METHOD AND DEVICE FOR BONDING SUBSTRATES

Abstract

A substrate holder for curving a substrate the substrate holding including a fixing plate for fixing the substrate, curving means for curving the fixing plate, wherein the fixing plate is constituted such that the curvature of the substrate can be adjusted in a targeted manner, as well as a corresponding method.

Claims

1-12. (canceled)

13. A substrate holder for curving a substrate, said substrate holder comprising: a fixing plate for fixing the substrate; and curving means for curving the fixing plate, wherein the fixing plate is comprised such that curvature of the substrate is adjustable in a targeted manner, and wherein the fixing plate is mounted in a hinged manner.

14. The substrate holder according to claim 13, wherein thickness of the fixing plate varies.

15. The substrate holder according to claim 13, wherein a homogeneous curvature of the substrate is adjustable.

16. The substrate holder according to claim 13, wherein a rear side of the fixing plate is formed such that a homogeneous curvature of the fixing plate results.

17. The substrate holder according to claim 13, wherein reaction forces produced during the curving of the fixing plate can be compensated by at least one compensation means.

18. The substrate holder according to claim 17, wherein the at least one compensation means is a curvable compensation plate.

19. The substrate holder according to claim 13, wherein the fixing plate is thicker in the centre of the fixing plate than at the edge of the fixing plate.

20. The substrate holder according to claim 13, wherein the fixing plate is formed tapered towards the edge of the fixing plate.

21. The substrate holder according to claim 13, wherein the fixing plate is formed symmetrically with respect to the centre of the fixing plate.

22. A bonding device comprising at least one substrate holder according to claim 13.

23. A method for bonding first and second substrates, comprising the following steps, fixing the first substrate on a first substrate holder according to claim 13; fixing the second substrate on a second substrate holder according to claim 13; aligning the first and second substrates with respect to one another, wherein at least one of the first and second substrates is curved; bringing the first and second substrates into contact with each other; adjusting curvature of at least one of the first and second substrates in a targeted manner.

24. The method according to claim 23, wherein the curvature of at least one of the first and second substrates is adjusted homogeneously.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0138] FIG. 1a shows an initial state of a substrate holder in the prior art,

[0139] FIG. 1b shows a final state of a substrate holder in the prior art,

[0140] FIG. 2a shows an initial state of a substrate holder according to the invention without a compensation plate,

[0141] FIG. 2b shows a final state of a substrate holder according to the invention without a compensation plate,

[0142] FIG. 3a shows an initial state of an extended substrate holder according to the invention with a compensation plate,

[0143] FIG. 3b shows a final state of an extended substrate holder according to the invention with a compensation plate,

[0144] FIG. 4 shows a first embodiment according to the invention of a substrate holder according to the invention with a compensation plate,

[0145] FIG. 5 shows a second embodiment according to the invention of a substrate holder according to the invention with a compensation plate,

[0146] FIG. 6a shows a third, preferred embodiment according to the invention of a substrate holder with a compensation plate in a side and plan view in an initial state,

[0147] FIG. 6b shows a third, preferred embodiment according to the invention of a substrate holder with a compensation plate in a side view in a final state.

[0148] Identical components and components with the same function are denoted with the same reference numbers in the figures.

DETAILED DESCRIPTION OF INVENTION

[0149] The following two descriptions of the figures and their respective figures, which show two states of a substrate holder in the prior art, are kept as general as possible in order to illustrate the basic concept. It concerns a description that is as simple as possible and schematic diagrams, with no claim to completeness.

[0150] FIG. 1a shows a diagrammatic representation of an initial state of a substrate holder 1 in the prior art, the fixing plate surface 3f whereof can be curved. Substrate holder 1 comprises a fixing plate 3, which can be mounted in particular by means of a plate bearing 2, in particular at the periphery. In the present case, plate bearing 2 is in particular a fixed bearing, which in particular is also not designed hinged. It would of course also be conceivable for fixing plate 3 to be connected mechanically directly to the remainder of substrate holder 1. It is important that there is a surface described as fixing plate surface 3f, which can be curved. Fixing plate 3 is therefore designed and/or mounted such that it can be curved.

[0151] In particular, substrate fixings 4 are present on plate 3, with the aid of which a substrate 7 can be fixed on plate 3. As to how substrate fixings 4 are controlled, this is not relevant for an understanding of the device from the prior art and will not be explained in greater detail here.

[0152] FIG. 1b shows a diagrammatic representation of a final state of a substrate 1 in the prior art. In this special case, substrate holder 1, when viewed from outside, is curved in a convex manner, because an overpressure is built up in hollow 5. The overpressure arises due to the fact that, via an adjustment means 6, in the special case an opening, a valve or a nozzle, a gas or gas mixture with an overpressure relative to the surrounding atmosphere flows into hollow 5. Adjustment means 6 can alternatively be a mechanical adjustment means. The use of an overpressure is thus described here merely by way of example.

[0153] In this state, a number of fundamental problems arise. The first problem is that the curvature of fixing plate surface 3f, and therefore also of substrate 7, is generally inhomogeneous, i.e. the curvature changes, generally with the location. This is a generally undesired state. The inhomogeneity of the curvature can only be detected with difficulty in the figure. This problem is thus primarily connected with the fact that bearings 2 are designed as fixed bearings, i.e. the number of degrees of freedom is too small or even zero.

[0154] Bearings 2, which are usually designed such that they can transfer reaction forces and/or moments to fixing plate 3, are therefore a further problem in the prior art. In particular, bearings 2 in the prior art are not designed hinged. Bearings 2 in the prior art are therefore usually capable of transferring a moment.

[0155] A further problem is that an arbitrary adjustment element 6, which is responsible for the deformation of fixing plate 3, always produces a counterforce. Generally speaking, and expressed in physical terms, according to Newton's third law a counterforce arises, standardised to the area a corresponding counter-pressure, which bends substrate holder 1 in the other direction. This undesired curving of substrate holder 1 retroacts in particular on plate bearing 2 and thus also influences the curving behaviour of fixing plate 3, as well as the curving of substrate 7 fixed on fixing plate 3.

[0156] This is connected with the aforementioned problem that plate bearing 2 in the prior art is designed such that reaction forces and/or moments can be transferred. Even if a final state is adjusted in control-related terms, a retroaction via substrate holder 1 can be found, which is absolutely undesired, since measurements have shown that a bonding result to be implemented is thus made worse. It is explicitly mentioned and emphasised that the aforementioned mechanical retrocoupling effects obviously do not depend on the type of adjustment means 6, in the present illustrative case an opening through which a gas or a gas mixture flows, just as little as on the presence of a hollow 5.

[0157] Adjustment means 6 can just as well be a mechanical adjustment means, a pin, piezo pile, a bellows or any other adjustment means which can curve fixing plate 3. In these cases, there would probably also be no corresponding hollow 5. The fundamental physical law always demands that a mechanical retrocoupling takes place on the substrate holder.

[0158] The following descriptions of the figures and/or the figures, which each show two states of two substrate holder's 1′, 1″ according to the invention, are kept as general as possible, in order to illustrate the basic concept. It concerns a description that is as simple as possible and schematic diagrams, without any claim to completeness. The embodiments according to the invention are then described in greater detail in further figures.

[0159] The inventive idea is again illustrated with the aid of a device, in which a fluid is used in order to create an overpressure in hollow 5, which curves fixing plate 3 on which substrate 7 is fixed. It is again emphasised that the inventive idea is not bound to the use of a fluid and/or a hollow 5. The inventive aspect could be implemented just as well with the aid of mechanical, pneumatic, electrical, piezoelectrical adjustment means 6, as will subsequently be shown and demonstrated in special embodiments.

[0160] FIG. 2a shows a diagrammatic representation of an initial state of a substrate holder 1′ according to the invention with which at least one homogeneous curvature can be adjusted. It is assumed that substrate 1′ has such a great bending resistance that the problem of the mechanical retrocoupling, the elimination or reduction of which is described in greater detail in subsequent figures, does not yet occur here. An increase in the bending resistance can for example be achieved very easily, in that several components of substrate holder 1′, in particular substrate holder 1′ as a whole, are designed thicker. Bearing 2′ is important, which is produced such that no or only very small reaction forces and/or moments are transferred to fixing plate 3. In particular, the shape of hollow plate surface 3h is selected such that subsequent curving of fixing plate 3 produces a well-defined, in particular homogeneous, curvature.

[0161] FIG. 2b shows a diagrammatic representation of a final state of a substrate holder 1′ according to the invention, with which at least one homogeneous curvature can be adjusted. Even if substrate holder 1′ according to the invention has a higher bending resistance, it must nonetheless, even though only to a small extent, also be slightly curved when an adjustment means 6 is used. This curvature is however relatively small on account of the relatively high bending resistance. Nonetheless, forces and/or moments arise, which would be transferred to fixing plate 3 without bearing 2′.

[0162] By means of special bearing 2′, a still well-defined, in particular homogeneous, curvature on fixing surface 3f and therefore substrate 7 can be adjusted, since possible reaction forces and/or moments are not transferred, or are so only to a small extent, to fixing plate 7. Bearing 2′ assists the formation of a homogeneous curvature in addition to the components already produced in a solid construction. In the special case, an adjustment means 6 is used to adjust the curvature, wherein it is an opening, a nozzle or a valve, to which a fluid, in particular a gas mixture, preferably air, is pressed.

[0163] Through the use of a fluid, the embodiment according to the invention with the specially shaped hollow plate surface 3h acquires particular significance. Through the use of a fluid, which exerts a homogeneous and isotropic pressure on hollow plate surface 3h, a force distribution assumed along hollow plate surface 3h in which the forces are always normal to hollow plate surface 3h can be assumed.

[0164] On this assumption, it is particularly easy with the aid of numerical simulations, in particular finite elements methods, to calculate a suitable shape of hollow plate surface 3f, in order to obtain the desired, in particular homogeneous, curvature on fixing surface 3f, and therefore on fixed substrate 7. Such a special shape of hollow plate surface 3f improves still further the formation of a homogeneous curvature of fixing plate surface 3f and therefore of substrate 7.

[0165] FIG. 3a shows a diagrammatic representation of an initial state of a further improved substrate holder 1″ according to the invention, with which at least one homogeneous curvature can be adjusted and with which harmful influences of mechanical retrocoupling on plate holder 2′ can be further minimised. Such an improvement according to the invention is especially advantageous when substrate holder 1″ has been designed relatively thin and has a very small bending resistance.

[0166] The mechanical retroaction can then no longer be ignored and should at least be reduced, preferably completely eliminated, by the improved embodiment according to the invention. The advantages of the specially shaped hollow plate surface 3h will not be dealt with further here. Substrate holder 1″ comprises a fixing plate 3 and a compensation plate 3′, which are mounted by means of a plate bearing 2′. Plates 3, 3′ are designed and/or mounted such that they can be curved.

[0167] For the sake of completeness, it is mentioned that plate 3, from the theoretical viewpoint, must not be an independent component, but could rather be part of substrate holder 1′. Only the presence of a fixing plate surface 3f is important.

[0168] However, boundary conditions would thus arise, which make the production of a constant curvature of fixing plate surface 3f almost impossible. The most preferred embodiment according to the invention thus makes provision such that fixing plate 3 represents an independent component. The inventive effect is thus primarily in the use of a compensation plate 3′.

[0169] In the subsequent description of the figures, therefore, each embodiment according to the invention is represented with the preferred design-related solution of two plates. In particular, substrate fixings 4 are located on fixing plate 3, with the aid of which a substrate 7 can be fixed on fixing plate 3. As to how substrate fixings 4 are controlled, this is not relevant for an understanding of the device and will not be explained further here. It is shown in the following figures how substrate fixings 4, which are constituted as vacuum fixings, are controlled.

[0170] FIG. 3b shows a diagrammatic representation of a final state of further improved substrate holder 1″ according to the invention. By means of an adjustment means 6, in the present special case an opening, a valve or a nozzle, a fluid is pressed into a hollow 5, which leads to curving of the two plates 3, 3′. In contrast with the prior art according to figure la, no curving of fixing 2 or other parts of substrate holder 1′ takes place and therefore no additional moment, acting by fixing 2, arises on fixing plate 3 and substrate 7 fixed thereon. The curving of fixing plate 3 thus takes place only through the effect of adjustment means 6.

[0171] Compensation plate 3′ can thus be regarded as a kind of “sacrificial plate”, the sole purpose of which is preventing or at least minimising the force effect on the remaining components of substrate holder 1′. In the special case, plates 3, 3′, in particular at their periphery, must be sealed. The representation of the details, in particular of the seal, is dispensed with for the sake of clarity in this schematic diagram. The seal will however be dealt with in greater detail and a subsequently represented figure of the most preferred embodiment.

[0172] In the further figures, the different embodiments according to the invention are dealt with and represented individually and in detail.

[0173] FIG. 4 shows a first, preferred embodiment according to the invention, wherein the two plates 3, 3′ are set as an electrical potential with the same sign, in particular the same value. In order to prevent the two plates 3, 3′ forming an electrically conductive self-contained body, plate 3, 3′ must be electrically insulated from one another at their contact points by means of electrical insulation 14. Otherwise, according to the laws of physics, all the charges at hollow plate surfaces 3h, 3h′, which form hollow 5, would migrate outwards.

[0174] The self-contained body would form a Faraday cage and would enable the storage of charge only at the outer side. Electrical insulation 14 ensures that the two plates 3, 3′, from the electrostatic viewpoint, do not form a self-contained conductive body, but each form a conductive body. The generation of charges at the substrate surfaces, which form hollow 5, is thus possible. The charges present on hollow plate surfaces 3h, 3h′ or the two plates 3, 3′ themselves accordingly represent, together with required electric circuit 15, adjustment means 6′.

[0175] FIG. 5 shows a second, preferred embodiment according to the invention, wherein an adjustment means 6″ is present between the two plates 3, 3′. Adjustment means 6″ can for example be an electrically and/or pneumatically and/or hydraulically controllable mechanical adjustment means. The use of an electrically controllable piezo pile would also be conceivable. Adjustment means 6″ could also be two very strong electric magnets, which create two magnetic fields in an electrically controlled manner and thus repel one another, so that the two plates 3, 3′ are driven apart. An embodiment would also be conceivable in which two plates are set at the same electrical potential and repel one another due to their electrostatic charge.

[0176] FIG. 6a shows the third preferred embodiment according to the invention in a side view, a detailed view and a plan view in an initial state. This embodiment according to the invention is an embodiment from FIGS. 3a and 3b described in very much more detail. The representation comprises (i) the specially produced bearing 2′, via which almost no or only very small reaction forces and/or moments can be transferred, as well as (ii) compensation plate 3′.

[0177] The importance of this embodiment is based primarily on the fact that a fluid is used for curving the two plates 3, 3′, which on account of a static pressure has an isotropic, i.e. uniform force effect on the two plates 3, 3′, but in particular fixing plate 3. All the aforementioned features in FIG. 6a can in particular also be used in the previously mentioned and dealt-with substrate holders of FIGS. 3 and 4. On account of the importance of this embodiment, they are however described in detail in this figure.

[0178] Fixing plate surface 3f of fixing plate 3 is preferably mounted or contacted at its periphery via a plate bearing projection 2′v and plate surface 3h of fixing plate 3 via a seal 12. Seal 12 again preferably lies on lower compensation plate 3′, and in particular on a plate bearing platform 2′p. Seal 12 seals the peripheries of plates 3, 3′ against one another and nonetheless permits the curving of the two plates 3, 3′.

[0179] At this point, it is mentioned once again that the curvatures are extremely small, i.e. the radii of curvature are very large. A point on an arbitrary surface of one of the two plates 3, 3′ is displaced in the z-direction by only some few nanometres, micrometres, but in the rarest cases by millimetres. Such small curvatures also make it possible to keep such a delicate structure mechanically stable. In particular, plate bearing projection 2′v can be constituted very fine.

[0180] Substrate 7 is fixed by substrate fixing 4. In the special case, the drawing shows that the parts of substrate fixing 4 extend through hollow 5. These parts are in particular constituted expandable. It can for example be a hose, a fed-in tube or any other line which is capable of evacuating the region between substrate 7 and fixing plate 3. In particular, there are a plurality of outlet openings of substrate fixing 3, which are arranged in particular symmetrically about the centre. It is thus made possible for a pin 11 to be located in the centre of fixing plate 3, which has a favourable effect on the bonding behaviour.

[0181] FIG. 6b shows the third, preferred embodiment according to the invention in a side view in a final state. Adjustment means 6, in this special case a non-concentric opening, a valve or a nozzle, pumps a fluid into hollow 5. Fixing substrate 3 is curved according to the invention. The curving of compensation plate 3′ preferably takes place up to a groove 13, which is introduced into compensation plate 3′ around the entire circumference.

[0182] The curving is thus concentrated on the central part of compensation plate 3′ and it is ensured that a still smaller moment and/or a still smaller force acts mechanically on plate bearing 2′, which in this case is comprised especially of a plate bearing projection 2′v, a seal 12 and a plate bearing platform 2′p (see enlarged view in FIG. 6a). As a result of this further design-related improvement according to the invention, a mechanical retrocoupling on fixing plate 3 is completely prevented or at least minimised to an extent such that it is negligible.

LIST OF REFERENCE NUMBERS

[0183] 1,1′,1″,1′″ Substrate holder [0184] 2, 2′ Plate bearing [0185] 2′v Plate bearing projection [0186] 2′p Plate bearing platform [0187] 3 Fixing plate [0188] 3′ Compensation plate [0189] 3f Fixing plate surface [0190] 3h, 3h′ Hollow plate surface [0191] 4 Substrate fixing [0192] 5 Hollow/intermediate space [0193] 6, 6′, 6″ Adjustment means/curving means [0194] 7 Substrate [0195] 11 Pins [0196] 12 Seal, in particular sealing ring [0197] 13 Groove [0198] 14 Electrical insulation [0199] 15 Electric circuit