JPS5821107A - Inspecting device for pattern - Google Patents

Abstract

PURPOSE:To inspect the patterns of an object to be inspected by the use of a storage device for small capacity by detecting only the angles of the local patterns of said object and coding said angle in accordance with the codes corresponding to point symmetry. CONSTITUTION:The angles of the local patterns of an object to be inspected are detected and the patterns are classified to two in accordance with 90 deg. and 135 deg. of the angles. Further if the patterns are so classified that within the same angle the patterns wherein said angle assumes point symmetry with respect to the center of the patterns are not included, the patterns of a small quantity such as 32 kinds are coded by 2 bits, etc. of different codes. Thus the patterns for the corresponding designs that serve as references for comparison are stored in a storage device of small capacity and the patterns of IC chips, etc. are inspected by the use of the storage device of small capacity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention compares a pattern transferred to a mask or reticle with design data forming the pattern in the IC manufacturing process to determine whether or not it has been transferred normally.
The present invention relates to an inspection device for a pattern to be inspected.

Conventionally, this type of equipment has been inspected by comparing chips with the same pattern group on the same mask, or by developing design data as bit patterns on an image memory.
An inspection method has been considered in which image data obtained from a mask or reticle is compared pixel by pixel.

However, according to the former method, if each chip has the same defect (common defect), it is impossible to recognize it as a defect. In many cases, tests such as the chip comparison method were not possible. On the other hand, the latter method
For example, since it is a comparison with the design data from which the pattern was created, it is possible to recognize common defects between chips, and it is also possible to inspect with a reticle. Strength・
However, the amount of data that has to be prepared by converting the head pitch data into pixel units on the image memory, that is, the capacity of one image memo, is enormous, and it takes too much time for the computer to input and output it. However, the disadvantage was that the device was large and complex.

SUMMARY OF THE INVENTION An object of the present invention is to solve these drawbacks and provide a defect inspection device that does not require a device that stores a huge amount of information and can quickly determine the presence or absence of a pattern defect by referring to design data. .

Summary of the present invention to achieve the above objects &'! a scanning means for scanning a geometric pattern formed on an object to be inspected based on design information and generating a video signal corresponding to the i<turn; - a detection means that generates detection information when it is detected that a pattern in a local area on the object to be inspected has a predetermined feature prepared in advance, and combines the detection information with the design information. In an apparatus that inspects whether a pattern is formed on an object to be inspected as designed by checking, the detection means prepares two types of codes in advance and detects a predetermined pattern from the pattern in the local area. It is equipped with an encoding circuit that detects angles and gives a code of 10,000 to 10,000 angles that are the same angle and have a point-symmetrical relationship, and gives the other code to the other corner, and the given code is An object of the present invention is to provide a pattern inspection device characterized in that the detection information is output.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. The object to be inspected, for example, the reticle 1, which is placed on the moving stage 14 and has a pattern drawn thereon, is imaged by the imaging device 2 in only a predetermined small area on the reticle 1. This area becomes one screen to be inspected. Also, reticle 1 is
Transmission illumination is performed by a strobe device 15. Imaging device 2
The analog video signal is converted into a binary image signal by the next binarization circuit 3, and noise removal processing such as smoothing is performed as necessary. - The cutting circuit 4 cuts out binary information corresponding to a local area in one screen to be inspected, for example, a rectangular area, based on the input of the binary image signal.

This local rectangular area is - for example l 6X in the image
It is composed of an area corresponding to 16 pixels. This is the second
This will be explained in more detail with reference to figures. In FIG. 2, one screen image 100 to be inspected is scan line 1 of the imaging device 2.
Rask scanning is performed by 01. In the embodiment, it is assumed that the number of scanning lines in the image 100 is 1024 in the vertical direction.

Since the pattern on the reticle 1 is generally drawn using chrome on a glass plate, the analog video signal is a time-series signal corresponding to brightness or darkness, that is, a black and white image. The control circuit 5 generates a clock pulse 1024 times for each scanning line in the image 100, and the binarization circuit 3 samples the analog video signal for each clock pulse and outputs a pixelated binary image signal. do.

The cutout circuit 4 has a 16-bit shift register 104 and a 16-bit shift register 104.
15 stages of 024-bit shift registers 105 are connected in series, and finally a 16-bit shift register 104 is connected in series. The binary image signal is input to the first 16-bit shift register 104, and is sequentially transferred into the serial register array in synchronization with a clock pulse generated by the control circuit 5. As mentioned above, since the analog video signal for one scanning line is binarized by sampling 1024 times, the binary image signal converts the image 100 into 1024 times.
A time-series signal is obtained by dividing the signal into x1024 pixels and expressing one pixel in binary logic of "0" or "1". When sampling is performed once in the binarization circuit 3, the serial register string becomes 1
The logic value corresponding to each pixel is transferred to the next bit. In this embodiment, the binarization circuit 3 samples one scanning line with 1024 clocks, and then samples with 16 clocks during the retrace period, and the extraction circuit 4 also shifts 16 times during the retrace period. be done. And 1
The cutting section 103 consisting of six shift registers 104 is
Binary pixel information of a local rectangular area (hereinafter referred to as a window) 102 of 16×16 pixels in the image 100 is held. Further, as the scanning progresses, the window 102 moves in the image 100 at a rate of one pixel (every clock pulse), and the binary information of 16×16 pixels sequentially cut out from the entire surface of the image 100 is
The signal is input to the corner detection circuit 6 and edge detection circuit 7 shown in FIG. When the bright and dark edges within the window 102 (corresponding to the pattern edges on the reticle 1) are in a predetermined corner pattern prepared in advance, the corner detection circuit 6 classifies the edges into four types according to the corners. Output type information.

The edge detection circuit 7 detects the existence of edges that appear to be corners within the window 102 even when, for example, the corners of the imaged pattern on the reticle 1 are rounded due to the influence of the imaging optical system and are not detected by the corner detection circuit 6. On the other hand, the design data at the time of pattern creation of the reticle 1 stored on the magnetic tape (hereinafter referred to as MT) 9 is detected by the computer 10.
is loaded into.

As an example, the design data of MT9 stores the entire surface of the reticle as a set of rectangular patterns as shown in FIG. Actual circuit patterns are created by complexly combining these rectangular patterns. Here, one rectangular pattern is represented by five parameters: width W, height H, center coordinate values (x, y) in a predetermined xy coordinate system on the reticle 1, and rotation angle θ.

In FIG. 1, a computer 10 outputs design data corresponding to one screen area on a reticle 1 imaged by an imaging device 2. In FIG. Based on the input of the design data, the storage circuit 11 detects only the corners of the designed pattern edges simultaneously with the above-mentioned corner detection circuit 6, extracts four types of corner information, and stores them.

At this time, the storage circuit 11 sequentially stores corner information that should be present in one screen from the design data in an order according to the movement of the window 102 described above. And in the memory circuit 11,
For example, all corner information of pattern edges existing on one screen is held. The corner information for one screen is stored in a storage device (not shown) of the computer 10 as information for one screen. During this time, the computer 10 outputs design data for the next one screen.

(?)
One or more angle information is extracted from the design data and stored in the computer 10 from the storage circuit 11. Reticle 1 on d device
The operations up to storing the angle information corresponding to all the screens are performed before the actual comparison test.

Once the angle information has been accumulated in the storage device of the computer 10 in this manner, the actual inspection is then started. At this time, total n
The machine 10 controls a driving means 13 that moves the stage 14 two-dimensionally to align it with an area corresponding to one screen on the reticle 1 to be imaged. At the same time, the computer 10 transfers the corner information for one screen from the storage device to the storage circuit 11.

Then, in response to clock pulses from the control circuit 5, the angle information in the storage circuit 11 is sequentially sent to the angle information extraction circuit 12. The cutting area of the corner information cutting circuit 12 (hereinafter simply referred to as the corner cutting circuit 12) is determined to be smaller than the window 102 described above. The corner cutting circuit 12 sequentially cuts out corner information based on design data from 0 to (10) in synchronization with a clock pulse.

As mentioned earlier, the clock pulse of the control circuit 5 is
Since the window 102 is moved within one screen, the corner cutting circuit 12
The cutout area (hereinafter referred to as a reference window) and the window 102 move in the same direction in synchronization with the clock pulse.

The comparison circuit 8 receives the corner information output from the corner detection circuit 6, the detection result output from the edge detection circuit 7, and the corner extraction circuit 12.
information is input, and when the pattern on the reticle and the pattern on the design data are different, defect information is output to the computer 10.

Specifically, if there is even one corner information of the same type as the corner information of the corner detection circuit 6 in the reference window information, it is determined that there is no defect. Further, when the corner information is located at the center of the reference window, if the edge detection circuit 7 detects something that looks like a corner edge or a simple straight edge in the window 102, it is determined that there is no defect.

As described above, the comparison circuit 8 sequentially compares the angle information obtained from one imaged screen with the angle information held in the memory circuit 11, and provides the calculation acid 10 with defect information in real time. Output.

By performing this operation on the entire surface of one reticle, defect inspection of one reticle is completed.

In FIG. 1, control of the strobe device 15 will be described later.

Next, the angle detection circuit 6 will be explained in detail, but before that, the characteristics of the IC pattern will be explained. in general,
The IC pattern is made by combining many rectangular patterns as shown in FIG.

The twisted IC pattern is determined so that the rotation angle θ of the rectangular pattern is 45° or 135° with respect to the xy coordinate system on the reticle. It is extremely rare for the rotation angle θ to be any other value. Therefore, here, we will consider 90' and (2) 135 degrees as the angles of the pattern edges on the reticle 1 or in the design created by combining these rectangular patterns.

FIG. 4 is a diagram showing the classification of corners of pattern edges.

In the figure, 32 squares A to FFt indicate areas corresponding to the windows 102 cut out by the cutout circuit 4. In each square, the shaded area indicates a logic "1" area corresponding to, for example, a chrome surface, and the peaked area indicates a logic "0" area corresponding to a glass surface. 9 corner of pattern edge
If the angles are limited to 00° and 135°, the angles appearing within the window 102 are limited to 32 types as shown in FIG. As a method of classifying angles, it is possible to classify these 32 types as they are into 32, that is, to give them 32 different codes.
Doing so will result in 5 in binary representation for 32 classifications.
Bits (25=32) are required. Therefore, as shown in Figure 4, these 32 types are classified into four.

First, the angle of the pattern edge is classified into 92 angles of 90° and 135°, and for these two classifications, the points are symmetrical with respect to the center point in the window 102 (approximately the center pixel of the cut out 16×16 pixels). Things that have this relationship are divided into two categories so that they do not fall into the same group, and each of the four categories is given a different code. Further, inverted patterns having the same angle are placed in the same group. That is, in the figure, for example, angles A and B are in an inverted relationship, and these two angles are considered to be in the same group.

Thus, among the 90° angles, the angle A-I (is 0 in binary)
0, angles I to P are classified as 01 in binary, and 135
Among the angles of °, the angle Q-X is 10 in binary, and the angle Y-F
Assuming that F is 11, it is classified into four and represented by 2 bits. binary numbers (00, OX) representing the following four categories.

10, °11) is called a code. For example, angles B and L are both 90° angles, but because they are point symmetrical, they are given different codes. The classification based on point symmetry even if the angles are the same is related to the appearance of corner defects and the comparison operation of the comparator circuit 8. This will be discussed later.

The corner detection circuit 6 is equipped with these 32 types of corner patterns as reference patterns, so-called templates.
Matching is performed with the pattern (bit pattern) appearing in 02.

FIG. 5 shows 16×16 bits formed by a 16-stage register 104 corresponding to the window 102 cut out by the cutout circuit 4 described in FIG.

Here, for example, to detect the corner A or B shown in FIG.
All you have to do is check the logical value of the bit.

Figure 6 is an AND circuit that detects the corner of A of this person or B, and inputs ■ to ■ are all "1", and input ■
When ~O are all "0", "1" is output. In order to detect the angle of rLn, it is sufficient to remove the inverters for inputs 2 to 2 and pass the inverters through each of inputs 2 to 2.

Thirty-two such AND circuits are prepared for each of the 32 types of corner patterns shown in Figure 4.
Binary information from predetermined bits of the 16×16 bits corresponding to the reference pattern is input.

FIG. 7 shows the configuration of an angle detection circuit 6 that detects an angle using the AND circuit as described above and outputs a 2-bit code. The matching circuit 106 is connected to the A-ZZ 32 shown in FIG.
It is composed of 32 AND circuits that each output a logic "1" when a different corner is detected. Each AND circuit is connected to the cut-out section 103 of the cut-out circuit 4 shown in FIG.
Enter value information.

The 32 output signals of matching circuit 106 are divided into four groups. That is, the outputs of the eight AND circuits that detect A-H shown in FIG. 4 are converted into 8-bit data D,
, the outputs of the eight AND circuits that detect I to P are the 8-bit data D2, the outputs of the eight AND circuits that detect Q-X are the 8-bit data D3, and the eight AND circuits that detect Y to FF are the 8-bit data D3. The output of the circuit is input as 8-bit data D4 to four 8-bit input OR circuits 107, 108, 109°110, respectively. The encoder 111 inputs the four output signals of each OR circuit, encodes the 4-bit binary signals, and outputs them as codes C, , C,.

Next, the operation of this circuit will be explained.

For example, when the corner of C shown in FIG. The AND circuit outputs "0". Therefore, among the 8 bits of data D1, 1 bit becomes "1" and 7 bits become "0", so the output of OR circuit 107 outputs "1", and the other three OR circuits 108, 109, 110 both output rOJ. At this time, the encoder 111 receives input B.

is "1" and input Bt e B3 + B4 is "o" 2
A binary number obtained by subtracting 1 from the binary number encoded with the value signal is output as a 2-bit code c, IC2. That is, when the corner of the FF shown in FIG. 4 appears in the window 102, which is C, Ct-00 in the above case, the inputs of the encoder 111 are input B, -B, rOJ, input B, is "1", so the code becomes C,C,=11. Note that the encoder 111 outputs the following information when any one of the inputs B1 to B4 becomes "1", that is, when a corner is detected.
Outputs flag F. Flag F becomes “1” when a corner is detected.
" is not detected, "0" is set.

Next, the edge detection circuit 7 shown in FIG. 1 will be explained. Figure 8 shows the 9X9 set for edge detection.
Shows a rectangular area of pixels. This area is located approximately at the center of the aforementioned 16×16 pixels. Therefore, edge detection is performed based on information from an area 120 made up of 9 x 9 bits out of the 16 x 16 bit cutting section 103 that cuts out information of 1'6 x 16 pixels shown in FIG. . The position of the center bit (corresponding to the center pixel) of the 9×9 bit area 120 is shown in FIG. 1゛-6X I
Of the M bits, the bits are (H, 9) in the vertical and horizontal directions. The bits to focus on for lake and edge detection are 9×
Bits located every 4 bits around the 9 bits ■～■
There are eight.

FIG. 9 is a circuit diagram specifically showing the configuration of the edge detection circuit T. Eight exclusive OR circuits (hereinafter referred to as EX-O
Let it be R. ) 121 inputs binary signals from the peripheral 8 bits (1) to (2) of the 9×9 bit area 120. If even one of these 8 bits has a different logical value, the OR circuit 122 outputs a logical value rlJ, indicating that some edge has been detected.

Each of the eight EX-OR 1210 inputs is taken from two bits located next to each other among the eight bits of interest in the 9x9 bit area 120.

For example, suppose that something that looks like a corner appears in the 9x9 bit area 120 as shown in FIG.

The shaded area is an area of logical value "1". Then (//) Since the inputs ■ and ■ of the edge detection circuit 7 and the inputs q) and ■ have different logical values, the OR circuit 122 has a logical value of "1".
Output. Furthermore, even if a straight edge simply appears in the area 120, the OR circuit 1
22 outputs a logical value "1".

The edge detection circuit [7] described above operates in real time together with the scanning of the imaging device 2 during reticle inspection. However, in order to more reliably detect that some pattern edge has appeared in this 9 x 9 bit area 120, input all 32 bit binary signals located around the 9 x 9 bits. , check its status as described above. In this case, if all the surrounding 32 bits have the same logical value, it is not an edge of the pattern, but if even one of the 32 bits has a different logical value, an edge is detected.

Next, the memory circuit (16) 11 that reads design data from the MT 9 shown in FIG. 1 and holds corner information will be explained with reference to FIG.

1 The storage circuit 11 includes a 1024 x 1024 bit frame memory 130 that converts the design data into a binary image of "0" and "1" as a design pattern corresponding to one screen, and the image capture from the frame memory 130. Device 2
A readout circuit 131 is provided for reading out the time-series angler binary signal in accordance with the scanning order. The switch S is switched to the a side during non-inspection and to the b side during inspection. A binary image signal from the binarization circuit 3 shown in FIG. 2 is input to the b side. From the output signal of the readout circuit 131, the above-mentioned cutout circuit 4
As a result, binary information 133 of a local rectangular area in the frame memory 130 is extracted.

However, since the bit pattern generated in the frame memory 130 is based on the design data, the rectangular area has good linearity at the boundary between "1" and "0", and the rectangular area is rounded and cut. It can be extracted from an area smaller than the 16×16 bits of the output circuit 4. The extracted binary information 133 is input to a detection circuit 135 similar to the above-mentioned corner detection circuit 6, and the corners are classified into four types. The output 134 of the detection circuit 135 is a code representing the classification (00, 01, 10°11
) and a flag indicating whether or not a corner has been detected. The input/output control circuit (hereinafter referred to as 10th circuit) 136 is the output 134
Based on the input, the code is stored in the reference data memory 137 and the flag is stored in the flag memory 138.

The above storage operation is performed during non-inspection.

At the time of inspection, the switch S is set to the b side, and the output information of the cutout circuit 4 is transmitted to the corner detection circuit 6 and the edge detection circuit II described above.
7 input. At the same time, the Ilo circuit 136 outputs the code and flag stored in the reference data memory 137 and flag memory 138 as reference information 139.

Similarly, the readout circuit 131, the I10 circuit 136, and the cutout circuit 4 operate based on the clock pulse of the control circuit 5 shown in FIG. Further, the reference data memory 137 holds the corner information of only the pit rows in the horizontal direction (scanning - 8 scanning degrees) where the corners exist in the frame memory 130, and the flag memory 138 holds the corner information of only the rows of pits and pits in the horizontal direction where the corners exist in the frame memory 130. It consists of the same number of bits in the vertical direction, here 1024 bits, and the horizontal bit string (1024 bits) in the frame memory 130.
24 columns) has a corner, the corresponding flag memory 138
``1'' is held in the bit of , and ``0'' is held if there is no power. This operation is all performed by the 10 circuit 136.

Next, referring to FIG. 12, the operation of the reference data memory 137 to hold corner information will be described.

In FIG. 12, the binary information 133 extracted by the extraction circuit 4 corresponds to a rectangular area 140 (hereinafter referred to as window 140) in the figure. This window 140, as shown by the arrow,
The frame memory 130 is scanned. The reference data memory 137 stores 5 data for one horizontal scan of the window 140.
12 bits are available.

(6) It is called Mori. ) When the window 140 horizontally scans a cornered part as shown in the figure, there is no corner at the beginning of the scan, so the flag of the detection circuit 135 is "0", and the beginning of one line of memory is "0" is written in the part.

Then, every time the window 140 scans two bits, binary logic is stored in adjacent bits, one bit apart, in one line of memory. Therefore, one line of memory compresses 1024 bits of information in the horizontal direction of the frame memory 30 to 1/2 and holds it.

When the eclipse progresses further and the window 140 captures the upper left corner of the pattern 132, the corresponding bit in the memory for one line holds "1" indicating the presence of a corner, and the two bits following that bit are The codes □c, C, output by the detection circuit 135 are held. Then, rOJ is written to the corresponding bit in the memory for one line where there is no corner. In this manner (4), when the window 140 scans once the portion where the corner exists, reference data for one line is created as shown in FIG.

Therefore, if the bit pattern 132 converted into a binary image based on the design data exists as an actual pattern in the frame memory 130 shown in FIG. Information as shown in the diagram is retained. There are four corners on the bit pattern 132, and the detection circuit 135 outputs the code of each corner according to the classification shown in FIG. Similarly, since corners exist in the bit pattern in the frame memory 130 only on two horizontal bit strings, the reference data memory 130
37, reference data is held only in two lines of memory L1*LR. On the other hand, out of the 1024 bits, the flag memory 138 contains flag data for one screen in which two bits corresponding to the two horizontal bit strings of the frame memory 13000 are set to "1", and all other bits are set to "0". is created. Similarly, in the above explanation, the reference data memory 137 and the flag memory 138 hold only an area corresponding to one screen of 1024 x 1024 bits, but in reality, defects in the reticle are detected based on the input of the video signal of the imaging device f2. Before inspection, reference data and flag data are created from the design data for each screen on the reticle, and are held in the storage device of the computer 10 described above. For example, if the entire surface of the reticle is to be inspected by dividing it into 10×10 screens, that is, 100 screens, the storage device will need a memory capacity with a fixed bit length of 1024×100 bits for storing flag data. On the other hand, for storage of reference data, a memory capacity of one line of 512 bits is required, corresponding to the number of logical "1" bits in the flag memory 138.

Therefore, for example, 1024×10 in the flag memory 13B
If there are 1000 "1"s in 0 bits, a capacity of 512 bits x 100 lines is required for storing reference data.

By the way, the Ilo circuit 136 stores data in the reference data memory 137 and the flag memory 138 based on the output 134 of the detection circuit 135 as described above.

Further, during inspection, control is performed so that the stored data is sequentially output from each memory as reference information 139. The reference information 139 indicates that the flag in the flag memory 138 is “
0”, convert “0” to 512 as a time-series logic signal.
If the flag is "1", data for one line of the reference data memory 137 corresponding to the flag is output in time series.

Next, the corner cutting circuit 12 and comparison circuit 8 which operate during the inspection shown in FIG. 1 will be explained with reference to FIG. 14.

The corner cutting circuit 12 is composed of a series shift register array. A reference window 150 is defined as nine stages of 10-bit registers 160 in the series shift register array.

Each 10 bit (2/) bit register 160 contains 512 bit registers 16
1 are connected in series.

Reference information 139 from I10 circuit 136 is transferred bit by bit from a 10-bit register 160 to a serial shift register column in synchronization with the clock pulse of control circuit 5 and shifted. The timing of the shift is actually such that it shifts once every two clock pulses. 90 of 10 x 9 bits of reference window 150
The binary information 151 corresponding to bits is input to the comparator circuit 8 as is.

Here, the operations of the circuit 136, the corner cutting circuit 12, and the comparison circuit 8 will be explained.

The control circuit 5 controls the first one of one horizontal scanning line shown in FIG.
Before outputting the clock, the I10 circuit 136 checks whether the flag of the bit corresponding to the scan line in the flag memory 138 is "0" or "1", and if it is "1", One line of reference data (512 bits) in 137 is output as reference information 139, one bit every two clock pulses. If the flag is "0", then during the horizontal scan period (
1024 clock) outputs 512 bits of "0" as reference information 139 every two clock pulses. These outputs are sequentially shifted by a series of shift registers. Furthermore, during the retrace time of the imaging device 2, 10 bits of "0" are generated as the reference information 139, and the serial shift register array is also shifted 10 times. In this way, in response to the start of an examination, the reference data in the reference data memory 138 is sequentially extracted by the reference window 150. Similarly, from the start of the inspection, the corner detection circuit 6 and edge detection circuit 7 are also activated to output corner information of the pattern on the reticle.

FIG. 15(a) is an example of corner information appearing in the reference window 150. If the bit position of the 10X9 pit of the rectangular reference window 150 is expressed as (Xy), then Y=4 and y=s
The bit string in the X direction is a logical value imported from the reference data, and the other y columns have a logical value "0" imported due to the flag "0". This is indicated by a [・1 mark] in the figure.

As mentioned above, in synchronization with the cutting operation of the corner cutting circuit 12,
As shown in FIG. 2, the window 102 in one screen that captures the reticle pattern also moves. At this time, the window 102 is the 15th
When a corner of the pattern as shown in FIG.
Output =oo.

When the comparison circuit 8 detects "1" in the flag F, the binary information 151 in the reference window 150 is converted to 1 from (x, y) = (1, 1) to (x, y) = (to, 9). Examine each bit,
When you find a bit that is “1”, the following 2
The logic value of the bit and the code output by the angle detection circuit 6 are compared. If there is no such code in the reference window 150, the comparison circuit 8 outputs information ER indicating that there is a defect.
Output R. This comparison is performed when the corners of the design data pattern are formed on the reticle.

However, if the corners of the pattern are formed unreliably and the corner detection circuit 6 does not output flag F, this comparison will not be carried out, so even if the corner itself does not exist at the corresponding position on the reticle It is considered that Considering such a case, when the center bit of the reference window 150 in FIG. When there is a corner in the data, if the edge detection circuit 7 detects some kind of edge and the result is "1", the comparison circuit 8 determines that there is no defect. Information E
Output RR. However, this information ERR includes not only information regarding the presence or absence of a defect, but also information regarding the location of the defect. This can be easily obtained by counting the clocks of the control circuit 5.

Furthermore, the four classification methods of corner detection and output circuit 6 are related to the above-mentioned comparison method. This will be explained in detail with reference to FIG. In the figure, the shaded area indicates the reference .(,,'/)-n, and the dotted line indicates the corner D1 on the design data. Some corners of the pattern on the reticle are missing as a defect. When the angle detection circuit 6 classifies the angle R1+R2*R3 of the pattern on the reticle, the code is R1
(01), R2 (00).

Becomes R3 (Ol). On the other hand, only DI(Ol) exists as a code in the reference window 150.

When the corner R2 of the pattern is detected from the operation of the comparison circuit 8 described above, it is detected as a defect because no identical code exists in the reference window 150.

In this way, if some of the corners of the pattern on the reticle are missing or deformed within the area corresponding to the reference window 150, the corners such as R, , R, and the corners such as R2 may be separated from each other. By classifying, that is, using different codes, defects can be detected even with a small number of codes.

In this way, when the corner detection circuit 6 outputs a code, the comparison circuit 8 checks the flags and codes that exist in the reference window 150, so one screen captured by the imaging device 2 is Even when there is a slight deviation from a design area determined in advance from design data, the deviation can be inspected without any correction.

In addition, in the embodiment of the present invention, the matching circuit in the corner detection circuit 6 detects one corner pattern by converting a binary code from bits ① to 0013 of 16×16 bits, as shown in FIG. It's being taken out. As shown in this figure, among the 16×16 bits, there is a margin of 1 bit between the extraction bits through which the edge of the bit pattern passes, for example, between bits ■ and ■, and between bits ■ and ■. In general, ITv
The bit pattern imaged and binarized by the above method does not have smooth straight lines and tends to have irregularities. Therefore, in order to prevent angle detection from becoming impossible due to the allowance for unevenness, a margin is provided.

Although not shown in the above description of the embodiment, the stage 14
The two-dimensional position is always measured as coordinate values using a light wave interferometer or the like. The coordinate values of this stage 14 are
It is input to the computer 10. When the imaging device, for example ITv2, images the reticle 1 and starts an actual inspection, the computer 10 controls the driving means 13 according to the coordinate values of the stage 14.

That is, in stage 14, ITv2 is 1 of reticle 1.
When an area corresponding to one screen is imaged and the comparison operation as described above is completed, it moves to image an adjacent area corresponding to one screen. At this time, the ITv2 inputs one screen by the light emission of the strobe device 15 shown in FIG. This will be explained based on FIG. 17.

In FIG. 17, waveform (4) indicates the light emission timing of the strobe device 150, waveform (B) indicates the operation timing of the comparison test as described above, and waveform (C) indicates the timing for one screen from the storage device of the computer 10. The operation timing for transferring reference data and flag data to the storage circuit 11, and ITv
This represents the timing of so-called afterimage erasure, in which the light-receiving surface of No. 2 is charged with discharged charges according to the image.

Now, the area for one screen to be inspected on reticle 1 is ITV
2, that is, when the computer 10 determines that the coordinate value of the stage 14 is a predetermined value, it outputs a light emission start signal to the strobe device 15 at time t. At time t, a charge is generated on the light receiving surface of the ITV 2 in accordance with the pattern image of the area on the reticle 1 to be inspected. From time t2, the ITV 2 starts scanning and, as mentioned above, reads the code in the reference data of the storage circuit 11,
The comparison circuit 8 compares the code output from the corner detection circuit 6 to begin the inspection. Then, at time t, 1
The inspection of the screen is completed. After time t3, the computer 10
The data for the next one screen (references and flags) accumulated in the storage device of is stored in the reference data memory 137 of the storage circuit 11.
, are transferred to the flag memory 13B. When the transfer is completed at time t4, the computer 10 again outputs the light emission amount (3 start signal) to the strobe device 15.
During the so-called transfer period, afterimage erasure of the ITV2 is performed. Here, the stage 14 that moves the reticle 1 is moved by the driving means 13 between times t2 and t4 so that the ITV 2 images the next screen.

The above operations are repeated over the entire surface of the reticle 1.

In this way, only when the strobe device 15 emits a flash, the I
Since the TV 2 is inputting images, the stage 14 can actually be moved by continuously controlling its speed, rather than moving it step by step. Then, the coordinate values of the stage 14 measured by the interferometer are
The computer 10 may output a light emission start signal when the value corresponds to the next screen. Also, stage 1
4 at a constant speed, and the strobe device 15 fires a flash at regular intervals according to the moving speed, and the above-mentioned comparative inspection, transfer, (]/), and afterimage erasing operations are performed during the flashing interval. You can also do this. By doing this, inspection can be performed at high speed even when the stage 14 is moved step by step.

Further, in the above-described embodiment, one screen in which the ITv2 images the reticle 1 needs to match a designed area prepared in advance as one screen based on design data. Therefore, when placing the reticle 1 on the stage 14, the rotational deviation of the reticle is corrected and the origin of the coordinates of the stage 14 is set. This will be explained with reference to FIG.

FIG. 18(,) shows the pattern drawing area 2 in the reticle 1.
01 is subdivided into a matrix. In the figure, one square of the matrix corresponds to one screen area imaged by the ITV2. Reticle 1 is the first
When placed on the stage 14 shown in the figure by simple positioning, the two-dimensional movement of the stage 14, that is, the origin serving as the coordinate reference is set. The origin is set by clearing a counter (not shown) in the drive means 13 to zero. This counter is stage 14
The count value increases or decreases as the stage 14 moves.

This origin is determined from, for example, an area 202 corresponding to 3×3 screens located at a corner of the drawing area 201. Normally, the origin can be set in only one screen area a in the upper left corner, but if a pattern is not formed in area a, the origin cannot be determined, so for now, the origin can be set in nine areas a ''-i of the 3x3 screen.
Taking this into account, any one of these nine areas is selected and used for setting the origin.

Now, assuming that some pattern 206 is formed in one screen area i among these nine areas, one screen area i is determined as the origin. The solid line shown in FIG. 18(b) represents the area 11, that is, one screen imaged in ■Tv2.

Therefore, the needle setting data corresponding to one screen area i is read out from the computer 10 as described above, and the pattern that should exist in the design is stored in the frame memory 130 in the storage circuit 11 as shown in FIG. Develop as a pattern. Then, the time-series binary code outputted by the readout circuit 131 is input to an image reproduction device, that is, a monitor television, and a designed pattern corresponding to one screen area i is reproduced on the television screen. This area of the television screen is represented by a design area 205 indicated by a broken line in FIG. 18(b). I on this TV screen
When the image signals of the TV 2 are played back at the same time, the overlapping state of the pattern 206 on the reticle 1 and the designed pattern 207 can be observed.

The pattern 206 on the reticle 1 moves across the TV screen as the stage 14 moves, so to actually determine the origin, move the stage 14 and align it with the designed pattern 207 on the TV screen. Assuming that, all you have to do is clear the counter mentioned above.

Next, a minute rotational error of the reticle 1 is corrected (j/) by using an area corresponding to one screen in areas 203 and 204 located at two locations apart on the side. 'Here, reticle 1
Considering the virtual xy coordinates shown in Figure 18 (,), each screen area subdivided into a matrix is
It follows these 17 coordinates. If the axes of the xy coordinates are not made to coincide with the dimensional movement direction of the stage 1402, one screen to be captured by the ITv crab will shift from the designed area as the stage 14 moves.

Therefore, as explained in FIG. 18(b), first, a pattern 'k having a specific edge parallel to the X axis (referred to as the first horizontal edge) is created in one screen area j in the area 203.
Find out by ITV. At this time, the y-coordinate value of the edge is also determined from the design data. When a horizontal edge is found, this 1. Screen area j is reproduced on the television screen as described above. Then, from the design data (da ρ) corresponding to one screen area m in area 204, a design data having a second horizontal edge with the same y coordinate value as the first horizontal edge found in one screen area j is obtained. Find patterns. This operation is performed by the computer 10. If that pattern is found, the stage 14 is moved parallel to the X axis. Then, one screen area m is imaged by the ITV, reproduced on the TV screen, and the first horizontal edge and the second horizontal edge are superimposed.

If there is no second horizontal edge with the same -y coordinate value, the process is repeated by finding the first horizontal edge for one screen area k in area 203. This superposition is achieved by a micro-rotation mechanism (not shown) provided on the stage 14.
This is done by slightly rotating the reticle 1 with respect to the stage 14. At this time, the center of rotation is the area 20 of the reticle 1.
A value near 3 is desirable.

In addition, as mentioned above, when setting the origin, it is necessary to select the area on one screen in which the pattern is formed from the nine areas a-1, but this is due to the design of each area prepared during non-inspection. This can be done extremely easily by examining the feature information, that is, the corner information in the example.

In the above, the positioning in this apparatus has been explained as visual positioning using a monitor TV, but in reality, the signal read from the frame memory 130 and the
2. A servo mechanism that inputs the binary image signal output from the binarization circuit 3 to the computer 10, detects the difference between the two signals by the computer 10, and controls the stage 14 so that the difference becomes approximately zero. can be provided to automatically align the position.

In addition, as described in the explanation of FIG. 11, during actual inspection, the frame memory 130 and the readout circuit 131 do not operate, but by connecting them as shown in FIG. The comparison operation of the comparison circuit 8 can be prohibited for dust and scratches. FIG. 19 shows the connections during actual testing, with the switch S1 being switched to the b side. Before the actual comparative inspection, the imaging device 2 scans a plain image without a pattern, that is, an image showing only dust and scratches on the light receiving surface. The binary image signal output at this time is input to the frame memory 130 to generate a binary image corresponding to dust and scratches.

If dust or scratches are present, a logic "1" is input to the corresponding bit of the frame memory 130, for example, and if there is no dirt or scratches, a logic "0" is input. Next, when the imaging device 2 starts scanning the original image of the pattern, in synchronization with this scanning,
The readout circuit 131 outputs the logic (value) of the bit corresponding to one pixel being scanned in time series from the frame memory 130. This time series binary signal is input to the comparator circuit 8 as an inhibition signal INK. The comparison circuit 8 performs a comparison test as described above, and at this time, if the prohibition signal rNIr is, for example, logic "1", it either prohibits the comparison operation or indicates that there is a defect even if the comparison operation is performed. The defect information ERR is not output.

By using the frame memory 130 in this manner, it is possible to prevent in real time that the light receiving surface is inspected as if it has a defect due to dust or scratches. Further, in addition to prohibition due to dust or scratches, it is also possible to manipulate the binary image generated in the frame memory 130 to set an arbitrary area in one screen to be inspected as a comparison prohibition area.

However, it is not necessary to generate a binary image of dust or scratches on the light-receiving surface of the frame memory 130 by capturing it with the imaging device 2 every time one screen is inspected. This is because the position of dust or scratches on the light-receiving surface does not change in a short period of time (2 da). Therefore, frame memory 13
Binary image data of dust and scratches of 0 is stored in the storage device of the computer 10, and is stored in the frame memory 13 when necessary.
Just transfer it to 0. Since the amount of garbage increases over time, it is a good idea to update the data from time to time.

As described above, in the embodiments of the present invention, the objects to be inspected are reticles and masks for manufacturing semiconductor ICs, but the present invention can also be applied to masks for manufacturing other printed circuit boards with slight modifications. At this time, if the printed circuit board pattern is designed using pattern creation data using CAD (computer aided design), format the data so that it can be handled as design information for this device.
Just convert it. In addition, patterns on reticles and masks are imaged by scanning the image with an imaging device such as an ITV, but by directly scanning the pattern with a spot such as a laser beam, the reflected light or transmitted light that changes depending on the pattern is captured. It may be detected and an image signal may be generated.

---------7 Hereinafter, embodiments of the present invention have been described, but in short, the present invention provides design information on an object to be inspected, such as a noticle or a mask, by the imaging device 2 as a scanning means. The geometric pattern formed based on the pattern is scanned, and the video signal generated according to the pattern is inputted to a detection means consisting of an extraction circuit 4 and an angle detection circuit 6 for extracting information on a local area. , the corners of the pattern detected in the local area are encoded according to the angle, and one corner with the same angle and point symmetry is given a predetermined code, and the other corner is given a different code. Make sure to give the sign. The pattern is then inspected by comparing and collating the code given to the detected corner with information regarding the designed corner detected in advance from the design information by the comparing circuit 8.

Therefore, according to the present invention, there is no need to store a pattern that has been short-circuited by a scanning means such as an ITV by converting it into pixels for each scanning line, as in the prior art. In other words, it is not necessary to retain the t8gf* of the pattern that appears for each scanning line, and only the corners of the pattern are extracted and encoded, so the amount of information to be retained is It has the advantage of not requiring a storage device for loss degrees.In this case, the corners of the pattern are encoded by angle and point symmetry, and the code given to one corner of the pattern, e.g. Since a small binary number is sufficient for binary numbers, the number of information to be retained is further reduced.In addition, since the code is represented by a small value, that is, a small number of bits, the comparison can be made at high speed! It also has the advantage of being able to

[Brief explanation of drawings]

1 is a block diagram showing an embodiment of the present invention, ・FIG. 2 is a diagram showing a part of FIG. 1, especially the cutout circuit 4 in more detail, and FIG. A diagram showing a rectangular pattern as an example of read design data using xy coordinates, FIG. 4 is a diagram showing classification of corners of pattern edges, and FIG. 5 is a diagram showing a rectangular pattern cut out by the cutting circuit 4 shown in FIG. 2. 16x16 bit diagram corresponding to the window, Figure 6 is a diagram showing an AND circuit that detects the corner shown in Figure 4, Figure 7 is a diagram that detects the corner with the AND circuit shown in Figure 6, and generates a 2-bit code. Figure 8 is a diagram showing a rectangular area of 9x9 pixels set for edge detection. Figure 9 is a circuit diagram showing the configuration of the edge detection circuit. Figure 10 is a diagram showing the configuration of the edge detection circuit. 11 is a diagram showing the details of the storage circuit, FIG. 12 is a diagram showing the frame memory in the storage circuit, and FIG. 13 is a diagram showing the 9x9 bit area based on the design data.
If there is a bit pattern 132 converted into a value image,
A diagram showing information held in the reference data memory 137 and the flag memory 138. FIG. 14 shows the corner cutting circuit 12 and comparison circuit 8 that operate during inspection.
FIG. 15(a) is a diagram for explaining an example of corner information appearing in the reference window 150, and FIG.
) is a diagram showing a state in which the window 102 captures the corner of the pattern,
FIG. 16 is a diagram showing the pattern on the reticle (hatched area) corresponding to the area of the reference window 150 and the corner (dotted line) on the design data. FIG. 17 is a diagram showing the light emission timing of the strobe device (waveform (A)
), the operation timing (waveform (B)) of the comparison test, and the operation timing (waveform (C)) of transferring one screen worth of reference data and flag data from the storage device to the storage circuit, FIG. (a) is a diagram showing how the pattern drawing area in the reticle is subdivided into a matrix, and Figure 18 (b)
is a diagram showing one screen area i shown in FIG. 18(a) and the corresponding design data being reproduced on a television screen, and FIG. It is a figure which shows the connection at the time of the actual inspection of etc. [Explanation of symbols of main parts] 1...Object to be inspected2...Imaging device 4...Cutout circuit 6...Angle detection circuit 7...Edge detection circuit 8...Comparison circuit 9 ... Magnetic tape 10 ... Computer 11 ... Memory circuit 12 ... Angular information extraction circuit 106 ... Matching circuit 107 to 11G ... OR circuit 111 ... Encoder rotor, mouth, mouth 2 factors Minister's bow prisoner ~ old (field

Claims (1)

[Claims] scanning means for scanning a geometric pattern formed on the object to be inspected based on design information and generating a video signal corresponding to the pattern; detecting means that generates detection information when it is detected that a pattern in a local area of the area has a predetermined feature prepared in advance; In a device that inspects whether a pattern is formed on an inspection object as designed,
The detection means prepares two types of codes in advance, and
An encoding circuit is provided that detects a predetermined corner from the pattern in the local area, and gives one code to one corner that is the same angle and has a point-symmetric relationship, and gives the other code to the other corner. 1. A pattern inspection device comprising: a pattern inspection device that outputs a given code as the detection information.