Wafer singulation film

Abstract

The invention relates to a wafer singulation film (100) for a wafer (200). Said wafer singulation film comprises a carrier film (105) which has an adhesive layer (125) on one side. The adhesive layer (125) has a microstructuring with adhesive regions and non-adhesive regions. The microstructuring of the adhesive layer (125) is complementary to a microstructuring on the surface of the wafer (200).

Description

[0001] Description

[0002] title

[0003] Wafer separation film

[0004] The present invention relates to a wafer dicing film that is bonded to a wafer to secure individual chips during dicing. Furthermore, the invention relates to a manufacturing method for a wafer dicing film. Finally, the invention relates to the use of the wafer dicing film for dicing chips from the wafer.

[0005] State of the art

[0006] During chip manufacturing, a large number of chips are manufactured on a wafer. These chips can contain, for example, MEMS elements. After processing, the wafer is separated into individual chips so that they can be assembled and packaged separately. Various separation methods are known for this, such as laser dicing (stealth dicing) or mechanical sawing.

[0007] Carrier foils are already known that have an adhesive layer with which the carrier foil is bonded to the wafer. These carrier foils are used, for example, for expanding the wafer and / or as a carrier element to fix the individual chips during singulation and subsequently detach them from the carrier foil in a defined manner.

[0008] DE 103 42 981 A1 discloses a first film, also referred to as an adhesive film, which is adhered to the chips of the wafer. A release film is applied to the first film. By removing the release film, the first film is also removed in predetermined areas that are not to remain on the wafer. It is intended that individual areas of the wafer are partially or selectively not provided with the first adhesive film. The individual areas are to be assigned to individual chips. Consequently, structuring with areas the size of entire chips is provided. If the release film is removed, some chips remain attached and are thus separated, while others remain on the wafer.

[0009] In the case of known carrier films with an adhesive layer, the adhesive layer covers the entire chip and thus also functional elements, such as sensor surfaces and chemically sensitive layers, which can be contaminated by the adhesive or damaged by the bonding.

[0010] Disclosure of the invention

[0011] A wafer singulation film for a wafer is proposed. The wafer singulation film has a thin carrier film with a microstructured adhesive layer applied to one side, with which the carrier film is adhered to the wafer, and is used for expanding the wafer and / or is used as a carrier element to fix individual chips during singulation and subsequently to be able to detach them from the carrier film in a defined manner. The carrier film can preferably have a thickness between 35 μm and 300 μm, particularly preferably between 50 μm and 150 μm, and can be stretched when lateral force is applied. The adhesive layer can preferably have a thickness between 3 μm and 30 μm, particularly preferably between 5 μm and 20 μm. The adhesive layer has a microstructure with adhesive areas and non-adhesive areas. The microstructure of the adhesive layer is on the order of magnitude of the functional elements, e.g.the sensor surfaces or chemically sensitive layers of the chips. The non-adhesive regions preferably have a lateral dimension in at least one spatial dimension in the range from 30 pm to 3000 pm, and particularly preferably in the range from 100 pm to 1000 pm. The non-adhesive regions thus have the size of the functional elements of the chips and are thus significantly smaller than the chips themselves. The microstructuring is complementary or at least partially complementary to a microstructuring on the surface of the wafer with which the functional elements of the chips are formed.This means that the adhesive layer of the wafer singulation film is microstructured in such a way that – after aligning the microstructured surface of a wafer to the wafer singulation film with the microstructured adhesive layer – when the wafer and the wafer singulation film are bonded, predetermined areas of the microstructured surface of the wafer are covered by the non-adhesive areas of the adhesive layer of the wafer singulation film. The microstructuring on the surface of the wafer can be determined in advance and is already known during the wafer design. Thus, the wafer itself is not necessary to determine the microstructuring, only its layout.

[0012] In this way, on the one hand, a reliable fixation of the individual chips during and after the wafer is separated on the wafer separation film is achieved. On the other hand, it prevents the particularly sensitive functional elements, which are microstructured on the surface of the wafer, from having their quality or the resulting functionality adversely affected by contact with the adhesive layer or subsequent detachment from the adhesive layer. For example, it prevents a functional coating present in partial areas of the wafer surface from being at least partially detached from the wafer surface when the wafer is separated from the wafer separation film, or residues of the adhesive layer from remaining on the functional coating, which in both cases can lead to a restriction or reduction of the functionality of the coating.This is particularly advantageous for chemical or gas sensors, which have a chemically sensitive layer for identifying gases. Any contamination of the chemically sensitive layer severely impairs the function of the gas sensor. Thus, the use of the wafer separation film opens up new possibilities for the design of the microstructures present on the wafer.

[0013] Microstructuring can be advantageously achieved by at least partially removing the adhesive layer in the non-adhesive areas. In the adhesive areas, the adhesive layer remains unchanged. Thus, the adhesive layer does not come into contact with the functional elements in the specified areas of the wafer surface.

[0014] The removal of the adhesive layer in the non-adhesive areas can be achieved, for example, by scanning precisely these areas of the adhesive layer using an ultrashort pulse laser in order to achieve a highly defined ablation of the adhesive layer in these areas by what is known as "ablation". The underlying carrier film remains intact, so that a continuous layer remains which forms the structural basis of the wafer separation film. By using ultrashort laser pulses, in particular with a (medium) wavelength in the ultraviolet wavelength range, for example between 200 and 400 nm, in particular 355 nm, a particularly reliable ablation of the adhesive layer can be achieved in many cases, since the adhesive layer and in particular the polymer carrier layer underneath can achieve a high absorption of the electromagnetic radiation at the adhesive layer.

[0015] By using ultrashort laser pulses for structuring the adhesive layer of the wafer singulation film, a particularly precise and "clean" (without redeposition) microstructuring of the adhesive layer of the wafer singulation film can be achieved, which complements the microstructures introduced into the wafer. On the other hand, a pulse duration in the range of less than 20 picoseconds can sufficiently minimize thermal heat input and prevent the resulting thermally induced deformation of the wafer singulation film. Furthermore, a particularly variable, individually adaptable geometry of the microstructuring of the adhesive layer of the wafer singulation film can be achieved, which is optimized for the microstructuring of the wafer to be singulated.In comparison to the production of a wafer separation film by means of punching, for example, a possible deformation of the wafer separation film due to the application of mechanical force can also be avoided.

[0016] Microstructuring can be advantageously achieved by applying a passivated adhesive layer to the non-adhesive areas. Passivation involves curing, crosslinking, and / or polymerizing the adhesive layer, so that no adhesive effect is present in these areas. Thus, the adhesive layer in the non-adhesive areas is deprived of its active adhesive ability and converted into a glassy passive layer. This glassy layer can then contact the functional elements in the specified areas on the wafer surface, but can no longer contaminate or damage them.

[0017] Ultraviolet radiation can be used to passivate the adhesive layer. For example, short-wave laser radiation in the ultraviolet range can be used for this, which locally irradiates the non-adhesive areas. Passivation—i.e., curing, crosslinking, and / or polymerization—in the non-adhesive areas of the adhesive layer can be achieved by locally defined exposure to UV radiation. Possible light sources include frequency-multiplied Nd:YAG lasers (neodymium yttrium aluminum garnet lasers), for example, or excimer lasers, which emit light pulses with pulse durations in the nanosecond range, wavelengths of 308 nm (XeCl), 248 nm (KrF), or 193 nm (ArF), and energies in the range of 10 mJ to 1 J.

[0018] In addition, a mask exposure unit can be advantageously used, which, using a mask, enables exposure and thus passivation of the adhesive in partial areas of the adhesive layer. The use of a mask is particularly suitable for producing a large number of wafer separation films with identically microstructured adhesive layers in a short time. The mask exposure unit can optionally also have an alignment device to suitably align a microstructured wafer, i.e., for example, complementarily to the microstructuring of the adhesive layer of the wafer separation film, and to enable defined bonding of the wafer and the wafer separation film.

[0019] Advantageously, the adhesive layer is based on an acrylate adhesive. Exposure to a sufficient dose of ultraviolet radiation and the resulting cleavage of photoinitiators into free radicals triggers the formation of polymer chains, thus resulting in passivation—i.e., the curing, crosslinking, and / or polymerization of the adhesive in the adhesive layer.

[0020] Both types of microstructuring can also be combined. This means that the adhesive layer is microstructurized both by at least partially removing the adhesive layer in the non-adhesive areas and by passivating the adhesive layer in these non-adhesive areas. For this purpose, the ultrashort pulse laser used to remove the adhesive layer can use a wavelength in the ultraviolet range, so that passivation is also carried out in addition to ablation. This can primarily passivate residues of the adhesive layer that may remain in this area after removal. The microstructuring of the adhesive layer can have non-adhesive areas that are strip-shaped. The strip-shaped non-adhesive areas preferably alternate with the adhesive areas, which are also strip-shaped, in one direction.This allows for easy microstructuring by scanning the non-adhesive areas in stripes in a particularly simple and rapid manner. Especially when using an ultrashort pulse laser, this can perform the stripe scanning without the need to block (shutter) the laser beam in between.

[0021] Alternatively, the microstructuring of the adhesive layer can comprise a plurality of non-adhesive regions, in particular of similar shape, which are arranged periodically along a predeterminable grid. The non-adhesive regions preferably alternate with adhesive regions that are also arranged in the grid. The grid spacing between two similarly shaped regions along the grid in at least one spatial dimension is preferably in the range between 50 pm and 15,000 pm, and particularly preferably in the range between 200 pm and 2,000 pm. The microstructuring can be easily implemented using a step-and-repeat process. Especially when using an ultrashort pulse laser, this can move over the wafer separation film multiple times, each time performing an ablation or passivation.The grid is particularly useful for dicing the wafer into rectangular, especially square, chips, which are often used in practice and allow particularly simple dicing of the wafer into chips, for example by means of stealth dicing and expanding the wafer on the wafer dicing film.

[0022] The wafer singulation film is preferably clamped in a clamping frame with a pre-tension. The pre-tension is selected to be sufficiently high to ensure that no permanent or prolonged contact occurs between the surface of the wafer and the adhesive layer as a result of sagging. The mechanical resonance frequency of the clamped wafer singulation film, which should preferably be between 20 Hz and 200 Hz and particularly preferably between 50 Hz and 100 Hz, can be used to select the pre-tension. This pre-tension provides the flatness of the film, which is a prerequisite for precise optical processing by the laser. It also ensures that the adhesive areas of the wafer singulation film do not sag or remain in contact with the wafer for an extended period.

[0023] Finally, the invention also relates to a wafer dicing film, as described above, comprising a wafer. The wafer has a microstructure on its surface. The microstructure is formed by the functional elements, e.g., the sensor surfaces or the chemically sensitive layers, of the chips on the wafer. The wafer dicing film has a carrier film having an adhesive layer on one side. The adhesive layer has a microstructure with adhesive regions and non-adhesive regions. The microstructure of the adhesive layer is complementary or at least partially complementary to the microstructure on the surface of the wafer. For a detailed explanation of the elements and the resulting advantages, reference is made to the above description.

[0024] Furthermore, a method for producing a wafer singulation film for a wafer is proposed. A carrier film is provided. The carrier film has a homogeneous adhesive layer on one side, which is applied to the wafer. The adhesive layer is then structured with a microstructure with adhesive areas and non-adhesive areas. The microstructure of the adhesive layer is designed in the size order of the functional elements, for example, the sensor surfaces or chemically sensitive layers of the chips. The non-adhesive areas are therefore the size of the functional elements of the chips and are thus significantly smaller than the chips themselves. The microstructure is designed complementarily to a microstructure on the surface of the wafer with which the functional elements of the chips are formed.This means that the adhesive layer of the wafer singulation film is microstructured in such a way that – after aligning the microstructured surface of a wafer to the wafer singulation film with the microstructured adhesive layer – when the wafer and the wafer singulation film are bonded, predetermined areas of the microstructured surface of the wafer are covered by the non-adhesive areas of the adhesive layer of the wafer singulation film. Before the structuring of the adhesive layer is carried out, the microstructuring of the wafer surface can preferably be detected. For example, precisely those areas are detected which have a sensitive functional coating that could be adversely affected by contact with the adhesive layer of the wafer singulation film. Based on the detected areas, the complementary microstructuring of the adhesive layer on the carrier film is then structured.The non-adhesive areas of the adhesive layer are formed according to the detected areas of the surface in order to prevent contact with the sensitive coating of the substrate.

[0025] Before the adhesive layer is structured, the carrier film with the adhesive layer can preferably be clamped in a clamping frame with a pre-tension. In particular, this is a clamping frame that is conventionally used for wafer dicing. By clamping the carrier film with the homogeneous adhesive layer onto the clamping frame, it can be ensured that the upper side of the carrier film with the adhesive layer is in a sufficiently pre-tensioned state (almost) in one plane. The mechanical resonance frequency of the clamped wafer dicing film, which should preferably be between 20 Hz and 200 Hz and particularly preferably between 50 and 100 Hz, can be used to select the pre-tension. On the one hand, the pre-tension ensures that the film is flat, which is a prerequisite for precise optical processing by the laser.Secondly, it ensures that the adhesive areas of the wafer separation film do not "sag" or remain in contact with the wafer for extended periods. This enables particularly simple, reliable, and precise microstructuring of the adhesive layer, for example, using a laser micromachining system.

[0026] The microstructuring can advantageously be achieved by at least partially removing the adhesive layer in the non-adhesive regions. In the adhesive regions, the adhesive layer remains unchanged. Thus, the adhesive layer does not come into contact with the functional elements in the specified regions of the wafer surface. Preferably, the microstructuring of the adhesive layer is carried out by removal using ultrashort laser pulses with a pulse duration of, for example, less than twenty picoseconds. By using ultrashort laser pulses, in particular, thermal effects on the carrier film during processing of the adhesive layer can be sufficiently minimized, so that undesirable thermally induced deformation of the wafer separation film can be prevented and sufficient dimensional accuracy of the complementary microstructuring can be ensured.The wavelength of the laser is preferably selected with regard to the optical absorption characteristics of the adhesive layer. For example, a mode-locked, frequency-converted Nd:YAG laser can be used as a pulsed laser light source or short-pulse laser. Frequency conversion occurs by tripling the light frequency or reducing the laser wavelength by a third, from 1064 nm to 354.7 nm, in a sequence of nonlinear optical processes in converter crystals (e.g., potassium dihydrogen phosphate KDP, barium betaborate BBO).

[0027] Microstructuring can be advantageously achieved by applying a passivated adhesive layer to the non-adhesive areas. Passivation involves curing, crosslinking, and / or polymerizing the adhesive layer, so that no adhesive effect is present in these areas. Thus, the adhesive layer in the non-adhesive areas is deprived of its active adhesive ability and converted into a glassy passive layer. This glassy layer can then contact the functional elements in the specified areas on the wafer surface, but can no longer contaminate or damage them.

[0028] Preferably, the microstructuring of the adhesive layer is carried out by passivation by means of the action of a sufficient dose of ultraviolet radiation and a resulting cleavage of photoinitiators into free radicals, which triggers the formation of polymer chains in these partial areas, so that the passivation (curing / crosslinking / polymerization) of the adhesive of the adhesive layer takes place.

[0029] Both types of microstructuring can also be combined. This involves microstructuring the adhesive layer, which is achieved both by at least partially removing the adhesive layer in the non-adhesive areas and by passivating the adhesive layer in these non-adhesive areas.

[0030] Preferably, the carrier film of the wafer singulation film has a sufficiently high optical absorption in the wavelength range of the laser so that passivation or removal of the adhesive layer can be carried out, in particular using the above-mentioned ultrashort pulse laser with a suitable wavelength.

[0031] If the film is based on a polymer, the aforementioned pulsed laser light source, or short-pulse laser, can use a wavelength in the ultraviolet radiation range of the electromagnetic spectrum. For example, a wavelength of 354.7 nm from a frequency-tripled Nd:YAG laser can be used. Another advantage of short-pulse laser ablation is the avoidance of ejections and redeposition of ablated material around the cut edge.

[0032] It may be possible to incorporate additional particles, such as soot particles or other types of nanoparticles, into the wafer separation film, which cause optical absorption of the film at other wavelengths as well, for example, in the visible or near-infrared range of the electromagnetic radiation spectrum. Consequently, different types of ultrashort pulse lasers can be used for microstructuring the adhesive layer, for example, pulsed Nd:YAG lasers at their primary wavelength of 1064 nm in the near-infrared range.

[0033] The aforementioned wafer dicing film can be used for dicing chips from a wafer. For this purpose, the wafer dicing film is provided with an adhesive layer with microstructures that complement the microstructures on the wafer surface. The wafer dicing film and the wafer are then aligned so that the microstructures of the adhesive layer match the microstructures on the wafer surface. Subsequently, the wafer surface is bonded to the wafer dicing film via the adhesive layer, or conversely, the wafer dicing film with the adhesive layer is bonded to the wafer surface. Finally, the wafer is dicing.

[0034] The wafer singulation film according to the invention can advantageously be applied to the wafer in just a single bonding step. In particular, compared, for example, to the use of a first non-structured carrier film layer and a second microstructured adhesive layer with through-hole recesses, advantageously no joining of multiple film layers is required after microstructuring the adhesive layer in order to form a wafer singulation film with a microstructured adhesive layer. Furthermore, when a wafer surface is sealed gas-tight with the wafer singulation film, the volume of air (or a gas) enclosed between the wafer surface and the wafer singulation film is particularly low, since the combination of the adhesive layer with a carrier film allows the microstructured adhesive layer to have a particularly low layer thickness.Thus, the occurrence of air (or gas) inclusion between the wafer and the wafer dicing film when adhering the wafer to the wafer dicing film can be advantageously reduced.

[0035] Short description of the drawings

[0036] Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

[0037] Figures 1 A, B each show a side view of a wafer singulation film according to an embodiment of the invention.

[0038] Figure 2 shows a side view of a wafer singulation film according to another embodiment of the invention.

[0039] Figures 3 A, B each show a side view of the wafer dicing film and a wafer during (Figure 3 A) and after (Figure 3 B) bonding.

[0040] Figures 4 A and B each show a top view of the wafer dicing film before (Figure 4 A) and after (Figure 4 B) bonding to the wafer. Figures 5 A and B each show a flow diagram of embodiments of a manufacturing method according to the invention for the wafer dicing film.

[0041] Figure 6 shows a flow diagram of an embodiment of a method according to the invention for using the wafer singulation film for singulating chips of a wafer.

[0042] Figures 7 AE show schematically the implementation of the manufacturing process and the application to the wafer using cross-sectional views.

[0043] Figures 8 AD schematically show the implementation of the manufacturing process and the application to the wafer using top view representations according to one embodiment.

[0044] Figures 9 AD schematically show the implementation of the manufacturing process and the application to the wafer using top view representations according to a further embodiment.

[0045] Embodiments of the invention

[0046] Figures 1A and B each show a cross-sectional view of an exemplary embodiment of the wafer singulation film 100 according to the invention with a microstructured adhesive layer 125 according to one embodiment. The wafer singulation film 100 has a carrier film 105 and the microstructured adhesive layer 125 arranged on one side of the carrier film 105. Furthermore, the wafer singulation film 100 has a silicone coating 110 arranged on the other side of the carrier film 105. The silicone coating 110 serves to enable the wafer singulation film 100 to be transported or stored in a wound form and to enable easy unwinding of the wafer singulation film 100 despite the adhesive layer 125.In this exemplary embodiment, the microstructuring of the adhesive layer 125 is implemented such that in predetermined regions of the wafer separation film 100, the adhesive layer 125 has been completely removed from the carrier film 105, while in other regions, the adhesive layer 125 is present in a homogeneous form on the carrier film. The regions in which the adhesive layer 125 has been removed are therefore no longer adhered to a wafer (see Figures 3 A, B) and are therefore referred to as non-adhesive regions. The regions in which the adhesive layer 125 is still present are referred to as adhesive regions.

[0047] Figure 1B shows that, due to manufacturing reasons, the carrier film 105 is partially removed in the non-adhesive regions. Thus, a thinning of the carrier film 105 may occur in these non-adhesive regions. Furthermore, the surface of the carrier film 105 has increased roughness in the non-adhesive regions. The increased surface roughness in the non-adhesive regions may, in particular, also be associated with a change in the optical properties in these regions of the wafer singulation film 100. This is particularly advantageous when aligning the wafer singulation film 100 with the microstructured adhesive layer 125 relative to a microstructured wafer (see Figure 3), in order to enable particularly simple optical alignment thanks to the visibility of the structures in the wafer singulation film 100.

[0048] Figure 2 shows a further embodiment of the wafer singulation film 100 according to the invention with a microstructured adhesive layer 125. This embodiment differs from the previous embodiment in that the adhesive layer 125 is microstructured in such a way that the adhesive layer 125 is passivated in predeterminable regions of the wafer singulation film 100, while in other regions the adhesive layer 125 is present in a homogeneous and non-passivated form on the carrier film 125. The passivation cures, crosslinks, and / or polymerizes the adhesive layer 125, so that it loses its adhesive properties and thus non-adhesive regions are formed. In the regions that have not been passivated, the adhesive layer 125 retains its adhesive properties, so that adhesive regions continue to exist there. Since the adhesive layer 125 is not removed, its surface remains essentially flat.

[0049] Independently of the embodiments described above, the carrier film 105 consists, for example, of plasticized polyvinyl chloride (PVC) and has a thickness of, for example, 65 μm. The adhesive layer 125 on the upper side of the carrier film 105 is, for example, acrylate-based and has, for example, a thickness of 10 μm. Figures 3 A and B each show a cross-sectional view of a connection between the wafer dicing film 100 with the microstructured adhesive layer 125 and a wafer 200 with a surface coating 205 that is present in partial areas of a surface of the wafer 200. In Figure 3 A, the wafer 200 is applied to the wafer dicing film 100 from the side of the adhesive layer 125. The wafer 200 is adhesively bonded to the wafer dicing film 100 by the adhesive layer 125 (see Figure 3 B).

[0050] The adhesive layer 125 of the wafer singulation film 100 has, as described above, a microstructure such that in the adhesive regions, an adhesive bond is established between the adhesive layer 125 and the surface of the wafer 200. In the non-adhesive regions, interaction between the adhesive layer 125 and the surface of the wafer 200 is avoided due to the recesses in the adhesive layer 125 or the passivation of the adhesive layer 125. In the non-adhesive regions, the surface of the wafer 200 can be in contact with the carrier film 105 of the wafer singulation film 100 and / or with the passivated regions of the adhesive layer 125 of the wafer singulation film 100.

[0051] The microstructure of the adhesive layer 125 of the wafer singulation film 100 is formed complementary (or at least partially complementary) to the surface coating 205 of the wafer 200. The wafer 200 and the wafer singulation film 100 can be aligned with each other such that the partial regions with the surface coating 205 of the wafer 200 do not overlap with the adhesive regions of the adhesive layer 125 of the wafer singulation film 100.

[0052] With appropriate alignment of the wafer 200 to the wafer singulation film 100, the surface coating 205 of the wafer 200 is prevented from coming into contact with the active adhesive layer 125 of the wafer singulation film 100 when the wafer 200 is adhered to the wafer singulation film 100. This prevents undesired impairment of the integrity of the surface coating 205 due to contact with the adhesive regions of the adhesive layer 125. Furthermore, residues of the adhesive layer 125 are prevented from remaining on the surface coating 205 when the wafer 200 is removed and the chips (not shown here) of the wafer 200 are singulated, and / or parts of the surface coating 205 are prevented from being undesirably detached due to the adhesive forces to the adhesive layer 125. Both of these can adversely affect the functionality of the surface coating 205.

[0053] Figure 3B shows the completed connection of wafer 200 to a wafer singulation film 100. Wafer 200 is bonded to adhesive layer 125 of wafer singulation film 100. Due to the design of the microstructured adhesive layer 125, after bonding wafer 200 to wafer singulation film 100, the adhesive regions of adhesive layer 125 only come into contact with those portions of the surface of wafer 200 where no surface coating 205 is present. The portions of the surface of wafer 200 that have surface coating 205 only come into contact with the non-adhesive regions of adhesive layer 125, i.e., the recesses of the adhesive layer and / or the passivated regions of adhesive layer 125.This ensures the functionality of the surface coating 205, which would be adversely affected by permanent contact with the adhesive areas of the adhesive layer 125 of the wafer singulation film 100.

[0054] Figure 4A shows a top view of the wafer singulation film 100, as shown in Figure 1B, taken using a microscope. In this exemplary embodiment, the wafer singulation film 100 has a strip-shaped microstructuring of the adhesive layer 125. In this case, the non-adhesive regions have been created by removing the adhesive layer 125, whereby a roughness of the surface of the carrier layer 105 is created, which becomes visible as dark regions 106 due to the reduced optical transmittance of the wafer singulation film 100. The non-adhesive regions of the adhesive layer 125, which are shown here as dark regions 106, are oriented vertically in a strip-like manner and, for example, each have a width b of approximately 1000 pm and a distance d of approximately 1000 pm from one another. The adhesive regions of the adhesive layer 125 are also arranged in a strip-like manner and thus also have a width d of approximately 1000 pm.

[0055] Figure 4B shows a top view, taken using a microscope, of wafer 200 connected to wafer singulation film 100, as shown in Figure 3B. In this exemplary embodiment, wafer singulation film 100 also has a strip-shaped microstructuring of the adhesive layer 125, corresponding to Figure 4A. The non-adhesive regions of adhesive layer 125 are also created by removing adhesive layer 125 and thus again appear as dark regions 106. They are oriented vertically in a strip-shaped manner. The adhesive regions of adhesive layer 125 are also oriented vertically in a strip-shaped manner. Wafer 200 has a complex microstructuring of surface coating 205. Predefined subregions of microstructuring 205 of wafer 200 overlap with the strip-shaped non-adhesive regions of wafer singulation film 100.In this way, an undesirable interaction of the adhesive layer 125 with the partial regions of the wafer 200 in which a surface coating 205 is present can be avoided.

[0056] In other embodiments not shown, the wafer separation film 100 has a grid-like microstructuring of the adhesive layer 125. Several similarly shaped non-adhesive regions and several similarly shaped adhesive regions are arranged periodically, alternating along a predeterminable grid. The grid spacing between two similarly shaped regions along the grid in at least one spatial dimension is, for example, 1000 pm.

[0057] Figures 5 A and B show flow diagrams of an embodiment of the inventive manufacturing method 1000 for a wafer singulation film 100. Initially, a carrier film 105 with a homogeneous adhesive layer 125 is provided 1010. Subsequently, the microstructure of the adhesive layer 125 on the carrier film 105 is structured 1020.

[0058] In an exemplary embodiment, the structuring 1020 of the microstructuring of the adhesive layer 125 is carried out by removing predeterminable regions of the wafer singulation film 100. The removed regions have no significant or at least significantly reduced adhesiveness and are referred to as non-adhesive regions. In contrast, the adhesive layer 125 is not removed in other regions. The adhesive layer 125 continues to have its adhesiveness in these regions, and these regions are referred to as adhesive regions. The removal is carried out using an ultrashort pulse laser, wherein the adhesive layer is removed in predeterminable subregions by scanning predeterminable regions of the wafer singulation film 100 with the laser beam.For this purpose, the wafer separation film 100 can be arranged, for example, on a table that can be moved in two spatial directions and / or the laser beam can be deflected by means of a mirror optics.

[0059] The laser is merely an example of a frequency-tripled pulsed Nd:YAG laser.The pulse duration of the laser is, for example, approximately 10 picoseconds, the wavelength of the laser is, for example, 355 nm, the spot diameter of the laser is, for example, 18 pm (FWHM), the repetition rate of the laser is, for example, 500 kHz, the average radiation power of the laser is, for example, 800 mW, the pulse energy is, for example, 1.6 pJ, the travel speed of the laser beam on the surface of the wafer singulation film is, for example, 400 mm / s, which corresponds to a pulse overlap of approximately 95%, the distance between the lines along which the wafer singulation film 100 is scanned is, for example, 10 pm and the orientation of the lines along which the wafer singulation film 100 is scanned is, for example, oriented parallel to the alignment of the strip-shaped regions according to Figure 4 in which the adhesive layer 125 is removed.

[0060] In particular, a short pulse duration in the picosecond range (or femtosecond range) can advantageously prevent thermal deformation of the wafer separation film 100 during the microstructuring of the adhesive layer 125. In particular, this enables highly defined ablation of the adhesive layer 125, thereby avoiding thermal damage to the surrounding material and thus, in particular, adverse impairment of the dimensional accuracy of the wafer separation film 100.

[0061] A wavelength in the ultraviolet range, in particular between 200 nm and 400 nm, i.e., e.g., 355 nm, can ensure, for example, high absorption of the laser radiation by the adhesive layer to be structured. In this way, reliable and defined ablation of the adhesive layer 125 can be achieved. A spot diameter of the laser beam in the plane of the adhesive layer 125 to be structured in the range of less than 20 pm can achieve spatially precise microstructuring of the adhesive layer 125. In order to achieve the smallest possible spot diameter in the plane of the adhesive layer 125, this corresponds in particular (almost) to a focal plane of the optics of the laser beam.

[0062] In an exemplary embodiment, the structuring 1020 of the microstructuring of the adhesive layer 125 is performed by removing it within predeterminable regions of the wafer dicing film 100. The removed regions have no significant or at least significantly reduced adhesiveness and are referred to as non-adhesive regions. In contrast, the adhesive layer 125 is not removed in other regions. The adhesive layer 125 retains its adhesiveness in these regions, and these regions are referred to as adhesive regions.

[0063] In an alternative embodiment, the structuring 1020 of the microstructuring of the adhesive layer 125 is carried out by passivating predeterminable regions of the adhesive layer 125 of the wafer dicing film 100 by curing, crosslinking, and / or polymerizing the adhesive of the adhesive layer 125. The passivated regions have no significant or at least significantly reduced adhesiveness and are referred to as non-adhesive regions. In contrast, the adhesive layer 125 is not passivated in other regions. The adhesive layer 125 retains its adhesiveness in these regions, and these regions are referred to as adhesive regions.

[0064] The passivation of the adhesive layer 125, for example, in the case of an adhesive layer 125 based on an acrylate adhesive, is caused by the action of a sufficient dose of ultraviolet radiation and the cleavage of photoinitiators into free radicals. This triggers the formation of polymer chains, resulting in passivation of the adhesive of the adhesive layer 125. The high energy of ultraviolet photons is particularly advantageous for triggering polymerization reactions by inducing free radicals. After passivation of the adhesive layer by curing, crosslinking, and / or polymerization of the adhesive of the adhesive layer 125 in predetermined areas, interaction of the passivated non-adhesive areas with the sensitive surface microstructure of the wafer 200 during the bonding of the wafer 200 to the wafer dicing film 100 can be advantageously sufficiently reduced.

[0065] The passivation of the adhesive layer 125 by exposure to a sufficient dose of ultraviolet radiation can be carried out, for example, similarly as before, by scanning the surface with a laser beam of ultraviolet wavelength or by using a mask exposure device with a mask and the use of an ultraviolet radiation source such as a mercury vapor lamp or an excimer laser.

[0066] According to Figure 5 B, in a further embodiment, the method 1000 comprises the steps of detecting 1005 the microstructure of the surface of the wafer 200 and clamping 1015 the wafer singulation film 100 in a clamping frame 500.

[0067] When detecting 1015 the microstructure of the surface of the wafer 200, the surface coating 205 of the wafer 200 and sensitive functional elements are detected, which have a particularly sensitive coating that can be adversely affected by contact with the adhesive layer 125 of the wafer dicing film 100. The structuring 1020 of the microstructure of the adhesive layer 125 of the wafer dicing film 100 is then carried out based on the detected surface coating 205 and the sensitive functional elements. For this purpose, a microstructuring of the adhesive layer 125 is formed on the carrier film 105 that is complementary to the microstructure of the surface of the wafer 200. In this process, the adhesive layer 125 is removed or passivated (see above) to match the surface coating 205 and the functional elements in order to prevent contact with the sensitive coating of the wafer 200.

[0068] When clamping 1015 the carrier film with a homogeneous adhesive layer 125 onto the clamping frame 500, a clamping frame 500 conventional for dicing wafers is used. As a result, the upper side of the carrier film 105 with the adhesive layer 125 is (almost) in a pre-tensioned state in a plane. This pre-tensioning provides, on the one hand, a flatness of the film, which is a prerequisite for precise optical processing by the laser. On the other hand, it ensures that the adhesive regions of the wafer dicing film 100 do not "sag" on the wafer 200 or remain in contact with it for an extended period of time. The pre-tensioning of the carrier film 105 in the clamping frame 500 provides a sufficiently high mechanical restoring force, which reliably prevents prolonged contact between the non-adhesive regions of the wafer dicing film 100 and the wafer 200.The preload is selected such that a mechanical resonance frequency of the clamped wafer separation film 100 is between 50 and 100 Hz. By mechanically impacting the wafer separation film 100 and analyzing the acoustic spectrum of the mechanical vibration of the wafer separation film 100, it can be checked whether the wafer separation film 100 was clamped into the clamping frame 500 with sufficiently high preload. In this way, a particularly simple, reliable, and precise microstructuring of the adhesive layer 125 is possible, for example, using a laser micromachining system.

[0069] Figure 6 shows a flow diagram of an embodiment of the method according to the invention for singulating 2000 the wafer 200 using the wafer singulation film 100. Initially, the wafer singulation film 100 with the microstructured adhesive layer 125 is provided 2005 for the wafer 200 with the microstructured surface coating 205. As already described above, the adhesive layer 125 has a microstructure that is complementary to the microstructure on the surface of the wafer 200.

[0070] Then, the wafer 200 with the surface coating 205 is aligned 2010 with the wafer singulation film 100 with the microstructured adhesive layer 125, such that the sensitive partial regions of the surface coating 205 with the functional elements of the wafer 200 overlap with the non-adhesive regions of the adhesive layer 125 of the wafer singulation film 100 with the microstructured adhesive layer. In other embodiments, the wafer singulation film 100 is aligned 2010 with the wafer 200. The alignment 2010 can be performed, for example, using an optical signal, wherein the wafer singulation film 100 is designed to be at least partially transparent for this purpose. Furthermore, the alignment 2010 can be performed using a mechanical auxiliary device, which allows a particularly precise alignment of the wafer singulation film 100 with the wafer 200 or vice versa.Here too, the pre-tensioning of the pre-structured wafer separation film 100 in the clamping frame 500 explained above is very advantageous because it prevents the wafer separation film from “sagging,” thereby preventing it from undesirably coming into premature contact with the wafer 200 during the alignment process 2010.

[0071] Subsequently, the wafer 200 is bonded 2015 to the wafer singulation film 100 with a microstructured adhesive layer 125. In this case, the surface of the wafer 200 adheres to the adhesive regions of the adhesive layer 125 of the wafer singulation film 100 in areas where no sensitive functional elements are present. Bonding 2015 of the wafer 200 to the wafer singulation film 100 is carried out in a directed manner, in particular, so that the inclusion of air or another gas between the surface of the wafer 200 and the wafer singulation film 100 can be minimized or completely prevented. The prestressing of the wafer singulation film 100 now ensures that the adhesive regions do not come into contact with the surface of the wafer 100, or at least not for an extended period of time.

[0072] Finally, the wafer 200, which is bonded to the wafer dicing film 100 with the microstructured adhesive layer 125, is separated into a plurality of microstructured chips by a dicing step 2020. The dicing step 2020 can be performed, for example, by sawing the wafer 200 or by a so-called stealth dicing process, wherein predetermined breaking points are first introduced into the wafer 200 using a laser, and then a defined dicing of the wafer 200 into a plurality of microstructured chips is induced by expanding the wafer dicing film 100.

[0073] The microstructured chips resulting from the singulation 2020 of the wafer 200 are detached 2025 from the wafer singulation film 100 with the microstructured adhesive layer 125. The detachment 2025 can, for example, be carried out automatically using a pick-and-place robot. The detachment 2025 can, if necessary, be facilitated by a prior, extensive exposure of the singulation film 100 to ultraviolet radiation, which reduces the adhesive force of the adhesive layer 125. Figure 7 schematically shows the implementation of the above-described methods for production 1000 and singulation 2000 using sectional views. Figure 7A shows a carrier film 105 with a homogeneous adhesive layer 120 and a back-side silicone coating 110, which serves as the starting point for the production of the wafer singulation film 100 according to the invention.Figure 7B shows the wafer singulation film 100 with the structured adhesive layer 125 after structuring 1020. Reference is made to Figure 1A and its description. Figure 7C shows a wafer 200 with a microstructured surface coating 205, which is present in partial regions of the surface of the wafer 200. Figure 7D shows an arrangement of the wafer singulation film 100 shown in Figure 7B with the microstructured adhesive layer 125 and the wafer 200 shown in Figure 7C, which arrangement is present after alignment 2010. The partial regions of the wafer 200 with the surface coating 205 are aligned in a manner complementary to the regions of the wafer singulation film 100 with the adhesive layer 125. Figure 7 E shows a combination of the wafer 200 shown in Figure 7 D and the wafer singulation film after bonding 2015.The previously performed alignment 2010 ensures that the surface coating 205 of the wafer 200 does not come into contact with the adhesive areas of the adhesive layer 125 of the wafer separation film 100. In addition to the precise alignment, the pre-tensioning of the carrier film 100 in the clamping frame 500 also contributes to this. Reference is made to Figures 3A and 3B and their descriptions.

[0074] Figure 8 schematically shows the implementation of the above-described methods for production 1000 and singulation 2000 using top view representations. Figure 8A shows a carrier film 105 with a homogeneous adhesive layer 120, which is clamped with a sufficiently large pre-tension on a clamping frame 500 and serves as a starting point. Figure 8B shows the wafer singulation film 100 with a structured adhesive layer 125 after structuring 1020. The microstructured adhesive layer 125 is characterized in particular by a grid-like arrangement of, in this example, square-shaped regions in which the adhesive layer has been removed and / or passivated to form the microstructured adhesive layer 125. Figure 8C shows a wafer 200 with a microstructured surface coating 205.The surface coating 205 is characterized in particular by a grid-like arrangement of square-shaped regions in this example, in which the surface coating 205 is present. Figure 8 D shows a combination of the wafer separation film 100 shown in Figure 8 B with the microstructured adhesive layer 125 on the clamping frame 500 and the wafer 200 shown in Figure 8 C after alignment 2010 and bonding 2015.

[0075] In addition to such a complementary structure of the surface coating 205 of the wafer and the structured adhesive layer 125, a partially complementary microstructuring of the adhesive layer 125 is also possible, as shown in the exemplary embodiment of Figure 9.

[0076] Figure 9 shows schematically the implementation of the above-described methods for production 1000 and separation 2000 using top view representations and differs from Figure 8 only in that a strip-shaped, partially complementary microstructuring of the adhesive layer 125 is present.

[0077] The partially complementary microstructuring of the adhesive layer 125 shown in Figure 9 is characterized by an arrangement of mutually parallel, vertically striped regions in which the adhesive layer 125 has been removed and / or passivated. Such a striped microstructuring of the adhesive layer 125 can be produced particularly easily using a laser micromachining system. Reference is also made to Figure 4A and its description. The regions each have a constant distance d from one another. This distance d corresponds to the horizontal distance in the grid-like arrangement of the regions of the surface coating 205 of the wafer 200, which in this example are also square-shaped.

[0078] It can be provided that the non-adhesive regions with removed and / or passivated adhesive layer 125 are formed larger than the partial regions of the surface coating 205 in order, on the one hand, to allow a tolerance in the alignment 2010 of the wafer separation film with the microstructured adhesive film 125 and the wafer 200 and, on the other hand, to produce a reliable adhesive connection between the wafer 200 and the adhesive film 125.

[0079] In addition, the wafer singulation film 100 preferably has an optical transparency in a predetermined wavelength range, at least in partial regions, in order to thus permit an optically based alignment 2010 of the wafer singulation film 100 and the wafer 200. This can, for example, be the visible wavelength range of electromagnetic radiation with wavelengths between 400 nm and 800 nm or a partial wavelength range thereof. It is advantageous that the structuring of the wafer singulation film is also optically recognizable, i.e. visible, in this optical spectral range, which enables the optically based alignment 2010 of the wafer singulation film 100 and the wafer 200.

Claims

Claims 1. Wafer singulation film (100) for a wafer (200), comprising a carrier film (105) having an adhesive layer (125) on one side, characterized in that the adhesive layer (125) has a microstructuring with adhesive areas and non-adhesive areas, wherein the microstructuring of the adhesive layer (125) is complementary or at least partially complementary to a microstructuring on the surface of the wafer (200).

2. Wafer singulation film (100) according to claim 1 , characterized in that the non-adhesive areas have a lateral dimension in the range of 30 pm to 3000 pm.

3. Wafer singulation film (100) according to claim 1 or 2, characterized in that the non-adhesive areas have a lateral dimension in the range of 100 pm to 1000 pm.

4. Wafer singulation film (100) according to one of claims 1 to 3, characterized in that the microstructuring of the adhesive layer (125) is achieved by at least partially removing the adhesive layer (125) in the non-adhesive areas.

5. Wafer singulation film (100) according to one of claims 1 to 3, characterized in that the microstructuring of the adhesive layer (125) is achieved by passivating the adhesive layer (125) in the non-adhesive areas.

6. Wafer singulation film (100) according to one of claims 1 to 5, characterized in that the non-adhesive areas are formed in a strip shape.

7. Wafer singulation film (100) according to one of claims 1 to 5, characterized in that the non-adhesive areas are arranged periodically in a predefinable grid. Wafer singulation film (100) according to any one of claims 1 to 7, characterized in that the wafer singulation film (100) is clamped in a tensioning frame with a pre-tension. Wafer singulation film (100) according to any one of claims 1 to 8 with a wafer (200), wherein the wafer has a microstructure on its surface. Method (1000) for producing a wafer singulation film for a wafer, comprising (1010) providing a carrier film (105) having a homogeneous adhesive layer (120) on one side, characterized by structuring (1020) the adhesive layer (125) with a microstructure having adhesive areas and non-adhesive areas, wherein the microstructure is formed complementary to a microstructure on the surface of the wafer (200).Method (1000) according to claim 10, characterized in that the microstructuring on the surface of the wafer is detected (1005) before the structuring (1020) of the adhesive layer (125) is carried out. Method (1000) according to claim 10 or 11, characterized in that the carrier film with the adhesive layer is clamped in a tensioning frame with a pre-tension before the structuring of the adhesive layer is carried out. Method (1000) according to any one of claims 10 to 12, characterized in that the microstructuring of the adhesive layer (125) is achieved by at least partially removing the adhesive layer (125) in the non-adhesive areas. Method (1000) according to claim 13, characterized in that the removal of the adhesive layer (125) is carried out by scanning with an ultrashort pulse laser. Method (1000) according to any one of claims 10 to 12, characterized in that the microstructuring of the adhesive layer (125) This is achieved by passivating the adhesive layer (125) in the non-adhesive areas. Method (1000) according to claim 15, characterized in that the passivation is carried out by means of ultraviolet radiation. Use (2000) of a wafer singulation film (100) according to any one of claims 1 to 8 for singulating chips from a wafer (200) comprising the following steps: providing the wafer singulation film (2005) with the adhesive layer (125) having a microstructure complementary to the Microstructuring on the surface of the wafer (200) is, alignment (2010) of the wafer singulation film (100) and the wafer (200) with each other, so that the microstructuring of the adhesive layer (125) is aligned with the microstructuring on the surface of the wafer, bonding (2015) of the surface of the wafer (200) and the wafer- Singulation film (100) over the adhesive layer (125) and singulation (2020) of the wafer (200).

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