JPH02141646A - Foreign-matter inspecting apparatus - Google Patents

Abstract

PURPOSE:To make it possible to perform the optimum correction by providing a sensitivity correcting means which corrects the detected sensitivity in correspondence with a scanning position based on sensitivity correcting characteristics which are read out of storing means. CONSTITUTION:Temporary basic-sensitivity correcting characteristics Xc are selected through a terminal device 6 in order to determine a reference correcting value. A body to be inspected which is to become a standard is prepared. Then, a computer main body 20 reads the data of the characteristics Xc out of a disk device 35. The data are sent into a RAM 23a through the CPU 2. A signal 32 in compliance with the characteristics Xc is applied to a voltage controlled amplifier 5 as a control volt age. Under this state, foreign matter inspection for the body to be inspected is performed with laser light. A signal PS is sent into correcting signal generators 22 and 23 from a counter 4. Correcting signals 31 and 32 are outputted and multiplied in a multiplier 26. The signals are applied into the amplifier 25 as correction control signals. Then an original signal S1 is multiplied by a signal 11 in the amplifier 5. The result is sent into the CPU 2 as a signal 10. When the magnitude of the signal 10 is larger than a certain level in the CPU 2, the foreign matter data are displayed on a display device 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a foreign matter inspection device using a light beam.

[Prior Art] Conventionally, there has been an apparatus that scans an object to be inspected using a light beam and inspects foreign objects on the object by using reflected light or scattered light from the foreign object on the object. It is used.

FIG. 5 shows a schematic structure of a foreign matter inspection device using a laser light source and a photomultiplier tube as a detector.

In the figure, R is a reticle or the like that is the object to be inspected by this foreign matter inspection device, and a reticle with a bevel can also be used in this device.

Reference numeral 100 denotes a slider that holds the object to be inspected and moves and scans it in the Y direction, so that the position in the Y direction can be read by an encoder or the like.

Reference numeral 102 denotes a scanner mirror for a laser beam LB serving as a light source, and the laser beam is focused into a spot light and irradiated onto the object to be inspected via a lens system 104. The SL on the object to be inspected is scanned by the scanner 102 with the laser beam L.
This is a locus (scanning area) when the B spot (elliptical) light is one-dimensionally scanned in the X direction.

The scanner 102 and slider 100 are used to scan the entire surface of the object to be inspected in the XY plane. Here, a, b,
c is a typical position on SL, and b indicates the center on key SL.

The line jlLb is the surface to be inspected of the optical axis of the lens system 104 (X-
It is a projection onto the Y plane) and is parallel to the Y axis. This X
The angle α in the ZY plane between the Y plane and the scanning beam is 20
° ~ 45 @, and in the case of a reticle with a pellicle, about 45 ° is good. A line j2a parallel to the X axis is a line on the test surface that is an extension of SL, and J2c passes through the center line on SL
This is a line on the test surface extending in a direction that intersects b and Ia at the same point.

AX is the optical axis of the light receiving lens system Gl whose projection is 1a, M is a bending mirror, and 106A is a photomultiplier (hereinafter simply referred to as photomultiplier).

The forward axis AX is determined to pass approximately through the center of the SL, and the lens system G has an angle of view such that the entire SL can be seen through the mirror M1.

Therefore, if a foreign object exists at any of points a, b, or c on the SL, the scattered light of the scanning beam due to the foreign object will reach the light receiving surface of the photomultiple 106A. Here, the angle β between AXI and Ua is about 10° to 45°.

108A is a photomultiplier having an optical axis AX3 whose projection is nc, and similarly to 106A, it is equipped with a mirror and a lens system (not shown). Here, the angle between j2c and AX3 is also lO
It is about 45° to 45°.

106B and 108B are photomultis that look into this SL from the back side of the object to be inspected, and their respective optical axes AX2. AX4 is AX, respectively, across the surface to be inspected.

They are arranged almost in plane symmetry with AX3, and each is similarly equipped with a mirror and a lens system (not shown). Each of these photomultiples is also designed for the scattered light of the scanning beam to reach through the transparent part of the reticle when a foreign object is present on the SL, and when the scattered light reaches it, a detection function corresponding to its intensity is used. It outputs the signal S, etc.

FIG. 6 shows a conventional example of a detection signal processing circuit of this foreign object inspection device.

Photoelectric detection signal S from Photomaru 106A, 108A, etc.
1. S2 (the photomultipliers 106B and 108B are also omitted as they are the same) is a voltage control amplifier or multiplier (hereinafter simply vC
A) 110, 112 are manually operated.

Here, the drive circuit 116 of the scanner 102 uses an internal counter to convert a scanning position information signal (count value, hereinafter simply referred to as PS) of the spot light on the SL in the X direction to a VCA (voltage control amplifier). Controller 114
The controller 114 outputs the control voltage CVICVa corresponding to the PS to VCAIIo and 112, respectively.
Output to.

The photoelectric detection signals S, , S, are amplified or multiplied by the control voltages CVl, CV2 in the VCAIIo, 112, and are inputted as a foreign object detection signal after A/D conversion to the processor and computer. Based on this, the presence or absence of a foreign object, its size, etc. is determined.

Here, due to the change in the beam spot position in the X direction on the SL, for example, foreign objects of the same shape and size may be
Even if it exists at each of points a, b, and c above, each point a,
b, C to each photomare (or light receiving lens system G)
3 etc.), the light-receiving solid angle, or the light-receiving sensitivity of each photomultiply, the magnitude of the detection signals S, , S, differs, resulting in uneven detection sensitivity depending on the scanning position.

Therefore, the photoelectric signal S from each photomultiple.

Control voltage cv as amplification factor or multiplication amount for 32 etc.
,, cv2, etc. according to the scanning position so that the same size detection output signal is obtained from the same size foreign object regardless of the change in the scanning position on the SL, and Unevenness in foreign object detection sensitivity is corrected.

The foreign object detection signal whose detection sensitivity has been corrected according to the scanning position and the above-mentioned ps are taken into a processor 2 and a computer 1 including an A/D converter and the like, as shown in FIG.

By the way, in such a foreign matter inspection device, the foreign matter detection sensitivity must be -like over the entire surface of the object to be inspected.
For example, depending on conditions such as the relative positional relationship of the photoelectric detector to the object to be inspected and the manner in which the photoelectric detector is mounted, the foreign object detection sensitivity may not be the same over the entire surface. This can be considered to be sensitivity unevenness inherent to the device.

Furthermore, the objects to be inspected with this type of equipment are subject to differences in material, such as the thickness of the pellicle in the case of a reticle with a pellicle, as well as uneven reflectance, which may affect the inspection results due to foreign substances. There are inherent factors that contribute to this. This can be considered to be due to sensitivity unevenness due to differences in the objects to be inspected.

Therefore, by adding a new appropriate correction to the detection output of the photoelectric detector according to the object to be inspected, the foreign object detection output as a foreign object detection device can be adjusted to the object being inspected, regardless of the object to be inspected and the scanning position of the light beam. It needs to be constant across the entire body.

Therefore, as shown in FIG. 7, a method (gain/offset adjustment circuit 19) was devised in which the correction amount (control voltage) of the detection sensitivity is adjusted depending on the object to be inspected. In this figure, the counter 4 is provided in the scanner drive circuit 116 of FIG. 6, and only one system of VCAIIO is shown here for convenience (the others are the same).

Here, the photoelectric detection signal S from the VCA controller 114,
The control voltage CV, for VC is adjusted by the analog gain/offset circuit 19 using the trimmers 19a, 19b, etc., and becomes the corrected control voltage cv,', which becomes VC
Applied to AIIO. Here, 6 is a terminal device (man-machine interface between the calculator 2 and the operator) consisting of a keyboard, CRT, etc.

When using such an analog gain/offset circuit 19, it is necessary to use the same material as the reticle as the object to be inspected.
A standard object to be inspected is prepared by attaching microparticles of a standard size in a -like distribution in the X and Y directions to a sample with a structure (for example, with a pellicle), and the sensitivity is corrected by the VCA controller 114. The test is executed under the condition (using the control voltage CV) and the results are displayed on the terminal device 6.

At this time, it is sufficient if the detection results of the sizes of particles arranged in the X direction are approximately constant, but if they vary, adjust the trimmers 19a and 19b to obtain the best results. It is necessary to perform an operation to drive the control voltage C■ to 1°.

Here, the detection signal from the photoelectric detector (original signal S1), the position of the laser beam (X axis), and the correction value (
14) etc. are shown in Figure 3. In the figure, the target detection sensitivity must be constant (target detection sensitivity characteristic) regardless of the scanning position, as shown at 15.

However, as shown in FIG. 3, the original signal (Sl) usually differs in magnitude depending on the scanning position of the laser beam. Therefore, in order to match the target detection sensitivity characteristic 15, a correction value (
14) and perform sensitivity correction for foreign object detection (original signal level correction).

Conventionally, the characteristics of the correction value (14) have been determined using the gain/offset circuit 19 shown in FIG. 7 in the following procedure.

First, the operator applies a predetermined control voltage Cvl to the VCAIIO from the V CA $J controller 114, changes the magnitude of the detection signal S according to the scanning position, and compares it with the actual object to be inspected. Perform a foreign body test using the same sample. At this time, the operator looks at the inspection results displayed on the terminal device 6 and checks the original detection signal output (or VCAIIO) of the foreign object inspection device.
The control voltage C
V, is adjusted by the offset/gain adjustment circuit 19 for further correction. And the control voltage CV after the correction.

The foreign matter inspection is carried out again using the test result, and the same readjustment is carried out again based on the inspection results, and this control voltage correction work is repeated until the control voltage c v ,' is reached to obtain the optimum detection result.

After this work is completed, the hardware always performs constant sensitivity correction (target detection sensitivity).

[Problems to be Solved by the Invention] Incidentally, such adjustment of detection sensitivity needs to be performed on the entire surface of the object to be inspected, and it is difficult to adjust it accurately and finely for each part of each scanning position. This is because the adjustment of the offset/gain adjustment circuit 19 is performed by moving the trimmer inside it, so each worker has to decide in which direction and how much to move the trimmer independently based on the inspection results. This is because you have to make a decision.

For this reason, there is a large disparity between workers regarding the amount of adjustment of this trimmer, and there is a problem that there is a large difference in working time, adjustment results, and inspection results between skilled workers and inexperienced workers. was there.

Furthermore, in conventional devices such as those described above, only a limited number of correction values are written in the VCA controller (correction signal generator), so correction values with trends that match reality are not necessarily prepared. If there is not, the next best correction value with a similar tendency will be used, and in some cases, no matter how much adjustment is made, the detection sensitivity characteristic may not match characteristic 13 in Figure 3. As shown, there is also the problem that it does not match the target detection sensitivity characteristic 15, and correct correction cannot be performed.

In this case, the control voltage output from the VCA controller passes through a gain/offset circuit fixed by hardware, so it is difficult to change the value for each test or to prepare a large number of circuits.

The present invention solves these conventional problems, and allows any worker of any level to easily operate the machine in a short period of time.
It is an object of the present invention to provide a foreign matter inspection device that is equipped with means that can measure the best correction value for all objects to be inspected, and that can obtain stable inspection results in any case.

[Means for Solving the Problems] In order to solve the above-mentioned problems, in the present invention, a light beam is irradiated onto the surface of an object to be inspected, and is scanned along a predetermined region of the surface to identify the objects that exist within the region. Scattered light generated from a minute foreign object is received by a charged detector placed at a unique spatial position with respect to the area, and the minute foreign object is detected based on the magnitude of a photoelectric signal from the photoelectric detector. In this case, in a foreign object inspection device that corrects foreign object detection sensitivity according to the scanning position of the light beam, when a standard object to be inspected is inspected, a target detection sensitivity is obtained corresponding to the scanning position. storage means for storing a first sensitivity correction characteristic such as: a detection sensitivity obtained when a predetermined test object is inspected under correction by the first sensitivity correction characteristic, and a detection sensitivity set as a target; A second sensitivity correction characteristic that can obtain the target detection sensitivity is calculated for each part of the scanning area by comparing the difference with the target detection sensitivity characteristic, and the calculated second sensitivity correction characteristic is used as the second sensitivity correction characteristic. computing means for storing in the storage means; reading out both the first sensitivity correction characteristic and the second sensitivity correction characteristic, or only the first sensitivity correction characteristic from the storage means; The present invention is characterized by comprising a sensitivity correction means for correcting the detection sensitivity according to the scanning position based on the scanning position.

[Function] The foreign object inspection device according to the present invention is provided with means for storing the first sensitivity correction characteristic and the second sensitivity correction characteristic, respectively, as described above, and can obtain an appropriate inspection result depending on the object to be inspected. Thus, it is possible to create an optimal control voltage by arbitrarily calling only the first sensitivity correction characteristic or both the first and second sensitivity correction characteristics, and to apply highly accurate correction.

Here, the first sensitivity correction characteristic refers to the amount of correction (( For example, as shown in Figure 3, if the original ε sensitivity characteristic O(S+) is shown depending on the conditions unique to the device, the target Sensitivity characteristics. It is sufficient to call the first sensitivity correction characteristic x+lz) that provides correction according to the scanning position such that (15) is obtained. In this case, accurate correction is performed for the same object to be inspected for which the first sensitivity correction characteristic was set.Furthermore, based on the recalled first sensitivity correction characteristic xl,
For example, the detection sensitivity when inspecting a certain object is
Even if characteristic 13 in the figure differs from the target sensitivity characteristic, the difference can be quantitatively understood by the calculation means, so characteristic 13 can be easily adjusted to the target detection sensitivity and corrected to (15). is possible. For this modification, in the present invention, the first
The sensitivity correction characteristics of
The sensitivity correction characteristic X2 of is newly stored.

In this way, the foreign object inspection apparatus can always obtain appropriate foreign object inspection results by calling the second sensitivity correction characteristic arbitrarily in response to various conditions (mainly differences unique to the object to be inspected).

Here, in the present invention, the processing circuit for the photoelectric detection signal and the circuit for correcting the control signal in the foreign object inspection device are as follows:
The conventional circuit shown in the block diagram shown in FIG. 7 has been changed to the circuit shown in the block diagram shown in FIG.

Here, the conventional gain offset adjustment circuit 19 is abolished, and a line (in FIG. 1) for sending predetermined data from the processor (CPU) 2 to the correction signal generation circuit 3 (conventional VCA controller 114) A data bus 8 connecting the device CPU 2 and the correction signal generator 3) has been added. The correction signal 11 from the correction signal generator 3 functions as a control voltage for the VCA 5 as in the conventional case, and the original signal S is corrected by the VCA 5 to a voltage 1o whose gain is corrected according to the scanning position.

Also, from the computer 1 of this device, the C
Data on predetermined sensitivity correction characteristics is sent to the PU 2 and the correction signal generation circuit 3, and the CPU 2 is able to send test results corrected based on the data to the computer 1.

Furthermore, within the correction signal generation circuit 3, the correction signal 1
The first standard is 1. Alternatively, a storage means such as a RAM, which can be easily written and retrieved, is provided as a storage location for the data of the second sensitivity correction characteristic.

Therefore, the temporarily stored sensitivity correction characteristic data can be freely rewritten or added.

Furthermore, in order to adjust the detection sensitivity, the calculator 1 includes:
A function that reads the test results from the test based on the sensitivity correction characteristic data previously sent to the correction signal generation circuit 3, and calculates the correction distortion necessary to correct the detection sensitivity at that time to the target detection sensitivity. Added.

For this reason, it has become possible to assist the adjustment work of detection sensitivity using the computer.

An example of the detection sensitivity adjustment in the foreign object inspection apparatus according to the present invention is as follows.

First, the operator operates the terminal device 6 to select a temporary correction value (sensitivity correction characteristic that is the seed for obtaining the first sensitivity correction characteristic) from the console of the computer 1, and then inputs the data of the correction value. The signal is transferred to the correction signal generation circuit 3.

In this state, a foreign matter inspection of a standard inspection object (with reference particles) is performed based on the detection sensitivity associated with the corrected control voltage (correction signal 11).

The foreign substance inspection results are displayed on the console, so the operator can confirm them.

Here, it is determined from the test results inside the computer 1 whether the detection sensitivity characteristics are equal to the target sensitivity characteristics. If the detection sensitivities are equal, the detection results (sensitivity correction characteristics) are adopted as they are; if the detection sensitivities are uneven, the first one is used.
The amount by which the temporary correction value should be modified in order to obtain the sensitivity correction characteristic of is calculated for each portion of the scanning line SL of the light beam.

The sensitivity correction characteristic obtained by the correction value calculated by this calculation is transferred to the correction signal generation device 3 as a new first sensitivity correction characteristic. This first sensitivity correction characteristic is mainly for correcting sensitivity unevenness due to conditions unique to the apparatus.

Next, using the detection sensitivity associated with the control voltage (signal 11) based on this corrected correction value (first sensitivity correction characteristic) as a new standard, foreign matter inspection is performed using the same object to be inspected as before. Execute.

The new foreign object test results are displayed on the console, so the operator confirms whether they are correct.

Here, if the detection sensitivity still needs to be corrected, the correction value is corrected again and the foreign object inspection is performed. At this point, the operator can also modify the correction value again.

The correction value (first sensitivity correction characteristic) corrected and optimized through the above operations is stored in a storage means such as a disk device.

In this method, since there is no need to adjust the hardware of the correction signal generation circuit 3 itself, the adjustment circuit can be omitted.

Also, use Calculator 1 to determine how much the correction value should be corrected.
Since the results can be grasped quantitatively using the terminal device 6, any worker can obtain certain results in a short time.

Furthermore, in the foreign object inspection apparatus according to the present invention, in order to correct unevenness in detection sensitivity caused by differences inherent in the object to be inspected, after the actual foreign object inspection of the object to be inspected, a second sensitivity correction characteristic is used in addition to the first sensitivity correction characteristic. This configuration allows the sensitivity correction characteristics of No. 2 to be set in the correction signal generation circuit 3. Since the second sensitivity correction characteristic differs slightly depending on the object to be inspected, a plurality of assumed characteristics are stored in the disk device of the computer 1, for example.

Therefore, in the embodiment of the present invention, for example, it is possible to separately correct the original signal (S+3) based on the data of the first sensitivity correction characteristic and the data of the second sensitivity correction characteristic. By selecting only the second sensitivity correction characteristic that depends on the object to be inspected without changing the first sensitivity correction characteristic set according to the conditions unique to the device, unique detection sensitivity can always be obtained. Here, the second sensitivity correction characteristic can be considered to correspond to the characteristic of the difference between the target detection sensitivity characteristic D0 and characteristic 13 in FIG. 3.This second sensitivity correction characteristic The determination of the characteristics can also be performed using the calculator 1 in the same procedure as the determination of the first sensitivity correction characteristics.

However, in this case, the second sensitivity correction characteristic is determined by inspecting an object of the same quality as the object to be actually inspected, with the sensitivity unevenness corrected using the first sensitivity correction characteristic. Since the second sensitivity correction characteristic only corrects differences specific to the object to be inspected, it must be used together with the first sensitivity correction characteristic during actual inspection.

With this configuration, it is possible to perform much more detailed correction than in the past, and foreign matter inspection can be performed with uniform detection sensitivity regardless of the scanning position.

[Example] Embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a block diagram showing an embodiment of the present invention, and includes two correction signal generators 22, 23 and a multiplier that constitute the correction signal generation circuit 3 in the basic block diagram shown in FIG. 26 has been added, and the main body 20 and disk device 35 that constitute the computer 1 have been added. The correction signal generator 23 stores the first sensitivity correction characteristic and the like, and also includes a memory (RAM) 23 a that is addressed in response to position information PS from the counter 4 at the time of reading, and a RAM 23 a.
D/A that converts the digital output of a into an analog signal 32
A converter 23b is provided.

On the other hand, the correction signal generator 22 includes a memory (RAM) 22a that stores second sensitivity correction characteristics and the like, and is addressed in response to the position information PS at the time of reading.
D/ which converts the output of RAM22a into analog signal 31
A converter 22b is provided. The multiplier 26 converts the signal 11 corresponding to the product of the analog signals 31 and 32 into a VCA.
Output to 5. The disk device 35 stores a plurality of first sensitivity correction characteristics to be set in the RAM 23a and a plurality of second sensitivity correction characteristics to be set in the RAM 22a.

Next, the operation of each part at each stage when adjusting the detection sensitivity of this embodiment will be explained using the flowchart shown in FIG.

First, in order to determine the reference correction value (correction value according to the first sensitivity correction characteristic), the basics for creating the first sensitivity correction characteristic are selected by the operator from the terminal device 6 or automatically selected. Select a tentative correction sensitivity characteristic XC that becomes
Prepare a standard object to be inspected. (Start) The computer main body 20 reads the data of the selected sensitivity correction characteristic Xc from the disk device 35 and sends it to the device CPU 2 via the bidirectional data bus 7. The device CPU2 is
The sent correction value is sent to the RAM 23a in, for example, 23 of the correction signal generator through the data bus 8. (Step 50
) Here, at the start of the detection sensitivity adjustment, the RAM 22a of the correction signal generator 22 contains the following information, regardless of the position of the scanning line SL.
It is necessary to set a correction characteristic that generates a signal 31 that always receives a one-time sensitivity correction. (Step 52) Now, the signal 32 according to this sensitivity correction characteristic
5, the object to be inspected is set in a foreign matter inspection device and a foreign matter inspection is performed by scanning the laser beam. (Step 54) Here, the counter 4 sends a signal ps having a value corresponding to the scanning position of the laser beam to the correction signal generators 22 and 23. In each correction signal generator, the correction value accessed according to the counter value PS is read from the RAMs 22a and 23a, D/A converted by the D/A converters 22b and 23b, and the correction signal 3
Output as 1 and 32. This correction signal 31.32
are multiplied by a multiplier 26 and applied to the VCA 5 as a correction control signal 11 used for final sensitivity correction.

The photoelectric detection signal (original signal) S+ from the photoelectric detector is VC
At A5, the correction control signal 11 and the signal are combined to form a corrected signal IO, which is sent to the device CPU2. Device CPU2
When the magnitude of the corrected signal 10 is above a certain level, it converts the magnitude of the signal 10 into a digital value for each scanning position and stores it in its own buffer as foreign object information.

After the foreign object inspection is completed, the device cPL12 sends the stored foreign object information data to the computer main body 20 via the bidirectional data bus 7, and the main body 20 analyzes the sent data and displays it on the console 6. do.

The operator grasps the rough distribution of the data from the displayed content and determines whether or not to end the adjustment (whether or not correction of the correction characteristic Xc is necessary).

(Step 56) If you want to make further adjustments, use the following method to adjust the correction characteristic
Modify c.

First, the target detection sensitivity characteristics. Set.

It is desirable that this setting is as flat as possible, as shown in FIG. 3, but it may be changed intentionally.

From this target sensitivity characteristic 00, correction value correction 2 is calculated by the following method. (Step 58) xn = Xc x (
Do/D) This operation is repeated for each portion of the scanning area.

The correction value X modified in this way. New RAM2
Send to 3a. (Step 59) This corrected correction value
. Execute the foreign object inspection again using (Step 54
) If the same operation is repeated several times and the measured result of the foreign object inspection approaches the target value, or if the operator instructs the operator to terminate, the computer 2o returns the correction value X used in the last foreign object inspection. is saved in the disk device 35 with an appropriate name given as the correct first sensitivity correction characteristic X. (Step 60) Through the above operations, the first sensitivity correction characteristic x1 for correcting sensitivity unevenness due to conditions unique to the apparatus is determined.

Next, we will explain how to determine the second sensitivity correction characteristic x2.
The basic procedure may be the same as the flow shown in FIG.

First, an arbitrary object to be inspected is prepared, and a foreign matter inspection is performed with the sensitivity corrected using only the first sensitivity correction characteristic. For this purpose, step 5 in FIG. 4 reads the first sensitivity correction characteristic XI from the disk device 35 and stores it in the RAM 2.
3a, steps 52, 54
．． 56 is executed in the same manner as above.

In this case, if Do is the average value of the detection sensitivity in the Y direction after being corrected by the first sensitivity correction characteristic X, then
Target detection sensitivity. Correction fix to obtain. is xn=
-(Do 10'). Here K is a constant. - Therefore, the calculation in step 58 in FIG.
- Changed to (Do 10') and repeats the correction amount X for each scanning position. is calculated. Step 59 in FIG. 4 is then changed to set the calculated correction IE[X n in the RAM 22a as a new correction characteristic.

That is, when determining the second sensitivity correction characteristic, RA
It is necessary to leave the first sensitivity correction characteristic set in M32a as it is.

In this way, repeat steps 54, 56...
Target detection sensitivity characteristics. When this is achieved, the process proceeds to step 60 in the same way as in FIG.
The correction characteristic 2a is changed to be stored in the disk device 35 as the second sensitivity correction characteristic x2.

Such sensitivity adjustment is performed for various cases (for example, differences due to reticle material thickness, presence or absence of a pellicle, differences due to pellicle material film thickness, etc.), and the optimal second sensitivity correction for each case is determined. What is necessary is to obtain the characteristic X2 and store it in the disk device 35.

In actual foreign matter inspection, the first sensitivity correction characteristic x1 is set in the RAM 23a, and the 1x characteristic or the second sensitivity correction characteristic X2 is set in the RAM 22a by operator selection or automatic selection. set. Therefore, the size of the foreign object attached to the object to be inspected can be determined based on the detection sensitivity that is uniform over the entire surface of the object to be inspected, using the optimal correction value based on the data of each sensitivity correction characteristic that has been set. can be done.

As described above, in this embodiment, the first sensitivity correction characteristic XI,
The detection sensitivity is corrected by changing the magnitude of the original signal (S,) according to the scanning position using the second sensitivity correction characteristic X, but the original signal (S+) is not corrected at all. The detection sensitivity may be corrected by software processing using the characteristics XI and X2 after the data is input into the CPU 2 without adding the values.

Correction of the detection sensitivity can also be carried out by modulating the brightness of the scanning beam LB according to the scanning position, but this is not possible with a method in which the light receiving element looks at the scanning area from multiple spatial positions at the same time. Limited to one light receiving element.

However, the scan of the beam LB is n at the same position on the object to be inspected.
If a method is adopted in which one of the n light-receiving elements to be focused on (which captures the signal) is switched one by one for each scan, the brightness of the beam will be modulated every n beam scans. Optimal detection sensitivity can be obtained for each light receiving element.

As described above, in this embodiment, the case where foreign matter attached to a reticle or mask is inspected is illustrated, but the beam spot is scanned on the surface to be inspected (flat or curved surface), and the optical information from the scanning area is spatially transmitted. The method of this embodiment can be applied as is to a defect inspection device (flaw inspection, etc.) that detects defects using a photoelectric detection system that can be viewed from one direction. Of course, similar effects can be obtained when inspecting a single pellicle.

[Effects of the Invention] As described above, according to the present invention, it is no longer necessary to adjust the hardware of the device that provides a control signal to the detection signal in order to correct the foreign object detection sensitivity according to the scanning position in the foreign object inspection device. This eliminates the need for a circuit for adjusting the control voltage.
This has the effect of simplifying the sensitivity adjustment circuit for foreign object detection.

The adjustment amount for correcting the control voltage due to changes in the inspected object can be determined by the absolute amount of how much the correction value is to be corrected, rather than by vague amounts such as how much the trimmer is turned as in the past. This has the effect of minimizing variations due to individual differences among workers, and allowing constant adjustment results to be obtained regardless of the experience of the worker.

Here, since the amount of adjustment for correction of the control signal can be obtained quantitatively, processing by a computer or the like is easy, and the adjustment time can be significantly shortened, and furthermore, it is possible to automate the adjustment.

Furthermore, since the conventional sensitivity correction is performed by the hardware of the device that provides the correction control signal, there was a problem that once the sensitivity was adjusted, it was not easy to change or modify the correction. As a data storage device for correction sensitivity characteristics, it is possible to store as many types of correction values (especially the second sensitivity correction characteristic By selecting the correction value, you can always apply the optimum correction.

Therefore, with the foreign object inspection device according to the present invention, foreign object inspection can be performed on the entire surface of the object to be inspected with various detection sensitivities. It has the advantage that it can be done regardless of the level etc.

Furthermore, for example, according to the embodiment shown in FIG.
It is easily possible to obtain only a new correction value (second sensitivity correction characteristic X2) for further modifying the correction without touching the sensitivity correction characteristic xl of There is an advantage that only the sensitivity correction characteristic x 2 of 2 can be freely changed, and correction can be quickly realized on the spot.

FIG. 7 is a block diagram showing a signal processing system of a conventional foreign matter inspection device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of a signal processing system in a foreign object inspection device according to an embodiment of the present invention, and FIG. FIG. 3 is a diagram showing the relationship between the original signal sensitivity and the correction sensitivity to the control signal depending on the spot position X of the laser beam. FIG. A flow chart diagram showing the adjustment operation of the foreign object detection sensitivity in the device according to the embodiment, FIG. 5 is a perspective view showing the schematic structure of the foreign material inspection device suitable for this embodiment, and FIG. Block diagram showing the basic configuration of the sensitivity correction circuit, [Explanation of symbols of main parts] 1... Computer, 2... Device CPU, 3... Control signal and correction signal generation circuit, 4... Counter, 5...
Multiplier (VCA), 6... Terminal device, 7... Bidirectional data bus, 8... Data bus, S, , S,... Photoelectric detection signal, 10... Corrected original image No. 3, 11...
- Control signal, 22.23... Correction signal generator, 22a
, 23a... RAM, 22b, 23b... D/A converter, 31° 32... Control and correction signal, 35...
Disk device, ps...Scanning position information signal. Agent: Patent Attorney Tadashi Sato Figure 3 Figure 6 Figure 7

Claims (1)

[Claims] A light beam is irradiated onto the surface of an object to be inspected while scanning along a predetermined region of the surface, and scattered light generated from minute foreign matter existing within the region is uniquely distributed to the region. When detecting the minute foreign matter based on the magnitude of the photoelectric signal from the photoelectric detector, the foreign matter is detected according to the scanning position of the light beam. In a foreign object inspection device configured to correct sensitivity, a first sensitivity correction characteristic is set so that a desired target detection sensitivity is obtained for each portion of the scanning area by the light beam when a standard inspection object is inspected. Storage means for storing: Comparing the difference between the detection sensitivity obtained when a predetermined inspected object is inspected based only on the first sensitivity correction characteristic and the target detection sensitivity, Calculate a second sensitivity correction characteristic for obtaining the target detection sensitivity for each time,
calculation means for storing the second sensitivity correction characteristic in the storage means; and: reading out both the first and second sensitivity correction characteristics or only the first sensitivity correction characteristic from the storage means; A foreign matter inspection apparatus comprising: a sensitivity correction means for correcting detection sensitivity according to the scanning position based on the obtained sensitivity correction characteristic.