now the present invention will be clarified in detail by an embodiment thereof shown in the attached drawings . in fig1 there are shown a support frame 1 and vibration preventing mechanisms 2 , 3 independently provided on the support frame 1 . on the vibration preventing mechanism 2 there is fixed a base 4 , on which is provided an x - y stage 5 for movement in x - and y - directions on the base 4 . on the x - y stage 5 there is provided a z - stage 6 for movement in the z - direction . a θ - rotation stage 7 is provided on the z - stage 6 to achieve rotational movement thereon . these stages ( x - y , z , θ ) are respectively driven by motors . a wafer 8 is placed on the θ - rotation stage 7 , which is equipped with a suction mechanism to support the wafer thereon by vacuum suction . a probe card 9 is fixed on a support 10 extended from the base 4 . a microscope 11 is fixed on a casing 12 for observing the wafer 8 placed on the stage 7 . a ccd linear sensor 13 scans the wafer 8 for aligning the same . an ic chip formed on the wafer 8 is brought into contact with probe needles 9a by vertical movement of the z - stage 6 . the signals obtained from probe needles 9a are supplied , through the probe card 9 , to a tester separate from the wafer inspecting apparatus , and an inspection output concerning the wafer 8 is obtained from the tester . naturally the tester may be integrally constructed with the wafer inspecting apparatus . in the present embodiment , a right - hand inspection unit is composed of the above - explained components 4 - 7 , 9 - 11 and 13 . a left - hand inspection unit is composed of a base 14 , an x - y stage 15 , a z - stage 16 , a θ - rotation stage 17 , a probe card 19 , a support 20 , a microscope 21 and a sensor 22 which are respectively the same as the components 4 - 7 , 9 - 11 and 13 of the right - hand inspection unit . a wafer 18 is placed on the θ - rotation stage . the right - hand inspection unit and the left - hand inspection unit are respectively supported by the vibration preventing mechanism 2 , 3 independently provided on the support frame 1 , and these mechanisms prevent mutual transmission of vibration . a control unit 23 is provided with a microcomputer ( mcu ) 23a provided with a calculating unit , memories , an i / o port etc . and controls the stages 5 - 7 , 15 - 17 , a wafer carrier transport mechanism , and a wafer loading mechanism to be explained later . in the following there will be explained the wafer carrier transport mechanism and the wafer loading mechanism . these mechanisms are respectively housed in 31 and 32 shown in fig2 . wafer cassettes 33a , 33b , each containing plural wafers are transported by a transport mechanism ( not shown ) in succession to a position b . the cassette 33a brought to the position b is supported on a table 34a shown in fig3 and is elevated to a broken - line position by an elevator 34 . a motor 35 shown in fig3 vertically drives the table 34a of the elevator 34 . the elevator 34 and the motor 35 constitute a part of the above - mentioned transport mechanism . a support member 36 fixed on the support frame 1 is provided with a guide member 37 and a worm 38 which is driven by a motor 39 . a motor 40 is provided with a worm gear ( not shown ) meshing with worm 38 , and moves to the left or to the right along the x - direction in fig3 by the forward or reverse rotation of the motor 39 , along the guide member 37 . the motor 40 is provided with a shaft 41 to which an arm 42 is attached . the arm 42 is rotated clockwise or anticlockwise about the shaft 41 in fig2 by the forward or reverse rotation of the motor 40 . in the present embodiment the wafer loading mechanism is composed of the above - mentioned components 36 - 42 . a support member 43 is fixed on the support frame 1 and supports a motor 44 which rotates a stage 45 for prealignment of the wafer . now reference is made to fig4 for explaining the function of the apparatus of the present invention . at first , in response to an instruction from the mcu 23a in the control unit 23 , the transport mechanism brings the cassettes 33a , 33b in succession to the position b , and the cassette brought to position b is elevated to the broken - line position shown in fig3 by the elevator 34 . in step 100 the mcu 23a identifies if a wafer is present on the θ - rotation stage 7 . if not , step 101 identifies whether a wafer is present on the prealignment stage 45 . if absent again , step 102 outputs an instruction to bring a wafer to pre - alignment stage 45 . then the loading mechanism and the prealignment stage function in the following manner according to a subroutine of the mcu 23a . at first the motor 39 is activated in the forward direction to shift the motor 40 to the left in fig3 whereupon a wafer contained in the cassette 33a is placed on the arm 42 . then the motor 39 rotates in the reverse direction , thereby shifting the motor 40 and the arm 42 to the right . the motor 40 is then stopped at a suitable position , and is activated to rotate the arm 42 by 180 ° about the shaft 41 . in this manner the wafer is brought to the position of the pre - alignment stage 45 and is placed thereon . subsequently the motor 40 is shifted to the left by the rotation of the motor 39 and returns to the position shown in fig2 and 3 . however the arm 42 remains directed toward the stage 45 . the stage 45 , supporting the wafer , effects pre - alignment by rotation . upon completion of the wafer pre - alignment , the mcu 23a outputs an instruction , in step 103 , to set the wafer on the θ - rotation stage 7 . in case step 101 identifies the presence of a wafer on the stage 45 , and if the pre - alignment is already completed , the program proceeds directly to step 103 . on the other hand , in case step 101 identifies the presence of a wafer on the stage 45 but the pre - alignment is not yet completed , the pre - alignment is continued , and , upon completion thereof , the program proceeds to step 103 . in response to the instruction in step 103 , the loading mechanism and the fine alignment stages ( x - y , z and θ - stages 5 - 7 ) function in the following manner according to a subroutine of the mcu 23a . at first the motor 39 is rotated in the reverse direction to shift the motor 40 to the right , together with the arm 42 directed toward the pre - alignment stage 45 . after the pre - aligned wafer is placed on the arm 42 , the motor 39 is rotated in the forward direction to shift the motor 40 to the left in fig3 . thus the motor 40 returns to the position shown in fig2 and 3 . then the motor 40 is rotated in the forward direction to rotate the arm 42 clockwise , in fig2 by 90 °, thereby bringing the wafer to a position c . at the same time the x - y stage 5 is driven by a motor ( not shown ) to bring the θ - rotation stage 7 also to the position c . in this manner the wafer is placed on the θ - rotation stage 7 , which fixes the wafer by suction . subsequently the motor 40 is rotated in the forward direction to rotate the arm 42 by 90 ° clockwise , thus bringing it to the state shown in fig2 . also the θ - rotation stage 7 returns to the position shown in fig1 and 2 by the movement of the x - y stage 5 . then the mcu 23a drives the x - y stage in the x - and y - directions , illuminates the wafer with an illuminating optical system ( not shown ) and receives reflected light from the wafer with the sensor 13 , thereby obtaining information on the position of chips formed on the wafer . based on this information , the mcu 23a finely moves the stages 5 - 7 to achieve fine alignment of the wafer . the wafer 8 shown in fig1 shows a state after such alignment . upon completion of the fine alignment of the wafer 8 , the mcu 23a supplies a signal to the tester , and simultaneously drives the z - stage 6 with a motor ( not shown ) to elevate the θ - rotation stage 7 . in this manner the chip formed on the wafer 8 is brought into contact with the probe needles 9a and is inspected by the tester . upon completion of the chip inspection , the mcu 23a outputs a signal to drive the z - stage 6 , thereby lowering the θ - rotation stage 7 . then the x - y stage 5 is moved by one chip , and the θ - rotation stage 7 is elevated to bring the next chip into contact with the probe needles 9a for inspection by the tester . plural chips formed on the wafer 8 are inspected by repeating the above - explained procedure . after outputting the wafer setting instruction in step 103 , the mcu 23a immediately proceeds to step 106 to identify whether a wafer is present on the θ - rotation stage 17 , without awaiting the completion of the above - explained wafer inspection . consequently the above - explained procedure of wafer setting , fine alignment and wafer inspection is conducted simultaneously with discrimination step 106 and ensuing steps . in case step 100 identifies the presence of a wafer on the θ - rotation stage 7 , the mcu 23a identifies , in step 104 , whether the wafer on stage 7 is already inspected . if not , the mcu 23a continues the wafer setting on the stage 7 , fine alignment of the wafer and wafer inspection , and immediately moves to step 106 , without awaiting the completion of wafer inspection . in this manner the procedure of wafer setting , fine alignment and wafer inspection is conducted simultaneously with discrimination step 106 and the ensuing steps . on the other hand , if step 104 identifies the completion of wafer inspection , the mcu 23a outputs an instruction , in step 105 , to return the wafer from the θ - rotation stage 7 to the carrier 33a . in response the loading mechanism and the fine alignment stage function in the following manner , according to a subroutine of the mcu 23a . at first the motor 40 is activated in the reverse direction to rotate the arm 42 by 90 ° anticlockwise from the position shown in fig2 . simultaneously the x - y stage 5 is activated to shift the θ - rotation stage 7 to the position c . then the vacuum suction is terminated and the wafer 8 is placed on the arm 42 . subsequently the stage 7 is shifted to a position shown in fig2 . however stage 7 may remain at the position c until the next wafer arrives . after the wafer 8 is placed on the arm 42 , the motor 40 is activated in the forward direction to rotate the arm 42 by 90 ° clockwise in fig2 thus returning arm 42 to the position shown in fig2 . subsequently the motor 39 is activated in the forward direction to shift the motor 40 to the left , thereby returning the wafer into the wafer cassette 33a . then the motor 40 returns to the position shown in fig3 by the rotation of the motor 39 . after return of the motor 40 , the mcu 23a returns to step 100 . when the mcu 23a proceeds from step 103 or 104 to step 106 , there is identified whether a wafer is present on the θ - rotation stage 17 . if absent , step 107 identifies whether a wafer is present on the pre - alignment stage 45 . if absent again , step 108 outputs an instruction to bring a wafer to pre - alignment stage 45 . thus a wafer is brought from the cassette 33a to the pre - alignment stage 45 in the same manner as in step 102 , thereby conducting pre - alignment of the wafer . upon completion of pre - alignment , step 109 releases an instruction to set the wafer on the θ - rotation stage 17 . on the other hand , in case step 107 identifies the presence of a wafer on the stage 45 , there is thereafter conducted a procedure the same as that when the presence of a wafer is identified in step 101 . in response to the instruction in step 109 , the mcu 23a controls the loading mechanism and the stages 15 - 17 according to a subroutine , in the same manner as the wafer setting from the stage 45 to the stage 7 , fine alignment of the wafer and wafer inspection in step 103 . however the control in step 109 is different from that in step 103 in the rotating direction of the arm 42 , in that the stages 15 - 17 are activated instead of the stages 5 - 7 , in that the stage 17 is brought to a position θ at the wafer setting thereon , and in that the wafer on the stage 17 is inspected by the probe needles 19a . in this manner the wafer is set on the stage 17 , then subjected to fine alignment and inspected . the wafer inspection is conducted with the same tester mentioned before . after outputting the wafer setting instruction in step 109 , the mcu 23a immediately moves to step 112 to identify whether a wafer is present on the pre - alignment stage 45 , without awaiting the completion of wafer inspection . consequently as in the aforementioned steps 103 and 106 , the procedure of the wafer setting , fine alignment of the wafer and wafer inspection is conducted simultaneously with the discrimination step 112 and ensuing steps . on the other hand , in case the presence of a wafer on the prealignment stage 45 is identified in step 106 , the mcu 23a identifies , in step 110 , whether the wafer on the θ - rotation stage 17 is already inspected . if not , the mcu 23a continues the wafer setting on the stage 17 , fine alignment thereof and wafer inspection , and immediately proceeds to step 112 without awaiting the completion of wafer inspection . thus , as in the aforementioned steps 104 and 106 , the procedure of wafer setting , fine alignment and wafer inspection is conducted simultaneously with the discrimination step 112 and ensuing steps . if step 110 identifies the completion of wafer inspection , the mcu 23a outputs , in step 111 , an instruction to return the wafer from the stage 17 to the cassette 33a . in response the loading mechanism and the fine alignment stages 15 - 17 function according to a subroutine of the mcu 23a , whereby the wafer 18 on the stage 17 is returned to the cassette 33a in the same manner as in step 105 and the state shown in fig2 and 3 is restored . however the above - mentioned procedure is different from that of the step 105 in rotating direction of the arm 42 , in that the stages 15 - 17 are activated and in that the stage 17 is brought to a position d . when the loading mechanism is returned to the state shown in fig2 and 3 , the mcu 23a returns to step 106 . the mcu 23a , upon proceeding from step 109 or 110 to step 112 , identifies whether a wafer is present on the pre - alignment stage 45 , and , if absent , outputs an instruction in step 113 to transfer a wafer to stage 45 . then , according to a subroutine of the mcu 23a , in the same manner as in steps 102 and 108 , a wafer stored in the cassette 33a is brought to the pre - alignment stage 45 and is subjected to pre - alignment . upon completion of the wafer pre - alignment , the mcu 23a returns to step 100 . the procedure in case step 112 identifies the presence of a wafer on the stage 45 is the same as when the presence of a wafer on the stage 45 is identified in step 101 or 107 . upon completion of the pre - alignment , the mcu 23a returns to step 100 . in the present embodiment , if the loading mechanism receives a second instruction while it is operated under a first instruction , for example the instructions in steps 103 and 111 , the loading mechanism executes the second instruction after the operation according to the first instruction is completed . however the time from the wafer setting on the θ - rotation stage 7 or 17 to the completion of wafer inspection is much longer than the functioning time of the loading mechanism . consequently it is not expected that the loading mechanism will receive two instructions at the same time as mentioned above . in the present embodiment , the discrimination in step 100 , 101 , 104 , 106 , 107 , 110 or 112 is achieved by the mcu 23a itself through identification of the control status of the loading mechanism , pre - alignment stage , fine alignment stage etc . according to the flow chart shown in fig4 . for example the discrimination of step 100 is achieved in the following manner . the mcu 23a identifies that the θ - rotation stage does not have a wafer , if the arm 42 has completed an operation of receiving the wafer from the stage 7 and if a wafer supply operation from arm 42 to the stage 7 has not been conducted . the motors 35 , 39 , 40 , 44 and the motors ( not shown ) for driving the stages 5 - 7 , 15 - 17 are driven by signals supplied from the mcu 23a through drivers ( not shown ). the wafer cassette is removed by the transport mechanism , when the wafer inspection is completed for all the wafers contained in a cassette , and a new wafer cassette is brought to the position b . thereafter the above - explained stages of loading , pre - alignment , wafer setting , fine alignment and wafer inspection are repeated . in the present embodiment , as explained in the foregoing , it is possible to load and inspect a wafer in an inspection unit ( steps 106 - 109 or 100 - 103 ) while another wafer is inspected in the other inspection unit ( step 103 or 109 ). in the foregoing description , the program is designed to proceed from step 105 to 100 and from step 111 to 106 , but it may also be designed to proceed from step 105 to 112 and from step 11 to 112 . in addition , electromagnetic shield members 46 , 47 may be provided as indicated with broken lines in fig2 in order to reduce the influence to an inspection unit of electromagnetic noise generated in the other inspection unit . the use of such shield members is desirable , therefore , in case considerable electromagnetic influence is anticipated between the inspection units . an apparatus shown in fig5 a and 5b is provided with a distribution mechanism with an arm 111a rotatable about a shaft 111b , and a microscope 110 is provided at the end of arm 111a as observing means . the microscope 110 is rotatable , with respect to the end of the arm 111a , about the optical axis of an objective lens 110a which is parallel to the above - mentioned shaft 111b , so that the eyepiece 110b of the microscope 110 can be directed to the front side of the apparatus regardless of the rotational position of the arm 111a . stated differently , the microscope 110 can revolve both around the shaft 111b and on the optical axis of the objective lens 110a . except as explained above , the structure of the apparatus is identical with that of the apparatus shown in fig1 and 3 . when a chip formed on the wafer 8 is brought into contact with the probe needles 9a by the elevation of the θ - rotation stage , the operator moves the microscope 110 to the broken - line position in fig5 a to observe the contact state of the chip and the probe needles 9a . on the other hand , at the inspection of the chip formed on the wafer 8 , the microscope 110 is brought to the full - line position . as shown in fig6 a , the arm 42 for extracting the wafer 100 &# 39 ; from the wafer cassette is provided at the front end thereof with a vacuum chuck 42a for fixing the wafer by suction . at a suitable position above arm 42 , there are provided a ccd line sensor 53 in which photodiodes are arranged in the y - direction , an optical system 54 and a light source 55 . the light emitted by the light source 55 is reflected by the wafer 100 &# 39 ;, and is focused onto the line sensor 53 by the optical system 54 , whereby the pattern on the wafer 100 can be captured as a linear image . thus , the surface of the wafer 100 &# 39 ; is scanned by a movement of the wafer 100 &# 39 ; in the direction of arrow f2 parallel to the x - axis , and corresponding image signals are produced from the line sensor 53 . also as shown in fig6 b , the stage 7 is provided with a vacuum check 7a for fixing the wafer by suction . above stage 7 there are provided a ccd line sensor 13 in which photodiodes are arranged in the y - direction , an optical system 61 , a light source 62 and a half mirror 63 , whereby the light emitted from the light source 62 passes through the half mirror 63 , is then reflected by the wafer 100 &# 39 ; and enters the line sensor 13 through the half mirror 63 and the optical system 61 . an arrow f3 is parallel to the x - axis . in the apparatus of the present invention , the alignment operation is controlled by the microcomputer 23a . in the following description reference will be made to a flow chart shown in fig1 for explaining the pre - alignment procedure . at first , in step 200 , the microcomputer 23a activates the arm 42 to extract a wafer 100 &# 39 ; from the wafer cassette by vacuum suction . the wafer 100 &# 39 ; is then moved in the direction of arrow f5 for transfer to the stage 45 . in the course of this movement , step 201 is executed whereby the output signals of the line sensor 53 , representing the image on the wafer 100 &# 39 ;, are read after a / d conversion . the image signals thus obtained are subjected to data processing in the microcomputer 23a to determine the wafer size , and the position of the center of the wafer or of the orientation flat of the wafer . as shown in fig6 a , the light from the light source 55 is reflected by the wafer 100 &# 39 ; during the movement thereof in direction f5 , is then reduced in size by the optical system 54 and guided to the line sensor 53 . in this manner the surface of the wafer 100 &# 39 ; is scanned as represented by vertical lines in fig7 and corresponding image signals are produced from the line sensor 53 . step 202 detects , from the image signals , points corresponding to the edge of the wafer 100 &# 39 ; as shown in fig8 wherein the x - axis represents the amount of movement of the arm 42 while the y - axis corresponds to the positions of plural photodiodes . said points are determined from the contrast between the wafer 100 &# 39 ; and the background . succeeding step 203 detects the wafer size , which is determined as the maximum of the distance the in y - direction of two edge points shown in fig8 . then step 204 calculates the rate of variation , slope or differential , of the lines connecting the points shown in fig8 thus obtaining the result shown in fig9 wherein the y &# 39 ;- axis represents the rate of variation . a line c1 - c2 represents the rate of variation of the upper line in fig8 and a line d1 - d2 represents the rate of variation of the lower line in fig8 . in case the orientation flat 100a of the wafer 100 &# 39 ; is not parallel to the y - axis or the the direction of array of the line sensor 53 , as shown in fig8 the rate of variation remains constant in a portion corresponding to the orientation flat , as exemplified by line e - f in fig9 . therefore , the orientation flat 100a is identified as parallel to the y - axis if there is no such portion in which the rate of variation is constant , and , if otherwise , the orientation flat 100a is identified as not parallel to the y - axis . also the position of the orientation flat 100a , i . e . above or below the x - axis , can be determined from whether such portion appears in the line c1 - c2 or d1 - d2 . step 205 determines , in case the orientation flat 100a is not parallel to the y - axis , the direction thereof or the angle thereof to the x - axis . referring to fig1 , angle θ between the x - axis and a vertical line to the orientation flat , passing through a temporary center h , determined in advance on the x - axis , is represented by : ## equ1 ## wherein ( xe , ye ) and ( xf , yf ) are coordinates of end points e , f of the orientation flat , as shown in fig1 . the direction of the orientation flat can be determined from this equation . next step 206 calculates the position of center g of the wafer 100 &# 39 ;. two lines k - l , m - n , respectively parallel to the y - and x - axis are assumed on the wafer 100 &# 39 ; but outside the orientation flat 100a , with coordinates k ( xk , yk ), l ( xl , yl ), m ( xm , ym ) and n ( xn , yn ). the coordinates ( xg , yg ) of the center g of the wafer 100 &# 39 ; is represented by : ## equ2 ## the distance between center g and the aforementioned temporary center h is determined by : wherein ( xh , yh ) are the coordinates of temporary center h , wehrein yh = 0 . step 207 causes the arm 42 to load the wafer 100 on the stage 45 . step 208 rotates the stage 45 supporting the wafer 100 &# 39 ; by the angle θ calculated in step 205 , whereby the rotational aberration of the wafer 100 &# 39 ; to the apparatus at the loading onto the stage 7 by the arm 42 is practically cancelled . step 209 moves the x - y stage to the position c shown in fig2 and step 210 causes the arm 42 to load the wafer 100 &# 39 ; on the stage 7 . the above - mentioned values dx , dy are used as correction values in the displacement of the stage 7 from the position c shown in fig2 in step 209 , prior to the loading of the wafer 100 from the arm 42 to stage 7 . more specifically , the stage 7 is displaced from the position c in such a manner that the center of stage coincides with the point g , whereby the center g of the wafer 100 &# 39 ; coincides with the center of stage 7 . now reference is made to fig1 for explaining the fine alignment procedure in the apparatus of the present invention . at the loading of the wafer from the arm 42 to the stage 7 , plural pins are temporarily pushed out from stage 7 to lift the wafer 100 &# 39 ; from the arm 42 . in this state the arm 42 is extracted , and pins are retracted to place the wafer 100 &# 39 ; on the stage 7 . for conducting this operation , the front end of the arm 42 is square u - shaped . the pattern on the wafer 100 &# 39 ; placed on the stage 7 is determined , through the optical system 61 , by the line sensor 13 . the corresponding output signals from line sensor 13 are supplied , after a / d conversion , to the microcomputer 23a for fine alignment . at first , in step 300 , the microcomputer 23a drives the stage 5 in such a manner that the center g of the wafer 100 &# 39 ; approximately coincides with a reference position of the apparatus . output signals of the line sensor 13 are read in step 301 . as an example , reading an area qa in fig1 provides image data as shown in fig1 ( a ). so - called streets 58 , which are unexposed areas between the chips on the wafer , have higher reflectance and give rise to signal level changes as shown in fig1 ( a ). when the wafer 100 &# 39 ; is shifted , in step 302 , by one chip size as represented by area qb , the edges of the output signals of the line sensor 13 are slightly shifted as shown in fig1 ( b ), since the streets 58 and the line sensor 13 are not necessarily orthogonal . step 303 reads the output of sensor 13 . step 304 calculates the angle θa . the inclination angle θa of the street 58 to the line sensor 13 is given by : ## equ3 ## wherein y1 , y2 are edge positions and cx is the chip size . step 305 rotates the wafer 100 &# 39 ; by angle θa by means of the stage 7 . then step 306 moves the wafer 100 &# 39 ; at a pitch corresponding to the chip size in the positive x - direction , with respect to the line sensor 13 as shown in fig1 . there is therefore determined a position x 1 , at which the output of the line sensor 13 does not show the distribution shown in fig1 , or at which a street 58 cannot be found , and a position x 2 which is inside the position x 1 by one chip size . this is defined as the end position in the positive x - direction . similarly the wafer 100 &# 39 ; is stepwise moved by one chip size in the negative x - direction , and there are determined a position x 4 at which the street 58 cannot be found , and an end position x 3 which is inside position x 4 by one chip size . step 307 calculates an inclination correcting angle θb between the wafer 100 &# 39 ; and the line sensor 13 , which is determined by : ## equ4 ## wherein y2 or y3 is the edge position of a signal corresponding to a street when the line sensor 13 is positioned at x2 or x3 , as shown in fig1 ( a ) or 15 ( b ). step 308 rotates the wafer 100 &# 39 ; by correcting angle θb to complete the fine alignment . after the completion of the fine alignment , a code , for example of semi standard , or a bar code , provided in the vicinity of the orientation flat 100a , is read by the line sensor 13 as shown in fig1 , while the wafer 100 &# 39 ; is moved by the stage 7 in either direction indicated by the arrows , and the obtained information is used for wafer administration . subsequently there is searched a first chip which is to be subjected to inspection or further working . at first , as shown in fig1 , the wafer 100 &# 39 ; is moved to a position pa at which the central portion of the wafer in the x - direction can be viewed by the line sensor 13 . then the wafer is stepwise moved , by one chip size at a time , in the negative - y - direction to find a position pb where two streets 58 cannot be found simultaneously . then the wafer 100 &# 39 ; is stepwise moved , by one chip size at a time , in the x - direction to find a position pc where no street can be found . the first chip 59 is present at a position pd which is in front of position pc by one chip size . fig1 ( a ) shows the output signal of the line sensor 13 when it is located at the position pc , and the wafer is so adjusted in position that the street 58 coincides with an original poing y 0 for alignment on the line sensor 13 , as shown in fig1 ( b ). the y - address of the stage 7 in this state becomes the original point on the y - axis for alignment . subsequently the wafer 100 &# 39 ; is moved , as shown in fig2 , from e to f where the line sensor is positioned on a street 58 , whereby the output of the line sensor varies from a state shown in fig2 ( a ) to a state in fig2 ( b ). the address x 0 of the x - axis of the stage in this state becomes the original point on the x - axis for alignment . the alignment procedure for the wafer 100 &# 39 ; is thus completed . thereafter the chips on wafer 100 &# 39 ; are subjected , on the stage 7 , to wafer inspection and further working . the foregoing explanation of fine alignment has been limited to the right - hand inspection unit , but similar procedure and structure are applicable also to the left - hand inspection unit . also the alignment conducted on the stage 45 may also be achieved on the stage 7 or 5 and 15 or 17 . as shown in fig2 , the microcomputer 23a controls the function of the above - explained apparatus through an interface 84 . there are also provided a driver 70 for driving the line sensor 13 ; and a / d converter 90 for a / d conversion of the output of line sensor 13 ; a driver 71 for driving the line sensor 53 ; and a / d converter 91 for a / d conversion of the output of line sensor 53 ; a driver 72 for driving a motor 15a for moving the x - y stage 15 in the x - direction ; a driver 73 for driving a motor 15b for moving the x - y stage 15 in the y - direction ; a driver 74 for driving a motor 16a for moving the z - stage 16 in the z - direction ; a driver 75 for driving a motor 17a for rotating the θ - rotation stage 17 ; a driver 76 for driving a motor 5a for moving the x - y stage 5 in the x - direction ; a driver 77 for driving a motor 5b for moving the x - y stage 5 in the y - direction ; a driver 78 for driving a motor 6a for moving the z - stage 6 in the z - direction ; a driver 79 for driving a motor 7a for rotating the θ - rotation stage 7 ; and drivers 80 , 81 , 82 , 83 for respectively driving the motors 35 , 39 , 40 , 44 . the microcomputer 23a controls said drivers 70 - 83 through the interface 84 to cause the apparatus to function according to the flow charts shown in fig4 and 16 .