WO2013132906A1

WO2013132906A1 - Liquid sample holder for electron microscope and method for manufacturing same

Info

Publication number: WO2013132906A1
Application number: PCT/JP2013/051239
Authority: WO
Inventors: 日▲高▼　貴志夫; 尚平寺田; 辰己平野; 悠香腰越
Original assignee: 株式会社日立製作所
Priority date: 2012-03-09
Filing date: 2013-01-23
Publication date: 2013-09-12
Also published as: JP2013187096A

Abstract

A liquid sample holder (10) for an electron microscope according to the present invention comprises: a pair of silicon substrates (11) into which a liquid sample (15) is inserted; an electron beam transmitting window (12) that is disposed on the pair of substrates; a frame body (16) having a thickness of equal to or less than 200 nm that is disposed at a position surrounding the window for the injection of the liquid sample; and a sealing resin (17) that is sealed on an outer side of the frame body to allow the frame body to be adhered to the pair of substrates and to seal the liquid sample inside the frame body. A silicon nitride film (13) and a silicon oxide film (14) are formed at a position on the surfaces of the pair of substrates which are in contact with the liquid sample. Therefore, the scattering of an electron beam can be inhibited, and thus a high-resolution observation can be made.

Description

Liquid sample holder for electron microscope and method for manufacturing the same

The present invention mainly relates to a sample holder for liquid sample observation used in a scanning transmission electron microscope.

Precise investigation at the atomic level of electrochemical reactions such as fine plating wiring of substrates in the semiconductor business field and chemical reactions of batteries for electric vehicles has become an essential issue for related technologies under development . In the automotive industry, in particular, de-fossil fuels are an urgent issue as a response to the green environment.

In the practical application of electric vehicles, there is a problem to improve the performance of battery materials such as high output and high reliability, but there is a limit to solving the problems only by using current materials. Therefore, it is necessary to develop a member in which the atomic level arrangement at the nano level is controlled for the positive and negative electrode materials.

In order to conduct a material property and performance inspection in a battery cell structure, as a conventional method, it has been broken after battery performance evaluation, and members have been observed using an electron microscope. However, for more accurate performance inspection, it is necessary to observe the electrochemical ion movement in situ. For this purpose, a method of observing the electrochemical behavior in which atoms move between the positive electrode and the negative electrode and diffuse or penetrate after reaching the positive electrode or the negative electrode becomes essential in the holder of the electron microscope.

Therefore, conventionally, for example, as shown in FIG. 7, a pair of silicon substrates 11 having a silicon nitride film 14 formed on the surface is provided in a vacuum atmosphere, and windows 12 for electron beam EB transmission are formed on the substrate 11 by chemical etching or the like. Then, a liquid sample 15 was made to flow between the substrates 11, and this was irradiated with an electron beam EB and observed with an electron microscope.

In addition, it is also necessary to observe a reaction which can not be performed in a vacuum in the atmosphere, in the bonding form of the solder nanoparticles used for metal bonding.

In addition, various improvements and improvements have been proposed as sample holders for liquid sample observation used in scanning transmission electron microscopes. For example, in Patent Document 1, in an electron microscope that takes out an electrical signal from a sample and observes it, a good electrical connection can be obtained at the time of sample exchange, the exchange operation can be easily performed, and the thickness of the sample holder is reduced. In order to realize a sample holder capable of avoiding the drift of the observation image due to charge accumulation, a configuration is disclosed in which one side of the sample stage is coated with an insulating coating, which shares a terminal for applying a voltage and a pressing member ing.

Further, in Patent Document 2, in sample observation using a transmission electron microscope or the like, heating / voltage application is performed without replacing the sample holder, and changes in the sample are observed to change the sample in the atmosphere. In order to provide a sample holder free from adhesion or damage to the sample such as dirt or the like, a configuration is disclosed in which a heating means is installed on the sample holder.

In addition, in order to provide a sample holder in which the sample can be easily arranged in the two-axis inclined holder in Patent Document 3, the chip-on cartridge is configured of a mounting portion and a shuttle, and one end of the mounting portion is mounted at the tip of the introducing portion. The shuttle is disclosed a configuration of sample holders that are each removably attached to the other end of the attachment.

Further, Patent Document 4 discloses a configuration that provides a diaphragm-type gas atmosphere sample holder which is biaxially tiltable, does not have an operation failure due to burrs of parts, and has high sample position reproducibility. A sealing block having a diaphragm type gas atmosphere sample chamber is supported by a pair of Y rotary shafts and bearings. The inside of the gas supply side pipe, the gas discharge side pipe, and the diaphragm type gas atmosphere sample chamber serving as the gas flow path is kept airtight with the vacuum by the rubber O-ring, and the sealing block is airtight with the vacuum centering around the Y axis. Inclined operation while keeping the

Japanese Patent Application Publication No. 2003-263969 Unexamined-Japanese-Patent No. 2004-022192 Unexamined-Japanese-Patent No. 2005-293865 JP, 2009-117196, A

In general, in order to hold the liquid sample in the vacuum chamber of the electron microscope, the membrane of the liquid sample contact portion of the sample holder needs a sufficient strength. As the thickness of the film increases, the strength improves, but the absorption of the electron beam by the film material increases, so the thicker the film, the lower the beam intensity of the electron beam, which is unsuitable for high resolution observation. In addition, if the wettability between the membrane surface and the liquid sample is poor, the liquid sample is repelled from the membrane to form a sphere, so that the liquid sample can not be well contained inside the sample holder. Therefore, it is necessary to solve these problems.

The present invention relates to a liquid sample holder of an electron microscope for observing a liquid sample by irradiating an electron beam in a vacuum atmosphere, a pair of substrates sandwiching the liquid sample, a window for transmitting an electron beam provided on the pair of substrates, A frame for injecting a liquid sample provided at a position surrounding a window between the pair of substrates, and a seal between the pair of substrates and the outside of the frame for bonding the pair of substrates and the frame together with the liquid sample A silicon nitride film and a silicon oxide film are formed on the surface of a pair of substrates having a sealing resin for sealing in a frame and in contact with a liquid sample.

Further, in the liquid sample holder of the electron microscope, the pair of substrates is formed of a silicon substrate.

In the liquid sample holder of the electron microscope, the thickness of the silicon oxide film is set to 1 nm to 10 nm.

In the liquid sample holder of the electron microscope, the thickness of the silicon nitride film is set to 1 nm to 50 nm.

In the liquid sample holder of the electron microscope, the stacking order of the sample holder is characterized in the order of silicon nitride film / silicon oxide film / liquid sample / silicon oxide film / silicon nitride film.

In the liquid sample holder of the electron microscope, the total thickness of the two sets of silicon nitride films and silicon oxide films in the pair of substrates is set to 60 nm to 100 nm.

In the liquid sample holder of the electron microscope, the height of the frame sandwiched between the pair of substrates is set to 1 nm to 10,000 nm.

In the liquid sample holder of the electron microscope, the height of the frame sandwiched between the pair of substrates is set to 1 nm to 200 nm.

Furthermore, a storage container for fixing a liquid sample holder of an electron microscope is provided, and the storage container is detachably fixed to a sample cell holder provided in the electron microscope.

Furthermore, in the electron microscope, the storage container of the liquid sample holder is characterized by being made of copper or a copper alloy.

Furthermore, a pair of substrates sandwiching the liquid sample, a window for electron beam transmission provided on the pair of substrates, a frame provided at a position surrounding the window between the pair of substrates, and a frame between the pair of substrates A sealing resin for sealing a pair of substrates and a frame while sealing the liquid sample in the frame, and a silicon nitride film and a silicon oxide film on the surface of the pair of substrates in contact with the liquid sample In the method of manufacturing a liquid sample holder of an electron microscope which observes a liquid sample in a vacuum atmosphere, forming a frame having a closed region with a fixed height on the surface of a lower substrate by providing two upper and lower substrates. The liquid sample is formed, injected into the frame, and a sealing resin is applied to the outer periphery of the frame to bond the upper and lower substrates and the frame to seal the liquid sample.

Furthermore, in a method of manufacturing a liquid sample holder for an electron microscope, a window for electron beam transmission has a silicon nitride film formed on the substrate surface, then a silicon oxide film is formed on the silicon nitride film, and the substrate back surface is removed. It is characterized in that two layers of a silicon nitride film and a silicon oxide film are left on the surface.

Further, in the method of manufacturing a liquid sample holder of an electron microscope, the formation of the frame is characterized in that the frame made of tungsten is laminated on the surface of the silicon oxide film of the substrate by the FIB processing method.

The present invention relates to a liquid sample holder of an electron microscope for observing a liquid sample by irradiating an electron beam in a vacuum atmosphere, a pair of substrates sandwiching the liquid sample, a window for transmitting an electron beam provided on the pair of substrates, And a frame provided at a position surrounding the window between the pair of substrates, and sealed on the outside of the frame between the pair of substrates to bond the pair of substrates and the frame together and seal the liquid sample in the frame. And forming a silicon nitride film and a silicon oxide film on a pair of substrate surfaces in contact with the liquid sample, thereby forming an observation liquid sample of the sealing resin and oxidation with a narrow gap enabling high resolution. This produces the effect that a sample holder free from contamination of the silicon film observation window can be produced.

BRIEF DESCRIPTION OF THE DRAWINGS Sectional block diagram which shows the liquid sample holder in the Example of this invention. BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram of the liquid sample holder in the Example of this invention. The SEM image of the frame structure in the Example of this invention. The schematic block diagram of the sample holder lower part in the Example of this invention. BRIEF DESCRIPTION OF THE DRAWINGS The whole schematic block diagram of the liquid sample cell holder in the Example of this invention. Explanatory drawing which shows the STEM image and EDX elemental-analysis result of the liquid sample in the Example of FIG. 1 of this invention. The schematic diagram which shows the liquid sample observation part in the scanning transmission electron microscope of a prior art example.

The present invention is a liquid sample holder for an electron microscope, comprising a silicon nitride film covering a window for observation of a silicon substrate, using a pair of substrates made of silicon or the like in which a window for observation is formed at the center, A silicon oxide film covering the surface of the film is formed, a frame is formed on the surface of the silicon oxide film, a liquid sample for observation is injected inside the frame, and two silicon holders are joined with a sealing resin. It is formed and characterized by the following points.
(1) The sample holder has a structure in which a liquid sample is sandwiched between two silicon substrates.
(2) A window through which an electron beam passes is opened at the center of both silicon substrates, and the window is covered with a silicon nitride film. The film thickness of the silicon nitride film is desirably 50 nm or less.
(3) The surface of the silicon nitride film is covered with a silicon oxide film, and a frame is sandwiched between the silicon oxide films facing each other. The thickness of the silicon oxide film is preferably 10 nm or less.
(4) The liquid sample for observation is in contact with the silicon oxide film at the top and the bottom, and the periphery is in contact with the inner periphery of the frame. When high resolution is realized, the height of the frame is preferably 200 nm or less.
(5) The sealing resin for bonding is in contact with the silicon oxide film at the top and bottom, with the periphery in the open air, and the inside with the outer periphery of the frame.

The invention will now be described by way of example.

FIG. 1 is a cross-sectional view seen from the side of the main body of the sample holder showing the first embodiment. Here, 10 denotes a sample holder, 11 denotes a pair of upper and lower silicon substrates, and 12 denotes a window for electron beam EB transmission formed at the center of the silicon substrate.

A silicon nitride film 13 and a silicon oxide film 14 are formed on the surface of the silicon substrate 11. After a silicon nitride film 13 is formed on the surface of a silicon substrate 11 by CVD or the like, the surface is oxidized to form a hydrophilic silicon oxide film 14, and then the silicon substrate 11 of the base material is perforated and removed by chemical etching or the like. A window 12 about 100 μm in diameter is formed.

15 is a liquid sample for observation, 16 is a frame, and 17 is a sealing resin. The liquid sample 15 for observation is injected into the frame 16, and the upper and lower silicon substrates 11 are adhered with the sealing resin 17 to seal the liquid sample 15 for observation.

The electron beam EB is incident from the window 12 of the upper silicon substrate 11, passes through the silicon nitride film 13 and the silicon oxide film 14, irradiates the liquid sample 15, and again the silicon oxide film 14 and silicon nitride film of the lower silicon substrate 11 It passes 13 sequentially and emits from the lower window 12.

Since this sample holder has a geometrical shape which is line-symmetrical vertically with respect to the horizontal axis passing through the liquid sample portion in FIG. 1, the electron beam is viewed even when the upper and lower sides are reversed as viewed from the horizontal axis of the liquid sample 15 center. The passing order is the same.

The electron beam EB does not always come in contact with the frame 16 but passes through only the inside of the frame 16. The frame 16 is present between the liquid sample 15 and the sealing resin 17 and clearly separates the liquid sample 15 and the sealing resin 17 to prevent the liquid samples from invading and mixing with each other. This means that the sealing resin to the surface of the hydrophilic silicon oxide film 14 is in direct contact with the liquid sample 15 in a region where the electron beam EB incident from the window 12 passes through the silicon nitride film 13, the silicon oxide 14 and the liquid sample 15. 17 can prevent contamination. That is, the sealing resin 17 on the surface of the silicon oxide film 14 has an effect of preventing the observation of the liquid sample 15 with the electron microscope.

Further, since the electron beam EB absorbs the electron beam EB every time it passes through the silicon nitride film 13, the silicon oxide film 14, and the liquid sample 15, the beam intensity attenuates as it becomes thicker as a function of its thickness. Therefore, the total thickness of the silicon nitride film 13 and the silicon oxide film 14 in the silicon substrate 11 provided on the upper and lower sides is preferably 60 to 100 nm. That is, the thickness of the silicon nitride film 13 and the silicon oxide film 14 in one silicon substrate 11 is preferably 30 to 50 nm. The silicon nitride film 13 mainly gives strength to the window 12, and the silicon oxide film 14 gives water repellency to the window 12. Furthermore, the composite film achieves strength to withstand the atmospheric pressure of a liquid sample in a vacuum atmosphere.

In addition, the liquid sample 15 is desirably 10 μm or less in general, and desirably 200 nm or less in thickness for achieving high resolution over 10 nm. If the thickness is larger than this, the Rutherford scattering significantly reduces the resolution.

Next, the frame structure will be described with reference to FIG. The sample holder 10 needs to prepare two substrates of plane symmetry in the upper and lower direction, but when forming the frame 16, it is placed so that the silicon oxide film 14 faces the upper surface using the lower substrate 11 . A frame 16 is provided to surround the electron beam transmission region at a position sufficiently separated from the electron beam transmission region. Since the height of the frame 16 becomes the thickness of the liquid sample 15, in order to obtain a high resolution image, the lower the height of the frame 16, the higher the resolution. Therefore, controlling the height of the frame 16 controls the resolution of the sample holder 10.

An SEM image when the frame structure shown in FIG. 2 is formed on the silicon oxide film 14 is shown in FIG. WCO gas 6 is introduced into the FIB vacuum chamber using a FIB (Focused Ion Beam) apparatus on the silicon oxide film 14 and the WCO gas is decomposed by Ga ion irradiation 6WCO → W + 6CO
A frame 16 made of W was formed on the silicon oxide film 14 using tungsten (W) which becomes solid by reaction. Therefore, the SEM image of FIG. 3 is a specific example of the frame structure of FIG. The SEM image in FIG. 3 was tilted 45 ° to expose the sidewalls to ensure uniformity of the thickness and height of the frame. According to the result of forming the frame 16 using FIB, a sound frame structure with less variation in the thickness and height of the wall of the frame 16 was obtained.

The laminated structure of the sample holder 10 is shown in FIG. As described above, the sample holder 10 is divided into upper and lower two substrates, and the lower silicon substrate 11 shown in FIG. 4 is placed with the silicon oxide film 14 as the uppermost surface, and the frame 16 is formed thereon. And a liquid sample 15 was injected therein. The liquid sample 15 remained without overflowing due to the effect of the frame 16.

Subsequently, in order to bond the upper and lower two silicon substrates, the sealing resin 17 was applied and filled so as to be in contact with the outer periphery of the frame 16. The stacking order of the sample cells in this state is, from the top, the sealing resin 17, the silicon oxide film 14, the silicon nitride film 13, and the silicon substrate 11 in this order.

In order to produce the sample holder 10, a substrate in which the silicon substrate 11, the silicon nitride film 13 and the silicon oxide film 14 are sequentially stacked from the top is covered on the laminated silicon substrate prepared in FIG. The sealing resin 17 was solidified as it was. In order to transmit the electron beam EB to the sample holder 10 and observe the liquid sample 15, the positions of the windows 12 of the upper and lower two silicon substrates 11 must be matched. For that purpose, the optical axis was confirmed using visible light instead of the electron beam EB. That is, it was confirmed that the area through which light passes through the two windows 12 of the sample holder 10 from the lower side is a sufficient size using visible light of the LED.

FIG. 5 shows an embodiment of the structure of the whole liquid sample cell holder. The sample holder 10 was installed at the bottom 23 of the storage container 20 at a position where the window 12 of the sample holder 10 and the hole 22 opened in the storage container bottom 23 do not prevent the electron beam EB from transmitting each other. For fixing the two, a method was used in which the outer peripheral portion of the sample holder 10 and the bottom portion 23 of the storage container 20 were joined using an adhesive resin.

After bonding the sample holder 10 and the storage container 20 with an adhesive resin, the sample holder 10 and the storage container 20 were placed on the liquid sample cell holder 30. The liquid sample cell holder 30 is provided with a washer (not shown) for fixing the storage container 20 to the cell holder bottom 31. Therefore, the optical axis through which the electron beam EB passes can pass through the window 12 of the sample holder 10, the hole 22 of the storage container 20 and the hole 32 of the liquid sample cell holder 30, and the holes mutually reduce their area. It does not disturb.

In order to perform STEM (Scanning Transmission Electron Microscope) observation and elemental analysis by EELS (Electron Energy Loss Spectroscopy) or EDX (Energy Dispersive X-ray Spectroscopy), the sample holder 10, the storage container 20, and the liquid sample cell holder 30 It has a structure in which three parts are stacked one after another. The sample holder 10, the storage container 20, and the liquid sample cell holder 30 are separated and independent from each other, so replacement of the liquid sample 15 is easy, and after contamination such as contamination adhering from the outside at the time of electron beam irradiation by STEM observation etc. Since it is easy to replace with the new sample holder 10 and the storage container 20, the uncontaminated liquid sample 15 can be used. Therefore, STEM observation and EELS or EDX analysis using the liquid sample 15 always free of contamination has become possible.

FIG. 6 shows an Au nanoparticle image by STEM observation of this example, and an elemental analysis result of nanoparticle and liquid sample by EDX.

Au nanoparticles are shown as white particles with a diameter of about 10 nm, and the measurable resolution of the distance between the particles showed a high performance of about 1 nm.

EDX was used because it was difficult to determine from the EELS spectrum of the H ₂ O molecule to verify the presence of the liquid sample. In EDX, the spectrum of H can not be measured, and since O is also contained in the silicon oxide film 14, it can not be determined. Therefore, a saturated aqueous solution of lithium chloride (LiCl) was prepared, and the presence of a liquid sample was confirmed by the spectrum of chlorine (Cl) contained therein. The measurement was performed in two places for the nanoparticle and the liquid sample to verify that the nanoparticle is Au and Cl derived from LiCl in the liquid sample is present in both. Thus, it can be demonstrated that the liquid sample 15 in the sample holder 10 can be subjected to STEM observation and EELS or EDX analysis using the liquid sample cell holder 30.

According to the present invention, with the above configuration, the sample holder can be manufactured with a narrow gap enabling high resolution and without contamination of the observation liquid sample and the silicon oxide film observation window by the sealing resin, and the storage container portion Since it is detachable from the liquid sample holder of the electron microscope, it has an effect that can always be observed with a new silicon nitride film and silicon oxide film.

10: sample holder 11: silicon substrate 12: window 13: silicon nitride film 14: silicon oxide film 15: liquid sample 16: frame 17: sealing resin 20: storage container 21: outer frame 22, 32: hole 23: Storage container bottom 30: Liquid sample cell holder 31: Cell holder bottom

Claims

In a liquid sample holder of an electron microscope for observing a liquid sample by irradiating an electron beam in a vacuum atmosphere,
A pair of substrates sandwiching the liquid sample, a window for transmitting an electron beam provided on the pair of substrates, and a frame for injecting the liquid sample provided at a position surrounding the window between the pair of substrates A sealing resin which is applied and filled on the outside of the frame between the pair of substrates to bond the pair of substrates and the frame and seal the liquid sample in the frame; A liquid sample holder for an electron microscope, wherein a silicon nitride film and a silicon oxide film are formed on the surface of the pair of substrates in contact with the above.
The liquid sample holder for an electron microscope according to claim 1, wherein the pair of substrates is formed of a silicon substrate.
The liquid sample holder for an electron microscope according to claim 1 or 2, wherein the silicon oxide film has a thickness of 1 nm to 10 nm.
The liquid sample holder for an electron microscope according to claim 1 or 2, wherein the silicon nitride film has a thickness of 1 nm to 50 nm.
5. The liquid sample holder for an electron microscope according to any one of claims 1 to 4, wherein the stacking order of the sample holder is in the order of silicon nitride film / silicon oxide film / liquid sample / silicon oxide film / silicon nitride film. What is claimed is: 1. A liquid sample holder for an electron microscope, characterized in that
The liquid sample holder for an electron microscope according to any one of claims 1 to 5, wherein a total thickness of the two sets of silicon nitride films and silicon oxide films in the pair of substrates is 60 nm to 100 nm. Electron microscope liquid sample holder.
7. The liquid sample holder for an electron microscope according to any one of claims 1 to 6, wherein the height of the frame sandwiched between the pair of substrates is 1 nm to 10,000 nm. Liquid sample holder.
The liquid sample holder for an electron microscope according to claim 7, wherein the height of the frame sandwiched between the pair of substrates is 1 nm to 200 nm.
A storage container for fixing the liquid sample holder of the electron microscope according to any one of claims 1 to 8 is provided, and the storage container is detachably fixed to a sample cell holder provided in the electron microscope. microscope.
The electron microscope according to claim 9, wherein the storage container is made of copper or a copper alloy.
Between a pair of substrates sandwiching a liquid sample, a window for electron beam transmission provided on the pair of substrates, a frame provided at a position surrounding the window between the pair of substrates, and a pair of substrates The pair of substrate surfaces that are sealed on the outside of the frame and have a sealing resin that adheres the pair of substrates and the frame while sealing the liquid sample in the frame, and are in contact with the liquid sample In a method of manufacturing a liquid sample holder of an electron microscope for observing a liquid sample in a vacuum atmosphere, in which a silicon nitride film and a silicon oxide film are formed on
Two frames of upper and lower layers are provided, the frame having a closed area having a certain height is formed on the surface of the lower substrate, the liquid sample is injected into the frame, and the seal is performed on the outer periphery of the frame A method of manufacturing a liquid sample holder for an electron microscope, characterized in that a resin is applied, and the upper and lower two layers of substrates and the frame are adhered to each other to seal the liquid sample.
The method according to claim 11, wherein the window for electron beam transmission forms a silicon nitride film on the surface of the substrate, and then the silicon oxide film is formed on the silicon nitride film. And removing the back surface of the substrate to leave two layers of the silicon nitride film and the silicon oxide film on the front surface of the substrate.
The method for manufacturing a liquid sample holder of an electron microscope according to claim 11 or 12, wherein the frame is formed by laminating a frame made of tungsten on the surface of the silicon oxide film of the substrate by an FIB processing method. The manufacturing method of the liquid sample holder of the electron microscope characterized by the above.