Abstract:
A processing apparatus uses a focused charged particle beam to process a micro sample that is supported on a micro mount part. The micro mount part is supported on a micro sample stage and locally cooled by a cooling unit. The micro mount part is thermally independent of the micro sample stage and, due to its small size, can be cooled rapidly by the cooling unit.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a processing apparatus which has a cooling sample stage allowing reduction of thermal drift and which uses a focused charged particle beam. 
   In recent years, in preparing a sample for an electronic microscope in order to observe a particular area such as observing a defective part of a semiconductor device, a method of using a charged particle beam is utilized. More specifically, a sample is processed in such ways that ions are accelerated, focused and applied onto a particular area of a device or the like to be an observation target and a desired slice is cut out, and that a sample is cut to provide desired depth or a shape in order to expose an observation part when an observation target exists inside. 
   When a sample to be an observation target is a material vulnerable to heat, it is necessary to process the sample while it is being cooled. In addition, charged particle beam irradiation often damages a sample, but it is reported that a sample is cooled to reduce damage caused by a charged particle beam. 
   At present, when a sample is cooled in a charged particle beam processing apparatus, a sample state is cooled for processing. Here, typically, when a sample is cooled, the entire sample stage is cooled. However, when the entire sample stage is cooled, problems arise that it takes a long time to stabilize the temperature of a sample, and that cooling the entire sample tends to generate a temperature gradient and thus a drift tends to occur caused by thermal expansion and contraction, causing highly accurate processing to be difficult. For the measures against the drift, there is a method in which the temperature of a sample is set to a desired temperature beforehand and the structure of the surface and the cross section and the information of the sample are acquired for accurate observation or processing. However, the equipment becomes in a large scale, and the method is not a convenient method for solving problems. 
   [Patent Reference 1] JP-A-2003-194746 
   The invention has been made in view of the circumstances. An object is to provide a processing apparatus which uses a focused charged particle beam and which can promptly cool a sample, reduce a thermal drift, suppress a position shift caused by thermal expansion and contraction, and improve processing accuracy. 
   SUMMARY OF THE INVENTION 
   A first aspect according to the invention is a processing apparatus using a focused charged particle beam characterized by including: a micro sample stage having a micro mount part on which a micro sample is placed, the micro sample is processed with the focused charged particle beam, wherein the micro mount part is thermally independent of the micro sample stage and has a cooling unit which cools the micro mount part. 
   In the first aspect, since the sample and the mount stage are minute, they can be cooled promptly. Since the contraction displacement caused by cooling is small, a thermal drift can be reduced to improve processing accuracy. 
   A second aspect according to the invention is the processing apparatus using the focused charged particle beam in the first aspect, characterized by including a sample stage on which a sample is placed, the sample is processed with the focused charged particle beam. 
   In the second aspect, since the micro sample stage and the sample stage are provided, the micro sample and the sample can be handled at the same time. 
   A third aspect according to the invention is the processing apparatus using the focused charged particle beam in the first or second aspect, characterized in that the micro sample is cut out of the sample. 
   In the third aspect, the micro sample can be cut out of any places in the sample in any size and any shapes, and it can be processed or observed while it is being cooled on the micro mount part. 
   A fourth aspect according to the invention is the processing apparatus using the focused charged particle beam in any one of the first to third aspects, characterized by including a micro sample stage which is formed of a material having a lower heat conduction than that of the micro mount part. 
   In the fourth aspect, the micro sample stage formed of the material having a lower heat conduction than that of the micro mount part is provided, and thus heat conduction from the micro sample and the micro mount part to the micro sample stage can be prevented to effectively cool only the micro sample and the micro mount part. 
   A fifth aspect according to the invention is the processing apparatus using the focused charged particle beam in the fourth aspect, characterized in that the cooling unit is an electronic cooling mechanism which cools by supplying electric power thereto. 
   In the fifth aspect, the micro mount part is cooled by small-sized electronic cooling mechanism, and thus the micro sample can be cooled promptly. 
   A sixth aspect according to the invention is the processing apparatus using the focused charged particle beam in the fourth aspect, characterized in that the cooling unit is a probe in which a cooling medium is filled and which is abutted against the micro mount part. 
   In the sixth aspect, the micro mount part is cooled by a fine tube or the probe which contains a cooling medium and has the sharp tip end, and thus the micro sample can be cooled promptly. 
   A seventh aspect according to the invention is the processing apparatus using the focused charged particle beam in the fourth aspect, characterized in that the cooling unit is a cooling tube which is disposed on the micro mount part and through which a cooling medium flows. 
   In the seventh aspect, the micro mount part is cooled by the cooling tube which contains the cooling medium, and thus the micro sample can be cooled promptly. 
   An eighth aspect according to the invention is a processing apparatus using a focused charged particle beam characterized by including: a top plate on which a sample is placed, the sample being processed with the focused charged particle beam; and a bottom plate which is disposed in parallel with the top plate, wherein a special mount stage is formed by connecting the top plate to the bottom plate with a connecting member, the special mount stage is supported by a special mount stage support which is formed of a material having a lower heat conduction than the special mount stage, one of the top plate and the bottom plate is fixed on a special mount stage support side, and the connecting member is cooled, whereby a cooling unit is provided which directs thermal contraction directions of the top plate and the bottom plate in directions opposite to each other. 
   In the eighth aspect, since the connecting member of the top plate to the bottom plate is cooled, thermal contraction is directed in the opposite directions in the top plate and the bottom plate, and the drift amount is reduced. In addition, since the sample is not required to be the cut out micro sample, the drift amount is reduced even though a sample is greater than the micro sample. 
   A ninth aspect according to the invention is the processing apparatus using the focused charged particle beam in the eighth aspect, characterized by including a sample stage on which the sample is placed, the sample is processed with the focused charged particle beam. 
   In the ninth aspect, since the special mount stage and the sample stage are provided, a plurality of the samples can be handled at the same time. 
   A tenth aspect according to the invention is the processing apparatus using the focused charged particle beam in the eighth or ninth aspect, characterized in that the cooling unit is an electronic cooling mechanism which cools by supplying electric power thereto. 
   In the tenth aspect, the connecting member is cooled by electronic cooling mechanism, and thus the sample can promptly cooled. 
   An eleventh aspect according to the invention is the processing apparatus using the focused charged particle beam in the eighth or ninth aspect, characterized in that the cooling unit is a probe in which a cooling medium is filled and which is abutted against the micro mount part. 
   In the eleventh aspect, the connecting member is cooled by a fine tube or the probe which contains a cooling medium and has the sharp tip end, and thus the micro sample can be cooled promptly. 
   A twelfth aspect according to the invention is the processing apparatus using the focused charged particle beam in the eighth or ninth aspect, characterized in that the cooling unit is a cooling tube which is disposed on the micro mount part and through which a cooling medium flows. 
   In the twelfth aspect, the micro mount part is cooled by the cooling tube which contains the cooling medium, and thus the micro sample can be cooled promptly. 
   A thirteenth aspect according to the invention is the processing apparatus using the focused charged particle beam in any one of the first to seventh aspects, characterized by including a sample stage holder on which the sample stage or the micro sample stage is detachably placed. 
   In the thirteenth aspect, the sample stage or the micro sample stage can be replaced. 
   A fourteenth aspect according to the invention is the processing apparatus using the focused charged particle beam in the fifth or seventh aspects, characterized by including a sample stage holder on which the micro sample stage having the sample stage or the cooling unit is detachably placed, wherein the sample stage holder is provided with a contact which is connected to the cooling unit to supply a cooling source. 
   In the fourteenth aspect, the micro sample stage or the sample stage can be replaced, and the cooling mechanism can be detached. 
   A fifteenth aspect according to the invention is the processing apparatus using the focused charged particle beam in any one of the eighth to twelfth aspects, characterized by including a sample stage holder on which the sample stage or the special mount part support is detachably placed. 
   In the fifteenth aspect, the special mount part support or the sample stage can be replaced. 
   A sixteenth aspect according to the invention is the processing apparatus using the focused charged particle beam in the tenth or twelfth aspect, characterized by including a sample stage holder on which the micro sample stage having the sample stage or the cooling unit is detachably placed, wherein the sample stage holder is provided with a contact which is connected to the cooling unit to supply a cooling source. 
   In the sixteenth aspect, the micro sample stage or the sample stage can be replaced, and the cooling mechanism can be detached. 
   ADVANTAGE OF THE INVENTION 
   The processing apparatus using the focused charged particle beam according to the invention can promptly cool the sample and can relax a thermal drift by the special mount stage which can reduce the sample and the sample mount part in size and can reduce the position change of the mount stage caused by thermal expansion and contraction. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view depicting the micro sample stage and the sample stage of the processing apparatus using the focused charged particle beam according to the first embodiment of the invention. 
       FIG. 2  is a perspective view depicting the micro sample stage and the sample stage of the processing apparatus using the focused charged particle beam according to the first embodiment of the invention. 
       FIG. 3  is a perspective view depicting the micro sample stage and the sample stage of the processing apparatus using the focused charged particle beam according to the first embodiment of the invention. 
       FIG. 4  is a perspective view depicting the special mount stage and the special mount stage support of the processing apparatus using the focused charged particle beam according to the second embodiment of the invention. 
       FIG. 5  is a diagram illustrative of the special mount stage and the special mount stage support of the processing apparatus using the focused charged particle beam according to the second embodiment of the invention. 
       FIG. 6  is a perspective view depicting the case in which the special mount stage and the special mount stage support of the processing apparatus using the focused charged particle beam according to the second embodiment is placed on the micro sample stage according to the first embodiment of the invention. 
       FIG. 7  is a perspective view depicting the movable sample stage of the processing apparatus using the focused charged particle beam according to the third embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Embodiments of the invention will be described in detail with reference to the drawings. 
   First Embodiment 
     FIGS. 1 to 3  show the detail of a micro sample stage and a sample stage of a processing apparatus using a focused charged particle beam according to a first embodiment of the invention. The first embodiment is an exemplary implementation provided with the micro sample stage and the sample stage. 
     FIG. 1  shows the case in which an electronic cooling mechanism is used for a cooling unit.  FIG. 2  shows the case in which a probe filled with a cooling medium is used for a cooling unit.  FIG. 3  shows the case in which a cooling tube containing a cooling medium is used for a cooling unit. 
   As shown in  FIGS. 1 to 3 , the processing apparatus using the focused charged particle beam according to the embodiment is provided with a sample  1  which is processed with a focused charged particle beam, and a sample stage  2  on which the sample  1  is placed. A micro sample  3  which is cut out of the sample  1  with the focused charged particle beam is placed on a micro mount part  4 . The micro mount part  4  is provided on a micro sample stage  5 . The micro sample stage  5  is supported by the sample stage  2  or provided beside the sample stage  2 . The combination of the micro mount part  4  and the sample stage  5  is smaller than the sample stage  1 . The micro mount part  4  is formed of a material having a lower heat conduction than that of the micro sample stage  5 , and is thermally independent of the micro sample stage  5 . Thus, the micro mount part  4  is cooled separately from the micro sample stage  5 , and the cooling effect can be prevented from running off to the micro sample stage  5  which is adjacent to the micro mount part  4 . Therefore, the sample mount part  4  is cooled by a cooling unit (any one of an electronic cooling mechanism  6 , a fine tube or a probe  7 , and a cooling tube  8 ), and thus only the micro mount part  4  is cooled with no reduction in the cooling effect due to heat conduction to the other members. The micro sample  3  is a micro piece which is cut out of the sample  1 . Therefore, the sample itself is minute, and has small expansion and contraction caused by heating and cooling. Therefore, a reduction in processing accuracy caused by a thermal drift can be prevented. In addition, the micro mount part  4  on which the micro sample  3  being a micro piece is placed is significantly small as well. Therefore, only the micro mount part  4  can be cooled which is very small and thermally independent of the micro sample stage  5 , and thus the micro sample  3  is cooled promptly. 
   The micro sample stage  5  according to the embodiment is supported by the sample stage  2 , but they may be independent separately. In addition, in the embodiment, the micro sample  3  is considered to be cut out of the sample  1 , but it may not be cut out as long as it can be placed on the micro mount stage  4 . Alternatively, the sample  1  is not necessarily placed on the sample stage  2 . 
   For the example of the sample cooling unit, as shown in  FIGS. 1 to 3 , the following is named: the electronic cooling mechanism  6 , the fine tube or the probe  7  which is abutted against the micro mount stage  4 , and the cooling tube  8  which is disposed on the micro mount stage  4  and through which the cooling medium flows. For an example of the electronic cooling mechanism, a Peltier element and the like are named, and for the cooling medium filled in the probe  7  or the cooling tube  8 , liquid nitrogen and the like are named. The cooling unit, the electron cooling mechanism, and the coolant are not limited to the units and the materials described above, and other units and materials may be used. 
   Second Embodiment 
     FIGS. 4 to 5  show the detail of a special mount stage and a special mount stage support of a processing apparatus using a focused charged particle beam according to a second embodiment of the invention. The second embodiment is an exemplary implementation provided with the special mount stage and the special mount stage support. 
     FIG. 4  shows a perspective view depicting the special mount stage and the special mount stage support, and  FIG. 5  shows a diagram illustrative of the special mount stage and the special mount stage support. 
   As shown in  FIGS. 4 to 5 , the processing apparatus using the focused charged particle beam according to the embodiment is provided with a special mount stage  11  on which a sample  1  processed with a focused charged particle beam is placed, and a special mount stage support  12  in an L-shape which supports the special mount stage  11 . The special mount stage  11  is configured of a top plate  13  on which the sample is directly placed, a bottom plate  14  which is in parallel with the top plate  13 , and a connecting member  15  which connects one end of the top plate  13  and the bottom plate  14  to each other. An end part  14   a  of the bottom plate  14  on the opposite side of the connecting member  15  is fixed to a vertical wall part  12   a  in an L-shape. In addition, an end part  13   a  of the top plate  13  on the opposite side of the connecting member  15  is not fixed to the vertical wall part  12   a  in an L-shape, which is in a free state. The special mount stage support  12  is formed of a material having a lower heat conductivity than that of the special mount stage  11 , and the special mount stage  11  is thermally independent of the special mount stage support  12 . The connecting member  15  is abutted against a cooling unit. Therefore, the special mount stage  11  is cooled by the cooling unit, and thus only the special mount stage  11  is cooled with no reduction in the cooling effect caused by heat conduction to the other members. For the cooling unit, the same means as similar to that of the first embodiment, and the connecting member  15  is cooled by the cooling mechanism. Since one of the end parts of the top plate  13  or the bottom plate  14  of the special mount stage  11  is fixed to the special mount stage support  12  (in the exemplary implementation, the end part on the bottom plate side), the connecting member is cooled to direct the thermal contraction directions of the top plate  13  and the bottom plate  14  opposite to each other as shown in arrows in the drawing. More specifically, since the end part on the bottom plate  14  side is fixed to the special mount stage support  12 , the bottom plate  14  shrinks in the right direction in the drawing, and the top plate  13  shrinks in the left direction in the drawing. Therefore, even though the sample is not minute as in the first embodiment, a drift caused by thermal contraction can be relaxed, and a reduction in processing accuracy can be prevented. 
   Third Embodiment 
     FIG. 6  relates to a third embodiment according to the invention, which shows a perspective view depicting a micro sample stage and a sample stage in which the special mount stage and the special mount stage support according to the second embodiment are disposed on the micro sample stage according to the first embodiment of the invention. The third embodiment is an exemplary implementation provided with the special mount stage and the special mount stage support on the sample stage. 
   As shown in  FIG. 6 , the embodiment shows an example that the special mount stage support  12  shown in  FIGS. 4 to 5  is supported by the micro sample stage  5  according to the first embodiment. A sample  1  is placed on a sample stage  2 , a micro sample stage  5  is supported by the sample stage  2 , and a special mount stage support  12 , a special mount stage  11  and a micro sample  3  are supported by the micro sample stage  5 . Since the sample itself is minute, a drift caused by thermal contraction is small, and a drift is further relaxed by the structure of the special mount stage  11  and the special mount stage support  12 . The effect of preventing a reduction in processing accuracy can be more improved. The special mount stage support  12  and the special mount stage  11  supported by the micro sample stage  5  are also minute, and the connecting member  15  configuring the special mount stage  11  (see  FIGS. 4 and 5 ) can be cooled promptly. 
   Also in the embodiment, the micro sample stage  5  is supported by the sample stage  2 , but they may be independent separately. In addition, in the embodiment, the micro sample  3  may not be cut out of the sample  1 , and the sample  1  is not necessarily placed on the sample stage  2 . 
   Fourth Embodiment 
     FIG. 7  shows a perspective view depicting a movable sample stage of a processing apparatus using a focused charged particle beam according to a fourth embodiment of the invention. The fourth embodiment is an example that the sample stage  2  according to the first embodiment is placed on a movable sample stage  31 , and the sample stage  2  is provided with the micro sample stage  5  having the electronic cooling mechanism  6  shown in  FIG. 1 . 
   As shown in the drawing, the movable sample stage  31  is provided with a base plate  32  which is a component on the apparatus main body side and which holds a sample stage  2  and a micro sample stage  5  formed in one piece with the sample stage  2  (hereinafter, called a sample stage  2 ) and moves them in reciprocating motion in the directions (indicated by arrows in the drawing). The sample stage  2  is formed detachably on one end side with respect to the base plate  32  (on the right side in the drawing). 
   Thus, the sample stage  2  can be replaced separately with respect to the apparatus main body side. 
   A contact  33  is integrally disposed on the other end side of the base plate  32  (on the left side in the drawing), and a power source connecting part  35  is disposed on the contact  33 . To the power source connecting part  35 , electric power is supplied from a power source  34 . 
   The sample stage  2  is slidably held on the base plate  32 . Thus, a power source connecting part (not shown) of the electronic cooling mechanism  6  is connected to the power source connecting part  35  at a predetermined slide position, and electric power from the power source  34  is supplied to the electronic cooling mechanism  6 . Therefore, it is unnecessary that the sample stage  2  itself is provided with an electric power supply source. Thus, the configuration of the sample stage  2  can be simplified as well as the sample stage  2  can be replaced easily. 
   In addition, in  FIG. 7 , the movable sample stage  31  is taken and described as an example which holds the sample stage  2  shown in  FIG. 1 , but the sample stage  2  shown in  FIG. 3 , that is, the sample stage  2  integrally formed with the micro sample stage  5  having the cooling tube  8  may be adapted as well. In this case, to the contact  33 , instead of the power source connecting part  35 , a liquid nitrogen supply port is provided which is connected to the cooling tube  8 , and a passage from an external supply source is connected to the liquid nitrogen supply port. 
   In addition, a device having the special sample stage  11  shown in  FIGS. 4 and 5  may be detachable with respect to the base plate  32 . In this case, when the electronic cooling mechanism is adapted as the cooling unit, the contact  33  having the power source connecting part  35  shown in  FIG. 7  is used. When the cooling tube through which liquid nitrogen flows is adapted, the contact having the liquid nitrogen supply port is used. Furthermore, the sample stage  2  shown in  FIG. 6  may be detachable with respect to the base plate  32 , which can be also used for the sample stage with no cooling mechanism. 
   The invention can be used in the industrial fields of the processing apparatus using the focused charged particle beam having the cooling mechanism which can promptly cool a sample can relax a thermal drift.