Device and method for scanning wafers

Abstract

The present description relates to a scanning device comprising a base (62), a first carriage (67A) slidably mounted relative to the base (62) and comprising a first arm (68A), a first emitter (74) of a first light beam (75) fastened to the first arm (68A), a second carriage (67B) slidably mounted relative to the base (62) and comprising a second arm (68A), a mirror or a receiver (76) of the light beam fastened to the second arm (68B), and means for varying the spacing between the first and second arms (68A, 68B).

Description

[0001] DESCRIPTION

[0002] TITLE: Device and method for scanning wafers This patent application claims priority from French patent application FR2502608, which will be considered as forming an integral part of this description.

[0003] technical field

[0004]

[0001] This description relates generally to devices and methods for scanning wafers, in particular semiconductor wafers.

[0005] Previous technique

[0006]

[0002] To process batches of semiconductor wafers, for example silicon wafers, a cassette is generally used into which several wafers are loaded for simultaneous processing once the cassette has been filled. The cassette is used to move the wafers from one processing machine to another during a manufacturing process using semiconductor wafers, for example, the manufacture of electronic components.

[0007]

[0003] It is known to count the number of wafers present in the cassette during the manufacturing process. This operation can be carried out using optical means. This is referred to as scanning the cassette using a scanning device.

[0008]

[0004] The size of the cassettes depends on the size of the semiconductor plates that are loaded into them and the size of the processing machine in which the cassette must be placed.

[0009]

[0005] It is desirable to be able to use the same scanning device with cassettes and semiconductor plates of different sizes. Summary of the invention

[0010]

[0006] An embodiment overcomes all or part of the drawbacks of known scanning devices and methods.

[0011]

[0007] One embodiment provides a scanning device comprising a base, a first carriage mounted in a sliding connection relative to the base and comprising a first arm, a first emitter of a first light beam fixed to the first arm, a second carriage mounted in a sliding connection relative to the base and comprising a second arm, a mirror or a receiver of the light beam fixed to the second arm, and means for varying the gap between the first and second arms.

[0012]

[0008] According to one embodiment, the device comprises a guide rail fixed to the housing, the first trolley being mounted by means of a sliding connection on the guide rail and the second trolley being mounted by means of a sliding connection on the guide rail.

[0013]

[0009] According to one embodiment, the means for varying the gap between the first and second arms include a first rack fixed to the first carriage, a second rack fixed to the second carriage, a gear transmission mechanism cooperating with the first rack and with the second rack, and an electric motor driving the gear transmission mechanism.

[0014]

[0010] According to one embodiment, the first rack includes first teeth, and the second rack includes second teeth, the toothed wheel cooperating with the first teeth and with the second teeth.

[0015]

[0011] One embodiment also provides for a transfer installation comprising a robotic arm and a scanning device as defined above attached to the robotic arm.

[0016]

[0012] According to one embodiment, the transfer installation further includes a first cassette support on which a first cassette containing semiconductor wafers is intended to be placed.

[0017]

[0013] According to one embodiment, the first cassette support includes a device for detecting the size of the first cassette among several sizes.

[0018]

[0014] According to one embodiment, the installation further comprises a first device for detecting protrusion of one of the semiconductor wafers out of the first cassette when the first cassette is on the first cassette support, the first device for detecting protrusion of one of the wafers in the first cassette comprising a second emitter of a second light beam, in a different direction from the first light beam, and means for moving the second emitter relative to the first support.

[0019]

[0015] According to one embodiment, the installation further includes a second cassette support on which a second cassette containing semiconductor wafers is intended to be placed.

[0020]

[0016] According to one embodiment, the installation further comprises a second device for detecting protrusion of one of the semiconductor wafers out of the second cassette when the second cassette is on the second cassette support, the second device for detecting protrusion of one of the wafers in the second cassette comprising a third emitter of a third light beam, in a different direction from the first light beam, and means for moving the third emitter relative to the second support.

[0021]

[0017] One embodiment also provides a scanning method implementing the scanning device as defined above, comprising the simultaneous sliding of the first carriage and the second carriage relative to the housing until the gap between the first arm and the second arm is equal to a given gap, and the command of the first emitter to emit the first light beam.

[0022]

[0018] According to one embodiment, the method includes detecting the size of the first cassette among several sizes by means of the first cassette size detection device and controlling the scanning device until the gap between the first arm and the second arm is equal to a given gap that depends on the detected size.

[0023]

[0019] According to one embodiment, the method further comprises controlling the protrusion detection device to move the second emitter relative to the first support to a given position that depends on the detected size. Brief description of the drawings

[0024]

[0020] These features and advantages, as well as others, will be described in detail in the following description of particular embodiments, given by way of non-limiting example, in relation to the accompanying figures, among which:

[0025]

[0021] Figure 1 is a partial and schematic perspective view of an embodiment of a plate transfer installation;

[0026]

[0022] Figure 2 is a partial and schematic perspective view of a cassette loaded with plates;

[0023] Figure 3 is a partial and schematic perspective view of an embodiment of a scanning device for the installation of Figure 1 in a first configuration of use;

[0027]

[0024] Figure 4 is a partial and schematic perspective view of the scanning device of Figure 3 in which part of a housing is not present;

[0028]

[0025] Figure 5 is a partial and schematic perspective view of the scanning device of Figure 3 in a second usage configuration;

[0029]

[0026] Figure 6 is a partial and schematic perspective view of an embodiment of a cassette support for the installation of Figure 1 in the absence of a cassette;

[0030]

[0027] Figure 7 is a partial and schematic perspective view, with a partial section of the cassette support of Figure 6 in the presence of a cassette 30;

[0031]

[0028] Figure 8 is a partial and schematic perspective view, with a partial section of a part of the installation of Figure 1 comprising a protrusion detection device;

[0032]

[0029] Figure 9 is a partial and schematic perspective view of a variant of the installation of Figure 1 in which only a cassette support is present; and

[0030] Figure 10 is a partial and schematic perspective view of the installation of Figure 1, part of the loading bays not being shown.

[0033] Description of the implementation methods

[0034]

[0031] The same elements have been designated by the same reference numerals in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same reference numerals and may have identical structural, dimensional and material properties.

[0035]

[0032] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been shown and are detailed. In particular, the general operation of a plate transfer installation is well known to those skilled in the art and is not described in detail.

[0036]

[0033] Unless otherwise specified, when reference is made to two elements connected together, this means directly connected without intermediate elements other than conductors, and when reference is made to two elements connected (in English "coupled") together, this means that these two elements can be connected or linked through one or more other elements.

[0037]

[0034] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "superior", "lower", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures or to a plate transfer installation in a normal operating position.

[0038]

[0035] Unless otherwise specified, the expressions "approximately", "roughly", "about", and "in the order of" mean to within 10% or 10°, preferably to within 5% or 5°.

[0039]

[0036] Figure 1 is a partial and schematic perspective view of an embodiment of a wafer transfer installation 10, in particular of semiconductor wafers.

[0040]

[0037] Installation 10 comprises:

[0041] -at least one cassette support 20 on which rests a cassette 30, two cassette supports 20 being shown as an example in figure 1;

[0042] - for each cassette support 20, a loading bay 40 containing the cassette support 20 and comprising a front face 41 including an opening 42, the loading bay 40 further comprising a sliding front door 43, shown in the lower position in figure 1, and which can slide upwards to cover the opening 42, and a sliding side door 44, shown in the upper position in figure 1, which, when in the lower position, allows a user to access the support 20;

[0043] - a robotic arm 50 operating a pallet 52 for handling the plates 12;

[0044] - a scanning device 60 for the 12 plates, also carried by the robotic arm 50; and

[0045] - a module, not shown, configured to control the robotic arm 50 and the scanning device 60.

[0046]

[0038] The installation 10 may be located in an enclosure, not shown in figure 1, for example under a controlled atmosphere.

[0047]

[0039] Figure 2 is a partial and schematic perspective view of a cassette 30 loaded with wafers 12.

[0048]

[0040] Each cassette 30 comprises a base 31, a lid 32, and two side walls 33, extending from the base 31 to the lid 32. The base 31, the lid 32, and the side walls 33 define an internal volume 34 in which the pads 12 are housed. Each side wall 33 comprises slots 35 or grooves, open on the side of the internal volume 34. Each pad 12 is arranged in the cassette 30 by being inserted into one of the slots 35 in each side wall 33. The slots 35 are spaced vertically in the side walls 33 such that when the pads 12 are placed in the cassette 30, each pair of adjacent pads 12 is separated by a pitch, for example, between 1 mm and 2 cm. The number of 12 plates loaded in cassette 30 is, for example, between 6 and 50. Each 12 plate can have a substantially circular shape.For example, the diameter of the plate 12 can vary from 25 mm to 450 mm. The plates 12 placed in the same cassette 30 have the same diameter.

[0049]

[0041] Figure 3 and Figure 4 are partial and schematic perspective views of an embodiment of the scanning device 60.

[0050]

[0042] The scanning device 60 comprises:

[0051] - a housing 61 comprising a lower part of housing 62, also called the base, and an upper part of housing 63, fixed to the lower part of housing 62, and delimiting, with the lower part of housing 62, a cavity 64, a first opening 65A and a second opening 65B each communicating the cavity 64 with the outside of the housing 61, the upper part of housing 63 not being shown in figure 4;

[0052] - a guide rail 66, visible in figure 4, fixed to the lower part of the housing 62;

[0053] - first and second carriages 67A, 67B each mounted by means of a sliding connection on the guide rail 66, the first carriage 67A comprising a first arm 68A projecting out of the cavity 64 through the first opening 65A and the second carriage 67B comprising a second arm 68B projecting out of the cavity 64 through the second opening 65B; - a first rack 69A, for example straight, fixed to the first carriage 67A and comprising first teeth 7 OA and a second rack 69B, for example straight and extending parallel to the first rack 69A, fixed to the second carriage 67B and comprising second teeth 70B oriented on the side of the first teeth 70A;

[0054] - an electric motor 71, for example a stepper motor, a servomotor or a DC motor, comprising an output shaft, not visible in the figures;

[0055] - a support 72 on which the electric motor 71 is fixed; - a gear transmission mechanism 73 driven by the output shaft of the electric motor 71 and cooperating with the first teeth 70A of the first rack 69A and with the second teeth 70B of the second rack 69B;

[0056] - an emitter 74 of a light beam 75 disposed at the end of the first arm 68A, the light beam 75 being supplied by a light-emitting diode light source and conveyed by an optical fiber;

[0057] - a receiver 76 of the light beam 75, for example an optical sensor, disposed at the end of the second arm 68B opposite the emitter 74; and

[0058] - an optical amplifier 77 for controlling the transmitter 74 and the receiver 76, the upper part of the housing 63 comprising an opening 78, the optical amplifier 77 extending partly outside the cavity 64 by the opening 78, the part of the optical amplifier 77 located outside the cavity 64 being able to include a user-accessible interface, the lower part of the housing comprising an opening 79 for the passage of the power and control cables, not shown, of the electric motor 71 and the optical amplifier, these cables running along the robotic arm 50.

[0043] According to one embodiment, the scanning device 60 includes limit switches and a home position sensor.

[0059]

[0044] The operation of the scanning device 60 is as follows: when activated, the electric motor 71 rotates its output shaft. The output shaft, in turn, drives the gear transmission mechanism 73, which simultaneously engages with the two racks 69A and 69B. The two racks 69A and 69B are then moved in parallel directions and opposite directions. Depending on the direction of rotation of the output shaft of the electric motor 71, the movements of the racks 69A and 69B cause the arms 68A and 68B to move closer together or further apart. Arms 68A and 68B can therefore be moved between a first extreme position in which the gap between transmitter 74 and receiver 76 is maximum and a second extreme position in which the gap between transmitter 74 and receiver 76 is minimum.Arms 68A and 68B can be stopped in intermediate positions between the first extreme position and the second end position if plates of more than two different sizes need to be scanned. In one embodiment, the two arms 68A and 68B move symmetrically with respect to a plane of symmetry of the scanning device 60. In another embodiment, the two arms 68A and 68B move simultaneously. As an alternative, the rack and pinion mechanism can be replaced by a different drive mechanism.

[0060]

[0045] Figure 3 represents the scanning device 60 when the gap between the transmitter 74 and the receiver 76 is maximum and Figure 5 is a figure analogous to Figure 3 and represents the scanning device 60 when the gap between the transmitter 74 and the receiver 76 is minimal.

[0061]

[0046] To perform a scanning operation, the scanning device 60 is brought by the robotic arm 50 to the cassette 30, for which the scanning operation is to be performed, through the opening 42, so that the arms 68A and 68B of the scanning device 60 are inserted slightly into the cassette 30 between the side walls 33 and the edges of the wafers 12. The scanning device 60 is then moved vertically so that, during the movement of the scanning device 60, the light beam 75 is interrupted by each wafer 12 housed in the cassette 30.

[0062]

[0047] Figure 6 is a partial and schematic perspective view of an embodiment of the cassette support 20 and the front 41 in the absence of a cassette 30 and Figure 7 is a partial and schematic perspective view of the cassette support 20 of Figure 6 and the front 41 in the presence of a cassette 30 containing plates 12, the cassette support 20, the front 41, the cassette 30 and the plates 12 being shown in section in Figure 7.

[0063]

[0048] The cassette support 20 includes a substantially horizontal face 21 on which the cassette 30 rests. The cassette support 20 includes guide elements 22 which project from the face 21 and which allow the placement on the face 21 of a rear stop 23 and a front stop 24, visible in figure 7, the cassette 30 resting on these stops 23, 24. By way of example, in figures 6 and 7, five guide elements 22 corresponding to pads are shown. According to one embodiment, the cassette support 20 further includes a device 25 for detecting the dimensions of the cassette 30 which is placed on the face 21. According to one embodiment, the detection device 25 includes switches 26, for example push-button switches, the number of switches 26 being equal to the number of possible sizes of cassette 30. By way of example, three switches 26 are shown in Figures 6 and 7.

[0064]

[0049] The base 31 of the cassette 30 does not correspond to a solid plate but to an openwork structure and includes a crossbar ("H-bar") 36 connecting the two side walls 33. The switches 26 are arranged so that, when the cassette 30 is placed on the stops 23, 24, the crossbar 36 presses on one of the switches 26. The switch 26 among the set of switches 26 on which the cassette 30 presses depends on the dimensions of the cassette 30 so that cassettes 30 of different dimensions actuate different switches 26. The actuated switch 36 transmits a signal to the control module of the scanning device 60. This advantageously enables automatic detection of the cassette size 30. The control module can then command the scanning device 60 so that the gap between the transmitter 74 and the receiver 76 is adapted to the detected size of the cassette 30.

[0065]

[0050] Before carrying out a scanning operation, it may be desirable, when the cassette 30 loaded with wafers 12 is placed on the cassette support 20, to detect whether a wafer 12 has partially left its position in the cassette 30 following the handling of the cassette 30. For this purpose, the installation 10 may include a protrusion detection device configured to detect whether a wafer 12 is projected outside the cassette 30 towards the opening 42.

[0051] Figure 8 is a partial and schematic perspective view of a part of the installation 10 of Figure 1 with a partial section in which the front 41 is equipped with a protrusion detection device 80.

[0066]

[0052] According to one embodiment, the protrusion detection device 80 comprises:

[0067] - a support 81 fixed to the facade 41, for example above the opening 42;

[0068] - a guide rail 82 fixed to the support 81;

[0069] - a trolley 83 mounted via a sliding connection on the guide rail 82;

[0070] - an electric motor 84 fixed to the support 81 and comprising an output shaft 85;

[0071] - a trapezoidal rod 86 with axis D, for example horizontal, driven in rotation by the output shaft 85;

[0072] - a trapezoidal nut 87 cooperating with the trapezoidal rod 86 and fixed to the carriage 83;

[0073] - a laser or optical reflecting sensor 88 fixed to the trolley 83 and comprising a light beam emitter 89 and a sensor adapted to detect the laser beam 89;

[0074] - a mirror 90 adapted to reflect the light beam 89, fixed to the facade 41 and positioned below the opening 42; and

[0075] - an optical / laser amplifier 91 for controlling the reflective sensor 88.

[0076]

[0053] As an alternative, the guide rail 82 can be replaced by a pad on which the carriage 83 slides or by any other means allowing the translation of the carriage 83.

[0077]

[0054] According to one embodiment, the amplifier 91 and the electric motor 84 are controlled by the control module of the installation 10. The actuation of the electric motor 84 causes the trapezoidal rod 86 to rotate and the trapezoidal nut 87 to move along the axis D of the trapezoidal rod 86 in one direction or the other depending on the direction of rotation of the trapezoidal rod 86. The translation of the trapezoidal nut 87 causes the carriage 83, and therefore the reflective laser sensor 88, to move along the axis D. The mirror 90 is large enough to reflect the laser beam 89 regardless of the position of the reflective laser sensor 88. The use of a reflective laser sensor 88 advantageously eliminates the need to move the emitter and the sensor of the laser beam 89 separately.

[0078]

[0055] Each type or size of cassette 30 used corresponds to a position of the reflective laser sensor 88 of the protrusion detection device 80. Thus, depending on the size of the cassette 30, the protrusion detection device 80 is positioned at the value defined for the cassette 30. The reflective laser sensor 88 is then activated to emit the light beam 89. When all the plates 12 are correctly arranged in the cassette 30, the light beam 89 is reflected by the mirror 90, and the reflected light beam 89 is detected by the reflective laser sensor 88. When a plate 12 is not correctly arranged in the cassette 30, it interrupts the path of the light beam 89, which is then not reflected by the mirror 90. The absence of detection of the light beam 89 by the reflective laser sensor 88 indicates the protrusion of a plate 12. An alert message can then be transmitted to the operator of the installation.

[0079]

[0056] According to one embodiment, the control module automatically detects the size of the cassette 30 placed on the cassette holder 20 by means of the cassette 30 dimension detection device 25 described above and automatically controls the protrusion detection device 80 to bring the reflective laser sensor 88 to the position corresponding to the size of the cassette 30 placed on the cassette holder 20. In the absence of protrusion of the plates 12, the scanning device 60 is automatically controlled by the control module to adapt to the size of the cassette 30.

[0080]

[0057] Figure 9 is a partial, schematic perspective view of a variant of the installation 10 in which only one cassette holder 20 is present. According to one embodiment, an operator can use different sizes of cassettes 30 with this same cassette holder 20. When one cassette 30 is processed, the next cassette 30 can be of a different size. The protrusion detection device 80 described previously in connection with Figure 8 is then advantageously used.

[0081]

[0058] Figure 10 is a partial, schematic perspective view of the installation 10 in which two cassette holders 20 are present, with only the front face 41 and the holder 20 of each loading bay 40 shown. According to one embodiment, each cassette holder 20 can be dedicated to a single cassette size. In this case, each loading bay 40 can be equipped with a protrusion detection device, which may be different from the protrusion detection device 80 described previously in relation to Figure 8 and which may include an emitter of a light beam fixed relative to the front face 41.

[0082]

[0059] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will be apparent to those skilled in the art. By way of example, in the embodiments described above, the arm 68A, 68B and the carriage 69A, 69B correspond to distinct parts. By way of variation, the arm 68A and the carriage 69A can form a single piece, and the arm 68A and the carriage 69A can form a single piece.

[0083]

[0060] Finally, the practical implementation of the embodiments and variants described is within the reach of a person skilled in the art, based on the functional indications given above.

Claims

DEMANDS 1. Scanning device (10) comprising a base (62), a first carriage (67A) mounted by means of a sliding connection relative to the base (62) and comprising a first arm (68A), a first emitter (74) of a first light beam (75) fixed to the first arm (68A), a second carriage (67B) mounted by means of a sliding connection relative to the base (62) and comprising a second arm (68A), a mirror or receiver (76) of the light beam fixed to the second arm (68B), and means (69A, 69B, 73, 71) for varying the gap between the first and second arms (68A, 68B).

2. Scanning device (10) according to claim 1, comprising a guide rail (66) fixed to the base (62), the first carriage (67A) being mounted by means of a sliding connection on the guide rail (66) and the second carriage (67B) being mounted by means of a sliding connection on the guide rail (66).

3. Scanning device according to claim 1 or 2, wherein the means for varying the gap between the first and second arms (68A, 68B) comprise a first rack (69A) fixed to the first carriage (67A), a second rack (69B) fixed to the second carriage (67B), a gear transmission mechanism (73) cooperating with the first rack (69A) and with the second rack (69B), and an electric motor (71) driving the gear transmission mechanism (73).

4. Scanning device according to claim 3, wherein the first rack (69A) comprises first teeth (70A), and wherein the second rack (69B) comprises second teeth (70D), the toothed wheel (73) cooperating with the first teeth (70A) and with the second teeth (70D).

5. Transfer installation (10) comprising a robotic arm (50) and a scanning device (60) according to any one of claims 1 to 4 fixed to the robotic arm (50).

6. Transfer installation (10) according to claim 5, further comprising a first cassette support (20) on which a first cassette (30) containing semiconductor wafers (12) is intended to be placed.

7. Transfer installation (10) according to claim 6, wherein the first cassette support (20) comprises a device (25) for detecting the size of the first cassette (30) among several sizes.

8. Transfer installation (10) according to claim 6 or 7, further comprising a first device for detecting protrusion (80) of one of the semiconductor wafers (12) out of the first cassette when the first cassette is on the first cassette support (20), the first device for detecting protrusion (80) of one of the wafers (12) in the first cassette (30) comprising a second emitter (88) of a second light beam (89), in a different direction from the first light beam (75), and means for moving the second emitter (88) relative to the first support (20).

9. Transfer installation (10) according to any one of claims 6 to 8, further comprising a second cassette support (20) on which a second cassette (30) containing semiconductor wafers (12) is intended to be placed.19 10. Transfer installation (10) according to claim 9, further comprising a second protrusion detection device (80) of one of the semiconductor wafers (12) out of the second cassette when the second cassette is on the second cassette support (20), the second protrusion detection device (80) of one of the wafers (12) in the second cassette (30) comprising a third emitter (88) of a third light beam (89), in a different direction from the first light beam (75), and means for moving the third emitter (88) relative to the second support (20).

11. Scanning method implementing the scanning device (10) according to any one of claims 1 to 4, comprising the simultaneous sliding of the first carriage (67A) and the second carriage (67B) relative to the base (62) until the gap between the first arm (68A) and the second arm (68B) is equal to a given gap, and the control of the first emitter (74) to emit the first light beam (75).

12. Scanning method according to claim 11 for a transfer installation according to claim 7, comprising detecting the size of the first cassette (30) among several sizes by means of the first cassette (30) size detection device (25) and controlling the scanning device (60) until the gap between the first arm (68A) and the second arm (68B) is equal to a given gap which depends on the detected size.

13. Scanning method according to claim 12 for a transfer installation according to claim 8, further comprising control of the detection device 20 protrusion (80) to move the second emitter (88) relative to the first support (20) to a given position which depends on the detected size.

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