Method and device for bonding substrates

Abstract

A method and corresponding device for bonding a first contact surface of a first substrate to a second contact surface of a second substrate. The method includes the steps of arranging a substrate stack, formed from the first substrate and the second substrate and aligned on the contact surfaces, between a first heating surface of a first heating system and a second heating surface of a second heating system.

Claims

1. A bonding device for bonding a first substrate to a second substrate, the bonding device comprising: a first chuck configured to hold the first substrate and/or apply pressure to the first substrate, the first chuck including a first surface configured to contact a substrate surface of the first substrate; a second chuck configured to hold the second substrate and/or apply pressure to the second substrate, the second chuck including a second surface configured to contact a substrate surface of the second substrate, at least one of the first surface and the second surface being formed by a plurality of protrusions; flow channels located between the protrusions of the least one of the first surface and the second surface; a gas supply configured to introduce gas into the flow channels to provide convective and/or conductive heating; and an arm bounding an entire radial peripheral area of the protrusions of the at least one of the first surface and the second surface, the arm including a passage configured to control leakage of an excess amount of the introduced gas from the flow channels.

2. The bonding device according to claim 1, wherein the second surface is formed by the protrusions, said second surface being less than 90% of the substrate surface of the second substrate.

3. The bonding device according to claim 1, wherein the flow channels have a depth of less than 1 mm relative to the first and/or second surfaces.

4. The bonding device according to claim 1, wherein the plurality of protrusions includes at least 50 of the protrusions.

5. The bonding device of claim 1, wherein the protrusions are equally-distributed.

6. The bonding device according to claim 1, wherein the first surface is formed by the plurality of protrusions, said first surface being less than 90% of the substrate surface of the first substrate.

7. The bonding device according to claim 1, wherein diameters of the first and second surfaces are respectively less than diameters of the first and second substrates.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1a a diagrammatic overview of a first embodiment of a vacuum cluster with specifically two attached modules,

(2) FIG. 1b a diagrammatic overview of a second embodiment of a vacuum cluster with seven attached modules,

(3) FIG. 2 a diagrammatic cross-section of an embodiment, according to the invention, of a bonding system before the loading of a substrate stack,

(4) FIG. 3 a diagrammatic cross-section of the embodiment according to FIG. 2 when placing the substrate stack on loading pins,

(5) FIG. 4 a diagrammatic cross-section of the embodiment according to FIG. 2 in the case of the removal of a robot arm from the substrate stack,

(6) FIG. 5 a diagrammatic cross-section of the embodiment according to FIG. 2 in the case of the removal of the robot arm from the module,

(7) FIG. 6 a diagrammatic cross-section of the embodiment according to FIG. 2 with symmetrical heating of the substrate with two heating systems,

(8) FIG. 7 a diagrammatic cross-section of the embodiment according to FIG. 2 in the case of the symmetrical approaching of the heating systems relative to the substrate stack,

(9) FIG. 8 a diagrammatic cross-section of the embodiment according to FIG. 2 in the case of the symmetrical approaching of the heating system relative to the substrate with contact of the first heating system with parts of the loading pins according to the invention,

(10) FIG. 9 a diagrammatic cross-section of the embodiment according to FIG. 2 when the substrate stack is brought into contact symmetrically,

(11) FIG. 10 a side view of a cross-section of the surrounding area of a studded bond chuck and a studded pressure plate,

(12) FIG. 11 a top view of a studded bond chuck according to the invention, and

(13) FIG. 12 a top view of a studded pressure plate according to the invention.

(14) In the figures, the features that are the same or that have the same effect are identified with the same reference numbers.

DETAILED DESCRIPTION OF THE INVENTION

(15) FIG. 1a shows a diagrammatic overview of a unit 38 that is designed in particular as a vacuum cluster, preferably as a high-vacuum cluster. The unit 38 is comprised of precisely two modules attached to a vacuum transfer chamber 4, a module with an alignment system 1 and a module with a bonding system 6 according to the invention. A robot 34 that is designed in particular as a process robot draws substrates 35, 36 (identical here) from a loading container 39 and transports the first substrate 35 and the second substrate 36, in particular at the same time, along a vacuum transfer section 5 into the alignment unit 1. The loading container 39 can also in particular be a lock or can act as such. The two substrates 35, 36 are aligned with one another and are attached, in particular temporarily, on a first contact surface 35k of the first substrate 35 and a second contact surface 36k of the second substrate 36 to form a substrate stack 14. As an alignment unit, for example, the units from the patent specifications PCT/EP 2013/075831 or PCT/EP 2013/062473 could be used. An optimal alignment is then provided when the structures that are to be aligned with one another, in particular also the alignment marks, optimally fit into one another according to the overlay model known in the industry. A corresponding description of such an overlay model is found in the patent specification PCT/EP 2013/061086.

(16) Then, the robot 34 transports the attached and aligned substrate stack 14 in the bonding system 6, in particular by receiving the first substrate 35 on a first surface 35o or the second substrate 36 on a second surface 36o. The surfaces 35o, 36o are in each case facing away from the contact surfaces 35k, 36k.

(17) The unit 38′ according to FIG. 1b shows a vacuum cluster that is comprised of several modules connected by a vacuum transfer chamber 4′. The modules may differ from one another in their functionality. In particular, modules for heating or cooling substrates or substrate stacks, purification modules, plasma modules, enameling modules with centrifugal enameling devices or spray-enameling devices, bonders 1 and debonders, coating modules, and alignment modules 6 are conceivable. The modules are preferably arranged in a circular or star-shaped manner around a vacuum transfer chamber 4′.

(18) The vacuum transfer chamber 4′ is connected via valves 2 to the various modules. The modules as well as the vacuum transfer chamber 4′ can be evacuated independently of one another by the valves 2, but are always preferably located on the same vacuum level, preferably the high-vacuum level of the bonding system 6.

(19) The bonding system 6 is depicted in FIGS. 2 to 9 in various processing states. The bonding system 6 is designed on a static supporting structure 23 in the form of a base plate and on columns attached to the base plate. The bonding chamber 10 is attached to the columns.

(20) The bonding chamber 10 has a chamber opening 6o that can lock with the valve 2 for loading the bonding chamber 10.

(21) The valve 2 is formed from a lock drive 24, in particular in the form of an actuator, supported on the base plate. The lock drive 24 serves to open and close a floodgate 27 that is driven by the lock drive 24, a floodgate that opens and closes the chamber opening 6o by a slot 6s. The valve 2 has seals 28 for sealing the bonding chamber 10 against the surrounding area in the closed state of the valve 2.

(22) In addition, the bonding system 6 comprises a receiving system 18 for receiving the substrate stack 14. The receiving system 18 comprises a substrate base with a base plane E, on which the substrate stack 14 is laid down with the second surface 36o, so that the second surface 36o lies in the base plane E.

(23) The substrate base is formed by at least two loading pins 21, in the embodiment shown four loading pins 21, running through the bonding chamber 10. The bonding chamber 10 is sealed by seals 20 surrounding the loading pins 21 relative to the surrounding area of the bonding chamber 10. The seals 20 simultaneously serve for sliding, translatory guiding of the loading pins 21.

(24) The latter are attached on an in particular common adjustment plate 21p on the ends of the loading pins 21 opposite the substrate base. The loading pins 21 are preferably coupled to one another mechanically by the adjustment plate 21p and are moved in a translatory manner crosswise to the base plane E by an adjustment drive 22 that acts in particular centrically on the adjustment plate 21p, an adjustment drive 22 preferably in the form of a single loading pin actuator, or as an alternative by means of several loading pin actuators.

(25) Within the loading pins 21, a second heating system 26 is arranged for heating the second surface 36o and an in particular full-surface, attached second pressure plate 25 on the second heating system 26. The second pressure plate 25 has a second heating surface 19, which can be arranged below the base plane E, parallel to the latter. The heating system 26 and the pressure plate 25 are connected securely to the bonding chamber 10 and are static, i.e., cannot move relative to the base plane E.

(26) Opposite to the second heating surface 19, a first heating surface 15 can be arranged parallel to the base plane E and above the latter. The first heating surface 15 is arranged on a first pressure plate 29, which in turn is attached to a first heating system 30, in particular on the full surface.

(27) The heating system 30 can be adjusted by drive means crosswise to the base plane. The heating system 30 is attached to an adjustment rod that runs through the bonding chamber 10. The adjustment rod is moved on the end opposite to the heating system 30 from a positional actuator 8 to control the position, in particular a separation distance A from the first heating surface 15 to the first surface 35o of the first heating surface 15. For pressurization, in particular after bringing the first surface 35o into contact with the first heating surface 15 and bringing the second surface 36o into contact with the second heating surface 19, a force actuator 9, which can apply the higher compressive force that is necessary for bonding, is used. The bonding chamber 10 is sealed by the seals 31, sealing the drive means, relative to the surrounding area.

(28) The drive means are suspended on a supporting structure 7, comprising of a cover plate and columns supporting the cover plate.

(29) The process according to the invention is described below based on FIGS. 2 to 9.

(30) In a first step according to the invention in accordance with FIG. 2, the robot 34 is moved, in particular transferred, with the substrate stack 14 into a bonding chamber 10 of the bonding system 6. In the first step, the receiving system 18 according to the invention is located on a starting level for receiving the substrate stack 14. In the starting level, the substrate stack 14 relative to the contact surfaces 35k, 36k is preferably positioned symmetrically to the first heating surface 15 and to the second heating surface 29. This symmetrical starting position is primarily important when the second pressure plate 25 and/or the first pressure plate 29 were preheated by the corresponding heating systems 26, 30 thereof.

(31) In a second step according to the invention in accordance with FIG. 3, the positioning of the substrate stack 14 is done in such a position that the attachments 11 for attaching the substrate stack, in particular magnetic clamps 11, with the heating surfaces 15, 19 subsequently being brought together, can be received precisely in recesses of the pressure plates 25, 29 provided for this purpose.

(32) In addition, attention must be paid that the substrate stack 14 is loaded and positioned as centrically as possible to the loading pins 21 in order to prevent sliding or slipping.

(33) In a third step according to the invention in accordance with FIG. 4, the robot 34 is removed from the substrate stack 14 so that the substrate stack 14 rests on the loading pins 21. The second top side 36o now lies in the base plane E.

(34) In a fourth step according to the invention in accordance with FIG. 5, the removal of the robot 34 from the bonding chamber 10 as well as the closing of the lock 27 are carried out. After the closing, the interior of the bonding system 6 can be evacuated via a pump 16 with a still higher vacuum should the vacuum prevailing in the adjoining vacuum transfer chamber 4 be set too low for the bonding process.

(35) In a fifth step according to the invention in accordance with FIG. 6, the symmetrical heating of the two surfaces 35o, 36o of the substrate stack 14 facing away from one another is now carried out. It would also be conceivable, of course, that the two heaters 26 and 30 were already set and were kept at bonding temperature before the insertion of the substrate stack 14, which reduces the heating time of the pressure plates 29, 30 and the heating systems 26, 30 virtually to zero.

(36) The heating is done by heat output produced by the heating systems 26, 30 and released over the heating surfaces 15, 19 as radiation heat 17.

(37) The idea according to the invention is shown in particular in this process step. By the symmetrical positioning of the substrate stack 14, the temperature fields above and below the substrate stack 14 can be set in a fully equivalent manner, provided that the two heating systems 26, 30 are controlled with the same output and the same parameters and the pressure plates 25, 29 have the same or at least very similar properties and geometries/dimensions.

(38) The substrate stack 14 is in particular not limited over the entire surface by a frictional force in its radial thermal expansion, but rather rests only peripherally on the loading pins 21. As a result, it can expand almost free-floating symmetrically, without stresses or bulges being caused.

(39) A further significant advantage is that the contact of the two substrates 35, 36 of the substrate stack 14 with two heating surfaces 15, 19 is avoided at least during the heating process.

(40) In a sixth step according to the invention in accordance with FIG. 7, the symmetrical approaching of the substrate stack 14 onto the second heating surface 19 and the first heating surface 15 is carried out. The second pressure plate 25 (in particular bond chuck) is in this case static and does not move. Rather, the loading pins 21 are moved by means of the loading pin actuators 22 onto the first heating surface 15. At the same time, the first heating surface 15 is moved to the second heating surface 19 or the substrate stack 14.

(41) In order to keep the separation distance A between the substrate stack 14 and the first heating surface 15 equal to the separation distance B between the substrate stack 14 and the second heating surface 19, the first heating surface is moved at twice the speed of the loading pins 21. Another speed profile would also be conceivable, however, in order to produce a specific separation function and thus temperature function on the substrate stack and thus an at least partially asymmetrical approaching.

(42) According to the invention, a reversal in which the first heating surface 15 is statically designed and the loading pins 21 as well as the second heating surface 19 move in the direction of the first heating surface 15 would also be conceivable.

(43) In a special embodiment, an in particular identically quick, reverse movement of the two heating surfaces 15, 19 in the case of static loading pins 21 would also be conceivable.

(44) In a seventh step according to the invention in accordance with FIG. 8, finally the heating surfaces 15, 19 are brought into contact with the substrate stack 14. The force that is applied in this connection by the positional actuator 8 is sufficient to press both substrates 35 and 36 on one another so strongly that the thus produced frictional force no longer allows a mutual shifting along the base plane E (frictional connection).

(45) The bonding system 6 can now be flushed with gas.

(46) Preferably, the gas is introduced by lines within the second pressure plate 25 and/or first pressure plate 29 and is distributed when using a first pressure plate 29 and/or second pressure plate 30 with studs 37 or an additional studded pressure plate 42, 42′, each applied on the pressure plates, between the studs 37 in the flow channels 32.

(47) Gas that is fed between the studs 37 can be held up by an arm 40 that is located on the studs 37 on the sides of the pressure plate 25, 29 and that extends over the entire radial side area. The arm seals in particular in a positive manner with the substrate 35, 36 to be processed on its peripheral side.

(48) In addition, it is conceivable to provide the arm 40 with a passage 41 that makes possible a controlled leakage of the excess gas from the studded surface. The passage 41 is advantageously smaller than 10 μm in diameter, preferably smaller than 7 μm, and more preferably smaller than 5 μm.

(49) If no studs 37 or studded pressure plates 42, 42′ are used, the gas is distributed by the existing surface roughness of the heating surfaces 15, 19, which replaces the studs 37.

(50) FIG. 12 shows a diagrammatic top view, not to scale, of the studded pressure plate 42, attached to the first pressure plate 29, with several studs 37 with a stud height H. The density of the studs 37 is kept very low in FIGS. 11 and 12 in order to increase clarity.

(51) Preferably, the studded pressure plates 42, 42′ in each case have at least 50, in particular regularly- and/or equally-distributed, studs 37, more preferably in each case at least 100, more preferably in each case at least 200, and more preferably in each case at least 400.

(52) FIG. 11 shows a diagrammatic sectional view according to the line of intersection A-A of FIG. 10 with the second pressure plate 25 with the studded pressure plate 42′. In this depiction, it is recognized that the entire surface of the substrates 35, 36 does not rest on the studs 37, thereby the probability of the contamination of the substrates 35, 36 is reduced.

(53) The separation distances A and B are reduced to zero, so that contact exists between heating surfaces 15, 19 of the studded pressure plates 42, 42′ and the surfaces 35o, 36o.

(54) TABLE-US-00002 List of Reference Symbols  1 Alignment system  2 Valves  4, 4′ Vacuum transfer chamber  5 Vacuum transfer section  6 Bonding system  6o Chamber opening  6s Slot  7 Supporting structure  8 Positional actuator  9 Force actuator 10 Bonding chamber, in particular vacuum chamber 11 Attachments 14 Substrate stack 15, 15′ First heating surface 16 Pump 17 Radiation heat 18 Receiving system, in particular substrate base 19, Second heating surface 19′ 20 Seals 21 Loading pins 21p Adjustment plate 22 Adjustment drive, in particular loading pin actuator 23 Supporting structure 24 Lock drive 25 Second pressure plate 26 Second, in particular lower, heating system 27 Valve 28 Lock seals 29 First pressure plate 30 First, in particular upper, heating system 31 Seals 32 Flow channels 34 Robot, in particular process robot 35 First, in particular upper, substrate 35k First contact surface 35o First surface 36 Second, in particular lower, substrate 36k Second contact surface 36o Second surface 37 Studs 38, Unit, in particular vacuum cluster, 38′ preferably high-vacuum cluster 39 Locks 40 Arm 41 Passage 42, Studded pressure plate 42′ A Separation distance B Separation distance E Base plane H Stud height