Abstract:
The objective of the present invention is to maintain the surrounding of a sample at atmospheric pressure and efficiently detect secondary electrons. In a sample chamber of a charged particle device, a sample holder ( 4 ) has: a gas introduction pipe and a gas evacuation pipe for controlling the vicinity of a sample ( 20 ) to be an atmospheric pressure environment; a charged particle passage hole ( 18 ) and a micro-orifice ( 18 ) enabling detection of secondary electrons ( 15 ) emitted from the sample ( 20 ), co-located above the sample ( 20 ); and a charged particle passage hole ( 19 ) with a hole diameter larger than the micro-orifice ( 18 ) above the sample ( 20 ) so as to be capable of actively evacuating gas during gas introduction.

Description:
TECHNICAL FIELD 
     The present invention relates to an environmental control charged particle observation system. The system is used, in observation of a sample with a charged particle device e.g. an electron microscope, for efficiently detecting secondary electrons generated from the sample and performing efficient heating-observation on the sample while controlling the pressure in the vicinity of the sample. Accordingly, in analysis of degradation process in a recent fuel cell or the like, it is greatly useful for observation of dynamic change of the structure upon gas introduction and heating, by coordinating the observation environment of the electron microscope with actual operational environment. 
     BACKGROUND ART 
     In a charged particle device e.g. an electron microscope, in observation of a sample using a transmission electron image or a secondary electron image, in the field of electron microscope, observation is basically performed in a state where high-vacuum environment is maintained in the vicinity of the sample, in accordance with kind of charged particles to be detected for observation. However, in recent years, it is necessary to observe the sample in an actual operational environment. For example, when the dynamic change of the sample is observed while the sample is heated, a technique of performing observation in a state where the surrounding of the sample is in a low-vacuum state while introducing gas is being established. At this time, it is necessary that the charged particle device does not adversely affect the electron gun. There is a large limit on maintenance of the pressure in the vicinity of the sample at the actual operational environment, i.e. so-called atmospheric pressure. It is necessary to provide a holder for loading the sample with a structure for this purpose. 
     For example, in observation of the sample, a structure to isolate only the surrounding of the sample, using a thin film which charged particles pass through such as a diaphragm, above and below the sample, to attain atmospheric pressure in the vicinity of the sample, is known (Japanese Unexamined Patent Application Publication No. 2011-175809). 
     Further, there is a sample heating holder with a gas introduction mechanism, for observing the dynamic change of the sample when heated while controlling the pressure by blowing arbitrarily selected gas to the sample while heating the sample (Japanese Unexamined Patent Application Publication No. 2008-108429). 
     CITATION LIST 
     Patent Literature 
     
         
         Patent literature 1: Japanese Unexamined Patent Application Publication No. 2011-175809 
         Patent literature 2: Japanese Unexamined Patent Application Publication No. 2008-108429 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     The above-described techniques are particularly concerned with observation using a transmission electron image. There has not been any technique of simultaneous observation of the transmission electron image and secondary electron image. Since only the surrounding of the sample is maintained at atmospheric pressure, the secondary electrons are blocked with the diaphragms and the secondary electrons cannot be detected. 
     Accordingly, to detect secondary electrons and perform observation using them, a holder, provided with a secondary electron detection passage above a sample using a minute orifice, and a coil heater for heating the sample via the orifice on a charged particle passage, is to be contrived and proposed. It is possible to observe dynamic change of the sample with detection of secondary electrons by controlling the pressure in the vicinity of the sample and heating the sample by introduction of gas. 
     That is, the present invention has an object to maintain the surrounding of a sample at atmospheric pressure and efficiently detect secondary electrons. 
     Solution to Problem 
     To attain the above object, the present invention adopts the configuration in the claims. 
     For example, one of the features is to enable pressure control in the vicinity of the sample and to efficiently detect secondary electrons, to observe dynamic change of the sample. Further, in control of the pressure in the vicinity of the sample, it is a sample holder having a differential exhaust hole to avoid advertise effect on the electron gun of the charged particle device e.g. electron microscope. The holder has a minute orifice as a secondary electron passage. It is provided with a gas introduction nozzle and a minute vacuum gauge for control of the pressure in the vicinity of the sample. Further, it has a heater for heating the sample. 
     Further, to maintain the surrounding of the sample in the atmospheric pressure environment, it is necessary to isolate only the surrounding of the sample from a sample chamber of the charged particle device and perform gas introduction. At this time, a diaphragm is used in the charged particle passage for observation of the sample. Although the charged particles pass through the diaphragm, detection of the secondary electrons is impossible, which adversely affects the observation. Regarding this problem, in the present invention, for example, when the sample holder is used, a minute orifice is provided above the sample, while a diaphragm is provided below the sample, with respect to the charged particle passage. With this configuration, the surrounding of the sample is maintained in the atmospheric pressure environment. Further, observation using secondary electrons is possible, thus the problem is solved. 
     Note that when the sample holder is used, since the minute orifice for the secondary electron passage is also used as an exhaust hole upon gas introduction, when it is overlapped with a passage hole for charged particles generated from the electron gun of the charged particle device e.g. an electron microscope, adverse effect such as degradation of the electron gun might occur. On the other hand, in the present invention, for example, by shifting the position of the charged particle passage hole from the minute orifice provided in the sample holder, the gas exhausted from the minute orifice is not directly exhausted to the electron gun, thus the problem is solved. Otherwise, when a larger exhaust hole is provided on the opposite side to the minute orifice of the sample holder, the gas is exhausted from the larger exhaust hole. Even this configuration, where the charged particle passage hole and the minute orifice are provided coaxially, does not adversely affect the electron gun. Thus the problem is solved. 
     Advantageous Effects of Invention 
     With the present invention, it is possible to observe dynamic change using secondary electrons while controlling the pressure in the vicinity of a desired sample. Further, since it is possible to perform observation while heating the sample, the invention greatly contributes to research of degradation process in the field of fuel cell. Further, it is possible to load, in addition to a powder sample, a micro sample formed with the charged particle device e.g. a focused ion beam processing observation device, in the sample holder according to the present invention. Accordingly, it is possible to greatly reduce working time from process to observation by enabling all the series of work steps from process to observation with one holder, which contributes to rapid advancement of researches in various fields. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic diagram of a charged particle device sample chamber and a sample holder according to an embodiment of the present invention, showing the positional relationship among charged particles in a charged particle device sample chamber for observation, a charged particle passage provided in the sample holder, and a sample. 
         FIG. 2  shows the positional relationship between secondary electrons, emanated from the tip of the sample holder and from the sample, and a secondary electron detector, according to an embodiment of the present invention. 
         FIG. 3  shows a cross-sectional diagram of the tip of the sample holder according to an embodiment of the present invention. 
         FIG. 4  shows a bird&#39;s-eye view of the tip of the sample holder according to an embodiment of the present invention. 
         FIG. 5  is a schematic diagram of the charged particle device and the sample holder according to an embodiment of the present invention, showing the positional relationship among the charged particles in the charged particle device sample chamber for observation, the charged particle passage provided in the sample holder, and the sample. 
         FIG. 6  shows a cross-sectional diagram of the tip of the sample holder according to an embodiment of the present invention. 
         FIG. 7  shows a development view of the tip of the sample holder according to an embodiment of the present invention. 
         FIG. 8  shows a development view of the tip of the sample holder according to an embodiment of the present invention. 
         FIG. 9  shows the positional relationship between the tip of the sample holder and the charged particles, according to an embodiment of the present invention. 
         FIGS. 10A and 10B  show cross-sectional diagrams of the tip of the sample holder according to an embodiment of the present invention:  FIG. 10A  is a diagram where a diaphragm is provided above the sample at the tip of the sample holder;  FIG. 10B  is a diagram where the diaphragm is provided below the sample at the tip of the sample holder. 
         FIG. 11  is a schematic diagram of a cap at the tip of the sample holder according to an embodiment of the present invention. 
         FIGS. 12 a   - 12 C are explanatory diagrams schematizing a series of operations from manufacture to observation of the sample at the tip of the sample holder according to an embodiment of the present invention:  FIG. 12A  is a bird&#39;s-eye view of the tip of the sample holder schematically showing sample loading by microsampling;  FIG. 12B  is a bird&#39;s-eye view of the tip of the sample holder schematically showing thin film processing on the sample; and  FIG. 12C  is a cross-sectional diagram of the tip of the sample holder schematically showing observation. 
         FIG. 13  shows an embodiment of sample observation according to the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
       FIG. 1  shows a basic conceptual diagram of the present invention. With respect to a sample holder tip cap  3  to block only the sample holder  4  provided in a charged particle device sample chamber  2  and the surrounding of the sample  20 , the sample holder tip cap  3  is provided with a charged particle passage hole (micro orifice)  18  through which charged particles A 1  pass, to enable observation of charged particles. The charged particle device sample chamber  2  is maintained in a high vacuum state with a vacuum pump  5  and a valve  6 . The sample holder  4  has a gas introduction pipe  26  and a gas exhaust pipe  25  to vary the pressure in the vicinity of the sample  20 . It has a structure to supply gas from a gas storage unit  10  via the gas pressure control valve  6  to control a flow rate upon gas introduction, and to exhaust the gas with the exhaust vacuum pump  5  and the valve  6 . Further, a pressure gauge  11  to detect the pressure in the vicinity of the sample  20  is connected to the sample holder  4 . Further, the sample holder  4  is provided with a heater  16  to heat the sample  20 . A sample-heating temperature control unit  12  to control the temperature of the heater  16  is connected to the sample holder. 
       FIG. 2  shows a conceptual diagram of a detailed structure of the tip of the sample holder  4  described in  FIG. 1 . The sample holder  4  is provided with an O-ring  21  to atmospherically block only the surrounding of the sample  20  with the sample holder tip cap  3 . Further, it has a sample holder tip cap fixing screw  22  to fix the sample holder tip cap  3 . In the sample holder tip cap  3 , the charged particle passage hole (micro orifice)  18  through which the charged particles A 1  pass is provided in positions above and below the sample  20 . The charged particle passage hole (micro orifice)  18  above the sample  20  has a hole diameter to pass secondary electrons  15  emanated from the sample  20 . It is possible to perform image observation with an image display unit  14  via secondary electron detector  13 . 
       FIG. 13  shows an observation example at this time. In  FIG. 13 , an observation image with the secondary electrons  15  and an observation image with transmission electrons are contrasted with each other. It is possible to enable surface observation using the secondary electron image in addition to observation of inner structure of material using the transmission image upon in situ observation of structural change of the sample, as a new in situ observation technique. Further, the sample holder  4  is provided with the heater  16  in which the sample  20  is loaded, and has a screw to fix the heater  16 . To enhance exhaust capacity, a charged particle passage and gas exhaust hole  19  below the sample  20  has a hole diameter larger than that of the charged particle passage hole (micro orifice)  18  above the sample  20 . With this configuration, the gas exhausted upon gas introduction is exhausted in a direction lower than an occurrence direction of the charged particles A 1 . Accordingly, a structure not to influence the electron gun of the charged particle source  28  e.g. an electron microscope is obtained. 
       FIG. 5  shows a basic conceptual diagram of the present invention. With respect to the sample holder tip cap  3  to block only the sample holder  4  provided in the charged particle device sample chamber  2  and the surrounding of the sample  20 , the sample holder tip cap  3  is provided with the charged particle passage hole (micro orifice)  18  through which the charged particles A 1  pass, to enable observation of charged particles. At this time, in the sample holder tip cap  3 , the charged particle passage hole (micro orifice)  18  through which the charged particles A 1  pass is provided above the sample  20 , and below the sample  20 , a diaphragm  32  separates the surrounding of the sample  20  from the charged particle device sample chamber  2  for passing the charged particles A 1 . Further, the charged particle passage hole (micro orifice)  18  provided above the sample  20  at the sample holder tip cap  3  is provided in a position not coaxial with a charged particle passage and gas exhaust hole  31  for charged particles emanated from the charged particle source  28 . Accordingly, the gas exhausted from the charged particle passage hole (micro orifice)  18  positioned above the sample  20  at the sample holder tip cap  3  is injected in a direction different from the occurrence direction of the charged particles A 1 . Thus a structure not to influence the electron gun of the charged particle source  28  e.g. an electron microscope is obtained. Further, constituent elements of the charged particle device sample chamber  2  and the sample holder  4  are the same as those in  FIG. 1 . 
     First Embodiment 
       FIG. 3  shows an embodiment of the present invention, and shows the tip of the sample holder  4  described in  FIG. 1  in detail. As in the case of  FIG. 2 , the sample holder  4  is provided with the O-ring  21  to atmospherically block only the surrounding of the sample  20  with the sample holder tip cap  3 . Further, it has the sample holder tip cap fixing screw  22  to fix the sample holder tip cap  3 . In the sample holder tip cap  3 , the charged particle passage hole (micro orifice)  18  through which the charged particles A 1  pass is provided in the positions above and below the sample  20 . The charged particle passage hole (micro orifice)  18  above the sample  20  has a hole diameter to pass the secondary electrons  15  emanated from the sample  20 . It is possible to enable image observation with the image display unit  14  via the secondary electron detector  13 . Further, in addition to the charged particle passage and gas exhaust hole  19  below the sample  20 , a structure to positively perform differential exhaust in a direction different from the direction of generation source of the charge particles A 1  by providing a gas exhaust hole  23  is provided. With this configuration, the gas exhausted upon gas introduction is exhausted in a direction lower than the occurrence direction of the charged particles A 1 , which does not influence the electron gun of the charged particle source  28  e.g. an electron microscope. 
     Second Embodiment 
       FIG. 4  shows an embodiment of the present invention and is a detailed diagram of the tip of the sample holder  4 . The sample holder  4  is provided with the heater  16  for loading the sample  20 , and the sample  20  is loaded there. Further, it has a structure provided with the gas introduction pipe  26  and the gas exhaust pipe  25  directed to the sample  20 , and has a minute pressure measuring element  24  to detect the pressure in the vicinity of the sample  20 . 
     Third Embodiment 
       FIG. 6  shows an embodiment of the present invention and shows the tip of the sample holder  4  described in  FIG. 5  in detail. 
     Fourth Embodiment 
       FIG. 10  shows an embodiment of the present invention, and shows an example where the positions of the diaphragm  32  and the charged particle passage and gas exhaust hole  19  corresponding to the charged particles A 1  passages above and below the sample  20  at the tip of the sample holder  4  described in  FIG. 6  are reversed in accordance with purpose. For example, in the case of observation using transmission electrons, to avoid trouble of the charged particle source  28  due to exhaust from the charged particle passage and gas exhaust hole  19 , the sample holder tip cap  3  is provided as shown in  FIG. 10 -( a ). In the case of observation using the secondary electrons  15 , the sample holder tip cap  3  is provided, with the arrangement relationship in  FIG. 5  as a condition, as shown in  FIG. 10 -( b ). 
     Fifth Embodiment 
       FIG. 11  shows an embodiment of the present invention. It has a structure changeable by a user in accordance with a pressure condition in the vicinity of the sample  20 , by preparing plural sample holder tip caps  3  to be attached to the tip of the sample holder  4  having different hole diameters of the charged particle passage and gas exhaust hole  19 . 
     Sixth Embodiment 
       FIG. 12  shows an embodiment of the present invention. The sample holder  4  has a structure provided with a notch in an emission direction of charged particles B 35  e.g. focused ion beam for loading the micro sample  20  manufactured by microsampling with the charged particle device e.g. a focused ion beam process device. With this structure, it is possible to enable thin film processing on the sample  20  with the charged particles B 35  e.g. a focused ion beam. Further, in the structure, the sample holder tip cap  3  is attached, and in addition, the direction of the sample  20  is rotated at 90°, for observation of the thin-film processed sample  20  with the charged particle device e.g. an electron microscope different from the aforementioned device. 
     REFERENCE SIGNS LIST 
     
         
           1  charged particles A 
           2  charged particle device sample chamber 
           3  sample holder tip cap 
           4  sample holder 
           5  vacuum pump 
           6  valve 
           7  gas pressure control valve 
           8  micro-pressure measurement element connector 
           9  sample heating connector 
           10  gas storage unit 
           11  pressure gauge 
           12  sample-heating temperature control unit 
           13  secondary electron detector 
           14  image display unit 
           15  secondary electrons 
           16  heater (sample loading portion) 
           17  heater fixing screw 
           18  charged particle passage hole (micro orifice) 
           19  charged particle passage and gas exhaust hole 
           20  sample 
           21  O-ring 
           22  sample holder tip cap fixing screw 
           23  gas exhaust hole 
           24  minute pressure measuring element 
           25  gas exhaust pipe 
           26  gas introduction pipe 
           27  sample holder tip cap fixing screw hole 
           28  charged particle source 
           29  condenser lens A 
           30  condenser lens B 
           31  charged particle passage and gas exhaust hole 
           32  diaphragm 
           33  sample holder tip cap storage box 
           34  microprobe 
           35  charged particles B