DE102016014796A1 - Method for improving the surface quality of a surface resulting from crack propagation - Google Patents

Abstract

The present invention relates to a method for producing a solid state layer (4). This method comprises at least the steps of generating a plurality of modifications (9) by means of laser beams inside a solid (1) for forming a release plane (8), introducing an external force into the solid (1) to generate stresses in the solid ( 1), wherein the external force is such that the stress causes crack propagation to separate the solid layer from the solid along the release plane (8), treating the surface of the solid layer exposed by the separation of the surface to increase the strength of the internal structure Solid state layer and / or for reducing the mechanical stress acting on the internal structure of the solid state layer (4) in a machining process, changing the surface quality of the treated surface of the solid state layer (4) by means of polishing.

Description

The present invention relates in each case to a method for producing a solid-state layer, according to claim 12, to a method for increasing the surface quality of a surface exposed by a crack guide of an ingot or a wafer separated from the ingot or of a wafer separated solid fraction or the exposed by the separation of the solid content surface of the wafer and according to claim 14 on an ingot or a wafer.

A number of components of the semiconductor industry are needed on thinned solid layers or substrates. However, since thin substrates are difficult to handle in conventional processes, and also wafers can only be made to a specific thickness with conventional wire sawing processes, the most common form of fabrication of such components on thin substrates is the grinding away or backside thinning of the substrate after final processing.

Here, a conventional wafer is finished before the final desired substrate thickness is achieved by removing the excess material in a final polishing and polishing step. This circumstance is unfavorable for two reasons: on the one hand valuable material is lost in the grinding step, on the other hand the grinding / polishing step has the potential of damaging the substrate the potential for a total loss of the already processed components, which already accounts for a large part of the added value of the product Wafers included.

Furthermore, ingots are cut into individual wafers, the wafers and / or the ingot then being further treated.

Another method for thinning solids is the document WO2914 / 177721 A1 disclosed. According to this method, a polymer layer is applied to a solid. You tempering the polymer layer voltages are then generated in the solid, through which a solid layer is separated from the remaining solid.

After every crack-based separation and similar separation processes, a surface treatment is necessary. Here, the laser structures and surface roughness / defects are removed from the last process step and a polished surface of optical quality is produced.

The more material that has to be removed in this step to finish processing the workpiece, the worse the overall raw material (ingot / boule) yield.

In particular, at the first engagement of the grinding wheel with the split surface particles can be separated from the surface, which are significantly larger than that of the abrasive. (SiC is also widely used as an abrasive because of its high hardness.) A diamond-based abrasive is used to grind SiC.) These particles can then generate consequential damage to the wafer through deep scratches or grind marks.

It is thus the object of the present invention to provide an improved process for producing solid state layers. The improved manufacturing method should preferably reduce the material losses.

The aforementioned object is achieved by a method according to claim 1 for the preparation of a solid state layer. The method according to the invention preferably comprises at least the steps of generating a multiplicity of modifications by means of laser beams inside a solid to form a release plane, introducing an external force into the solid for generating stresses in the solid, the external force being so strong that the stresses cause crack propagation to separate the solid layer from the solid along the release plane, treating the surface of the solid layer exposed by the separation of the surface to increase the strength of the inner structure of the solid layer and / or reduce the internal structure in a machining process the solid state layer acting mechanical stress, changing the Surface finish of the treated surface of the solid state layer by polishing.

Additionally or alternatively, the aforementioned problem is solved by a method according to claim 2 for producing a solid state layer. The method according to the invention preferably comprises at least the steps of generating a multiplicity of modifications by means of laser beams inside a solid to form a release plane, introducing an external force into the solid for generating stresses in the solid, the external force being so strong that the stresses cause crack propagation to separate the solid layer from the solid along the release plane, treating the surface of the residual solid exposed by the separation of the surface to increase the strength of the internal structure of the residual solid, and / or to reduce the internal structure in a machining process of the residual solids acting mechanical stress, changing the surface quality of the treated surface of the solid state layer by means of polishing, re-generating a variety of modifications by means of laser beams inside a solid for Ausbi In another release plane, wherein the laser beams are introduced into the solid body via the polished surface, reintroducing an external force into the solid to create stresses in the solid, the external force being so strong that the stresses cause crack propagation to separate a solid another solid state layer of the solid along the Ablöseebene causes.

Both aforementioned methods are based on the inventive idea that the propagation of microcracks in a machining step, such as grinding, polishing or lapping, should be limited or prevented, since such microcracks must be removed to obtain the required surface quality. The average roughness of the treated surface should be less than 150 nm, in particular less than 100 nm or less than 80 nm or less than 50 nm or less than 20 nm.

This is necessary on the one hand with regard to the exposed surface of the separated solid layer, since this is e.g. for initiating further laser radiation for later thinning or for producing or arranging further layers and / or components to serve. On the other hand, this makes sense for the exposed surface of the residual solid remaining after the separation of the solid-body layer, since further laser beams are to be introduced via the exposed surface for separating a further solid-state layer into the residual solid.

Further preferred embodiments of the present invention are the subject of the following description parts and the subclaims.

According to a further preferred embodiment of the present invention, before being polished and after the treatment, the exposed surface is treated by machining, in particular ground or lapped. This embodiment is advantageous because compared to a polishing treatment, a significantly faster removal of material can be realized. It is also possible within the scope of the present invention to treat the surface exposed as a result of a cutting treatment, in particular a milling or lapping treatment, such that in a subsequent machining step, in particular polishing, the strength of the internal structure of the residual solid or the Solid layer is increased and / or reduced in a machining process on the internal structure of the residual solids or the solid state layer mechanical stress is reduced.

According to a further preferred embodiment of the present invention, the treatment for reducing the mechanical stress acting on the inner structure of the residual solid or the solid layer in the machining process comprises the arrangement of a filling material on the exposed surface, wherein at least in sections during grinding or polishing the filling material and the Solid material are removed at the same time. In addition or as an alternative, the treatment for reducing the mechanical stress acting on the internal structure of the residual solids during the machining process may include reducing the surface roughness by means of etching, whereby the etching can be brought into contact with a tool for machining, in particular grinding or polishing Surface is enlarged. In both cases, the micro-crack propagation is limited or prevented. As an alternative or in addition to the etching, one or more other chemical treatment methods and / or laser polishing (laser-driven melting of the surface) can be used.

According to a further preferred embodiment of the present invention, the solid has or consists of SiC.

It has been found that in 4H-SiC, which is grown in 4 ° off-angle crystals, the crack always runs into this 4 ° and forms a kind of saw tooth when splitting. The mechanical stresses during splitting or crack initiation and crack initiation may also lead to microdefects and subsurface damage (subsurface damage) in the substrate, which must be polished away. According to the invention, the machining is carried out so that the microcracks are not further driven into the material during machining.

The treatment for increasing the strength of the internal structure of the solid layer or the residual solid may be effected according to a further preferred embodiment of the present invention by annealing or locally fusing or laser polishing. This solution is advantageous because the material is "healed" before the cutting treatment, i. the micro-cracks close again and thereby the strength of the inner structure is improved or the micro-crack propagation is limited or prevented.

The solid has according to a further preferred embodiment of the present invention, silicon, in particular PV silicon, or consists thereof.

According to the present description, a solid-state starting material is preferably understood to be a monocrystalline, polycrystalline or amorphous material. Monocrystallines having a strongly anisotropic structure are preferred because of the strong anisotropic atomic binding forces. The solid-state starting material preferably has a material or a combination of materials from one of the main groups 3, 4, 5 and / or subgroup 12 of the Periodic Table of the Elements, in particular a combination of elements of the 3rd, 4th, 5th main group and the subgroup 12th , such as zinc oxide or cadmium telluride.

In addition to silicon carbide, the semiconductor source material may include, for example, silicon, gallium arsenide GaAs, gallium nitride GaN, silicon carbide SiC, indium phosphide InP, zinc oxide ZnO, aluminum nitride AlN, germanium, gallium (III) oxide Ga2O3, aluminum oxide Al2O3 (sapphire), gallium phosphide GaP, indium arsenide InAs, indium nitride InN, aluminum arsenide AlAs or diamond.

The solid or workpiece (e.g., wafers) preferably comprises a material or combination of materials from one of the major groups 3, 4, and 5 of the Periodic Table of the Elements, e.g. SiC, Si, SiGe, Ge, GaAs, InP, GaN, Al2O3 (sapphire), AlN. Particularly preferably, the solid has a combination of the fourth, third and fifth group of the periodic table occurring elements. Conceivable materials or material combinations are e.g. Gallium arsenide, silicon, silicon carbide, etc. Further, the solid may comprise a ceramic (e.g., Al 2 O 3 - alumina) or may be made of a ceramic, preferred ceramics being e.g. Perovskite ceramics (such as Pb, O, Ti / Zr containing ceramics) in general, and lead magnesium niobates, barium titanate, lithium titanate, yttrium aluminum garnet, especially yttrium aluminum garnet crystals for solid state laser applications, SAW ceramics ( surface acoustic wave), such as Lithium niobate, gallium orthophosphate, quartz, calcium titanate, etc. in particular. The solid body thus preferably has a semiconductor material or a ceramic material or particularly preferably the solid body consists of at least one semiconductor material or a ceramic material. The solid is preferably an ingot or a wafer. The solid is particularly preferably a material which is at least partially transparent for laser beams. It is thus further conceivable that the solid body comprises a transparent material or partially made of a transparent material, such as e.g. Sapphire, exists or is made. Other materials which may be used here as solid material alone or in combination with another material are e.g. "Wide band gap" materials, InAlSb, high temperature superconductors, especially rare earth cuprates (e.g., YBa2Cu3O7). It is additionally or alternatively conceivable that the solid body is a photomask, wherein as photomask material in the present case, preferably any known to the filing date photomask material and more preferably combinations thereof can be used. Furthermore, the solid may additionally or alternatively comprise or consist of silicon carbide (SiC).

The modifications may represent a phase transformation of silicon carbide into silicon and carbon.

The laser application according to the invention preferably effects a substance-specific spatially resolved accumulation of the energy input, from which results a defined temperature control of the solid at a defined location or at defined locations as well as in a defined time. In a concrete application, the solid may consist of silicon carbide, whereby preferably a strongly localized tempering of the solid to a temperature of e.g. more than 2830 +/- 40 ° C is made. This tempering results in new substances or phases, in particular crystalline and / or amorphous phases, the resulting phases preferably being silicon (silicon) and DLC (diamond-like carbon) phases which are produced with significantly reduced strength. By this strength-reduced layer then gives the separation area or the Ablöseebene.

According to a preferred embodiment of the present invention, a receiving layer is arranged on an exposed surface of the composite structure for introducing the external force, wherein the receiving layer comprises a polymer material and the receiving layer for thermally, especially mechanically, generating stresses in the solid body, wherein the thermal Loading is a cooling of the receiving layer to a temperature below the ambient temperature, wherein the cooling takes place such that the polymer material of the receiving layer makes a glass transition and wherein the tensions a crack in the solid propagates along the Ablöseebene, the first solid layer of the solid separated or the external force is introduced by an application of the solid with ultrasound in the solid, wherein the solid in this case preferably in a filled with a liquid container ter is arranged.

This embodiment is advantageous since, in particular when using the receiving layer, a very precise application of force and thus crack initiation and / or crack guidance can be effected.

In addition or as an alternative to the aforementioned embodiments, the abrasive or the material removal device can be modified, in particular, a fine grain of the abrasive can be provided or suitable grinding parameters such as speeds / delivery rate u. Ä. Be specified.

According to a further preferred embodiment of the present invention, the modifications are preferably produced by means of a multiphoton excitation, in particular a two-photon excitation, wherein initially a multiplicity of base modifications are produced on an at least partially homogeneously extending, in particular curved, line, in particular in the homogeneously extending section become. The basic modifications are preferably generated with predefined process parameters, the predefined process parameters preferably comprising the energy per shot and / or the shot density, wherein at least one value of these process parameters and preferably both values or all values of these process parameters or more than two values of these process parameters Dependent on the crystal lattice stability of the solid is set, the value being chosen so that the crystal lattice remains intact around the respective base modifications, further generating trigger modification for triggering subcritical cracks, wherein at least one process parameter for generating the trigger modifications of at least a process parameter for generating the base modifications is different, preferably, a plurality of process parameters are different from each other, and / or the trigger modifications are generated in a direction that is to the direction of the line, entl the base modifications are generated, inclined or spaced, wherein the subcritical cracks propagate less than 5mm.

According to a preferred embodiment, the solid-state material is silicon, wherein the numerical aperture is between 0.5 and 0.8, in particular 0.65, the irradiation depth between 200 .mu.m and 400 .mu.m, in particular at 300 .mu.m, the pulse spacing is between 1 .mu.m and 5 .mu.m, in particular at 2μm, the line spacing is between 1μm and 5μm, especially at 2μm, the pulse duration is between 50ns and 400ns, especially at 300ns, and the pulse energy is between 5μJ and 15μJ, especially at 10μJ.

According to a preferred embodiment, the solid-state material is SiC, the numerical aperture being between 0.5 and 0.8, in particular 0.4, the irradiation depth between 100 μm and 300 μm, in particular at 180 μm, the pulse spacing is between 0.1 μm and 3 μm , in particular at 1μm, the line spacing is between 20μm and 100μm, especially at 75μm, the pulse duration is between 1ns and 10ns, especially at 3ns, and the pulse energy is between 3μJ and 15μJ, especially at 7μJ.

The receiving layer according to a further preferred embodiment of the present invention consists massively at least predominantly and preferably completely of the polymer material, wherein the glass transition of the polymer material is between -100 ° C and 0 ° C, in particular between -85 ° C and -10 ° C or between 80 ° C and -20 ° C or between -65 ° C and -40 ° C or between -60 ° C and -50 ° C.

According to another preferred embodiment of the present invention, the polymeric material of the receiving layer is or consists of a polymer hybrid material forming a polymer matrix having a filler in the polymer matrix, the polymer matrix preferably being a polydimethylsiloxane matrix and wherein the mass fraction of the polymer matrix on the polymer hybrid material is preferably 80% to 99% and particularly preferably 90% to 99%.

According to the invention, therefore, a polymer hybrid material is specified for use in a splitting method in which at least two solid sections are produced from a solid starting material. The polymer hybrid material according to the invention comprises a polymer matrix and at least one first filler embedded therein. Insofar as in the following of one or the filler is mentioned, should also be included the possibility of multiple fillers. For example, the filler may comprise a mixture of different materials, e.g. As metal particles and inorganic fibers.

As polymer matrix, it is possible to use any polymer or a mixture of different polymers, with the aid of which it is possible to generate the voltages necessary for a division of the solid starting material. For example, the polymer matrix may be formed as an elastomer matrix, preferably as a polydiorganosiloxane matrix, particularly preferably as a polydimethylsiloxane matrix. Such polymer materials are particularly easy to use as a matrix material in combination with fillers, since the properties can be flexibly adjusted due to the variable degree of crosslinking and adapted to the respective filler and the solid-state starting material to be divided. According to one embodiment, the mass fraction of the polymer matrix on the polymer-hybrid material is 80% to 99%, 10 preferably 90% to 99%.

The first filler may be of organic or inorganic nature and consist of both a chemical element and a chemical compound or a mixture of substances, for example an alloy.

The first filler is designed to act as a reactant, initiator, catalyst, or promoter during debonding of the polymer hybrid material from the solid portion after division, and thereby to faster release of the polymer as compared to a polymeric material without a first filler Hybrid material from the solid-state section leads after division.

The specific chemical composition and configuration of the first filler and its mass fraction is dependent in particular on the specific material of the polymer matrix, which is to be detached, the solvent used for this and the reactants used. Furthermore, the material of the solid state starting material and the dimensions of the solid state starting material to be divided also play a role.

The concrete proportion of the first filler in the polymer matrix is highly dependent on the material of the filler and its mode of action. On the one hand, despite its filler, the polymer matrix must be able to do justice to its task of generating stresses. On the other hand, the proportion of the first filler must be high enough to achieve the desired effect on the polymer removal. The respective optimum mass fraction of the first filler can be determined by the person skilled in the art within the scope of simple experiments carried out in a concentration-dependent manner.

To improve the mechanical properties may additionally a further filler, such. As fumed silica contribute in the form of an inorganic network in the polymer. In addition to these strong interactions in the form of the network, less strong interactions can contribute to the improvement through purely hydrodynamic enhancements. By way of example, a targeted increase in viscosity should be mentioned, which enables improved processing in the splitting method and thus can contribute to improved manufacturing tolerances. Furthermore, by this interaction, a reduction of the internal

Degrees of freedom in terms of structural reorientation difficult with increasing reinforcement.

This leads to a desired lowering of the glass transition temperature of the polymer used in the polymer hybrid material, which allows the advantage of a lower temperature in the splitting process. According to the invention, the first filler in a polymer hybrid material for accelerating the detachment of the polymer hybrid material from a solid section, which is divided by division by means of a splitting process, in which a solid starting material is divided into at least two solid sections, is used.

The first filler may be distributed in the polymer matrix such that the mass fraction of the first filler from the outside, i. H. lower boundary surface of the polymer hybrid material, which is connected during the splitting process with the solid state starting material, in the direction of a parallel to the lower interface disposed further interface of the polymer hybrid material, decreases. This means that the mass fraction of the filler near the solid state starting material or section is greater than in the other regions of the polymer hybrid material. This distribution of the first filler allows a particularly effective removal of the polymer-hybrid material after the separation, since the first filler is close to the interface to the solid section and can exert its effect there. At the same time, the remaining areas of the polymer-hybrid material have less or no proportions of the first filler, so that the function of the polymer is influenced as little as possible.

In one embodiment, the polymer hybrid material is layered, wherein only one of the solid state starting material facing layer has the first filler, while the remaining polymer hybrid material is free of the first filler.

Further, a lower portion of the polymer hybrid material adjacent to its lower interface may be free of the first filler. Thus, a range sequence may result as follows: Adjacent to the solid state starting material there is first an area without first filler, followed by an area with a high proportion of first filler and then an area with a low proportion of first filler or without first filler.

These and all ranges described below may be in the form of layers, i. H. the region extends predominantly parallel to the interface of the solid state starting material to which the polymer hybrid material is applied and has a longitudinal and transverse extent at least in the region of this interface.

A lower region without a first filler can be provided, in particular, in the event that the first filler adversely affects the adhesion of the polymer hybrid. Material on the solid state starting material deteriorates. To avoid this, an area without a first filler is first arranged, followed by an area with a high proportion of the first filler, so that the first filler can fulfill its function. A lower layer without a first filler may, for example, have a thickness between 10 .mu.m and 500 .mu.m, for example 100 .mu.m.

Furthermore, an upper portion of the polymer hybrid material adjacent to its upper interface may be free of the first filler. By the upper interface is meant the interface which confines the polymer-hybrid material opposite the lower interface and the solid state starting material to the environment. Lower and upper interfaces can be arranged parallel to each other.

Such an upper region without a first filler may be provided in particular if the first filler adversely affects the heat transfer between the environment and the polymer hybrid material, for example if the cooling of the polymer hybrid material were to be delayed.

The first filler may comprise or consist of a material capable of reacting with a reactant, preferably an oxidant, to release a gaseous product.

As a result, cavities can be generated in the polymer matrix, which allow for faster access of the reactants and solvents to the polymer matrix and any sacrificial layer present and, moreover, effect a faster removal of the educts and dissolved constituents.

By generating gaseous reaction products, additional driving forces can be introduced to further assist in the removal of the polymer hybrid material.

The formation of additional cavities and the formation of gaseous reaction products accelerate the polymer removal and therefore contributes to an increase in the overall yield of the splitting process. By varying the proportion of the first filler, the cavity density can be selectively influenced in the boundary region between the solid body section and the polymer hybrid material or between the sacrificial layer and the polymer hybrid material.

The first filler may comprise a metal, in particular aluminum, iron, zinc and / or copper or consist of a metal, in particular the aforementioned metals.

"Consisting of" includes all materials referred to above, that technologically caused impurities or technologically caused admixtures, the z. B. the preparation of the fillers and their distribution or attachment to the polymer matrix are useful, may be included.

Metallic fillers may be treated with oxidizing agents, e.g. Hydrochloric acid, nitric acid, citric acid, formic acid or sulfamic acid react to release a gaseous product and thereby be removed from the polymer hybrid material.

For example, aluminum reacts with concentrated hydrochloric acid to form solvated metal ions and hydrogen according to the following HCl + 2 Al + 12 H2O! 2 [AlCl3 * 6 H2O] + 3 H2 Equation: 6

Similarly, the reaction of zinc as a filler by reaction with concentrated hydrochloric acid leads to the formation of 5 additional cavities: Zn + 2 HCl! ZnCl2 + H2 In the examples mentioned, the generation of hydrogen introduces additional driving forces which are responsible for the removal of the polymer. Continue to support hybrid materials. In addition, the first filler may improve the thermal conductivity within the polymer hybrid material, for example, by having the first filler having a higher thermal conductivity than the polymer of the polymer matrix. This may be the case, for example. Another advantage in the case where the first filler comprises a metal is the improved thermal diffusivity within the polymer hybrid material. As a result of improved thermal conductivity, the stresses generated by the cooling of the solid state starting material can be more effectively, i. H. be faster and with less consumption of coolant, be generated. Increasing this can increase the overall yield of the splitting process.

Furthermore, a second filler can be provided in the polymer hybrid material which increases the adhesion of the polymer hybrid material on the solid state starting material compared to a polymer hybrid material without a second filler. Preferably, the adhesion is increased compared to a polymer material without filler.

For example, the second filler may be a filler that can be activated by plasma. Plasma activation results in new surface species that can be created to interact more strongly with the surface of the solid state surface. As a result, the adhesion of the polymer hybrid material is improved.

The type of surface species achievable by the plasma treatment is primarily dependent on the process control of the plasma process. For example, during the plasma treatment, gases such as nitrogen, oxygen, silanes or chlorosilanes can be added, so that, for example, polar groups are formed which can interact more strongly with the surface of the solid starting material.

The second filler may be distributed in the polymer matrix 15 such that the mass fraction of the second filler increases toward the lower interface. For example, the polymer-hybrid material may contain the second filler only in a region adjacent to the lower interface, which region may also be formed as a layer in the sense of the above definition.

This allows the placement of the second filler preferably near the interface between polymer hybrid material and solid state starting material, thereby improving adhesion and thus enabling greater force transfer into the solid state starting material to be divided. For example, the second filler may comprise core-shell polymer particles or core-shell polymer particles.

In this case, preference is given to particles whose polymer composition differs from the polymer matrix of the polymer hybrid material in that in particular the surface, i. H. the shell, the core-shell particles is more activated, z. B. by means of low temperature plasma.

Examples of these are core-shell particles comprising a polysiloxane core with an acrylate shell or comprising a nanoscale silicate core with an epoxy shell or comprising a rubber particle core with an epoxy shell or comprising a nitrile rubber particle core with an epoxy -Bowl. The second filler may be prepared by means of low temperature plasma, e.g. Cold plasma, be activated. For example, the plasma can be generated by means of dielectric barrier discharge (DBE). In this case, electron densities in the range of 1014 to 1016 m-3 can be generated. The average temperature of DBE-generated "cold" nonequilibrium plasma (plasma volume) is approximately 300 ± 40 K at ambient pressure. The average temperature of the non-thermal plasma generated by DBE is about 70 ° C at ambient pressure.

In the case of DBE treatment, for example, the surface is subjected to uni- or bipolar pulses with pulse durations from a few microseconds to a few tens of nanoseconds and amplitudes in the single-digit to double-digit kilovolt range. In this case, no metallic electrodes in the discharge space and thus no metallic impurities or electrode wear are to be expected.

In addition, a high efficiency is advantageous because no charge carriers have to leave or enter the electrodes.

Dielectric surfaces can be modified at low temperatures and chemically activated. The surface modification can be carried out, for example, by an interaction and reaction of the surface species by ion bombardment.

Furthermore, specifically process gases, such. As nitrogen, oxygen, hydrogen, silanes or chlorosilanes, z. For example, SixHyEz where E = F, Cl, Br, I, O, Hundx = 0 to 10, z = 0 to 10, SiH4, Si (EtO) 4 or Me3SiOSiMe3 are added in a plasma treatment to, for example, add certain surface chemical groups produce. The second filler can furthermore be activatable by means of corona treatment, flame treatment, fluorination, ozonation or UV treatment or eximer irradiation. By such activation, for example, polar groups are generated on the surface of the second filler which can interact with the surface of the solid state starting material to improve adhesion. The polymer hybrid material may further comprise a third filler as compared to a polymer hybrid material having a first or to a polymer hybrid material having a first and a second filler. This third filler has a higher thermal conductivity and / or a higher modulus of elasticity compared to the polymer of the polymer matrix.

For example, the modulus of elasticity of the polymer at low temperature conditions is in the lower single-digit gigapascal range (about 1-3 GPa), while, for example, metallic fillers have an E-modulus in the two-digit to three-digit gigapascal range. With a corresponding high filler content, a percolating filler network is possible, allowing for improved "force coupling" into the solid state starting material.

The percolation is significantly influenced by the volumetric fill level of the respective fillers (eg 0.1% by volume, 130% by volume to 10% by volume depending on the aspect ratio). With increasing introduction of force, the viscoelastic layer structure of the polymer structure can be immersed and several percolation paths become effective. Here, improved heat transfer can be enabled, as it is too improved contact of the fillers with the surface of the solid state starting material can occur.

The mechanical stability of the polymer hybrid material is achieved faster even at low temperatures. In sum, there is a lower standard deviation of the corresponding structural property profiles such. B. breaking stress and elongation at break of the polymer-hybrid material and thus to an increase in the overall yield of the splitting process. The spatially resolved property profile changes (stress peaks in the polymer hybrid material) and thus in the solid state are smaller, which leads to a higher overall yield of the splitting process and a better quality of the solid sections produced.

The third filler can provide improved heat transfer between the environment and polymer hybrid material and faster heat conduction within the polymer hybrid material, so that the polymer hybrid material can be cooled faster and the splitting process performed faster overall and thus more effectively can be.

By increasing the modulus of elasticity, higher voltages can be generated for the division of the solid state starting material, so that it is also possible to split solid starting materials for which a particularly high voltage is required.

In addition, the third filler can also be used to influence the thermal expansion coefficient. The aim is to maximize the difference between the coefficients of thermal expansion of the polymer hybrid material and the solid state starting material to be divided in order to generate additional stresses necessary for the division. Preferably, the third filler has a high thermal expansion coefficient, d. H. an expansion coefficient higher than that of the polymer matrix. For example, the thermal expansion coefficient of the third filler may be more than 300 ppm / K.

The third filler may be distributed in the polymer matrix such that the mass fraction of the third filler increases toward the upper interface to allow faster heat transfer, particularly at the interface to the environment.

The third filler may comprise a metal, in particular aluminum, iron, zinc and / or copper, or consist of one of the metals mentioned. Metals are generally characterized by high thermal conductivity and thermal conductivity.

The described fillers (first, second, third filler) may be distributed in particulate form in the polymer matrix, wherein the particle size in the um and nm range, based on at least one dimension of the particle, may be. In addition to a spherical shape, the filler particles can also assume other configurations, for example a rod-shaped or disc-shaped form.

The filler particles can have all particle size distributions, for example monomodal or bimodal, narrow, in particular monodisperse, or broad. The fillers can be attached to the polymer matrix both physically, e.g. B. by embedding in the polymer network, as well as be chemically attached. Furthermore, one or more of the fillers described may comprise or consist of inorganic or organic fibers, for example carbon, glass, basalt or aramid fibers, provided that the functions described above are compatible therewith. Optionally, another filler may be added comprising or consisting of said fibers.

Fibers usually have strongly anisotropic properties. By a direction-dependent positioning of the filler in the polymer-hybrid material, there is the possibility of a targeted influencing the necessary for the division of the solid state starting material voltages. This can help increase the overall yield of the splitting process. An additional advantage, in the case where an organic or inorganic filler is used as a pulp having a highly anisotropic structure, is that it can achieve an improvement in mechanical properties within the polymer-hybrid material.

The described fillers may also comprise or consist of core-shell particles. Additionally or alternatively, a further filler may be provided comprising or consisting of core-shell particles in the polymer hybrid material.

The use of core-shell polymer particles in addition to an improved activatability also allows a new design of energy-absorbing mechanisms, which in total to an impact and fracture toughness increase, in particular an increase in the low-temperature impact strength of the polymer hybrid material when used in splitting Method and thus can also contribute to a higher overall yield of the splitting method. For example, a mechanical destruction of a sheet of a polymer hybrid material may occur with less likelihood, so the possibility a reuse of the film can be favored.

For example, by suppressing the crack propagation due to core-shell polymer particles, destruction of the film in the splitting process can be prevented and thus recycling paths can be opened up.

In this case, contained elastomer particles can undergo plastic deformation and form cavities, whereby further additional energy can be absorbed. Likewise, an additional energy absorption is compensated by the shear flow of the matrix, which improves the overall mechanical properties. Core-shell particles are characterized by the fact that a generally spherical core of a material is surrounded by a shell of a second material. The shell can either completely encase the core or be permeable. The materials may be both inorganic materials, such as. As metals, or organic materials such. As polymers act. For example, two different metals can be combined with each other. But it is also possible to surround a core of a polymer with a shell of a metal or a second polymer.

Core-shell particles allow the combination of the properties of the first and second materials. For example, via an inexpensive polymer core the

Size and density of the filler particles are set, while the metallic shell can react as described above. Due to their often monodisperse particle size distribution, the properties of the core-shell particles can also be accurately predicted and adjusted.

In addition, one or more fillers (first, second and / or third filler) may be carbon in the form of carbon black, graphite, chopped carbon fibers, carbon nanofibers, preferably in the form of carbon nanotubes. carbon nanotubes, CNT), such as multi-walled carbon nanotubes (MWCNT) as well as single-walled carbon nanotubes (SWCNT). Carbon nanotubes are cylindrical graphite sheets made up of a different number of cylinders.

If these tubes consist of only one cylinder, they are called singlewalled carbon nanotubes (SWCNT). If there are two or more cylinders, either double-walled (DWCNT) or multi-walled carbon nanotubes (MWCNT) are created. These may preferably be concentrically nested in one another.

According to various embodiments, the third filler MWCNTs include or consist of these, since they have a particularly high thermal conductivity (> 3000 W * (m * K) -1) and at the same time have a very high tensile strength in the range of 5-60 GPa. The high mechanical stability is reflected in high tear values, extreme elasticity and a very good durability of the filler.

This is based on the sp2-hybridized strong σ-C-C bonds linked to a delocalized p orbital as an n bond to three adjacent carbon atoms. This bending up to 90 ° are possible.

Even higher property values can be achieved with SWCNT (modulus of elasticity: 410 GPa to 4150 GPa vs. graphite: 1000 GPa, SWCNT: thermal conductivity approx. 6000 W * (m * K) -1). However, here shows a worse performance / cost ratio compared to MWCNT. The cylinder diameters of MWCNT are typically in the range of 1 nm to 100 nm, preferably 5 to 50 nm, with a length of 500 nm to 1000 microns.

According to further embodiments, the third filler may comprise MWCNT and at the same time the second and / or first filler may comprise or consist of carbon black, since here too an improvement of the thermal conductivity (eg up to 200 W * (m * K) -1) can be achieved. Since the use of exemplary carbon black having a significantly lower tensile strength with values of <0.4 GPa, a combination of both or other fillers is possible and can lead to an improvement in the Gesamtplitausbeute and to improve the overall costs in the splitting process.

Here, the average diameter of the carbon black particles (carbon black) in the range of 5 nm to 500 nm, preferably from 20 nm to 200 nm, more preferably from 40 nm to 100 nm.

Furthermore, the fillers may comprise or consist of silica, for example fumed silica. In addition or as an alternative, a further filler comprising or consisting of silicic acid may be provided in the polymer hybrid material.

Pyrogenic silica can form a three-dimensional network and thereby contribute to the improvement of mechanical stability. Thus, such a filler of the targeted adjustment of the mechanical properties of the Serve polymer hybrid material. One or more of the said fillers (first, second, third filler) may be of the same material, as long as this is compatible with the function attributed to them. For example, both the first and the third filler comprise aluminum or consist of aluminum. As described above, aluminum can be used both to generate cavities and thus to accelerate the detachment of the polymer hybrid material from the solid body section and to increase the thermal conductivity. Such a configuration simplifies the manufacturing process, since it may be sufficient to add only one or two fillers to perform all functions.

First and second and possibly third filler can also consist of different materials. This allows an individual and thus better adaptation of the filler to the desired function.

A film of the invention comprises a polymer hybrid material as described above. The film may have a thickness of, for example, 0.5 to 5 mm.

An inventive polymer hybrid material or a film according to the invention is applied to at least this surface so that a corresponding composite structure results. The applied polymer-hybrid material or the applied film are also referred to below as recording layer. The thickness of such a receiving layer may be, for example, between 0.5 mm and 5 mm, in particular between 1 mm and 3 mm. Optionally, the polymer hybrid material or the film can also be applied to a plurality of exposed surfaces, in particular to surfaces arranged parallel to one another.

The thermal exposure preferably means that the receiving layer is cooled below the ambient temperature and preferably below 10 ° C and more preferably below 0 ° C and more preferably below -10 ° C or below -40 ° C.

The cooling of the receiving layer is most preferably such that at least a part of the receiving layer completes a glass transition. The cooling can be a cooling to below -100 ° C, the z. B. by means of liquid nitrogen is effected. This embodiment is advantageous because the receiving layer contracts as a function of the temperature change and / or undergoes a glass transition and the resulting forces are transferred to the solid state starting material, whereby mechanical stresses can be generated in the solid, which trigger a crack and / or or crack propagation, wherein the crack first propagates along the first release plane to cleave the solid layer.

In a further step, the polymer hybrid material or the film is removed from the solid section, for example by a chemical reaction, a physical detachment process and / or mechanical removal.

The detachment process of the polymer hybrid material from the solid section can at moderate ambient temperature, for. B. in the range of 20 ° C to 30 ° C, preferably in the higher temperature range of 30 ° C to 95 ° C, z. B. from 50 ° C to 90 ° C, or for example in a lower temperature range between 1 ° C and 19 ° C.

The elevated temperature range may allow for shortening of a chemical release reaction due to an increase in the reaction rate, e.g. Example, in the case of using a sacrificial layer between the polymer hybrid material and the solid. In the case of the use of a sacrificial layer, the detachment may take place in aqueous solution, advantageously at a pH in the range 2-6. According to various embodiments, the dissolution process may take the form of a treatment with a solution of a suitable apolar solvent, for example Ambient temperatures in the range of 1 ° C to 50 ° C are preferred and from 20 ° C to 40 ° C are particularly preferred.

A particular advantage here is the detachment without a temperature effect on the film. This can advantageously aliphatic and aromatic hydrocarbons such. As toluene, n-pentane, n-hexane, but also halogenated solvents, such as. As carbon tetrachloride, are applied. In this case, additional forces can be introduced into the polymer hybrid material to be detached and the interface to the solid body section, since a very strong reversible swelling of the polymer-hybrid material can occur due to a solvent treatment, as a result of which the removal is simplified as a whole.

According to further embodiments, a combination 25 with the above-described detachment mechanism of the sacrificial layer and the treatment with a suitable non-polar solvent can be carried out - also without affecting the temperature of the film.

A stabilizing layer for limiting deformation of the exposed layer or parts may be disposed or formed on the exposed layer or exposed parts of the resulting composite structure, wherein the deformations result from the introduced by means of the recording layer mechanical stresses. The side with components is thus preferably protected and held (eg against warping of the substrate or the solid and gray space conditions). This can be done via soluble polymers (organics) or holding layers. This embodiment is advantageous because it limits interactions with, for example, small mem- brane structures. The surface finish of a wafer-finished wafer is usually not regular, which can lead to field swell and local surface damage if it is moved too sharply or abruptly. Thus, this embodiment represents a solution which provides good protection of the solid state layer and the layers and / or components arranged thereon and / or produced, in particular against mechanical damage or destruction.

The aforementioned object is also achieved according to the invention by a method according to claim 12 for increasing the surface quality of a surface exposed by a crack guide of an ingot or a wafer separated from the ingot or a solid portion separated from a wafer or the surface of the wafer exposed by the separation of the solid portion solved. This method preferably comprises at least the steps of: treating the surface of the solid-state layer exposed by the separation of the surface to increase the strength of the inner structure of the solid-state layer and / or reducing the mechanical stress acting on the inner structure of the solid-state layer during a machining process and modifying the Surface finish of the treated surface of the solid state layer by polishing. This solution is advantageous because significant material savings can be realized by limiting microcracking and / or spreading.

According to a particular embodiment of the present invention, the treatment for reducing the mechanical stress acting on the inner structure of the residual solids according to a particular embodiment of the present invention, the arrangement of a filler on the exposed surface, wherein at least in sections, the filler material and the solid material are removed at the same time during grinding or polishing or the treatment for reducing the mechanical stress acting on the inner structure of the residual solids during the machining process comprises a reduction of the surface roughness by means of etching, wherein the etching increases the area to be contacted with a tool for machining, in particular grinding or polishing or the treatment for increasing the strength of the internal structure of the solid-state layer is effected by annealing or local fusing or laser polishing.

Furthermore, the present invention still relates to a wafer or ingot which is produced by a previously mentioned method, wherein the treated surface shines, in particular an average roughness of less than 150 nm, in particular less than 100 nm or less than 80 nm or less 50nm or less than 20nm. An inventive effect on the ingot is that this is much more economical, since thinner wafers can be split off and result in less material losses in the preparation of the ingot for further solid-state layer separation.

Furthermore, the objects of the patent application filed on 07.12.2016 with the German Patent and Trademark Office DE 10 2016 123 679.9 fully incorporated by reference into the subject matter of this protective right.

Further advantages, objects and characteristics of the present invention will be explained with reference to the following description of appended drawings, in which the separation process according to the invention is shown by way of example. Components or elements which are preferably used in the method according to the invention and / or which at least substantially coincide in the figures in terms of their function, may here be identified by the same reference numerals, these components or elements need not be quantified or explained in all figures.

• 1a die Veränderung eines mittels Tempern modifizierten Festkörpers;
• 1b das Einsparpotential bei einem mittels Tempern modifizierten Festkörpers gegenüber einem nicht modifizierten Festkörper, bei dem sich die Mikrorisse weiter ausbreiten können;
• 2 einen Vergleich von drei Schleifprozessen und den jeweiligen Materialverlustreduzierungen der einzelnen vorgenommenen Behandlungen.
• 1a zeigt ein Beispiel für einen Temperschritt zur Entfernung von Subsurface-Damage (Tiefenschäden). Es ist ersichtlich, dass nach dem Temperschritt eine Vielzahl oder die Mehrzahl oder alle Mikrorisse 1 aus dem Festkörper ausgeheilt werden konnten.
• 1b zeigt die sich daraus beim Materialabtrag mittels einer Materialabtrageeinrichtung 10 ergebende Materialeinsparung 11 gegenüber einem unbehandelten Festkörper. Diese Verfahren werden erfindungsgemäß bevorzugt bei Silizium eingesetzt.

Show:

• 1a the change of a temper-modified solid;
• 1b the potential for savings in a temper-modified solid compared to an unmodified solid in which the microcracks can propagate further;
• 2 a comparison of three grinding processes and the respective material loss reduction of the individual treatments carried out.
• 1a shows an example of an annealing step to remove subsurface damage. It can be seen that after the annealing step, a large number or the majority or all of the microcracks 1 could be healed out of the solid.
• 1b shows it from the material removal by means of a Materialabtrageeinrichtung 10th resulting material savings 11 compared to an untreated solid. These methods are used according to the invention preferably in silicon.

Damage can thus be properly healed before sanding / polishing takes place.

2 shows at ( 1 ) a grinding process without intermediate step and surface treatment. In this grinding process cracks or microcracks resulting from the separation from the donor substrate are produced 2 when grinding as longer cracks or microcracks 4 into the depth of the solid 1 driven, which require additional grinding and therefore additional grinding losses.

By ( 2 ) shows a grinding process in which a job of a protective layer 8th to fill the surface contours is made. The filling of the surface or of microcracks can be done with a coating or additional materials, which mitigates or prevents sharp edges and thus breakouts and crack growth during grinding. The protective layer 8th thus causes an inhibition of crack growth during grinding and / or avoids breakouts on sharp edges. It can be seen that when grinding mechanically into the solid state 1 introduced forces are locally lower than without a protective layer 8th because the contact surface between the chip removal device 10 , in particular grinding tool or grinding device, and the solid surface is larger. Compared to a grinding process without prior treatment, the reference numeral 12 realize schematically marked material savings.

By (3), an etching step for rounding surface contours is shown - also for outbreak and crack growth inhibition. The existing cracks or microcracks are thus shortened 6. It can be seen that when grinding mechanically into the solid 1 introduced forces are locally lower than without an etching step (especially against the case ( 1 )), since the contact surface between chip removal device, in particular grinding tool or grinding device, and the solid surface is greater compared to an untreated surface. Compared to a grinding process ( 2 ) can be by the reference numeral 14 realize schematically marked material savings.

Generally, the process of cleaving solid state layers of solids to minimize surface roughness (particularly average roughness) is optimized to obtain the smallest possible thickness variation of the final wafer and thereby minimize grinding / polishing losses.

LIST OF REFERENCE NUMBERS

1

solid

2

Output microcracks

4

enlarged microcracks

6

shorter etched microcracks

8th

filling layer

10

Material removing device

11

first savings

12

second savings

14

third savings

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2914/177721 A1 [0005]
• DE 102016123679 [0110]

Claims (14)

Process for producing a solid state layer at least comprising the steps: Generating a plurality of modifications by means of laser beams inside a solid (1) to form a release plane, Introducing an external force into the solid (1) to create stresses in the solid (1), the external force being strong enough for the stresses to cause crack propagation to separate the solid layer from the solid along the release plane, Treating the surface of the solid-state layer exposed by the separation of the surface in order to increase the strength of the inner structure of the solid-state layer and / or to reduce the mechanical stress acting on the inner structure of the solid-state layer during a machining process, Change the surface finish of the treated surface of the solid layer by polishing. Process for producing a solid state layer at least comprising the steps: Generating a plurality of modifications by means of laser beams inside a solid (1) to form a release plane, Introducing an external force into the solid (1) to create stresses in the solid (1), the external force being strong enough for the stresses to cause crack propagation to separate the solid layer from the solid along the release plane, Treating the surface of the residual solids released by the separation of the surface for increasing the strength of the internal structure of the residual solids and / or for reducing the mechanical stress acting on the internal structure of the residual solids during a cutting process, Changing the surface quality of the treated surface of the solid state layer by polishing, reproducing a plurality of modifications by means of laser beams inside a solid (1) to form a further release plane, wherein the laser beams are introduced into the solid body (1) via the polished surface, reintroducing an external force into the solid (1) to create stresses in the solid (1), the external force being strong enough to cause crack propagation to separate another solid layer from the solid (1) along the release plane , Method according to one of the preceding claims, characterized in that prior to polishing and after treatment, the exposed surface treated by machining, in particular ground or lapped, is. Method according to one of the preceding claims, characterized in that the treatment for reducing the mechanical stress acting on the internal structure of the residual solids or the separated solid layer in the cutting process comprises the arrangement of a filling material on the exposed surface, wherein at least in sections during grinding or polishing the filling material and the solid-state material are removed at the same time or the treatment for reducing the mechanical stress acting on the internal structure of the residual solid or the separated residual solid layer in the cutting process comprises a reduction of the surface roughness by means of etching, wherein the etching with a tool for machining , in particular the grinding or polishing, contactable surface is increased. Method according to one of the preceding claims, characterized in that the solid body comprises or consists of SiC. Method according to one of Claims 1 to 3 , characterized in that the treatment for increasing the strength of the internal structure of the solid layer or the residual solid is effected by annealing or local melting or laser polishing. Method according to Claim 6 , characterized in that the solid body comprises or consists of silicon. Method according to one of the preceding claims, characterized in that for introducing the external force, a receiving layer on an exposed surface of the composite structure is arranged, wherein the receiving layer comprises a polymer material and the receiving layer for, in particular mechanical, generating stresses in the solid is thermally acted upon wherein the thermal impingement comprises cooling the receptive layer to a temperature below the ambient temperature, the cooling being such that the polymeric material of the receptive layer forms a glass transition, and wherein the tensions propagate a crack in the solid along the release plane, which is the first Solid layer separates from the solid. Method according to one of the preceding claims, characterized in that the modifications are produced by multiphoton excitation, wherein a plurality of base modifications are first generated on an at least partially homogeneously extending, in particular curved, line, in particular in the homogeneously extending section, wherein these base modifications are generated with predefined process parameters, wherein the predefined process parameters preferably the energy per shot and / or the weft density, wherein at least one value of these process parameters and preferably both values or all values of these process parameters or more than two values of these process parameters is determined as a function of the crystal lattice stability of the solid, wherein the value is chosen such that the crystal lattice the respective base modifications remain intact, further generating trigger modification for triggering subcritical cracks, wherein at least one process parameter for generating the trigger modifications of at least one process parameter for generating the Ba Preferably, several process parameters are different from each other, and / or the trigger modifications are generated in a direction that is inclined or spaced to the course of the line along which the base modifications are generated, with the subcritical cracks being less spread as 5mm. Method according to one of the preceding claims, characterized in that the solid-state material is silicon, wherein the numerical aperture between 0.5 and 0.8, in particular at 0.65, the Einstrahltiefe between 200μm and 400μm, in particular at 300μm, is the Pulse spacing between 1 .mu.m and 5 .mu.m, in particular at 2 .mu.m, the line spacing is between 1 .mu.m and 5 .mu.m, in particular at 2 .mu.m, the pulse duration is between 50ns and 400 ns, in particular at 300 ns, and the pulse energy is between 5 .mu.J and 15 .mu.J, in particular at 10 .mu.J, or the solid state material is SiC, wherein the numerical aperture is between 0.5 and 0.8, in particular at 0.4, the irradiation depth between 100 .mu.m and 300 .mu.m, in particular at 180 .mu.m, the pulse spacing is between 0.1 .mu.m and 3 .mu.m, in particular at 1μm, the line spacing between 20μm and 100μm, in particular at 75 microns, is, the pulse duration between 1ns and 10ns, in particular at 3ns, and the pulse energy zwi 3μJ and 15μJ, especially at 7μJ, lies. Method according to one of the preceding claims, characterized in that the receiving layer mass moderately at least majority, and preferably consists entirely of the polymer material, wherein the glass transition of the polymer material between - 100 ° C and 0 ° C, in particular between -85 ° C and -10 ° C. or between -80 ° C and -20 ° C or between -65 ° C and -40 ° C or between -60 ° C and -50 ° C, wherein the receiving layer is preferably made of a polymer hybrid material, the forming a polymer matrix having a filler in the polymer matrix, wherein the polymer matrix is preferably a polydimethylsiloxane matrix and wherein the mass fraction of the polymer matrix on the polymer hybrid material is preferably 80% to 99% and more preferably 90% to 99%. A method for increasing the surface quality of a surface exposed by a crack guide of an ingot or a wafer separated from the ingot or a solid portion separated from a wafer or the surface of the wafer exposed by the separation of the solid portion, at least comprising the steps: Treating the surface of the solid-state layer exposed by the separation of the surface in order to increase the strength of the inner structure of the solid-state layer and / or to reduce the mechanical stress acting on the inner structure of the solid-state layer during a machining process, Change the surface finish of the treated surface of the solid layer by polishing. Method according to Claim 12 , characterized in that the treatment for reducing the mechanical stress acting on the internal structure of the residual solids in the machining process comprises the arrangement of a filling material on the exposed surface, wherein at least in sections, the filler material and the solid material are removed during grinding or polishing or the Treatment for reducing the mechanical stress acting on the internal structure of the residual solids in the cutting process comprises a reduction of the surface roughness by means of etching, wherein the etching is increased with a tool for machining, in particular grinding or polishing, in contactable surface or Treatment to increase the strength of the internal structure of the solid state layer is effected by annealing or local melting or laser polishing. Wafer or ingot produced according to a previously mentioned method, characterized in that the treated surface shines.

Images