Method for bonding metallic contact areas with solution of a sacrificial layer applied on one of the contact areas

Abstract

A method for bonding of a first, at least partially metallic contact surface of a first substrate to a second, at least partially metallic contact surface of a second substrate, with the following steps, especially the following progression: application of a sacrificial layer which is at least partially, especially predominantly soluble in the material of at least one of the contact surfaces to at least one of the contact surfaces, bonding of the contact surfaces with at least partial solution of the sacrificial layer in at least one of the contact surfaces.

Claims

1. A method for bonding of a first, at least partially metallic, contact surface of a first substrate to a second, at least partially metallic, contact surface of a second substrate, the first and second contact surfaces being formed as hybrid surfaces, the method comprising: removing oxides from the first and second contact surfaces, applying a sacrificial layer to at least one of the first and second contact surfaces, the sacrificial layer being at least predominantly soluble in material of at least one of the first and second contact surfaces, and bonding the first and second substrates with a solution of the sacrificial layer in the at least one of the first and second contact surfaces, wherein the sacrificial layer is comprised of water, wherein the at least one of the first and second contact surfaces is formed of several bond regions of the first and second substrates and bulk material which surrounds the bond regions.

2. The method as claimed in claim 1, wherein the sacrificial layer is applied with a thickness of less than 1000 nm.

3. The method as claimed in claim 1, wherein a ratio of a thickness of the sacrificial layer to a thickness of the first and second substrates is less than 1.

4. The method as claimed in claim 1, wherein at least one of the first and second contact surfaces is located in blanket fashion on one bond region of the first and second substrates.

5. The method as claimed in claim 1, wherein the sacrificial layer consists completely of water.

6. The method as claimed in claim 1, wherein the sacrificial layer is applied with a thickness of less than 100 nm.

7. The method as claimed in claim 1, wherein the sacrificial layer is applied with a thickness of less than 10 nm.

8. The method as claimed in claim 1, wherein the sacrificial layer is applied with a thickness of less than 1 nm.

9. The method as claimed in claim 1, wherein a ratio of a thickness of the sacrificial layer to a thickness of the first and second substrates is less than 10.sup.2.

10. The method as claimed in claim 1, wherein a ratio of a thickness of the sacrificial layer to a thickness of the first and second substrates is less than 10.sup.4.

11. The method as claimed in claim 1, wherein a ratio of a thickness of the sacrificial layer to a thickness of the first and second substrates is less than 10.sup.6.

12. The method as claimed in claim 1, wherein a ratio of a thickness of the sacrificial layer to a thickness of the first and second substrates is less than 10.sup.8.

13. A method for bonding of a first, at least partially metallic, contact surface of a first substrate to a second, at least partially metallic contact surface of a second substrate, the first and second contact surfaces being formed as hybrid surfaces, the method comprising: removing oxides from the first and second contact surfaces, respectively forming a plurality of cavities in at least one of the first and second substrates to define metallic bond regions in at least one of the first contact surface of the first substrate and the second contact surface of the second substrate, applying a sacrificial layer to the at least one of the first and second contact surfaces, the sacrificial layer being at least predominantly soluble in material of the at least one of the first and second contact surfaces, and bonding the first and second substrates with a solution of the sacrificial layer in the at least one of the first and second contact surfaces, wherein the sacrificial layer is comprised of water.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a side view of a first embodiment of the invention with a blanket bond region,

(2) FIG. 2 shows a side view of a second embodiment of the invention with several local bond regions,

(3) FIG. 3 shows a side view of a third embodiment of the invention with several local bond regions in the substrate,

(4) FIG. 4 shows empirical measurement data of the contact angle between the liquid droplet edge and the surface of copper/copper oxide, as a function of time,

(5) FIG. 5 shows a schematic plan view of a cluster system which contains the device,

(6) FIG. 6 shows a side view of the first embodiment of the invention in which two layer systems with blanket bond regions are bonded to one another,

(7) FIG. 7 shows a side view of the second embodiment of the invention in which two layer systems with blanket bond regions are bonded to one another, and

(8) FIG. 8 shows a side view of a third embodiment of the invention with a blanket bond region

DETAILED DESCRIPTION OF THE INVENTION

(9) In the figures, the same components or components with the same effect are identified with the same reference numbers. The drawings show only schematically the embodiments of the invention and are not to scale. Thus mainly the relative thicknesses of the sacrificial layer, the bond regions and the substrates are disproportionate to one another, in exactly the same way as the ratio of the indicated thicknesses to the diameter of the substrates.

(10) FIG. 1 shows a layer system 7 comprising a first substrate 1 with an interface 1o, a bond region 3 with a bond region surface 3o, and the sacrificial layer 4 with the sacrificial layer surface 4o. The bond region 3 extends in the first embodiment over the entire interface 1o of the substrate 1. The bond region surface 3o in this case forms a first contact surface of the first substrate 1. The bond region 3 can be in particular a material-integral (therefore comprising the same material) and/or monolithic component of the first substrate 1. The sacrificial layer 4 is applied in a blanket manner on the first contact surface.

(11) FIG. 2 shows a layer system 7 in which several bond regions 3 which are preferably regularly distributed over the interface 1o with corresponding bond region surfaces 3o are applied on the first substrate. The bond regions 3 thus form a topography over the surface 1o of the substrate 1. In the illustrated preferred embodiment the bond regions 3 are surrounded by a bulk material 5. The bulk material can be any metal, nonmetal, a ceramic or a polymer, such as for example a resist. Preferably it will be in any case a ceramic, especially Si.sub.xN.sub.4 or Si.sub.xO.sub.xN.sub.x, still more preferably an oxide ceramic, especially SiO.sub.2. The bond region surfaces 3 and the bulk material surfaces 5o form a common plane E, specifically the first contact surface. The evenness of the bond region surfaces 3 and of the bulk material surfaces 5o as well as their coplanarity allow an optimum deposition of the sacrificial layer 4 on the first contact surface.

(12) FIG. 3 shows a layer system 7 comprising a structured first substrate 1 with an interface 1o and several bond regions 3 which are distributed preferably regularly in the substrate 1, with bond region surfaces 3o. The substrate 1 has been structured by etching so that cavities 2 have formed in the substrate 1. The cavities 2 which have formed in this manner are filled with the material for the bond regions 3, especially using a PVD or CVD process. The material of the bond regions 3 which has been deposited over the common plane E is then removed by a backthinning process. Removal as far as the plane E by grinding processes, polishing processes, chemical-mechanical polishing, etc. would be conceivable. The substrate 1 which has been produced in this way with the cavities 2 which by filling with material form the bond regions 3 and thus jointly the contact surface is then covered on the latter with the sacrificial layer 4.

(13) The deposition of the sacrificial layers 4 for all embodiments of the invention can take place such that the material for the sacrificial layer 4 is deposited until the necessary layer thickness is achieved. The second method includes making the sacrificial layer 4 thicker than desired in a first step and reducing it to the desired thickness in a second step, a backthinning process. In this case the use of grinding processes and/or polishing processes and/or chemical-mechanical polishing would also be conceivable. In the case of liquid sacrificial layers the required layer thickness can also be continuously built up by the sacrificial layer being allowed to grow. Thus, it is known for example which equilibrium layer thickness arises on the surface of a substrate when an atmosphere with corresponding atmospheric humidity is produced. A well defined layer thickness on the substrate surface can be produced by the dedicated control of temperature, pressure and moisture content.

(14) As is respectively shown in FIGS. 6-8, two layer systems 7, 7, 7 are produced, they are bonded to one another at low temperatures and/or with low pressures on the bond regions with the formation of a prebond.

(15) Before prebonding, the sacrificial layer surfaces 4o can be wetted in addition with a liquid, preferably water. Preferably the applied water layers are thinner than 100 nm, more preferably thinner than 10 nm, most preferably thinner than 1 nm, most preferably of all only a monolayer. For example, the use of a bilayer system comprising one SiO.sub.2 layer and one water layer located on it would be conceivable. The SiO.sub.2 layer is for example roughly 1.5 nm thick, the water layer on the SiO.sub.2 layer arises solely by the condensation of the water molecules in the atmosphere.

(16) During and/or prior to the approach process, the two substrates 7, 7, 7 can be aligned via alignment marks and/or other alignment features along the plane E in the x and/or y direction. The contact of the two sacrificial layers 4 to one another takes place preferably at one point by one of the two substrates 1, 1 being convexly shaped by a pin. After the two sacrificial layer surfaces 4o make contact, a bond wave is formed which strongly joins the two sacrificial layer surfaces to one another by a prebond.

(17) In another method step of the invention, heat treatment and/or a bond step is carried out at low temperatures. The increased temperature and/or the action of a force leads to a diffusion of the atoms of the sacrificial layers 4 into the bond regions 3, 3. The atoms of the sacrificial layers 4 are preferably completely dissolved in the bond regions 3, 3 and/or the bulk material 5 surrounding them and thus lead to an inventive direct bond of the bond region materials at temperatures as low as possible. The direct bond can take place for example by one of the methods in patent EP2372755 or patent PCT/EP2012/069268 to which reference is made in this respect.

(18) The embodiment of the invention for producing sacrificial layers is preferably part of a module 8 (sacrificial layer module) of a cluster 9, especially a low vacuum cluster, preferably a high vacuum cluster, most preferably an ultrahigh vacuum cluster. The cluster 9 includes an interior space 10 which can be evacuated and which can be separated hermetically to all existing modules via module lock doors 11. Within the interior space 10 a robot 12 transports the product wafer 1 from module to module. The product wafers 1 travel via a cluster lock 15 of one input FOUP 13 for the incoming product wafer into the interior space 10. After successful processing of the product wafer 1 within the cluster 9, the robot 12 deposits the product wafer 1 again via a FOUP lock 15 in one output FOUP 14.

REFERENCE NUMBER LIST

(19) 1, 1 substrate 1o, 1o interface 2 cavities 3, 3 bond region 3o, 3o bond region surface 4 sacrificial layer 4o sacrificial layer surface 5 bulk material 5o bulk material surface 7, 7, 7 layer systems 8 module 9 cluster 10 interior space 11 module lock door 12 robot 13 input FOUP 14 output FOUP 15 cluster lock door