Device and method for bonding substrates

Abstract

A method for bonding a contact surface of a first substrate to a contact surface of a second substrate comprising of the steps of: positioning the first substrate on a first receiving surface of a first receiving apparatus and positioning the second substrate on a second receiving surface of a second receiving apparatus; establishing contact of the contact surfaces at a bond initiation site; and bonding the first substrate to the second substrate along a bonding wave which is travelling from the bond initiation site to the side edges of the substrates, wherein the first substrate and/or the second substrate is/are deformed for alignment of the contact surfaces.

Claims

1. A device for bonding of a first substrate to a second substrate on respective contact surfaces of the substrates, the device comprising: a first mounting apparatus configured to accommodate the first substrate on a first mounting surface, the first mounting apparatus being a lower mounting apparatus; a second mounting apparatus configured to accommodate the second substrate on a second mounting surface the second mounting apparatus being an upper mounting apparatus; contact means for bringing the contact surface of the first substrate into contact with the contact surface of the second substrate at a bond initiation site; fixing means for fixing the first substrate and/or the second substrate solely in a region of side edges of the substrates on the first and/or second mounting surfaces; and deformation means for deforming the first substrate and/or the second substrate for alignment of the contact surfaces outside the bond initiation site before and/or during the bonding, the deformation means comprising mechanical actuating means configured to mechanically actuate the first and/or second mounting apparatus, the mechanical actuating means comprising an actuating element of the first mounting apparatus, the actuating element being configured to actuate the first mounting surface of the first mounting apparatus to adjust a radius of curvature of the first mounting surface of the first mounting apparatus, wherein a radius of curvature of the first substrate and a radius of curvature of the second substrate deviate only marginally from each other at least in a region at which the contact surfaces are brought into contact at a bond front of a bonding wave.

2. The device as claimed in claim 1, wherein the radii of curvature of the substrates deviate from each other at the bond front less than 5%.

3. The device as claimed in claim 1, wherein the radii of curvature of the substrates are the same at the bond front.

4. The device as claimed in claim 1, wherein the deformation means is configured to encompass the first mounting apparatus, and wherein the first mounting apparatus is deformable on the first mounting surface in a lateral direction, convexly, concavely, or in a combination of one or more thereof.

5. The device as claimed in claim 1, wherein the deformation means is configured encompass the second mounting apparatus, and wherein the second mounting apparatus is deformable on the second mounting surface in a lateral direction, convexly, concavely, or in a combination of one or more thereof.

6. The device as claimed in claim 1, wherein the mechanical actuating means further comprises a pin of the second mounting apparatus, the pin being configured to mechanically actuate the second substrate to adjust the radius of curvature of the second substrate.

7. The device as claimed in claim 1, wherein the actuating element comprises a pull rod and/or a push rod configured to actuate the first mounting surface of the first mounting apparatus to adjust a radius of curvature of the first mounting surface of the first mounting apparatus.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic cross section of a first embodiment of the device as claimed in the invention,

(2) FIG. 2 shows a schematic cross section of a second embodiment of the device as claimed in the invention,

(3) FIG. 3 shows a schematic cross section of a third embodiment of the device as claimed in the invention,

(4) FIG. 4 shows a schematic cross section of a fourth embodiment of the device as claimed in the invention,

(5) FIG. 5 shows a schematic cross section of a fifth embodiment of the device as claimed in the invention,

(6) FIG. 6 shows a schematic of the method step of bonding as claimed in the invention,

(7) FIG. 7a shows a schematic of a bonded substrate pair with an alignment fault dx in the region of one side edge of the substrates,

(8) FIG. 7b shows a schematic enlargement of two substrates in the region of a bonding wave as claimed in the invention,

(9) FIG. 7c shows a schematic enlargement of two substrates without alignment faults/run-out faults,

(10) FIG. 7d shows a schematic enlargement of two substrates with alignment faults/run-out faults and

(11) FIG. 8 shows a symbolic representation of the possible overlay or run-out fault.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(12) In the figures, the same components and components with the same function are labeled with the same reference numbers.

(13) FIG. 1 shows a lower first mounting apparatus 1 as a substrate sample holder, which apparatus 1 is comprised of a base body 9 and a mounting body 2. The mounting body 2 has a first mounting surface 2o which is located to the top in the direction of an opposing second mounting apparatus 4. In the embodiment illustrated, first mounting surface 2o is convexly curved. The mounting body 2 is made interchangeable as a module and can be separated from the base body 9. The base body 9 is thus used as an adapter between the mounting body 2 and a lower mounting unit of the bonder (not shown). This makes it possible to carry out a prompt change between different modular mounting bodies 2 with different radii R of curvature if necessary.

(14) On the mounting body 2, there are fixing means 6 in the form of vacuum paths with which a lower first substrate 3 can be fixed on the mounting surface 2o.

(15) Since the radius of curvature R is preferably very large, and thus the curvature is essentially undetectable with the naked eye (the representation in the figures is highly exaggerated and schematic), it is to execute the first mounting apparatus without fixing means 6 and to finally place the first substrate on the mounting surface 2o. Adhesion by electrostatic, electrical or magnetic fixing means is also conceivable as claimed in the invention.

(16) The second mounting apparatus 4, which is made as a substrate sample holder, is comprised of a base body 2′ with a second mounting surface 2o′ which can be aligned in particular in concentric sections equidistantly to corresponding concentric sections of the first mounting surface 2o.

(17) The base body 2′ has an opening 5 in the form of a hole and fixing means 6′ similarly to the fixing means of the first mounting apparatus 1.

(18) The fixing means 6′ are used to fix an upper, second substrate 8 on one side facing away from the contact surface 8k of the second substrate 8.

(19) Actuating means in the form of a pin 7 are used for deformation (here: deflection) and thus for the primarily point approach of the second substrate 8 to the curved first substrate 3, especially in the region of a curvature maximum.

(20) In one special embodiment, it is conceivable to make the mounting body 2 of temperature-resistant and/or corrosion-resistant material to form a stretchable component which can be expanded and contracted pneumatically and/or hydraulically, in particular a pillow.

(21) FIG. 2 shows a second embodiment with a mounting body 2″ in which the first mounting surface 2o can be deformed in a controlled manner by an actuating element 10, which in the embodiment shown is a pull rod and/or push rod. The mount 2″ has a concentrically running fixing section 16 and a deformation section 17 which encompasses the first mounting surface 2o. The deformation section 17 has at least predominantly a constant thickness and thus a predominantly constant bending stiffness. The actuating element 10 is located and fixed, on the actuating side of the deformation section 17 facing away from the mounting surface 2o. By means of the actuating element 10, the deformation section 17 can be deformed in the micrometer range and can be curved convexly and concavely. The actuating element 10 travels more than 0.01 μm, preferably more than +/−1 μm, more preferably more than +/−1 μm, still more preferably more than +/−100 μm, most preferably more than +/−1 mm, most preferably of all more than +/−10 mm. Otherwise, the embodiment according to FIG. 2 corresponds to the embodiment according to FIG. 1.

(22) FIG. 3 shows a third embodiment with a first mounting apparatus 1 with a mounting body 2″. The mounting body 2′″ has the first mounting surface 2o for accommodating the first substrate 3. Furthermore, the first mounting apparatus 1 in this embodiment has temperature control means 11 for temperature control (heating and/or cooling) of the mounting body 2′″ at least in the region of the first mounting surface 2o, and preferably the entire mounting body 2′″.

(23) In the first procedure, the first substrate 3 is fixed on the heated mounting body 2′″ only after reaching its expansion which has been caused by the temperature difference. In this way, the first substrate 3 expands according to its own coefficient of thermal expansion.

(24) In a second procedure, the first substrate 3 is fixed on the mounting body 2′″ before thermal loading by the temperature control means 11. By changing the temperature control means 11, the mounting body 2′″ and thus the first mounting surface 2o with the first substrate 3 fixed on it expand in the lateral direction. Preferably, the mounting body 2′″ has essentially the same coefficient of thermal expansion as the first substrate 3. Otherwise, the third embodiment corresponds to the above-described first and second embodiments.

(25) FIG. 4 shows a fourth embodiment with a base body 9′ with a mounting section 18 for accommodating a mounting body 2.sup.IV. The base body 9′ comprises a shoulder section 19 which adjoins the mounting section 18 and which is made circumferential. The shoulder section 19 is used as a stop for actuating elements 12, which are used for deformation of the mounting body 2.sup.IV in the lateral direction. The actuating elements 12 in the form of plurality of pulling and/or pushing elements 12 are arranged and distributed on the lateral periphery of the mounting body 2.sup.IV. The actuating elements 12 are used for deformation of the mounting body 2.sup.IV in the lateral direction, by mechanical expansion and/or compression, preferably in the micrometer range. The mounting body 2.sup.IV is expanded/compressed by more than 0.01 μm, preferably more than +/−1 μm, more preferably more than +/−1 μm, still more preferably more than +/−100 μm, most preferably more than +/−1 mm, most preferably of all more than +/−10 mm. The actuating elements 12 can be made as purely mechanical and/or pneumatic and/or hydraulic and/or piezoelectric components.

(26) Otherwise, the fourth embodiment corresponds to the above described first, second and third embodiments. In the fourth embodiment it is especially important that the adhesion between the substrate 1 and the mounting body 2.sup.IV is so great that the substrate 1 during elongation or compression of the mounting body 2.sup.IV is likewise accordingly elongated or compressed by the actuating elements 12.

(27) FIG. 5 shows a fifth embodiment in which the first mounting apparatus 1 and the second mounting apparatus 4 are vertically aligned. The first mounting apparatus 1 has a base body 9″ and a mounting body 2.sup.V which is fixed by the base body 9″. The mounting body 2.sup.V encompasses the first mounting surface 2o which is located vertically in this embodiment and on which the first substrate 3 is fixed via fixing elements 6.

(28) The second mounting apparatus 4 encompasses a base body 9′″ which is located oppositely for accommodating and fixing a mounting body 2.sup.VI. The mounting body 2.sup.VI is used to accommodate and fix the second substrate 8 on its vertically arranged mounting surface 2o′. For deformation of the second substrate 8, an opening 5 (analogous to opening 5 according to FIG. 1) with an actuating means in the form of a pin 7 is provided. Pin 7 is made to deform the second substrate 8 through the opening 5, specifically on one side facing away from the contact surface 8k of the second substrate 8. The pin 7 defines a bond initiation site 20 when the substrates 3, 8 make contact by deformation of the second substrate 8.

(29) Aside from the opening 5 and the pin 7, the first mounting apparatus 1 and the second mounting apparatus 4 are made symmetrical in the embodiment according to FIG. 5. Preferably, the first mounting apparatus also has a corresponding opening and a corresponding pin so that a symmetrical deformation of the substrates 3, 8 is enabled. By simultaneously releasing the fixing means 6, 6′ after the deformed substrates 3, 8 make contact at a bond initiation site 20 which is located in particular in the center of the substrates 3, 8, the substrates 3, 8 behave identically so that even for the lack of an influence of a gravitational force on the deformation in the direction of the contact surfaces 3k, 8k onto one another no alignment faults occur during the advance of the bonding wave. This applies when the predominant number of factors, which influence the bonding wave or alignment faults, i.e., the thickness of the substrates or the bending stiffness of the substrates, is the same. The bending stiffness is the resistance which a body opposes to bending impressed on it. The higher the bending stiffness, the greater the bending moment must be to achieve the same curvature.

(30) The bending stiffness is a pure material and geometrical property which is independent of the bending moment (assuming that the bending moment does not change the moment of inertia by a change in the cross section). The cross section of a wafer through its center is a very good approximation of a rectangle with a thickness t3 and wafer diameter D. The bending stiffness is the product of the modulus of elasticity and the planar moment of inertia for homogeneous cross sections. The planar moment of inertia of a rectangle around an axis normal to the thickness would be directly proportional to the third power of the thickness. Therefore, the moment of inertia and thus the bending moment are influenced by the thickness. The bending moment arises by the action of the gravitational force along the substrate. For a constant bending moment, e.g., a constant gravitational force, substrates with greater thicknesses due to their greater bending moments are less curved than substrates with lower thicknesses.

(31) FIG. 6 schematically shows the bonding process, wherein a radius R of curvature of the first mounting apparatus 1 is shown highly exaggerated for illustration purposes. The radius of curvature is several meters at diameters of the substrates 3, 8 in the range from 1 inch to 18 inches and thicknesses of the substrates 3, 8 in the range from 1 μm to 2000 μm.

(32) After contact-making of the substrates 3, 8 on contact surfaces 3k, 8k in the region of the bond initiation site 20, which site 20 lies in the center of the substrates 3, 8, and after cancellation of the fixing (release) of the second substrate 8 from the second mounting apparatus 4, bonding begins. A bonding wave with a bond front 13 runs concentrically from the bond initiation site 20 to the side edges 8s, 3s of the substrates 3, 8.

(33) In doing so, the bonding wave displaces the gas 15 (or gas mixture 15) which is shown by arrows between the contact surfaces 3k, 8k.

(34) The substrate 3 is deformed by the mounting apparatus 1 such that the alignment faults of corresponding structures 14 of the substrates 3, 8 are minimized.

(35) The substrate 8 deforms during travel of the bonding wave (after bond initiation and release from the mounting apparatus 4) based on the acting forces: gas pressure, gas density, velocity of the bonding wave, weight, natural frequency (spring behavior) of the substrate 8.

(36) In the illustrated exemplary embodiment which corresponds to the first two embodiments according to FIGS. 1 and 2, the deformation takes place by curvature of the substrates 3, 8, a radius R of curvature of the upper substrate 8, especially at each instant on the bond front 13, corresponding essentially to the radius R1 of curvature of the lower substrate 3. If one of the two mounting surfaces 2o, 2o′ is flat and thus also the radius of the corresponding substrate 3 or 8 which is supported on the flat mounting surface 2o or 2o′ is infinitely large, the radius of the correspondingly opposite substrate 8 or 3 is set to be correspondingly large, in the boundary case infinitely large. Thus, inventive compensation of the run-out fault by two substrates 3 and 8 approaching one another, whose radii of curvature are infinitely large, therefore whose contact surfaces 3k, 8k are parallel to one another, is also disclosed. This inventive special case would be suitable mainly in a vacuum environment in order to join the two substrates 3 and 8 to one another since it would not be necessary to bond the two substrates 3 and 8 to one another by a bonding wave which is pushing an amount of gas in front of it out of the bond interface and which is propagating from the bond center. The difference of the radii R1 and R of curvature is especially smaller than 100 m, preferably smaller than 10 m, more preferably smaller than 1 m, most preferably smaller than 1 cm, most preferably of all smaller than 1 mm.

(37) It is conceivable to control the atmosphere by choosing the gas 15 or the gas mixture 15 and the pressure and/or the temperature the bond velocity.

(38) FIGS. 7a to 7d illustrate in enlarged form possible alignment faults dx according to FIGS. 7a and 7d, which as claimed in the invention according to FIGS. 7b and 7c are at least predominantly eliminated by the deformation of the substrates 3, 8.

(39) The described method steps, especially movements and parameters, are controlled by an especially software-supported control apparatus (not shown).

REFERENCE NUMBER LIST

(40) 1 first receiving/mounting apparatus 2, 2′, 2″, 2′″, 2.sup.IV, 2.sup.V, 2.sup.VI receiving/mounting body 2o first receiving/mounting surface 2o′ second receiving/mounting surface 3 first substrate 3k first contact surface 3s side edge 4 second receiving/mounting apparatus 5 opening 6, 6′ fixing means 7 pin 8 second substrate 8k second contact surface 8s side edge 9, 9′, 9″, 9′″ base body 10 actuating element 11 temperature control means 12 actuating element 13 bond front 14, 14′ structure 15 gas/gas mixture 16 fixing section 17 deformation section 18 mounting section 19 shoulder section 20 bond initiation site dx alignment fault d1, d2 diameter R, R1 radius of curvature