JP4249498B2 - Surface inspection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface inspection apparatus for inspecting foreign matters adhering to a substrate such as a wafer and a scratch on the surface of a substrate in a semiconductor manufacturing process, and more particularly to a surface inspection apparatus having a substrate centering function.
[0002]
[Prior art]
A semiconductor device is manufactured by forming a large number of semiconductor elements on a semiconductor wafer such as silicon. However, due to high-density integration, the processing is further miniaturized, and the diameter of the wafer is increased to improve the yield. Has been promoted.
[0003]
Foreign matter adhering to the wafer with high density integration and miniaturization greatly affects product quality and product yield. For this reason, an inspection process is incorporated in the semiconductor manufacturing process, and the surface of the wafer is inspected by an inspection apparatus to inspect the adhesion state of foreign matters attached to the wafer or the presence or absence of scratches.
[0004]
Wafer surface inspection is performed by rotating the wafer at high speed, irradiating the surface of the wafer with a laser beam and scanning it in the circumferential direction, receiving the laser beam reflected on the wafer surface, and depending on the reflection status, foreign matter adhesion, scratches, etc. Is detected.
[0005]
As described above, while the diameter of a wafer becomes larger and larger, it is required to further reduce the inspection time and improve productivity, and the wafer rotation speed at the time of inspection is also increased. Therefore, during the wafer inspection, a large centrifugal force acts on the held wafer. In addition, the amount of eccentricity between the wafer center and the rotation center of the surface inspection apparatus greatly affects the centrifugal force acting on the wafer.
[0006]
Further, when foreign matter and scratches on the wafer surface are detected, the positions (coordinates) of the foreign matter and scratches are shown with reference to the edge of the wafer. The edge of the wafer is held by the surface inspection device and is detected in a rotated state. However, if the amount of eccentricity of the wafer is large, the edge of the wafer will move greatly due to the rotation, making it difficult to detect the edge accurately. Thus, the accuracy of the reference coordinates is deteriorated. For this reason, the accuracy of the position information of the detected foreign matter and scratch is also lowered.
[0007]
For this reason, when the wafer is held by the surface inspection apparatus, the center of the wafer and the rotation center of the surface inspection apparatus need to be exactly matched.
[0008]
Conventionally, wafer centering has a separate centering device in addition to the surface inspection device, the wafer is centered by the centering device, and then transferred to the surface inspection device by the wafer transfer mechanism. The centering of the wafer by the centering apparatus is reflected when the surface inspection apparatus holds the wafer.
[0009]
As an inspection apparatus for performing wafer orientation adjustment, centering, and the like before inspection, there is one disclosed in Patent Document 1, for example.
[0010]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-118898
[Problems to be solved by the invention]
However, the conventional wafer centering described above has the following problems.
[0012]
Since the centering of the wafer is performed by a separately provided centering device, a centering device is required and there is a possibility that an error may occur during transfer from the centering device to the surface inspection device.
[0013]
In addition, the alignment between the surface inspection apparatus and the centering apparatus must be performed via a wafer transfer mechanism, which causes problems such as troublesome adjustment.
[0014]
In view of such a situation, the present invention makes it possible to center a wafer by the surface inspection apparatus itself, and to perform centering of the wafer quickly and accurately.
[0015]
[Means for Solving the Problems]
The present invention includes a chuck unit including a wafer chuck that holds and rotates a wafer, and a pair of alignment plates that can be moved toward and away from each other about the rotation center of the wafer chuck, and holds the wafer by the alignment plate. The present invention relates to a surface inspection apparatus that performs centering of a wafer chuck and a wafer, and the alignment plate has opposite sides in contact with the wafer, and at least one of the alignment plates has an arc shape in which the opposite side has a curvature equivalent to the outer periphery of the wafer. The alignment plate has opposite sides that contact the wafer, and at least one of the alignment plates is formed by a plurality of straight lines that are circumscribed by the wafer. Engagement and multiple pairs of alignment plates The surface of the alignment plate is provided in a step shape, and the opposite sides of each pair of alignment plates are arc-shaped with different curvatures, and at least one of the alignment plate and the wafer chuck can move up and down. The plate is attached to a rack that is driven symmetrically by a pinion, and the pinion relates to a surface inspection device that is rotated via a torque clutch.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
First, the outline of the surface inspection apparatus will be described with reference to FIGS.
[0018]
The surface inspection apparatus includes a wafer transfer unit 1, a surface inspection unit 2, and a cassette transfer stage 3, and is installed in a clean room (not shown).
[0019]
The surface inspection unit 2 is disposed adjacent to one side surface of the wafer transport unit 1, and the cassette transfer stage 3 is disposed adjacent to the other side surface of the wafer transport unit 1.
[0020]
The surface inspection unit 2 includes an inspection stage 4 on which a wafer 5 is placed, a motor 6 that rotates the inspection stage 4 at a high speed, an alignment device 7 (described later) provided for the cassette transfer stage 3, and an inspection laser beam. A laser light source 8 that emits light, a light projecting unit 9 that irradiates the surface of the wafer 5 with a laser beam, a reflected light of the laser beam from the surface of the wafer 5, and a light reception state that is converted into an electrical signal and input to the computer 11 Unit 12, a light receiving sensor 13 for detecting scattered light reflected on the surface of the wafer 5, a light receiving signal from the light receiving sensor 13 is amplified, and necessary signal processing such as A / D conversion is performed and output to the computer 11. The computer 11 controls the light emission state of the laser light source 8 based on the signal from the light receiving unit 12, and the signal processing unit 14 has a signal processing unit 14. Based on signals from 4 calculates the Suto of particles adhering to the wafer 5.
[0021]
The calculation result in the computer 11, that is, the surface inspection result is output to the printer 15 and the monitor 16. An inspection start command or inspection conditions are input to the computer 11 from the operation unit 17.
[0022]
The computer 11 has a built-in surface inspection program and a sequence program for driving and controlling the transfer robot 18 of the wafer transfer unit 1 to load and unload the wafer 5 to and from the wafer transfer unit 1. A control signal is issued. The surface inspection program includes a program for performing surface inspection of the target wafer and a calibration program. The calibration program can be automatically activated according to predetermined conditions. Conditions include the time when the wafer 5 to be inspected is changed, the elapsed time of surface inspection, the number of inspections, the usage time of the laser light source 8, and the degree of contamination in the apparatus. Further, it can be arbitrarily operated according to the will of the operator.
[0023]
The cassette 19 loaded with the wafer 5 is transferred to and placed on the cassette transfer stage 3.
[0024]
The wafer transfer unit 1 includes a frame 21, a sealed casing (not shown) constituted by a panel (not shown) provided on the frame 21, and a power source (not shown) provided at the lower part of the casing. ), The drive unit 22, the transfer robot 18 erected on the bottom surface of the housing, the clean unit 23 provided on the upper portion of the housing, and the like. A wafer transfer space 24 is formed inside the housing.
[0025]
The clean unit 23 sends purified air downward, and a clean air flow is formed in the wafer transfer space 24 from above to below.
[0026]
The transfer robot 18 is provided with multi-node arms 25, 25. The arm 25 can be bent and stretched, rotated and moved up and down, and can transfer a wafer.
[0027]
Hereinafter, an outline of the operation of the surface inspection apparatus will be described.
[0028]
The cassette 19 containing the wafer 5 to be inspected is transferred to the cassette transfer stage 3.
[0029]
Next, the wafer 5 to be inspected is transferred from the cassette 19 on the cassette transfer stage 3 to the inspection stage 4.
[0030]
The transfer robot 18 unloads the wafer 5 from the cassette 19 and transfers it onto the inspection stage 4 in cooperation with raising / lowering, rotation, and bending. The arm 25 is withdrawn from the surface inspection unit 2. The alignment apparatus 7 centers the wafer 5 on the inspection stage 4.
[0031]
When centering is completed, the wafer 5 is chucked by a wafer chuck (not shown) of the inspection stage 4, the inspection stage 4 is rotated by the motor 6, and surface inspection is started.
[0032]
On the inspection stage 4, the light projection unit 9 irradiates and scans the wafer 5 with a laser beam, and the light receiving sensor 13 detects scattered light. The scattered light is converted into an electric signal by the light receiving sensor 13, subjected to signal processing by the signal processing unit 14, and input to the computer 11. The computer 11 calculates the number of foreign matters, the particle size, and the like based on the signal from the signal processing unit 14. The calculated result is stored in a required storage means (not shown) such as a hard disk and further displayed on the monitor 16.
[0033]
When the surface inspection of the first wafer 5 is completed, the first robot 5 is returned from the inspection stage 4 to the cassette 19 by the transfer robot 18, and the surface inspection of the second wafer 5 is performed. Followed by Thereafter, a predetermined number of the wafers 5 are sequentially inspected.
[0034]
Since the reflectance and reflection state on the surface of the wafer 5 are different depending on the film type formed on the surface of the wafer 5, the sensitivity adjustment of the light receiving unit 12 is performed when the film type of the wafer 5 to be inspected changes. Etc. are calibrated.
[0035]
In the following, the alignment stage 7 for centering the wafer 5 on the inspection stage 4 and the inspection stage 4 will be described with reference to FIGS. 7 shows the main part of the inspection stage 4, and FIG. 8 shows the main part of the alignment device 7.
[0036]
First, the inspection stage 4 will be described.
[0037]
An elevating guide 28 is vertically attached to a base plate 27 fixed to a structural member (not shown) constituting the frame 21 of the surface inspection apparatus, and a slider 29 is slidably provided on the elevating guide 28. A lift block 31 having a concave planar shape is fixed to the slider 29.
[0038]
A lifting platform 32 is fixed to the upper end of the lifting block 31, and a chuck unit 33 is attached to the lower surface of the lifting platform 32. A nut block 34 is attached to the back surface of the elevating block 31, and the nut block 34 is screwed into an elevating screw rod 35. The elevating screw rod 35 is rotatably attached to the base plate 27 via a bearing 36.
[0039]
The chuck unit 33 has a substrate rotation motor (not shown). A rotation shaft 37 of the substrate rotation motor protrudes upward through the lifting platform 32, and a wafer chuck 38 is fitted to the upper end of the rotation shaft 37. I wear it. Suction grooves 39 are formed concentrically on the upper surface of the wafer chuck 38, and the suction grooves 39 are connected to a vacuum exhaust device (not shown).
[0040]
A horizontal shelf 41 is fixed to the lower end of the base plate 27, a motor mounting seat 42 is fixed to the lower surface of the shelf 41, and a lifting motor 43 is mounted on the motor mounting seat 42. The output shaft 45 is connected to the elevating screw rod 35 through a shaft joint 44. Further, a rotation angle detector (not shown) is provided with respect to the output shaft of the elevating motor 43, and the rotation angle detector rotates the elevating motor 43 and the elevating screw rod 35, that is, elevating the chuck unit 33. The amount is to be detected.
[0041]
The alignment device 7 will be described.
[0042]
A pair of horizontal guides 46f and 46r are attached to the shelf plate 41, a horizontal slider 48f is slidably provided on the horizontal guide 46f, and a horizontal slider 48r is slidably provided on the horizontal guide 46r. The slider 48r and the horizontal slider 48f are arranged point-symmetrically. Rack gears 51f and 51r are fixed to the horizontal slider 48f and the horizontal slider 48r in a point-symmetric arrangement, respectively, and a pinion gear 53 is engaged with the rack gears 51f and 51r.
[0043]
A motor support base 54 is attached to the lower surface of the shelf plate 41, an alignment motor 55 is attached to the motor support base 54, and the pinion gear 53 is connected to the output shaft 56 of the alignment motor 55 via a torque clutch 58. It is fitted. The torque clutch 58 rotates idly when a torque exceeding a predetermined value is applied, and a torque exceeding a predetermined value is not transmitted to the pinion gear 53.
[0044]
An angle detector 57 is provided in association with the output shaft 56, and the angle detector 57 detects the rotation amount of the alignment motor 55 and the output shaft 56, that is, the rotation amount of the pinion gear 53. A shield plate 60 is provided on one of the slide seats 59f and 59r, and a position detector 61 is provided on the shelf plate 41. The position detector 61 detects the shield plate 60. .
[0045]
The slide seats 59f and 59r are fixed to the rack gears 51f and 51r, respectively, and support plates 62f and 62r are erected on the slide seats 59f and 59r, respectively. The upper ends of the support plates 62f and 62r are located near the upper surface of the wafer chuck 38, and the alignment plates 64f and 64r, alignment plates 65f and 65r, and alignment plates 66f and 66r are stepped on the upper ends of the support plates 62f and 62r. Is provided. The alignment plates 64f and 64r, the alignment plates 65f and 65r, and the alignment plates 66f and 66r are thicker than the wafer 5 to be inspected.
[0046]
The alignment plate 64f and the alignment plate 64r are symmetrical, the alignment plate 65f and the alignment plate 65r are symmetrical, and the alignment plate 66f and the alignment plate 66r are symmetrical.
[0047]
The alignment plates 64f and 64r, the alignment plates 65f and 65r, and the alignment plates 66f and 66r have arcs on opposite sides, and the alignment plates 64f and 64r, the alignment plates 65f and 65r, and the alignment The radii of the arcs are different from those of the plates 66f and 66r. That is, the arc diameters of the alignment plates 64f and 64r are the largest, the arc diameters of the alignment plates 65f and 65r are intermediate, and the alignment plates 66f and 66r are the smallest. Further, each arc diameter is the same as the diameter of the wafer 5 to be inspected by the surface inspection apparatus. For example, the alignment plates 64f and 64r are for an 8-inch wafer, and the arc diameter is 8 inches. 65f and 65r are for a 7-inch wafer, the arc diameter is 7 inches, and the alignment plates 66f and 66r are for a 6-inch wafer, and the arc diameter is 6 inches. Furthermore, it is preferable that the arc V length has a length sufficient to contact the outer periphery of the wafer beyond the V notch and the orientation flat formed on the wafer.
[0048]
Hereinafter, the operation of the inspection stage 4 and the alignment apparatus 7 will be described.
[0049]
The diameter of the wafer 5 to be inspected is input to the computer 11 from the operation unit 17. The computer 11 drives the lifting motor 43. By driving the lifting motor 43, the lifting screw rod 35 rotates, and the wafer chuck 38 moves up and down via the nut block 34 and the lifting block 31. The amount of vertical movement of the wafer chuck 38 is detected by the amount of rotation of the nut block 34 and is controlled by the computer 11. The upper surface of the wafer chuck 38 corresponds to the level of the alignment plate 64f, 64r, the alignment plate 65f, 65r, the inner wafer diameter of the alignment plates 66f, 66r, for example, the level of the alignment plates 64f, 64r. Further, the pinion gear 53 is rotated by the alignment motor 55, and the alignment plates 64f and 64r are retracted to the maximum position via the slide seats 59f and 59r.
[0050]
The wafer 5 is transferred from the cassette 19 to the wafer chuck 38 by the arm 25. The alignment motor 55 is rotated so that the alignment plates 64 f and 64 r are close to the wafer 5. The alignment plates 64f and 64r move symmetrically about the rotation center of the wafer chuck 38. When the center of the wafer 5 is deviated from the center of the wafer chuck 38, the alignment plates 64f and 64r are displaced. The wafer 5 is moved so as to correct, and the wafer 5 is held in a state where the center of the wafer chuck 38 and the center of the wafer 5 coincide with each other.
[0051]
Further, by making the opposite sides of the alignment plates 64f and 64r have an arc shape having the same curvature as the outer periphery of the wafer 5, the wafer 5 to be measured has notches such as an orientation flat and a V notch. Even in this case, it is possible to accurately contact the circular arc portion on the outer periphery of the wafer, and accurate alignment can be performed.
[0052]
The amount of movement of the alignment plates 64f and 64r is detected by the angle detector 57 and controlled by the computer 11. Further, since the pinion gear 53 is rotated via the torque clutch 58, the holding force of the wafer 5 by the alignment plates 64f and 64r does not exceed a predetermined value, that is, the holding force for damaging the wafer 5. Damage of the wafer 5 due to wafer alignment is prevented.
[0053]
Since the alignment plates 64f and 64r move symmetrically, the alignment of the wafer 5 and the wafer chuck 38 is reliably and quickly performed, and immediately after the alignment or in a state where the alignment is performed. Since the wafer is chucked by the wafer chuck 38, no misalignment occurs between the wafer 5 and the wafer chuck 38.
[0054]
The wafer 5 is sucked by the wafer chuck 38, the alignment motor 55 is driven, the pinion gear 53 is rotated, and the rack gears 51f and 51r, the slide seats 59f and 59r, and the support plates 62f and 62r are passed through. The alignment plates 64f and 64r are separated from the wafer 5.
[0055]
The wafer chuck 38 is rotated by the chuck unit 33, and the wafer 5 is irradiated with a laser beam and scanned to perform surface inspection of the wafer 5.
[0056]
When the surface inspection is completed, the wafer 5 is unloaded by the arm 25, the next wafer 5 is transferred to the wafer chuck 38, and the surface inspection is continuously repeated.
[0057]
When the type of wafer to be inspected is changed, a change in the diameter of the wafer is input to the computer 11 from the operation unit 17. The level of the wafer chuck 38 is changed by the computer 11. Thus, the above-described alignment operation is performed, and surface inspection is performed.
[0058]
The surface of the alignment plate that contacts the wafer may have a shape other than an arc, for example, a V shape. In the case of the V shape, the alignment plates 64, 65, 66 may be of a single type by appropriately selecting the angle and size of the V shape. The centering of the wafer can be performed regardless of the presence of a V notch or the like because the opposite side of the alignment plate only needs to abut three points on the outer periphery of the wafer. In addition, when an arc shape or a V shape is formed on one side of a pair of alignment plates, the one alignment plate has a function of correcting the position of the wafer in two directions, a forward and backward direction and a direction perpendicular to the forward and backward direction. The opposite side of the alignment plate may have a linear shape orthogonal to the advancing / retreating direction. Further, the shape of the opposite side of the alignment plate is not limited to the circular arc shape and the V shape, and may be constituted by three or more straight lines that can circumscribe the outer periphery of the wafer.
[0059]
In addition, by changing the shape of the opposite side of the alignment plate, it is possible to cope with wafers of various sizes, for example, wafers having a diameter of 2 to 8 inches in the inch series, or diameters of 100 to 400 mm in the millimeter series. It is possible to deal with the following wafers.
[0060]
Furthermore, since each alignment plate only needs to move symmetrically, the drive mechanism is not limited to a rack and pinion, and the slide seats may be moved in a symmetrical manner via a timing belt. Further, instead of the wafer chuck 38 moving up and down, the alignment plate may be moved up and down, and each of the wafer chuck 38 and the alignment plate may be moved up and down. Two or more alignment plates can be provided.
[0061]
【The invention's effect】
As described above, according to the present invention, a chuck unit including a wafer chuck capable of holding and rotating a wafer and a pair of alignment plates capable of moving close to and away from each other about the rotation center of the wafer chuck are provided. Since the wafer chuck is held and the wafer chuck and the wafer are centered, high-precision alignment can be performed without causing center misalignment between the centered wafer and the wafer chuck. It is sure to be quick. In addition, the contact portion of the alignment plate with the outer periphery of the wafer has an arc shape having the same curvature as that of the outer periphery of the wafer, so that the shape of the wafer is irregular due to a notch such as an orientation flat or V notch. However, accurate alignment can be performed.
[0062]
Plural pairs of alignment plates are provided stepwise, and the opposite sides of each pair of alignment plates are arc-shaped with different curvatures, and at least one of the alignment plate and the wafer chuck can be moved up and down. Alignment work can be performed.
[0063]
Furthermore, the pair of alignment plates are attached to a rack that is driven symmetrically by a pinion, and the pinion is rotated via a torque clutch, so that an excessive load is not applied to the wafer during alignment, and the wafer is damaged. Demonstrate the excellent effect of preventing.
[Brief description of the drawings]
FIG. 1 is a schematic front view of a surface inspection apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic plan view of the surface inspection apparatus according to the embodiment of the present invention.
FIG. 3 is a schematic configuration diagram of a surface inspection apparatus according to an embodiment of the present invention.
FIG. 4 is a front view showing a main part of the embodiment of the present invention.
FIG. 5 is a plan view showing a main part of the embodiment of the present invention.
FIG. 6 is a front view showing an elevating drive unit of the inspection stage according to the embodiment of the present invention.
FIG. 7 is a plan view showing a main part of the inspection stage according to the embodiment of the present invention.
FIG. 8 is a plan view showing a main part of the alignment apparatus according to the embodiment of the present invention.
[Explanation of symbols]
4 Inspection stage 5 Wafer 7 Alignment device 33 Chuck unit 35 Lifting screw rod 38 Wafer chuck 43 Lifting motor 51 Rack gear 53 Pinion gear 55 Alignment motor 58 Torque clutch 64 Alignment plate 65 Alignment plate 66 Alignment plate

Claims (2)

A chuck unit including a wafer chuck that holds a wafer and is rotatable and can be lifted and lowered, a plurality of alignment plates that can be moved close to and away from each other about the rotation center of the wafer chuck, and the rotation, lifting and lowering of the wafer chuck, and the plurality of pairs A plurality of alignment plates arranged in steps, each pair of alignment plates having opposite sides abutting against the wafer, and wafers of different sizes. The opposite side has an arc shape having a curvature equivalent to the outer periphery of the wafer held by the alignment plate, and the computer raises and lowers the wafer chuck in accordance with the diameter of the held wafer. Corresponds to the size of the wafer holding the level The alignment plate is fit to the level position, the surface inspection apparatus and performs centering of the wafer chuck and the wafer is clamped to the wafer in the alignment plate. The surface inspection apparatus according to claim 1, wherein the plurality of pairs of alignment plates are attached to a rack that is driven symmetrically by a pinion, and the pinion is rotated via a torque clutch.

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