JPH06236838A - Semiconductor exposure device - Google Patents

Abstract

PURPOSE:To obtain highly precise transmittivity of a reticle from density data by a method wherein the transfer image of the reticle, formed on a plate by projection exposure, is converted to image data, it is taken in an image treatment device and the data is treated there. CONSTITUTION:The surface of a plate 6 is coincided with the autofocus position of a projection lens 3 using the same autofocus mechanism as one which is used when a wafer is exposed, and the image of a reticle 2 is projected on the plate 6. The image of a reticle 2 is transferred to the area on the plate 6 where photochromic-agent is spread. Then, the image data of the area part of the reticle 2 image formed on the plate 6 is taken in an image treatment device 9 through the intermediary of an off-axis microscope 7 and a CCD camera 8. The average density data in each area is measured, the average density of the entire picture is computed, and the transmittivity of the reticle 2 is calculated. As a result, the transmittivity of the reticle 2 can be computed in a short period of time by conducting only one exposing operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor exposure apparatus having a function of automatically measuring the transmittance of a reticle.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor exposure apparatus, especially a stepper, when measuring the transmittance of a reticle, for example,
As shown in FIG. 3, the pattern of the reticle 2 is projected onto the moving stage 4 via the projection lens 3, and the light quantity of this projected image is moved to the moving stage 4 by the photodetector 11 provided on the moving stage 4. A method of measuring while moving a little is used. A detector for measuring the illuminance unevenness of the apparatus is generally used as the photodetector 11, and its configuration is, for example, as shown in FIG. 4, in which a pinhole 43 of about 0.3 mmφ is arranged above the detector 41. It is a thing.

In the above structure, for example, 1 of the reticle 2
When measuring the transmittance of the area of 00 mm □, as shown in FIG. 5, while moving the moving stage 4 at a pitch of 0.2 mm in each of the X and Y directions, P1, P2, P3
The reticle transmittance is measured by measuring the light amount of each point up to the last Pn point in the order of points ... And comparing the total of these measurement points with the light amount in the absence of the reticle 2.

[0004]

However, in the above-mentioned conventional example, for example, an area of 100 mm □ of the reticle (20 mm □ on the wafer surface when the reduction ratio of the projection lens is ⅕) is set to 1 mm pitch on the reticle ( 0.
(2 mm pitch), 10,000 points must be measured. Especially, in the case of excimer stepper, the laser oscillation frequency is 400 Hz and 10 points are required for 1 point measurement.
Even if 0 pulse exposure is required, it takes 2,500 seconds to measure 10,000 points by exposure alone. Further, if the stage drive time is set to 0.3 seconds per point, there is a problem that it takes a total of 5,200 seconds to measure 100 mm square in the entire reticle transmittance measurement.

The transmittance of the reticle needs to be remeasured when the opening of the masking blade is changed.
When the reticle is frequently exchanged as in C, the conventional method has a problem that the measurement time is too long. Also, in terms of economic efficiency, particularly in the case of the excimer stepper, gas consumption is large, and this is not an efficient method.

An object of the present invention is to allow the semiconductor exposure apparatus to measure the transmittance of a reticle in a short time in view of the problems of the prior art.

[0007]

To achieve this object, according to the present invention, in a semiconductor exposure apparatus for projecting and transferring a reticle pattern onto a semiconductor wafer arranged on a moving stage, the reticle pattern is arranged on the moving stage. A plate having a surface capable of forming an image by exposure light, an image capturing means for obtaining image data of a transfer image of the reticle pattern formed on the plate by the exposure light via an image capturing means, and an image capturing means obtained thereby. Data processing means for obtaining the transmittance of the reticle based on the obtained image data.

As the plate, for example, a plate coated with a photochromic agent or a wafer coated with a photochromic agent can be used. This apparatus usually has a microscope for mark detection at the time of pre-aligning the semiconductor wafer, the image pickup means includes this microscope as a part, and the image of the transfer image obtained through this microscope is used as image data. Can be configured to be converted to and output. In this case, the microscope may have a magnification switching mechanism. The image capturing means may capture the image data while dividing the image data while moving the moving stage, or may capture the image data all at once.

[0009]

In this structure, the transfer image of the reticle pattern is formed by positioning the plate at the exposure position by the moving stage and projecting and exposing the reticle pattern on the plate in the same manner as in ordinary exposure. . The formed transfer image is converted into image data by the image pickup means and stored in the memory or the like of the image capturing means. Then, the reticle transmittance is obtained by processing this image data. Therefore, the time required during that time is considerably shortened as compared with the conventional case in which exposure of 100 pulses is required to measure one point.

[0010]

1 is a block diagram of a stepper according to an embodiment of the present invention, in which 1 is an illuminating device which emits exposure light, 2 is a reticle illuminated by the illuminating device, and 3 is an illuminated reticle 2.
A projection lens for projecting the above pattern onto the wafer, 4 is a moving stage, 5 is a chuck for placing the wafer on the moving stage 4, and 6 is a photochromic agent applied on the moving stage 4. Plate, 7 is an off-axis microscope, 8 is an image obtained through the off-axis microscope 7 and is converted into image data 1024 × 102.
4 is a CCD camera, 9 is an image processing device that processes the image data output by the CCD camera 8 and outputs density data,
Reference numeral 10 denotes a control CPU that obtains the transmittance of the reticle 2 based on the density data from the image processing device 9 and controls the drive of the illumination device 1 and the moving stage 4. The off-axis microscope 7 is for pre-alignment (pre-alignment mark measurement) of the wafer by the TV (CCD camera 8), and an image of the area of 1 mm □ on the wafer surface (1 mm □ on the reticle surface) is passed through this. It is captured in an image frame memory of 1000 × 1000 pixels.

In the above structure, when measuring the transmittance of the reticle, the CPU 10 first drives the moving stage 4 so that the plate 6 is located below the projection lens 3. The plate 6 has a surface coated with a photochromic agent sufficient to project the entire image of a 100 mm square (20 mm square on the wafer surface) reticle. Next, the surface of the plate 6 is aligned with the focus position of the projection lens 3 by using the same autofocus mechanism as that used for normal wafer exposure (not shown). Then, the illumination device 1 is turned on, and the image of the reticle is projected on the plate 6. As a result, an image 21 of the reticle is transferred onto the surface of the plate 6 coated with the photochromic agent as shown in FIG. 2, and this image is held for several seconds to several minutes. Here, as the photochromic agent, a type in which an image remains for about 3 minutes after exposure is used. next,
The moving stage 4 is driven, the image of the area a1 (1 mm □) of the reticle image 21 formed on the plate 6 is positioned under the off-axis microscope 7, and the image data is stored in the off-axis microscope 7 and the CCD camera 8. It is taken into the image processing device 9 via. The CPU 10 stores the average density data of the area a1 output from the image processing device 9 based on the image data in a memory (not shown). Next, CP
U10 drives the moving stage 4 again, and similarly reads and stores the average density data of the area a2. Thereafter, similarly, the average density data in each area from the area a3 to the last area an is measured and stored. And CP
U10 obtains the average density of the entire screen (in this case, 20 mm □) from the stored density data of each area, and calculates the transmittance of the reticle 2. In this case, the resolution per pixel is 5 μm □ on the reticle surface.

According to this, the processing time until the transmittance is obtained is 120 seconds, assuming that the driving time of the stage is 0.2 seconds and the time of capturing and processing the image is 0.1 seconds.

In the above embodiment, the reticle image of 20 mm square formed on the plate is divided into 1 mm square and read by the image processing apparatus. You should go. At present, it is sufficient that the measurement accuracy of the reticle transmittance is about 10%. Therefore, the entire area of 20 mm □ of the reticle image 21 formed on the plate 6 can be collectively input by the image processing apparatus. The off-axis microscope may be provided with a mechanism for switching to the magnification of 7. In this case, the measurement is completed by only one exposure time, one image processing time, and two stage driving times.

Although the plate 6 coated with the dedicated photochromic agent used on the moving stage 4 is used in the above embodiment, the plate for projecting the reticle image is not limited to this and, for example, the same photochromic agent is coated. A wafer may be used.

It is also possible to increase the sensitivity of the microscope 7, expose a reticle image on a wafer coated with a normal resist, analyze the latent image by image processing means, and obtain the reticle transmittance from the density.

[0016]

As described above, according to the present invention, the pattern of the reticle is transferred onto the plate placed on the stage, and the projection image of the reticle formed on the plate is used as image data. The transmittance of the reticle is calculated based on the data taken into the processing device, so that the transmittance of the reticle can be obtained with high accuracy and once exposure in a short time.

[Brief description of drawings]

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

FIG. 2 is a schematic diagram showing a transferred image of a reticle pattern on a plate, which is observed in the apparatus of FIG.

FIG. 3 is a configuration diagram of a stepper according to a conventional example.

FIG. 4 is a cross-sectional view showing a photodetector for measuring transmittance in the device of FIG.

5 is an explanatory diagram for explaining a method of measuring transmittance in the apparatus of FIG.

[Description of Reference Signs] 1: Illuminator, 2: Reticle, 3: Projection lens, 4: Moving stage, 5: Wafer chuck, 6: Plate coated with photochromic agent, 7: Off-axis microscope,
8: CCD camera, 9: image processing device, 10: CPU for controlling stepper.

Claims (6)

[Claims] 1. A semiconductor exposure apparatus for projecting and transferring a reticle pattern onto a semiconductor wafer arranged on a moving stage, the plate being provided on the moving stage and having a surface capable of forming an image by exposure light, Image capturing means for obtaining image data of the transfer image of the reticle pattern formed on the plate by exposure light through the image pickup means, and data for obtaining the transmittance of the reticle based on the image data obtained thereby. A semiconductor exposure apparatus comprising: a processing unit. 2. The semiconductor exposure apparatus according to claim 1, wherein the plate is a plate coated with a photochromic agent. 3. The semiconductor exposure apparatus according to claim 1, wherein the plate is a wafer coated with a photochromic agent. 4. A microscope for mark detection at the time of pre-aligning the semiconductor wafer, wherein the image pickup means includes this microscope as a part, and the image of the transfer image obtained through the microscope is used as image data. 2. The semiconductor exposure apparatus according to claim 1, wherein the semiconductor exposure apparatus is converted into and output. 5. The semiconductor exposure apparatus according to claim 4, wherein the microscope has a magnification switching mechanism. 6. The semiconductor exposure apparatus according to claim 1, wherein the image capturing means captures the image data in a divided manner while moving the moving stage.