JPH0641920B2 - Foreign object detection method and apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a reticle device in which foreign matter adhesion preventing means in which a pellicle is attached to a frame used in a reduction projection exposure apparatus is mounted on a reticle having a circuit pattern formed thereon. For example, the present invention relates to a foreign matter detection method and apparatus suitable for detecting foreign matter on the surface of an object to be inspected such as a pellicle surface.

[Prior Art] A conventional foreign matter detection device of this type is disclosed in, for example, Japanese Patent Laid-Open No. 60-67845.
As described in No. 6, a parallel beam is applied as a strip from a diagonal direction to the surface of an object to be inspected, such as a thin film called a pellicle, which is affixed on a glass substrate such as a photomask and a reticle, with a strip-like irradiation. There is proposed a method in which scattered light of a foreign substance existing in a portion is detected by focusing it by an imaging lens and forming an image on a one-dimensional image sensor.

[Problems to be Solved by the Invention] In the above-mentioned conventional technology, the entire image of the illumination area on the surface of the object to be inspected is projected by a single imaging lens to form an image on the one-dimensional image sensor, and the image exists in the illumination area. It detects the scattering reaction of foreign matter, and uses a tilting optical system to avoid the influence of stray light from other than foreign matter. However, since the numerical aperture (NA) of the imaging lens is different because it is a tilting optical system, the imaging magnification is different, and the same foreign matter is present in the central portion and the end portion of the strip illumination portion on the surface of the inspection object such as a thin film. The scattered light intensity is different,
There is a problem in that it is necessary to set the reference level (threshold value) for foreign matter detection in accordance with this.

The object of the present invention is to solve the above-mentioned problems of the prior art by eliminating the influence of the unevenness of the light amount by each imaging lens on the surface of the object to be inspected, with the same detection sensitivity, and of stray light from other than the detection imaging region. An object of the present invention is to provide a foreign matter detection method and an apparatus therefor which can be quickly detected by a simple configuration without being affected.

[Means for Solving the Problems] In order to achieve the above object, the present invention scans an object to be inspected linearly in a predetermined direction by a scanning means, and the surface of the object to be inspected scanned linearly. Focused band-shaped light extending substantially from the scanning direction to a direction substantially perpendicular to the scanning direction in a diagonal direction having a desired inclination angle from the vertical direction by a focused-band light beam irradiation means configured by arranging a plurality of light emitting elements The beam is irradiated, and the scattered and reflected light from the surface of the object to be inspected is irradiated by the focused band-shaped light beam so that the optical axis direction is substantially perpendicular to the surface of the object to be inspected. An image forming lens group composed of a plurality of image forming lenses arranged in a zigzag pattern in the band direction so that the image areas overlap each other is condensed and imaged at the image forming position. Provided in the strip and extending in the strip direction. The scattered reflection light generated from areas other than the detection area on the surface of the object to be inspected is shielded by the light shielding means formed by the window-shaped opening, and each of the scattered reflection light images formed by passing through the light shielding means is described above. The plurality of photoelectric conversion units arranged corresponding to the plurality of imaging lenses receive light, and the foreign matter attached on the surface of the inspection object is detected based on the signal obtained from each of the plurality of photoelectric conversion units. And a foreign matter detection method. Further, according to the present invention, a scanning means for linearly scanning an object to be inspected in a predetermined direction, and an almost oblique direction having a desired inclination angle from a vertical direction on the surface of the object to be inspected linearly scanned by the scanning means. Focusing band light beam irradiating means constituted by arranging a plurality of light emitting elements for irradiating a focusing band light beam extending from the scanning direction in a direction substantially perpendicular to the scanning direction, and irradiation by the focusing band light beam irradiating means The optical axis direction is set substantially perpendicular to the surface of the object to be inspected so that the scattered and reflected light from the surface of the object to be inspected is condensed by the focused band-shaped light beam and focused at an image forming position. An imaging lens group composed of a plurality of imaging lenses arranged in a zigzag pattern in the belt-shaped direction so that the imaging regions on the surface of the object to be examined overlap in the belt-shaped direction, and the imaging lens group is provided at the imaging position. Slits extending in the strip direction Is formed in the opening, the light shielding means for shielding the scattered reflected light generated from the non-detection imaging area of the object to be inspected surface, is disposed corresponding to the plurality of imaging lenses,
A plurality of photoelectric conversion means for receiving each of the scattered reflected light images formed through the light shielding means, and on the surface of the object to be inspected based on a signal obtained from each of the plurality of photoelectric conversion means. The foreign matter detection device is characterized in that it is configured to detect foreign matter adhered to the. Further, the present invention is characterized in that, in the foreign matter detection device, a linear image sensor is used as the plurality of photoelectric conversion means. Further, the present invention is characterized in that, in the foreign matter detecting device, the length of the slit-shaped opening of the light shielding means in the longitudinal direction is variable.

[Operation] With the above configuration, foreign matter attached on the surface of the object to be inspected such as the pellicle surface in the reticle device is simply scanned in one direction on the surface of the object to be inspected. It is possible to perform quick detection with a simple configuration without affecting the unevenness of the light amount due to the image lens, with the same detection sensitivity, and without being affected by stray light from other than the detection image forming area. Further, in the embodiment, since the length in the longitudinal direction of the slit-shaped opening of the light shielding means is variable, it is adapted even if there is some variation in the width dimension of the object to be inspected, and stray light from areas other than the detected image forming area is adapted. It is possible to stably detect only the foreign matter attached on the surface of the inspection object without receiving the light.

[Embodiment] Hereinafter, FIGS. 1 to 10 showing an embodiment of the present invention will be described.

As shown in FIG. 1, the foreign matter detection device 11 attaches a pellicle 3 to the upper surface of a glass substrate 1 including a photomask and a reticle via a frame 2, and the surface of the pellicle 3 is symmetrically inclined in an obliquely upward direction. Illuminating means 4 for arranging the strip-shaped illumination on the surface of the pellicle 3 is provided, and is arranged on a strip-shaped illuminating part (not shown) formed between them by the illuminating means 4, and the lens array 6 and the light shielding means 7 are provided. A photoelectric conversion means 5 including a photoelectric conversion element (for example, a linearly arranged one-dimensional image sensor) 8 is provided. Further, the glass substrate 1 is placed on a stage, and when the motor 92 is driven by a command (number of pulses) of the encoder 91, the stage 9 has a feed screw 93 and a nut 94 connected thereto.
It is configured so that it can be moved in the y direction via.

As shown in FIG. 2, the illumination means 4 is a semiconductor laser, L
A plurality of light emitting elements 41 including EDs are linearly arranged in the x direction, and a light source image (light emitting point image) of each light emitting element is collected by a condenser lens 42.
To irradiate the surface of the pellicle 3 with the strip-shaped irradiation section 43.
Is formed.

The light emitting element 41 may be of a type incorporating a condenser lens. In this case, the condenser lens 42 is unnecessary.

The light emitting element 41 may be a combination of an element having a linear light emitting source and the condenser lens 42.

As shown in FIG. 4, the lens array 6 shown in FIG. 1 is formed by arranging a plurality of minutely formed imaging lenses 61 each having a large diameter of about 1 mm linearly in the x direction. There is. Since the imaging lens 61 is formed of a lens having a parabolic refraction distribution 62 from the center to the periphery as shown in FIG. 3, when the incident light 63 enters the imaging lens 61, it is incident. The light 63 travels in a sine shape or a helical shape at a constant cycle, whereby it is possible to image the central portion of the surface of the pellicle 3 and its periphery with the same sensitivity. By the way, the structure and operation of the imaging lens 61, which is not the embodiment of the present invention, will be explained based on FIG. 4 and FIG. That is, since the imaging lens 61 is arranged linearly in the x direction as shown in FIG. 4, the foreign matter 10 present on the surface of the pellicle 3 can be detected over a wide range.

That is, the imaging area (field of view) 64 of each imaging lens 61 is several mm.
However, since this is projected onto the light receiving surface of the photoelectric conversion element 8, it becomes possible to detect over a wide range by disposing a plurality of imaging lenses 61 on a straight line.

Further, by arranging a plurality of the image forming lenses 61 on a straight line, the image projected on the light receiving surface of the photoelectric conversion element 8 is a superposed image of the image forming lenses 61.

That is, as shown in FIG. 5, the imaging lens 61 has a light quantity distribution.
65, and the light amount of the lens array 6 (FIG. 1) is the sum of the light amounts of the individual imaging lenses 61. for that reason,
Cyclic light intensity unevenness associated with the arrangement pitch P of the imaging lenses 61
66, and the same foreign matter in the center and the periphery of the imaging area 64
Even if it is 10, the light receiving intensity on the light receiving surface of the light receiving conversion element 8 is slightly different. In the present invention, in order to solve this problem, it is necessary to reduce the array pitch P of the imaging lenses 61 and increase the degree of overlap (overlap) of the imaging regions 64 of the adjacent imaging lenses 61. As a result, it is possible to reduce the unevenness of the light amount 66 and prevent the foreign matter 10 from being overlooked. Therefore, in the present invention, the above-mentioned problems can be solved by arranging the imaging lenses 61 linearly and zigzag in the x direction at a high density as shown in FIG. However, in this case, the photoelectric conversion element 8 is the imaging lens 61.
It is necessary to make the light receiving surface of a size capable of receiving the image forming regions 64 for the two columns.

The shading means 7 shown in FIG. 1 is composed of two flat shading plates 71a and 71b, which are superposed on each other and arranged to be movable in the x direction, as shown in FIG. 8, and these two shading plates. 71a, 71b are openings 72a, 72b that are formed on the opposite end surfaces of the respective 71a, 71b and have a predetermined length in the x direction, a motor 74 that rotates in both the forward and reverse directions 73a, 73b, and this motor 74. A lead screw 76 having a screw portion 75a and a right screw portion 75b, and these left screw portions 7
Two nuts 77, which are respectively screwed into the 5a and the right screw part 75b, and fixed to the end faces in the y direction of the two light shield plates 71a and 71b.
a and 77b, and by rotating the motor 74 in the forward direction 73a or the reverse direction 73b, two light shield plates 71a, 7b
1b moves in the opposite outward or inward direction to make the opening length l of the two openings 72a, 72b variable, and thereby the shape and dimensions of the glass substrate 1 and the pellicle 3 in the x direction are changed. Even if stray light is prevented and the foreign matter 10
Can be detected.

That is, as shown in FIG. 7, as stray light, scattered light 44 from the frame 2 to which the pellicle 3 is attached and the pellicle 3 are
The scattered light 45 generated when the light passing through hits the circuit pattern 12 formed on the surface 11 of the glass substrate 1 is considered.
In order to prevent these stray light from reaching the light receiving surface of the photoelectric conversion element 8, as shown in FIG. 9, a region indicated by a dot-dash line about 1 to 2 mm from the inside of the frame 2 of the pellicle 3 is a foreign substance. Foreign matter on the pellicle 3 when the effective detection area 31 is 10
It is necessary to detect 10 in this effective detection area 31.

Therefore, in the present invention, the light shielding means 7 is installed immediately before the lens array 6 side of the photoelectric conversion element 8 (FIG. 7), and the opening lengths of the openings 72a and 72b (FIG. 8) of the light shielding means 7 are set. l
Is formed variably according to the shape and size of the effective detection area 31 (FIG. 9), so stray light is prevented and stable foreign matter is prevented.
It is possible to perform 10 detections.

In general, after cleaning the glass substrate 1, the pellicle 3 (FIG. 7) is provided with a circuit pattern forming surface 11 of the glass substrate 1,
And, it is adhered to both surfaces of the glass substrate 1 after confirming that there is no minute foreign substance of about 1 to 2 μm on the non-formed surface, but the shape dimension of the glass substrate 1 also changes as the circuit pattern 12 becomes finer. At the same time, the shape and size of the pellicle 3 are diversified, but the detection of the foreign matter 10 needs to be compatible with all of them. On the other hand, in the light shielding means 7 of the present invention, since the opening length l of the openings 72a and 72b is variable (FIG. 8), it is possible to cope with the diversification of the shape dimensions of the glass substrate 1 and the pellicle 3. It is possible to

As shown in FIGS. 4 and 5, the photoelectric conversion element 8 responds to the received light intensity when the foreign object image 10 'from the light shielding means 7 is projected on the light receiving surface formed by a plurality of pixels. Electrical signal 81 (see FIG. 10) is output, and this electrical signal 81
Is compared with the electric signal level (reference level, threshold value) corresponding to the received light intensity of the formation dimension of the foreign matter 10 to be detected in advance, and the presence of the foreign matter 10 is detected when the electric signal 81 is above or below the reference level. Is formed in.

Although not shown in the figure, the photoelectric conversion element 8 counts the drive pulse of each pixel to generate an electric signal 81
Since it is formed so that the position of the pixel outputting is detected, it is possible to know the existing position of the foreign matter 10 on the pellicle 3 in the x direction.

Since the foreign matter detection device 11 according to the present invention is configured as described above, a foreign matter inspection method will be described next.

A glass substrate 1 mounted on a stage 9 shown in FIG.
After mounting the pellicle 3 through the frame 2 on the upper side, the motor 92 of the above-described object table 9 is driven to move the glass substrate 1 in the y direction to the set position 13 shown by the solid line in FIG. When,
As shown in FIG. 10, the electric signal 81 of the photoelectric conversion element 8 is the electric signals 82, 83 of the reflected light of the frame 2 of the pellicle 3 and the pellicle 3
It becomes an electric signal 84 of scattered light due to the foreign matter 10 above. In this case, the electric signals 82, 83 other than the foreign matter 10 are all stray light.

Therefore, according to the present invention, the distance L inside the frame 2 of the pellicle 3 is calculated from the electric signal 81 of the photoelectric conversion element 8, and the effective detection area 31 for the distance L is calculated to determine the effective detection area 31 in the x direction. The opening length l of the openings 72a and 72b of the light shielding device 7 is set so as to match the length.

In this way, the opening length l of the openings 72a and 72b of the light shielding device 7
After setting, the glass substrate 1 is set to the motor 92 of the stage 9.
Is driven in the y direction, the inspection origin 14 (which is the end face of the glass substrate 1 as shown in FIG. 9) is returned to the set position 13 in the y direction shown by the solid line, and the glass substrate 1 is returned again. The foreign substance 10 on the surface of the pellicle 3 is detected by being moved in the opposite direction by driving the motor 92 of the stage 9.

The setting position 13 in the y direction may be set to any position as long as the electric signals 82 and 83 of the reflected light of the frame 2 of the pellicle 3 are obtained as the electric signal 81 of the photoelectric conversion element 8. Ideally, it should be closer to the inspection origin 14.

Therefore, the foreign matter detecting device according to the present invention can stably detect the foreign matter over a wide inspection area of the pellicle 3. Further, since the structure is simple and the size and weight can be reduced, it can be easily incorporated into an exposure device and the like, and therefore it is suitable for detecting foreign matter on the surface of the pellicle before exposure.

Next, FIG. 11 showing an example in the case of not being an embodiment of the present invention will be explained. In the figure, the illuminating means 4 is installed in a right obliquely upward direction with respect to the surface of the pellicle 3, and the photoelectric detecting means comprising a lens array 6, a light shielding means 7 and a photoelectric conversion device 8 is provided in a left oblique upward direction opposite to the illuminating means 4. This is the case where 5 is installed.

A twelfth example showing another example which is not the embodiment of the present invention
In the figure, an illuminating means 4 is installed right above the pellicle 3, and two sets of lens arrays 6 are arranged so that the illuminating means 4 in the obliquely upward and leftward direction can detect a band-like illuminating position formed on the pellicle 3. This is the case where the photoelectric detection means 5 including the light shielding device 7 and the photoelectric conversion device 8 is installed.

Further, FIG. 13 showing still another embodiment of the present invention is a case where the foreign matter 10 existing on the surface of the pellicle 3 attached to the lower side of the glass substrate 1 is detected.

In this case, the foreign substance 10 can be detected by installing two sets of the foreign substance detecting devices 11 having the structures shown in FIGS. 1 to 10.

EFFECTS OF THE INVENTION According to the present invention, the surface of the object to be inspected is simply scanned in one direction by a foreign substance adhering to the surface of the object to be inspected such as a pellicle surface in a reticle device or the like. In the above, the influence of the unevenness of the light amount due to each image forming lens is eliminated, the detection sensitivity is the same, and the influence of stray light from other than the detection image forming area is not exerted, and the detection can be performed quickly with a simple structure. This has the effect of significantly improving the yield in manufacturing.

[Brief description of drawings]

FIG. 1 is a perspective view showing a foreign matter detecting device on a pellicle film of a glass substrate used in a semiconductor device according to an embodiment of the present invention, and FIG. 2 is an enlarged perspective view of an illuminating means shown in FIG.
1 is a characteristic explanatory view of an imaging lens forming the lens array shown in FIG. 1, FIG. 4 is an enlarged perspective view showing a lens array which is not an embodiment of the present invention, and FIG. 5 is a case in the case shown in FIG. FIG. 6 is a perspective view showing unevenness of light amount of the lens array, FIG. 6 is a perspective view showing a lens array for preventing unevenness of light amount according to an embodiment of the present invention, FIG. 7 is an explanatory view of stray light other than foreign matter, and FIG. Fig. 1 is an enlarged perspective view of the light-shielding device shown in Fig. 1, Fig. 9 is a plan view of a glass substrate with a pellicle, and Fig. 10 is a diagram showing electric signals due to reflected light from a pellicle frame and scattered light from foreign matter on the pellicle film. FIG. 11 is a supplementary explanatory view of a foreign matter detecting device showing an example when it is not the embodiment of the present invention, and FIG. 12 is a supplementary explanatory diagram of a foreign matter detecting device showing another example when it is not the embodiment of the present invention. FIG. 13 is a foreign matter detection showing still another embodiment of the present invention. It is an explanatory view of a device. 1 ... Glass substrate, 2 ... Frame, 3 ... Pellicle, 4 ...
Illumination means, 5 ... Detection means, 6 ... Lens array, 7 ...
… Shading device, 8 …… Photoelectric conversion element, 10 …… Foreign matter, 11 ……
Foreign object detection device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-55-149829 (JP, A) JP-A-59-99237 (JP, A) Jitsuko 51-22707 (JP, Y2)

Claims (4)

[Claims] 1. A convergent band light beam irradiating means constituted by scanning an inspection object linearly in a predetermined direction by a scanning means and arranging a plurality of light emitting elements on the surface of the inspection object linearly scanned. Is irradiated with a focused band-shaped light beam that extends from the scanning direction in a direction substantially perpendicular to the scanning direction in an oblique direction having a desired inclination angle from the vertical direction, and the irradiated focused band-shaped light beam inspects the object to be inspected. Scattered reflected light from the surface is staggered in the strip-shaped direction so that the image forming regions of the surface of the inspected object are overlapped in the strip-shaped direction with the optical axis direction being substantially perpendicular to the surface of the inspection object. An imaging lens group composed of a plurality of arranged imaging lenses collects the light to form an image at an imaging position, and is provided at the imaging position, and is formed by a slit-shaped opening extending in the band direction. The surface of the object to be inspected by the light shielding means Of the plurality of photoelectric conversion means arranged so as to shield the scattered reflected light generated from other than the detection region and to associate each of the scattered reflected light images formed by transmitting through the light shielding means with the plurality of imaging lenses. A foreign matter detecting method, comprising: detecting a foreign matter that is received by each of the plurality of photoelectric conversion means and detecting a foreign matter that has adhered to the surface of the inspection object based on a signal obtained from each of the plurality of photoelectric conversion means. 2. A scanning means for linearly scanning an object to be inspected in a predetermined direction, and an oblique direction having a desired inclination angle from a vertical direction on a surface of the object to be inspected linearly scanned by the scanning means. Focusing band light beam irradiating means constituted by arranging a plurality of light emitting elements for irradiating a focusing band light beam extending from the scanning direction in a direction substantially perpendicular to the scanning direction, and irradiation by the focusing band light beam irradiating means The optical axis direction is set substantially perpendicular to the surface of the object to be inspected so that the scattered and reflected light from the surface of the object to be inspected is condensed by the focused band-shaped light beam and focused at an image forming position. An imaging lens group composed of a plurality of imaging lenses arranged in a zigzag pattern in the belt-like direction so that the imaging regions on the surface of the object to be inspected overlap in the belt-like direction; Slit shape extending in the strip direction A light blocking unit formed of an opening for blocking scattered reflected light generated from a region other than the detection image forming region of the surface of the object to be inspected, and the light blocking unit disposed corresponding to the plurality of image forming lenses and transmitting through the light blocking unit. A plurality of photoelectric conversion means for receiving each of the scattered reflected light images to be imaged, and detecting foreign matter adhering to the surface of the object to be inspected based on a signal obtained from each of the plurality of photoelectric conversion means. A foreign matter detection device having the above-mentioned configuration. 3. The foreign matter detection device according to claim 2, wherein the plurality of photoelectric conversion means are linear image sensors. 4. The foreign matter detecting apparatus according to claim 2, wherein the slit-shaped opening of the light shielding means has a variable length in the longitudinal direction.