JPH0247503A - Wire width measurer - Google Patents

Abstract

PURPOSE:To prevent the abrasion of a driving part and to improve the precision in measurement by moving a lens or a mirror which is light instead of a heavy sample stage on the occasion of focusing. CONSTITUTION:The image of a sample 5 on a sample stage 4 is formed on a photodetector 1 by using an objective lens 3 and an eyepiece 2. The focusing on the occasion is executed by moving the eyepiece 2 in relation to the photodetector 1 by a driving device 6a, instead of moving the sample stage 4, and by varying thereby an optical path. The objective lens 3 may be moved instead of moving the eyepiece 2. Since a part moved is the lens 2 or 3 being lighter in weight than the sample stage 4, the abrasion of a gear or the like caused by the weight of the sample stage 4 is lessened.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a line width measuring device for semiconductor device manufacturing, and in particular,
This invention relates to a line width measuring device that measures the line width of a sample by detecting differences in optical contrast using a photodetector.

[Conventional technology]

Conventionally, this type of line width measuring instrument basically focuses an image of a sample 5 on a sample stage 4 onto a photodetector 1 using an objective lens 3 and an eyepiece 2, as shown in FIG. Focusing at this time was performed by moving the sample stage 4 up and down using the drive device 6b and changing the distance between the sample 5 and the objective lens 3.

[Problem to be solved by the invention]

In the conventional line width measuring instrument mentioned above, the sample stage 4 was moved up and down mechanically by hand or a motor using a combination of gears, etc. However, the sample stage 4 was raised and lowered in order to measure the line width of minute semiconductor devices. Accurate flatness, tilt accuracy, and 1 position accuracy were required, and a considerable amount of weight was required. As a result, gears and the like are subject to severe wear, reducing their positional accuracy. This decrease in positional accuracy causes a focus shift in the optical system during measurement, resulting in a serious problem of lowering measurement accuracy and lowering the yield and quality of products.

An object of the present invention is to provide a line width measuring device that solves the above problems.

[Differences between the invention and the prior art]

The present invention differs from the conventional line width measuring device described above in that focusing is performed by changing the optical distance between the device and the photodetector.

[Means to solve the problem]

To achieve the above object, the present invention provides a line width measuring device that measures the line width of a sample based on the difference in optical contrast of the sample, which includes a lens or mirror that forms an image of the sample on a photodetector; It has a mechanism that performs focusing by changing the optical path length between the lens or mirror and the photodetector.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

(Example 1) FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

In the figure, the configuration in which an image of a sample 5 on a sample stage 4 is formed on a photodetector 1 via an eyepiece lens 2 and an objective lens 3 is the same as the conventional one.

The present invention is equipped with a drive device 6a that moves the eyepiece lens 2 (or objective lens 3) relative to the photodetector 1 and performs focusing by changing the optical path length.

In the embodiment, focusing is performed by moving the eyepiece 2 (or objective lens 3).

In the present invention, the movable parts are the lenses 2 and 3, which are lighter than the sample stage 4, and there is less wear on gears and the like due to the weight of the sample stage 4.

(Example 2) FIG. 2 is a configuration diagram showing a second embodiment of the present invention.

In this embodiment, a concave mirror 7.8 is used as an optical system, and as in FIG.
Alternatively, it is attached to the objective mirror 8, and focusing is performed by moving the eyepiece mirror 7 or the objective mirror 8.

Since this embodiment uses a mirror as the optical system, it has the advantage of not being affected by chromatic aberration.

〔Effect of the invention〕

As explained above, the present invention uses a four-pronged motor, etc., which is effective in preventing wear of the driving part and improving measurement accuracy by changing the moving part during focusing from a heavy sample stage to a light lens or mirror. Even when focusing automatically, since the moving part is light, the time for focusing can be shortened and positioning accuracy can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the present invention, FIG. 2 is a block diagram showing a second embodiment of the present invention, and FIG. 3 is a block diagram showing a conventional example. 1... Photodetector 2... Objective lens 3...
Eyepiece lens 4... Sample stage 5... Sample
6a... Drive device 7... Eyepiece mirror
8... Objective mirror Sodo Hiiragi 5r:, :, q) Figure 1 Figure 2 ~ Figure 20- Figure 3

Claims (1)

[Claims] (1) In a line width measuring device that measures the line width of a sample based on the difference in optical contrast of the sample, a lens or mirror that forms an image of the sample on a photodetector, and the lens or mirror and the photodetector A line width measuring instrument characterized by having a mechanism that performs focusing by changing the optical path length between the line width measuring device and the line width measuring device.