JP2008203151A - Wafer surface inspection method, and device therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wafer surface inspection method capable of enhancing detection precision of a defective part such as a superfine crack, chip, flaw on a wafer surface, and detection precision of position coordinates of a foreign matter such as dust thereon, without generating a sacrifice by a through-put in wafer surface inspection, and capable of enhancing detection precision of coordinates of a wafer edge, and a device therefor. <P>SOLUTION: A laser beam 14a is emitted to a surface of a rotating wafer 13, a scattered beam is received to detect the defective part and the foreign matter on the surface of the wafer 13. A beam diameter of the laser beam is reduced in the vicinity of the edge of the wafer, and a feed speed of the laser beam is thereby made slow to detect an accurate edge position (position of the edge 13a). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention rotates a non-pattern wafer having no pattern among wafers at high speed, irradiates the surface with laser light, receives reflected scattered light, and detects defects, dust, etc. on the surface of the wafer. The present invention relates to a wafer surface inspection method and apparatus therefor.

  As a conventional non-pattern wafer surface inspection apparatus using light scattering technology, for example, a base movable in the X-axis direction is provided, and this base is provided so as to be driven in the X-axis direction by a feed driving means. The holding stage is rotatably held, and a laser beam is irradiated onto the wafer held on the stage from a laser light source disposed above the stage, and the scattered light of the laser beam reflected from the wafer is received. There is known one provided with a light receiving means.

  In this surface inspection apparatus, the stage on which the wafer is held is rotationally driven by the rotational driving means, and the laser beam is irradiated to the rotational center of the wafer on the stage. From this state, the stage is fed in the X axis direction by the feed driving means. By moving at a speed, the laser beam spirally scans the wafer surface (wafer surface). Then, along with this spiral scanning, the light receiving means receives the scattered light of the laser beam reflected from the wafer surface, so that the position information (XY coordinates) of the defect on the wafer surface and the dust attached to the wafer surface. The position information (XY coordinates) of the foreign matter such as can be obtained from the rotation angle of the wafer and the feed amount in the X-axis direction of the wafer.

  By the way, in such a scanning type non-pattern wafer surface inspection apparatus, the positional accuracy of the position information (XY coordinates) of foreign matter such as defects on the wafer surface and dust is determined by the beam diameter and the amount of movement during X-axis movement for each rotation. (Scanning pitch).

  That is, the smaller the beam diameter of the laser beam or the movement amount (scanning pitch) of the laser light source, the better the coordinate accuracy. However, the size of the beam diameter and scanning pitch also affects the throughput (measurement time), which is the main performance of the apparatus, so that it is appropriately sized in consideration of the point that accuracy can be secured to some extent. .

  In addition, as a conventional wafer surface inspection apparatus, when detecting defects such as scratches and foreign matter on the wafer edge, illumination light such as a laser is irradiated near the wafer edge as shown in FIG. 5 to inspect the defect near the wafer edge. In some cases, laser irradiation is performed with a constant laser beam diameter and a constant movement amount (pitch) of the laser light source, regardless of the surface or edge of the wafer (for example, Patent Documents). 1 and 2).

  Further, as a conventional wafer surface inspection apparatus, there is also known an apparatus that irradiates a wafer edge with a laser beam, observes its appearance with a video camera or an infrared camera, and inspects defects on the edge (for example, Patent Document 3). , 4).

In addition, as a conventional wafer surface inspection apparatus, a laser light source is used, and a photomultiplier or the like is used as a detector to detect diffracted light due to the type of defects or surface roughness at the edge of the inspection object (wafer). Also known is one that can detect cracks, chips, scratches, and the like, and detect surface roughness based on frequency components (see Patent Document 5).
JP 2001-255278 A (paragraph number 0078, FIGS. 36 to 38) Japanese Patent Laying-Open No. 2006-201179 (paragraph number 0086, FIGS. 36 to 38) JP 2000-46537 A JP 2000-136916 A Japanese Patent No. 2999712 (paragraph number 0012, paragraph number 0010, and FIGS. 2 to 3)

  However, along with the miniaturization of the pattern transferred to the wafer, the detection accuracy of the position coordinates of defective parts such as ultra-fine cracks, chips and scratches on the wafer surface and the detection accuracy of the position coordinates of foreign matters such as dust are improved. In addition, it is necessary to detect the scattered light signal from the wafer edge with high precision and separate it from the scattered light signal from the defect or foreign matter and the scattered light signal from the wafer edge to specify the exact edge position.

  Therefore, as shown in FIG. 5, the conventional wafer surface inspection apparatus in which the surface inspection is performed with a constant laser beam diameter and a constant movement amount (pitch) of the laser light source regardless of the surface or edge portion of the wafer. As the pattern transferred to the wafer is miniaturized, the scattered light from the wafer edge cannot be separated from the signal of the scattered light from the defective portion or foreign matter and detected with high precision.

  In addition, even with conventional wafer surface inspection apparatuses using video cameras and infrared cameras, observations using video cameras and infrared cameras are used, so that sufficient accuracy can be obtained to distinguish wafer edges from defective parts and foreign objects. There wasn't.

  Therefore, the present invention improves the detection accuracy of defective portions such as ultra-fine cracks, chips, and scratches on the wafer surface and the detection accuracy of the position coordinates of foreign matters such as dust without sacrificing the throughput of the wafer surface inspection. An object of the present invention is to provide a wafer surface inspection method and apparatus capable of improving the detection accuracy of wafer edge coordinates at the same time.

  In order to achieve this object, the present invention provides a wafer surface inspection method for irradiating a surface of a rotating wafer with laser light and receiving scattered light with a light receiving means to detect defective portions and foreign matter on the surface of the wafer. The wafer surface inspection method and apparatus for detecting an accurate edge position by reducing the beam diameter of the laser beam and reducing the scan pitch of the laser beam in the vicinity of the edge of the wafer.

  According to such a method and its apparatus, it is possible to improve the detection accuracy of the position coordinates of the minute defect portion on the wafer surface and the detection accuracy of the position coordinates of the foreign matter without sacrificing the throughput of the wafer surface inspection. At the same time, the detection accuracy of the coordinates of the edge of the wafer can be improved.

Embodiments of the present invention will be described below with reference to the drawings.
[Constitution]
The wafer surface inspection apparatus according to the present invention has a fixed base 1 extending in the X-axis direction as shown in FIGS. 1 (a) and 1 (b). A pair of parallel guide rails 2 and 2 extending in the X-axis direction are provided on the fixed base 1, and a slide base (movable table) 3 slides (movable) in the X-axis direction on the guide rails 2 and 2. It is attached to.

  The slide base 3 is driven and fed in the X-axis direction by a base feeding device (base feeding means) 4. The base feed device 4 includes bearing protrusions 5 and 6 integrally provided at both ends in the longitudinal direction (X-axis direction) of the fixed base 1, and is rotatably held by the bearing protrusions 5 and 6 and guided. A feed screw 7 provided in parallel to the rails 2 and 2 and a drive motor (feed motor) 8 fixed to the bearing projection 6 and rotating the feed screw 7 are provided. The drive motor 8 is a pulse motor.

  A drive motor (rotation drive means) 9 is fixed on the slide base 3. The drive motor 9 has an output shaft 9a, and a chuck 10 is attached to the upper end of the output shaft 9a. Since a known structure can be adopted for the chuck 10, the description thereof is omitted. The drive motor 9 is a pulse motor.

  A circular disk (disk) 11 for holding a wafer is disposed on the chuck 10, and a mounting shaft 12 is integrally formed at the center of the lower surface of the disk (stage) 11 as shown in FIG. Is provided. The mounting shaft 12 is detachably attached to the chuck 10 and is held so as not to rotate relative to the axis.

  A non-pattern wafer 13 is held (fixed) on the upper surface of the disk 11. Here, the non-patterned wafer 13 refers to an unused wafer whose surface is not processed.

  Further, a laser light source 14 that irradiates the surface (upper surface) of the wafer 13 with a laser beam 14 a at a predetermined angle θ is disposed above the wafer 13. The laser light source 14 is fixed to a frame or a bracket (not shown). In addition, when the laser beam 14a is regularly reflected on the surface of the wafer 13, the reflected beam 14b is reflected at an angle θ in front of the laser beam 14a.

  In addition, a light receiving sensor 15 that receives forward scattered light is disposed at a portion located on the front side in the irradiation direction of the laser beam 14a and above the reflected beam 14b. The light receiving sensor 15 uses a photomultiplier (PMT, that is, a photomultiplier tube). The optical axis 15 a of the light receiving sensor 15 is directed to the irradiation position P of the laser beam 14 a on the wafer 13.

  Furthermore, if a plane including the optical axes of the laser beam 14a and the reflected beam 14b is defined as a first vertical plane, and a plane perpendicular to the first vertical plane is defined as a second vertical plane, the plane is lateral to the second vertical plane. The center of the light receiving sensor 16 is disposed. A photomultiplier (PMT, ie, a photomultiplier tube) is also used for the light receiving sensor 16. The optical axis 16a of the light receiving sensor 16 is also directed to the irradiation position P of the laser beam 14a on the wafer 13.

  Further, an edge detection sensor 17 having an optical axis in the first vertical plane and obliquely below the edge of the wafer 13 is disposed on the front side in the irradiation direction of the laser beam 14a. A photomultiplier (PMT or photomultiplier tube) is also used for the edge detection sensor 17.

Further, as shown in FIG. 2, the drive motors 8 and 9 are rotationally driven and controlled by an arithmetic control circuit (control means) 18. The arithmetic control circuit 18 also controls the operation of the laser light source 14. In addition, detection signals from the light receiving sensors 15 and 16 are input to the arithmetic control circuit 18, and detection signals from the edge detection sensor 17 are input to the arithmetic control circuit 18. A memory 19 is connected to the arithmetic control circuit 18.
[Action]
Next, the operation of the wafer surface inspection apparatus having such a configuration will be described together with the contents of control by the arithmetic control circuit 18.
Step S1
The arithmetic control circuit 18 controls the drive motor 8 in step S1 of FIG. 4 to position the slide base 3 at the initial position shown in FIG. At this initial position, the center of the wafer 13 is irradiated with a laser beam 14 a emitted from the laser light source 14. In addition, at this initial position, the arithmetic control circuit 18 sets the spot diameter of the laser beam 14a to “large”, and when the laser beam 14a is irradiated on the surface of the wafer 13, it is shown by a two-dot chain line in FIG. The operation of the laser light source 14 is controlled so as to obtain a relatively large elliptical beam spot 14c, and the process proceeds to step S2. In FIG. 3, the major axis of the beam spot 14c is indicated by Ba.
Step S2
In step S <b> 2, the arithmetic control circuit 18 drives and controls the drive motor 9 to rotate the wafer 13 integrally with the disk 11. On the other hand, the arithmetic control circuit 18 drives and controls the drive motor 8 to rotate the feed screw 7 to feed and move the slide base 3 in the X-axis direction and in the direction opposite to the irradiation direction of the laser beam 14a, and proceeds to step S3. To do.

  By such rotation of the wafer 13 and movement of the wafer 13 in the X-axis direction, the laser beam 14a is spirally irradiated on the surface of the wafer 13, and the irradiation position of the laser beam 14a on the wafer 13 is 1 in the wafer 13. When rotated, the pitch of the wafer 13 is shifted by one pitch.

  At this time, when there is no defect such as ultra fine cracks, chips, scratches or foreign matter such as dust at the irradiation position P of the surface of the wafer 13 with the laser beam 14a, the laser beam 14a is regularly reflected from the surface of the wafer 13. Thus, a forward reflected beam 14b is obtained.

  Further, if there is a foreign matter such as an extremely fine crack, a chip, a scratch or the like or a foreign matter such as dust at the irradiation position P of the surface of the wafer 13 of the laser beam 14a, the laser beam 14a is irregularly reflected due to the defective portion or the foreign matter. Becomes scattered light. The scattered light is detected by the light receiving sensors 15 and 16, and the scattered light detection signal of the light receiving sensors 15 and 16 is input to the arithmetic control circuit 18. And the detection position of a defective part and a foreign material is detected as a two-dimensional coordinate (X, Y) from the rotation amount of the drive motors 8 and 9. In addition, the arithmetic control circuit 18 stores the two-dimensional coordinates (X, Y) of the detection position of the defective part or the foreign matter in the memory 19.

  In this step S2, the arithmetic control circuit 18 keeps the rotational speed of the drive motor 9 constant and increases the rotational speed of the drive motor 8, and feeds the slide base 3 in the X-axis direction by the feed screw 7 (feed pitch). That is, the control is set so that the scan pitch P1) is increased. Note that the rotation speed of the drive motor 9 is reduced and the rotation speed of the drive motor 8 is kept constant, and the scan pitch (feed pitch or feed amount) P1 of the slide base 3 in the X-axis direction by the feed screw 7 is “large”. It can also be controlled to become.

When the irradiation position of the laser beam 14a becomes a predetermined position (for example, a position of 1.0 mm to 1.5 mm) from the edge (periphery) 13a of the wafer 13 by such control, the arithmetic control circuit 18 proceeds to step S3. . Since the approximate distance from the center of the wafer 13 to the edge 13a is known in advance, the laser beam 14a is moved in the X-axis direction from the state where the laser beam 14a is applied to the center of the wafer 13, and the laser is moved. When the irradiation position of the beam 14a on the wafer 13 is moved in the radial direction from the center of the wafer 13, the timing for shifting to the processing in step S3 can be determined from the amount of movement of the irradiation position in the radial direction.
Step S3
In step S3, the arithmetic control circuit 18 switches the diameter of the laser beam 14a from “large” to “small”. That is, the arithmetic control circuit 18 changes the diameter of the laser beam 14 a from “large” to “small” at the peripheral edge of the wafer 13, and the laser beam 14 a is irradiated onto the surface of the wafer 13 in FIG. The operation of the laser light source 14 is controlled so that the elliptical beam spot 14c indicated by the dashed line becomes a beam spot 14d having a small diameter Bb as indicated by the dashed line. In the present embodiment, the diameter Bb of the beam spot 14d is set to about 1/4 or less of the major diameter Ba of the beam spot 14c, but the present invention is not necessarily limited to this.

  In accordance with this control, the arithmetic control circuit 18 switches the scan pitch by the laser beam 14a from “large” to “small”, and proceeds to step S4. That is, the arithmetic control circuit 18 switches the scan pitch of the laser beam 14a from P1 to P2, and proceeds to step S4. In this embodiment, the scan pitch P1 is set to about 1/4 of the scan pitch P2, but is not necessarily limited to this.

  This switching can be realized by setting one of the drive motors 8 and 9 to a constant rotation speed and changing the other rotation speed of the drive motors 8 and 9.

That is, the arithmetic control circuit 18 keeps the rotational speed of the drive motor 9 constant and decreases the rotational speed of the drive motor 8 to feed the slide base 3 in the X-axis direction by the feed screw 7 (feed pitch or scan). The pitch is set so as to be reduced. In addition, the rotation speed of the drive motor 9 is increased and the rotation speed of the drive motor 8 is kept constant, so that the scan pitch (feed pitch, that is, feed amount) of the slide base 3 in the X-axis direction by the feed screw 7 becomes “small”. It can also be controlled.
Step S4
In this step 4, the arithmetic control circuit 18 inspects (measures) whether or not there is a defective portion or a foreign substance on the surface of the wafer 13 until the edge 13 a of the wafer 13 is detected. That is, the arithmetic control circuit 18 inspects (measures) whether or not there is a defective portion or a foreign substance on the surface of the wafer 13 until the laser beam 14a is separated from the edge 13a and directly enters the edge detection sensor 17.

  When the laser beam 14 a deviates from the edge 13 a and directly enters the edge detection sensor 17, an edge detection signal is output from the edge detection sensor 17, and this edge detection signal is input to the arithmetic control circuit 18.

Even in step S4, when the calculation control circuit 18 detects the detection position of the defective portion or the foreign matter, the calculation control circuit 18 stores the two-dimensional coordinates (X, Y) of the detection position in the memory 19 as described above.
Step S5
In step S <b> 5, upon receiving the edge detection signal from the edge detection sensor 17, the arithmetic control circuit 18 ends the inspection (measurement) as to whether or not there is a defective portion or foreign matter on the surface of the wafer 13.

  By such inspection, the edge 13a of the wafer 13 can be detected with ultra-precision (ultra-high accuracy). In addition to the detection of the edge 13a, the position of the notch 13b provided on the outer periphery of the wafer 13 as shown in FIG.

Further, as described above, in detecting a defective portion or a foreign object using the laser beam 14a, the laser beam 14a having a normal beam diameter is used until the irradiation position of the laser beam 14a on the wafer 13 approaches the outer periphery of the wafer 13. . In addition, when the irradiation position of the laser beam 14a on the wafer 13 approaches the outer periphery of the wafer 13, the beam diameter of the laser beam 14a and the movement amount (scanning pitch) of the irradiation position of the laser beam 14a are switched to a small value. In addition, a detection means (edge detection sensor 17) dedicated to edge detection is provided, and detection signals from the detection means (edge detection sensor 17) are detected from the light receiving sensors 15 and 16 for detecting the scattered light of the defective portion or the foreign matter. The signal is processed separately from the signal. Under these conditions, the throughput (through-put, ie, measurement time) for detecting defective portions and foreign matters can be made appropriate from the center of the wafer 13 to the vicinity of the outer periphery. The coordinate detection accuracy of the edge 13a of the wafer 13 can be improved by narrowing the scan pitch for detecting the foreign matter. Thereby, the coordinate detection accuracy of the edge 13a of the wafer 13 can be improved without causing the sacrifice of excessive throughput.
(Modification)
In the embodiment described above, an example in which the edge 13a of the wafer 13 is directly detected by the edge detection sensor 17 has been described. However, the present invention is not necessarily limited thereto.

  For example, a configuration may be adopted in which a Z sensor (height sensor) 20 for detecting reflected light (scattered light) from the edge 13a as shown in FIG. In this case, when the Z sensor 20 detects the reflected light from the edge 13 a, a detection signal is output from the Z sensor 20 and this detection signal is input to the arithmetic control circuit 18. In addition, the arithmetic control circuit 18 detects the edge 13 a of the wafer 13 based on the detection signal from the Z sensor 20 and the edge detection signal from the edge detection sensor 17.

  As described above, the wafer surface inspection method according to the embodiment of the present invention irradiates the surface of the rotating wafer 13 with the laser beam 14a, receives the scattered light, and removes defects and foreign matter on the surface of the wafer 13. I try to detect it. In addition, in the vicinity of the edge of the wafer, the beam diameter of the laser beam is reduced, the feeding speed of the laser beam is reduced, and the accurate edge position (position of the edge 13a) is detected.

  According to such a method, it is possible to improve the detection accuracy of the position coordinates of the ultra-fine defect portion on the wafer surface and the detection accuracy of the position coordinates of the foreign matter without sacrificing the throughput of the wafer surface inspection. The detection signal of the edge 13a of the wafer 13 is separated from the detection signal of the scattered light from the defective portion or foreign matter and is detected with high precision, so that the detection accuracy of the coordinates of the edge 13a of the wafer 13 can be improved.

  The wafer surface inspection apparatus according to the embodiment of the present invention includes a wafer rotating means (drive motor 9) for rotating the wafer 13, a laser light source 14 for irradiating the surface of the rotating wafer 13 with laser light, Laser light source moving means (base feeding device 4) for changing the irradiation position P of the laser light 14a from the center toward the edge 13a at a predetermined moving speed, and scattered light detection for detecting scattered light reflected from the surface of the wafer 13 Means (light receiving sensors 15 and 16) and edge scattered light detecting means for detecting scattered light reflected from the vicinity of the edge 13a, the beam diameter of the laser light being reduced in the vicinity of the edge, and laser light moving means And a control means for changing the laser light irradiation position and detecting the edge position by the edge scattered light detection means. Wafer surface inspection apparatus according to claim.

  According to such a configuration, it is possible to improve the detection accuracy of the position coordinates of the ultra-fine defect portion on the wafer surface and the detection accuracy of the position coordinates of the foreign matter without sacrificing the throughput of the wafer surface inspection. The detection signal of the edge 13a of the wafer 13 is separated from the detection signal of the scattered light from the defective portion or foreign matter and is detected with high precision, so that the detection accuracy of the coordinates of the edge 13a of the wafer 13 can be improved.

  Further, in the wafer surface inspection apparatus according to the embodiment of the present invention, the edge scattered light detection means (edge detection means 17) is arranged from the horizontal side surface of the wafer 13 below the wafer 13 horizontally.

  According to this configuration, when the laser beam 14 a from the laser light source 14 deviates from the edge of the wafer 13, the edge scattered light detection means (edge detection means 17) can reliably detect the edge of the wafer 13.

  Furthermore, in the wafer surface inspection apparatus according to the embodiment of the present invention, the edge scattered light detecting means (Z sensor 20) is arranged on the substantially optical path of the laser beam 14a irradiated near the edge.

  According to this configuration, the edge of the wafer 13 can be detected from the scattered light from the edge of the wafer 13 by the edge scattered light detection means (Z sensor 20). At this time, the scattered light from the defective part or the foreign matter and the scattered light from the edge of the wafer 13 can be distinguished and detected with good accuracy.

  In the modified example, the edge detection unit 17 and the Z sensor 20 are combined as the edge scattered light detection unit. However, only one of the edge detection unit 17 and the Z sensor 20 is used as the edge scattered light detection unit. But it ’s okay.

(A) is a schematic perspective view of the wafer surface inspection apparatus according to the present invention, and (b) is a side view of the wafer surface inspection apparatus of (a). It is a control circuit diagram of the wafer surface inspection apparatus of FIG. FIG. 2 is an explanatory view of wafer inspection by the wafer surface inspection apparatus of FIG. 1. It is a flowchart explaining the test | inspection by the control circuit of FIG. It is a schematic perspective view which shows the modification of the wafer surface inspection apparatus which concerns on this invention. FIG. 6 is a control circuit diagram of the wafer surface inspection apparatus in FIG. 5.

Explanation of symbols

9 ... Drive motor (wafer rotating means)
13: Wafer 13a: Edge (edge position)
14a: Laser light 14: Laser light source 15, 16: Light receiving sensor (scattered light detecting means)
17 ... Edge detection means (edge scattered light detection means)
20 ... Z sensor (edge scattered light detection means)

Claims (4)

In a wafer surface inspection method for irradiating a surface of a rotating wafer with a laser beam and receiving scattered light with a light receiving means to detect defective portions and foreign matter on the surface of the wafer,
A wafer surface inspection method characterized by detecting a precise edge position by reducing a beam diameter of a laser beam, slowing a feed rate of the laser beam in the vicinity of the edge of the wafer.   Wafer rotating means for rotating the wafer, a laser light source for irradiating the surface of the rotating wafer with laser light, and a laser light source moving means for changing the irradiation position of the laser light at a predetermined moving speed from the center of the wafer toward the edge And scattered light detection means for detecting scattered light reflected from the surface of the wafer, and edge scattered light detection means for detecting scattered light reflected from the vicinity of the edge, and the beam diameter of the laser light in the vicinity of the edge And a control means for detecting the position of the edge by means of the edge scattered light detection means, and reducing the moving speed of the laser light moving means, reducing the scan pitch of the laser light, and detecting the edge position by the edge scattered light detection means . The wafer surface inspection apparatus according to claim 2,
An apparatus for inspecting a wafer surface, characterized in that the edge scattered light detection means is arranged horizontally from the horizontal side surface of the wafer. In the wafer surface inspection apparatus according to any one of claims 2 and 3,
An apparatus for inspecting a wafer surface, characterized in that the edge scattered light detection means is arranged on a substantially optical path of laser light irradiated near the edge.

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