JP7382560B2 - Wafer detection device, wafer detection method, and prober - Google Patents

Description

The present invention relates to a wafer detection device and a wafer detection method for detecting a plurality of wafers housed in a cassette, and a prober equipped with this wafer detection device.

In a semiconductor manufacturing process, when a plurality of chips of a semiconductor device are formed on a wafer, a wafer level test is performed in which a prober is used to electrically test whether each chip operates normally. This prober includes a loader section that supplies and collects wafers to be inspected, and a measurement unit (prober main body) that inspects the wafers supplied from the loader section. The loader section also includes a load port on which a cassette containing a plurality of wafers is placed, and a transport unit (loader transport section) that transports the wafers between the cassette and the measurement unit (see Patent Document 1). ).

A plurality of wafers are housed in the cassette at intervals along the vertical direction. The loader section has a sensing device (wafer detection device) that performs wafer sensing (also called wafer mapping) to detect the presence or absence of wafers at each wafer storage position (for example, slot) in the cassette placed in the load port. is provided.

For example, this sensing device scans a transmission type detection sensor composed of a light emitting part and a light receiving part vertically along the wafer storage position for each wafer in a cassette, thereby detecting the wafers at each wafer storage position. The presence or absence is detected (see Patent Document 2).

Japanese Patent Application Publication No. 2018-067603 Japanese Patent Application Publication No. 2004-153281

By the way, when performing the wafer sensing described in Patent Document 2, in order to improve the reliability of wafer transport by the transport unit, the sensing device not only detects the presence or absence of wafers at each wafer storage position, but also detects the presence or absence of wafers at each wafer storage position. Variations in wafer position and thickness are detected at the same time for each storage position. The sensing device determines that a detection error by the detection sensor has occurred when the variations in the position and thickness of the wafer deviate significantly from expected values.

At this time, the sensing device may erroneously determine that a detection error has occurred even though the variations in the position and thickness of the wafer are actually normal. In this case, it is necessary to restart the prober, resulting in time loss. Furthermore, in a prober in which the measurement unit has multiple measurement sections (measurement stages) and one transport unit transports the wafer to the multiple measurement sections, when the transport unit stops, the multiple measurement sections are affected. This results in a huge time loss.

Therefore, for example, when performing wafer sensing, it is possible to reduce the occurrence of false detection errors by slowing down the scanning speed at which the detection sensor is scanned in the vertical direction, but in this case, the throughput of wafer sensing decreases. A problem arises.

The present invention has been made in view of the above circumstances, and provides a wafer detection device and a wafer detection method that can both accurately determine the occurrence of a detection error and prevent a decrease in throughput, and a wafer detection device that includes the wafer detection device. The purpose is to provide a prober.

A wafer detection device for achieving the object of the present invention detects a wafer in a cassette that accommodates a plurality of wafers at intervals along a first direction, and includes a detection sensor that detects the wafer; A scanning mechanism that scans the detection sensor at a first speed in a first direction along the wafer storage position of each wafer in the cassette, and detects a detection error by the detection sensor based on the detection result of the detection sensor scanning in the first direction. a determination unit that determines whether or not a detection error has occurred, and when the determination unit determines that a detection error has occurred, controls the scanning mechanism to move the detection sensor at a predetermined second speed and when the determination unit determines that a detection error has occurred. and a scan control unit that rescans in the first direction at a second speed at which the probability of erroneously determining whether a detection error has occurred is lower than the first speed.

According to this wafer detection device, since the scanning speed of the detection sensor is changed from the first speed to the second speed only when rescanning the detection sensor, the occurrence of the first detection error can be determined without reducing the throughput of the device. It is possible to accurately determine whether or not this is an erroneous determination.

A wafer detection apparatus according to another aspect of the present invention includes a first wafer detection section that detects the presence or absence of a wafer at each wafer accommodation position based on the detection result of the wafer at each wafer accommodation position by the detection sensor.

In the wafer detection device according to another aspect of the present invention, a second device detects at least one of the wafer position and wafer thickness variation for each wafer accommodation position based on the detection result of the wafer for each wafer accommodation position by the detection sensor. Equipped with a wafer detection section.

In the wafer detection device according to another aspect of the present invention, the detection sensor is provided at a position shifted in a second direction perpendicular to the first direction from the wafer accommodation position for each wafer, and the detection sensor is provided at a position shifted in a second direction perpendicular to the first direction. a light emitting section that emits test light in a third direction perpendicular to both the first direction and the second direction; and a test light that is spaced apart from the light emitting section in the third direction and that is emitted from the light emitting section. and a light receiving section that receives the light, and the inspection light parallel to the third direction passes through the wafer accommodation position for each wafer in response to the scanning of the detection sensor in the first direction by the scanning mechanism. Thereby, wafers can be detected for each wafer accommodation position within the cassette.

In the wafer detection device according to another aspect of the present invention, the determination unit re-determines whether a detection error has occurred based on the detection result of the detection sensor during rescanning in the first direction, and the determination unit re-determines whether or not a detection error has occurred. a repetition control unit that executes repetition control to repeatedly perform re-scanning of the detection sensor by the scan control unit and re-determination by the determination unit when it is determined that a detection error has occurred, the repetition control unit: When the determination section determines that a detection error has not occurred, or when the determination section determines that a detection error has occurred even after repeating the repetitive control a predetermined number of times, the repetitive control is stopped. Thereby, it is possible to determine with high accuracy whether or not the determination by the determination unit as to whether a detection error has occurred for the first time is an erroneous determination.

A prober for achieving the object of the present invention includes: a load port on which a cassette that accommodates a plurality of wafers at intervals along a first direction is placed; a measurement unit that inspects the electrical characteristics of the wafer; A prober comprising a transport unit that transports a wafer between a measurement unit and a cassette, and the above-mentioned wafer detection device.

A wafer detection method for achieving the object of the present invention detects a wafer in a cassette that accommodates a plurality of wafers at intervals along a first direction, and includes a detection sensor for detecting the wafer. A scanning step of scanning in a first direction at a first speed along the wafer storage position of each wafer in the cassette, and based on the detection result of the detection sensor during scanning in the first direction, whether or not a detection error has occurred by the detection sensor. and a probability that the detection sensor is at a predetermined second speed and the determination step incorrectly determines whether or not a detection error has occurred when it is determined in the determination step that a detection error has occurred. a scanning control step of rescanning in the first direction at a second speed lower than the first speed.

The present invention can both accurately determine the occurrence of a detection error and prevent a decrease in throughput.

FIG. 3 is an external perspective view of the prober. FIG. 3 is a schematic diagram of the prober seen from above. It is an external perspective view of a cassette. FIG. 3 is a perspective view of the sensing device moved to an inspection position. It is an explanatory view for explaining scanning of a detection sensor by a scanning mechanism. 6 is a top view of the detection sensor, etc. in FIG. 5. FIG. FIG. 3 is a functional block diagram of an overall control section of the prober. It is a graph showing the relationship between the scanning speed of the three load ports and the average value and standard deviation 3σ of the variation in the thickness of the wafer W under the first installation environment. It is a graph showing the relationship between the scanning speed of the three load ports and the average value and standard deviation 3σ of the variation in the thickness of the wafer W under the second installation environment. 3 is a flowchart showing the flow of cassette wafer sensing processing using a prober.

[Prober configuration]
FIG. 1 is an external perspective view of the prober 10. FIG. 2 is a schematic diagram of the prober 10 viewed from above. In addition, the X-axis direction (corresponding to the third direction of the present invention), the Y-axis direction (corresponding to the second direction of the present invention), and the Z-axis direction (corresponding to the first direction of the present invention) in the figure are are perpendicular to each other. Further, the X-axis direction and the Y-axis direction are parallel to the horizontal direction, and the Z-axis direction is parallel to the vertical direction (perpendicular to the horizontal direction).

As shown in FIGS. 1 and 2, the prober 10 includes a measurement unit 12 that inspects the wafer W, and a loader section 14 that supplies the wafer W to the measurement unit 12 and collects the wafer W from the measurement unit 12. Be prepared. Further, the prober 10 includes a display section 15. The display unit 15 is, for example, a touch panel type monitor on which an operator inputs various operations and displays various information.

The measurement unit 12 includes a plurality of measurement sections 16 arranged along the X-axis direction. Each measuring section 16 inspects the electrical characteristics of the wafer W supplied from the loader section 14 (wafer level inspection). Further, within the measurement unit 12, a general control section 40 (see FIG. 7) is provided, which will be described in detail later.

The loader section 14 includes a plurality of load ports 18 , cassettes 20 (also referred to as pods) placed in each load port 18 , and a transport unit 22 that transports wafers W between each measurement section 16 and each cassette 20 . , has.

FIG. 3 is an external perspective view of the cassette 20. As shown in FIG. 3, the cassette 20 has a plurality of slots (stages may also be used; illustration is omitted) along the Z-axis direction, and each slot allows a plurality of wafers W to be attached to each other along the Z-axis direction. It is a container that is stored at intervals. An opening window 20a is formed on the side surface of the cassette 20 on the measurement unit 12 side for use in taking out and returning the wafer W by the transport unit 22.

Returning to FIGS. 1 and 2, the transport unit 22 includes a transport unit drive mechanism (not shown), is configured to be movable in the X-axis direction and the Z-axis direction, and has a rotation axis parallel to the Z-axis direction. It is configured to be rotatable around the center. Further, the transport unit 22 includes a transport arm configured to be extendable and retractable in the front and back, and holds the wafer W by vacuum suction by the transport arm. Thereby, the wafer W in the cassette 20 is taken out from the cassette 20 by the transport unit 22 and then transported to each measurement section 16 of the measurement unit 12. In addition, the inspected wafer W that has been inspected in each measuring section 16 is returned from each measuring section 16 into the cassette 20 by the transport unit 24 in the reverse path.

Further, within the loader section 14, a sensing device 30 (corresponding to the wafer detection device of the present invention) is provided for each load port 18. Each sensing device 30 performs wafer sensing to detect the presence or absence of a wafer W, its position, variations in thickness, etc. for each wafer accommodation position (slot) in the cassette 20. Each sensing device 30 is provided at a position shifted in the Y-axis direction (towards the measurement unit 12) from the wafer housing position of each wafer W in the cassette 20.

Each sensing device 30 is held movably forward and backward in the Y-axis direction by a device moving mechanism (not shown). Each device moving mechanism moves the sensing device 30 to an inspection position where at least a portion of a detection sensor 32 (see FIG. 4), which will be described later, is inserted into the inside of the cassette 20 when performing wafer sensing. Furthermore, each device moving mechanism retracts the sensing device 30 from the cassette 20 to a retracted position where it does not interfere with the transport of the wafer W by the transport unit 22, except when performing wafer sensing.

In this embodiment, the sensing device 30 is provided for each load port 18, but by making the sensing device 30 movable in the X-axis direction using the device moving mechanism described above, one sensing device 30 can handle each load port 18. Wafer sensing may be enabled for the cassette 20.

FIG. 4 is a perspective view of the sensing device 30 moved to the testing position. As shown in FIG. 4, the sensing device 30 includes a transmission type detection sensor 32 and a scanning mechanism 34.

The detection sensor 32 includes an arm 36, a light emitting section 38A, and a light receiving section 38B. The arm 36 has a shape in which both ends of the arm 36 in the X-axis direction protrude into the cassette 20 in the Y-axis direction. Both ends of the arm 36 in the X-axis direction hold the light emitting section 38A and the light receiving section 38B at intervals in the X-axis direction. Note that the positions of the light emitting section 38A and the light receiving section 38B in the Y-axis direction and the Z-axis direction are aligned. Further, the distance between the light emitting section 38A and the light receiving section 38B in the X-axis direction is not particularly limited as long as at least a portion of the wafer W can fit between the light emitting section 38A and the light receiving section 38B. When the sensing device 30 is moved to the inspection position by the device moving mechanism described above, a part of the wafer W in the cassette 20 is located between the light emitting section 38A and the light receiving section 38B when viewed from the Z-axis direction. .

The light emitting section 38A uses, for example, a known light emitting diode or laser light source, and emits test light L parallel to the X-axis direction toward the light receiving section 38B. The light receiving section 38B uses, for example, a known photoelectric sensor or the like, receives the test light L emitted from the light emitting section 38A, and outputs a detection signal (electrical signal).

FIG. 5 is an explanatory diagram for explaining the scanning of the detection sensor 32 by the scanning mechanism 34. As shown in FIG. 5 and FIG. 4 described above, the scanning mechanism 34 uses various linear motion mechanisms such as a ball screw mechanism, a linear motor mechanism, and a slide mechanism. The scanning mechanism 34 holds the detection sensor 32 movably in the Z-axis direction, and scans the detection sensor 32 in the Z-axis direction at a standard speed described below during wafer sensing. Thereby, the detection sensor 32 is scanned at the standard speed in the Z-axis direction along the wafer storage position of each wafer W in the cassette 20. As a result, the inspection light L parallel to the X-axis direction passes through each wafer accommodation position (each wafer W) in the cassette 20 while moving in the Z-axis direction.

FIG. 6 is a top view of the detection sensor 32, etc. in FIG. 5. As shown in FIG. 6, when the scanning mechanism 34 starts scanning the detection sensor 32 in the Z-axis direction, the detection sensor 32 moves from either the upper or lower direction of the Z-axis toward the other. During this movement, if none of the wafers W in the cassette 20 are present between the light emitting section 38A and the light receiving section 38B, as shown by reference numeral 6A in FIG. 6, the light receiving section 38B emits light. It receives the inspection light L emitted from the section 38A and outputs a detection signal.

On the other hand, during the above-mentioned movement, if any of the wafers W in the cassette 20 is present between the light emitting section 38A and the light receiving section 38B, as shown by reference numeral 6B in FIG. The emitted inspection light L is blocked by the wafer W. As a result, the light receiving section 38B does not receive the test light L and therefore does not output a detection signal of the test light L.

Therefore, depending on whether the light receiving section 38B is outputting a detection signal of the inspection light L, it can be determined whether the wafer W is present between the light emitting section 38A and the light receiving section 38B. Therefore, based on the detection signal output from the detection sensor 32 while the scanning mechanism 34 scans the detection sensor 32 in the Z-axis direction, the presence or absence of the wafer W at each wafer storage position in the cassette 20 is determined, as will be described in detail later. It is possible to detect variations in the position (position in the Z-axis direction) and thickness of each wafer W housed in the cassette 20.

FIG. 7 is a functional block diagram of the overall control section 40 of the prober 10. In addition, in FIG. 7, in order to prevent the drawing from becoming complicated, only the functions related to wafer sensing among the various functions of the overall control unit 40 are illustrated.

As shown in FIG. 7, the overall control unit 40 controls the operation of each part of the prober 10 based on input operations on the touch panel display unit 15. This overall control unit 40 functions as a wafer detection device of the present invention together with the sensing device 30 described above.

The overall control unit 40 is an arithmetic device such as a personal computer, and includes an arithmetic circuit including various processors, memories, and the like. Various processors include CPU (Central Processing Unit), GPU (Graphics Processing Unit), ASIC (Application Specific Integrated Circuit), and programmable logic devices [for example, SPLD (Simple Programmable Logic Devices), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Arrays)]. Note that the various functions of the overall control unit 40 may be realized by one processor, or may be realized by a plurality of processors of the same type or different types.

A storage unit 42 is connected to the overall control unit 40 in addition to the display unit 15, the detection sensor 32, the scanning mechanism 34, etc. described above.

The storage unit 42 stores standard speed information 44 and optimal speed information 46 in addition to the control program executed by the overall control unit 40. The standard speed information 44, which will be described in detail later, is information indicating the scanning speed of the detection sensor 32 in the Z-axis direction when performing the first (first) wafer sensing on a new cassette 20. Further, the optimum speed information 46, which will be described in detail later, is information indicating the scanning speed of the detection sensor 32 in the Z-axis direction at the time of retrying wafer sensing (when the detection sensor 32 rescans).

The overall control unit 40 operates as a wafer detection unit 50, a determination unit 52, a scan control unit 54, a repetition control unit 56, and a display control unit 58 by executing a control program (not shown) in the storage unit 42 during wafer sensing. Function.

The wafer detection section 50 corresponds to a first wafer detection section and a second wafer detection section of the present invention. The wafer detection unit 50 detects each wafer storage position in the cassette 20 based on a detection signal of the inspection light L input from the detection sensor 32 while the detection sensor 32 is scanning in the Z-axis direction (including during rescanning described later). The presence or absence of the wafers W, and the position (Z-axis direction position) and thickness variation of each wafer W housed in the cassette 20 are detected.

Specifically, the wafer detection unit 50 determines whether the detection signal of the inspection light L from the detection sensor 32 is turned on or off, the position of the detection sensor 32 in the Z-axis direction, the position of each known slot in the cassette 20, Based on this, the presence or absence of a wafer W is detected for each wafer storage position in the cassette 20. Further, the wafer detection unit 50 detects the position (Z axial position) and thickness in the Z-axis direction. Further, the wafer detection unit 50 detects variations in the thickness of each wafer W in the cassette 20 based on the above-described thickness detection result for each wafer W. Note that the thickness variation referred to here is, for example, the difference between the maximum value and the minimum value of the thickness.

The determination unit 52 determines whether a detection error has occurred by the detection sensor 32 during wafer sensing, based on the detection result (detection signal) of the detection sensor 32 during scanning in the Z-axis direction (including during rescanning).

For example, similar to the wafer detection unit 50 described above, the determination unit 52 detects the position of each wafer W and variations in the thickness of each wafer W based on the detection signal of the detection sensor 32 during scanning, and generates a “position detection result”. When both the "thickness variation detection result" and the "thickness variation detection result" deviate from a predetermined expected value (assumed range), it is determined that a detection error of the detection sensor 32 has occurred. Conversely, the determination unit 52 determines that a detection error of the detection sensor 32 has not occurred when at least one of the position detection result and the thickness variation detection result is within the expected value. Note that if both the position detection result and the thickness variation detection result are within expected values, it is determined that a detection error of the detection sensor 32 has not occurred, and in other cases, it is determined that a detection error of the detection sensor 32 has occurred. You may.

Further, instead of the determination unit 52 detecting the position of each wafer W and the variation in the thickness of each wafer, the determination unit 52 may acquire these detection results from the wafer detection unit 50.

The scan control unit 54 controls scanning of the detection sensor 32 in the Z-axis direction by the scanning mechanism 34 . When performing wafer sensing for the cassette 20 for the first time, the scanning control section 54 drives the scanning mechanism 34 to scan the detection sensor 32 in the Z-axis direction at a standard speed based on the standard speed information 44 in the storage section 42. Further, the scan control unit 54 drives the scanning mechanism 34 based on the optimum speed information 46 in the storage unit 42 when the determination unit 52 determines that a detection error of the detection sensor 32 has occurred after the first wafer sensing is performed. Then, the detection sensor 32 is caused to scan again in the Z-axis direction at the optimum speed. As a result, wafer sensing for the cassette 20 is retried.

The standard speed corresponds to the first speed of the present invention. This standard speed is, for example, a scanning speed determined by the manufacturer of the prober 10, and is registered in the standard speed information 44 in the storage unit 42 by the manufacturer. Note that the user of the prober 10 may be able to register the standard speed in the standard speed information 44 and change the standard speed registered in the standard speed information 44.

The optimum speed corresponds to the second speed of the present invention. This optimum speed is a scanning speed determined by the user of the prober 10, and is registered in the optimum speed information 46 in the storage unit 42 by the user. Note that the optimal speed registered in the optimal speed information 46 can be changed by the user.

The optimum speed is defined as the probability that the determination unit 52 will erroneously determine whether a detection error has occurred (hereinafter simply referred to as the erroneous determination probability of a detection error) under the installation environment of the load port 18 (cassette 20) than the above-mentioned standard speed. The scanning speed also decreases. The misjudgment here means, for example, even if the position of each wafer W and the variation in the thickness of each wafer are actually within the range of expected values, the judgment unit 52 makes a judgment based on the detection signal of the detection sensor 32. The result is that "a detection error has occurred."

The optimum speed is determined by differences in the installation environment of the load port 18 (for example, the type of floor, vibration of the clean room air conditioner, etc.) and variations in the performance of the scanning mechanism 34 (if the scanning mechanism 34 is provided for each load port 18). (if applicable) and other factors.

FIG. 8 shows the scanning speed of the three load ports 18 [LP1 (symbol 8A), LP2 (symbol 8B), and LP3 (symbol 8C)] in FIG. 2 under the first installation environment and the variation in the thickness of the wafer W. It is a graph showing the relationship between the average value and standard deviation 3σ (indicated simply as "3σ" in the figure). FIG. 9 shows the scanning speed of the three load ports 18 [LP1 (symbol 9A), LP2 (symbol 9B), and LP3 (symbol 9C)] under a second installation environment different from the first installation environment and the wafer W. This is a graph simply showing the relationship between "3σ" and the display in the 3σ diagram of the average value and standard deviation of thickness variations. Note that the symbol STD in FIGS. 8 and 9 indicates the standard speed described above.

As shown in FIG. 8, under the first installation environment, the lower the scanning speed, the smaller the average value and standard deviation 3σ of the thickness variation of the wafer W. Here, the larger the bar (average value and standard deviation 3σ) in each graph, the larger the variation in the thickness of the wafer W, that is, the higher the probability of misjudgment of detection error. Conversely, the smaller the bar (average value and standard deviation 3σ) in each graph, the smaller the variation in the thickness of the wafer W, that is, the lower the probability of misjudgment due to detection error. Therefore, under the first installation environment, by minimizing the scanning speed, the probability of misjudgment due to a detection error is minimized.

On the other hand, as shown in FIG. 9, under the second installation environment, the average value and standard deviation 3σ of the variation in the thickness of the wafer W do not necessarily become the minimum at the minimum scanning speed, that is, a false determination of a detection error occurs. probability is not minimized.

In this way, the optimum speed differs depending on the installation environment of the load port 18 (cassette 20). Therefore, for each installation environment of the load port 18 (cassette 20), the user can determine the scanning speed and the index value (in this embodiment, the average value and standard The correspondence relationship with the deviation 3σ) is determined in advance through experiments or simulations, and the optimum speed is determined based on the results. The user then registers the determined optimal speed in the optimal speed information 46 in the storage section 42 by operating the touch panel display section 15.

The scanning mechanism 34 causes the detection sensor 32 to rescan in the Z-axis direction at the optimum speed and retry wafer sensing in response to the judgment by the judgment unit 52 as to whether a detection error has occurred, thereby performing the initial wafer sensing at the standard speed. In comparison, the probability of misjudgment due to detection error is reduced. Therefore, even if the determination unit 52 incorrectly determines whether a detection error has occurred during the first wafer sensing, the determination unit 52 will make a correct determination (whether or not a detection error has occurred) by retrying the subsequent wafer sensing at the optimal speed. (judgment)) becomes more likely. In other words, the probability of misjudgment due to detection error can be reduced.

When the scanning mechanism 34 executes rescanning in the Z-axis direction (wafer sensing retry) of the detection sensor 32 at the optimum speed, the determination unit 52 determines whether the detection sensor 32 is rescanning the detection sensor 32 during rescanning based on the detection result of the detection sensor 32 during the rescanning. Re-determine whether a detection error has occurred. Thereby, it is possible to determine with high precision whether or not the determination of the occurrence of a detection error by the determination unit 52 during the first wafer sensing is an erroneous determination.

The repetition control unit 56 controls the scan control unit 54 and the determination unit 52 to cause the scanning mechanism 34 to rescan the detection sensor 32 at the optimum speed (retry wafer sensing) and to prevent the determination unit 52 from causing a detection error. Iterative control is performed to repeatedly perform the determination of presence or absence. This repetitive control is executed when the determination unit 52 determines that a detection error has occurred in the first re-determination, and when the designated number of retries for wafer sensing is set to two or more. Note that the above-described designated number of times is set by the user operating the touch panel display unit 15.

The repetitive control by the repetitive control unit 56 is performed when the determining unit 52 determines through re-judgment that no detection error has occurred, or even if the repetitive control is repeated a predetermined number of times, the determining unit 52 performs a re-judgment to detect the detection error. The process ends when it is determined that an error has occurred. By repeatedly performing control in this manner, it is possible to more accurately determine whether or not the determination of the occurrence of a detection error by the determination unit 52 during the first wafer sensing is an erroneous determination.

The display control unit 58 controls the display on the display unit 15. This display control unit 58 continues to perform detection even in the final re-judgment (hereinafter referred to as final re-judgment) of the determination unit 52, which is performed after the wafer sensing retry has been executed a specified number of times (one or more times). When it is determined that an error has occurred, an error display is displayed on the display unit 15. This allows the user to be notified of the occurrence of an abnormality.

Note that the overall control unit 40 stops the operation of at least the loader unit 14 of the prober 10 when the final re-judgment of the determination unit 52 determines that a detection error has occurred.

[Prober action]
FIG. 10 is a flowchart showing the flow of wafer sensing processing of the cassette 20 (corresponding to the wafer detection method of the present invention) using the prober 10 having the above configuration.

As shown in FIG. 10, when a new cassette 20 is placed on the load port 18, the overall control unit 40 starts wafer sensing processing for this cassette 20. First, the scan control unit 54 drives the scanning mechanism 34 to scan the detection sensor 32 in the Z-axis direction at a standard speed based on the standard speed information 44 in the storage unit 42 (step S10, the scanning step of the present invention). equivalent). As a result, a detection signal of the inspection light L is sequentially output from the detection sensor 32 scanning in the Z-axis direction to the integrated control unit 40.

Then, the wafer detection unit 50 detects the presence or absence of a wafer W at each wafer storage position in the cassette 20 and the storage position in the cassette 20 based on the detection signal of the inspection light L sequentially inputted from the detection sensor 32 during the above-described scanning. The position and thickness variations of each wafer W are detected. This completes the first wafer sensing for the cassette 20, that is, the wafer sensing at the standard speed.

Furthermore, the determination unit 52 detects variations in the position and thickness of each wafer W based on the detection signals of the inspection light L that are sequentially input from the detection sensor 32 during the above-described scanning, and detects variations in the position and thickness of each wafer W based on the detection results of the detection sensor 32. It is determined whether a detection error has occurred (step S12, corresponding to the determination step of the present invention). If the determination unit 52 determines that no detection error has occurred, the overall control unit 40 ends the wafer sensing and starts the next process (NO in step S12).

On the other hand, when the determination unit 52 determines that a detection error has occurred, the scan control unit 54 starts retrying wafer sensing for the cassette 20 (YES in step S12).

Specifically, the scan control unit 54 drives the scanning mechanism 34 to rescan the detection sensor 32 in the Z-axis direction at the optimum speed based on the optimum speed information 46 in the storage unit 42 (steps S14, S16, main (equivalent to the scan control step of the invention). As a result, the probability of misjudgment due to a detection error is reduced compared to the initial wafer sensing at the standard speed. At this time, if the optimum speed is slower than the above-mentioned standard speed, it takes time to rescan the detection sensor 32, but this rescanning is performed only when retrying wafer sensing. Therefore, even if the wafer sensing is retried, it only takes an extra few seconds, and the effect on the overall operating time of the prober 10 is negligible. Further, since unnecessary restart of the prober 10 based on a false determination of a detection error can be prevented, throughput can be improved.

When rescanning of the detection sensor 32 is executed, based on the detection results of the detection sensor 32 during this rescanning, the wafer detection unit 50 performs various detections described above, and the determination unit 52 re-determines whether a detection error has occurred. (Step S18) is executed. Thereby, it is possible to accurately determine whether or not the first (step S12) determination of the occurrence of a detection error by the determination unit 52 is an erroneous determination. Note that when the determination unit 52 determines whether or not a detection error has occurred in the re-judgment, that is, when the previous determination of the occurrence of a detection error was an erroneous determination, the overall control unit 40 ends the wafer sensing and starts the next process. (NO in step S18).

On the other hand, if the determination unit 52 determines in the re-determination whether a detection error has occurred (YES in step S18) and the designated number of retries for wafer sensing is set to one (NO in step S20), The process advances to step S24, which will be described later.

Further, if the determination unit 52 determines through re-judgment whether a detection error has occurred (YES in step S18), and the specified number of retries for wafer sensing is set to two or more (YES in step S20). , the repetition control unit 56 operates. Then, the repetition control unit 56 controls the scan control unit 54 and the determination unit 52 to perform repetition control to repeatedly perform re-scanning of the detection sensor 32 (wafer sensing retry) and re-determination by the determination unit 52. (Step S16 to Step S22). Thereby, it is possible to determine with high precision whether or not the determination by the determination unit 52 that the first detection error has occurred is an erroneous determination.

This repetitive control ends when the determination unit 52 determines in the re-determination that a detection error has not occurred (NO in step S18), or when the determination unit 52 determines in the final re-determination that a detection error has occurred ( (YES in step S22). If the determination unit 52 determines that no detection error has occurred in the re-determination during the repeated control (NO in step S18), the overall control unit 40 ends the wafer sensing and starts the next process.

On the other hand, if the determination unit 52 determines that a detection error has occurred in the final re-determination (NO in step S20 or YES in step S22), the display control unit 58 causes the display unit 15 to display an error display (step S24). Further, at the same time as or before or after this error display, the overall control section 40 stops at least the loader section 14 of the prober 10.

[Effects of this embodiment]
As described above, in this embodiment, when a detection error occurs during the first wafer sensing in which the detection sensor 32 is scanned at the standard speed, a retry of wafer sensing is performed in which the detection sensor 32 is rescanned at the optimum speed. By doing so, it is possible to accurately determine whether or not the determination of the occurrence of the first detection error is an erroneous determination. Therefore, it is possible to accurately determine whether a detection error has occurred. Furthermore, if the optimal speed is slower than the standard speed, if the detection sensor 32 is scanned at the optimal speed during normal operation of the prober 10 (for example, during initial wafer sensing), the throughput of the prober 10 will decrease. In this embodiment, the detection sensor 32 is rescanned at the optimum speed only when retrying wafer sensing, so the above-described drop in throughput is prevented. As a result, in this embodiment, it is possible to both accurately determine the occurrence of a detection error and prevent a decrease in throughput.

Furthermore, in this embodiment, since it is possible to accurately determine whether a detection error has occurred, restarting the prober 10 based on an erroneous determination and the time loss associated with this can be prevented. In particular, in the prober 10 of this embodiment in which the wafer W is transported to a plurality of measurement units 16 by one transport unit 22, the transport unit 22 may stop due to an erroneous determination, and due to this stop, the wafer W may be transferred to a plurality of measurement units 16. This prevents the influence from occurring and causing a very large time loss.

[others]
The determination unit 52 of the above embodiment determines whether a detection error has occurred based on the position of each wafer W and the variation in the thickness of each wafer W. For example, the magnitude of the detection signal output from the detection sensor 32 It may be determined whether a detection error has occurred based on whether or not the value is within an expected value (an expected range). Further, the determination unit 52 may determine whether a detection error has occurred based on the position of each wafer W, the variation in thickness of each wafer W, and the magnitude of the detection signal.

In the embodiment described above, wafer sensing is performed using the transmission type detection sensor 32 including the light emitting section 38A and the light receiving section 38B. The type of sensor is not particularly limited as long as it can detect variations in the position and thickness of W, etc.). For example, a camera having an image sensor may be used as the detection sensor 32, and the presence or absence of the wafer W may be detected by analyzing images (including moving images) taken by the camera during scanning and rescanning.

In the embodiment described above, when performing repetitive control by the repetition control unit 56, the detection sensor 32 is repeatedly rescanned at the same optimal speed, but the optimal speed may be changed each time the rescanning is performed. For example, in a case where the lower the optimal speed is, the lower the probability of a false determination of a detection error is, the optimal speed may be lowered stepwise each time re-scanning is repeated. Thereby, the time required for retrying wafer sensing can be shortened.

In the above embodiment, the standard speed information 44 and the optimal speed information 46 are stored in the storage unit 42, but the standard speed information 44 and the optimal speed information 46 may also be stored in a server on the Internet or the like. In this case, the scan control unit 54 accesses a server on the Internet and refers to the standard speed information 44 and the optimal speed information 46, respectively.

The wafer detection unit 50 of the above embodiment detects the presence or absence of a wafer W at each wafer storage position in the cassette 20 and the variations in the position and thickness of each wafer W stored in the cassette 20. , only one of the variations in position and thickness of each wafer W may be detected. Further, the wafer detection unit 50 may detect only the presence or absence of the wafer W.

In the above embodiment, the Z-axis direction is parallel to the vertical direction, but the Z-axis direction may be non-parallel to the vertical direction.

In the above embodiment, the wafer sensing for the cassette 20 set in the prober 10 has been described. The present invention is also applicable to wafer sensing for the cassette 20.

10...Prober,
14...Loader section,
18...load port,
20...cassette,
30...sensing device,
32...detection sensor,
34...scanning mechanism,
38A...light emitting part,
38B...light receiving section,
40... General control unit,
42...Storage unit,
44...Standard speed information,
46...Optimum speed information,
50...wafer detection unit,
52...determination section,
54...scan control section,
56...Repetition control section,
58...Display control section

Claims (4)

A wafer detection device that detects a wafer in a cassette that accommodates a plurality of wafers at intervals along a first direction,
a detection sensor that detects the wafer;
a scanning mechanism that scans the detection sensor in the first direction at a first speed along a wafer accommodation position for each of the wafers in the cassette;
a determination unit that determines whether a detection error has occurred by the detection sensor based on a detection result of the detection sensor scanning in the first direction;
scanning control for controlling the scanning mechanism to rescan the detection sensor in the first direction at a second speed changed from the first speed when the determination unit determines that the detection error has occurred; Department and
A wafer detection device comprising: The determination unit re-determines whether or not the detection error has occurred based on the detection result of the detection sensor during re-scanning in the first direction;
When it is determined in the re-judgment by the determination unit that the detection error has occurred, repeat control is executed to repeatedly perform re-scanning of the detection sensor by the scan control unit and re-determination by the determination unit. Equipped with a repeat control section,
If the repetition control unit determines that the detection error has not occurred, or if the determination unit determines that the detection error has occurred even after repeating the repetition control a predetermined number of times. 2. The wafer detection apparatus according to claim 1, wherein the repetitive control is stopped at . a load port on which a cassette accommodating a plurality of wafers at intervals along the first direction is placed;
a measurement unit that inspects the electrical characteristics of the wafer;
a transport unit that transports the wafer between the measurement unit and the cassette;
The wafer detection device according to claim 1 or 2,
A prober equipped with. A wafer detection method for detecting a wafer in a cassette that accommodates a plurality of wafers at intervals along a first direction,
a scanning step of scanning a detection sensor that detects the wafer in the first direction at a first speed along a wafer accommodation position for each of the wafers in the cassette;
a determination step of determining whether a detection error has occurred by the detection sensor based on a detection result of the detection sensor scanning in the first direction;
a scanning control step of rescanning the detection sensor in the first direction at a second speed changed from the first speed when it is determined in the determination step that the detection error has occurred;
A wafer detection method having.

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