JPH0954443A - Exposure method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the degradation in throughput even if the frequencies of exchanging reticles are high. SOLUTION: Reticle alignment microscopes AS1A, AS1B are internally provided with index marks 28A, 28b and the lower part of the reticle 5 is provided with shutters 10A, 10B for shielding the illumination light for alignment. The mispositioning quantity of the first sheet of the reticle 5 with respect to a reference mark member 6 is determined by the reticle alignment microscopes AS1A, AS1B and the base line quantity of an alignment sensor AS2 is determined. The differences between the positions at the pattern centers of the reticle 5 and the central positions of the index marks 28A, 28B are then stored. For the second and subsequent reticles, the operation on the reticle side and the operation on the wafer side are executed in parallel in the state of closing the shutters 10A, 10B. In such a case, the differences between the position of the pattern centers of the reticles and the central positions of the index marks are determined by the reticle alignment microscopes AS1A, AS1B and the already determined base line quantity is corrected by these differences.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image of a pattern such as a mask (reticle) in a lithography process for manufacturing a semiconductor device, a liquid crystal display device, an image pickup device (CCD, etc.), a thin film magnetic head, etc. The present invention relates to an exposure method for exposing a photosensitive substrate (wafer or the like) and an exposure apparatus using this exposure method, and is suitable for application particularly when the frequency of mask replacement is high.

[0002]

2. Description of the Related Art In a projection exposure apparatus such as a stepper used for manufacturing a semiconductor element or the like, a reticle as a mask and a wafer (or a glass plate or the like) as a photosensitive substrate are accurately aligned (aligned). )do it,
It is required to expose the circuit pattern formed on the reticle onto the photoresist layer on the wafer. Therefore, various alignment sensors are used.

For example, an LSA (Laser Step Alignment) method, in which a laser beam is applied to an alignment mark in the form of a dot row on a wafer, and the position of the mark is detected using light diffracted or scattered by the mark, a halogen lamp FIA (Field Image Alignment) method that performs image processing to measure the image data of the alignment mark imaged by illuminating with light having a wide wavelength band with the light source as the light source, or the same frequency for the diffraction grating alignment mark on the wafer. Or, irradiate laser light with slightly changed frequency from two directions,
LIA (Laser Interferer), which measures the position of the alignment mark from the phase of two generated diffracted lights that interfere with each other.
There is an alignment sensor such as the ometric alignment method.

Further, as a conventional alignment method,
TTL (through-the-lens) method that measures the position of the alignment mark (wafer mark) on the wafer through the projection optical system, and OFF that directly measures the position of the wafer mark on the wafer without going through the projection optical system・ The Axis method was the mainstream. Recently, a TTR for detecting a positional deviation amount between an alignment mark (reticle mark) on a reticle and a wafer mark via a projection optical system and a reticle.
(Through the reticle) method is also used.

Precise alignment is performed by optimally combining the above alignment sensor and alignment method. At the same time, there has been a demand for further improvement in productivity from the past, and a measure for maintaining alignment accuracy and shortening alignment time is always required. FIG. 4 is a flow chart for explaining an example of a conventional exposure method. In this case, a reticle alignment microscope is used as a sensor for measuring the center of a reticle pattern, and finally wafer alignment (fine alignment) is performed. ) An alignment sensor of LSA type and TTL type is used as an alignment sensor for performing the above. As shown in FIG. 4, first, in step 201, the reticle is loaded on the reticle stage, and in the next step 202, using the reticle stage and reticle alignment microscope,
A reticle search is performed to detect the alignment mark on the reticle. Then, in the next step 203, the distance between the center of the two reference marks on the reference mark member on the wafer stage and the projected image of the center of the two alignment marks on the reticle (hereinafter referred to as the “pattern center”) is determined. To be measured. This is reticle alignment. In the next step 204, measurement for detecting a baseline amount, which is a relative distance between the detection center of the LSA alignment sensor and the pattern center of the reticle, is performed. In this case, the position where the amount of light received by the photoelectric sensor in the alignment sensor is maximized is detected while moving the wafer stage.

With the above steps, a series of preparation steps such as reticle alignment and baseline measurement (hereinafter referred to as "reticle preparation step") are completed, and then a series of preparation steps such as pre-alignment related to wafer (hereinafter referred to as "preparation step"). Wafer preparation step ”) is performed. First, step 2
At 05, the wafer is loaded on the wafer stage. next,
In step 206, search alignment is performed to detect the rough position of the wafer, and the search alignment mark on the wafer is detected by the LSA type alignment sensor. By calculating the detection result, the rough position of the wafer mark detected in the next fine alignment is detected. That is, in step 207, the position of the wafer mark attached to a predetermined number of shot areas (sample shots) selected from all the shot areas on the wafer is detected by using the LSA type alignment sensor, and the detection result is obtained. By performing statistical processing, array coordinates of all shot areas are calculated. This is an enhanced global alignment (hereinafter referred to as “EGA”) alignment method. Then, in step 208, each shot area on the wafer is sequentially positioned at the exposure position based on the baseline amount obtained in step 204 and the array coordinates calculated in step 207, and the pattern image of the reticle is exposed. .

Next, in step 209, it is confirmed whether or not the process for one lot of wafers is completed. If completed, the wafer and reticle are unloaded in steps 212 and 213, respectively, and the exposure process is completed. Step 209
If there is an unexposed wafer in step 210, it is checked in step 210 whether the reticle needs to be replaced. If not, the wafer is replaced in step 205B, and step 206 is performed until the predetermined number of wafers are completed. ~ 208
Is repeated. When the reticle is exchanged in step 210, the reticle is exchanged in step 201A, and step 20 is performed in the same manner as in steps 202 to 204 above.
In each of 2A to 204A, after reticle search, reticle alignment, and baseline measurement are performed, the wafer is exchanged in step 205A, and exposure is performed in a sequence returning to step 206 again.

[0008]

According to the above-mentioned prior art, the reticle preparation process including the baseline measurement of the alignment sensor for performing the final alignment every time the reticle is exchanged and the wafer preparation process are connected in series. Is processed. Therefore, when the number of wafers processed by one reticle is small and the reticle is frequently replaced, as in the case of ASIC (application-specific IC) production, one reticle is used as in DRAM production. Compared to the case where a large number of wafers are processed, the ratio of the time required for the reticle preparation process and the wafer preparation process is increased, and the throughput of the exposure process for a predetermined number of wafers (the number of wafers processed per unit time) is reduced. There is an inconvenience.

In view of the above-mentioned problems, it is an object of the present invention to provide an exposure method having a high throughput of the exposure process even in the production of a product type in which reticles are frequently exchanged. Another object of the present invention is to provide an exposure apparatus that can carry out such an exposure method.

[0010]

An exposure method according to the present invention positions a mask stage (9) for positioning a mask (5) and a substrate (13) to which the pattern of the mask (5) is transferred. And a reference mark member (6) on which predetermined reference marks (16B, 16A) are formed
And a substrate stage (15) provided with a mask (5) on which a plurality of transfer patterns and alignment marks (8A, 8B) are formed.
In the exposure method for transferring the pattern of 1) onto a plurality of substrates, when the pattern of the first mask of the plurality of masks is sequentially transferred onto the first substrate to be exposed, Is placed on the mask stage (15), and the illumination light for measurement (IL1A, IL
1B) to irradiate the mask with the alignment marks (8A, 8B) of the mask and the predetermined reference marks (16B, 16A) on the substrate stage (15) to detect the positional deviation amount (step 103). The mask is aligned with respect to the predetermined reference marks (16B, 16A) based on the detection result, and the patterns of the second and subsequent masks of the plurality of masks are exposed to the second substrate. At the time of transfer onto the upper surface, the measurement illumination light (IL1A, IL1B) is radiated from above the mask to detect the position of the alignment mark of this mask (step 103A).
At the same time, the substrate is aligned (step 107A) with the measurement illumination light (IL1A, IL1B) blocked between the mask and the substrate (step 111).

According to such an exposure method of the present invention, with respect to the second and subsequent masks, the position of the substrate is aligned in parallel with the detection of the position of the alignment mark of the mask. The time required for aligning the mask and the substrate is shortened as compared with the case where the processes are performed in series. That is, conventionally, the operation on the mask side such as detecting the position of the alignment mark of the mask and the operation on the substrate side such as the alignment of the substrate are performed using the same substrate stage (15). Both actions could not be performed in parallel. However, in the present invention, the positions of the alignment marks of the second and subsequent masks are set to the substrate stage (15).
Since the detection is performed without using, it is possible to perform the parallel processing of the operation on the mask side and the operation on the substrate side. When detecting the position of the alignment mark of the mask, the illumination light for measurement (IL1A, IL1B) is not shielded as in the conventional case, the illumination light is irradiated onto the substrate through, for example, the projection optical system. Then, since the substrate is exposed unnecessarily, the mask side operation and the substrate side operation cannot be performed in parallel. However, in the present invention, since the substrate is aligned with the measurement illumination light shielded, the substrate alignment is not affected by the measurement illumination light.

Further, the exposure apparatus according to the present invention positions the mask stage (9) for positioning the mask (5) and the substrate (13) to which the pattern of the mask (5) is transferred, and also performs predetermined positioning. Mark (16B, 16
In an exposure apparatus having a substrate stage (15) having a reference mark member (6) on which A) is formed, an illumination for measurement is applied from above the mask (5) mounted on the mask stage (9). By irradiating light (IL1A, IL1B), the alignment marks (8A, 8B) of this mask and the predetermined reference mark (16) on the substrate stage (15) thereof.
B, 16A) and the alignment sensor (AS1A, AS1B) for detecting the amount of positional deviation with the mask (5) mounted on the mask stage (9) and the substrate stage (15). A shutter member (10A, 10B) which is freely arranged and blocks the measuring illumination light (IL1A, IL1B) when it is arranged between the mask (5) and its substrate stage (15). It is provided.

According to the exposure apparatus of the present invention, since the shutter members (10A, 10B) for blocking the measurement illumination light (IL1A, IL1B) are provided, the measurement illumination light (IL1A, IL1B) is provided. Can be shielded. Therefore, the exposure method of the present invention described above can be implemented. In this case, the alignment sensor (AS1) on the mask (5) mounted on the mask stage (9).
A, AS1B) is preferably provided with index marks (28A, 28B) serving as a reference for positioning the mask.

According to this, the alignment mark (8A, 8B) of the mask (5) with respect to the index mark (28A, 28B) for the first mask, and the predetermined reference mark on the reference mark member (6). (16B, 16A) Relative positional deviation with the alignment sensor (AS1A, AS
1B), for example, if measured with a photoelectric sensor or the like,
For the second and subsequent masks, the alignment sensor (AS1A, AS1B) may measure the relative positional relationship between the alignment mark of the mask and the index mark (28A, 28B) by the photoelectric sensor. That is, the relative positional relationship between the alignment marks of the second and subsequent masks and the predetermined reference marks (16B, 16A) of the reference mark member (6) is the measured value for the first mask previously measured and It is calculated from the measured values for the second and subsequent masks. Therefore, for the second and subsequent masks, the alignment illumination light (IL1A, IL1B) is applied to the reference mark member.
Since it is not necessary to irradiate, the operation on the mask side and the operation on the substrate side can be performed in parallel.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION An example of an embodiment of an alignment method according to the present invention will be described below with reference to FIGS. In this example, the present invention is applied to a stepper type projection exposure apparatus when exposing one lot of wafers while sequentially changing the reticle. FIG. 2 shows an overall schematic configuration of the projection exposure apparatus of this example. In FIG.
At the time of exposure, the reticle 5 is irradiated with the exposure illumination light from the exposure illumination system AL, and the pattern of the reticle 5 is reduced to, for example, 1/5 through the projection optical system 18 under the illumination light, and the photoresist is applied. Is projected onto each shot area on the wafer 13 coated with. As the illumination light for exposure, not only the i-line of a mercury lamp (wavelength: 365 nm) but also excimer laser light (wavelength: 248 nm, 193 nm, etc.) can be used. Here, the Z axis is taken parallel to the optical axis AX of the projection optical system 18, the X axis is taken parallel to the plane of FIG. 2 on the plane perpendicular to the Z axis, and the Y axis is taken perpendicular to the plane of FIG.

In this case, the reticle 5 is held on the reticle stage 9, and the reticle stage 9 holds the projection optical system 1.
The reticle 5 is positioned in the X direction, the Y direction, and the rotation direction (θ direction) within a plane perpendicular to the optical axis AX of 8. The X-coordinate, Y-coordinate, and rotation angle of the reticle stage 9 are constantly measured by a movable mirror (not shown) fixed on the reticle stage 9 and a laser interferometer installed outside, and the measured values govern the operation of the entire apparatus. It is supplied to a central control system (not shown) for controlling. Predetermined reticle marks (not shown) are formed in the vicinity of the pattern area of the reticle 5, and a pair of alignment marks 8A and 8B for reticle alignment are also formed outside them. Further, an exchange arm 3 for exchanging the reticle is installed near the reticle stage 9. When the reticle is exchanged, the exchange arm 3 moves the previous reticle to the reticle stage 9.
While unloading from above via the first arm, a new reticle is loaded onto the reticle stage 9 via the second arm.

On the other hand, the wafer 13 is placed on the wafer stage 15 via a wafer holder (not shown). The wafer stage 15 positions the wafer 13 in the X direction, the Y direction, and the rotation direction (θ direction) within a plane perpendicular to the optical axis AX of the projection optical system 18, and positions the wafer 13 in the focal direction (Z direction). Also do. The X-coordinate, the Y-coordinate, and the rotation angle of the wafer stage 15 (wafer 13) are constantly measured by the movable mirror 14b fixed on the wafer stage 15 and the laser interferometer 14a installed outside, and the measured value is the central control system. Is being supplied to. Wafer marks in the form of dot rows for wafer alignment are formed in each shot area of the wafer 13. One of them, for example, the X-axis wafer mark is shown as a wafer mark 21. In addition, a reference mark member 6 formed with dot-line-like reference marks having the same pitch as the wafer marks is fixed near the wafer 13 on the wafer stage 15. FIG.
The reference mark member 6 is moved into the exposure field of the projection optical system 18, and the reference mark on the reference mark member 6 is illuminated by the alignment illumination light.
At the time of exposure, the shot area to be exposed on the wafer 13 is moved into the exposure field of the projection optical system 18.

On the reference mark member 6, a pair of reference marks 16A, 1 for a reticle alignment microscope, which will be described later, are provided.
6B and a reference mark 17 formed of a dot-line-shaped mark for an LSA type alignment sensor. Further, an exchange arm 7 for exchanging a wafer is installed near the wafer stage 15, and when the wafer is exchanged, the exchange arm 7 transfers the previous wafer to the wafer via the first arm. The operation of unloading from the stage 15 and loading a new wafer onto the wafer stage 15 via the second arm is performed.

Next, the configurations and operations of the reticle alignment microscope and the wafer alignment sensor provided in the projection exposure apparatus of this example will be described. The projection exposure apparatus of this example is provided with various alignment sensors, but in FIG. 2, among them, a pair of reticle alignment microscopes AS1A and AS1B of the TTR system, and a X axis of the TTL system and the LSA system are used. The alignment sensor AS2 is shown. In addition, in FIG. 2, the alignment sensor AS for the X-axis is shown.
Although only 2 is shown, an LSA type alignment sensor (not shown) for the Y axis is also installed.

First, a pair of reticle alignment microscopes AS1A and AS1B are provided above the reticle 5. At the time of reticle alignment, the alignment illumination light IL1A, I in the same wavelength range as the illumination light for exposure is emitted from the respective tips of the illumination light guides 2A, 2B of the reticle alignment microscopes AS1A, AS1B.
L1B is ejected. Alignment illumination light IL1A, I
L1B is reflected in the horizontal direction by the half prisms 21A and 21B via the condenser lenses LA and LB, respectively, enters the mirrors 22A and 22B via the reference index plates 11A and 11B, and is reflected downward respectively there. The alignment marks 8A and 8B formed on the back surface side of the reticle 5 are irradiated with light through the objective lenses 27A and 27B. In addition,
The reference index plates 11A and 11B will be described later.

A part of the alignment illumination light is reflected by the alignment marks 8A and 8B. The reflected light, as detection light, reverses the incident optical path, and the objective lens 27A,
The light enters the reference index plates 11A and 11B via 27B and the mirrors 22A and 22B. The detection light is the reference index plate 1
After entering the half prisms 21A and 21B through 1A and 11B and passing through the half prisms 21A and 21B, respectively, through relay lenses 26A and 26B, photoelectric sensors 1A and 1B including image pickup devices such as two-dimensional CCDs are provided. Incident.

On the other hand, the alignment illumination lights IL1A and IL1B which have passed through the reticle 5 are projected by the projection optical system 18 respectively.
The reference marks 16B and 16A of the reference mark member 6 provided on the wafer stage 15 are irradiated via the laser beam. A pair of left and right shutters 10A and 10B are provided between the reticle 5 and the projection optical system 18. The shutters 10A and 10B are located near the back surface of the reticle 5 and
And the alignment illumination light IL.
1A, IL1B and the illumination light for exposure are retracted to a position where they are not blocked. Further, the shutters 10A and 10B are configured to be movable in the X direction by a drive system (not shown), and alignment illumination lights IL1A and IL are respectively provided as necessary.
1B can be shielded from light.

When the alignment illumination lights IL1A and IL1B are applied to the reference marks 16B and 16A, reflected light or the like is generated. The reflected light and the like from the reference marks 16B and 16A are transmitted again through the projection optical system 18 and the reticle 5 so as to return to the incident optical paths as detection light, and then, similarly to the detection light from the alignment marks 8A and 8B, Objective lenses 27A, 27B and mirrors 22A, 2
The light enters the reference index plates 11A and 11B via 2B. The detected light enters the half prisms 21A and 21B via the reference index plates 11A and 11B, passes through the half prisms 21A and 21B, respectively, and then enters the photoelectric sensors 1A and 1B through the relay lenses 26A and 26B. To do. The image pickup surfaces of the photoelectric sensors 1A and 1B are the mark forming surfaces of the reference index plates 11A and 11B, the pattern forming surface of the reticle 5, and the mark forming surface on the reference mark member 6 under the alignment illumination lights IL1A and IL1B, respectively. It is conjugated.

The reference index plates 11A and 11B have the same structure and are formed of a substantially circular transparent glass plate.
Reticle alignment microscopes AS1A and AS1 respectively
It becomes perpendicular to the optical axis of B, and the reference index plates 11A and 11B
Is located near the optical axis. Further, on the reference index plates 11A and 11B, index marks 28A and 28B formed of thin cross marks centered on the respective center portions.
Are formed.

On the image pickup surface of the photoelectric sensor 1A, an image in which the alignment mark 8A, the reference mark 16B and the index mark 28A are superposed is formed.
An image in which the alignment mark 8B image, the reference mark 16A image, and the index mark 28B image are overlapped with each other is formed on the imaging surface of. FIG. 3 shows a state on the image pickup surface of the photoelectric sensor 1A. In FIG. 3, the image 8AR of the alignment mark 8A, the image 16BR of the reference mark 16B, and the image 28 of the index mark 28A are shown on the image pickup surface of the photoelectric sensor 21A.
The ARs are shown with their centers approximately coincident. Actually, these image positions do not coincide with the central portion and a deviation occurs, so that the deviation is obtained by image processing and the deviation of the central portion of the pattern of the reticle 5 is measured.

Further, in FIG. 2, the TTL method and L
The SA type X-axis alignment sensor AS2 is installed near the upper side surface of the projection optical system 18. The alignment sensor AS2 is used for wafer alignment for final positioning of the reticle 5 and the wafer 13. At the time of wafer alignment, the laser beam IL2 emitted from the laser light source 4 is reflected in the horizontal direction by the mirror 25, passes through the half prism 23, and is reflected by the mirror 2.
At 4, the light is reflected toward the upper part of the projection optical system 18, passes through the projection optical system 18, and is irradiated almost vertically to the vicinity of the wafer mark 21 on the wafer 13. Wafer stage 1 in that state
5 to drive the wafer mark 21 so that the laser beam I
Cross the irradiation point of L2. The diffracted light of the laser beam IL2 from the wafer mark 21 returns to the incident optical path and passes through the projection optical system 18 again. The diffracted light that has passed through the projection optical system 18 is reflected in the horizontal direction by the mirror 24 and enters the half prism 23. The diffracted light is reflected downward by the half prism 23 and enters the light receiving surface of the light receiving sensor 12 including a photodiode or the like. This detection signal is processed to measure the amount of light incident on the light receiving sensor 12, and the X coordinate of the wafer stage 15 when the amount of light becomes maximum becomes the X coordinate of the wafer mark to be detected. In the case of the baseline measurement of the alignment sensor AS2, the reference mark member 6 is moved to the exposure field of the projection optical system 18 as shown in FIG.
The upper reference mark 17 is illuminated by the laser beam IL2. In this case, the relative position of the detection center of the alignment sensor AS2 with respect to the reference mark member 6 is measured.

Next, the exposure operation of this example will be described.
FIG. 1 is a flow chart for explaining the exposure method of this example. As shown in FIG. 1, in this example, when using the second and subsequent reticles, a reticle preparation step and a wafer preparation step are performed. And proceed in parallel. First step 10
1, the first reticle (referred to as reticle 5 in FIG. 2) is loaded onto the reticle stage 9 by the exchange arm 3. At that time, a patterning error with respect to the outer shape of the reticle 5 and a positioning error during transfer of the reticle remain, so that the centers of the two alignment marks are respectively aligned with the reticle alignment microscope AS1.
It is not in the detection area of A and AS1B. Therefore, in the next step 102, while driving the reticle stage 9 of FIG. 2, a reticle search is performed to bring the alignment marks 8A and 8B on the reticle 5 to the centers of the detection areas of the corresponding reticle alignment microscopes AS1A and AS1B, respectively. Set.

In the next step 103, the shutter 1
With the 0A and 10B retracted (opened), the wafer stage 15 is driven to perform the reticle alignment, and the centers of the reference marks 16A and 16B on the reference mark member 6 are substantially aligned with the optical axis of the projection optical system 18. Position on AX. Then, the reticle alignment microscope AS1A, A
The amount of positional deviation between the reference marks 16A and 16B and the alignment marks 8B and 8A is measured via S1B. That is, the alignment marks 8A, 8B and the reference marks 16B, 16A on the reference mark member 6 are irradiated with the alignment illumination light IL1A, IL1B from the illumination light guides 2A, 2B of the reticle alignment microscopes AS1A, AS1B, and the alignment marks 8A, 8B. And fiducial mark 1
The detection light from 6B and 16A is detected by photoelectric sensors 1A and 1B. On the light receiving surfaces of the photoelectric sensors 1A and 1B, in addition to the images of the alignment marks 8A and 8B and the reference marks 16A and 16B on the reference mark member 6, the reference index plates 11A and 1B.
Images of the index marks 28A and 28B of 1B are also formed. These image pickup signals are digitally image-processed through A / D conversion, and the alignment mark 8A, the reference mark 16B,
And the first relative positional relationship of the reference index plate 11A on the wafer, the alignment mark 8B, and the reference mark 16.
A and the second relative positional relationship of the reference index plate 11B on the wafer are calculated by the central control system.

The distance between the alignment marks 8A and 8B and the pattern center of the reticle, the distance between the reference marks 16A and 16B and the measurement center position of the reference mark, and the reference index plate 1.
The distances between 1A and 11B and the measurement centers of the reference index plates 11A and 11B are precisely measured in advance, and the reticle 5 is obtained by averaging the previously calculated first relative positional relationship and second relative positional relationship. The relative displacement amount between the position of the midpoint (pattern center) of the projected images of the upper alignment marks 8A and 8B on the wafer stage 15 and the position of the midpoint (measurement center) of the reference marks 16A and 16B is the center. Required by the control system. Furthermore, the midpoint (pattern center) of the projected images of the alignment marks 8A and 8B with respect to the center (center of the index mark) of the virtual conjugate image of the index marks 28A and 28B on the reference index plates 11A and 11B on the wafer stage. The amount of deviation is also calculated. Where X at the center of the reticle pattern
Direction and Y direction position is P _A1 , reference marks 16A, 16
The position of the measurement center of B is P _B1 , and the reference index plates 11A and 11B
The position of the center of the index mark of is set as P _C1 . The difference between these positions (P _A1 -P _C1 ) and (P _A1 -P _B1 ) are stored in the central control system. Note that, for example, the difference (P _A1 −P _C1 ) is
It has two components, the X-direction component and the Y-direction difference,
Below, it will be considered as a component in the X direction.

Next, in step 104, the baseline measurement of the TTL type alignment sensor AS2 is performed. That is, another reference mark 17 on the reference mark member 6 is the LSA.
Type alignment sensor AS2 so that it passes through the irradiation position of the alignment illumination light IL2 of the wafer stage 15
Is scanned in the X direction, the diffracted light from the reference mark 17 is detected by the photoelectric sensor 12, and the irradiation position of the alignment illumination light IL2 (the detection center of the alignment sensor AS2) is measured. In this case, if the distance that the wafer stage 15 moves in the X direction from the state of step 103 until the position of the reference mark 17 matches the detection center of the alignment sensor AS2 in the X direction is P _D , the pattern center of the reticle 5 will be described. The baseline amount B ₀ of the alignment sensor AS2, which is the distance in the X direction between the detection center of the alignment sensor AS2 and the detection center of the alignment sensor AS2, is calculated by the following equation.

B₀= P_D-(P_A1−P_B1) (1) This calculated baseline amount B₀Is the position P_A1And position
P_C1Difference (P_A1−P _C1) With the central control system
You. Next, in step 105, the first in one lot
Wafer (hereinafter referred to as wafer 13) is attached to the wafer exchange arm 7.
Therefore, it is loaded on the wafer stage 15. at the time
Then, as in the case of the reticle, the wafer of each shot area is
The position of the mark is the final alignment (fine alignment).
Alignment sensor AS2
It is not within the range that can be detected quickly. Then step
At 106, for example, search alignment on the wafer 13 is performed.
Alignment sensor AS for the position of the dot mark (not shown)
2 and process this detection result to
Calculate the rough coordinates of the wafer mark.

Next, in step 107, fine alignment of the wafer is performed via the alignment sensor AS2 by, for example, the enhanced global alignment (EGA) method. That is, the positions of the wafer marks of a predetermined number of shot areas (sample shots) on the wafer 13 are measured by the alignment sensor AS2 and the Y-axis alignment sensor, and the measurement results are statistically processed to determine the center of all shot areas. The array coordinates are calculated. In the next step 108, the previous step 1
Baseline amount B ₀ obtained in step 04, and step 107
Each shot area is positioned at the exposure position based on the array coordinates obtained in step 1, and the pattern of the reticle 5 is exposed through the projection optical system 18. Above, the first wafer 1
The process of transferring the pattern of the first reticle 5 for 3 is completed.

Next, in step 109, it is confirmed whether or not exposure has been completed for all the wafers in one lot. If completed, in step 115, the wafer and reticle are unloaded, and the exposure process is completed. If all wafers have not been exposed, then step 110 determines if the reticle needs to be replaced. If the reticle needs to be replaced, step 101A and step 105A are processed in parallel, and the reticle preparation process and the wafer preparation process are performed in parallel.

First, the reticle preparation process will be described. In step 101A, the reticle is replaced with a new reticle. Next, in step 111, the shutters 10A and 10B are closed, and the alignment illumination light IL1 of the reticle alignment microscopes AS1A and AS1B.
The optical paths of A and IL1B to the wafer stage 15 side are blocked. Then, in step 102A, a reticle search is performed as in step 102, and then in step 103A, reticle alignment microscope AS1.
The reticle alignment is performed by A and AS1B.
However, in this step 103A, the photoelectric sensors 1A and 1B in the reticle alignment microscopes AS1A and AS1B are used.
The images of the alignment marks 8A and 8B formed on the surface of the reticle and the images of the index marks 28A and 28B of the reference index plates 11A and 11B are subjected to image processing, and the pattern center of the reticle and the reference index plate 1 are processed.
The difference in position from the center of the index marks 1A and 11B is obtained. Here, the position of the obtained reticle pattern center in the X direction and the Y direction is set as position P _Aj, and the position of the center of the index mark is set as position P _Cj . Then, the baseline amount B _j of the alignment sensor AS2 for the new reticle is
Using the baseline amount B ₀ of the equation (1), it is calculated from the following equation.

B _j = B ₀ + (P _Aj −P _Cj ) − (P _A1 −P _C1 ) (2) Here, the movement correction amount ΔB is ΔB = (P _Aj −P _Cj ) −
Putting (P _A1 −P _C1 ), the baseline amount B _j is as follows. B _j = B ₀ + ΔB (3) Then, when this reticle alignment is completed, the irradiation of the alignment illumination light IL1A, IL1B is interrupted, and the shutters 10A, 10B are opened in step 112.

Next, the wafer preparation process following step 105A will be described. Shutter 1 in step 111
Since 0A and 10B are closed, the alignment illumination light at the time of reticle search and reticle alignment is blocked at the upper part of the projection optical system 18. Further, since the baseline amount is calculated by calculation without driving the wafer stage 15, the wafer preparation process can be performed in parallel with the reticle preparation process. First, in step 105A, the wafer is replaced with a new wafer, and in step 106A, a wafer search is performed in the same manner as in step 106 described above.
Next, in step 107A, fine alignment of the wafer is performed by the EGA method using the alignment sensor AS2.

When the steps relating to the reticle and wafer preparation process described above are completed, in step 108A, the wafer amount is calculated based on the baseline amount B _j obtained in step 103A and the array coordinates of each shot area obtained in step 107A. Each shot area is positioned, and the pattern of the reticle is exposed on each shot area of the wafer. When step 108A ends, the process returns to step 109 again.

On the other hand, if it is not necessary to replace the reticle in step 110, the process proceeds to step 105B to replace the wafer, then the process proceeds to step 106B, and the wafer search is performed in step 106B as in step 106A. In the next step 107B, wafer alignment is performed as in step 107A. Then step 1
The process moves to the exposure step of 08A. Then, steps 105B to 107B and 108A are repeated until the exposure of a predetermined number of wafers using the same reticle is completed.

As described above, according to this example, the difference between the position of the previous reticle and the position of the new reticle is determined by the reference index plates 11A, 11B of the reticle alignment microscopes AS1A, AS1B.
It is obtained through the index mark of and is added as a correction to the original baseline amount. Therefore, since the wafer stage is not used in the reticle preparation process, the reticle and wafer can be independently prepared for exposure. During reticle search and reticle alignment, the shutters 10A and 10A shown in FIG.
Since B is closed, the alignment illumination light IL1
A and IL1B do not reach the wafer. When the alignment illumination light is irradiated onto the wafer 13 through, for example, the projection optical system 18 as in the prior art, unnecessary exposure of the wafer occurs, so that the operation on the reticle side and the operation on the wafer side cannot be performed in parallel. . However, in the present invention, the wafer is not exposed by the alignment illumination light IL1A, IL1B because the alignment of the wafer is performed with the alignment illumination light IL1A, IL1B shielded by the shutters 10A, 10B. This is also the reticle preparation process,
This enables parallel operation with the wafer preparation process.

Further, the total time required for the reticle preparation step and the wafer preparation step is almost the same as the time for the reticle preparation step only, and the time required for the wafer preparation step is omitted as compared with the conventional example. Will be equivalent to Therefore, even when the reticle is frequently exchanged as in the exposure step in the manufacture of an ASIC (application-specific IC), it is possible to perform the production without lowering the throughput of the exposure step.

In the above-described embodiment, the LSA type alignment sensor is used as the final alignment sensor of the wafer, but the same can be applied to the FIA type alignment sensor. It should be noted that the present invention is not limited to the above-described embodiments, and various configurations can be taken without departing from the gist of the present invention.

[0042]

According to the exposure method of the present invention, with respect to the second and subsequent masks, the position of the substrate is aligned in parallel with the position of the alignment mark on the mask.
Compared with the conventional case where both are processed in series, the time required for aligning the mask and the substrate is shortened, and there is an advantage that throughput (productivity) is high. In this case, since the position of the substrate is adjusted while the illumination light for measurement is shielded, the substrate is unnecessarily exposed by being irradiated with the illumination light for measurement onto the substrate via, for example, the projection optical system. There is no adverse effect such as that.

Further, according to the exposure apparatus of the present invention, since the shutter member for blocking the illumination light for measurement is provided, the illumination light for measurement can be blocked by the shutter member at any time. Therefore, the illumination light can be blocked by a simple mechanism. When an index mark serving as a reference for positioning the mask is provided in the alignment sensor on the mask mounted on the mask stage, the alignment mark of the mask with respect to the index mark with respect to the first mask, and If the relative displacement of the reference mark member with respect to the predetermined reference mark is measured, for the second and subsequent masks, the relative position relationship between the alignment mark and the index mark of the mask is determined by the alignment sensor. It may be measured with a photoelectric sensor. Therefore, for the second and subsequent masks, it is not necessary to irradiate the reference mark member with the alignment illumination light, so that the operation on the mask side and the operation on the substrate side can be performed in parallel with a simple configuration.

[Brief description of drawings]

FIG. 1 is a flowchart illustrating an example of an embodiment of an exposure method according to the present invention.

FIG. 2 is a schematic configuration diagram showing an example of a projection exposure apparatus used in an embodiment of an alignment method according to the present invention.

FIG. 3 is a diagram showing an image picked up by a photoelectric sensor 1A of the reticle alignment microscope AS1A of FIG.

FIG. 4 is a flowchart showing an example of a conventional alignment method.

[Explanation of symbols]

 1A, 1B Photoelectric sensor 2A, 2B Light guide for illumination 3 Replacement arm (for reticle) 4 Laser light source 5 Reticle 6 Reference mark member 7 Replacement arm (for wafer) 8A, 8B Alignment mark 9 Reticle stage 10A, 10B Shutter 11A, 11B Reference index plate 12 Photoelectric sensor 13 Wafer 15 Wafer stage AS1A, AS1B Reticle alignment microscope AS2 LSA alignment sensor 16A, 16B Reference mark 17 Reference mark 28A, 28B Index mark

Claims (3)

[Claims] 1. An exposure apparatus comprising: a mask stage for positioning a mask; and a substrate stage for positioning a substrate on which the pattern of the mask is transferred and having a reference mark member on which a predetermined reference mark is formed. In the exposure method of sequentially transferring a plurality of transfer patterns and a mask pattern on which alignment marks are formed onto a plurality of substrates using, the first mask of the plurality of masks is used. When the pattern is transferred onto the first substrate to be exposed, the first mask is placed on the mask stage, and illumination light for measurement is irradiated from the mask to align the mask. The amount of positional deviation between the mark and the predetermined reference mark on the substrate stage is detected, and the position of the mask with respect to the predetermined reference mark is detected based on the detection result. When performing the adjustment, when transferring the pattern of the mask of the second and subsequent masks of the plurality of masks onto the second substrate to be exposed, irradiating the measurement illumination light from the mask, In parallel with detecting the position of the alignment mark of the mask, the second substrate is aligned while the illumination light for measurement is blocked between the mask and the second substrate. Exposure method characterized by 2. An exposure apparatus having a mask stage for positioning a mask and a substrate stage for positioning a substrate on which the pattern of the mask is transferred and having a reference mark member on which a predetermined reference mark is formed. In, an alignment sensor for irradiating a measuring illumination light from a mask mounted on the mask stage to detect a positional deviation amount between the alignment mark of the mask and the predetermined reference mark on the substrate stage. And is arranged so that it can be inserted and removed between a mask mounted on the mask stage and the substrate stage, and shields the illumination light for measurement when the mask is placed between the mask and the substrate stage. And a shutter member for controlling the exposure. 3. The exposure apparatus according to claim 2, wherein an index mark serving as a reference for positioning the mask is provided in the alignment sensor on the mask mounted on the mask stage. Exposure equipment.