JPH1114575A - Photothermal reflection-type sample analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photothermal reflection-type sample analyzer in which the alignment of heating light by a local heating light source with laser probing light is not required, in which the agreement condition of the heating light with the laser probing light does not become out of order even when the analyzer is moved and which has a structure capable of miniaturizing the analyzer itself. SOLUTION: A photothermal reflection-type sample analyzer is provided with a local heating light source 22 which heats a sample 21, with a laser probing light source 24 which radiates laser probing light to the sample 21 and with a photodetector 26 which detects the intensity of the laser probing light reflected from the sample 21, and the sample is evaluated on the basis of a detection result by the photodetector 26. In the photothermal reflection-type sample analyzer, a heating optical path which reaches the sample 21 from the local heating light source 22, a probe optical path which reaches the sample 21 from the laser probing light source 24 and a reflection optical path which reaches the photodetector 26 from the sample 21 are formed of optical fibers, and at least the tip part on the side of the sample 21 out of all of the heating optical path, the probe optical path and the reflection optical path which are formed of the optical fibers is composed of one optical fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a local heating light source for heating a sample, a laser search light source for emitting laser search light to the sample, and a light for detecting the intensity of the laser search light reflected from the sample. The present invention relates to a light reflection type sample analyzer that includes a detector and performs sample evaluation based on a detection result of the photodetector.

[0002]

2. Description of the Related Art A photothermal reflection type sample analyzer of this type detects, for example, various characteristics of a semiconductor device, detection of pinholes, cracks, distortions, etc. on the surface or inside of a solid sample, or identification of an internal structure or a defect of a laminated sample. Can be performed nondestructively and with high resolution.

By the way, as shown in FIG. 3, for example, a photothermal reflection type sample analyzer of this type transmits a local heating light source 3 for radiantly heating an analysis point 2 of a sample 1 and a laser search beam 4 to the sample 1 as shown in FIG. The main components are a laser search light source 5 to be emitted and a photodetector 7 for detecting the intensity of the reflected light 6 of the laser search light 4 reflected from the sample 1, and as auxiliary components,
A beam expander (enlarger) 8, a deflecting beam splitter 9, a quarter-wave plate 10, a dichroic mirror 11, an optical modulator 12, a lens 13, and an optical filter 14 for selectively transmitting the reflected light 6 are provided. I have. As the local heating light source 3, a lamp light source or a laser light source can be used.

In the above-mentioned sample analysis by the light-heat reflection type sample analyzer, the local heating light source 3 intermittently irradiates the analysis point 2 of the sample 1 and heats it. This is performed by irradiating the laser search light 4 and measuring the reflected light 6 of the laser search light 4 by the photodetector 7. The measurement principle is that, for example, if there is a defect such as a pinhole immediately below the analysis point 2, the sample temperature changes depending on the presence or absence of the defect, and the reflectance of the laser search light 4 at that portion changes. The change in the reflected light 6 is measured to evaluate a sample such as a defect such as a pinhole or a non-uniformity. Identification is also possible.

The above measuring principle is called the so-called photothermal effect, and among various types of photothermal effects, a sample analyzer based on this photothermal reflection is higher than a sample analyzer utilizing other photothermal effects. It has the feature of good spatial resolution, and it is generally said that it is possible to obtain a submicron-order spatial resolution.

[0006]

However, in order to actually realize a high spatial resolution, the spot diameter of the laser light as the local heating light source and the laser search light of the laser search light source on the sample, or the laser beam of the two laser lights, is used. Conditions such as spatial matching on the sample and accuracy of sample movement during scanning must be satisfied.

The most difficult of these conditions is
It is said that the laser light serving as the local heating light source and the laser search light of the laser search light source are spatially coincident. That is,
When using a recent stepping motor type moving device for scanning, the accuracy of about 0.1 μm can be obtained relatively easily by using a recent stepping motor type moving apparatus, but it is necessary to match both laser beams with a positional accuracy of 0.1 μm or less. Is generally considered difficult.

Further, in order to accurately align the two laser beams, all the components interposed in the heating optical path, the search optical path, and the reflection optical path, such as each light source and lens, are extremely precisely mounted on a solid surface plate. There is a problem that the device itself must be assembled and the device itself becomes large.

[0009] However, even if assembled precisely, the alignment of the two laser beams is likely to be misaligned due to a temporal change in the ambient environment conditions such as the temperature, and the correction and adjustment of the alignment of the two laser beams requires considerable time and labor. There's a problem. For this reason, the conventional sample analyzer cannot basically move.

Accordingly, the present invention does not require the positioning of the heating light of the local heating light source and the laser search light, and does not cause a deviation in the matching condition between the heating light and the laser search light even when the apparatus is moved. It is another object of the present invention to provide a light-heat reflection type sample analyzer having a structure that can be downsized.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a local heating light source for heating a sample, a laser search light source for emitting laser search light to the sample, and reflection from the sample. A photothermal reflection type sample analyzer that includes a photodetector that detects the intensity of the laser search light, and performs sample evaluation based on the detection result of the photodetector, wherein a heating optical path from the local heating light source to the sample, All of the search optical path from the laser search light source to the sample and the reflected optical path from the sample to the photodetector are formed by optical fibers, and of the heating optical path, the search optical path, and the reflected optical path formed by these optical fibers, In addition, at least the tip portion on the sample side is constituted by one optical fiber.

[0012]

According to the above construction, the heating light of the local heating light source is
Laser search light of the laser search light, just above the sample,
Since they are emitted from a single optical fiber, the two rays are automatically spatially coincident on the sample and no coincidence errors occur.

For this reason, it is not necessary to perform a difficult operation of arranging various optical components spatially precisely and making both light beams spatially coincide with each other as in the related art.

Further, since the coincidence condition of the two light beams does not change, it is not necessary to perform a troublesome operation such as a periodic inspection for position adjustment, correction and adjustment as in the related art.

Furthermore, by configuring all the optical paths of the heating optical path, the search optical path, and the reflected optical path by optical fibers, various optical components can be also configured by optical fiber-compatible small parts, and the device can be downsized. The portability of the device is also easily obtained.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a photothermal reflection type sample analyzer according to the present invention will be described below with reference to FIGS.

As shown in FIG. 1, the photothermal reflection type sample analyzer according to the present invention
, A search optical path 25 from the laser search light source 24 to the sample 21, and a reflection optical path 27 from the sample 21 to the photodetector 26 are all formed by optical fibers.

[0018] Of the entire optical path formed by these optical fibers, at least the distal end on the sample 21 side is formed by a single optical fiber. The tip of the optical fiber is formed in a front lens processing fiber portion 28 in which a front lens is processed, and plays a role of focusing light to an extremely narrow light spot without using a separate lens.

In FIG. 1, all the thick lines connecting the parts with reference numerals indicate optical fibers, and reference numerals 29 a and 29 b indicate fiber couplers. The fiber couplers 29a and 29b serve to combine or separate light transmitted from two different systems of optical fibers, and commercially available ones can be used.

A light detecting semiconductor 30 is connected to the fiber coupler 29a, and constantly monitors the light amount of the local heating light source 22. Since the light detecting semiconductor 30 requires only a very weak light amount, for example, the fiber coupler 2
9a, the light amount in the direction of the light detection semiconductor 30 is set to 1
And the light amount in the direction of the sample 21 is set to 99.

At the tip of the optical fiber on the sample 21 side, there is provided a microscope unit 31 used for searching for a site to be measured. The microscope unit 31 has an eyepiece 32 and an objective lens (not shown).
For example, after selecting a measurement target portion by visual observation, similarly to a normal microscope, an objective lens of another magnification is rotated and selected for use. Since the front-end lens processing fiber portion 28 is fixed, the measurement of the selected portion to be measured can be immediately performed.

The fiber coupler 29b must equally serve the role of guiding the light from the laser search light source 24 to the sample 21 and the role of guiding the reflected light from the sample 21 to the photodetector 26, and have a branching ratio of 50. : 50, a terminator 33 is connected to absorb unnecessary light from the laser search light source 24 without reflection. Further, an optical filter 34 is provided between the laser search light source 24 and the fiber coupler 29b, and selectively transmits the laser search light.

As the optical fiber used in the present invention, it is desirable to use a single-mode optical fiber having a small core diameter because of the demand for high resolution.

The sample 21 is placed on a sample scanning stage 35.
The sample 21 is placed on the top, and the analysis of the sample 21 is performed as follows.

The excitation light (wavelength a μm) emitted from the local heating light source 22 is transmitted to a fiber coupler 29 a for wavelength a μm.
Light detecting semiconductor 3 for observing the amount of excitation light
In the direction of 0 and in the direction of the spherical lens processing fiber portion 28,
It branches at a ratio of 1:99. On the other hand, the laser search light source 2
The laser search light (wavelength b μm) emitted from 4 is transmitted by the fiber coupler 29b for wavelength b μm in the direction of the terminator 33 and in the direction of the fiber coupler 29a for a μm.
The beam is branched at a ratio of 0:50, and is irradiated with the excitation light of the local heating light source 22 in a state where the spot diameter is narrowed by the spherical lens processing fiber portion 28 and completely coincides with the same point of the sample 21. No matching work between the light beam and the laser search light is required.

Each component of the optical system can be formed integrally with the optical fiber. Therefore, even if each component is displaced, it does not affect the coincidence condition between the excitation light beam and the laser search light. , Maintaining the relative positional relationship between each part, monitoring,
No modification is required. Further, by selecting the spot diameter of the light on the sample 21 and the curvature and shape of the processing of the spherical lens of the optical fiber, it is possible to sufficiently realize the diameter of the submicron level.

Next, the system configuration of the entire apparatus shown in the block diagram of the optical system configured as described above will be described with reference to FIG. A, B, and C in FIG. 2 respectively correspond to A, B, and C in the block diagram of the optical system shown in FIG.

This system comprises a lock-in 36,
It comprises a function generator 37, a personal computer 38, a scanning stage controller 39, a driver 40 for an excitation laser light source, and a modulation device 41 for modulating a light beam emitted from the light source. The modulation signal from the function generator 37 and the excitation laser The DC signal from the light source driver 40 is added by the modulator 41 and sent to the local heating light source 22 in FIG. 1 as a modulation signal. Here, the modulation frequency of the excitation light beam depends on the modulation signal frequency of the function generator 37.

The detection signal obtained from the photodetector 26 in FIG. 1 is synchronized with the reference signal from the function generator 37 by the lock-in amplifier 36 to detect a signal having heat wave information. The amplitude signal and the phase signal obtained by the lock-in amplifier 36 are finally taken into the personal computer 38. The lock-in amplifier 36, the function generator 37, and the personal computer 38 are connected to each other by GPIB, and all can be controlled from the function generator 37. Further, the amount of movement of the sample scanning stage 35 in FIG. 1 is controlled by a personal computer 38 via a scanning stage controller 37.

[0030]

As described above, according to the present invention, it is not necessary to align the heating light of the local heating light source and the laser search light, and even if the apparatus is moved, the matching condition between the heating light and the laser search light is disturbed. Thus, it is possible to obtain a light-heat reflection type sample analyzer having a structure in which no problem occurs and the apparatus itself can be downsized.

[Brief description of the drawings]

FIG. 1 is a block diagram of an optical system of an embodiment of a photothermal reflection type sample analyzer according to the present invention.

FIG. 2 is a system configuration diagram of the above.

FIG. 3 is a block diagram of a conventional example.

[Explanation of symbols]

 Reference Signs List 21 Sample 22 Local heating light source 23 Heating light path 24 Laser search light source 25 Search light path 26 Photodetector 27 Reflection light path 28 Front lens processing fiber parts 29a, 29b Fiber coupler 30 Photodetection semiconductor 31 Microscope part 32 Eyepiece lens 33 Terminator 34 Light Filter 35 Sample scanning stage 36 Lock-in amplifier 37 Function generator 38 Personal computer 39 Scanning stage controller 40 Driver for excitation laser light source 41 Modulator

Claims (1)

[Claims] 1. A laser light source for heating a sample, a laser search light source for emitting laser search light to the sample, and a photodetector for detecting the intensity of the laser search light reflected from the sample. In a photothermal reflection type sample analyzer that evaluates a sample based on a detection result of a photodetector, a heating optical path from the local heating light source to the sample, a search optical path from the laser search light source to the sample, and the light detection from the sample. All the reflected light paths leading to the instrument are formed by optical fibers, and at least the distal end of the sample side of the heating light path, the search light path, and the reflected light path formed by these optical fibers is constituted by one optical fiber. A light-heat reflection type sample analyzer.