JPH05215696A - Method and apparatus for inspecting defect - Google Patents

Abstract

PURPOSE:To keep defect detection sensitivity constant regardless of the lowering of the output of an inspection light irradiation device. CONSTITUTION:In a defect inspecting method wherein a wafer 1 is irradiated with inspection light 21 by an inspection light irradiation device 20 and the scattered light 31 of the inspection light of the wafer is detected by a scattered light detector 34 to inspect a defect, the initial output value of the inspection light 21 applied from the inspection light irradiation device 20 at the beginning is preliminarily measured and the output value of the device 20 is measured periodically and non-periodically. This measured value is compared with the initial output value and, when the measured output value is judged to be deteriorated with respect to the initial output value, correction control is applied to the inspection light irradiation device 20 so that the measured output value becomes equal to the initial output value corresponding to a deteriorated quantity value. Since the detection sensitivity of the scattered light detector 34 is held to the initial detection sensitivity by increasing the output value of the device 20, the detection sensitivity of the detector 34 can be kept constant regardless of the deterioration of the device 20 with the elapse of time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a defect inspection apparatus, and more particularly,
The present invention relates to a technique for detecting minute foreign matter on a wafer surface such as a semiconductor LSI wafer or a glass mask with high sensitivity, and for example, to a technique effectively used in a method for manufacturing a semiconductor integrated circuit device.

In the present specification, the term "wafer" simply means, in principle, a wide range of semiconductor wafers, masks, reticles and other plate-like materials for manufacturing integrated circuits.

The term "defect" simply includes, as a general rule, both foreign particles and defects in the pattern itself caused by foreign particles.

Furthermore, when simply referring to "integrated circuit device", in principle, a semiconductor integrated circuit (monolithic I
C) broadly includes a single transistor formed on a semiconductor wafer and an integrated circuit formed on an insulating plate such as sapphire or garnet.

[0005]

2. Description of the Related Art In general, as semiconductor devices are highly integrated and patterns are made finer, the line width of circuit patterns is 1 μm.
It is about m or less. In order to manufacture such a semiconductor device with a high yield, it is necessary to inspect foreign substances adhering to the surface of the wafer as a wafer, quantitatively grasp the cleanliness of various process apparatuses, and appropriately manage the process. In order to accurately manage the process as described above, in the manufacturing process of the integrated circuit device, conventionally, an automatic foreign substance inspection is performed on the wafer by the foreign substance inspection device.

[0006] Conventional foreign matter inspection devices are roughly classified into two categories. The first is an image comparison type foreign matter inspection apparatus that compares a standard pattern stored in advance. This type of foreign matter inspection apparatus has high accuracy but low throughput and is expensive. The second is a foreign matter inspection apparatus that uses inspection light. This type of foreign matter inspection device
The accuracy is medium, but the throughput is high and the price is medium.

As a foreign matter inspection device using inspection light, an inspection light irradiation device for irradiating a wafer with the inspection light and a photoelectron multiplier as a scattered light detector for detecting scattered light of the inspection light on the wafer. Some tubes are provided with a tube and are configured to detect the presence or absence, size, etc. of foreign matter based on the detection result by the photomultiplier tube.

In the foreign matter inspection apparatus using this photomultiplier tube, when the output of the inspection light irradiation apparatus decreases, the detection sensitivity decreases, so that the detection sensitivity is tracked to the decrease in the output of the inspection light irradiation apparatus. It needs to be corrected.

Therefore, in the foreign matter inspection device using this photomultiplier tube, when the output of the inspection light irradiation device is lowered, the signal detected by the photomultiplier tube is the initial value of the inspection light irradiation device. The detection sensitivity is kept constant by correcting the voltage applied to the photomultiplier tube so as to match it.

Further, as another example of the foreign matter inspection apparatus using the inspection light, there are two types of an inspection light irradiation apparatus for irradiating the wafer with the inspection light and a scattered light detector for detecting scattered light of the inspection light on the wafer. And a two-dimensional solid-state image sensor, and is configured to detect the presence or absence, size, etc. of a foreign matter based on the detection result of the two-dimensional solid-state image sensor.

As an example of describing a conventional foreign matter inspection apparatus for patterned wafers, Japanese Patent Laid-Open Publication Nos. 54-101390, 59-186324, 59-65428, and 55-55 are disclosed. 124008 and Japanese Patent Application No. 62-311904.

Further, as an example in which a similar technique is described, Japanese Patent Application Laid-Open Publication No. 62-223649,
JP-A-62-223650, JP-A-62-22365
1, JP-A-63-82348, JP-A-64-354.
No. 5, Japanese Patent Application No. Sho 63-41999, etc.,
There is.

Further, as an example in which a technique using similar polarized light is described, Japanese Patent Application No. 62-272958 is cited.
, Japanese Patent Application No. 62-279238, Japanese Patent Application No. 63-3
23276 and so on.

As an example in which a method of adjusting the light quantity is described, Japanese Patent Application Laid-Open Publication No. 60-18895.
No. 0 and No. 62-106324.

[0015]

Generally, as the integrated circuit device is highly integrated and the wiring pattern is miniaturized, the foreign matter management on the wafer becomes more and more important, and the foreign matter for automatically inspecting the foreign matter is increased. It is an important factor in the reliability of the foreign matter inspection apparatus to always detect the foreign matter in the inspection apparatus with a constant sensitivity.

However, in the foreign matter inspection device using the conventional photomultiplier tube, when the output of the inspection light irradiation device decreases, the signal detected by the photomultiplier tube is the initial output value of the inspection light irradiation device. Since the detection sensitivity is automatically kept constant by correcting the voltage applied to the photomultiplier tube so that it matches that in the above, is there a decrease in the output of the inspection light irradiation device? ,
Alternatively, the present inventor has clarified that it is difficult to determine whether the photomultiplier tube is deteriorated.

Further, in a foreign matter inspection apparatus using a two-dimensional solid-state image pickup device as a photodetector, a correction function for coping with a decrease in output of the inspection light irradiation apparatus is not provided, so that the detection sensitivity is lowered. There is a problem that is done.

An object of the present invention is to provide a defect inspection technique capable of always maintaining a constant defect detection sensitivity regardless of the deterioration of the photodetector and the reduction of the output of the inspection light irradiation device.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0020]

The typical ones of the inventions disclosed in the present application will be outlined below.

That is, in the defect inspection method for inspecting a defect by irradiating the inspection object with the inspection light by the inspection light irradiation device and detecting the scattered light of the inspection light on the inspection object by the scattered light detector, The initial output value of the inspection light emitted from the inspection light irradiation device in advance is measured in advance, and the output value of the inspection light irradiation device is measured regularly or irregularly before or after the start of the inspection. When it is determined that the measured output value is deteriorated with respect to the initial output value by comparing the initial output value, the measured output value is made equal to the initial output value in correspondence with the deteriorated amount value. Correction control is executed for the inspection light irradiation device and / or the scattered light detector.

[0022]

According to the above-mentioned means, the output value of the inspection light irradiation device itself is automatically controlled so as to become the initial output value, so that the detection sensitivity can be improved without changing the capability of the scattered light detector side. It can always be kept constant. When the output of the inspection light irradiation device reaches the limit, the output value cannot be increased, so that the limit of the inspection light irradiation device can be recognized. As a result, it is possible to cope with a decrease in detection sensitivity by replacing the inspection light irradiation device.

On the other hand, when the detection sensitivity is lowered despite the increase in the output value of the inspection light irradiation device, it can be recognized that the scattered light detector is deteriorated, not the limit of the inspection light irradiation device. As a result, it is possible to deal with a decrease in detection sensitivity by replacing the scattered light inspection device.

[0024]

1 is a block diagram showing a wafer foreign matter inspection apparatus according to an embodiment of the present invention, and FIGS. 2A and 2B are explanatory diagrams for explaining a detection sensitivity correction method. (a) is a diagram and (b) is a plan view showing a wafer.

In the present embodiment, the defect inspection apparatus according to the present invention is configured as a wafer foreign matter inspection apparatus 10 for inspecting a foreign matter 2 on a wafer 1. This foreign matter inspection apparatus 1
At 0, a detection sensitivity correction device 40 is attached.

The wafer foreign matter inspection apparatus 10 is provided with a stage device 11. The stage device 11 includes an X stage and a Y stage for scanning a wafer 1 as an inspection object, and a θ stage for rotating in a θ direction. (Not shown), an automatic focusing mechanism (not shown), and a controller 12 for controlling them. And
In order to inspect the entire surface of the wafer 1, the stage device 1
The X / Y scan of the wafer 1 is executed by 1. During this scanning, the coordinate position information about the wafer 1 as the inspection object is sequentially input from the controller 12 to the foreign matter determination device described later.

An inspection light irradiation device 20 is installed above the stage device 11. The inspection light irradiation device 20 includes a laser light irradiation device 22 that irradiates the wafer 1 with a laser light 21 as inspection light, and a condenser lens 23 that condenses the laser light 21. Is irradiated to the wafer 1 as the inspection object held on the stage device 11.

When the height of the surface of the wafer 1 fluctuates when the wafer 1 is irradiated with the laser light 21, the laser light 2 is emitted.
The foreign matter detection performance is deteriorated due to the fluctuation of the irradiation position of No. 1, so the automatic focusing mechanism (stage device 11
It is equipped inside. ) Is required. An automatic focusing mechanism of this type is disclosed in, for example, Japanese Patent Laid-Open No. 58-7054.
A projection fringe pattern contrast detection method such as that disclosed in Publication No. 0 can be used, the description of which is provided.

A scattered light detection device 30 is installed directly above the stage device 11. This scattered light detection device 30 is
An objective lens 32 that collects the scattered light 31 diffusely reflected on the surface of the wafer 1 as it is irradiated onto the surface of the wafer 1 and a scattered light detector 34 that collects the scattered light 31 collected by the objective lens 32 Relay lens 33 for forming an image on the light receiving surface
And a scattered light detector 34 for detecting the scattered light 31. In this embodiment, the scattered light detector 34 is composed of a solid-state image pickup photoelectric conversion element.

A foreign matter determination device 35 is connected to the scattered light detector 34, and the foreign matter determination device 35 determines presence / absence and size of foreign matter on the wafer 1 based on the detection data from the scattered light detector 34. In addition, the coordinate position of the foreign substance is specified by collating the determined data with the coordinate position data from the controller 12 of the stage device 11.

In this embodiment, the inspection light irradiation device 20 is additionally provided with a detection sensitivity correction device 40. That is, on the optical axis of the condensing lens 23 in the inspection light irradiation device 20, a mirror 41 for extracting the laser light 21 as the inspection light out of the optical path is provided, and this mirror 41 is an appropriate driving device. It is adapted to be detached from the optical axis at an appropriate time by (not shown).

An inspection photodetector 42 is arranged at one side of the optical axis of the condenser lens 41 so as to be positioned on the total reflection line of the mirror 41 when it is interposed on the optical axis. .. That is, the inspection light detector 42 is configured to directly detect the laser light 21 as the inspection light taken out of the optical path by the mirror 41.

A gradation circuit 43 as an output value measuring device is connected to the inspection photodetector 42. The gradation circuit 43 receives an electric signal from the inspection photodetector 41 as A
By performing D / D conversion, for example, 256 bits (2
56 gradations). And
The output value of the laser light 21 is substantially measured by this gradation step.

A correction circuit 44 is connected to the gradation circuit 43. The controller 12 of the stage device 11 is connected to the other input terminal of the correction circuit 44. On the other hand, the laser light irradiation device 22 in the inspection light irradiation device 20 and the scattered light detector 34 in the scattered light detection device 30 are connected to the output terminals of the correction circuit 44, respectively. The correction circuit 27 creates a correction control signal based on the data from the gradation circuit 43 by a detection sensitivity correction operation as described later, and sends the correction control signal to the laser beam irradiation device 22 at a suitable time. ..

Next, a foreign matter inspection method in the foreign matter inspection apparatus 10 having the above-mentioned configuration will be briefly described.

First, the inspection light irradiation device 20 irradiates the wafer 1 with the laser light 21 as inspection light. By the irradiation of the laser light 21, scattered light 31 is generated from the foreign substance 2 as a defect on the wafer 1 and a circuit pattern (not shown), and the scattered light 31 is condensed by the objective lens 32 and also a relay lens. An image is formed on the scattered light detector 34 through 33.

At this time, scattered light 31 from the circuit pattern
Has a regularity, the scattered light 31 from the circuit pattern is shielded by a light shielding element (not shown) formed of a spatial filter or an analyzer provided on the Fourier transform surface of the pattern surface of the wafer 1. . On the other hand, foreign matter 2
Since the scattered light 31 from is irregular, it passes through the spatial filter or the analyzer and is imaged on the scattered light detector 34. Therefore, only the foreign matter 2 can be detected.

The detection signal of the scattered light 31 from the foreign matter 2 detected by the scattered light detector 34 is input to the foreign matter determination device 35. The foreign matter determination device 35 determines the presence or absence of the foreign matter 2 and the size thereof based on this detection signal, and collates this determination data with the coordinate position data from the controller 12 of the stage device 11 to determine the foreign matter 2 Specify the coordinate position of.

The data relating to the foreign matter 2 thus determined and whose coordinate position is specified is, for example,
The foreign matter determination device 35 outputs the timely output to a host computer (not shown), a display device (not shown), or the like, which integrally executes the production control.

A detection sensitivity correction device 40 is added to the foreign matter inspection device 10, and the detection value correction device 40 causes the output value of the laser beam 21 irradiated onto the wafer 1 to always be the initial output value. Since it is maintained, the detection sensitivity is always maintained constant. The operation of the detection sensitivity correction device 40 will be described below with reference to FIG.

The output of the laser light irradiation device 22 in the inspection light irradiation device 20 deteriorates with time while being used. When the intensity of the laser light 21 decreases due to the deterioration of the output with time, the illuminance of the scattered light 31 decreases, and the detection output of the scattered light detector 34 decreases. Therefore, even when the same foreign matter 2 is detected, for example, the size of the foreign matter 2 detected at the first time and the second time may vary. In this case, since the size of the foreign matter for the first time does not match the size of the foreign matter for the second time, there is a risk of erroneous determination in the above-described automatic determination by the foreign substance determination device 35.

In order to prevent such a situation, in this embodiment, the detection sensitivity is corrected as follows.

Now, a wafer 1 for sun ring as shown in FIG. 2B is prepared. On this wafer 1, a foreign substance 2 whose size, shape, etc. are specified is formed in advance at the specified coordinate position.

FIG. 2A is a diagram showing the detection output of the scattered light detector 34. In FIG. 2A, the vertical axis shows the detection output (mV) and the horizontal axis shows the gradation ( Bit) are taken respectively.

At the beginning of use (initial stage) of the inspection light irradiation device 20, the foreign matter 2 on the wafer 1 shown in FIG. 2B is scattered when the inspection light irradiation device 20 is irradiated with the laser light 21. Characteristic line A of the initial output value of the photodetector 34
Becomes as shown by the solid curve in FIG.

The characteristic line B of the output value of the scattered light detector 34 when the inspection light irradiation device 20 irradiates the laser light 21 on the foreign substance 2 on the wafer 1 after a certain period of use is shown in FIG. As indicated by the dashed curve.

Therefore, by changing the output of the laser light irradiation device 22 of the inspection light irradiation device 20, the following correction control is added so that the characteristic curve B after use becomes the initial characteristic curve A. ..

First, at the beginning (initial stage) of use of the inspection light irradiation device 20, the mirror 41 in the detection sensitivity correction device 40 is inserted into the irradiation light path of the laser light 21. When the laser light 21 is emitted from the laser light irradiation device 22 of the inspection light irradiation device 20 at this time, the laser light 21 as the inspection light is totally reflected by the mirror 41 and is detected by the inspection light detector 42. ..

The laser light 21 detected by the inspection light detector 42 is converted into an electric signal proportional to the intensity of the laser light 21 at the initial stage in the inspection light detector 42. The converted electric signal is transmitted to the gradation circuit 43, and is converted by the gradation circuit 43 into a gradation signal corresponding to the intensity of the laser light 21.

A gradation signal corresponding to the initial intensity of the laser beam 21 that has been adjusted by the gradation circuit 43 is transmitted to the correction circuit 44. In the correction circuit 44, this gradation signal is used as the initial output value of the laser light irradiation device 22, and the correction circuit 43
It is stored in the storage circuit built in the.

Thereafter, for example, after the inspection light irradiation device 20 has been used for a preset period, the detection sensitivity correction device 4
The mirror 41 at 0 is re-entered into the irradiation optical path of the laser light 21. When the laser light 21 is emitted from the laser light irradiation device 22 of the inspection light irradiation device 20 at this time, the laser light 21 as the inspection light is totally reflected by the mirror 41 and is detected by the inspection light detector 42. ..

The laser light 21 detected by the inspection light detector 42 is converted into an electric signal proportional to the intensity of the laser light 21 at that time (current) in this inspection light detector 42. The converted electric signal is the gradation circuit 4
3 and is converted by the gradation circuit 43 into a gradation signal corresponding to the current intensity of the laser light 21. The converted gradation signal is transmitted from the gradation circuit 43 to the correction circuit 44 as the current output value of the laser light irradiation device 22.

In the correction circuit 44, the current output value input in real time from the gradation circuit 43 is compared with the initial output value stored in advance in the correction circuit 43. By this comparison, the difference value between the initial output value and the current output value is obtained, and the correction control signal is created based on this difference value. This correction control signal is transmitted to the laser light irradiation device 22 of the inspection light irradiation device 20.

Then, the correction control signal causes the laser beam irradiation device 22 to perform control to increase the intensity of the laser beam 21 which has been lowered due to deterioration over time to the initial intensity. That is, based on this correction control signal, the laser light irradiation device 22 of the inspection light irradiation device 20 enhances the intensity output of the laser light 21 as the inspection light, so that
The correction control is executed so that the used characteristic curve B shown in (a) becomes the initial characteristic curve A.

That is, when the intensity output value of the laser light 21 is increased to the initial output value, the scattered light 31 on the foreign matter 2
Since the illuminance of 1 corresponds to the initial illuminance, the detection output value of the scattered light detector 34 becomes the same level as the initial output value.

As described above, in this embodiment,
Since the output value of the laser light irradiation device 22 of the inspection light irradiation device 20 is enhanced in a timely manner, the detection sensitivity of the scattered light detector 34 is maintained at the initial detection sensitivity. Regardless, the detection sensitivity of the foreign matter inspection device 10 is maintained constant.

That is, since the output value of the laser light irradiation device 22 itself of the inspection light irradiation device 20 is automatically controlled to be the initial output value, it is possible to change the capability of the scattered light detector 34 side without changing. The detection sensitivity can always be kept constant.

When the output of the laser light irradiation device 22 of the inspection light irradiation device 20 reaches its limit, the output value cannot be increased, so that the limit of deterioration over time in the laser light irradiation device 22 is recognized. be able to. As a result, the replacement work of the laser beam irradiation device 22 can cope with the decrease in the detection sensitivity of the foreign matter inspection device 10.

On the other hand, when the detection sensitivity of the scattered light detector 34 decreases despite the increase of the output value of the laser light irradiation device 22, the detection sensitivity does not decrease due to the deterioration of the laser light irradiation device 22 with time. Can be recognized as deterioration over time on the scattered light detector 34 side. As a result, the replacement work on the scattered light inspecting device 34 side can cope with the decrease in the detection sensitivity of the foreign matter inspection device 10.

According to the above embodiment, the following effects can be obtained. Since the output value of the laser light irradiation device 22 of the inspection light irradiation device 20 is enhanced in a timely manner, the scattered light detector 3
Since the detection sensitivity of No. 4 is maintained at the initial detection sensitivity, the detection sensitivity of the scattered light detector 34 can be maintained constant regardless of the deterioration with time of the laser light irradiation device 22.

As described above, since the detection sensitivity of the scattered light detector 34 can always be kept constant, the inspection accuracy in the foreign substance inspection device 10 can be kept constant, and the quality and reliability of the foreign substance inspection device can be maintained. Can be increased.

By automatically controlling the output value of the inspection light irradiation device 20 itself to be the initial output value, the detection sensitivity of the foreign substance inspection device 10 can be improved without changing the capability of the scattered light detector 34 side. Can always be kept constant.

When the output of the inspection light irradiation device 20 reaches the limit of deterioration over time, the output value cannot be increased, so that the limit of the inspection light irradiation device 20 can be recognized. As a result, it is possible to cope with the decrease in detection sensitivity of the foreign matter inspection device 10 by the replacement work of the inspection light irradiation device 20.

When the detection sensitivity of the scattered light detector 34 is reduced despite the increase in the output value of the inspection light irradiation device 20, it is not the limit of the inspection light irradiation device 20 but that of the scattered light detector 34 side. It can be recognized as deterioration over time. As a result, it is possible to cope with the decrease in the detection sensitivity of the foreign matter inspection apparatus 10 by replacing the scattered light detector 34.

FIG. 3 is a block diagram showing a foreign matter inspection apparatus for a wafer which is another embodiment of the present invention.

Wafer particle inspection apparatus 1 according to the second embodiment
0A differs from the wafer foreign matter inspection apparatus 10 according to the first embodiment in that the detection sensitivity correction apparatus 40A is configured to use the output of the scattered light detector 34.
That is, the output of the scattered light detector 34 is transmitted to the gradation circuit 43.

Next, the operation of the wafer foreign matter inspection apparatus 10A according to the second embodiment will be described to explain the detection sensitivity correction method in the wafer foreign matter inspection method according to the second embodiment of the present invention.

Now, a sampling wafer 1 as shown in FIG. 3 is prepared. On this wafer 1, a foreign substance 2 whose size, shape, etc. are specified is formed in advance at the specified coordinate position.

First, at the beginning (initial stage) of use of the inspection light irradiation device 20, the sampling wafer 1 is set on the stage device 11. When the foreign material 2 on the wafer 1 is irradiated with the laser light 21 as the inspection light from the laser light irradiation device 22 of the inspection light irradiation device 20, the laser light 21 is diffusely reflected on the foreign material 2. The scattered light 31 due to the irregular reflection is condensed by the objective lens 32, and is imaged on the scattered light detector 34 by the relay lens 33. As a result, the scattered light detector 34 detects the scattered light 31.

The scattered light 31 detected by the scattered light detector 34 is converted into an electric signal proportional to the intensity of the scattered light 31 at the initial stage in the scattered light detector 34. This converted electric signal is transmitted to the gradation circuit 43 in the detection sensitivity correction device 40A, and is converted into a gradation signal corresponding to the intensity of the scattered light 31 in the gradation circuit 43.

The scattered light 3 that is tuned by the grading circuit 43
The gradation signal corresponding to the initial intensity of 1 is transmitted to the correction circuit 44 in the detection sensitivity correction device 40A. Correction circuit 4
4, the gradation signal is stored in the storage circuit built in the correction circuit 43 as an initial output value of the scattered light detector 34.

After that, for example, after the inspection light irradiation device 20 has been used for a preset period, the sampling wafer 1 is set again on the stage device 11. When the laser light 21 is irradiated from the laser light irradiation device 22 of the inspection light irradiation device 20 onto the foreign matter 2 on the wafer 1, the laser light 21
Diffusely reflects on the foreign matter 2. The scattered light 31 due to the irregular reflection is condensed by the objective lens 32, and is imaged on the scattered light detector 34 by the relay lens 33. As a result, the scattered light detector 34 detects the scattered light 31. At this time, since the laser light irradiation device 21 has deteriorated with time, the intensity of the laser light 21 is lower than the initial intensity.

The laser light 21 detected by the scattered light detector 34 is converted into an electric signal proportional to the intensity of the laser light 21 at that time (current) at this scattered light detector 34. The converted electric signal is the gradation circuit 4
3 and is converted by the gradation circuit 43 into a gradation signal corresponding to the current intensity of the laser light 21. The converted gradation signal is transmitted from the gradation circuit 43 to the correction circuit 44 as the current output value of the laser light irradiation device 22.

In the correction circuit 44, the current output value input from the gradation circuit 43 in real time is compared with the initial output value stored in advance in the correction circuit 43. By this comparison, the difference value between the initial output value and the current output value is obtained, and the correction control signal is created based on this difference value. This correction control signal is transmitted to the laser light irradiation device 22 of the inspection light irradiation device 20.

Then, with this correction control signal, the laser beam irradiation device 22 executes control to increase the intensity of the laser beam 21 reduced due to deterioration over time to the initial intensity. That is, based on this correction control signal, the laser light irradiation device 22 of the inspection light irradiation device 20 enhances the intensity output of the laser light 21, so that the characteristic curve B after use shown in FIG. The correction control is executed so that the initial characteristic curve A becomes.

That is, when the intensity of the laser light 21 is increased to the initial output value, the illuminance of the scattered light 31 on the foreign substance 2 coincides with the initial illuminance. Therefore, the detection output value of the scattered light detector 34 is increased. Also becomes the same level as the initial output value.

As described above, also in the second embodiment, the output value of the laser light irradiation device 22 of the inspection light irradiation device 20 is timely enhanced, so that the scattered light detector 3 can be obtained.
Since the detection sensitivity of No. 4 is maintained at the initial detection sensitivity, the detection sensitivity of the scattered light detector 34 is maintained constant regardless of the deterioration with time of the laser light irradiation device 22.

That is, since the output value of the laser light irradiation device 22 itself of the inspection light irradiation device 20 is automatically controlled so as to be the initial output value, the capability of the scattered light detector 34 side does not have to be changed. The detection sensitivity of the foreign matter inspection device 10A can always be kept constant.

When the output of the laser light irradiation device 22 of the inspection light irradiation device 20 reaches its limit, the output value cannot be increased, so that the limit of deterioration over time in the laser light irradiation device 22 is recognized. be able to. As a result, the replacement work of the laser beam irradiation device 22 can cope with the decrease in the detection sensitivity of the foreign matter inspection device 10A.

On the other hand, when the detection sensitivity of the scattered light detector 34 decreases despite the increase in the output value of the laser light irradiation device 22, the detection sensitivity does not decrease due to the deterioration of the laser light irradiation device 22 with time. Can be recognized as deterioration over time on the scattered light detector 34 side. As a result, the replacement work on the scattered light inspecting device 34 side can cope with the decrease in the detection sensitivity of the foreign matter inspection device 10.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Needless to say.

For example, in the above embodiment, the case where the detection sensitivity correction device is configured to perform correction control on the inspection light irradiation device side has been described. However, for example, a photomultiplier tube is used as a scattered light detector. In such a case, correction control may be performed to enhance the detection sensitivity on the scattered light detector side. Further, both the inspection light irradiation device side and the scattered light detector side may be configured to be correction-controlled.

The output value measuring device in the detection sensitivity correction device is not limited to the gradation circuit, but may be an illuminance meter or the like.

In the above description, the case where the invention made by the present inventor is mainly applied to the foreign matter inspection technique of the wafer which is the field of application which is the background has been described, but the invention is not limited thereto and other than the foreign matter inspection. The present invention can be applied to the defect inspection technology for wafers, and further for the defect inspection technology for plate-like objects such as photomasks.

[0085]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.

The initial output value of the inspection light initially emitted from the inspection light irradiation device is measured in advance, and the output value of the inspection light irradiation device is measured regularly or irregularly before or after the start of the inspection. When the measured output value is compared with the initial output value and it is determined that the measured output value has deteriorated with respect to the initial output value, the measured output value becomes equal to the initial output value corresponding to the deteriorated amount value. By performing correction control on the inspection light irradiation device so that the output value of the inspection light irradiation device itself becomes the initial output value, the ability of the scattered light detector side is improved. Even if it is not changed, the detection sensitivity of the defect inspection apparatus can always be kept constant.

[Brief description of drawings]

FIG. 1 is a block diagram showing a wafer foreign matter inspection apparatus according to an embodiment of the present invention.

FIG. 2A is a diagram for explaining the detection sensitivity correction method, and FIG. 2B is a plan view showing the same wafer.

FIG. 3 is a block diagram showing a foreign matter inspection apparatus for a wafer which is another embodiment of the present invention.

[Explanation of sign]

DESCRIPTION OF SYMBOLS 1 ... Wafer (inspection object), 2 ... Foreign material, 10 and 10A ... Wafer foreign material inspection apparatus, 11 ... Stage apparatus, 12 ... Controller, 20 ... Inspection light irradiation apparatus, 21 ... Laser light (inspection light), 22 ... Laser light irradiation device, 23 ... Condensing lens,
30 ... Scattered light detection device, 31 ... Scattered light, 32 ... Objective lens, 33 ... Relay lens, 34 ... Scattered light detector, 35 ...
Foreign matter determination device, 40, 40A ... Detection sensitivity correction device, 41
Mirror, 42 ... Inspection light detector, 43 ... Gradation circuit (output value measuring device), 44 ... Correction circuit

Claims (4)

[Claims] 1. A defect inspection method for inspecting a defect by irradiating an object to be inspected with an inspection light by an inspection light irradiation device and detecting scattered light of the inspection light on the object to be inspected by a scattered light detector, The initial output value of the inspection light emitted initially from the inspection light irradiation device is measured in advance, and the output value of the inspection light irradiation device is measured either before or after the start of the inspection, regularly or irregularly. If it is determined that the measured output value has deteriorated with respect to the initial output value by comparing with the initial output value, the measured output value should be equal to the initial output value corresponding to the deteriorated amount value. A defect inspection method, wherein correction control is executed for the inspection light irradiation device and / or the scattered light detector. 2. A defect inspection method for inspecting a defect by irradiating an inspection object with an inspection light by an inspection light irradiation device and detecting scattered light of the inspection light on the inspection object by a scattered light detector, The initial output value of the scattered light detector when the inspection light from the inspection light irradiating device is initially irradiated to the predetermined inspection object is measured in advance, and the inspection light is output before or after the inspection is started. With the inspection light by the irradiation device, the output value in the scattered light detector when the predetermined object to be inspected is irradiated regularly or irregularly, and compares the measured value with the initial output value, When it is determined that the measured output value is deteriorated with respect to the initial output value, the inspection light irradiation device and / or the inspection light irradiation device and / or the inspection light irradiation device are set so that the measured output value becomes equal to the initial output value corresponding to the deteriorated amount value. The above A defect inspection method comprising performing correction control on a scattered light detector. 3. A stage device for holding an inspection object, an inspection light irradiation device for irradiating the inspection object with inspection light, and a scattered light detector for detecting scattered light of the inspection light on the inspection object. In a defect inspection device comprising a defect determination device for determining a defect based on the detection result of the scattered light detector, a detection sensitivity correction device is connected to the inspection light irradiation device. Is an inspection light detector for extracting and detecting inspection light emitted from the inspection light irradiation device from an irradiation light path to an object to be inspected, and an output value measuring device for measuring an output value detected by the inspection light detector. The measured output value of this output value measuring device is compared with a pre-measured initial output value, and a correction signal is created by the difference value between the measured output value and the initial output value, and the inspection light irradiation device and / or Or the scattered light detection Defect inspection apparatus characterized by comprising a correction circuit for correcting the output of. 4. A stage device for holding an inspection object, an inspection light irradiation device for irradiating the inspection object with inspection light, and a scattered light detector for detecting scattered light of the inspection light on the inspection object. And a defect inspection apparatus comprising a defect determination device for determining a defect based on the detection result of the scattered light detector, comprising a detection sensitivity correction device for correcting the detection sensitivity in the scattered light detector, The detection sensitivity correction device is an initial output value pre-measured in the scattered light detector of the scattered light when the inspection light by the inspection light irradiation device is initially irradiated to a predetermined object to be inspected, or before or after the start of the inspection. After that, when the inspection light by the inspection light irradiating device is irradiated to the predetermined object to be inspected, the scattered light detector compares the output value measured regularly or irregularly, and the output for measuring the difference value. value Defects comprising: a constant device and a correction circuit that creates a correction control signal based on this difference value and sends the correction control signal to the inspection light irradiation device and / or the scattered light detector. Inspection equipment.