JPH02285314A - Method for positioning light cutting microscope device and its optical means - Google Patents

Abstract

PURPOSE:To increase the peak detection accuracy of light intensity and to obtain a light-cut image with high resolution by providing a light limiting means which has slit width W between a 2nd optical means and an optical detecting means where reflected light from an object to be measured is made incident. CONSTITUTION:The incident light limiting means 7 which has the slit width W is provided between the 2nd optical means 15 and optical detecting means 16 where the reflected light L2 from the object 18 to be measured is made incident. Consequently, the reflected light from the object 18 to be measured is cut off by the incident light limiting means 17 except reflected light L3 which has the slit width 17, and consequently only the reflected light L3 which has the slit width W can be made incident on the optical detecting means 16. The optical detecting means 16 can, therefore, obtain a steep-rising light intensity distribution based upon the reflected light L3 with the slit width W. Consequently, the peak can accurately be detected and the light-cut image of a waving surface shape with high resolution can be obtained.

Description

[Detailed Description of the Invention] [Summary] Regarding a light cutting microscope device, particularly a device that aligns the surface of an object to be measured with a surface undulation shape and the focal point of an optical means, all reflected light from the object to be measured is optically detected. The purpose of this method is to take in the reflected light at the desired position on the surface of the object to be observed, without it entering the measuring device, and to align the focal point of the optical device at that position with good brightness and high reproducibility. a light source that generates a light source, a first optical means for irradiating the measurement light onto the object to be measured, a sample stage on which the object to be measured is installed, a sample stand driving means for driving the sample stand, and a first optical means for irradiating the object to be measured with the measurement light; a second optical means for capturing the reflected light;
In the light-cutting microscope apparatus, which includes a light-cutting means for detecting the reflected light and acquiring a light-cutting image of the object to be measured, a slit having a slit width W is provided between the second optical means and the optical detecting means. The structure includes providing an incident light limiting means.

[Industrial application field]

The present invention relates to a light sectioning microscope device and a method for positioning its optical means, and more specifically to a device and method for focusing the optical means on a sample having a surface undulation shape.

In recent years, optical cutting microscopes that use linear laser light as measurement light have been used to measure and inspect minute shapes such as wiring patterns of semiconductor devices.
boundaries are used.

At this time, there is a need for an apparatus and method that can detect the peak of the light intensity of the optically sectioned image and accurately align the focus of the optical means even if the sample surface has a undulating shape. .

[Conventional technology]

6 to 8 are explanatory diagrams related to conventional examples.

FIG. 6 shows a configuration diagram of a conventional optical cutting microscope device.

In the figure, the light cutting microscope device includes a laser light generation source 1
．． Mirrors 2a, 2b, slit 3. Incoming objective lens 4
1 Reflection side objective lens 5. It consists of a camera 6, an imaging lens 7, a stage 8, and a stage driving device 9.

The function of the device is that first, a laser beam 11 is irradiated and redirected from a laser beam generating at to a mirror 2a, and the laser beam 1
1 is a linear (light cutting line) laser beam 12 caused by a slit 3
Then, the linear laser beam 12 is irradiated onto the object to be measured (sample) 10 placed on the stage 8 via the incident-side objective lens 4 . Next, reflected light j! from sample 10!
3 is captured by the reflective objective lens 5, and the reflected light t
3 is deflected by the mirror 2b, and it is directed to the imaging lens 7.
The light is incident on the camera 6 via. As a result, a photocutting image of the wiring pattern of the semiconductor device, etc. is acquired, and the sample 1 is
0 @ thin shape measurement and its inspection are performed.

FIGS. 7(a) and 7(b) are explanatory diagrams related to a conventional method for aligning optical means, and FIG. 7(a) shows a state in which a light cutting line is irradiated onto a sample having a stepped portion. It shows.

In the figure, it is assumed that the focus of the incident-side objective lens 4 that irradiates the sample 10 with the light cutting line 12 and the focus of the reflection-side objective lens 5 that makes the reflected light 13 from the sample 10 enter are aligned in advance. do.

Therefore, the alignment of the optical means referred to here means aligning the optical system, which has lost its focus between the focal point of the incident side objective lens 4 and the reflective side objective lens 5, on the surface of the sample placed on the stage 8. In other words, it refers to alignment in the vertical direction (FIG. 4(a)).

FIG. 2B shows a light-cut image of the step surface of the sample captured by the camera 6.

In the figure, the light-cutting image of the step surface shows that the light-cutting cotton 12 from the incident-side objective lens 4 is located above the step surface of the sample IO (
The reflected light component reflected by the convex part) and the lower part of the step surface (
The reflected light 13 is divided by the reflected light component reflected by the concave portion) and taken into the camera 6, and the reflected light 13 is obtained by photoelectric conversion or the like.

At this time, the light intensity of the reflected light 13 can be 1'f as two light intensity distributions having an upper peak and a lower peak. By detecting the peak of the light intensity of this reflected light 13, both objective lenses 4.5 and 4.5 are focused in advance.
Sample 10 with a stepped surface such as an optical system and a wiring pattern
vertical alignment.

[L that the invention tries to solve! 4! Figures 8(a) and 8(b) are explanatory diagrams related to the problems of the conventional method, and Figure 8(a) shows a state in which a light cutting line is irradiated to a sample with an undulating surface shape. .

In the figure, a sample 10a with an undulating surface shape is not a wiring pattern of a semiconductor device having a stepped surface, but is a semiconductor wafer, a disk bat, etc., which has surface undulations due to some reason.

When the sample 10a with this undulating surface shape is irradiated with the optical cutting line 12, the reflected light r3 representing the cross section of the undulating surface shape, etc.
is obtained (Figure (a)).

FIG. 6B shows a light-cut image of a sample with a undulating surface shape captured by the camera 6.

In the figure, the light-cutting image of the undulating surface shape is different from the light-cutting image of the stepped surface, in that the light intensity distribution of reflected light 13 has an upper peak and a lower peak like the light intensity distribution of the stepped surface. .

Therefore, when vertical alignment is performed between the sample having the undulating surface shape and the optical means by detecting the light intensity peak of the reflected light 13, the following problem occurs.

Since the light intensity peak of the 0-reflected light 13 does not rise sharply like the upper and lower peaks in the case of a stepped surface, the detection accuracy of the light intensity peak is poor, and positioning with good reproducibility cannot be performed.

■As a result, the desired observation position and the focal position of the optical system of both objective lenses are not matched, resulting in an unclear image.

The present invention was created in view of the problems of the prior art, and focuses the optical means on the desired position to observe the surface of the object to be measured, without causing the reflected tip from the object to be measured to enter the light detecting means. The object of the present invention is to provide a light cutting microscope device and a method for positioning its optical means, which enables positioning of the optical device with high precision and reproducibility.

[Means for Solving the Problems] FIG. 1 shows a principle diagram of a light cutting microscope device of the present invention.

The device includes a light fill that generates measurement light L1, a first optical means 12 that irradiates the measurement target 18 with the measurement light L1, and a sample stage 13 on which the measurement target 18 is installed.
A sample stage driving means 14 that drives the sample stage 13, a second optical means 15 that captures the reflected light L2 from the object to be measured 18, and a light detection means 16 that detects the reflected light L2.
In the light-cutting microscope apparatus for acquiring a light-cutting image of the object to be measured 18, the second optical means 15
and the optical detection means 16, an incident light limiting means 17 having a slit width W is provided. Second
In the alignment method of the optical means for aligning the focal point of the optical means 12.15 and the surface of the object to be measured 18 placed on the sample stage 13, the reflected light L2 from the object to be measured 18 is divided into a slit width W. Through the incident light limiting means 17 of
The sample stage 13 or the optical means 12.15' is set so that the light intensity of the reflected light L3 having the slit width W taken into the light detection means 16 and into the incident light limiting means 17 is maximized.
and stop the sample stage 13 or the optical means 12.15 at the position where the light intensity is maximum.
Achieve the above objectives.

[Effect]

According to the device of the present invention, an incident light limiting means 17 having a slit width W is provided between the second optical means 15 and the light detecting means 16.

Therefore, the reflected light L2 from the object to be measured 18 is filtered by the incident light limiting means 17 except for the reflected light L3 having the slit width W.
Its passage is blocked, and only the reflected light L3 having the slit width W that has escaped the blocking can be taken into the photodetecting means 16.

As a result, the light detection means 16 can obtain a light intensity distribution with a sharp rise based on the reflected light L3 of the slit width W, compared to a conventional light intensity distribution, and this light intensity distribution allows accurate peak detection. It becomes possible to perform detection.

Further, according to the method of the present invention, the reflected light L with the slit width W
The sample stage 13 or the optical means 12.15 is stopped at the position where the light intensity of 3 is maximum.

Therefore, if the position of the slit of the incident light limiting means 17 is set at the center of the optical detecting means 16 and it is assumed that this is the position desired by the observer, the first slit is always located at the position desired by the observer. It becomes possible to bring the focus of the second optical means 12.degree. 15 to a specific position on the sample surface with good reproducibility and high precision.

This makes it possible to obtain a high-resolution light-cut image of the undulating surface shape and the like.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

2 to 5 are diagrams for explaining a light sectioning microscope device according to an embodiment of the present invention and a method of positioning its optical means, and FIG. A configuration diagram is shown.

In the figure, reference numeral 21 denotes a laser generation source which is an example of the light source 11, and generates a laser beam Ll in the direction of the mirror 22a. 22a to 22C are first optical means 1
A mirror slit and an incident side objective lens, which are one example of No. 2, are shown respectively. Mirror 22a emits laser light L
22b is a function to change the laser beam L11 into a cotton-like laser beam (light cutting line) L12, and the incident side objective lens 22c focuses the light cutting line L12 on the stage 23. Each has the function of irradiating in a direction.

Reference numeral 23 denotes a stage which is an example of a sample stage, on which an object to be measured 28 is placed. 24 is a stage driving device which is an example of a sample stage driving means, and x, y, z
It has a function of moving the stage 23 in the direction.

Reference numerals 25a to 25c each indicate a reflection side objective lens, a mirror, and an imaging lens, which are one embodiment of the second optical means 15. The reflective objective lens 25a
It has a function of condensing the reflected lights 1 and 21 from the mirror 25b and passing them along the optical axis toward the mirror 25b. The mirror 25b receives the reflected light L21 from the reflective objective lens 25a.
is directed toward the imaging lens direction 25c. The imaging lens 25c forms an image of the reflected light L21 and the like.

A camera 26 is an embodiment of the light detection means, and has a function of capturing reflected light L21 etc. from the object to be measured. The camera 26 is an image acquisition device such as a solid-state image sensor, and has a function of detecting the light intensity of the captured reflected light L21 etc. For example, the light intensity of the reflected light L21 etc. can be confirmed by the observer at a glance. A digital display device or the like may be provided to sequentially display the counted value.

Up to now, the structure is similar to that of a conventional light sectioning microscope device, but the light sectioning microscope device of the present invention is provided with the following components.

That is, 27 provided immediately in front of the camera 26 is a light shielding slit which is an example of the incident light limiting means 17, and allows a part of the reflected light L22 of the reflected light L21 that has passed through the imaging lens 25c to pass therethrough. It has a function of allowing only the reflected light L22 to enter the camera 26. The light shielding slit 26 will be explained in detail in FIG. 3.

Reference numeral 28 denotes a sample with a undulating surface shape, which is an example of the object to be measured 18, and is a semiconductor wafer, a disk bat, or the like that has surface undulations for some reason.

In addition, 29 is a control means, which is used when automatically aligning the optical means of the light sectioning microscope apparatus of the present invention. The control means 29 has a function of controlling the output of the stage driving device 24 based on the detected peak value of the light intensity of the reflected light 122 etc. output from the camera 26.

FIG. 3 is an explanatory diagram of the light shielding slit 27 according to the embodiment of the present invention.

In the figure, the light shielding slit 27 has a slit opening 27a having a slit width W in a black plate. The slit width W may be on the order of several hundred [μm]. The opening direction of the slit opening 27a is the slit 22b for the light cutting line.
perpendicular to the opening direction. Further, the opening position of the slit is set so that its focal point coincides with the image acquisition position desired by the observer, for example, near the center of the camera.

In addition, the light-shielding slit 27 is provided just in front of the camera 26, and is attached only when vertically aligning the focus of the optical means 22c, 25a with the surface of the object to be measured 28; it is removed during normal image observation. be.

As a result, the reflected light L21 passing through the imaging lens 25c
A part of the reflected light L22 is passed through, and the reflected light L22 is
can be incident on the camera 26.

FIG. 4 is a diagram showing the relationship between an acquired image and light intensity according to an embodiment of the present invention, and FIG. 4 (a) shows a sample 28 with an undulating surface shape.
This shows the state in which the optical cutting line is irradiated.

In the same figure (b), L21 is sample 2 with an undulating surface shape.
This is the reflected light obtained when 8 is irradiated with the light cutting line L12. This reflected light L21 is transmitted to the reflecting side objective lens 25a, the mirror 25b, the imaging lens 25c and the light shielding slit 27.
The image is captured by the camera 26 via the camera 26.

FIG. 2B shows the reflected light L22 captured by the camera 26 and its light intensity distribution.

In the figure, A is an image captured by the camera 26,
This is an image obtained by a part of the reflected light L22 of the reflected light L21 that has entered the light shielding slit 27. Further, 1 is the light intensity of the reflected light L22, and is set in advance by the incident side objective lens 22c.
When an optical system whose focal point coincides with that of the reflective objective lens 25a is vertically aligned to a sample 28 having an undulating surface shape, the maximum value is reached when the focal point coincides with the surface of the sample 28.

These relationships can be used to align the optical means in the vertical direction, which will be described later.

In this way, according to the light-cutting microscope device according to the embodiment of the present invention, the light-shielding slit 27 with the slit width W is provided between the imaging lens 25c and the camera 26 and just before the camera 26. ing.

Therefore, the reflected light L2 from the sample 28 with the undulating surface shape
1 is blocked by the light-shielding slit 27, except for the reflected light L22 having the slit width W, from passing through, and only the reflected light L22 having the slit width W that is not blocked can be taken into the camera 26.

As a result, the camera 26 can obtain a light intensity distribution with a sharp rise based on the reflected light L22 of the slit width W, compared to a conventional light intensity distribution, and this light intensity distribution allows t# to detect a peak with good accuracy. It becomes possible to do this.

FIG. 5 shows a flowchart relating to a method for positioning optical means according to an embodiment of the present invention.

In the figure, first, in step P1, prior to focus positioning of the optical system, the slit 22b and the light shielding slit 27b are
and remove. At this time, no sample is placed on the stage 23.

Next, in step P2, the focal positions of the incident side objective lens 22c and the reflection side objective lens 25a are aligned. The focus positioning at this time is performed by a positioning method, etc., which the present inventor is currently applying for separately. According to this, a plate for focus alignment is placed on the stage 23, the focus of the incident side objective lens 22c is first aligned with the focus alignment plate, and then the focus of the reflection side objective lens 25a is aligned therewith. It is something to do. Thereby, the focus of the incident side objective lens 22c and the focus of the reflection side objective lens 25a can be matched.

Next, in step P3, an object (sample) 28 to be measured, such as an undulating surface shape, is placed on the stage 23.

At this time, the alignment plate used for the previous focus alignment is removed and the sample 28 is placed on the stage 23 instead.

Next, in step P4, the slit 22b for the light cutting line and the light shielding slit 27 are attached. At this time, when looking at the image acquired by the camera 26, although the acquired image as shown in FIG. Because the image is aligned with the image, the obtained image is unclear.

Therefore, in step P5, the stage 23 is adjusted, and the light intensity of the reflected light L22 having the slit width W that is incident on the camera 26 is detected. At this time, in the embodiment of the present invention, stage 23
is moved up and down in the Z direction by manually or automatically driving the stage drive device via the control means 29. As a result, the light intensity (a) (b) between the explanation of the shielding slit according to the embodiment of the present invention and the W slit light intensity according to the implementation example of the present invention!) 1ilj image and light Relationship diagram with strength Figure 4 (a) Explanation regarding the problem of the conventional method

Claims (2)

[Claims] (1) A light source (11) that generates measurement light (L1), a first optical means (12) that irradiates the measurement light (L1) onto the object to be measured (18), and the object to be measured (18) A sample stand (13) for installing the sample stand (13), a sample stand driving means (14) for driving the sample stand (13), and a second optical means (2) for taking in the reflected light (L2) from the object to be measured (18). 15) and a light detection means (16) for detecting the reflected light (L2), and a light sectioning microscope apparatus for acquiring a light sectioning image of the object to be measured (18), wherein the second optical means A light cutting microscope apparatus characterized in that an incident light limiting means (17) having a slit width W is provided between the optical detecting means (15) and the optical detecting means (16). (2) A method for positioning the optical means of the light sectioning microscope device according to claim 1, comprising the step of aligning the first and second optical means (12
, 15) and the object to be measured (
18) In the method for aligning the optical means with the surface of the object to be measured (18), the reflected light (L2) from the object to be measured (18) is passed through the incident light limiting means (17) with a slit width W to the light detecting means. (16) and the incident light limiting means (17) so that the light intensity of the reflected light (L3) with the slit width W is maximized.
, 15) and stopping the sample stage (13) or the optical means (12, 15) at a position where the light intensity is maximum.