EP2994935A1

EP2994935A1 - Method for bonding metallic contact areas with dissolution of a sacrificial layer applied on one of the contact areas in at least one of the contact areas

Info

Publication number: EP2994935A1
Application number: EP13734099.8A
Authority: EP
Inventors: Bernhard REBHAN
Original assignee: EV Group E Thallner GmbH
Current assignee: EV Group E Thallner GmbH
Priority date: 2013-07-05
Filing date: 2013-07-05
Publication date: 2016-03-16
Also published as: US9640510B2; CN105340070B; KR102158960B1; TW201513234A; TWI645476B; EP3301706A1; US20160071817A1; SG11201600043RA; KR20200071150A; WO2015000527A1; CN105340070A; CN110310896B; TW202236441A; KR20160030164A; TWI735814B; TW202034409A; TWI775080B; JP2016524335A; KR102124233B1; TWI826971B

Abstract

The present invention relates to a method for bonding a first at least partly metallic contact area of a first substrate (1, 1') with a second at least partly metallic contact area of a second substrate with the following steps, more particularly the following sequence: - applying to at least one of the contact areas a sacrificial layer (4) which is soluble at least partly, more particularly predominantly, in the material of at least one of the contact areas, - bonding the contact areas with at least partial dissolution of the sacrificial layer (4) in at least one of the contact areas. The contact areas can be arranged over the whole area on a bonding region (3). Alternatively, the contact areas can be formed from a plurality of bonding regions (3') which are surrounded by bulk material (5) or arranged in substrate cavities (2). A liquid (e.g. water) can be used to produce a pre-bond between the substrates.

Description

METHOD OF BONDING METALLIC CONTACT SURFACES UNDER SOLVING ONE

ONE OF THE CONTACT SURFACES OPERATED LAYER IN AT LEAST ONE OF THE

CONTACT SURFACES

Description

The present invention relates to a method for bonding a first contact surface of a first substrate to a second contact surface of a second substrate according to claim 1.

For several years, the so-called bonding technology has been used in the semiconductor industry. The bonding technology allows a connection of two or more, usually very precisely to each other

aligned, substrates. This connection is permanent in most cases, so irreversible. Irreversible means that the separation of the two substrates after the bonding process is no longer possible without their destruction or at least their partial destruction. Connecting the substrates reveals that there are different chemical and physical mechanisms that create a permanent bond.

Of particular interest are non-metallic surfaces. at

non-metallic surfaces, it comes by pure contact to form a so-called prebond.

This spontaneous forming, reversible, caused by surface effects, compound of the two substrates is called Prebond to them of the later, caused by an additional heat treatment real, no longer separable, so irreversible, actual Bond too differ. Nevertheless, the Prebond produced in this way is characterized by a strength that can not be underestimated. Although such interconnected wafers for a permanent bond even at higher

Temperatures must be heat treated, the strength of the Prebonds already sufficient to fix the two substrates until the next process step. The Prebond is an extremely useful tool for pre-fixing two substrates, especially after an alignment process, as the two substrates are not allowed to move towards each other after the alignment process. The prebond is likely to be on Van der Waals

Forces due to permanent and induced dipoles at the

Surface of the substrates are present. Since the Van der Waals forces are very weak, a correspondingly large contact surface is required, so that there is a significant adhesion between the substrates.

Unpolished solid surfaces, however, do not optimally contact with correspondingly high roughness. In the case of pure solid state contact, prebonds are therefore predominantly between very flat, polished ones

Substrate surfaces. Under certain circumstances, isolated, covalent bonds between the substrate surfaces may even occur at room temperature, even without additional temperature and / or force loading of the substrates. The number of covalent compounds formed at room temperature, however, should be negligible.

In particular, the use of liquids could increase a corresponding adhesion between substrates. On the one hand, the liquid compensates for unevenness on the surfaces of the substrates and forms even, preferably even permanent, dipoles. A pronounced Prebondfähigkeit is mainly found on non-metallic surfaces. Semiconductors such as silicon, ceramics, above all oxides, metal oxides which are polished and extremely flat, show a corresponding behavior upon contacting.

For non-metallic surfaces, ie surfaces which show a predominantly covalent bonding character, such as Si, Si0 _2, etc., a previously applied liquid film can during through Heat treatment resulting covalent bonds even contribute to the reinforcement of the permanent bond. The non-metallic surfaces are subjected to a heat treatment after the Prebond. The

Thermal activation creates covalent bonds between the two

Surfaces and thus creates an irreversible connection. For example, single crystal, high precision cut and ground silicon wafers are mainly formed by the formation of covalent connections between the two silicon wafers

Silicon atoms welded together. If a silicon oxide is located on a silicon wafer, the formation of covalent silicon-oxide and / or oxide-oxide bonds is predominant. It has been found that the use of very thin layers of liquid, mostly water, causes or at least improves the formation of the covalent bonds between the surfaces. The liquid layers are only a few nanometers thick or even consist of only one

Monolayer of the liquid. The liquid layers thus do not necessarily improve only the Prebondverhalten but also carry

crucial for the formation of covalent compounds. The reason is, in the case of water mainly in the provision of oxygen as

Connecting atom between the atoms of the substrate surfaces to be bonded together. The binding energy between the hydrogen and the oxygen of a water molecule is small enough to be refracted with the introduced energy. As new

Reactants for the oxygen are then in particular the atoms of the substrate surfaces in question. One has to mention, however, that it is

There are surfaces in which such processes in which atoms of the

Liquid directly participate in the permanent bonding process of the substrate surfaces, not necessarily occur.

The bonding process is completely different with pure metal surfaces. Since metals are chemically and physically completely different due to their metallic binding character, a completely different bonding strategy is required. Metals are bonded together, especially at higher temperatures and usually under very high pressure. The high temperatures, lead to increased diffusion along the surfaces and / or the grain boundaries and / or the volume. Due to the increased mobility of the atoms, different physical and chemical effects occur, which lead to a welding of the two surfaces. The disadvantage of such metal bonds is therefore particularly in the use of very high

Temperatures and pressures to ensure a connection of both substrates. In the vast majority of cases, however, you will not find pure metal surfaces. Almost all metals (with

Exception of very inert metals such as Pt, Au and Ag) coat in the atmosphere with a, albeit very thin, oxide layer. This oxide layer is sufficient to also between those with a very thin

Oxide layer covered metal surfaces to produce a Prebond.

However, this oxide layer is in turn undesirable if one intends to directly bond two metals together, for example, to connect two conductive contacts together.

The heat treatment of the substrates requires correspondingly long heating and cooling times. The high temperatures can also lead to disturbances in functional units such as microchips and especially in memory chips and damage them to uselessness.

Furthermore, substrates with corresponding surfaces must be aligned with each other before the actual bonding step. This once performed alignment may not be destroyed until the final, so permanent bonding process. Especially at higher levels

Temperatures are generally, however, due to the

different thermal expansion coefficients of different materials and the resulting thermal expansions, to a shift of different subregions of the substrates to each other. In the worst case, the two substrates to be joined consist of two different materials with different thermal expansion coefficients. These shifts are the greater, ever greater is the difference in the thermal expansion coefficients of the different materials.

The object of the present invention is to provide a most efficient method for low-temperature and / or low-pressure bonding of materials.

The present object is achieved with the features of claim 1. Advantageous developments of the invention are specified in the subclaims. The scope of the invention also includes all

Combinations of at least two features specified in the description, in the claims and / or the drawings. At specified

Value ranges are also within the limits mentioned values as limit values disclosed and be claimed in any combination claimable.

The invention is based on the idea to deposit at least one ultrathin sacrificial layer on at least one of the contact surfaces of the substrates to be bonded, which during the inventive

Bonding step dissolved in the surrounding material or consumed at the interface. A further aspect of the invention is that the bonding of metal surfaces by a previous wetting process with a material, in particular at least predominantly a liquid,

preferably at least predominantly water, is used as a sacrificial layer, in particular for producing a pre-bond between the substrates. Also conceivable is a combination of several sacrificial layers

on top of each other, with particular preference the deposition of a solid

Sacrificial layer and a deposited thereon liquid sacrificial layer. In general, therefore, several sacrificial layers can be applied one above the other.

Although the disclosed invention is basically suitable for all classes of materials that meet the necessary requirements, above all Metals suitable for the embodiment of the invention. Therefore, in the further disclosure, the embodiment of the invention

exemplified on metal surfaces.

The substrate consists in particular of silicon, wherein on the substrate a, in particular metallic, preferably consisting of Cu, bonding layer is applied at least in bonding areas. As far as the bonding layer does not cover the entire substrate, the bonding regions are preferably surrounded by bulk material, in particular the substrate, and together form the, in particular flat, contact surface.

According to another, in particular independent, aspect of

present invention are to be joined together

Bonding areas coated with a sacrificial layer, which on the one hand is able to produce a Prebond, the atoms are solved on the other hand after the Prebond with the lowest possible temperature treatment of / in the material of the bond areas. The material layer preferably consists of a material in which the solubility limit for the material of the sacrificial layer is never reached. According to the invention, the material of the sacrificial layer dissolves completely in the material layer on at least one of the contact surfaces, preferably on both contact surfaces. The concentration is preferably given in atomic percent (at%).

According to the invention, the solubility of the material of the sacrificial layer in, in particular metallic, material is at least one of the contact surfaces between 0 at% and 10 at%, with preference between 0 at% and 1 at%, more preferably between 0 at% and 0. 1 at %, most preferably between 0 at% and 0.01 at%, most preferably between 0 at% and 0.001 at%, most preferably between 0 at% and 0.0001 at%. ,

According to the invention, the thickness of the sacrificial layer is less than 10 nm, more preferably less than 10 nm, more preferably less than 1 nm, most preferably less than 1 nm. The ratio of the thickness of the sacrificial layer to the thickness of the substrates, in particular bonding regions of the substrates , is - 2 -4 less than 1, preferably less than 10 ^" , preferably less than 10 ^" , more preferably less than 10 ^"6 , even more preferably less than 10 ^{" 8}

The sacrificial layer can be applied to at least one of the contact surfaces by any desired deposition method. Preference is given to deposition processes which produce as coarse-grained and / or at least predominantly monocrystalline sacrificial layers. In accordance with the invention conceivable deposition methods are in particular:

• Atomic Layer Deposition,

Electrochemical deposition,

Physical Vapor Deposition (PVD),

Chemical Vapor Deposition (CVD),

Vapor deposition by condensation and / or

Resublimation such as the direct separation of water from water vapor on a surface,

Plasma deposition,

• Nashemic deposition processes,

• sputtering and / or

Molecular Beam Epitaxy.

According to the invention, it is advantageous if the sacrificial layer, in particular Si, is applied to the substrate in situ together with the bonding layer, in particular Cu. As a result, the formation of oxide on the bonding layer is avoided.

The sacrificial layer according to the invention consists in particular of a material which is suitable for forming a pre-bond and has a solubility in the bonding and / or bulk region at the contact surfaces of at least one of the substrates to be contacted. The sacrificial layer consists in particular at least partially, preferably predominantly, of at least one of the following materials or substances:

• metals, in particular o Cu, Ag, Au, Al, Fe, Ni, Co, Pt, W, Cr, Pb, Ti, Te, Sn and / or Zn,

• alloys,

• Semiconductors (with appropriate doping), in particular

Elementary semiconductors, preferably

^■ Si, Ge, Se, Te, B and / or a-Sn,

o compound semiconductors, preferably

^■ GaAs, GaN, InP, In _x Ga _x N, InSb, InAs, GaSb, A1N, InN, GaP, BeTe, ZnO, CuInGaSe _2, ZnS, ZnS e, ZnTe, CdS, CdSe, CdTe, Hg (l -x ) Cd (x) Te, BeSe, HgS, Al _x Gai _x As, GaS, GaSe, GaTe, InS, InSe, InTe, CuInSe ₂ , CuInS ₂ , CuInGaS ₂ , SiC and / or SiGe,

o Organic Hlableiter, preferably

^■ flavanthrone, perinone, Alq3, perinone, tetracene,

Quinacridone, pentacene, phthalocyanines, polythiophene, PTCDA, MePTCDI, acridone and / or indanthrone,

• Liquids, in particular

o water,

o alcohols,

o aldehydes,

o ketones,

o Ether,

o acids,

o bases.

In a first embodiment according to the invention, the bonding region is a layer extending over the entire contact surface of the substrate. The roughness of the surface of the bond area is reduced in particular by known methods. It is preferred to use a chemical-mechanical polishing (CMP) process. Thereafter, the entire bond area surface is covered with the sacrificial layer according to the invention. The sacrificial layer is applied in such a way or after the application that the average roughness values are less than Ι μιη, preferably less than 500nm, more preferably less than 1 Ωm, even more preferably less than 1 mm, most preferably less than 1nm.

In a second embodiment according to the invention, a plurality of bonding regions distributed over the entire contact surface are provided. In particular, the bonding regions form a topography which projects beyond the contact surface of at least one of the substrates, ie project beyond its surface. The bond areas are preferably surrounded by any bulk material. In particular, the surfaces of the bulk material and the bond area surface form a common plane E. The surfaces consisting of conductive areas and surrounded by non-conductive areas are also known as hybrid surfaces. The non-conductive

Areas consist of a dielectric and insulate the conductive ones

Areas. The simplest conceivable embodiment would be contact pads isolated by dielectrics for charge transport. By bonding these hybrid surfaces, a conductive connection between the substrates via the allied contact points can be achieved.

The sacrificial layer according to the invention over the entire surface on the contact surfaces, so both on the Bulkmaterialoberfläche and the

Bonding area surfaces deposited. The local bond areas are, in particular, copper plugs (copper pads),

Metal joints or metal frames for the

Packaging. Cu pads are used in particular for the electrical connection between functional units in the different layer systems. Metal j oints could in particular be silicon vias (TSVs). For example, a metal frame may be a micro package for a MEMS device. These functional units have not been shown in the drawings for the sake of clarity. In a third embodiment according to the invention, a plurality of bond regions distributed over the entire contact surface are provided directly within the substrate, wherein the substrate is first patterned by etching techniques and then filled with the corresponding bond region material and subsequently covered by the sacrificial material.

In a bonding step according to the invention, the two substrates formed as arbitrary layer systems are approximated so that the sacrificial layer (s) applied on the contact surfaces touch each other and form a prebond. The roughness of the sacrificial layer surfaces can be largely reduced by chemical and / or mechanical methods, preferably eliminated. In certain layer systems, the layer systems can be aligned with one another in an alignment unit in front of the prebond.

Before the pre-bonding, the sacrificial layer surfaces can, according to the invention, be wetted with a liquid, preferably with water. With preference the applied liquid layer is thinner than 10 nm, more preferably thinner than 1 nm, most preferably thinner than 1 nm, most preferably only one monolayer. For hydrophilic surfaces, it is sufficient to expose the substrate to the ambient atmosphere. The surface is then wetted by the water vapor from the atmosphere.

The liquid can be applied according to the invention in particular by condensation. In a particular embodiment, the substrate to be coated, preferably in the cooled state, in a

heated room with vapor-saturated atmosphere introduced. Due to the low temperature of the substrate, the liquid condenses abruptly on its surface.

In an alternative embodiment of the invention, the material of the

Sacrificial layer, in particular as a liquid, by a

Schleuderbelackungsprozess applied. In a further alternative embodiment of the invention, the material of the sacrificial layer, in particular as a liquid, by a

Sprühbelackungsanlage sprayed onto the contact surface of at least one of the substrates.

In particular embodiments, the water is through a

Steam pressure (bubbler) introduced into the reaction chamber in which the substrate is located. For this purpose, inert gases such as argon, helium, nitrogen are driven through a water bath. The inert gas supports the water during evaporation and saturates the reaction chamber with water vapor. The water condenses on the surface of the substrate and forms a very thin film of water. By cooling the substrate, the condensation of the water can be supported.

In a further particular embodiment, the water is evaporated in a simple evaporator and passed to the surface of the substrate. In contrast to the bubbler is not necessarily working with an inert gas, but the temperature of the water is brought as close to the boiling point to increase the kinetic energy of the water and thus to accelerate the evaporation. By evacuating the reaction chamber, the boiling point can be reduced accordingly and the process can thus be optimized.

From the consideration that special reaction chambers can be built, which can deposit the sacrificial layers according to the invention precisely results accordingly also a system according to the invention, referred to in the further course of the patent as a reaction chamber.

The Prebond is preferably initiated at a contact point of the contact surfaces and spreads over the entire surface by a bonding wave. The contact of both sacrificial layer surfaces can be produced in particular by a pin which bends one of the two substrates, so that the contact surface of this substrate convexly deformed and with the sacrificial layer surface of the second, in particular plan on one

Receiving surface resting substrate is brought into contact.

After the formation of the prebond, the two bonded substrates are heat treated. The heat treatment takes place at the lowest possible temperatures, ideally at room temperature. The temperature is less than 500 ° C, more preferably less than 400 ° C, more preferably less than 300 ° C, even more preferably less than 200 ° C, most preferably less than 100 ° C, most preferably less than 50 ° C.

By a very thin embodiment of the sacrificial layer according to the invention, a rapid diffusion of atoms of the sacrificial layer, in particular exclusively, in the bond areas is made possible. The diffusion according to the invention is accelerated and / or promoted by a heat treatment. With preference, the atoms of the sacrificial layer dissolve

According to the invention completely in the material of the bonding area and / or the bulk material. Also conceivable in accordance with the invention is a process in which the atoms of the bonding regions dissolve in the sacrificial layer, which is technically identical to the embodiment described above due to the extremely small thickness of the sacrificial layer.

With preference, the substrates during the inventive

Diffusion process of the atoms of the sacrificial layer in the bond areas pressurized. In particular, the pressure on the surface is between 0.10 MPa and 10MPa, preferably between 0.1 MPa and 8MPa, more preferably between I MPa and 5MPa, most preferably between 1.5MPa and 3MPa. These values correspond approximately to a load of 1 kN to 320 kN for a 200 mm substrate.

The surface of the sacrificial layer should be before the invention

Prebondvorgang free of contamination and / or at least predominantly, preferably completely, free of oxides. In particular, it can also be necessary to rid the material on which the sacrificial layer is applied, of oxide before the sacrificial layer is applied. Before a Prebondvorgang invention therefore preferably a cleaning of the sacrificial layer surface is made. The removal of oxides can be carried out by physical and / or chemical methods known to those skilled in the art. These include chemical reduction by gases and / or

Liquids with appropriate removal of the waste products,

mechanical removal of the oxides by sputtering and / or plasma and / or CMP and / or one or more of the following methods:

• Chemical oxide removal, in particular

o gaseous reducing agent,

o liquid reducing agent,

• Physical oxide removal, in particular

plasma,

o Ion Assisted Chemical Etching,

o Fast Ion Bombardment (FAB, sputtering),

o loops,

o polishing.

Chemical removal of oxides is the removal of the oxide by a chemical process. A chemical process is a matter of transformation. In this case, the oxide is reduced by a reducing agent in the gaseous and / or liquid phase and oxidizes the reducing agent corresponding to the new compound. The oxidized reducing agent, ie the reaction product is removed accordingly. A typical reducing agent is, for example, hydrogen.

Physical oxide removal is the removal of the oxide by a physical process. In a physical process, there is no material conversion but a purely mechanical removal of the oxide from the surface of the substrate. The most commonly used physical reduction technology is plasma technology. In this case, a plasma is generated, which is accelerated by appropriate fields on the surface of the substrate and a corresponding physical oxide removal accomplished. It is also conceivable

Using a sputtering technology. In contrast to the plasma, a statistical many-body system is not generated in the reaction chamber, but instead ions are generated in an antechamber and accelerated to a substrate. Finally, grinding and polishing would be called oxide removal processes. By a grinding or polishing tool, the oxide is gradually removed. Sanding and polishing is particularly suitable as a pretreatment process when dealing with very thick oxide layers in the micrometer range. For the correct removal of oxide layers in the nanometer range, these methods are less suitable.

Evidence of surface cleanliness can be made very quickly and easily with the contact angle method. It is known that non-oxidic surfaces, especially pure copper, are more hydrophilic

Own properties. This is reflected above all by a very small contact angle. When the surface oxidizes to the oxide, especially copper to copper oxide, the surface properties become more and more hydrophobic. A measured contact angle is correspondingly large. To illustrate the change in the contact angle as a function of time, and thus as a function of the copper oxide thickness, the contact angle of a

Water drop after defined time units, starting from the time of complete oxide removal of the native copper oxide, measured. Of the

Contact angle approaches a saturation value with increasing time. This relationship could be explained by the change in the electronic structure of the surface due to the rapidly growing copper oxide. From a certain copper oxide layer thickness further increase of the oxide no longer contributes significantly to the change in the electronic structure of the surface, which is reflected in a logarithmic decay of the contact angle (see Figure 4).

The resulting oxides are preferably before coating the bond area surfaces and / or Bulkmaterialoberflächen with the Sacrificial layer surfaces and / or before bonding the

Sacrificial layer surfaces removed together. The one mentioned here

Contact angle method serves the fast, precise and

cost-efficient evaluation of the oxide state. She comes without

complicated chemical and / or physical analysis apparatus.

Contact angle measuring devices can be placed in corresponding module groups of the

Device for fully automatic measurement and characterization of the surfaces to be installed. Alternative measuring methods would be the

Ellipsometry or any other known optical and / or electrical method.

In a further embodiment according to the invention, a bonding process is carried out between the bond area surfaces with water as the sacrificial layer. The idea according to the invention is that of

Bond surface surfaces completely clean of oxide and in a subsequent, directly on the Oxidenfernung following step, a

Wetting the bonding surface surfaces with water, which allows a Prebond between the Bondbereichsoberflächen at room temperature. The wetting takes place by one of the already mentioned

Possibilities like PVD, CVD, spin coating,

Vapor phase deposition or exposure of the substrate surface in an atmosphere which has a sufficiently high humidity, with preference even saturated with water vapor.

The application of the sacrificial layers takes place in a reaction chamber. With preference, the reaction chamber can be evacuated. The, in particular continuous, evacuation of the reaction chamber is also advantageous to allow a targeted adjustment of the atmosphere. Preferably, the reaction chamber is part of a module of a vacuum cluster, preferably part of a low vacuum cluster, more preferably a high vacuum cluster, most preferably part of a vacuum cluster

Ultrahigh vacuum cluster. The pressure in the reaction chamber is less than 1 bar, more preferably less than 10 ¹ mbar, more preferably less than 10 - ^" 3 mbar, most preferably less than 10 - ^" 5 mbar, most preferably less than 10 - ^" 8 mbar.

Further advantages, features and details of the invention will become apparent from the description of preferred embodiments and from the drawings. These show in:

1 shows a side view of a first embodiment according to the invention with a full area bonding area,

2 shows a side view of a second embodiment according to the invention with a plurality of local bonding areas,

3 shows a side view of a third embodiment according to the invention with a plurality of local bond areas in the substrate,

4 empirical measurement data of the contact angle

between the liquid drop edge and the surface of

Copper / copper oxide, as a function of time and

Fig. 5 is a schematic plan view of a device containing the

Cluster system.

In the figures, identical or equivalent components are identified by the same reference numerals. The drawings show only schematically the embodiments of the invention and are not to scale. In particular, the relative thicknesses of the sacrificial layer, the bonding areas and the substrates are disproportionate to each other, as is the ratio of the mentioned thicknesses to the diameter of the substrates.

FIG. 1 shows a layer system 7, comprising a first substrate 1 with an interface lo, a bonding region 3 with a bond region surface 3o, and the sacrificial layer 4 with the sacrificial layer surface 4o. Of the Bonding region 3 extends in the first embodiment over the entire interface area lo of the substrate 1. In this case, the bonding area surface 3o forms a first contact area of the first substrate 1. The bonding region 3 may be a component of the first substrate 1, in particular material-integral (ie consisting of the same material) and / or monolithic. The sacrificial layer 4 is applied over the entire area on the first contact surface.

FIG. 2 shows a layer system 7 'in which several, preferably

regularly distributed over the interface l o bond areas 3 'with

corresponding bond area surfaces 3o 'are applied to the first substrate. The bond areas 3 'thus form a topography over the surface 10 of the substrate 1. In the shown, preferred

Embodiment, the bonding regions 3 'surrounded by a bulk material 5. The bulk material may be any metal, non-metal, ceramic or polymer, such as a resist. However, preference will be given to a ceramic, in particular S1 ₃ N ₄ or Si _x O _x N _x , even more preferably an oxide ceramic, in particular Si0 ₂ . The bonding area surfaces 3 'and the bulk material surfaces 5o form a common plane E, namely the first contact area. The flatness of the bond area surfaces 3 'and the bulk material surfaces 5 o and their coplanarity allow optimal deposition of the

Sacrificial layer 4 on the first contact surface.

FIG. 3 shows a layer system 7 "comprising a structured first substrate 1 'with an interface l o' and a plurality of bonding regions 3 ', preferably distributed regularly in the substrate 1'

Bonding area surfaces 3o '. The substrate 1 has been patterned by etching, so that cavities 2 have formed in the substrate 1 '. The resulting cavities 2 are filled with the material for the bond areas 3 ', in particular with a PVD or CVD process. The deposited over the common plane E material of the bond areas 3 'is then removed by a Rückdünnprozess. It would be conceivable Removal down to the level E by grinding processes, polishing processes, chemical-mechanical polishing, etc. The substrate 1 'produced in this way with the cavities 2, which form the bonding areas 3' and thus jointly the contact area by filling with material, is subsequently

According to the invention covered at this with the sacrificial layer 4.

For all the embodiments according to the invention, the deposition of the sacrificial layers 4 can take place in such a way that material for the sacrificial layer 4 is deposited until the required layer thickness is reached. The second method is to form the sacrificial layer 4 thicker than desired in a first step and in a second step, a

Re-thinning process to reduce to the desired thickness. Also conceivable in this case would be the use of grinding processes and / or

Polishing processes and / or chemical mechanical polishing. In the case of liquid sacrificial layers, the required layer thickness can also

be continuously built by growing the sacrificial layer. For example, we know which equilibrium layer thickness is formed on the surface of a substrate when an atmosphere with

corresponding humidity is generated. Through the targeted control of temperature, pressure, and humidity, one can create a well-defined layer thickness at the substrate surface.

After two layer systems 7, 7 ', 7 "are produced, they are at low temperatures and / or with low pressures on the

Bond areas bonded together to form a Prebond.

Before pre-bonding, the sacrificial layer surfaces 4o may be filled with a

Liquid, with preference water, additionally wetted. With preference, the applied water layers are thinner than 10 nm, more preferably thinner than 1 nm, most preferably thinner than 1 nm, most preferably only one monolayer. For example, the use of a two-layer system, consisting of a Si0 ₂ layer and a water layer thereon, would be conceivable. The Si0 ₂ layer is approx. 1 .5 nm thick, the water layer on the Si0 ₂ layer is formed solely by the condensation of the water molecules in the atmosphere.

During and / or before the approach process, the two substrates 7, 7 ', 7 "can be aligned in the x and / or y direction via alignment marks and / or other alignment features along the plane E. The contact of the two sacrificial layers 4 takes place with each other Preferably at a point where one of the two substrates 1, 1 'is convexly formed by a pin After contacting the two sacrificial layer surfaces 4o, a bonding wave is formed which connects both sacrificial layer surfaces firmly together by a prebond.

In a further method step according to the invention, a

Heat treatment and / or a bonding step performed at low temperatures. The elevated temperature and / or the force leads to a diffusion of the atoms of the sacrificial layers 4 in the bond areas 3, 3 '. The atoms of the sacrificial layers 4 are preferably completely dissolved in the bond areas 3, 3 'and / or the surrounding bulk material 5 and thus lead to a direct bond according to the invention

Bond area materials at lowest possible temperatures. Of the

For example, direct bond can be obtained by one of the methods in the

Patent specification EP2372755 or the patent PCT / EP20 12/069268, to which reference is made.

The embodiment according to the invention for producing the sacrificial layers is preferably part of a module 8 (sacrificial layer module) of a cluster 9, in particular a low-vacuum, preferably a high-vacuum, with the greatest advantage of an ultra-high vacuum cluster. The cluster 9 consists of an evacuable interior 1 0, which is hermetically separable to all existing modules via module lock gates 1 1. Within the

In the interior 10, a robot 12 transports the product wafer 1 from module to module. The product wafers 1 arrive via a cluster lock 15 of an input FOUP 1 3 for the incoming product wafer 1 in the Interior 10. After a successful processing of the product wafer 1 within the cluster 9, the robot 12 sets the product wafer 1 again a FOUP lock 15 in an output FOUP 14 from.

Method for bonding contact surfaces

B e z u c e s i n e s i s, 1 'Substrate

o, lo 'interface

wells

, 3 'bond area

o, 3o 'bond area surface

sacrificial layer

o O film surface

bulk material

o Bulk material surface

, 7 ', 7 "layer systems

module

cluster

0 interior

1 module lock gate

2 robots

3 input FOUP

4 output FOUP

5 cluster lock gate

Claims

- 22 - Bonding of contact surfaces P at e nt an sp rü che

1. A method for bonding a first, in particular at least partially metallic, contact surface of a first substrate (1, 1 ') with a second, in particular at least partially metallic, contact surface of a second substrate with the following steps, in particular the following sequence:

Applying one in the material at least one of

Contact surfaces at least partially, in particular predominantly, releasable sacrificial layer (4) on at least one of the contact surfaces, bonding of the substrates (1, 1 ') with at least partial release of the sacrificial layer (4) in at least one of the contact surfaces.

- 23 -

A method according to claim 1, wherein the sacrificial layer (4) is deposited to a thickness of less than 1000 nm, preferably less than 10 nm, more preferably less than 1 nm, most preferably less than 1 nm.

3. The method according to any one of the preceding claims, wherein the sacrificial layer at least predominantly, in particular completely consists of at least one of the following materials:

• metals, in particular

o Cu, Ag, Au, Al, Fe, Ni, Co, Pt, W, Cr, Pb, Ti, Te, Sn and / or Zn,

• alloys,

• Semiconductors (with appropriate doping), in particular

Elementary semiconductors, preferably

^■ Si, Ge, Se, Te, B and / or a-Sn,

o compound semiconductors, preferably

o Organic Hlableiter, preferably

^■ flavanthrone, perinone, Alq3, perinone, tetracene,

• Liquids, in particular

o water,

o alcohols,

o aldehydes,

o ketones,

o Ether,

o acids,

o bases. - 24 -

Method according to one of the preceding claims, in which

Ratio of the thickness of the sacrificial layer (4) to the thickness of the substrates (1, 1 '), in particular bonding regions (3, 3') of the substrates (1, 1 '),

- 2 - 4 less than 1, more preferably less than 10 ^" , preferably less than 10 ^" , more preferably less than 10 ^"6 , even more preferably less than 10 - ^" 8.

The method of claim 1, wherein at least one of

Contact surfaces of a plurality of bond areas (3, 3 ') and the

Bonding regions (3, 3 ') surrounding bulk material (5) is formed.

The method of claim 1, wherein at least one of

Contact surfaces over the entire surface of a bonding area (3) is arranged.