METHOD FOR SEPARING A PLATE INTO INDIVIDUAL COMPONENTS

Description

[0001] The invention relates to the separation of a wafer into a plurality of detached individual components, also known as chip singulation or wafer dicing. US 2008 / 003780, US 2010 / 233867, US 2016 / 035616 and WO 2008 / 005979 describe such methods.

[0002] Conventionally, a plate is manufactured by depositing on a wafer a stack of layers of semiconductors, metal or other, for example a channel layer, a barrier layer, etc. It is known to structure these layers by means of lithography, so that the chips can fulfill functionalities defined by specifications.

[0003] Post-processing is then planned (“back end process” in English).

[0004] Among the post-processing steps, a testing step can help identify potentially defective chips or classify chips according to various specifications. The measurements taken during this testing step involve physical contact with the board.

[0005] Then the singulation process takes place, that is, the resulting plate is cut into several individual components.

[0006] To do this, the plate is placed on a flexible, elastic, stretchable and sticky dicing film, and the assembly is installed on a vacuum table equipped with a suction system. The suction via holes defined in the vacuum table holds the assembly during the actual cutting.

[0007] Cutting can be done by sawing, but we also know cutting by grooving and cleaving, laser cutting and cutting by engraving.

[0008] In the case of laser cutting, protective layers can be removed and cleaning carried out.

[0009] In the case of sawing, water cleaning is carried out ("thorough water jet cleaning" in English).

[0010] Then the individual components are detached from the cutting film.

[0011] The plate can have a thickness of around 100 µm, but this thickness tends to decrease with the miniaturization of components and the increase in the frequencies of electrical signals in new areas of application. Plates of 25 or 50 µm are already encountered.

[0012] The thinner the plate, the greater the risk of damaging it, or even breaking it, during these post-manufacturing treatments, which imposes more constraints, particularly in terms of handling.

[0013] In particular, measurements taken before cutting and detaching may no longer be fully valid. This can lead to economic and reliability losses when these chips are subsequently mounted in subassemblies.

[0014] There is therefore a need for a less restrictive method of separating a plate into individual components.

[0015] A method of post-processing a wafer to obtain a plurality of detached individual electrical, optical or optoelectronic components is provided, comprising a) providing a substrate, b) fixing the plate to the substrate by means of a sacrificial layer between this plate and this substrate, the sacrificial layer being made of one (or more) material(s) in the solid state (advantageously rigid) at ambient temperature and pressure, and having a transformation temperature towards one or more gaseous compounds at ambient pressure of between 80°C and 600°C, c) separating the plate fixed on the substrate into a plurality of plate portions, d) increasing the temperature and / or decreasing the surrounding pressure to a sufficiently high temperature and / or to a sufficiently low pressure, respectively, to transform the sacrificial layer fixed to the plurality of plate portions into gaseous compound(s), the plurality of plate portions then resting directly on said substrate.

[0016] In step c), the separation of the plate into a plurality of plate portions may be carried out so as to leave the substrate in one piece. In other words, the separation does not affect the substrate.

[0017] Step d) may be carried out while the plurality of plate portions are attached to a single-piece substrate (a single substrate for a plurality of plate portions). The transformation into gaseous compound(s) of the sacrificial layer leaves the plurality of plate portions on this substrate.

[0018] Thus, rather than a flexible, elastic, stretchable and sticky cutting film, a relatively easy-to-remove sacrificial layer is used, which can facilitate post-manufacturing processes (e.g., measurements, cutting steps, transportation steps, etc.)

[0019] With the method described above, the elimination of the sacrificial layer can be relatively simple to carry out, in the sense that it is sufficient, for example, to heat to a sufficient temperature, the material(s) of the sacrificial layer then being eliminated from the assembly by transformation into one or more compounds in the gaseous state.

[0020] Surprisingly, once the sacrificial layer is transformed, the individual components can adhere slightly to the substrate, this adhesion being high enough that the entire substrate plus individual components can be transported easily, and at the same time low enough that each component can be grasped and detached from the substrate without risk of damaging it.

[0021] Furthermore, once the sacrificial layer is transformed, the location of the components is known, even if the entire substrate plus components have been transported. This eliminates the need for shape recognition tools to capture the components.

[0022] In some cases, it will even be possible to carry out electrical measurements on the components in order to sort them according to various specifications, and the information obtained will then allow the sorting of the chips during sampling, which will be representative of the final state of the chips.

[0023] Furthermore, there may no longer be any trace of this sacrificial layer remaining on the components. To the extent that the sacrificial material(s) used are completely transformed into one or more gaseous compounds by decomposition, sublimation or vaporization, when, after separation into chips and any associated cleaning operations, the temperature is raised above the transformation temperature, cleaning of the detached individual chips is no longer necessary.

[0024] The invention can also make it possible to avoid the step of illumination with ultraviolet radiation which is carried out in the prior art to reduce the adhesion of the flexible and sticky dicing film. This step takes place in the prior art after dicing, so that the adhesion remains high during separation, but before gripping the components, in order to facilitate the detachment of the flexible dicing film. In this case, in practice, residual adhesion always remains in the prior art, which makes the detachment of thin and fragile chips risky, especially when it is necessary to avoid bending the chips so as not to damage their structures. The invention can make it possible to reduce the adhesion of the chips to the substrate to a much lower value. This can be particularly interesting for chips with a thickness of less than 100 µm, and when the chips are made of materials which cleave easily, such as for example GaAs or InP.

[0025] To the extent that the assembly formed by the sacrificial layer and the substrate is more rigid than the cutting film of the prior art, the invention can make it easier to carry out on a very thin plate all the conventional technological manufacturing operations, after thinning, such as lithography, resin deposition, photo exposure, resin development, material layer deposition, etching, delacquering, cleaning, with a lower risk of cleavage of the plate, it being understood that the temperature during the operation remains lower than the transformation temperature of the sacrificial material. The sacrificial material can be chosen which has a sufficiently high transformation temperature for this, within the limit that the components on the chips must not be degraded during the transformation.

[0026] Step d) can advantageously be carried out until more than 90% by mass of the material(s) of the sacrificial layer is eliminated (by transformation), advantageously more than 99%, advantageously the entirety of this sacrificial layer.

[0027] The substrate can be flexible or rigid.

[0028] For example, in the case of a plate attached to a rigid substrate, the test steps can be carried out on the plate while it is attached to the substrate via the sacrificial layer. The risk of damage linked to the measurements is therefore lower due to the thickness of the assembly, and the choice of a substrate with good mechanical strength.

[0029] In some cases, electrical measurements (to classify the chips) may be performed after separation, because the chips are still attached to the substrate at the same fixed distances as they were before separation. The classifications resulting from these measurements may be more reliable than in the prior art.

[0030] The invention also makes it easier to transport the plate, because thanks to the rigidity provided by the substrate, the risk of damage is reduced. The invention can in particular make it easier to implement measurements at remote sites, because transport is thus less risky, and relatively simple.

[0031] The invention can thus significantly improve performance.

[0032] Advantageously, once the plate is fixed to the substrate, all the steps preceding step c) of separation are carried out under temperature and pressure conditions such that the sacrificial layer remains solid.

[0033] Operations such as transportation, measurements, mechanical cutting, etc. can be carried out at room temperature and pressure, i.e. the sacrificial layer is then solid.

[0034] The post-treatment method can thus advantageously comprise at least one treatment step carried out at ambient temperature and pressure, for example a measuring step, a transport step, a polishing step, a mechanical cutting step, or other.

[0035] Other operations such as laser cutting or other may involve an increase (possibly local) in temperature and / or pressure. Care should then be taken to maintain temperature and pressure conditions such that the sacrificial layer remains solid.

[0036] To eliminate the sacrificial layer, the temperature can be raised to the transformation temperature into one or more gaseous compounds, or to a higher temperature.

[0037] Of course, if the step of eliminating the sacrificial layer is carried out under a pressure different from ambient pressure, the temperature can be adapted to ensure the elimination of the sacrificial layer, particularly in the case of transformation by sublimation or vaporization.

[0038] The increase in temperature can thus be carried out in conjunction with a decrease in the surrounding pressure.

[0039] Alternatively, one can simply create a vacuum, without increasing the temperature, to eliminate the sacrificial layer, especially if the surrounding temperature is already high.

[0040] Advantageously, during step d), the temperature is increased to a temperature between 80°C and 600°C, advantageously a temperature above 100°C, advantageously 150°C, advantageously 200°C.

[0041] This temperature may advantageously be less than 500°C, advantageously be less than 400°C, advantageously be less than 350°C.

[0042] Advantageously, this temperature can be in a range between 230°C and 350°C.

[0043] The plate and substrate can be chosen to remain in the solid state when the temperature is increased.

[0044] The substrate can be advantageously reused.

[0045] The sacrificial layer can, at ambient pressure, be transformed into one or more gaseous compounds at a temperature between 80°C and 600°C, advantageously between 230°C and 350°C.

[0046] Advantageously and in a non-limiting manner, the sacrificial layer has a transformation temperature into one or more gaseous compounds, at ambient pressure, greater than 100°C, advantageously 150°C, advantageously 200°C.

[0047] Advantageously and in a non-limiting manner, the sacrificial layer has a transformation temperature into one or more gaseous compounds, at ambient pressure, of less than 500°C, advantageously less than 400°C, advantageously less than 350°C.

[0048] Advantageously, this transformation temperature into one or more gaseous compounds, at ambient pressure, can be in a range between 230°C and 350°C.

[0049] The ambient pressure may be between 50 kPa and 105 kPa, advantageously between 80 kPa and 105 kPa, for example equal to 101 kPa.

[0050] The ambient temperature may be between 0°C and 50°C, advantageously between 15°C and 35°C, for example between 20°C and 25°C.

[0051] By "transformation into one or more gaseous compounds" we mean both decomposition into one or more gaseous compounds and evaporation or sublimation.

[0052] By "decomposition temperature" is meant the temperature leading to the decomposition of half of the material in one hour.

[0053] The substrate may be a sapphire, silicon, glass, metal or other substrate.

[0054] The substrate may or may not be less than a millimeter thick.

[0055] It is advisable to choose for the substrate one (or more) material(s) resistant to the transformation temperature into one or more gaseous compounds of the sacrificial layer.

[0056] The plate can be rigid, or alternatively flexible. In the latter case, the plate and the substrate (e.g. a metal substrate) can, for example, be rolled into a roll. This roll can have a profile diameter of around 60 cm, for example.

[0057] In the case of a flexible plate, laser cutting may be preferred to carry out step c) of separation.

[0058] The plate may have a thickness of less than a millimeter, typically less than 200 µm, advantageously less than or equal to 100 µm.

[0059] The plate may comprise crystalline, semi-crystalline or amorphous materials, for example a semiconductor material, metal, a dielectric material, glass, a ceramic material, a polymer, or the like, a combination of these materials, for example in layers, a mixture of these materials, or the like.

[0060] In the case of a semiconductor wafer, the wafer may, for example, comprise essentially (i.e., more than 80% by mass) silicon Si, germanium Ge, gallium arsenide GaAs, indium arsenide InAs, indium phosphide InP, gallium phosphide GaP, gallium antimonide GaSb, indium antimonide InSb, silicon carbide SiC, gallium nitride GaN, aluminum nitride AlN, and / or diamond. These materials may be combined in layers, mixed, or otherwise.

[0061] The wafer from which the plate is made may essentially comprise one or more of these materials.

[0062] These materials can be doped or not.

[0063] In one embodiment, grooves may be provided on one face of the plate prior to fixing the plate to the substrate. The depth of these grooves does not reach the opposite face of the plate.

[0064] A groove depth equal to or slightly greater than the desired thickness of the chips when they are detached can be provided.

[0065] This groove formation step can, for example, be carried out by engraving, for example plasma engraving, by laser, and / or mechanically, for example using a saw blade.

[0066] This groove forming step can be relatively easy to carry out since the plate can at this stage have a relatively high thickness, for example of the order of 600 µm or 800 µm.

[0067] The grooved plate can then be attached via the sacrificial layer to the substrate (step b)).

[0068] Advantageously and in a non-limiting manner, this fixing can be carried out with the grooved face on the substrate side, that is to say that the face defining the grooves is then on the substrate side.

[0069] It can be provided that in step c), the plate is then slightly hollowed out at the locations of the grooves, for example until reaching the grooves or in such a way as to allow easy cleavage, to separate the plate into plate portions.

[0070] But advantageously, during separation step c), the plate can be thinned on the face opposite the grooved face. This thinning can, for example, be obtained by lapping, using a grinding wheel, by polishing, by chemical attack, or otherwise.

[0071] In an advantageous embodiment, the plate is thinned until it reaches the grooves, so that the thinning results in a separation of the plate into several plate portions.

[0072] Alternatively, thinning can be stopped while the grooves are not reached, particularly in the case of subsequent separation by cleavage. It is also possible to provide for the separation to be achieved by making cuts on the thinned plate fixed to the substrate, for example by means of laser, engraving, or other means. These cuts may be relatively shallow.

[0073] Advantageously, before detachment, while the chips are still attached to the substrate by the sacrificial layer, one or more processing steps can be provided, for example to add components, perform masking, etch holes (“via-holes” in English), etc. When the substrate is rigid, these processing steps can be relatively simple to carry out because the locations and alignments are relatively well controlled. These processing steps can occur before or after the separation step.

[0074] Advantageously, separation step c) may comprise a step of cutting the plate fixed to the substrate with the sacrificial layer, in particular when the plate has not been grooved.

[0075] In one embodiment, the cutting of the wafer into chips can be carried out (or induced, i.e. the cutting is followed by cleavage) mechanically, for example by means of a saw blade, in particular in the case of a rigid wafer. Due to the support provided by the sacrificial layer and the substrate, the risk of breakage or damage linked to the cutting is less than in the prior art, in which the thin wafer rests on a flexible, elastic and stretchable film.

[0076] A blade, such as a circular saw, can be arranged so that the depth of the cut reaches the substrate, particularly in the case of a silicon substrate.

[0077] Alternatively, the blade may be arranged to reach only the sacrificial layer, particularly in the case of a sapphire substrate.

[0078] A groove can be formed, for example, with a diamond, and then a cleavage can be provided.

[0079] In one embodiment, the cutting may be performed by engraving.

[0080] For example, the plate can be covered with one (or more) masking material(s) in which openings corresponding to the future contours of the components are defined.

[0081] To mask, you can, for example, use a simple layer of photosensitive resin.

[0082] In the case where a resin does not sufficiently resist the etching of the wafer materials, a layer of a material that resists etching may be used, such as a dielectric material such as silicon oxide or silicon nitride, or a metal such as nickel. The openings in this material that delimit the chips may be obtained by photolithography using conventional means known to those skilled in the art.

[0083] A step of removing the masking material(s) may be provided, advantageously prior to the increase in temperature leading to the elimination of the sacrificial layer.

[0084] We can provide wet chemical etching, photolithography, or other.

[0085] Advantageously, the cutting can be carried out by means of plasma etching. The invention makes it possible to avoid the constraints imposed by the flexible dicing film. Indeed, most of these flexible films are made from materials that degrade when the temperature rises above 100°C or 150°C, i.e. at temperatures easily reached when applying a plasma.

[0086] In particular, in the case of a plate made from a SiC wafer, this plate can reach even higher temperatures when applying a plasma, which in the prior art prohibits this type of cutting for this type of plate. Especially since parts of the flexible cutting film would then be directly exploded by plasma. The invention can thus make it possible to carry out separation by plasma cutting of a plate from a SiC wafer.

[0087] In another embodiment, several successive etchings may be carried out, particularly in the case of a plate comprising a stack of layers. Each etching may correspond to one or more layers.

[0088] In another embodiment, the cutting can be carried out or induced by means of a laser. Here again, the invention can make it possible to limit the tensions and deformations of the edges of the components, particularly in the case of a rigid sacrificial film.

[0089] For example, we can combine laser and cleavage (induced cutting).

[0090] In one embodiment, cutting may be conducted or induced by a combination of engraving(s), laser cutting, and / or mechanical cutting.

[0091] In one embodiment, step d) of increasing the temperature to remove the sacrificial layer may be accompanied by a reduction in pressure, for example to 1000 Pa or less, in order to facilitate this removal.

[0092] The method may further comprise a step of gripping the components thus obtained, for example using a rubber vacuum tool.

[0093] The invention makes it possible to carry out this capture without creating relatively high voltages, again limiting the risk of damage to the components. The methods known from the prior art, involving capture of a component resting on a flexible and generally relatively adhesive film, are likely to lead to damage which is sometimes not optically detectable, but which can affect the operation of the capacitors and transistors integrated in the component.

[0094] In one embodiment, the sacrificial layer may be polymer-based, i.e. comprise at least 50%, advantageously at least 70% or 90% by mass of raw polymers, advantageously between 99% and 100% by mass of raw polymers.

[0095] These raw polymers may advantageously consist, for example, of more than 70% by mass, advantageously of more than 90% by mass, advantageously between 99% and 100% by mass, of polypropylene carbonate molecules, other polycarbonates and / or polynorbornene molecules.

[0096] In this case, we are talking about polymers that decompose at a temperature between 80°C and 600°C, and which during this decomposition are transformed entirely into gaseous compounds, without residues.

[0097] In another embodiment, a material such as anthracene or camphor may be used as the sacrificial material, which can be removed by sublimation by raising the temperature under reduced pressure, without residue.

[0098] It should be noted that the plate can be attached to the substrate on the back side ("backside" in English) via the sacrificial layer, or on its other side ("front side" in English). Attaching to the back side can have the advantage of facilitating access to the components on the front side, particularly during the test stages.

[0099] In one embodiment, the attachment of the plate to the substrate via the sacrificial layer may be carried out at a temperature above a glass transition temperature of the material(s) of the sacrificial layer, advantageously by applying a uniaxial pressure force normal to the plate (for example of 10 or 30 N / cm 2< ) and / or under an ambient pressure of less than 50 kPa, advantageously under a high vacuum. Molecular attachment may thus be achieved, i.e. electrostatic forces such as Van der Waals forces participate in the attachment. This may be particularly advantageous in the case of a relatively weakly adhesive sacrificial layer material.

[0100] In the present application, "on" means both "directly on" and "indirectly on", that is to say that a layer deposited on another can be in contact with this other layer, or separated from this other layer by one or more intermediate layers.

[0101] One or more sacrificial layers may be provided, provided that the set of at least one layer is in contact with the plate and with the substrate. In other words, the sacrificial layer in contact with the plate and the substrate, and whose transformation to the gaseous state can cause the plate portions to adhere slightly to the substrate, may comprise several sub-layers, for example a first sub-layer made of a first material directly on the substrate and a second sub-layer made of a second material distinct from the first material, between the first sub-layer and the plate, and in contact with the first sub-layer and the plate.

[0102] This can be reformulated by stating that the plate is fixed to the substrate by a set of at least one sacrificial layer, in contact with the plate and with the substrate and that it is this set which is made of material(s) in the solid state (advantageously rigid) at ambient temperature and pressure, and having a transformation temperature towards one or more gaseous compounds at ambient pressure of between 80°C and 600°C, and that it is this set of at least one layer which is then transformed into one or more gaseous compounds.

[0103] The material(s) between the plate separated into plate portions and the substrate having been transformed into gaseous compound(s), these plate portions are then directly on the substrate, and, surprisingly, can adhere slightly to the substrate.

[0104] The invention is in no way limited by the way in which the sacrificial layer is applied to the substrate. For example, it may be possible to mix the material(s) of the sacrificial layer with a solvent, in order to obtain a liquid that is deposited on the substrate. The solvent then evaporates, leaving the material(s) of the sacrificial layer in place. A spinner may be used to obtain a layer of equal thickness over the entire surface, as used for spreading photosensitive resins on plates in the semiconductor industry.

[0105] Advantageously, the substrate may have a lateral expansion coefficient equal to or close to (relative difference of less than 5%) the lateral expansion coefficient of the plate. Thus, during the temperature increase required by various technological operations and during the temperature increase carried out in order to eliminate the sacrificial layer and / or during a temperature increase during measurements, it is possible to avoid creating tensions on the plate, which could cleave it, or which could lead to early delamination of the substrate-sacrificial layer-plate assembly.

[0106] The invention will be better understood with reference to the figures, which illustrate embodiments given by way of example and without limitation. THE figures 1 to 6 are sectional views, and very schematic, illustrating an example of a method according to an embodiment of the invention. The figures 7 to 11are sectional views, and very schematic, illustrating an example of a method according to another embodiment of the invention.

[0107] Identical references will be used from one figure to another to designate identical or similar elements.

[0108] In reference to the figure 1 , a rigid substrate 2 is provided, for example a sapphire substrate.

[0109] This substrate 2 is covered with a sacrificial layer 3.

[0110] This sacrificial layer is composed of more than 99% by mass of polymer molecules, for example polypropylene carbonate molecules.

[0111] This polymer material 3 can for example be applied to the substrate by the same usual methods of applying a photosensitive resin.

[0112] The polymer can be applied in solution in a solvent, with this solvent evaporating quickly after application.

[0113] Solvent evaporation can be completed by annealing at a temperature below the decomposition temperature of polypropylene carbonate.

[0114] A plate 1 is deposited on this polymer material 3, which is securely fixed by applying mechanical pressure perpendicular to the plate, at a temperature above the glass transition temperature of the sacrificial material.

[0115] As illustrated in the figures, this plate may comprise interconnections 7 and a metallization layer 8 (ground plane).

[0116] The solid material of layer 3 ensures the fixing of plate 1 to substrate 2, as illustrated by the figure 2 .

[0117] Plate 1 was obtained from a wafer, for example of GaAs, on which the elements constituting a semiconductor integrated circuit were deposited in a manner known per se, such as a barrier layer, a channel layer, drains, sources, etc. not shown here.

[0118] In this example, plate 1 is in contact with sacrificial layer 3 via its backside.

[0119] In this example, plate 1 may for example have a thickness of the order of 50 µm, and be intended to be used for components that process signals with frequencies of 300 GHz, which require the thickness not to be greater, to avoid parasitic transmission modes inside the chip.

[0120] In reference to the figure 2, which represents the plate 1 fixed to the substrate 2 before cutting, it is relatively easy to carry out transport and measurement operations using a probe, because the thickness of the substrate 2 compensates for the low thickness of the plate 1 and provides the mechanical strength necessary to considerably limit the risk of damage.

[0121] These measurements can sometimes be accompanied by temperature increases, under conditions such that the sacrificial layer remains intact, in which case it is wise to choose a substrate with an expansion coefficient close to that of the plate. In this example, the substrate is a sapphire substrate and the plate is of the GaAs type, but one could consider a substrate made of the same material as that of the wafer from which the plate is made.

[0122] In reference to the figure 3, to prepare the cutting step, photoresist material 4 is deposited so as to define rectilinear openings 5, corresponding to the future cuts.

[0123] Conventionally, rectilinear openings extending perpendicularly to the plane of the drawing will be provided, like those 5 visible in the figure, and other rectilinear openings parallel to each other and crossing the rectilinear openings extending perpendicularly to the plane of the sheet.

[0124] With engraving or laser cutting methods, these openings are not necessarily straight.

[0125] This grid of cutouts can thus define thousands of future components on the same plate.

[0126] Then a plasma is applied, so as to etch the plate 1 at the locations of the cutouts 5, as illustrated by the figure 4 . We can use RIE type engraving (for “Reactive Ion Etching”) in English).

[0127] The plate 1 is then cut into a plurality of plate portions 1', each corresponding to an individual component. In this example, these portions 1' rest on the same sacrificial layer 3.

[0128] The substrate, however, is not cut and remains in one piece.

[0129] A second plasma, of dioxygen, can then be applied to remove the mask 4 and dig out the sacrificial layer at the locations defined by the openings 5, as illustrated by the Figure 5 .

[0130] Then the temperature is increased, to 270°C for example, so that the polymers of the sacrificial layer 3 decompose and evaporate, as illustrated in the figure 6 .

[0131] The components 1' then adhere to the substrate 2 by relatively weak forces (probably Van der Waals), thus making it possible to move the assembly while maintaining the positions of the components 1" on the substrate.

[0132] A tool 6 performing a slight vacuum suction can make it possible to easily detach the components 1' from the substrate 2.

[0133] In the embodiment of the figures 7 to 11 , we start by defining grooves 19 on for example a front face of a thick plate 11.

[0134] On this front face, interconnections 17 have already been obtained by methods of the type known from the prior art, which symbolize the presence of an integrated circuit

[0135] These grooves 19 can be hollowed out by methods known per se, for example by engraving, by laser, or by mechanical means.

[0136] The locations of the grooves correspond to the edges of the future chips.

[0137] These grooves will be dug deeper than the final thickness of the chips.

[0138] Then, as illustrated on the figures 7 and 8, the plate 11 is attached on the front face side to a substrate 12 via a sacrificial layer 13.

[0139] Holes may then be dug through the substrate 12.

[0140] Then the plate 11 is thinned to the final thickness of the chips, which has the effect of separating the chips. For example, the plate 11 can be polished until it reaches the grooves 19.

[0141] The plate portions 11' can then have a thickness of the order of 50 µm or 100 µm.

[0142] After cleaning and possible technological steps such as drilling via-holes through the chips and metallizing the back side of the chips (see reference 18 on the figure 10 ), annealing is carried out at the transformation temperature of the sacrificial layer (or above), to detach the chips from the substrate.

[0143] As illustrated in the figure 11, the sacrificial layer has then disappeared, and the 11" chips adhere slightly to the 12 substrate.

[0144] In an alternative embodiment, not shown, holes ("via-holes" in English) can be etched prior to the thinning step. It will then be advisable to clean the holes once the thinning has been carried out.

[0145] In an alternative embodiment, not shown, the plate can be grooved on its rear face and fixed to the substrate by its rear face. Once thinned, various treatments can be carried out, for example deposition of layers, engravings, etc., and this is all the easier if the substrate is rigid because the alignments are then controlled.

Claims

1. Process for back end processing of a plate (1) in order to obtain a plurality of individual detached electrical, optical or optoelectronic components (1''), comprising: a) providing a substrate (2), b) attaching the plate to the substrate by means of a sacrificial layer (3) between this plate and this substrate, the sacrificial layer being in contact with the plate and with the substrate, the sacrificial layer being made from at least one material that is in a solid state at ambient temperature and ambient pressure, the sacrificial layer having a transformation temperature into one or more gaseous compounds at ambient pressure of between 80°C and 600°C, c) separating the plate attached on the substrate into a plurality of plate portions attached on the substrate, the substrate remaining as a single piece, and d) increasing the temperature and / or reducing the surrounding pressure to a sufficiently high temperature and / or a sufficiently low pressure, respectively, in order to transform the sacrificial layer attached to the plurality of plate portions into one or more gaseous compounds, the plurality of plate portions resting then directly on said substrate.

2. Process according to claim 1, wherein separation step c) comprises a step of dicing the plate (1) attached to the substrate (2) by the sacrificial layer (3).

3. Process according to claim 2, wherein the plate (1) is diced by etching.

4. Process according to claim 3, wherein the etching is plasma etching.

5. Process according to any one of claims 2 to 4, wherein the dicing is carried out or induced by means of a laser.

6. Process according to any one of claims 2 to 5, wherein the dicing is carried out or induced mechanically, for example by means of a saw blade.

7. Process according to any one of claims 1 to 6, wherein, prior to step b) of attaching the plates (11) to the substrate, grooves (19) are hollowed out on one face, referred to as the grooved face, of the plate, said grooves not reaching the face of the plate opposite to said grooved face, during the attachment step b), said grooved face is in contact with the sacrificial layer (13), during the separation step c), the plate is thinned via the face opposite said grooved face, at least until the grooves are reached.

8. Process according to any one of claims 1 to 7, wherein the sacrificial layer (3; 13) comprises at least 70% by mass of crude polymers.

9. Process according to claim 8, wherein said crude polymers consist of more than 70% by mass of polypropylene carbonate molecules, other polycarbonate molecules and / or polynorbornene molecules.

10. Process according to any one of claims 1 to 9, wherein the plate (1; 11) is obtained from a wafer essentially comprising silicon Si, germanium Ge, gallium arsenide GaAs, indium arsenide InAs, indium phosphide InP, gallium phosphide GaP, gallium antimonide GaSb, indium antimonide InSb, silicon carbide SiC, gallium nitride GaN, aluminium nitride AlN, and / or diamond.

11. Process according to any one of claims 1 to 10, wherein the sacrificial layer (3; 13) has a transformation temperature to the gaseous state at 100 kPa of between 80°C and 600°C, advantageously between 230°C and 350°C.

12. Process according to any one of claims 1 to 11, wherein the attachment of the plate (1; 11) to the substrate (2; 12) via the sacrificial layer (3; 13) is carried out at a temperature greater than a glass transition temperature of the material or materials of the sacrificial layer.

13. Process according to any one of claims 1 to 12, wherein the plate (1; 11) and the substrate (3; 13) have expansion coefficients that are equal or vary by less than 5%.