JP2004047284A - Cathode luminescence composite device and measuring method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To confirm a measuring position and to analyze a sample at high spatial resolution. <P>SOLUTION: An atomic force microscope with a probe in its light condensing system is installed in the cathode luminescence composite device which detects light from a sample irradiated by a electron beam. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a cathodoluminescence composite apparatus, and more particularly to a cathodoluminescence composite apparatus that irradiates a sample with an electron beam and analyzes light generated from the sample by the electron beam irradiation, and a measurement method using the apparatus. It is.
[0002]
[Prior art]
A cathodoluminescence device that irradiates a sample with an electron beam and analyzes light generated from the sample by the electron beam irradiation is already commercially available. Some photoluminescence spectrometers and Raman spectrometers that irradiate a sample with light and analyze the light generated from the sample by the light have been commercially available.
[0003]
Various elements for electronic devices have been steadily becoming more highly integrated and miniaturized, and the need for analysis of minute regions has been increasing year by year. However, the currently available cathode luminescence device, photoluminescence spectroscopy device, or Raman spectroscopy device has a problem that the spatial resolution and the accuracy of position confirmation are not always sufficient. This is because, in a photoluminescence spectrometer or a Raman spectrometer that irradiates a sample with light and further analyzes light generated from the sample, the spatial resolution is limited to at most about 1 μm due to the diffraction limit of light. .
[0004]
As a method for improving the spatial resolution, using light called an evanescent field that does not propagate in space, a spatial resolution equal to or less than the diffraction limit of light can be achieved. Mag. 6,356 (1928). Some near-field microscopes applying this principle are already commercially available. However, the measurement position is confirmed with an optical microscope, and there is a problem that the position cannot be confirmed with high spatial resolution. Therefore, it has not always been sufficient for the analysis of various miniaturized electronic device elements.
[0005]
On the other hand, in a cathodoluminescence device that uses an electron beam as a narrow excitation source, the measurement position can be easily confirmed with a secondary electron image (SEM image) or a transmission electron image (TEM image). Cathodoluminescence generally occurs through the process of (1) generation of carriers by an electron beam, (2) diffusion of generated carriers, and (3) radiative recombination of carriers.
[0006]
In a commercially available cathodoluminescence device, for example, as described in Naoki Yamamoto, “Applied Physics,” Vol. 69, No. 10, (2000), an elliptical mirror or a parabolic mirror is used for the light-collecting portion. The spatial resolution of a cathodoluminescence device using an elliptical mirror or a parabolic mirror for the light condensing part is mainly determined by the penetration length of the electron beam and the diffusion length of carriers generated by the electron beam.
[0007]
Here, the penetration length of the electron beam is substantially determined by the acceleration voltage, and the penetration length becomes shorter as the acceleration voltage becomes lower. Therefore, when a sample with a short carrier diffusion length is measured at a low acceleration voltage, a spatial resolution of up to about 100 nm can be achieved.
[0008]
However, since light is condensed using an elliptical mirror or a parabolic mirror, light from almost the entire area of the sample is condensed. There is a problem that the thickness is reduced to about μm to several tens μm.
[0009]
[Problems to be solved by the invention]
It is an object of the present invention to provide a cathodoluminescence composite device capable of confirming a measurement position with high spatial resolution and analyzing a sample with high spatial resolution, and a measuring method using the device.
[0010]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that such an object can be achieved by using a cathodoluminescence composite device using an atomic force microscope with a probe as a probe in a light collection system. Thus, the present invention has been completed.
[0011]
That is, the present invention provides an atomic force microscope using a probe as a light-collecting system in a cathodoluminescence device that irradiates a sample with an electron beam and detects light generated from the sample by the electron beam irradiation. The cathodoluminescence composite device characterized by the above features is the gist thereof.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
The electron beam that can be used in the present invention is not particularly limited as long as the beam diameter of the electron beam can be reduced to several tens of nm or less. As a device capable of supplying these electron beams, a commercially available electron microscope capable of observing one or more of a secondary electron image, a reflected electron image, and a transmitted electron image is used, and is preferably used.
[0013]
There is no particular limitation on the type of electron gun that emits an electron beam. For example, any electron gun such as a thermionic emission type, a field emission type, a Schottky emission type, or a thermal field emission type can be used. Among them, a Schottky emission type or a thermal field emission type electron gun is preferably used because of its high spatial resolution and high current density.
[0014]
In the present invention, it is necessary to use an atomic force microscope using a probe as a probe as a light collection system. There is no particular limitation as long as it is an atomic force microscope using a probe as a probe, and a commercially available atomic force microscope is preferably used. The control method is not particularly limited, and a known method such as an optical lever method or a share force method can be used. Using an atomic force microscope with a probe as a probe, it is possible to collect only light from a specific position on the sample, and it is not affected by carrier diffusion, so that spatial resolution can be dramatically improved. Can be.
[0015]
In the present invention, which wavelength region of light generated from the sample by electron beam irradiation is not particularly limited, but is preferably in the range of 50 to 4000 nm, more preferably 100 to 2000 nm in the ultraviolet, visible, and near infrared regions. Detects electromagnetic waves.
[0016]
The constituent material of the probe is not particularly limited, but preferably the main constituent material is quartz glass. With quartz glass, light can be efficiently collected. Here, “mainly” means that the content is 60% by weight or more. The probe may be composed only of quartz glass, but may contain other components as long as the effects of the present invention are not impaired and less than 40% by weight. Above all, a silica glass fiber having a structure in which Ge is added and the refractive index of the central portion is increased is more preferable because the light collection efficiency is increased.
[0017]
As another preferred embodiment of the probe used in the present invention, there is a mode in which the probe is formed of a metal having a hollow inside or a semiconductor having a hollow inside. Although there is no particular limitation on the type of metal or semiconductor used, W, Si, GaAs, and the like, which are generally used for an atomic force microscope, are preferably used. By hollowing the interior, light from the sample propagates inside the cavity and can be efficiently propagated and detected.
[0018]
Preferably, two or more probes are used in the present invention. By using two or more probes, the light collection efficiency can be greatly improved. Further, with the improvement of the light collection efficiency, the measurement time can be shortened, and the sample drift and the sample damage can be minimized. Further, it is more preferable that two or more probes are radially arranged around the tip of the probe. By being arranged radially, not only can the light-collecting efficiency be significantly improved, but also high light-collecting efficiency can be maintained for a sample having large surface irregularities. Furthermore, for example, simultaneous measurement of the same location of cathodoluminescence and Raman scattering, and simultaneous measurement of the same location of cathodoluminescence and photoluminescence can also be performed.
[0019]
It is preferable to provide a metal thin film having a thickness of 0.1 nm to 100 nm on the surface of the probe used in the present invention. By providing the metal thin film, a surface-enhanced Raman effect occurs between the sample and the probe, so that the signal intensity is dramatically increased. In addition, the light collection efficiency of the probe is greatly improved. Further, by providing a metal thin film, an effect of preventing the probe from being charged up by an electron beam during observation of a secondary electron image can be expected.
[0020]
It is preferable that the material of the metal thin film be one material selected from the group consisting of Ag, Cu, and Au as a main constituent material. This is because Ag, Cu, and Au have a large surface-enhanced Raman effect among metal materials, and the signal intensity is significantly increased. Here, “mainly” means that the content is 60% by weight or more.
[0021]
The cathodoluminescence composite device of the present invention is preferably capable of irradiating a sample with incident light through a probe. If the sample can be irradiated with incident light through the probe, for example, not only cathodoluminescence measurement but also Raman scattering measurement and photoluminescence measurement can be performed. Furthermore, by using two or more probes, for example, simultaneous measurement of cathodoluminescence and Raman scattering at the same location and simultaneous measurement of cathodoluminescence and photoluminescence at the same location can be performed. In addition, by introducing periodically modulated light from the probe, various types of modulation can be measured.
[0022]
It is preferable that the cathodoluminescence composite device of the present invention is provided with a spectroscopic device for dispersing the light collected by the probe. The spectroscopic device is preferably at least one spectroscopic device selected from the group consisting of a diffraction grating type spectrometer, a prism type spectrometer, an optical filter type spectrometer, and a dichroic mirror type spectrometer. By providing a spectroscopic device, not only an intensity image but also a spectrum can be measured, and more detailed information of a sample can be obtained. Furthermore, for example, by measuring and analyzing spectra at all measurement points, it is possible to visualize not only the intensity image but also the location dependence of the signal intensity peak position and the location dependence of the signal line half-width. It becomes.
[0023]
The measurement items to be measured using the cathodoluminescence composite device of the present invention are not particularly limited as long as the information is obtained from light generated from the sample. Preferably, the cathodoluminescence spectrum, the cathodoluminescence intensity distribution image, the Raman spectrum, the Raman intensity It is at least one of a distribution image, a photoluminescence spectrum, and a photoluminescence intensity distribution image.
[0024]
The sample that can be analyzed by the cathodoluminescence composite device of the present invention is not particularly limited, but is particularly effective for analyzing semiconductors, oxides, nitrides, ferroelectrics, and the like. In particular, elements for various electronic devices that use at least one selected from semiconductors, oxides, nitrides, and ferroelectrics are becoming ever more highly integrated and miniaturized year by year. It is a sample suitable for analysis using a possible cathodoluminescence combined device of the present invention.
[0025]
The cathodoluminescence composite device of the present invention is a semiconductor laser, a light emitting diode, a photodiode, a transistor, a semiconductor integrated circuit, a CCD device, an optical fiber, a ceramic capacitor, a liquid crystal display (LCD) device, among other devices for various electronic devices. It is effectively used for analyzing plasma display (PDP) panels, organic EL elements, diamond films, and the like.
[0026]
By installing the cathodoluminescence composite device of the present invention, for example, in-line or off-line for manufacturing various electronic device elements, it is possible to expect an improvement in yield and a dramatic improvement in quality.
[0027]
【Example】
Hereinafter, the effects of the present invention will be further described with reference to examples.
[0028]
(Example 1)
An atomic force microscope using a single optical fiber as a probe is provided as a focusing system on an S-4300SE scanning electron microscope manufactured by Hitachi, Ltd., and the light from the probe is subjected to HR-320 spectroscopy manufactured by Joban Yvon. A cathodoluminescence composite device for spectroscopy was prepared. The atomic force microscope was manufactured by modifying JEOL's JSPM4210 so that it could be installed inside the scanning electron microscope. The optical fiber probe used was one in which 5 nm of Ag was deposited on the surface. Using this apparatus, the cathodoluminescence spectrum and cathodoluminescence intensity distribution image of the cleaved cross section of the multiple quantum well consisting of GaAs 20 nm / AlGaAs 60 nm were measured at a measurement temperature of 30 K, an electron beam acceleration voltage of 5 kV, and a sample current of 0.1 nA. No signal of the GaAs layer was detected from the cathode luminescence spectrum near the center of the AlGaAs layer. The thickness of the active layer obtained from the cathodoluminescence intensity distribution image was 22.0 nm on average.
[0029]
(Comparative Example 1)
A cathodoluminescence intensity distribution image and a cathodoluminescence spectrum of a cleaved cross section of a multiple quantum well composed of GaAs 20 nm / AlGaAs 60 nm were measured using the same apparatus as in Example 1 except that an elliptical mirror was used as a light focusing system. The GaAs layer and the AlGaAs layer could not be clearly distinguished from the cathodoluminescence intensity distribution image.
[0030]
(Example 2)
The S-4300SE scanning electron microscope manufactured by Hitachi, Ltd. was equipped with an atomic force microscope using four optical fiber probes with 5 nm of Ag deposited on the surface as a light-collecting system. A cathodoluminescence composite device for performing spectroscopy with an HR-320 spectrometer manufactured by Hitachi, Ltd. was produced. The four optical fiber probes were arranged so as to be radial with the probe tip as the center. Using this apparatus, a polished section of a ceramic capacitor made of a barium titanate sintered body having an average particle size of about 200 nm was measured at a measurement temperature of 30 K, an electron beam acceleration voltage of 10 kV, and a sample current of 1 nA. The light emission from the barium titanate sintered body was about 10 times stronger on average than the case where one optical fiber was used, and the measurement time was reduced to about 1/10.
[0031]
(Example 3)
Using the cathodoluminescence composite device of Example 2, a laser beam having a wavelength of 514.5 nm was introduced into one of the optical fiber probes, and a polished cross section of a ceramic capacitor made of a barium titanate sintered body having an average particle size of about 200 nm was used. Irradiation. The Raman scattering spectrum generated from the sample was measured using another optical fiber probe. The measurement was performed at room temperature. It was observed that the Raman scattered light intensity was weak at the crystal grain boundaries and the cathodoluminescence intensity was also weak. By this measurement, it was possible to evaluate the structure of the crystal grain boundaries of the barium titanate sintered body having an average particle diameter of about 200 nm.
[0032]
(Comparative Example 2)
Using a T-64000 Raman spectrometer manufactured by Joban Yvon, at room temperature, a microscopic Raman scattering spectrum of a polished section of a ceramic capacitor made of a barium titanate sintered body having an excitation wavelength of 514.5 nm and an average particle size of about 200 nm was measured. Although a spectrum was obtained, the crystal grain boundaries could not be confirmed with an optical microscope, and the measurement position could not be specified.
[0033]
【The invention's effect】
According to the present invention, a cathodoluminescence spectrum, a cathodoluminescence intensity distribution image, a Raman spectrum, a Raman intensity distribution image, a photoluminescence spectrum, and a photoluminescence intensity distribution image of a miniaturized element for various electronic devices can be obtained with high spatial resolution. .

Claims (15)

A cathode luminescence device for irradiating a sample with an electron beam and detecting light generated from the sample by the electron beam irradiation, wherein an atomic force microscope using a probe as a probe is provided as a light collecting system. Luminescence composite device. The cathodoluminescence composite device according to claim 1, wherein a main constituent material of the probe is quartz glass. 2. The combined cathode luminescence device according to claim 1, wherein the probe is made of a metal having a hollow inside or a semiconductor having a hollow inside. The cathodoluminescence composite device according to any one of claims 1 to 3, wherein two or more probes are provided. The cathodoluminescence composite device according to claim 4, wherein two or more probes are arranged substantially radially around the tip of the probe. The combined cathode luminescence device according to any one of claims 1 to 5, wherein a metal thin film having a thickness of 0.1 nm to 100 nm is provided on a surface of the probe. The composite device according to claim 6, wherein a main constituent material of the metal thin film is one material selected from the group consisting of Ag, Cu, and Au. The cathodoluminescence composite device according to any one of claims 1 to 7, wherein the sample can be irradiated with incident light through a probe. At least one spectroscopic device selected from the group consisting of a diffraction grating type spectrometer, a prism type spectrometer, an optical filter type spectrometer, and a dichroic mirror type spectrometer to disperse the light collected by the probe The cathodoluminescence composite device according to any one of claims 1 to 8, wherein A measuring method for measuring a cathodoluminescence spectrum or a cathodoluminescence intensity distribution image using the cathodoluminescence composite device according to claim 1. A measurement method for measuring at least one of a Raman spectrum, a Raman intensity distribution image, a photoluminescence spectrum, and a photoluminescence intensity distribution image using the cathodoluminescence composite device according to claim 1. The method according to claim 10, wherein the sample is a semiconductor. The method according to claim 10, wherein the sample is an oxide or a nitride. The measurement method according to claim 10, wherein the sample is a ferroelectric substance. The method according to any one of claims 12 to 14, wherein the sample is an element for various electronic devices.