Sensor station and method for measuring wafers

Abstract

Sensor station for measuring wafers (1), comprising at least one sensor device (2) for measuring at least one property of a wafer (1) and at least one section of a conveying device (3), wherein the conveying device (3) defines a conveying direction, wherein the moving wafers (1) along the conveying device define a space (4) to be kept clear for the moving wafers (1), wherein the sensor device (2) generates at least one measuring point on a bottom and / or on a top of the space to be kept clear (4), wherein the sensor device (2) is supported by a main support (13), wherein the sensor station has a calibration device (5), wherein the calibration device (5) comprises at least one arm (6) and a drive system (7) for moving the arm (6), wherein a reference piece (8) is arranged on the arm (6), wherein the arm (6) is movably mounted so that the reference piece (8) can assume a rest position and a measuring position, wherein the reference piece (8) is arranged outside and within a range of the sensor device (2) in the rest position and in the measuring position characterized by the fact that the conveying device (3) comprises at least one section of an endless conveyor, wherein the reference piece (8) is located at least partially within the space to be kept clear (4) in the measuring position.

Description

[0001] The invention relates to a sensor station and a method for measuring wafers, comprising at least one sensor device for measuring at least one property of a wafer and at least one section of a conveying device, wherein the conveying device defines a conveying direction, wherein the moving wafers along the conveying device determine a space to be kept clear for the moving wafers, and wherein the sensor device generates at least one measuring point on a bottom side and / or on a top side of the space to be kept clear.

[0002] Such a sensor station for measuring wafers is known from US 8,825,444 B1. The sensor station comprises a sensor device for measuring at least one property of a wafer, which is located on a movable platform so that the wafers can be moved under the sample beam. Furthermore, the sensor station includes a calibration device with at least one arm and a drive system for moving the arm. A reference piece is arranged on the arm, which can assume a rest position and a measuring position.

[0003] Another sensor station is known from WO 2015 / 199930 A1. This known sensor station comprises three sensor devices, each containing a near-infrared superluminescent diode, for three-lane thickness measurement of wafers. The wafers are moved along a conveyor system in the form of an endless belt with two individual belts, thus defining a space to be kept clear. The sensor devices are, for example, arranged above the space to be kept clear and each generates a measuring point on the upper side of the space.

[0004] Another such sensor station is known from KR 10 2016 0021979 A. A conveyor in the form of an endless belt with two individual belts conveys wafers through this sensor station, the moving wafers defining a space to be kept clear. The sensor station comprises three sensor devices, each with a pair of sensors. The sensors are designed as capacitive thickness sensors. A first sensor of each sensor device is arranged above, and a second sensor below, the space to be kept clear. The first and second sensors of each sensor device generate three measuring points on the top and bottom surfaces of the space to be kept clear.

[0005] It has been found that the thickness measurements of such sensor stations generally do not correspond to the specified measurement accuracies of the sensors, so that the measurement accuracy of the sensor stations is relatively poor compared to the measurement accuracies of the sensor types used. The object of the present invention is therefore to further improve the measurement accuracy of the sensor stations, preferably without having to resort to, for example, more expensive or slower sensors. Preferably, it is an object of the present invention to improve the measurement accuracy of the sensor stations such that a simple standard deviation of at most 0.3 µm is achieved between two calibration processes, or preferably at a throughput of at least 6000 wafers per hour.

[0006] To solve the aforementioned problem, the invention teaches a sensor station for measuring wafers, comprising at least one sensor device for measuring at least one property, in particular a thickness, of a wafer, and at least one section of a conveying device, wherein the conveying device defines a conveying direction, wherein the moving wafers along the conveying device define a space to be kept clear for the moving wafers, wherein the sensor device generates at least one measuring point on a bottom and / or on a top of the space to be kept clear, wherein the sensor device is supported by a main support. wherein the sensor station has a calibration device, wherein the calibration device comprises at least one arm and a drive system for moving the arm, wherein a reference piece - preferably with a known property, in particular a thickness - is arranged on the arm, wherein the arm is movably mounted so that the reference piece can assume a rest position and a measuring position, wherein the reference piece is arranged outside in the rest position and within a range of the sensor device in the measuring position, characterized by the fact that the conveying device comprises at least one section of an endless conveyor, wherein the reference piece in the measuring position is located at least partially within the space to be kept clear.

[0007] The invention is based on the understanding that the sensors in the sensor station are subject to a largely unpredictable drift, which can significantly distort measurement results. The calibration device allows calibration measurements to be performed at regular intervals on the reference piece within the sensor station. The values ​​measured on the wafers can thus be corrected accordingly, so that sensor drift no longer has a significant influence on the measurements. As a result, the aforementioned problem is solved.

[0008] The term "arranged within range of the sensor device" means, in particular, that the reference piece can be measured by the sensor device without the need to remove, modify, or, preferably, readjust the sensor device or, even more preferably, mechanically manipulate / switch it. The term "at least one property of a wafer" includes, for example, a saw-cut profile of a wafer surface and / or a wafer deflection and / or—particularly preferably—a wafer thickness.

[0009] Preferably, the reference piece is arranged at one end of the arm. Preferably, the known thickness of the reference piece is less than 1.0 mm, more preferably less than 0.5 mm, and even more preferably less than 0.3 mm. Advantageously, the known thickness of the reference piece is greater than 0.1 mm, more preferably greater than 0.12 mm, and particularly preferably greater than 0.14 mm or 0.16 mm. Ideally, the known thickness of the reference piece is 0.2 mm. The reference piece may, for example, be made of or comprise metal, preferably steel. Typically, wafers have square or quasi-square (square with chamfered corners) dimensions with an edge length or length of 125 mm, 156 mm, or 163 mm, and a wafer thickness of typically 0.15 mm to 0.18 mm.These wafers define a space to be kept clear, which corresponds, for example, to a strip the length of the sensor station with a thickness of 0.18 mm and a width of 156 mm.

[0010] Advantageously, the reference piece is positioned completely outside the space to be kept clear in its rest position. The phrase "measuring position at least partially within the space to be kept clear" means, in particular, that the reference piece or other objects located partially within the space to be kept clear would collide with the conveyed wafers during operation of the sensor station. If, however, the reference piece is located completely outside the space to be kept clear, a collision between the wafers and the reference piece is impossible. Advantageously, the rest position of the reference piece is located downstream of the measuring point in a top view. It is preferred that the reference piece be positioned above the space to be kept clear in its rest position, which is particularly advantageous in the case of a solid design of the main support, for example, made of mineral material / rock / granite.According to another preferred embodiment, the main support comprises aluminium, wherein the rest position of the reference piece can be located above or below the space to be kept clear.

[0011] It is particularly within the scope of the invention if the calibration device comprises at least one linear guide, wherein the linear guide preferably defines a linear movement section of the arm between the measuring position and the rest position. This has the advantage that, due to the confined space in the area of ​​the sensor device, the reference piece can reach the measuring point more easily compared to, for example, a rotary movement. Preferably, the linear movement section is the only linear movement section or, indeed, the only movement section between the rest position and the measuring position. Advantageously, the direction of movement of the linear movement section is aligned parallel to the conveying direction in a top view. Advantageously, the linear guide comprises a linear rail and, further advantageously, a carriage corresponding to the linear rail. It is preferred that the linear rail is mounted on the arm or...The linear guide is attached to the upper side of the arm. Preferably, the linear guide includes a stationary support element. It is preferred that a carriage is attached to the underside of the stationary support element. Preferably, the arm is movable relative to the support element between the measuring position and the rest position of the reference piece.

[0012] The calibration device preferably includes a stop for defining the measuring position. Advantageously, a section of the stationary support element or the linear guide forms a stop bearing. Preferably, the arm includes a stop element, which is further preferably designed as a stop screw. It is preferred that the stop bearing and the stop element touch each other in the measuring position of the reference piece and expediently do not touch each other in the rest position of the reference piece. The stop element is advantageously arranged above the linear rail. It is expedient if a stop surface of the stop element faces towards the sensor device.

[0013] It is particularly within the scope of the invention that the calibration device comprises at least one spring. The spring may, for example, be designed as a helical spring. It is preferred that the spring is connected between the drive source or the electric motor and the arm, so that the arm is elastically mounted relative to the drive system or the drive source. It is preferred that the spring or the drive system or the drive train is designed such that, in the measuring position of the reference piece, the spring generates a contact pressure of the stop element against the stop bearing. Preferably, the spring is extended in the measuring position of the reference piece, so that a contact pressure of the stop element acts on the stop bearing. According to a preferred embodiment, the drive system includes a rest position sensor for detecting when the rest position has been reached.A first end of the spring is advantageously connected to the drive train, for example to a lever or a crossmember. A second end of the spring is preferably attached to the arm. Preferably, at least one arm is assigned two springs, and the arm is more preferably arranged between the two springs in a top view.

[0014] It is highly preferred that the arm includes at least one driver for transferring the reference piece to the rest position. The driver may, for example, be designed as a roller or guide roller. Advantageously, one axis of the roller or driver is oriented perpendicular to the conveying direction in plan view. It is preferred that the driver is arranged in a rear third of the arm. It is advantageous if the driver projects from both sides of the arm so that, in a preferred embodiment, a lever part with a lower, fork-shaped end can contact the driver on both sides. Preferably, the driver is arranged in plan view between the first and second ends of the spring. The spring is preferably designed such that it exerts a tensile force on the arm, so that the driver of the arm—particularly in the rest position and / or sectionally during the transfer from the measuring to the rest position—is held in place by the reference piece.Conversely - is pressed against the drivetrain or is pressed in the direction of the drivetrain.

[0015] It is within the scope of the invention that the sensor device comprises two sensors. Preferably, a first sensor of the sensor device is arranged above the space to be kept clear, and preferably a second sensor is located below the space to be kept clear. Advantageously, a measuring point is assigned to each of the first and second sensors, with the two measuring points preferably overlapping in a top view. Advantageously, the sensor device, or the first and / or the second sensor of the sensor device, comprises a light source and a light detector. It is possible that the light source emits light with a wavelength above 550 nm. Preferably, the light source emits visible light. It is particularly preferred that the light source is a diode, and preferably a laser diode. It is advantageous that the light detector comprises at least one row of diodes with a plurality of pixels.It is particularly preferred that the first and / or second sensor or sensor device is a triangulation sensor or includes a triangulation sensor. Advantageously, the first and second sensors are identical in construction.

[0016] According to a preferred embodiment, the sensor station comprises a plurality of sensor devices. Advantageously, the sensor devices are arranged side by side in a top view, with the measuring points associated with the sensor devices advantageously forming a connecting line, the connecting line preferably being oriented transversely—in particular perpendicularly—to the conveying direction. Preferably, the sensor station comprises at least three sensor devices for generating three measuring lines on the top and / or bottom surface of the wafers. It is preferred that a first measuring line runs in a middle third of the wafer, whereas the second and third measuring lines run in a left and right third of the wafer, respectively. It is possible for the sensor station to comprise four or more sensor devices for generating four or more measuring lines. For example, the sensor station comprises five sensor devices.Advantageously, each sensor on a wafer is assigned a measurement track for mapping a saw-cut profile, or each sensor device is assigned a measurement line for mapping a wafer thickness. It is possible to convert a measurement track on the surface of a wafer into a measurement line by calculating the difference between the two. It is preferred that a plurality of measurement tracks be generated on both the top and bottom surfaces of the wafers. It is advantageous that each measurement line comprises at least 2000 measurements, preferably at least 5000 measurements, and particularly preferably at least 10000 measurements per wafer.

[0017] According to a preferred embodiment, the main support comprises – preferably predominantly – a metal, and in particular aluminum. In a specific embodiment, the main support comprises a mineral material. The mineral material preferably comprises rock, and particularly preferably granite. It is advantageous for the main support to have a lower support group arranged below the space to be kept clear. Advantageously, the main support also comprises an upper support group arranged above the space to be kept clear. The main support advantageously includes one or more recesses between the upper and lower support groups for guiding the conveying device or the wafers through the main support. According to a preferred embodiment, the lower support group comprises at least one main block.The upper support group preferably comprises side walls which, in a top view, at least partially and preferably completely enclose the at least one sensor device. Preferably, the upper support group has at least one intermediate wall, so that the upper support group forms at least two chambers for at least two sensor devices. Advantageously, the at least one sensor is attached to an inner side of a side wall or the intermediate wall. The wall thickness of the side walls or the intermediate wall is preferably at least 15 mm, more preferably at least 20 mm, and particularly preferably at least 25 mm. Ideally, the wall thickness of the side walls or the intermediate wall is at least 30 mm. It is advantageous if the wall thickness of the side walls or the intermediate wall is at most 100 mm, preferably at most 80 mm, and particularly preferably at most 70 mm. Ideally, the wall thickness of the side walls or the intermediate wall is...The partition wall should be no more than 60 mm thick.

[0018] According to a highly advantageous embodiment, the sensor station has a base frame, preferably with at least one damper arranged between the base frame and the main support. The damper can be, for example, pneumatic or hydraulic. The damper particularly preferably comprises an elastic element, and especially a rubber element. It is advantageous if at least three dampers are arranged on the base frame. According to a preferred embodiment, the main support rests on the at least one damper. It is particularly preferred if the sensor device(s) is / are attached to the main support, and especially if rigidly attached. Preferably, the calibration device is attached to the main support, and especially if rigidly attached.According to a particularly preferred embodiment, a front end element and / or a rear end element of the conveying device is arranged on the base frame, wherein, further preferably, the at least one damper is not interposed between the front end element and / or the rear end element on the one hand and the base frame on the other, so that preferably the front end element and / or the rear end element are not damped or are not supported by the main support.

[0019] The calibration device preferably comprises a computing unit configured to use measured values ​​determined by the sensor device on the reference piece for calibrating measured values ​​determined by the sensor device on the wafers. It is preferred that the measured values ​​on the reference piece or on the wafers represent the thickness of the reference piece or the wafers. Preferably, the calibration device includes a control unit for the arm. The control unit is preferably configured to move the arm from the rest position to the measuring position and vice versa. Advantageously, the wafers to be measured are individually removed from a first collection container by a removal station located upstream of the sensor station. The separated wafers then preferably pass through the sensor station and are subsequently fed to a sorting station.Advantageously, the wafer material flow in the sensor station is stopped when the first collection container is empty. Conveniently, the wafer material flow in the sensor station is started as soon as the first collection container has been replaced by a second one. Preferably, the times of stopping and starting the wafer material flow in the sensor station for the purpose of container exchange define an interruption period. The wafer material flow can be stopped, for example, by stopping the conveying device. Preferably, the wafer material flow is stopped by not transferring any further wafers to the conveying device, preferably with the conveying device operating at least intermittently and preferably continuously during the interruption period.It is particularly preferred that the last wafer of the first collection container and the first wafer of the second collection container define the interruption time. The expression "in the sensor station" preferably means "within / the range of the sensor device" and especially preferably "at the at least one measuring point." It is particularly preferred that the computing unit and / or the control unit is / are configured such that the sensor device measures the reference piece during the interruption time. Advantageously, the measured values ​​obtained from the reference piece are used to calibrate measured values ​​obtained from wafers. The interruption time may, for example, be up to 10, 7, or 5 seconds. Advantageously, the interruption time is at least 0.5, 1.0, 1.5, or 2 seconds.

[0020] Preferably, the continuous conveyor comprises at least two endless individual belts that are at least partially parallel to each other. Advantageously, a complete continuous conveyor is assigned to the sensor station. The term "complete continuous conveyor" means, in particular, that the rotation of the continuous conveyor defines its extent in the conveying direction and, preferably, that the continuous conveyor is not capable of conveying wafers from preceding stations to the sensor station or from the sensor station to subsequent stations without the assistance of additional conveying equipment. Advantageously, the continuous belt or the individual belts comprise an elastomer, the elastomer preferably being part of a layer in contact with the wafers. Each of the two individual belts is preferably at least 5 mm, more preferably at least 10 mm, particularly preferably at least 12 mm, and ideally at least 14 mm wide.Advantageously, each of the two individual bands is at most 40 mm wide, preferably at most 30 mm wide, particularly preferably at most 25 mm wide, and ideally at most 18 mm wide. The distance between the two individual bands, viewed from above, is advantageously at least 20 mm wide, preferably at least 30 mm wide, particularly preferably at least 35 mm wide, and ideally at least 40 mm wide. It is advantageous if the distance between the two individual bands, viewed from above, is at most 110 mm wide, preferably at most 90 mm wide, particularly preferably at most 80 mm wide, and ideally at most 70 mm wide.

[0021] It is within the scope of the invention that a motor, in particular an electric motor, is assigned to the conveying device. It is advantageous if the motor has a motor shaft projecting from a motor housing on one side or—preferably—on both sides. Preferably, the motor shaft is rigidly connected to one or more drive wheels on at least one side and, more preferably, on both sides of the motor housing. The drive wheel(s) expediently have a width suitable for accommodating a single belt. It is advantageous if the conveying device includes at least one, preferably two, pressure rollers per drive wheel. The one or two pressure rollers are preferably arranged such that the single belt wraps around the drive wheel by at least 90°, preferably at least 120°, and particularly preferably at least 150°.It is advantageous if the conveyor system has at least two, and preferably at least three, deflection rollers for the endless belt or for each individual belt. Advantageously, the at least one pressure roller and / or the deflection rollers are designed to accommodate a single belt.

[0022] The conveyor or continuous conveyor is preferably guided by the main support. Advantageously, the conveyor comprises a front end element at its front end and a rear end element at its rear end. The front end element includes at least one deflection roller and preferably two deflection rollers for the continuous belt or for each individual belt. The rear end element preferably has one or more drive wheels and preferably includes at least one deflection roller for the continuous belt or for each individual belt. Furthermore, at least one pressure roller and preferably two pressure rollers for the continuous belt or for each individual belt are provided on the rear end element. The front and / or rear end element may, for example, be made of steel and preferably have a steel housing. It is highly preferred that the front end element and / or the rear end element is / are attached to the base frame.Advantageously, the lower support group or one / the main block of the lower support group is arranged between the front end element and the rear end element, preferably leaving a gap between the front or rear end element on the one hand and the lower support group or the main block on the other.

[0023] According to a particularly preferred embodiment, the conveying device, the endless conveyor, or the individual belts rest at least partially on the main support, the lower support group, or the main block. Preferably, a first section of the conveying device, the endless conveyor, or the individual belts rests in the conveying direction in front of the at least one measuring point on the main support, the lower support group, or the main block. Advantageously, a second section of the conveying device, the endless conveyor, or the individual belts rests in the conveying direction behind the at least one measuring point on the main support, the lower support group, or the main block. It is particularly preferred if the main support, the lower support group, or the main block defines at least one section of a path of movement—especially in the vertical direction—of the conveying device, the endless conveyor, or the individual belts by resting on it.This ensures that the conveyor is decoupled from its drive at the measuring point, thus reducing any vibrations emanating from the drive in that area. Another advantage is that, at the measuring point, the wafers behave synchronously with the sensor device with respect to any vertical movements, thereby reducing any relative vertical movements between the wafers and the sensor device.

[0024] According to a preferred embodiment, the drive system comprises a drive source and a drive train. The drive source preferably includes at least one electric motor. The drive train preferably comprises a connecting rod or at least one spindle. According to a first embodiment, the drive source is connected to the connecting rod. Advantageously, the connecting rod is connected to a lever element, which is rotatably mounted on a lever axis. The lever element is preferably connected to the at least one arm or arms relative to the connecting rod. Preferably, the lever element is connected to the at least one arm via at least one spring.

[0025] According to a second embodiment, the drive source, or the at least one electric motor, is connected to a spindle of the drive train. Advantageously, the drive source comprises two electric motors, each connected to a spindle. A crossbeam is preferably connected to one end of the at least one spindle, so that the drive source can push the at least one arm from the rest position to the measuring position via the spindle and the crossbeam. The crossbeam is oriented transversely and preferably perpendicular to the conveying direction in a top view. Advantageously, at least one spring is arranged between the crossbeam and the at least one arm, so that the at least one arm is held in place relative to the drive source.The traverse is elastically mounted. Advantageously, the traverse includes at least one opening and the arm at least one driver, the driver projecting through the opening so that the traverse can pull the at least one arm from the measuring position to the rest position.

[0026] To solve the aforementioned problem, the invention teaches a method for measuring wafers, wherein wafers to be measured are taken from a first collection container and fed to a sensor station according to the invention, wherein the wafers are guided through the sensor station by means of a conveying device, wherein the sensor station comprises at least one sensor device, wherein the sensor device measures at least one property of the wafers, wherein the material flow of the wafers in the sensor station is stopped when, for example, the first collection container is empty, and wherein the material flow of the wafers in the sensor station is started as soon as, for example, the first collection container has been replaced by a second collection container, wherein the times of the stop and the start of the material flow of the wafers in the sensor station define an interruption time.wherein, within the interruption time, the sensor device measures a reference piece with a known value of the property, wherein the measurement of the reference piece is used to calibrate measured values ​​of the wafers, characterized by the fact that the conveying device comprises at least one section of an endless conveyor, wherein the reference piece in the measuring position is located at least partially within the space to be kept clear.

[0027] Advantageously, the reference piece is in a measuring position during measurement. The properties of the wafers advantageously correspond to their thickness. It is advantageous that the reference piece is moved to a rest position after measurement. Advantageously, the wafer material flow in the sensor station is restarted after the reference piece has left the measuring position or reached the rest position. It is advantageous that the wafer material flow in the sensor station is stopped again when the second collection container is empty. Advantageously, the reference piece is then moved from the rest position back to the measuring position.

[0028] The invention is explained in detail below using two exemplary embodiments. These are shown in schematic representation. Fig. 1 a section of the sensor station according to the invention in a perspective side view, Fig. 2 a main support of the sensor station Fig. 1 in a top view, Fig. 3 the sensor station of the Fig. 1 in a full side view, Fig. 4 the sensor station of the Fig. 1 in a full rear view, Fig. 5 a side view of an arm of the sensor station Fig. 1 in a measuring position, Fig. 6 the arm out Fig. 5 during the beginning of the transfer from the measuring position to a resting position, Fig. 7 the arm out Fig. 5 during the transfer from the measuring position to the resting position, Fig. 8 the arm out Fig. 5 in the resting position, Fig. 9 a sensor station according to the invention of a second embodiment in a perspective top view and Fig. 10 the sensor station Fig. 9 in a perspective view from below.

[0029] In the Fig. 1 and Fig. Figure 2 shows a sensor station according to the invention from two perspectives or a top view. For clarity, the side walls facing the viewer have been omitted. Fig. 1 and parts in Fig. 2 omitted. The sensor station from the Fig. 1 and Fig. 2 may, for example, be located downstream of a wafer removal station (not shown here) in which a removal device takes individual wafers 1 from a collection container and transfers them to a continuous conveyor. In this embodiment, the continuous conveyor then passes the wafers 1 to the sensor station. The sensor station can be arranged upstream of a wafer sorter (also not shown here), so that the sensor station is part of a wafer line.

[0030] The wafers 1 from the preceding station are transferred by a conveying device 3 (see below). Fig. 1) picked up by the sensor station, transported in a conveying direction F and through cutouts 43 (see Fig. 4) in a main support 13, 36, 37 through the main support 13 to the end of the sensor station. There, the wafers 1 are then transferred to the wafer sorter, for example. The wafers 1 define according to Fig. 1. Their movement creates a space 4 that must be kept clear; if an object were located in this space 4, the wafers 1 would collide with said object. In this embodiment, a total of six sensors 12 for measuring the wafers 1 are located approximately in the middle of the sensor station.

[0031] According to the, the funding facility 3 comprises Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7 to Fig. Figure 8 describes an endless belt which, in this embodiment, has two parallel individual belts 14. The individual belts 14 are preferably each guided over three deflection rollers 18 and driven by a drive wheel 20. Preferably, two pressure rollers 19 are adjacent to the drive wheel 20, so that each individual belt 14 wraps around the drive wheel 20 by approximately 180°. In this embodiment, both drive wheels are driven by a common electric motor. The two front deflection rollers 18, on the one hand, and the rear deflection roller 18, the two pressure rollers 19, and the drive wheel 20 (each individual belt 14) are connected to a front end element 35a and a rear end element 35b, respectively. The rear end element 35b may include the electric motor of the conveyor 3 (not shown) and—like the front end element 35a—comprise a steel housing.

[0032] The two end elements 35 a,b may, for example, be attached to a base frame 39 by means of screws, s. Fig. 3 and Fig. 4. The substructure 39 preferably comprises steel, wherein steel further preferably constitutes a relatively or absolutely predominant proportion of the substructure 39. The main support 13 of this particular embodiment comprises a plurality of granite blocks, which are fastened to one another by means of screw connections and together form the main support 13. The main support 13 may preferably be mounted on three dampers 40, which in turn are attached to the substructure 39 and serve for vibration damping. The main support 13 comprises a lower support group 36 arranged below the space to be kept clear 4 and an upper support group 37 located above the space to be kept clear 4. The lower support group 36 may have a main block 42 made of granite, on which the individual bands 14 bear over a length of, for example, 350 mm.In this way, the wafers 1 in the area of ​​the sensors 12 as well as the sensors 12 themselves are decoupled from the drive of the individual belts 14 and exhibit only very slight relative movements to each other in the vertical direction.

[0033] The main support 13 of this embodiment encloses a total of three sensor devices 2 (see below). Fig. 1 and Fig. 2), wherein each sensor device 2 has one sensor 12 arranged above and one below the space 4 to be kept clear. Preferably, the sensors 12 are laser triangulation sensors, such that each sensor 12 has a laser diode as a transmitter and a diode array as a receiver. The light beam of each sensor 12 is projected onto the top or bottom surface of the respective wafer 1, reflected there, and detected by the respective diode array. If, for example, the distance of a wafer 1 to the sensor 2 increases, the light beam is detected by a slightly more outwardly located pixel of the diode array. This pixel shift follows trigonometric relationships, by which the distance of the wafer 1 to the sensor 2 can be determined in the sub-micrometer range.

[0034] The points where the light beam intersects the top or bottom surface of the space 4 to be kept clear are preferably called measuring points. Due to the movement of the wafers 1, the measuring point of each sensor 12 experiences a corresponding relative movement to the wafer 1. As a result, the stationary sensors 12 scan the wafers 1 in a line-like fashion and each captures one measurement track per wafer 1. Each sensor 12 may, for example, capture 15,000 measurements per measurement track or wafer 1.

[0035] By arranging a sensor 12 above and a sensor 12 below the space to be kept clear 4, a measurement track can be determined on each side of the wafer 1, providing information about the respective saw groove profile. Advantageously, the wafers 1 are placed on the wafer line so that the saw grooves are located perpendicular to the conveying direction F in a top view. Furthermore, the thickness of each wafer 1 can also be determined by arranging the sensors 12 above and below the space to be kept clear 4. For this purpose, a measurement track on the top side and a measurement track on the bottom side are converted into a measurement line by calculating the difference between them. This measurement line represents both the thickness and the deflection of the wafer 1 along its length. By providing a total of three sensor devices 2, each with two sensors 12, a total of six measurement tracks and three measurement lines can be created. For example, two measurement tracks or...One measurement line in the middle of wafer 1, two further measurement tracks or one further measurement line in a left third of wafer 1, and two further measurement tracks or one further measurement line in a right third of wafer 1. A total deviation – for example, regarding thickness – can also be determined across all measurement tracks.

[0036] The three lower sensors 12 of this embodiment are arranged in and attached to the lower support group 36. Corresponding recesses are provided in the lower support group 36 for the arrangement of the lower sensors 12. The upper support group 37 comprises side walls 21 and an intermediate wall 22. The upper sensors 12 are located between the side walls 21 and the intermediate wall 22, respectively, and are each attached to the corresponding side wall 21 or intermediate wall 22. A view of Fig. Figure 2 illustrates the arrangement of the upper sensors 12 within the upper support group 37. In this embodiment, the sensors 12 are attached to the main support 13 by means of screws and each has a plug connector 38 for sensor connection cables. Outer walls 23 made of sheet metal delimit the sensor station on its right and left sides.

[0037] The sensor station includes, with regard to Fig. 1. Furthermore, a calibration device 5 according to the invention, which preferably has three arms 6, each with a reference piece 8 arranged at the end of the respective arm. The three reference pieces 8 each have a thickness that corresponds, for example, to an average thickness of the wafer 1. Preferably, the thickness variation of each reference piece 8, determined by the top and bottom surfaces, is very small, and in particular, the respective thickness or thickness variation of the reference piece 8 is precisely known. The calibration device 5 is in Fig. 2 not shown.

[0038] A drive system 7 of the calibration device 5 is preferably configured to drive the three arms 6 with their reference pieces 8 such that the reference pieces 8 move from a rest position and are ultimately located precisely at the six measuring points, thus assuming the position of the wafers 1 (measuring position). This preferably occurs whenever the material flow of the wafers 1 is interrupted for a short time because an empty collection container at the beginning of the wafer line needs to be replaced by a full one. During this interruption, the drive system 7—preferably with the conveyor 3 running—moves the reference pieces 8 to the measuring position. Reference measurements are then taken, which are used to calibrate the measured values ​​recorded on the wafers 1. This largely compensates for any drift of the sensors 12, thus significantly increasing the measurement accuracy.During the reference measurements, the empty collection container is replaced with a full one. The reference pieces 8 are then returned to their respective rest positions, and the wafers 1 from the full collection container are successively fed to the conveyor 3.

[0039] The drive system 7 of the exemplary embodiment of the Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7 to Fig. 8 comprises an electric motor 15, to which a connecting rod 16 is preferably connected. The connecting rod 16 is advantageously connected to a lever section 24, which is pivotable about a lever axis 25. The three arms 6 are connected to each of the three lower ends of the three-part lever section 24, so that the arms 6 extend from the Fig. The reference pieces 8 can be moved from the rest position shown in section 1 to the measuring position, thus positioning them at the six measuring points. The movement process between the measuring and rest positions is described below. Fig. 5, Fig. 6, Fig. 7 to Fig. 8 can be seen.

[0040] In Fig. Figure 5 shows an enlarged side view of two sensors 12 of a sensor device 2, an arm 6 and the associated drive system 7. Fig. 3 the reference piece 8 is in a measuring position and thus within the space to be kept clear 4 directly above the individual bands 14. The connecting rod 16 was moved by the electric motor 15 so that it is in the rearmost position, whereby the arm 6 in turn is in the frontmost position due to the leverage of the lever part 24.

[0041] At each of the three lower, fork-shaped ends of the lever part 24, two springs 27 are preferably attached with their first spring end, while the other spring end engages a rear section of the respective arm 6. In a top view, the respective arm 6 is preferably located between the two springs 27 assigned to it, as well as between two prongs of the respective fork-shaped lower end of the lever part 24. As a result, the movements of the lever part 24 and the arms 6 are elastically mounted relative to each other via six springs 27. In the measuring position, the springs 27 are preferably in a more extended state, so that they exert a tensile force on the arm 6, which acts in the direction of the sensor device 2.

[0042] This tensile force is advantageously absorbed by a stop 10, 11 in the form of a stop element 11 designed as a stop screw on the arm 6, wherein the stop element 11 abuts a stop bearing 10 of a rigid support element 26. The support element 26 preferably has a carriage 30 on its underside, which is rigidly connected to the support element 26 and is therefore immovable relative to the support element 26. A linear rail 29 is advantageously attached to the upper side of the arm 6, which is slidably mounted on the carriage 30. The support element 26 is expediently supported by a suspension 28. The suspension 28, the support element 26, and the carriage 30 are components of a linear guide 9. The linear guide 9 determines the direction of movement of the arm 6 and, via the stop bearing 10 of the support element 26, also the precise location of the measuring position. In the measuring position, the arm 6 is thereby separated from the electric motor 15.decoupled from the drive train 16, 24, so that any vibrations of the electric motor 15 or of the lever part 24 are not transmitted to the arm 6.

[0043] In the next, in Fig. In step 6, the measurements were temporarily stopped and the connecting rod 16 was set in motion, so that the right end of the connecting rod 16 rotated approximately 45° counterclockwise. This caused the lower end of the lever part 24 to shift slightly to the right, while the reference piece 8 remained in the measuring position. This is due to the springs 27, which are located in Fig. 5 were in a more stretched state and in Fig. 6 still exert a tensile force on the arm 6 in the direction of the sensor device 2, so that the stop element 11 has not yet detached from the stop bearing 10. However, it shows Fig. 6 the moment just before the stop element 11 has detached from the stop bearing 10.

[0044] In Fig. At step 7, the electric motor 15 rotated approximately 35° further, causing the lower end of the lever part 24 to move slightly further to the right. In doing so, the lower end of the lever part 24 struck a driver 41 of the arm 6, causing the arm 6 to move synchronously to the right with the lower end of the lever part 24. This disengaged the stop element 11 from the stop bearing 10. The springs 27 now exert only a slight tensile force on the driver 41 and the lifting part 24. In this embodiment, the driver 41 is designed as a roller, which projects transversely to the conveying direction on both sides when viewed from above. In particular, Fig. As can be seen from Figure 7, the reference piece 8 is no longer located at its two measuring points; instead, the reference piece 8 is now located above the space to be kept clear 4. However, the arm 6 still protrudes into the space to be kept clear 4 with its lower edge.

[0045] This is then with regard to Fig. This is no longer the case because the lever part 24 has moved the arm 6 further to the right via the driver 41, as the electric motor 15 has now rotated the connecting rod 16 by almost 180°. Here, the lower edge of the arm 6 is also clearly above the space 4 to be kept clear, so that the wafers 1 – as shown – can again be passed through the sensor station and measured. The reference piece 8 is now in the rest position, which is determined by a rest position sensor 34 (see figure 8). Fig. 8) is determined.

[0046] Fig. 9 and Fig. Figure 10 shows a perspective side view and a perspective view from below of a second embodiment according to the invention. The second embodiment differs from the first embodiment according to the Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7 to Fig. 8 especially with regard to the drive system 7. Thus, the drive system 7, or the drive source of the second embodiment, has two electric motors 15, which are arranged to the left and right of the two individual belts 14 in the top view. The electric motors 15 each drive a spindle 17, so that a crossbeam 31 can be moved back and forth. Two springs 27 are arranged between the crossbeam 31 and the upper ends of the arms 6 (see figure 8). Fig. 9), so that the arms 6 are elastically mounted in relation to the traverse 31.

[0047] The linear guide 9 of the second embodiment is almost identical to that of the first embodiment, so that the arms 6 of the second embodiment perform the same movement as those of the first embodiment. The upper ends of the arms 6 of the second embodiment also have stop elements 11 in the form of stop screws, which interact with stop bearings 10 of the support elements 26. In the second embodiment, a rest position sensor 34 is also provided, which detects the rest position of the crossbeam 31 and thus of the arms 6 or the reference pieces 8. In both embodiments, the conveyor 3, the main support 13, and the sensor device 2 are also identical or substantially identical.

[0048] With regard to Fig.Figure 10 shows that the traverse 31 has openings 32 on its underside. Drivers 33 protrude through these openings 32 and are attached to the undersides of the arms 6. The drivers 33 serve to move the arms 6 from the measuring position to the rest position.

Claims

[1] Sensor station for measuring wafers (1), comprising at least one sensor device (2) for measuring at least one property of a wafer (1) and at least one section of a conveying device (3), wherein the conveying device (3) defines a conveying direction, wherein the moving wafers (1) along the conveying device define a space (4) to be kept clear for the moving wafers (1), wherein the sensor device (2) generates at least one measuring point on a bottom and / or on a top of the space to be kept clear (4), wherein the sensor device (2) is supported by a main support (13), wherein the sensor station has a calibration device (5), wherein the calibration device (5) comprises at least one arm (6) and a drive system (7) for moving the arm (6), wherein a reference piece (8) is arranged on the arm (6), wherein the arm (6) is movably mounted so that the reference piece (8) can assume a rest position and a measuring position, wherein the reference piece (8) is arranged outside and within a range of the sensor device (2) in the rest position and in the measuring position characterized by , that the conveying device (3) comprises at least one section of an endless conveyor, wherein the reference piece (8) is located at least partially within the space to be kept clear (4) in the measuring position. [2] Sensor station according to claim 1, wherein the calibration device (5) comprises at least one linear guide (9), wherein the linear guide (9) defines a linear movement section of the arm (6) between the measuring position and the rest position. [3] Sensor station according to one of claims 1 or 2, wherein the calibration device (5) has a stop (10, 11) for defining the measurement position. [4] Sensor station according to one of claims 1 to 3, wherein the drive system (7) has at least one spring (27). [5] Sensor station according to one of claims 1 to 4, wherein the sensor device (2) has two sensors (12). [6] Sensor station according to one of claims 1 to 5, wherein the sensor station has a base frame (39) wherein at least one damper (4) is arranged between the base frame (39) and the main support (13). [7] Sensor station according to one of claims 1 to 6, wherein the endless conveyor has two endless single belts (14) that are at least partially parallel to each other. [8] Sensor station according to one of claims 1 to 7, wherein the conveying device (3) rests section by section on the main support (13). [9] A method for measuring wafers (1), wherein wafers (1) to be measured are taken from a first collection container and fed to a sensor station according to any one of claims 1 to 8, wherein the wafers (1) are guided through the sensor station by means of a conveying device (3), wherein the sensor station comprises at least one sensor device (2), wherein the sensor device (2) measures at least one property of the wafers (1), wherein the material flow of the wafers (1) is stopped in the sensor station, wherein the material flow of the wafers (1) is started in the sensor station, wherein the times of stopping and starting the material flow of the wafers (1) in the sensor station define an interruption time, wherein within the interruption time the sensor device (2) measures a reference piece (8) with a known value of the property, wherein the measurement of the reference piece (8) is used to calibrate measured values ​​of the wafers (1), characterized by, that the conveying device (3) comprises at least one section of an endless conveyor, wherein the reference piece (8) is located at least partially within the space to be kept clear (4) in the measuring position.

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