Defective product inspection apparatus, probe positioning method and probe moving method

For adjusting a positional relationship between a specimen and a probe to measure an electric characteristic of the specimen through a contact therebetween, a base table holding a specimen table holding the specimen and a probe holder holding the probe is positioned at a first position to measure the positional relationship between the probe and the specimen at the first position, and subsequently positioned at a second position to measure the positional relationship therebetween at the second position so that the probe and the specimen are contact each other at the second position, the specimen table and the probe holder are movable with respect to each other on the base table at each of the first and second positions to adjust the positional relationship between the probe and the specimen, and a measuring accuracy at the second position is superior to a measuring accuracy at the first position.

BACKGROUND OF THE INVENTION

The present invention relates to a defective product inspection apparatus (probe apparatus), a probe positioning method and a probe moving method, for measuring an electric characteristic of a microscopic area of an electronic element.

A defective product inspection apparatus is well known as the prior art, in which a probe contacts an area of a specimen (an electronic element) at which an electric characteristic needs to be inspected. An electric current-voltage characteristic or the like of the electronic element can be measured through the probe.

JP-A-9-326425 discloses that a probe is arranged in a specimen chamber of a scanning electron microscope (SEM) to measure a minute electric potential characteristic.

JP-A-2000-147070 discloses a probe apparatus in which a probe information image showing an information for operating desirably a probe is formed on a display, a specimen and the probe are shown in the probe information image on the display, a probe operating image area for moving the probe is formed on the display, the probe is moved through a probe controller in accordance with an operating signal from the probe operating image area, and a movement amount from an actual current position of a front end of the probe to a target position thereof is calculated by designating each of the actual current position of the front and of the probe and the target position of the front and of the probe on the probe information image so that the probe controller operates in accordance with the movement amount to move the probe to the target position.

JP-A-2000-181898 discloses a probe apparatus including a charged particle beam projection device, a specimen stage for holding a specimen holder with a specimen thereon, a specimen chamber containing the specimen stage, a probe driving mechanism for moving the probe to contact the specimen in the specimen chamber, a specimen antechamber including a first stocker connected through a valve to the specimen chamber to store temporarily the specimen holder, and a first transfer device for moving the specimen holder at least between the specimen antechamber and the specimen chamber.

JP-A-2002-523784 discloses that an optical microscope slides on a microscope bridge to move to a position on a wafer chuck, and is rotated to a position for preventing from standing in the way of enabling the probe to firstly be positioned in an area of the specimen to which an user's attention is drawn.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide a defective product inspection apparatus and method for adjusting a positional relationship between a specimen and a probe, by which apparatus and method an electric characteristic of the specimen can be measured efficiently (with making a time period needed for the inspection as small as possible) while the specimen is restrained from being damaged.

According to the invention, a defective product inspection apparatus for measuring an electric characteristic of a specimen through (or with) a contact between a probe and the specimen (so that the measured electric characteristic is compared with a predetermined electric characteristic to judge whether the specimen as a product is defective or not), comprises, a specimen table for holding the specimen thereon, a probe holder for holding the probe thereon, a first measuring device for measuring a positional relationship between the probe and the specimen, and a second measuring device for measuring the positional relationship between the probe and the specimen, wherein (a measuring accuracy (resolution capability, magnification or the like) of the second measuring device is superior to a measuring accuracy (resolution capability, magnification or the like) of the first measuring device,) the apparatus further includes a base table holding thereon the specimen table and the probe holder in such a manner that the specimen table and the probe holder are movable with respect to each other on the base table to adjust the positional relationship between the probe and the specimen on the base table so that a contact area of the probe and a desired area of the specimen are capable of being brought into contact with each other, and the base table is movable between (or from) a first position at which the positional relationship between the probe and the specimen is measurable by the first measuring device and (or to) a second position at which the positional relationship between the probe and the specimen is measurable by the second measuring device. Incidentally, the specimen table is movable with respect to the base table, and the probe holder is movable with respect to the base table, so that a positional relationship between the specimen table and the base table and a positional relationship between the probe holder and the base table are adjustable independent of each other, and one of the positional relationship between the specimen table and the base table and the positional relationship between the probe holder and the base table is adjustable when the other one the positional relationship between the specimen table and the base table and the positional relationship between the probe holder and the base table is stationary.

Since (the measuring accuracy of the second measuring device is superior to the measuring accuracy of the first measuring device, and) the a base table holding thereon the specimen table and the probe holder in such a manner that the specimen table and the probe holder are movable with respect to each other on the base table to adjust the positional relationship between the probe and the specimen on the base table so that a contact area of the probe and the desired area of the specimen are capable of being brought into contact with each other, and the base table is movable between (or from) the first position at which the positional relationship between the probe and the specimen is measurable by the first measuring device and (or to) the second position at which the positional relationship between the probe and the specimen is measurable by the second measuring device, a time period which is needed for measuring the positional relationship between the probe and the specimen at the second position with the measuring accuracy superior to the measuring accuracy at the first position can be decreased by the measurement at the first position, so that the electric characteristic of the specimen can be measured efficiently. If the probe and the specimen are brought into contact with each other at the second position, a time period which is needed for bringing the probe and the specimen into contact with each other at the second position can be minimized, so that the electric characteristic of the specimen can be measured efficiently. The base table may be movable with respect to at least one (or each) of the first and second measuring devices.

If the first measuring device is capable of measuring the positional relationship between the probe and the specimen when the specimen is prevented from being irradiated with at least one of an ion beam and an electron beam, the specimen is prevented from being damaged by the at least one of the ion beam and the electron beam. If the second measuring device is capable of measuring the positional relationship between the probe and the specimen by irradiating the specimen with at least one of an ion beam and an electron beam, the specimen is restrained from being damaged by the at least one of the ion beam and the electron beam, by the decrease of the time period for at least one of measuring the positional relationship between the probe and the specimen at the second position and bringing the probe and the specimen into contact with each other at the second position.

The first measuring device may be capable of measuring the positional relationship between the probe and the specimen in each of first and second directions perpendicular to each other, so that the distance between the probe and the specimen in each of first and second directions perpendicular to each other can be measured to increase the accuracy for measuring the positional relationship. If the first direction is parallel to a thickness direction of the specimen, the first measuring device has a first magnification for magnifying an image corresponding to the positional relationship between the probe and the specimen in the first direction and a second magnification for magnifying another image corresponding to the positional relationship between the probe and the specimen in the second direction, and the first magnification is higher than the second magnification so that a contact or distance between the probe and specimen in the first direction is measurable more accurately in comparison with an overlap or distance between the probe and specimen in the second direction, the time period for at least one of measuring the positional relationship between the probe and the specimen at the second position and bringing the probe and the specimen into contact with each other at the second position can be decreased so that the electric characteristic of the specimen can be measured efficiently.

The defective product inspection apparatus may further comprises a specimen chamber being capable of being kept in vacuumed condition and containing therein the first and second positions (more preferably also a third position as described below) in such a manner that the probe and the specimen are kept (continuously) in the vacuum environment of the specimen chamber (to prevent the probe and the specimen from taken out from the vacuum environment, that is, the specimen chamber of vacuumed condition containing therein the first, second and third positions), while the base table is moved between (or from) the first position and (or to) the second position, so that the specimen is prevented completely by the vacuumed condition of the specimen chamber from being damaged by an environment matter surrounding the specimen chamber.

The apparatus further may comprise a third position at which the probe is replaced by another probe, and the base table may be movable among the first, second and third positions in the specimen chamber, so that the specimen is prevented completely by the vacuumed condition of the specimen chamber from being damaged by the replacement or exchange of the probe. It is preferable for increasing the efficiency for measuring the electric characteristic of the specimen that a distance between the first and second positions is shorter than a distance between the second and third positions.

The first measuring device may include at least one of an optical microscope and a CCD camera.

If the probe and the specimen are capable of (manually or automatically): being moved with respect to each other at least in a first direction parallel to the thickness direction of the specimen, while the positional relationship between the probe and the specimen is measured at the first position by the first measuring device, to be positioned to respective adjacent (relative) positions at which (a distance between the contact area of the probe and the desired area of the specimen is not more than a predetermined value (may be zero for making the contact area of the probe and the desired area of the specimen overlap at least partially each other) as seen in a first direction parallel to a thickness direction of the specimen and the contact area of the probe, and/or a distance between or among the probes is as seen in the first direction is not more than a predetermined value and being more than zero and) the desired area of the specimen are separated from each other to form therebetween a clearance of value being not more than a predetermined value (as small as possible) and being more than zero in the first direction, and subsequently being moved with respect to each other at least in the first direction to bring the contact area of the probe and the desired area of the specimen into contact with each other while the positional relationship between the probe and the specimen is measured at the second position by the second measuring device, the time period for at least one of measuring the positional relationship between the probe and the specimen at the second position and bringing the probe and the specimen into contact with each other at the second position can be minimized so that the electric characteristic of the specimen can be measured efficiently, and the specimen is restrained from being damaged at the second position (by at least one of ion beam or electron beam).

It is preferable for decreasing the time period for at least one of measuring the positional relationship between the probe and the specimen at the second position and bringing the probe and the specimen into contact with each other at the second position that the positional relationship between the probe and the specimen is fixed while the base table moves from the first position to the second position.

It is preferable for correctly bringing the contact area of the probe and the desired area of the specimen into contact with each other that the positional relationship between the probe and the specimen is a positional relationship between the contact area of the probe and the desired area of the specimen.

According to the invention, in a method for adjusting a positional relationship between a specimen and a probe to measure an electric characteristic of the specimen through (or with) a contact between the probe and the specimen (so that the measured electric characteristic is compared with a predetermined electric characteristic to judge whether the specimen as a product is defective or not), comprises the steps of: positioning a base table holding thereon a specimen table holding the specimen and a probe holder holding the probe, at a first position to measure the positional relationship between the probe and the specimen at the first position, and subsequently positioning the base table at a second position to measure the positional relationship between the probe and the specimen at the second position so that a contact area (preferably a front end) of the probe and a desired area of the specimen are capable of contacting each other at the second position,

the base table holds the specimen table and the probe holder at each of the first and second positions in such a manner that the specimen table and the probe holder are movable with respect to each other on the base table to adjust the positional relationship between the probe and the specimen, and a measuring accuracy (resolution capability, magnification or the like) at the second position is superior to a measuring accuracy (resolution capability, magnification or the like) at the first position. Incidentally, the specimen table is movable with respect to the base table, and the probe holder is movable with respect to the base table, so that a positional relationship between the specimen table and the base table and a positional relationship between the probe holder and the base table are adjustable independent of each other, and one of the positional relationship between the specimen table and the base table and the positional relationship between the probe holder and the base table is adjustable when the other one the positional relationship between the specimen table and the base table and the positional relationship between the probe holder and the base table is stationary.

Since the base table holds the specimen table and the probe holder at each of the first and second positions in such a manner that the specimen table and the probe holder are movable with respect to each other on the base table to adjust the positional relationship between the probe and the specimen, and the measuring accuracy (resolution capability) at the second position is superior to a measuring accuracy (resolution capability) at the first position, a time period which is needed for measuring the positional relationship between the probe and the specimen at the second position with the measuring accuracy (resolution capability) superior to the measuring accuracy (resolution capability) at the first position can be decreased by the measurement at the first position, so that the electric characteristic of the specimen can be measured efficiently.

It is preferable for minimizing the time period for at least one of measuring the positional relationship between the probe and the specimen at the second position and bringing the probe and the specimen into contact with each other at the second position, that the probe and the specimen are capable of being moved with respect to each other at least in a first direction parallel to the thickness direction of the specimen at the first position, while the positional relationship between the probe and the specimen is measured, to be positioned to respective adjacent (relative) positions at which (a distance between the contact area of the probe and the desired area of the specimen is not more than a predetermined value (may be zero for making the contact area of the probe and the desired area of the specimen overlap at least partially each other) as seen in a first direction parallel to a thickness direction of the specimen and/or a distance between or among the probes as seen in the first direction is not more than a predetermined value and being more than zero, and) the contact area of the probe and the desired area of the specimen are separated from each other to form therebetween a clearance of value being not more than a predetermined value (as small as possible) and being more than zero in the first direction, and subsequently the probe and the specimen are moved with respect to each other at least in the first direction at the second position to bring the contact area of the probe and the desired area of the specimen into contact with each other while the positional relationship between the probe and the specimen is measured.

If at the first position, the positional relationship between the probe and the specimen is measured when the specimen is prevented from being irradiated with at least one of an ion beam and an electron beam, the specimen is prevented from being damaged by the at least one of the ion beam and the electron beam. If at the second position, the positional relationship between the probe and the specimen is measured while irradiating the specimen with at least one of an ion beam and an electron beam, the specimen is restrained from being damaged by the at least one of the ion beam and the electron beam, by the decrease of the time period for at least one of measuring the positional relationship between the probe and the specimen at the second position and bringing the probe and the specimen into contact with each other at the second position.

If at the first position, the positional relationship between the probe and the specimen in each of first and second directions perpendicular to each other is measured, the first direction is parallel to a thickness direction of the specimen, and a first magnification for magnifying an image corresponding to the positional relationship between the probe and the specimen in the first direction is higher than a second magnification for magnifying another image corresponding to the positional relationship between the probe and the specimen in the second direction (so that a contact or distance between the probe and specimen in the first direction is measurable more accurately in comparison with an overlap or distance between the probe and specimen in the second direction), a contact or distance between the probe and specimen in the first direction is measurable more accurately in comparison with an overlap or distance between the probe and specimen in the second direction, and the time period for at least one of measuring the positional relationship between the probe and the specimen at the second position and bringing the probe and the specimen into contact with each other at the second position can be decreased so that the electric characteristic of the specimen can be measured efficiently.

If a vacuum environment is kept around the base table so that the probe and the specimen are kept (continuously) in the vacuum environment (to prevent the probe and the specimen from taken out from the vacuum environment, that is, the specimen chamber of vacuumed condition containing therein the first, second and third positions) while the base table is moved between (or from) the first position and (or to) the second position, the specimen is prevented completely by the vacuumed condition of the specimen chamber from being damaged by an environment matter surrounding the specimen chamber.

If the base table is moved among the first position, the second position and a third position at which the probe is replaced by another probe in the specimen chamber, the specimen is prevented completely by the vacuumed condition of the specimen chamber from being damaged by the replacement or exchange of the probe.

If the positional relationship between the probe and the specimen is fixed while the base table moves from the first position to the second position, the time period for at least one of measuring the positional relationship between the probe and the specimen at the second position and bringing the probe and the specimen into contact with each other at the second position can be decreased.

DETAILED DESCRIPTION OF THE INVENTION

As shown inFIG. 1, a defective product inspection device1has a specimen chamber7containing a specimen stage including a specimen holder2on which a specimen is to be held, and a specimen holder receiver17holding the specimen holder2, and a probe stage6including a probe unit33. An electronic optical device4(a charged particle apparatus) such as an SEM (scanning electron microscope), a focused ion beam (FIB) device or the like including an ion pump44is arranged on a frame of the specimen chamber7to opposite to the specimen holder2. Further, a probe rough-approaching image forming device10is arranged in the vicinity of the electronic optical device4. A charged particle beam (electron beam or ion beam) is projected from the electronic optical device4toward the specimen holder to monitor movements of the specimen and a probe3.

The probe rough-approaching image forming device10arranged in the vicinity of the electronic optical device4on an upper surface of the frame of the specimen chamber7has a probe rough-approaching optical microscope and a CCD camera for obtaining an image so that a condition in rough approach of the probe3with respect to the specimen is monitored by obtaining its image. Further, the probe rough-approaching image forming device10has a probe rough-approaching image forming device10afor monitoring in a vertical direction and a probe rough-approaching image forming device10bfor monitoring in a horizontal direction, so that the condition in rough approaching between the prove and the specimen can be monitored securely in two directions perpendicular to each other. In this case, a magnification of the probe rough-approaching image forming device10bfor magnifying the image corresponding to the condition in rough approaching as seen in the horizontal direction is made higher than a magnification of the probe rough-approaching image forming device10afor magnifying the image corresponding to the condition in rough approaching as seen in the vertical direction, because the image corresponding to the condition in rough approaching obtained by the probe rough-approaching image forming device10aneeds to include a plurality of the probes3which need to be approached each other and horizontally positioned over respective areas of the specimen so that at least one electric characteristic of the specimen is detected from the areas of the specimen after the probes3are brought into contact with the areas of the specimen respectively. Each of the probes is moved downwardly to a position adjacent to the specimen while monitoring the image corresponding to the condition in rough approaching as seen in the horizontal direction, and the probes are moved to be adjacent to each other and be separated from each other with a slight distance therebetween or thereamong as seen in the vertical direction. Subsequently, each of the probes is brought into contact with the respective one of the areas of the specimen by moving downwardly each of the probes while monitoring a difference between a focusing condition of each of the probes and a focusing condition of the corresponding one of the areas of the specimen to be decreased in an image as seen in the vertical direction formed by the electronic optical device4, that is, while monitoring a focusing position of the electronic optical device4at which each of the probes is focused and a focusing position of the electronic optical device4at which the corresponding one of the areas of the specimen or an area closely adjacent to the corresponding one of the areas of the specimen is focused. If a distance between each of the probes and the corresponding one of the areas of the specimen is made as small as possible before the downward movement of each of the probes on the basis of the image formed by the electronic optical device4, a time period for the downward movement of each of the probes for the contact between each of the probe and the corresponding one of the areas of the specimen on the basis of the image formed by the electronic optical device4can be small to decrease an amount of the charged particle beam with which the specimen is irradiated by the electronic optical device4. Therefore, the magnification of the probe rough-approaching image forming device10bis made higher than the magnification of the probe rough-approaching image forming device10ato improve an accuracy for measuring a positional relationship between each of the probes and the corresponding one of the areas of the specimen.

A stage includes a base table49on which a specimen stage50on which the specimen holder2for holding the specimen is mounted and the probe unit33are mounted, and a base plate48on which the base table49is guided linearly and moved horizontally to position a combination of a set of the probes and the specimen at desired one of a fine or finish positioning position just under the electronic optical device4for measuring extremely accurately the positional relationship between each of the probes (preferably the front end contacting areas of the probes) and the corresponding one of the areas of the specimen and bringing each of the probes into contact with corresponding desired electrode of the specimen by moving each of the probes (preferably with an extremely slight adjustment of the positional relationship between each of the probes and the corresponding desired electrode of the specimen as seen in the thickness direction of the specimen), a rough-approaching positioning position just under the probe rough-approaching image forming device10for measuring the positional relationship between or among the probes and the positional relationship between each of the probes and the specimen and positioning each of the probes or the set of the probes with respect to the specimen to make a distance between or among the probes to be included by an area as seen in the direction parallel to the thickness direction not more than a visible or measurable scope of the electronic optical device4and to make a distance between each of the probes and the specimen or a distance between the set of the probes and the specimen as seen in another direction perpendicular to the thickness direction not more than a predetermined value and more than zero so that each of the proves and the set of the probes are separated slightly (as shortly as possible while keeping a minimum distance or clearance therebetween) from the specimen as seen in another direction perpendicular to the thickness direction of the specimen, and a probe exchange position just under a probe exchange chamber9for removing desired one of the prove holders31including the respective probes3from corresponding one of the probe units33to be withdrawn into the probe exchange chamber9and subsequently bringing a substitute one of the probe holders31from the probe exchange chamber9to be set onto the corresponding one of the probe units33. The stage is attached to a side surface of the specimen chamber7through a plate71. As shown inFIG. 2, the plate71is movably supported on the specimen chamber7by a guide connecting plate71aand a roller guide71b. As shown inFIG. 3, the stage is drawn out of the specimen chamber7along the roller guide71bwhen a maintenance of the stage is done or the probe unit is exchanged. Guide blocks48aattached to a lower surface of the specimen chamber7support vertically the stage through sliding members48bof low-friction high polymer material between upper surfaces of the guide blocks48aand a lower surface of the base plate48.

The probe stage6has the probe units33including the probe holders31for holding the probes3respectively, a probe unit base34on which the probe units33are mounted and a probe unit bracket35connecting the probe unit base34to the base table49. Each of the probe units33can generates a movement of respective one of the probes3in three directions perpendicular to each other with respect to the probe unit base34fixed to the base table49. The base plate48can be fixed to the side wall of the specimen chamber7by a fixing member47. The specimen chamber7includes a specimen exchange chamber8and the probe exchange chamber9.

The plate71includes a feed-through to supply a signal for controlling the probe driving motion of each of the probe units33, and a signal for controlling a motion of each of x, y, z tables61,62,63of the specimen stage50into the specimen chamber7.

Although the specimen exchange chamber8is arranged on a right side surface inFIG. 1, the specimen exchange chamber8may be arranged at a front side surface in the vicinity of the electronic optical device4so that the specimen can be exchanged easily when the specimen table is under the electronic optical device4. An inside of the specimen exchange chamber8and an inside of the specimen chamber7are connected to each other by a gate valve21. The inside of the specimen exchange chamber8is connected by a dry pump52to be vacuumed. Therefore, the exchange of the specimen holder with the specimen thereon can be performed by a transfer member29while a vacuum condition is kept in the specimen chamber7.

The probe exchange chamber9is arranged adjacently to the electronic optical device4and the probe rough-approaching image forming device10awhile its distance from the probe rough-approaching image forming device10ais smaller than its distance from the electronic optical device4. An inner side of the probe exchange chamber9is connected to the inside of the specimen chamber7through a gate valve23. The probe exchange chamber9is fluidly connected to a turbo molecular pump (TMP)51and the dry pump (DP)52connected to the turbo molecular pump to perform a vacuuming operation. While maintaining a high vacuum in the specimen chamber7, the probe holder31is exchanged by an exchange mechanism55. The specimen chamber7is fluidly connected to the TMP11through a gate valve53and the TMP11is connected to DP12. A frame of the specimen chamber7is supported by a bracket25shown by an alternate long and short dash line. A control device13including a probe unit control part and a stage control part and another control device13A for controlling a high vacuuming operation of the TMP11and DP12are arranged. The control device13A controls also TMP51and DP52.

Further, the defective product inspection apparatus1includes a display device14including an image display part15and an image display control part16, and a probe operation signal and a stage operation signal from the image display control part16are transmitted to the probe unit control part and the stage control part to control the probe units33and the stage.

The probe is exchanged, after the x and Y tables of the probe unit to be exchanged are positioned at respective predetermined positions (for example, back end positions), and the z table thereof is positioned at a predetermined position (for example, upper most end position).

The specimen stage50is driven to position an area of the specimen which should be made visible on the image display part15for displaying the image generated by the electronic optical device4, that is, needs to be contacted by the probes, into the visible or measurable scope of the electronic optical device4for monitoring both the set of the probes and the area of the specimen after the base table49is moved on the base plate48and the X-Y tables64and65are driven so that the set of the proves is positioned in the visible or measurable scope of the electronic optical device4, and subsequently each of the probes3is brought into contact with the corresponding one of the electrodes on the area of the specimen by driving the x, y and z tables of the corresponding one of the probe units33while monitoring each of the probes and the specimen on the image display part15. The condition in contact and distance between the probe and the electrode of the specimen in the direction parallel to the thickness direction of the specimen is measurable from the focusing conditions of the electronic optical device4on the front end (contact area) of the probe and the electrode surface or a surface area of the specimen closely adjacent to the electrode surface, that is, a focusing position of the electronic optical device4at which the front end (contact area) of the probe is focused and a focusing position of the electronic optical device4at which the electrode surface or the surface area of the specimen closely adjacent to the electrode surface is focused.

A drive mechanism for the probes and the stages are not necessarily limited, but the drive mechanism for the probes may have a piezo-electric element, DC motor or ultrasonic motor, and the drive mechanism for the stages may have a pulse motor, DC motor or ultrasonic motor.

1. Structure and operation of each element

As shown inFIG. 4, the probes3(six inFIG. 4) are held by the probe holders31respectively to form six of the probe units31respectively to be supported on the probe unit base34.

FIG. 5shows in detail the probe holder and the probe unit. As shown in (a) part ofFIG. 5, the probe holder31is inserted into the z table83of the probe unit33and held stationarily thereto by a plate spring84. An assembled condition of the probe unit33is shown in (b) part ofFIG. 5. The probe holder31includes the probe3to be contacted with the specimen, a probe support bar85for fixing the probe3and a probe arm86for fixing the probe support bar85. The probe support bar85has a tubular shape. The probe arm86includes a support bar fixing member87, an insulating ring88, a connection pipe89and an insulating ring90, and the insulating ring90is connected to a probe holder base91. The support bar fixing member87is isolated from the connection pipe89by the insulating ring88, and the connection pipe89is isolated from the probe holder base91by the insulating ring90. The support bar fixing member87extends in the connection pipe89to a back surface of the probe holder base91to contact a probe signal outlet electrode101when the probe holder31is inserted in the z table83. The probe signal outlet electrode101is isolated from the z table83. The connection pipe89contacts a guard signal outlet electrode102when the probe holder31is inserted in the z table83. A grounded signal is obtained from the z table83. The probe signal from the probe signal outlet electrode101, the guard signal from the guard signal outlet electrode102and the grounded signal from the z table83are connected to a three-phase coaxial cable, taken out from the specimen chamber7through a three-phase coaxial hermetic connector mounted on the specimen chamber7, and connected through the three phase coaxial cable to an electric characteristic measuring apparatus such as a semiconductor parameter analyzer or the like to measure the electric characteristic.

The structure of the stage is shown inFIGS. 6-9. The stage includes the base table49(as the claimed base table) and the specimen stage50.

The specimen stage50includes the y table62, x table61and z table63,63ato be driven respective driving mechanisms to be moved in respective y, x and z directions to align the area of the specimen within the visible or measurable scope of the electronic optical device4. Incidentally, the positional relationship among the probes is adjusted by the x and y tables of the prove units33in accordance with the positional relationship among the electrodes on the area of the specimen to align the probes respectively with the electrodes on the area of the specimen in the thickness direction of the specimen under the electronic optical device4after the positional relationship between or among the probes is adjusted under the probe rough-approaching image forming device10so that the probes are included by an area as seen in the thickness direction of the specimen not more than the visible or measurable scope of the electronic optical device4, and each of the probes is driven in the thickness direction of the specimen by corresponding one of the z tables of the prove units33to be brought into contact with the corresponding one of the electrodes under the electronic optical device4. Under the electrodes under the electronic optical device4, each of the probes is moved by the y and x tables of the corresponding one of the prove units33to make each of the probes and the corresponding one of the electrodes overlap each other as seen in the thickness direction. The x and y tables of the prove units33are used to adjust the positional relationship among the probes in accordance with the positional relationship among the desired electrodes of the specimen as seen in the thickness direction of the specimen, and the z tables of the prove units33are used to bring each of the probes into contact with the corresponding one of the desired electrodes of the specimen. The x and y tables of the specimen stage50are used to align the area including the desired electrodes of the specimen with the visible or measurable scope of the electronic optical device4, and the z table of the specimen stage50may be used to make a distance between the area including the desired electrodes of the specimen and the set of probes (the set of the contact areas of the probes to be positioned in accordance with the positional relationship among the desired electrodes of the specimen) as small as possible under the probe rough-approaching image forming device before bringing each of the probes into contact with the corresponding one of the desired electrodes of the specimen by the z tables of the prove units33under the electronic optical device4.

The y and x tables62and61are driven by the respective DC motors through respective ball-screws in the specimen chamber and guided by cross-roller guides. As shown inFIG. 7, the z table63is moved by driving a ball screw63eby the DC motor63bmounted on the z table body63athrough bevel gears63g,63hand shafts63c,63d. The z table is guided linearly by a cross-roller guide. The specimen holder2for holding a specimen2ais fixed to the specimen holder receiver17mounted on the z table63. Therefore, the specimen2ais movable with respect to an electron beam69in x, y and z directions. The specimen holder2on the z table63is movable among a measuring position, a specimen exchange position and a probe exchange position. The measuring position is a position at which a distance between the probe and the specimen2ais decreased to be made as small as possible under the probe rough-approaching image forming device10and the probe is brought into contact with the specimen2aunder the electronic optical device4, the specimen exchange position is a position lower than the measuring position, and the probe exchange position is a position lower than the specimen exchange position, so that an undesirable contact between the probe3and the specimen2ais prevented during each of the probe exchange operation and the specimen exchange operation. The stage50may includes a positional sensor such as a linear scale, an encoder or the like to measure quantitatively the position of each of the tables of the stage50during the operations, so that an accuracy and repeatability of the movement is obtainable. Examples of arrangement of the positional sensors are shown inFIGS. 7 and 8. The positional condition of the z table is measurable by the encoder63fconnected to the shaft63cas shown inFIG. 7. The positional conditions of the e table61and y table62are measurable by the linear scales mounted as shown inFIG. 8. The linear scale has mirrors61a,62amounted on the x table61and y table62and sensor elements61b,62b. In this case, the encoder for measuring the rotary angle of the DC motor is used for the z table, and the linear scales are used for the x table61and y table62, but the encoders, linear scales or combinations thereof may be used for all of the tables.

During the monitoring by the SEM, the specimen2amounted on the specimen stage50is electrically grounded through the specimen stage50and the specimen chamber7to prevent an effect by a charging up. When an electric characteristic of the specimen2ais measured, the specimen2ais preferably isolated electrically from the specimen stage50and the specimen chamber7. Further, for preventing the effect of the charging up, a beam blanking is effective. For the electrical insulation, as shown inFIG. 9, an insulating member18is arranged between the specimen holder receiver17and the z table63, the specimen holder receiver17with the specimen2athereon is connected to a cable20, and the cable20extends from the fixing member47through the plate71to an outside of the vacuumed environment so that the cable20is connected to a grounded terminal through a switch19. By this structure, during the SEM monitoring, the specimen2ais grounded by operating the switch19to prevent the effect caused by the noise. Further, by connecting the cable20through the switch19not to the ground but to an electric characteristic measuring device, the electric characteristic of the specimen2asuch as absorption current or the like is measurable without the effect of the noise from the specimen stage50and the specimen chamber7. Further, the specimen holder receiver17may includes a guard electrode and a grounded electrode similarly to the probe units33and the probe holders31as shown inFIG. 5, so that the cable is connected through the three phase coaxial cable to the outside of the vacuumed environment. Therefore, the electric isolation for the specimen2ais improved.

With making reference toFIG. 10, a process for positioning the specimen2aand the probes3in the specimen chamber is explained.

As shown inFIG. 6, the base table49includes the Y table64and X table65to be positioned in y and x directions respectively. The stage50and each of the prove holders31are mounted on the base table49to adjust and fix the positional relationship between the specimen2aand each of the probes on the base table49.

On the base table49, the probe units33forming the probe stage6, the probe unit base34for supporting the probe units33and the probe unit bracket35are mounted. Each of the prove units33can position the probe in y, x and z directions through the prove holder31supported by each of the prove units33.

As shown inFIG. 10, the base table49is moved on the base plate48along a linear guide by a ball-screw and a servo motor to position briefly a combination of the specimen and the set of the probes with respect to each of the probe rough-approaching image forming device10, the electronic optical device4and the probe exchange chamber9. The Y table64and X table65of the base table49position accurately the combination of the specimen and the set of the probes with respect to each of the probe rough-approaching image forming device10, the electronic optical device4and the probe exchange chamber9.

Therefore, the combination of the specimen and the set of the probes are positioned to each of A position under the electronic optical device4, B position under the probe rough-approaching image forming device10and C position under the probe exchange chamber9while the vacuumed environment surrounding the combination of the specimen and the set of the probes is being kept during the movement of the combination of the specimen and the set of the probes among the A, B and C positions within the specimen chamber.

The SEM arranged on the upper portion of the specimen chamber is an example of the electronic optical device4for monitoring the positional relationship between each of the probes (each of the contact areas of the proves) and the corresponding one of the electrodes of the specimen to bring each of the probes in contact with the corresponding one of the electrodes of the specimen. The vacuuming operation for the SEM is performed by the ion pump44. On the other hand, the probe rough-approaching image forming device10including the optical microscope monitors the positional relationship between each of the probes and the corresponding one of the electrodes of the specimen without irradiating the specimen to bring each of the probes to a position close to the corresponding one of the electrodes of the specimen with making a distance (more than zero) between each of the probes and the corresponding one of the electrodes of the specimen as small as possible.

The specimen chamber4includes an upper cover and a specimen chamber case as the frame, the base48is attached to the plate71through the fixing member47at the side surface of the specimen chamber case, the probe units33are mounted on the base table49in the specimen chamber, and the specimen exchange chamber8is attached to another side surface of the specimen chamber case. The probe rough-approaching image forming device10, the electronic optical device4and the probe exchange chamber9are mounted on the upper cover. The specimen chamber7is fixed to a bearing plate mounted on a vibration absorbing mount on the bracket25. The specimen chamber7is vacuumed by the turbo molecular pump (TMP)11and the dry pump (DP)12.

(5) Optical Microscope for Rough-Approaching, CCD Camera and Rough-Approaching Image Forming Device

The specimen2awhose electrical characteristic needs to be measured is a semiconductor including plugs generally connected a gate, a source, a drain and a well respectively to be connected by the probes respectively. The plug may have a minimum diameter of tens of nanometers, so that a SEM with high resolution is necessary for bringing the probe into contact with the plug. However, by irradiating the semiconductor specimen with the electron and/or ion beam, there is a probability of that the semiconductor specimen is damaged, so that it is preferable for a time period of irradiating the semiconductor specimen with the electron and/or ion beam to be made as short as possible. Therefore, on the basis of the image of the probe rough-approaching image forming device10displayed on the image display part15, a distance between each of the probes and corresponding one of the plugs (electrodes) of the specimen as seen in the thickness direction of the semiconductor specimen is made as small as possible or preferably zero, and a gap or clearance therebetween as seen in a direction perpendicular to the thickness direction is made as small as possible but is prevented from being zero. This operation is performed while an image showing the positional relationship between the probes and the specimen surface as obtained by the probe rough-approaching optical microscope and the CCD camera attached thereto and displayed on the image display portion15is monitored.

The magnification on the image display portion15is tens to form an image including the specimen2aand the probes3adjacent to each other as close as possible.

A light source is arranged in the vicinity of the probe rough-approaching optical microscope. The monitoring by the probe rough-approaching optical microscope and CCD camera and the light supply from the light source into the specimen chamber is performed through a window aperture39as shown inFIG. 1.

The specimen exchange chamber8is arranged to exchange the specimen2awhile keeping the environment vacuum condition surrounding the specimen2ain the specimen chamber7and vacuumed by the dry pump52. The specimen exchange chamber8can be isolated fluidly from the specimen chamber7by the gate valve21. When the specimen2ais introduced into the specimen chamber7, a male screw of a front end of an exchange bar29as a transfer member for the specimen2aand the specimen holder2is screwed into a female screw of the specimen holder2with the specimen2athereon, the gate valve21is opened, and the specimen holder2is inserted onto the specimen holder receiver17attached to an upper end of the z table63of the specimen stage50. When the specimen2ais taken out of the specimen chamber, a reverse operation is performed. Therefore, a time period for the specimen exchange can be decreased.

The probe exchange chamber9is arranged to exchange the probe3while keeping the environment vacuum condition surrounding the probe3in the specimen chamber7so that a time period for the probe exchange is decreased. The probe exchange chamber9can be isolated fluidly from the specimen chamber7by the gate valve23. The probe exchange chamber9is vacuumed by the turbo molecular pump51and the dry pump52. The turbo molecular pump51is used to accelerate a vacuuming operation for the probe exchange chamber9, because if the vacuuming operation for the probe exchange chamber9is brought about by the dry pump52without the turbo molecular pump51, a great volume of the probe exchange chamber9in which a pressure cannot be decreased sufficiently within a short time period by the dry pump52without the turbo molecular pump51causes a great increase of the inner pressure of the specimen chamber7when the gate valve23is opened to exchange the probe3so that a time period for making the pressure in the specimen chamber7at the same value as the previous pressure before opening the gate valve23becomes long.

In the probe exchange chamber9, a stocker (not shown) for holding the probe holders31is arranged and moved by a ball-screw with respect to a probe exchange bar92. The probe holder31is moved below the probe exchange bar92to be withdrawn from the stocker or contained in the stocker. A latch key96at a lower end of an exchange rod94arranged in a probe exchange bar outer tube93coaxial with the probe exchange bar92is rotated by90degrees to engage with a latch receiver95on the probe holder31to be connected to the probe exchange bar92. The exchange rod94is rotated by 90 degrees in a reverse direction to disengage the latch key96from the latch receiver95. The stocker including the used probe holders31is taken out of the probe exchange chamber9, and unused ones of the probe holders31are inserted onto the stocker to be introduced into the probe exchange chamber9.

When the probe holder31is transferred from the stocker to the probe unit33, the latch key96of the probe exchange rod94is engaged with the latch receiver95on the probe holder31, and the probe exchange bar92is moved upward by a rack-and-pinion mechanism to withdraw the probe holder31from the stocker. The gate valve23is opened and the probe exchange bar92is moved downward to introduce the probe holder31into the specimen chamber. As shown inFIG. 5, the holder receiver is arranged on the z table83of the probe unit33. The base table49is driven to move the holder receiver below the transferred probe holder31, the probe exchange bar92is rotated to make orientations of the holder receiver and the probe holder31consistent with each other, and the exchange bar92is moved downward to insert the probe holder31into the holder receiver. The latch key96is disengaged from the latch receiver95, the probe exchange bar92is moved upward to be withdrawn into the probe exchange chamber9, and the gate valve23is closed.

2. Control System

The SEM, the probe units33and the tables of the stages are controlled by respective control circuits and computers contained by the control device13. The SEM, the probe units33and the tables of the stages are controllable from a operating panel or GUI on the monitor.

The control device13includes a stage controller for controlling the tables of the stages, and a probe controller for controlling the probe units33independent of the stages. The image control part16includes a secondary electron detector control part, a control part for the electron beam emitting optical system and so forth. In addition, a calculation treatment part has a function of displaying an image showing the specimen holder, the specimen2aand the positional relationship between the proves and the specimen2a.

The probe units33and the tables of the stages are driven by operating an operating display of the image display part to supply an operating signal through the image display control part to the probe unit control part and the stage control part. Alternatively, an operating panel including a joy-stick may be used to drive the units33and the tables of the stages.

The electron beam generated by an electron gun is emitted through a condensing lens and an objective lens to the specimen2ato be irradiated, and the secondary electron generated from the specimen2ais detected by the secondary electron detector to generate a signal so that the signal is electrically treated variously in the display to form an image of the specimen surface on the monitor on the image display part15of the display device14.

A signal for controlling each of the operations of the x, y and z tables of each of the probe units33from the control circuit13in the bracket25as shown inFIG. 1is supplied to each of the probe units33in the specimen chamber7through a feed-through attached the plate71of the stages. Input signals supplied to the specimen2athrough the probes3attached to the probe holders31and output signals generated from the specimen2aare transmitted with respect to a semiconductor parameter analyzer through a three phase coaxial hermetic connector attached to the specimen chamber7.

Signals generated by the control circuit in the bracket25to control the operations of the x, y and z tables61,62and63of the specimen stage50on the base plate49are supplied to the specimen stage50in the specimen chamber through the feed-through attached to the plate71. Signals for controlling the operations of the x and y tables64and65are also supplied to the base plate49through the feed-through attached to the plate71.

The display device14displays a rough-approaching image taken by the probe rough-approaching image forming device10, a contacting image taken by the electron optical device4to show a positional relationship between each of the probes and the specimen brought into contact with each other, the probe operating image and an image showing a sequence of the operating.

The user operates the probes3and the specimen2ato be positioned accurately with respect to each other along the sequence of the operating displayed on the display device14, while monitoring the rough-approaching image and the contacting image.

As shown inFIG. 12A, the rough-approaching image taken by the probe rough-approaching image forming device10A shows the positional relationship between each the probes and the specimen as seen in the thickness direction of the specimen with the magnification of, for example, 10. As shown inFIG. 12B, the rough-approaching image taken by the probe rough-approaching image forming device10B shows the positional relationship between each the probes and the specimen as seen in the direction perpendicular to the thickness direction of the specimen with the magnification of, for example, 25 increased by 2.5 times in comparison with the magnification of the rough-approaching image taken by the probe rough-approaching image forming device10A to enable a distance between each of the probes3and the specimen2aas seen in the direction perpendicular to the thickness direction of the specimen to be made as small as possible but to be prevented from decreasing to zero. As shown inFIG. 12C, the contacting image taken by the electron optical device4shows the positional relation ship between each of the probes3(each of the contact areas of the probes) and the corresponding one of the electrodes or plugs100of the specimen2ato be brought into contact with each other, with the magnification of thousands to ten-thousands. The electrodes or plugs100are connected respectively to the gate, source, drain and so forth in the specimen2a.