JPH075370A - Multi-surface simultaneous measurement microscope device - Google Patents

Abstract

PURPOSE:To widen the observation and measurement range in the thickness direction of a sample by equally dividing the optical path of an objective lens into three by an optical path dividing means, and dividing it into a proper number more than two according to the sample. CONSTITUTION:This device is equipped with an objective lens 1, optical path dividing means 2 arranged at the back part of the objective lens 1, which divides an optical path L of an objective lens 1, plural image pickup means 3, 4 and 5 arranged on each divided optical path L1, L2, and L3 divided by the optical path dividing means 2, which convert sample images enlarged by the objective lens 1 into electric signals, control unit 6 which processes the signals from those image pickup means 3, 4 and 5 so that the plural sample images can be overlapped, and television monitor 7 which displays the overlapped sample images based on a video signal from the control unit 6. Image pickup surfaces 3S1, 4S2 and 5S3 of the image pickup means 3, 4, and 5 are arranged in a conjugating position according to positions S1, S2, and S3 at which the optical axial direction of the objective lens 1 is different.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiple surface simultaneous measurement microscope apparatus for simultaneously observing and measuring surfaces of a sample surface in different thickness directions.

[0002]

2. Description of the Related Art As a wafer pattern becomes finer, a microscope apparatus having a high resolution is required. The relationship between the resolution R and the depth of focus D is generally R = (1.22λ) / (2NA) D = (2NA ² ) + 1 / (7M × NA). However, λ: wavelength, NA: numerical aperture, M: magnification.

As described above, the resolving power R and the depth of focus D are inversely proportional, and the higher the resolution (higher magnification), the shallower the depth of focus D becomes. For example, the depth of focus D of an objective lens with 100 × and NA = 0.9 is about 0.3 (μm). For example, in the case of an apparatus that performs overlay measurement of wafers, it is very small with respect to steps 1 to 3 (μm) on the wafer surface. Therefore, when observing and measuring the upper and lower patterns of the wafer surface, it is necessary to move the stage on which the wafer is moved up and down to change the focus position.

[0004]

However, when the stage is moved up and down, high-precision control is required in order to obtain the right angle accuracy between the objective lens and the stage and the up and down movement accuracy of the stage. There has been a problem that accurate measurement values cannot be obtained unless dynamic accuracy is obtained.

On the other hand, the numerical aperture NA is reduced and the depth of focus D
However, there is a problem in that the resolution R decreases when a large number is taken.

The present invention has been made in view of the above circumstances, and its object is to simultaneously observe and measure a plurality of surfaces in different thickness directions of a sample simultaneously and accurately while having a high resolution. It is to provide a measuring microscope device.

[0007]

In order to solve the above-mentioned problems, the multi-surface simultaneous measurement microscope apparatus according to the invention of claim 1 is
An objective lens, an optical path splitting unit disposed behind the objective lens, which splits the optical path of the objective lens to form a plurality of sample images, and each split optical path split by the optical path splitting unit, A plurality of image pickup means for converting each of the plurality of sample images into an electric signal, a signal processing means for processing signals from the image pickup means so that the plurality of sample images overlap each other, and a signal from the signal processing means. Display means for displaying the sample images superposed based on each other, and the image pickup surfaces of the plurality of image pickup means are arranged at conjugate positions with respect to a plurality of predetermined positions in the optical axis direction of the objective lens.

In the multi-surface simultaneous measurement microscope apparatus according to the second aspect of the present invention, optical members movable along the optical axis are arranged between the optical path splitting means and the image pickup means.

[0009]

[Function] Since a plurality of sample images corresponding to a plurality of predetermined positions different in the thickness direction of the sample are superimposed and displayed on the display means, simultaneous observation / measurement in a wide range in the thickness direction of the sample is possible. It will be possible.

Further, by disposing optical members movable along the optical axis between the optical path splitting means and the respective image pickup means, the distance between a plurality of predetermined positions different in the thickness direction of the sample. Can be changed and various samples can be measured.

[0011]

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

FIG. 1 is an overall configuration diagram of a multi-plane simultaneous measurement microscope apparatus according to an embodiment of the present invention.

Behind the magnifying objective lens 1, an optical path splitting means 2 for equally splitting the optical path L of the objective lens 1 into three parts is arranged. The optical path splitting means 2 may be one that is electrically adjusted, and does not necessarily have to be equally split. Image pickup tubes 3, 4, and 5 are arranged on the respective divided optical paths L ₁ , L ₂ , and L ₃ . The image pickup surface 3s ₁ of the image pickup tube 3 is located at a position S1 in front of the objective lens 1 and the image pickup tube 4
Imaging surface 4s ₂ of the front of the position S2 of the objective lens 1, the imaging surface 5s ₃ of an image pickup tube 5 is arranged in front of the position S3 and the conjugate position of the objective lens 1, the imaging surface 3s _1, 4s
_The image formed in ₂ , 5s ₃ is converted into a video signal. The above corresponds to the upper surface of a three-layer pattern formed on the surface of a sample (wafer) not shown, and each of the image pickup tubes 3, 4, and 5 has a different pattern surface in the thickness direction of the sample (means the width of the depth of focus). ) Is imaged.

The image pickup tubes 3, 4, 5 are connected to the control unit 6, and the control unit 6 superimposes the sample images. The control unit 6 is a TV monitor 7
, And the superimposed sample image is displayed on the television monitor 7. The television monitor 7 is connected to the control unit 8, and the control unit 8 uses the sample image synthesized by the television monitor 7 to perform various processes and calculations.

Next, the operation of the multi-surface simultaneous measurement microscope device will be described.

The light fluxes from the positions S1, S2 and S3 are equally divided into three by the optical path dividing means 2, and the positions S1, S2 and S2 are formed on the image pickup surfaces 3s ₁ , 4s ₂ and 5s ₃ of the respective image pickup tubes 3.
Sample images corresponding to S3 are formed. Each sample image is converted into a video signal by the image pickup tubes 3, 4, 5 and the image signal is sent from the image pickup tubes 3, 4, 5 to the control unit 6. The control unit 6 inputs the video signals from the image pickup tubes 3, 4, 5 and superimposes the sample images. After that, the superimposed sample images are displayed on the television monitor 7, and the control unit 8 uses the images synthesized on the television monitor 7 to perform various processes and calculations.

According to the multi-sided simultaneous measurement microscope apparatus of this embodiment, even when a high resolution (high magnification) objective lens 1 is used, compared with the conventional example using the same objective lens, the thickness direction of the sample is increased. The observation and measurement range of is tripled.

The positions S1, S2 and S3 can be changed by shifting the position of the sample in the optical axis direction. Therefore, for example, even if the thickness of the wafer changes, simultaneous measurement is possible.

Further, the image pickup surfaces 3s ₁ of the image pickup tubes 3, 4, 5
By independently shifting 4s ₂ and 5s ₃ , the positions S1,
The distance between S2 and S3 can also be changed. Therefore, it can be applied to other types of samples having different distances between pattern surfaces.

FIG. 2 is an overall configuration diagram of a multi-face simultaneous measurement microscope apparatus according to another embodiment of the present invention. The same parts as those in the above-described embodiment are designated by the same reference numerals and the description thereof will be omitted.
In this embodiment, as shown in FIG. 2, it is possible to insert or remove optical members such as relay lenses 9a, 9b, 9c for changing the optical path length in each of the divided optical paths L ₁ , L ₂ , L _3. The positions S1, S2, S3 conjugate with respect to the imaging surfaces 3s ₁ , 4s ₂ , 5s ₃ can be changed, and the relay lenses 9a, 9b, 9c can be divided into the split optical paths L ₁ , L 3.
_2, L ₃ position by moving in the direction of S1, S2, S3 may also be varied. That is, the positions S1, S2, S3 may be predetermined according to the sample to be observed, or may be changed while observing the television monitor 7.

In each of the above-mentioned embodiments, the optical path L of the objective lens 1 is equally divided into three by the optical path dividing means 2. However, depending on the sample, the optical path L may be divided into two or more appropriate numbers so that the thickness direction of the sample is increased. The observation and measurement range of can be expanded.

In order to selectively connect the video signals from the respective image pickup tubes 3, 4, 5 to the control unit 6,
If a switch (not shown) is arranged between each of the image pickup tubes 3, 4, 5 and the control unit 6, the position S
Not only the sample image at a desired position among S1, S2 and S3 can be observed and measured, but also the sample images at a plurality of desired positions can be superposed and observed.

Furthermore, since the horizontal scanning line of the television monitor 7 is limited, if the sample image by the objective lens 1 is converted into a video signal as it is, the resolution on the television monitor 7 is low when the sample image is observed. However, the imaging surface 3s
_The image plane on which ₁ , 4s ₂ and 5s ₃ are placed is further 2 to 10
If a relay lens that doubles the magnification is provided and the image pickup surfaces 3s ₁ , 4s ₂ , and 5s ₃ of the image pickup tubes 3, 4, 5 are placed on the image surface enlarged by the relay lens, a sufficiently high resolution is obtained. A sample image of the image can be displayed on the television monitor 7. In this case, the magnification of each relay lens can be changed to also correct the variation in magnification due to the different distances from the objective lens to the positions S1, S2 and S3.

[0024]

As described above, according to the multi-face simultaneous measurement microscope apparatus of the present invention, it is possible to perform simultaneous observation and measurement in a wide range in the thickness direction of the sample, even though it has a high resolution, and is stable. The measured value can be obtained.

Further, by disposing optical members movable along the optical axis between the optical path splitting means and each of the image pickup means, the distance between a plurality of predetermined positions different in the thickness direction of the sample. Can be changed and various samples can be measured.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a multiple surface simultaneous measurement microscope apparatus according to an embodiment of the present invention.

FIG. 2 is an overall configuration diagram of a multiple surface simultaneous measurement microscope apparatus according to another embodiment of the present invention.

[Explanation of symbols]

 1 Objective Lens 2 Optical Axis Splitting Means 3, 4, 5 Imaging Means 6 Control Unit 7 Television Monitor 8 Control Unit

Claims (2)

[Claims] 1. An objective lens, an optical path splitting unit disposed behind the objective lens and splitting an optical path of the objective lens to form a plurality of sample images, and each split light split by the optical path splitting unit. A plurality of image pickup means arranged on the road for converting the plurality of sample images into electric signals, and a signal processing means for processing signals from the image pickup means so that the plurality of sample images overlap each other; Display means for displaying the sample images superimposed on the basis of the signal from the means, and the image pickup surfaces of the plurality of image pickup means are respectively conjugated to a plurality of predetermined positions in the optical axis direction of the objective lens which are different from each other. A multi-face simultaneous measurement microscope device characterized by being placed in a position. 2. The multi-surface simultaneous measurement microscope apparatus according to claim 1, wherein optical members movable along the optical axis are arranged between the optical path dividing unit and the respective image pickup units.