JPH0774859B2 - Mask observation device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low reflectance mask observing apparatus used for manufacturing semiconductors and the like.

Configuration of Conventional Example and Problems Thereof A conventional method of observing a low-reflectance mask by an epi-illumination microscope is shown in FIG. 1 to FIG. A mask 4 having a light shielding pattern 3 is placed on the lower surface of the glass substrate 2 below,
Further, nothing is placed below it as shown in FIG. 1, a diffuse reflection plate 5 is placed as shown in FIG. 2, or a plane reflecting mirror 6 is placed as shown in FIG.
The epi-illumination light is incident through the objective lens 1 so as to fill the space between the light paths 7 and 8, and the epi-illumination lights 7 to 8 are also focused near the light-shielding pattern 3 of the mask 4 in which the microscope is in focus. After that, in the conventional example of FIG. 1, the light is transmitted and diverged downward, and in the conventional example of FIG. 2, it is diffusely reflected by the lower diffuse reflection plate 5, and a part of the diffusely reflected light does not have the light shielding pattern 3 of the mask 4. Returning to the objective lens 1 through the portion, in the conventional example of FIG. 3, the light is specularly reflected by the regular reflection mirror 6 below, spreads and travels as the paths 9 and 10 of the light, and part of the illumination light returns to the objective lens 1. It was a thing.

However, in the above configuration, when the material of the light-shielding pattern 3 of the mask 4 has a low reflectance, which is generally used, the illumination light transmitted through the portion without the light-shielding pattern 3 is as shown in FIG. Since it does not return to the objective lens 1, when viewed under a microscope, the gray light-shielding pattern 3 can only be seen in a dark background with a low contrast, and in FIGS. The black light-shielding pattern 3 is only visible in the inside with low contrast, and it is difficult to see with low contrast in either case. In the case of FIGS. 2 and 3, the focus of the reflected light incident on the objective lens 1 from below is low. Since it does not match the light-shielding pattern to be observed, it has the drawback that the resolution of the microscope decreases and the in-focus position becomes unclear, making it difficult to see the image. In microscopic observation with camera or the like has a disadvantage in that the image is not well visible.

The present invention, in view of the above drawbacks, in the inspection and measurement of the low reflectance mask, using the epi-illumination microscope when the transmitted light illumination from below cannot be used, the image contrast is good,
This provides an observation apparatus in which the in-focus position is clear and the image resolution is good.

Configuration of the invention, the mask observation apparatus of the present invention, for the mask to be observed, epi-illumination microscope placed on one side, and a reflection plate placed on the opposite side to reflect light in the incident direction, the reflection plate is ,
It is a structure in which minute spherical glasses are densely arranged and fixed on a plane, and has a unique effect that the contrast and resolution of an image are good and the focusing position is clear in pattern observation of a low reflectance mask.

Description of Embodiments One embodiment of the present invention will be described below with reference to FIG. Reference numeral 11 is an objective lens of a microscope having an epi-illumination device, 12 is a glass substrate of a mask 14 placed below the objective lens 11, 13 is a low-reflectance light-shielding pattern which is an object to be observed of the mask 14, and 15 is a mask of the mask 14. It is a reflector that reflects light in a direction substantially opposite to the incident light placed below, and its structure is such that minute spherical glass 16 is densely arranged on a sheet 17 and fixed by a resin 18 that transmits light. .

The operation of the microscope observing apparatus configured as described above will be described below. The epi-illumination light fills the space between the light paths 19 and 20 and is incident so as to focus substantially on the observation portion of the mask 14, and most of the portion hitting the light shielding pattern 13 is absorbed, and the transmitted portion of the mask 14 The light that has passed through hits the reflection plate 15, and most of the light is refracted and reflected by the minute spherical glass inside, and is reflected almost in the incident direction as the light paths 21 and 22, and the mask 14 is observed again. The light is focused substantially on the spot and further advances into the objective lens 11, so that the light-shielding pattern 13 can be clearly seen in black in a bright background and the in-focus position of the microscope becomes clear to the observer.

As described above, according to the present invention, in observation of a low-reflectance mask, when transmitted light illumination from below cannot be performed, an epi-illumination microscope is used, and a small spherical surface is formed below the observed mask. Low reflectivity by placing a reflector consisting of glass closely arranged on a flat surface in the direction of incidence and fixing the minute spherical glass densely on a flat surface. The light-shielding pattern can be observed with good contrast and resolution, and its practical effect is great.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an observation state in which nothing is placed below a conventional mask, FIG. 2 is a schematic diagram showing an observation state in which a diffuse reflection plate is placed below a conventional mask, and FIG. 3 is a conventional mask. Schematic diagram showing an observation state in which a plane reflecting mirror is placed below
FIG. 1 is a schematic diagram showing a mask observation device according to an embodiment of the present invention. 11 …… Objective lens, 13 …… Shading pattern, 14 …… Mask, 16 …… Spherical glass, 19,20 …… Path of incident illumination light.

Claims (1)

[Claims] 1. An epi-illumination microscope for illuminating an object through an objective lens placed on one side of an observed mask having a portion for blocking light and a portion for transmitting light, and an epi-illumination arranged on the opposite side of the mask. A mask observing device comprising a reflecting plate that reflects illumination light substantially in the incident direction, and the reflecting plate is formed by closely arranging and fixing minute spherical glasses on a flat surface.