JPS58158923A - Common defect detecting method of regular pattern - Google Patents

Abstract

PURPOSE:To peform common defect detection at little misdetection, by a method wherein the pattern of a first sheet is compared to the pattern of a second sheet or subsequent sheets in prescribed coordinate region about defect coordinate of the first patterns, and common defect is found. CONSTITUTION:Defect signal of pattern in a first sheet is detected by a detect discrimination circuit 15b. The defect signal is correlated to address signal from X-Y coordinate signal generating unit 14 and the coorelation signal is stored in RAM 107 of a defect recognition system 16. Defect signal of pattern in a second sheet is detected, and the defect signal is correlated to the address signal and the correlation signal is stored in the RAM 107. The defect data of pattern in the first sheet and the defect data of pattern in the second sheet both stored in the RAM 107 are compared by CPU 105 so as to determine whether common defect exists or not. The decision is effected regarding whether defect coordinate of pattern of the second sheet exists in prescribed coordinate region, for example, in 3X3 coordinate region about defect coordinate of pattern of the first sheet. In this constitution, misdetection is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inspection method using a laser beam diffraction pattern spatial frequency filtering method for detecting defects in a regular pattern using a light diffraction phenomenon, and in particular to an inspection method for inspecting a plurality of patterns. The present invention relates to a method for detecting a common defect in a plurality of patterns to be inspected, each of which has unit apertures regularly arranged, from bright spots appearing on an inverse Fourier transform surface.

Laser light pattern spatial frequency filtering method (hereinafter simply referred to as spatial filtering method) using laser light has recently been used as a method for detecting defects in regular patterns such as metal filters and IC masks.
is now being used. This spatial filtering method avoids the complexity of the conventional method of scanning a two-dimensional image with a microscopic beam and processing the resulting output signal with an electronic computer. , there are no problems such as long processing time or high cost, and two-dimensional ll1g1
It has the advantage of easy spatial parallel processing and high-speed inspection using an inexpensive optical system. For this reason, it is mainly used as a defect inspection device for industrial products having regular two-dimensional patterns, such as metal meshes and IC masks.

The basic optical system configuration of this type of defect inspection apparatus is shown in FIG. That is, the laser beam 2 emitted from the laser oscillator 1 is expanded by the collimator 3 and becomes a round beam 4, which reaches the object to be inspected 5Kfi. The object to be inspected 5 is placed on the front focal plane of the 7-Lier transformation lens 7, and KFi is placed on the back focal plane.
A Fourier transform spectrum of the object to be inspected 5 appears due to the light diffracted when passing through the object to be inspected. Further, a spatial filter 8 (for example, a negative photographic film recording the intensity distribution of the Fourier transform spectrum, a directional high-cut spatial filter, etc.) is disposed on the back focal plane of the 7-lier transform lens 7, and the object to be inspected is Among the Fourier transformed spectra of the sample 5, only the spectrum corresponding to the normal pattern is absorbed by the spatial filter 8, and the spectrum corresponding to the defective pattern is transmitted.

Here, since the spatial filter 8 is arranged on the front focal plane of the inverse Fourier transform lens 10, the light 9 transmitted through the spatial filter 8 is inversely Fourier transformed by the inverse 7-lier transform lens l (1, A spatially filtered inverse Fourier transform image, that is, only the defective portion of the object to be inspected 5 appears on the back focal plane of the conversion lens lO.This is detected by the photodetector 11.Then, the inverse Fourier transform image of the inverse Fourier transform lens appears. If a screen is placed in place of the photodetector 11 on the back focal plane, the defect will appear as a bright spot on the screen, making it possible to visually recognize the defect.

The pattern to be inspected in this defect inspection device is, for example, the second
As shown in the figure, one-unit rectangular apertures P are arranged regularly, and defects in turns include a third
There is one as shown in Figure (A)=-(D).

Therefore, these defects in the pattern to be inspected can be confirmed.
! It is also necessary to quickly detect KL.

Hitherto, several proposals have been made by the applicant of this patent as this type of defect inspection device (for example, Japanese Patent Application Laid-Open No. 11-117
No. 106, JP-A-56-133830, etc.).

However, with these defect inspection devices, pattern 1
Since each sheet is inspected, it is not possible to detect essential defects in the manufacturing process, such as defects in the original mask, defects in the exposure device, defects in the etching device, and other defects that result in the same type of defective products occurring one after another.

The present invention has been made in view of the above-mentioned points. First, the first object to be inspected is moved in the X direction and the Y direction within a plane perpendicular to the optical axis to detect the address and detect defects on the entire surface of the object to be inspected. Then, defect detection scanning is performed for the second and subsequent sound objects in the same way, and the defect detection scan is performed for the second and subsequent sound objects in a 93x3 coordinate range centered on the defective coordinates of the first pattern. The present invention provides a method for comparing common defects and detecting common defects.

An embodiment of the present invention will be described below with reference to FIGS. 4 to 1i.

Since FIG. 4 shows an example of the configuration of a rounding device for implementing the present invention, this device is used in combination with the optical system of FIG. 1.

In this figure, the output light is a half mirror, which extracts a part of the output light from the laser oscillator 1 and supplies it to the control signal generation unit 13 to detect fluctuations in the laser intensity. photodetector 11
The output of the defect detection unit 15 which is optically coupled to is corrected.

The output line of defect unit 15 is provided to defect recognition system 16 . Address signals from the x-y coordinate signal generating unit 14 are also seen in the defect recognition system 16. This address signal is given every time the object to be inspected 5 moves a predetermined distance in accordance with the movement in the X direction and the Y direction within a plane perpendicular to the optical axis.

As a result, the defect recognition system 16 detects the defect.
The defect detection signal from the X-Y coordinate signal generating unit 15 is correlated with the address signal from the X-Y coordinate signal generation unit 14 to determine the defect position coordinates, and a printout is sent together with the input information from the keyboard 17, for example, via the printer 8. can.

FIG. 5 shows the signal processing system having the configuration shown in FIG. 4 in more detail. First, the control signal generation unit 13 for correcting laser intensity fluctuations consists of a laser intensity fluctuation correction signal generation circuit 13m and a control signal generation section 13b, and when the intensity of the laser beam changes, it corrects the laser intensity fluctuations. The output of the signal generation circuit 13m changes, and based on this, the control signal generation section 13b1.'1 forms a control signal and supplies it to the defect discrimination circuit 15b of the defect detection unit.

The defect determination circuit 15b provides the data interface 103 of the defect recognition system 16 with defect data obtained by determining the level of the signal from the photoelectric converter 15m optically coupled to the photodetector 11.

In the defect recognition system 16, the address signal from the x-y coordinate signal generation unit 14 is given to the address interface 101, and the address signal of the inspected object 5 is given to the defect recognition system 16 via the x-y stage controller 19 and the The X-Y stage interface 102 exchanges signals for scanning movement. Address interface 101, X-Y stage interface 1
02 and data interface 103 are sent to the CPU 105 and RAM 107 via a path line 104.
It performs calculations based on inputs from the program in the ROM 106 and the switches 109, keyboard 110, etc. from the console interface 108, and outputs its output via the console interface 108.7'11111.

FIG. 6 shows an example of scanning of the object 5 to be inspected using the apparatus of the present invention. This scanning can be understood as a relative movement between the object to be inspected 5 and the photodetector 11, and the photodetector 11 is configured as an array in which a predetermined number of unit detectors are linearly arranged. Defect detection scanning is performed by moving the inspection object 5 relative to the inspection object 5 in a direction perpendicular to its longitudinal direction.

If the length of the array is L, then the photodetector 11 is 1 in the X direction.
After scanning once, the photodetector 11 is moved by L in the Y direction to perform the next scan in the X direction, and then the photodetector 11 is moved by L in the Y direction.
By repeating the operation of moving the inspection object 1 and scanning in the X direction, the entire surface of the object to be inspected 5 can be scanned. In this case, it is reasonable to perform scanning in the X direction by alternately repeating scanning in one direction and the other direction as shown in the figure. The amount of movement of the photodetector 11 in the X direction and the Y direction is detected by a linear encoder or the like, and this detection signal is used as an address signal.

FIG. 7 shows an example of the configuration of a position detecting section for detecting and scanning only a predetermined surface of the object to be inspected when performing the scanning shown in FIG. 6. In this case, a marker M is provided at a predetermined portion of the object to be inspected 5, and this marker M is fixedly attached to a sensor S, , S, or the like, which is fixed in a predetermined positional relationship with respect to the photodetector 11.

and 81.84: The inspection object 5 is fed in the X direction and the Y direction by detecting the following. Sensor S1.
The range between S2 is the drive system acceleration range'), S3+84
The same goes for the one in between. The reason why there are two acceleration ranges is because the object to be inspected 5 is transported in two directions in the X direction.

As shown in FIG. 6, the feeding in the X direction and the Y direction is repeated, and when the object is sent in the X direction, the surface to be inspected of the object 5 is
is scanned for defect detection. This scanning is repeated a predetermined number of times t
9. When the inspection is repeated the number of times covering the entire surface of the object 5 to be inspected, it returns to the setting position.

These operations are performed by the CPU 105 in the defect recognition system 16 shown in FIG. an X-Y stage controller 19 via an x-y stage interface 102;
This is done by applying the X-Y stage Drino (20).

Now, when the switch 109 of the defect recognition system 16 is operated, a start signal is generated, and the stage on which the inspected object 5 is mounted is moved from the setting position in the X direction via the X-Y stage controller 19 and the X-Y stage driver. begins to move in one direction. When marker M is detected by sensor S1, this detection signal is, for example, x-
The signal is given to the system 16 via the y-coordinate signal generation unit 14, and based on this signal, the system 16 operates the X-Y stage controller 19 and the X-Y stage driver 20 to accelerate the stage. Then, at the same time that marker M is detected by sensor S2, xy position l11g! An address counter/tally reset signal is applied from the i-number generation unit 14 to the cinematem 16, and after the count contents of an address counter (not shown) are cleared, counting of address signals is started. From now on, marker M is sensor S.
The defect detection scanning of the inspected object 5 is performed until a defect is detected in step 3, and the resulting defect data is sent to the system 16, which generates defect position data based on the data from the X-Y coordinate generation unit 14 by interrupt processing. Calculated, this is RAM107
will be written to.

When the marker M is detected by the sensor S, the defect detection scan is completed, and the object 5 to be inspected is then sent in the X direction until it passes the marker M or the sensor S4. When the marker M passes the sensor S4, the system 16
, the stage is moved by one pitch (L) in the Y direction by applying an X-Y stage driver, and then the stage is moved in the opposite direction to the X direction. In this case, marker M is first detected by sensor S4 and then S, , S2 . The signals are sequentially detected by Sl. Then, the area between sensors S4 and 83 becomes an acceleration area, and the area between sensors S and 82 becomes an area to be inspected. When passing the position of S4, the Y direction movement is performed again and the
A forward feed in the direction is performed.

When the entire surface of the inspected object 5 is scanned after such stage feeding, a scan stop signal is given from the system 16 to the X-Y stage controller 19 and the X-Y stage drino (head), and defect detection scanning is started. At the same time, the stage is returned to its setting position.

The coordinates written together with the defect data by this defect detection scan can be expressed as follows. In other words, a) Number of apertures of the photodetector; N A) Number of apertures of the photodetector; n (1, 2, 3...N)
c) Length in the Y direction of one aperture of the photodetector: l 2) Number of scans;
When I (1, 2, 3...), the defect coordinates (X
17) is expressed as ・EX,/(1,N-n)], and the Y-direction scanning amount, that is, the Y-direction feed amount, is L=N・! It is expressed as

FIGS. 8 and 9 are flowcharts showing the procedure of the method of the present invention performed using the above-mentioned apparatus, and the following description will be made according to this flowchart.

First, the device is started and a defect signal of the first notch turn is detected (81). 6cx when detecting this defective signal
, detect the address signal from the y stage (8z).

Then, by associating the defect signal with the address signal, RAM1
07 (FIG. 5) (S3).

Next, a second pattern is set in the apparatus and a defect signal of the second pattern is detected (84). When this defective signal is detected, the address signal from the XSY stage is detected (
8sJ. Then, the defect signal and address signal are stored in association with each other in the RAM 107 (FIG. 5) (S6).

The first sheet (turn defect data) and the second sheet (turn defect data) stored in the RAM 107 (Fig. 5) are stored in the CP.
U105 (FIG. 5) is used to compare and determine whether there is a common defect. This determination is made as to whether or not the defect coordinates of the second pattern exist within a 3×3 coordinate range centered on the defect coordinates of the first pattern (S7).

As a result, the tolerance for minute irregularities in defect positions between objects to be inspected and the mechanical detection position accuracy of the device is widened, and it is possible to prevent common defects from being overlooked.

If the defect coordinates corresponding to the second pattern do not exist, the defect coordinates are canceled (Ss)L, and if they do exist, the common defect coordinates are output (s9). This output is performed, for example, by a printer 111K (FIG. 5).

FIG. 9 shows step 5I-83 (84 to 86) of detecting and storing the defect signal and address signal in FIG. 8 in detail, especially step 5a (Ss). explain.

That is, after detecting a defective signal (Sl or 84) and detecting an address signal (82 or Ss), it is checked whether the defective addresses are consecutive (S11).
do. First, it is determined whether or not it is continuous (812).
and if it is not consecutive, store the defective address (813)
do. When memorizing, judge whether there is memory overflow (
814) L/, if the memory is over, send the message (Sls); otherwise, move to the next step in FIG.

On the other hand, if it is continuous, the region designation line is calculated (Sls) to divide the pattern portion of the object to be inspected into regions, and then it is determined whether or not the defect is still within the region designation line (817). If it is within the area, the defective address is stored (81g).

If it is outside the inspection target area, it is first determined whether the number of consecutive pieces in the Y direction is greater than or equal to a predetermined number ED(Y) (819), and if it is, the defective address is canceled (8201).

Next, the same procedure is adopted for the X direction.

As a result, the defect address is memorized only when there are abnormally consecutive defects even outside the inspection target area (8183
10 shows in more detail the procedure for checking the continuity of defective addresses in FIG. 9.

First, it is determined whether the defect is at the edge of the defect detection scanning range (8111), and if it is not, the continuity in the Y direction is checked (8114), and then the continuity in the X direction is checked (8114). (8115) Do. On the other hand, at the end of the defect detection scanning range, consideration must be given to the possibility that defects are continuous between the adjacent defect detection scanning range. Therefore, the end defect address is stored in memory (811
2) L, check the edge of the next defect detection scan (s11
3J and check the continuity.

By detecting this defect continuity, the inspection range can be expanded to the vicinity of the periphery of the pattern of the object to be inspected.

FIGS. 11(a) and 11(b) show examples of the object 5 to be inspected by the method of the present invention; FIG. 11(a) is an IC mask, and FIG. 11(b) is a shadow mask. In the case of an IC mask, the pattern of the object to be inspected is circular, and a square area designation line B indicated by a broken line is set inside this circle.

In addition, in the case of a shadow mask, the pattern part A has a CRT film surface shape, and a rectangular area is specified inside it.
Set.

As described above, the present invention detects the address of the first object to be inspected by moving it in the X direction and the Y direction within a plane perpendicular to the optical axis in an optical system using a laser beam diffraction pattern spatial frequency filtering method. A defect detection scan is performed on the entire surface of the object, and then a defect detection scan is performed on the second and subsequent objects in the same manner, and a 3X3 image centered on the defect coordinates of the first pattern is
Since the coordinate range is compared with the second and subsequent patterns to detect common defects, it is possible to limit the detection target and perform common defect inspection with fewer oversights. Common defects are highly likely to develop into serious problems such as loft-out, and being able to reliably detect common defects is extremely advantageous in terms of manufacturing technology.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the optical system configuration of a defect inspection apparatus using a spatial filtering spatial frequency method used in the present invention, and FIG. 2 is a diagram showing a pattern in which unit rectangular openings are regularly arranged as an example of an inspection target. 30(A) to 30(B) are diagrams showing examples of defects in the pattern of FIG. 2, FIG. 4 is a diagram showing a defect signal and scanning signal detection system of the device according to the present invention, and FIG. 1s8 is a diagram showing an embodiment of the present invention, FIGS. 6 and 7 are explanatory diagrams of the scanning operation for defect detection in the above embodiment, FIG. 1s8 is a flowchart showing the procedure of the method of the present invention, and FIG. , FIG. 1θ is a flowchart showing a procedure that can be performed in combination with the procedure shown in FIG.
FIGS. 1(a) and 1(b) are explanatory diagrams showing examples of objects to be inspected by the method of the present invention. 1... Laser oscillator, 3... Collimator, 5...
Object to be inspected, 8... Spatial frequency filter, 11... Optical inspection device, 15... Defect detection unit, 16... Defect recognition system. S...sensor, M...marker. Applicant's agent Kiyoshi Inomata Figure 1 (A) (B) (C)
(D)-( Figure 10

Claims (1)

[Claims] 1. A pattern in which unit apertures are regularly arranged is arranged in an optical system using a laser beam diffraction pattern spatial frequency filtering method to obtain an inverse Fourier transform image, and by this transformation, the pattern is In the method for detecting defects, a first object to be inspected is
direction, and in the Y direction to perform address detection while performing defect detection scanning on the entire surface of the object to be inspected, and then scanning the second object to be inspected for defect detection in the same manner as in the first object to be inspected;
This was obtained by testing the first test object. A method for detecting common defects in a regular pattern, characterized in that common defects are detected by comparing the inspection results of the second object to be inspected in a predetermined coordinate range centered on the defective pallet or mark. . 2. The method according to claim 1, wherein the predetermined coordinate range is a 3×3 coordinate range. 3.4I Claims 1 to 9 are the method according to claim 2, wherein the defect detection scan of the second object to be inspected is performed to detect pattern surrounding information by detecting continuity of defects. A common defect detection method for regular patterns that enables discrimination from defect information.