JPH0231103A - Apparatus for detecting three-dimensional shape of pattern - Google Patents

Abstract

PURPOSE:To efficiently and accurately detect the thickness and cross-sectional shape of a transparent pattern by finely moving an objective lens or a pinhole along an optical axis on the basis of the shift quantity of a focal position generated on the basis of the difference between the refractive indice of two laser beams having different wavelengths. CONSTITUTION:Two laser beams oscillated from laser beam sources 20, 21 are brought to two coaxial beams having specific polarizing components by a beam splitter 23 and further reflected by a beam splitter 24 to be converged by an objective lens 25 as it is to irradiate the predetermined position of the surface of a transparent pattern 1. Thereafter, the laser beam reflected from the under surface of the pattern 1, that is, the upper surface of a substrate 2 passes through a lens 25 and subsequently transmits through the splitter 24 to be converged by a converging lens 27 and is incident to a photodetector 29 through a pinhole 28. At this time, by finely moving the lens 25 in a direction A, the peak as the light signal of laser beam can be detected by the photodetector 29.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a pattern three-dimensional shape detection device for inspecting a pattern formed on a substrate, and aims to efficiently and accurately measure the three-dimensional shape of a transparent fine pattern. A coaxial optical system including two laser light sources that oscillate light, at least two beam splitters that guide the two acid laser beams to one objective lens placed facing the sample, and a coaxial optical system that includes two laser beams that oscillate light. and an optical system that guides the laser light traveling backward through the objective lens to a confocal optical system consisting of a focusing lens, a pinhole, and a photodetector using one beam splitter in the coaxial optical system, and The lens or pinhole is configured to be able to move slightly along the optical axis.

[Industrial application field]

The present invention relates to an inspection device for fine patterns on a substrate, and more particularly to a three-dimensional pattern shape detection device for efficiently and accurately measuring the three-dimensional shape of a transparent fine pattern.

[Conventional technology]

FIG. 3 is a diagram showing an example of a conventional fine pattern detection method.

In the figure, numeral 1 indicates a pattern formed on a substrate 2 and having a thickness of approximately several μm.

Conventionally, the thickness h or cross-sectional shape (
In order to detect the profile), a method called photosection method is often used.

That is, a sheet-like laser beam 3 is applied to the pattern 1.
(in the case of the figure, the angle θ with respect to the vertical plane)
), and the shape (A in the figure) in which the laser beam 3 cuts the pattern 1 is read by an optical system 4 installed on the optical axis substantially perpendicular to the irradiation angle of the laser beam 3, and further The signal is led to the detector 5 and subjected to arithmetic processing to be displayed on the monitor image 6 as, for example, a pattern surface reflection position 6b relative to the substrate part reflection light 6a, and the difference h' therebetween is detected.

Since the hl detected here is proportional to the height h of the pattern 1, the thickness h and cross-sectional shape of the pattern 1 are detected by reading hl.

In this case, if the pattern 1 is formed of an optically opaque material, efficient and accurate pattern detection is possible.

However, if the pattern 1 is optically transparent, such as a resist in photo-etching technology, the irradiated laser beam 3 is hardly reflected on the pattern surface, so the pattern surface reflection level is not as high as the above-mentioned reflection level. Even if 1i6b was formed, it was weak, and although the thickness could be detected, it was impossible to detect the actual cross-sectional shape of the pattern from the pattern surface reflection position 6b.

[Problem to be solved by the invention]

Conventional pattern detection methods have a problem in that the cross-sectional shape cannot be detected when the pattern is optically transparent.

[Means to solve the problem]

The above problem is solved by a coaxial optical system that includes two laser sources that emit light of different wavelengths and at least two beam splitters that guide the two laser beams to one objective lens placed opposite the sample. an optical system that guides the laser beam reflected by the sample and traveling backward through the objective lens to a confocal optical system including a focusing lens, a pinhole, and a photodetector using one beam splitter in the coaxial optical system; The problem is solved by a pattern three-dimensional shape detection device that is configured with the above-mentioned objective lens or pinhole that can be moved slightly along the optical axis.

[For production]

When two light beams with different wavelengths are irradiated onto the same part of a transparent pattern, a difference in refractive index within the pattern causes a shift in the focal position.

Therefore, by detecting and calculating this focal position shift, it is possible to know the thickness of the transparent pattern, and by moving the light beam or pattern part in a direction perpendicular to the longitudinal direction of the pattern, the cross-sectional shape of the pattern can be determined. Can be easily detected.

In the present invention, two laser beams with different wavelengths are irradiated onto a transparent pattern, and the amount of shift in the focal point (in other words, the focusing position) caused by the difference in refractive index is adjusted by finely moving the objective lens or pinhole along the optical axis. By doing so, it is detected by a photodetector.

Therefore, the thickness and cross-sectional shape (profile) of the transparent pattern can be detected efficiently and accurately.

〔Example〕

FIG. 1 is a principle diagram explaining the present invention, and FIG. 2 is a configuration diagram showing an embodiment of the present invention.

In FIG. 1, 1 indicates a pattern with a thickness of several μm formed on a substrate 2, which is the same as in FIG. 3, and the substrate 2 is placed on an X-Y table 9. It is placed.

10 is along the optical axis S in the direction A shown in the figure (vertical direction on the paper)
11 is a focusing lens on the detection side, 12 is a pinhole, and 13 is a photodetector.

Note that the focusing lens 11. The optical system consisting of the pinhole 12 and the photodetector 13 is usually called a confocal optical system as the smallest unit for detecting the strength of an optical signal.

Also, 14 indicated by a dotted line is a polarizing beam splitter, and 15
is a projection lens.

Here, the parallel laser beam (1) with a wavelength λ1 and the laser beam (2) with a wavelength λ2 are simultaneously emitted from the projecting lens 15 and reflected in the direction of the pattern 1 by the polarizing beam splitter 14.

After the reflected laser beams ■ and ■ pass through the objective lens 10, the laser beam ■ with a wavelength λ1 enters the pattern 1, focuses at a predetermined position F on the lower surface of the pattern, that is, the surface of the substrate 2, and is reflected. After that, each optical system is arranged so that the light passes through the objective lens 10 and the polarizing beam splitter 14, is further focused by the focusing lens 11, is focused at Fl in the pinhole 12, and enters the photodetector 13 as a strong optical signal. ing.

On the other hand, the laser beam (2) with a wavelength λ2 enters the transparent pattern 1 in the same way as the laser beam (2), but since the wavelength is different, there is a difference in the refractive index within the pattern, and the laser beam (2) follows a different optical path than the laser beam (2). follow.

That is, the laser beam (2) is focused on the Fl point within the pattern in the figure.

Therefore, even if the laser beam (1) reflected from the lower surface of the pattern, that is, the surface of the substrate 2, passes through the objective lens 10 and the polarizing beam splitter 14 and is further focused by the focusing lens 11, it is not focused at the pinhole 12 but is focused at, for example, Fl'. Only a weak optical signal reaches the photodetector 13.

Here, when the objective lens 10 is slightly moved in the optical axis direction to align the focal position F° in the pattern 1 of the laser beam (2) with the point F on the substrate 2, the reflected light (9) of the laser beam (2) is reflected by the laser beam (2). Since it follows almost the same optical path as the light (1) 9, it is focused by Fl in the pinhole 12 portion, and a strong optical signal can be made incident on the photodetector 13.

This means that by moving the objective lens 10, a strong optical signal will reach the photodetector 13 for each of the laser beams (2) and (2), and the thickness of the transparent pattern 1 will be can be calculated.

Furthermore, if the pattern 1 is moved in the direction B in the figure on the X-Y table 9 without projecting the laser beam, the optical signal reaching the photodetector 13 will change rapidly at a position outside the area where the pattern exists. The cross-sectional shape can be detected by calculating the degree of .

Here, for example, the working distance of the objective lens 10 is U, the incident angle of laser beam ■■ to pattern 1 (=outgoing angle from the pattern) is θ, and the refraction angle of laser beam ■ of wavelength λ1 in pattern 1 is α( In this case, the refractive index is nl), and the refraction angle of the laser beam ■ in pattern 1 with wavelength λ2 is β (in this case, the refractive index is n2), then the thickness h of transparent pattern 1 is sin α=rzsin θ sin By determining the working distance U of the objective lens 10 from β=n2sin θ, the thickness h and cross-sectional shape of the pattern 1 can be detected.

On the other hand, with the objective lens 10 fixed, the pinhole 12 in the confocal optical system is indicated by a dotted line from the position of Fl.
Even if the photodetector 13 is slightly moved to position 1, a strong optical signal reaches the photodetector 13.

Therefore, we have confirmed that the same effect can be obtained even if the working distance of the pinhole is detected.

In FIG. 2, (A) shows an example of the overall configuration, and B) shows an example of a detection signal.

In Figure (A), a substrate 2 on which a transparent pattern 1 is formed is placed on an X-Y table 9.

20 and 21 are laser light sources that emit laser beams of different wavelengths (λ1, λ2), for example, 20 is a laser light source with a wavelength of 400 μm shown by a solid line, and 21 is a laser light source 9 shown by a broken line.
They each oscillate light with a wavelength of 00 μm.

22a and 22b are filters; 23 is a beam splitter that makes the two light beams coaxial and sends them out as a specific polarized component; 24 is a beam splitter that reflects only a specific polarized component and transmits other polarized components; 25 is a light beam 26 is a reflection mirror, 27 is a focusing lens, 28 is a pinhole, 29 is a photodetector, and 30 is a monitor image that is displayed by processing the signal of the photodetector 29. ing.

Here, the two light beams oscillated from the laser light sources 20 and 21 are turned into coaxial two beams with specific polarization components by the beam splitter 23, and then reflected by the beam splitter 24 and then focused by the objective lens 25 to become transparent. A predetermined position on the surface of pattern 1 is irradiated.

After that, Hf5 is applied to the lower surface of transparent pattern 1, that is, i+t
The light beam reflected from the upper surface of 2 passes through the objective lens 25, passes through the beam splitter 24, is focused by the focusing lens 27, passes through the pinhole 28, and is directed to the photodetector 29.
is configured to be incident on the

At this time, by slightly moving the objective lens 25 in the direction shown in the drawing using a focus moving mechanism (not shown), the photodetector 29 can detect the peak as an optical signal for each of the light beams (1) and (2).

Figure (B) shows an example of a detection signal in the monitor image 30 of Figure (A), in which the horizontal axis X represents time and the vertical axis Y represents signal power.

In this case, the curve obtained by moving the objective lens 25 becomes a curve showing two peaks as shown in the figure, so the working distance U of the objective lens 25 is calculated from the time Δt between the peaks, as explained in FIG. 1. , the thickness and cross-sectional shape of the transparent pattern 1 can be detected efficiently and accurately.

As explained in FIG. 1, even if the objective lens 25 in FIG. 2(A) is fixed and the pinhole 28 of the confocal optical system is slightly moved in the direction B in the diagram along the optical axis by a moving mechanism (not shown), Exactly the same effect can be obtained.

〔Effect of the invention〕

As described above, the present invention can provide a pattern three-dimensional shape detection device that can efficiently and accurately detect the thickness and cross-sectional shape of a transparent pattern formed on a substrate.

23 and 24 represent a beam splitter, 25 an objective lens, 26 a reflecting mirror, 27 a focusing lens, 28 a pinhole, 29 a photodetector, and 3o a monitor image.

[Brief explanation of the drawing]

FIG. 1 is a principle diagram explaining the present invention, FIG. 2 is a configuration diagram showing an embodiment of the present invention, and FIG. 3 is a diagram showing an example of a conventional fine pattern detection method. In the figure, 1 is a transparent pattern, 2 is a substrate, 9 is an X-Y table, 20.21 is a laser light source, 22a and 22b are filters,

Claims (1)

[Claims] Two laser light sources (20, 21
); and a coaxial optical system including at least two beam splitters (23, 24) for guiding the two laser beams to one objective lens (25) disposed facing the sample; The laser beam that is reflected and travels backward through the objective lens (25) is transmitted through one beam splitter (
24) using a focusing lens (27) and a pinhole (28).
) and an optical system leading to a confocal optical system consisting of a photodetector (29), and the objective lens (25) or pinhole (28) can be moved slightly along the optical axis. Shape detection device.