JP7506847B2 - Tilt angle detection device and tilt angle detection method - Google Patents

Description

The present invention relates to a prober that performs electrical testing of multiple chips formed on a semiconductor wafer and a prealignment method for the same.

In recent years, FOWLP (Fan Out Wafer Level Package) has been attracting attention as a new method of manufacturing packages. Unlike the conventional circular silicon wafers described in Patent Documents 1 and 2, this substrate may be manufactured in a square shape.

JP 2016-192484 A JP 2016-157883 A

When attempting to transport the target square substrate, the pre-alignment method used for conventional circular wafers cannot be applied. For example, when transporting a workpiece to an inspection table (chuck) where it is inspected by a prober, an inspection-related device, the orientation of the workpiece must be aligned to a certain extent (pre-alignment). The conventional method of holding the center of the wafer and rotating it to detect the orientation flat or notch with a sensor is not possible due to the square shape. In addition, the substrate does not have any positioning features equivalent to the orientation flat or notch of the wafer.

The present invention was made in consideration of these circumstances, and aims to provide a prober that can prealign square-shaped substrates that cannot be prealigned using conventional methods.

The present invention provides a prober that transports rectangular substrates from a storage section in which the substrates are stored to a pre-alignment section, transports the substrates pre-aligned by the pre-alignment section to an inspection section, and inspects the substrates by the inspection section. The prober is equipped with a length detection sensor that detects the length of the substrate along the transport direction when the substrate is transported from the storage section to the pre-alignment section, and a width detection sensor that continuously detects the width of the substrate along a direction perpendicular to the transport direction when the substrate is transported from the storage section to the pre-alignment section.

The above-mentioned prober preferably includes a calculation unit that calculates the amount of eccentricity of the substrate with respect to a predetermined reference coordinate and the tilt angle of the substrate with respect to the wafer transport direction from the length of the substrate detected by the length detection sensor and the width of the substrate continuously detected by the width detection sensor, and the pre-alignment unit preferably performs pre-alignment of the substrate based on the amount of eccentricity and the tilt angle of the substrate with respect to the predetermined reference coordinate calculated by the calculation unit.

It is also preferable that the length detection sensor be configured with a fiber amplifier.

It is also preferable that the width detection sensor is configured as a distance measurement sensor.

The present invention also provides a pre-alignment method for a prober that transports rectangular substrates from a storage section in which the substrates are stored to a pre-alignment section, transports the substrates pre-aligned by the pre-alignment section to an inspection section, and inspects the substrates by the inspection section, the prober including a length detection sensor that detects the length of the substrate along the transport direction when the substrate is transported from the storage section to the pre-alignment section, and a width detection sensor that continuously detects the width of the substrate along a direction perpendicular to the transport direction when the substrate is transported from the storage section to the pre-alignment section, the prober performing the steps of: calculating the amount of eccentricity of the substrate with respect to a predetermined reference coordinate and the tilt angle of the wafer with respect to the substrate transport direction from the length of the substrate detected by the length detection sensor and the width of the substrate continuously detected by the width detection sensor; and pre-aligning the substrate based on the amount of eccentricity and the tilt angle of the substrate with respect to the predetermined reference coordinate.

According to the present invention, since a square-shaped substrate can be pre-aligned while the transfer arm is moving, there is no time required just for pre-alignment, and the time can be significantly reduced compared to conventional wafer pre-alignment, improving throughput.

FIG. 1 is a top view showing the configuration of a prober 10. A side view of the inspection unit 16 1 is a top perspective view of the substrate chuck 20. A top perspective view of the loader unit 14. 1 is a top perspective view of a substrate cassette 46. FIG. 2 is a perspective view showing the configuration of a pre-alignment sensor unit 60; FIG. 1 is a diagram for explaining the central coordinates of the calibration jig Q. FIG. 2 is a diagram for explaining the amount of eccentricity and the tilt angle of a substrate W. Flowchart showing the flow of pre-alignment processing

Below, a preferred embodiment of the prober according to the present invention will be described in detail with reference to the attached drawings.

Figure 1 is a top view showing the configuration of a prober 10 according to an embodiment of the present invention.

[Configuration of prober 10]
The prober 10 is comprised of a prober body 12 and a loader section 14 adjacent to the prober body 12. The prober body 12 has a substrate chuck 20 having a holding surface 18 on which a substrate W is placed. The substrate W may be quadrilateral in shape, i.e., square or rectangular.

The loader section 14 also has a transport unit 40, a load port 45, a substrate cassette 46, and a pre-alignment sensor unit 60. The transport unit 40 has a transport arm 48 and a sub-chuck 50a on the transport unit 40 side. The loader section 14 has a sub-chuck 50b on a different stage from the sub-chuck 50a on the transport unit 40 side. The sub-chuck 50b is for rotating a substrate W with a large warp.

The substrate cassette 46 is a dedicated cassette that is placed on the load port 45. The substrates W in the substrate cassette 46 are detected by a mapping sensor (not shown). Since it is expected that the substrates W are warped, it is advisable to place the mapping sensor in the center of the front of the load port 45, facing the side of the substrate cassette 46 from which the substrates W are removed, and the opposite side.

Figure 2 is a side view of the inspection unit 16 disposed inside the prober body 12 (see Figure 1). Also, the substrate chuck 20 is shown in vertical section.

The inspection unit 16 includes a substrate chuck 20 having a holding surface (substrate holding surface) 18 on which the substrate W is placed, and a probe 22 that comes into contact with a semiconductor device (not shown) of the substrate W placed on the holding surface 18 of the substrate chuck 20 to inspect the electrical characteristics of the semiconductor device.

[Configuration of the substrate chuck 20]
2, a suction groove 19 is provided on the holding surface 18 of the substrate chuck 20, the suction groove 19 being centered on the central axis of the substrate chuck 20. The suction groove 19 is connected to a vacuum source 23 via a vacuum path 21. By sucking air in the vacuum path 21 with the vacuum source 23, the substrate W placed on the holding surface 18 of the substrate chuck 20 is vacuum-sucked by the suction groove 19 and is suctioned and held on the holding surface 18 of the substrate chuck 20. In addition, an electromagnetic valve 24 that opens the vacuum path 21 to the atmosphere is provided on the vacuum path 21, and the opening and closing of the electromagnetic valve 24 is controlled by a control unit 25.

The substrate chuck 20 has a plurality of through holes 26 that penetrate in the vertical direction, and three straight rod-shaped pins (push-up members) 28A, 28B, and 28C are inserted into each of the through holes 26. The pins 28A, 28B, and 28C are arranged along concentric circles centered on the central axis of the substrate chuck 20. In other words, the pins 28A, 28B, and 28C are provided at positions spaced apart from each other.

The lower ends of the pins 28A, 28B, and 28C are connected to the horizontal surface of a plate 30 that is arranged horizontally below the substrate chuck 20. The right end of the plate 30 is connected to a nut 36 that is screwed onto a screw shaft 34 of a ball screw device (wafer peeling mechanism) 32.

The screw shaft 34 is disposed vertically, and the nut 36 is connected to a linear guide 38 that guides the vertical movement of the nut 36. Furthermore, the left end of the plate 30 is provided with a linear guide 40 that guides the vertical movement of the plate 30.

Therefore, by driving the motor 42 of the ball screw device 32 to rotate the screw shaft 34 forward or backward, the nut 36 can be moved vertically along the screw shaft 34. Therefore, when the nut 36 is moved upward, the three pins 28A, 28B, 28C are simultaneously moved upward via the plate 30, and the upper ends of the pins 28A, 28B, 28C are protruded upward from the holding surface 18 of the substrate chuck 20 as shown by the two-dot chain line. When the upper ends of the protruded pins 28A, 28B, 28C move to the receiving position for the substrate W, the driving of the motor 42 is stopped, and the substrate W transported from the loader unit 14 in FIG. 1 is placed on the upper ends of the pins 28A, 28B, 28C.

Then, the nut 36 is moved downward, and the upper ends of the three pins 28A, 28B, and 28C are simultaneously recessed from the holding surface 18 of the substrate chuck 20 as shown by the solid lines. This places the substrate W on the holding surface 18 of the substrate chuck 20.

The substrate W placed on the holding surface 18 is adsorbed and held on the holding surface 18 as described above, and then the electrical characteristics of the semiconductor device are inspected by the probe 22 and a tester (not shown). The method for inspecting the electrical characteristics is well known, so it will not be described here.

Figure 3 is a top perspective view of the substrate chuck 20. A rectangular suction groove 19 is provided on the holding surface 18 of the substrate chuck 20, centered on the central axis of the wafer chuck 20. A supply port 27 is provided in the suction groove 19. By sucking air from the supply port 27 connected to the vacuum path 21 by the vacuum source 23 in Figure 2, the wafer W placed on the holding surface 18 of the substrate chuck 20 is vacuum-sucked by the suction groove 19, and the substrate W is suction-held on the holding surface 18 of the substrate chuck 20.

As shown in Figures 1, 4 and 5, the loader section 14 is composed of a substrate cassette 46 placed on a load port 45, a transport arm 48, sub-chucks 50a and 50b, a pre-alignment sensor 52, etc.

As shown in FIG. 1, the underside of an uninspected substrate W stored in a substrate cassette 46 is vacuum-adsorbed and held by the transport arm 48 moving linearly in the direction of arrow A. The wafer W is then removed from the substrate cassette 46 by the transport arm 48 moving linearly in the direction of arrow B, and transferred to the sub-chuck 50a. The substrate W is adsorbed and held by the sub-chuck 50a.

A rotating unit that rotates the sub-chuck 50a around a vertical axis is connected to the sub-chuck 50a, and the wafer W adsorbed to the sub-chuck 50a is rotated by this rotating unit. The rotation of the substrate W by the rotating unit rotates the substrate W to a desired angle and positions it at a predetermined position. The above operations complete the pre-alignment before the substrate W is placed on the holding surface 18 of the substrate chuck 20 of the prober body 12.

When pre-alignment is complete, the substrate W is held by suction at its underside by the transport arm 48. The substrate W is then rotated 90 degrees horizontally toward the prober body 12, and then carried into the prober body 12 by the linear movement of the transport arm 48 in the direction of arrow C in FIG. 1, and is delivered to the upper ends of the pins 28A-28C shown by the two-dot chain line in FIG. 2. The transport arm 48 then moves linearly in the direction of arrow D in FIG. 1, and returns to its original initial position. Furthermore, when inspection by the probe 22 in FIG. 2 is completed, the transport arm 48 moves linearly again in the direction of arrow C to the prober body 12 to receive the substrate W for which inspection has been completed.

[Configuration of pre-alignment sensor unit 60]
FIG. 6 is an enlarged perspective view of a main portion of the pre-alignment sensor unit 60, showing its configuration.

The pre-alignment sensor unit 60 has a width/angle detection sensor 61 consisting of two pairs of sensors, a length detection sensor 62 consisting of a pair of sensors, and a drive motor 63.

The width/angle detection sensor 61 may be configured with a known laser distance sensor or the like. The length detection sensor 62 may be configured with a known fiber sensor or the like. These sensors may also be replaced with an imaging device capable of capturing images.

When the transport arm 48 is pulling out the substrate W in the direction of arrow B, the width/angle detection sensor 61 continuously detects the distance between the two line segments corresponding to the two edges of the substrate W along the direction B and both ends of the calibration jig Q (see Figure 8), thereby detecting the tilt angle of the substrate W with respect to the pull-out direction of the transport arm 48 of arrow B (hereinafter simply referred to as the tilt angle). Note that even if the substrate W is trapezoidal, the width of the substrate W can be continuously detected as long as the base of the trapezoid is parallel to the pull-out direction B of the substrate W.

The length detection sensor 62 detects the length of the substrate W along the direction of arrow B when the substrate W is pulled out in the direction of arrow B by the transport arm 48. Specifically, the length can be detected by detecting the time required to pull out the substrate W, i.e., the time from the start to the end of detection of the substrate W, and multiplying this pull-out time by the pull-out speed of the transport arm 48. The length of the substrate W may also be detected by detecting the distance from both ends of the calibration jig Q.

The drive motor 63 drives the width/angle detection sensor 61 and the length detection sensor 62 in the sensor drive direction X, thereby enabling detection of the width, tilt angle, and length of substrates W of various sizes. Note that the length detection sensor 62 may be fixed and not movable.

The control unit 25 is composed of a computer such as a CPU (Central Processing Unit), and controls the drive motor 63 to operate in conjunction with the transfer arm 48 pulling out the substrate W in the direction of arrow B. The control unit 25 also has a built-in or removable memory that manages type data that specifies the vertical and horizontal dimensions of each type of substrate W.

7 and 8 show a pre-alignment calculation method using a width/angle detection sensor 61 and a length detection sensor 62. First, as shown in FIG. 7, the width/angle detection sensor 61 and the length detection sensor 62 scan a square calibration jig Q of a predetermined size with one side parallel to the substrate withdrawal direction B, and detect its width and length. The control unit 25 calculates the center coordinates of the calibration jig Q by dividing the detected width and length by 2. The control unit 25 then sets the center coordinate O of the calibration jig Q as the center of the coordinate axis for the pre-alignment calculation. Note that the center coordinate O of the calibration jig Q is assumed to coincide with the center of rotation of the sub-chuck 50a.

Next, the control unit 25 controls the width/angle detection sensor 61, the length detection sensor 62, and the drive motor 63 to detect the inclination angle and length of the substrate W along the direction of arrow B when the transport arm 48 pulls out the substrate W in the direction of arrow B.

8(a), the control unit 25 determines a linear function y=α1x+β1 indicating the inclination of the center line of the substrate W with respect to the pull-out direction B of the substrate W along the transport direction of the transport arm 48, and a linear function y= ₁ / _α1x + _β2 indicating the inclination of the center line of the substrate W with respect to the direction perpendicular to the pull-out direction B, from the detected width and length of the substrate W and the central coordinate O of the calibration jig Q. These _inclinations and intercepts are determined from six coordinates _a1 ( _Xa1 , _Ya1 ), _b1 ( _Xb1 , _{Yb1 )} , _c1 ( _Xc1 , _Yc1 ), _d1 (Xd1, _Yd1 ), _L1a ( _XL1a , _YL1a ), and _L1b ( _XL1b , _YL1b ).

As shown in part (b) of Figure 8, based on the coefficients of these linear expressions (slope α1 and ₁ /α1, intercepts _β1 and _β2 ), the control unit 25 determines the amount of deviation (eccentricity) X between the center coordinate O of the calibration jig Q and the center of the substrate W in the pull-out direction B, the amount of deviation (eccentricity) Y between the center coordinate O of the calibration jig Q and the center of the substrate W in the direction perpendicular to the pull-out direction B, and the tilt angle θ of the substrate W with respect to the pull-out direction B.

Pre-alignment is completed by moving and rotating the substrate W by an amount that offsets the eccentricity X, Y and tilt angle θ of the substrate W.

Figure 9 is a flowchart showing the flow of the pre-alignment process. This process is controlled by the control unit 25. The program that defines this process is stored in a memory connected to the control unit 25.

In S1, the drive motor 63 moves the width/angle detection sensor 61 and the length detection sensor 62 to positions corresponding to the side edges of the substrate W (see P0-61, P0-62 in FIG. 6) based on the size of the substrate W specified in the product type data. This operation is performed before the transport arm 48 starts to move, so it does not affect throughput. The transport arm 48 then pulls out the substrate W from the substrate cassette 46.

In S2, the width/angle detection sensor 61 and the length detection sensor 62 detect the width and length of the substrate W in conjunction with the substrate W being pulled out by the transport arm 48.

In S3, the eccentricity amount X, Y and tilt angle θ of the substrate W are calculated from the detection results of the width/angle detection sensor 61 and the length detection sensor 62. The transport arm 48 refers to the eccentricity amount X, Y of the substrate W and places the substrate W on the sub-chuck 50a so that the center of the substrate W coincides with the jig center O.

In S4, the sub-chuck 50a rotates the substrate W so as to offset the tilt angle θ of the substrate W.

In S5, the transport arm 48 transports the substrate W to a position where the center of the substrate W coincides with the center of the substrate chuck 20. After this, probing of the substrate W placed on the substrate chuck 20 is performed. After probing, the substrate W is unloaded from the substrate chuck 20 by the transport arm 48 and stored in a cassette.

The above process allows the square-shaped substrate to be pre-aligned as the transport arm 48 moves, eliminating the time required just for pre-alignment, resulting in a significant reduction in time compared to conventional wafer pre-alignment and improving throughput.

In addition, conventional pre-alignment sensors, motors, etc. may also be placed on the prober 10. This makes it possible to transport conventional circular wafers.

10... prober, 20... substrate chuck, 48... transfer arm, 50a... sub-chuck, 61... width and angle detection sensor, 62... length detection sensor

Claims (2)

A tilt angle detection device for detecting a tilt angle of a rectangular substrate transported along a transport direction by a transport unit,
a width/angle detection sensor including a first sensor and a second sensor spaced apart in the vertical direction, the first sensor and the second sensor spaced apart in the vertical direction, the width/angle detection sensor continuously detecting only both edges of the substrate separated in a direction different from the transport direction when the substrate is transported along the transport direction;
a detection unit that detects an inclination angle of the substrate from both edges of the substrate detected by the width/angle detection sensor;
a gap adjustment unit that adjusts a gap between the first sensor and the second sensor in the vertical direction;
A tilt angle detection device comprising: 1. A tilt angle detection method for detecting a tilt angle of a rectangular substrate transported along a transport direction by a transport unit, comprising:
a step of adjusting a vertical distance between the first sensor and the second sensor in a width/angle detection sensor including a first sensor and a second sensor spaced apart from each other in a vertical direction, the first sensor and the second sensor being spaced apart from each other in a vertical direction defined as a direction parallel to the substrate and perpendicular to the transport direction;
a step of continuously detecting only both edges of the substrate separated in a direction different from the transport direction by the width/angle detection sensor when the substrate is transported along the transport direction;
detecting an inclination angle of the substrate from both edges of the substrate detected by the width/angle detection sensor;
The tilt angle detection method includes the steps of:

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