JPS6346744A - Position detector - Google Patents

Abstract

PURPOSE:To sense a position with high precision by memorizing correction value data at every small region in the image sensing plane of a first position sensing means and correcting positional information obtained by the first position sensing means by a corresponding correction value. CONSTITUTION:The image of a mark on a wafer taken by a CCD camera 1 is converted into a digital signal by a CCU 21 and an analog-digital converter 22 and analyzed by a position sensing section 23 at a correction-value take-in mode. Consequently, the positional information of the wafer obtained is transmitted over a CPU 24. On the other hand, an optical interference data from a laser interferometer received by a receiver 5 is sent to the CPU 24 through an interface 27. The CPU 24 compares these data and computes a correction value in the region in an image plane, and the correction value is memorized to a non-volatile memory 25. When the position of the wafer is detected by a normal detection mode, positional information from the CCD camera is corrected by the correction value memorized to the non-volatile memory 25, thus sensing the position of the wafer with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a position detection device in a semiconductor printing apparatus, and more particularly to a position detection device that can detect the position of an object such as an exposed object with high precision. .

[Description of the Prior Art] As semiconductor integrated circuits become more sophisticated and highly integrated, there is a growing demand for highly accurate position detection of objects to be exposed in semiconductor printing apparatuses. Conventionally, devices that perform such position detection include a means for moving the object with high precision (a so-called sending means) and a means for transmitting a position detection pattern placed on the object to a photoelectric conversion means such as a CCD camera. It consisted of an optical system for imaging, a means for processing photoelectrically converted data, etc.

By the way, in this type of position detection apparatus, there are deviations in the arrangement positions of various parts of the apparatus, distortions in the optical system, etc., so it is necessary to correct the result of detecting the position of the object to be exposed. Therefore, in the past, the detection results were corrected using a fixed correction value.

[Problems to be Solved by the Invention] However, even if such correction is performed, position detection may not be possible with high accuracy. For example, the distortion of the optical system varies depending on the position from the center of the optical axis, and the center of the optical axis and the center of the photoelectric conversion means cannot be precisely aligned. Therefore, the position detection result has the disadvantage that it is accurate only in the vicinity where the correction value is measured.

SUMMARY OF THE INVENTION In view of the problems of the conventional type described above, it is an object of the present invention to provide a position detection device that can detect the position of an object in a semiconductor printing apparatus with higher precision.

[Means and Operations for Solving the Problems] To achieve the above object, the present invention provides a position detection device for a semiconductor printing apparatus, which captures an image of a mark placed on an object whose position is to be detected. a first position detecting means for detecting the position of the object by using the first position detecting means; a second position detecting means for detecting the position of the object with higher accuracy than the first position detecting means;
means for dividing the imaging screen of the position detecting means into predetermined small regions and calculating a correction value by comparing position information measured by each of the first position detecting means and the second position detecting means in each region; , means for storing correction values for each of the regions, and the position information detected by the first position detection means is automatically corrected using the correction values stored in the storage means.

As a result, correction value data is stored for each small area within the imaging screen of the first position detection means, and thereafter,
By correcting the position information obtained by the first position detecting means with a corresponding correction value, highly accurate position detection becomes possible.

[Explanation code for the example] Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 shows the configuration of a position detection device according to an embodiment of the present invention. In the figure, 1 is a CCD camera that photoelectrically converts image data, and is a first position detection means. 2 is an off-axis microscope that images a mark on a wafer, which is an object to be measured, onto a photoelectric conversion element; 3 is an off-axis microscope that images an incident laser beam
4 is a laser interferometer,
5 is a receiver that receives optical interference data from the laser interferometer 4, and 6 is an optical software, which constitute the second position detection means. Further, 7 is a motor that drives the wafer, which is an object to be measured, in the X direction, 8 is a motor that drives the wafer in the Y direction, 9 is an XY stage, and 10 is a Z, θ
11 is a wafer which is an object to be measured; 12 is a reticle stage that can drive a reticle on which a pattern to be printed on the wafer 11 is formed in the X, Y, and θ directions; 13 is a reticle; 14 is a laser tube which is the light source of the interferometer. 15 is a light source that generates exposure light for forming a reticle pattern on a wafer; 16 is a display device; 17
18 is a control box, and 18 is a projection lens that images the pattern on the reticle onto the wafer.

FIG. 2 is a block diagram showing the configuration of the FI circuit of the device of this embodiment. The functions of each component of the apparatus of this embodiment will be explained with reference to FIGS. 1 and 2.

First, the wafer 11 is mechanically aligned in a wafer supply device, which is not shown in the configuration diagram of FIG. 1, and then set on the wafer stage 1o. After that, the XY stage 9 is driven so that the measurement pattern printed on the wafer can be detected by the off-axis microscope 2, and an image of the measurement pattern is captured by the CCD camera 1 for more precise positioning. , detects the position of the wafer.

Here, position detection has a correction value acquisition mode and a normal detection mode. In the correction value capture mode, a correction value is obtained by comparing the position detected in the screen by the CCD camera and the reading of the laser interferometer on the XY stage. The correction values obtained in this way are, for example, divided into 16 small areas in each of the X and Y force directions of the screen imaged by a CCD camera, and the correction values for each of the small areas are calculated and stored in a non-volatile memory. Write. In the normal detection mode, the position detection result is corrected by referring to the correction value for the corresponding small area in the memory, thereby reducing the distortion of the optical system and the photoelectric conversion device (in this case, the CCD).
It is possible to correct the pixel arrangement distortion of , allowing for more accurate measurement.

That is, in FIG. 2, in the correction value import mode, C
The image of the mark on the wafer 11 captured by the CD camera 1 is CC
It is converted into a digital signal by U 21 and analog/digital converter 22, and analyzed by position detection section 23. As a result, the obtained position information of the wafer 11 is transmitted to the CPU.
Sent to 24th. On the other hand, optical interference data from the laser interferometer received by the receiver 5 is sent to the CPU 24 via the interface 27. The CPU 24 compares these data, calculates a correction value for that area on the screen, and stores it in the nonvolatile memory 25. And from then on,
When detecting the wafer position in normal detection mode, CC
By correcting the position information from the D camera with the correction value stored in the nonvolatile memory 25, the position of the wafer can be detected with high precision. 26 is a memory that stores programs and the like.

Next, the acquisition sequence in the correction value acquisition mode will be explained with reference to the flowchart in FIG.

When the correction value import sequence starts, first step S
Initialization is performed in step S1, and the wafer is placed on a wafer stage in step S2. Next, in step S3, position detection is performed, and in step S4, the XY stage is driven so that the mark is at the initial position within the screen of the CCD camera. In step S5, a CCD camera performs position detection to obtain position information, and in step S6, data from the laser interferometer is read. Then, in step S7, it is determined whether position data have been taken for all measurement points. If not, in step S8, the XY stage is moved to the next measurement position, and the process returns to step S5. After acquiring data for all measurement points in step S7, the position detection results and correction values for each area are calculated in step S9, and the obtained correction value data is stored in the nonvolatile memory. With the above steps, correction value data can be obtained.

In this embodiment, since the correction value is obtained by comparing the position detection result with the measurement data of the laser interferometer, optical distortion and distortion of the photoelectric conversion element can be measured with very high precision. Then, distortion measurement data (correction value data) corresponding to each area on the screen projected by the photoelectric conversion element is written to nonvolatile memory, and during normal position detection, the detection data and the detection area on the screen written to this nonvolatile memory are Since the measured value is corrected using the corresponding correction data, the position of the wafer can be detected with higher accuracy.

In this example, a laser interferometer is used as a position base for the object to be measured. A similar effect can be obtained by using a detection means such as an optical scale or a capacitance sensor.

Further, in this embodiment, a CCD is used as a photoelectric conversion element, but if an image pickup tube is used instead, the distortion of the image pickup tube itself is greater than that of a CCD, so it is more effective to apply the present invention. Furthermore, if very high-precision measurement is not required, the distortion of the optical system may be increased to the extent that it does not affect position detection, so the optical system can be made more inexpensive.

In this example, the device automatically imports the correction value,
It is equally effective to measure manually, write correction data manually, for example, in a P-ROM, and perform correction accordingly.

[Effects of the Invention] As explained above, according to the present invention, the detected position within the screen detected from data from the photoelectric conversion element and the measurement data of the laser interferometer at that time are compared, and the small area within the screen is detected. The correction value is calculated and saved in non-volatile memory, and during normal position measurement, the correction data for the most recent screen position from which the position measurement value was obtained is loaded from the non-volatile memory and the measurement value is corrected. Therefore, highly accurate position detection can be performed at all times.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a position detection device according to an embodiment of the present invention, Fig. 2 is a block diagram of a processing circuit of the device of the above embodiment, and Fig. 3 is a correction value acquisition mode of the above embodiment. This is a flowchart. 1: CCD camera, 2: Off-axis microscope, 4:
Laser interferometer, 5: receiver, 6: optical sphere, 7.8: motor, 9: XY stage, 10: Zθ stage, 11: wafer, 14: laser tube, 17: control box, 18 two projection lenses,
23: Position detection unit, 24: CPU. 25: Non-volatile memory.

Claims (1)

[Scope of Claims] 1. A position detection device in a semiconductor printing apparatus, comprising: a first position detection means that detects the position of the object by capturing an image of a mark placed on the object whose position is to be detected; a second position detecting means for detecting the position of the object with higher accuracy than the first position detecting means; means for calculating a correction value by comparing the position information measured by each of the position detection means and the second position detection means, and means for storing the correction values for each area, the first position detection means A position detection device characterized in that position information detected by the above is automatically corrected using a correction value stored in the storage means. 2. The position detection device according to claim 1, wherein calculation and storage of the correction value are automatically performed. 3. The position detection device according to claim 1 or 2, wherein the first position detection means is a CCD camera or an image pickup tube. 4. Claim 1, wherein the second position detection means is a laser interferometer, an optical scale, or a capacitance sensor.
The position detection device according to item 1, 2 or 3.