Abstract:
An evacuation use sample chamber is constituted by a top table  21  which is provided with a recessed portion disposed in a sample chamber main body  10  and for mounting a sample  8  and a groove portion surrounding the recessed portion; a stage  20  which holds the top table  21  and is displaceable in front and back, right and left and up and down directions together with the top table  21 ; a sample chamber cover  11  which covers above the sample chamber main body  10  including the top table  21 ; and an evacuation use pipe  21 C which communicates with the groove portion and evacuates gas between the bottom face of the sample chamber cover  11  and the top face of the top table  21  including the sample  8 . Thereby, an evacuation use sample chamber which performs a stable evacuation and keeps around a sample at a predetermined high vacuum and a circuit pattern forming apparatus which permits a highly accurate pattern drawing over the entire region of the sample are provided.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a sample chamber which is maintained in high vacuum around a sample through evacuation therefrom and a circuit pattern forming apparatus using the same.  
           [0003]    2. Conventional Art  
           [0004]    In an apparatus which forms or inspects circuit patterns such as for a semiconductor device and a magnetic head and circuit patterns such as masks and reticles for forming circuit patterns for a semiconductor device, these circuit patterns are formed and inspected through irradiation of charged particles onto samples. In such instance, it is unavoidable that the charged particles, in particular electron beams have to be used in vacuum. For this reason, the circuit pattern formation and inspection is performed while placing samples in a gas evacuated vacuum chamber.  
           [0005]    Hereinbelow, an electron beam pattern drawing apparatus which draws a circuit pattern on a sample by making use of electron beams will be explained taking up as an example.  
           [0006]    An electron beam pattern drawing apparatus is one in which through generation of electron beams under a super high vacuum environment and scanning therewith LSI patterns are formed on a semiconductor substrate or a glass substrate called as a mask which is used for an exposure apparatus such as a stepper.  
           [0007]    [0007]FIG. 12 shows a structure of a conventional electron beam pattern drawing apparatus. As shown in FIG. 12, electron beams  3  emitted from an electron gun  2  in a column  1  are shaped into a rectangular shape by a diaphragm  4  and a shaping deflector  5 , and are image-formed on a desired position of a sample  8  by an electron lens  6  and a deflector  7 . The sample  8  is fixed on an XY stage  9  through a sample holder or directly.  
           [0008]    The position of the sample  8  on the XY stage  9  is managed by measuring the distance between a bar mirror  13  and a laser interference meter  12 , and through feed forwarding the obtained information to the deflector  7  a highly accurate circuit pattern can be formed. Inside of a sample chamber  10  is kept in a high vacuum environment to thereby prevent energy loss of the electron beams  3 .  
           [0009]    Now, a transportation route of the sample  8  will be explained.  
           [0010]    The sample  8  is transported by a transportation device  16  in a load chamber  14  located adjacent to the sample chamber  10  from external in atmospheric circumstance into the load chamber  14 , which is preliminarily gas-evacuated from atmospheric state into vacuum state. When the vacuum in the load chamber  14  reaches at the same level as that in sample chamber  10 , a valve  15  is opened and the sample  8  is transported onto the XY stage  9 . After completing pattern drawing, a reverse route is traced, in that inside of the load chamber  14  is returned from vacuum into atmospheric circumstance and thereafter, the sample  8  is transported into outside. With the above series of operations, the transportation of the sample can be carried out while keeping the sample chamber  10  in vacuum state, thereby, an improvement of throughput is achieved.  
           [0011]    During drawing of a circuit pattern by an electron beam pattern drawing apparatus, it is necessary to keep the electron beam passage in high vacuum so as to prevent energy loss of the electron beams as has been referred to above, however, there were the following problems in conventional apparatuses.  
           [0012]    (1) It was required to evacuate the entire sample chamber in high vacuum, therefore, a vacuum pump of high performance as well as large capacity was indispensable.  
           [0013]    (2) Once the inside of the sample chamber was placed in atmospheric circumstance due to such as maintenance and failure thereof, it took a few hours to restore the circumstance into high vacuum which reduced available time of the apparatus.  
           [0014]    (3) In order to keep the inside of the sample chamber in high vacuum, parts used inside the sample chamber were restricted to inactive materials and, in particular, many kinds of resins and lubricants could not be used.  
           [0015]    (4) Mechanism which use gas such as air could not be mounted in the sample chamber.  
           [0016]    In order to overcome the above problems, until now apparatuses which keep around the passage of the electron beams and a part of the stage in vacuum state are, for example, disclosed in JP-A-1-128525 (1989), JP-A-8-17709 (1996) and JP-B-3-23631 (1991). These apparatuses are provided with a flange  60  which includes a function of vacuum evacuation at the bottom face of the column  1  as shown in FIG. 13 and perform differential evacuation while managing the gap between the sample  8  and the flange  60 .  
           [0017]    In the flange  60  apertures  60 A for vacuum evacuation are formed which permits differential evacuation with the circumference of the stage  9 .  
           [0018]    However, in the apparatuses as disclosed such as in JP-A-1-128525 (1989), JP-A-8-17709 (1996) and JP-B-3-23631 (1991), although it is possible to keep the electron beam passage in vacuum upto the sample  8  regardless to the atmosphere of the stage  9 , a pressure difference due to a local differential evacuation is caused on the sample  8 . Accordingly, at a top table  21  the region of the pressure difference varies in accordance with the displacement of the sample  8  which possibly causes attitude change of the top table  21  and deformation thereof.  
           [0019]    Further, when performing pattern drawing (exposure, inspection) over the entire surface of a sample, because of the existence of a gap between edges of the sample  8  and a sample holding mechanism or the top table  21 , amount of gas which flows in through the gap increases which makes difficult to obtain a stable vacuum. Namely, in order to keep a stable differential evacuation condition it is necessary to prevent the apertures  60 A from protruding beyond the outer circumference of the sample  8  as shown in FIG. 13. As a result, in a range of distance R from outer circumference of the sample  8  toward the center thereof a pattern drawing can not be performed, thereby, a possible pattern drawing range around the outer circumference of the sample is wasted and a yielding of the sample  8  with regard to pattern drawing range is reduced.  
         SUMMARY OF THE INVENTION  
         [0020]    An object of the present invention is to provide an evacuation use sample chamber which performs a stable evacuation and keeps around a sample at a predetermined high vacuum and a circuit pattern forming apparatus which permits a highly accurate pattern drawing over the entire region of the sample.  
           [0021]    In order to achieve the above object, an evacuation use sample chamber according to the present invention is characterized, in that the evacuation use sample chamber is constituted by a table which is provided with a recessed portion disposed in a sample chamber main body and for mounting a sample and a groove portion surrounding the recessed portion; a stage which holds the table and is displaceable in front and back, right and left and up and down directions together with the table; a sample chamber cover which covers above the sample chamber main body including the table; and an evacuation use pipe which communicates with the groove portion and evacuates gas between the bottom face of the sample chamber cover and the top face of the table including the sample.  
           [0022]    More specifically, the present invention provides the following sample chamber and device.  
           [0023]    The present invention provides an evacuation use sample chamber which is characterized by comprising, a sample chamber main body; a table which is provided with a recessed portion disposed in the sample chamber main body and for mounting a sample and a groove portion surrounding the recessed portion; a stage which holds the table and is displaceable in front and back, right and left and up and down directions together with the table; a sample chamber cover which covers above the sample chamber main body including the table; and an evacuation use pipe which communicates with the groove portion and evacuates gas between the bottom face of the sample chamber cover and the top face of the table including the sample.  
           [0024]    Preferably, the evacuation use sample chamber comprises a pressure gauge which permits measurement of pressure in a region surrounded by the sample chamber cover, the table and a passage of charged particle beams to be irradiated onto the sample.  
           [0025]    Preferably, the sample chamber cover is provided with an open and close cover which opens and closes the passage of the charged particle beams to be irradiated onto the sample.  
           [0026]    Preferably, the evacuation use sample chamber is provided with a means which evacuates a region surrounded by the sample chamber cover, the table, the passage of the charged particle beams and the open and close cover, measures pressure therein with the pressure gauge and operates the open and close cover after the measured pressure reaches at a same level as in a passage other than the region of the charged particle beams.  
           [0027]    Preferably, the sample table includes a sample up and down moving mechanism which is used when transporting the sample.  
           [0028]    Preferably, the height of the upper face at the outer circumferential side from the groove portion of the table is selected higher than the upper face at the inner circumferential side from the groove portion.  
           [0029]    With the above structure, differential evacuation between the bottom face of the sample chamber cover and the top face of the table can be performed, thereby, the atmosphere around the sample can be kept in high vacuum. Further, since the inside of the groove which can always be evacuated is in vacuum condition, a pressure difference acting on the sample and the table is kept constant regardless to the movement of the sample. Thereby, the attitude accuracy of the table and the deformation state thereof are kept constant during pattern drawing. In the present specification “differential evacuation” implies an evacuation method in which a certain region is divided into different pressure (vacuum) regions of more than two.  
           [0030]    Further, through evacuation via the evacuation use groove portion on the table while coming close the table toward the bottom face of the sample chamber cover, differential evacuation on the upper face of the table can be performed, and even in a case when the inside of the sample chamber is not in high vacuum, the passage of the charged particle beams upto the sample can be kept in high vacuum. Further, when carrying in the sample, the above differential evacuation is impossible, therefore, for the purpose of maintaining a predetermined degree of vacuum in the column, the open and close cover which closes a hole portion forming the passage of the charged particle beams is provided.  
           [0031]    Further, the present invention provides an evacuation use device which is characterized by comprising a table which is provided with a recessed portion for mounting a sample and a groove portion surrounding the recessed portion; a stage which holds the table and is displaceable in front and back, right and left and up and down directions together with the table; a member which covers above the table; and an evacuation use pipe which communicates with the groove portion and evacuates gas between the bottom face of the member and the top face of the table including the sample.  
           [0032]    Preferably, the evacuation use device comprises a pressure gauge which permits measurement of pressure in a region surrounded by the member, the table and a passage of charged particle beams to be irradiated onto the sample.  
           [0033]    Preferably, the member is provided with an open and close cover which opens and closes the passage of the charged particle beams to be irradiated onto the sample.  
           [0034]    Preferably, the distance between the recessed portion and the groove portion provided for the table is selected more than the radius of a passage hole for the charged particle beams provided at the bottom face of the open and close cover.  
           [0035]    Preferably, the pressure gauge is provided at the open and close cover.  
           [0036]    Preferably, the evacuation use device is provided with a means which evacuates a region surrounded by the member, the table, the passage of the charged particle beams and the open and close cover, measures pressure therein with the pressure gauge and operates the open and close cover after the measured pressure reaches at a same level as in a passage other than the region of the charged particle beams.  
           [0037]    Preferably, the sample table includes a sample up and down moving mechanism which is used when transporting the sample.  
           [0038]    Preferably, an air pad which evacuates gas is provided on the upper face of the table at the outer circumferential side from the groove portion.  
           [0039]    Preferably, the height of the upper face of the air pad is selected lower than the upper face between groove portion and the air pad on the table.  
           [0040]    Preferably, the height of the upper face of the air pad is selected higher than the upper face of the table at the outer circumferential side from the air pad.  
           [0041]    Preferably, a gas lubrication is performed between the upper face of the pad and the bottom face of the member and the table is slidably moved by making use of the bottom face of the member as a guide face.  
           [0042]    Further, the present invention is to provide a circuit pattern forming apparatus which comprises a column for irradiating charged particle beams onto a sample and an evacuation use sample chamber in which the sample is placed and which evacuates gas around the placed sample to keep vacuum therein and wherein under the condition kept in vacuum the charged particle beams are irradiated onto the upper face of the placed sample to form a circuit pattern on the upper face of the sample, which is characterized, in that the evacuation use sample chamber comprises a sample chamber main body; a table which is provided with a recessed portion disposed in the sample chamber main body and for mounting the sample and a groove portion surrounding the recessed portion; a stage which holds the table and is displaceable in front and back, right and left and up and down directions together with the table; a sample chamber cover which covers above the sample chamber main body including the table; and an evacuation use pipe which communicates with the groove portion and evacuates gas between the bottom face of the sample chamber cover and the top face of the table including the sample.  
           [0043]    Further, the present invention is to provide a circuit pattern inspection apparatus which comprises a column for irradiating charged particle beams onto a sample on which a circuit pattern is formed and an evacuation use sample chamber in which the sample is placed and which evacuates gas around the placed sample to keep vacuum therein and wherein under the condition kept in vacuum the charged particle beams are irradiated onto the upper face of the placed sample to inspect the circuit pattern on the upper face of the sample, which is characterized, in that the evacuation use sample chamber comprises a sample chamber main body; a table which is provided with a recessed portion disposed in the sample chamber main body and for mounting the sample and a groove portion surrounding the recessed portion; a stage which holds the table and is displaceable in front and back, right and left and up and down directions together with the table; a sample chamber cover which covers above the sample chamber main body including the table; and an evacuation use pipe which communicates with the groove portion and evacuates gas between the bottom face of the sample chamber cover and the top face of the table including the sample. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0044]    [0044]FIG. 1 is a constitutional diagram of an electron beam pattern drawing apparatus representing a first embodiment of the present invention;  
         [0045]    [0045]FIG. 2 is a perspective view of a top table in the electron beam pattern drawing apparatus in FIG. 1;  
         [0046]    [0046]FIG. 3 is a cross sectional view taken along line A-A in FIG. 2;  
         [0047]    [0047]FIG. 4 is a detailed view of C portion in the top table in FIG. 3 and shows differential evacuation action around a wafer;  
         [0048]    [0048]FIG. 5 is a view showing another example of differential evacuation action in FIG. 4;  
         [0049]    [0049]FIG. 6 is a constitutional diagram of an electron beam pattern drawing apparatus representing a second embodiment of the present invention;  
         [0050]    [0050]FIG. 7 is a perspective view of a top table in the electron beam pattern drawing apparatus in FIG. 6;  
         [0051]    [0051]FIG. 8 is a cross sectional view taken along line B-B in FIG. 7;  
         [0052]    [0052]FIG. 9 is a view showing differential evacuation action around a wafer on the top table in FIG. 7;  
         [0053]    [0053]FIG. 10 is a detailed view of D portion in the top table in FIG. 9 and shows differential evacuation action around a wafer;  
         [0054]    [0054]FIG. 11 is a view showing another example of differential evacuation action in FIG. 10;  
         [0055]    [0055]FIG. 12 is a constitutional diagram of a conventional electron beam pattern drawing apparatus; and  
         [0056]    [0056]FIG. 13 is an enlarged view of a flange portion in the conventional electron beam pattern drawing apparatus. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0057]    Hereinbelow, an evacuation use sample chamber and a circuit pattern forming apparatus representing one embodiment of the present invention will be explained, while taking an electron beam pattern drawing apparatus as an example, with reference to the drawings.  
         [0058]    An electron beam pattern drawing apparatus is one in which through generation of electron beam under a super high vacuum environment and scanning therewith LSI patterns are formed on a semiconductor substrate or a glass substrate called as a mask which is used for an exposure apparatus such as a stepper.  
         [0059]    At first, a first embodiment will be explained with reference to FIGS. 1 through 5.  
         [0060]    [0060]FIG. 1 shows a constitution of an electron beam pattern drawing apparatus representing the first embodiment of the present invention. As shown in FIG. 1, a column  1  is mounted on a sample chamber cover  11 , and inside a sample chamber (also called as a work chamber)  10  a sample stage (also called a sample displacement stand or a displacement table device) which is movable in XYZ directions in the drawing, namely an XYZ stage  20  is disposed. The sample chamber cover  11  is designed to be driven by a motor  40  and a friction drive mechanism  41  and is attached with an open and close cover  42  which maintains vacuum inside the column  1 . In the XYZ stage  20 , Z stage  23  movable in Z direction is mounted on an XY stage  9  movable in XY directions and a top table  21  which holds a sample  8  is coupled to the Z stage  23  by an expandable actuator  22 . Further, a bar mirror  13  is attached to the top table  21  and through measurement by laser distance variation to a laser interference meter  12  management of sample position can be performed.  
         [0061]    The top table  21  will be explained with reference to FIGS. 2 and 3. FIG. 2 shows a perspective view of the top table  21  and FIG. 3 shows a cross sectional view taken along line A-A in FIG. 2.  
         [0062]    On the top table  21 , a sample use recessed portion  21 F having depth of about the thickness of the sample  8  and an evacuation use groove portion  21 E surrounding the same are formed, and pin Z mechanisms  21 A which are used during sample transportation are attached below respective holes. Further, at the time of transportation a pin  21 D passes through the hole  21 B and acts on the pin Z mechanism to lift up the top table and to facilitate the sample transportation.  
         [0063]    Further, in order to perform differential evacuation stably, it is necessary to keep flow rate of gas to be evacuated at constant. When it is designed in such a manner that distance AD between the sample use recessed portion  21 F and the evacuation use groove portion  21 E as illustrated in the drawing is determined more than the radius of an electron beam passage use hole formed in the bottom face of the sample chamber cover  11  and even when the edge of the sample is shifted in XY directions with reference to the center of column the electron beam passage use hole covers inside the evacuation use groove portion, a circuit pattern can be stably drawn over the entire surface of the sample.  
         [0064]    Now, a series of flow from carrying in the sample into the sample chamber  10  to carrying out the same after completing a circuit pattern drawing will be explained. At a predetermined position of the XYZ stage  20  the sample  8  carried in is held on the top table  21  and the sample  8  is displaced immediately below the column  1 . Thereafter, the top table  21  is displaced upward by the Z stage  23  into a detectable range of a Z sensor  19  which can detects position in height direction and inclination of the sample  8 .  
         [0065]    Subsequently, the distance between the upper face of the sample  8  and the bottom face of the sample chamber cover  11  and parallelism of the sample  8  with respect to the bottom face of the sample chamber cover  11  are detected by means of the Z sensor  19  and the actuator  22  is caused to expand or contract so as to assume a distance and parallelism which permit differential evacuation. While keeping a predetermined distance (a few μm-10 and a few μm) and parallelism, vacuum evacuation is performed through the evacuation use tube  21 C so as to depressurize a region surrounded by the evacuation use groove portion  21 E, the bottom face of the sample chamber cover  11  and the open and close cover  42 , and the degree of vacuum in the region is measured by a pressure gauge  50  attached on the sample chamber cover  11 .  
         [0066]    After the region reaches to the degree of vacuum in the column  1 , the open and close cover  42  is opened to start a pattern drawing. After completing the pattern drawing, the open and close cover  42  is closed to shield the inside of the column  1 , and after terminating the evacuation from the top table  21 , the sample  8  is lowered by driving the Z stage  23 , then the sample  8  is carried out at the sample transportation position by displacing the XY stage  9 .  
         [0067]    Now, the differential evacuation around a wafer will be explained with reference to FIG. 4.  
         [0068]    Since the distance between the upper face of the top table  21  and the bottom face of the sample chamber cover  11  is narrow as from a few μm to 10 and few μm, when a flow rate of evacuated gas from the upper face of the top table  21  is sufficiently large with respect to a flow rate flowing into the evacuation use groove portion  21 F from inside the sample chamber  10  being in low vacuum, depressurization rapidly advances after the start of evacuation because of small volume of the region surrounded by the evacuation use groove portion  21 E, the bottom face of the sample chamber cover  11  and the open and close cover  42 .  
         [0069]    Further, the smaller the distance G 1  between the upper face of the top table  21  and the bottom face of the sample chamber cover  11 , the less is the flow rate from the region in low vacuum. Accordingly, when it is designed to evacuate the environment around the sample  8  into high vacuum in the shortest time, it is sufficient as illustrated in FIG. 5 to provide a step in the top table  21  and to determine the distance G 1  between the upper face of the top table  21  at the outer portion from the evacuation use groove portion  21 E and the bottom face of the sample chamber cover  11  smaller than the distance G 2  between the upper face of the top table  21  and the bottom face of the sample chamber cover  11 .  
         [0070]    Now, a second embodiment will be explained with reference to FIGS. 6 through 11.  
         [0071]    [0071]FIG. 6 shows a constitution of an electron beam pattern drawing apparatus representing the second embodiment of the present invention.  
         [0072]    As illustrated in FIG. 6, the XYZ stage  20  is guided by an air bearing and is movable in XYZ direction like the first embodiment, and in place of the sample chamber which maintains vacuum, the sample chamber cover  11 , on which the column  1  is mounted, is supported by a framework  31  provided with a variation eliminating mechanism  32 .  
         [0073]    A region surrounded by the framework  31 , a base disk  33  and the sample chamber cover  11  (which corresponds to the inside of the sample chamber in the first embodiment) is in the atmospheric state, therefore, such preliminary evacuation installation as the load chamber is unneeded for the sample transportation. Further, because of the use of the air bearing no lubricants such as lubricant oil are needed, therefore, possible contamination such as inside the column and parts around the sample can be greatly reduced.  
         [0074]    The structure of the top table  21  and the differential evacuation of the second embodiment will be explained with reference to FIGS. 7 through 9. FIG. 7 shows a perspective view of the top table  21  of the second embodiment, FIG. 8 shows a cross sectional view taken along line B-B in FIG. 7, and FIG. 9 is a diagram showing the differential evacuation action.  
         [0075]    The top table  21  is provided with, in addition to the mechanism as explained in connection with the first embodiment, an air pad  21 I of a porous material such as ceramics which permits passing of gas and a gas supply use tube  21 J which permits supply of compressed gas. In the present embodiment, through blowing out gas fed from the gas supply use tube  21 J from the upper face of the air pad  21 I, the top table  21  can be supported through the air bearing with respect to the bottom face of the sample chamber cover  11 .  
         [0076]    In the structure of the top table  21  as explained in connection with the first embodiment, when the environment around the top table  21  is in atmospheric pressure and the environment around the sample  8  is in high vacuum, a high pressure caused by the pressure difference will act onto the bottom face of the top table  21 , thereby, the top table  21  possibly contacts to the bottom face of the sample chamber cover  11 .  
         [0077]    According to the second embodiment through the gas supply pressure from the air pad  21 I the distance G 3  between the top table  21  and the bottom face of the sample chamber cover  11  is kept constant and the above possible contact can be avoided.  
         [0078]    Further, through managing the profile irregularity of the bottom face of the sample chamber cover  11 , the top table  21  moves following the bottom face of the sample chamber cover  11 , thereby, variation amount in the height direction of the top table  21  can be reduced.  
         [0079]    Further, FIG. 10 is an example where a step AZ is provided between the upper face of the air pad  21 I and the upper face of the top table  21  at the outer circumferential side in order to reduce air flow rate flown in into the evacuation use groove portion  21 E from the air pad  21 I. In the present structure, since the distance G 3  between the bottom face of the sample chamber cover  11  and the air pad  21 I is selected larger than the distance G 1  between the bottom face of the sample chamber cover  11  and the upper face of the top table  21 , the air fed from the air pad  21 I can be easily flown out from the top table  21 , thereby, the environment around the sample can be kept in further higher vacuum.  
         [0080]    Further, as shown in FIG. 11 through provision of the evacuation use groove portion in two or more steps, it is possible to evacuate around the sample more rapidly into a high degree of vacuum.  
         [0081]    Hereinabove, the circuit pattern forming apparatuses have been explained by taking the electron beam pattern drawing apparatuses as examples, the circuit pattern forming apparatus of the present invention can be used as a circuit pattern inspection apparatus for inspecting circuit patterns for samples on which circuit patterns are already formed.  
         [0082]    According to the present invention, through the stable gas evacuation the environment around the sample can be kept in high degree of vacuum constantly, thereby, an evacuation use sample chamber which can realize always stable vacuum is provided.  
         [0083]    Further, through use of the evacuation use sample chamber a circuit pattern forming apparatus can be provided which permits a pattern drawing (exposure, inspection) over the entire face of a sample under environment condition of the sample chamber in low degree of vacuum or in atmospheric pressure while keeping the electron beam passage in high vacuum and without deteriorating the attitude accuracy of the top table.