JP2675628B2 - Photomask inspection method and inspection apparatus - Google Patents

Description

DETAILED DESCRIPTION [Table of Contents] Outline Industrial field of application Conventional technology (Fig. 6) Problem to be solved by the invention Means for solving the problem Structure of the first invention Structure of the second invention Structure of the third invention Structure of the fourth invention Structure of the fifth invention Operation of the first invention Operation of the second invention Operation of the third invention Operation of the fourth invention Operation of the fifth invention Implementation Example First embodiment (Figs. 1 and 2) Second embodiment (Figs. 3 and 4) Third embodiment (Fig. 5) Effect of the invention [Outline] Used in a semiconductor manufacturing process or the like Regarding a photomask inspection method for inspecting a mask pattern defect of a photomask, a repetitive pattern is formed on one surface of a transparent substrate for the purpose of enabling highly accurate inspection of a mask pattern defect The photo from one side of the photomask A region of the mask is irradiated with light, and a pattern image of the one region formed by the reflected light is formed on the pattern surface of the other region of the photomask having a pattern having the same shape as the pattern of the one region. The image is formed, and the defect of the mask pattern is inspected according to the presence or absence of passing light in the other area.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask inspection method and an inspection apparatus for inspecting a mask pattern defect of a photomask used in a semiconductor manufacturing process or the like.

In recent years, the miniaturization of semiconductor devices is progressing. Therefore, in the photomask manufacturing process,
An important issue is to reliably detect a mask pattern defect that causes a decrease in yield and reliability of the device and to manufacture a photomask having no mask pattern defect.

[Prior Art] Conventionally, as a photomask inspection apparatus, a photomask inspection apparatus whose schematic configuration is shown in FIG. 6 has been proposed.

This photomask inspection apparatus is provided with light sources 1A and 1B, objective lenses 2A and 2B, imaging devices 3A and 3B, and a logical operation circuit 4.

Also, 5 denotes a photomask, and is configured to form a pattern 7A, 7B of the same shape using the chrome C _r on one surface of the photomask 5 is a transparent glass substrate 6.

This photomask inspection device uses the light 8A emitted by the light source 1A.
Is irradiated from the other surface side of the photomask 5 to the area 9A including the one pattern 7A, the pattern image of the area 9A is captured by the imaging device 3A through the objective lens 2A, and the image signal S _A is obtained by the logical operation circuit 4 The light 8B emitted from the light source 1B from the other surface side of the photomask 5 to the area 9B including the other pattern 7B.
And the pattern image of the region 9B is picked up by the image pickup device 3B via the objective lens 2B, and the image signal S _B is taken by the logical operation circuit 4
Then, in the logic operation circuit 4, the image of pattern 7A and the image of pattern 7B are superposed, and a logical operation of S _A + S _B is performed, and it is determined whether or not there is a defect in the mask pattern from the result. To do.

That is, according to such a photomask inspection apparatus, S _A + S _B
When a result of = 0 is obtained, it can be determined that the mask pattern has no defect.

On the other hand, when the result that S _A + S _B ≠ 0 is obtained, pattern 7A
Alternatively, it can be determined that there is a pinhole defect in 7B or patterns 7A and 7B, or there is a pin spot defect (residue, residual defect) in region 9A or 9B or 9A and 9B.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention] However, in such a conventional photomask inspection apparatus, two independent optical systems, that is, an optical system including a light source 1A, an objective lens 2A, and an imaging device 3A, a light source 1B, and an objective are provided. Since the optical system including the lens 2B and the image pickup device 3B is provided, when there are individual differences in the constituent elements, for example, when there is variation in sensitivity between the image pickup devices 3A and 3B, the mask pattern The defect detection rate is reduced, and especially when the light sources 1A and 1B have uneven illuminance,
If the signal-to-noise ratio (S / N ratio) of 3A and 3B is low and there is a difference, false defects may be detected and mask pattern defect inspection may not be possible with high accuracy. There was a problem.

In view of such a point, the present invention has an object to provide a photomask inspection method and an inspection apparatus capable of highly accurately inspecting a mask pattern for defects.

[Means for Solving the Problems] The above objects are respectively achieved by the following first invention and fifth invention.

Configuration of the First Invention A first invention is a photomask inspection method, in which a region of the photomask is irradiated with light from one face side of the photomask formed by repeatedly forming a pattern on one face of a transparent substrate, Forming a pattern image of the one region by the reflected light on a pattern surface of another region of the photomask having a pattern of the same shape as the pattern of the one region,
The mask pattern is inspected for the presence or absence of passing light in the other area.

Configuration of Second Invention A second invention is a photomask inspecting apparatus, which also implements the first invention, wherein one surface of a photomask is formed by forming a repetitive pattern on one surface of a transparent substrate. Light irradiation means for irradiating one region of the photomask from the side, and a pattern image of the one region, the pattern image of the other region of the photomask having a pattern having the same shape as the pattern of the one region An image forming means for forming an image on a surface and a passing light detecting means for detecting passing light in the other area are provided.

Configuration of Third Invention A third invention is a photomask inspection method, in which one region of the photomask is irradiated with light from the other surface side of the photomask in which a repeated pattern is formed on one surface of a transparent substrate. Forming a pattern image of the one region by the passing light on a pattern surface of another region of the photomask having a pattern having the same shape as the pattern of the one region,
It is configured by a method of inspecting a mask pattern for defects according to the presence / absence of reflected light in the other area.

Configuration of Fourth Invention A fourth invention is a photomask inspection apparatus, which also carries out the third invention, and is a photomask in which a repetitive pattern is formed on one surface of a transparent substrate. A light irradiating means for irradiating the one area of the photomask from the surface side, and a pattern image of the one area of the other area of the photomask having a pattern having the same shape as the pattern of the one area. An image forming means for forming an image on the pattern surface and a reflected light detecting means for detecting reflected light in the other area are provided and configured.

Configuration of Fifth Invention A fifth invention is a photomask inspection apparatus, which also implements the first and third inventions, and is a photomask in which a repetitive pattern is formed on one surface of a transparent substrate. First photo-irradiating means for irradiating light to one region of the photomask from one side of the mask, and the photomask having a pattern image of the one region, which has the same shape as the pattern of the one region. Forming means for forming an image on the pattern surface of the other area, passing light detecting means for detecting the passing light in the other area, and irradiating the one area with light from the other surface side of the photomask. The second light irradiating means and the reflected light detecting means for detecting the reflected light in the other area are provided.

[Operation] Operation of the first invention In the first invention, when the pin spot defect does not exist in one region and the pin hole defect does not exist in the pattern of the other region, in the other region, There is no light passing through the photomask.

On the other hand, when there is a pin spot defect in one area or when there is a pin hole defect in the pattern of another area, there is light passing through the photomask in another area.

Therefore, by confirming the presence or absence of passing light in the other region, it is possible to confirm the existence of the pin spot defect in the one region or the pin hole defect in the other region.

Here, in the first invention, unlike the conventional example shown in FIG. 6, the defect inspection of the mask pattern of the photomask can be performed by one independent optical system. FIG. 6 It is possible to eliminate the inconvenience of the defect detection rate of the mask pattern and the detection of pseudo defects due to the individual difference of each element constituting the optical system of the conventional example.

Operation of the Second Invention In the second invention, the light irradiating means irradiates the light of one area, and the image forming means forms the pattern image of the one area on the pattern surface of the other area and passes it. It is configured so that the presence or absence of passing light passing through other areas can be determined by the light detecting means.

 Therefore, the first invention can be implemented.

Operation of the third invention In the third invention, when the pinhole defect does not exist in the pattern of the one region and the pin spot defect does not exist in the other region, the reflected light from the other region is not exist.

On the other hand, when there is a pinhole defect in the pattern of one area or when there is a pin spot defect in another area, the reflected light from the other area exists.

Therefore, by confirming the presence or absence of the reflected light in the other region, it is possible to confirm the existence of the pinhole defect in the one region or the pin spot defect in the other region.

Here, also in the third invention, as in the first invention, it is configured such that the defect inspection of the mask pattern of the photomask can be performed by one independent optical system. It is possible to eliminate the disadvantages such as a decrease in the defect detection rate of the mask pattern and the detection of pseudo defects due to the individual difference of each element constituting the optical system of the conventional example.

Operation of the Fourth Invention In the fourth invention, the light irradiating means irradiates the one area with light, and the image forming means forms an image of the pattern of the one area on the pattern surface of the other area and reflects it. It is configured so that the presence or absence of reflected light in other areas can be determined by the light detection means.

 Therefore, the third invention can be implemented.

Action of the Fifth Invention In the fifth invention, among these constituent elements, a first light irradiating means for irradiating one region from one surface side of the photomask, and a pattern image of the one region are formed in the one region. When the image forming means for forming an image on another area having the same pattern as the above and the passing light detecting means for detecting the passing light in the other area are used, the configuration is the same as that of the second invention. .

 Therefore, the first invention can be implemented.

Further, among the constituent elements, second light irradiation means for irradiating one region from the other surface side of the photomask, and a pattern image of the one region on another region having the same pattern as the one region When using the image forming means for forming an image on and the reflected light detecting means for detecting the reflected light in other areas,
It has the same configuration as the invention of.

 Therefore, the third invention can be implemented.

[Examples] Hereinafter, various examples of the present invention will be described with reference to FIGS. 1 to 5, but the present invention is not limited to these examples. In addition, in these FIGS. 1 to 5, parts corresponding to those in FIG.
The overlapping description is omitted.

First Embodiment FIG. 1 is a schematic configuration diagram showing a main part of a first embodiment of the present invention.

In FIG. 1, 10 is a light source such as a mercury lamp, 11 is a condenser lens, 12 is an aperture, and 13 is a shutter. These light source 10, condenser lens 11, and aperture 1
2 and the shutter 13 constitute a light irradiation means, and a pattern is formed from one surface side of the photomask 5 including the light 14 emitted from the light source 10.
The area 9A including 7A can be irradiated. In addition,
An alternate long and two short dashes line X indicates an optical path.

Also, 15 is an objective lens, 16 and 17 are beam splitters,
Reference numeral 18 denotes an objective lens, and the objective lens 15, the beam splitters 16 and 17, and the objective lens 18 constitute an image forming means so that the pattern image of the pattern 7A in the region 9A can be formed on the pattern 7B. There is.

Further, 19 is a shutter, 20 is a condenser lens, 21 is a photodetector consisting of, for example, a photomultiplier tube, and these shutter 19, condenser lens 20 and photodetector 21 constitute passing light detection means, and include a pattern 7B. Light passing through the area 9B can be detected. Reference numeral 22 is an output terminal of the photo detector 21.

Further, 23 and 24 are autofocus devices, and the autofocus device 23 is configured to be able to automatically control the vertical position of the objective lens 15 so that the focus position of the objective lens 15 is set on the surface of the pattern 7A. Has been done. Also, the autofocus device 24
Is configured so that the vertical position of the objective lens 18 can be automatically controlled so that the focus position of the objective lens 18 is set on the surface of the pattern 7B.

Further, 25 is a stage (mask holder) for holding the photomask 5, and 26 is a stage driving motor. The stage 25 and the stage driving motor 26 constitute a photomask moving device, and the photomask 5 is moved in a plane direction. It can be moved freely.

In the first embodiment configured in this way, the light source 10
When is turned on and the shutters 13 and 19 are opened, the light 14 emitted from the light source 10 is applied to the region 9A including the pattern 7A, and a part thereof is reflected by the pattern 7A. 27 shows this reflected light.

Here, the objective lens 15, by the autofocus device 23,
Since the upper and lower positions are set so that the focal point is located on the pattern 7A, the reflected light 27 passes through the objective lens 15 to become parallel light, which is further reflected by the beam splitters 16 and 17, and the objective lens Area passing through 18 and including pattern 7B
Irradiate 9B.

Here, the objective lens 18 is provided by the autofocus device 24.
Since the vertical position is set so that the focal point is located on the pattern 7B, the pattern image of the pattern 7A by the reflected light 27 is formed on the pattern 7B.

Here, supposing that there is no pin spot defect in the area 9A, only the reflected light 27 from the pattern 7A exists as the reflected light in the area 9A. Then, this reflected light 27 is irradiated on the pattern 7B,
An image of pattern 7A will be formed on 7B. That is, in this case, the reflected light 27 is not emitted to the outside of the pattern 7B.

Therefore, the photodetector 21 does not detect the passing light unless the pattern 7B has a pinhole defect.

On the other hand, as shown in FIG. 2A, even if the pin spot defect does not exist in the area 9A, if the pin hole defect 28 exists in the pattern 7B, a part 29 of the reflected light 27 passes through the pattern 7B. Will be detected by the photodetector 21.

Further, as shown in FIG. 2B, even if there is no pinhole defect in the pattern 7B, if there is a pin spot defect 30 in the region 9A, in addition to the reflected light 27 from the pattern 7A in the region 9A, , Light reflected by pin spot defect 30
31 is present, and as a result, this reflected light 31
In 9B, the light is radiated to the outside of the pattern 7B and is detected by the photodetector 21.

If the positions of patterns 7A and 7B are reversed,
Even when the pattern 7A has a pinhole defect or the region 9B has a pin spot defect, the photodetector 21 will detect the passing light.

In this way, in the first embodiment, defects in the mask pattern of the photomask 5 can be detected.

Here, in the first embodiment, unlike the conventional example shown in FIG. 6, since only one independent optical system including one light source 10 is provided, the optical system of the conventional example shown in FIG. It is possible to eliminate the inconveniences of the defect detection rate of the mask pattern and the detection of pseudo defects due to the individual differences of the constituent elements, and to perform the mask pattern defect inspection with high accuracy.

In the first embodiment, the moving speed of the stage 25 can be increased by expanding the illumination area by adjusting the aperture 12, and by doing so, the inspection time can be shortened. .

On the contrary, when the illumination area is narrowed, the moving speed of the stage 25 must be reduced. In this case, however, the aberration in the optical system can be reduced, so that the inspection can be performed with higher accuracy.

Second Embodiment FIG. 3 is a schematic configuration diagram showing a main part of a second embodiment of the present invention.

In FIG. 3, 32 is a light source such as a mercury lamp, 33 is a condenser lens, 34 is an aperture, and 35 is a shutter. These light source 32, condenser lens 33, and aperture 34
Also, the shutter 35 constitutes a light irradiation means so that the light 36 emitted from the light source 32 can be irradiated onto the region 9A including the pattern 7A from the other surface side of the photomask 5. The two-dot chain line Y indicates the optical path.

Further, in the second embodiment, the objective lens 15, the beam splitters 16, 17 and the objective lens 18 are provided as in the first embodiment, and the objective lens 15, the beam splitters 16, 17 and the objective lens 18 are combined. Forming image means, area 9A
The pattern image of the pattern 7A is formed on the pattern 7B.

Further, 37 is a shutter, 38 is a condenser lens, 39 is a photodetector comprising, for example, a photomultiplier tube, and the shutter 37, the condenser lens 38 and the photodetector 39 constitute a reflected light detection means, and include a pattern 7B. The light reflected by the area 9B and passing through the objective lens 18 and the beam splitter 17 can be detected by the photodetector 39 via the condenser lens 38. Incidentally, 40 is an output terminal of the photodetector 39.

Others are the same as those in the first embodiment.

In the second embodiment configured as described above, the light source 32
When is turned on and the shutters 35 and 37 are opened, the light 36 emitted from the light source 32 is applied to the area 9A including the pattern 7A, and of these, the light applied to the outside of the pattern 7A passes through the area 9A. 41 shows this passing light.

Here, the objective lens 15, by the autofocus device 23,
Since the vertical position is set so that the focal point is located on the pattern 7A, the passing light 41 passes through the objective lens 15 to become parallel light, which is further reflected by the beam splitters 16 and 17, and the objective lens 18 And is irradiated to the region 9B side including the pattern 7B.

Here, the objective lens 18 is provided by the autofocus device 24.
The upper and lower positions are set so that the focal point is located on the pattern 7B.
The image of 7A is formed on the pattern 7B as a black image (dark image).

Assuming that the pattern 7A has no pinhole defect, only the passing light 41 that has passed through the outside of the pattern 7A exists as the passing light in the region 9A. Then, the passing light 41 is applied to the region 9B, and the image of the pattern 7A is formed on the pattern 7B as a black image. That is, in this case, the passing light 41 is not irradiated onto the pattern 7B.

Therefore, the photodetector 39 does not detect the reflected light from the region 9B unless there is a pin spot defect in the region 9B.

On the other hand, as shown in FIG. 4A, even if the pinhole defect does not exist in the pattern 7A, if the pin spot defect 42 exists in the region 9B, a part of the passing light 41 will be a pin spot defect. It is reflected by 42, which is detected by the photodetector 39.

Further, as shown in FIG. 4B, even if the pin spot defect does not exist in the region 9B, if the pin hole defect 43 exists in the pattern 7A, the light passing through in the region 9A is outside the pattern 7A. In addition to the passing light 41 passing therethrough, there is a passing light 44 due to the pinhole defect 43, and as a result, this passing light 44 is irradiated on the surface of the pattern 7B and reflected, so that this is detected by the photodetector 39. It

If the positions of patterns 7A and 7B are reversed,
The photodetector 39 will detect the reflected light also when there is a pin spot defect in the area 9A or when there is a pinhole defect in the pattern 7B.

In this way, in the second embodiment, the defect of the mask pattern of the photomask 5 can be detected.

In this second embodiment as well, unlike the conventional example shown in FIG. 6, since only one independent optical system consisting of one light source 32 is provided, the optical system of the conventional example shown in FIG. It is possible to eliminate the inconveniences of the defect detection rate of the mask pattern and the detection of pseudo defects due to the individual differences of the constituent elements, and to perform the mask pattern defect inspection with high accuracy.

Also in the second embodiment, the moving speed of the stage 25 can be increased by expanding the illumination area by adjusting the aperture 34. By doing so, the inspection time can be shortened. .

On the contrary, when the illumination area is narrowed, the moving speed of the stage 25 must be reduced. In this case, however, the aberration in the optical system can be reduced, so that the inspection can be performed with higher accuracy.

Third Embodiment FIG. 5 is a schematic configuration diagram showing a main part of a third embodiment of the present invention.

The third embodiment is a combination of the first embodiment and the second embodiment.

In the third embodiment, the light source 10 and the condenser lens 1
1. When using the aperture 12, the shutter 13, the objective lens 15, the beam splitters 16 and 17, the objective lens 18, the shutter 19, the condenser lens 20 and the photodetector 21, the first
The configuration is similar to that of the embodiment.

Therefore, in this case, in the positional relationship shown in FIG. 5, there is a pinhole defect 28 in the pattern 7B as shown in FIG. 2A, or in the area 9A as shown in FIG. 2B. If there are spot defects 30, these can be detected.

When the light source 32, the condenser lens 33, the aperture 34, the shutter 35, the objective lens 15, the beam splitters 16 and 17, the objective lens 18, the shutter 37, the condenser lens 38 and the photodetector 39 are used, the second embodiment is performed. The configuration is similar to the example.

Therefore, in this case, with the positional relationship shown in FIG. 5, as shown in FIG.
These can be detected when there is 42 or when there is a pinhole defect 43 in the pattern 7A as shown in FIG. 4B.

Thus, in this third embodiment, the one area 9A
And the fifth area without reversing the positional relationship with the other area 9B.
In the positional relationship shown in the figure, the mask pattern of the photomask 5 can be inspected for defects.

Therefore, according to the third embodiment, the defect inspection of the mask pattern can be performed with high accuracy, and the first and second embodiments can be performed.
It is possible to obtain a special effect that it can be performed more easily than in the embodiment.

[Effects of the Invention] As described above, according to the present invention, unlike the conventional example shown in FIG. 6, the defect inspection of the mask pattern of the photomask can be performed by one independent optical system. Therefore, as in the conventional example shown in FIG. 6, inconveniences such as a decrease in the defect detection rate of the mask pattern and the detection of pseudo defects due to the individual difference of each element forming the optical system are eliminated, and the defect inspection of the mask pattern is highly accurate. There is an effect that can be done.

In particular, the fifth invention is configured by combining the second invention and the fourth invention, so that according to the fifth invention, a special effect that the inspection method can be simplified. There is.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a main part of a first embodiment of the present invention, FIGS. 2A and 2B are diagrams used for explaining the first embodiment, and FIG. 3 is a second embodiment of the present invention. FIG. 4A and FIG. 4B are diagrams used to explain the second embodiment, and FIG. 5 is a schematic configuration diagram showing the main part of the third embodiment of the present invention. FIG. 6 is a schematic configuration diagram showing a main part of a conventional photomask inspection apparatus. 5 …… Photomask 7A, 7B …… Pattern 10, 32 …… Light source 11, 20, 33, 38 …… Condenser lens 12, 34 …… Aperture 13, 19, 35, 37 …… Shutter 15, 18 …… Objective lens, 16, 17 …… Beam splitter 21, 39 …… Photodetector 28, 43 …… Pinhole defect 30, 42 …… Pin spot defect

Claims (5)

(57) [Claims] 1. A photomask, which is formed by repeatedly forming a pattern on one surface of a transparent substrate, is irradiated with light from one surface of the photomask, and a pattern image of the one area is formed by the reflected light. An image is formed on a pattern surface of another region of the photomask having a pattern having the same shape as the pattern of one region, and a defect of the mask pattern is inspected by the presence or absence of passing light in the other region. Photomask inspection method. 2. A light irradiating means for irradiating light to one region of the photomask from one side of the photomask, which is formed by repeatedly forming a pattern on one face of a transparent substrate, and a pattern image of the one region, An image forming means for forming an image on a pattern surface of the other area of the photomask having a pattern having the same shape as the pattern of the one area, and a passing light detecting means for detecting the passing light in the other area are provided. A photomask inspection apparatus characterized in that 3. A region of the photomask formed by repeatedly forming a pattern on one surface of a transparent substrate is irradiated with light from one side of the photomask, and a pattern image of the one region is formed by the passing light, An image is formed on a pattern surface of another region of the photomask having a pattern having the same shape as the pattern of the one region, and a defect of the mask pattern is inspected by the presence or absence of reflected light in the other region. Photomask inspection method. 4. A light irradiating means for irradiating light to one region of the photomask from the other surface side of the photomask, which is formed by repeatedly forming a pattern on one surface of a transparent substrate, and a pattern image of the one region, An image forming unit for forming an image on a pattern surface of the other region of the photomask having a pattern having the same shape as the pattern of the one region; and a reflected light detecting unit for detecting reflected light in the other region, A photomask inspection apparatus characterized by the following. 5. A first light irradiating means for irradiating light to one region of the photomask from one side of the photomask in which a pattern is repeatedly formed on one face of the transparent substrate, and a pattern image of the one region. An image forming means for forming an image on a pattern surface of the other area of the photomask having a pattern of the same shape as the pattern of the one area, and a transmitted light detecting means for detecting light passing through the other area. A second light irradiation means for irradiating the one area with light from the other surface side of the photomask, and a reflected light detection means for detecting reflected light in the other area. Photomask inspection device.