JPS5928841B2 - pattern scanning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pattern scanning device used in pattern recognition devices, pattern inspection devices, and the like.

Many studies have been conducted in various fields regarding pattern recognition devices that recognize information about patterns. There are various purposes such as pattern dimension inspection, pattern recognition, and pattern transmission, but in each case, it is necessary to detect the information contained in the pattern in some form, convert it into a more convenient form, and process it. be. In this case, first, a device is required that scans the pattern and detects information contained in the pattern while dividing it into minute pixels. Various types of pattern scanning devices have been proposed in the past, and generally there are two types: one that scans the entire surface of the pattern to be inspected, and one that scans a specific portion of the pattern to be inspected.

In the former method, the drive mechanism for the pattern to be inspected is relatively simple, but since unnecessary parts are also scanned, the scanning time is inevitably longer and, for example, when inspecting patterns for defects, The processing of the signals obtained by scanning is complicated, which is particularly inconvenient for inspecting extremely complex patterns such as mask patterns for IC manufacturing. The latter method scans only the desired scanning area, reducing the scanning time; however, since this scanning area has fixed dimensions, it is difficult to scan a pattern where similar pattern parts are regularly present. It is advantageous for scanning applications and is not suitable for scanning irregular patterns, such as masks for C manufacturing, for example. The purpose of the present invention is to eliminate the above-mentioned conventional drawbacks, shorten the scanning time, simplify the processing of signals obtained by scanning, and also be effective for complex and irregular patterns such as masks for IC manufacturing. It is an object of the present invention to provide a pattern scanning device that can perform scanning.

Another object of the present invention is to provide a novel pattern scanning device, and in particular to provide a pattern scanning device having the ability to scan any part of a pattern in any order. That is.

The present invention enables efficient scanning of only necessary portions of the test pattern by scanning predetermined portions of various sizes of the test pattern in a predetermined order. This was done based on the recognition that the scanning time is shorter, the processing of the signals obtained by scanning is easier, and even complex and irregular patterns can be effectively scanned. .

When using such a pattern scanning device of the present invention to inspect defects in a mask for IC manufacturing, for example, it is necessary to read and inspect information for each pixel of the pattern to be inspected. As mentioned above, the pattern scanning device divides the pattern to be inspected into several parts and scans them. Therefore, unless the movement of the table and scanning are synchronized, the signals obtained by scanning will be processed pixel by pixel. It is inconvenient to do so.

Furthermore, another object of the present invention is to provide a pattern scanning device in which scanning and table movement are synchronized in order to eliminate the above-mentioned disadvantages.

The present invention enables efficient scanning of only necessary portions of the test pattern by scanning predetermined portions of various sizes of the test pattern in a predetermined order. This was done based on the recognition that the scanning time is shorter, the processing of the signals obtained by scanning is easier, and even complex and irregular patterns can be effectively scanned. .

When using such a pattern scanning device of the present invention to inspect defects in a mask for IC manufacturing, for example, it is necessary to read and inspect information for each pixel of the pattern to be inspected. As mentioned above, the pattern scanning device divides the pattern to be inspected into several parts and scans them. Therefore, unless the movement of the table and scanning are synchronized, the signals obtained by scanning will be processed pixel by pixel. In order to achieve such an object, the present invention further provides a device for detecting the scanning position of the scanning mechanism, and supplies a scanning position signal from this device to a control circuit to detect the scanning position signal. ,
The table is moved in accordance with the sequence command and the table movement amount in synchronization with scanning, and the scanning signal obtained from the scanning mechanism is controlled by the scanning position signal and the sequence command,
The present invention is characterized in that only a scanning signal corresponding to a predetermined scanning area is supplied as a scanning output signal.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a front view showing the configuration of an example of the pattern scanning device of the present invention, and FIG. 2 is a side view thereof, in which a part of the internal structure is diagrammatically shown. A table 2 movable in the Y direction along a guide surface is provided on a base 1 of the device. This Y-direction table can be manually moved using a handle 3. Furthermore, a motor 4 is provided so that the Y-direction table 2 can be electrically moved via a gear 5. In order to detect the amount of movement of this Y-direction table 2,
A diffraction grating 6 is attached to the side surface of the table 2, and a moiré fringe detector 7 is provided in opposition thereto. In this case, the amount of movement of the table 2 can be accurately detected as a digital amount. A table 8 guided so as to be movable in the x direction is provided on the Y direction table 2.

A pattern 9 to be inspected is placed on this X-direction table 8. Like the Y-direction table 2, this X-direction table 8 can also be moved manually by a handle 10, and can also be moved electrically by a motor 1-1 via a gear 12. Furthermore, a diffraction grating 13 and a moire fringe detector 1 are used to detect the amount of movement of the x-direction table 8.
4 will be provided. Further, a light beam 15 is provided, and the light emitted from the light beam illuminates the pattern 9 from below through an illumination optical system (lens, reflector, etc.) arranged inside the base 1.

The image of pattern 9 is magnified by objective lens 16 and divided into two by semi-transparent mirror 17. The light transmitted through the semi-transparent mirror 17 is reflected by the reflecting mirrors 18 and 19, and an image of the pattern 9 is projected onto the screen 20. This screen 20 is used for observation when the test pattern 9 is set on the x-direction table 8. The light reflected by the half-transparent mirror 17 is reflected by the reflecting mirrors 19 and 18, and the image of the test pattern 9 is transferred to the straight end 22 of the linear-circular converter 21 of a set of optical fibers.
imaged on top. Optical fiber set straight-circle converter 21
One end of a large number of optical fibers is arranged in a straight line to form a linear end 22, and the other end is arranged in a circular shape to form a circular scanning end 23. A scanning element 24 made of a crank-shaped fiber is provided opposite the circular scanning end 23, and is rotated by a motor 25. The image formed on the straight edge 22 in this way is scanned sequentially for each minute pixel, and is applied to the photoelectric element 27 via the fiber 26, which outputs an electric signal according to the information of the pattern 9. is obtained. A radial grid 2 is attached to the shaft of the motor 25.
8 is fixed, and the scanning element 2 is fixed by a light source 29 and a photoelectric detector 30.
4 generates a pulse signal according to the scanning position. In addition to the grating, the radial grating plate 28 is further provided with raised marks in places, which are detected by a light source 31 and a photoelectric detector 32, and are detected at specific positions during one rotation of the scanning element 24, that is, during one scanning period. Only scan synchronization pulses are generated.
FIG. 3 is a block diagram showing the structure of an electric circuit section that cooperates with the above-mentioned mechanical section in an example of the pattern scanning apparatus of the present invention. The pulse outputs supplied from the moiré fringe detectors 14 and 7, which detect the amount of movement of the X-direction table 8 and the Y-direction table 2, and therefore the amount of movement of the test pattern 9 in the X and Y directions, are sent to counters 33 and 3, respectively.
Count by 4.

Furthermore, a pulse output from a detector 30 for detecting the scanning position of the scanning element 24 and a scanning synchronization pulse from a scanning synchronization detector 32 are supplied to a counter 35 . The counter 35 is the detector 30
The pulses from the detector 32 are counted and reset by the scan synchronization pulses from the detector 32. Counter 35 will therefore provide a signal representative of the scan position for each scan. These counters 33, 34, 35
The output of the control circuit 36 is supplied to the control circuit 36. This control circuit 36 is further supplied with signals for commanding the scanning range, scanning area, and scanning order from a sequence command circuit 37, and also supplies signals for commanding the scanning range, scanning area, and scanning order.
7. The configuration and operation of the control circuit 36 will be described in detail later, but here it processes the above-mentioned signals to generate X and Y drive signals for driving the x motor 11 and the Y motor 4, and also generates a scanning output signal. . FIG. 4 shows a portion of a mask original plate used for IC manufacturing, which is an example of a test pattern to be scanned by the pattern scanning device of the present invention. The original plate of such a mask contains various fine pattern parts, and high accuracy is required in the dimensions of each part and the mutual positional relationship of the patterns, as well as unnecessary patterns such as scratches and adhesion. Therefore, strict inspection of these items is required during the manufacturing process. Therefore, it is necessary to scan the surface of the original mask using some method and then accurately capture the internal information.
In the present invention, such a mask is not inspected in its entirety, but only the necessary portions are extracted and scanned.
For this purpose, the pattern of the mask to be inspected is divided into pattern portions having various sizes, and these pattern portions are scanned in a predetermined order. By scanning only the necessary portions in this manner, the scanning time can be shortened, and the processing of the signals obtained by the scanning can also be simplified. Further, since the size and shape of each scanning range can be set arbitrarily, complex and irregular patterns can be efficiently scanned. The test pattern 9 shown in FIG. 4 is a transparent substrate 4.
It is assumed that a complex pattern exists within the area 41 indicated by hatching at 0.

Therefore, this shaded area 41 is designated as a scanning range, and this range is to be thoroughly scanned. Now select the X and Y axes as shown in Figure 4, and these will correspond to the X and Y axes in Figures 1 and 2.
The test pattern 9 is set on the table 8 so as to match the Y direction. As mentioned above, this setting can be done while observing the screen 20. Further, the scanning direction by the linear one-circle converter 21 coincides with the X direction, and the scanning range is S. shall be. This scanning range S. is shorter than the dimension of the scanning range 41 of the test pattern 9 in the X direction. The scanning portion 41 therefore also has a scanning range S. The image is divided into several parts as the minimum unit, and these divided parts are sequentially scanned. In this way, the scanning range S
. By limiting , the scanner becomes compact. Fourth
In the example shown in the figure, the scanning portion 41 is defined by a straight line A-B parallel to the Y axis.
The image is divided into two parts, and each divided part is scanned separately and continuously.

First, the left half of the scanning portion 41 of the pattern 9 is scanned sequentially from the upper left, and the first scan by the scanner 21 is the fourth scan.
Set it so that it corresponds to the part indicated by the broken line in the figure.

This scanning has a certain width, but for convenience, in Fig. 4, it is represented by straight lines Pl and Ql passing through the center of the 0 point P.
When scanning 1, a reset pulse signal is applied from the detector 32, and the contents of the counter 35 are reset to zero. The scanning element 24 rotates and scans from left to right. When it reaches point Q1 after scanning SO, it returns from point Q1 to point P1 and the counter 35 is reset again. On the other hand, a command is given from the sequence command circuit 37 to set Xll to Xl2 as the scanning area, and the contents of the count 35 are changed to P1 to Xl.
The scanning signal from the photoelectric element 27 is blocked by a gate until l, the gate is opened when P1 to Xll, and the scanning signal is supplied as a scanning output signal, and when it reaches Xl2 to Q1, the gate is closed again and scanning is performed. Try to block the signal.
In this way, the scanning output signal is XllXl2
You will only get what corresponds to . After the first scan is completed in this way, a Y drive signal is generated by the scan synchronization pulse, thereby moving the Y direction table 2 by △Y in the Y direction, and then in the same manner as described above. A second scan is performed in the X direction. The scanning continues in the same manner. However, in addition to this method of intermittently moving in the Y direction, it is also possible to perform similar scanning while continuously moving. In this case, the linear end 22 of the scanner 21 may be tilted with respect to the X-axis direction, and set so that it deviates from the starting point of scanning by an amount exactly corresponding to ΔY. Next, when the position Xmlxm2 is reached, the length of the scanning area changes, and the sequence command circuit 37 outputs
A command corresponding to 2 is supplied, and the gate described above is
~Open for the time to scan Xm2. Thereafter, scanning continues in the scanning area of this length until the final scanning area Xnlxn2 is reached. When the scanning of Xnlxn2 is completed, the scanning of the left half is completed, and the scanning of the right half is performed next.

In the right half, the scanning part exists from the intermediate position, so
X, Y drive signals are generated to position the scan position at point P2. These signals are sent to the sequence command circuit 37.
Generated based on instructions given by. Also in this case, Xl3Xl4 is commanded as the scan area and the scan signal is gated to generate the scan output signal for this period. As described above, when scanning a pattern to be inspected in the apparatus of the present invention, for example, when optically scanning in the X direction and moving the table in the Y direction, the table drive mechanism is operated by a Y drive signal synchronized with the scanning. , it is possible to perform high-speed scanning required for pattern scanning, and it can be moved intermittently or continuously in the Y direction, so efficient pattern scanning can be performed and a quick and highly accurate scanning output signal can be obtained. .

Furthermore, the table 1 drive mechanism is operated by a Y drive signal synchronized with scanning in the X direction, for example, output from the control circuit, and is also used for two-dimensional scanning in cooperation with the scanner, so that The scanning output signal can be obtained only in the desired scanning area, and the scanning time can be shortened.

Also, since the scan output signal is obtained only for the scan area, the mechanism for comparing it with, for example, a reference signal to determine whether the pattern is good or bad is simplified. Furthermore, since the size and shape of the scanning portion can be selected arbitrarily, even complex patterns can be efficiently scanned. FIG. 5 is a plotter diagram showing the detailed configuration of the control circuit 36 shown in FIG. 4.

The contents of the command from the sequence command circuit 37 are stored in the command value register 45, and among these commands, command information regarding table coordinate values is supplied to the comparison circuit 46. A comparison circuit 46 compares the coordinate command information with the signals from the counters 33 and 34, and supplies the difference signal as an X, Y drive signal. Of the command information, information for commanding the scanning area of the scanner is sent to a comparator circuit 47 where it is compared with the scan position signal from the counter 35 and provides a gate signal to the gate 48. The scanning signal from the detector 27 is supplied to this gate 48, and the scanning signal corresponding to the scanning area defined by the command information is gated out as a scanning output signal. The scan synchronization pulse from the photoelectric detector 32 resets the counter 35 as described above and also supplies the pulse to a synchronization circuit 49 to generate X, Y drive signals in synchronization with the scan.
The invention is not limited only to the examples described above, but can be modified in many ways.

For example, although the above-described example uses a fiber-optical linear-to-circular transducer as the scanner, any other type of scanner may be used, such as a flying spot scanner. Furthermore, the movement amount detector of the X and Y tables is not limited to the above-mentioned diffraction grating or moiré fringe detector.
A rotary encoder, an optical interferometer, etc. can be used.

[Brief explanation of the drawing]

FIG. 1 is a front view showing the configuration of an example of the pattern scanning device of the present invention, FIG. 2 is a side view thereof, FIG. 3 is a block diagram showing the configuration of an example of the control device, and FIG. 4 is a pattern scanning device of the present invention. A diagram showing an example of the operation when a pattern is scanned by the scanning device, and FIG. 5 is a block diagram showing the detailed configuration of the control circuit. 1...Base, 2...Y-direction table, 4...Y-direction table drive motor, 6,1
3... Diffraction grating, 7, 14... Moire fringe detector, 8... X direction table, 9...
...Test pattern, 11...X-direction table drive motor, 15...Illumination light source, 16...
...Objective lens, 21...Optical fiber set straight-circle converter, 24...Scanner, 25...
...Motor, 27...Photoelectric element, 29,31
......Light source, 30, 32...Photoelectric detector, 33, 34, 35...Counter, 36...
... Control circuit, 37 ... Sequence command circuit, 40 ... Test pattern base, 41 ...
...Scanning range, SO...Scanning length, 45...
... Command value register, 46, 47 ... Comparison circuit, 48 ... Gate, 49 ... Synchronization circuit.

Claims (1)

[Claims] 1.
a table movable in the direction and the Y direction, a table drive mechanism for moving the table in the two directions, a movement amount detection means for detecting the amount of movement of the table in the two directions, and a table placed on the table. a scanner that optically scans the X direction or the Y direction of the test pattern to obtain a scanning signal according to information of the test pattern; and a scanner that generates a scanning position signal according to the scanning position of the scanner. scanning position detecting means; scanning synchronizing pulse generating means for generating a scanning synchronizing pulse only at a specific position during a scanning period of the scanner; A sequence command device for instructing the scanning range of and the scanning order of these scanning ranges, and an X and Y table with respective signals from the movement amount detection means, scanning position detection means, scan synchronization pulse generation means and sequence command device as inputs. a control circuit that generates a drive signal, and the table drive mechanism is also operated by a Y drive signal that the control circuit outputs in synchronization with the first scan synchronization pulse, and the table drive mechanism A pattern scanning device characterized in that it is also used for scanning. 2. The control circuit includes a first comparison circuit that compares the sequence command and the table movement amount and outputs a difference signal, a gate circuit that gates out a scanning output signal representing the brightness and darkness of the test pattern, and the scanning position detection means. a second comparison circuit that compares the scanning position detection signal from the first comparison circuit with the sequence command and outputs a gate signal to the gate circuit; a synchronization circuit for converting the drive signal, the control circuit outputs a Y drive signal synchronized with the scan synchronization pulse to cause the table drive mechanism to perform two-dimensional scanning in cooperation with the scanner; , wherein the scanning signal is controlled by the scanning position signal and the sequence command so that only the scanning signal corresponding to a predetermined scanning area is supplied as the scanning output signal. pattern scanning device.