JPH07128250A - Foreign matter inspection device for photomask for manufacturing semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the erroneous detection of a chrome pattern, and shorten the inspection time at multi-phase inspection in a foreign matter inspection device for photomask for manufacturing a semiconductor device. CONSTITUTION:The transmitted light from the upper light source of a photomask 1, the reflected light by a chrome pattern 3 of the lower light source, and the respective optical signals made by light absorption and light scatter of foreign matter are imaged on a photosensor 13, and the optical signal output in each signal detecting position is detected, whereby the adhesion of a foreign matter is judged. A surface with foreign matter adhering on it can be identified by the fluctuation of the foreign matter signal detecting position by the rotation of an optical system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection apparatus for detecting foreign matters on a photomask (hereinafter referred to as a mask) for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art Regarding a conventional foreign matter inspection device on a mask,
A reflected light image recognition type inspection apparatus will be described with reference to FIG. 7.

FIG. 7 is a block diagram of a reflected light image recognition type foreign matter inspection apparatus. In FIG. 7, this foreign matter inspecting apparatus is an inspecting apparatus in the case where a plurality of semiconductor chip patterns are formed on a single photomask 1 by chrome patterns 3 at regular intervals, and an optical system using a first light source 4 is provided. The relative position of the optical system including the second light source 7 and the second light source 7 is adjusted by the interval of the repeated pattern of the photomask 1, and the reflected light images of the same pattern of a plurality of chips are detected by the first photosensor 22 and the second photosensor 23. Then, the signal processing unit 14 performs an image comparison inspection to detect the presence or absence of foreign matter.

For example, when the adhered foreign matter 19 exists on the first light source 4 side, the input images (incident light intensity) to the first photosensor 22 and the second photosensor 23 are different,
It is determined that there is a foreign substance (or a defect). The inspection device can be moved by the moving stage 2.

Between the light sources 4 and 7 and the photomask 1, half mirrors 20 and 21, lenses 24 and 2, respectively.
5 is interposed, and a light shielding plate 26 is provided below the moving stage 2.

FIG. 8 shows a flow chart of the above-described conventional foreign matter detection. In FIG. 8, in process A, the relative positions of the optical systems of both light sources 4 and 7 are adjusted according to the chip interval on the photomask 1.

Next, in process B, inspection light is made incident on the photomask 1 from both light sources 4 and 7, and the reflected light image of the photomask is detected by the photosensors 22 and 23, respectively.

In the next processing C, the signal processing unit 14 compares and inspects the input images (incident light intensity) of both photosensors 22 and 23. In the next process D, it is determined whether or not the comparison image has a difference equal to or higher than the determination level. If there is a difference, it is determined in the next process F that there is a foreign substance (defect). If not, it is determined in process E that there is no foreign substance. To do.

It should be noted that this type of inspection apparatus is capable of detecting not only foreign matter adhesion but also defects such as missing of the chrome pattern 3, but for the image comparison inspection of repeated patterns, one photomask is used. It is not mounted on a reduction projection type exposure apparatus or the like because it cannot be applied except when only one chip is formed.

The reduction projection type exposure apparatus is equipped with a laser scattered light detection type foreign matter inspection apparatus, but in this case, since it is not an image recognition type, erroneous detection of a chrome pattern or pellicle on a photomask is carried out. An increase in inspection time due to an increase in inspection surface at the time of mounting poses a problem, and it is difficult to increase the detection sensitivity with the miniaturization of patterns.

[0011]

This conventional foreign matter inspection apparatus has a problem that when inspecting one mask, the inspectable mask is limited to the one having a plurality of chips of the same pattern. .

Further, when a foreign substance is detected, it is impossible to identify which inspection surface is attached to the surface. Therefore, there is a problem in that it is not possible to determine the degree of influence of image formation during wafer exposure due to the foreign substance attached surface and the size of the detected foreign substance. It was

Further, the foreign particle inspection device mounted on the reduction projection type exposure device or the like uses a laser scattered light detection type. In this case, inspection by erroneous detection of chrome pattern 1 at high sensitivity setting, sticking of pellicle, etc. There is a problem that the inspection time increases when the number of surfaces increases.

[0014]

SUMMARY OF THE INVENTION The present invention provides a foreign matter inspection device for a semiconductor device manufacturing photomask for detecting foreign matter or defects on the upper surface and lower surface of a semiconductor device manufacturing photomask, the irradiation light incident on the photomask. A means for detecting the foreign matter or the defect by changing the angle of is provided.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A mask foreign matter inspection apparatus according to an embodiment of the present invention will be described with reference to FIG. In FIG. 1, one embodiment of the present invention is an inspection example of a photomask 1 on which a chrome pattern 3 is formed, and an inspection area is a moving stage 2
Is changed by.

The photomask particle inspection apparatus for semiconductor device manufacturing according to the present embodiment has an optical system for irradiating the photomask 1 with test light and detecting the intensity level of the transmitted light of the photomask 1 of this irradiation light. Based on the optical system that irradiates the inspection area of the photomask 1 with the reference light and detects the reflected light of the irradiated light of the photomask 1, and the intensity level of the transmitted light of the photomask 1 and the reflected light, the shield of the photomask 1 is detected. A signal processing unit 14 for detecting and identifying the light portion, the light transmitting portion, and the foreign matter attached portion
And an optical system unit rotation mechanism portion 16 for identifying the foreign matter adhering surface, and a stage movement mechanism portion for changing the inspection area of the photomask 1.

The first light source 4 is a light source for detecting the transmitted light in the inspection area of the mask and is converted into parallel light by the first diaphragm 5 and the first collimator lens 6, and the test light from the upper surface of the mask. Irradiate. The test light is the half mirror 10,
The image sensor 1 and the third diaphragm 12 form the photo sensor 1
An image is formed as a transmitted light image at 3.

The second light source 7 is a light source for detecting the reflected light in the inspection area of the mask, which is converted into parallel light by the second diaphragm 8 and the second collimator lens 9, and is masked by the half mirror 10. It is illuminated from the bottom.

When the chrome pattern 3 is irradiated with this reference light, the light reflected under the mask and transmitted through the half mirror 10 is reflected by the photosensor 13 similarly to the transmitted light of the first light source 4. It forms an image.

A method of detecting a foreign substance based on the intensity levels of the transmitted light of the first light source 4 and the reflected light of the second light source 7 in FIG. 1 will be described with reference to FIG.

In FIG. 2A, the photo sensor 13
There is transmitted light 17 that has entered the optical system, and other reflected light 18 gives an optical signal output as a voltage value by photoelectric conversion. Referring to (B) of FIG. 2 showing the horizontal axis of the signal detection position by the photo sensor 13 and the vertical axis of the output level of the optical signal, the second portion is obtained in the portion A of the chrome pattern 3 in (B).
The optical signal output value b of the reflected light 18 from the light source 7 is obtained.

In the transparent portion B (B) where no foreign matter is attached, the optical signal output value a of the transmitted light is obtained. In the transmissive portion C to which foreign matter is attached, the light from the first and second light sources 4 and 7 is absorbed and scattered by the foreign matter, so that the optical signal output value is smaller than the output values a and b. c.

By setting the foreign matter determination level d to a value lower than the output values a and b and higher than the output value c, it is possible to detect the foreign matter adhered portion C of the mask light transmitting portion by the signal processing portion 14.

Next, a method of discriminating the adhering surface of the detected adhering foreign matter 19 will be described. When the adhered foreign matter 19 is detected, the detected foreign matter is the optical system unit rotary shaft 15 of FIG.
The movable stage 2 is fixed so as to be positioned on the axis of the optical system unit rotation shaft 15 and the optical system unit rotation shaft 15 is fixed.
As shown in FIG. 3, it is rotated by 6 at a constant angle.

The initial optical system unit rotary shaft 15 is fixed in a horizontal position with respect to the chrome pattern surface of the photomask 1. Further, the second light source 7 stops the irradiation of light.

FIG. 4A is a side view when the foreign matter 19 is attached to the lower surface of the mask, and FIG. 5 is a case where the foreign matter 19 is attached to the upper surface of the mask. In any case, the optical signal output before the rotation of the optical system unit is assumed to be the same as that in FIG.

At this time, if the foreign matter 19 is attached to the lower surface of the mask as shown in FIG. 4B, the signal detection position of the foreign matter 19 is the same as that in FIG. 2B. On the other hand, if the foreign matter 19 is attached to the upper surface of the mask as shown in FIG.
Depending on the height of the foreign material 19 from the chrome pattern 3, the foreign material 1
The signal detection position of 9 changes. By detecting the change amount Δ of the signal detection position in (B), it is possible to determine whether the foreign matter adheres to the upper surface or the lower surface.

In the reduction projection type exposure apparatus, since the image forming property of the foreign matter changes depending on the size and the adhering surface of the foreign matter, the signal detection width of the foreign matter (corresponding to the foreign matter size) and the signal detection position change amount when the optical system rotates. It is possible to determine whether or not the detected foreign matter is imaged at the time of wafer exposure based on the result of the (foreign matter adhesion surface).

FIG. 6 shows a flow chart of foreign matter detection of this embodiment described above. In FIG. 6, first, in process A, the transmitted light image of the photomask 1 in the inspection area is incident on the photosensor 13 by the inspection light of the light source 4, and the reflected light image of the photomask 1 in the inspection area is incident on the photosensor 13 by the inspection light of the light source 7. To do.

In the next process B, the input image (incident light intensity) of the photo sensor 13 is inspected by the signal processing section.

In the next processing C, an image (incident light intensity)
It is determined whether or not there is an area having a signal intensity equal to or lower than the foreign matter determination level.
If there is a foreign substance, in the next process E, the foreign substance size is calculated from the area of the foreign substance signal area after it is determined that there is a foreign substance.

In the next process F, the photomask 1 is moved by the moving stage 2 so that the detected foreign matter is located on the rotation axis of the optical system unit.

In the next process G, the incidence of light from the light source 7 is stopped, the rotation axis of the optical system unit is rotated by a fixed angle, and the adhering surface of the foreign matter 19 is determined from the amount of movement of the foreign matter detection position.

In the next process H, it is determined whether or not a foreign substance forms an image in the exposure process on the basis of the foreign substance size and the result of the foreign substance adhered surface.

[0035]

As described above, the present invention has the optical system for identifying the light shielding part, the transmitted light part, and the foreign matter adhering part of the mask in the inspection area of the mask. (Same chip) Image recognition type foreign matter inspection that is not based on comparison is possible, highly sensitive foreign matter detection is possible without erroneous detection of chrome pattern, especially because it has an optical mechanism that detects the foreign matter adhesion surface. It is possible to inspect all the inspection surfaces at one time, and the inspection time does not increase even if the inspection surfaces increase due to pellicle attachment or the like.

[Brief description of drawings]

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

2A and 2B are a side view and a characteristic diagram of foreign matter detection according to one embodiment.

FIG. 3 is a block diagram of a foreign substance adhering surface detection operation of the embodiment of FIG.

4A and 4B are a side view and a characteristic diagram of detection of a foreign substance adhering surface in one embodiment of FIG.

5A and 5B are a side view and a characteristic diagram of the foreign matter adhering surface detection in the embodiment of FIG.

FIG. 6 is a flow diagram of an embodiment of FIG.

FIG. 7 is a block diagram of a conventional photomask foreign matter inspection apparatus for manufacturing a semiconductor device.

FIG. 8 is a flowchart of a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photomask 2 Moving stage 3 Chrome pattern 4,7 Light source 5,8,12 Aperture 6,9 Collimator lens 11 Imaging lens 14 Signal processing unit 15 Optical system unit rotating shaft 16 Optical system unit rotating mechanism unit 17 Transmitted light 18 Reflection Light 19 Foreign matter 10, 20, 21 Half mirror 13, 22, 23 Photo sensor 24, 25 Lens 26 Light shield plate

Claims (2)

[Claims] 1. A foreign matter inspection device for a semiconductor device manufacturing photomask for detecting foreign matter or defects on the upper surface and lower surface of a semiconductor device manufacturing photomask, wherein the foreign matter is changed by changing an angle of irradiation light incident on the photomask. Alternatively, a foreign matter inspection device for a photomask for manufacturing a semiconductor device, which is provided with means for detecting a defect. 2. The photomask foreign matter inspection apparatus for manufacturing a semiconductor device according to claim 1, further comprising means for determining whether the foreign matter or defect is on the upper surface or the lower surface of the photomask.