JP2950372B2 - Reticle inspection equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a reticle inspection apparatus for inspecting pattern defects of a reticle used to form a pattern on a semiconductor wafer.

[0002]

2. Description of the Related Art A reticle is used for forming a predetermined pattern on a semiconductor wafer made of silicon or the like in a process of manufacturing a semiconductor integrated circuit device. If the reticle itself has a pattern defect, the reticle defect is transferred to many semiconductor integrated circuit devices. Therefore, it is important to inspect the reticle and correct the pattern defect if any.

In general, two methods of inspecting pattern defects on a reticle, a die comparison inspection method also called a die-to-die method and a database comparison inspection method also called a die-to-database method, have been widely adopted. I have.

The die comparison inspection method is an inspection method in which first and second dies having the same pattern and a predetermined pattern length are imaged and compared on one reticle. On the other hand, the database comparison inspection method is an inspection method in which a die on a reticle is imaged and compared with a die having a regular pattern created in a database in advance. In general, the time required to compare the data between dies or between dies and data is much longer than the time required to image the reticle dies in either inspection method. is there. Due to this situation, there is a problem that a waiting time is generated in the image pickup system and, as a result, the entire inspection time becomes longer.

As a countermeasure against the above problem, the present inventor has proposed a technique for shortening the comparison processing time. According to this method, each frame is sequentially scanned by a scanning optical system in a form in which a continuous first and second die are divided into a plurality of overlapping frames having a predetermined frame length, and a plurality of scanned frames are prepared. The images are sequentially distributed to the image comparison units, and the respective frames of the first die and the corresponding frames of the second die are image-compared in parallel by a plurality of image comparison units.

Consideration has been given to applying such a parallel processing method to a die comparison inspection system using a single scanning optical system. The parallel processing type die comparison inspection method using a single scanning optical system is advantageous in terms of economy because parallel processing can be performed without preparing a plurality of expensive scanning optical systems.

[0007]

In a parallel processing type die comparison inspection system using a single scanning optical system, an image comparison unit in which a plurality of frames of both first and second dies to be compared with each other are prepared. Is difficult to distribute to the same image comparison unit.

This will be described with reference to FIG. In this conventional method, for a reticle in which first and second dies having the same pattern and pattern length are arranged in parallel in the pattern length direction, a single scanning optical system uses the first and second dies. It continuously scans and outputs a series of image signals. The frame distribution unit converts a series of image signals from the scanning optical system into a frame having a predetermined frame length and a constant frame overlap (the number of scans) a.
15 frames (frame number = 1)
15), and these 15 consecutive frames are sequentially output to four distribution destinations. Four image comparison units (hardware numbers = 1 to 4) as four distribution destinations
In parallel with the frame from the frame distribution unit, the image of the frame of the first die and the corresponding frame of the second die are compared to detect a pattern defect in the second die.

However, the frame of frame number 8 extends over the rear end of the first die and the front end of the second die, and the amount of mismatch (the number of scans) N between the front end of the second die and the front end of the frame of frame number 9 is N. It is only shifted. Moreover, while the start frame (frame number 1) of the first die is input to the image comparison unit of hardware number 1,
The start frame of the second die to be compared with the start frame of the first die (frame number 8) is input to the image comparison unit of hardware number 4, and each subsequent frame is also input to a different image comparison unit. This makes image comparison impossible.

In order to avoid such a situation, a buffer memory for temporarily storing a whole series of image signals corresponding to the entire lengths of the first and second dies arranged in parallel is provided between the scanning optical system and the frame distributor. A method is conceivable in which data is appropriately extracted from the buffer memory when the data is divided into a plurality of frames. However, this method is not rational because it requires a large-capacity buffer memory and requires a long time for memory access.

It is an object of the present invention to provide a reticle inspection apparatus which has a simple structure and can detect a pattern defect of a reticle in a short time by comparing images of dies in parallel.

[0012]

According to the present invention, a reticle in which first and second dies having the same pattern and a predetermined pattern length are continuously arranged in the pattern length direction is used. The first and second dies are sequentially scanned in a form in which the first and second dies are divided into a plurality of overlapping frames having a predetermined frame length, and the scanned frames are sequentially distributed to a plurality of distribution destinations. Frame and the corresponding second frame
In a reticle inspection device that compares images of each frame of the die in parallel at the plurality of distribution destinations and detects a pattern defect in the second die, the predetermined frame length and the predetermined pattern length Reticle inspection apparatus characterized in that it has a frame overlap adjusting means for calculating the relationship between the frames and using the calculated relationship to adjust the overlap length between the frames.

According to the present invention, there is also provided the reticle inspection device for adjusting the overlap length such that the frame overlap adjusting means adjusts the overlap length so that the tip of the second die coincides with the tip of the frame.

According to the present invention, further, the frame overlap adjusting means adjusts the overlap length such that the number of frames of each of the first and second dies is a natural number times the plurality of distribution destinations. The reticle inspection device to be adjusted is obtained.

According to the present invention, for a reticle in which first and second dies having the same pattern and a predetermined pattern length are continuously arranged in the pattern length direction, the first and second dies are continuous. Is divided into a plurality of overlapping frames having a predetermined frame length, and the respective frames are sequentially scanned, and the scanned frames are sequentially distributed to a plurality of distribution destinations. In a reticle inspection apparatus for comparing a corresponding frame of the second die with an image in parallel at the plurality of distribution destinations and detecting a pattern defect in the second die, the predetermined frame length and the A frame overlap adjusting unit that calculates a relationship with a predetermined pattern length and adjusts an overlap length between the frames using the calculated relationship. Reticle inspection device that can be obtained.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A reticle inspection apparatus according to one embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a reticle inspection apparatus according to one embodiment of the present invention. In FIG. 1, the present reticle inspection apparatus is used for a reticle in which first and second dies having the same pattern and a predetermined pattern length are continuously arranged in the pattern length direction. Is a predetermined frame length and is divided into a plurality of overlapping frames, and sequentially scans each frame to image a reticle. A scanning optical system 10 using, for example, a laser beam, and a series of images from the scanning optical system 10 An A / D conversion unit 20 for converting a signal from analog to digital, a frame distribution unit 30 for sequentially distributing a scanned frame to a plurality of distribution destinations,
A frame buffer for temporarily storing frames of the first die is provided, and each frame of the first die and each corresponding frame of the second die are image-compared in parallel at a plurality of distribution destinations. (Four in this example) image comparison units 50-1 to 50-4 as a plurality of distribution destinations for detecting a pattern defect in the second die, and control for controlling the overall operation of the present apparatus. And a part 60.

Further, the reticle inspection apparatus has frame overlap adjusting means for calculating a relationship between a predetermined frame length and a predetermined pattern length, and adjusting the overlap length between frames by using the calculated relationship. ing. The frame overlap adjusting means is included in the frame distributor in this example. The frame overlap adjusting means is arranged such that the tip of the second die coincides with the tip of the frame, and the number of frames of each of the first and second dies is a natural number multiple of the plurality of image comparison units 50-1 to 50-4. The overlap length is adjusted so as to be a number (a natural number multiple of 4).

FIG. 3B is a conceptual diagram of a reticle for explaining the operation of the present apparatus.

As shown in FIG. 3A, conventionally, the overlap length a between the frames is constant, and the frame of frame number 8 extends over the rear end of the first die and the front end of the second die. , The tip of the second die and the tip of the frame of frame number 9 are shifted by the amount of mismatch (number of scans) N. Moreover, while the start frame of the first die (frame number 1) is input to the image comparison unit of hardware number 1, the start frame of the second die to be compared with the start frame of the first die (Frame number 8) is input to the image comparison unit of hardware number 4, and the subsequent frames are also input to different image comparison units, so that image comparison is impossible.

On the other hand, in the present apparatus, as shown in FIG. 3B, the end of the second die coincides with the end of the frame, and the number F of frames of the first and second dies is plural. Of the image comparison units 50-1 to 50-4 (repetition cycle K
= 4), so that the overlap length is adjusted to be a natural number multiple of (4). Thus, each frame of the first die and each frame of the second die to be compared are distributed (input) to the same image comparison unit.

The overlap length and the frame for which the overlap length is changed are based on the following equations. In the following formula, b is the overlap length of the first half of the die, c is the overlap length of the second half of the die, d is the number of frames in the second half when the overlap length is c, S and M are quotients obtained by dividing N by F, and It is too much.

When N ≦ F: b = a, c = a + 1, d = N Equation 1 When N> F: b = a + S, c = b + 1, d = M Equation 2 FIG. FIG. 3 is a block diagram illustrating a detailed configuration of a first embodiment.

In FIG. 2, a frame distribution unit 30 includes a register control unit 31 and a changed frame setting register 32.
, A first half overlap position register 33, a second half overlap position register 34, a frame comparator 35, a selector 36
, A frame counter 37, an OR circuit 43, a scan counter 38, an OR circuit 39, a scan number comparator 40, a frame start control unit 41
And frame control units 42-1, 42-2, 42-3, and 42-4.

The operation of the present apparatus will be described below with reference to FIGS.

The register control unit 31 stores a value calculated in advance in each register before inspecting the reticle. Specifically, ((the number F of frames of each of the first and second dies)-(the number d of frames in the latter half when the overlap length c of the latter half of the die)) is stored in the change frame setting register 32.
The first half overlap position register 33 stores ((the total number of scans per frame P)-(the first half overlap length b)), and the second half overlap position register 34 stores (((the total number of scans P per frame)). -(Overlap length c of the second half of the die)
Is set.

Here, for example, P = 20, the overlap length a between frames a = 1, the mismatch amount N = 13, and the image comparison unit 50-1
Assuming that the number (repetition cycle) K = 4 and the number F of frames of the first and second dies is F = 8, the aforementioned N
> F corresponds to (Equation 2). N / F = 13
/8=1...5, where S = 1 and M = 5. Therefore, b = 2, c = 3, and d = 5 are obtained from Expression 2.

Therefore, the set value of the change frame setting register 32 is "3" (Fd), and the first half overlap position register 33
Is "18" (P-b), and the set value of the second half overlapping position register 34 is "17" (P-c).

When the inspection is started, first, a scan start pulse is input to the frame start control section 41, the frame counter 37, and the scan counter 38, and the frame counter 37 and the scan counter 38 are reset and the values are respectively reset. It becomes “0”.

The frame comparator 35 stores the count value of the frame counter 37 and the changed frame setting register 3
Then, when the count value of the frame counter 37 is larger than or equal to the set value of the change frame setting register 32 (A ≧ B), the select signal is made high and output to the selector 36. On the other hand, A <B
At this time, the select signal is low. Here, the count value of the frame counter 37 at the time of input of the scan start pulse is “0”, and the change frame setting register 32
Is "3", the select signal is low.

The selector 36 is connected to the frame comparator 3
5 is low, the set value of the first half overlap position register 33 is selected, while the select signal is h.
When it is high, the setting value of the second half overlapping position register 34 is selected and output to the scan number comparator 40. Since the select signal is low when the scan start pulse is input, the set value “18” of the first half overlapping position register 33 is output to the scan number comparator 40.

The frame start control unit 41
When the scan start pulse is input, a start signal is sent to the frame control unit 42-1. When one scan pulse starts to be continuously input to scan the first die, the frame control unit 42-1 starts fetching A / D data from the time when the start signal from the frame start control unit 41 is received. To start. And 1
An image corresponding to a frame (P = 20 scans) is acquired, and an image signal is transferred to the image comparison unit 50-1.

On the other hand, the scan counter 38 counts one scan pulse and outputs the count number to the scan number comparator 40. Scan number comparator 40
, Sequentially compares the number of scans with the overlapping position, and outputs a coincidence pulse (A = B) to the frame start control unit 41 when they coincide with each other. This coincidence pulse passes through the frame start control unit 41, the frame counter 37, and the OR circuit 39, and is output to the scan counter 3
8 is input. Here, initially, the overlapping position 18 in the first half is used.
Therefore, when the scan count reaches “18”, a coincidence pulse is output from the scan number comparator 40.

The frame start control unit 41
When the coincidence pulse is input, the next frame control unit 42-2
To send a start signal. The frame control unit 42-2 includes:
The acquisition of A / D data is started from the time when the start signal comes. Then, an image for one frame is acquired, and an image signal is transferred to the image comparison unit 50-2. That is, the frame of frame number 1 and the frame of frame number 2 have an overlap length for two scans.

Thereafter, the frame start control unit 4
1 switches the frame control unit and sends out a start signal each time a coincidence pulse is input. Frame control unit 4
When transmission to 2-4 is completed, the frame control unit 42-1 is returned again.
And the transmission of the start signal is repeated. Each frame control unit starts taking in the A / D data from the time when the start signal arrives, acquires an image for one frame, and transfers the image signal to each image comparison unit. This operation is repeated each time a start signal is input.

The frame counter 37 counts the coincidence pulse from the scan number comparator 40 as one frame number, and sends out the fetched frame number to the frame comparator 35.

The frame count advances, and the count value of the frame counter 37 is changed to the changed frame setting register 32.
Becomes “3”, the frame comparator 35
Makes the select signal (A ≧ B) high. When the select signal becomes high, the selector 36 selects the set value “17” of the second-half overlap position register 34 and outputs it to the scan number comparator 40. Therefore, the overlap length between subsequent frames is equivalent to three scans.

When the loading of the first die is completed, the second
Are input to the frame counter 37 via the OR circuit 43 and the frame counter 3
The count value of 7 is reset to “0”. When the count value of the frame counter 37 becomes "0", the select signal of the frame comparator 35 becomes low again, and the selector 36 selects the value of the first half overlap position register 33 and sends it to the scan number comparator 40.
Therefore, the overlap length between frames returns to two scans.

Thereafter, a frame is taken in the second die in the same sequence as that of the first die, and the image signal of the second die is divided into frames in the same manner as the image signal of the first die. Distributed to

As described above, by appropriately switching the overlap length between the frames, the tip of the second die and the tip of the frame are made to coincide with each other, and the frames of the first and second dies to be compared with each other are determined. It can be distributed to the same image comparison unit.

[0041]

The reticle inspection apparatus according to the present invention comprises a frame overlap adjusting means for calculating a relationship between a predetermined frame length and a predetermined pattern length, and adjusting the overlap length between frames using the calculated relationship. Therefore, with a simple configuration, it is possible to compare the images of the dies in parallel and detect the pattern defect of the reticle in a short time.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a reticle inspection device according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a detailed configuration of a frame distribution unit illustrated in FIG. 1;

FIGS. 3A and 3B are conceptual diagrams for explaining the operation of the reticle inspection apparatus according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Scan optical system 20 A / D conversion part 30 Frame distribution part 31 Register control part 32 Change frame setting register 33 First half overlapping position register 34 Second half overlapping position register 35 Frame comparator 36 Selector 37 Frame counter 38 Scan counter 39, 43 OR circuit 40 Scan number comparator 41 Frame start control unit 42-1, 42-2, 42-3, 42-4 Frame control unit 50-1, 50-2, 50-3, 50-4 Image comparison unit 60 Control unit

Claims (4)

(57) [Claims] 1. A reticle in which first and second dies having the same pattern and a predetermined pattern length are successively arranged in the pattern length direction, the continuous first and second dies are separated by a predetermined frame. Each frame is sequentially scanned in a form divided into a plurality of long and overlapping frames, and the scanned frames are sequentially distributed to a plurality of distribution destinations, and each frame of the first die and the corresponding A reticle inspection apparatus that compares images of respective frames of two dies in parallel at the plurality of distribution destinations and detects a pattern defect in the second die, wherein the predetermined frame length and the predetermined pattern length And a frame overlap adjusting means for adjusting an overlap length between the frames using the calculated relationship. Inspection equipment. 2. The reticle inspection apparatus according to claim 1, wherein the frame overlap adjusting means adjusts the overlap length such that a tip of the second die coincides with a tip of a frame. 3. The frame overlap adjusting means adjusts the overlap length such that the number of frames of each of the first and second dies is a natural number multiple of the plurality of distribution destinations. 3. The reticle inspection device according to 1. 4. A scanning optical system for sequentially scanning each frame and imaging a reticle in a form in which the continuous first and second dies are divided into a plurality of overlapping frames having a predetermined frame length. , The frame
Beam overlap with the adjusting means, a frame distribution section sequentially distributed to a plurality of distribution destinations on the respective frames are sequentially scanned to adjust the overlap length between them, temporarily stores frames of the first die A frame buffer for detecting a pattern defect in the second die by comparing images of each frame of the first die and corresponding frames of the second die in parallel with each other; The reticle inspection apparatus according to claim 1, further comprising a plurality of image comparison units serving as distribution destinations.