JP3531895B2 - Projection exposure equipment - Google Patents

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 for exposing a resist on a substrate with a design pattern to manufacture a semiconductor device and the like, and a device manufacturing method using the exposure apparatus.

[0002]

2. Description of the Related Art In a collective exposure type exposure apparatus, when a projection optical system is composed of a lens, an image forming area has a circular shape. However, since a semiconductor integrated circuit is generally rectangular in shape, the transfer area in the case of collective exposure is a rectangular area inscribed in the circular image forming area of the projection optical system. Therefore, even in the largest transfer area, 1 / the diameter of the circle
It is a square with sides of √2. On the other hand, by using a slit-shaped exposure area having a diameter approximately equal to that of the circular imaging area of the projection optical system, the reticle and the wafer are scanned and moved in synchronization with each other to enlarge the transfer area. A scanning exposure method (step-and-scan method) has been proposed. In this method, when a projection optical system having an image forming area of the same size is used, a larger transfer area is secured as compared with the step-and-repeat method in which a projection lens is used to perform batch exposure for each transfer area. be able to. That is, since the optical system does not limit the scanning direction, the stroke of the scanning stage can be secured, and the transfer area approximately √2 times can be secured in the direction perpendicular to the scanning direction. .

In an exposure apparatus for manufacturing a semiconductor integrated circuit, it is desired to enlarge the transfer area and improve the resolution in order to cope with the manufacture of chips with a high degree of integration. The fact that a smaller projection optical system can be adopted is advantageous in terms of optical performance and cost, and the step-and-scan type exposure apparatus is drawing attention as the mainstream of future exposure apparatuses.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the performance of a projection exposure apparatus, especially a step-and-scan type projection exposure apparatus, especially the alignment accuracy of an original or a substrate.

[0005]

In order to achieve the above object, in the present invention, an illumination optical system for illuminating a predetermined illumination area on an original plate and a position substantially conjugate with the original plate in the illumination optical system are provided. A masking blade arranged to vary the illumination area, a projection optical system for projecting an original pattern in the illumination area onto a substrate, and an original stage capable of moving the original in a predetermined direction with respect to the illumination area. An optical axis of the projection optical system having a substrate stage capable of moving the substrate in a predetermined direction with respect to a projection region conjugate with the illumination region, and an alignment system for measuring positions of the original plate and the substrate. In the projection exposure apparatus which scans the original plate, the substrate, and the masking blade together perpendicularly to the substrate to sequentially project the pattern on the original plate onto the substrate, The results are characterized in that a means for correcting corresponding to the position of the masking blade.

In a preferred embodiment of the present invention, the correction means has means for calculating a correction value of the positional deviation detection result by an operation using the masking blade position as a variable. As the alignment system, an off-axis alignment system that measures the position of the substrate by off-axis, a non-exposure light TTL alignment system that measures the position of the substrate by predetermined non-exposure light through the projection optical system, Exposure for measuring a deviation between a first reference mark provided on the original stage and a second reference mark provided on the substrate stage with a light beam having substantially the same wavelength as the exposure light through the projection optical system. An optical TTR alignment system, an original plate alignment system for measuring a deviation between a pattern on the original plate and a third reference mark provided on the original plate stage, a focus detection system for measuring the position of the pattern surface of the substrate, and the like. It can be illustrated. The masking blade and the alignment system are supported by a projection optical system surface plate that supports a lens barrel of the projection optical system. Among the alignment systems, an off-axis alignment system, a non-exposure light TTL alignment system, and focus detection are provided. The system measures the position of the substrate or substrate surface with reference to the lens barrel of the projection optical system. More preferably, the alignment system detects the positional deviation with the masking blade positioned at a predetermined position.

[0007]

In the projection exposure apparatus, the lens barrel surface plate that supports the lens barrel of the projection optical system is generally the apparatus reference,
An alignment system for aligning the original plate and the substrate is also attached to the lens barrel surface plate. Further, in the step-and-scan type exposure apparatus, during scanning exposure, acceleration / deceleration of the original stage and substrate stage and vibration settling (idling)
During the period, a masking blade that limits the illumination area (exposure area) on the reticle is scanned in synchronization with the original stage and the substrate stage so that shots other than the exposure target shot are not exposed.

The present inventors have found that the lens barrel surface plate is deformed by an unbalanced load and a reaction force at the time of acceleration / deceleration when the masking blade is moved, and such deformation is caused by the overlay accuracy and focus accuracy of the exposure apparatus. The inventors have found that the exposure accuracy has a non-negligible effect, and that the above-mentioned deformation depends on the position of the masking blade, and arrived at the present invention.

According to the present invention, in the alignment system for aligning the original plate and the substrate, the alignment measurement values of the original plate and the substrate are corrected in accordance with the masking blade position. It is possible to reduce deterioration of accuracy.

[0010]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the arrangement of a scanning exposure apparatus according to an embodiment of the present invention. This device projects a part of the reticle pattern onto a wafer in a slit shape through a projection optical system, and scans the reticle and the wafer in synchronism with each other relative to the projection optical system to scan the reticle pattern. This is a step-and-scan type exposure apparatus that exposes a wafer and performs this scanning exposure with respect to a plurality of transfer areas (shots) on the wafer while interposing step movement for repeating the exposure. In FIG. 1, an illumination optical system 1 illuminates a predetermined area on the reticle 2 held by the reticle stage 11 in a slit shape. A projection optical system 3 projects the pattern of the area illuminated by the illumination optical system 1 on the reticle 2 onto the wafer 6 held on the wafer stage 5 at a predetermined reduction ratio.

The reticle stage 11 is driven in the X direction by a linear motor (not shown), and the wafer stage 5 is driven in the X and Y directions by an X direction linear motor and a Y direction linear motor (not shown). The synchronous scanning of the reticle 2 and the wafer 6 is performed by moving the reticle stage 11 and the wafer stage 5 in opposite directions in the X direction at a constant speed ratio (for example, 4: 1). A Z-tilt stage (not shown) is mounted on the wafer stage 5, and a wafer chuck (not shown) that holds the wafer is mounted on the Z-tilt stage.

The wafer stage 5 is the wafer stage base 1
9 and the reticle stage 11 is provided on the reticle stage surface plate 27.
7. Blade stage 34 and projection optical system 3 described later
Is provided on the lens barrel surface plate 10. Stage surface plate 19
The lens barrel base 10 is supported on the base frame 17 at three points via the three dampers 18. The damper 18 is an active damper that actively suppresses or eliminates vibration in the six axis directions, but a passive damper may be used.

Laser interferometers 7 and 8 measure the positions of the reticle stage 11 and the wafer stage 5, respectively, with reference to the lens barrel. The measurement values of the laser interferometers 7 and 8 are sent to a control device (not shown) together with the measurement values (alignment values) by the scopes 12, 14, 15, and 16 which will be described later, and in this control device, the reticle is based on these measurement values. The stage 11 and the wafer stage 5 are driven to position the reticle 2 and the wafer 6 such as step movement and synchronous scanning.

The light projecting means 9a and the light receiving means 9b constitute a focus sensor for detecting whether or not the wafer 6 on the wafer stage 5 is located on the focus surface (image surface) of the projection optical system 3. There is. That is, the light projecting means 9a fixed to the lens barrel surface plate 10 irradiates the wafer 6 with light from an oblique direction, and the position of the reflected light is detected by the light receiving means 9b to detect the optical axis of the projection optical system 3. The position of the surface of the wafer 6 in the direction is detected. The light projecting means 9a has a light emitting element such as an LED, and the light receiving means 9b has a light receiving element such as a CCD sensor.

Reference numeral 12 denotes exposure light or light having substantially the same wavelength as that of the exposure light, and the reticle 2 or the first reference plate 4 on the reticle stage 11 and the wafer 6 or the second reference plate on the wafer stage 5 through the projection optical system 3. It is an exposure light TTR scope that can observe 13 and 13 simultaneously. The first reference plate 4 is fixed near both ends of the reticle stage 11 in the X direction, and at least one of the first reference plate 4 is fixed so as to come within the slit-shaped illumination area of the illumination optical system 1 when the reticle stage 11 comes to the reticle exchange position. There is. Second reference plate 13
Is fixed to the wafer stage 5 at a position where it does not interfere with the wafer 6.

Reference numeral 14 denotes a FRA (fine reticle alignment) scope for detecting a relative positional deviation between the reticle 2 and a reticle reference plate (not shown) fixedly mounted on the reticle stage 11 at the reticle exchange position, and 15 is on the wafer stage 5. Is a non-exposure light TTL scope for measuring the positional deviation of the wafer 6 with respect to the reference of the wafer 6 with non-exposure light through the projection optical system 2. A correction optical system (not shown) for correcting the aberration between the exposure light and the non-exposure light in the projection optical system 3 is provided in the optical path of the non-exposure light TTL scope 15.
Further, a prism (not shown) is provided for allowing non-exposure light to enter the projection optical system 3 from the scope 15 side and taking out reflected light from the wafer 6 from the projection optical system 3.

Reference numeral 16 denotes a wafer 6 with respect to its own reference.
It is an off-axis scope for measuring the position shift of the outside of the visual field of the projection optical system 3. Reference numeral 34 is a blade stage for scanning a scanning masking blade for limiting the illumination light flux so as to prevent exposure of shots other than the exposure target shot during acceleration / deceleration and idle running of the reticle stage 11 before and after scanning exposure. The position of the blade stage 34 is constantly measured by an encoder (not shown),
At least immediately before and after the start and end of scanning exposure, scanning is performed in synchronization with the reticle stage 11.

In this structure, when the wafer 6 is loaded onto the wafer stage 5 from the front portion (front side of FIG. 1) of the apparatus by the transporting means (not shown), and the predetermined alignment is completed, the exposure apparatus performs scanning exposure and While repeating the step movement, the pattern of the reticle 2 is exposed and transferred onto a plurality of transfer areas on the wafer 6. During scanning exposure, the reticle stage 11 and the wafer stage 5 are moved in the X direction (scanning direction) at a predetermined speed ratio to scan the pattern on the reticle 2 with slit-shaped exposure light, and the projected image By scanning 6 the pattern on the reticle 2 is exposed to a predetermined transfer area on the wafer 6. During scanning exposure, the height of the wafer surface is measured by the focus sensor 9 (9a, 9b), and the height and tilt of the wafer stage 5 are controlled in real time based on the measured values, and focus correction is performed. After the scanning exposure for one transfer area is completed, the wafer stage 5 is driven to move the wafer stepwise in the X direction and / or the Y direction to position another transfer area with respect to the start position of the scanning exposure, Perform scanning exposure. By combining the step movement in the X and Y directions and the movement for the scanning exposure in the X direction, each transfer area on the wafer can be sequentially and efficiently exposed. The arrangement of the transfer areas, the positive or negative Y scanning direction, the order of exposure to each transfer area, and the like are set.

FIG. 2 is a block diagram showing a control system of the apparatus shown in FIG. In the figure, 51 is an alignment value correcting means, 52 is an alignment measuring means, and 53 is a stage positioning means. The stage 531 in the stage positioning means 53 corresponds to the reticle stage 11, the wafer stage 5, the blade stage 34 and their drive systems in FIG. 1, and the stage position measurement value 532 is the laser interferometers 7, 8 and the encoder in FIG. It corresponds to the measured value by. The alignment measurement value 521 in the alignment measurement means 52 is the focus sensor 9 and the scope 1 of FIG.
The measured values are 2, 14, 15, and 16. The alignment value correction means 51 stores the relationship between the position of the reticle stage 11 and the correction values of the measurement values by the scopes 12, 14, 15, 16 as an AA correction value table 511 or a correction function. Such a correction value may be determined in advance by measuring an error at a plurality of positions of the blade stage 34 using a reference reticle or a reference wafer and determining the error.

The position of the stage 531 is the laser interferometer 7,
8 and the measured value by the encoder, and the measured value 5
32 is input to the stage position calculator 534. Also,
The position measurement value of the blade stage 34 by the encoder is also input to the comparator 512 in the alignment value correction means 51. The comparator 511 reads the correction value of the position of the blade stage 34 indicated by the position measurement value of the blade stage 34 or the position in the vicinity thereof for each sensor 9 and each scope. The interpolation calculator 513 calculates the correction value of each scope and sensor when the blade stage 34 is at the current position based on these correction values. The alignment measuring means 52 corrects the measurement value 521 by the sensor 9 and each scope with the correction value from the interpolation calculator 513, and converts it into the alignment value of each stage 11, 5, 34 by the alignment value calculator 522. This alignment value is input to the stage position calculator 534 of the stage positioning means 53. Stage position calculator 534
This alignment value and the measured value of the stage position 532
The positioning target value 533 of each stage is calculated based on the above and given to the drive system of the stage 531. Stage 531
In this drive system, each stage 11,
Position 5, 34.

In this way, the focus sensor 9 and each scope 12, which are caused by the deformation of the lens barrel surface plate 10 due to an unbalanced load when the blade stage 34 moves or a reaction force during acceleration / deceleration,
It is possible to correct the error in the alignment measurement values of 14, 15, 16 and minimize the deterioration of the alignment measurement accuracy. In this case, alignment accuracy can be further improved by placing each stage in a fixed position as much as possible and performing alignment measurement. For example, alignment measurement by the off-axis scope 16 and the non-exposure light TTL scope 15 is performed with the blade stage 34 at the first shot exposure standby position and the reticle stage 11 at the reticle exchange position or the first shot exposure standby position. , FRA scope 14 is the first to measure the blade stage 34 and the wafer stage.
It may be performed in a state where the reticle stage 11 is placed at the shot exposure standby position or at the reticle exchange position or the first shot exposure standby position.

FIG. 3 shows the reticle or wafer alignment operation in the apparatus of FIG. During alignment,
First, the stage on which the alignment target (wafer and / or reticle) is mounted is moved to the alignment measurement position. Next, alignment measurement is performed using the alignment scope. At the same time, the alignment correction value according to the stage position is calculated. An alignment value is calculated based on these alignment measurement values and alignment correction values. Then, it is determined whether or not the alignment is completed. If the alignment is not completed, the above operation is repeated for the next alignment measurement position. The stage target value is calculated based on the stage position and the alignment value in parallel with the determination of the alignment end. If the determination is the alignment end, the process proceeds to the exposure sequence to perform the scanning exposure using the stage target value. Run.

The measurement values of the focus sensor 9 for performing focus correction during scanning exposure and the measurement values for scanning the blade stage 34 are the same as those described above except that they are also executed during scanning exposure. Then, the measured value can be corrected.

Example of Manufacturing Micro Device FIG. 4 shows a micro device (semiconductor chip such as IC or LSI,
A flow of manufacturing a liquid crystal panel, a CCD, a thin film magnetic head, a micromachine, etc. is shown. In step 1 (circuit design), a semiconductor device circuit is designed. In step 2 (mask manufacturing), a mask having the designed circuit pattern is manufactured. On the other hand, in step 3 (wafer manufacturing), a wafer is manufactured using a material such as silicon. Step 4
The (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by the lithography technique using the mask and the wafer prepared above. The next step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip by using the wafer manufactured in step 4, such as an assembly process (dicing, bonding), a packaging process (chip encapsulation), and the like. including. Step 6
In (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. A semiconductor device is completed through these processes and shipped (step 7).

FIG. 5 shows a detailed flow of the wafer process. In step 11 (oxidation), the surface of the wafer is oxidized. In step 12 (CVD), an insulating film is formed on the wafer surface. In step 13 (electrode formation), electrodes are formed on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted in the wafer. Step 15
In (resist processing), a photosensitive agent is applied to the wafer. In step 16 (exposure), the circuit pattern of the mask is printed and exposed on the wafer by the exposure apparatus described above. In step 17 (development), the exposed wafer is developed. In step 18 (etching), parts other than the developed resist image are removed. In step 19 (resist stripping), the resist that is no longer needed after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

By using the manufacturing method of this embodiment, a highly integrated semiconductor device, which has been difficult to manufacture in the past, can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an alignment value correction system in the exposure apparatus of FIG.

3 is a diagram showing a flow of an alignment measurement sequence of the apparatus of FIG.

FIG. 4 is a diagram showing a flow of manufacturing a micro device.

5 is a diagram showing a detailed flow of the wafer process in FIG.

[Explanation of symbols]

1: Illumination optical system, 2: Reticle, 3: Projection optical system, 4:
First reference plate, 5: wafer stage, 6: wafer,
7, 8: laser interferometer, 9 (9a, 9b): focus sensor, 10: lens barrel surface plate, 11: reticle stage, 1
2: exposure light TTR scope, 13: second reference plate,
14: FRA (fine reticle alignment) scope, 15: non-exposure light TTL scope, 16: off-axis scope, 17: base frame, 18: damper, 1
9: Wafer stage surface plate, 27: Reticle stage surface plate, 34: Blade stage, 51: Alignment value correction means, 511: AA correction value table, 512: Comparator, 513: Interpolation calculator, 52: Alignment measurement means, 521: Alignment measurement value, 522: Alignment value calculator, 53: Stage positioning means, 531: Stage, 532: Stage position measurement value, 533: Stage target value, 534: Stage position calculator.

Claims (7)

(57) [Claims] 1. An illumination optical system for illuminating a predetermined illumination area on an original plate, a masking blade arranged at a position substantially conjugate with the original plate in the illumination optical system for varying the illumination area, and the inside of the illumination area. A projection optical system for projecting the pattern on the original plate onto a substrate, an original stage capable of moving the original plate in a predetermined direction with respect to the illumination region, and a predetermined substrate with respect to a projection region conjugate with the illumination region. A substrate stage movable in the direction of, and an alignment system for measuring the positions of the original plate and the substrate, by scanning the original plate, the substrate and the masking blade together perpendicularly to the optical axis of the projection optical system. In a projection exposure apparatus that sequentially projects the pattern on the original onto the substrate, the position measurement result by the alignment system is corrected corresponding to the position of the masking blade. Projection exposure apparatus being characterized in that a means. 2. The projection exposure apparatus according to claim 1, wherein the correction means has a means for calculating a correction value of the positional deviation detection result by calculation using a position of the masking blade as a variable. 3. The projection exposure apparatus according to claim 1, wherein the alignment system detects the positional deviation by placing the masking blade at a predetermined position. 4. The off-axis alignment system for measuring the position of the substrate by off-axis, and the non-exposure light TTL alignment for measuring the position of the substrate with predetermined non-exposure light via the projection optical system. System, the deviation between the first reference mark provided on the original stage and the second reference mark provided on the substrate stage is measured through the projection optical system with a light flux having substantially the same wavelength as the exposure light. Exposure light TTR alignment system, an original plate alignment system that measures a deviation between a pattern on the original plate and a third reference mark provided on the original plate stage, and a focus detection system that measures the position of the pattern surface of the substrate 2. At least one of the above is included.
4. The projection exposure apparatus according to any one of 3 to 3. 5. The projection exposure apparatus according to claim 4, wherein the off-axis alignment system, the non-exposure light TTL alignment system, and the focus detection system perform measurement with reference to the lens barrel of the projection optical system. 6. The projection optical system surface plate that supports the lens barrel of the projection optical system, wherein the masking blade and the alignment system are supported.
6. The projection exposure apparatus according to any one of 5. 7. A device manufacturing method using the apparatus according to claim 1.