JP2008091690A - Appearance inspection equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the appearance inspection equipment capable of adjusting the wafer position easily and quickly. <P>SOLUTION: The appearance inspection equipment 1 has a wafer holding section 4 which holds a wafer W in the XYZ directions while allowing the wafer W to be freely rotated around the Z axis, and a peripheral imaging section 5 which is arranged nearby to observe the peripheral portion of the wafer W. A wafer position at the observation location is preset using a presetting section 52, which avoids significant shift of the wafer position and simplifies time-consuming adjustment of focusing and the like. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an apparatus for inspecting the appearance of a substrate such as a wafer.

In a semiconductor manufacturing factory or the like, a semiconductor wafer is inspected for a scratch or a defect generated during the process by inspecting a peripheral portion of the semiconductor wafer or the entire wafer surface including the peripheral portion. As this substrate inspection apparatus, a mounted wafer can be rotated by a drive mechanism and a stage smaller than the wafer diameter, an XY stage on which this stage is installed, and three observation optics for observing the peripheral portion, side surface, and lower portion of the wafer Some have a system (see, for example, Patent Document 1). Each of the three optical systems has an automatic focusing mechanism, and images are picked up by a television camera installed in each observation optical system, and a detection image is input to the image processing apparatus for inspection. At this time, the center position of the wafer is positioned at the rotation center of the drive mechanism by the alignment mechanism. In the case of observing the peripheral edge of the wafer more strictly, an operation is performed in which the inner side is always measured a predetermined distance from the outer periphery of the wafer in conjunction with the driving mechanism of the XY stage.
Japanese Patent Laid-Open No. 2001-221749

However, when observing while rotating the wafer, the observation position moves from the screen if the wafer is displaced from the rotation center position of the stage. When the wafer position deviates greatly, it becomes impossible to observe depending on the magnification. For this reason, it is necessary to always provide an alignment device that can detect the deviation amount within a predetermined distance.
In addition, since the wafer is distorted during the manufacturing process, the periphery of the wafer moves in a direction perpendicular to the main surface in addition to the movement in the plane parallel to the main surface by rotating the stage. There is. Therefore, when observing the side surface while rotating the wafer, the image of the side surface on the observation screen moves even if the autofocus mechanism can focus. When large distortion occurs at the peripheral edge of the wafer, observation may be impossible depending on the magnification. In order to avoid such a situation, the observation optical system and the stage are configured to be relatively movable in the direction perpendicular to the main surface, and the amount of movement in the direction perpendicular to the main surface of the peripheral edge of the wafer is detected. Therefore, it is necessary to always provide a distance sensor for controlling the position of the side surface of the wafer to be constant.
Thus, in the conventional visual inspection apparatus, since it was necessary to install an alignment apparatus and a distance sensor, there existed a problem that more cost started.
The present invention has been made in view of such circumstances, and it is a main object of the present invention to be able to deal with eccentricity and distortion of the shape due to wafer stage rotation and to influence an inexpensive appearance inspection apparatus.

The present invention that solves the above-described problems includes a wafer holding unit that rotatably holds a wafer, and a peripheral imaging unit that acquires an enlarged image of the peripheral part of the wafer, and the wafer holding unit, the peripheral imaging unit, Is an appearance inspection device configured to be relatively movable, and to perform an appearance inspection of the peripheral portion of the wafer, and adjusting the arrangement of the peripheral imaging unit or the wafer holding unit so that a predetermined position of the peripheral portion on the wafer can be observed And a preset setting unit for registering the input wafer position as a preset value, and an inspection control unit for moving the wafer in accordance with the preset value so that an appearance inspection can be performed. An appearance inspection apparatus was obtained.
In this appearance inspection apparatus, the initial position at the observation position of the wafer at the time of inspection is registered in advance as a preset value. At the time of inspection, since the wafers are arranged according to the preset value, it is not necessary to provide a detection device and perform calculation such as a change amount of the position detected by the detection device, and the inspection can be performed as it is.

  According to the present invention, since the position of the wafer peripheral portion is controlled using the preset value, it is not necessary to provide an apparatus for detecting the wafer position during observation, and an inexpensive appearance inspection apparatus can be realized.

  As shown in FIG. 1, the appearance inspection apparatus 1 has a base portion 2 fixed to a frame (not shown) or the like, and an inspection portion 3 is mounted on the base portion 2. The inspection unit 3 includes a wafer holding unit 4 on which a wafer W to be inspected is placed, and a peripheral imaging unit 5 that is disposed in the vicinity of the wafer holding unit 4 and acquires an image of the peripheral part of the wafer W. The wafer holding unit 4 and the peripheral imaging unit 5 are controlled by the apparatus control unit 6. A surface inspection unit such as a microscope that can observe the entire surface of the wafer W may be provided in addition to the peripheral imaging unit 5.

  The wafer holding unit 4 has an X stage 11 fixed to the base unit 2 and movable in the horizontal direction indicated by X in FIG. 1, and on the X stage 11, the Y axis is a horizontal direction orthogonal to the X axis. A movable Y stage 12 is mounted. Further, a Z stage 13 that is movable in the Z direction in the height direction orthogonal to the XY direction is mounted on the Y stage 12. As a result, the wafer holding unit 4 can move the wafer W relative to the peripheral imaging unit 5 in a three-dimensional manner. Further, the Z stage 13 is provided with a rotating unit 14. The rotating unit 14 has a rotating shaft 15 that can rotate around the Z axis. Each stage 11-13 and the rotating shaft 15 are driven using a servo motor, a ball screw, and a speed reduction mechanism. A stepping motor or a linear motor can be used as the drive source. A rotating plate 16 is provided at the upper end of the rotating shaft 15. On the upper surface of the rotating plate 16, a suction unit (not shown) that holds the wafer W by vacuum suction is provided.

  The peripheral imaging unit 5 is supported by an arm unit 21 fixed to the base unit 2. The peripheral imaging unit 5 has a substantially C shape having a recess 22 that can receive the peripheral part of the wafer W in a side view, and a camera capable of imaging the peripheral part of the wafer W is provided. FIG. 2 shows an example of a trinocular peripheral imaging unit. The camera can image the first camera 25 that can image the upper surface of the peripheral portion of the wafer W, the second camera 26 that can image the side surface of the peripheral portion of the wafer W, and the lower surface of the peripheral portion of the wafer W. And a third camera 27. Each of the cameras 25 to 27 includes an imaging element 28 such as a CCD (Charge Coupled Device) and a zoom lens 29, and a half mirror 30 is installed on the optical axis, so that coaxial illumination using the illumination device 31 is performed. It is configured to be possible. Note that the number of cameras can be arbitrarily changed, such as one or five. When only one camera is used, the imaging position can be changed by supporting the camera movably, or the imaging position can be changed by a movable mirror while the camera is fixed. The illumination device 31 is not limited to the coaxial illumination, and one or more illumination devices 31 may be provided at positions away from the cameras 25 to 27. It is preferable that the illuminating device 31 enables the peripheral portion to be observed in a bright field.

  The apparatus control unit 6 shown in FIG. 1 controls the driving of the stages 11 to 13 and the rotation unit 14 of the wafer holding unit 4, vacuuming for suction, and zooms of the cameras 25 to 27 of the peripheral imaging unit 5. Adjustment, dimming of the illumination device 31, and reception of image signals of the cameras 25 to 27 are performed. For example, a motor driver circuit, a driver circuit for controlling opening / closing of a vacuuming valve, and the like are included. Furthermore, the device control unit 6 is also connected to a computer 41.

  The computer 41 is a general-purpose computer in which an input unit such as a mouse 42, a keyboard 43, and a joystick 48, and a monitor 44 that displays various settings and an image of a peripheral part are connected. The mouse 42, the keyboard 43, and the monitor 44 are interfaces that can be operated by the examiner, and are operating devices used for teaching described later. The computer 41 includes an input / output (I / O) device 45 to which the device control unit 6, mouse 42, keyboard 43, and monitor 44 are connected, a control unit 46, and a storage device 47 that stores data such as recipes. Have. The control unit 46 includes a CPU (Central Processing Unit) and the like, and includes an inspection control unit 51 that performs inspection according to a recipe, a preset setting unit 52 that performs processing for registering preset values, and a recipe registration unit that registers recipes. 53 can be divided into functions. The computer 41 may be mounted on the appearance inspection apparatus 1 or may be provided separately from the apparatus. The computer 41 and the device control unit 6 may form a single control device.

Next, the operation of this embodiment will be described.
In this appearance inspection apparatus 1, the preset value of the observation position is registered when the inspection is started. When actually inspecting, the position of the wafer W or the cameras 25 to 27 is moved according to the preset value, and the observation inspection is performed as it is.

First, processing for registering preset values will be described with reference to the flowchart of FIG. First, a manual teaching mode is selected in a state where there is no wafer W in the wafer holder 4 (step S101). The teaching mode is selected by pressing a teaching button provided in hardware in the apparatus control unit 6 or by pressing a teaching button provided on a screen provided as a GUI (Graphical User Interface) on the monitor 44. . The teaching button may be provided either on the hardware or on the software, or may be provided on both (hereinafter the same for each button).
When the teaching mode is selected, the preset setting unit 52 loads the wafer W into the wafer holding unit 4 (step S102). The wafer W is positioned and loaded from a macro inspection device, a micro inspection device, or a wafer cassette (not shown) by a transfer device such as a robot. The wafer W is attracted and held by the wafer holder 4 after being positioned by an alignment device (not shown). Here, it is assumed that when the wafer is transferred to the wafer holding unit 4 by the transfer device, a position shift inherent in the transfer device occurs and eccentricity occurs. When the delivery position of the wafer W and the installation position of the peripheral imaging unit 5 are different, the wafer holding unit 4 moves after receiving the wafer W, and moves the wafer W to the installation position of the peripheral imaging unit 5.

When the wafer W moves to the installation position of the peripheral imaging unit 5, first, the position of the notch of the wafer W is searched. Here, a sensor for searching for the notch position may be provided. Next, it is rotated by a predetermined angle based on the position of the notch. The predetermined angle can be arbitrarily determined by the inspector. The inspector operates the joystick 48 so that a predetermined observation position on the peripheral edge of the wafer W is within the visual field of the cameras 25 to 27, that is, within the monitor screen, and the wafer holder 4 is in the XYZ direction so as to be in focus. The position is adjusted (step S103). The wafer holder 4 may be moved in the XYZ directions using the mouse 42 or the keyboard 43 instead of the joystick 48 or in combination with the joystick 48. When using the joystick 48, the wafer holder 4 can be moved directly. When the mouse 42 or the keyboard 43 is used, the wafer holding unit 4 is moved via the GUI displayed on the monitor 44.
Furthermore, since the angle of the chamfered portion of the lot of cameras 25 to 27 and the wafer W to be used may be different, the observation angle in the plane perpendicular to the wafer surface is set so that the angle is easier to observe in bright field observation. Adjust. If necessary, if the zoom is adjusted and the lighting device 31 is dimmed, the observation position at this time is stored (step S104). When storing the observation position (the position of the wafer holding unit 4 in the XYZ directions), the inspector presses the storage button on the operation panel of the apparatus control unit 6 or clicks the storage button displayed on the monitor 44 with the mouse. . Information such as the XYZ coordinates, zoom, and light control of the wafer holding unit 4 is stored in the storage device 47 as data of the first observation position.

  Returning from step S105 to step S103, the wafer W is rotated again by a predetermined angle. The predetermined angle here is an angle obtained by dividing 360 ° by the number when the number of observation positions is set in advance. Further, the observation may be performed while rotating, and the angle may be the angle when the screen is shifted on the monitor 44 or the focus is shifted. With respect to the second and subsequent observation positions, the same operation is performed to store the observation position data in the storage device 47. When registration is completed for all observation positions (Yes in step S105), the inspector presses the calculation button. The preset setting unit 52 calculates an operation flow based on all the registered observation position data (step S106). The calculation button is provided on the operation panel of the apparatus control unit 6 or displayed on the monitor 44. The operation flow may be created by arranging the data at each observation position in order, may be interpolated between the data at each observation position, or may be smoothed. When the peripheral edge of the wafer W is distorted in a direction perpendicular to the main surface, the follow-up of the operation flow with respect to the wafer shape is improved by performing interpolation between data and smoothing.

After calculating the operation flow, the inspection control unit 51 performs a test run according to the operation flow (step S107). For example, when there are a plurality of observation positions in the circumferential direction, these observation positions sequentially move within the observation field of view of the cameras 25 to 27. When smoothing is applied, the trajectory of the wafer W between successive observation positions changes smoothly.
If the result of the trial run is good (Yes in step S108), the inspector presses the preset setting button. The preset setting unit 52 causes the storage device 47 to record the operation flow data as a preset value (step S109). The preset setting button is provided on the operation panel of the apparatus control unit 6 or displayed on the monitor 44.

  Next, when the inspection is actually performed, the inspection control unit 51 performs the position control of the wafer W by the XYZ position control of the wafer holding unit 4 according to the preset value. When there is almost no deviation between the wafer position reproduced by the preset value and the position of the wafer W currently being inspected, the peripheral portion of the wafer W can be observed without fine adjustment. Even if there is a deviation between the two, the amount of deviation is reduced by the preset value, so that the observation can be performed only by finely adjusting the focus position by the automatic focus mechanism if necessary. For fine adjustment of the wafer position, at least one of a mouse 42, a keyboard 43, and a joystick 48 functioning as an operation device during inspection is used.

  Further, data of imaging conditions such as the wafer position reproduced by the preset value and the brightness of illumination is created, and this data and the preset value are created as a recipe and stored in the storage device 47 by the recipe registration unit 53. You may let them. Using preset values or recipes registered in this way, inspection is performed without installing an inspection device that detects the position of the wafer used during observation, such as when continuously inspecting wafers W having substantially the same shape. it can.

  In this embodiment, the observation position is taught using the wafer W, and the data at this time is registered as a preset value so that it can be used for actual inspection. Therefore, individual differences and undulations occur in the wafer W. Even if a certain positional deviation always occurs when the transfer device delivers the wafer W to the wafer holding unit 4 after alignment, the peripheral portion of the wafer W and the observation positions of the cameras 25 to 27 are detected. Therefore, the focus adjustment by the automatic focusing mechanism of the cameras 25 to 27 is fine adjustment. In the conventional apparatus configuration, it is necessary to always provide an alignment apparatus and a distance sensor. However, in this embodiment, it is not necessary to use a sensor to correct the wafer position, and the apparatus can be made inexpensive. . In particular, since the observation position of the peripheral portion of the wafer W is kept constant by teaching, it can be set with higher accuracy.

(Second Embodiment)
This embodiment is characterized in that shape data of the peripheral portion of the wafer such as a design value or an actual measurement value is used as a preset value. The apparatus configuration is the same as that of the first embodiment.
A flowchart for registering preset values in this embodiment is shown in FIG. First, the set value input button is pressed to select the set value input mode (step S201). The set value input button is provided in hardware in the apparatus control unit 6 or on a screen provided as a GUI to the monitor 44. The set value input buttons may be provided either on the hardware or on the software, or may be provided on both (hereinafter the same for each button).

  Next, data on the shape of the wafer W is input (step S202). As the design value of the wafer W, for example, as shown in FIG. 5, the thickness T1 of the wafer W, the thickness T2 of the end surface, the horizontal length L1 of the surface F1 polished obliquely at the peripheral edge, The angle α that F1 makes with the vertical direction is input from CAD (Computer Aided Design) data, actual measurement data, specification data, or the like. For inputting data, at least one of a mouse 42, a keyboard 43, and a joystick 48, which are input units, is used. In the case of CAD data, it can also be captured by a recording medium or communication. The input unit at this time is a drive device or a communication device for reading a recording medium.

The preset setting unit 52 calculates a preset value of the wafer position using the input data (step S203). Since the arrangement of the wafer holding unit 4 and the peripheral imaging unit 5 is a value unique to the apparatus and is known, each camera 25 to 27 with respect to the peripheral part of the wafer W using the wafer size and the design value of the wafer W described above. And the distance between the peripheral portion and each of the cameras 25 to 27 is calculated. From the magnification required for observation and the working distance (WD) of the cameras 25 to 27 at that time, the position, focus, and zoom of the wafer holder 4 in the XYZ directions are determined as preset values.
When these calculations are completed, the inspector presses a preset setting button to register the preset value in the storage device 47 (step S204). The preset setting unit 52 may register a result obtained by adding the rotation speed of the wafer W, illumination conditions, and the like to the calculation result of the wafer position. Note that a trial run may be performed in the same manner as in the first embodiment before the preset value is registered.

After the preset value is registered in this way, the peripheral portion of the wafer W is inspected. Wafers W are arranged according to preset values, and magnified images are acquired by cameras 25-27. Inspect for visual damage by visual observation.
Further, when the processing described with reference to FIG. 3 in the first embodiment is performed using the preset value created in this embodiment, a highly accurate preset value can be created in a short time.

  In this embodiment, since the shape of the wafer W is input as data and the preset value is calculated by combining the values unique to the apparatus, the preset value can be quickly compared with the case where the preset value is set for each observation position. Can be created. The effect of using the preset value is the same as that of the first embodiment.

Note that the present invention can be widely applied without being limited to the above-described embodiment.
For example, when the peripheral imaging unit 5 is a single lens system, information on the angle when the camera is rotated and the angle when the mirror is rotated are also stored as preset values.
The joystick 48 is not an essential component, and other input devices may be used.
The wafer holding unit 4 is not limited to the configuration of the embodiment as long as it can move the wafer W in three directions XYZ and can rotate the wafer W. Instead of moving the wafer W to XYZ, the peripheral edge imaging unit 5 may be mounted on the X stage, Y stage, and Z stage so as to be movable in three directions of XYZ. Further, a mechanism movable in at least one direction of XYZ may be provided on the wafer holding unit 4 side, and a mechanism movable in the remaining two directions may be provided on the peripheral imaging unit 5 side. In other words, the wafer holding unit 4 and the peripheral imaging unit 5 are configured to be relatively movable so that the focal position of the peripheral imaging unit 5 always coincides with the position to be observed on the peripheral part of the wafer W within a predetermined range. It only has to be controlled.

It is a figure which shows schematic structure of the external appearance inspection apparatus which concerns on this Embodiment. It is a figure which shows the example of arrangement | positioning of the camera of a peripheral imaging part. It is a flowchart explaining the process which sets a preset value. It is a flowchart explaining the process which calculates a preset value by data input. It is a figure which shows the example of the data of the shape of the wafer used for calculation of a preset value.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Appearance inspection apparatus 4 Wafer holding part 5 Peripheral imaging part 42 Mouse (input part, operation apparatus, operation apparatus at the time of inspection)
43 Keyboard (input unit, operation device, inspection operation device)
48 Joystick (input unit, operation device, operation device during inspection)
51 Inspection Control Unit 52 Preset Setting Unit W Wafer

Claims (3)

A wafer holding unit that rotatably holds the wafer, and a peripheral imaging unit that acquires an enlarged image of the peripheral part of the wafer, wherein the wafer holding unit and the peripheral imaging unit are configured to be relatively movable, An appearance inspection apparatus for performing an appearance inspection of a peripheral portion,
An input unit for inputting information for adjusting the arrangement of the peripheral imaging unit or the wafer holding unit so that a predetermined position of the peripheral part on the wafer can be observed;
A preset setting unit for registering the input wafer position as a preset value;
An inspection control unit that moves the wafer in accordance with preset values so that visual inspection can be performed;
An appearance inspection apparatus characterized by comprising:   The appearance inspection apparatus according to claim 1, wherein the input unit is an operation device that manually moves the wafer holding unit in order to teach a wafer position.   The appearance inspection apparatus according to claim 1, wherein the input unit is an apparatus for inputting data on a shape of a peripheral portion of a wafer.

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