JP2017207522A - Microscopic raman spectrometer and raman microspectroscopic system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microscopic Raman spectrometer and a Raman microspectroscopic system which can perform position detection of a minute sample equal to or smaller than the wavelength of Raman exciting light and Raman measurement.SOLUTION: A microscopic Raman optical system 100 includes: an oblique irradiation optical system 130 irradiating a minute sample 10 with a laser beam for detecting a position of the minute sample 10 on a principal surface of a semiconductor wafer; and a vertical irradiation optical system irradiating the minute sample 10 with a laser beam for exciting Raman scattered light. The laser beam for detecting a position of the minute sample 10 is emitted to the minute sample 10 from an oblique direction with respect to the principal surface of the semiconductor wafer, and the laser beam for exciting the Raman scattered light is emitted to the minute sample 10 from an orthogonal direction with respect to the principal surface of the semiconductor wafer. The position of the minute sample 10 is recognized by a dark field microscopic image.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a microscopic Raman spectroscopic device and a microscopic Raman spectroscopic system.

  As a background art in this technical field, there is JP-A-2001-215193 (Patent Document 1). This publication describes a micro-Raman spectroscopy system that can use foreign matter information obtained by a foreign matter inspection apparatus. This microscopic Raman spectroscopic system employs a stage having a function of reproducing an image of a foreign substance under an optical microscope based on positional information of the foreign substance obtained in advance by another foreign substance inspection apparatus. The microscopic Raman spectroscopic system has a function of searching for a substance name of a foreign substance from a measured Raman spectrum of the foreign substance based on a built-in database.

JP 2001-215193 A

  However, when the size of the foreign matter is not more than the wavelength of the Raman excitation light, for example, 1 μm or less, even if the position is known by the foreign matter inspection apparatus, it is difficult to detect the position by the above-described microscopic Raman spectroscopy system of Patent Document 1.

  In addition, since the foreign matter is minute, if the background Raman signal is strong or the SN ratio is bad, there is a possibility that the Raman measurement cannot be performed.

  In addition, since the foreign matter is very small, the Raman measurement point is small and the exposure time is long. Therefore, there is a possibility that the Raman measurement cannot be performed due to the drift of the foreign matter due to temperature or the movement of the foreign matter itself.

  In order to solve the above-described problems, a microscopic Raman optical system according to the present invention includes one or more first lasers that irradiate a sample with a first laser beam for detecting the position of the sample on the surface of the specimen. The optical system and one or more second optical systems that irradiate the sample with a second laser beam for exciting the Raman scattered light. The first laser light is irradiated onto the sample from a first direction having a first angle of less than 90 degrees with respect to the surface of the inspection object, and the position of the sample is recognized by a dark field microscopic image.

  According to the present invention, it is possible to provide a microscopic Raman spectroscopic device and a microscopic Raman spectroscopic system capable of detecting the position of a micro sample having a size equal to or smaller than the wavelength of Raman excitation light and performing Raman measurement.

  Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

1 is a configuration diagram illustrating an example of a micro Raman optical system provided in a micro Raman spectroscopic apparatus according to Embodiment 1. FIG. It is a schematic diagram explaining the aspect of the various irradiation of the laser beam for exciting the laser beam for detecting the position of the micro sample by Example 1, and a Raman scattered light. (A) is a schematic diagram which shows the optical system which branched the Raman excitation light and employ | adopted oblique illumination and epi-illumination. (B) is a schematic diagram showing an optical system in which Raman excitation light is branched and a plurality of oblique illuminations are employed. (C) is a schematic diagram showing an optical system that employs oblique illumination without branching Raman excitation light. (D) is a schematic diagram showing an optical system that adopts epi-illumination by tilting a minute sample without branching Raman excitation light. 1 is a perspective view showing an example of a micro Raman analysis system according to Example 1. FIG. 1 is a cross-sectional view showing an example of a micro Raman analysis system according to Example 1. FIG. FIG. 3 is a schematic diagram showing an enlarged view of a first microscopic Raman optical system (regions ahead of respective objective lenses of an oblique optical system and an episcopic optical system) according to Example 1; (A), (b), (c), and (d) are the image figures which show an example of the scanning electron microscope image of the microparticle by Example 1, a bright field image, a dark field image, and a Raman image, respectively. is there. FIG. 6 is a schematic diagram showing an enlarged view of a second microscopic Raman optical system (regions ahead of respective objective lenses of an oblique optical system and an episcopic optical system) according to Example 1; FIG. 6 is a schematic diagram showing an enlarged view of a third microscopic Raman optical system (regions ahead of respective objective lenses of an oblique optical system and an episcopic optical system) according to Example 1. (A) And (b) is a schematic diagram which shows an example of the Raman measurement of the micro sample by Example 1, and the schematic diagram which shows the other example of the Raman measurement of the micro sample by Example 1, respectively. (A) and (b) are image diagrams when the laser beam of the oblique optical system according to Example 1 is irradiated to a wide field range, and the laser beam of the oblique optical system according to Example 1 is irradiated to a narrow field range. It is an image figure in the case. It is an image figure which shows the whole visual field image of a camera at the time of irradiating the laser beam of the oblique optical system by Example 1 to a narrow visual field range. FIG. 3 is an image diagram for explaining a minute sample tracking function according to Example 1; 6 is an image diagram illustrating a scanning method of Raman imaging according to Embodiment 1. FIG. FIG. 6 is a flowchart for explaining an example of an operation flow of the microscopic Raman spectroscopic device according to the first embodiment. FIG. 6 is a cross-sectional view showing an example of a micro Raman analysis system including a load port type micro Raman spectroscopic device according to a second embodiment. FIG. 6 is a cross-sectional view showing an example of a simple microscopic Raman spectroscopic apparatus according to Example 3.

  In the following embodiments, when necessary for the sake of convenience, the description will be divided into a plurality of sections or embodiments. However, unless otherwise specified, they are not irrelevant to each other, and one is the other. There are some or all of the modifications, details, supplementary explanations, and the like.

  Further, in the following embodiments, when referring to the number of elements (including the number, numerical value, quantity, range, etc.), especially when clearly indicated and when clearly limited to a specific number in principle, etc. Except, it is not limited to the specific number, and may be more or less than the specific number.

  Further, in the following embodiments, the constituent elements (including element steps) are not necessarily indispensable unless otherwise specified and clearly considered essential in principle. Needless to say.

  In addition, when referring to “consisting of A”, “consisting of A”, “having A”, and “including A”, other elements are excluded unless specifically indicated that only that element is included. It goes without saying that it is not what you do. Similarly, in the following embodiments, when referring to the shapes, positional relationships, etc. of the components, etc., the shapes are substantially the same unless otherwise specified, or otherwise apparent in principle. And the like are included. The same applies to the above numerical values and ranges.

  Further, in the drawings used in the following embodiments, hatching may be added to make the drawings easy to see even if they are plan views. In all the drawings for explaining the following embodiments, components having the same function are denoted by the same reference numerals in principle, and repeated description thereof is omitted. Hereinafter, the present embodiment will be described in detail with reference to the drawings.

  In Example 1, an example of a microscopic Raman spectroscopic apparatus and microscopic Raman spectroscopic system for performing Raman measurement on a micro sample on a semiconductor wafer will be described.

  Here, the micro sample on the semiconductor wafer indicates a micro foreign material that lowers the manufacturing yield, a local strain that affects device characteristics, a carrier concentration, or the like, and is required to have Raman activity. Further, the micro sample particularly indicates a micro sample or a micro site exceeding the diffraction limit of laser light, and the size of the micro sample is not more than the wavelength of Raman excitation light, for example, 1 μm or less.

  Moreover, although the semiconductor wafer was illustrated as a test body, it is not limited to this. That is, the Raman analysis can analyze not only a minute sample on a semiconductor wafer but also a carbon-based material such as carbon nanotube or graphene. For example, the stress of the carbon nanotube can be detected from the shift of the peak appearing in the Raman spectrum. Alternatively, the number of graphene layers can be detected from the ratio of the intensity of one band of the Raman spectrum to the intensity of the other band.

  FIG. 1 is a configuration diagram illustrating an example of a micro Raman optical system provided in the micro Raman spectroscopic apparatus according to the first embodiment.

  The optical axis 150 of the microscopic Raman optical system 100 is indicated by a thick line in FIG.

  The Raman excitation light emitted from the laser 101 is branched through the beam splitter 134 and becomes two laser lights (illumination lights). One laser beam passes through the oblique optical system, the other laser beam passes through the epi-illumination optical system, and the two laser beams are irradiated onto the minute sample 10 on the semiconductor wafer. Here, oblique illumination refers to irradiating laser light obliquely with a certain angle (less than 90 degrees) with respect to the surface of the inspection object having the micro sample 10 (the main surface of the semiconductor wafer in the first embodiment). In other words, the optical system is called an oblique optical system. In addition, irradiation with laser light perpendicular to the surface of the inspection object having the micro sample 10 (the main surface of the semiconductor wafer in the first embodiment) is called epi-illumination, and the optical system is called epi-illumination optical system.

  In the first embodiment, the Raman excitation light emitted from the laser 101 is branched and guided to the oblique optical system and the episcopic optical system. However, two or more lasers having different wavelengths from each other are not branched. May be implemented. By mounting multiple lasers, a wavelength band that avoids fluorescence can be used, or different wavelength bands can be used for oblique and epi-illumination optical systems, so a wide range of Raman spectra can be measured simultaneously. be able to.

  The Raman scattered light emitted from the minute sample 10 by the irradiated laser light is guided to the spectroscope 125 through the confocal optical system. A detector 126 such as a high sensitivity cooled CCD (Charge Coupled Device) is mounted on the spectroscope 125, and the detected Raman scattered light can be spectrally displayed.

  In Example 1, since the Raman measurement of the micro sample 10 on the semiconductor wafer is illustrated, the configuration of the upright microscope (metal microscope) is used for the microscopic Raman optical system 100. However, the configuration of the inverted microscope is used. It can also be used.

  Next, the micro Raman optical system 100 will be described in detail.

  The Raman excitation light is emitted from the laser 101, subjected to polarization adjustment by a polarization adjuster 102 such as a polarizing plate or a wave plate, and the intensity is adjusted by an attenuation filter 103. Furthermore, the wavelength band of the Raman excitation light is limited by the laser line filter 104 and is adjusted to an arbitrary intensity distribution by the spatial filter 105 to form a beam.

  The beam-formed Raman excitation light is branched by the beam splitter 134, and one laser beam is guided to the oblique optical system 130, and the other laser beam is guided to the incident optical system. The beam splitter 134 is equipped with an intensity adjustment mechanism, and can change the intensity distribution ratio of the laser light. The intensity distribution ratio of the laser light can be changed, for example, by replacing the beam splitter 134 or rotating the polarization.

  The oblique optical system 130 is independent of the Raman detection optical system and the incident optical system. The laser light of the oblique optical system 130 is used as illumination light for dark field microscope for detecting the position of the minute sample 10.

  In the oblique optical system 130, the laser light is polarized by the polarization adjuster 133 and can be irradiated to an arbitrary position by the scanning optical system 132 configured by a galvanometer mirror or the like. Further, the oblique optical system 130 can irradiate the minute sample 10 with the laser light narrowed down to the vicinity of the diffraction limit by the objective lens 131.

  The objective lens 131 may be an immersion lens. The objective lens 131 is equipped with a focus adjustment mechanism (not shown), and can be focused and defocused. In addition to the focus adjustment mechanism, a lens exchange mechanism (not shown) such as a revolver is mounted and can be converted into an arbitrary lens.

  The laser beam of the oblique optical system 130 is used for illumination of the dark field microscope by defocusing and illuminating the entire field of view. Dark field microscopic illumination may illuminate a portion of the field of view. Further, the laser light of the oblique optical system 130 is irradiated to the vicinity of the diffraction limit as much as the performance of the objective lens 131, and can also be used for excitation of Raman scattered light.

  By this oblique optical system 130, the position detection and the Raman measurement of the minute sample 10 having the wavelength of the Raman excitation light or less, for example, 1 μm or less can be performed. The position detection and Raman measurement of the micro sample 10 will be described later.

  The epi-illumination optical system is also used as the Raman detection optical system. A Raman detection optical system may be mounted separately from the incident light optical system. The laser light of the epi-illumination optical system is used as illumination light for exciting Raman scattering.

  The laser light of the epi-illumination optical system is reflected by the beam splitter 115 to the micro sample 10 side, can be irradiated to an arbitrary position by the scanning optical system 110, and is irradiated to the micro sample 10 by the objective lens 111.

  The scanning optical system 110 includes, for example, a galvanometer mirror 114, a scanning lens 113, and an imaging lens 112. Further, the imaging lens 112 of the scanning optical system 110 is also used as an imaging lens for a field image. That is, the Raman scattered light of the micro sample 10 including the peripheral region is branched by the beam splitter 141 and guided to a camera (video camera) 142 such as a CMOS (Complementary Metal Oxide Semiconductor) or a CCD, and an optical microscopic image (bright field image). Or a dark field image).

  The laser light is guided by the oblique optical system or the epi-illumination optical system and applied to the micro sample 10. The light scattered by the micro sample 10 includes Raman scattering light, which is very weak, but is inelastically scattered light having a wavelength or frequency different from that of Rayleigh scattered light. This Raman scattered light is guided to the spectroscope 125 through a route opposite to the laser light of the epi-illumination optical system.

  The Raman scattered light is collected by the objective lens 111, passes through the beam splitter 115 through the scanning optical system 110, and is collected by the imaging lens 121. The condensed Raman scattered light further passes through the confocal pinhole 122, is collimated by the collimating lens 123, is guided to the spectroscope 125 through the Raman filter 124, and is a detector 126 such as a high-sensitivity cooled CCD. Detected by.

  The imaging lens 121, the confocal pinhole 122, the collimating lens 123, and the objective lens 111 are referred to as a confocal optical system. In general, in a mechanism used for a confocal laser microscope or the like, a clear image can be obtained by removing light other than the focal position of the objective lens by a confocal pinhole. Similarly, in the case of microscopic Raman spectroscopy, Raman measurement is performed only on a focused portion (point). By scanning with the scanning optical system 110, another point in the field of view can be measured.

  The Raman filter 124 removes Rayleigh scattered light that is elastically scattered light and transmits only Raman scattered light that is inelastically scattered light.

  The Raman scattered light guided to the spectroscope 125 is split and guided to the detector 126 to become a Raman spectrum. The difference between the frequency of the Raman scattered light and the frequency of the Raman excitation light is called a Raman shift and is used for the horizontal axis of the Raman spectrum. In general, by using a Raman shift, a Raman spectrum that does not depend on the wavelength of the Raman excitation light can be obtained.

  In Example 1, the Raman measurement is a measurement of a Raman spectrum. A Raman spectrum shows a spectrum specific to a substance and is used for identification and quantification of the substance.

  In Example 1, the Raman analysis is to obtain or calculate a peak wave number, a band width, a peak shift amount, a band area, and the like from, for example, a Raman spectrum obtained by Raman measurement. In addition, searching a Raman spectrum from a database and creating a Raman image from a plurality of Raman spectra in the field of view are called Raman analysis. Here, the Raman image refers to a mapping of arbitrary analysis data obtained from the Raman spectrum, and for example, FIG. 6D described later shows a Raman image.

  In the microscopic Raman optical system 100 shown in FIG. 1, the Raman excitation light emitted from the laser 101 is branched, and the laser light for detecting the position of the micro sample 10 is applied to the oblique optical system, and the Raman scattered light is emitted. Although the laser beam for excitation is guided to the epi-illumination optical system, the present invention is not limited to this.

  FIG. 2 is a schematic diagram illustrating various modes of irradiation of laser light for detecting the position of a micro sample and laser light for exciting Raman scattered light according to the first embodiment.

  FIG. 2A is a schematic diagram of an optical system showing the microscopic Raman optical system 100 described with reference to FIG. 1 described above. The laser light LAP for detecting the position of the micro sample 10 is obliquely illuminated, and Raman is used. The laser beam LAE for exciting the scattered light is incident illumination.

  FIG. 2B is a schematic diagram of an optical system that branches Raman excitation light emitted from a laser and obliquely irradiates a minute sample with a plurality of laser beams. The laser beam LAP for detecting the position of the micro sample 10 and the laser beam LAE for exciting the Raman scattered light are oblique illumination, and these are irradiated to the micro sample 10 from different oblique optical systems. The optical system shown in FIG. 2B will be described in detail with reference to FIG.

  FIG. 2C is a schematic diagram of an optical system that obliquely irradiates the minute sample 10 with laser light without branching the Raman excitation light emitted from the laser. That is, the laser beam LAP for detecting the position of the minute sample 10 is also used as the laser beam LAE for exciting the Raman scattered light.

  FIG. 2D is a schematic diagram of an optical system that irradiates the minute sample 10 with laser light without branching the Raman excitation light emitted from the laser. That is, by tilting the micro sample 10, the epi-illumination becomes oblique illumination with respect to the micro sample 10, and is substantially the same optical system as in FIG.

  FIG. 3 is a perspective view illustrating an example of a micro Raman analysis system according to the first embodiment.

  The micro Raman analysis system 200 includes a micro Raman spectroscopy apparatus 201, a system controller 202, and a mini-environment wafer transfer system 203.

  The system controller 202 controls all of the micro Raman analysis system 200. The system controller 202 also serves to control the microscopic Raman spectroscopic device 201. However, another system controller that controls the microscopic Raman spectroscopic device 201 may be mounted so that the system controller and the system controller 202 communicate with each other. .

  The mini-environment wafer transfer system 203 includes a load port 204, a fan filter unit 207, a wafer transfer robot 209, an aligner 211, and a display 212.

  The aligner 211 has a function of detecting the eccentricity amount and notch direction of the semiconductor wafer 206 and aligning them.

  The display 212 is a touch panel that also serves as an input, and has a role as an interface of the microscopic Raman spectroscopy system 200. In addition to communication with the production plant host, the results of the Raman analysis can be displayed on the display 212 and immediately fed back to the production process.

  The load port 204 has a mechanism for opening and closing a cassette for storing the semiconductor wafer 206, for example, a FOUP (Front Opening Unified Pod) 205.

  The fan filter unit 207 has a fan and a filter for making the inside of the mini-environment wafer transfer system 203 and the inside of the microscopic Raman spectroscopic device 201 a clean environment. Has the function of downflow.

  The wafer transfer robot 209 has a wafer transfer mechanism for supplying the semiconductor wafer 206 to the microscopic Raman spectroscopic device 201 and discharging it from the microscopic Raman spectroscopic device 201. Further, the wafer transfer robot 209 transfers the semiconductor wafer 206 to the sample chamber in a form in which the eccentricity detected by the aligner 211 is corrected, and roughly positions the semiconductor wafer 206 for Raman measurement.

  FIG. 4 is a cross-sectional view illustrating an example of a micro Raman analysis system according to the first embodiment.

  The microscopic Raman spectroscopic device 201 includes a microscopic Raman optical system 100, a sample chamber 301, a sample chamber atmosphere adjuster / detector 302, a stage 303, a vibration isolation device 305, and a base 306.

  The sample chamber 301 is surrounded by a casing in order to stabilize the atmosphere around the sample, and the semiconductor wafer 206 is placed thereon. Since the sample chamber 301 may be in any environment, the sample chamber 301 can be evacuated, purged with nitrogen, or pressurized. However, since it is preferable that the drift of the micro sample 10 due to temperature or the environment of the sample chamber 301 is small, a temperature regulator and a temperature measuring instrument are mounted as the sample chamber atmosphere regulator and detector 302.

  The sample chamber atmosphere adjuster is a mechanism for constructing a measurement environment. For example, a pressure gauge is used when adjusting a pressure such as vacuum or high pressure, and an oxygen concentration meter is used when purging with nitrogen, for example. However, even if the micro sample drifts due to the environment of the sample chamber 301, the scanning optical system (the scanning optical systems 110 and 132 in FIG. 1 described above) is used so that the micro sample does not deviate from the field of view of the objective lens. Can be measured. Further, the stage 303 may be used so that the minute sample does not come out of the field of view of the objective lens.

  The stage 303 has a mechanism for moving a minute sample into the field of view in combination with the wafer transfer robot 209.

  Here, for example, if a mechanism for inclining the micro sample is provided on the stage 303, by tilting the micro sample, the epi-illumination becomes oblique illumination with respect to the micro sample as shown in FIG. . Further, if the optical system for detecting the position of the minute sample and the optical system for exciting the Raman scattered light are shared, one optical system is sufficient.

  The vibration isolator 305 is a mechanism that floats the microscopic Raman optical system 100, the sample chamber 301, and the stage 303, and can remove disturbance vibrations.

  The base 306 supports the microscopic Raman optical device 201 via the vibration isolation device 305. A system controller may be mounted on the base 306.

  FIG. 5 is an enlarged schematic diagram of the first microscopic Raman optical system according to the first embodiment. In FIG. 5, the area | region ahead of each objective lens of an oblique optical system and an epi-illumination optical system is expanded and shown.

  FIG. 5 shows an example in which the light of the optical axis 605 of the oblique optical system is used for detecting the position of the minute sample, and the light of the optical axis 603 of the incident optical system is used for exciting the Raman scattered light and detecting the Raman scattered light. ing. The objective lens 131 is intentionally defocused and irradiates an oblique illumination range 604 wider than the range 602 of the microscopic field (the field of view of the objective lens 111). In this case, instead of defocusing, the objective lens 131 may be converted into one having a low magnification, and the microscopic field range 602 may be irradiated.

  A spot 601 is a spot of laser light of the epi-illumination optical system, and is a confocal measurement range (detection range of Raman scattered light) of the Raman detection optical system.

  The spot 601 can be scanned by the scanning optical system (the scanning optical system 110 shown in FIG. 1 described above) in the microscopic field range 602.

  FIGS. 6 (a), (b), (c), and (d) are scanning electron microscope (SEM) images, bright field images, dark field images, and It is an image figure which shows an example of a Raman image. The diameter of the microparticle is 0.1 μm.

  FIG. 6A shows an SEM image of the micro sample 10 obtained by a scanning electron microscope. The micro sample 10 is a particle having a diameter of 0.1 μm, and is a sample whose size can be recognized by an electron microscope or an atomic force microscope (AFM).

  FIG. 6B shows an image (bright field image) obtained by measuring the minute sample 10 with illumination of the epi-illumination optical system. In the bright field image, the position of the minute sample 10 cannot be grasped. At this time, light using a white LED (Light Emitting Diode) (not shown) as a light source is introduced into the incident optical system by a beam splitter. The irradiation range of this white LED is the same as the spot 601 shown in FIG.

  Further, the light source for bright field often interferes with the Raman measurement of the minute sample 10. Since the light source for bright field enters the detector 126 as noise, it is turned off during Raman measurement. With this, it is impossible to continue to detect the position of the micro sample 10 and follow it.

  However, in the microscopic Raman optical system according to Example 1, the position of the minute sample 10 is detected without obstructing the Raman measurement by obliquely irradiating laser light having the same wavelength as the laser light used for exciting the Raman scattered light. Can continue.

  FIG. 6C shows an image (dark field image) obtained by measuring the minute sample 10 with illumination of the oblique optical system. In the dark field image, the position of the minute sample 10 that could not be detected in the bright field image can be detected.

  Even the minute sample 10 whose position is difficult to detect in the bright field image can be detected as long as it is a dark field image in which Raman scattered light is observed. The shape of the micro sample 10 can be confirmed by SEM or AFM. If the shape of the micro sample 10 is known in advance, the shape of the micro sample 10 can be modeled (calculated) from Raman scattered light.

  By the way, the Raman scattered light greatly depends on the shape of the micro sample 10, the polarization of the laser light, and the incident angle of the laser light. Therefore, although omitted in FIG. 1 described above, the polarization controllers 102 and 133 (see FIG. 1 described above) have, for example, a polarization adjusting mechanism. While measuring the Raman spectrum (for example, while exposing a high-sensitivity cooled CCD), the average value of the Raman scattered light can be obtained by changing or continuing to change the polarization state.

  In addition, the microscopic Raman spectroscopic device has a mechanism capable of changing the incident angle of the laser beam. For example, the mechanism is a mechanism in which the mounting base of the oblique optical system can be tilted on the stage to obtain the optimum Raman scattered light. Angle adjustment mechanism. These mechanisms are effective in, for example, Raman measurement of the micro sample 10 whose shape cannot be known unless it is SEM or AFM.

  In FIG. 6D, the position of the minute sample 10 detected by oblique illumination is scanned by the scanning optical system 110 (see FIG. 1 described above) or the stage 303 (see FIG. 4 described above), and Raman imaging is performed. An image (Raman image) is shown.

  The Raman image is an image showing the intensity distribution of the peak of the Raman spectrum peculiar to the micro sample 10. As shown in FIG. 6D, it can be seen that the Raman measurement of the micro sample 10 has been performed.

  Furthermore, in the Raman measurement of the micro sample 10, in addition to the problem that the position of the micro sample 10 cannot be detected, the Raman scattered light of the micro sample 10 is buried in the background Raman signal, the Raman activity is weak, or the SN ratio There are problems such as bad.

  In that case, the laser beam irradiated from the oblique optical system to the minute sample 10 is narrowed to near the diffraction limit and irradiated from an oblique direction.

  FIG. 7 is an enlarged schematic view of the second microscopic Raman optical system according to the first embodiment. In FIG. 7, the area | region ahead of each objective lens of an oblique optical system and an epi-illumination optical system is expanded and shown.

  The incident light optical system described with reference to FIG. 5 is used for irradiating a minute sample with laser light focused to near the diffraction limit by an oblique optical system and detecting Raman scattered light. As a result, the SN ratio can be improved and background information can be reduced.

  The reason is that Raman scattered light or fluorescence in the background is excited by oblique illumination, so that the laser light that irradiates a minute sample from the oblique optical system is narrowed to near the diffraction limit, so that the background of the Raman detection optical system is reduced. This is because a structure in which a Raman signal does not enter or is difficult to enter can be achieved. Similarly, with respect to other noises, an optical system for detecting the position of a minute sample and an optical system for exciting Raman scattered light are separated, so that only necessary signals can be selected.

  Furthermore, the Raman measurement of a minute sample can be performed by combining the excitation of the Raman scattered light by the oblique optical system and the excitation of the Raman scattered light by the incident optical system. The ratio between the laser intensity of the oblique illumination and the laser intensity of the epi-illumination is arbitrarily adjusted, and the Raman measurement of the minute sample is performed by changing the ratio appropriately for each minute sample.

  In these cases, the spot of the laser beam of the oblique optical system and the detection position of the Raman scattered light are the same position 701, and the coincidence of the positions of the two is determined by the scanning optical systems 110 and 132 (described above) prepared on the respective axes. 1) and the stage 303 (see FIG. 4 described above).

  At this time, since the microscopic Raman optical system is configured so that the spot of the laser beam of the epi-illumination system and the detection position of the Raman scattering light are the same, the laser beam of the epi-illumination optical system is the detection position of the Raman scattering light. It can also be used to accurately grasp (confocal position). Matching of the spots 701 is performed by image processing of both oblique illumination and epi-illumination.

  In this second optical system, an optical system for detecting the position of a minute sample and an optical system for exciting Raman scattered light are provided separately. For example, as shown in FIGS. 2 (c) and 2 (d) described above. Laser light focused to near the diffraction limit can also be used for an optical system that does not branch Raman excitation light.

  FIG. 8 is an enlarged schematic view of the third microscopic Raman optical system viewed from the upper surface according to the first embodiment. In FIG. 8, the area | region ahead of each objective lens of an oblique optical system and an epi-illumination optical system is expanded and shown.

  Two systems of oblique illumination are implemented. One is illumination that detects the position of a minute sample, and the other is illumination that excites Raman scattered light, and Raman measurement is performed by a spectroscope through an incident light optical system. Done. Therefore, an objective lens 802 is added to the oblique optical system. Further, the spot of one laser beam of the oblique optical system and the spot of the laser light of the incident optical system become a spot 801 at the same position.

  In this way, when using a plurality of oblique optical systems, or when using both an incident optical system and an oblique optical system, if the wavelengths of the laser beams of the respective optical systems are different from each other, by switching the optical system, Multiple wavelengths can be used for the laser light. Using laser beams with a plurality of wavelengths may be an effective measure for a small sample such as a measure against fluorescence.

  In addition, since it is possible to illuminate simultaneously with a plurality of oblique optical systems, Raman measurement can be performed while detecting the position of a minute sample, so that a follow-up function described later can be realized only with oblique illumination.

  In addition, there is an advantage that the position of a minute sample can be detected while exciting Raman scattered light by oblique illumination and epi-illumination.

  FIGS. 9A and 9B are a schematic diagram illustrating an example of Raman measurement of a micro sample according to Example 1, and a schematic diagram illustrating another example of Raman measurement of a micro sample according to Example 1, respectively.

  As shown in FIG. 9A, the micro sample 10 is sufficiently small with respect to the spot 701 of the optical axis 605 of the oblique optical system and the optical axis 603 of the incident optical system.

  Therefore, as shown in FIG. 9B, the micro-Raman optical system according to the first embodiment can be used for illumination of chip-enhanced Raman analysis or surface-enhanced Raman analysis.

  Here, in the chip-enhanced Raman analysis, it is possible to accurately irradiate the minute sample 10 with the tip 902 of the tip (probe) 903 approached. Alternatively, in the surface-enhanced Raman analysis, the laser beam to the micro sample 10 on the fine particle group substrate 901 can be accurately irradiated. Thereby, only the Raman signal of the enhancement part by the chip 903 or only the Raman signal of the enhancement part of the fine particle group substrate 901 can be detected.

  FIGS. 10A and 10B are an image diagram when the laser beam of the oblique optical system according to the first embodiment is irradiated on a wide field range, and the laser beam of the oblique optical system according to the first embodiment in a narrow field range. It is an image figure at the time of irradiation.

  As shown in FIGS. 10A and 10B, when there are many protrusions on the semiconductor wafer, it is better to irradiate a narrow field of view than to irradiate a wide field of view in order to limit the measurement part. It is valid.

  FIG. 11 is an image diagram illustrating a full-field image of the camera when the narrow-angle range is irradiated with the laser beam of the oblique optical system according to the first embodiment. In the figure, reference numeral 1102 denotes the narrow visual field range shown in FIG.

  As shown in FIG. 11, the position of a minute sample can be recognized as a spot 1202 by Raman scattered light.

  FIG. 12 is an image diagram illustrating the function of following a micro sample according to the first embodiment.

  When the target of Raman measurement is a micro sample, the Raman scattered light of the micro sample is buried in the Raman signal in the background, the Raman activity is weak, or the SN ratio is low. There is a problem that the position of the micro sample moves with respect to the optical system.

  The spot 1202 is about 1 μm in the case of visible light although it depends on the wavelength of the laser beam and the optical system. On the other hand, the stage on which the micro sample is placed and the member that supports the optical system often move by about 0.1 to 3 μm due to expansion and contraction only when the temperature of 1 ° C. changes, so the position of the micro sample changes. Thus, the laser beam for detecting the position of the minute sample and the laser beam for exciting the Raman scattered light may be deviated.

  In addition, even a minute sample with strong Raman activity often requires long-time exposure. Therefore, the position of the spot and the position of the minute sample may be shifted while the Raman scattered light is detected by irradiating the laser beam.

  However, the illumination of a narrow visual field range by a dark field can automatically follow the position of the micro sample by using the scanning optical system by the system controller, so that the position shift of the micro sample can be avoided. For example, as shown in FIG. 12, the spot 1202 can be moved to the spot 1301.

  This function can also be used when a micro sample moves in a living body, a cell, a bacterium, or the like. In addition, since the exposure time can be extended by the follow-up function, this is an effective function even for a micro sample with weak Raman activity.

  FIG. 13 is an image diagram illustrating a scanning method of Raman imaging according to the first embodiment. The image obtained by this scanning method is the Raman image shown in FIG.

  By scanning the spot 1202 used for detecting the position of the minute sample and exciting the Raman scattered light in the scanning direction 1402 with the scanning optical system or the stage, using the Raman scattered light of the minute particles by the dark field image as a mark, the Raman image is obtained. can get.

  Next, an example of the operation of the micro Raman analysis system will be described with reference to FIG.

  The worker gives an instruction to the system controller 202 through the display 212. A command command may be sent from a PC (Personal Computer) or the like via the interface of the system controller 202.

  The micro Raman analysis system 200 starts Raman measurement based on a command issued to the system controller 202. The Raman measurement is automatically performed by a program installed in advance in the system controller 202.

  When the FOUP 205 containing the semiconductor wafer 206 is placed on the load port 204 of the mini-environment wafer transfer system 203, the mini-environment wafer transfer system 203 opens the FOUP 205, and the wafer transfer robot 209 holds the semiconductor wafer 206. To do. The wafer transfer robot 209 transfers the semiconductor wafer 206 to the sample chamber.

  Thereafter, Raman measurement by the microscopic Raman spectroscopic device 201 is started.

  Next, an example of the operation flow of the micro Raman analysis apparatus will be described with reference to FIG. 14 and the above-described FIGS. 1, 3, and 4. FIG. FIG. 14 is a flowchart illustrating an example of an operation flow of the microscopic Raman spectroscopic device according to the first embodiment.

  Each operation is automatically performed based on a command and data preset in the system controller 202.

<Step P1>
The measurement sample is moved to the range of the microscopic field by the wafer transfer robot 209 or the stage 303.

<Step P2>
Narrow range irradiation (spot irradiation) or wide range irradiation is selected according to the measurement sample. The irradiation range of the oblique illumination is selected by a mechanism for replacing the objective lens 131 or an autofocus mechanism.

<Step P3>
The intensity of the oblique illumination is adjusted by the attenuation filter 103.

<Step P4>
Sets the polarization of oblique illumination. Since the intensity of the Raman scattered light changes depending on the shape of the measurement sample, it is necessary to set an appropriate polarization direction. However, when the measurement sample is the particle sample 10, it cannot be grasped unless the shape of the measurement sample is confirmed with an electron microscope or the like. Therefore, the oblique optical system has a mechanism that can slightly change the polarization direction while exposing the highly sensitive cooled CCD during Raman measurement. An average value can be obtained by changing the polarization direction. Sets whether to enable or disable the variable polarization. When the variable operation is not performed, the position is fixed where the intensity of Rayleigh scattered light detected by the camera 142 is the highest. If the shape of the measurement sample is known in advance, it is skipped while it is fixed.

<Step P5>
Set the irradiation position of oblique illumination. The irradiation position is determined as illumination light for detecting the position of the measurement sample or exciting Raman scattered light. The irradiation position is set by the scanning optical system 132.

<Step P6>
It is confirmed whether or not the setting of the irradiation position of the oblique illumination has been completed. If there are two or more oblique optical systems, Step P2 to Step P5 are repeated once again for another axis.

<Step P7>
Sets the intensity of epi-illumination. The intensity of the epi-illumination is set by changing the distribution ratio with the beam splitter 134 or adjusting the intensity with the attenuation filter after branching. Here, for example, the intensity of the epi-illumination is set to be weak for the purpose of detecting the detection position of the measurement sample, or the intensity of the epi-illumination is set to be strong for exciting the Raman scattered light. When bright field microscopic illumination is required in addition to Raman measurement, illumination such as a lamp or LED is adjusted in the same incident optical system.

<Step P8>
The irradiation position and measurement point of the epi-illumination are determined by the scanning optical system 110.

<Step P9>
When the measurement sample drifts or the measurement sample itself moves, a tracking function is set to determine whether or not the laser beam is to be tracked.

<Step P10>
The measurement sample is irradiated with laser light, and Raman measurement is started. The measurement of the detector 126 (exposure of the high sensitivity cooled CCD) is started.

<Step P11>
According to the step P4, if necessary, the polarization direction is changed during the Raman measurement (the polarization direction is changed).

<Step P12>
According to step P9, if necessary, the position of the measurement sample is constantly monitored and followed by the scanning optical systems 110 and 132 so that the laser beam is always irradiated.

<Step P13>
The measurement of the detector 126 (exposure of the high sensitivity cooled CCD) is terminated. The Raman excitation light is stopped and the Raman measurement is terminated.

<Step P14>
The Raman scattered light measured by the spectroscope 125 and the detector 126 is spectrally displayed and stored.

<Step P15>
Spectrum evaluation and analysis are performed, for example, the intensity of an arbitrary wave number is stored. Here, for example, one pixel of the Raman image shown in FIG. 6D can be measured.

  Spectral evaluation and analysis can be used in various ways. For example, there are uses such as detecting a shift amount of an arbitrary peak, specifying a substance from a Raman spectrum, or understanding a structure from an intensity ratio of a plurality of peaks. The measurement sample does not necessarily need to be particles, and if it is a semiconductor wafer, it is also effective for measuring local strain (stress).

  In the operation flow described with reference to FIG. 14, an example in which one measurement point is measured is shown. However, in the case of Raman imaging, laser scanning, stage scanning, or repeated Raman measurement is required. If it is not necessary, this setting portion can be omitted, and after moving to another measurement point, steps P10 to P14 are repeated under the same conditions. Here, an operation flow for acquiring a plurality of Raman spectra as in Raman imaging is omitted.

  In the first embodiment, a micro Raman optical system including one optical system for detecting the position of a micro sample and one optical system for exciting Raman scattered light has been described. However, the present invention is not limited to this. The micro-Raman optical system may include two or more micro-Raman optical systems each including one optical system that detects the position of a minute sample and one optical system that excites Raman scattered light.

  As described above, according to the first embodiment, the position of a minute sample that cannot be recognized by a bright field image can be detected, so that Raman measurement and Raman analysis can be performed.

  In addition, since the sample is a minute sample, Raman scattered light that is buried in the background Raman signal or noise can be detected by using oblique illumination.

  Further, even when the micro sample drifts and causes a positional shift, or when the micro sample itself moves, the same measurement point can be followed. By following, the SN ratio can be improved and the exposure time can be shortened. Being able to shorten the exposure time can avoid mistakes that cause the minute sample to be burned out.

  In Example 2, a micro Raman spectroscopic apparatus having the same size as the load port will be described. In the microscopic Raman spectroscopic system 200 and the microscopic Raman spectroscopic apparatus 201 shown in FIG. 3 described above, the description of the components having the same reference numerals already described and the parts having the same functions will be omitted.

  FIG. 15 is a cross-sectional view illustrating an example of a micro Raman analysis system including a load port type micro Raman spectroscopic apparatus having the same size as the load port according to the second embodiment. The basic configuration of the load port type microscopic Raman spectroscopic apparatus is the same as that of the microscopic Raman spectroscopic apparatus 201 shown in FIG.

  Since the number of components that can be mounted is reduced, the purpose of Raman measurement is limited, and the number of measurement samples is limited.

  However, a foundry of a semiconductor manufacturer is required to reduce the footprint. For example, a load port type microscopic Raman spectroscopic device 402 may be mounted on an empty port of another semiconductor manufacturing apparatus or semiconductor inspection apparatus 401. If possible, it is convenient. It can also be used as an option for other devices.

  In Example 3, a simple microscopic Raman spectroscopic apparatus having the same size as the FOUP will be described. In the microscopic Raman spectroscopic system 200 and the microscopic Raman spectroscopic apparatus 201 shown in FIG. 3 described above, the description of the components having the same reference numerals already described and the parts having the same functions will be omitted.

  FIG. 16 is a cross-sectional view showing an example of a simple microscopic Raman spectroscopic apparatus having the same size as the FOUP. The basic configuration of the simple microscopic Raman spectroscopic apparatus is the same as that of the microscopic Raman spectroscopic apparatus 201 shown in FIG.

  Since the mounting space is limited, the position of Raman measurement is determined by the wafer transfer robot 209 (see FIG. 3 described above) and the stage 303.

  Since the simple microscopic Raman spectroscope 501 has a size that can be easily carried, only one foundry can be used for the foundry, and when necessary, it can be used for Raman measurement as if it were a tester.

  The resolution and throughput of the simple microscopic Raman spectroscopic device 501 are lower than those of the microscopic Raman spectroscopic device 201 shown in FIG. However, the simple microscopic Raman spectroscopic device 501 can have a small footprint and can be manufactured at low cost.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  For example, in the above-described embodiment, a micro sample having a size equal to or smaller than the wavelength of Raman excitation light, for example, 1 μm or smaller, is exemplified as the measurement sample. However, the measurement sample is not limited to this, and is larger than the wavelength of Raman excitation light. The present invention can also be applied to these samples.

10 Micro Sample 100 Micro Raman Optical System 101 Laser 102 Polarization Adjuster 103 Attenuation Filter 104 Laser Line Filter 105 Spatial Filter 110 Scanning Optical System 111 Objective Lens 112 Imaging Lens 113 Scanning Lens 114 Galvano Mirror 115 Beam Splitter 121 Imaging Lens 122 Focusing pinhole 123 Collimating lens 124 Raman filter 125 Spectrometer 126 Detector 130 Oblique optical system 131 Objective lens 132 Scanning optical system 133 Polarization adjusters 134 and 141 Beam splitter 142 Camera 150 Optical axis 200 Micro Raman spectroscopic system 201 Micro Raman spectroscope 202 system controller 203 mini-environment wafer transfer system 204 load port 205 FOUP
206 Semiconductor wafer 207 Fan filter unit 209 Wafer transfer robot 211 Aligner 212 Display 301 Sample chamber 302 Sample chamber atmosphere controller and detector 303 Stage 305 Vibration isolator 306 Base 401 Semiconductor manufacturing apparatus or semiconductor inspection apparatus 402 Load port type micro Raman Spectroscopic apparatus 501 Simple microscopic Raman spectroscopic apparatus 601 Spot 602 Microscopic field range 603 Optical axis 604 of incident optical system Oblique illumination range 605 Optical axis 701, 801 spot 802 of oblique optical system Objective lens 901 Fine particle group substrate 902 Tip of chip 903 tip
1202, 1301 Spot 1402 Scan direction LAE, LAP Laser light

Claims (5)

One or more optical systems for detecting the position of the sample on the surface of the inspection object and irradiating the sample with laser light for exciting Raman scattered light;
The laser beam is applied to the sample from a first direction having a first angle of less than 90 degrees with respect to the surface of the inspection object,
A micro Raman spectroscopic apparatus in which the position of the sample is recognized by a dark field microscopic image. The micro Raman spectroscopic apparatus according to claim 1,
The microscopic Raman spectroscopic apparatus, wherein the optical system has a scanning mechanism for scanning the laser beam in a microscopic field. The micro Raman spectroscopic apparatus according to claim 2,
A microscopic Raman spectroscopic device in which the laser beam follows the position of the sample. The micro Raman spectroscopic apparatus according to claim 1,
The optical system has a mechanism for changing the polarization of the laser light,
A microscopic Raman spectroscopic device that irradiates the sample with the laser light while changing the polarization of the laser light. The micro Raman spectroscopic apparatus according to claim 3,
The micro Raman spectroscopic apparatus, wherein the one or more optical systems include a focus adjustment mechanism and an incident angle adjustment mechanism.