Method for processing wafer and protective film

Abstract

Method for processing wafer and protective film. The present invention relates to a method for processing a wafer having a device area on one side, the device area having a plurality of devices. The method comprises providing a protective film and applying the protective film for covering the devices on the wafer to the one side of the wafer so that the front surface of the protective film is in direct contact with the one side of the wafer. The method also comprises heating the protective film during and / or after applying the protective film to the one side of the wafer so that the protective film is attached to the one side of the wafer, and processing the side of the wafer opposite to the one side. In addition, the present invention relates to a method for processing such a wafer, wherein a liquid adhesive is dispensed only onto a peripheral portion of the protective film and / or only onto a peripheral portion of the wafer.

Description

Technical Field

[0001] The present invention relates to a method of processing a wafer such as a semiconductor wafer, the wafer having a device region on one side, the device region having a plurality of devices. Background Art

[0002] In the semiconductor device manufacturing process, a wafer with a device area having a plurality of devices (usually divided by a plurality of dividing lines) is divided into individual wafers. This manufacturing process usually includes a grinding step for adjusting the thickness of the wafer and a cutting step for cutting the wafer along the dividing lines to obtain individual wafers. The grinding step is performed from the back side of the wafer opposite to the front side of the wafer where the device area is formed. In addition, other processing steps such as polishing and / or etching may also be performed on the back side of the wafer.

[0003] To protect devices formed on the wafer during processing of the wafer, for example, from cracking, deformation, and / or contamination caused by debris, grinding water, or cutting water, a protective film or sheet may be applied to the front side of the wafer prior to processing.

[0004] Such protection of the device is particularly important if the device region has an uneven surface structure. For example, in known semiconductor device manufacturing processes such as wafer level chip scale packaging (WLCSP), the device region of the wafer is formed with a plurality of protrusions (e.g., bumps) protruding from the planar surface of the wafer. These protrusions are used, for example, to establish electrical contact with the devices in the respective wafer (e.g., when the wafer is incorporated into electronic devices such as mobile phones and personal computers).

[0005] In order to reduce the size of such electronic devices, semiconductor devices must be reduced in size. Therefore, the wafer on which the devices are formed is ground to a thickness in the μm range (eg, in the range of 20 to 100 μm) in the above-mentioned grinding step.

[0006] In known semiconductor device manufacturing processes, problems may arise during processing (e.g., in a grinding step) if protrusions (e.g., bumps) are present in the device region. In particular, the risk of wafer breakage during processing is significantly increased due to the presence of these protrusions. Furthermore, if the wafer is ground to a smaller thickness (e.g., a thickness in the μm range), the protrusions in the device region on the front side of the wafer may lead to deformations of the back side of the wafer, thus compromising the quality of the resulting wafer.

[0007] Therefore, when processing a wafer with a device region having such an uneven surface structure, the use of a protective film or sheet is particularly important.

[0008] However, particularly for sensitive devices such as MEMS, there is a problem that when a film or sheet is peeled off from a wafer, the device structure on the wafer may be damaged due to the adhesive force of an adhesive layer formed on the protective film or sheet, or may be contaminated by adhesive remaining on the device.

[0009] Therefore, there remains a need for a reliable and efficient method of processing wafers having device regions that minimizes any risk of contamination and damage to the wafer. Summary of the invention

[0010] Therefore, the object of the present invention is to provide a reliable and efficient method for processing a wafer with a device area, which is able to minimize any risk of contamination and damage to the wafer. This object is achieved by a wafer processing method having the technical features of claim 1 and a wafer processing method having the technical features of claim 13. Preferred embodiments of the invention are derived from the dependent claims.

[0011] The present invention provides a method for processing a wafer having a device area on one side, the device area having a plurality of devices. The method comprises: providing a protective film or sheet and applying the protective film or sheet to the one side of the wafer in order to cover the devices on the wafer, so that the front surface of the protective film or sheet is in direct contact with the one side of the wafer. In addition, the method comprises: heating the protective film or sheet during and / or after applying the protective film or sheet to the one side of the wafer so that the protective film or sheet is attached to the one side of the wafer, and processing the side of the wafer opposite to the one side.

[0012] The protective film or sheet is applied to the one side of the wafer (i.e., the front side of the wafer) so that the front surface of the protective film or sheet is in direct contact with the one side of the wafer. Therefore, there is no material, in particular, no adhesive, between the front surface of the protective film or sheet and the one side of the wafer.

[0013] Therefore, any possible contamination or damage to the device formed in the device region due to, for example, the adhesive force of the adhesive layer or adhesive remaining on the device can be eliminated.

[0014] During and / or after the protective film or sheet is applied to the one side of the wafer, the protective film or sheet is heated so that the protective film or sheet is attached to the one side of the wafer. An attachment force between the protective film or sheet and the wafer is thus generated by the heating process, which attachment force holds the protective film or sheet in its position on the wafer. Therefore, no additional adhesive material is required to attach the protective film or sheet to the one side of the wafer.

[0015] In particular, by heating the protective film or sheet, a form fit such as positive fit and / or material bonding (e.g., adhesive bonding) can be formed between the protective film or sheet and the wafer. The terms "material bonding" and "adhesive bonding" define that the protective film or sheet and the wafer are attached or connected due to atomic and / or molecular forces acting between the two components.

[0016] The term "adhesive bonding" refers to the presence of these atomic and / or molecular forces acting to attach or adhere the protective film or sheet to the wafer, and does not imply the presence of an additional adhesive between the protective film or sheet and the wafer. On the contrary, as already detailed above, the front surface of the protective film or sheet is in direct contact with the one side of the wafer.

[0017] The method of the present invention thus allows for reliable and efficient processing of a wafer having a device region, thereby minimizing the risk of any contamination and damage to the wafer, in particular, the devices formed in the device region.

[0018] The method may further include allowing the protective film or sheet to cool after the heating process. In particular, the protective film or sheet may be allowed to cool to its initial temperature (i.e., its temperature before the heating process). The protective film or sheet may be allowed to cool to, for example, its initial temperature before processing the side of the wafer opposite to the one side (i.e., the back side of the wafer).

[0019] As already detailed above, the adhesion force between the protective film or sheet and the wafer is generated by the heating process. The protective film or sheet may be attached to the wafer in the heating process itself and / or in a subsequent process in which the protective film or sheet is allowed to cool.

[0020] The protective film or sheet may be softened by a heating process, for example, to conform to the wafer surface of the one side of the wafer (e.g., to absorb the wafer topography). Upon cooling to, for example, its initial temperature, the protective film or sheet may be re-hardened, for example, to form a form fit and / or material bond with the wafer.

[0021] The protective film or sheet may be heat-resistant up to a temperature of 180° C. or more, preferably up to a temperature of 220° C. or more, and more preferably up to a temperature of 250° C. or more.

[0022] The protective film or sheet may be heated to a temperature in the range of 60 to 150° C., preferably 70 to 140° C., more preferably 80 to 130° C., even more preferably 90 to 120° C. Particularly preferably, the protective film or sheet is heated to a temperature of about 100° C.

[0023] During and / or after applying the protective film or sheet to said one side of the wafer, the protective film or sheet may be heated for a duration in the range of 1 minute to 10 minutes, preferably 1 minute to 8 minutes, more preferably 1 minute to 6 minutes, even more preferably 1 minute to 4 minutes, and still more preferably 1 minute to 3 minutes.

[0024] The protective film or sheet may be heated directly and / or indirectly.

[0025] The protective film or sheet may be heated by directly applying heat thereto, for example, using a heat application device (e.g., a heated roller, a heated stamp, etc.) or a heat radiation device. The protective film or sheet and the wafer may be placed in a container or chamber (e.g., a vacuum chamber), and the internal volume of the container or chamber may be heated to heat the protective film or sheet. The container or chamber may be provided with a heat radiation device.

[0026] The protective film or sheet may be heated indirectly, for example, by heating the wafer before and / or during and / or after the protective film or sheet is applied to the side of the wafer. For example, the wafer may be heated by placing the wafer on a support or carrier (e.g., a chuck table) and heating the support or carrier.

[0027] For example, the support or carrier (e.g., chuck table) may be heated to a temperature in the range of 60° C. to 150° C., preferably 70° C. to 140° C., more preferably 80° C. to 130° C., even more preferably 90° C. to 120° C. Particularly preferably, the support or carrier may be heated to a temperature of about 100° C.

[0028] These methods may also be combined, for example, by using a heat applying device (eg, heated rollers, etc.) or a heat radiating device for directly heating the protective film or sheet, and also indirectly heating the protective film or sheet through the wafer.

[0029] Preferably, the protective film or sheet is pliable, elastic, flexible, stretchable, soft and / or compressible in its heated state. In this way, it can be particularly reliably ensured that the protective film or sheet conforms to the wafer surface of the one side of the wafer (e.g., absorbing the wafer topography). As will be described in further detail below, this is particularly advantageous if the device area is formed with protrusions protruding from the planar surface of the wafer.

[0030] Preferably, the protective film or sheet hardens or hardens at least to a certain extent when cooling, so as to become more rigid and / or strong in the cooled state. In this way, particularly reliable protection of the device during subsequent processing (e.g. grinding and / or polishing) of the wafer can be ensured.

[0031] The method may further comprise removing the protective film or sheet from the wafer after processing its back side. The protective film or sheet may be heated before and / or during the removal of the protective film or sheet from the wafer. In this way, the removal process may be facilitated.

[0032] The device region may further have a plurality of dividing lines for dividing a plurality of devices.

[0033] The wafer may also have a peripheral edge region on its front side that is free of devices and formed around the device region.

[0034] The wafer may be, for example, a semiconductor wafer, a glass wafer, a sapphire wafer, a ceramic wafer (e.g., an aluminum oxide wafer (Al 2 O 3 ) ceramic wafers), quartz wafers, zirconium oxide wafers, PZT (lead zirconate titanate) wafers, polycarbonate wafers, metals (e.g., copper, iron, stainless steel, aluminum, etc.) or metallized material wafers, ferrite wafers, optical crystal material wafers, resins (e.g., epoxy resins), coated or molded wafers, etc.

[0035] In particular, the wafer may be, for example, a Si wafer, a GaAs wafer, a GaN wafer, a GaP wafer, an InAs wafer, an InP wafer, a SiC wafer, a SiN wafer, a LT (lithium tantalate) wafer, a LN (lithium niobate) wafer, or the like.

[0036] The wafer may be made of a single material or a combination of different materials (eg, two or more of the above materials). For example, the wafer may be a Si and glass bonded wafer, in which a wafer element made of Si is bonded to a wafer element made of glass.

[0037] The wafer may have any type of shape. In its top view, the wafer may have, for example, a circular shape, an oval shape, an elliptical shape, or a polygonal shape (eg, a rectangular shape or a square shape).

[0038] The protective film or sheet may have any type of shape. In its top view, the protective film or sheet may have, for example, a circular shape, an oval shape, an elliptical shape, or a polygonal shape (eg, a rectangular shape or a square shape).

[0039] The protective film or sheet may have substantially the same shape or the same shape as the wafer.

[0040] The protective film or sheet may have substantially the same shape or the same shape as the device area of ​​the wafer. For example, the protective film or sheet may have substantially the same outer diameter as the outer diameter of the device area, and the protective film or sheet may have substantially the same shape or the same shape as the device area of ​​the wafer.

[0041] The device area may be formed with a plurality of protrusions or bumps protruding from the planar surface of the wafer. The protrusions or bumps protruding from the planar surface of the wafer may be buried in a protective film or sheet.

[0042] The protrusions or projections (eg, bumps) may protrude, extend or protrude from a planar surface (substantially flat surface) of the wafer. The protrusions or projections may define a surface structure or topography of the side of the wafer (ie, its front side), making this side uneven.

[0043] These bumps or protrusions can be used, for example, to establish electrical contact with devices in individual chips or wafers after the wafer has been singulated, for example, when the chips or wafers are incorporated into electronic devices such as mobile phones and personal computers.

[0044] The protrusions may be arranged irregularly or in a regular pattern.Only some of the protrusions may be arranged in a regular pattern.

[0045] The protrusions may have any type of shape. For example, some or all of the protrusions may be spherical, hemispherical, cylindrical or cylindrical (e.g., a cylindrical or cylindrical shape having a circular, elliptical or polygonal (e.g., triangular, square, etc.) cross-section or bottom), conical, truncated cone or stepped shape.

[0046] At least some of the protrusions may be caused by elements formed on the planar surface of the wafer. At least some of the protrusions may be caused by elements that partially or completely penetrate the wafer in the direction of its thickness (e.g., in the case of through silicon vias (TSVs)). These latter elements may extend along part of the wafer thickness or along the entire wafer thickness.

[0047] The height of the protrusion in the thickness direction of the wafer may be in the range of 20 to 500 μm, preferably 30 to 400 μm, more preferably 40 to 250 μm, even more preferably 50 to 200 μm, still even more preferably 70 to 150 μm.

[0048] All protrusions may have substantially the same shape and / or size. Alternatively, the shape and / or size of at least some of the protrusions may differ from each other.

[0049] In the wafer processing method of the present invention, the protrusions or bumps protruding from the planar surface of the wafer can be buried in a protective film or sheet. Therefore, any negative impact of surface unevenness caused by the presence of protrusions in the device area on subsequent wafer processing steps can be reduced or even eliminated.

[0050] In particular, by embedding the bumps in a protective film or sheet, the bumps may be protected from any damage during wafer processing (eg, in subsequent grinding and / or dicing steps).

[0051] Furthermore, if the wafer is ground to a smaller thickness (e.g., a thickness in the μm range), the protrusions of the device area on the front side of the wafer may cause deformation of the back side of the wafer due to the reduced thickness of the wafer and the pressure applied to it during the grinding process. This latter effect is known as "pattern transfer" because the pattern of the protrusions on the front side of the wafer is transferred to the back side of the wafer and causes undesirable unevenness of the back side surface of the wafer, thus compromising the quality of the resulting chips or wafers.

[0052] The protective film or sheet acts as a cushion or buffer between the front side of the wafer and, for example, a support or carrier on which the front side of the wafer rests during processing (e.g., grinding and / or polishing) the back side of the wafer, thereby helping to achieve a consistent and even distribution of pressure during processing. Thus, pattern transfer or cracking of the wafer during processing of its back side can be prevented.

[0053] The method may further comprise applying pressure to a rear surface of the protective film or sheet, opposite to its front surface, during and / or after applying the protective film or sheet to the one side of the wafer. In this way, the front surface of the protective film or sheet is pressed against the one side of the wafer. Thus, it can be particularly effective to ensure that the protective film or sheet is reliably attached to the wafer.

[0054] Pressure may be applied to the rear surface of the protective film or sheet before and / or during and / or after heating the protective film or sheet. Pressure may be applied to the rear surface of the protective film or sheet before processing the rear side of the wafer.

[0055] Pressure may be applied to the rear surface of the protective film or sheet by a pressure applying device (eg, a roller, a stamp, a film, etc.).

[0056] Particularly preferably, a combined heat and pressure applying device (eg, a heated roller or a heated stamp) may be used. In this case, pressure may be applied to the rear surface of the protective film or sheet while heating the protective film or sheet.

[0057] As will be described in further detail below, pressure may be applied to the rear surface of the protective film or sheet in a vacuum chamber.

[0058] The protective film or sheet can be applied and / or attached to the front side of the wafer in a reduced pressure atmosphere (in particular, under vacuum). In this way, it can be reliably ensured that there are no gaps and / or bubbles between the protective film or sheet and the wafer. Thus, any stress or strain on the wafer during processing of its back side (e.g. due to expansion of these bubbles during the heating process) is avoided.

[0059] For example, the step of applying and / or attaching the protective film or sheet to the one side of the wafer may be performed in a vacuum chamber. In particular, a vacuum laminator may be used to apply and / or attach the protective film or sheet to the one side of the wafer. In such a vacuum laminator, the wafer is placed on a chuck table in a vacuum chamber with the back side of the wafer in contact with the upper surface of the chuck table and the front side of the wafer oriented upward. The chuck table may be, for example, a heated chuck table.

[0060] The protective film or sheet to be applied to the front side of the wafer is held at its peripheral portion by an annular frame and placed above the front side of the wafer in a vacuum chamber. The upper portion of the vacuum chamber above the chuck table and the annular frame is provided with an air inlet closed by an expandable rubber membrane.

[0061] After the wafer and the protective film have been loaded into the vacuum chamber, the chamber is evacuated and air is supplied to the rubber film through the air inlet, so that the rubber film expands into the evacuated chamber. In this way, the rubber film moves downward in the vacuum chamber to push the protective film or sheet toward the front side of the wafer, thereby sealing the peripheral wafer portion with the protective film or sheet and pressing the film or sheet against the device area on the front side of the wafer. Thus, the protective film can be tightly applied to the front side of the wafer to follow the contour of the device area (e.g., the contour of a protrusion or bump present therein).

[0062] The protective film or sheet may be heated during and / or after it is applied to the side of the wafer, for example by heating the chuck stage.

[0063] Subsequently, the vacuum in the vacuum chamber is released, and the protective film or sheet is held in its position on the front side of the wafer by the adhesion force generated through the heating process and the positive pressure in the vacuum chamber.

[0064] Alternatively, the rubber film may be replaced by a soft stamp or a soft roller (eg, a heated soft stamp or a heated soft roller).

[0065] Processing the side of the wafer opposite to the one side (ie, the wafer back side) may include or consist of grinding and / or polishing and / or etching the side of the wafer opposite to the one side.

[0066] In particular, processing the side of the wafer opposite to the one side may comprise or consist of grinding the side of the wafer opposite to the one side for adjusting the wafer thickness. In this case, the method of the invention may be used in a particularly advantageous manner.

[0067] In particular, during the grinding process, considerable pressure is applied to the back side of the wafer. This pressure can lead to damage to the wafer, such as cracking and / or deformation thereof, in particular if the wafer is ground to a smaller thickness (e.g., a thickness in the μm range). For example, as already detailed above, a pattern of protrusions or bumps formed on the front side of the wafer can be transferred to the back side of the wafer.

[0068] In the method of the present invention, the protective film or sheet acts as a cushion or buffer between the front side of the wafer and, for example, a support or carrier (e.g., a chuck table) on which the front side of the wafer rests during grinding of the back side of the wafer. Thus, a more consistent and uniform pressure distribution during grinding can be achieved, thereby reducing or even eliminating the risk of pattern transfer or wafer cracking during grinding.

[0069] The method may further include dicing the wafer, for example, along separation lines that separate the plurality of devices.

[0070] The wafer may be diced from its front side or back side. The dicing of the wafer may form part of or constitute processing of the side of the wafer opposite to said one side.

[0071] Cutting can be performed by mechanical cutting (e.g., by blade scribing or sawing) and / or by laser cutting and / or by plasma cutting. The wafer can be cut in a single mechanical cutting step, a single laser cutting step, or a single plasma cutting step. Alternatively, the wafer can be cut by a series of mechanical cutting and / or laser cutting and / or plasma cutting steps.

[0072] Laser cutting can be performed, for example, by ablative laser cutting and / or by stealth laser cutting (i.e., by applying a laser beam to form a modified region within the wafer, and / or by applying a laser beam to form a plurality of hole regions in the wafer). Each of these hole regions can include a modified region and a space in the modified region that is open to the surface of the wafer.

[0073] The dicing of the wafer may be performed with the protective film or sheet attached to the wafer. In this way, it is ensured that the pressure applied during the dicing step is more uniformly and evenly distributed throughout the wafer during dicing, thus reducing or even minimizing any risk of damaging the wafer during the dicing step (e.g. cracking of the sidewalls of the resulting chips or dies). In this case, it is particularly preferred to dicing the wafer from its back side.

[0074] The outer diameter of the protective film or sheet may be greater than the outer diameter of the wafer. In this way, the handling, manipulation and / or transportation of the wafer may be facilitated. In particular, as will be described in detail below, the peripheral portion of the protective film or sheet may be attached to the annular frame.

[0075] The outer diameter of the protective film or sheet may be smaller than the outer diameter of the wafer.

[0076] The outer diameter of the protective film or sheet may be substantially the same as the outer diameter of the wafer.

[0077] The outer diameter of the protective film or sheet may be substantially the same as the outer diameter of the device region. In this way, particularly efficient resource usage is ensured while reliably protecting the devices formed in the device region.

[0078] The method may further include cutting the protective film or sheet. The protective film or sheet may be cut so that its outer diameter is larger than the outer diameter of the wafer or smaller than the outer diameter of the wafer or substantially the same as the outer diameter of the wafer or substantially the same as the outer diameter of the device region.

[0079] The step of cutting the protective film or sheet may be performed before or after applying the protective film or sheet to the wafer.

[0080] The step of cutting the protective film or sheet may be performed before or after attaching the protective film or sheet to the wafer.

[0081] The method may also include attaching the peripheral portion of the protective film or sheet to the annular frame. In particular, the peripheral portion of the protective film or sheet may be attached to the annular frame so that the protective film or sheet closes the central opening of the annular frame (i.e., the area within the inner diameter of the annular frame). In this way, the wafer attached to the protective film or sheet (in particular, attached to its central portion) is held by the annular frame through the protective film or sheet. Therefore, a wafer unit including a wafer, a protective film or sheet and an annular frame is formed, thereby facilitating the processing, manipulation and / or transportation of the wafer.

[0082] The step of attaching the outer peripheral portion of the protective film or sheet to the annular frame may be performed before or after applying the protective film or sheet to the wafer.

[0083] The step of attaching the outer peripheral portion of the protective film or sheet to the annular frame may be performed before or after attaching the protective film or sheet to the wafer.

[0084] The step of attaching the peripheral portion of the protective film or sheet to the ring frame may be performed before or after processing the back side of the wafer.

[0085] The ring frame may be a semiconductor size ring frame. Herein, the term "semiconductor size ring frame" refers to a ring frame having a size (standardized size) (particularly, an inner diameter (standardized inner diameter)) of a ring frame for holding a semiconductor wafer.

[0086] The dimensions (particularly, the inner diameter) of the ring frame for holding semiconductor wafers are defined in the SEMI standards. For example, the dimensions of the tape frame for 300 mm wafers are defined in the SEMI standard SEMI G74, and the dimensions of the plastic tape frame for 300 mm wafers are defined in the SEMI standard SEMI G87. The ring frame may have a frame dimension for holding semiconductor size wafers having a size of, for example, 3 inches, 4 inches, 5 inches, 6 inches, 8 inches, 12 inches, or 18 inches.

[0087] The peripheral portion of the protective film or sheet may be attached to the annular frame by a substantially annular or annular adhesive layer. Herein, the term "substantially annular" defines that the shape of the adhesive layer may deviate from a perfect annular shape, for example due to the presence of one or more flat or straight portions, notches and / or grooves. The substantially annular or annular adhesive layer may be arranged between the protective film or sheet and the annular frame.

[0088] A substantially annular or ring-shaped adhesive layer may be applied to the peripheral portion of the front surface of the protective film or sheet. The adhesive layer may be provided only in the peripheral portion of the front surface of the protective film or sheet.

[0089] A substantially annular or ring-shaped adhesive layer may be applied to the surface of the outer peripheral portion of the ring-shaped frame to be attached to the protective film or sheet.

[0090] The substantially annular or annular adhesive layer may be a continuous adhesive layer. Alternatively, the substantially annular or annular adhesive layer may be a discontinuous adhesive layer. In particular, in the substantially annular or annular adhesive layer, the adhesive may be arranged in a discontinuous form such as a dot form, a strip form (e.g., a straight and / or curved strip) etc.

[0091] The substantially annular or annular adhesive layer may be heat resistant up to a temperature of 180°C or above, preferably up to a temperature of 220°C or above, more preferably up to a temperature of 250°C or above.

[0092] The inner diameter of the substantially annular or annular adhesive layer may be substantially equal to or greater than the inner diameter of a semiconductor-sized annular frame used to hold semiconductor-sized wafers.

[0093] As used herein, the term "semiconductor size wafer" refers to a wafer having the size (standardized size) of a semiconductor wafer, in particular a diameter (standardized diameter) (i.e., outer diameter). The size of a semiconductor wafer, in particular the diameter (i.e., outer diameter) is defined in the SEMI standard. For example, a semiconductor size wafer may be a Si wafer. The size of a polished single crystal Si wafer is defined in SEMI standards M1 and M76. A semiconductor size wafer may be a 3 inch, 4 inch, 5 inch, 6 inch, 8 inch, 12 inch, or 18 inch wafer.

[0094] The inner diameter of the substantially annular or ring-shaped bonding layer is greater than the outer diameter of the wafer.

[0095] The outer diameter of the substantially annular or ring-shaped adhesive layer may be larger than the inner diameter of a semiconductor-sized annular frame for holding semiconductor-sized wafers.

[0096] The method may further include attaching a buffer layer to a rear surface of the protective film or sheet opposite to the front surface thereof.

[0097] As already detailed above, the device region may be formed with a plurality of protrusions or projections (eg, bumps) protruding from the planar surface of the wafer. The protrusions or projections protruding from the planar surface of the wafer may be buried in the buffer layer.

[0098] By burying the bumps or projections in the buffer layer, the bumps or projections are particularly reliably protected from any damage during wafer processing, for example in subsequent grinding and / or dicing steps.

[0099] The protective film or sheet covers the devices formed in the device area of ​​the wafer, thereby protecting the devices from damage and contamination. In addition, the protective film or sheet facilitates the removal of the buffer layer from the wafer after processing. In particular, since the front surface of the protective film or sheet is in direct contact with the front side of the wafer, that is, there is no adhesive between the front surface of the protective film or sheet and the front side of the wafer, the protective film or sheet and the buffer layer can be removed from the wafer in a particularly simple and effective manner.

[0100] The buffer layer may be formed of any type of material that allows the protrusions or bumps protruding from the planar surface of the wafer to be buried. For example, the buffer layer may be formed of a resin, an adhesive, a gel, or the like.

[0101] The buffer layer may be heat-resistant up to a temperature of 180° C. or more, preferably up to a temperature of 220° C. or more, and more preferably up to a temperature of 250° C. or more.

[0102] The buffer layer may have a thickness in the range of 20 to 300 μm, preferably 50 to 250 μm, and more preferably 80 to 200 μm.

[0103] Attaching a buffer layer to the rear surface of a protective film or sheet is particularly advantageous for wafers having a relatively high degree of surface roughness or unevenness on its front side (e.g., due to the presence of protrusions or projections such as bumps). In this case, the protrusions or projections may not be completely buried in the protective film or sheet, so that there is at least a certain degree of surface unevenness on the rear surface of the protective film or sheet. The surface unevenness can be absorbed by further burying the protrusion or projection of the buffer layer. Therefore, the protrusion or projection can be protected in a particularly reliable manner. In addition, as will be described in detail below, the distribution of stress or strain on the wafer during its processing can be further improved.

[0104] The front surface of the buffer layer may be in contact with the rear surface of the protective film or sheet.The rear surface of the buffer layer opposite to the front surface thereof may be substantially parallel to the side of the wafer opposite to the one side.

[0105] In this case, when processing (e.g., grinding, polishing and / or dicing) the wafer backside, a suitable back pressure may be applied to the back surface of the buffer layer (e.g., by placing the back surface on a support or carrier such as a chuck table).

[0106] Since the planar rear surface of the buffer layer is substantially parallel to the wafer rear side, the pressure applied to the wafer during processing (e.g., grinding by a grinding wheel of a grinding device) is evenly distributed over the wafer, thereby minimizing pattern transfer (i.e., the pattern defined by the protrusions or protrusions in the device area is transferred to the processed (e.g., ground) wafer rear side) and any risk of wafer cracking. In addition, the substantially parallel alignment of the flat, planar rear surface of the buffer layer with the wafer rear side allows processing steps to be performed with high precision, thereby achieving a particularly consistent and uniform wafer thickness, for example after grinding.

[0107] In addition, the protective film or sheet acts as an additional cushion or buffer between the wafer front side and the buffer layer, thus further contributing to a consistent and uniform pressure distribution during processing such as grinding. Thus, pattern transfer or wafer cracking during processing can be particularly reliably prevented.

[0108] The rear surface of the buffer layer may be made substantially parallel to the wafer backside by applying pressure to the rear surface of the buffer layer.The pressure may be applied directly to the rear surface of the buffer layer, i.e., without additional elements or components between the pressing means for applying pressure and the rear surface of the buffer layer.

[0109] For example, by applying parallel pressing forces to the back side of the wafer and the back surface of the buffer layer, for example in a mounting chamber (e.g., a vacuum chamber), the wafer and the buffer layer can be pressed together with the protective film or sheet arranged therebetween. The pressure can be applied, for example, using two parallel pressing plates. The pressing plate can be a heated pressing plate, thereby allowing the protective film or sheet to be heated during the pressing process.

[0110] The buffer layer can be cured by an external stimulus (e.g., UV radiation, heat, electric field, and / or chemical agent). In this case, the buffer layer hardens to at least some extent when the external stimulus is applied. For example, the buffer layer can be formed of a curable resin, a curable adhesive, a curable gel, etc.

[0111] The buffer layer may be configured to exhibit a certain degree of compressibility, elasticity and / or flexibility after it is cured, i.e., to be compressible, elastic and / or flexible after curing. For example, the buffer layer may be such that it enters a rubbery state by curing. Alternatively, the buffer layer may be configured to reach a rigid, hard state after curing.

[0112] Preferred examples of the UV-curable resin used as the buffer layer in the processing method of the present invention are ResiFlat from DISCO and TEMPLOC from DENKA.

[0113] The method of the present invention may further include applying an external stimulus to the buffer layer to cure the buffer layer after applying the protective film or sheet to the one side of the wafer. The external stimulus may be applied to the buffer layer after attaching the protective film or sheet to the one side of the wafer.

[0114] An external stimulus may be applied to the buffer layer prior to processing (eg grinding) the wafer backside. In this way, protection of the wafer during processing and processing accuracy may be further improved.

[0115] The protective film or sheet facilitates the removal of the attached curable or cured buffer layer from the wafer. In particular, due to the presence of the protective film or sheet, the buffer layer can be removed from the wafer in a reliable and simple manner, thereby avoiding any residues (e.g., resin, adhesive or gel residues) in the device area, thus preventing contamination of the device and minimizing the risk of damaging the protrusions or bumps during the removal process.

[0116] If the curable buffer layer exhibits a certain degree of compressibility, elasticity and / or flexibility, ie is compressible, elastic and / or flexible (eg rubbery) after curing, the cured buffer layer may be removed in a particularly reliable and efficient manner after curing.

[0117] If the buffer layer is configured to achieve a rigid, hard state upon curing, removal of the buffer layer from the wafer may be facilitated by applying an external stimulus to the cured buffer layer to soften or remove the buffer layer to at least some extent. For example, some buffer layers, such as those formed from DENKA's UV-curable resin TEMPLOC, may be treated by applying hot water after curing to soften the cured buffer layer and allow particularly easy removal of the buffer layer from the wafer.

[0118] The buffer layer may be attached to the rear surface of the protective film or sheet before applying the protective film or sheet to the one side of the wafer.

[0119] In this case, the protective film or sheet and the buffer layer may be laminated first to form a protective sheet including the buffer layer and the protective film or sheet attached to the buffer layer. The protective sheet formed in this manner may then be applied to the one side of the wafer, for example so that the protrusions or convexities protruding from the planar surface of the wafer are covered by the protective film or sheet and buried in the protective film or sheet and the buffer layer, and the rear surface of the buffer layer is substantially parallel to the side of the wafer opposite to the one side (i.e., the rear side of the wafer). When the protective sheet is applied to the one side of the wafer, the front surface of the protective film or sheet is applied to the one side of the wafer.

[0120] In this way, the wafer handling method can be carried out in a particularly simple and efficient manner. For example, the protective sheet can be prepared in advance, stored for later use, and used for wafer handling when required. The protective sheet can thus be manufactured in large quantities, making its production particularly efficient in terms of time and cost.

[0121] The buffer layer may be attached to the rear surface of the protective film or sheet after applying the protective film or sheet to the one side of the wafer.

[0122] In this case, the protective film or sheet is first applied to the one side of the wafer, and the one side of the wafer to which the protective film is applied is subsequently attached to the front surface of the buffer layer, for example so that the protrusions or convexities protruding from the planar surface of the wafer are buried in the protective film or sheet and the buffer layer, and the rear surface of the buffer layer is substantially parallel to the side of the wafer opposite to the one side. This method allows the protective film or sheet to be attached to the one side of the wafer with particularly high precision (in particular, with respect to the protrusions or convexities protruding from the planar surface of the wafer).

[0123] The buffer layer may be attached to the rear surface of the protective film or sheet before and / or during and / or after attaching the protective film or sheet to the one side of the wafer.

[0124] The method of the present invention may also include removing the protective film or sheet and the buffer layer from the wafer. The protective film or sheet and the buffer layer may be removed from the wafer after a process such as grinding. For example, the protective film or sheet and the buffer layer may be removed from the wafer after grinding but before cutting, or after grinding and cutting. In this way, the individual chips or wafers obtained in the cutting process may be separated and picked up in a simple and reliable manner. For example, if the protective film and the buffer layer are provided in the form of the protective sheet described in detail above, the protective sheet may be removed from the wafer after grinding or after grinding and cutting.

[0125] The buffer layer and the protective film or sheet may be removed separately (ie, one after the other).For example, the buffer layer may be removed first, and then the protective film or sheet may be removed.

[0126] The wafer can be cut before the protective film or sheet and the buffer layer are removed from the wafer. In this case, the wafer is safely protected by the protective film and the buffer layer during the cutting process. Therefore, any damage to the wafer during cutting can be particularly reliably avoided.

[0127] Alternatively, the dicing of the wafer can be performed after the protective film or sheet and the buffer layer are removed from the wafer. This method allows the individual chips or wafers to be separated and picked up immediately after the dicing step. In this case, it is particularly preferred to perform the dicing step from the front side of the wafer.

[0128] The method may further include attaching a substrate to the rear surface of the buffer layer such that the front surface of the substrate is in direct contact with the rear surface of the buffer layer.

[0129] The material of the substrate is not particularly limited.

[0130] The substrate may be made of a soft or pliable material such as, for example, a polymer material, such as polyvinyl chloride (PVC) or ethylene vinyl acetate (EVA).

[0131] Alternatively, the substrate may be made of a rigid or hard material, such as polyethylene terephthalate (PET) and / or silicon and / or glass and / or stainless steel (SUS).

[0132] For example, if the substrate is made of polyethylene terephthalate (PET) or glass and the buffer layer can be cured by external stimulation, the buffer layer can be cured using radiation (e.g., UV radiation) that can be transmitted through polyethylene terephthalate (PET) or glass. If the substrate is made of silicon or stainless steel (SUS), a cost-effective substrate is provided.

[0133] Additionally, the substrate may be formed from combinations of the materials listed above.

[0134] The substrate may be heat-resistant up to a temperature of 180° C. or more, preferably up to a temperature of 220° C. or more, and more preferably up to a temperature of 250° C. or more.

[0135] The substrate may have a thickness in the range of 30 to 1500 μm, preferably 40 to 1200 μm, more preferably 50 to 1000 μm. Particularly preferably, the substrate has a thickness in the range of 30 to 250 μm. A thickness of 50 μm of the substrate is particularly preferred. For example, the substrate may be a polyethylene terephthalate (PET) film having a thickness of 50 μm.

[0136] The buffer layer and substrate may be attached to the rear surface of the protective film or sheet before or after the protective film or sheet is applied to the front side of the wafer. In particular, the protective film or sheet, the buffer layer and the substrate may be laminated first to form a protective sheet comprising the substrate, the buffer layer and the protective film or sheet attached to the buffer layer. The protective sheet formed in this manner may then be applied to the front side of the wafer so that the front surface of the protective film or sheet is in direct contact with the front side of the wafer.

[0137] The protective film or sheet can be made of plastic such as a polymer. Particularly preferably, the protective film or sheet is made of a polyolefin. For example, the protective film or sheet can be made of polyethylene (PE) or polypropylene (PP).

[0138] Polyolefin films have material properties that are particularly advantageous for use in the wafer processing method of the present invention. In particular, these films are pliable, stretchable and soft in the heated state (e.g. when heated to a temperature in the range of 60° C. to 150° C.). Thus, it can be particularly reliably ensured that the protective film or sheet conforms to the wafer surface of the one side of the wafer (e.g. absorbing the wafer topography). This is particularly beneficial if the device area is formed with protrusions or bumps protruding from the planar surface of the wafer.

[0139] Furthermore, the polyolefin film hardens and solidifies when cooling, so as to become more rigid and strong in the cold state. Thus, particularly reliable protection of the device during subsequent processing of the wafer (eg grinding and / or polishing) can be ensured.

[0140] The protective film or sheet may have a thickness in the range of 5 to 200 μm, preferably 8 to 100 μm, more preferably 10 to 80 μm, and even more preferably 12 to 50 μm. Particularly preferably, the protective film or sheet has a thickness in the range of 80 to 150 μm. In this way, it can be ensured that the protective film or sheet is sufficiently flexible and pliable to fully conform to the contour of the device area, and at the same time, exhibits sufficient thickness to reliably and effectively protect the device formed in the device area.

[0141] The present invention also provides a method for processing a wafer having a device area on one side, the device area having a plurality of devices, wherein the method includes providing a protective film or sheet, providing a liquid adhesive, and dispensing the liquid adhesive onto the protective film or sheet and / or onto the wafer. In addition, the method includes applying a protective film or sheet for covering the devices on the wafer to the one side of the wafer (i.e., the front side of the wafer), and processing the side of the wafer opposite to the one side (i.e., the back side of the wafer). The liquid adhesive is dispensed only onto the peripheral portion of the protective film or sheet and / or only onto the peripheral portion of the wafer.

[0142] The wafer may have the properties, characteristics and features described in detail above.

[0143] The protective film or sheet may have the properties, characteristics and features described in detail above. In particular, the protective film or sheet may be used in combination with a buffer layer or a buffer layer and a substrate, as described in detail above.

[0144] The buffer layer may be attached to the rear surface of the protective film in substantially the same manner as detailed above.

[0145] The substrate may be attached to the rear surface of the buffer layer in substantially the same manner as detailed above.

[0146] The step of processing the side of the wafer opposite to the one side may be performed in the manner described in detail above.

[0147] According to this method, the liquid adhesive is dispensed only onto the peripheral portion of the protective film or sheet and / or only onto the peripheral portion of the wafer.

[0148] Therefore, the adhesive force between the protective film or sheet and the wafer generated by the adhesive is greatly reduced, for example, compared to the case where the adhesive is applied to the entire front side of the wafer. Therefore, any damage to the device formed in the device area, for example due to the adhesive force of the adhesive, can be significantly reduced or even completely prevented.

[0149] Furthermore, in this way, possible contamination of the component in the component region, for example due to adhesive residues on the component, can be substantially reduced or even completely avoided.

[0150] Dispensing the adhesive in liquid form onto the peripheral portion of the protective film or sheet and / or the peripheral portion of the wafer allows the adhesive to be applied in an accurate and efficient manner. In particular, the adhesive can be accurately metered to reliably avoid contamination of the device formed in the device area.

[0151] The method thus allows for reliable and efficient processing of a wafer having a device region, minimizing any risk of contamination and damage to the wafer, in particular, the devices formed in the device region.

[0152] The wafer may have any type of shape. In its top view, the wafer may have, for example, a circular shape, an oval shape, an elliptical shape, or a polygonal shape (eg, a rectangular shape or a square shape).

[0153] The protective film or sheet may have any type of shape. In its top view, the protective film or sheet may have, for example, a circular shape, an oval shape, an elliptical shape, or a polygonal shape (eg, a rectangular shape or a square shape).

[0154] The protective film or sheet may have substantially the same shape or the same shape as the wafer.The protective film or sheet may have substantially the same shape or the same shape as the device area of ​​the wafer.

[0155] The liquid adhesive may be dispensed only onto a peripheral portion of the protective film or sheet and / or only onto a peripheral portion of the wafer to form an adhesive layer having a substantially annular or ring-shaped shape.

[0156] The liquid adhesive may be dispensed to form a continuous adhesive layer. Alternatively, the liquid adhesive may be dispensed to form a discontinuous adhesive layer. In particular, in the adhesive layer formed by the liquid adhesive, the adhesive may be arranged in a discontinuous form such as a dot form, a strip form (e.g., a straight and / or curved strip) etc.

[0157] The adhesive may be heat resistant up to a temperature of 180°C or more, preferably up to a temperature of 220°C or more, more preferably up to a temperature of 250°C or more.

[0158] The liquid adhesive may be, for example, a liquid adhesive produced by Brewer Science, such as 220 material (see http: / / www.brewerscience.com / product-categories / wafer-level-packaging / ).

[0159] The liquid adhesive can be dispensed using a dispenser. The dispenser can be, for example, a mechanical dispenser or an air pulse dispenser.

[0160] The dispenser may be, for example, a dispenser produced by Musashi Engineering, such as dispenser ML-5000XII (see http: / / www.musashi-engineering.co.jp.e.cn.hp.transer.com / products / ).

[0161] The protective film or sheet may be attached to the one side of the wafer by an adhesive dispensed onto a peripheral portion of the protective film or sheet and / or onto a peripheral portion of the wafer.

[0162] In particular, the liquid adhesive may be dispensed onto a peripheral portion of the protective film or sheet and / or a peripheral portion of the wafer, and the protective film or sheet may be applied to the one side of the wafer such that the peripheral portion of the protective film or sheet is attached to the peripheral portion of the wafer via the adhesive.

[0163] In some embodiments, the liquid adhesive is dispensed only onto the peripheral portion of the protective film or sheet and not onto the wafer. In other embodiments, the liquid adhesive is dispensed only onto the peripheral portion of the wafer and not onto the protective film or sheet. In addition, the liquid adhesive may be dispensed onto the peripheral portion of the protective film or sheet and onto the peripheral portion of the wafer.

[0164] A protective film or sheet may be attached to the side of the wafer prior to dispensing the liquid adhesive.

[0165] In particular, the protective film or sheet may be attached to the side of the wafer in the manner detailed above by heating the protective film or sheet during and / or after applying the protective film or sheet to the side of the wafer. The protective film or sheet may be attached to the side of the wafer using the method detailed above.

[0166] Subsequently, after the protective film or sheet has been attached to said side of the wafer, a liquid adhesive may be dispensed. The liquid adhesive may be dispensed to seal or cover any gaps that may exist between the protective film or sheet and the wafer at the peripheral portion thereof. By dispensing the adhesive in liquid form, it can be particularly reliably ensured that these gaps are effectively sealed or covered.

[0167] The liquid adhesive may be dispensed onto the protective film or sheet and / or onto the wafer before and / or after the protective film or sheet is applied to the one side of the wafer. The liquid adhesive may be dispensed onto the protective film or sheet and / or onto the wafer after the protective film or sheet is applied to the one side of the wafer but before the protective film or sheet is attached to the one side of the wafer.

[0168] Liquid adhesive may be dispensed onto the protective film or sheet and / or onto the wafer after the protective film or sheet has been applied to the one side of the wafer, and the protective film or sheet may be attached to the one side of the wafer by the adhesive so dispensed. Also in this case, dispensing the adhesive in liquid form allows particularly precise and efficient application of the adhesive.

[0169] The liquid adhesive may be dispensed onto the protective film or sheet and / or onto the wafer such that after the protective film or sheet is applied to the one side of the wafer, no adhesive is present in the device region of the wafer. In particular, adhesive may be present only in a peripheral edge region of the front side of the wafer, which peripheral edge region is free of devices and is formed around the device region. After the protective film or sheet is applied to the one side of the wafer, the region of the protective film or sheet where no adhesive is present may have substantially the same shape and / or size as the device region of the wafer.

[0170] The liquid adhesive may be dispensed onto a peripheral portion of the front surface of the protective film or sheet (ie, the surface of the protective film or sheet to be applied to the wafer) and / or onto the peripheral side edges of the protective film or sheet.

[0171] The liquid adhesive may be dispensed onto a peripheral portion of the front side of the wafer and / or onto a peripheral side edge of the wafer.

[0172] The outer diameter of the protective film or sheet may be larger than the outer diameter of the wafer.

[0173] The outer diameter of the protective film or sheet may be smaller than the outer diameter of the wafer.

[0174] The outer diameter of the protective film or sheet may be substantially the same as the outer diameter of the wafer.

[0175] The outer diameter of the protective film or sheet may be substantially the same as the outer diameter of the device region. BRIEF DESCRIPTION OF THE DRAWINGS

[0176] In the following, non-limiting examples of the present invention are described with reference to the accompanying drawings, in which:

[0177] Figure 1 is a cross-sectional view showing a wafer to be processed by the method of the present invention;

[0178] Figure 2 is a cross-sectional view showing a step of applying a protective film to a wafer according to a first embodiment of the method of the present invention;

[0179] Figure 3 is a perspective view showing a step of applying a protective film to a wafer according to the first embodiment;

[0180] Figure 4 is a cross-sectional view showing a step of applying heat and pressure to a protective film according to a first embodiment;

[0181] Figure 5 is a cross-sectional view showing a step of applying heat and pressure to a protective film according to a modification of the first embodiment;

[0182] Figure 6 is a cross-sectional view showing a protective film and an annular frame used in a second embodiment of the method of the present invention;

[0183] Figure 7 is a cross-sectional view showing a step of applying heat and pressure to a protective film according to a second embodiment;

[0184] Figure 8 It is shown Figure 7 A cross-sectional view showing the result of the step of applying heat and pressure to the protective film;

[0185] Fig. 9 is a cross-sectional view showing a step of applying heat and pressure to a protective film according to a third embodiment of the method of the present invention;

[0186] Fig.10 is a cross-sectional view showing the result of a step of applying heat and pressure to a protective film according to a fourth embodiment of the method of the present invention;

[0187] Fig.11 is a cross-sectional view showing a step of cutting away a portion of a protective film according to a fourth embodiment;

[0188] Fig.12 It is shown Fig.11 A cross-sectional view showing the result of a step of cutting away a portion of the protective film;

[0189] Fig.13 is a cross-sectional view showing a result of a step of grinding the back side of a wafer according to a fourth embodiment;

[0190] Fig.14 is a cross-sectional view showing the result of a step of grinding the back side of a wafer according to a fifth embodiment of the method of the present invention;

[0191] Fig.15 is a cross-sectional view showing a step of cutting away a portion of a protective film according to a fifth embodiment;

[0192] Fig.16 It is shown Fig.15 A cross-sectional view showing the result of a step of cutting away a portion of the protective film;

[0193] Fig.17 is a cross-sectional view showing a protective film and a buffer layer used in a sixth embodiment of the method of the present invention;

[0194] Fig.18 is a cross-sectional view showing the result of a step of applying heat and pressure to a protective film according to a sixth embodiment;

[0195] Fig.19 is a cross-sectional view showing the result of a step of applying heat and pressure to a protective film according to a seventh embodiment of the method of the present invention;

[0196] Fig. 20is a cross-sectional view showing the result of the step of applying heat and pressure to the protective film according to a modification of the seventh embodiment of the method of the present invention;

[0197] Fig.21 is a cross-sectional view showing the result of a step of grinding the back side of a wafer according to a modification of the seventh embodiment;

[0198] Fig. 22 is a cross-sectional view showing a protective film, a buffer layer, and an annular frame used in an eighth embodiment of the method of the present invention;

[0199] Fig.23 is a cross-sectional view showing a step of applying heat and pressure to a protective film according to an eighth embodiment;

[0200] Fig.24 is a cross-sectional view showing the result of the steps of dispensing an adhesive and applying a protective film to a wafer according to a ninth embodiment of the method of the present invention;

[0201] Fig.25 is a cross-sectional view showing the result of the steps of dispensing an adhesive and applying a protective film to a wafer according to a tenth embodiment of the method of the present invention;

[0202] Fig.26 is a cross-sectional view showing the result of the steps of dispensing an adhesive and applying a protective film to a wafer according to an eleventh embodiment of the method of the present invention;

[0203] Fig. 27 is a cross-sectional view showing the result of the steps of dispensing an adhesive and applying a protective film to a wafer according to a twelfth embodiment of the method of the present invention;

[0204] Fig.28 is a cross-sectional view showing the result of the steps of dispensing an adhesive and applying a protective film to a wafer according to a thirteenth embodiment of the method of the present invention; and

[0205] Fig.29 is a cross-sectional view showing the result of the steps of dispensing an adhesive and applying a protective film to a wafer according to a fourteenth embodiment of the method of the present invention. DETAILED DESCRIPTION

[0206] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Preferred embodiments relate to a method for processing a wafer W.

[0207] The wafer W may be, for example, a surface of its front side 1 (see Figure 1) is formed on a MEMS wafer with a MEMS device. However, the wafer W is not limited to a MEMS wafer, but may also be a CMOS wafer with a CMOS device (preferably a solid-state imaging device) formed on its front side 1 or a wafer having other types of devices on the front side 1.

[0208] The wafer W may be made of a semiconductor (e.g., silicon). Such a silicon wafer W may include devices such as IC (integrated circuit) and LSI (large scale integrated circuit) on a silicon substrate. Alternatively, the wafer may be an optical device wafer configured by forming an optical device such as an LED (light emitting diode) on an inorganic material substrate such as ceramic, glass, or sapphire. The wafer W is not limited thereto and may be formed in any other manner. In addition, a combination of the above exemplary wafer designs is also possible.

[0209] The thickness of the wafer W before grinding may be in the μm range, preferably in the range of 625 to 925 μm.

[0210] The wafer W preferably exhibits a circular shape. However, the shape of the wafer W is not particularly limited. In other embodiments, the wafer W may have, for example, an oval shape, an elliptical shape, or a polygonal shape (eg, a rectangular shape or a square shape).

[0211] The wafer W is provided with a plurality of intersecting dividing lines 11 formed on its front side 1 (see Figure 3 ) (referred to as streets), thereby dividing the wafer W into a plurality of rectangular areas in which devices 7 such as the previously described devices are respectively formed. These devices 7 are formed in the device area 2 of the wafer W. In the case of a circular wafer W, the device area 2 is preferably circular and arranged concentrically with the outer circumference of the wafer W.

[0212] like Figures 1 to 3 Schematically shown in FIG, the device area 2 is surrounded by an annular peripheral edge area 3. In this peripheral edge area 3, no device is formed. The peripheral edge area 3 is preferably arranged concentrically with the device area 2 and / or the outer circumference of the wafer W. The radial extension of the peripheral edge area 3 can be in the mm range, preferably in the range of 1 to 3 mm.

[0213] For example Figure 1 and Figure 2 As schematically shown in FIG. 1 , the device region 2 is formed with a plurality of protrusions 14 protruding from the planar surface of the wafer W. The protrusions 14 may be, for example, bumps for establishing electrical contact with the device 7 of the device region 2 in a separate chip or wafer. The height of the protrusions 14 in the thickness direction of the wafer W may be in the range of 20 to 500 μm.

[0214] In the following, reference will be made to Figures 1 to 5 A method of processing a wafer W according to a first embodiment of the present invention is described.

[0215] Figure 1 A cross-sectional view of a wafer W to be processed by a method according to a first embodiment of the present invention is shown. Figure 2 and Figure 3 4 is a diagram showing a step of applying a protective film 4 to a wafer W according to this first embodiment. In this step, a protective film 4 for covering the devices 7 on the wafer W is applied to the front side 1 of the wafer W, as shown in FIG. Figure 2 Indicated by the arrow in .

[0216] The protective film 4 preferably has the same shape as the wafer W (ie, a circular shape in the present embodiment) and is attached concentrically therewith. The diameter of the protective film 4 is approximately the same as that of the wafer W, such as Figures 2 to 4 Schematically shown in FIG.

[0217] The protective film 4 covers the device 7 (including the protrusion 14) formed in the device region 2, thereby protecting the device 7 from damage or contamination. In addition, as will be described in detail below, the protective film 4 serves as a cushion layer in subsequent processing of the wafer W (eg, in a subsequent grinding step).

[0218] like Figure 2 As shown, the protective film 4 has a front surface 4a and a rear surface 4b. The protective film 4 is applied to the front side 1 of the wafer W so that the front surface 4a of the protective film 4 is in direct contact with the front side 1 of the wafer. Figures 2 to 4 ) between the substrate and the substrate.

[0219] The protective film 4 is made of polyolefin. For example, the protective film 4 may be made of polyethylene (PE) or polypropylene (PP).

[0220] The protective film 4 may have a thickness in the range of 5 to 200 μm, preferably 80 to 150 μm. For example, the protective film 4 may have a thickness of 80 μm.

[0221] After applying the protective film 4 to the front side 1 of the wafer W, the protective film 4 is heated so that the protective film 4 is attached to the wafer front side 1 .

[0222] Specifically, the wafer W to which the protective film 4 is applied may be placed on the chuck table 20 (see Figure 4 ) and the chuck table 20 can be heated, for example, to a temperature in the range of 60° C. to 150° C. Particularly preferably, the chuck table 20 is heated to a temperature of approximately 100° C. The chuck table 20 can be heated, for example, for a duration in the range of 1 minute to 10 minutes.

[0223] In addition, if Figure 4 As shown, pressure is applied to the rear surface 4b of the protective film 4 by means of a roller 30. Figure 4As indicated by the arrow in , the roller 30 moves along the rear surface 4 b of the protective film 4 , thereby pressing the protective film 4 against the front side 1 of the wafer W.

[0224] The roller 30 may be a heated roller. In addition to or instead of heating the protective film 4 by the heated chuck stage 20 , heat may be applied to the protective film 4 by the heated roller 30 .

[0225] The protective film 4 is attached to the front side 1 of the wafer W by heating the protective film 4 using the heated chuck stage 20 and / or the heated roller 30 .

[0226] Specifically, the heating process generates an adhesive force between the protective film 4 and the wafer W that holds the protective film 4 at its position on the wafer W. In particular, by heating the protective film 4 , a form fit and / or material bonding is formed between the protective film 4 and the wafer W.

[0227] By applying pressure to the rear surface 4 b of the protective film 4 , the front surface 4 a of the protective film 4 is pressed against the front side 1 of the wafer W. Therefore, reliable attachment of the protective film 4 to the wafer W can be ensured particularly effectively.

[0228] In the attached state of the protective film 4, the protrusions 14 protruding from the planar surface of the wafer W are completely buried in the protective film 4, as shown in FIG. Figure 4 Schematically shown in FIG.

[0229] After the protective film 4 is attached to the front side 1 of the wafer W, the back side 6 of the wafer W opposite to its front side 1 is processed (see Figures 1 to 3 ). The back side 6 of the wafer W can be processed by grinding and / or polishing and / or etching and / or cutting. Particularly preferably, the back side 6 of the wafer W is processed by grinding.

[0230] In particular, the wafer W with the protective film 4 attached can be removed from the chuck table 20 and turned over so that the wafer back side 6 faces upward. Subsequently, processing of the wafer back side 6 can be performed (for example, by grinding). This grinding step is described below with reference to Fig.13 The fourth embodiment of the method of the present invention is described in detail.

[0231] During processing (e.g., grinding) of the back side 6 of the wafer W, the wafer W may be placed on a support (not shown) such as a chuck table so that the back surface 4b of the protective film 4 contacts the upper surface of the support. The protective film 4 reliably protects the wafer W (particularly, the device 7 and the protrusion 14) from any damage during wafer processing.

[0232] After the back side 6 of the wafer W has been ground, the wafer W may be cut along the separation lines 11 to obtain individual chips or dies (not shown).

[0233] For example, the protective film 4 may be removed (eg, peeled off) from the wafer W after grinding its back side 6. This removal process may be facilitated, for example, by heating the protective film 4 before and / or during removal from the wafer W.

[0234] Subsequently, the wafer W can be cut from its front side 1 along the dividing lines 11. In this way, chips or dies completely separated from each other are obtained. Cutting the wafer W can be performed by mechanical cutting (eg, using a blade or a saw) and / or laser cutting and / or plasma cutting.

[0235] After the chips or wafers are completely separated from each other in the dicing step, they may be picked up, for example, using a pick-up device (not shown). The spacing between the individual chips or wafers may be increased before the pick-up process to facilitate the pick-up process.

[0236] Figure 5 The step of applying heat and pressure to the protective film 4 according to a modification of the first embodiment of the method of the present invention is shown. This modification is different from the first embodiment only in that the diameter of the protective film 4 is smaller than the outer diameter of the wafer W. In particular, the diameter of the protective film 4 may be substantially the same as the outer diameter of the device region 2.

[0237] In the following, reference will be made to Figures 6 to 8 A method of processing a wafer W according to a second embodiment of the present invention is described.

[0238] The method according to the second embodiment is different from the method according to the first embodiment in that the diameter of the protective film 4 is larger than the outer diameter of the wafer W and the outer peripheral portion of the protective film 4 is attached to the annular frame 40 (see Figures 6 to 8 ). In the description of the second embodiment, elements substantially the same as those of the first embodiment are denoted by the same reference numerals, and repeated detailed descriptions thereof are omitted.

[0239] Figure 6 The protective film 4 and the annular frame 40 are shown before the protective film 4 is attached to the annular frame 40 . Figure 7 and Figure 8 The attached state of the protection film 4 and the ring frame 40 is shown.

[0240] In particular, the outer peripheral portion of the protective film 4 is attached to the annular frame 40 so that the protective film 4 closes the central opening of the annular frame 40. In this way, the wafer W attached to the protective film 4 (in particular, attached to the central portion thereof) is held by the annular frame 40 through the protective film 4. Thus, a wafer unit including the wafer W, the protective film 4 and the annular frame 40 is formed, thereby facilitating the handling, manipulation and / or transportation of the wafer W (see Figure 7 and Figure 8 ).

[0241] In the present embodiment, the step of attaching the outer peripheral portion of the protective film 4 to the annular frame 40 is preferably performed before applying the protective film 4 to the wafer W. In this way, the step of applying the protective film 4 to the wafer W can be further facilitated by using, for example, the annular frame 40 for handling and transporting the wafer W.

[0242] like Figures 6 to 8 As shown, the outer peripheral portion of the protective film 4 is attached to the annular frame 40 through an annular adhesive layer 42. The adhesive layer 42 is arranged between the protective film 4 and the annular frame 40.

[0243] After the protective film 4 is applied to the wafer W, Figure 4 Heat and pressure are applied to the protective film 4 in the same manner as described in detail for the first embodiment, thereby attaching the protective film 4 to the wafer W (see Figure 7 ).

[0244] Figure 8 Show Figure 7 The result of the step of applying heat and pressure to the protective film 4 is shown. Figure 8 As indicated in , the wafer topography originating from the protrusions 14 is not completely absorbed by the protective film 4. Therefore, surface unevenness is generated on the rear surface 4b of the protective film 4. Such surface unevenness may occur in the case of protrusions 14 having a relatively large height. In this case, if it is desired to completely absorb the wafer topography, a buffer layer may be provided on the rear surface 4b of the protective film 4, as will be described in detail below for the fourth to eighth embodiments of the method according to the present invention.

[0245] After the protective film 4 is attached to the wafer W, the wafer W may be processed substantially in the same manner as described above in detail with respect to the first embodiment.

[0246] In the following, reference will be made to Fig. 9 A method of processing a wafer W according to a third embodiment of the present invention is described.

[0247] The method according to the third embodiment is different from the method according to the first embodiment in the process of applying the protective film 4 to the wafer W and the process of applying pressure to the rear surface 4b of the protective film 4. In the description of the third embodiment, elements substantially the same as those of the previous embodiment are denoted by the same reference numerals, and repeated detailed descriptions thereof are omitted.

[0248] In particular, Fig. 9 As shown, a vacuum laminator is used to apply the protective film 4 to the front side 1 of the wafer W. In the vacuum laminator, the wafer W is placed on the chuck table 20 in a vacuum chamber (not shown) in a state where the wafer rear side 6 is in contact with the upper surface of the chuck table 20 and the wafer front side 1 is oriented upward. The chuck table 20 is a heated chuck table.

[0249] The protective film 4 is held at its peripheral portion by an annular spacer 60 disposed between the wafer front side 1 and the protective film 4. In this way, the protective film 4 is placed above the wafer front side 1 in the vacuum chamber (see Fig. 9 The upper portion of the vacuum chamber above the chuck table 20 and the protective film 4 is provided with an air inlet 50 which is closed by an expandable rubber membrane 52 .

[0250] After the wafer W and the protective film 4 have been loaded into the vacuum chamber, the chamber is evacuated and air is supplied to the rubber film 52 through the air inlet 50, so that the rubber film 52 expands into the evacuated chamber. In this way, the rubber film 52 moves downward in the vacuum chamber (as shown in FIG. Fig. 9 ), to push the protective film 4 against the wafer front side 1, thereby pressing the protective film 4 against the device area 2 of the wafer front side 1. Thus, the protective film 4 can be tightly applied to the wafer front side 1 to follow the contour of the device area 2 (in particular, the contour of the protrusions 14 present therein).

[0251] The protective film 4 is heated during and / or after its application to the wafer front side 1 by heating the chuck table 20 .

[0252] The rubber film 52 further serves to apply pressure to the rear surface 4 b of the protective film 4 after the protective film 4 is applied to the wafer W. In this way, reliable attachment of the protective film 4 to the wafer W can be ensured particularly effectively.

[0253] Subsequently, the vacuum in the vacuum chamber is released and the protective film 4 is held in its position on the wafer front side 1 by the adhesion force generated by the heating process and the positive pressure in the vacuum chamber.

[0254] Alternatively, the rubber film 52 may be replaced by a soft stamp or a soft roller (eg, a heated soft stamp or a heated soft roller).

[0255] After the protective film 4 is attached to the wafer W, the wafer W may be processed substantially in the same manner as described above in detail with respect to the first embodiment.

[0256] In the following, reference will be made to Figures 10 to 13 A method of processing a wafer W according to a fourth embodiment of the present invention is described.

[0257] The method according to the fourth embodiment is different from the method according to the second embodiment in that the buffer layer 8 and the substrate 9 are provided on the rear surface 4b of the protective film 4 (see, for example Fig.10 ). In the description of the fourth embodiment, elements substantially the same as those of the previous embodiments are denoted by the same reference numerals, and repeated detailed descriptions thereof are omitted.

[0258] In particular, buffer layer 8 is attached to rear surface 4 b of protective film 4 such that the front surface of buffer layer 8 is in direct contact with rear surface 4 b of protective film 4 .

[0259] like Fig.10 As shown, the protrusions 14 are buried in the protection film 4 and the buffer layer 8. Therefore, the wafer topography is completely absorbed.

[0260] The buffer layer 8 may be formed of a resin, an adhesive, a gel, etc. The buffer layer 8 may have a thickness in the range of 20 to 300 μm.

[0261] The substrate 9 is attached to the rear surface of the buffer layer 8 such that the front surface of the substrate 9 is in direct contact with the rear surface of the buffer layer 8 .

[0262] The material of the substrate 9 is not particularly limited.

[0263] The substrate 9 may be made of a soft or pliable material such as, for example, a polymer material, for example polyvinyl chloride (PVC) or ethylene vinyl acetate (EVA).

[0264] Alternatively, the substrate 9 may be made of a rigid or hard material, such as polyethylene terephthalate (PET) and / or silicon and / or glass and / or stainless steel (SUS).

[0265] For example, if the substrate 9 is made of polyethylene terephthalate (PET) or glass and the buffer layer 8 can be cured by external stimulation, radiation (e.g., UV radiation) that can be transmitted through the polyethylene terephthalate (PET) or glass can be used to cure the buffer layer 8. If the substrate 9 is made of silicon or stainless steel (SUS), a cost-effective substrate 9 is provided.

[0266] Additionally, substrate 9 may be formed from a combination of the materials listed above.

[0267] The substrate 9 may have a thickness in the range of 30 to 1500 μm, preferably 40 to 1200 μm, more preferably 50 to 1000 μm. Particularly preferably, the substrate 9 has a thickness in the range of 30 to 250 μm. A thickness of 50 μm of the substrate 9 is particularly preferred. For example, the substrate 9 may be a polyethylene terephthalate (PET) film having a thickness of 50 μm.

[0268] The substrate 9 and the buffer layer 8 each have a substantially circular shape. The diameters of the substrate 9 and the buffer layer 8 are substantially the same as each other and are larger than the diameter of the wafer W. The diameters of the substrate 9 and the buffer layer 8 are smaller than the diameter of the protective film 4 .

[0269] The buffer layer 8 and the substrate 9 may be attached to the rear surface 4 b of the protective film 4 before or after the protective film 4 is applied to the front side 1 of the wafer W. In particular, the protective film 4, the buffer layer 8, and the substrate 9 may be laminated first, thereby forming a protective sheet including the substrate 9, the buffer layer 8, and the protective film 4 attached to the buffer layer 8. The protective sheet formed in this manner may then be applied to the front side 1 of the wafer W so that the front surface 4 a of the protective film 4 is in direct contact with the wafer front side 1.

[0270] Subsequently, the protective film 4 is heated to attach the protective sheet to the front side 1 of the wafer W. The protective film 4 may be heated in substantially the same manner as described in detail above for the first embodiment (ie, using the heated chuck stage 20) (see Fig.10 ).

[0271] In addition, two parallel pressure plates are used to apply pressure to the rear surface 9b of the substrate 9. During the pressure application process, one plate applies pressure against the rear surface 9b of the substrate 9 and the other plate applies pressure against the rear side 6 of the wafer W. In this way, it is ensured that the rear surface 9b of the substrate 9 is substantially parallel to the rear side 6 of the wafer W. Fig.10 Indicated by the dotted arrow in .

[0272] The press plate may be a heated press plate, allowing the protective film 4 to be heated during the pressing process by the wafer W and / or by the substrate 9 and the buffer layer 8. This heating process may be performed in addition to or as an alternative to heating the protective film 4 using the heated chuck stage 20.

[0273] The buffer layer 8 can be cured by external stimulation (e.g., UV radiation, heat, electric field and / or chemical reagents). In this case, the buffer layer 8 hardens at least to a certain extent when the external stimulation is applied. For example, the buffer layer 8 can be formed of a curable resin, a curable adhesive, a curable gel, etc.

[0274] Preferred examples of the UV-curable resin used as the buffer layer 8 in the present embodiment are ResiFlat of DISCO Corporation and TEMPLOC of DENKA.

[0275] The method of this embodiment may further include applying an external stimulus to the buffer layer 8 to cure the buffer layer 8 after applying the protective film 4 to the front side 1 of the wafer W. The external stimulus may be applied to the buffer layer 8 after attaching the protective film 4 to the front side 1 of the wafer.

[0276] An external stimulus may be applied to the buffer layer 8 before processing (eg grinding) the wafer back side 6. In this way, protection and processing accuracy of the wafer W during processing may be further improved.

[0277] Fig.11 The subsequent step of cutting away the portion of the protective film 4, the buffer layer 8 and the substrate 9 that laterally extends beyond the circumference of the wafer W is shown. Fig.11 . These portions may be cut away, for example, by mechanical cutting (eg, using a blade or saw), laser cutting, or plasma cutting. Cutting away these portions facilitates the handling of the wafer unit in subsequent processing steps.

[0278] Fig.12 Show Fig.11 Results of the cutting steps are shown.

[0279] After this dicing step, the back side 6 of the wafer W is processed (ie subjected to a grinding process) as will be described in detail below.

[0280] The rear surface 9b of the substrate 9, which is a flat, planar surface, is placed in contact with Fig.10 The wafer W is ground on the top surface of the same chuck table (not shown) as the chuck table 20 in FIG. Subsequently, the back side 6 of the wafer W is ground for adjusting the wafer thickness to a value in the range of, for example, about 20 to 100 μm. This thickness may be the final thickness of the chip or wafer. Fig.13 The results of this grinding step are shown.

[0281] The grinding of the back side 6 of the wafer W can be performed using a grinding device (not shown). The grinding device may include a spindle housing, a spindle rotatably accommodated in the spindle housing, and a grinding wheel mounted to the lower end of the spindle. A plurality of abrasive members may be fixed to the lower surface of the grinding wheel, wherein each abrasive member may be formed by a diamond abrasive member, which is configured by fixing diamond abrasive grains using a bonding agent such as a metal bond or a resin bond. The grinding wheel with the abrasive member is rotated at high speed by, for example, using a motor to drive the spindle.

[0282] In the grinding step, the chuck table holding the wafer unit and the grinding wheel of the grinding apparatus are rotated, and the grinding wheel is lowered to bring the abrasive member of the grinding wheel into contact with the back side 6 of the wafer W, thereby grinding the back side 6 .

[0283] Since the planar rear surface 9b of the substrate 9 placed on the top surface of the chuck table of the grinding apparatus is substantially parallel to the rear side 6 of the wafer W (see Fig.10 ), so the pressure applied to the wafer W by the grinding wheel during the grinding process is evenly and uniformly distributed over the wafer W. Thus, any risk of pattern transfer or cracking of the wafer W can be minimized. Furthermore, the substantially parallel alignment of the flat, planar rear surface 9 b of the substrate 9 with the rear side 6 of the wafer W allows the grinding step to be performed with high precision, thus achieving a particularly consistent and uniform wafer thickness after grinding.

[0284] Further processing of the wafer W, ie, dicing thereof and picking up of separated chips or die, may be performed substantially in the same manner as detailed above for the first embodiment.

[0285] In the following, reference will be made to Figures 14 to 16 A method of processing a wafer W according to a fifth embodiment of the present invention is described.

[0286] The method according to the fifth embodiment differs from the method according to the fourth embodiment in the order of the steps of cutting the protective film 4 and grinding the wafer back side 6. In the description of the fifth embodiment, elements substantially the same as those of the previous embodiment are denoted by the same reference numerals, and repeated detailed descriptions thereof are omitted.

[0287] In particular, in the method of the fifth embodiment, the back side 6 of the wafer W is first ground while the protective film 4 is still attached to the annular frame 40 . Fig.14 The result of this grinding step is shown in FIG. Fig.13 Grinding is performed in the same manner as described in detail for the fourth embodiment.

[0288] Subsequently, the portions of the protective film 4, the buffer layer 8 and the substrate 9 that extend laterally beyond the circumference of the wafer W are cut away. Fig.15 This cutting step is basically as described above with reference to Fig.11 The same manner as described in detail for the fourth embodiment is performed. Fig.16 Show Fig.15 Results of the cutting steps are shown.

[0289] Further processing of the wafer W, ie, dicing thereof and picking up of separated chips or die, may be performed substantially in the same manner as detailed above for the first embodiment.

[0290] In the following, reference will be made to Fig.17 and Fig.18 A method of processing a wafer W according to a sixth embodiment of the present invention is described.

[0291] The method according to the sixth embodiment is different from the method according to the first embodiment in that the buffer layer 8 is provided on the rear surface 4b of the protective film 4 (see Fig.17 and Fig.18 ). In addition, the method according to the sixth embodiment differs from the methods according to the fourth and fifth embodiments, in particular, in that no substrate is provided on the rear surface 8b of the buffer layer 8. In the description of the sixth embodiment, elements substantially the same as those of the previous embodiments are denoted by the same reference numerals, and repeated detailed descriptions thereof are omitted.

[0292] In the method of the sixth embodiment, if Fig.17As shown, the protective sheet 10 is formed by attaching a buffer layer 8 to the rear surface 4b of the protective film 4. The protective sheet 10 thus includes the protective film 4 and the buffer layer 8 attached to the protective film 4. The buffer layer 8 may have the same properties and characteristics as detailed above for the fourth embodiment.

[0293] The diameters of the protective film 4 and the buffer layer 8 are substantially the same as each other and the same as the diameter of the wafer W (see Fig.18 ).

[0294] The protective sheet 10 is applied to the front side 1 of the wafer W so that the front surface 4a of the protective film 4 is in direct contact with the wafer front side 1. Subsequently, the protective film 4 is heated to attach the protective sheet 10 to the front side 1 of the wafer W. The protective film 4 can be heated in substantially the same manner as described in detail above for the first embodiment (i.e., using the heated chuck stage 20) (see Fig.18 ).

[0295] In addition, two parallel pressure plates are used to apply pressure to the rear surface 8b of the buffer layer 8. In the pressure application process, one plate is pressed against the rear surface 8b of the buffer layer 8, and the other plate is pressed against the rear side 6 of the wafer W. In this way, it is ensured that the rear surface 8b of the buffer layer 8 is substantially parallel to the wafer rear side 6.

[0296] The press plate may be a heated press plate, allowing the protective film 4 to be heated by the wafer W and / or by the buffer layer 8 during the pressing process. This heating process may be performed in addition to or as an alternative to heating the protective film 4 using the heated chuck stage 20.

[0297] Fig.18 The result of the step of applying heat and pressure to the protective film 4 is shown in . As indicated in this figure, the wafer topography originating from the protrusions 14 is completely absorbed by the protective film 4 and the buffer layer 8 .

[0298] The buffer layer 8 may be made of a curable material and may be cured in substantially the same manner as described in detail above with respect to the fourth embodiment.

[0299] Subsequently, the back side 6 of the wafer W is ground in substantially the same manner as described in detail above for the fourth embodiment.

[0300] Further processing of the wafer W, ie, dicing thereof and picking up of separated chips or die, may be performed substantially in the same manner as detailed above for the first embodiment.

[0301] In the following, reference will be made to Figures 19 to 21 A method of processing a wafer W according to a seventh embodiment of the present invention is described.

[0302] The method according to the seventh embodiment differs from the method according to the sixth embodiment in that a substrate 9 is attached to the rear surface 8b of the buffer layer 8. In the description of the seventh embodiment, substantially the same elements as those of the previous embodiment are denoted by the same reference numerals, and repeated detailed descriptions thereof are omitted.

[0303] The substrate 9 is attached to the rear surface 8b of the buffer layer 8 so that the front surface of the substrate 9 is in direct contact with the rear surface 8b of the buffer layer 8 (see Fig.19 ). The substrate 9 may have the same properties and characteristics as described in detail above for the fourth embodiment.

[0304] The diameters of the protective film 4, the buffer layer 8 and the substrate 9 are substantially the same as each other and the same as the diameter of the wafer W (see Fig.19 ).

[0305] The protective film 4 , the buffer layer 8 and the substrate 9 may be attached to the wafer front side 1 in substantially the same manner as described in detail above for the fourth embodiment.

[0306] Fig.19 The result of this attachment process is shown in FIG. The rear surface 9b of the substrate 9 is substantially parallel to the rear side 6 of the wafer W, as shown in FIG. Fig.19 Indicated by the dotted arrow in .

[0307] Subsequently, the back side 6 of the wafer W is ground in substantially the same manner as described in detail above for the fourth embodiment.

[0308] Further processing of the wafer W, ie, dicing thereof and picking up of separated chips or die, may be performed substantially in the same manner as detailed above for the first embodiment.

[0309] Fig. 20 and Fig.21 A modification of the seventh embodiment of the method of the present invention is shown. This modification differs from the seventh embodiment mainly in that the diameter of the protective film 4 is smaller than the buffer layer 8 and the buffer layer 8 extends beyond the protective film 4 .

[0310] Specifically, the diameter of the protective film 4 is substantially the same as the diameter of the device region 2 of the wafer W (see Fig. 20 and Fig.21 ).

[0311] The protective film 4 , the buffer layer 8 and the substrate 9 may be attached to the wafer front side 1 in substantially the same manner as described in detail above for the fourth embodiment. Fig. 20 The result of this attachment process is shown in .

[0312] As shown in this figure, the buffer layer 8 surrounds the outer circumference of the protective film 4 and is in direct contact with the wafer front side 1. This arrangement provides a particularly stable and strong attachment of the protective sheet (in particular, the protective film 4) to the wafer front side 1. The strength of this attachment can be further enhanced by curing the buffer layer 8.

[0313] Subsequently, the back side 6 of the wafer W is ground in substantially the same manner as described in detail above for the fourth embodiment. Fig.21 The results of this grinding process are shown in .

[0314] Further processing of the wafer W, ie, dicing thereof and picking up of separated chips or die, may be performed substantially in the same manner as detailed above for the first embodiment.

[0315] In the following, reference will be made to Fig. 22 and Fig.23 A method of processing a wafer W according to an eighth embodiment of the present invention is described.

[0316] The method according to the eighth embodiment is different from the method according to the second embodiment in that the buffer layer 8 is provided on the rear surface 4b of the protective film 4 (see, for example Fig. 22 ). In the description of the eighth embodiment, elements substantially the same as those of the previous embodiments are denoted by the same reference numerals, and repeated detailed descriptions thereof are omitted.

[0317] The buffer layer 8 may be attached to the rear surface 4 b of the protective film 4 in substantially the same manner as described above in detail with respect to the fourth embodiment.

[0318] The diameters of the protective film 4 and the buffer layer 8 are substantially the same as each other and are larger than the diameter of the wafer W (see Fig.23 ).

[0319] The protective sheet including the protective film 4 and the buffer layer 8 is attached to the wafer front side 1 in substantially the same manner as described above in detail for the protective film 4 of the second embodiment. In particular, after the protective sheet is applied to the wafer front side 1, the protective sheet 4 is heated by the heated chuck stage 20 and / or the heated roller 30 (see Fig.23 ). In addition, pressure is applied to the rear surface 8b of the buffer layer 8 by means of the roller 30.

[0320] After attaching the protective sheet to the front side 1 of the wafer W, the back side 6 of the wafer W is ground substantially in the same manner as detailed above for the fourth embodiment.

[0321] Further processing of the wafer W, ie, dicing thereof and picking up of separated chips or die, may be performed substantially in the same manner as detailed above for the first embodiment.

[0322] In the following, reference will be made to Fig.24A method of processing a wafer W according to a ninth embodiment of the present invention is described.

[0323] The method according to the ninth embodiment differs from the method according to the first embodiment particularly in that an adhesive layer 12 is provided at the peripheral portion of the protective film 4 and the wafer W. In the description of the ninth embodiment, elements substantially the same as those of the previous embodiment are denoted by the same reference numerals, and repeated detailed descriptions thereof are omitted.

[0324] although Fig.24 Protrusions or bumps protruding from the planar surface of the wafer W (eg, the protrusions 14 detailed above) that may be present in the device region 2 of the wafer W are omitted.

[0325] In the method of the ninth embodiment, before applying the protective film 4 for covering the device 7 on the wafer W to the front side 1 of the wafer W, a liquid adhesive is dispensed onto the protective film 4 and / or the wafer W using a dispenser (not shown), for example. Fig.24 As shown, an adhesive layer 12 is formed. The liquid adhesive is dispensed only on the peripheral portion of the protective film 4 and / or only on the peripheral portion of the wafer W. The adhesive layer 12 has a ring shape. The adhesive layer 12 is arranged so that no adhesive exists in the device region 2 of the wafer W.

[0326] The liquid adhesive may be, for example, a liquid adhesive produced by Brewer Science, such as 220 materials.

[0327] The dispenser may be, for example, a dispenser produced by Musashi Engineering, such as dispenser ML-5000XII.

[0328] The adhesive layer 12 may be a continuous adhesive layer. Alternatively, the adhesive layer 12 may be a discontinuous adhesive layer. In particular, in the adhesive layer 12, the adhesive may be arranged in a discontinuous form such as a dot form, a strip form (e.g., a straight and / or curved strip), etc.

[0329] The liquid adhesive may be dispensed only onto the peripheral portion of the protective film 4 without being dispensed onto the wafer W. Alternatively, the liquid adhesive may be dispensed only onto the peripheral portion of the wafer W without being dispensed onto the protective film 4. Furthermore, the liquid adhesive may be dispensed onto both the peripheral portion of the protective film 4 and the peripheral portion of the wafer W.

[0330] The liquid adhesive is dispensed to form an adhesive layer 12 in direct contact with the peripheral portion of the front surface of the protective film 4 and with the peripheral portion of the front side 1 of the wafer W.

[0331] The diameter of the protective film 4 is substantially the same as the diameter of the wafer W (see Fig.24).

[0332] After dispensing the liquid adhesive in the manner detailed above, the protective film 4 is applied to the front side 1 of the wafer W. The protective film 4 is attached to the front side 1 of the wafer W by means of the adhesive layer 12 .

[0333] After attaching the protective film 4 to the wafer front side 1 , the back side 6 of the wafer W is ground in substantially the same manner as detailed above for the fourth embodiment.

[0334] Further processing of the wafer W, ie, dicing thereof and picking up of separated chips or die, may be performed substantially in the same manner as detailed above for the first embodiment.

[0335] In the following, reference will be made to Fig.25 A method of processing a wafer W according to a tenth embodiment of the present invention is described.

[0336] The method according to the tenth embodiment differs from the method according to the ninth embodiment in the diameter of the protective film 4 and the arrangement of the adhesive layer 12. In the description of the tenth embodiment, substantially the same elements as those of the previous embodiment are denoted by the same reference numerals, and repeated detailed descriptions thereof are omitted.

[0337] although Fig.25 Protrusions or bumps protruding from the planar surface of the wafer W (eg, the protrusions 14 detailed above) that may be present in the device region 2 of the wafer W are omitted.

[0338] like Fig.25 As shown, the diameter of the protective film 4 is larger than the diameter of the wafer W. The liquid adhesive is dispensed to form an adhesive layer 12 that is in direct contact with the peripheral portion of the front surface of the protective film 4 and with the peripheral portion of the front side 1 of the wafer W and a portion of the peripheral side edge of the wafer W. The adhesive layer 12 has an annular shape. The adhesive layer 12 is arranged so that no adhesive is present in the device region 2 of the wafer W.

[0339] The protection film 4 is attached to the front side 1 of the wafer W by means of an adhesive layer 12 .

[0340] After attaching the protective film 4 to the wafer front side 1 , the back side 6 of the wafer W is ground in substantially the same manner as detailed above for the fourth embodiment.

[0341] Further processing of the wafer W, ie, dicing thereof and picking up of separated chips or die, may be performed substantially in the same manner as detailed above for the first embodiment.

[0342] In the following, reference will be made to Fig.26 A method of processing a wafer W according to an eleventh embodiment of the present invention will be described.

[0343] The method according to the eleventh embodiment differs from the method according to the tenth embodiment in the arrangement of the protective film 4 and the adhesive layer 12. In the description of the eleventh embodiment, substantially the same elements as those of the previous embodiments are denoted by the same reference numerals, and repeated detailed descriptions thereof are omitted.

[0344] although Fig.26 Protrusions or bumps protruding from the planar surface of the wafer W (eg, the protrusions 14 detailed above) that may be present in the device region 2 of the wafer W are omitted.

[0345] The diameter of the protective film 4 is larger than the diameter of the wafer W. In addition, Fig.26 As shown, the peripheral portion of the protective film 4 is bent downward so that the peripheral portion of the front surface of the protective film 4 is in direct contact with a portion of the peripheral side edge of the wafer W.

[0346] Liquid adhesive is dispensed to form an adhesive layer 12 in direct contact with the peripheral side edge of the protective film 4 and with a portion of the peripheral side edge of the wafer W. The adhesive layer 12 has a ring shape. The adhesive layer 12 is arranged so that no adhesive exists in the device region 2 of the wafer W.

[0347] The liquid adhesive may be dispensed onto the protective film 4 and / or onto the wafer W before applying the protective film 4 to the wafer W. Alternatively, the liquid adhesive may be dispensed onto the protective film 4 and / or onto the wafer W after applying the protective film 4 to the wafer W.

[0348] The protective film 4 is attached to the front side 1 of the wafer W via the adhesive layer 12. In addition, the protective film 4 can be attached to the wafer front side 1 by heating the protective film 4 during and / or after applying the protective film 4 to the wafer front side 1. In particular, the protective film 4 can be attached to the wafer W using the method detailed above for the first embodiment.

[0349] For example, the protective film 4 may first be attached to the wafer W by heating the protective film 4 in the manner detailed above. Subsequently, after the protective film 4 has been attached to the wafer W, a liquid adhesive may be dispensed. The liquid adhesive may be dispensed to seal or cover any gap that may exist between the protective film 4 and the wafer W at its peripheral portion (see Fig.26 ).

[0350] After attaching the protective film 4 to the wafer front side 1 , the back side 6 of the wafer W is ground in substantially the same manner as detailed above for the fourth embodiment.

[0351] Further processing of the wafer W, ie, dicing thereof and picking up of separated chips or die, may be performed substantially in the same manner as detailed above for the first embodiment.

[0352] In the following, reference will be made to Fig. 27 A method of processing a wafer W according to a twelfth embodiment of the present invention is described.

[0353] The method according to the twelfth embodiment differs from the method according to the ninth embodiment in the arrangement of the adhesive layer 12. In the description of the twelfth embodiment, substantially the same elements as those of the previous embodiment are denoted by the same reference numerals, and repeated detailed descriptions thereof are omitted.

[0354] although Fig. 27 Protrusions or bumps protruding from the planar surface of the wafer W (eg, the protrusions 14 detailed above) that may be present in the device region 2 of the wafer W are omitted.

[0355] The diameter of the protective film 4 is substantially the same as that of the wafer W (see Fig. 27 ).

[0356] The liquid adhesive is dispensed to form an adhesive layer 12 that is in direct contact with a portion of the peripheral side edge and a portion of the front surface of the protective film 4 and a portion of the peripheral side edge and a portion of the front side 1 of the wafer W. The adhesive layer 12 has an annular shape. The adhesive layer 12 is arranged so that there is no adhesive in the device area 2 of the wafer W.

[0357] The liquid adhesive may be dispensed onto the protective film 4 and / or onto the wafer W before applying the protective film 4 to the wafer W. Alternatively, the liquid adhesive may be dispensed onto the protective film 4 and onto the wafer W after applying the protective film 4 to the wafer W.

[0358] The protective film 4 is attached to the front side 1 of the wafer W via the adhesive layer 12. In addition, the protective film 4 can be attached to the wafer front side 1 by heating the protective film 4 during and / or after applying the protective film 4 to the wafer front side 1. In particular, the protective film 4 can be attached to the wafer W using the method detailed above for the first embodiment.

[0359] For example, the protective film 4 may be first attached to the wafer W by heating the protective film 4 in the manner detailed above. Subsequently, after the protective film 4 has been attached to the wafer W, the liquid adhesive may be dispensed. The liquid adhesive may be dispensed to seal or cover any gap that may exist between the protective film 4 and the wafer W at its peripheral portion (see Fig. 27 ).

[0360] After attaching the protective film 4 to the wafer front side 1 , the back side 6 of the wafer W is ground in substantially the same manner as detailed above for the fourth embodiment.

[0361] Further processing of the wafer W, ie, dicing thereof and picking up of separated chips or die, may be performed substantially in the same manner as detailed above for the first embodiment.

[0362] In the following, reference will be made to Fig.28 A method of processing a wafer W according to a thirteenth embodiment of the present invention is described.

[0363] The method according to the thirteenth embodiment differs from the method according to the ninth embodiment in the diameter of the protective film 4 and the arrangement of the adhesive layer 12. In the description of the thirteenth embodiment, substantially the same elements as those of the previous embodiments are denoted by the same reference numerals, and repeated detailed descriptions thereof are omitted.

[0364] although Fig.28 Protrusions or bumps protruding from the planar surface of the wafer W (eg, the protrusions 14 detailed above) that may be present in the device region 2 of the wafer W are omitted.

[0365] The diameter of the protective film 4 is smaller than the diameter of the wafer W. The diameter of the protective film 4 is substantially equal to the device region 2 of the wafer W (see Fig.28 ).

[0366] Liquid adhesive is dispensed to form adhesive layer 12 in direct contact with the peripheral side edge of protective film 4 and with a portion of front side 1 of wafer W. Adhesive layer 12 has an annular shape. Adhesive layer 12 is arranged so that adhesive does not exist in device region 2 of wafer W.

[0367] The liquid adhesive may be dispensed onto the protective film 4 and / or onto the wafer W before applying the protective film 4 to the wafer W. Alternatively, the liquid adhesive may be dispensed onto the protective film 4 and onto the wafer W after applying the protective film 4 to the wafer W.

[0368] The protective film 4 is attached to the front side 1 of the wafer W via the adhesive layer 12. In addition, the protective film 4 can be attached to the wafer front side 1 by heating the protective film 4 during and / or after applying the protective film 4 to the wafer front side 1. In particular, the protective film 4 can be attached to the wafer W using the method detailed above for the first embodiment.

[0369] For example, the protective film 4 may be first attached to the wafer W by heating the protective film 4 in the manner detailed above. Subsequently, after the protective film 4 has been attached to the wafer W, the liquid adhesive may be dispensed. The liquid adhesive may be dispensed to seal or cover any gap that may exist between the protective film 4 and the wafer W at its peripheral portion (see Fig.28 ).

[0370] After attaching the protective film 4 to the wafer front side 1 , the back side 6 of the wafer W is ground in substantially the same manner as detailed above for the fourth embodiment.

[0371] Further processing of the wafer W, ie, dicing thereof and picking up of separated chips or die, may be performed substantially in the same manner as detailed above for the first embodiment.

[0372] In the following, reference will be made to Fig.29 A method of processing a wafer W according to a fourteenth embodiment of the present invention is described.

[0373] The method according to the fourteenth embodiment differs from the method according to the ninth embodiment in the diameter of the protective film 4 and the arrangement of the adhesive layer 12. In the description of the fourteenth embodiment, substantially the same elements as those of the previous embodiments are denoted by the same reference numerals, and repeated detailed descriptions thereof are omitted.

[0374] although Fig.29 Protrusions or bumps protruding from the planar surface of the wafer W (eg, the protrusions 14 detailed above) that may be present in the device region 2 of the wafer W are omitted.

[0375] The diameter of the protective film 4 is larger than the diameter of the wafer W (see Fig.29 ).

[0376] The liquid adhesive is dispensed to form an adhesive layer 12 in direct contact with the peripheral portion of the front surface of the protective film 4 and with a portion of the peripheral side edge of the wafer W and a portion of the front side 1 .

[0377] The adhesive layer 12 has a ring shape. The adhesive layer 12 is arranged so that no adhesive exists in the device region 2 of the wafer W.

[0378] The arrangement of the adhesive layer 12 according to the fourteenth embodiment is also different from that according to the ninth embodiment in that the annular portion of the front side 1 of the wafer W arranged between the substantially circular device area 2 and the inner circumference of the annular adhesive layer 12 is free of any adhesive (see Fig.29 ). In contrast, in the arrangement of the ninth embodiment, the adhesive layer 12 is arranged so that its inner circumference is arranged directly adjacent to the device region 2 (see Fig.24 ).

[0379] The liquid adhesive may be dispensed onto the protective film 4 and / or onto the wafer W before applying the protective film 4 to the wafer W. Alternatively, the liquid adhesive may be dispensed onto the protective film 4 and onto the wafer W after applying the protective film 4 to the wafer W.

[0380] The protective film 4 is attached to the front side 1 of the wafer W via the adhesive layer 12. In addition, the protective film 4 can be attached to the wafer front side 1 by heating the protective film 4 during and / or after applying the protective film 4 to the wafer front side 1. In particular, the protective film 4 can be attached to the wafer W using the method detailed above for the first embodiment.

[0381] For example, the protective film 4 may be first attached to the wafer W by heating the protective film 4 in the manner detailed above. Subsequently, after the protective film 4 has been attached to the wafer W, the liquid adhesive may be dispensed. The liquid adhesive may be dispensed to seal or cover any gap that may exist between the protective film 4 and the wafer W at its peripheral portion (see Fig.29 ).

[0382] After attaching the protective film 4 to the wafer front side 1 , the back side 6 of the wafer W is ground in substantially the same manner as detailed above for the fourth embodiment.

[0383] Further processing of the wafer W, ie, dicing thereof and picking up of separated chips or die, may be performed substantially in the same manner as detailed above for the first embodiment.

[0384] The protective film 4 of the ninth to fourteenth embodiments may be used in combination with the buffer layer 8 of the previous embodiments or in combination with the buffer layer 8 and the substrate 9 in substantially the same manner as described above in detail.

Claims

1. A method for processing a wafer (W), the wafer (W) having a device region (2) on one side (1), the device region (2) having a plurality of devices (7), wherein: The method comprises the following steps: Providing a protective film (4); Applying the protective film (4) for covering the device (7) on the wafer (W) to the one side (1) of the wafer (W) so that the front surface (4a) of the protective film (4) is in direct contact with the one side (1) of the wafer (W), so that there is no adhesive between the front surface (4a) of the protective film (4) and the one side (1) of the wafer (W); heating the protective film (4) during and / or after applying the protective film (4) to the one side (1) of the wafer (W) so that the protective film (4) is attached to the one side (1) of the wafer (W); and processing the side (6) of the wafer (W) opposite to the side (1), When the protective film (4) is removed from the wafer (W), contamination or damage to the device (7) formed in the device area (2) due to the adhesive force of the adhesive layer or the adhesive remaining on the device (7) can be avoided.

2. The method according to claim 1, wherein The device region (2) is formed with a plurality of protrusions (14) protruding from a planar surface of the wafer (W), and The protrusions (14) protruding from the planar surface of the wafer (W) are buried in the protective film (4).

3. The method according to claim 1 or 2, further comprising: During and / or after applying the protective film (4) to the one side (1) of the wafer (W), pressure is applied to a rear surface (4b) of the protective film (4) opposite to its front surface (4a).

4. The method according to claim 1 or 2, wherein: The step of processing the side (6) of the wafer (W) opposite to the side (1) includes grinding the side (6) of the wafer (W) opposite to the side (1) to adjust the wafer thickness.

5. The method according to claim 1 or 2, wherein: The outer diameter of the protective film (4) is greater than the outer diameter of the wafer (W) or smaller than the outer diameter of the wafer (W) or is substantially the same as the outer diameter of the wafer (W) or is substantially the same as the outer diameter of the device region (2).

6. The method according to claim 1 or 2, further comprising: The outer peripheral portion of the protective film (4) is attached to the annular frame (40).

7. The method according to claim 6, wherein: The peripheral portion of the protective film (4) is attached to the annular frame (40) by a substantially annular adhesive layer (42).

8. The method according to claim 1 or 2, wherein: A buffer layer (8) is attached to a rear surface (4b) of the protective film (4) opposite to its front surface (4a), The device region (2) is formed with a plurality of protrusions (14) protruding from a planar surface of the wafer (W), and The protrusions (14) protruding from the planar surface of the wafer (W) are buried in the buffer layer (8).

9. The method according to claim 8, wherein The front surface of the buffer layer (8) is in contact with the rear surface (4b) of the protective film (4), and A rear surface (8b) of the buffer layer (8) opposite to its front surface is substantially parallel to the side (6) of the wafer (W) opposite to the side (1).

10. The method according to claim 8, wherein: The buffer layer (8) can be cured by external stimulation.

11. The method according to claim 10, further comprising: After the protective film (4) is applied to the one side (1) of the wafer (W), the external stimulus is applied to the buffer layer (8) to cure the buffer layer (8).

12. The method according to claim 8, wherein The buffer layer (8) is attached to the rear surface (4b) of the protective film (4) before applying the protective film (4) to the one side (1) of the wafer (W), or The buffer layer (8) is attached to the rear surface (4b) of the protective film (4) after applying the protective film (4) to the one side (1) of the wafer (W).

13. The method according to claim 8, wherein: A substrate (9) is attached to the rear surface (8b) of the buffer layer (8).

14. The method according to claim 1 or 2, wherein: The protective film (4) is made of polymer.

15. The method according to claim 14, wherein: The polymer is a polyolefin.

16. The method according to claim 10, wherein: The external stimulus is UV radiation, heat, an electric field and / or a chemical agent.

17. A method for processing a wafer (W), the wafer (W) having a device region (2) on one side (1), the device region (2) having a plurality of devices (7), wherein: The method comprises the following steps: Providing a protective film (4); providing a liquid adhesive; dispensing the liquid adhesive onto the protective film (4) and / or onto the wafer (W); applying the protective film (4) for covering the devices on the wafer (W) to the one side (1) of the wafer (W); and processing the side (6) of the wafer (W) opposite to the side (1), wherein the liquid adhesive is dispensed only onto a peripheral portion of the protective film (4) and / or only onto a peripheral portion of the wafer (W), so that no adhesive is present in the device area (2) of the wafer (W), wherein the protective film (4) is attached to the one side (1) of the wafer (W) before dispensing the liquid adhesive, and the protective film (4) is attached to the one side (1) of the wafer (W) by heating the protective film (4) during and / or after applying the protective film (4) to the one side (1) of the wafer (W), wherein an adhesive force between the protective film (4) and the wafer (W) is generated by the heating, and When the protective film (4) is removed from the wafer (W), contamination or damage to the device (7) formed in the device area (2) due to the adhesive force of the adhesive layer or the adhesive remaining on the device (7) can be avoided.

18. The method according to claim 17, wherein: A buffer layer (8) is attached to the rear surface (4b) of the protective film (4).

19. The method according to claim 18, wherein: A substrate (9) is attached to the rear surface (8b) of the buffer layer (8).

20. The method according to claim 17, wherein: The protective film (4) is made of polymer.

21. The method according to claim 20, wherein: The polymer is a polyolefin.

22. A protective film (4), the protective film (4) being configured to be used in a method for processing a wafer (W), the wafer (W) having a device region (2) on one side (1), the device region (2) having a plurality of devices (7), wherein: The protective film (4) is configured to be applied to the one side (1) of the wafer (W) so that the front surface (4a) of the protective film (4) is in direct contact with the one side (1) of the wafer (W), wherein no adhesive is present on the front surface (4a) of the protective film (4); The protective film (4) is configured so that an adhesion force between the protective film (4) and the wafer (W) is generated by heating the protective film (4), and the adhesion force attaches the protective film (4) to the one side (1) of the wafer (W); and The protective film (4) is configured so that when the protective film (4) is removed from the wafer (W), contamination or damage to the device (7) formed in the device area (2) due to the adhesive force of the adhesive layer or the adhesive remaining on the device (7) can be avoided.

23. The protective film (4) according to claim 22, wherein: The protective film (4) is configured to soften by being heated.

24. The protective film (4) according to claim 23, wherein: The protective film (4) is configured to re-harden when cooled down.

25. The protective film (4) according to any one of claims 22 to 24, wherein: The protective film (4) is configured such that, by heating the protective film (4), a form fit and / or a material bond is formed between the protective film (4) and the wafer (W).

26. The protective film (4) according to any one of claims 22 to 24, wherein: The protective film (4) can withstand heat up to a temperature above 180°C.

27. The protective film (4) according to any one of claims 22 to 24, wherein: The protective film (4) is configured so that an adhesion force between the protective film (4) and the wafer (W) is generated by heating the protective film (4) to a temperature in the range of 60°C to 150°C, and the adhesion force attaches the protective film (4) to the one side (1) of the wafer (W).

28. The protective film (4) according to any one of claims 22 to 24, wherein: The protective film (4) is configured so that an adhesion force between the protective film (4) and the wafer (W) is generated by heating the protective film (4) for a duration in the range of 1 minute to 10 minutes, and the adhesion force attaches the protective film (4) to the one side (1) of the wafer (W).

29. The protective film (4) according to any one of claims 22 to 24, wherein: The protective film (4) is configured to be pliable, elastic, flexible, stretchable, soft and / or compressible when in a heated state.

30. The protective film (4) according to any one of claims 22 to 24, wherein: The protective film (4) has a thickness in the range of 5 μm to 200 μm.

31. The protective film (4) according to any one of claims 22 to 24, wherein: The protective film (4) is made of polymer.

32. The protective film (4) according to claim 31, wherein: The polymer is a polyolefin.

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