Abstract:
An inspection method for inspecting electric characteristics of devices formed on a target object using an apparatus including a vertical drive mechanism for lifting and lowering a movable mounting table and a control unit for controlling the vertical drive mechanism. The vertical drive mechanism includes an elevation shaft connected to the mounting table and a servo motor for driving the elevation shaft to lift and lower the mounting table. The control unit has a servo driver including a position control part for controlling a position of the motor, a torque control part for controlling a torque of the motor as a probe card is expanded or contracted by a change in temperature and a switching part for switching the position control part and the torque control part. The method includes heating or cooling the target object, controlling a position of the motor, and controlling a torque of the motor.

Description:
CROSS-REFERENCE(S) TO RELATED APPLICATIONS 
       [0001]    This application is a continuation application of pending U.S. application Ser. No. 12/146,081, filed on Jun. 25, 2008, which claims priority to Japanese Patent Application No. 2007-227182, filed on Aug. 31, 2007. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to an inspection apparatus and an inspection method; and, more particularly, to an inspection apparatus and an inspection method capable of shortening an inspection time. 
       BACKGROUND OF THE INVENTION 
       [0003]    A conventional inspection apparatus includes, e.g., a mounting table for mounting thereon a target object (e.g., a wafer) to be inspected, the mounting table having therein a temperature controller for controlling the temperature of the wafer, a vertical drive mechanism for moving the mounting table up and down, an XY table for moving the mounting table and the vertical drive mechanism in X and Y directions, a probe card arranged above the mounting table, and an alignment mechanism for accurately aligning a plurality of probes of the probe card with a plurality of electrode pads of the target object placed on the mounting table. The temperature of the wafer placed on the mounting table is controlled to a predetermined value by the temperature controller. A specified device formed on the wafer is brought into electrical contact with the probes of the probe card through the alignment mechanism. Then, the probe card is overdriven by a prescribed overdrive amount so that the electric characteristics of the device can be inspected under a predetermined contact load. 
         [0004]    In some cases, the inspection apparatus performs a high temperature inspection by heating the wafer to a high temperature of, e.g., 100° C. or more. In other cases, the inspection apparatus carries out a low temperature inspection by cooling the wafer to a temperature of, e.g., minus several tens of degrees centigrade. When performing the high temperature inspection or the low temperature inspection, the target object is heated or cooled to a predetermined inspection temperature by the temperature controller provided in the mounting table. While controlling the position of the mounting table with the vertical drive mechanism, the device and the probes are brought into contact with each other under a specified contact load. The high temperature inspection or the low temperature inspection is performed in this state. The vertical drive mechanism includes, e.g., a ball screw connected to the mounting table and a stepping motor for rotating the ball screw. The stepping motor controls the amount of rotation of the ball screw and, eventually, controls the vertical position of the mounting table with increased accuracy. 
         [0005]    In case of performing, e.g., the high temperature inspection of the wafer, the wafer placed on the mounting table is heated to, e.g., 100° C. or more, by use of the temperature controller provided in the mounting table. The wafer placed on the mounting table is aligned with the probes of the probe card by means of the alignment mechanism. In a state that the wafer and the probes are in contact with each other under the predetermined contact load, the electric characteristics of the wafer are inspected at a high temperature of 100° C. or more. 
         [0006]    In an initial stage of the inspection, however, the probe card is not yet heated while the wafer is already heated to a temperature of 100° C. or more by the temperature controller. Thus, there exists a great temperature difference between the wafer and the probe card. For this reason, if the wafer is overdriven by a predetermined amount to bring the probes into contact with a first device of the wafer when inspecting the latter, the probe card is heated and gradually expanded by the heat radiated from the wafer during the contact. Therefore, the device and the probes make contact with each other under a load greater than the predetermined contact load, which may possibly cause damage to the device or the probes. 
         [0007]    In view of this, the high temperature inspection is performed after preheating and completely heat-expanding the probe card. As the probe card becomes greater in size, however, it takes a long time, e.g., 20 to 30 minutes, to preheat the probe card. For example, Japanese Patent Laid-open Publication No. 2007-088203 (JP2007-088203A) discloses a technique of shortening a preheating time of the probe card by making the probes of the probe card brought into direct contact with a wafer heated to a predetermined temperature and preheating the probe card near the wafer. 
         [0008]    In the technique disclosed in JP2007-088203A, however, a preheating time is still required in addition to an actual inspection time. Therefore, there is a limit in shortening the total inspection time. Furthermore, if the wafer is moved away from the probe card during index movement of a target object, the probe card is cooled to thereby change the height of the tips of the probes. For this reason, the contact load is changed each time when the index movement is carried out. In this case, however, it is impossible to control the contact load. Meanwhile, when performing a low temperature inspection of the wafer, there is a need to cool the probe card to a temperature near the wafer temperature. 
       SUMMARY OF THE INVENTION 
       [0009]    In view of the foregoing, the present invention provides an inspection apparatus and an inspection method capable of shortening an inspection time by inspecting a target object without preliminarily heating or cooling a probe card during high temperature inspection or low temperature inspection, and also capable of performing the inspection with increased reliability by positively preventing damage of the probe card and the target object. 
         [0010]    In accordance with an aspect of the present invention, there is provided an inspection apparatus for inspecting electric characteristics of a plurality of devices formed on a target object, the apparatus including: a movable mounting table having therein a temperature controller; a vertical drive mechanism for lifting and lowering the mounting table; a control unit for controlling the vertical drive mechanism; and a probe card having a plurality of probes arranged above the mounting table, the target object being heated or cooled to a specified temperature by means of the temperature controller and being inspected while the devices and the probes of the probe card are brought into contact with each other under a predetermined contact load by means of the vertical drive mechanism, wherein the vertical drive mechanism comprises an elevation shaft connected to the mounting table and a servo motor for driving the elevation shaft to lift and lower the mounting table, wherein the control unit comprises a servo driver which includes a position control part for controlling a position of the servo motor, a torque control part for controlling a torque of the servo motor as the probe card is expanded or contracted by a change in temperature and a switching part for switching the position control part and the torque control part. 
         [0011]    Preferably, the servo driver is connected to a master computer for monitoring the inspection apparatus, and the master computer includes a position command part for transmitting a position command signal to the position control part, a torque command part for transmitting a torque command signal to the torque control part and a switching command part for transmitting a switching command signal to the switching part based on the torque of the servo motor. 
         [0012]    The servo driver may further include a storage part for storing a torque value indicative of a contact load available each time when the electric characteristics of the devices are inspected. 
         [0013]    In this case, the storage part may store upper and lower limit values of the predetermined contact load. 
         [0014]    Preferably, the torque control part controls a contact load of the devices and the probes in keeping with thermal expansion or contraction of the probe card to become equal to the predetermined contact load. 
         [0015]    In this case, the torque control part may stop the servo motor when a contact load of the devices and the probes falls outside a range between the upper and lower limit values. 
         [0016]    In accordance with another aspect of the present invention, there is provided an inspection method for inspecting electric characteristics of a plurality of devices formed on a target object by using an inspection apparatus which comprises a movable mounting table having therein a temperature controller; a vertical drive mechanism for lifting and lowering the mounting table; a control unit for controlling the vertical drive mechanism; and a probe card having a plurality of probes arranged above the mounting table, the vertical drive mechanism including an elevation shaft connected to the mounting table and a servo motor for driving the elevation shaft to lift and lower the mounting table, the inspection method comprising: a first step of heating or cooling the target object to a predetermined temperature; a second step of controlling a position of the servo motor until the target object and the probes come into contact with each other; and a third step of controlling a torque of the servo motor after the target object and the probes has come into contact with each other. 
         [0017]    The inspection method may further comprise a step of storing a torque value indicative of a contact load available each time when the electric characteristics of the devices are inspected. 
         [0018]    In the third step, a contact load of the devices and the probes may be controlled in keeping with thermal deformation of the probe card to become equal to a predetermined contact load. 
         [0019]    In the third step, a contact load of the devices and the probes may be controlled to fall within a range between upper and lower limit values of a predetermined contact load. 
         [0020]    In the third step, the servo motor may be stopped when a contact load of the devices and the probes falls outside a range between upper and lower limit values of a predetermined contact load. 
         [0021]    In accordance with the present invention, it is possible to provide an inspection apparatus and an inspection method capable of shortening an inspection time by inspecting a target object without preliminarily heating or cooling a probe card during high temperature inspection or low temperature inspection, and also capable of performing the inspection with increased reliability by positively preventing damage of the probe card and the target object. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The objects and features of the present invention will become apparent from the following description of embodiments given in conjunction with the accompanying drawings, in which: 
           [0023]      FIG. 1  is a view for explaining major parts of an inspection apparatus in accordance with an embodiment of the present invention; 
           [0024]      FIG. 2  is a flowchart illustrating an inspection method of the present invention performed by the inspection apparatus shown in  FIG. 1 ; and 
           [0025]      FIGS. 3A and 3B  are views for explaining the inspection method illustrated in  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0026]    Hereinafter, an embodiment of the present invention will be described with reference  FIGS. 1 to 3 . 
         [0027]    First, an inspection apparatus of the present embodiment will be described with reference to  FIG. 1 . As shown in  FIG. 1 , the inspection apparatus  10  of the present embodiment includes, e.g., a mounting table  11  for mounting thereon a target object (e.g., a wafer) W, the mounting table  11  having therein a temperature controller, a vertical drive mechanism  12  for raising and lowering the mounting table  11 , an XY table (not shown) on which the mounting table  11  and the vertical drive mechanism  12  are arranged, a probe card  13  arranged above the mounting table  11  and provided with a plurality of probes  13 A and an alignment mechanism (not shown) for aligning the wafer W mounted on the mounting table  11  with the probes  13 A of the probe card  13 . In a high temperature inspection for example, the vertical drive mechanism  12  is designed to change the current position of the mounting table  11  in response to the thermal expansion of the probe card  13 , thereby keeping a predetermined contact load at all times so that the inspection can be performed in a stable manner. 
         [0028]    In case of performing the high temperature inspection of the wafer W, the wafer W placed on the mounting table  11  is heated to a temperature of, e.g., 100° C. or more by means of the temperature controller. While the mounting table  11  is moved in X and Y directions, the wafer W placed on the mounting table  11  is aligned with the probes  13 A by the alignment mechanism. After the wafer W is index-moved by the XY table, the vertical drive mechanism  12  brings one of a plurality of devices formed in the wafer W into electrical contact with the probes  13 A under a predetermined contact load. Then, the electric characteristics of each of the devices are inspected at a specified high temperature. 
         [0029]    As can be seen in  FIG. 1 , the vertical drive mechanism  12  includes a ball screw  14  connected to and suspended from the center of a lower surface of the mounting table  11 , a servo motor  15  for rotating the ball screw  14 , the servo motor  15  having an encoder  15 A, and a servo driver  16  for controlling the operation of the servo motor  15 . The servo motor  15  is position-controlled or torque-controlled by the servo driver  16 . A nut member  14 A is threadedly coupled to the ball screw  14  and a pulley  15 B is attached to the servo motor  15 . A power transmission belt  17  is wound around the nut member  14 A and the pulley  15 . The torque of the servo motor  15  is transferred to the ball screw  14  via the pulley  15 A, the power transmission belt  17  and the nut member  14 A so that the mounting table  11  can be moved up and down. 
         [0030]    Use of the servo motor  15  and the servo driver  16  in the vertical drive mechanism  12  ensures that, even if the probe card  13  is thermally expanded, the servo driver  16  controls the position of the servo motor  15  in a below-described manner until the wafer W and the probes  13 A come into contact with each other. Thus, the servo driver  16  controls the mounting table  11  with increased accuracy so that the wafer W placed on the mounting table  11  can make electric contact with the probes  13 A. After the mounting table  11  is overdriven to assure electric contact between the wafer W and the probes  13 A, the position control of the servo motor  15  is switched to the torque control. Then, the servo driver  16  controls the torque of the servo motor  15  with increased accuracy so that the contact load between the wafer W and the probes  13 A becomes equal to a predetermined contact load. 
         [0031]    More specifically, the servo driver  16  is connected to a master computer  20  through a network as shown in  FIG. 1  and is operated by various kinds of command signals issuing from the computer  20 . The servo driver  16  includes a position control part  161  for controlling the position of the servo motor  15  in response to the command signals issuing from the master computer  20 , a torque control part  162  for controlling the torque of the servo motor  15  in response to the command signals issuing from the master computer  20 , and a switching part  163  for switching the position control part  161  and the torque control part  162  in response to the command signals issuing from the master computer  20 . The servo driver  16  is designed to control the position or torque of the servo motor  15 . 
         [0032]    As shown in  FIG. 1 , the master computer  20  includes a position command part  21  for transmitting a position command signal P to the position control part  161 , a torque command part  22  for transmitting a torque command signal T 1  to the torque control part  162 , a switching command part  23  for transmitting a switching command signal C to the switching part  163 , and a monitoring part  24  for monitoring the mounting table  11  through the servo motor  15 . Even when the probe card  13  is thermally expanded during the high temperature inspection, the monitoring part  24  monitors the mounting table  11  with reference to a feedback signal F or a torque signal T 2  issuing from the servo motor  15 . Based on the monitoring results, the position command signal P, the torque command signal T 1  or the switching command signal C is transmitted to the servo driver  16 . Thus, one of the devices of the wafer W placed on the mounting table  11  is made to contact with the probes  13 A under a predetermined contact load so that the high temperature inspection can be performed with increased reliability. Furthermore, the monitoring part  24  monitors the whole inspection process of the wafer W performed in the inspection apparatus  10  and transmits the switching command signal C to the servo driver  16  each time when the inspection of each device of the wafer W is completed. In addition, the master computer  20  is also connected to servo drivers of other inspection apparatuses to monitor the latter. 
         [0033]    As shown in  FIG. 1 , the position control part  161  includes a comparator  161 A for comparing the position command signal P transmitted from the master computer  20  with the feedback signal F supplied from the encoder  15 A to generate a digital deviation signal, a D/A converter  161 B for converting the digital deviation signal generated in the comparator  161 A to an analog signal, and an amplifier  161 C for amplifying an electric current supplied from the D/A converter  161 B. The position control part  161  is designed to rotatingly drive the servo motor  15  based on an output current I fed from the amplifier  161 C. 
         [0034]    As can be seen in  FIG. 1 , the torque control part  162  includes a comparator  162 A for comparing the torque command signal T 1  issuing from the master computer  20  with the current value (the torque signal) T 2  supplied from the servo motor  15  to generate a digital deviation signal, a D/A converter  162 B for converting the digital deviation signal generated in the comparator  162 A to an analog signal, and an amplifier  162 C for amplifying the analog signal supplied from the D/A converter  162 B. The torque control part  162  is designed to control the torque of the servo motor  15  based on a torque signal (an electric current) T fed from the amplifier  162 C. The torque control part  162  further includes a storage part  162 D for storing, as a torque value, the contact load available in the previous high temperature inspection and the tolerance values (the upper and lower limit values) of the contact load. The torque value stored in the storage part  162 D is set as a contact load when the next device is subjected to the high temperature inspection. Furthermore, the torque value is controlled to fall within a permissible torque range between an upper and a lower limit value available during the high temperature inspection. The torque control part  162  is designed to stop the inspection in the event that the torque value falls outside the permissible torque range for any reason. 
         [0035]    As shown in  FIG. 1 , the switching part  163  is operated in response to the switching command signal C issuing from the master computer  20  and is designed to alternately switch the position control part  161  and the torque control part  162 . For example, the servo motor  15  lifts up the mounting table  11  with a constant torque under the control of the position control part  161  to thereby bring the wafer W placed on the mounting table  11  into contact with the probes  13 A, and the torque is changed if the mounting table  11  is overdriven thereafter. At this time, the monitoring part  24  of the master computer  20  is monitoring the torque signal T 2 . If the torque signal T 2  is changed due to the overdrive of the mounting table  11 , a switching command signal is transmitted from the switching command part  23  to the switching part  163 . Consequently, the position control part  161  is switched to the torque control part  162  which in turn controls the torque of the servo motor  15 . In a conventional case, the probe card  13  is thermally expanded and the tips of the probes  13 A are pressed against the corresponding device. As a result, the contact load exceeds a predetermined value, which may possibly cause damage to the device or the probes. 
         [0036]    In the present embodiment, however, the servo motor  15  is switched from the position control to the torque control and is reversely rotated a little bit to slightly reduce the torque, whereby the torque is controlled to become a torque value corresponding to the predetermined contact load. Once the high temperature inspection is completed under the predetermined contact load, the master computer  20  performs index movement of the wafer W in response to the signals supplied from the inspection apparatus  10  and then transmits a switching command signal C to the servo driver  16  to switch the torque control to the position control. Subsequently, the next device is subjected to the high temperature inspection. 
         [0037]    Next, an inspection method using the inspection apparatus  10  of the present embodiment will be described with reference to  FIGS. 1 to 3 . 
         [0038]    If the wafer W is mounted on the mounting table  11  in a conventional manner, the wafer W is heated to a high temperature of 100° C. or more by means of the temperature controller. During this, the mounting table  11  is moved in the X and Y directions and the wafer W is aligned with the probes  13 A of the probe card  13  by means of the alignment mechanism. After the alignment is completed, the mounting table  11  is moved in the X and Y directions so that the device to be inspected first arrives just below the probes  13 A. 
         [0039]    Once the first device of the wafer W arrives just below the probes  13 A, the master computer  20  transmits a position command signal P to the position control part  161  of the servo driver  16 . Then, as illustrated in  FIG. 2 , the servo driver  16  begins to control the position of the servo motor  15  (step S 1 ). In the position control part  161 , the comparator  161 A receives the position command signal P from the master computer  20  and also receives the feedback signal F from the encoder  15 A of the servo motor  15 . Then, the comparator  161 A transmits a deviation signal indicative of the deviation between the position command signal P and the feedback signal F to the D/A converter  161 B. The D/A converter  161 B converts the deviation signal to an analog signal and transmits the analog signal to the amplifier  161 C. The amplifier  161 C amplifies the electric current received from the D/A converter  161 B and applies the amplified current to the servo motor  15 , thus lifting up the mounting table  11 . As the mounting table  11  is lifted up and the wafer W is moved toward the probe card  13 , the probe card  13  is gradually heated and thermally expanded by the heat radiated from the mounting table  11 . Then, the mounting table  11  is overdriven to bring the wafer W and the probes  13 A into electrically conducting contact with each other (step S 2 ). 
         [0040]    The probes  13 A are directly heated by the wafer W due to the contact between the probes  13 A and the wafer W. Also, the probe card  13  is gradually heated by the heat radiated from the mounting table  11 , thereby causing heat expansion of the probe card  13  as a whole. As a result, as indicated by a dashed dotted line in  FIG. 3A , the height of electric contact between the electrode pads Dp of the device D and the probes  13 A becomes lower than an original contact height. Therefore, the probes  13 A are pushed up to the position indicated by a solid line in  FIG. 3A . Consequently, the electrode pads Dp and the probes  13 A come into contact with each other under a contact load greater than the predetermined contact load. 
         [0041]    In the present embodiment, as illustrated in  FIG. 2 , the master computer  20  monitors the torque generated in the servo motor  15  by the overdrive (step S 3 ) and stores the current torque T 2  of the servo motor  15  in the storage part  162 D of the servo driver  16  (step S 4 ) as shown in  FIG. 1 . At the same time, the master computer  20  transmits a switching command signal C to the switching part  163  of the servo driver  16  and allows the switching part  163  to switch the position control part  161  to the torque control part  162  (step S 5 ) so that the torque control part  162  can perform torque control. 
         [0042]    In the servo driver  16 , the comparator  162 A compares the current torque signal T 2  supplied from the servo motor  15  with the torque signal transmitted from the storage part  162 D to determine whether or not there is a change in torque due to a difference between both signals (step S 6 ). If the torque is changed, a deviation signal indicative of the same is transmitted to the amplifier  162 C to control the torque of the servo motor  15 . Then, the servo driver  16  rotates the ball screw  14  in the reverse direction so that the torque of the servo motor  15  can be reduced to the predetermined torque. Thus, the probes  13 A are lowered from the position indicated by a dashed dotted line in  FIG. 3B  to the position indicated by a solid line (step S 7 ). In this state, the high temperature inspection of the device D is performed under the predetermined contact load. The torque value of the servo motor  15  available at this time is registered and stored in the storage part  162 D. The torque value thus registered is used in the second device inspection. 
         [0043]    During this process, the master computer  20  continues to monitor the change in torque and transmits a switching command signal C to the servo driver  16  if the position of the mounting table  11  is adjusted by the torque change. As illustrated in  FIG. 2 , the servo driver  16  allows the switching part  163  to switch the torque control part  162  to the position control part  161  (step S 8 ). The position of the servo motor  15  is controlled to return the mounting table  11  back to a lowermost position. Then, the wafer W is index-moved to bring the next device D to a position just below the probes  13 A (step S 9 ). In this state, the process returns to step S 1  where the servo motor  15  is controlled to bring the device D and the probes  13 A into contact with each other. 
         [0044]    In case of performing the high temperature inspection of the second device D, steps  1  to  5  are repeated in the same manner as set forth above. The current torque value is compared with the previously registered torque value by means of the comparator  162 A. The torque of the servo motor  15  is controlled on the basis of the previously registered torque value and the device D is subjected to the high temperature inspection. 
         [0045]    If the thermal expansion of the probe card  13  ceases to exist while repeating the inspection, the servo driver  16  is switched to the torque control. This ensures that the torque of the servo motor  15  is not changed even if the electrode pads Dp of the device D and the probes  13 A come into contact with each other. Therefore, the process proceeds from step S 6  to step S 10  in  FIG. 2  and the high temperature inspection of the device D is performed while the mounting table  11  is kept in the current position. In this inspection, the wafer W remains spaced apart from the probes  13 A during the index-movement of the wafer W. For this reason, the probe card  13  is cooled a little bit by temporarily radiating heat. However, this has little influence on the inspection. Even if the inspection is affected by this, it is possible to perform the inspection of the wafer W under the predetermined contact load at all times since the torque of the servo motor  15  continues to be controlled by the servo driver  16 . 
         [0046]    With the present embodiment described above, the servo motor  15  is used as the vertical drive mechanism  12  of the mounting table  11  and the torque of the servo motor  15  is controlled by the servo driver  16 . This makes it possible to immediately perform the high temperature inspection of the wafer W without having to preheat the probe card  13 . Elimination of the preheating time helps greatly shorten the inspection time. Furthermore, it is possible to surely prevent damage of the probe card  13  and the wafer W, thereby enabling the inspection to be performed with increased reliability. 
         [0047]    With the present embodiment, the servo driver  16  is connected to the master computer  20  that monitors the inspection apparatus  10 . The master computer  20  includes the position command part  21  for transmitting the position command signal P to the position control part  161 , the torque command part  22  for transmitting the torque command signal T 1  to the torque control part  162 , and the switching command part  23  for transmitting the switching command signal C to the switching part  163  based on the torque of the servo motor  15 . This makes it possible to monitor the operating state of the vertical drive mechanism  12  at all times. Therefore, the high temperature inspection can be performed with increased reliability by bringing the wafer W placed on the mounting table  11  into contact with the probes  13 A under the predetermined contact load at all times. 
         [0048]    Furthermore, the servo driver  16  is provided with the storage part  162 D for storing the torque value indicative of the contact load available each time when the high temperature inspection of the device D is performed. This makes it possible to set the predetermined contact load in keeping with the expansion of the probe card  13 . Moreover, the storage part  162 D is designed to store the upper and lower limit values of the predetermined contact load. This eliminates the possibility that the device D and the probes  13 A make contact with each other under a load falling outside the predetermined contact load, thereby reliably preventing damage of the device D and the probes  13 A. In addition, the torque control part  162  controls the contact load between the device D and the probes  13 A to become equal to the predetermined contact load in keeping with the thermal change of the probe card  13 . This makes it possible to perform the inspection under a constant contact load at all times even if the probe card  13  undergoes thermal expansion. 
         [0049]    The present invention is not limited to the above-described embodiment at all and the constituent elements of the present invention may be suitably changed in design. For example, although the servo motor and the ball screw are connected by means of the power transmission belt in the above description, it may be possible to directly connect the servo motor to the ball screw. Furthermore, although the high temperature inspection of the wafer W is described in the foregoing embodiment, the present invention may be equally applied to a low temperature inspection of the wafer. Moreover, although the wafer is described as an example of the target object in the foregoing embodiment, the present invention may be applied to the inspection of a glass substrate of a liquid crystal display. 
         [0050]    The present invention can be applied to an inspection apparatus for inspecting electric characteristics of a target object such as a semiconductor wafer or the like.