TWI832419B - Image capturing device for capturing images of photomask - Google Patents

Abstract

An imaging device for capturing images of a mask, including: a light source; a slit plate; a half-reflecting 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 then passes through the adjustable focus objective lens to form a strip beam that gradually narrows from wide to narrow along the illumination direction, and then illuminates the surface of the semi-reflective film on a mask, and penetrates the semi-reflective film The film is irradiated on the surface of the photomask. The illuminated area on the surface of the semi-reflective film is elongated and has a first width. The illuminated area on the surface of the photomask is elongated and has a second width. Width; wherein the first width is ten times or more than the second width.

Description

Image capturing device for capturing images of photomask

The present invention relates to the imaging technology of penetrating transparent objects, and particularly refers to an imaging device for capturing images of a photomask that can penetrate a semi-reflective film to capture an image of a photomask.

The current optical inspection technology uses light to project onto the object to be tested, and then when there are defects on the surface of the object to be tested, they 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 samples to detect defects.

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

my country's early published patent No. 201917375 disclosed an optical detection method. In this case, a light shield with a slit was used to block part of the light beam of the light source, and then the light source was allowed to penetrate the light-transmitting object, and the image was captured. Set on the light-transmitting object to capture the image. This technology can only be used to detect transparent objects, but it cannot detect the specific surface of the transparent object. Therefore, this technology cannot be applied to the need to penetrate the semi-reflective film and then detect the surface of the mask.

The main purpose of the present invention is to provide an imaging device for capturing images of a photomask, which can penetrate the semi-reflective film to clearly capture the image of the surface of the photomask to facilitate subsequent correct detection.

In order to achieve the above object, the present invention proposes an imaging device for capturing images of a reticle, which includes: a light source that emits light along a first optical axis; a slit plate with a linear slit located on the first optical axis; An optical axis; a half-reflecting mirror is located on the first optical axis. The light emitted by the light source passes through the slit and is irradiated on the half-reflecting mirror, and part of the light is reflected and irradiated along a second optical axis, and the rest is The light penetrates the half-reflecting mirror, the second optical axis and the first optical axis intersect a predetermined angle, and the predetermined angle is less than 180 degrees; an adjustable focus objective lens is located on the second optical axis, the aforementioned The light reflected by the half-reflecting mirror and illuminated along the second optical axis passes through the adjustable focus objective lens and is illuminated on a mask. 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 light irradiated along the second optical axis penetrates the semi-reflective film and is irradiated on the surface of the mask; and a camera is located on the second optical axis so that the semi-reflective mirror is located at the adjustable focus objective lens and the camera, the camera captures the image of the mask surface through the semi-reflective film along the second optical axis; wherein, the light emitted by the light source is shaped into a narrow strip of light through the slit. It is emitted, and is reflected by the semi-reflective mirror and then 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 from wide to narrow along the illumination direction, and then illuminates the semi-reflective film. The illuminated area on the surface of the semi-reflective film is strip-shaped and has a first width, and the strip-shaped beam partially penetrates the semi-reflective film and irradiates the surface of the mask, and the surface of the mask The illuminated area is elongated and has a second width. The camera is used to capture images 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 present invention can achieve an extremely clear image of the surface of the photomask, so as 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 explain in detail the technical characteristics of the present invention, the following preferred embodiments are cited and described with reference to the drawings, wherein:

As shown in Figures 1 to 3, a preferred embodiment of the present invention proposes an imaging device 10 for capturing images of a reticle, which mainly consists of a light source 11, a slit plate 13, a half mirror 15, and an adjustable focus The objective lens 17 and a camera 19 are assembled together with a first tube 21 and a second tube 25, 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 may adopt a mechanism that can adjust the width of the slit 131 as needed, or the slit 131 may have a fixed width after determining the required width of the slit 131 .

The half-reflecting mirror 15 is installed in the second tube 25 and located on the first optical axis A1. The light emitted by the light source 11 passes through the slit 131 and then irradiates the half-reflecting mirror 15, and part of the light is reflected. The light is irradiated along a second optical axis A2, and the remaining light penetrates the half-reflecting mirror 15. The second optical axis A2 and the first optical axis A1 intersect 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 installed at one end of the second tube 25 and is located on the second optical axis A2. The light system reflected by the half mirror 15 and illuminated along the second optical axis A2 passes through the adjustable focus objective lens 17. The focusing objective lens 17 is illuminated on a reticle 91. The focus-adjustable objective lens 17 can be operated to adjust the focal length. The reticle 91 is attached with a semi-reflective film 92. The aforementioned light irradiated along the second optical axis A2 It penetrates the semi-reflective film 92 and irradiates the surface of the photomask 91 .

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

One end of the first tube 21 is assembled to the tube body of the second tube 25 and aligned with the half-reflecting mirror 15 , and the first tube 21 and the second tube 25 are spatially connected.

The light emitted by the light source 11 is shaped into a narrow strip of light through the slit 131 and emitted, and is reflected by the half-reflecting mirror 15 and then passes through the adjustable focus objective lens 17, and is further affected by the adjustable focus lens 17. The focusing objective lens 17 focuses to form a strip beam L that gradually narrows from wide to narrow along the irradiation direction, and then irradiates the surface of the semi-reflective film 92. The illuminated area on the surface of the semi-reflective film 92 is elongated and has a With the first width W1, the strip-shaped light beam L partially penetrates the surface of the semi-reflective film 92 and irradiates the surface of the photomask 91. The illuminated area on the surface of the photomask 91 is elongated and has a With the second width W2, the camera 19 is used to capture images of the surface of the reticle 91 through the semi-reflective film 92 through the adjustable focus objective lens 17. In actual implementation, the camera 19 can preferably use a line scan system, and can be matched with the irradiation area of the strip beam L, so that the narrow width of the irradiation area does not affect the imaging results. However, a general camera can match the image Processing technology can also achieve imaging results, 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, in this example it is twenty times.

In actual implementation, as shown in FIG. 3 , a detection platform 99 and a lifting driving platform 31 may be further provided. The detection platform 99 is used to carry the photomask 91, and the second tube 25 is provided on the lifting driving platform 31. The lifting driving platform 31 drives the second tube 25 together with the first tube 21 relative to the The detection stage 99 moves closer or further away. In addition, a matting plate 251 is further provided in the second tube 25, and the matting plate 251 is located at a position where the light emitted by the light source 11 partially penetrates the half-reflecting mirror 15, so as to absorb the light irradiated thereon. light, thereby preventing light from being reflected back to the half-reflecting mirror 15.

In this embodiment, the first tube 21 is arranged in a bent shape. In Figures 1 to 3, the first tube 21 has a bent portion 211, and a reflector is provided in the bent portion 211 of the first tube 21. The mirror 22 can reflect the light from the light source 1 and illuminate the semi-reflecting mirror 15 . This structure allows the first tube 21 to be partially parallel to the second tube 25, thereby reducing the space occupied by the overall structure. In this embodiment, the structure in which the first tube 21 shown in FIGS. 1 to 3 is in a bent state will be used for explanation. In other implementation structures, as shown in FIG. 4 , the first tube 21 can also be changed into a straight tube shape without bending, and is not limited to the aforementioned bent state.

The structure of this embodiment has been described above. Next, the operation status of this embodiment will be described.

As shown in FIG. 3 and FIG. 5 to FIG. 7 , a photomask 91 is placed on the detection stage 99 before use. Then the lifting driving stage 31 is operated to drive the second tube 25 to move together with the first tube 21 to adjust the distance between the focus-adjustable objective lens 17 and the reticle 91 and adjust the distance between the focus-adjustable objective lens 17 and the reticle 91 . focal length. By adjusting the above two, the width of the strip beam L irradiated on the surface of the semi-reflective film 92 and the width irradiated on the surface of the photomask 91 can be adjusted so that the first width W1 is the second width W2 Twenty times, and the area where the strip beam L irradiates the surface of the mask 91 is a detection area IA, which is in a long strip shape.

As shown in FIGS. 8 to 9 , taking the conventional technology as an example, the illumination method is such that the first width is only slightly wider than the second width. Therefore, the strips are emitted from the adjustable focus objective lens 17 ′. After passing through the surface of the semi-reflective film 92', the light beam L' will be illuminated on the surface of the photomask 91', and the light illuminated on the surface of the photomask 91' will be reflected to the semi-reflective film 92'. 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 is reflected again when it is irradiated on the surface of the photomask 91', and this This repeatedly reflected light will cause blur in the image capture, and the illuminated area on the surface of the mask 91' is also regarded as the detection area IA', and is circular.

However, this embodiment can greatly improve the blurring situation. As shown in FIG. 2, FIG. 6 and FIG. 10, when in use, the slit 131 of the slit plate 13 is used to emit the light source 11. After the light is shaped, the strip beam L is emitted from the focus-adjustable objective lens 17. The light irradiated by the strip beam L will illuminate the surface of the photomask 91 after penetrating the surface of the semi-reflective film 92. The light irradiated on the surface of the photomask 91 will be irradiated on the surface of the semi-reflective film 92 after reflection. The key point of this case is that in this embodiment, the first width W1 is twenty times the second width W2, so that the light actually irradiating on the surface of the photomask 91 only has the first width after reflection. Light with a width of one-twentieth (that is, 5%) of W1 will be reflected to the surface of the semi-reflective film 92. Therefore, the light actually reflected to the surface of the semi-reflective film 92 is very small. Therefore, these When a small amount of light is reflected from the surface of the semi-reflective film 92 to the surface of the photomask 91, a large part of it will fall outside the area directly illuminated by the strip beam L on the surface of the photomask 91. Therefore, the area outside the area directly illuminated by the strip beam L will appear very dark during image capture, so it can be ignored in the back-end image processing comparison after image capture. In this way, in the image captured by the camera 19, only the area on the surface of the mask 91 directly illuminated by the strip beam L is brighter, while other parts are very dark. Therefore, in During actual detection, the area on the surface of the mask 91 that is directly illuminated by the strip beam L can be used as the detection area IA. In Figures 6 and 10, the detection area IA is the surface of the mask 91. The portion of the second width W2 is marked.

Then, it is only necessary to move the photomask 91 to make the strip beam L scan across the entire surface of the photomask 91, or to move the lifting and lowering driving stage 31 laterally to scan the strip beam L across the surface of the photomask 91. This means that the detection area IA is constantly moving, and the surface of the photomask 91 can be completely and clearly imaged to facilitate subsequent image processing or manual detection and comparison.

It can be understood from the above description that the present invention can achieve an extremely clear image capture of the surface of the photomask 91 to facilitate subsequent correct detection. Compared with the previous technology, the image obtained is clearer, and the detection results can be more accurate. to be correct.

It should be added that the aforementioned relationship between the first width W1 and the second width W2 is only an example and is not used to limit the patent scope of this case. In fact, the slit 131 can also be regarded as The width, the brightness of the light source 11, and the distance between the adjustable focus objective lens 17 and the light mask 91 determine the multiple relationship between the first width W1 and the second width W2, and the determining factor is the actual For the clarity of the image, according to the technology of the present invention, it is better that the first width W1 is at least ten times or more than the second width W2. Figure 11 shows that the first width W1 is The state of ten times the second width W2, in this case, can make the light actually irradiated on the surface of the photomask 91 after reflection, only one-tenth (that is, 10%) of the first width W1 A width of light will be reflected to the surface of the semi-reflective 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: Image capturing device for capturing images of the photomask 11:Light source 13: Slit board 131:Slit 15: Half mirror 17,17’: Adjustable focus objective lens 19:Camera 21:First tube 211: Bending part 22:Reflector 25:Second tube 251:Matting plate 31: Lifting drive platform 91,91’: photomask 92,92’: Semi-reflective film 99:Testing station A1: first optical axis A2: Second optical axis IA, IA’: detection area L, L’: strip beam W1: first width W2: second width

Figure 1 is a perspective view of a preferred embodiment of the present invention. Figure 2 is a schematic diagram of the internal structure of a preferred embodiment of the present invention. Figure 3 is an assembly schematic diagram of a preferred embodiment of the present invention. Figure 4 is another schematic diagram of the internal structure of a preferred embodiment of the present invention. Figure 5 is an operation schematic diagram of a preferred embodiment of the present invention. Figure 6 is a schematic diagram of lighting according to a preferred embodiment of the present invention. Figure 7 is a schematic diagram of the irradiation results in Figure 6, showing the irradiation range when light shines on the surface of the mask. Figure 8 is a schematic diagram of the operation of the conventional technology. Figure 9 is a schematic diagram of the irradiation results in Figure 8, showing the irradiation range when light shines on the surface of the mask. Figure 10 is a partial enlarged view of Figure 6. Figure 11 is a schematic diagram of operation in another state similar to Figure 10.

10: Image capturing device for capturing images of the photomask

11:Light source

13: Slit board

131:Slit

15: Half mirror

17: Adjustable focus objective lens

19:Camera

21:First tube

211: Bending part

22:Reflector

25:Second tube

251:Matting plate

A1: first optical axis

A2: Second optical axis

Claims (7)

An imaging device for capturing images of a photomask, including: a light source that emits light along a first optical axis; A slit plate having a linear slit located on the first optical axis; A half-reflecting mirror is located on the first optical axis. The light emitted by the light source passes through the slit and is illuminated on the half-reflecting mirror. Part of the light is reflected and illuminated along a second optical axis, and the remaining light is transmitted through. For the half-reflecting mirror, the second optical axis and the first optical axis intersect a predetermined angle, and the predetermined angle is less than 180 degrees; An adjustable focus objective lens is located on the second optical axis. The light system reflected by the half-reflecting mirror and illuminated along the second optical axis passes through the adjustable focus objective lens and is illuminated on a mask. The adjustable focus objective lens It can be operated to adjust the focal length, wherein the reticle is attached with a semi-reflective film, and the light irradiated along the second optical axis penetrates the semi-reflective film and irradiates the surface of the reticle; and A camera is located on the second optical axis such that the half-reflective mirror is located between the adjustable focus objective lens and the camera, and the camera captures images of the mask surface through the semi-reflective film along the second optical axis; The light emitted by the light source is shaped into a narrow strip of light through the slit and emitted, and is reflected by the half-reflecting mirror and then passes through the adjustable focus objective lens, and is further focused by the adjustable focus objective lens. A strip-shaped beam gradually narrowing along the illumination direction is formed, and then irradiated on 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 beam And part of it penetrates the semi-reflective film and illuminates the surface of the mask. The illuminated area of the surface of the mask is elongated and has a second width. The camera is used to capture the light through the adjustable focus objective lens. Image acquisition on the mask surface; Wherein, the first width is ten times or more than ten times of the second width. The imaging device for capturing images of a mask according to claim 1, further comprising 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-reflecting mirror and the adjustable focus objective lens are installed on the second tube, one end of the first tube is assembled on the body of the second tube and aligned with the half-reflecting mirror, and the first tube and the second tube The tubes are spatially connected. The imaging device for capturing images of a mask according to claim 2, wherein: the light source and the slit plate are located in the first tube, the camera and the half-reflecting mirror are located in the second tube, and the The adjustable focus objective lens is located at one end of the second tube. According to the imaging device for capturing images of a photomask according to claim 2, the slit plate can adjust the width of the slit. The imaging device for capturing images of a photomask according to claim 2, which further includes a detection platform and a lifting drive platform; the detection platform is used to carry the photomask, and the second pipe is located on the The lifting driving platform drives the second tube together with the first tube to move closer to or farther away from the detection platform relative to the detection platform. The imaging device for capturing images of a reticle according to claim 2, wherein: a matting plate is provided inside the second tube, and the matting plate is located at a position after part of the light emitted by the light source penetrates the half-reflecting mirror . According to the imaging device for capturing an image of a photomask according to claim 2, wherein: the first tube has a bending portion, and a reflector is provided in the bending portion of the first tube.

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