TWM636876U - Image capturing device for photomask - Google Patents

Abstract

An imaging device for imaging a photomask, comprising: a light source; a slit plate; a half mirror; an adjustable focus objective lens; and a camera; wherein, the light emitted by the light source passes through the slit plate , the reflection of the semi-reflective mirror passes through the adjustable focus objective lens to form a strip-shaped light beam that gradually narrows along the irradiation direction, and then irradiates the surface of the semi-reflective film on a photomask, and penetrates the semi-reflective The film is irradiated on the surface of the mask, the illuminated area on the surface of the semi-reflective film is strip-shaped and has a first width, and the illuminated area on the surface of the mask is strip-shaped and has a second width. width; wherein the first width is ten times or more than the second width.

Description

Image pickup device for photomask image pickup

This creation is related to the imaging technology of penetrating transparent objects, in particular, it refers to an imaging device for imaging the mask that can penetrate the semi-reflective film to capture the image.

The current optical detection technology is to project light on the object to be tested, and then when there are defects on the surface of the object to be tested, it can be displayed in the illuminated area, and then the image is taken, and the obtained image is processed by image processing or It is a manual judgment method for direct identification or comparison with the model to detect defects.

However, in the existing known optical inspection technology, when the object to be tested is a photomask, its surface will have the problem that it is difficult to detect defects because of the semi-reflective film. This is because when the light shines on the semi-reflective film, it will penetrate When the light on the upper surface of the semi-reflective film is irradiated on the lower surface of the semi-reflective film, it will be reflected back, and when the reflected light is irradiated on the upper surface of the semi-reflective film, it may be reflected again and then irradiated to the lower surface . In this way, a large amount of scattering noise will be generated due to repeated reflections in the semi-reflective film, which will result in undetectable results. Therefore, this is a problem that needs to be solved.

my country's early publication No. 201917375 patent discloses an optical detection method. In this case, a light-shielding film with slits is used to shield part of the light beam from the light source, and then the light source penetrates the light-transmitting object, and the image capture model The group captures images on the light-transmitting object. This technique can only be used for the detection of transparent objects, but it cannot detect the specific surface of the transparent object. Therefore, this technology cannot be applied to the requirement of detecting the surface of the mask after penetrating the semi-reflective film.

The main purpose of this creation is to provide an image capturing device for capturing images on the mask, which can clearly capture images on the surface of the mask through the semi-reflective film, so as to facilitate subsequent correct detection.

In order to achieve the above purpose, this creation proposes an imaging device for imaging a mask, comprising: a light source emitting light along a first optical axis; a slit plate having a linear slit located at the first optical axis An optical axis; a half reflector, located on the first optical axis, the light emitted by the light source passes through the slit and illuminates the half reflector, and part of the light is reflected and irradiated along a second optical axis, and the rest The light then penetrates the half mirror, the second optical axis and the first optical axis have a predetermined angle, and the predetermined angle is less than 180 degrees; an adjustable focus objective lens is located on the second optical axis, and the aforementioned The light reflected by the half mirror and irradiated along the second optical axis passes through the adjustable focus objective lens and irradiates a mask, and the adjustable focus objective lens can be operated to adjust the focal length, wherein the mask is attached with a A semi-reflective film, the aforementioned light system irradiated along the second optical axis penetrates the semi-reflective film and is irradiated on the surface of the mask; Between the camera and the camera, the camera passes through the semi-reflective film along the second optical axis to take an image of the surface of the mask; wherein, the light emitted by the light source passes through the slit and is shaped into a narrow strip of light After being reflected by the semi-reflective mirror, it passes through the adjustable focus objective lens, and is further focused by the adjustable focus objective lens to form a strip beam that gradually narrows along the irradiation direction, and then irradiates on the semi-reflective film The illuminated area on the surface of the semi-reflective film is strip-shaped and has a first width. The strip-shaped light beam also partially penetrates the semi-reflective film and irradiates the surface of the mask. The surface of the mask The illuminated area is elongated and has a second width, and the camera is used to take an image of the mask surface through the adjustable focus objective lens; wherein, the first width is ten times the second width or ten times more.

In this way, the invention can achieve a very clear image of the surface of the mask to facilitate subsequent correct detection. Compared with the image obtained by the previous technology, the image is clearer, and the detection result can be more accurate.

In order to describe the technical characteristics of this creation in detail, the following preferred embodiments are given below and described in conjunction with the drawings, wherein:

As shown in Figures 1 to 3, a preferred embodiment of the invention proposes an image pickup device 10 for photomask imaging, which mainly consists of a light source 11, a slit plate 13, half reflectors 15, and an adjustable focus The objective lens 17 and a video camera 19 are formed, and cooperate with a first tube 21 and a second tube 25 to assemble, wherein:

The light source 11 is installed in the first tube 21 and emits light along a first optical axis A1.

The slit plate 13 is installed in the first tube 21 and has a linear slit 131 located on the first optical axis A1. The slit plate 13 can adopt a mechanism that can adjust the width of the slit 131 as required, and can also select a slit 131 with a fixed width after determining the required width of the slit 131 .

The half mirror 15 is installed in the second tube 25 and is located on the first optical axis A1. The light emitted by the light source 11 passes through the slit 131 and irradiates the half mirror 15, and part of the light is reflected. While illuminating along a second optical axis A2, and the rest of the light then penetrates the half mirror 15, the second optical axis A2 and the first optical axis A1 form a predetermined angle, and the predetermined angle is less than 180 degrees. In this embodiment, the predetermined angle is 90 degrees.

The adjustable focus objective lens 17 is mounted on one end of the second tube 25 and is located on the second optical axis A2. The focus objective lens 17 is irradiated on a reticle 91, and the adjustable focus objective lens 17 can be operated to adjust the focal length, wherein the reticle 91 is pasted with a semi-reflective film 92, and the aforementioned light irradiated along the second optical axis A2 It penetrates the semi-reflective film 92 and irradiates the surface of the mask 91 .

The video camera 19, installed in the second tube 25, is located on the second optical axis A2 so that the half mirror 15 is located between the adjustable focus objective lens 17 and the video camera 19, and the video camera 19 is positioned along the second optical axis A2. The axis A2 passes through the semi-reflective film 92 to capture an image on the surface of the mask 91 .

Wherein, one end of the first tube 21 is assembled on the tube body of the second tube 25 and aligned with the half mirror 15 , and the first tube 21 and the second tube 25 communicate in space.

Wherein, the light emitted by the light source 11 passes through the slit 131 and is shaped into a narrow strip of light to exit, and then passes through the adjustable focus objective lens 17 after being reflected by the half mirror 15, and is further subjected to the adjustable focus. The focusing objective lens 17 focuses and forms strip light beam L gradually narrowing along the irradiation direction, and then irradiates on the surface of the semi-reflective film 92, and the illuminated area on the surface of the semi-reflective film 92 is strip-shaped and has a First width W1, the strip light beam L partially penetrates the surface of the semi-reflective film 92 and irradiates the surface of the mask 91, the illuminated area of the surface of the mask 91 is strip-shaped and has a With a second width W2, the camera 19 is used to capture an image on the surface of the mask 91 through the adjustable focus objective lens 17 and through the semi-reflective film 92 . In actual implementation, the camera 19 can preferably use a line scan system, and can match the irradiation area of the strip light beam L, so that the width of the narrow side of the irradiation area does not affect the imaging result. However, a general camera is combined with an image Processing technology can also achieve the result of imaging, and the camera 19 in this case is not limited to the line scan system.

Wherein, the first width W1 is ten times or more than the second width W2, and twenty times is taken as an example in this example.

In actual implementation, as shown in FIG. 3 , a detection platform 99 and a lift driving platform 31 may be further provided. The detection platform 99 is used to carry the photomask 91, and the second tube 25 is arranged on the lift drive platform 31, and the lift drive platform 31 drives the second tube 25 together with the first tube 21 relative to the The detection table 99 moves to approach or move away. In addition, a light extinction plate 251 is further provided in the second tube 25, and the light extinction plate 251 is located at the position where the light emitted by the light source 11 passes through the half mirror 15, so as to absorb the light irradiated on it. light, thereby preventing light from being reflected back to the half mirror 15.

In this embodiment, the first tube 21 is bent. In FIG. 1 to FIG. The mirror 22 can reflect the light from the light source 1 and irradiate it to the half mirror 15 . Such a structure can make the first tube 21 partially parallel to the second tube 25, thereby reducing the space occupied by the overall structure. In this embodiment, the first pipe 21 shown in FIGS. 1 to 3 is bent for illustration. In other implementation structures, as shown in FIG. 4 , the first tube 21 can also be changed into a straight tube without bending, and is not limited to the aforementioned bending state.

The configuration of the present embodiment has been described above, and the operation state of the present embodiment will be described next.

As shown in FIG. 3 and FIG. 5 to FIG. 7 , before use, a photomask 91 is placed on the testing table 99 . Then operate the lifting drive table 31 to drive the second tube 25 to move together with the first tube 21, thereby adjusting the distance between the adjustable focus objective lens 17 and the reticle 91, and adjusting the adjustable focus objective lens 17 focal length. Through the adjustment of the above two, it is possible to adjust the width of the strip light beam L irradiated on the surface of the semi-reflective film 92 and the width irradiated on the surface of the mask 91, so that the first width W1 is equal to the second width W2 Twenty times of that, and the area where the strip beam L is irradiated on the surface of the mask 91 is an inspection area IA, which is in the shape of a strip.

As shown in Figures 8 to 9, the prior art is taken as an example, and the illumination mode is such that the first width is only slightly wider than the second width. The light beam L' will irradiate the surface of the mask 91' after passing through the surface of the semi-reflective film 92', and the light irradiated on the surface of the mask 91' will be reflected to the semi-reflective film after being reflected. The surface of the reflective film 92' is then reflected on the surface of the semi-reflective film 92' and illuminates the surface of the photomask 91' again, and then reflects again when it is irradiated on the surface of the photomask 91', and this This kind of repeatedly reflected light will cause the blurring of the image, and the irradiated area on the surface of the mask 91' is also used as the detection area IA', which is circular.

However, this embodiment can greatly improve the occurrence of this blurred situation. As shown in FIG. 2, FIG. 6 and FIG. After the light is shaped, the focusable objective lens 17 emits the strip beam L, and the light irradiated by the strip beam L will irradiate on the surface of the mask 91 after penetrating the surface of the semi-reflective film 92, The light irradiated on the surface of the mask 91 will be irradiated to the surface of the semi-reflective film 92 after being reflected. The key point of this case is that the first width W1 of this embodiment is twenty times the second width W2, so that the light actually irradiated on the surface of the mask 91 has only the first width after reflection. The light of 1/20th (being 5%) width of W1 can be reflected to the surface of this semi-reflective film 92, therefore, in fact the light reflected to the surface of this semi-reflective film 92 is seldom, therefore, these When very little light is reflected to the surface of the mask 91 by the surface of the semi-reflective film 92 again, a large part will fall outside the area directly irradiated by the strip light beam L on the surface of the mask 91, Therefore, the area other than the area directly irradiated by the strip light beam L will appear very dark when the image is taken, so it can be ignored in the back-end image processing and comparison after the image is taken. In this way, in the image captured by the camera 19, only the area directly irradiated by the strip light beam L on the surface of the mask 91 is brighter, while other parts are very dark. During actual detection, the area where the surface of the photomask 91 is directly irradiated by the strip beam L can be used as the detection area IA. In FIGS. 6 and 10 , the detection area IA is the surface of the photomask 91. The portion of the second width W2 is indicated.

Then, only need to move the photomask 91 to make the strip beam L scan through the entire surface of the photomask 91, or move the lifting drive table 31 laterally to make the strip beam L scan over the surface of the photomask 91, This is equal to the continuous movement of the detection area IA, so that a complete and clear image of the surface of the mask 91 can be taken to facilitate subsequent image processing or manual detection and comparison.

It can be understood from the above description that this creation can achieve very clear images of the surface of the mask 91 for subsequent correct detection, and the images obtained by the prior art are clearer, and the detection results can be more accurate. for correct.

It should be added that the aforesaid relationship that the first width W1 is twenty times the second width W2 is only an example, and is not intended to limit the scope of the present patent. In fact, the slit 131 can also be regarded as Width, the brightness of the light source 11, and the distance between the adjustable focus objective lens 17 and the mask 91 determine the multiple relationship between the first width W1 and the second width W2, and the determining factor is the actual selection As far as the sharpness of the image is concerned, in terms of the technology of this creation, it is a better situation that the first width W1 is at least ten times or more than ten times the second width W2. Figure 11 shows that the first width W1 is The state of ten times of the second width W2, in this case, can make the light actually irradiated on the surface of the mask 91 only have one-tenth (ie 10%) of the first width W1 after reflection The light rays with a width of 100000000000000000000000000000000000000000000000000000000000000000000 etc. are reflected to the surface of the semi-reflecting film 92 . In addition, the multiple relationship between the first width W1 and the second width W2 is not limited to an integer multiple relationship.

10: The imaging device for imaging the mask 11: Light source 13: Slit plate 131: Slit 15: half mirror 17,17': Adjustable focus objective lens 19: Camera 21: First Tube 211: bending part 22: Mirror 25: Second pipe 251: matting board 31: Lifting drive table 91,91': mask 92,92': semi-reflective film 99: Testing table A1: The first optical axis A2: Second optical axis IA,IA': detection area L, L': strip beam W1: first width W2: second width

Fig. 1 is the perspective view of a preferred embodiment of this creation. Fig. 2 is a schematic diagram of the internal structure of a preferred embodiment of the invention. Fig. 3 is a schematic diagram of assembly of a preferred embodiment of the invention. Fig. 4 is another schematic view of the internal structure of a preferred embodiment of the invention. Fig. 5 is a schematic diagram of the operation of a preferred embodiment of the invention. Fig. 6 is a schematic diagram of illumination of a preferred embodiment of the invention. FIG. 7 is a schematic diagram of the irradiation result of FIG. 6, showing the irradiation range when the light shines on the surface of the mask. Fig. 8 is a schematic diagram of the operation of the prior art. FIG. 9 is a schematic diagram of the irradiation result of FIG. 8, showing the irradiation range when the light shines on the surface of the mask. Fig. 10 is a partially enlarged view of Fig. 6 . Fig. 11 is a schematic diagram of operation in another state similar to Fig. 10 .

10: The imaging device for imaging the mask

11: Light source

13: Slit plate

131: Slit

15: half mirror

17: Adjustable focus objective lens

19: Camera

21: First Tube

211: bending part

22: Mirror

25: Second pipe

251: matting board

A1: The first optical axis

A2: Second optical axis

Claims (7)

An imaging device for imaging a photomask, comprising: a light source emitting light along a first optical axis; a slit plate having a linear slit located on the first optical axis; A half reflective mirror, located on the first optical axis, the light emitted by the light source passes through the slit and irradiates the half reflective mirror, and part of the light is reflected and irradiated along a second optical axis, and the rest of the light passes through In the half mirror, the second optical axis and the first optical axis form a predetermined angle, and the predetermined angle is less than 180 degrees; An adjustable focus objective lens, located on the second optical axis, the aforementioned light system reflected by the half mirror and irradiated along the second optical axis passes through the adjustable focus objective lens and irradiates on a reticle, the adjustable focus objective lens It can be operated to adjust the focal length, wherein a semi-reflective film is attached to the mask, and the aforementioned light irradiated along the second optical axis penetrates the semi-reflective film and irradiates on the surface of the mask; and a camera, located on the second optical axis so that the half mirror is located between the adjustable focus objective lens and the camera, and the camera passes through the semi-reflective film along the second optical axis to take an image of the mask surface; Wherein, the light emitted by the light source passes through the slit and is shaped into a narrow strip of light to exit, and then passes through the adjustable focus objective lens after being reflected by the half mirror, and is further focused by the adjustable focus objective lens And form the strip-shaped light beam that gradually narrows along the irradiation direction, and then irradiate the surface of the semi-reflective film, the illuminated area on the surface of the semi-reflective film is elongated and has a first width, the strip-shaped light beam And part of it penetrates through the semi-reflective film and irradiates the surface of the mask, and the illuminated area on the surface of the mask is elongated and has a second width. Photomask surface capture; Wherein, the first width is ten times or more than the second width. According to the imaging device for imaging the photomask described in claim 1, it further includes a first tube and a second tube, the light source and the slit plate are installed on the first tube, the camera, the The half mirror and the adjustable focus objective lens are mounted on the second tube, one end of the first tube is assembled on the body of the second tube and aligned with the half mirror, and the first tube and the second The tubes are connected in space. According to the imaging device for imaging a photomask described in claim 2, wherein: the light source and the slit plate are located in the first tube, the camera and the half mirror are located in the second tube, and the The adjustable focus objective lens is arranged at one end of the second tube. According to the imaging device for imaging a photomask according to claim 2, wherein: the slit plate can adjust the width of the slit. According to the imaging device for imaging the photomask described in claim 2, it further includes a detection platform and a lift driving platform; the detection platform is used to carry the photomask, and the second pipe is arranged on the An elevating driving table, the elevating driving table is used to drive the second pipe together with the first pipe to move closer to or away from the detection table. According to the imaging device for imaging the photomask described in claim 2, wherein: a matting plate is provided in the second tube, and the matting plate is located at the position where the light emitted by the light source passes through the half-reflecting mirror . According to the imaging device for imaging a photomask as described in claim 2, wherein: the first tube has a bent portion, and a reflector is arranged in the bent portion in the first tube.

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