JP4385699B2 - Semiconductor wafer direction adjusting method and semiconductor wafer direction adjusting apparatus - Google Patents

Description

  The present invention relates to a technique for adjusting the direction of a semiconductor wafer held on a platen in a vacuum chamber of an ion implantation apparatus in a step of performing an ion implantation process on a semiconductor wafer.

  In a general ion implantation apparatus, a wafer cassette having a plurality of semiconductor wafers (hereinafter sometimes simply referred to as “wafers”) mounted on the outside of the machine body is provided. Further, a general wafer has a substantially V-shaped notch indicating a crystal orientation, and is inserted into the wafer cassette in a state in which the direction is aligned based on the notch.

  During the ion implantation process, wafers are taken out from the wafer cassette one by one and fed into a vacuum chamber. The operation of guiding the wafer to the vacuum chamber is performed by a robot arm or the like. In this vacuum chamber, a wafer holding device called a “platen” is provided. The wafer introduced into the vacuum chamber is placed on the upper surface of the platen in a state adjusted so that the notch is aligned with a predetermined orientation. Thereafter, the wafer is held on the platen by static electricity. Then, the platen stands upright, and ion implantation is performed on the wafer. Since the platen is provided with a rotation mechanism, the direction of the notch can be finely adjusted as necessary.

  In the conventional ion implantation apparatus, it is inspected whether the notch of the wafer is directed in the correct direction at a position before the vacuum chamber or the like. This inspection is generally performed using a linear sensor or the like, but can also be performed by image processing after acquiring a two-dimensional image of the wafer.

  For example, in Patent Document 1 below, a wafer in the middle of conveyance is imaged, and an edge corresponding to the outline of the wafer is extracted from the obtained image, or the light and dark states at the wafer periphery and its vicinity are extracted. It is described that the notch of the wafer is detected by this method.

JP 2000-31245 A (see paragraphs [0008] to [0010])

As described above, in the conventional ion implantation apparatus, it is confirmed whether or not the notch is oriented in the correct direction before introducing the wafer into the vacuum chamber. However, even if the wafer up to the front of the vacuum chamber is correctly oriented, there is a possibility that a deviation occurs when it is placed on the platen. As described above, the platen is provided with the rotation mechanism, but it is impossible to correct the deviation unless the notch deviation is detected at the time of installation.
Therefore, in order to perform the ion implantation process with high accuracy, it is desirable to detect the direction of the notch after placing the wafer on the platen.

  In addition, when the notch detection method disclosed in Patent Document 1 is executed in a vacuum chamber, if a member around the platen enters the field of view of the camera, or a shadow occurs in a part of the imaging region, Noise may be mixed in the edge extraction or the light / dark extraction result of the image, and the notch may not be detected correctly. Also, since the notch is very small compared to the wafer body, if the entire wafer is included in the field of view of the camera, the notch on the image becomes very small. For this reason, it is difficult to detect the position of the notch with high accuracy.

  The present invention has been made paying attention to the above-mentioned problem.After the wafer is placed on the platen in the vacuum chamber, by detecting how much the notch is deviated from the accurate direction, the wafer is immediately before the ion implantation process. It is an object to adjust the direction with high accuracy so that high-precision ion implantation processing can be performed.

  Further, in the present invention, the rotation angle of the platen necessary for aligning the notch in the correct direction (in this specification, this angle is referred to as “correction angle”) is obtained with high accuracy, and wafer direction adjustment can be performed easily and easily. The purpose is to perform with high accuracy.

Another object of the present invention is to accurately adjust the direction of the wafer so that accurate detection can be performed even when the direction in which the notch is to be placed is not suitable for detection.
Furthermore, the present invention adjusts the field of view of the imaging means so that an image with sufficient resolution can be generated for the notch, thereby performing notch detection processing with higher accuracy and performing wafer orientation adjustment with higher accuracy. For the purpose.

In the method for adjusting the direction of a semiconductor wafer according to the present invention, a circular semiconductor wafer having a notch formed at one location on the outer peripheral edge is placed on a platen that rotates about a central portion, and is supported by the platen. The semiconductor wafer is imaged from above by the camera, and the direction of the semiconductor wafer is adjusted by controlling the rotation operation of the platen based on the result of processing the image generated by the imaging. The following first to sixth steps Execute.

In the first step, when the semiconductor wafer is placed on the platen, the direction from the center point of the semiconductor wafer toward the correct position of the notch is set as a reference direction, and the angle formed by the reference direction with respect to a predetermined direction. θT is registered as a reference angle. In the second step, imaging is performed by setting the field of view of the camera so that at least a part including at least the notch of the outer peripheral edge of the semiconductor wafer supported on the platen is included in the field of view of the camera. In the third step, an edge pixel group representing the outer periphery of the semiconductor wafer is detected from an image generated by imaging, and the center point of the arc is determined based on a portion of the detected edge pixel group constituting the arc. Detect as the center point. In the fourth step, the position of the notch is detected based on edge pixels that do not form an arc in the edge pixel group detected in the third step . In the fifth step, a direction from the center point of the semiconductor wafer toward the notch is specified based on the detection results of the third and fourth steps, and an angle θN formed by the direction with respect to the specific direction is calculated. In the sixth step, a difference θ between the angle θN specified in the fifth step and the reference angle θT is obtained, and the platen is rotated by controlling the rotation direction and the rotation angle of the platen based on the value of the angle θ. Adjust the direction of the semiconductor wafer.

Furthermore, in the second step, when the center point of the semiconductor wafer is aligned with the center point of the platen based on the reference angle θT registered in the first step, the direction corresponding to the reference direction is It is determined whether or not it is included in an appropriate area that spreads with a width of a predetermined angle from the center point, and when it is determined that the direction is included in the appropriate area, imaging is performed without rotating the platen, When it is determined that the direction is outside the appropriate area, the difference α between the reference angle θT and the angle formed by the direction from the center point of the platen toward one point in the appropriate area with respect to the specific direction is adjusted. The angle is obtained, and the imaging is executed after the platen is rotated by controlling the rotation direction and angle of the platen based on the value of the adjustment angle α.

In the third step of the above method, after executing processing for extracting edges (contour lines) included in the image generated by imaging in the second step, for example , according to the method described in Patent Document 2 below. Thus , points constituting an arc can be extracted from the edge pixel group representing the outer peripheral edge of the semiconductor wafer . In the fourth step, for example among groups of edge pixels representing the outer periphery of the semiconductor wafer, to erase the points constituting a circular arc, to extract the equivalent of the notch contours from the left edge pixel, V-shaped Coordinates of predetermined representative points such as the center of gravity of the pattern are detected.

JP 2002-140713 A (see paragraphs [0034] to [0042] FIGS. 3 to 5)

According to the above method, the rotation direction and the rotation angle of the platen are controlled according to the value of the difference θ between the angle θN representing the notch direction obtained by image processing and the reference angle θT representing the reference direction registered in advance. By doing so, it becomes possible to eliminate the deviation of the notch with respect to the reference direction.

  Here, since the actual wafer rotates about the center point of the platen, the center point of the wafer needs to be correctly aligned with the center point of the platen to correct the notch displacement. Can be considered. However, according to the present invention, when the center point of the wafer on the image is the reference point, the reference angle and the direction of the notch are shown regardless of the positional relationship between the center point of the wafer and the center point of the platen. The difference from the angle can be the rotation angle (correction angle) of the platen necessary for aligning the notch with the reference direction. The basis for this will be described below.

FIG. 10 schematically shows the relationship between the notch direction and the reference direction in an image obtained by imaging a wafer.
In the figure, O is the center point of the wafer, and R is the center point of the platen. In this example, both are the same. Further, the contour line of the wafer to be processed is represented as a circle W, the notch position detected on the image is indicated as a point N, and the correct notch position is indicated as a point T. The platen and the wafer are rotated with the direction of arrow F (counterclockwise) in the figure as the positive direction (the same applies to FIG. 11).

  In the above description, when the center point O of the wafer is a reference point, a vector from the point O to the point N can be considered as a notch direction. Similarly, a vector from point O to point T can be used as the reference direction. Therefore, in this example, a line segment OQ (Q is a point on the outline of the wafer) is set from the center point O toward the positive direction of the x axis, and the notch is determined according to the angle viewed from the line segment OQ counterclockwise. An angle θN indicating the direction of the angle (hereinafter referred to as “notch angle θN”) and an angle θT indicating the reference direction are represented. That is, θN = ∠NOQ and θT = ∠TOQ.

  Therefore, in this example, the difference θ (∠NOT) between the reference angle θT and the notch angle θN is the notch deviation amount. In this example, since the center point O of the wafer coincides with the center point R of the platen, the point N is aligned with the position of the point T by rotating the wafer by the angle θ about the center point R. be able to. Therefore, the difference value obtained by calculating the difference between the notch angle θN and the reference angle θT corresponds to a correction angle for aligning the notch with the reference direction.

  Next, FIG. 11 shows an example in which the center point O of the wafer is displaced from the center point R of the platen. In the figure, N indicates the position of the notch detected on the image, as in the previous figure, and the magnitude θN of ∠NOQ is obtained as the notch angle.

  In this example, the notch must be aligned with the center point O in the direction corresponding to the reference angle θT, as in the example of FIG. That is, it is necessary to move the notch with respect to the center point O by the difference θ between the reference angle θT and the notch angle θN.

In the example of FIG. 11, it is assumed that the wafer is rotated in the positive direction by the angle θ about the point R. In the figure, the circle W _C indicated by a dotted line is the outline of the wafer after the angle θ rotation. Further, by this rotation, the point O to point _{O C,} the point N to point _{N C,} respectively move. The movement, in the wafer before the rotation, when the center point R, the intersection of the contour line W lines and wafer connecting O and P, by rotation of the wafer, this point P is a point P _C in FIG. To do.

According to the above, since the points O _C , P _C and N _C after the rotation should be located with the same relationship as the points O, P and N before the rotation,
_{∠P c O c N c = ∠PON} ··· (1) to become.

When the line segment RQ ′ is set in the positive direction of the x axis with the center point R as a reference,
∠P _c RQ ′ = ∠PRQ ′ + θ (2)

Further, when (the _{Q c} point on the wafer) line segments _O c _Q c going from point _{O c} in the positive direction of the x-axis to set the line segment OQ, segment _O c _{Q c,} is the line segment RQ', either Is also parallel to the x-axis,
_{∠POQ = ∠PRQ' ∠P C O C Q} C = ∠P C RQ' ··· (3) to become.

Therefore, the following relationship is established by the equations (2) and (3).
_{∠P C O C Q C = ∠POQ} + θ ··· (4)
Furthermore, subtracting the equation (1) from the above equation (4),
_{∠N C O C Q C = ∠NOQ} + θ
= ΘN + θ (5)
Accordingly, since it is _{∠N C O C Q C = θT} , N c point viewed from the point _{O C} can be considered to be located in the same direction as the T point as viewed from the point O in FIG. 10.

  According to the above, even when the center point O of the wafer is deviated from the center point R, the notch is positioned corresponding to the reference direction θT by rotating the wafer by the angle θ around the center point R of the platen. Can be moved to. That is, by rotating the platen with the difference θ between the reference angle θT and the notch angle θN as a correction angle, the notch can be correctly aligned with the reference direction.

Therefore, the direction of the notch of the wafer on the platen is represented by an angle formed by a vector from the center point O to the notch N with respect to a specific direction (in the example of FIGS. 10 and 11, the direction from the point O to the point Q). By calculating the difference θ between the angle θN representing the direction of the notch obtained from the image and the reference angle θT, and controlling the rotation of the platen according to the value of θ, the center point of the wafer and the center point of the platen The wafer direction can be adjusted to an appropriate direction without considering the positional relationship.

10 and 11 , when the direction of measuring the reference direction θT and the notch angle θN is aligned with the positive direction of the platen rotation, the notch angle θN is subtracted from the reference angle θT. It is desirable to do. In this case, if the obtained correction angle θ is positive, the platen can be rotated in the positive direction, and if the correction angle θ is negative, the platen can be rotated in the negative direction.

In the process of detecting the center point of the semiconductor wafer in the third step , for example, the method disclosed in paragraph [0008] of Patent Document 1 described above can be applied. However, according to the method described in Patent Document 3 below, even when a part of the wafer is to be imaged as described later, the center point can be obtained with high accuracy.

International Patent Publication WO99 / 52072 Pamphlet

In the above method , the appropriate area is an area included in the field of view of the imaging means, and can be considered as an area where the notch can be detected with high accuracy. For example, a region with a good illumination state, a region that does not include obstacles such as peripheral members, and the like can be considered as appropriate regions.

In the present invention, when the center point of the semiconductor wafer is aligned with the center point of the platen, if it is determined that the direction specified as corresponding to the reference direction is outside the appropriate region, the center of the platen A difference α between an angle formed by the direction from the point toward a predetermined representative point of the appropriate region (for example, the center position of the region) with respect to the specific direction and the reference angle θT is obtained, and the platen is determined based on the value of the angle α. The platen is rotated by controlling the rotation direction and rotation angle. In this way, as long as the notch is not extremely deviated from the reference direction, the notch can be put in an appropriate region by rotating the platen. Therefore, by imaging the wafer after the rotation processing and executing the third to fifth steps, it is possible to accurately detect the notch that has moved into the appropriate region and obtain the angle θN representing the direction .

When imaging is performed after the platen is rotated in order to put the notch in an appropriate region, the difference θ between the angle θN obtained from the image generated by this imaging and the reference angle θT is the original deviation of the notch with respect to the reference direction. The platen rotation angle α is added to the amount . Therefore, also in this case, in the sixth step , the notch can be aligned with the reference direction by controlling the rotation direction and rotation angle of the platen based on the value of the angle θ and rotating the platen .

According to the above method , even when the notch is defined in an area where it is difficult to detect, the detection process is performed after the platen is rotated so that the notch enters the appropriate area, and the correction amount in consideration of the rotation angle is obtained. Obtainable. Therefore, no matter how the reference direction of the notch is determined, it is possible to accurately detect the correction angle necessary for aligning the notch with the reference direction and accurately adjust the direction of the wafer.

In the above method , if it is necessary to determine whether or not the direction of the notch is correct, the determination may be made after correcting the reference angle with the rotation angle α before detection .

Next, in a preferable aspect of the above-described method for adjusting the direction of the semiconductor wafer , in the second step, a range including a point corresponding to the center point of the platen and a part of the outer peripheral edge among the semiconductor wafers supported by the platen is a camera. The field of view of the camera is set so as to correspond to the field of view, and imaging is performed .

In the above aspect, since the partial image including the central portion and part of the edge is generated instead of the entire image of the semiconductor wafer, an image having a sufficient resolution can be obtained for the notch portion . Also, if the direction outside the appropriate area in the field of view of the imaging means is the reference direction, a correction angle that takes into account the notch in the appropriate area by rotating the platen and takes the rotation angle into account Can be obtained.

  According to the above aspect, an image having a sufficient resolution can be generated for the notch, and the position can be detected with high accuracy. Therefore, the correction angle can be obtained with higher accuracy, and the accuracy of wafer direction adjustment can be improved.

Next, in the semiconductor wafer direction adjusting apparatus according to the present invention, a platen that supports a circular semiconductor wafer having a notch formed at one location on the outer peripheral edge on the upper surface rotates around a central point as an axis. By controlling the rotating operation, the direction of the semiconductor wafer supported by the platen is adjusted. When the semiconductor wafer is placed on the platen, the center point of the semiconductor wafer is positioned at the correct position of the notch. Registration means for registering an angle θT formed by a direction toward a predetermined direction as a reference angle representing a reference direction to be taken by the notch; above the platen, at least of the outer peripheral edge of the semiconductor wafer on the platen imaging means partially deployed to include a field of view; imaging processing for the semiconductor wafer placed on said platen As but is performed in a state that includes a notch of the semiconductor wafer within the field of view of the imaging means, the imaging control means controls the imaging by the rotation and image capturing means of the platen; through the image capturing is performed by the control of the imaging control unit Edge pixel detection means for detecting an edge pixel group representing the outer peripheral edge of the semiconductor wafer from the generated image; based on a portion constituting the arc in the edge pixel group detected by the edge pixel detection means; First detection means for detecting a point as the center point of the semiconductor wafer; second detection means for detecting the position of the notch based on an edge pixel that does not form an arc among the edge pixel group detected by the edge pixel detection means; Based on the detection results of the first and second detection means, the direction from the center point of the semiconductor wafer toward the notch is specified, and this is detected. An angle calculating means for determining an angle θN formed by the direction of the specific direction; obtaining a difference θ between the angle θN calculated by the angle calculating means and a reference angle θT registered in the registering means, Direction adjusting means for adjusting the direction of the semiconductor wafer by rotating the platen by controlling the rotation direction and the rotation angle of the platen based on the value.

The imaging means is, for example, a shutter camera, and can be installed in association with a window portion formed at an appropriate position in the vacuum chamber.

Further, the imaging control unit is configured to generate a direction corresponding to the reference direction when the center point of the semiconductor wafer is aligned with the center point of the platen based on the reference angle θT registered in the registration unit. Is determined to be included in an appropriate area extending with a predetermined angle width from the center point of the platen, and when it is determined that the direction is included in the appropriate area, imaging is performed without rotating the platen. On the other hand, when it is determined that the direction is outside the appropriate region, the angle formed by the direction from the center point of the platen toward one point in the appropriate region with respect to the vector along the specific direction and the reference angle θT Is obtained as an adjustment angle, and the platen is rotated according to the value of the adjustment angle α, and then imaging is performed.

According to the said structure, the direction adjustment method of the semiconductor wafer mentioned above can be performed, and the direction of the wafer after installing in a platen can be adjusted with a sufficient precision.
In addition, it is desirable that the reference angle for various wafers is registered in the registration means of the semiconductor wafer direction adjusting device. The reference angle can also be acquired by receiving an input from a host system or the like.

  According to the present invention, when the wafer to be ion-implanted is placed on the platen of the vacuum chamber, the amount of rotational deviation of the notch with respect to the reference direction is detected, so that the ion implantation process is performed after correctly adjusting the wafer direction. Therefore, the accuracy of the ion implantation process can be guaranteed.

  Further, according to the present invention, even when the center point of the wafer is displaced from the center point of the platen, the wafer direction can be easily and accurately determined by the correction angle obtained with the center point of the wafer on the image as the reference point. Can be adjusted.

  Further, according to the present invention, even when the notch is placed in a region not suitable for detection, the correction angle can be obtained with high accuracy and the wafer direction can be adjusted. It is also possible to narrow the field of view of the imaging means so as to ensure a sufficient resolution for the notch, and to perform highly accurate detection processing within this field of view. Therefore, the wafer direction can be adjusted with high accuracy, so that the accuracy of the wafer injection process can be improved.

FIG. 1 shows an electrical configuration of an ion implantation apparatus to which the present invention is applied.
This ion implantation apparatus sequentially conducts an ion implantation process by introducing a plurality of wafers to a vacuum chamber, and includes a main controller 1 by a computer, a memory unit 2, an input unit 3, a monitor device 4, and a wafer carry-in / out process device. 5, a platen control device 6, an ion generation processing device 7, a vacuum chamber control device 8, a safety management device 9, and an inspection device 10 are connected.

  The memory unit 2 is, for example, a hard disk device, and in addition to a program necessary for processing of the main control device 1, the type of wafer to be processed and various setting data (indicating the direction of the notch when placing the wafer on the platen) Data, ion implantation angle, reference data used for wafer orientation inspection, etc.). The input unit 3 is a keyboard or the like, and is used to input data storage work and commands to the memory unit 2. The monitor device 4 displays the contents of the setting data and the processing results (inspection results by the inspection device 10 and information on whether or not the ion implantation processing has been performed properly) and the wafer obtained by the camera 110 described later. The image and the edge image are set to be displayed.

  The wafer carry-in / out processing apparatus 5 includes a wafer cassette that can store a plurality of wafers, a wafer transfer robot arm, a robot arm drive mechanism, and the like. The platen control device 6 is for controlling operations of a motor 23 and an arm portion 24 of the platen 22 described later. The ion generation processing device 7 includes an ion beam generation source, a mass analyzer, a high voltage generation circuit, an ion beam accelerator, a beam focusing lens, a beam scanning circuit, and the like. The vacuum chamber control device 8 includes a vacuum chamber door opening / closing device, a vacuum pump and its driving unit, and a vacuum degree measuring unit.

  The safety management device 9 is for emergency stop of various devices when an abnormality occurs, and includes an emergency stop switch, an interlock unit, a human detection sensor, an abnormality detection sensor in each of the devices described above, and the like. The safety management device 9 is provided with an independent control computer, and when an abnormality is detected, the emergency stop process is executed by communication with the main control device 1 or the main power supply of the device is shut off. I am doing so.

  The inspection device 10 is for determining whether or not the wafer placed on the platen in the vacuum chamber is placed in the correct orientation. Like the safety management device 9, the inspection device 10 includes an independent control computer, Processing is executed by communication with the control device 1. Further, in the inspection apparatus 10, when it is determined that the orientation is not correct, a correction angle (platen rotation angle) necessary to correct the orientation is calculated and output to the main controller. Yes.

  FIG. 2 shows a detailed configuration of the inspection apparatus 10. This inspection apparatus 10 has a substrate 100 as a main body, and is attached to an appropriate body of an ion implantation apparatus. In addition to the control unit 101 including the CPU 102, ROM 103, and RAM 104, the substrate 100 includes an image input unit 105, an image memory 106, a timing control unit 107, an edge extraction unit 108, and a communication interface 109 (shown as I / F in the figure). ) Etc. are installed.

  Furthermore, the inspection apparatus 10 of this embodiment includes a shutter camera 110 (hereinafter simply referred to as “camera 110”) having a CCD as a peripheral device. The image input unit 105 is connected to the camera 110 and includes a camera interface circuit, an A / D conversion circuit for digitally converting a grayscale image, and the like. The edge extraction unit 108 is a dedicated IC including a shift register, a differentiation circuit, and the like, and executes edge extraction processing while sequentially acquiring each pixel data input from the image input unit 105 and converted. In the edge extraction process of this embodiment, an edge having a width of several pixels can be extracted from the peripheral portion of the wafer by extracting pixels whose density difference from the vicinity is a predetermined value or more. .

  The image memory 106 is set so as to individually store the digital image converted by the image input unit 105 and the edge image generated by the edge extraction processing of the edge extraction unit 108. The communication interface 109 is used for communication with the main control device 1. The communication interface 109 receives an inspection start command from the main control device 1, and sends data such as an inspection result and a correction amount to the main control device 1 (details will be described later). Used to send back. The communication interface 109 can also transmit an image stored in the image memory 106.

  When the CPU 102 receives an inspection start command from the main controller 1, the CPU 102 executes an inspection procedure described later based on a program in the ROM 103, and performs an inspection for suitability of the wafer orientation and a correction angle calculation process. The ROM 103 of the inspection apparatus 10 also incorporates a program for checking the rotation operation of the platen in the vacuum chamber. This operation check of the platen is performed before the start of the ion implantation process, and is performed using two marks (details will be described later) set on the platen.

FIG. 3 shows an internal configuration of the vacuum chamber together with an installation example of the camera 110.
In the illustrated vacuum chamber 21, a support base 23 is provided at the center of a floor plate 21 b, and a disk-shaped platen 22 is attached to the upper surface of the floor 21 b via an arm portion 24 and a motor 25. The wafer 11 to be processed is fixedly supported on the upper surface of the platen 22 by static electricity.

  The arm portion 24 includes a jack portion 24a and a joint portion (not shown), and normally supports the surface of the platen 22 in a horizontal state and vertically stands the surface of the platen 22 during the ion implantation process. The support base 23 is provided with a hollow control chamber (not shown) in which the motor 25, the drive circuit for the arm portion 24, and the like are accommodated.

  The camera 110 is installed behind the ceiling of the vacuum chamber 21 so as to be positioned directly above the platen 22. The field of view of the camera 110 is adjusted so that the optical axis is directed in the vertical direction and the range from the periphery of the platen 22 to the outside is imaged. Further, the camera 110 has a zoom-up function. Depending on the type of the wafer 11 to be inspected, the direction of the optical axis and the magnification are adjusted to narrow the field of view so that only a part of the wafer 11 is imaged. Thus, an image with higher resolution than usual is generated.

  Further, two fluorescent lamps 30 and 31 having a predetermined length are arranged on the back of the ceiling in parallel to the depth direction (a direction perpendicular to the drawing sheet) so as to sandwich the camera 110 in the center.

  The ceiling plate 21a of the vacuum chamber 21 is opaque, but a window portion (not shown) in which transparent glass is fitted is formed only at a position corresponding to the installation position of the camera 110 and the fluorescent lamps 30 and 31. The In addition, the periphery of these window parts is reinforced by metal frame bodies 26, 27, and 28 from the back side, and the camera 110 and the fluorescent lamps 30, 31 are provided above the metal frame bodies 26, 27, and 28, respectively.

  Further, on the upper surface of the floor plate 21b of the vacuum chamber 21, in order to diffusely reflect the light from the fluorescent lamps 30 and 31, a minute convex portion 29 is formed over the entire surface. Further, the size of the window portion on the camera 110 side is adjusted so that the specular reflection light from the wafer 11 escapes to the outside of the window (see the dotted arrow in the figure). Thereby, at the time of an inspection, an image with a dark image of the wafer 11 and a bright background portion is generated. Note that the illumination method is not limited to the above, and for example, transmitted illumination through the floor plate 21b may be performed.

  As shown in FIG. 4A, concentric marks M1 and M2 are provided on the upper surface of the platen 22 at one location in the vicinity of the central portion and the peripheral edge, respectively. These marks M1 and M2 are formed by printing or marking on the surface of the platen 22, and the radius of the concentric circle and the ratio thereof are set to be different values for each mark. These marks M1 and M2 are used to inspect whether the platen 22 is rotating properly before the introduction of the wafer 11 into the vacuum chamber 21.

  FIG. 4B schematically shows a change in the position of the mark M2 accompanying the rotation of the platen 22. In the figure, a1 indicates the position of the mark M2 before the platen 22 rotates, and a2 indicates the position of the mark M2 after the platen 22 rotates 180 °. If the platen 22 rotates 180 °, the mark M2 should also move to a position rotated 180 °, so that the point b located between a1 and a2 corresponds to the position of the center mark M1. be able to.

  The inspection apparatus 10 images the platen 22 with the camera 110 and executes an inspection related to the propriety of the rotation operation based on the principle of FIG. In this inspection, first, the platen 22 in a stationary state is imaged, and then the process of imaging by rotating the platen 22 by 90 ° is executed for three cycles. That is, assuming that the rotation angle of the platen 22 in the first photographing is 0 °, an image corresponding to each rotation angle of 0 °, 90 °, 180 °, and 270 ° is obtained.

  The inspection apparatus 10 performs an extraction process on at least one of the four images (for example, an image at a rotation angle of 0 °) for the center mark M1, and calculates the coordinates of the center point of the mark M1. On the other hand, for the outer mark M2, extraction processing is individually performed on all the four images, and the coordinates of the center point of the mark M2 are calculated. Further, images having a rotation angle of 180 ° are combined (an image corresponding to a rotation angle of 0 ° and an image corresponding to 180 °, and an image corresponding to a rotation angle of 90 ° and an image corresponding to 270 ° are combined. Will be.) For each group, a line segment connecting two points (corresponding to the points a1 and a2 in FIG. 5 (2)) extracted as the center point of the mark M2 is set, and the midpoint of this line segment is set. Are compared with the center point of the mark M1. Here, if the distance between the coordinates of the midpoint of the line segment and the coordinates of the center point of the mark M1 is within a predetermined error range, it is determined that the platen 22 is rotating normally.

  In the above inspection, the coordinates of the center point are extracted after each mark M1, M2 is extracted by pattern matching processing on the image input from the camera 110.

  If it is determined in the above inspection that the platen 22 is rotating correctly, even if it is determined in the wafer orientation inspection that the orientation of the wafer 11 on the platen 22 is not appropriate, the wafer is determined based on the correction angle. 11 can be correctly adjusted. That is, only after it is confirmed that the platen 22 is rotating properly, the ion implantation process can be performed by accurately adjusting the direction of the wafer 11.

  In the ion implantation process, it is necessary to change the orientation of the crystal axis of the wafer depending on which position of the wafer is ion-implanted. That is, the notch direction of the wafer 11 on the platen 22 is determined based on the design data of the wafer 11. In the ion implantation apparatus of this embodiment, the direction in which the notch should be (reference direction) is defined as the direction viewed from the center point of the wafer 11. For each type of wafer to be manufactured, a reference angle indicating the reference direction is input in advance from a host system (not shown) or the input unit 3 and is registered in the memory unit 2.

  FIG. 5 shows an example of setting the direction of the notch and the notch angle indicating the direction. O in the figure is the center point of the wafer. In this embodiment, the coordinates of the center of gravity of the substantially V-shaped cutout pattern are used as representative points indicating the positions of the notches. N in the figure indicates the extracted representative point.

In this embodiment, the vector P _N extending from the center point O to the point N and the direction of the notch. Also, setting the vector X ₀ in the direction along the positive direction of the x-axis from the center point O, and the angle θN formed by the vector P _N and the notch angle to the vector X _0. Since the platen 22 of this embodiment rotates counterclockwise as a positive direction, the notch angle θN is also measured counterclockwise.

Reference direction, similarly to the vector P _N, is represented as a vector directed to the coordinate position where there is a representative point of the notch from the center point O. The reference angles, the vector is represented as an angle formed with respect to the vector X _0.

  The inspection apparatus detects the center point of the wafer 11 and the coordinates of the representative point N of the notch in the image obtained by the camera 110. Then, using these detection results, the notch angle is calculated based on the principle of FIG. Further, the difference between the reference angle corresponding to the wafer to be inspected and the calculated notch angle is obtained, and whether or not the wafer direction is appropriate is determined based on whether or not the value is within a predetermined error range. If it is determined that the direction of the wafer is not correct, the difference between the reference angle and the notch angle is output to the main controller 1 as a correction angle for adjusting the notch to the reference direction. Main controller 1 adjusts the direction of the wafer by rotating platen 22 according to the direction and angle indicated by the correction angle, and then starts the ion implantation process.

Further, in this embodiment, as described above, a predetermined type of wafer is picked up by narrowing the field of view of the camera 110 and inspected using the image. Further, the main controller 1 will be described in detail later, but if the reference direction of the wafer 11 to be inspected is not properly included in the field of view of the camera 110, the main controller 1 controls the platen 22 so that the notch can be imaged. After the rotation, the inspection apparatus 10 is operated to perform the inspection. The main controller 1 outputs a control signal indicating the direction and angle of rotation to the platen controller 6 to realize the rotation operation of the platen 22 according to the target direction and angle.

  FIG. 6 is an example of an image obtained by the camera 110 with a limited field of view. In this example, a partial image including the center point O and the entire image N1 of the notch is generated for the wafer 11 to be inspected. Further, I1 and I2 in the figure correspond to both side edges of the field of view of the camera 110.

Hereinafter, as shown in FIG. 6, a flow of a series of processes will be described using a wafer to be inspected while limiting the visual field of the camera 110 as an example.
FIG. 7 shows a processing procedure executed in the main controller 1 of the ion implantation apparatus. Note that ST in the figure is an abbreviation for STEP. In the following description, following this, each step is indicated as “ST”. In addition, both the angle θ and the angle α in FIG. 7 are positive values.

  First, at the start of processing, the system waits for a production instruction command from a host system not shown. This production instruction includes the type of wafer to be produced, the number of produced sheets, and the like. When a production instruction command is received, the process proceeds from ST1 to ST2, and setting data necessary for processing a wafer corresponding to the production instruction is read from the memory unit 2 and set in an internal RAM or the like. The setting data includes the reference angle and data for inspection.

  Next, in ST 3, the wafer carry-in / out processing device 5 is driven to take out the first wafer 11 from the wafer cassette and carry it into the vacuum chamber 21. In the next ST4, the wafer 11 is placed on the platen 22. In ST3 and ST4, the movement of the robot arm is controlled so that the notch of the wafer 11 is positioned on the platen 22 with the notch of the wafer 11 facing the direction corresponding to the reference angle data.

  In next ST5, it is determined whether or not the notch of the wafer 11 can be imaged. This determination is made by comparing the angle range indicating the field of view of the camera 110 with the reference angle θT of the notch. The range of the field of view can be represented by angles δ1 and δ2 indicating the directions of both side edges I1 and I2 (shown in FIG. 6) of the field of view as viewed from the center point of the platen. That is, vectors indicating directions viewed from the center point of the platen are set for both side edges of the field of view, and these vectors are replaced with angles in the same manner as in FIG. The larger angle can be the upper limit value δ1, and the smaller angle can be the lower limit value δ2.

  In order to detect the representative point of the notch with high accuracy, it is desirable to form an image of the notch at a position separated from both side edges I1 and I2 of the visual field by a sufficient distance as shown in FIG. Therefore, in ST5, when δ2 <θT <δ1 with respect to the reference angle θT and both (δ1−θT) and (θT−δ2) exceed a predetermined threshold, “YES” Make a decision. If this “YES” determination is made, the process proceeds to ST6 and the reference angle θT of the notch is transmitted to the inspection apparatus. Further, in ST7, the inspection apparatus 10 is used to inspect whether the wafer is installed in the correct orientation. Here, the inspection apparatus 10 executes a process described later, and transmits a final determination result in the process to the main control apparatus 1.

  When a determination result (“OK” flag) indicating that the orientation of the wafer is correct is transmitted from the inspection apparatus 10, ST8 becomes “YES” and the process proceeds to ST19. In ST19, after the platen control device 6 is driven to raise the surface of the platen 22 vertically, the ion generation processing device 7 is driven to execute a series of ion implantation processes based on the design data.

  On the other hand, when a determination result (“NG” flag) indicating that the orientation of the wafer 11 is inappropriate is transmitted from the inspection apparatus 10, ST8 becomes “NO” and the process proceeds to ST9. In ST9, along with the NG flag, it is checked whether or not a correction angle necessary for wafer direction adjustment is transmitted. If the correction angle θ is transmitted here, the process proceeds from ST9 to ST10, and the platen 22 is rotated by the correction angle θ to adjust the orientation of the wafer 11 to be correct. The correction angle θ is expressed as the reference angle θT minus the notch angle θN. In this example, since it is assumed that θ takes a positive value, in ST10, the platen rotates in the positive direction.

  In this way, the notch is aligned with the reference direction by rotating the platen by the correction angle. After this, the process proceeds to ST19 and the ion implantation process is started.

  Next, when the determination of ST5 is “NO”, that is, when it is determined that the notch is not properly included in the camera field of view, the process proceeds to ST11 and is necessary for putting the notch into the camera field of view. A simple rotation angle α (hereinafter referred to as “adjustment angle α”) is calculated. In ST11, for example, an average value δ3 of the δ1 and δ2 is obtained, and a value obtained by subtracting the reference angle θT from the average value δ3 (δ3-θT) is set as the adjustment angle α.

  In the next ST12, the platen 22 is rotated by the adjustment angle α. In this example, since it is considered that α also takes a positive value, in ST12, the platen 22 is rotated in the positive direction.

  In the next ST 13, the reference angle θT of the notch is corrected to a value obtained by adding the adjustment angle α, and this is transmitted to the inspection apparatus 10. In ST14, the wafer orientation inspection is started. The procedure of this inspection is the same as ST7, but the appropriateness of the direction of the notch and the calculation process of the correction angle are performed by the reference angle θT corrected by the adjustment angle α. When the “OK” flag is transmitted by this inspection, ST15 becomes “YES”, the process proceeds to ST16, and the platen is rotated in the negative direction by the angle α. As a result, the notch returns to the position before the inspection.

  If the “NG” flag and the correction angle are transmitted from the inspection apparatus 10, ST15 is “NO”, ST17 is “YES”, and the process proceeds to ST18. In ST18, the platen is rotated in the negative direction by the amount obtained by subtracting the correction angle θ from the adjustment angle α. As a result, the notch moves from the position before the inspection to a position rotated by θ around the center point R of the platen.

  As described above, when the platen is rotated before the inspection, after the inspection, the platen is rotated in the negative direction regardless of whether “OK” or “NG” is obtained, and then ST19. Proceed to

  In ST19, an ion implantation process is executed based on the design data. When the series of processing ends, the process proceeds to ST20, and the fact that the processing has been normally completed is stored in the memory unit 2. In ST21, a process of removing the wafer 11 from the platen 22 and carrying it out of the vacuum chamber 21 is executed.

  When the inspection apparatus 10 transmits an error code indicating that correction is impossible together with the NG flag (when ST9 is “NO” or ST17 is “NO”), the process proceeds to ST23, A process of writing an error code into the memory unit 2 (error process) is executed. Thereafter, the process proceeds to ST21, and a process of removing the wafer 11 from the platen 22 and carrying it out of the vacuum chamber 21 is executed.

  After unloading the wafer, the process proceeds to ST22 to check whether the production is finished. Here, when there is a wafer to be processed, ST22 becomes “NO”, the process returns to ST3, the next wafer is introduced into the vacuum chamber 21, and the same procedure is executed thereafter. When the number of wafers instructed by the production instruction has been processed, ST22 becomes “YES” and the processing is terminated.

  Note that the wafer 11 that has undergone the above-described processing is accommodated in the same wafer cassette (which stores processed wafers) regardless of whether normal processing has been performed. However, in ST20 and ST23, since the identification number of the wafer 11 is associated with the information to be stored, even if there is a defective wafer 11, it is possible to prevent the wafer 11 from flowing into the subsequent process. it can.

  Next, with respect to the wafer orientation inspection in ST7 and ST14, specific processing executed on the inspection apparatus 10 side will be described with reference to FIG. In FIG. 8, it is assumed that the process starts from ST101.

  Prior to executing this procedure, the CPU 102 of the inspection apparatus 10 receives various inspection data from the main control apparatus 1 and stores them in the RAM 104. Thereafter, in the first ST101, the timing controller 107 gives a drive signal to the camera 110 to perform imaging. Along with this imaging operation, A / D conversion processing by the image input unit 105 and edge extraction processing by the edge extraction unit 108 are executed, and grayscale image data of a predetermined gradation and binary edge image data are stored in the image memory 106. Stored. It is assumed that the field of view of the camera 110 is adjusted in a limited range in advance.

The processes of ST102 to ST104 are performed on the edge image.
In ST102, processing for extracting the center point of the wafer is executed in the edge image. This process is performed based on the method of Patent Document 3 described above. In short, for each edge pixel on the image, a line segment slightly longer than the radius of the wafer is set in a direction along the density gradient (direction from a bright part to a dark part). As a result, among the peripheral edges of the wafer included in the image, the line segments from the edge pixels constituting the arc portion other than the notch intersect in the vicinity of the center point O. Therefore, a representative point is extracted from a set of points where a predetermined number or more of line segments intersect, and this is set as the center point O of the wafer.

  According to the above method, even if only a part of the wafer 11 is included in the generated image, the position of the center point O can be obtained with high accuracy. If the center point O is successfully extracted, ST103 is “YES” and the process proceeds to ST104, where a process of detecting a notch on the edge image is executed. Hereinafter, this process will be briefly described.

  In this detection process, edge pixels corresponding to the constituent points of the arc are extracted on the image based on the method disclosed in Patent Document 2 described above. By this extraction process, constituent points other than the notches are extracted from the constituent points of the wafer outline.

  Next, the constituent points of the extracted arc are deleted, and a set of edge pixels reflecting the notch characteristics is extracted from the remaining edges. The notch of the wafer is not completely V-shaped, and is formed with the tip portion (the deepest portion of the cut) chamfered (see N1 in FIG. 6), so the pixels constituting the tip portion are It is likely to be considered as a constituent point of an arc. On the other hand, since both side edges of the V-shaped pattern are linear, it is considered that a predetermined number of edge pixels are connected to each other.

  Therefore, by the process of erasing the constituent points of the arc, as shown in FIG. 9, the edge 13c at the tip portion disappears and the edges 13a and 13b at both side edges are left separated as shown in FIG. Become. Therefore, in ST104, a pair of edge sets corresponding to the edges 13a and 13b are extracted from the edge image after deleting the constituent points of the arc. Further, the position of the notch is detected by obtaining the center of gravity for each pair of sets and obtaining the coordinates of the midpoint between the centers of gravity. In addition, the calculation method of the position of a notch is not limited to the above. For example, a pair of edge sets are integrated including pixels (pixels other than the edge pixels) between them, and in this integrated set, A representative point such as the center of gravity may be obtained.

  Further, the notch detection process is not limited to the above. For example, an inflection point at which the edge direction changes greatly may be extracted by performing contour tracking processing on edge pixels. Since most of the edge pixels on the image are constituent points of the arc and are enlarged, the direction does not change greatly in the arc portion. On the other hand, for the substantially V-shaped pattern corresponding to the notch, the direction of the edge changes greatly at the two incision start points and at the tip part (the deep part of the incision), so the notch is accurately detected. be able to.

  When the position of the notch is detected in this way, ST105 becomes “YES” and the process proceeds to ST106. In ST106, the notch angle is calculated based on the method shown in FIG. In the subsequent ST107, a difference between the notch angle and the reference angle transmitted from the main controller is obtained, and it is checked whether or not the difference is within a predetermined error range. If this difference is within the error range, ST107 is “YES”, the process proceeds to ST108, the above-mentioned “OK” flag is set to ON, and is transmitted to main controller 1.

  When the difference exceeds the error, the process proceeds from ST107 to ST109. In ST109, an “NG” flag indicating that the orientation of the wafer is inappropriate is set to ON, the difference is set as a correction angle, and transmitted to the main controller 1 together with the NG flag. Since the correction angle is obtained by subtracting the notch angle from the reference angle, if this difference becomes a negative value, it means that it is necessary to reversely rotate the platen 22.

If the center point extraction process has failed in ST102, ST103 becomes “NO” and the process proceeds to ST110. If the notch cannot be detected in ST104, ST105 becomes “NO”, and the process similarly proceeds to ST110.
In ST110, the “NG” flag is set, an error code indicating the reason why the correction cannot be performed is set, and these are transmitted to the main controller 1. The value of the error code varies depending on which of ST103 and ST105 is “NO”.

  According to the above embodiment, the notch angle and the reference angle are shown with the center point O of the wafer 11 on the image as a reference, and the platen 22 is rotated with the difference between these angles as a correction angle. As already described with reference to FIGS. 10 and 11, the above method was used to determine whether the center point O of the wafer 11 and the center point R of the platen 22 coincide or do not coincide. By rotating the platen 22 by the correction angle, the notch can be aligned with the reference direction.

  7 and 8, the partial image of the wafer 11 is generated by narrowing the field of view of the camera 110. Therefore, an image having a higher resolution of the notch portion than that of the entire wafer is obtained. be able to. In addition, according to the method of the above-mentioned Patent Document 3, the center point can be obtained with high accuracy even if it is a partial circle. Can be sought. Therefore, the correction angle can be obtained with high accuracy, and the wafer direction can be adjusted with high accuracy.

  In the procedure of FIGS. 7 and 8, the reference angle θT is corrected by the adjustment angle α for the purpose of inspecting whether or not the wafer is oriented in the correct direction. If it is not necessary to output the flag data, even if the platen 22 is rotated before photographing, the correction angle θ is obtained using the original reference angle θT, and the platen 22 is rotated by the angle θ. Good.

  Furthermore, even when the entire wafer 11 is imaged, there may be areas suitable for detection of notches and areas not suitable for the field of view of the camera 110 due to factors such as uneven illumination and positional relationships with surrounding members. Can be inspected by the same method as in FIG. That is, if the reference direction of the wafer 11 to be inspected is included in an area not suitable for detection, the platen 22 is rotated by a predetermined adjustment angle so that the notch is included in an area suitable for detection. Just do it. When a deviation amount is detected by this inspection, the notch can be aligned in the reference direction by rotating the platen 22 with a value obtained by adding the adjustment angle to the deviation amount as a correction angle.

  By the way, the side surface (surface in the thickness direction of the periphery) of the wafer is not a vertical surface but a curved surface. In the above embodiment, the camera 110 and the light source are arranged as shown in FIG. 3 so that the specular reflected light from the surface of the wafer 11 does not enter the camera 110. However, the specular reflected light from the side surface of the wafer 11 is used. May enter the camera 110. The curvature over the entire circumference of this side surface is not uniform and varies between solids, so it is difficult to prevent the incidence of specular reflected light by adjusting the optical system.

  When specular reflection light from the side surface of the wafer 11 enters the camera 110, halation occurs at the periphery of the wafer, which may be erroneously detected as a notch. The procedure shown in FIG. 8 is based on the assumption that only one notch is detected. When a plurality of portions that are regarded as notches are detected, ST105 becomes “NO” and orientation adjustment is impossible. It will be judged. In order to prevent such a problem, the following process may be performed after the wafer 11 is placed on the platen 22. In this process, in order to simplify the description, it is assumed that the entire wafer 11 is imaged.

  First, imaging is performed immediately after the wafer 11 is placed on the platen 22, and a notch on the obtained image is detected. The detected notch angle is stored in the RAM 104 of the inspection apparatus 10 or the like. Next, the platen 22 is rotated by a predetermined angle, imaging is performed again, and a second notch detection process is executed on the obtained image. Here, if the notch angle detected in the second process is compared with the notch angle detected first, an angle difference corresponding to the rotation angle of the platen should be obtained for the original notch. On the other hand, with regard to halation, when the relationship with the light source changes due to the rotation of the wafer 11, the reflected light from the previous halation occurrence site does not enter the camera 110 or is reflected from another site during the second imaging. There is a high possibility that an angle difference following the rotation of the platen 22 cannot be obtained, such as light entering the camera 110. Therefore, a set of notch candidates whose difference in notch angle corresponds to the rotation angle of the platen 22 between the image obtained at the first time and the image obtained at the second time is regarded as a notch, and the others are noise caused by halation. As a result, the original notch can be accurately identified by removing the influence of the specular reflection light from the side surface of the wafer 11.

In the above two images, when a plurality of sets of notch candidates whose difference in notch angle corresponds to the rotation angle of the platen 22 is found, the platen 22 may be rotated again to perform the same processing. However, even if this process is repeated a plurality of times, if there are multiple sets of notch candidates, it is desirable to abort the process and proceed to error processing.
When imaging a part of the wafer 11 as in the procedure of FIG. 7, following the imaging after rotating the platen 22 in order to put the notch into the field of view of the camera 110, the notch becomes the field of view of the camera 110. By rotating the platen 22 within a range that does not go out and performing the second imaging, the notch and the halation occurrence site can be separated and determined as described above. The same applies when no adjustment is required to bring the notch into the field of view of the camera 110.

  In this way, the notch and the halation occurrence site are identified, and when the notch is finally identified, the notch angle detected for the first time is checked against the reference angle for the notch, thereby Appropriate orientation can be determined. Further, if the orientation is not appropriate, the orientation of the wafer 11 can be adjusted by rotating the platen 22 by an angle corresponding to the difference between the reference angle and the notch angle, as in the above embodiment.

It is a block diagram which shows the structure of an ion implantation apparatus. It is a block diagram which shows the structure of an inspection apparatus. It is a figure which shows the structure in a vacuum chamber with the installation example of a camera or illumination. It is a figure explaining the example of the setting of the mark in a platen, and the principle of the test | inspection concerning rotation operation. It is a figure which shows the example of a setting of the direction of a notch and a notch angle. It is a figure which shows the image at the time of limiting the visual field of a camera and imaging a wafer. It is a flowchart which shows a series of processing procedures in an ion implantation apparatus. It is a flowchart which shows the procedure of the direction inspection of a wafer. It is a figure explaining the principle of notch detection. It is a figure explaining the concept of a correction angle. It is a figure explaining the concept of a correction angle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main controller 6 Platen control apparatus 10 Inspection apparatus 11 Wafer 21 Vacuum chamber 22 Platen 101 Control part 102 CPU
105 Image Input Unit 108 Edge Extraction Unit 109 Communication Interface 110 Camera

Claims (3)

A circular semiconductor wafer with a notch formed at one location on the outer periphery is placed on a platen that rotates around the center, and the semiconductor wafer supported by the platen is imaged from above with a camera. In the method of adjusting the direction of the semiconductor wafer by controlling the rotation operation of the platen based on the result of processing the generated image,
When a semiconductor wafer is placed on the platen, the direction from the center point of the semiconductor wafer toward the correct position of the notch is used as a reference direction, and an angle θT formed by the reference direction with respect to a predetermined direction is used as a reference. A first step of registering as an angle;
A second step of performing imaging by setting a field-of-view range of the camera so that at least a part including at least a notch of the outer periphery of the semiconductor wafer supported on the platen is included in the field-of-view of the camera;
An edge pixel group representing the outer periphery of the semiconductor wafer is detected from the image generated by the imaging, and a center point of the arc is determined based on a portion constituting the arc of the detected edge pixel group. A third step to detect as
A fourth step of detecting the position of the notch based on edge pixels that do not constitute an arc among the edge pixel group detected in the third step ;
A fifth step of identifying a direction from the center point of the semiconductor wafer toward the notch based on the detection results of the third and fourth steps, and calculating an angle θN formed by the direction with respect to the specific direction;
A difference θ between the angle θN specified in the fifth step and a reference angle θT is obtained, and the platen is rotated by controlling the rotation direction and the rotation angle of the platen based on the value of the angle θ, whereby the semiconductor wafer And a sixth step of adjusting the direction of
In the second step, when the center point of the semiconductor wafer is aligned with the center point of the platen based on the reference angle θT registered in the first step, a direction corresponding to the reference direction is the platen It is determined whether or not it is included in an appropriate area that spreads with a predetermined angle width from the center point of the image, and when it is determined that the direction is included in the appropriate area, imaging is performed without rotating the platen. When it is determined that the direction is outside the appropriate region, the difference α between the angle formed by the direction from the center point of the platen toward one point in the appropriate region with respect to the specific direction and the reference angle θT is calculated. Obtaining as an adjustment angle, controlling the rotation direction and rotation angle of the platen based on the value of the adjustment angle α, rotating the platen, and then performing imaging.
A method for adjusting the direction of a semiconductor wafer. In the second step, among the semiconductor wafers supported by the platen, the range of view of the camera is set such that a range including a point corresponding to the center point of the platen and a part of the outer periphery corresponds to the view of the camera. A method for adjusting the direction of a semiconductor wafer in which imaging is performed after setting. The direction of the semiconductor wafer supported by the platen is adjusted by controlling the operation of the platen that supports the circular semiconductor wafer having a notch formed at one location on the outer periphery on the upper surface and rotating around the center. A device,
When a semiconductor wafer is placed on the platen, an angle θT formed by a direction from the center point of the semiconductor wafer toward the correct position of the notch with respect to a predetermined direction is set as a reference direction that the notch should take. Registration means for registering as a reference angle to represent;
Imaging means arranged above the platen so as to include at least a part of the outer peripheral edge of the semiconductor wafer on the platen in the field of view;
Imaging control for controlling rotation of the platen and imaging by the imaging means so that an imaging process for the semiconductor wafer placed on the platen is performed in a state where the notch of the semiconductor wafer is included in the visual field of the imaging means Means,
Edge pixel detection means for detecting an edge pixel group representing an outer peripheral edge of the semiconductor wafer from an image generated by imaging executed by control of the imaging control means;
First detection means for detecting a center point of the arc as a center point of the semiconductor wafer based on a portion constituting the arc in the edge pixel group detected by the edge pixel detection means;
Second detection means for detecting the position of the notch based on edge pixels that do not constitute an arc of the edge pixel group detected by the edge pixel detection means;
Based on the detection results by the first and second detection means, an angle calculation means for specifying a direction from the center point of the semiconductor wafer toward the notch and obtaining an angle θN formed by the direction with respect to the specific direction;
A difference θ between the angle θN calculated by the angle calculation unit and the reference angle θT registered in the registration unit is obtained, and the platen is controlled by controlling the rotation direction and the rotation angle of the platen based on the value of the angle θ. A direction adjusting means for adjusting the direction of the semiconductor wafer by rotating it;
The imaging control means, based on the reference angle θT registered in the registration means, the direction corresponding to the reference direction when the center point of the semiconductor wafer is aligned with the center point of the platen, It is determined whether or not it is included in an appropriate area that spreads with a predetermined angle width from the center point of the platen, and when it is determined that the direction is included in the appropriate area, imaging is performed without rotating the platen. When it is determined that the direction is outside the appropriate region, the difference α between the angle formed by the direction from the center point of the platen toward one point in the appropriate region with respect to the specific direction and the reference angle θT is calculated. The direction of the semiconductor wafer, which is obtained as an adjustment angle, controls the rotation direction and rotation angle of the platen based on the value of the adjustment angle α, and executes imaging after rotating the platen Integer unit.

Images