JP2003294419A - Measuring instrument for infinitesimal dimension - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure and inspect an object to be measured without generating the collision of an object lens with the object to be measured, to certainly perform automatic focusing even with respect to a subject having a large area and to more shorten a focus detection time. <P>SOLUTION: A measuring instrument for an infinitesimal dimension has an ultraviolet microscope for obtaining a magnified image for measuring the minute dimension of the object to be measured, a stage loaded with the object to be measured and moving the predetermined region of the object to be measured to the visual field of the ultraviolet microscope, and a displacement sensor for measuring the distance from the end of the object lens of the ultraviolet microscope to the surface of the object to be measured. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses an ultraviolet microscope and further a two-dimensional image sensor such as a CCD camera to measure a minute dimension of an object to be measured, for example, a glass mask. The present invention relates to a measuring device, and more particularly to an automatic focus detection system for preventing a collision between various glass masks having different thicknesses and a microscope and for adjusting a focus for measuring a minute dimension in the glass mask.

[0002]

2. Description of the Related Art FIG. 6 shows the structure of a dimension measuring apparatus according to the prior art. In this figure, 1 is a microscope, and 2 is a revolver connected to the microscope 1 and equipped with a plurality of objective lenses having different focal lengths. This revolver 2
Is for making the optical axis of one of the plurality of objective lenses coincide with the optical axis of the other optical system in the microscope 1. The objective lens with its optical axis aligned will be hereinafter referred to as the “objective lens used”.

The magnified image of the object (subject) 3 magnified by the microscope 1 is picked up by the CCD camera 4, and the picked-up image signal is fed from the camera 4 to the dimension measurement arithmetic processing unit 5. The image signal waveform processing unit 50 electrically measures the dimensions of a desired portion of the captured image, and the measurement result is input to the image signal waveform processing unit 5.
0 to the TV monitor 11, where the DUT 3
The image and the dimension measurement value are displayed.

Generally, in order to improve the accuracy of dimension measurement,
As a process before the dimension measurement, an automatic focus detection process operation is performed to keep the distance (WD) between the objective lens used and the DUT 3 constant. Two automatic focus detection methods will be described below.

(First Automatic Focus Detection Method) The image contrast detection circuit 51 in the dimension measurement arithmetic processing unit 5 detects the contrast amount of the image as the focus component, and at the same time, the motor drive pulse generator 52 in the Z-axis direction. The motor is controlled by the motor drive pulse signal generated by
Thereby, the height of the microscope 1 is changed. Here, the focus component is detected at 30 Hz, which is the same as the TV frame rate.
It may be detected in a cycle. By doing so, the Z stage 6 that moves in the Z axis direction of the microscope with the motor drive pulse signal in the Z axis direction, and the microscope 1, the camera 4, and the revolver 2 attached to the Z stage 6 are moved up and down, and the focus component The maximum position is detected, and the microscope 1 is held at that position. Then, since the position where the focus component is maximum becomes the in-focus position, the objective lens 2 used
The distance to the DUT 3 becomes a predetermined distance, and the focus is achieved.

(Second Automatic Focus Detection Method) A laser beam is projected onto a DUT 3 from a microscope, particularly a laser autofocus unit 13 attached to the visible light microscope 1, and a spot reflected by the projected light is projected. The focus is determined by the position.

As described above, the focus is detected, the microscope 1 is positioned at the in-focus position, and the horizontal positioning of the DUT 3 is performed by the PC (personal computer).
X stage 7 and Y by 10 or stage operation unit 12
The stage 8 is controlled via the stage controller 9.

At this time, in the PC 10, the thickness of the object to be measured 3 and the measurement location are registered in advance, and the X stage 7 is set as the sample mounting position where it does not collide with the objective lens in use, that is, the position where it does not interfere. Place the device under test 3 and start the measurement.

After the measurement is started, the PC 10 turns the measured object 3
The height of the Z stage 6 is changed in accordance with the registered thickness of, and at that time, the interference between the objective lens used of the microscope 1 and the object to be measured 3 is prevented, and the measurement location is within the field of view of the microscope 1.
The X stage 7 and the Y stage 8 are moved to move the DUT 3
Horizontal positioning of.

[0010]

In order to realize the in-focus point detection of a microscope, particularly, a fine dimension measuring apparatus employing an ultraviolet microscope, the conventional techniques have the following drawbacks. That is, in the above-described first automatic focus detection method, the objective lens 2 and the DUT 3 are likely to interfere with each other because the Z axis is vertically swung in the focus detection operation.

Further, in the above-mentioned second automatic focus detection method, it is necessary for laser light to pass through the microscope and the objective lens. However, since the laser is mainly visible light, it does not pass through the ultraviolet microscope, and automatic focus detection by the ultraviolet microscope becomes impossible.

An object of the present invention is to perform measurement and inspection without causing interference between the objective lens used and the object to be measured, and to prevent damage to an expensive object to be measured.
Another object of the present invention is to reliably perform autofocus even on a subject having a large area, and further shorten the focus detection time.

[0013]

In order to solve the above-mentioned problems, the present invention provides an ultraviolet microscope for obtaining a magnified image for measuring a minute dimension of an object to be measured, and the object to be measured mounted on the ultraviolet microscope. It has a stage for moving a predetermined portion of the object to be measured into the field of view of the ultraviolet microscope, and a displacement sensor for measuring the distance from the end of the objective lens of the ultraviolet microscope to the surface of the object to be measured.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a minute dimension measuring apparatus according to an embodiment of the present invention. In this figure, the same symbols as those in FIG. 6 are components having the same functions, and their explanations are omitted. In FIG. 1, the DUT 3 has a corner of 200 mm to 1200 mm and a thickness of 1 m.
It is assumed that the object to be measured is a flat glass substrate having a size range of m to 12 mm. That is, various substrates having different sizes and thicknesses are to be measured.

A chrome line of a photomask is drawn on the upper side of the flat glass substrate, and the minute dimension measuring apparatus of the present invention measures the line width dimension in such a large-sized photomask. Is.

Hereinafter, the state of the measuring method in the case of measuring minute dimensions using the present invention will be described. First, as shown in FIG. 2, the DUT 3 is placed on the sample table 71. It should be noted that the sample table 71 is moved in the X direction by 130 in the movement of the DUT 3.
Move the X stage 7 moving 0 mm and the microscope 1 in the Y direction 120.
Y stage 8 moved to 0 mm and 12 mm in Z direction
It is performed by the Z stage 6 to be moved. Thus, the entire surface of the DUT 3 can be observed with a microscope.

Here, as for the mounting position of the DUT 3, the X stage 7 is moved to a position where the DUT 3 is farthest from the microscope 1, as shown in FIG. 2B. This position is a position where the objective lens used by the revolver 2 and the DUT 3 do not interfere with each other, and the transmission laser length measuring device 14 capable of measuring the thickness of the sample (maximum height of the DUT from the sample stand) at that position. Are arranged as shown in FIG. The transmission laser length measuring device 14 includes a light projecting unit 141 and a light receiving unit 142, and the distance between them is, for example, 1500 mm.
The thickness of the DUT 3 having a size of up to mm is 1 mm to
When the thickness is in the range of 12 mm, the thickness can be measured with the accuracy of 0.1 mm.

In this embodiment, the revolver 2 connected to the microscope 1 has magnifications of 5 times, 20 times, and 15 times, respectively.
An electric revolver having a 0 × objective lens is used, and the objective lens to be used can be selected by electrically rotating the revolver. The W.V. of the objective lens having a magnification of 5 times, 20 times, or 150 times. D is 12.2 mm, 10.7 mm,
It becomes 0.2 mm. In the minute dimension measuring apparatus of the present embodiment, even if the thickness of the object to be measured is in the range of about 0 mm to about 12 mm, the objective lens with a magnification of 5 does not interfere with the object to be measured 3. For this purpose, a lower limit limiter sensor for the Z-axis and a mechanism stopper are arranged, and an objective lens with a magnification of 150 is selected when measuring small dimensions, and an objective lens with a magnification of 5 is used for other operations. To be selected.

Further, as shown in FIG. 1, the displacement sensor 15
Is attached to the Z stage 6 to which the microscope 1 is attached, and moves up and down in the same manner as the microscope by moving the Z axis. As shown in FIG. 4, the displacement sensor 15 irradiates the sample with laser light obliquely downward from the laser source 151, and the position of the reflected light is detected by the line sensor 152 which is symmetrical to the laser source 151. , Its line sensor 152
The position of the element that received the light is detected at the position of the line sensor, and the detected value is converted into the interval (height) between the objective lens used and the sample.

The operation of the minute dimension measuring apparatus of this embodiment at the time of automated minute dimension measurement and the operation at the time of manual stage movement other than measurement will be described below.

(Operation at the time of automatic measurement) (1): As shown in FIG. 2A, the DUT 3 is placed on the sample table 71 at a predetermined mounting position. At that time, as shown in FIG. 3A, the DUT 3 is pressed against the three roller positioning guides 72 of the sample stand 71, and air is sucked to fix the DUT 3 to the sample stand 71. To do. And
As shown in FIG. 3B, the transmission type laser length measuring device 14
Then, the maximum height of the base material (substrate) of the DUT 3 is measured. (2): The objective lens with a magnification of 5 times is used as the objective lens, and the height position of the substrate and the W.V. The height of the microscope 1 in the Z-axis direction is changed so that the position D can be maintained. (3): In order to recognize the positional deviation error when the DUT 3 is fixed to the sample table 71, the alignment adjustment operation for recognizing the positional deviation and the angular deviation is performed. As shown in Figure 5,
The X stage 7 and the Y stage 8 are moved so that the alignment left side position 201 of the DUT 3 can be observed with the microscope 1. (4): Displacement sensor 15 that moves in the same way as the microscope 1.
Then, the height position of the DUT 3 is detected, and the Z stage 6 in the Z-axis direction is moved so that the detected position becomes the position Z ₅ on the line sensor of the displacement sensor 15. (5): The shift amount of the alignment left side position 201 is recognized by using image processing. (6): The X stage 7 and the Y stage 8 are moved so that the alignment right side 202 of the object to be measured can be observed with the microscope 1. Further, similarly to (4) and (5), the shift amount of the alignment right side position 202 is recognized by image processing. The amount of positional deviation and the amount of angular deviation are recognized from the registered coordinates of the left side 201 and the right side 202 and the measured coordinates, and alignment adjustment for eliminating the deviation is performed based on these. (7): If the alignment adjustment is insufficient,
An objective lens with a magnification of 20 is used as the objective lens described above.
Perform operations (3) to (6). Then, after recognizing the amount of positional deviation and the amount of angular deviation, alignment adjustment is performed, and then X adjustment is performed.
The stage 7 and the Y stage 8 move to the first measurement position 203. Then, the displacement sensor 15 detects the height position of the DUT 3, and the automatic focus is performed so as to move the Z axis so that the detected position becomes the position of Z ₁₅₀ on the line sensor of the displacement sensor 15. Make adjustments. Then, the revolver 2 is rotated so that the objective lens used is an objective lens with a magnification of 150 times, and minute dimension measurement is performed. (8): Next, move to the second measurement position 204, but before that, move the microscope 1 upward by a predetermined value Z _{of in the} Z-axis direction. Here, the predetermined value Z _of is a value determined by the plane error between the DUT 3 and the sample table 71, and in general,
The maximum is 0.1 mm. Such value microscope 1
Is raised so that the value does not interfere with the objective lens used when the XY stage automatically moves. After that, the XY stage is moved to the next second measurement position 204. (9): Then, the displacement sensor 15 detects the height position of the substrate, and the laser light is reflected to the position of Z ₁₅₀ which is the position on the line sensor corresponding to the objective lens used, that is, the object lens with a magnification of 150 times. Automatic focus adjustment is performed so that the Z-axis is moved so that light comes, and then minute dimension measurement is performed. (10): The above operations (8) and (9) are repeated for the subsequent measurement points. Here, since the microscope 1 and the displacement sensor 15 cannot be arranged coaxially and are apart from each other, the object 3 to be measured may not exist at the measurement position of the displacement sensor 15 depending on the measurement location. Regarding such a position, the measurement point is not moved below the microscope 1 but is moved below the displacement sensor, and the Z axis is moved so that the detection position on the line sensor is the position of Z ₁₅₀ . Move to the bottom of the microscope 1 to measure minute dimensions. (11): The objective lens used is an objective lens with a magnification of 5 times, and the DUT 3 is taken out at the substrate mounting position.

(Operation at the time of manual movement) When performing the XYZ movement manually, it is necessary to take the following interlocks. Specifically, for the XY axis movement, the objective lens used is always moved to the objective lens having a magnification of 5 times (WD = 12.2 mm). However, the XY fine movement movement can be performed if the height of the DUT 3 is within the effective range (0.2 mm) of the displacement sensor 15. Further, the movement of the Z axis is performed by the W. Only half of D can be moved to prevent erroneous collision between the DUT 3 and the objective lens used due to erroneous input of the switch.

[0023]

As described above, according to the present invention,
When moving the sample stage on the stage during automatic measurement or manually, it can be moved without interference between the objective lens and the DUT, without damaging expensive DUT. can do. In addition, even if a large substrate having a variation length of about 1 m is the object to be measured, it is possible to reliably perform autofocus (automatic focusing), and to detect the focus component of the above-described first conventional autofocus method. Sometimes the time for moving up and down can be omitted and the tact time can be improved.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a minute dimension measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining how the microscope 1 and the DUT 3 are arranged.

FIG. 3 is a view for explaining how the transmission laser length measuring device 14 and a roller positioning guide 72 are arranged.

FIG. 4 is a diagram for explaining how the displacement sensor 14 and a used objective lens are arranged.

FIG. 5 is a diagram showing an example of alignment positions and measurement positions.

FIG. 6 is a diagram showing a configuration example of a dimension measuring device according to a conventional technique.

[Explanation of symbols]

1: microscope, 2: revolver, 3: subject (object to be measured),
4: CCD camera, 5: dimensional measurement calculation processing device, 6: Z
Stage: 7: X stage, 8: Y stage, 9: Stage control unit, 10: PC (personal computer), 11: TV monitor, 12: Stage operation unit, 1
3: Laser autofocus unit, 14: Transmission type laser length measuring device, 141: Light emitting part, 142: Light receiving part, 15:
Displacement sensor, 151: Laser source, 152: Line sensor, 50: Video signal waveform processing section, 51: Image contrast detection circuit, 52: Motor drive pulse generating section, 71: Sample stage, 72: Roller positioning guide, 201: Alignment Left position, 202: Right alignment position, 20
3,204: measurement position.

Claims (3)

[Claims] 1. An ultraviolet microscope for obtaining a magnified image for measuring minute dimensions of an object to be measured, and a stage for mounting the object to be measured and moving a predetermined portion of the object to be measured into a field of view of the ultraviolet microscope. And a displacement sensor adapted to measure the distance from the end of the objective lens of the ultraviolet microscope to the surface of the object to be measured. 2. The minute dimension measuring apparatus according to claim 1, further comprising a length measuring device for measuring the thickness of the object to be measured mounted on the stage in the optical axis direction of the objective lens. And a minute dimension measuring device. 3. The minute dimension measuring apparatus according to claim 1 or 2, wherein a large glass photomask is used as an object to be measured.