning speed of −V _{W in} the exposure of a certain shot area and immediately starts moving to the next shot area after the exposure end time T _iE. However, unlike the X stage 11X, is moved to the next shot area. Immediately after the movement is completed, preparation for synchronization with the reticle stage 3 must be started. Therefore, it is necessary to be driven at a constant speed at the scanning speed V _W by the exposure start time T _jS of the next shot area. Therefore, the Y stage 11Y reverses the direction and accelerates after decelerating from the velocity -V _W to 0 during the time t _a3 from the exposure end time T _iE of a certain shot area to the time T _Y1. And the maximum speed V
reach _m3 Then, during the time t _b3 from the time T _Y1 to the time T _Y2 , after being driven at a constant speed at the maximum speed V _m3 , the time T _Y2.
The deceleration is started from, and the scanning speed V _W is reached at the time T _Y3 when the time t _{c3 has} elapsed. Then, the next exposure is performed from the time point T _jS after being settled at the scanning speed V _W for a certain settling time t _d3 . Therefore, the driving time T ₃ of the Y stage 11Y from the time T _iE at which the exposure of a certain area ends to the time T _Y3 at which the settling for the exposure of the next area starts is expressed by the following equation.

T ₃ = t _a3 + t _b3 + t _c3 (3) Usually, the projection magnification β of the projection optical system PL is a reduction magnification (for example, 1/4), and the scanning speed of the reticle stage 3 is Y.
Since the scanning speed of the stage 11Y is considerably higher than that of the stage 11Y, the driving time T ₁ required for reversing the reticle stage 3 determines the processing time of the exposure apparatus. Therefore, assuming that the reticle stage 3, the X stage 11X, and the Y stage 11Y have equivalent driving capabilities, the reticle stage 3,
If the next shot area is selected within the range where the following conditions are satisfied during the driving times T ₁ , T ₂ , and T ₃ of the X stage 11X and the Y stage 11Y, exposure of one wafer is required. It does not affect the processing time.

T ₁ ≧ T ₂ (4a) T ₁ ≧ T ₃ (4b) The above is the basic idea when determining the exposure order of each shot area in this example. This is because the operating time of the X stage 11X and the Y stage 11Y on the wafer W side has a sufficient margin with respect to the operating time of the reticle stage 3 which determines the exposure time in the scanning projection exposure apparatus in this case, that is, This makes good use of the redundancy in the exposure apparatus. As a result, in this example, the exposure order and the scanning direction of each shot area are determined without reducing the throughput, each shot area on the peripheral portion of the wafer W is accurately focused, and the pattern of the reticle R is formed on the peripheral portion. Can be transferred to each shot area with high precision. Hereinafter, a specific example of numerical values will be described.

In this case, the following specifications are assumed as the driving capability of the reticle stage 3, the X stage 11X, and the Y stage 11Y. (A) The maximum velocity and the average acceleration of the reticle stage 3 are 0.32 m / sec and 3 m / sec ² , respectively. (B) The maximum velocity and average acceleration of the X stage 11X are set to 0.25 m / sec and 3 m / sec ² , respectively.

(C) The maximum velocity and average acceleration of the Y stage 11Y are 0.25 m / sec and 3 m / sec, respectively.
Set to sec ² . (D) The synchronous settling time is 0.1 sec. (E) The projection magnification β is set to 1/4, and the scanning speeds of the Y stage 11Y and the reticle stage 3 are each 0.08 m.
/ Sec and 0.32 m / sec.

(F) Each shot area is a rectangular area having a size of 27 mm in the X direction and 35 mm in the Y direction including the scribe line area. In the case of the above numerical example, the driving time T ₁ required for folding (reversing) of the reticle stage 3 calculated from the equation (1) is 0.314 sec. Also, the X stage 11X, Y
The driving times T ₂ and T ₃ required for the stage 11Y to move for exposure of the next shot area are as follows from the expressions (2) and (3).

First, the adjacent shot area (X stage 1
In the case of 1X, the movement time to the shot area adjacent to the X direction and to the shot area adjacent to the Y direction in the case of Y stage 11Y) is 0.191 sec in the case of X stage 11X.
In the case of c and Y stage 11Y, it is 0.246 sec. In the case of the X stage 11X, the movement time to the next shot area that has jumped over the adjacent shot area is 0.
299sec, 0.386s for Y stage 11Y
ec.

As can be seen from the above calculated values, after the reticle stage 3 has finished the exposure of a certain shot area, the reticle stage 3 turns back and reaches the run-up start position for the exposure of the next shot area. It is possible to move to the next shot area that jumps over the shot area.
Further, the Y stage 11Y can complete the movement to the adjacent shot area. Therefore, in this example, in the X direction, the exposure order is within a range up to the second shot area with respect to the shot area exposed immediately before, and up to the shot area adjacent to the shot area exposed immediately before in the Y direction. It can be changed.

Next, a method of determining the exposure order of each shot area in this example will be described. In this case, the conditions such as the speed and acceleration of each stage and the size of each shot area of the wafer W are based on the above numerical examples. As described above, first, the order in which the movement path of the wafer W is the shortest is obtained. FIG.
Shows an example of an exposure order that is determined so that the movement path of the wafer W is the shortest. In FIG. 3, solid arrows A1 to A32 indicate the scanning paths of the wafer W, and the starting point of the arrow is the arrow. As indicated by the starting point E1 of A1, the starting point of the run-up of the scanning exposure of the wafer W with respect to the slit-shaped illumination field 6 is shown. Also, the dotted curve is as shown by the curve PA, as shown in the X stage 11X and the Y stage 1.
The movement path of the wafer W by the stepping drive of 1Y is shown.

Although the wafer W actually moves with respect to the fixed slit-shaped illumination field 6 as shown in FIG.
Further, in FIG. 4, the wafer W is stationary, and the scanning field and the moving path are shown as the illumination field 6 relatively moving on the wafer W. Further, due to the action of the movable shutter in the exposure illumination system LE, the illumination field 6 is irradiated with the illumination light only while the illumination field 6 scans the shot area. The exposure starts from the shot region S _{1,1 in} the first row at the end of the wafer W in the −X direction and the Y direction. In this case, the state in which the illumination field 6 is located at the end of the shot area S _2,2 below the shot area S _1,1 in the Y direction is used as the approach start point of the wafer W and along the scanning path indicated by the arrow A1. Scanning exposure is performed. After the scanning of the shot area S _1,1 is completed, the wafer W moves to the next approach start point along the movement path indicated by the dotted line PA. In this case, the next run-up start point is Y of the shot area S _1,2 to be exposed next.
Teruno field 6 is located outside the direction,
Teruno field 6 from the outside to the inside of the shot area
Is performed. However, in reality, the wafer W is scanned from the inside to the outside. After exposure is performed in the same operation until the shot area S _{l, 4} at the right end of the first column, the second column of the shot area right below the shot area S _{l, 4} from the shot area S _{l, 4} S _{2 , 6} and the exposure is performed by the same operation from the shot area S _2,6 toward the shot area S _2,1 at the end portion in the −X direction. Similarly, the exposure is performed by the same operation for the shot areas in the 3rd to 6th rows arranged in the X direction.
Arrow A for 32 shot areas S _{1,1 to} S _6,4
Exposure is performed in the order and the scanning direction indicated by 1, A2, A3, ..., A31, A32.

However, in this case, the shot areas S _1,2 , S _1,4 , S _2,1 , S _5,1 , S _6,2 , located at the peripheral portion of the wafer W in the scanning direction (Y direction), In _{S6 and S4,} there is an approach start point outside the shot area, and for these shot areas, the focus position cannot be accurately detected especially in the beginning period of the scanning exposure. That is, as shown in FIG. 6B, in the shot area located on the peripheral portion of the wafer W in the scanning direction and scanned in the outer peripheral direction with respect to the illumination field 6, the illumination field (focus position detection area) is detected. ) 6
The value of the focus position detected in step abruptly changes stepwise. Therefore, the correction operation of the focus position of the wafer W by the stage cannot be completely followed, and the error amount of the focus position remains.

Therefore, based on the above-described exposure sequence in which the movement path of the wafer W is the shortest, the focus position of each shot area is accurately detected even in the shot area at the peripheral portion of the wafer W in the scanning direction. Change the exposure order.
In this case, as described above, the X stage 11X, which moves in the non-scanning direction before the reticle stage 3 moves to the approach start position of the next shot area, has the next shot area that jumps over the adjacent shot area. It is premised that the Y stage 11Y that can move to the adjacent shot area can move to the adjacent shot area. Therefore, the degree of freedom for changing the exposure order is given up to two adjacent shot areas in the X direction and up to one adjacent shot area in the Y direction. The exposure order is reconfigured by giving the degree of freedom to change the exposure order up to the region. For example, from the shot area S _5,4 near the center of the lower part of the wafer W, the eight shot areas S _{4,3 to} S _4,5 , S around the next exposure shot area are provided.
_5,3, S _5,5, it is possible to select an optimum shot area from the S _6,2 ~S _{6, 4.}

FIG. 4 shows the exposure sequence of each reconstructed shot area. In FIG. 4, solid line arrows B1 to B32 show the scanning path of the wafer W, and the starting point of the arrow, as in FIG. Indicates the starting point of the run-up of the scanning exposure of the wafer W with respect to the slit-shaped illumination field 6 as indicated by the starting point F1 of the arrow B1. In addition, the dotted curve is the X stage 11X and the Y stage 1 as shown by the curve PB.
The movement path of the wafer W accompanying the stepping drive of 1Y is shown. In FIG. 4 as well, although the illumination field 6 is shown moving on the stationary wafer W, the wafer W actually moves with respect to the illumination field 6. Exposure is
Similar to the case of FIG. 3, the shot area S _{1,1 on} the first row of the wafer W is started. In this case, the shot area S _1,1
Scan exposure is performed along the scanning path indicated by arrow B1 with the state where the illumination field 6 is located at the end of the lower shot area S _{2,2 in} the Y direction as the starting point for the wafer W. During scanning exposure, the focus position detection systems 7a and 7b shown in FIG.
By driving the Z tilt stage 10 based on the detection result of, the auto focus and the auto leveling are performed. After the scanning of the shot area S _1,1 is completed, the wafer W moves to the approach start point of the next shot area along the movement path indicated by the dotted line PB.

In this case, the next shot area is the case of FIG.
Unlike shot area S_1,1In the second row underneath
Area S_2,2The order is changed to. That is, the shot area
S_{1, 1}After the exposure of the
Shot area S_1,1Shot area with the lower end of the
Area S_2,2Is exposed by scanning. Next, reverse the Y stage 11Y.
Rotate the X stage 11X at the same time
And move the wafer W along the movement path indicated by the dotted line PC.
The shot area S in the second row_2,2Right next to the shot area
Area S_2,3The scanning start point is the upper end of the
Area S_1,1Right next to shot area S_1,2Expose
You. Shot area S at the right end of the first row_1,4Up to similar movements
After the exposure is performed, the shot area S_1,4From
Area S_1,4Shot area S in the second column directly below_2,5Dew
Glow. Next, the shot area S at the right end of the third row_3,6of
Shot at the right end of the second row with the upper end as the starting point
Area S _2,6To expose. Similarly, shot area in the 3rd to 6th rows
Similar scanning is performed on the area, and 32 shot areas
Area S_1,1~ S_6,4Against arrows B1, B2, B3, ...
Exposure is performed in the order and scanning direction shown in B31 and B32.
You.

By selecting the exposure order and scanning direction, the shot area S in which the illumination field 6 is relatively scanned from the outer peripheral portion of the wafer W toward the inner side in FIG.
_With respect to _1,2 , S _1,4 , S _2,1 , S _5,1 , S _6,2 and S _6,4 , the scanning direction is changed from the inner side of the wafer W toward the outer peripheral portion, Since the illumination field 6 is relatively scanned and exposed from the inner side of the wafer W toward the outer peripheral portion in all the shot areas in the peripheral portion, the shot areas in those peripheral portions are also equivalent to the shot areas other than the peripheral portion. Exposure is performed in a focused state based on a precise focus position. In addition, exposure of all shot areas is completed within the same processing time as when processing is performed in the order of exposure by the shortest path in FIG.

If the exposure order that does not increase the processing time cannot be determined, for example, in the above numerical example, if the Y stage 11Y is given a degree of freedom to move to the next two shot areas, the processing time will be increased. There are also cases where the desired exposure sequence is obtained with minimal suppression. In this way, when the solution cannot be obtained under the first condition, the search is similarly performed while loosening the condition.

As described above, the present invention is not limited to the above-mentioned embodiments, and various configurations can be adopted without departing from the gist of the present invention.

[0042]

According to the exposure method of the present invention, since it is possible to perform the exposure while accurately focusing even in the shot area at the peripheral portion of the substrate, the pattern on the mask covers the entire shot area on the substrate. The yield of devices transferred with high precision and cut out from the substrate is improved. In this case, it is possible to expose the entire substrate in almost the same processing time as when exposing all shot areas on the substrate in the exposure order of the shortest path. There is an advantage in that the throughput (productivity) is hardly reduced even when compared to.

When the exposure order is set so that the amount of movement of the substrate in the non-scanning direction when sequentially exposing all shot areas on the substrate is set, the substrate is moved in the non-scanning direction. There is an advantage that the time is shortened and the total exposure time is shortened. Further, when the exposure order is set by selecting the shot area to be exposed next from the eight shot areas adjacent to the shot area, the selection of the exposure order is easy and the exposure time is almost the same. There are no advantages.

Further, when the exposure order is set without the non-exposure scanning of the mask, there is an advantage that the whole exposure time is shortened and the throughput is improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an entire projection exposure apparatus used in an example of an embodiment of the present invention.

2A is a diagram showing a velocity change of a reticle stage, FIG. 2B is a diagram showing a velocity change of a Y stage on a wafer side, and FIG. 2C is a diagram showing a velocity change of an X stage on a wafer side. .

FIG. 3 is a plan view showing an example of the exposure order of each shot area determined under the condition of simply scanning the wafer along the shortest path.

FIG. 4 is a plan view showing an exposure order of each shot area finally obtained in the example of the embodiment of the present invention.

5 is a diagram for explaining the operation of a focus position detection system used in the projection exposure apparatus of FIG.

6A is a diagram showing an arrangement on a wafer of measurement points of a focus position detection system used in the projection exposure apparatus of FIG.
(B) is a conceptual diagram showing a case where the wafer is scanned from the inner side toward the outer peripheral portion.

[Explanation of symbols]

 R reticle W Wafer PL Projection optical system 3 Reticle stage 5 Moving mirror (for reticle) 6 Illumination field on wafer 7a Light transmitting optical system (focus position detection system) 7b Light receiving optical system (focus position detection system) 10 Z tilt stage 11X X stage 11Y Y stage 12 Moving mirror (for wafer stage) 13 Reticle interferometer 15 Wafer interferometer 20 Main control system

Claims (4)

[Claims] 1. A photosensitive substrate is scanned in synchronism with alternating scanning of a mask on which a transfer pattern is formed in the opposite direction, so that a plurality of shot areas on the substrate are transferred to the transfer pattern. In the exposure method of sequentially exposing with an image, the substrate can be moved within the reversal time of the mask so that the scanning at the time of exposure of all shot areas of the peripheral portion of the substrate is performed from the inside of the substrate to the outside. An exposure method, wherein an exposure order of the plurality of shot areas is set based on a distance. 2. The exposure method according to claim 1, wherein the exposure order is set so that a movement amount of the substrate in the non-scanning direction is minimized when sequentially exposing all shot areas on the substrate. An exposure method characterized by being set. 3. The exposure method according to claim 1 or 2, wherein the exposure order is set by selecting a shot area to be exposed next from eight shot areas adjacent to the shot area. An exposure method comprising: 4. The exposure method according to claim 1, 2, or 3, wherein the exposure order is set without non-exposure scanning of the mask.