Patent Application
20120298710
The present invention generally relates to the treatment of materials, and more particularly substrates for electronics, optics optoelectronics.
More precisely, the invention relates to a device for splitting two wafers of material initially adjoining one another, according to a splitting plane.
It is specified, that adjoining wafers mean wafers positioned so as to be in physical contact. And adjoining wafers can accordingly:
be further connected by structural elements (this is the case especially for wafers defining between them an embrittlement plane such as mentioned hereinbelow, and which have undergone treatment—thermal for example—for completing only partial cleavage of the two wafers on either side of the embrittlement plane), or
on the contrary not be connected by any structural element, but made solid only by means of forces such as those corresponding to a suction effect between the adjoining but disjointed surfaces of the two wafers, and/or Van der Waals forces (this is the case especially for wafers initially originating from the same substrate, between which an embrittlement plane has been defined, and which have undergone thermal treatment or other to carry out complete cleavage between the two wafers on either side of the embrittlement plane).
The two adjoining wafers form an assembly are called a substrate.
Thus, such a device is used for the splitting of wafers of the Silicon On Insulator (SOI), Silicon On Anything (SOA), or even Anything On Anything (AOA) types. It is specified however that a particularly advantageous application of the device according to the invention, which will be described hereinbelow by way of non-limiting example, relates to the splitting of wafers of a structure of SOI type.
A manufacturing process for substrates of SOI type which is known by the generic name of the SMARTCUT™ process comprises the following main steps:
a step for implantation of species (ions or atoms) at a given depth of a substrate of semiconductor material such as monocrystalline silicon, so as to define an embrittlement plane in the substrate,
a step for fixing this substrate on a stiffener such as for example silicon optionally oxidised at the surface, then
a cleavage step intended to at least partially ensure fracture according to the embrittlement plane defined at the level of the layer of implanted species
a wafer is located on each side of the fracture (a first wafer corresponding to the part of the substrate of monocrystalline silicon which has been detached and optionally fixed on the stiffener, to constitute the SOI, and a second wafer which corresponds to the silicon residue).
In this type of process, whether the fracture which occurs during the cleavage step is complete or partial, the two wafers in practice remain adhered to one another (by simple suction effect in the case where the fracture was complete, the faces of the wafers being extremely smooth).
It therefore remains necessary in all cases to finalise their splitting to obtain both the final SOI substrate, and also the residue of the monocrystalline silicon, which could be recycled in the process.
There are substrate-splitting devices such as the device described in the European patent published under number EP 1 423 244. Such a device typically comprises
a base,
splitter means of substrate wafers, and
means for performing controlled displacement of some substrate wafers comprising at least one pusher mobile relative to the base of the device, with the pusher being capable of displacing substrates arranged in a support, and with the direction of storage of the substrates defining a longitudinal direction for the device.
The splitting device described in European patent EP 1 423 244 does not give total satisfaction with respect to the lack of reliability of the device, which results in the loss of substrates and prolonged stoppages of use of the device. Thus, there is a need for improved splitting devices and these are now provided by the present invention.
The present invention aims especially to increase the reliability of substrate-splitting devices in order to generally improve the splitting process of substrate wafers.
Thus, according to a first aspect, the present invention relates to a substrate-splitting device for splitting substrates that include a cleavage plane therein, the device comprising a base, means for performing controlled displacement of the substrates comprising at least one pusher that is mobile relative to the base, the pusher accommodating the substrates in a reception space on the pusher, wherein the pusher is capable of moving from a detection position to a position of engagement with the substrates for displacement thereof, with the direction of storage of the substrates defining a longitudinal direction, and detection means adapted for determining the absence or the presence of obstacles inside at least one region of the reception space of the pusher when the pusher is in a detection position.
The detection means is typically mounted in and forms part of the base and the pusher is configured to move vertically to displace substrates that are arranged in a substrates support. The detection means comprises at least one transmitter for sending a detection beam and a receiver associated with the transmitter for receiving the beam, with beam having a trajectory between the transmitter and receiver that passes through the at least one region of the reception space inside which the absence or the presence of obstacles can be determined when the pusher is in a detection position. Generally, the beam comprises electromagnetic waves and the transmitter and receiver face each other along a longitudinal direction on opposite sides of the reception space. The controlled displacement means immobilizes the pusher in the detection position when obstacles are detected but mobilizes the pusher to support or displace the substrates when no obstacles are detected.
The pusher preferably includes handling means which present a section profile in a section perpendicular to the longitudinal direction of the pusher comprising several zones having a distinct profile zone in the section perpendicular to the longitudinal axis. In this arrangement, the detection means is placed so as to define a region of the reception space associated with each of the section profile zones, so that the absence or presence of obstacles can be determined for each of the regions of the reception space associated with each of the zones. If desired, and advantageously, multiple transmitters and receivers are provided so that each zone has a transmitter and receiver associated with it to determine the absence or the presence of obstacles therein.
The detection position of the pusher is located between a retracted position of the pusher in the base and a position above the base to which the pusher is raised to displace or support the substrates. Also, the controlled displacement means immobilizes the pusher in the detection position until a determination is made by the detection means of the absence of obstacles inside the region(s) of the reception space. The pusher is immobilized in the detection position by the controlled displacement means each time the pusher returns to that position until that determination is made. Furthermore, the controlled displacement means can stop the displacement of the pusher in any position whenever obstacles are determined inside the regions of the reception space.
The invention also relates to a method for improving performance of a splitting device. This method comprises performing controlled displacement of substrates in the device by movement of at least one pusher that is mobile relative to a base of the device, wherein the pusher is capable of moving from a detection position to a position of engagement with the substrates for displacement thereof; accommodating substrates in a reception space on the pusher, and determining the absence or the presence of obstacles inside at least one region of the reception space of the pusher when the pusher is in a detection position.
The pusher is immobilized when obstacles are detected but it is not prevented from moving to engage the substrates when no obstacles are detected. Generally, the pusher moves vertically to support or displace substrates arranged in a substrates support, with the direction of storage of the substrates defining a longitudinal direction. The absence or presence of obstacles inside at least one region of the reception space of the pusher is preferably determined by transmitting a detection beam between a transmitter and receiver, with beam having a trajectory between the transmitter and receiver that passes through the at least one region of the reception space. Thus, the pusher is immobilized in the detection position until a determination is made by the detection means of the absence of obstacles inside the region(s) of the reception space. Also, the pusher is immobilized in any position when obstacles are detected but is mobilized to support or displace the substrates when no obstacles are detected.
Other characteristics and advantages of the present invention will emerge from the following description of the preferred embodiments. This description will be given in reference to the attached drawing figures, wherein:
The present invention preferably relates to a substrate splitting device wherein the substrates comprise two adjoining wafers defining between them a cleavage plane. The device comprises a base, means for splitting the substrate wafers, and means for performing controlled displacement of some substrate wafers comprising at least one pusher mobile relative to the base of the device comprising handling means for substrates, the handling means being adapted to accommodate substrates in a reception space of substrates on the pusher. The pusher is capable of displacing substrates arranged in a support, wherein the direction of storage of the substrates defines a longitudinal direction. The device also comprises detection means adapted to determine the absence or the presence of obstacles inside at least one region of the reception space of the pusher when the pusher is in a detection position, the region being located near the handling means for substrates
According to other advantageous and non-limiting characteristics:
the detection means are solid with the base;
the detection means comprise at least one transmitter for sending a beam of electromagnetic waves and a receiver associated with the transmitter for receiving the beam of electromagnetic waves, the trajectory of the beam of electromagnetic waves between the transmitter and the receiver defining a region of the reception space inside which the absence or the presence of obstacles is determined when the pusher is in a detection position;
a transmitter and a receiver associated with the transmitter are placed according to the longitudinal direction;
the reception space for substrates is located between the transmitter and the receiver when the pusher is in a detection position;
the substrate-handling means present a profile section in a section perpendicular to the longitudinal direction of the pusher comprising several zones characterised by a distinct profile zone in the section perpendicular to the longitudinal axis of the pusher, the detection means being placed so as to define a region of the reception space for substrates associated with each one of the zones, the absence or the presence of obstacles being determined for each one of the regions of the reception space for substrates associated with each one of the zones;
the detection position of the pusher is located between a retracted position of the pusher in the base and a position in which the pusher supports the substrates.
According to a second aspect the invention relates to a control process of the device according to any one of the preceding claims, in which the pusher is immobilised in its detection position until determination by the detection means of the absence of obstacles inside the regions of the reception space.
Each time the pusher reaches its detection position, the latter is preferably immobilised until determination by the detection means of the absence of obstacles inside the regions of the reception space.
Furthermore, the determination of the presence of obstacles inside the regions of the reception space by the detection means causes the stoppage of displacements of elements of the device.
As explained above, a substrate-splitting device is used for splitting various types of substrates that include two adjoining wafers defining between them a cleavage plane.
These substrates 2 are arranged on a support 8 shown in
Other complementary handling means (not shown) of substrates or of wafers resulting from the splitting of the substrates, are also provided, especially to feed the splitting device with substrates, and to evacuate the wafers that are detached or split from the substrates. These handling means are generally known and can be for example of FOUP type (Front Opening Unified Pod) or of FOSB type (Front Opening Shipping Box).
In this illustration, the first workstation ST1 of a substrate-splitting device 1 is designed to house a support 8 which can contain a plurality of substrates 2. A typical capacity of the support 8 is for example 25 to 50 substrates (
The substrates have a diameter of a few hundreds of millimetres, typically 300 mm. The substrates 2 are aligned in the support 8 according to a substrate-storage direction Y so that the faces of the substrates 2 are perpendicular to the direction of storage Y. Here, too, the rear face of a substrate is the face opposite to the active face, on which specific treatments (e.g., the constitution of optical or electronic structures, etc.) are to be made.
Housings uniformly distributed according to the direction of storage of the substrates are provided to this effect in the support 8, so that the substrates 2 are distributed uniformly according to a given reference pitch. The support 8 can be displaced by means of a mobile trolley 13 moving in the longitudinal direction Y to bring in and withdraw the support 8 of the first workstation ST1. The support 8 can originate directly from an oven in which the substrates 2 have undergone thermal treatment in light of causing or preparing the cleavage of each substrate into two wafers (typically a SOI or SOA wafer, and a silicon residue wafer).
As indicated above, the cleavage of these substrates 2 into two wafers must be finalized (that is, the two wafers must now split from one another). An assembly 12 of splitter means is represented at the level of the second workstation ST2, comprising apart from splitter means such as a separator, handling means for substrates, for example combs 121, 122.
A pusher 5, which is retracted in
The assembly 12 of substrate-splitter means is mounted for example on rails which run parallel to the direction X, with control means of the displacement of this assembly 12 being provided. Also, the splitter means assembly 12 comprises substrate-handling means or wafers in the form of combs 121, 122.
Thus, the assembly 12 of splitting means can be used for the handling of substrates or wafers, especially for the displacement of the latter from the support 8 to additional handling means (not shown) of FOUP type or of FOSB type by means of a carrier and an articulated arm. In the case of the use of FOUP, the FOUP containing a plurality of substrates in a horizontal position is brought near an articulated robotic arm of SCARA type (acronym for selective compliance assembly robot arm). The articulated robot moves the substrates from the FOUP to a tiltable carrier (not shown). The carrier tilts, with the substrates being in a vertical position, that is resting on their respective edge.
The combs 121, 122 of the assembly 12 are used to handle the substrates. The pusher 5 lifts the substrates to bring them to the level of the combs 121, 122. The combs 121, 122 then hold the substrates and the assembly 12 is displaced laterally according to the direction X to be positioned at the level of the support 8 on the first workstation ST1. The pusher 5, which accompanies the displacement of the assembly of the splitter means 12, is now also positioned at the level of the first station ST1. The pusher 5 is lifted up in the direction Z across of the support 8 and comes into contact with the substrates 2 to support them, while the combs 121, 122 of the assembly 12 release the substrates 2. The pusher 5 supporting the substrates 2 now redescends and in its movement deposits the substrates 2 on the support 8.
A similar handling process is carried out in the reverse direction during splitting of the substrates 2, after treatment to produce at least partial cleavage between the wafers.
As illustrated in
Such a profile section 6 of the pusher allows the latter to keep the substrates in a substrate-reception space 2 on the pusher 5. This reception space extends in the space located above the substrate-handling face comprising the upper face of the zones 7, on the opposite side of the base 51 of the pusher.
The position of each substrate 2 or wafer relative to the pusher 5 is automatically adjusted by cooperation of forms, the housings of the pusher 5 also being sufficiently adjusted to keep the substrates or the wafers in a vertical position. At the level of the first station ST1, the pusher 5 can also redescend with substrates or wafers, and deposit these substrates or wafers in the support 8, as it passes downwards through the openings of the structural elements of the support 8, the support 8 intercepting the substrates or wafers by arranging them in housings, while the pusher 5 continues its course downwards until it is retracted in the base 11. The same applies at the level of the second station ST2 with the carrier or any other substrate-handling means.
The operation starts from a situation in which:
the support 8 contains substrates 2 which have undergone cleavage (the cleavage having to be done mechanically, or not—in any case, according to the invention the two wafers will be split from each substrate) and is in the station ST1,
the assembly 12 of splitter means and the pusher 5 are opposite and vertical to the station ST1 (following displacement adapted according to the direction X of the
the splitter means 12 comprise symmetrical combs which are spread and opened; the ascension of the pusher 5 is the first to be controlled.
The pusher 5 gathers the substrates 2, each substrate 2 being received by a housing of the pusher 5 (located under the substrate for this purpose, the housings having also V-shaped slopes for forming a funnel and collecting a substrate). The pusher in position at the level of the station ST1 raises the substrates to a high position, in which the center of the substrates is at the height of the combs 121, 122 of the assembly 12, in the position illustrated in
The combs 121, 122 then engage in the substrates 2. The substrate-splitter means split the substrates. These splitter means comprise at least one separator, for example in the form of a blade engaging in the cleavage plane between the adjoining wafers. This separator is tightened on each substrate to carry out the splitting of the two wafers of each substrate and their separation, as explained in detail in patent EP 1 423 244. The pusher 5 holds the lower part of the substrates 2 during the splitting of the wafers.
Once the splitting is completed, the pusher 5 is taken back down empty and is retracted in the base 11, so that the wafers coming from the splitting of the substrates 2 are held just by the combs 121, 122 of the assembly 12. The assembly 12 of the splitter means is then displaced according to the direction X of
Means for handling wafers are placed at the level of the station ST2. These handling means are adapted to accommodate and hold wafers or substrates and the pusher 5 is capable of passing through structural elements of the handling means. In reference to the above example, this can be the tiltable carrier (not shown). The ascension of the pusher 5 is then controlled so that the latter comes into contact with the lower edge of the wafers by passing through the handling means. In this position, the pusher 5 supports the wafers. The combs 121, 122 of the assembly 12 then release the wafers so that the wafers are held by the pusher 5 only.
The pusher 5 and the wafers which it supports are then brought down. The pusher 5 passes downwards through the openings of the structural elements, the support 8, the support 8 intercepting the wafers by arranging them in housings, while the pusher 5 continues its course down until it is retracted in the base 11.
The combs 121, 122 can be adapted to release the wafers in several steps, for example just the wafers comprising the active faces of the substrates in a first step, then the other wafers, or vice versa. In this case, the same handling using the adapted handling means and the pusher 5 is carried out for each one of the steps.
It has been discovered during research aimed at optimizing the yield of the splitting process of substrate wafers that a significant reliability problem resulted from the breaking of substrate wafers. In fact, since the substrate wafers are subjected to varied mechanical and thermal stresses, the latter can break and damage the device. In the case of breakage of a substrate wafer before, during or after splitting, debris of various sizes then occur in the operating perimeter of the machine. The debris can be found on the pusher, more precisely on the handling face of substrates of the pusher. It can then happen that the debris prevents proper receipt of the substrates by the pusher in the substrate-reception space, which translates into misplaced substrates which cannot be split or which break in turn.
Also, the presence of these debris on the pusher can damage the base 11. In fact, the pusher can have to move laterally from one workstation to another. During these displacements, the pusher moves into a retracted position in the base 11, and moves laterally under plates 14 forming support for the support 8, to be positioned in the opening of another workstation to support the substrates or the wafers. Any possible debris present in the reception space can protrude into the reception space of the pusher and encounter part of the base 11 or structural elements, such as the support 8, during lateral displacement of the pusher from one workstation to another. This encounter can result in alteration of the handling face of the pusher 5, damage to the base 11 or structural elements, or even in deterioration of the displacement or control system of the pusher 5 resulting from the resistance opposed by the debris to displacement of the pusher 5.
The device 1 according to the present invention has detection means 9 adapted to determine the absence or the presence of obstacles inside at least one region of the reception space of the pusher 5 when the pusher 5 is in a detection position, this region being located near the handling means for substrates. These detection means are solid with the base 11 and are placed at the level of at least one workstation ST1, ST2, preferably the first station ST1, even though they can be placed at the level of each of the stations ST1, ST2.
For example, a transmitter 91 can send an electromagnetic wave beam 10 of laser beam type which is received by the receiver 92 to which it is associated, thus determining the absence of obstacles in the reception region defined by the trajectory of the laser beam. The presence of an obstacle, such as substrate debris, in this detection region, would prevent receipt of the laser beam by the receiver 92. Non-receipt of the laser beam by the receiver 92 determines the presence of obstacles in the region of the reception space.
A transmitter 91 and a receiver 92 associated with the transmitter 91 can be placed according to the longitudinal direction Y of the pusher, on either side of an opening 96 through which the pusher passes. These detection means 9 can be placed on a structure 95 which is fixed on the base 11 of the device 1, making the detection means solid with the base. The detection means 9 can also be covered by a hood 97 for protection.
The detection position of the pusher 5 is located between a retracted position of the pusher 5 in the base 11 and a high position in which the pusher 5 supports the substrates 2. The position of the pusher 5 when the latter is located between the detection means 9 defines a detection position of the pusher 5. A single one of the workstations can be fitted with detection means 9, preferably the first station ST1 where splitting takes place and where the substrates or wafers are the most likely to break. There is preferably a detection position for each of the workstations ST1, ST2, each of these being fitted with detection means 9.
More precisely, the pusher 5 is in a detection position when the beams 10 of electromagnetic waves pass through a region of the reception space of the pusher 5, the region being located near the substrate-handling means 52. The detection region must preferably be sufficiently close to the substrate-handling means 52 so that debris of a sufficient size to alter the handling of the substrates or the displacement of the pusher 5 and which would rest on the handling means 52 of the pusher 5, is at least in part in the detection region.
The detection means 9 are preferably activated only when the pusher 5 is in a detection position.
As explained earlier and illustrated in
The invention according to a second aspect relates to a control process of the device 1, in which, apart from the steps mentioned earlier, comprises a step according to which the pusher 5 is immobilised in its detection position until determination of the absence of obstacles inside the regions of the reception spaces 53 by the detection means 9.
Each time the pusher 5 reaches its detection position, it is preferably immobilised until determination of the absence of obstacles inside the regions of the reception spaces 53 by the detection means 9.
Furthermore, the determination of the presence of obstacles inside the regions of the reception spaces 53 by the detection means 9 causes the stoppage of the displacements of elements of the device 1.
Because of this, any debris, for example a piece of silicon, which might cut one or more beams 10, stops all movement of the splitting device 1, preventing any damage and alerting the user of the splitting device 1 of the necessity of cleaning the debris.
While the foregoing description details preferred embodiments, a skilled artisan will recognize many additional modifications and applications of the invention, all of which are deemed to be within the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1154510 | May 2011 | FR | national |
