Patent Publication Number: US-2002011854-A1

Title: Probe device

Description:
TECHNICAL FIELD  
       [0001] The present invention relates to a probe apparatus, and more particularly to a probe card with a plurality of probe terminals which are put in contact with a plurality of electrodes of an object to be tested, thereby to test electrical characteristics of the object.  
       BACKGROUND ART  
       [0002]FIGS. 6 and 7 show a conventional probe apparatus for testing electrical characteristics of semiconductor devices formed on a semiconductor wafer. The probe apparatus comprises a loader chamber  1  for pre-aligning a wafer W and feeding the wafer W, and a prober chamber  2  for receiving the wafer W from the loader chamber  1  and testing the electrical characteristics thereof. A probe card  7  is detachably attached to a head plate  8  which forms a top surface of the prober chamber  2 .  
       [0003] As is shown in FIG. 7, fork  3  and a sub-chuck  4  are provided in the loader chamber  1 . While the wafer W is being carried by the fork  3 , the wafer W is pre-aligned by the sub-chuck  4  with reference to its orientation flat.  
       [0004] A main chuck  5  and an alignment mechanism  6  having upper and lower cameras  6 A and  6 B are provided in the prober chamber  2 . The main chuck  5 , on which the wafer W is placed, cooperates with the alignment mechanism  6  while moving in X-, Y-, Z- and θ-directions, thereby aligning electrodes formed on the wafer W with probe terminals  7 A of the probe card  7 . Following the completion of alignment, the main chuck  5  rises to bring the electrodes on the wafer W placed on the main chuck  5  into electrical contact with the probe terminals  7 A. A test head T connected to the probe terminals inspects electrical characteristics of the semiconductor devices formed on the wafer W. A temperature adjustment mechanism is built in the main chuck. The temperature adjustment mechanism sets the temperature of the wafer W within a wide range of, e.g. −50° C. to +160° C. Thus, the wafer W can be tested at normal, low, or high temperatures.  
       [0005] When the electrical characteristics of the wafer W are to be inspected, the wafer W is placed on the main chuck  5 , the temperature of which has been set at a predetermined value by the temperature adjustment mechanism. The main chuck and alignment mechanism  6  cooperate to align the electrode pads of semiconductor devices formed on the wafer W with the probe terminals  7 A of the probe card. The main chuck  5  is raised to put the electrode pads of the semiconductor devices into electrical contact with the probe terminals  7 A. The test head T connected to the probe terminals  7 A inspects the electrical characteristics of the semiconductor devices.  
       [0006] As is shown in FIG. 6, the main chuck  5  is fixed to an XY-stage which is reciprocally movable in the X- and Y- directions (for convenience&#39; sake, an X-stage and a Y-stage being described as a single structure). The main chuck  5  is reciprocally moved in the X- and Y-directions by the XY-stage  9 .  
       [0007] A vertical drive mechanism  10  for moving the main chuck  5  in the Z-direction is fixed to the XY-stage  9 , as schematically shown in FIG. 8. The vertical drive mechanism  10  comprises a motor  10 B provided in, e.g. a cylindrical container  10 A, a ball screw  10 C rotated by the motor  10 B, and a nut member (not shown) engaged with the ball screw. The main chuck  5  is elevated in the Z-direction in FIG. 8 by means of the nut member in accordance with the rotation of the ball screw  10 C, so that the electrode pads of the semiconductor devices formed on the wafer W may be put in contact with the probe terminals  7 A of the probe card. The distance, over which the main chuck  5  is elevated, is measured, for example, by using the upper and lower cameras  6 A and  6 B and a target  6 C of alignment mechanism  6 . Based on the measured data, the vertical drive mechanism  10  is driven.  
       [0008] Specifically, the probe terminals  7 A, target  6 C and wafer W are imaged by the upper and lower cameras  6 A and  6 B, and the distance of elevation is calculated on the basis of the positional coordinates data.  
       [0009] The current size of wafers is 6 inches or 8 inches. If the size of wafers is increased to 12 inches in the future, the patterns of integrated circuits will be made much finer and the pitch of electrode pads will further decrease. To cope with this, conventional probe apparatuses have to solve various problems. For example, if the number of chips to be measured at a time increases, the number of electrode pads of each chip also increases. Accordingly, the number of probe terminals  7 A increases and the weight of the probe card increases up to, e.g. several kg. When chips located on a peripheral portion of the wafer are to be tested, part of the weight acts unevenly on a peripheral portion of the wafer (action due to offset load). Due to this action, the main chuck  5  is inclined as indicated by a dot-and-dash line in FIG. 8 in an exaggerated fashion. As a result, the XY-stage  9  deforms and there arises a variance in contact pressure (needle pressure) between respective probe terminals  7 A and wafer W. The reliability of inspection may thus deteriorate.  
       [0010] Furthermore, if the wafer size increases to, e.g. 12 inches, the distance between the center of the main chuck and the point of contact of the probe increases and accordingly the inclination of the main chuck  5  due to offset load increases. The variance in contact pressure of probe terminals  7 A further increases and in worse cases some of the probe terminals  7 A do not come in contact with the wafer W.  
       DISCLOSURE OF INVENTION  
       [0011] The present invention aims at solving the above problems.  
       [0012] Specifically, the invention aims at always keeping, even if objects to be inspected increase in diameter in the future, the mounting table horizontal in inspections and always putting the contact terminals and the object in contact under uniform pressure, thereby enhancing the reliability of the inspection.  
       [0013] The invention also aims at smoothly moving the mount table in the horizontal and vertical directions and controlling the vertical movement of the mount table very easily.  
       [0014] The applicant previously proposed an invention relating to the present apparatus in Japanese Patent KOKAI Application No. 11-26524. The previously proposed invention is improved in the present invention, and a probe apparatus wherein the vertical movement of the mounting table can be easily controlled is proposed.  
       [0015] According to a first aspect of the present invention, there is provided a probe apparatus comprising:  
       [0016] a probe card with a plurality of probe terminals, the probe card being disposed on an upper surface of an inside of a prober chamber for inspecting electrical characteristics of an object to be tested;  
       [0017] a mounting table, disposed below the probe card, for mounting of the object;  
       [0018] a drive mechanism for reciprocally driving the mounting table in one horizontal direction and another horizontal direction perpendicular to the one horizontal direction;  
       [0019] a vertical drive mechanism situated below the mounting table and having a vertical movement shaft, the vertical drive mechanism vertically driving the vertical movement shaft along a line extended downward from a center for an inspection of the probe card;  
       [0020] a vertically movable member, connected to a distal end portion of the vertical movement shaft, for supporting the mounting table and vertically moving the mounting table in accordance with vertical movement of the vertical movement shaft; and  
       [0021] a gap-maintaining mechanism for maintaining a gap between the vertically movable member and the mounting table.  
       [0022] It is preferable that the gap-maintaining mechanism have a static-pressure thrust gas bearing on the vertically movable member.  
       [0023] It is preferable that the gap-maintaining mechanism further include a magnetic action causing mechanism on the vertically movable member, the magnetic action causing mechanism functioning to attract the mounting table toward the vertically movable member.  
       [0024] It is preferable that the gap-maintaining mechanism comprise:  
       [0025] a static-pressure thrust gas bearing having at least one opening portion on an upper surface of the vertically movable member, and a mechanism for supplying compressed air to the opening portion; and  
       [0026] a magnetic action causing mechanism including at least one magnet on the upper surface of the vertically movable member.  
       [0027] It is preferable that the gap-maintaining mechanism include at least one spherical body rotatably provided between the vertically movable member and the mounting table.  
       [0028] It is preferable that the gap-maintaining mechanism further include a vacuum suction mechanism for drawing the mounting table toward the vertically movable member.  
       [0029] It is preferable that the gap-maintaining mechanism further include a magnetic action causing mechanism provided on the vertically movable member, the magnetic action causing mechanism functioning to attract the mounting table toward the vertically movable member.  
       [0030] It is preferable that the mechanism for reciprocally driving the mounting table comprise:  
       [0031] a first stage capable of vertically guiding the mounting table and reciprocally driving the same in a first horizontal direction; and  
       [0032] a second stage capable of supporting the first stage such that the first stage is reciprocally movable in the first horizontal direction, and capable of reciprocally moving in a horizontal direction perpendicular to the first horizontal direction. 
     
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
     [0033] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention.  
     [0034]FIG. 1 is a plan view showing an embodiment of a prober chamber of a probe apparatus according to the present invention.  
     [0035]FIG. 2 is a cross-sectional view showing a main part of the prober chamber shown in FIG. 1.  
     [0036]FIGS. 3A and 3B are perspective views showing examples of a static-pressure thrust air bearing provided in the prober chamber shown in FIG. 2.  
     [0037]FIG. 4 is a graph showing a relationship between a gap defined by the static-pressure thrust air bearing of the probe apparatus shown in FIG. 2 and the load on the Z-stage.  
     [0038]FIG. 5 is a cross-sectional view showing another embodiment of the probe apparatus according to the present invention.  
     [0039]FIG. 6 is a front view of a conventional probe apparatus, with a front side of the prober chamber being cut away.  
     [0040]FIG. 7 is a plan view of the probe apparatus shown in FIG. 6.  
     [0041]FIG. 8 is a cross-sectional view schematically showing the main chuck of the probe apparatus shown in FIG. 6. 
    
    
     BEST MODE OF CARRYING OUT THE INVENTION  
     [0042] The present invention will now be described on the basis of embodiments shown in FIGS.  1  to  5 . A probe apparatus  10  of the embodiment, as shown in FIGS. 1 and 2, is characterized by a vertical drive mechanism of a main chuck within a prober chamber  11 . Specifically, a main chuck  12 , on which a wafer W of, e.g. 12 inches is placed, is provided within the prober chamber  11  of the embodiment. A probe card  13  is fixed above the main chuck  12 . The main chuck  12 , as shown in FIGS. 1 and 2, is reciprocally moved in X- and Y-directions by a first stage (X-stage)  14  and a second stage (Y-stage)  15  and is vertically moved in an Z-direction by a Z-stage  16 . Thereby, the wafer W placed on the main chuck  12  is put in electric contact with probe terminals  13 A of the probe card  13 . In this contact state, the electrical characteristics of the wafer W are inspected.  
     [0043] The drive mechanisms for the X-, Y- and Z-stages  14 ,  15  and  16  will now be described in detail.  
     [0044] A cylindrical guide  14 A extending vertically downward is provided at a central portion of the x-stage. The Z-stage  16  for supporting the main chuck  12  is disposed inside the cylindrical guide  14 A. A plurality of axially extending LM guides  17  are provided on an inner peripheral surface of the cylindrical guide  14 A at regular intervals in the circumferential direction. When the Z-stage  16  is vertically moved in the Z-direction, the LM guides  17  guide the Z-stage  16 . A vertical drive mechanism  18  is fixed below the Z-stage  16  within the prober chamber  11 . A vertically movable member  19  is fixed to a top end of a drive shaft (e.g. ball screw)  18 A of the vertical drive mechanism  18 . The vertically movable member  19  vertically drives the Z-stage  16  in accordance with vertical movement of the drive shaft  18 A.  
     [0045] The center of the vertically movable member  19  and an inspection center of the probe card  13  (i.e. a center of a plurality of probe terminals) are situated on an extension line of the axis of the ball screw  18 A. This positional relationship remains unchanged even if the main chuck moves in the X- and Y-directions for inspection. In FIG. 2, numeral  11 A denotes a static plane (stationary plane) within the prober chamber  11 .  
     [0046] In this embodiment, as shown in FIG. 2, a small gap δ is defined between a bottom plate  22  provided at the lower part of the main chuck  16  and the vertically movable member  19 . With this gap δ maintained, the Z-stage  16  can smoothly be moved in the X-, Y- and Z-directions with respect to the vertically movable member  19 .  
     [0047] This gap δ is maintained by a gap maintaining mechanism. An example of the gap maintaining mechanism will now be described with reference to FIG. 3A. Opening portions  19 A are formed at a plurality of locations on one side surface of the vertically movable member  19 , as shown in FIG. 3A. An internal passage (not shown) connected to the opening portions  19 A is formed in the vertically movable member  19 . An air pipe  20  is connected to the opening portions  19 A of the internal passage provided on the side surface. During inspections, compressed air is always supplied to the internal passage via the air pipe  20  and the compressed air is jetted from the opening portions  19 A. The Z-stage  16  is lifted over the vertically movable member  19  by the pressure of the jetted air. The vertically movable member  19  functions as a static-pressure thrust air bearing having a square plane. During inspections, the Z-stage is moved in the X- and Y-directions over the vertically movable member  19  in an air slide method.  
     [0048] The probe apparatus according to this embodiment, as described above, is characterized by the structure in which the Z-stage is not held by the vertically movable member (static-pressure thrust air bearing)  19 . This structure may be improved.  
     [0049] In this probe apparatus, even after the vertical drive mechanism ceases to rise, the Z-stage  16  further rises due to inertia force so that more than a predetermined gap may be present between the Z-stage  16  and static-pressure thrust air bearing  19  (excessive rising). Owing to the excessive rising, the semiconductor wafer placed on the main chuck is brought into contact with the probe terminals  13 A under high pressure, and the probe terminals  13 A may be damaged. It is preferable that the probe apparatus described according to this embodiment be provided with an excessive rising prevention mechanism for preventing the Z-stage  16  from rising due to inertia force. A magnetic action causing mechanism utilizing a magnetic action may be adopted as an example of the excessive rising prevention mechanism. The magnetic action causing mechanism utilizes a magnetic action of a magnet (e.g. permanent magnet), thereby attracting the Z-stage  16  toward the static-pressure thrust air bearing  19  and maintaining the gap between the Z-stage  16  and vertically movable member  19  at a constant value δ. A permanent magnet  21  may be disposed at peripheral areas of the opening portions  19 A formed on the static-pressure thrust air bearing  19 . In the vertically movable member  19  shown in FIG. 3A, the opening portions  19 A are formed at the corners of the surface of the vertically movable member  19  and the permanent magnet is disposed in a cross-shaped groove formed among the opening portions  19 A. The bottom plate  22  of magnetic material, which is attached to the bottom surface of the Z-stage  16 , is attracted toward the vertically movable member  19  by the magnetic action of the permanent magnet  21 . Thus, the static-pressure thrust air bearing  19 , permanent magnet  21  and bottom plate  22  constitute gap maintaining means comprising the excessive rising prevention mechanism for maintaining the gap δ between the static-pressure thrust air bearing  19  and bottom plate  22  at a substantially constant value. The lift of the static-pressure thrust air bearing  19  and the attractive force of the permanent magnet  21  may be properly set according to the structure of the probe apparatus  10 .  
     [0050]FIG. 4 shows a relationship between a load performance and the gap δ between the static-pressure thrust air bearing  19  and Z-stage  16 . In FIG. 4, the load performance (ordinate) indicates, in its positive (+) direction, a load on the X-stage  16  in the direction of gravity. An intersection between a curve representing a load performance F of the air bearing and a line drawn from point F 0  indicates that the value of gap δ is maintained at H 0  (abscissa) because of balance between the magnet force at load performance F 0  and the lift force of the static-pressure thrust air bearing  19 . In this state, a varying load is zero. According to FIG. 4, if a load δ f 1  acts on the Z-stage  16  due to excessive rising at the time of inspection, the gap δ decreases from H 0  to H 1 . On the other hand, if an inertia force δf 2  acts on the Z-stage  16  when the vertical drive mechanism  18  stops and the Z-stage  16  ceases to vertically move, the gap δ increases from H 0  to H 2 .  
     [0051] Accordingly, if the gap maintaining mechanism comprises only the static-pressure thrust air bearing  19 , the gap the gap δ varies in a range exceeding H 2  at the time of inspection and the distance of vertical movement of the Z-stage  16  cannot exactly be controlled. In this embodiment, as described above, the excessive rising prevention mechanism comprising the permanent magnet  21  and bottom plate (magnetic body)  22  applies magnet force to the X-stage  16  so as to keep substantially constant the gap δ between the static-pressure thrust air bearing  19  and bottom plate  22  (in the range between H 1  and H 2  in FIG. 4). The gap δ should preferably be limited to the range of, e.g. 10 μm.  
     [0052] The X-stage  14  reciprocally moves in the X-direction on the Y-stage  15 . As is shown in FIG. 2, LM guides  24  are provided as an example of a pair of guide rails (hereinafter referred to as “X-guide rails”) on the Y-stage  15 . Engaging members  24 A (see FIG. 2) are provided on the lower surface of the X-stage  14 . The engaging members  24 A are engaged with the X-guide rails  24 . As is shown in FIG. 1, an X-directional ball screw (hereinafter referred to as “X-ball screw”)  25  is provided on the Y-stage  15  near the inner side of the left-side X-guide rail  24 . The X-ball screw  25  is engaged with a nut member (not shown) attached to the lower surface of the X-stage  14 . The X-ball screw  25  is rotated in forward and reverse directions to reciprocally move the X-stage  14  on the Y-stage  15  in the X-direction.  
     [0053] The Y-stage  15  is provided on a base frame  11 B of the prober chamber  11  and is reciprocally moved on the base frame  11 B in the Y-direction. Specifically, a pair of guide rails (hereinafter referred to as “Y-guide rails”)  26  extending the Y-direction are provided at both end portions in the X-direction on the base frame  11 B. Engaging members  26 A are attached to both end portions in the X-direction of the Y-stage  15 . These Y-guide rails  26  are engaged with the engaging members  26 A. In addition, a Y-directional ball screw (hereinafter referred to as “Y-ball screw”)  27  is provided on the base frame  11 B near the inner side of the Y-guide rail  26  (see the lower part of FIG. 1). The Y-ball screw  27  is rotated in forward and reverse directions by a motor  27 A. The Y-ball screw  27  is engaged with a nut member (not shown) attached to the lower surface of the Y-stage  15 . The Y-ball screw  27  is rotated forwardly and reversely to reciprocally move the Y-stage  15  on the base frame  11 B in the Y-direction.  
     [0054] An alignment bridge  28  of an alignment mechanism is provided in the prober chamber  11  so as to be movable along the paired guide rails  28 A provided in the Y-direction. An upper camera (not shown) attached to the alignment bridge  28  images the wafer W on the main chuck  12 . A lower camera (not shown) attached to the main chuck  12  images the probe terminals  13 A of probe card  13 . On the basis of the image data, the probe terminals  13 A and inspection electrode pads (not shown) formed on the wafer W are aligned. A mechanism proposed in Japanese Patent Application No. 10-054423 can be used as the alignment mechanism.  
     [0055] The operation of the probe apparatus according to the present invention will now be described.  
     [0056] If the probe apparatus  10  is driven, the Z-stage  16  is lifted by the vertical drive mechanism  18  along the cylindrical guide  14 A of X-stage  14 , while a predetermined gap is maintained between the Z-stage  16  and static-pressure thrust air bearing  19  by the gap maintaining means  23  comprising the static-pressure thrust air bearing  19 , permanent magnet  21  and bottom plate (magnetic body)  22 . Then a pre-aligned wafer W is loaded from the loader chamber (not shown) onto the main chuck  12  within the prober chamber  11 . With the alignment mechanism in operation, the Z-stage  16  is moved in the X- and Y-directions by the X- and Y-stages  14  and  15  while a gap is maintained between the Z-stage  16  and static-pressure air bearing  19 . In addition, the Z-stage  16  is rotated forwardly and reversely in the θ-direction. Thus, the wafer W on the main chuck  12  is aligned with the probe terminals  13 A of probe card  13 . When the aligned wafer W is to be inspected, the Z-stage  16  is moved in the X- and Y-directions by the X- and Y-stages  14  and  15  with the gap maintained. The wafer W on the main chuck  12  is brought to, and halted at, the initial position for inspection.  
     [0057] Following the above, the vertical drive mechanism  18  is operated, and the Z-stage  16  is raised by the static-pressure air bearing  19  in the state in which the Z-stage  16  is out of contact with the static-pressure thrust air bearing  19 . Accordingly, the electrode pads for inspection of wafer W on the main chuck  12  are put in contact with the probe terminals  13 A of probe card  13 . The vertical drive mechanism  18  halts after overdriving the Z-stage  16 . At this time, the attractive force due to the magnetic action between the permanent magnet  21  and bottom plate  22  prevents the Z-stage  16  from rising excessively due to inertia force and maintains the gap δ stably. As a result, the inspection electrode pads can be put in contact with the probe terminals  13 A under stabilized pressure.  
     [0058] The inspection position at the initial stage is on the peripheral portion of the wafer W. Consequently, in the prior art, the needle pressure of the probe terminals  13 A acts on the peripheral portion of the main chuck  12  in a biased manner. As a result, the main chuck is inclined, as shown in FIG. 8. In the embodiment of the present invention, the vertically moving member (static-pressure thrust air bearing)  19 , which is always positioned just below the inspection center of the probe card  13 , receives the needle pressure of the probe terminals  13 A. Thus, the needle pressure does not act on the peripheral portion of the main chuck  12  in a biased manner and the main chuck  12  is always supported horizontal. Accordingly, the probe terminals  13 A are put in contact with the wafer W under uniform pressure during the inspection, and the reliable inspection is always stably performed.  
     [0059] Although the gap δ between the Z-stage and vertically movable member varies from H 0  to H 1 , the gap in the range of H 1  is maintained. Thus, the probe terminals  13 A can be put in contact with the inspection electrode pads under a predetermined needle pressure. Subsequently, the wafer W is moved by index-feeding and the above inspection is repeated. The gap maintaining means  23  operates throughout the inspection to maintain the gap δ in the range between H 1  and H 2 .  
     [0060] As has been described above, according to the present embodiment, a downward extension line from the inspection center of the probe card  13  always coincides with the axis of the vertically movable member (static-pressure thrust air bearing)  19  of the vertical movement mechanism  18  for main chuck  12 . Accordingly, the needle pressure of the probe terminals  13 A is always received by the static-pressure thrust air bearing  19  situated immediately thereunder, and the load due to the needle pressure of the probe terminals  13 A is prevented from acting on the main chuck  12  in a biased manner. The mounting surface of the main chuck  12  is always kept horizontal and the probe terminals  13 A are exactly put in contact with the wafer W under uniform pressure at all times. Therefore, the reliability of inspection is enhanced.  
     [0061] Air with a predetermined pressure is fed to the static-pressure thrust air bearing  19 , whereby the gap-maintaining means  23  comprising the static-pressure thrust air bearing  19 , permanent magnet  21  and bottom plate (magnetic body)  22  can maintain the gap δ between the Z-stage  16  and static-pressure thrust air bearing  19  at a substantially fixed size. The main chuck  12  can smoothly moved in the horizontal direction, and the distance of vertical movement of the main chuck  12  can be controlled exactly and easily.  
     [0062]FIG. 5 shows a main part of another embodiment of the probe apparatus according to the present invention. The probe apparatus  10 A of this embodiment has the same structure as the preceding embodiment except for the gap-maintaining means. The same or similar structural elements as with the preceding embodiment are denoted by like reference numerals in the following description. Gap-maintaining means  23 A in the present embodiment, as shown in FIG. 5, comprises a spherical member  30 , provided on the vertically movable member  19 , for defining a gap δ between the Z-stage  16  and vertically movable member  19 , and vacuum suction means  31  for sucking the Z-stage  16  toward the vertically movable member  19 . The vacuum suction means  31  is always operated during inspections. The vertically movable member  19  is formed in a cap shape, and a recess  19 B is formed in an upper surface thereof. For example, one spherical member  30  is rotatably mounted at the center of the recess  19 B. An internal passage (not shown) is formed in the vertically movable member  19 . The internal passage communicates with at least one opening formed at the recess  19 B and also communicates with an opening formed at a side surface of the vertically movable member  19 . A vacuum pipe  31 A is connected to the opening at the side surface of the vertically movable member  19 , and the inside of the recess  19 B is evacuated by an evacuation device (not shown). The Z-stage  16  is vacuum-suctioned and prevented from excessively rising.  
     [0063] It is preferable that the gap δ between the Z-stage  16  and vertically movable member  19  be set at, e.g. 10 μm or less. If the gap exceeds 10 μm, the suction force of the vacuum suction means  31  for sucking the Z-stage  16  sharply decreases and the Z-stage  16  may not be prevented from rising excessively. The suction force of the vacuum suction means  31  can be properly set according to the structure, etc. of the probe apparatus  10 .  
     [0064] In the present embodiment, if the probe apparatus  10  is driven, the vacuum suction means  31  of the gap-maintaining means  23 A is operated and, with the gap δ provided between the vertically movable member  19  and Z-stage  16 , the Z-stage  16  is drawn toward the vertically movable member  19  by vacuum force. During the inspection, when the Z-stage  16  is overdriven and the vertically movable mechanism  18  stops, the excessive rising of the Z-stage  16  due to inertia force is prevented since the vacuum suction force of the vacuum suction means  31  is acting on the Z-stage  16 . In addition, the same advantageous effects as with the preceding embodiment can be expected.  
     [0065] According to the invention of claims  1  to  4 , even if objects to be inspected increase in diameter in the future, the mounting table is always kept horizontal in inspections and the contact terminals and the object are always put in contact under uniform pressure. Therefore, the reliability of the inspection is enhanced. Moreover, there is provided the probe apparatus wherein the mount table can be smoothly moved in the horizontal and vertical directions and the vertical movement of the mount table can be controlled very easily.  
     [0066] The present invention is not limited to the above-described embodiments.  
     [0067] The present invention covers all probe apparatuses wherein the downward extension line from the center of inspection of the probe card coincides with the axes of the vertical drive mechanism and vertically movable member provided within the prober chamber and inspections are performed in the state in which a predetermined gap is maintained by the gap-maintaining means between the mount table and the vertically movable member.  
     [0068] For example, in the above embodiments, the vertically movable member  19 , bottom plate  22 , Z-stage  16  and main chuck  12  have cylindrical shapes. However, these members may have other shapes.  
     [0069] In FIG. 3A, the opening portions  19 A are provided at four locations on the upper surface of the vertically movable member. The number of opening portions  19 A, however, may be at least one. Accordingly, two, three, five or more opening portions may be provided.  
     [0070] In addition, in FIG. 3A, the permanent magnet  21  has a cross-shape. However, the permanent magnet  21  may have another shape in consideration of the arrangement of the opening portions  19 A.  
     [0071] Although the permanent magnet is used as the magnetic action causing mechanism in FIG. 3A, an electromagnet may be substituted.  
     [0072] Other features and modifications of the invention are conceivable by a person skilled in the art. Therefore, the present invention is based on a broader standpoint and should not be limited to specific and typical embodiments described here in detail. Accordingly, various modifications may be made in the invention without departing from the broad concept of the invention defined in the attached claims and the scope of interpretation of equivalents of the defined invention.