JP3885576B2 - Microscope equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a microscope apparatus using an optical microscope.
[0002]
[Prior art]
In a microscope apparatus using an optical microscope, optical system errors (illumination telecentricity, imaging telecentricity, and coma aberration) greatly affect measurement accuracy.
[0003]
Conventionally, in order to improve measurement accuracy, for example, an adjustment pattern having a step difference of one-hundred wavelength of an illumination wavelength sensitive to an optical system error has been used.
[0004]
By using this adjustment pattern, the optical system error can be inferred from the change in luminance with respect to the focus offset amount. It can be adjusted to the optimal position without any.
[0005]
[Problems to be solved by the invention]
However, the above adjustment method has a problem that it is impossible to adjust the optical error in all regions of the illumination wavelength (the wavelength of illumination light) for the following two reasons.
[0006]
1. In actual adjustment, the adjustment pattern is illuminated with light having a predetermined wavelength width. On the other hand, the step of the adjustment pattern is usually determined assuming a specific wavelength (specific wavelength). Therefore, as the illumination wavelength goes away from the specific wavelength, the adjustment sensitivity becomes dull, and the error cannot be sufficiently suppressed at all wavelengths.
[0007]
2. Since the optical system always has chromatic aberration, the adjustment position of the adjustment mechanism varies depending on the illumination wavelength. For this reason, the conventional adjustment mechanism having a fixed position can only focus on one illumination wavelength.
[0008]
Therefore, when the measurement target pattern such as a semiconductor wafer or a liquid crystal substrate is highly integrated and miniaturized in the future, it may be impossible to ensure the measurement accuracy required by the conventional adjustment method.
[0009]
The present invention has been made in view of such circumstances, and provides a microscope apparatus capable of ensuring the required measurement accuracy even when the pattern to be measured is highly integrated and miniaturized. It is to be.
[0010]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 has an illumination aperture stop, an illumination optical system for irradiating an inspection object with illumination light from a light source, and an image of the inspection object , aperture imaging aperture in it has a microscope apparatus and an imaging optical system having an aberration correction lens and the objective lens, a first adjusting means for adjusting the position of the aperture the illumination aperture, the position of the aperture the imaging aperture A second adjusting means for adjusting; a third adjusting means for adjusting the position of the aberration adjusting lens ; and for correcting the illumination telecentration, imaging telecentricity, and coma aberration of both optical systems, A table in which the optimum positions of the image aperture stop and the aberration adjustment lens are stored in advance for each wavelength component, and the wavelength component of the reflected light from the inspection object is analyzed, and the main wavelength component is extracted, and the main wavelength component is extracted. Based on various wavelength components Has a color analyzer to determine the optimum position from the table it had, in accordance with the determination of the color analyzer, characterized in that it includes a position determining means for controlling said first to third adjustment means.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0015]
FIG. 1 is an overall configuration diagram of a microscope apparatus according to an embodiment of the present invention.
[0016]
The microscope apparatus includes an epi-illumination optical system 10, an imaging optical system 30, an image processing apparatus 40, a position determination unit (position determination unit) 75, a first position adjustment unit (first adjustment unit) 25, A second position adjusting unit (second adjusting unit) 65 and a third position adjusting unit (third adjusting unit) 55 are provided.
[0017]
The epi-illumination optical system 10 irradiates illumination light from the light source 11 to the measurement target pattern 5 or the adjustment pattern 6 (used for creating a position table described later) that is an inspection target.
[0018]
An optical fiber 12 that propagates illumination light is disposed in front of the light source (for example, a halogen lamp) 11, and an illumination aperture stop 20 is disposed in front of the optical fiber 12.
[0019]
Around the illumination aperture stop 20, fine movement mechanisms 21, 22, and 23 are provided for moving the illumination aperture stop 20 in the XYZ directions.
[0020]
In FIG. 1, a fine movement mechanism 21, a fine movement mechanism 22, and a fine movement mechanism 23 move the illumination aperture stop 20 in the X direction, the Y direction, and the Z direction, respectively.
[0021]
The fine movement mechanism 21, the fine movement mechanism 22, and the fine movement mechanism 23 are connected to the first drive unit 24. The fine movement mechanism 21, the fine movement mechanism 22, the fine movement mechanism 23, and the first drive unit 24 constitute a first position adjustment unit 25 that adjusts the position of the illumination aperture stop 20.
[0022]
A first relay lens 13, a field stop 14, and a second relay lens 15 are disposed in front of the illumination aperture stop 20, and an epi-illumination prism 16 that bends illumination light at a right angle is disposed in front of the second relay lens 15. .
[0023]
The imaging imaging optical system 30 has an objective lens 17 for observing an image of the measurement target pattern 5. The measurement target pattern 5 is placed on the stage 7.
[0024]
An aberration adjustment lens 50 is disposed on the optical path behind the objective lens 17, and the aberration adjustment lens 50 forms an image on the imaging surface of the CCD camera 41. An image processing unit 42 is connected to the CCD camera 41. The CCD camera 41 and the image processing unit 42 constitute an image processing device 40.
[0025]
Around the aberration adjustment lens 50, fine movement mechanisms 51, 52, and 53 for moving the aberration adjustment lens 50 in the XYZ directions are provided. In FIG. 1, a fine movement mechanism 51, a fine movement mechanism 52, and a fine movement mechanism 53 move the aberration adjustment lens 50 in the X direction, the Y direction, and the Z direction, respectively.
[0026]
The fine movement mechanism 51, the fine movement mechanism 52, and the fine movement mechanism 53 are connected to the third drive unit 54. The fine movement mechanism 51, the fine movement mechanism 52, the fine movement mechanism 53, and the third driving section 54 constitute a third position adjustment section 55 that adjusts the position of the aberration adjustment lens 50.
[0027]
An imaging aperture stop 60 is disposed between the objective lens 17 and the incident prism 16.
[0028]
Around the image forming aperture stop 60, fine movement mechanisms 61, 62, and 63 are provided for moving the image forming aperture stop 60 in the XYZ directions. In FIG. 1, a fine movement mechanism 61, a fine movement mechanism 62, and a fine movement mechanism 63 move the imaging aperture stop 60 in the X direction, the Y direction, and the Z direction, respectively.
[0029]
The fine movement mechanism 61, the fine movement mechanism 62, and the fine movement mechanism 63 are connected to the second drive unit 64. The fine movement mechanism 61, the fine movement mechanism 62, the fine movement mechanism 63, and the second drive section 64 constitute a second position adjustment section 65 that adjusts the position of the imaging aperture stop 60.
[0030]
A reflecting prism 31 is disposed between the reflecting prism 16 and the aberration adjusting lens 50. The reflecting prism 31 bends a part of the light transmitted through the reflecting prism 16 at a right angle.
[0031]
A relay lens 32 and a color sensor 71 are disposed on the optical path. The color sensor 71 is connected to the color analyzer 72. The color sensor 71 and the color analyzer 72 constitute a position determining unit 75 that controls the position adjusting units 25, 65, and 55.
[0032]
The color analyzer 72 is connected to the first drive unit 24, the second drive unit 64, and the third drive unit 54.
[0033]
The color analyzer 72 performs wavelength analysis based on the signal from the color sensor 71 and extracts main wavelength components of the reflected light of the measurement target pattern 5.
[0034]
In the color analyzer 72, positions of the illumination aperture stop 20, the image forming aperture stop 60, and the aberration adjustment lens 50 that are optimum for each wavelength component are stored in advance as a position table. This position table is created using an adjustment pattern 6 having a plurality of steps.
[0035]
Next, the operation of this microscope apparatus will be described.
[0036]
The illumination light emitted from the light source 11 propagates through the optical fiber 12 and irradiates the illumination stop 20. Thereafter, the illumination light passes through the first relay lens 13, the field stop 14, and the second relay lens 15, is bent at a right angle by the incident light prism 16, and irradiates the measurement target pattern 5 through the objective lens 17.
[0037]
Reflected light from the measurement target pattern 5 passes through the objective lens 17, and part of the diffracted light is limited by the imaging aperture stop 60. Thereafter, the reflected light passes through the epi-illumination prism 16 and the reflection prism 31 and reaches the aberration adjustment lens 50. The aberration adjustment lens 50 forms an image on the CCD camera 41.
[0038]
A part of the reflected light of the measurement target pattern 5 is bent at a right angle by the reflecting prism 31 and enters the color sensor 71 through the relay lens 32.
[0039]
The output signal from the color sensor 71 is input to the color analyzer 72, and the main wavelength component of the reflected light is extracted by the color analyzer 72.
[0040]
The color analyzer 72 compares the extracted main wavelength components with the position table to estimate optical system errors (illumination telecentricity, imaging telecentricity and coma aberration), and eliminate the errors so as to eliminate the errors. 60 and the aberration adjustment lens 50 are respectively determined in optimum positions, and driving signals for moving the illumination aperture stop 20, the imaging aperture stop 60 and the aberration adjustment lens 50 to those positions are sent to the first position adjustment unit 25 and the second position adjustment unit 25, respectively. The data is output to the position adjustment unit 65 and the third position adjustment unit 55, respectively.
[0041]
In the first position adjusting unit 25, the first driving unit 24 drives the fine movement mechanism 21, the fine movement mechanism 22, and the fine movement mechanism 23 based on the drive signal, and the illumination aperture stop 20 moves to an optimal position.
[0042]
In the second position adjustment unit 65, the second drive unit 64 drives the fine movement mechanism 61, the fine movement mechanism 62, and the fine movement mechanism 63 based on the drive signal, and the imaging aperture stop 60 moves to an optimal position.
[0043]
In the third position adjustment unit 55, the third drive unit 54 drives the fine movement mechanism 51, the fine movement mechanism 52, and the fine movement mechanism 53 based on the drive signal, and the aberration adjustment lens 50 moves to an optimal position.
[0044]
According to this embodiment, the illumination aperture stop 20, the imaging aperture stop 60, and the aberration adjustment lens 50 can be adjusted to optimal positions without an optical system error in all regions of the illumination wavelength used. Even when a measurement target pattern such as a semiconductor wafer or a liquid crystal substrate is highly integrated and miniaturized, the required measurement accuracy can be ensured.
[0045]
In the above embodiment, the image processing apparatus 40 is used. However, instead of the image processing apparatus 40, for example, an eyepiece may be used.
[0046]
The adjusting means of claim 1 corresponds to the first position adjusting unit 25, the second position adjusting unit 65, and the third position adjusting unit 55 of the embodiment.
[0047]
【The invention's effect】
As described above, according to the microscope apparatus of the present invention, various adjustment means such as an illumination aperture stop can be adjusted to an optimal position without an optical system error in all regions of the illumination wavelength. Even when the target pattern is highly integrated and miniaturized, the required measurement accuracy can be ensured.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a microscope apparatus according to an embodiment of the present invention.
[Explanation of symbols]
5,6 pattern (inspection object)
DESCRIPTION OF SYMBOLS 10 Epi-illumination system 11 Light source 17 Objective lens 30 Imaging optical system 25 1st position adjustment part 55 3rd position adjustment part 65 2nd position adjustment part 75 Position determination part (position determination means)

Claims (1)

An illumination optical system having an illumination aperture stop and irradiating an inspection object with illumination light from a light source;
In order to observe an image of the inspection object, a microscope apparatus including an imaging optical system having an imaging aperture stop, an aberration adjustment lens, and an objective lens,
First adjusting means for adjusting the position of the illumination aperture stop;
Second adjusting means for adjusting the position of the imaging aperture stop;
Third adjusting means for adjusting the position of the aberration adjusting lens ;
A table in which optimal positions of the illumination aperture stop, the imaging aperture stop, and the aberration adjustment lens are stored in advance for each wavelength component in order to correct illumination telecentration, imaging telecentricity, and coma aberration of both optical systems. When,
A color analyzer that analyzes a wavelength component of reflected light from the inspection object, extracts a main wavelength component, and determines an optimum position from the table based on the main wavelength component; And a position determining means for controlling the first to third adjusting means according to the determination of the instrument.

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