TWI894428B - A method for back grinding a wafer and a method for manufacturing an electronic device - Google Patents

Abstract

An object of the present invention is to provide a method for back grinding a wafer capable of suppressing the influence of surface unevenness of the wafer on back grinding and improving operability of the wafer after thinning. A solution to such object is a method for back grinding a wafer having unevenness on a surface, which has the following steps prior to the back grinding of the wafer: step (1) of forming a protective layer on the surface of the wafer; step (2) of planarizing a surface of the protective layer not in contact with the wafer; and step (3) of adhering the surface of the protective layer not in contact with the wafer to a support body via an adhesive layer.

Description

Wafer backside grinding method and electronic device manufacturing method

The present invention relates to a method for back grinding a wafer, particularly in a process for thinning a wafer having irregularities on its surface. More specifically, the invention relates to a method for back grinding a wafer that protects the wafer surface with a protective layer and then flattens the surface of the protective layer that does not contact the wafer. This method suppresses the effects of the irregularities on the wafer surface and improves workability in various subsequent wafer thinning processes.

To achieve high integration of semiconductor devices or to produce high-performance semiconductor devices, back grinding, in which wafers with circuits formed thereon are ground to a uniform and fine thickness, is widely practiced. However, in the manufacturing process of electronic devices such as semiconductor devices, circuits are formed on the surface of semiconductor wafers made of silicon or gallium-arsenic in the so-called back-end process, or bump electrodes are formed, resulting in unevenness on the wafer surface. Such electronic devices, particularly those used in power converters such as inverters and converters, have unevenness on the wafer surface due to their characteristics, structure, and manufacturing steps. If back grinding is performed directly after applying a protective layer such as protective adhesive tape in the subsequent steps, the surface irregularities of the wafer will be transferred to the backside of the wafer, causing these irregularities to be reflected in the thickness of the finished wafer. This can affect device characteristics, particularly in power devices.

One known method for back-grinding wafers to minimize the effects of surface irregularities is to support the wafer with adhesive tape and then use a planer to flatten the tape substrate to achieve a uniform thickness for the finished wafer (Patent Document 1). However, while this method can minimize variations in wafer thickness, it still presents operational challenges, such as difficulty transporting the thinned wafer.

Meanwhile, a method known for improving the handling efficiency of thinned wafers is to temporarily secure the wafer to a supporting substrate using a protective layer, thereby facilitating handling (Patent Document 2). However, this method may not adequately suppress variations in wafer thickness due to unevenness in the protective layer coating caused by, for example, irregularities on the wafer surface.

[Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Application Laid-Open No. 2009-43931

[Patent Document 2] Japanese Patent Application Laid-Open No. 2004-64040

In view of the above technical background, the object of the present invention is to provide a wafer backside grinding method that can suppress the impact of unevenness on the wafer surface and improve the operability after wafer thinning.

The inventors of this invention have discovered, through diligent research, that before back grinding, the wafer surface can be protected with a protective layer, the surface of the protective layer not in contact with the wafer can be flattened, and the flattened surface of the protective layer not in contact with the wafer can be bonded to a support via an adhesive layer. This approach solves the aforementioned problems and ultimately leads to the completion of the present invention.

That is, the present invention relates to the following:

[1] A method for back grinding a wafer is provided, which is a method for back grinding a wafer having uneven surfaces on its surface. The method comprises the following steps before back grinding the wafer: step (1) forming a protective layer on the surface of the wafer; step (2) flattening the surface of the protective layer that is not in contact with the wafer; and step (3) bonding the surface of the protective layer that is not in contact with the wafer to a support body via an adhesive layer.

Any of the following [2] to [15] is a preferred embodiment or implementation of the present invention.

[2] The backside grinding method of a wafer as described in [1], wherein the protective layer is a protective adhesive tape.

[3] The wafer backside grinding method as described in [2], wherein the base layer of the protective adhesive tape comprises at least one resin selected from the group consisting of PET, PEN, PBT, LCP, PI, PA, PEEK and PPS.

[4] The back grinding method of a wafer as described in any one of [1] to [3], wherein the wafer having a surface irregularity is a wafer having a surface irregularity formed by at least one of an electrode, a circuit pattern, polyimide, a defective mark, or a bump.

[5] The backside grinding method of a wafer as described in any one of [1] to [4], wherein the planarization step is a planarization step performed by cutting, grinding, or polishing.

[6] The backside grinding method of a wafer as described in [5], wherein the cutting is performed by cutting with a bite.

[7] The backside grinding method of a wafer as described in any one of [1] to [6], wherein the adhesive layer is a liquid adhesive or an adhesive tape.

[8] The back grinding method of a wafer as described in any one of [1] to [7], wherein the support body is made of glass, silicon, ceramic, metal, resin or a composite material thereof.

[9] A method for back grinding a wafer as described in any one of [1] to [8], wherein, after the aforementioned step (2) and before the aforementioned step (3), the method comprises the following step: forming the aforementioned adhesive layer on the surface of the protective layer not in contact with the wafer before planarization, the surface of the aforementioned support body, or both.

[10] The backside grinding method of a wafer as described in any one of [1] to [9], wherein after the backside grinding of the wafer, the backside processing step of the wafer is further included.

[11] The backside grinding method of a wafer as described in [10], wherein the backside processing step of the wafer comprises at least one of etching, electrode formation, ion implantation, and annealing.

[12] The backside grinding method of a wafer as described in any one of [1] to [11], wherein the thickness of the backside of the wafer after grinding is less than 200 μm.

[13] A method for manufacturing an electronic device, wherein the manufacturing step includes a backside grinding method of a wafer as described in any one of [1] to [12].

[14] A method for manufacturing an electronic device as described in [13], wherein the electronic device is a device having an electrode on the back side.

[15] The method for manufacturing an electronic device as described in [14], wherein the electronic device is an electric power device.

The wafer backside grinding method of the present invention can suppress the effects of surface irregularities during wafer backside grinding, improve wafer handling after thinning, and enable stable wafer handling during various post-thinning processing steps. This prevents damage to circuits formed on the wafer and suppresses unintended effects on the characteristics of electronic devices such as semiconductors. Furthermore, multiple and/or various steps can be performed on the wafer with high productivity and yield, significantly contributing to improved productivity of electronic devices such as semiconductors.

1: Semiconductor wafers, wafers

3: Protective adhesive tape

4: Adhesive layer

5: Support body

11: Wafer surface, surface

12: Backside and backside of wafer

31: Protective adhesive tape base layer, base layer

32: Adhesive layer of protective adhesive tape

33: Planarized protective adhesive tape substrate layer

FIG1 is a schematic diagram illustrating the steps of one embodiment of the present invention. (a) shows a wafer 1 having its back surface 12 ground by the present invention. (b) shows a wafer 1 having a protective adhesive tape 3 adhered to its surface 11 by step (1) using the protective adhesive tape 3 as a protective layer. (c) shows a wafer 1 having its base layer 31 of the protective adhesive tape 3 flattened by step (2). (d) shows a wafer 1 having an adhesive layer 4 formed on the base layer 33 of the flattened protective adhesive tape 3 obtained by step (2). (e) shows a wafer 1 having a support 5 bonded to the base layer 33 of the flattened protective adhesive tape 3 via the adhesive layer 4 by step (3).

The wafer back grinding method of the present invention is a method for grinding the back of a wafer having uneven surfaces. The wafer back grinding method comprises the following steps before grinding the back of the wafer: step (1) forming a protective layer on the surface of the wafer; step (2) flattening the surface of the protective layer that is not in contact with the wafer; and step (3) bonding the surface of the protective layer that is not in contact with the wafer to a support body via an adhesive layer.

Wafers with uneven surfaces:

The wafer back-ground using the method of the present invention has surface irregularities. Examples of these irregularities include electrodes, circuit patterns, thick polyimide films (5 to 20 μm) used as protective films, defective wafer markers (5 to 100 μm), gold bumps (10 to 100 μm) or solder bumps (50 to 300 μm) used for wire-bonding replacement bump bonding. The height of the irregularities can range from 5 to 300 μm.

The wafer material can be any material commonly used in the manufacture of electronic devices, capable of forming electronic circuits, and expected to be thinned as a polished substrate. Examples include, but are not limited to, silicon wafers or compound semiconductor wafers made of SiC, AlSb, AlAs, AlN, AlP, BN, BP, BAs, GaSb, GaAs, GaN, GaP, InSb, InAs, InN, or InP, crystal wafers, sapphire, or glass. Silicon wafers or compound semiconductor wafers may be doped.

In particular, wafers having uneven surfaces are wafers used in power devices such as inverters and converters.

Step (1):

Step (1) is a step of forming a protective layer on the surface of the wafer.

Protective layer:

A protective layer is used during backside grinding of wafers to prevent damage to electronic circuitry on the wafer surface and contamination from grinding debris or polishing water. Infeed grinding is typically used to grind the backside of a wafer. This involves suctioning and holding the wafer on a vacuum chuck. The chuck rotates, pressing a grinding tool such as a grindstone against the backside of the wafer while the wafer spins. During backside grinding, the protective layer covers the wafer surface to prevent direct contact with the chuck holding surface, potentially damaging the electronic circuitry on the wafer surface.

In one embodiment, the protective layer may be, for example, a protective adhesive tape, a protective resin layer, etc., and the protective layer is preferably a protective adhesive tape.

The protective layer of the present invention has a thickness suitable for protecting the wafer surface and can withstand planarization in the subsequent step (2), that is, it has a thickness that is redundant with the required cutting thickness.

The protective layer is preferably formed of a protective adhesive tape. When the protective layer is a protective adhesive tape, step (1) is to adhere the protective adhesive tape to the surface of the wafer. The adhesive tape can be adhered to the wafer surface by a known method, but preferably, an automatic adhesive device is used. The pressure, temperature, time, etc. are preferably adjusted appropriately according to the material or type of the wafer and the protective adhesive tape.

Protective adhesive tape

The protective adhesive tape used as the preferred protective layer in the method of the present invention is not particularly limited as long as it has the adhesiveness and cutting properties required to withstand the planarization in the later step (2), the adhesiveness required to withstand the later back grinding, the chemical resistance and heat resistance required to withstand the later back treatment step, and the ability to reduce contamination on the wafer surface. It can be removed from the wafer in a state where there is no particular restriction. Generally, for the back grinding of semiconductor wafers, it is preferably selected from the user of the protective adhesive tape and can also be used.

The materials of the base layer of the protective adhesive tape can be listed as follows: 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 Examples of the polyolefins include polypropylene (PP), block copolymer polypropylene (block PP), homogeneous polypropylene (homogeneous PP), polybutene (PB), polymethylpentene (PMP), ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer or ethylene-methacrylic acid copolymer and metal crosslinkers thereof (ionomers); polyesters include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), and liquid crystal polymer (LCP); and polyurethane (PU), polycarbonate (PC), polyimide (PI), polyetheretherketone (PEEK), polyetherimide (PEI), polyamide (PA), wholly aromatic polyamide, polyphenylene sulfide (PPS), fluororesins, polyvinyl chloride, polyvinylidene chloride, and cellulose-based resins. Furthermore, the aforementioned resins may be used alone as a single-layer substrate, or a combination of multiple resins, such as a blend, or a composite structure of different resins may be used. From the perspective of heat resistance, a substrate having a melting point or glass transition temperature of 100°C or higher, particularly 150°C or higher, is preferred.

In one embodiment, the backing layer of the protective adhesive tape preferably includes PET, PEN, PBT, LCP, PI, PA, PEEK, or PPS, taking the following conditions into consideration.

The base layer of the protective adhesive tape must be able to withstand flattening, so the thickness before flattening is preferably 10 to 1000 μm, with 25 to 500 μm being particularly preferred. If the thickness of the base layer of the protective adhesive tape becomes thinner, the protective layer becomes thinner, and the amount that can be polished during flattening is limited, so there is a tendency for the flattening effect of the protective layer to be reduced. Therefore, when the uneven shape on the wafer surface is large, the thickness accuracy of the wafer after polishing will be reduced due to its influence. On the other hand, if the protective layer before flattening becomes thicker, the rigidity of the protective layer is high, and there is a tendency for the processability to be reduced due to the shape of the tape, and the cutting performance when the tape is cut into the shape of the wafer to be reduced. Furthermore, due to its rigidity, the protective adhesive tape is not easily deformed, so the peelability during the protective layer removal step after back grinding of the wafer tends to be reduced.

Furthermore, the base layer of the protective tape preferably has a tensile modulus of 1×10 ⁷ Pa or greater at 23°C in accordance with JIS K7113, with a tensile modulus of 5×10 ⁷ Pa or greater being more preferred. A lower tensile modulus tends to affect the planarization of the base layer of the protective tape. Specifically, even after planarization, the unevenness of the wafer surface can reduce the wafer thickness accuracy after back grinding. On the other hand, considering the processability, cutting properties, and bendability of the base layer, a tensile modulus of 1×10 ¹⁰ Pa or less is preferred, and 6×10 ⁹ Pa or less is even more preferred.

The adhesive layer of the protective adhesive tape can be made of commonly used pressure-sensitive adhesives or curing adhesives. Furthermore, the adhesive layer can be a single layer or multiple layers. To conform to the unevenness of the wafer surface, a multi-layer structure consisting of a flexible intermediate layer and a low-contamination adhesive layer can be used.

Examples of pressure-sensitive adhesives include acrylic adhesives, rubber adhesives, and silicone adhesives. In terms of adhesion to semiconductor wafers or substrate layers, and the ability to clean the wafer after the protective adhesive tape is removed using ultrapure water or organic solvents such as alcohols, acrylic adhesives with an acrylic polymer as the base polymer are preferred.

Examples of the aforementioned curable adhesive include photocurable adhesives that crosslink and cure by light irradiation, and thermocurable adhesives that crosslink and cure by heating. Examples of the aforementioned photocurable adhesive include those containing a polymerizable polymer as a main component and a photopolymerization initiator. Examples of the aforementioned thermocurable adhesive include those containing a polymerizable polymer as a main component and a thermal polymerization initiator.

If the adhesive layer of the protective tape has a weak peeling force, the adhesive force on the wafer will be insufficient to withstand the shear force applied when flattening the tape's base layer, making it difficult to completely peel the tape from the wafer. On the other hand, if the peeling force is too strong, it may become difficult to peel the tape from the wafer. Therefore, from the perspective of final wafer peeling, the thickness is preferably between 5 and 500 μm, with 10 to 100 μm being particularly preferred. Except when the substrate is a silicon mirror wafer, the 180° peel adhesion (peel speed 300mm/min) according to JIS Z0237 (2009) is preferably 0.3 to 10N/25mm, with 0.5 to 7N/25mm being particularly preferred. Adjust appropriately within this range based on the process.

A protective resin layer can also be used as the protective layer. When the protective layer is a protective resin layer, it is applied by known methods such as rotational coating of a raw resin dissolved in a solvent or a liquid raw resin itself (hereinafter referred to as a precursor resin liquid). The layer is then hardened by light irradiation, heating, drying, etc., to function as a solid protective layer. Multiple layers can also be formed.

Protective resin layer:

The protective resin layer that can be used as the protective layer is not particularly limited as long as it has good adhesion and machinability to withstand the planarization in the later-described step (2), good adhesion to withstand the later-described back grinding, good chemical resistance and heat resistance to withstand the later-described back surface treatment step, and finally reduces contamination of the wafer surface. It can be removed from the wafer in a state where it is not particularly limited. It is preferably selected from a known material that temporarily fixes the device wafer to the support body, and can also be used. Examples of precursor resins include: rubber-based resins in which rubber, elastomers, etc. are dissolved in a solvent; one-component thermosetting resins based on epoxies, urethanes, etc.; two-component mixed reaction resins based on epoxies, urethanes, acrylics, etc.; hot melt adhesives; ultraviolet (UV) or electron beam curing resins based on acrylics, epoxies, etc.; and water-dispersible resins. Suitable UV curing resins are those made by adding a photopolymerization initiator and, as appropriate, additives to polymerizable vinyl oligomers such as urethane acrylates, epoxy acrylates, or polyester acrylates and/or acrylic or methacrylic monomers. Additives include thickeners, plasticizers, dispersants, fillers, flame retardants, and thermal aging agents. The protective resin layer can also be formed in multiple layers.

Step (2):

Step (2) is a step for flattening the surface of the protective layer that is not in contact with the wafer.

For example, when the protective layer is a protective adhesive tape, the step is to flatten the base layer of the protective adhesive tape. If the protective adhesive tape is attached to the surface of the wafer in step (1), the unevenness of the wafer surface will be transferred to the base layer of the protective adhesive tape. Furthermore, if back grinding is performed directly, the force of the back grinder will not be applied evenly, and the unevenness of the base layer of the protective adhesive tape will be reflected, and the unevenness will also be transferred to the back of the wafer. When the protective layer is formed by a protective resin layer, it is sometimes not possible to fully flatten it by simply rotating the coating, and sometimes unevenness will still be generated on the surface of the protective layer and transferred to the back of the wafer.

This flattens the backing layer of the protective adhesive tape onto which the irregularities have been transferred before back grinding, allowing the back grinder's force to be applied evenly and preventing the irregularities from being transferred to the back side of the wafer.

There are no specific restrictions on planarization, as long as it prevents the unevenness from being transferred to the back surface of the wafer. However, it is preferred that the following conditions be met.

Covering the entire surface being cut, the difference between the concave and convex portions of the surface of the protective layer not in contact with the wafer is preferably 5 μm or less, more preferably 3 μm or less, and particularly preferably 1 μm or less.

In one embodiment, the planarization is performed by cutting, grinding, or polishing.

In one embodiment, the cutting is performed using a tool. Compared to flattening by polishing on a grinder, tool cutting can solve problems such as grinding stone clogging during polishing and facilitate flattening. Tool cutting can be performed using a surface planer.

Step (3):

Step (3) is to connect the surface of the protective layer that is not in contact with the wafer to the support body via the adhesive layer to form a laminate.

Adhesive layer

The adhesive layer is used to bond the surface of the protective layer that is not in contact with the wafer to the support. The adhesive layer temporarily secures the wafer to the support. After processing is complete, the support can be easily separated using methods such as IR laser irradiation, UV irradiation, laser ablation, solvent stripping, heat/UV foaming, or mechanical stripping. A known temporary fixing material can be used, such as an adhesive tape applied by spin coating or other methods using a liquid adhesive (such as an adhesive dissolved in a solvent). The adhesive layer can be formed on the support, the protective layer, or both. The uneven thickness of the adhesive layer is preferably 5 μm or less, more preferably 3 μm or less, and particularly preferably 1 μm or less.

The adhesive layer is at least one selected from acrylic, silicone, polyimide, and rubber. When the adhesive layer is an adhesive tape, the adhesive tape may be a single layer, a laminate of multiple layers, or a double-sided tape including a base film.

Support body

The support preferably possesses sufficient strength and rigidity, as well as excellent heat resistance, chemical resistance, and thickness accuracy. Using such a support allows for stable wafer handling without warping, even after wafer thinning after polishing, enabling wafers to be fed into a wide variety of processes.

The support can be made of any known material. Preferred materials include silicon, sapphire, crystal, metals (such as aluminum, copper, steel, and stainless steel), various types of glass and ceramics, and resins (such as polyimide, polyamide, epoxy, phenol, polyphenylene oxide, polyetheretherketone, polyetherimide, wholly aromatic polyamide, and polyphenylene sulfide). The support can be composed of a single material or a combination of materials, including other materials deposited on a substrate. For example, a silicon wafer can have a deposited layer of silicon nitride or the like. Particularly preferred are supports composed of glass, silicon, ceramics, metal, resin, or a composite of these materials.

In one embodiment, the adhesive layer can be formed on the base layer of the protective adhesive tape before being flattened in step (2), or on the surface of the support, or on both surfaces. The adhesive layer can be formed by, for example, spin coating when the adhesive layer is a liquid adhesive (such as an adhesive dissolved in a solvent), or by laminating the adhesive tape when the adhesive layer is an adhesive tape, but the method is not limited to these.

Back grinding steps:

The backside grinding step typically involves grinding and polishing the wafer, but is not limited to this and can also include singulation.

When grinding or polishing a wafer with electrodes formed on its surface, the non-electrode surface (back surface) is also ground or polished. The thickness of the wafer after back grinding or polishing varies depending on the electronic device used in the resulting semiconductor device, but is preferably set to 200μm or less, and more preferably 50μm or less. This reduces the thickness of the resulting semiconductor device, and contributes to the miniaturization of the electronic device using such a semiconductor device.

When the wafer is ground or polished, in step (3), a laminate is formed with good thickness accuracy through the adhesive layer and the rigid support layer, so that the wafer can be ground with better processing accuracy, and after this grinding, the wafer is not damaged and can be supplied to the back side processing step described later, or can be easily separated from the support and the adhesive layer.

In one embodiment, the wafer backside grinding method of the present invention may further include at least one of a wafer backside processing step, a support removal step, an adhesive layer removal step, or a protective adhesive tape removal step after the wafer backside grinding.

Backside processing steps:

The wafer backside grinding method of the present invention further includes a step of processing and/or chemically treating the wafer as a backside treatment step after backside grinding of the wafer.

Examples of the aforementioned processing include, but are not limited to, annealing, back electrode formation (sputtering), evaporation, etching, chemical vapor deposition (CVD), physical vapor deposition (PVD), resist coating/patterning, reflow, and doping ion implantation.

The chemical treatments described above typically utilize acids, alkalis, or organic solvents. Examples include, but are not limited to, plating processes such as electrolytic plating and electroless plating, wet etching processes using hydrofluoric acid or tetramethylammonium hydroxide (TMAH), resist stripping processes using N-methyl-2-pyrrolidone, monoethanolamine, or DMSO, and cleaning processes using concentrated sulfuric acid, ammonia, or hydrogen peroxide solutions.

In one embodiment, the back surface treatment includes at least one of etching, electrode formation, ion implantation, and annealing.

Support removal steps:

The support removal step is a step of removing the support from the laminate. Examples of support removal methods include, but are not limited to, IR laser removal, UV irradiation, laser removal, solvent stripping, thermal/UV foaming, and mechanical stripping.

Protective layer and adhesive layer removal steps

The protective layer and adhesive layer removal step involves removing the protective layer from the thinned wafer. The protective layer and adhesive layer can be removed simultaneously or sequentially. Removal methods include peeling and cleaning.

In one aspect, a method for manufacturing an electronic device is provided, wherein the wafer backside grinding method of the present invention is included in the manufacturing steps. Specifically, a wafer processed by the wafer backside grinding method of the present invention can be further supplied to subsequent steps to produce a final product. When forming circuits, etc. on the wafer, steps commonly used in the manufacture of semiconductor devices or electronic devices, such as wafer dicing, die bonding, packaging, and sealing, are performed, and the resulting semiconductor device or electronic device can be manufactured as a finished product.

In one embodiment, the electronic device is an electrical device. As previously mentioned, electrical devices are used in power converters such as inverters and converters, and due to their characteristics, structure, and manufacturing steps, they may have irregularities on the surface of the wafer. According to the present invention, the effects of these irregularities on device characteristics can be suppressed.

Furthermore, it can suppress the effects of unevenness and improve workability in various processing steps, not only during wafer backside grinding, but also in polishing vertical through-silicon vias (TSVs) or wafers with large bumps.

The following further describes a wafer backside grinding method according to one embodiment of the present invention with reference to the drawings. However, the present invention is not limited to this embodiment.

(Implementation Type 1)

Reference numeral 1 in Figure 1(a) represents a semiconductor wafer (hereinafter referred to as a wafer) that has been thinned by back grinding. Wafer 1 is a silicon wafer, for example, and has a uniform thickness of, for example, 700 to 800 μm before processing. Surface 11 of wafer 1 is divided into a plurality of square devices by predetermined grid-like dividing lines. Electrodes and other components are formed on the devices, creating irregularities on surface 11 of wafer 1.

The wafer backside grinding method of this embodiment is shown in Figures 1(a) to (e). A protective adhesive tape 3 is applied to the surface 11 of the wafer 1. The base layer 31 of the protective adhesive tape 3 is then flattened by tool grinding. The flattened base layer 33 of the protective adhesive tape 3 is then bonded to a support 5 via an adhesive layer 4. Finally, the backside 12 of the wafer 1 is ground to a desired thickness (e.g., less than 200μm). The process is described in detail below.

As described above, this embodiment first applies protective adhesive tape 3 to surface 11 of wafer 1. This application is performed using an automated laminating device, reducing the pressure to below 100 Pa and heating the surface to below 100°C. As shown in Figure 1(b), the unevenness on surface 11 of wafer 1 is transferred to the base layer 31 of the applied protective adhesive tape 3.

Wafer 1, with protective adhesive tape 3 attached to its surface 11, is then flattened by cutting its base layer 31. This cutting is performed using a planer. This planer holds the backside 12 of wafer 1 on the suction surface of a vacuum chuck. The rotating cutting tool of the cutting unit engages and flattens the base layer 31 of protective adhesive tape 3.

Next, an adhesive layer 4 is formed on the flattened protective adhesive tape base layer 33. To form this adhesive layer 4, a so-called spin coating method is preferably employed. This method involves placing the flattened protective adhesive tape base layer 33 on a rotating table, with the wafer 1's center aligned with the table's rotation axis. The table is then rotated, and liquid adhesive is dripped onto the center of the rotating wafer 1. This adhesive is then applied centrifugally to the entire surface of the flattened protective adhesive tape base layer 33. In this manner, as shown in Figure 1(d), an adhesive layer 4 is formed on the flattened protective adhesive tape base layer 33.

Then, by bonding the support 5 to the adhesive layer 4, the laminate shown in Figure 1(e) is obtained. The laminate obtained in this manner has no unevenness on the flattened base layer 33 of the protective adhesive tape 3. Therefore, polishing the back surface 12 of the wafer 1 does not transfer the unevenness of the wafer surface 11. Even if the wafer 1 is thinned by backside grinding, the support 5 is still present, ensuring that subsequent handling processes maintain ease of transport and other handling characteristics.

Next, the back side 12 of the wafer 1 is polished to thin the wafer 1 to the desired thickness. A feed-type polishing device is suitable for backside polishing of the wafer 1. This polishing device holds the laminate by attaching the support 5 to the suction surface of a vacuum chuck-type chuck table. Two polishing units (one for rough polishing and one for finish polishing) sequentially perform rough and finish polishing on the back side 12 of the wafer 1.

To remove the thinned wafer 1, the protective adhesive tape 3 is removed after the support 5. Support 5 is removed by mechanically peeling by inserting a remover into the interface between support 5 and adhesive layer 4 and pulling up support 5. Protective adhesive tape 3 is removed by peeling it from wafer 1. Using protective adhesive tape 3 eliminates or minimizes the need for cleaning the wafer after peeling, resulting in excellent workability and lowering manufacturing costs for semiconductor and electronic devices.

(Implementation Type 2)

Using a protective resin layer instead of the protective adhesive tape 3 of Embodiment 1 protects the surface 11 of wafer 1. A spin coating method is suitable for this purpose. Wafer 1 is placed and held on a rotating table, with its surface 11 exposed, so that its center aligns with the table's rotation axis. The table rotates, and a precursor resin liquid is dripped onto the center of the rotating wafer 1. This liquid is then applied centrifugally to the entire surface 11 of wafer 1. The resulting film is then dried on a hot plate to completely remove the solvent from the film, forming a protective layer. The remaining steps are the same as those of Embodiment 1.

At this point, the protective layer is removed during a cleaning step, replacing the peeling of the protective adhesive tape 3 in Embodiment 1. During the cleaning step, with the protective layer facing upward, the wafer 1 is mounted on a rotating table. A cleaning solvent is sprayed on the wafer and placed on the table. After allowing the cleaning solvent to stand, the cleaning solvent is discarded and the cleaning solvent is reapplied and placed on the table again in the same manner. This process is repeated twice, and the wafer 1 is then rotated while being cleaned by spraying with isopropyl alcohol (IPA).

[Industrial Availability]

The wafer backside grinding method of the present invention can suppress the effects of surface irregularities on the wafer and improve operability in various post-wafer thinning processing steps. Therefore, it significantly contributes to productivity improvements in semiconductor and electronic devices. It has high applicability in various industries, including the electronic component industry within the semiconductor manufacturing industry, the electrical and electronics industry using electronic components, the transportation machinery industry, the information and communications industry, and the precision machinery industry.

1: Semiconductor wafer

3: Protective adhesive tape

4: Adhesive layer

5: Support body

11: Wafer surface

12: Back side of wafer

31: Protective adhesive tape substrate layer

32: Adhesive layer of protective adhesive tape

33: Planarized protective adhesive tape substrate layer

Claims (14)

A back grinding method for a wafer is a back grinding method for a wafer having a surface with uneven surfaces. The back grinding method comprises the following steps before grinding the back of the wafer: Step (1) is to form a protective layer on the surface of the wafer; Step (2) is to flatten the surface of the protective layer that is not in contact with the wafer; and Step (3) is to bond the surface of the protective layer that is not in contact with the wafer to a support via an adhesive layer, Wherein, the protective layer is a protective adhesive tape, and The wafer having an uneven surface is a wafer having uneven surfaces formed by at least one of an electrode, a circuit pattern, polyimide, a bad mark, or a bump formed on the surface. The wafer back grinding method as described in claim 1, wherein the base layer of the protective adhesive tape comprises at least one resin selected from the group consisting of PET, PEN, PBT, LCP, PI, PA, PEEK and PPS. The back grinding method of a wafer as described in claim 1 or 2, wherein the wafer having the uneven surface has an uneven surface with a height of 5 to 300 μm. The wafer backside grinding method as described in claim 1 or 2, wherein the planarization step is a planarization step performed by cutting, grinding, or polishing. The back grinding method of a wafer as described in claim 4, wherein the cutting is performed by tool cutting. The wafer backside grinding method according to claim 1 or 2, wherein the adhesive layer is a liquid adhesive or an adhesive tape. The wafer backside grinding method as described in claim 1 or 2, wherein the support body is composed of glass, silicon, ceramic, metal, resin or a composite material thereof. A back grinding method for a wafer as described in claim 1 or 2, wherein, after the aforementioned step (2) and before the aforementioned step (3), the following step is included: forming the aforementioned adhesive layer on the surface of the protective layer not in contact with the wafer before flattening, the surface of the aforementioned support body, or both. The wafer backside grinding method as described in claim 1 or 2, wherein after the backside grinding of the wafer, the backside processing step of the wafer is further included. The backside grinding method of a wafer as described in claim 9, wherein the backside processing step of the wafer includes at least one of etching, electrode formation, ion implantation, and annealing. The wafer backside grinding method as described in claim 1 or 2, wherein the thickness of the wafer after backside grinding is less than 200 μm. A method for manufacturing an electronic device includes the backside grinding method of a wafer as described in any one of claims 1 to 11 in the manufacturing steps. A method for manufacturing an electronic device as described in claim 12, wherein the electronic device is a device having an electrode on the back side. A method for manufacturing an electronic device as described in claim 13, wherein the electronic device is an electrical device.