阅读说明：本技术 用于衬底的表面处理的方法和设备 (Method and apparatus for surface treatment of substrates ) 是由 M.温普林格 于 2014-06-24 设计创作，主要内容包括：用于衬底的表面处理的方法和设备。本发明涉及如下方法,所述方法用于对衬底(1、1’)的至少主要地结晶的衬底表面(1o、1o’)的表面处理,使得通过所述衬底表面(1o、1o’)的非晶化在所述衬底表面(1o、1o’)处形成非晶层(2、2’、2")其中所述非晶层(2、2’、2")的厚度d＞0nm。此外,本发明涉及相应的设备。(A method and apparatus for surface treatment of a substrate. The invention relates to a method for the surface treatment of an at least predominantly crystalline substrate surface (1 o, 1o ') of a substrate (1, 1') in such a way that an amorphous layer (2, 2 ') is formed at the substrate surface (1 o, 1 o') by amorphization of the substrate surface (1 o, 1o '), wherein the thickness d of the amorphous layer (2, 2') is > 0 nm. Furthermore, the invention relates to a corresponding device.)

1. An apparatus for surface treatment of a substrate surface (1 o) of a substrate (1), having:

a process chamber for receiving the substrate (1), and

means for amorphizing the substrate surface (1 o) in the case of an amorphous layer (2, 2 ') being formed at the substrate surface (1 o), wherein the thickness d of the amorphous layer (2, 2') is > 0 nm.

2. Device according to claim 1, wherein the amorphization is carried out until the thickness d < 100nm of the amorphous layer (2, 2', 2 ").

3. Device according to claim 1, wherein the amorphization is carried out until the thickness dd of the amorphous layer (2, 2', 2 ") is < 50 nm.

4. Device according to claim 1, wherein the amorphization is carried out until the thickness d < 10nm of the amorphous layer (2, 2', 2 ").

5. Device according to claim 1, wherein the amorphization is carried out until the thickness d < 5nm of the amorphous layer (2, 2', 2 ").

6. Device according to claim 1, wherein the amorphization is carried out until the thickness d < 2nm of the amorphous layer (2, 2', 2 ").

7. The apparatus according to one of claims 1 to 6, wherein the amorphization is performed such that the average roughness of the substrate surface (1 o, 1 o') is reduced.

8. The apparatus according to one of claims 1 to 6, wherein the amorphization is performed such that the average roughness of the substrate surface (1 o, 1 o') is reduced to an average roughness of less than 10 nm.

9. The apparatus according to one of claims 1 to 6, wherein the amorphization is performed such that the average roughness of the substrate surface (1 o, 1 o') is reduced to an average roughness of less than 8 nm.

10. The apparatus according to one of claims 1 to 6, wherein the amorphization is performed such that the average roughness of the substrate surface (1 o, 1 o') is reduced to an average roughness of less than 6 nm.

11. The apparatus according to one of claims 1 to 6, wherein the amorphization is performed such that the average roughness of the substrate surface (1 o, 1 o') is reduced to an average roughness of less than 4 nm.

12. The apparatus according to one of claims 1 to 6, wherein the amorphization is performed such that the average roughness of the substrate surface (1 o, 1 o') is reduced to an average roughness of less than 2 nm.

13. The device according to one of claims 1 to 6, wherein the amorphization is induced by particle collisions with the substrate surface (1 o, 1 o').

14. The device according to one of claims 1 to 6, wherein the amorphization is induced by particle collisions with the substrate surface (1 o, 1 o') with ions.

15. The device according to one of claims 1 to 6, wherein the amorphization is caused by accelerating particles by particle collision with particles of the substrate surface (1 o, 1 o').

16. The apparatus of claim 13, wherein an angle of incidence between the substrate surface (1 o, 1 o') and the ion beam can be freely selected and set, wherein the angle of incidence lies between 75 ° and 90 °.

17. The apparatus of claim 16, wherein the angle of incidence is 90 °.

18. The apparatus of claim 13, wherein the kinetic energy of the particles is set between 1eV and 1000 keV.

19. The apparatus of claim 13, wherein the kinetic energy of the particles is set between 1eV and 100 keV.

20. The apparatus of claim 13, wherein the kinetic energy of the particles is set between 1eV and 10 keV.

21. The apparatus of claim 13, wherein the kinetic energy of the particles is set to be between 1eV and 200 eV.

22. The apparatus of claim 13, wherein the current density of the particles is set at 0.1mA/cm²And 1000mA/cm²In the meantime.

23. The apparatus of claim 13, wherein the current density of the particles is set at 1.0mA/cm²And 500mA/cm²In the meantime.

24. The apparatus of claim 13, wherein the current density of the particles is set at 50mA/cm²And 100mA/cm²In the meantime.

25. The apparatus of claim 13, wherein the current density of the particles is set at 70mA/cm²And 80mA/cm²In the meantime.

26. Apparatus according to claim 13Wherein the current density of the particles is set to 75mA/cm²。

27. The apparatus of one of claims 1 to 6, wherein the amorphization is performed in a process chamber, which is evacuated prior to the amorphization.

28. The apparatus according to one of claims 1 to 6, wherein the amorphization is performed in a process chamber which is evacuated to a pressure of less than 1bar prior to the amorphization.

29. The apparatus of one of claims 1 to 6, wherein the amorphization is performed in a process chamber, which is evacuated to less than 10 prior to the amorphization^-3Pressure of bar.

30. The apparatus of one of claims 1 to 6, wherein the amorphization is performed in a process chamber, which is evacuated to less than 10 prior to the amorphization^-5Pressure of bar.

31. The apparatus of one of claims 1 to 6, wherein the amorphization is performed in a process chamber, which is evacuated to less than 10 prior to the amorphization^-7Pressure of bar.

32. The apparatus of one of claims 1 to 6, wherein the amorphization is performed in a process chamber, which is evacuated to less than 10 prior to the amorphization^-8Pressure of bar.

33. The apparatus of one of claims 1 to 6, comprising a joining chamber, wherein the joining chamber is integrally connected to the processing chamber in a cluster unit.

34. The apparatus of one of claims 1 to 6, comprising a bonding chamber, wherein the bonding chamber is integrally connected to the process chamber in a cluster unit, wherein an evacuation is continuously maintained in the process chamber and in the bonding chamber.

35. The apparatus of one of claims 1 to 6, wherein the alignment of the substrates with respect to each other is performed after the amorphization.

36. The apparatus of claim 35, wherein contacting occurs after the aligning, wherein the contacting starts at a center and continues radially outward until full contact.

37. The apparatus of claim 36, wherein the contacting causes pre-fixation, wherein the bond firmness is between 0.01J/m²And 2.5J/m²In the meantime.

38. The apparatus of claim 36, wherein the contacting causes pre-fixation, wherein the bond firmness is between 0.1J/m²And 2J/m²In the meantime.

39. The apparatus of claim 36, wherein the contacting causes pre-fixation, wherein the bond firmness is between 0.5J/m²And 1.5J/m²In the meantime.

40. The apparatus of claim 36, wherein the contacting causes pre-fixation, wherein the bond firmness is between 0.8J/m²And 1.2J/m²In the meantime.

41. Device according to one of claims 1 to 6, wherein the process parameters are selected such that a complete conversion of the amorphous layer (2, 2', 2 ") into a crystalline phase takes place.

42. The apparatus according to one of claims 1 to 6, wherein the following gases and/or gas mixtures are ionized for amorphization:

-an atomic gas,

-a molecular gas, the molecular gas,

-a gas mixture.

43. The apparatus of claim 42, wherein

The atomic gas includes Ar, He, Ne, Kr,

the molecular gas comprises H₂、N₂、CO、CO₂，

The gas mixture comprises:

● synthesis gas FG (argon + hydrogen) and/or

● synthesis gas RRG (hydrogen + argon) and/or

● synthesis gas NFG (argon + nitrogen) and/or

● hydrogen gas.

44. A cluster unit comprising a device according to one of the preceding claims.

Technical Field

The invention relates to a method according to claim 1 or 8 and a corresponding device according to claim 10.

Background

In the semiconductor industry, different bonding techniques have been used for years to connect substrates to each other. This joining process is called splicing. A general distinction is made between temporary joining methods and permanent joining methods.

In the temporary bonding method, the product substrate is bonded to the carrier substrate so that the product substrate can be detached again after processing. The product substrate can be mechanically stabilized by means of a temporary bonding method. Mechanical stabilization ensures that the product substrate can be handled without bowing, deformation or damage. Stabilization by the carrier substrate is necessary during and after the back-side thinning process. The backside thinning process allows the product substrate thickness to be reduced to a few microns.

In the permanent bonding method, two substrates are continuously (i.e., permanently) bonded to each other. The permanent bonding of the two substrates also allows the manufacture of multilayer structures. These multilayer structures may be composed of the same or different materials. Different methods of permanent joining exist.

The ion-containing substrates are permanently connected to each other using a permanent bonding method of anodic bonding. In most cases, one of the two substrates is a glass substrate. The second substrate is preferably a silicon substrate. In this method, an electric field is applied along two substrates to be bonded to each other. The electric field is generated between two electrodes, which preferably contact both surfaces of the substrate. The electric field creates ion transport in the glass substrate and a space charge region between the two substrates. This space charge region causes a strong attraction of the surfaces of the two substrates, which come into contact with one another after being brought closer together and thus form a permanent connection. The joining process is therefore based mainly on maximizing the contact area of the two surfaces.

Another permanent bonding method is eutectic bonding. In the case of eutectic bonding, the alloy is produced at a eutectic concentration or adjusted during bonding. By exceeding the eutectic temperature (the temperature at which the liquid and solid phases of the eutectic are in equilibrium), the eutectic is completely melted. The resulting liquid phase of the eutectic concentration wets the surface of the still unliquefied region. During the solidification process, the liquid phase solidifies into a eutectic and forms a connecting layer between the two substrates.

Another permanent joining method is fusion joining. In the case of fusion bonding, two flat, pure substrate surfaces are bonded to one another by contact. Here, the joining process is divided into two steps. In a first step, the contacting of the two substrates is performed. The fixing of the two substrates is effected here predominantly by van der Waals forces. This fixation is called pre-bond (english pre-bond). This force allows the production of a fastening which is strong enough to bring the substrates into firm engagement with one another, so that a mutual displacement, in particular by applying a shearing force, is only possible with great force expenditure. On the other hand, the two substrates can be separated from each other again relatively easily, in particular by applying a normal force. The normal force acts here preferably at the edge in order to cause a wedge effect at the interface of the two substrates, which produces a continuous crack and thus in turn separates the two substrates from one another. To create a permanent fusion bond, the substrate stack is subjected to a heat treatment. The heat treatment results in the formation of a covalent link between the surfaces of the two substrates. This resulting permanent bond is only possible by using a relatively high force which in most cases accompanies the destruction of the substrate.

Publication US5441776 describes a method for bonding a first electrode to a hydrogenated amorphous silicon layer. The amorphous silicon layer is deposited at the surface of the substrate by a deposition process.

Publication US7462552B2 shows a method of depositing an amorphous silicon layer at the surface of a substrate using Chemical Vapor Deposition (CVD). The amorphous layer has a thickness between 0.5 and 10 μm.

In his publication US7550366B2, Suga et al report an amorphous layer of about 100nm thickness that is unexpectedly produced. The amorphous layer is located between two substrate surfaces that have been prepared by a surface activation process. The amorphous layer is a by-product of ion bombardment of the substrate surface with inert gas atoms and metal atoms. Therefore, the actual bonding process is performed between the iron atoms covering the amorphous layer.

Another technical problem is heat treatment. The bonded substrates are often already equipped with temperature-sensitive functional units, such as microchips, MEMs, sensors, LEDs. In particular, microchips have a relatively strong doping. At elevated temperatures, the doping elements have an increased diffusivity, which leads to an undesired, unfavorable distribution of the dopant in the substrate. Furthermore, thermal treatment is always associated with increased temperatures and therefore also with higher costs, generation of thermal voltages, and longer treatment times for heating and cooling. Furthermore, the bonding should be carried out at as low a temperature as possible in order to prevent displacement of different substrate regions composed of different materials and therefore generally also having different coefficients of thermal expansion.

Plasma treatment for purifying and activating the substrate surface would be one possibility for bonding at relatively low temperatures. However, in the case of oxygen affine (especially metal surfaces), this plasma method does not work or only works very poorly. The oxygen-affine metal oxidizes and generally forms a relatively stable oxide. The oxide in turn interferes with the bonding process. Such metals can also be joined to one another with relative difficulty by diffusion bonding. However, the bonding of plasma activated (especially monocrystalline) silicon forming a silicon dioxide layer works very well. The silicon dioxide layer is very suitable for bonding. The mentioned negative effects of the oxides do not therefore necessarily relate to all material classes.

There are various solutions in the literature describing direct bonding at low temperatures. The solution in PCT/EP2013/064239 consists in applying a sacrificial layer which dissolves in the substrate material during and/or after the bonding process. Another solution in PCT/EP2011/064874 describes the production of permanent connections by phase inversion. The publications mentioned relate in particular to metal surfaces which are more likely to be joined by metallic bonds than by covalent bonds. A direct bonding method of silicon optimized by surface purification is described in PCT/EP 2014/056545.

Another problem is the surface roughness of the surfaces/contact surfaces to be joined. In particular, when removing oxides and contaminants from the surface of substrates to be bonded to one another using known methods, a high roughness often results. On a microscopic scale, this roughness prevents the two surfaces from touching completely during the joining process, which negatively affects the effective joining strength. The two substrate surfaces are actually joined primarily at the surface maxima of the touch. There is therefore a conflict, in particular, between good purification and providing a surface which is as ideal as possible.

In the semiconductor industry, in particular, starting materials or materials of the same type are to be connected to one another. The same type results in the presence of the same physical and chemical properties across the junction. This is particularly important for connections through which current should be conducted, which connections should have a low corrosion tendency and/or the same mechanical properties. Among these types of starting materials, the following are mainly present:

● copper-copper

● aluminum-aluminum

● tungsten-tungsten

● silicon-silicon

● silica-silica.

Some of the metals used in the semiconductor industry are oxygen affine. Thus, under an oxygen-containing atmosphere, aluminum forms relatively strong alumina. In joining, such oxides negatively affect the result of the joining, since they are enclosed between the two materials to be joined to each other. Under extreme conditions, such oxides may completely prevent the bonding process; under optimal conditions, the oxide is surrounded. It is also conceivable to mechanically damage the oxide layer prior to embedding. The oxide is sufficiently thermodynamically stable without decomposing or becoming a solid solution. It remains as an oxide in the bonding interface and there has a negative effect on the mechanical properties. Similar problems arise for tungsten and/or copper bonding.

Disclosure of Invention

The object of the invention is therefore to specify a method and a device by means of which an optimum connection is achieved at the joint interface at the lowest possible temperature, in particular with the highest possible purity.

This object is achieved by the features of claims 1, 8 and 10. Advantageous developments of the invention are specified in the dependent claims. All combinations of at least two of the features described in the description, the claims and/or the drawings are also within the scope of the invention. In describing ranges of values, values lying within the mentioned boundaries should also be regarded as being disclosed as boundary values and can be claimed in any combination.

The basic idea of the invention is to produce a particularly predominantly amorphized layer with a defined thickness d at the substrate surfaces to be joined. The amorphized layer can in particular be applied to the substrate by a chemical and/or physical deposition process (preferably sputtering) or can be produced directly from the substrate. However, a main aspect of the invention is that the amorphized layer is not realized by a material applied by means of a physical and/or chemical process, but by a phase inversion of the substrate material. In this way, the deposition of especially undesirable or harmful materials can be completely dispensed with. Therefore, hereinafter, the second method is mainly discussed.

The invention relates in particular to a method for permanently joining two substrates, at least one, preferably both substrates being treated before joining as described later. The surface regions, in particular the contact side, of the two substrates or of at least one of the two substrates are (preferably completely) amorphized before the bonding process. In the following of this patent document, the entire substrate surface is described as amorphized surface regions, although it is also possible according to the invention to envisage amorphizing surface regions which are smaller than the substrate surface, in particular are separated from one another. By amorphization, a layer of nanometer thickness is produced in which atoms of at least one of the surfaces to be joined (contact side) are randomly arranged. This random arrangement leads to better joining results, in particular at relatively low temperatures. In order to produce the joint according to the invention, a purification of the surface (at least the contact side), in particular for removing oxides, is carried out. The purification and amorphization are preferably carried out simultaneously, even more preferably by the same treatment. An important aspect according to the invention is especially the use of low energy particles (especially ions) which are relatively low in energy but are sufficient to cause amorphization as described according to the invention.

The removal of the oxide from the substrate surface facilitates an optimal bonding process and a substrate stack with a correspondingly high bonding strength. This applies in particular to all materials in which an oxygen-containing atmosphere would form undesirable native oxides. This does not necessarily apply to intentionally created oxygen substrate surfaces, such as silicon oxide. In particular, according to the invention, harmful, unnecessary and/or natural, in particular metal oxides are removed, preferably at least predominantly, more preferably only. Preferably, the aforementioned oxide is removed to a large extent (especially completely) before the bonding process so as not to be embedded in the bonding interface (the contact surface of the two substrates). This embedding of oxide will lead to mechanical instability and very low bond strength. The removal of the oxide is performed by physical or chemical means. In a particularly preferred embodiment according to the invention, the removal of the undesired oxide is carried out using the same installation used to carry out the method according to the invention. Thereby, the following can be performed simultaneously, in particular in an optimal situation:

● oxide removal

● surface smoothing

● is amorphized.

In an alternative embodiment according to the present invention, the oxide removal is not performed in the same facility.

In this case, it must be ensured, in particular: re-oxidation of the substrate surface does not occur during the transfer of the substrate between the two facilities.

In other words, the idea according to the invention is, inter alia, to improve the bond robustness between two substrate surfaces by amorphization. Amorphization here solves a number of problems:

first, amorphization according to the present invention preferably occurs prior to substrate surface purification. In particular, the purification and amorphization of the substrate surface are performed simultaneously, more preferably by the same process.

Second, amorphization according to the present invention causes planarization of the substrate surface. In this case, the planarization is carried out during the amorphization, in particular additionally by the action of forces acting during the bonding process.

Third, a thermodynamically metastable state is produced at the substrate surface (junction interface) by amorphization. In a further process step (in particular after contacting the surfaces to be joined), the metastable state leads to a (reverse) conversion of a partial region of the amorphous layer into the crystalline state. In the ideal case, a complete conversion of the amorphous layer takes place. The resulting layer thickness is in particular greater than zero after the contact and the subsequent heat treatment of the amorphous layer.

The idea according to the invention is in particular to produce an amorphous layer composed of the existing base material of the substrate, in particular by means of particle bombardment. Preferably, no material is applied to the substrate surfaces to be joined prior to substrate joining.

The method according to the invention allows the production of a complete and/or full-surface, in particular homogeneous (sorteren) contact of two substrate surfaces, at least one, preferably both, of which are amorphized according to the invention. Contamination, inclusions, voids and craters are completely avoided by the complete contact.

The method according to the invention is used in particular for producing a complete and/or full-area and/or non-uniform contacting of two (preferably different) substrate surfaces. In particular, the following materials may be joined to each other in any combination.

● metal, especially

。Cu、Ag、Au、Al、Fe、Ni、Co、Pt、W、Cr、Pb、Ti、Te、Sn、Zn

● alloy

● semiconductor (with corresponding dopants), especially

. Elemental semiconductors, especially

■Si、Ge、Se、Te、B、Sn

. Compound semiconductors, especially

■GaAs、GaN、InP、InxGa1-xN、InSb、InAs、GaSb、AlN、InN、GaP、BeTe、ZnO、CuInGaSe2 、ZnS、ZnSe、ZnTe、CdS、CdSe、CdTe、Hg(1-x)Cd(x)Te、BeSe、HgS、AlxGa1-xAs、GaS、GaSe、GaTe、InS、InSe、InTe、CuInSe2、CuInS2、CuInGaS2、SiC、SiGe

● organic semiconductors, especially

. Flavochrome (Flavanthron), perinone (Perinon), Alq3, perinone, tetracene, quinacridone, pentacene, phthalocyanine, polythiophene, PTCDA, MePTCDI, acridone, indanthrene (indinthhron).

The following material combinations are preferably used according to the invention:

- GaN - Cu，

- GaAs - SiO2，

- Cu - Al。

although the embodiments according to the invention are primarily suitable for connecting two substrate surfaces composed of different materials, in the following of the present patent, for the sake of simplicity, reference is primarily made to connecting two substrate surfaces of the same type. In other words, the invention relates in particular to a method of direct joining. The invention is preferably based on the idea of amorphizing at least one surface of the substrate, in particular arranged at the contact side, prior to the bonding process. The amorphization is preferably not carried out by depositing material which sublimes and condenses amorphously on the substrate surface under the given deposition parameters, but in particular by modification, reshaping and/or phase inversion of the amorphous layer at the substrate surface. This is done in particular by introducing kinetic energy by particle bombardment, in particular ion bombardment, most preferably by low energy ion bombardment.

Amorphization of a film

Amorphization is understood as the random arrangement of atoms with respect to a well-defined arrangement of atoms in a crystal. The atoms may be atoms of a single-atomic, single-component system, atoms of a multi-atomic, multi-component system, atoms of a single-atomic, multi-component system, or atoms of a multi-atomic, multi-component system. A component is understood to be a constituent of a phase on a substance that can vary independently. The amorphous phase in particular has no short-range order and/or long-range order. The at least partially amorphous structure of the amorphous layer formed according to the invention is understood to mean a phase mixture consisting at least of an amorphous phase and a crystalline phase. The volume ratio between the amorphous phase and the total volume is called the degree of amorphization. According to the invention, the degree of amorphization is in particular greater than 10%, preferably greater than 25%, even more preferably greater than 50%, most preferably greater than 75%, and globally most preferably greater than 99%.

The amorphization according to the invention is in particular limited to the area near the surface of the substrates to be bonded to each other, preferably by selecting the process parameters during amorphization: temperature, pressure, ion energy, and/or ion current density. In particular, the material of the substrate remains at least predominantly (preferably completely) crystalline in this case, except for the layer amorphized according to the invention.

In the first embodiment according to the present invention, only the substrate surface of the first substrate is amorphized. The thickness d of the amorphous layer after production according to the invention in the substrate surface is in particular less than 100nm, preferably less than 50nm, more preferably less than 10nm, most preferably less than 5nm, and globally most preferably less than 2 nm.

According to a further development of the invention, the substrate surface of the first substrate and the substrate surface of the second substrate are amorphized. In a special embodiment according to the invention, the amorphization of the two substrate surfaces is carried out in the same installation, in particular simultaneously, in order to produce the same amorphous layer with the same process parameters. The resulting amorphous layer preferably has the same thickness d of the first amorphous layer of the first substrate₁And a thickness d of the second amorphous layer of the second substrate₂. In particular the ratio d of the thicknesses of two amorphous layers produced simultaneously₁/d₂Is 0.6<d₁/d₂<1.4, preferably 0.7<d₁/d₂<1.3, even more preferably 0.8<d₁/d₂<1.2, most preferably 0.9<d₁/d₂<1.1, globally most preferably 0.99<d₁/d₂<1.01。

The substrate surface has a low, but in particular not negligible, roughness before, during and after amorphization. In a preferred embodiment, the roughness of the substrate surface is reduced during the amorphization and has a minimum value after the amorphization. The roughness is specified either as the average roughness, the secondary roughness or as the average roughness depth. The determined values of the average roughness, the secondary roughness and the averaged roughness depth generally differ for the same measuring distance or measuring area, but are in the same order of magnitude range. The measurement of the surface roughness is carried out using one of the measuring devices (known to the person skilled in the art), in particular using a profilometer and/or an Atomic Force Microscope (AFM). The measurement area is in particular 200 μm x 200 μm. The following ranges of values for roughness are therefore to be understood as either the average roughness, the value of the secondary roughness or the value of the averaged roughness depth. According to the invention, the roughness of the substrate surface before amorphization is in particular less than 10nm, preferably less than 8nm, more preferably less than 6nm, most preferably less than 4nm, and globally most preferably less than 1 nm. The roughness of the substrate surface after amorphization is in particular less than 10nm, preferably less than 8nm, more preferably less than 6nm, most preferably less than 4nm, globally most preferably less than 1 nm.

The amorphization is preferably performed by particle collisions with the substrate surface. The particles are either charged or uncharged particles. It is preferable to use charged particles (ions) for acceleration, since charged particles can be technically accelerated more easily.

According to the invention, ions are preferably also used for purifying the substrate surface. Thus, according to the invention, in particular the purification (in particular oxide removal) of the substrate surface is combined with amorphization. However, the method according to the invention can also be used only for producing amorphous layers, provided that the substrate has been purified, in particular directly before the amorphization. The ratio between the total surface F of the substrate and the surface F to be purified is called the purity r. Before the joining process according to the invention, the purity is in particular greater than 0, preferably greater than 0.001, more preferably greater than 0.01, most preferably greater than 0.1, and globally most preferably 1.

r = f/F

The purification and/or the amorphization are preferably carried out in a vacuum chamber as the process chamber. Here, the vacuum chamber may be evacuated to less than 1bar, preferably less than 1mbar, more preferably less than 10 mbar^-3mbar, most preferably less than 10^-5mbar, globally most preferably less than 10^-8mbar. Especially before the ions are used for amorphization, the vacuum chamber is preferably evacuated to the pressure mentioned before, more preferably completely. In particular, the proportion of oxygen in the process chamber is greatly reduced, so that re-oxidation of the substrate surface is not possible.

According to the invention, in particular the following gases and/or gas mixtures are ionized for amorphization:

● atomic gas, especially

。Ar、He、Ne、Kr，

● molecular gas, especially

。H₂、N₂、CO、CO₂，

● gas mixture, especially

● synthesis gas FG (argon + hydrogen) and/or

● synthesis gas RRG (hydrogen + argon) and/or

● synthesis gas NFG (argon + nitrogen) and/or

● hydrogen and/or

The gas mixture used has, in particular, the following composition.

Ions are generated during the ionization process. The ionization process is preferably performed in an ion chamber. The generated ions leave the ion chamber and are preferably accelerated by an electric and/or magnetic field. It is also conceivable to deflect the ions by means of electric and/or magnetic fields. The ions are directed onto the substrate surface as an ion beam. The ion beam is characterized by an average ion density.

According to one embodiment of the present invention, the incident angle between the substrate surface and the ion beam can be freely selected and adjusted. The incident angle is defined as the angle between the substrate surface and the ion beam. The angle of incidence is in particular between 0 ° and 90 °, preferably between 25 ° and 90 °, more preferably between 50 ° and 90 °, most preferably between 75 ° and 90 °, globally most preferably exactly 90 °. The impact energy of ions on the substrate surface can be controlled by the angle of incidence of the ion beam.

Amorphization can be controlled by impact energy. In addition, contaminant removal (particularly oxide removal) can be controlled by the angle of incidence (and the associated impact energy of the ions on the substrate surface). Furthermore, the accurate selection of the angle of incidence allows control of the removal rate and thus the surface roughness. Thus, especially the angle of incidence is chosen such that amorphization, removal of contaminants (especially oxides), and surface smoothing are maximized for the desired result. Maximizing is understood in particular to mean completely removing contaminants, in particular oxides, an even further, in particular completely smoothing of the surface, i.e. reducing the roughness value to zero, and an optimal, in particular thick, amorphized layer.

According to another embodiment of the invention, the amorphization control is performed by adjusting the kinetic energy of the accelerated particles, in particular ions. The kinetic energy of the particles is especially adjusted between 1eV and 1000keV, preferably between 1eV and 100keV, more preferably between 1eV and 10keV, most preferably between 1eV and 1keV, and globally most preferably between 1eV and 200 eV.

The current density (number of particles, in particular ions, per time unit and area unit) is in particular at 0.1mA/cm²And 1000mA/cm²Is preferably 1.0mA/cm²And 500mA/cm²Is selected between, more preferably is 50mA/cm²And 100mA/cm²Is selected between, most preferably at 70mA/cm²And 80mA/cm²Is globally most preferably selected to be 75mA/cm²。

The treatment duration is in particular chosen between 1s and 200s, preferably between 10s and 200s, more preferably between 50s and 200s, and globally most preferably between 100s and 200 s.

Joining

The bonding is performed in particular in a separate bonding chamber, which is preferably integrally connected to the process chamber for amorphization in a cluster tool, and more preferably can be transported into the bonding chamber while continuously maintaining the process chamber evacuated.

After amorphizing at least one of the two substrate surfaces according to the invention, in particular an alignment of the two substrates with respect to one another is carried out. The alignment is preferably carried out by means of an alignment facility (aligner) and in accordance with alignment marks.

After the alignment of the two substrates with respect to one another, contact is made in particular. The contact preferably starts at the center and continues radially outward until full contact. The gas discharge is ensured by this contact. Furthermore, the two substrates are in contact with each other with as little distortion as possible.

The contacting preferably causes a pre-fixing, in particular a pre-engagement. The pre-engagement is characterized by a value between 0.01J/m²And 2.5J/m²The bonding firmness between is preferably between 0.1J/m²And 2J/m²Between 0.5J/m, more preferably²And 1.5J/m²The bonding strength between the two is most preferably between 0.8J/m²And 1.2J/m²The bonding firmness therebetween. The pre-bonding does not necessarily result in complete contact of the two substrate surfaces.

In a further step according to the invention, the actual bonding process of the pre-bonded substrates is carried out. The actual joining process consists in particular of a force and/or temperature action. The joining temperature according to the invention is in particular below 200 ℃, preferably below 150 ℃, more preferably below 100 ℃, most preferably below 100 ℃, and globally most preferably below 50 ℃. The engagement force according to the invention is especially greater than 0.01kN, preferably greater than 0.1kN, more preferably greater than 1kN, most preferably greater than 10kN, and globally most preferably greater than 100 kN. The corresponding pressure range is obtained by homogenizing the bonding force according to the invention over the area of the substrate. The substrate may have any shape. In particular, the substrate is circular and characterized by a diameter according to industry standards. The substrate may have any shape, but is preferably circular. For substrates, particularly so-called wafers, industry common diameters are 1 inch, 2 inches, 3 inches, 4 inches, 5 inches, 6 inches, 8 inches, 12 inches, and 18 inches. In principle, however, any substrate can be processed according to embodiments of the present invention, regardless of its diameter.

According to the invention, the pressure load causes the substrate surfaces to approach each other in a boundary layer (formed along the contact surfaces of the substrate surfaces) where contact has not yet been made by pre-bonding. The proximity of the substrate surface leads to a continuously smaller and eventually closed cavity. According to the invention, the amorphization plays a decisive role here because of the surface isotropic electrostatic attraction by the amorphous state. Since none of the amorphous layers of the substrate surface that are in contact with each other are crystalline, care has to be taken to continue the lattice and the adapted contact. Thus, contact of two substrate surfaces with an amorphous layer results in the creation of a new, larger amorphous layer. The transition proceeds smoothly and is characterized according to the invention in particular by the complete disappearance of the boundary layer.

The thickness of the entire bonded amorphous layer, in particular directly after the bonding process according to the invention, is in particular less than 100nm, preferably less than 50nm, more preferably less than 10nm, most preferably less than 5nm, and globally most preferably less than 2 nm.

The strength of the joint is influenced in particular by three decisive parameters, namely

● the thickness of the amorphous layer is greater,

● the roughness of the surface of the steel plate,

● act negatively,

● engagement force.

According to the invention, the bonding strength increases in particular with increasing thickness of the amorphous layer. The thicker the amorphous layer, the larger the number of atoms randomly arranged. The randomly arranged atoms are not determined by any long-range order parameter and/or short-range parameter, and the cavities are rather easily filled by the mentioned processes, in particular diffusion, and by the close proximity by applying pressure, since they do not have to be adapted to a regular lattice. The contact area and thus the bonding strength are increased by the filling. The increase in contact area is considered to be a decisive parameter for the strength of the joint. If the average thickness of the amorphous layer is less than the average roughness, sufficient atoms of the amorphous phase are not available to close the cavity. On the other hand, it must be mentioned that substrate surfaces with very small roughness also have correspondingly small cavities. In other words, the smaller the roughness of the substrate surface, the smaller the thickness of the amorphous layer may also be in order to obtain the desired bonding result. According to the invention, a relatively thick amorphous layer is achieved by a correspondingly high ion energy, which results in ions penetrating as deeply as possible into the substrate.

The effect of roughness should be understood similarly. The greater the roughness, the more difficult it is for the substrate surface to approach and the atoms of the amorphous substrate surface must expend more energy to fill the cavity and thus maximize the contact area.

The bond strength is also a function of the purity of the amorphous layer. Any stored atoms or ions may in particular cause instability, in particular a reduction in the bond strength. Thus, especially when the ions for amorphization remain in the amorphous layer after amorphization, they may also have a negative effect on the bond strength. In addition to the correspondingly low ion energy, therefore, the aim is also to achieve a current density which is as low as possible and a treatment duration which is as short as possible.

If the current intensity is multiplied by the treatment duration, ions that strike the substrate surface per unit area segment within the treatment duration are obtained. To minimize this number, the current density and/or processing time may be reduced. The fewer ions per unit area that strike the substrate surface, the fewer ions are embedded into the amorphous layer. Those particles which do not form any bonds with the material to be amorphized and which are present only as defects (in particular point defects) have a negative effect, in particular, on the bond strength. Noble gases are counted in particular as the particles, but molecular gases are counted as the particles as well.

In particular, according to the invention, it is possible to envisage the use of a gas or a mixture of gases whose ions are responsible for strengthening the bonding interface, in particular by forming new phases. A preferred possibility would be to use ionized nitrogen gas, which nitrifies the amorphous layer.

Similar considerations apply to all other types of elements which form a chemical compound (in particular a metallic, covalent or ionic bond) with the material of the amorphous layer. In order to be able to reduce the current density, preference is given in particular to substrate surfaces which already have a minimum roughness. The smoother the substrate surface, the fewer and lower energy ions are required to reduce roughness in accordance with the present invention. Thereby, the ion energy and/or ion current and thus the number of ions per unit area can be reduced, which in turn leads to a lower number of embedded ions and thus to fewer defects and ultimately to increased bond robustness.

The bonding strength is a function of the bonding force, since a higher bonding force leads to a stronger approach of the substrate surface and thus to a better contact surface. The higher the bonding force, the easier the substrate surfaces are to approach each other and thus close the cavity by the locally deformed region.

Thermal treatment

In particular, the heat treatment separate from the amorphization process is carried out in particular either during and/or after the joining in the splicer or after the joining in an external heat treatment module (in particular integrated into the cluster). The heat treatment module may be a heating plate, a heating tower, a furnace, in particular a continuous furnace or any other type of equipment generating heat.

The heat treatment is especially carried out at a temperature below 500 ℃, preferably below 400 ℃, more preferably below 300 ℃, most preferably below 200 ℃, and globally most preferably below 100 ℃.

The duration of the heat treatment is in particular chosen such that after the heat treatment the thickness of the amorphous residual layer according to the invention is less than 50nm, preferably less than 25nm, more preferably less than 15nm, most preferably less than 10nm, globally most preferably less than 5 nm. In particular, in most cases under investigation, the residual layer thickness never completely disappears, since complete conversion of the amorphous layer is only possible if the converted crystal lattices of the two substrate surfaces are completely adapted. Since a complete adaptation is not possible for energy and geometric reasons, residual layer thicknesses which are not zero remain in most cases described according to the invention.

In particular, a phase transition from the amorphous state to the crystalline state takes place during and/or after joining and/or with heat treatment.

In a very preferred embodiment according to the invention, the process parameters mentioned are selected such that a complete conversion of the amorphous layer into the crystalline phase takes place.

According to an advantageous embodiment, the purity of the converted material is selected, in terms of mass percentage (m%), in particular greater than 95m%, preferably greater than 99m%, more preferably greater than 99.9m%, most preferably greater than 99.99m%, and most preferably greater than 99.999m%, according to the invention. Better bonding results are achieved by the high purity of the substrate material.

Drawings

Further advantages, features and details of the invention emerge from the following description of a preferred embodiment and from the drawings. In the drawings: figure 1 shows a schematic, not to correct scale cross-sectional view of an embodiment of a substrate treated according to the invention in a first method step (amorphization) of an embodiment of a method according to the invention,

figure 2 shows a schematic cross-sectional view not to scale of a second method step (contacting/pre-joining) of an embodiment of the method according to the invention,

figure 3 shows a schematic cross-sectional view of a third method step (joining) not to the right scale,

FIG. 4 shows a schematic, not to scale cross-sectional view of a fourth process step (heat treatment), an

Fig. 5 shows a schematic, not to the right scale cross-sectional view of a facility/apparatus for producing an amorphous layer.

Detailed Description

In the figures, features that are identical or perform the same function are denoted by the same reference numerals.

Fig. 1 shows a schematic, not to scale cross-sectional view of a first substrate 1 with an amorphous layer 2 produced according to the invention at the substrate surface 1 o. The amorphous layer 2 also has a rough surface 2o in general. The roughness is preferably reduced to a minimum during removal of oxides or other products. The amorphous layer 2 extends from the substrate surface 1o into the substrate 1 over a depth (thickness d).

Fig. 2 shows a schematic, not to scale cross-sectional view of a pre-joint of two substrates 1,1' processed according to fig. 1. The pre-bonding process is characterized by the contact of the substrate surfaces 1o, 1o ' (contact surfaces) along the surfaces 2o, 2o ' of the amorphous layers 2, 2 '. Here, the contact is made in particular at the maximum point 2e of the surfaces 2o, 2 o'. The cavity 3 is formed here due to a roughness that is not zero but has been greatly reduced, in particular by the amorphization according to fig. 1. In a very particularly preferred case, as many maximum points 2e as possible partially (in particular completely) engage in the minimum points 2m in order to minimize the number of cavities 3 produced or their volume during the joining process.

The contacting of the surfaces 2o, 2o 'is achieved by the bonding process according to the invention, in particular by the application of a force transverse to the substrate surfaces 1o, 1o' at the opposing sides 1r, 1r 'of the substrates 1,1', and the (additive) thickness d of the common amorphous layer 2 ″ formed by the amorphous layers 2, 2 'is reduced to a (common) layer thickness d'. At this point in time, a distinction is preferably no longer possible between the joined surfaces 1o, 1o 'of the substrates 1,1' joined to one another. This property is also referred to as a specific feature of embodiments according to the present invention and is used to distinguish from other techniques. According to the present technical knowledge, it is not possible to produce an amorphous layer within a substrate without changing the (crystalline) structure in the ion transfer path. By studying the structure before and after the amorphous (residual) layer, a clear identification of the method according to the invention can be envisaged. The creation of a buried amorphous layer must be done by a bonding process according to the invention if the structure before and after the amorphous residual layer has not been clearly changed by ion bombardment.

This force loading results in particular in the approaching of atoms present in the amorphous phase, which atoms are arranged at the surfaces 1o, 1 o'. Due to the already comparatively small (in particular amorphized) dimensions of the cavity 3, the deformation of the maximum point 2e due to pure displacement of atoms (in particular supported by diffusion processes) is sufficient to practically completely close the cavity 3. Thus, the structure is not plasticized by a plasticizing process known from the theory of plasticity (such as an offset movement or bimorph formation), but at least predominantly (preferably exclusively) by a movement caused or supported by the approach and/or displacement and/or diffusion of the individual atoms.

In a further process step according to the invention according to fig. 4, a conversion of the amorphous layer 2 ″ is carried out, in particular at least predominantly by recrystallization. This conversion (in particular recrystallization) leads to a continuous reduction of the layer thickness d' up to the final layer thickness d ″ according to the invention, which, according to a highly preferred embodiment of the invention, is equal to 0 (zero). The ratio between d "/d and/or d"/d' is less than or equal to 1, preferably less than 0.5, more preferably less than 0.25, most preferably less than 0.1, and globally most preferably equal to 0. This results in a complete, virtually defect-free crystalline transition, in particular between the two substrates 1, 1'. This can occur during and/or shortly after the joining, in particular also in the joining chamber. In particular, the heating device of the bonder is used for heating the substrate stack during bonding (thermal treatment).

Fig. 5 shows an ion source 4, which accelerates the ions of an ion beam 5 onto a substrate surface 2o at an angle of incidence α with respect to the substrate surface 1 o.

List of reference numerals

1. 1' substrate

1o, 1o' substrate surface

1r, 1r' reverse side

2. 2', 2' amorphous layer

2o, 2o' surface

2e maximum point

2m minimum point

3 hollow cavity

4 ion source

5 ion Beam

d. d ', d' thickness

Angle of incidence of alpha