Wafer protection tape and method for manufacturing wafer protection tape

Abstract

The purpose of the present invention is to provide a tape for protecting the front surface of a wafer, which can sufficiently fill irregularities on the front surface of the wafer and can be removed without damaging the wafer after grinding of the back surface of the wafer. The purpose is achieved by: a tape that is for protecting, during grinding of the back surface of a wafer having irregularities on the front surface, the front surface of the wafer and that comprises a base material layer and a thermoplastic resin layer, which is in contact with the wafer on the surface opposite to the side on which the base material layer is positioned, the O / C on said surface, obtained by ESCA, being 18x10-3-54x10-3; and a tape that is for protecting, during grinding of the back surface of a wafer having irregularities on the front surface, the front surface of the wafer and that comprises a base material layer and a thermoplastic resin layer, which is in contact with the wafer on the surface opposite to the side on which the base material layer is positioned, the water contact angle on said surface being 90-103°.

Description

Wafer protection tape and method for manufacturing wafer protection tape

[0001] The present invention relates to a tape for protecting the surface of a wafer during back-grinding of a wafer having an uneven surface. More specifically, it relates to a wafer protection tape that achieves both bump absorption and peelability.

[0002] Backside grinding, a process that grinds wafers with circuits formed on them to a uniform and thin thickness, is widely used for the high integration of semiconductor devices or for the manufacture of high-performance semiconductor devices. Conventionally, adhesive tapes have been used to improve handling during backside grinding of wafers and to protect the wafer surface. For example, an adhesive film equipped with an acrylic adhesive layer has been proposed from the viewpoint of adhesion to the wafer, ease of peeling, and low contamination (Patent Document 1).

[0003] However, in the semiconductor device manufacturing process, circuits and other features may be formed on the surface of semiconductor wafers such as silicon and gallium arsenide in the so-called front-end process, or bump electrodes may be present, resulting in unevenness on the wafer surface. Among such semiconductor devices, power devices used in power converters such as inverters and converters have uneven wafer surfaces due to their characteristics, structure, and manufacturing process. In the case of wafers with such uneven surfaces, there are limitations to the absorption of unevenness by acrylic adhesive layers with a cross-linked structure. Therefore, if the wafer surface is protected with such adhesive tape and then the back side is ground, the unevenness of the wafer surface is transferred to the back side of the wafer, and the unevenness is reflected in the finished thickness of the wafer, which affects the device characteristics, especially in power devices. Therefore, in order to prevent damage to semiconductor wafers caused by grinding, even in wafers with such uneven surfaces, a semiconductor wafer surface protection sheet without an acrylic adhesive layer has been proposed (Patent Document 2).

[0004] Japanese Patent Publication No. 2002-53819, International Publication No. 2006 / 088074

[0005] However, with such semiconductor wafer surface protection sheets, it was not possible to adequately fill the gaps between bumps on wafers with a bump pitch (distance between the tops of bumps) of approximately 5 μm to 500 μm. Furthermore, on wafers with even narrower bump pitches, such as those with so-called narrow-pitch bumps of approximately 5 μm to 100 μm, it was even more difficult to fill the gaps between bumps.

[0006] Furthermore, even with wafers having such narrow-pitch bumps, if the bump-following ability of the surface in contact with the wafer, such as a protective sheet, is increased to sufficiently fill the gaps between the bumps, it may be impossible to peel the protective sheet from the wafer surface after the backside grinding of the wafer is completed.

[0007] In view of the above technical background, the object of the present invention is to provide a tape for protecting the surface of a wafer (hereinafter simply referred to as a "protective tape") that can sufficiently fill in the irregularities on the surface of the wafer (hereinafter also referred to as "bump absorption") and can be peeled off without damaging the wafer after backside grinding of the wafer.

[0008] As a result of diligent research, the inventors discovered that by applying a specific surface treatment to the surface of the protective tape that comes into contact with the wafer, it is possible to achieve both bump absorption and peelability. Further research led them to discover the conditions for a protective tape that can exhibit appropriate adhesive strength and excellent bump absorption, thus completing the present invention.

[0009] In other words, the embodiments of the present invention are as follows. However, the present invention is not limited to the following. [1] A tape for protecting the surface of a wafer having irregularities on its surface during back grinding, wherein the tape comprises a base layer and a thermoplastic resin layer, the thermoplastic resin layer is in contact with the wafer on the surface opposite to the side where the base layer is located, and the O / C of the ESCA analysis on the surface is 18 × 10 －３ ~54 x 10 －３ The O / C parameters for the ESCA analysis are as follows: X-ray output: 300W, photoelectron escape angle: 90°, measured vacuum level: 2 × 10⁻⁶ －７[2] A tape for protecting the surface of a wafer during back grinding of a wafer having irregularities on its surface, wherein the tape comprises a base layer and a thermoplastic resin layer, wherein the thermoplastic resin layer is in contact with the wafer on the surface opposite to the side where the base layer is located, and the water contact angle on the surface is 90° to 103°. [3] The tape according to [1] or [2], wherein the wafer has irregularities on its surface with a height of 5 μm to 300 μm at intervals of 5 μm to 500 μm. [4] The tape according to any one of [1] to [3], wherein the thermoplastic resin layer has a thickness of 30 μm to 600 μm. [5] The tape according to any one of [1] to [4], wherein the thermoplastic resin layer comprises a polyolefin. [6] The tape according to any one of [1] to [5], wherein the thermoplastic resin layer has an adhesive strength of 0.03 N / 25 mm to 5.0 N / 25 mm to a silicon wafer, and an adhesive strength of 0.05 N / 25 mm to 7.0 N / 25 mm to a polyimide-treated wafer. [7] A method for manufacturing a tape for protecting the surface of a wafer during back grinding of a wafer, comprising: step (a): providing a tape comprising a base layer and a thermoplastic resin layer; step (b): performing a surface treatment on the thermoplastic resin layer; and step (c): aging the surface-treated tape. [8] The surface treatment in step (b) is 150 (W・min / m ２ ) ~ 350 (W・min / m ２ A method for manufacturing a tape according to [7], wherein the discharge amount is corona-treated. [9] A method for manufacturing a tape according to [7] or [8], wherein step (c) is to leave the tape to stand for 60 to 84 hours at a temperature 6 to 26°C lower than the melting point of the resin contained in the thermoplastic resin layer.

[0010] The protective tape of the present invention achieves both good bump absorption and appropriate adhesion (peelability), thereby suppressing the influence of surface irregularities on the wafer during backside grinding and preventing damage to circuits and other features formed on the wafer during post-thinning processing. As a result, it is possible to suppress unintended effects on the characteristics of electronic devices such as semiconductor devices, enabling numerous and / or diverse processes to be carried out on the wafer with high productivity and yield, thereby greatly contributing to the improvement of productivity of electronic devices such as semiconductor devices.

[0011] The present invention relates to a tape for protecting the surface of a wafer having surface irregularities during back grinding, wherein the tape comprises a base layer and a thermoplastic resin layer, the thermoplastic resin layer in contact with the wafer on the surface opposite to the side where the base layer is located, and the O / C ratio of the ESCA analysis on the surface is 18 × 10 －３ ~54 x 10 －３ It is a tape.

[0012] Wafers with Surface Irregularities The wafers to be protected by the protective tape of the present invention have irregularities on their surface. Such surface irregularities of wafers can be derived from, for example, electrodes, circuit patterns, thick polyimide protective films (5 μm to 20 μm), defect marks for identifying defective chips (5 μm to 100 μm), gold bumps (10 μm to 100 μm) or solder bumps (50 μm to 300 μm) for bump bonding as an alternative to wire bonding.

[0013] In one embodiment of the present invention, a wafer may have surface irregularities with heights of 5 μm to 300 μm at intervals of 5 μm to 500 μm. Here, the intervals between the surface irregularities of the wafer may be, for example, the distance between bumps provided on the wafer surface. The height of the surface irregularities of the wafer may be, for example, the length of the portion of the bump electrode provided on the wafer surface that protrudes from the wafer surface.

[0014] The spacing between the surface irregularities of the wafer may be 5 μm to 400 μm, 5 μm to 300 μm, 5 μm to 200 μm, or 5 μm to 100 μm.

[0015] The height of the surface irregularities of the wafer may be 5 μm to 200 μm, 5 μm to 100 μm, or 5 μm to 50 μm.

[0016] The wafer material is typically a material used in the manufacture of semiconductor devices, capable of forming electronic circuits, etc., and expected to be thinned as a substrate to be ground. Examples include, but are not limited to, silicon wafers, compound semiconductor wafers such as SiC, AlSb, AlAs, AlN, AlP, BN, BP, BAs, GaSb, GaAs, GaN, GaP, InSb, InAs, InN, or InP, quartz wafers, sapphire, or glass. Silicon wafers and compound semiconductor wafers may be doped.

[0017] Examples of wafers with uneven surfaces include semiconductor devices, such as power device wafers used in power converters like inverters and converters.

[0018] The protective tape is used to prevent damage to electronic circuits and other components on the wafer surface during backside grinding, as well as contamination by grinding debris and grinding water.

[0019] To grind the back surface of a wafer, infeed grinding is commonly employed. This involves holding the wafer in a vacuum chuck-type chuck table, rotating the chuck table to rotate the wafer, and then pressing a grinding tool, such as a grinding wheel, against the back surface of the wafer. When grinding the back surface of a wafer in this way, the wafer surface is covered with protective tape to prevent direct contact between the wafer surface and the holding surface of the chuck table, thus preventing damage to the electronic circuits on the wafer surface.

[0020] The protective tape of the present invention includes a base layer and a thermoplastic resin layer. The thermoplastic resin layer is a layer that contacts the wafer on the surface opposite to the side where the base layer is located. In other words, with the protective tape of the present invention, by applying the protective tape to the surface of a wafer, a laminate is formed in the order of wafer, thermoplastic resin layer, and base layer. Of this laminate, the base layer is adsorbed by a chuck table, and the entire laminate is held. Therefore, since the surface of the wafer does not come into direct contact with the chuck table, electronic circuits and the like on the surface of the wafer are protected.

[0021] The material of the base layer is not particularly limited, as long as it is in direct contact with the chuck table and can be adsorbed and held by the chuck table. Examples of base layer materials include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), very low-density polyethylene (VLDPE), linear low-density polyethylene (L-LDPE), random copolymer polypropylene (random PP), block copolymer polypropylene (block PP), homopolypropylene (homo PP), polybutene (PB), polymethylpentene (PMP), ethylene-vinyl acetate copolymer (EVA), ethylene acrylic acid copolymer, ethylene methacrylic acid copolymer, and their metal crosslinked products (ionomers). Examples include polyolefins such as polyethylene terephthalate (PET), polyethylene terrenaphthalate (PEN), polyethylene terephthalate (PBT), and other polyesters. Furthermore, examples include polyurethane (PU), polycarbonate (PC), polyimide (PI), polyether ether ketone (PEEK), polyetherimide (PEI), polyamide (PA), fully aromatic polyamide, polyphenyl sulfide, fluororesin, polyvinyl chloride, polyvinylidene chloride, and cellulose resins. In addition, the above resins may be used individually as a single-layer substrate, or they may be blends of multiple resins or multilayer structures of different resins. Preferably, the material of the substrate layer is polyethylene terephthalate (PET).

[0022] The thickness of the base material layer is not particularly limited as long as it does not impair the functions of the thermoplastic resin layer described later. From the perspective of handling the protective tape, the thickness of the base material layer may be, for example, 10 μm to 1000 μm, preferably 20 μm to 500 μm, and more preferably 30 μm to 100 μm.

[0023] Thermoplastic resin layer As described above, the thermoplastic resin layer is the layer of the protective tape that directly contacts the wafer. The protective tape needs to prevent the processing water from entering the contact portion between the thermoplastic resin layer and the wafer during the back grinding of the wafer. Further, after the back grinding of the wafer, the protective tape needs to be peeled off without causing damage to the circuits and electrodes on the surface of the wafer and without causing so-called glue residue where a part of the protective tape remains on the wafer. The protective tape of the present invention is capable of providing an appropriate adhesive force that can achieve the above.

[0024] In the protective tape of the present invention, the O / C in the ESCA analysis on the surface of the thermoplastic resin layer that contacts the wafer is 18×10 －３ ~54×10 －３ Here, the O / C in the ESCA analysis is the ratio of the atomic concentration of oxygen atoms (O) to the atomic concentration of carbon atoms (C) in the atomic concentrations of carbon atoms (C), nitrogen atoms (N), oxygen atoms (O), and silicon atoms (Si), which is obtained by using the peak areas of carbon atoms (C), nitrogen atoms (N), oxygen atoms (O), and silicon atoms (Si) and the relative sensitivity factor (RSF) measured under the conditions of X-ray output: 300 W, photoelectron escape angle: 90°, measurement vacuum degree: 2×10 －７ Pa or less, and the number of integration times: 3 times.

[0025] The ESCA analysis can be measured, for example, using an X-ray photoelectron spectrometer (manufactured by Shimadzu Corporation, product name: ESCA-3400). In the measurement, Mg-Kα rays (1253.6 eV) can be used as the X-ray source.

[0026] The O / C in the ESCA analysis is 18×10 －３As a result, it is possible to prevent the treated water from entering the contact area between the thermoplastic resin layer and the wafer during backside grinding. In addition, the O / C ratio of the ESCA analysis is 54 × 10 －３ As a result of the following, the protective tape can be peeled off the wafer after backside grinding without damaging the circuits or electrodes on the wafer surface, and without leaving any adhesive residue. Therefore, as long as the O / C ratio of the ESCA analysis is within the above range, the protective tape has the appropriate adhesive strength described above.

[0027] The O / C value for ESCA analysis is preferably 20 × 10 －３ ~52 x 10 －３ It may be, and more preferably, 21 × 10 －３ ~47 x 10 －３ It may be 22 × 10 －３ ~27 x 10 －３ That's fine.

[0028] The O / C value in ESCA analysis can be increased by increasing the amount of discharge during surface treatment of the thermoplastic resin layer. In other words, the O / C value increases by introducing polar groups into the thermoplastic resin layer.

[0029] The O / C value in ESCA analysis can be reduced by decreasing the amount of discharge during surface treatment of the thermoplastic resin layer. Furthermore, the O / C value in ESCA analysis can be reduced by applying an aging treatment to the protective tape.

[0030] The protective tape of the present invention has a contact angle with water (hereinafter also referred to as the "water contact angle") of 90° to 103° at the surface in contact with the wafer of the thermoplastic resin layer. Preferably, the water contact angle is 92° to 99°.

[0031] Since the water contact angle is 90° or more, the adhesive force to the wafer is large, so that when the back surface of the wafer is ground, it is possible to prevent the processing water from entering the contact portion between the thermoplastic resin layer and the wafer. Further, since the water contact angle is 103° or less, the adhesive force to the wafer is small, so that after the back surface of the wafer is ground, the protective tape can be peeled off from the wafer without causing damage to the circuits and electrodes on the surface of the wafer and without causing adhesive residue. Therefore, when the water contact angle is within the above range, the protective tape has the above-described appropriate adhesive force.

[0032] In the present invention, the water contact angle of the thermoplastic resin layer is measured in accordance with JIS R3257 in an environment of 23°C and 50% RH, and the average of the measured values at any 10 points on the surface of the thermoplastic resin layer of the protective tape is defined as the water contact angle of the thermoplastic resin layer.

[0033] The water contact angle can be adjusted by surface treatment and aging treatment of the thermoplastic resin layer. When the discharge amount during the surface treatment of the thermoplastic resin layer is increased, the water contact angle becomes smaller, and when the aging treatment is performed, the water contact angle becomes larger.

[0034] As described above, the thermoplastic resin layer is the layer that directly contacts the wafer in the protective tape. Therefore, it preferably has an appropriate thickness in order to absorb the unevenness on the surface of the wafer.

[0035] In one aspect of the present invention, the thickness of the thermoplastic resin layer may be 30 μm to 600 μm. The thickness of the thermoplastic resin layer may preferably be 70 μm to 500 μm, and more preferably 90 μm to 300 μm. The thickness of the thermoplastic resin layer can be appropriately adjusted according to the height of the unevenness on the surface of the wafer to be protected by the protective tape.

[0036] The thermoplastic resin layer is required to be able to adequately conform to the surface irregularities of the wafer due to the heating and pressurizing applied when the protective tape is attached to the wafer. In one embodiment of the present invention, the thermoplastic resin layer includes a polyolefin. Such a thermoplastic resin layer may mainly contain an olefin copolymer. Preferably, the thermoplastic resin layer may contain an olefin copolymer having at least two α-olefins selected from α-olefins having 2 to 12 carbon atoms as its main unit components. In this invention, ethylene is considered a type of α-olefin.

[0037] Examples of α-olefins having 2 to 12 carbon atoms include ethylene, propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-heptene, 1-octene, and 1-decene.

[0038] Examples of olefin copolymers having at least two α-olefins selected from these α-olefins as the main unit components include ethylene-propylene copolymer, ethylene-1-butene copolymer, propylene-1-butene-α-olefin with 5 to 12 carbon atoms ternary copolymer, ethylene-propylene-α-olefin with 4 to 12 carbon atoms ternary copolymer, and propylene-1-butene-α-olefin with 5 to 12 carbon atoms three-component copolymer. Furthermore, these olefin copolymers may be used individually or in combination of two or more types.

[0039] The thermoplastic resin layer mainly contains an olefin copolymer, the content of which is usually 60% to 100% by weight, preferably 70% to 100% by weight, based on the total weight of the thermoplastic resin layer.

[0040] The thermoplastic resin layer may contain auxiliary components other than olefin copolymers, from the viewpoint of adjusting the softening temperature when applying protective tape. Examples of auxiliary components include thermoplastic elastomers, ethylene and α-olefin co-oligomers, and synthetic resins.

[0041] Examples of thermoplastic elastomers used as auxiliary components include polystyrene elastomers, polyolefin elastomers, polyurethane elastomers, and polyester elastomers. The thermoplastic elastomer is preferably a polystyrene elastomer or a polyolefin elastomer.

[0042] Examples of polystyrene-based elastomers include styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-ethylene-propylene-styrene block copolymer (SEPS), and other styrene-diene block copolymers or their hydrogenated products.

[0043] Polyolefin elastomers may be block copolymers of a polyolefin block forming a highly crystalline polymer such as polypropylene as the rigid part, and an amorphous monomer copolymer block as the flexible part. Examples of such block copolymers include olefin (crystalline)-ethylene-butylene-olefin (crystalline) block copolymer, polypropylene-polyethylene oxide-polypropylene block copolymer, and polypropylene-polyolefin (amorphous)-polypropylene block copolymer.

[0044] In co-oligomers of ethylene and α-olefins as minor components, the α-olefin may be, for example, α-olefins having 3 to 20 carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 4-methyl-1-pentene.

[0045] The synthetic resin used as a secondary component may be a component that readily alloys with the main component, an olefin copolymer. Examples of synthetic resins include low-density polyethylene, linear low-density polyethylene, α-olefin homopolymers having 3 to 20 carbon atoms, and vinyl acetate resin.

[0046] The thermoplastic resin layer may further contain commonly used additives such as UV absorbers, antioxidants, heat stabilizers, lubricants, softeners, and tackifiers.

[0047] As mentioned above, the protective tape is applied to the wafer to protect the wafer surface, and therefore requires sufficient adhesiveness to prevent processing water from entering between the wafer and the protective tape during the back grinding process. On the other hand, it also needs to be adhesively strong enough to be removed after back grinding without damaging the circuits and other components on the wafer surface.

[0048] In this context, the wafers to be protected by the protective tape are generally silicon wafers, and the circuit formation areas and other parts requiring protection are treated with polyimide. Therefore, it is preferable that the protective tape has appropriate adhesive strength on both the silicon wafer and the polyimide-treated wafer.

[0049] In one embodiment of the present invention, the thermoplastic resin layer has an adhesive strength of 0.03 N / 25 mm to 5.0 N / 25 mm to a silicon wafer, and an adhesive strength of 0.05 N / 25 mm to a polyimide-treated wafer.

[0050] The adhesive force to the silicon wafer may be 0.04 N / 25 mm to 4.5 N / 25 mm, preferably 0.05 N / 25 mm to 4.5 N / 25 mm, more preferably 0.1 N / 25 mm to 2.0 N / 25 mm, and even more preferably 0.2 N / 25 mm to 1.0 N / 25 mm.

[0051] The adhesive strength to the polyimide-treated wafer is preferably 0.07 N / 25 mm to 7.0 N / 25 mm, more preferably 0.1 N / 25 mm to 2.5 N / 25 mm, and even more preferably 0.1 N / 25 mm to 1.5 N / 25 mm.

[0052] In this invention, when measuring the adhesive strength to a silicon wafer or a polyimide-treated wafer, the value is shown to two decimal places only if it is less than 0.1 N / 25 mm.

[0053] The adhesion strength to silicon wafers and polyimide-treated wafers can be adjusted by surface treatment and aging treatment of the thermoplastic resin layer. Increasing the discharge amount during surface treatment of the thermoplastic resin layer increases the adhesion strength, while aging treatment decreases the adhesion strength.

[0054] The protective tape of the present invention is not particularly limited as long as it includes a base layer and a thermoplastic resin layer. For example, the protective tape of the present invention may be a two-layer protective tape in which the base layer and the thermoplastic resin layer are directly bonded, or it may be a three-layer tape in which the base layer and the thermoplastic resin layer are indirectly bonded via an adhesive layer or the like. The protective tape may also have a separator to protect the thermoplastic resin layer when not in use.

[0055] According to the protective tape of the present invention, the thermoplastic resin layer has appropriate adhesive strength to the wafer, so the protective tape can be peeled off without damaging the wafer after backside grinding. Furthermore, because the thermoplastic resin layer follows the bumps, it exhibits better bump absorption compared to, for example, protective tapes having an acrylic adhesive layer. Here, bump absorption can be determined, for example, by measuring the bump absorption diameter.

[0056] When protective tape is applied to a wafer, an interface can be observed at the boundary between the portion where the thermoplastic resin layer is in close contact with the wafer and the portion where the thermoplastic resin layer is not in close contact with the wafer. Since this interface appears circular with a bump at its center, in this invention, the diameter of this interface is defined as the "bump absorption diameter." The "bump absorption diameter" can be observed with an optical microscope.

[0057] The higher the bump absorption capacity, the larger the area where the thermoplastic resin layer is in close contact with the wafer, so the bump absorption diameter approaches the value of the bump diameter. The bump absorption diameter also varies depending on the size of the bump itself, but in the protective tape of the present invention, the bump absorption diameter is 2 times or less the bump diameter, and preferably 1.5 times or less the bump diameter.

[0058] The present invention may also provide a method for manufacturing a protective tape. That is, a method for manufacturing a tape for protecting the surface of a wafer during back grinding of a wafer is provided, comprising: step (a): providing a tape comprising a base layer and a thermoplastic resin layer; step (b): performing a surface treatment on the thermoplastic resin layer; and step (c): aging the surface-treated tape.

[0059] Step (a) Step (a) is a step of providing a tape comprising a base layer and a thermoplastic resin layer. The tape comprising the base layer and the thermoplastic resin layer is not particularly limited, and commercially available products may be used.

[0060] Step (b) Step (b) is a step in which a surface treatment is performed on the thermoplastic resin layer. By step (b), polar groups can be introduced to the surface of the thermoplastic resin layer that is in contact with the wafer of the protective tape, thereby providing sufficient adhesive strength to the thermoplastic resin layer.

[0061] The surface treatment is not particularly limited as long as it can introduce polar groups to the surface of the thermoplastic resin layer. The surface treatment may be, for example, an oxidation treatment such as corona treatment, plasma treatment, or flame treatment. Preferably, the surface treatment is corona treatment.

[0062] In one embodiment of the present invention, the surface treatment in step (b) is 150 (W·min / m ２ ) ~ 350 (W・min / m ２ The corona treatment may be a discharge amount of ) . In this application, the discharge amount of corona treatment refers to the discharge amount per unit area per unit time.

[0063] The discharge rate during corona treatment can be adjusted by the output of the processing device, the processing speed, and the length of the discharge electrode (electrode length). Specifically, the discharge rate during corona treatment is expressed by the following formula.

[0064] In the surface treatment of step (b), the adhesion force of the thermoplastic resin layer to the wafer can be increased by increasing the discharge amount of the corona treatment, and 150 (W·min / m) ２ ) ~ 350 (W・min / m ２The corona treatment with a certain discharge amount not only imparts sufficient adhesive strength to the thermoplastic resin layer, but also facilitates adjustment of the adhesive strength during subsequent aging.

[0065] The surface treatment in step (b) is 150 (W·min / m). ２ ) ~ 350 (W・min / m ２ The corona treatment is not limited to the discharge amount of ). For example, the surface treatment in step (b) may be carried out using a corona surface modification apparatus with an electrode length of 0.2 m, with the output power of the apparatus set to 50 W or 100 W and the processing speed set to a processing speed of 1.5 m / min.

[0066] Step (c) Step (c) is a process of aging the surface-treated tape. By aging, some of the polar groups introduced to the surface of the thermoplastic resin layer by the surface treatment can be embedded in the thermoplastic resin. As a result, the adhesive strength of the protective tape can be reduced to the extent that it can be peeled off after back grinding without damaging the circuits on the wafer surface.

[0067] Aging conditions may be met by leaving the protective tape undisturbed at a predetermined temperature for a predetermined period of time. Alternatively, aging may be performed under atmospheric pressure.

[0068] The aging temperature varies depending on the material of the thermoplastic resin layer of the protective tape, but from the viewpoint of preventing the resin contained in the thermoplastic resin layer from melting, it is preferable that the temperature be lower than the melting point of the resin contained in the thermoplastic resin layer. Such an aging temperature can be 6°C to 26°C lower than the melting point of the resin contained in the thermoplastic resin layer. For example, if the melting point of the resin contained in the thermoplastic resin layer is 66°C, the aging temperature may be 40°C to 60°C.

[0069] The aging period may vary depending on the aging temperature. For example, the aging period may be between 60 and 84 hours.

[0070] Therefore, in one embodiment of the present invention, step (c) may be to leave the tape standing for 60 to 84 hours at a temperature 6 to 26°C lower than the melting point of the resin contained in the thermoplastic resin layer.

[0071] The protective tape of the present invention allows for backside grinding of wafers, even those with narrow-pitch bumps, without being affected by surface irregularities. Furthermore, the protective tape can be peeled off after backside grinding without damaging the wafer. Therefore, the protective tape of the present invention enables more stable backside grinding of wafers, allowing the backside-ground wafer to be used in subsequent processes for more efficient manufacturing of the final product. If circuits or the like are formed on the wafer, processes such as dicing, bonding, packaging, and sealing, which are commonly used in the manufacture of semiconductor devices and electronic devices, can be performed to manufacture semiconductor devices and electronic devices as products.

[0072] The protective tape of the present invention is particularly suitable for the manufacture of electronic devices such as power devices, especially in terms of the size of the irregularities on the wafer surface and the bump pitch. Power devices are used in power converters such as inverters and converters, and due to their characteristics, structure, and manufacturing process, the wafer surface has irregularities. The protective tape of the present invention can suppress the influence of these irregularities on the device characteristics.

[0073] The protective tape of the present invention will be further described below with reference to examples. However, the present invention is not limited to these examples.

[0074] <Raw Materials> In the examples and comparative examples, the following raw materials were used to prepare the protective tape: PE1: Ethylene-α-olefin copolymer (manufactured by Mitsui Chemicals, Inc., product name: TAFMER A-4085S, melting point 66°C) PE2: Ethylene-α-olefin copolymer (manufactured by Mitsui Chemicals, Inc., product name: TAFMER A-4090S, melting point 77°C) PET1: Polyethylene terephthalate film (manufactured by Toray Industries, Inc., product name: Lumirror #50-T83)

[0075] <Preparation of Protective Tape Samples> Protective Tape Sample 1 A laminate was obtained by extruding PE1 to a thickness of 195 μm and laminating it with PET1. This laminate was cut to A4 size and designated as Protective Tape Sample 1. Hereinafter, the PE1 side will be referred to as the thermoplastic resin layer and the PET1 side as the base layer. Protective Tape Sample 2 A laminate was obtained by extruding PE2 to a thickness of 195 μm and laminating it with PET1. This laminate was cut to A4 size and designated as Protective Tape Sample 2. Hereinafter, the PE2 side will be referred to as the thermoplastic resin layer and the PET1 side as the base layer.

[0076] Example 1 A corona treatment was performed on the thermoplastic resin layer surface of protective tape sample 1 using a corona surface modification evaluation device (manufactured by Kasuga Electric Co., Ltd., product name: TEC-4AX, electrode length: 0.2 m) under the conditions of output 50 W, processing speed 1.5 m / min, and one processing cycle. Subsequently, the backgrind tape of Example 1 was obtained by heating in an oven under atmospheric conditions at 40°C for 72 hours.

[0077] In Example 2, corona treatment was performed on the thermoplastic resin layer surface of protective tape sample 1 using a corona surface modification evaluation device (manufactured by Kasuga Electric Co., Ltd., product name: TEC-4AX, electrode length: 0.2 m) under the conditions of output 100 W, processing speed 1.5 m / min, and one processing cycle. Subsequently, the backgrind tape of Example 2 was obtained by heating in an oven under atmospheric conditions at 40°C for 72 hours.

[0078] In Example 3, corona treatment was performed on the thermoplastic resin layer surface of protective tape sample 1 using a corona surface modification evaluation device (manufactured by Kasuga Electric Co., Ltd., product name: TEC-4AX, electrode length: 0.2 m) under the conditions of output 50 W, processing speed 1.5 m / min, and one processing cycle. Subsequently, the backgrind tape of Example 3 was obtained by heating in an oven under atmospheric conditions at 50°C for 72 hours.

[0079] In Example 4, corona treatment was performed on the thermoplastic resin layer surface of protective tape sample 1 using a corona surface modification evaluation device (manufactured by Kasuga Electric, product name: TEC-4AX, electrode length: 0.2 m) under the conditions of output 100 W, processing speed 1.5 m / min, and one processing cycle. Subsequently, the backgrind tape of Example 4 was obtained by heating in an oven under atmospheric conditions at 50°C for 72 hours.

[0080] Example 5 Corona treatment was performed on the thermoplastic resin layer surface of protective tape sample 1 using a corona surface modification evaluation device (manufactured by Kasuga Electric, product name: TEC-4AX, electrode length: 0.2 m) under the conditions of output 50 W, processing speed 1.5 m / min, and one processing cycle. Then, the backgrind tape of Example 5 was obtained by heating in an oven under atmospheric conditions at 60°C for 72 hours.

[0081] In Example 6, corona treatment was performed on the thermoplastic resin layer surface of protective tape sample 1 using a corona surface modification evaluation device (manufactured by Kasuga Electric, product name: TEC-4AX, electrode length: 0.2 m) under the conditions of output 100 W, processing speed 1.5 m / min, and one processing cycle. Subsequently, the backgrind tape of Example 6 was obtained by heating in an oven under atmospheric conditions at 60°C for 72 hours.

[0082] In Example 7, corona treatment was performed on the thermoplastic resin layer surface of protective tape sample 2 using a corona surface modification evaluation device (manufactured by Kasuga Electric Co., Ltd., product name: TEC-4AX, electrode length: 0.2 m) under the conditions of output 100 W, processing speed 1.5 m / min, and one processing cycle. Subsequently, the backgrind tape of Example 7 was obtained by heating in an oven under atmospheric conditions at 60°C for 72 hours.

[0083] Comparative Example 1: Protective tape sample 1 was prepared as the backgrind tape of Comparative Example 1 without corona treatment or subsequent heat treatment.

[0084] Comparative Example 2: Corona treatment was performed on the thermoplastic resin layer surface of protective tape sample 1 using a corona surface modification evaluation device (manufactured by Kasuga Electric Co., Ltd., product name: TEC-4AX, electrode length: 0.2 m) under the conditions of output 50 W, processing speed 1.5 m / min, and number of processing cycles 1. The protective tape sample after corona treatment was used as the backgrind tape of Comparative Example 2.

[0085] <Evaluation> The contact angle with water (water contact angle), ESCA, adhesive strength, and bump absorption of the backgrind tapes of the examples and comparative examples were evaluated. The evaluation method for each evaluation item is as follows.

[0086] <Contact angle with water (water contact angle)> Under conditions of 23°C and 50% RH, the water contact angle of the thermoplastic resin layer was measured at 10 points using a contact angle measuring instrument (manufactured by Kyowa Interface Science, product name: DM-702WA) in accordance with JIS R3257, and the average value was used.

[0087] <ESCA> Functional groups on the surface of the thermoplastic resin layer were analyzed using X-ray photoelectron spectroscopy (Shimadzu Corporation, product name: ESCA-3400) with the following X-ray sources: Mg-Kα rays (1252.0 eV), X-ray output: 300 W, and measurement vacuum level: 2 × 10⁻⁶ －７ Measurements were taken under conditions below Pa. The atomic concentrations of carbon (C), nitrogen (N), oxygen (O), and silicon (Si) atoms were determined using the peak areas and relative sensitivity coefficients (RSF). Quantification was performed using the ratio of the atomic concentration of oxygen (O) to the atomic concentration of carbon (C) (O / C). For carbon, nitrogen, and oxygen atoms, peaks originating from the 1s orbital were used, while for silicon atoms, the peak originating from the 2p orbital was used.

[0088] <Evaluation of Adhesion Strength> The adhesion strength of the backgrind tapes in the examples and comparative examples was evaluated using the following wafers as adherends: Silicon wafer (Advanced Material Technologies, product name: AMT-22412) Polyimide-treated wafer (Seiren KST): A silicon wafer was coated with a non-photosensitive polyimide (HD Microsystems, product name: PI3400), heated at 200°C for 60 minutes, and then heated again at 350°C for 60 minutes to obtain a wafer with a polyimide film thickness of 7 μm. The silicon wafer and the polyimide-treated wafer were cleaned by spraying ethanol onto the wafer surface and wiping it with a cloth before the evaluation test.

[0089] The backgrind tapes of Examples 1-6 and Comparative Examples 1-2 were cut to a width of 50 mm. Using a semi-automatic mounter (Technovision, product name: FMP-1433), the backgrind tapes were attached to wafers under the conditions of roll speed: 2 mm / sec, roll pressure: 0.4 MPa, and table temperature: 85°C. The wafers with the attached tapes were left for 1 hour at room temperature (23°C, 50% RH). After standing, using a tensile testing machine (Shimadzu Corporation, product name: Autograph AGS-X), one end of the backgrind tape was clamped, and the backgrind tape was peeled from the wafer surface at a peeling angle of 180 degrees and peeling speed of 300 mm / min. The stress at that time was measured and converted to N / 25 mm to determine the adhesive strength. When converting the adhesive strength to silicon wafers or polyimide-treated wafers, the value was shown to two decimal places only if the adhesive strength was less than 0.1 N / 25 mm. The adhesive strength of the backgrind tape in Example 7 was determined under the same conditions as in Example 7, except that the table temperature of the semi-automatic mounter was set to 95°C.

[0090] Adhesion to the wafer surface was evaluated according to the following criteria: ○: Adhesion strength of 0.2 N / 25 mm or more and 10.0 N / 25 mm or less △: Adhesion strength of 0.03 N / 25 mm or more and less than 0.2 N / 25 mm ×: Adhesion strength less than 0.03 N / 25 mm, or greater than 10 N / 25 mm, or impossible to peel off

[0091] <Evaluation of Bump Absorption Performance> The bump absorption performance of the backgrind tape was evaluated using a semiconductor wafer with bumps of 40 μm in height, 40 μm in distance between bumps, and 40 μm in diameter. The backgrind tapes of Examples 1 to 6 and Comparative Examples 1 to 2 were attached to the bumped semiconductor wafer using a semi-automatic mounter (Technovision, product name: FMP-1433) under the following conditions: roll speed: 2 mm / sec, roll pressure: 0.4 MPa, and table temperature: 85°C. The backgrind tape of Example 7 was attached to the bumped semiconductor wafer under the same conditions except that the table temperature of the semi-automatic mounter was set to 95°C.

[0092] The bump absorption performance after applying backgrind tape was evaluated using an optical microscope according to the following criteria: ○: Bump absorption diameter less than 80 μm ×: Bump absorption diameter 80 μm or more

[0093] Table 1 shows the wafer bonding surface material, output power and discharge amount of the corona treatment apparatus, oven heating temperature (aging temperature), water contact angle, ESCA, adhesive strength and adhesion evaluation to each wafer, and measured values ​​of the surface irregularity absorption diameter and bump absorption evaluation for the backgrind tapes of the examples and comparative examples. The discharge amount of the corona treatment was calculated using the following formula.

[0094] Table 1 shows that the protective tape of the present invention has appropriate adhesive strength to the wafer, allowing it to be peeled off without damaging the wafer. Furthermore, it can be seen that the protective tape of the present invention has excellent bump absorption properties even for wafers with narrow-pitch bumps.

[0095] The protective tape of the present invention suppresses the effects of surface irregularities on wafers, even those with narrow-pitch bumps, enabling backside grinding of the wafer. Furthermore, it allows for stable removal of the protective tape after backside grinding of the wafer, significantly contributing to improved productivity of semiconductor devices, electronic devices, etc., and has high applicability in various industrial fields, including the semiconductor process industry, the electronic components industry, the electrical and electronics industry that uses electronic components, the transportation machinery industry, the information and communication industry, and the precision equipment industry.

Claims

1. A tape for protecting the surface of a wafer having surface irregularities during back grinding, wherein the tape comprises a base layer and a thermoplastic resin layer, the thermoplastic resin layer in contact with the wafer on the surface opposite to the side where the base layer is located, and the O / C ratio of the ESCA analysis on the surface is 18 × 10 －３ ~54 x 10 －３ The O / C parameters for the ESCA analysis are as follows: X-ray output: 300W, photoelectron escape angle: 90°, measured vacuum level: 2 × 10⁻⁶ －７ The ratio of the atomic concentration of oxygen (O) to the atomic concentration of carbon (C) is determined by using the peak areas of carbon (C), nitrogen (N), oxygen (O), and silicon (Si) atoms, measured under conditions of Pa or less and a cumulative number of measurements of 3, and the relative sensitivity coefficient (RSF), for the atomic concentrations of carbon (C), nitrogen (N), oxygen (O), and silicon (Si).

2. A tape for protecting the surface of a wafer having an uneven surface during back grinding, wherein the tape comprises a base layer and a thermoplastic resin layer, the thermoplastic resin layer contacts the wafer on the surface opposite to the side where the base layer is located, and the water contact angle on the surface is 90° to 103°.

3. The tape according to claim 1 or 2, wherein the wafer has irregularities on its surface with a height of 5 μm to 300 μm at intervals of 5 μm to 500 μm.

4. The tape according to claim 1 or 2, wherein the thermoplastic resin layer has a thickness of 30 μm to 600 μm.

5. The tape according to claim 1 or 2, wherein the thermoplastic resin layer comprises a polyolefin.

6. The tape according to claim 1 or 2, wherein the thermoplastic resin layer has an adhesive strength of 0.03 N / 25 mm to 5.0 N / 25 mm to a silicon wafer, and an adhesive strength of 0.05 N / 25 mm to a polyimide-treated wafer.

7. A method for manufacturing a tape for protecting the surface of a wafer during back grinding of a wafer, comprising: step (a): providing a tape comprising a base layer and a thermoplastic resin layer; step (b): performing a surface treatment on the thermoplastic resin layer; and step (c): aging the surface-treated tape.

8. The surface treatment in step (b) is 150 (W·min / m) ２ ) ~ 350 (W・min / m ２ A method for manufacturing a tape according to claim 7, wherein the discharge amount is treated with corona.

9. The method for manufacturing a tape according to claim 7, wherein step (c) is to leave the tape standing for 60 to 84 hours at a temperature 6 to 26°C lower than the melting point of the resin contained in the thermoplastic resin layer.

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