JPH01166082A - Surface state checking device - Google Patents

Abstract

PURPOSE:To check the whole of the surface of a substrate like a mask, a reticle, or a pellicle with a certain detection sensitivity by arranging an optical waveguide having a refracting power in a part of a photodetecting system. CONSTITUTION:A convex lens 13 is adhered to the luminous flux emission exit side of an optical waveguide 10 to constitute a device. Consequently, the angle of divergence of the emitted luminous flux is reduced by the refracting action of the convex lens 13, and the luminous flux is received at an angle approximating the perpendicular by a photodetector 8. With respect to the shape of the convex lens 13, the curvature in the scan section of the beam must have a positive power, but the curvature in the section orthogonal to said section must not have a positive power and this section may be plane. Thus, the state of the surface to be measured of a mask, a reticle, or the like is checked with a certain detection sensitivity, and this check is not affected by the variance in sensitivity of the light receiving face of the photodetector, and a surface state checking device is obtained which can defect foreign matters or the like with a high precision.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a surface condition inspection device, and in particular to a photodetector for detecting defects and foreign matter on a mask, reticle, or wafer surface with high precision used in semiconductor manufacturing equipment. The present invention relates to a surface condition inspection device having a system.

(Prior Art) In semiconductor printing, when a pattern is transferred from a reticle or mask onto a wafer surface using a device, if there are defects such as dust on the reticle or mask, patterns other than the original reticle or mask pattern may be The shape of the defect will also be imprinted. Once that happens, dust on the reticle and mask must be detected and removed. Therefore, in recent years, it has become necessary not only to determine the presence or absence of the dust, but also to quickly and accurately know which surface of the reticle or mask the dust is attached to.

FIG. 5 is a schematic diagram showing an example of a conventional inspection method for a reticle with a pellicle.

This configuration example shows a case where a laser beam is incident on the reticle and pellicle surfaces obliquely from above. In the figure, 1 is a laser beam, 2 is a reticle, and a pellicle 3.4 is attached to the reticle 2. 5a, 5
b, 5c, 5d are SELFOC lenses, 6a, 6b, 6
c and 6d are field stops; 7a, 7b, 7c, and 7d are light guides made of fibers; and 8a, 8b, 8c, and 8d are light receiving elements. Among the members with subscripts a, b, c, and d, the members with the same subscript constitute one photodetection system.

There are four photodetection systems, 6-1.6-2.6-3.6-4, which inspect the pellicle top surface 3, reticle back surface 2-1, reticle pattern surface 2-2, and pellicle bottom surface 4, respectively. .

The laser beam is scanned by a vibrating element such as a polygon mirror or a galvano mirror over the surfaces of the reticle 2 and pellicles 3 and 4 in a direction perpendicular to the plane of the paper.

At this time, the optical system must be adjusted so that the image of the scanning line of the laser beam formed by the SELFOC lens 5a on each surface matches the longitudinal direction of the aperture (rectangular shape) of the field diaphragm 6a, etc., and the field diaphragm 6a etc., the scattered light beams from defects and foreign objects are not eclipsed and are transmitted to the light receiving element 8a.
The field diaphragm 6, which is the incident end face of the light guide 7a,
It is necessary to align with the aperture such as a.

In addition, in the configuration shown in the figure, for example, the back surface 2-
Scattered light from foreign objects, etc. on 1 is received only by the light detection system 6-2, and the other light detection systems 6-1, 6-3, 6-4 are vignetted by the field stops 6a, 6c, and 6d. , no light is received.

By arranging a photodetection system for each detection surface in this manner, it is possible to determine which surface a foreign object or the like is attached to.

FIG. 6 is a schematic diagram showing another example of a conventional surface condition inspection device. In this figure, the same elements as in FIG. 5 are given the same numbers.

In this configuration example, the beam is incident perpendicularly to the reticle 2 and pellicles 3 and 4, and the principle is the same as the case shown in FIG.

In the examples shown in FIGS. 5 and 6, selfoc lenses are used, but they may be replaced with cylindrical lenses or bar lenses. Alternatively, the light may be directly received by a light guide.

One of the important performances required of the surface condition inspection apparatus as described above is uniformity of detection sensitivity, in which when the same foreign matter is present on the scanning line of the beam, it is detected with the same output.

However, in the photodetection system 6-1 shown in Figure 5, the light guide is placed immediately after the field diaphragm, so some of the light guides may be disconnected, or the end faces of the individual light guides may not be uniformly processed. If this is not done, it will not be possible to obtain uniform output on the laser scanning line.

In other words, this type of device determines the size of a foreign object based on the intensity of the received and scattered light, so if there is a defect in the light kite as described above, even if there is the same foreign object, the size of the foreign object will differ depending on the location on the scanning surface. It will be judged as a foreign object of a different size. Furthermore, there is a drawback that foreign matter within the detection limit cannot be detected on the scanning surface.

Furthermore, even if there is no component defect in the light guide as described above, if there is sensitivity unevenness on the light receiving surface of the light receiving element, it may cause false detection.

If the light guides were bundled completely randomly, the light scattered by the foreign matter emitted from one point on the laser scanning line would spread over the entire light-receiving surface of the light-receiving element, and there would be no output unevenness depending on the detection location.

However, in reality, it is difficult to bundle the light guides completely randomly, so the portion of the light-receiving surface of the light-receiving element that is hit by the scattered light differs depending on the position of the foreign object on the scanning surface.

Therefore, if there is sensitivity unevenness on the light receiving surface of the light receiving element, output unevenness will occur.

As a solution to these problems, for example, JP-A-61
There is -105447.

According to this, as shown in FIG. 7, an optical waveguide member having a rectangular entrance aperture is arranged to face the surface to be measured so that the longitudinal direction of the entrance aperture substantially coincides with the scanning direction of the beam, The reflected light or the transmitted light from the surface to be measured is received through the optical waveguide member.

Such an optical member has the following functions.

In other words, as shown in FIG. 8, the beam scanning lines (Bl,
B2) Each point PI, P2. The scattered light of foreign matter emitted from P3 gradually intersects as it passes through the inner surface of the optical waveguide member 1o while being reflected, and almost all of the light is reflected on the light receiving surface of the light receiver (8) placed near the exit port. Equally uniform. As a result, diverging light from any position on the beam scanning line is uniformly photoelectrically converted, eliminating unevenness depending on the detection position. However, the biggest drawback of this optical member (10) is that the divergence angle of the emitted light beam is widened. The tendency is that the greater the ratio of the cross-sectional area of the entrance end to the cross-sectional area of the exit end, the greater the divergence angle of the emitted light beam.

A light-receiving element usually has a light-receiving orientation angle, and has a characteristic of being low in sensitivity to light beams that enter at a large angle to the normal to the light-receiving surface.

Therefore, even if the luminous flux is apparently made uniform, when the photoelectric output is taken, there is a drawback that unevenness occurs in the detection location.

(Problems to be Solved by the Invention) The present invention is capable of inspecting the surface condition of a surface to be measured such as a mask or reticle with a constant detection sensitivity, and also eliminates the influence of sensitivity unevenness on the light receiving surface of a light receiving element. The purpose of the present invention is to provide a surface condition inspection device that can detect foreign substances with high precision without being exposed to foreign substances.

(Means for Solving the Problems) An apparatus for measuring the surface condition of a surface to be inspected by scanning the surface to be inspected with a light beam and receiving scattered light from the surface to be inspected with a photodetector, the device comprising: A transmission member that diffuses and transmits the scattered light and a condenser lens that converges the diffused light emitted from the transmission member are disposed in the optical path of the scattered light, and the scattered light is transmitted through the condenser lens. is detected by a photodetector.

(Embodiment) FIG. 1 is a schematic diagram of a first embodiment of the present invention. Figure (A) is a schematic diagram of the scanning cross section of the beam. The same figure (B) is a sectional view orthogonal to it. The difference from FIG. 8 is that a convex lens (13) is bonded to the light beam exit side of the guiding waveguide 10. As can be seen from the figure, the divergence angle of the emitted light beam is weakened by the refraction effect of the convex lens 13, and the light is received by the light receiving element 8 at an almost vertical angle.

At this time, as for the shape of the convex lens 13, it is necessary that the curvature within the scanning cross section of the beam has a positive power as shown in the figure (A), but it is perpendicular to this as shown in the figure (B). The curvature within the cross section does not necessarily have to be the same,
It can be flat. In other words, the refractive optical element 13 may be a cylindrical lens or a toric lens. That is 2 above
It can be determined based on the divergence angle of the emitted light beam within the cross section.

Moreover, the optical waveguide 13 has this effect even if it is not bonded to the optical waveguide 10.

FIG. 2 is a schematic diagram showing another embodiment of the invention.

This embodiment is an application of the present invention to the conventional example shown in FIG. In this figure, the same elements as in FIG. 5 are given the same numbers. In the embodiment shown in FIG. 1, the scattered light from the foreign matter on the laser beam scanning line on each test surface is directly guided to the entrance opening of the leading wave tube and received. However, in this embodiment, the scattered light is re-imaged on the field stop 68 etc. using an imaging element 5a such as a SELFOC lens, and the scattered light flux passing there is made uniform by a leading wave tube 10a etc. The light is guided to the light receiving element 8a and the like.

In the case of the configuration of this embodiment, since the field stop 68 and the like are used, flare light can be blocked and inspection accuracy can be improved.

Furthermore, since the numerical aperture of the SELFOC lens is limited, only the light beam at a predetermined angle among the light scattered by foreign objects can be received at any position along the scanning line of the laser beam.

In particular, it is possible to configure the pattern surface of the reticle to selectively receive only the foreign object scattered light without receiving the pattern diffracted light.

FIG. 3 is a schematic diagram showing another embodiment of the present invention. 1st
The embodiments shown in Figs. 2 and 2 were configured to receive scattered light from foreign objects, but in this embodiment, the laser beam is directly reflected or directly transmitted on the inspection surface (if the substrate is transparent). The present invention is applied to a configuration that receives light (only 1).

In the figure, 1 is a laser beam, 2 is a substrate as an object to be measured, 5e and 5f are selfoc lenses, 6e and 6
f is a field stop, 10e and 10f are optical waveguides, 8e and 8f
is a light receiving element. The photodetection system 8-1, which is made up of members with the subscript e, receives reflected light directly from the inspection surface, and the photodetection system 8-2, which is made up of the members with the subscript f, transmits the reflected light through the inspection surface. Receives directly transmitted light. If there is no foreign matter on the inspection surface, the sum of the output of the light receiving element 8e that received the reflected light of the laser beam 1 on the inspection surface and the output of the light receiving element 8f that received the transmitted light is a constant value. etc., absorption and scattering of light will occur, so the sum of the outputs of the two light receiving elements will decrease.

Therefore, foreign matter can be detected with high precision by detecting a change in the output such that the sum decreases.

The photodetection systems 8-1 and 8-2 in this embodiment have the same configuration as the four photodetection systems shown in FIG. 2, and provide the same effects.

FIG. 4 is a schematic diagram of another embodiment of the present invention. This embodiment differs from the embodiment shown in FIG. 1 in that a convex lens 50 is also provided on the incident side of the leading waveguide 10.

In this example, the optical axis of the light guide is 00 on the beam scanning line.
Scattered light of dust at a position (P+, P3) far away from It has the function of bringing the optical axis closer to the direction along the optical axis 00' of the guide.

This facilitates total reflection of light within the guide, shortens the length of the light guide 10 in the optical axis direction, and makes the entire device more compact.

(Effects of the Invention) According to the present invention, by arranging a leading wave tube having refractive power in a part of the photodetection system, the entire surface of a substrate such as a mask, reticle, pellicle, etc. can be detected with a constant detection sensitivity. In addition, since it is possible to detect foreign substances with high precision without failing to detect foreign substances that are within the detection limit on a certain part of the substrate, the yield rate of the semiconductor manufacturing process can be improved. It is possible to achieve a surface condition inspection device that can be improved.

[Brief explanation of the drawing]

1(8), (B), FIG. 2, FIG. 3, and FIG. 4 are schematic diagrams showing respective embodiments of the present invention, and FIG. 5 is a schematic diagram showing each embodiment of the present invention. FIG. 6, FIG. 7, and FIG. 8 are schematic diagrams showing a conventional surface condition inspection device. In the figure, 1 is a laser beam, 2 is a reticle, 3 and 4 are pellicles, 8a, 8b, 8c, and 8d are light receiving elements, 5a,
5b, 5c, 5d, 5e, 5f are selfoc lenses,
6a, 6b, 6c, 6d. 6e, 6f are field stops, to, 11, 12° 10a, 1
0b, 10c, 10d, 10e. 10f is an optical waveguide, 13.50 is a convex lens, and 14 is a fiber. Patent applicant Canon Co., Ltd.

Claims (5)

[Claims] (1) A device that measures the surface condition of a surface to be inspected by scanning the surface to be inspected with a light beam and receiving scattered light from the surface to be inspected with a photodetector, wherein the optical path of the scattered light is A transmission member that diffuses and transmits the scattered light and a condenser lens that converges the diffused light emitted from the transmission member are provided, and the scattered light is detected by a photodetector via the condenser lens. A surface condition inspection device characterized by: (2) The light transmission member is comprised of an optical waveguide member having an entrance opening such that the longitudinal direction of the entrance opening coincides with the scanning direction of the light beam. Surface condition inspection device. (3) The surface condition inspection device according to claim 1, wherein the entrance opening and the exit opening of the optical waveguide member have different shapes having substantially equal areas. (4) The surface condition inspection device according to claim 1, wherein the optical waveguide member has a shape such that the light intensity distribution of the emitted light beam from the exit aperture is uniform. (5) The surface condition inspection apparatus according to claim 1, wherein the condenser lens is a cylindrical lens having a generatrix in a direction perpendicular to the scanning direction of the light beam.