Abstract:
An object of the invention is to provide an electron beam device and a sample holding device for the electron beam device that can observe the reaction between a sample and a gas at high resolution while a gas atmosphere is maintained even by using thin diaphragms. 
     To solve one of the problems described above, in an electron beam device having the function of separately exhausting an electron beam irradiation portion of an optical column, a sample chamber and an observation chamber, a gas supply means for supplying a gas to a sample and an exhaust means for exhausting a gas are provided to sample holding means, diaphragms are disposed above and below the sample to separate the gas atmosphere and vacuum of the sample chamber and to constitute a cell sealing the atmosphere around the sample, and a mechanism for spraying a gas is provided to the outside of the diaphragms. The gas sprayed outside the diaphragms has low electron beam scattering performance such as hydrogen, oxygen or nitrogen. The diaphragm is an amorphous film formed of a light element such as a carbon film, an oxide film and a nitride film capable of transmitting the electron beam.

Description:
RELATED APPLICATIONS 
     This application is the U.S. National Phase under 35 U.S.C. §371 of International Application No. PCT/JP2010/000282, filed on Jan. 20, 2010, which in turn claims the benefit of Japanese Application No. 2009-032124, filed on Feb. 16, 2009, the disclosures of which Applications are incorporated by reference herein. 
     TECHNICAL FIELD 
     This invention relates to an electron beam device for observing a sample by using electron beams and a sample holding device for such an electron beam device. More particularly, the invention relates to an electron beam device capable of conducting high resolution observation and high sensitivity analysis of a sample during reaction process in a high pressure gas atmosphere and immediately after the reaction by creating a minute gas space (atmospheric cell) of an atmospheric gas embracing the sample with diaphragms inside a sample chamber and precisely controlling the pressure inside the atmospheric cell, and a sample holding device for such an electron beam device. 
     BACKGROUND ART 
     In an electron beam device, a method for observing the change of a sample by heating the sample to a high temperature or cooling it is known besides a method for observing the sample at room temperature. In order to bring the condition closer to a practical condition, there is also a method that observes the change in a reaction gas atmosphere. 
     As for the observation in the gas atmosphere, methods are known that sandwich a sample between two grids and furnish a sample holder with a mechanism for introducing and exhausting a gas into and out from the grids as described in Patent Literatures 1 and 2. As described in Patent Literature 3, there is also known a method that arranges a cylindrical cover around a sample and forms two holes in the cover to which diaphragms transmitting the electron beams are bonded. 
     In conjunction with an electron microscope for observing on the real time basis the reaction of a sample under a high temperature specific atmosphere condition, Patent Literature 4 describes a method for observing various reactions by forming in a sample holder a sample chamber isolated from vacuum by a diaphragm for holding the sample in air-tight, a pipe for introducing a gas into the sample chamber and a sample heating mechanism, and heating the sample while it is kept under a specific atmosphere condition. 
     As described in Patent Literature 5, there is further known a method that a capillary tube for blowing a gas is disposed opposing a heater for heating a sample and observes a gas reaction at a high temperature. 
     As another prior art, Patent Literature 6 describes a method that a coolant basin storing therein a coolant for cooling a sample is disposed around a sample holding unit and cools the sample and then observes it. 
     As still another prior art, Patent Literatures 7, 8 and 9 disclose a transmission electron microscope observation method. A heating mechanism for heating a sample and a mechanism for rapidly cooling it by blowing a gas to a reaction portion are provided to a charged particle beam apparatus and after the reaction process is observed, the observation portion is carved out by a focused ion beam. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP-A-2000-133186 
     Patent Literature 2: JP-A-9-129168 
     Patent Literature 3: U.S. Pat. No. 5326971 
     Patent Literature 4: JP-A-51-267 
     Patent Literature 5: JP-A-2003-187735 
     Patent Literature 6: JP-A-2000-208083 
     Patent Literature 7: JP-A-2001-305028 
     Patent Literature 8: JP-A-2005-190864 
     Patent Literature 9: JP-A-2008-108429 
     SUMMARY OF INVENTION 
     Technical Problem 
     Because the gas atmosphere and vacuum are isolated and the gas reaction of the sample is observed, the prior art technologies described above do not consider the protection of the diaphragm through which the electron beam passes and there remains the problem that the diaphragm is broken in the observation at a high pressure. When a thick diaphragm is used to prevent the breakage, the image gets dim because the electron beam is scattered. 
     It is an object of the invention to provide an electron beam device capable of observing at high resolution the reaction between a sample and a gas under the state in which a gas atmosphere is maintained even when a thin diaphragm is used, and a sample holding device for such an electron beam device. 
     Solution to Problem 
     To solve one of the problems described above, in an electron beam device having the function of exhausting separately an electron beam irradiation portion of an optical column, a sample chamber and an observation chamber, the invention furnishes a sample holding means with a gas supply means for supplying a gas to a sample and an exhaust means for exhausting the gas, arranges diaphragms above and below the sample to isolate a gas atmosphere and the vacuum of the sample chamber and to constitute a cell sealing the atmosphere around the sample, and further provides a mechanism inside the sample chamber for spraying a gas to the outside of the diaphragms. 
     As the gas sprayed to the outside of the diaphragms, a gas having low electron beam scattering ability such as hydrogen, oxygen or nitrogen is used. 
     The material of the diaphragms is an amorphous film formed of a light element such as a carbon film, an oxide film and a nitride film each transmitting an electron beam. 
     Advantageous Effects of Invention 
     According to the invention, the minute gas space (atmospheric cell) of the atmospheric gas embracing the sample with the diaphragm is formed inside the sample chamber by using the electron beam device and the reaction between the sample and the gas can be observed with high resolution under the state where the gas atmosphere is maintained even by using the thin diaphragms. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a basic structural view of an electron beam device  1  and an sample holding device  6  for the electron beam device according to an embodiment of the invention. 
         FIG. 2  is a structural view of an electron beam sample chamber  14  and a sample holding device  6  for the electron beam device according to an embodiment. 
         FIG. 3  is a structural view of a sample holding device  6  for an electron beam device according to an embodiment; (a) an overall sectional view of the sample holding device  6  for the electron beam device, (b) a distal end sectional view of the sample holding device  6  for the electron beam device, and (c) a distal end top view of the sample holding device  6  for the electron beam device. 
         FIG. 4  is an explanatory view of the operation of the sample holding device  6  for an electron beam device according to an embodiment; (a) an overall sectional view of the sample holding device  6  for the electron beam device, (b) a distal end sectional view of the sample holding device  6  for the electron beam device, and (c) a distal end top view of the sample holding device  6  for the electron beam device. 
         FIG. 5  is a distal end sectional view of a sample holding device  6  for an electron beam device according to an embodiment. 
         FIG. 6  is an explanatory view of the operation of the sample holding device  6  for an electron beam device according to an embodiment. 
         FIG. 7  is a sectional view and top view of a sample holding device  6  for an electron beam device according to an embodiment. 
         FIG. 8  illustrates a sample holding device  6  for an electron beam device in an embodiment, wherein (a) is a sectional view of the sample holding device  6  for the electron beam device and (b) is a top view of the sample holding device  6  for the electron beam device. 
         FIG. 9  illustrates a sample holding device  6  for an electron beam device according to an embodiment; (a) a sectional view of the sample holding device  6  for the electron beam device, and (b) a top view of the sample holding device  6  for the electron beam device. 
         FIG. 10  illustrates a sample holding device  6  for an electron beam device according to an embodiment; (a) a sectional view of the sample holding device for the electron beam device, and (b) a top view of the sample holding device for the electron beam device. 
         FIG. 11  is an explanatory view of a sample holding device  6  for an electron beam device according to an embodiment. 
         FIG. 12  illustrates a sample holding device  6  for an electron beam device according to an embodiment. 
         FIG. 13  illustrates a sample holding device  6  for an electron beam device according to an embodiment; (a) a sectional view of the sample holding device  6  for the electron beam device, and (b) a top view of the sample holding device  6  for the electron beam device. 
         FIG. 14  is a structural view of an electron beam sample chamber  14  and a sample holding device  6  for an electron beam device according to an embodiment. 
         FIG. 15  is an explanatory view of the use of a sample holding device  6  for an electron beam device according to an embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
       FIG. 1  is a basic structural view of an electron beam device  1  and a sample holding device  6  for the electron beam device according to an embodiment of the invention. An optical column of the electron beam device  1  has an electron gun  2 , a condenser lens  3 , an objective lens  4  and a projection lens  5 . A sample holding device  6  for the electron beam device is interposed between the condenser lens  3  and the objective lens  4 . A fluorescent plate  7  is arranged below the projection lens  5  and a TV camera  8  is arranged below the fluorescent plate  7 . The TV camera  8  is connected to an image display unit  9 . An EELS detector  10  is attached to a lower part of the TV camera  8  and is connected to an EELS control unit  11 . An EDX detector  12  is installed above the sample holding device  6  for the electron beam device and is connected to an EDX control unit  13 . 
     The electron gun  2 , the condenser lens  3 , an electron beam sample chamber  14  and an observation chamber  15  are connected to mutually different vacuum pumps  17  through valves  16 , respectively. In the sample holding device  6  for the electron beam device, a sample  20  is loaded into a cell  19  sealed by a diaphragm  18  formed of an amorphous material of carbon, oxide or nitride. A distal end of a gas inlet pipe  21  and a distal end of a gas exhaust pipe  22  are inserted into the cell  19 . 
     A gas inlet pipe  21   a  is connected to a gas storage unit  24   a  through a gas pressure controlling valve  23   a . The gas exhaust pipe  22  is connected to a vacuum pump  17  through a valve  16 . A distal end of the gas inlet pipe  21   b  is inserted into the electron beam sample chamber  14  so that a gas can be blown to an outside of the cell of a diaphragm portion  18  and is connected to a gas storage unit  24   b  through a gas pressure controlling valve  23   b.    
     The electron beams  25  generated from the electron gun  2  are condensed by the condenser lens  3  and are irradiated to the sample  20 . The electron beams  25  passing through the sample  20  are subjected to image formation by the objective lens  4  and are enlarged and projected onto the fluorescent plate  7  by the projection lens  5 . Alternatively, the fluorescent plate  7  is lifted up, the electron beams are projected to the TV camera  8  and the transmission image is displayed on the image display unit  9 . 
       FIG. 2  illustrates a structural view of the electron beam sample chamber  14  and a partially enlarged view of the sample holding device  6  for the electron beam device according to one embodiment. The gas pressure inside the cell  19  from the gas inlet pipe  21   a  is regulated by the gas pressure controlling valve  23   a  and the sample  20  inside the gas is observed. The gas inside the cell  19  is exhausted by the vacuum pump  17  through the gas exhaust pipe  22 . 
     In this instance, the pressure difference between the inside and outside of the cell  19  is reduced by blowing the gas from the gas inlet pipe  21   b  to the electron beam sample chamber  14  to protect the diaphragm  18 . In this way, breakage of the diaphragm  18  is prevented even when the pressure inside the cell  19  is set to a higher level. 
     An intermediate chamber  26  partitioned by walls having a stop is formed between the electron beam sample chamber  14  and the electron gun  2 . When exhaust is made by a different vacuum pump  17 , it is possible to prevent the gas from directly reaching and breaking the electron gun  2 . 
     The diaphragm is made of a light element such as a carbon film, an oxide film or a nitride film capable of transmitting the electron beam. 
     A gas having low electron beam scattering ability such as hydrogen, oxygen or nitrogen is used as the gas to be jetted to the outside of the diaphragm. 
       FIG. 3  illustrates an overall sectional view (a), a distal end sectional view (b) and a distal end top view (c) of the sample holding device  6  for an electron beam device capable of moving the diaphragm horizontally according to an embodiment. The diaphragm  18  is attached to a diaphragm driving unit  27 . The diaphragm driving unit  27  is connected to a micrometer  28  disposed outside the optical column of the electron beam device  1 . The diaphragm driving unit  27  can be driven in the horizontal direction when the micrometer  28  is rotated. The sample  20  has a form in which it is fixed to a grid having a diameter of about 3 mm or is punched out into a disc having a diameter of about 3 mm and is fixed into the cell  19  by a ring spring  32 . An O-ring  30  is interposed between the diaphragm driving unit  27  and the main body of the sample holding device  6  for the electron beam device. When the diaphragm driving unit  27  is set in such a manner that the diaphragm  18  is arranged at the electron beam passage portion, the atmosphere inside the cell  19  can be isolated from the outside. The gas is introduced into the cell  19  through the gas inlet pipe  21   a  and the sample  20  can be observed in the gas atmosphere. 
     An embodiment wherein the diaphragm is movable will be explained with reference to  FIG. 4 . 
     The prior art does not consider the operation of the diaphragm portion, and EDX analysis and EELS analyses of the sample after the reaction are not possible. In addition, there has been a problem that the exchange of gas atmosphere for the reaction cannot be conducted in a short time. 
       FIG. 4  illustrates an overall sectional view (a) of the sample holding device  6  for the electron beam device when the diaphragm driving unit  27  is moved to open the cell  19  according to an embodiment, its distal end sectional view (b) and its distal end top view (c). Opening of the cell  19  can be made by rotating the micrometer  28  from outside the optical column of the electron beam device  1 , and gas exhaust inside the cell  19  after the gas reaction can be conducted in a short time. High resolution transmission image observation, EDX analysis and EELS analysis that have been impeded by the diaphragm  18  and the gas can be thereafter conducted quickly without losing the visual field. 
       FIG. 4  illustrates a structure in which the upper and lower diaphragms  18  move simultaneously but the micrometer  18  may well be adapted so that either one or both of the diaphragms  18  move discretely in the horizontal direction. 
     Another embodiment in which the diaphragm is movable in the vertical direction will be explained with reference to  FIG. 5 . 
     Because the prior art does not consider the adjustment of the distance between the gas space and the sample, there has remained a problem that high resolution observation is difficult owing to scattering of the electron beams by the gas when the gas pressure in the cell is high. 
       FIGS. 5  ( a, b, c ) illustrate the distal end sectional views of the sample holding device  6  (sample holder) for the electron beam device capable of moving the diaphragm  18  in the vertical direction according to one embodiment. 
     The diaphragm  18  is fixed to a support  31  and a screw is thread cut at a contact portion of the support  31  with the diaphragm operation portion  27 . Therefore, the diaphragm  18  can move in the vertical direction (a). 
     The diaphragm  18  can be brought closer to the sample  20  by thread cutting the center portion of the main body of the sample holding device  6  for the electron beam device (b). In consequence, it becomes possible to reduce the gas volume to inhibit the scatter of the electron beams and to conduct a higher resolution observation. 
     Only the upper diaphragm  18  can be moved by setting the lower diaphragm  18  to the center of the main body of the sample holding device  6  for the electron beam device with respect to the sample  20  and setting the upper diaphragm  18  to the diaphragm driving unit  27 . In consequence, it becomes possible to reduce the volume of the cell  19 , to restrict the gas volume and to conduct the higher resolution observation when the cell  19  is sealed by the diaphragm  18 . Exhaust of the cell  19  can be conducted in a short time after the reaction by moving the upper diaphragm  18  horizontally and releasing the cell  19 , and a high resolution observation immediately after the reaction and higher sensitivity EDX and EELS analyses can be conducted (c). 
       FIG. 6  illustrates an explanatory view of the case where the diaphragm  18  moves in the vertical direction. An O-ring  30  is fitted to the support  31  to which the diaphragm  18  is fixed, and isolates the inside of the cell  19  from outside. A specific driver  33  is used for the movement of the diaphragm  18 . A protruding portion formed on the specific driver  33  is fitted into and rotate a hole formed in the support  31 . Therefore, the support  31  having the diaphragm  18  fitted thereto is moved up and down. 
     A heating mechanism of the sample will be explained with reference to  FIG. 7 . 
       FIG. 7  illustrates a distal end sectional view (a- 1 , b- 1 ) of a sample holding device  6  for an electron beam device and its distal end top view (a- 2 , b- 2 ). A heater  34  is fixed by a screw  35  to the sample holding device  6  for the electron beam device inside the cell  19  of the sample holding device  6 . The heater  34  is connected to a heating power source  37  outside the electron beam device  1  through a lead wire  36 . The sample  20  is powder and adheres directly to the heater  34 . The gas is introduced through the gas inlet pipe  21   a  into the sealed cell  19  and a current is thereafter caused to flow through the heater  34 . As a result, the sample  20  is directly heated, the gas reaction takes place and its condition can be observed (a- 1 , a- 2 ). 
     The gas is exhausted while the current is allowed to flow through the heater  34 , the upper and lower diaphragms  18  are moved horizontally and the cell  19  is released. In this way, a high resolution observation of the sample  20  immediately after the reaction can be made inside the same visual field. Also, the EELS analysis can be made with high spatial resolution and with less influence of the diaphragm  18  when the analysis of a minute area is made by contracting the electron beams  25  (b- 1 , b- 2 ). 
     Evaporation to a heated sample will be explained with reference to  FIG. 8 . 
       FIG. 8  illustrates a distal end sectional view (a) of a sample holding device  6  for the electron beam device and its distal end top view (b) according to an embodiment. Another evaporation heater  34   b  for evaporating a different metal to the sample  20  is fixed by a screw  35   b  to the distal end portion of the sample holding device  6  for the electron beam device besides the sample  20  and the heater  34   a  for heating. The evaporation heater  34   b  is installed inside the cell  19  sealed by the diaphragm  18 . The evaporation heater  34   b  is connected to a lead wire  36   b  and is connected to a heating power source different from the power source for heating the sample  20  through the lead wires  36   b . A metal  38  for evaporation directly adheres to the evaporation heater  34   b . When the evaporation heater  34   b  is heated, the metal  38  for evaporation on the heater  34   b  is evaporated to the sample  20 . 
       FIG. 9  illustrates a distal end sectional view (a) of a sample holding device  6  for the electron beam device and its distal end top view (b) according to an embodiment. A sample  20   b  fixed to a grid having a diameter of about 3 mm or punched out into a disc having a diameter of about 3 mm is fitted to the distal end portion of the sample holding device  6  for the electron beam device besides the sample  20 , the heater  34   a  for heating and the evaporation heater  34   b . The sample  20   b  is fixed by a ring spring  32  inside the cell  19 . Consequently, the heater  34   a  for heating can be used also as the evaporation source, and a different kind of evaporation source can be evaporated to the sample  20   b . The sample  20   b  can be heated by utilizing radiation heat of the heater. 
       FIG. 10  illustrates a distal end sectional view (a) of a sample holding device  6  for the electron beam device and its distal end top view (b) according to an embodiment. A sample  20  fitted to the distal end portion of the sample holding device  6  for the electron beam device, and the heater  34  for heating can be connected to the heating power source  37  and a liquid nitrogen storage unit  39  through a lead wire  36 . A thermocouple  40  is arranged in the vicinity of the sample  20  to measure the temperature. The sample  20  is directly deposited to the heater  34 . The sample  20  and the heater  34  can be cooled when they are connected to the liquid nitrogen storage unit  39  through a cooling rod  29 . In this way, the reaction of the sample  20  can be observed over a wide temperature range. 
     An embodiment wherein a sample drift occurs owing to high temperature heating and cooling will be explained. 
       FIG. 11  is an explanatory view of the case where the sample is heated by using this embodiment. 
     When the sample holding device  6  for the electron beam device is set to the sample chamber  14  in the electron beam device  1 , the heater  34  receives the Lorentz force in the horizontal direction from the direction of the heating current because the magnetic field of the objective lens  4  extends in the vertical direction. 
       FIG. 12  illustrates a distal end top view of a sample holding device  6  for the electron beam device according to this embodiment. The diaphragm  18  of the sample holding device  6  for the electron beam device has an elliptic shape the major axis of which is coincident with the moving direction, or a rectangular shape. The moving direction of the heater  34  and the sample  20  during heating of the sample  20  is the horizontal direction from  FIG. 11 . Therefore, observation can be made smoothly without getting off from the visual field. 
       FIG. 13  illustrates a distal end sectional view (a) of a sample holding device  6  for the electron beam device and its distal end top view (b) according to an embodiment. A minute pressure gauge chip  41  is adapted to the main body of the sample holding device  6  for the electron beam device inside the cell  19  sealed by the diaphragm  18  and is connected to a pressure gauge  42  outside the electron beam device  1 . In consequence, the pressure inside the cell  19  sealed by the diaphragm  18  can be measured directly. 
       FIG. 14  illustrates an electron beam sample chamber  14  and a sample holding device  6  for the electron beam device according to an embodiment. The electron beam sample chamber  14  is disposed in the electron beam device  1  and has a structure such that the electron beams can pass through a central portion indicated by a center line. A minute pressure gauge chip  41   a  is adapted to the main body of the sample holding device  6  for the electron beam device inside the cell  19 . Moreover, another minute pressure gauge chip  41   b  is adapted to the main body of the sample holding device  6  for the electron beam device outside the cell  19 . The minute pressure gauge chip  41   b  is connected to a pressure gauge  42   b . Accordingly, the pressure inside the electron beam sample chamber  14  in the vicinity of outside of the cell  19  can be measured besides the internal pressure of the cell  19 . 
       FIG. 15  is an explanatory diagram for the use of the sample holding device  6  for the electron beam device in the embodiment illustrated in  FIG. 7 . 
     (1) The sample  20  is caused to adhere to the heating heater  34   a . A different kind of evaporation metal  38  is caused to adhere to the evaporation heater  34   b.    
     (2) The sample holding device  6  for the electron beam device is inserted into the electron beam sample chamber  14 . 
     (3) The sample  20  is observed under the state where the diaphragm  18  does not exist. If necessary, EDX analysis and EELS analysis is carried out. 
     (4) The cell  19  is sealed by the diaphragm  18 . A gas such as air is introduced and the pressure inside the cell  19  is set. When a possibility of the breakage of the diaphragm  18  due to a high pressure exists, the gas is introduced also to the outside of the cell  19 , that is to say, into the electron beam sample chamber  14 . 
     (5) The sample  20  is heated. The gas reaction of the sample with heating is observed and analyzed. 
     (6) Heating is stopped after the reaction. 
     (7) The diaphragm  18  is moved horizontally and the gas both inside and outside the cell  19  is exhausted. 
     (8) High resolution observation and analysis of the reaction product are conducted. 
     As described above, the reaction process in the gas atmosphere can be observed freely while the visual field of observation is kept without taking out the sample even once. 
     When the structures described above are combined, it becomes possible to precisely control the pressure inside the environmental cell, to observe the reaction process in a high pressure gas atmosphere or in a liquid, such as the crystal growing process by high temperature gas reaction, to observe the oxidation reduction reaction and organisms in a minute atmospheric space and to conduct high resolution observation and high sensitivity analysis immediately after the reaction in the high pressure gas atmosphere. 
     REFERENCE SIGNS LIST 
     
         
           1 : electron beam device 
           2 : electron gun 
           3 : condenser lens 
           4 : objective lens 
           5 : projection lens 
           6 : sample holding device for electron beam device 
           7 : fluorescent plate 
           8 : TV camera 
           9 : image display unit 
           10 : EELS detector 
           11 : EELS control unit 
           12 : EDX detector 
           13 : EDX control unit 
           14 : electron beam sample chamber 
           15 : observation chamber 
           16 : valve 
           17 : vacuum pump 
           18 : diaphragm 
           19 : cell 
           20 : sample 
           21 : gas inlet pipe 
           22 : gas exhaust pipe 
           23 : gas pressure control valve 
           24 : gas storage unit 
           25 : electron beam 
           26 : intermediate chamber 
           27 : diaphragm driving unit 
           28 : micrometer 
           29 : cooling rod 
           30 : O-ring 
           31 : support 
           32 : ring spring 
           33 : specific driver 
           34 : heater 
           35 : screw 
           36 : lead wire 
           37 : heating power source 
           38 : evaporation metal 
           39 : liquid nitrogen storage unit 
           40 : thermocouple 
           41 : minute pressure gauge chip 
           42 : pressure gauge