WO2022158485A1

WO2022158485A1 - Rear surface grinding method for wafer and electronic device production method

Info

Publication number: WO2022158485A1
Application number: PCT/JP2022/001764
Authority: WO
Inventors: 崇畦▲崎▼; 浩登安井; 周穂谷本; 孝鈴木; 仁木下
Original assignee: 三井化学東セロ株式会社
Priority date: 2021-01-21
Filing date: 2022-01-19
Publication date: 2022-07-28
Also published as: JPWO2022158485A1; TW202236407A

Abstract

The present invention addresses the problem of providing a rear surface grinding method for a wafer, in which the rear surface of a wafer is ground such that the impact of recesses and protrusions on the front surface of the wafer can be suppressed and in which handling after wafer thinning is improved. The present problem is solved by a rear surface grinding method for a wafer having recesses and protrusions on the front surface thereof, the rear surface grinding method for a wafer being characterized by comprising, prior to rear surface grinding of the wafer, a step (1) for forming a protective layer on the front surface of the wafer, a step (2) for flattening the surface of the protective layer that is not in contact with the wafer, and a step (3) for adhering a support to the surface of the protective layer that is not in contact with the wafer, with an adhesive layer therebetween.

Description

WAFER BACK GRINDING METHOD AND ELECTRONIC DEVICE MANUFACTURING METHOD

TECHNICAL FIELD The present invention relates to a method for grinding the back surface of a wafer, among methods for thinning a wafer having surface irregularities, and more specifically, after protecting the surface of the wafer with a protective layer, A wafer backside grinding method for suppressing the influence of unevenness on the wafer surface by flattening the non-contact surface, and the wafer backside having improved handleability in a wide variety of processing processes after wafer thinning. It relates to a grinding method.

　In order to achieve high integration of semiconductor devices or to manufacture high-performance semiconductor devices, wafers with circuits formed thereon are ground to a uniform thickness and thinness, and backside grinding is widely used. However, in the manufacturing process of electronic devices such as semiconductor devices, circuits or the like are formed on the surface of a semiconductor wafer made of silicon, gallium-arsenide, or the like in a so-called pre-process, or unevenness exists on the surface of the wafer due to bump electrodes or the like. sell. Among such electronic devices, power devices used in power converters such as inverters and converters in particular have irregularities on the surface of wafers due to their characteristics, structures, manufacturing processes, and the like. In the so-called post-process, if a protective layer such as a protective adhesive tape is created and the back surface is ground as it is, the unevenness on the surface of the wafer will be transferred to the back side of the wafer, and the unevenness will be reflected in the finished thickness of the wafer. In power devices, it affects device characteristics.

As a method of grinding the backside of a wafer that suppresses the effects of unevenness on the surface of the wafer, after supporting the wafer with adhesive tape, the base material of the tape is flattened with a surface planer, thereby making the finished thickness of the backside grinding of the wafer uniform. A method (Patent Document 1) is known. However, although this method can suppress variations in the finished thickness of the wafer, there is a problem in that handling properties such as transportability of the thinned wafer become difficult.

On the other hand, as a method for improving the handleability of thinned wafers, a method is known in which the wafer and support substrate are temporarily fixed with a protective layer to facilitate handling (Patent Document 2). However, in this method, there have been cases where the variation in the finished thickness of the wafer is not sufficiently suppressed due to uneven coating of the protective layer due to unevenness on the surface of the wafer.

Japanese Patent Application Laid-Open No. 2009-43931 Japanese Unexamined Patent Publication No. 2004-64040

In view of the above technical background, it is an object of the present invention to provide a wafer back grinding method capable of suppressing the effects of unevenness on the surface of the wafer and improving the handling properties after thinning the wafer. to do.

As a result of extensive studies, the present inventors have found that prior to grinding the back surface of the wafer, after protecting the surface of the wafer with a protective layer, the surface of the protective layer that is not in contact with the wafer is flattened, and through the adhesive layer, The inventors have found that the above problems can be solved by bonding the flattened surface of the protective layer that is not in contact with the wafer to the support, and have completed the present invention.
That is, the present invention
[1]
A method for grinding the back surface of a wafer having an uneven surface, comprising, prior to grinding the back surface of the wafer,
step (1) of forming a protective layer on the surface of the wafer;
Step (2) of flattening the surface of the protective layer that is not in contact with the wafer, and Step (3) of bonding the surface of the protective layer that is not in contact with the wafer and a support via an adhesive layer,
It relates to a method for grinding the back surface of a wafer, characterized by comprising:

[2] to [15] below are all preferable aspects or embodiments of the present invention.
[2]
The wafer backside grinding method according to [1], wherein the protective layer is a protective adhesive tape.
[3]
The back surface of the wafer according to [2], wherein the base layer of the protective adhesive tape contains at least one resin selected from the group consisting of PET, PEN, PBT, LCP, PI, PA, PEEK and PPS. grinding method.
[4]
Any one of [1] to [3], wherein the wafer having unevenness on the surface is a wafer having unevenness due to at least one of electrodes, circuit patterns, polyimide, defective marks, or bumps formed on the surface. 3. The wafer backside grinding method according to 1.
[5]
The wafer backside grinding method according to any one of [1] to [4], wherein the planarizing step is a step of planarizing by cutting, grinding, or polishing.
[6]
The wafer backside grinding method according to [5], wherein the cutting is performed by cutting with a cutting tool.
[7]
The wafer backside grinding method according to any one of [1] to [6], wherein the adhesive layer is a liquid adhesive or an adhesive tape.
[8]
The wafer backside grinding method according to any one of [1] to [7], wherein the support is made of glass, silicon, ceramic, metal, resin, or a composite material thereof.
[9]
After the step (2) and before the step (3), the adhesive layer is applied to the flattened surface of the protective layer that is not in contact with the wafer, the surface of the support, or both. The wafer backside grinding method according to any one of [1] to [8], comprising the step of forming
[10]
The wafer backside grinding method according to any one of [1] to [9], further comprising a wafer backside treatment step after the wafer backside grinding.
[11]
The wafer backside grinding method according to [10], wherein the wafer backside processing step includes at least one of etching, electrode formation, ion implantation, and annealing.
[12]
The wafer backside grinding method according to [1] to [11], wherein the thickness of the wafer after backside grinding is 200 μm or less.
[13]
A method for manufacturing an electronic device, including the wafer backside grinding method according to any one of [1] to [12] in the manufacturing process.
[14]
The method for manufacturing an electronic device according to [13], wherein the electronic device is a device having an electrode on the back side as well.
[15]
The method for manufacturing an electronic device according to [14], wherein the electronic device is a power device.

According to the wafer backside grinding method of the present invention, it is possible to suppress the influence of unevenness on the surface of the wafer when grinding the backside of the wafer, and the handling property after thinning the wafer is improved and the thickness is reduced. Since the wafer can be stably processed in a wide variety of subsequent processes, it prevents damage to the circuits formed on the wafer, suppresses unintended effects on the characteristics of electronic devices such as semiconductor devices, and protects the wafer. It is possible to perform a large number and/or a wide variety of processes with high productivity and yield, thereby greatly contributing to the improvement of productivity of electronic devices such as semiconductor devices.

It is a schematic diagram explaining the process in one embodiment of the present invention. (a) shows a wafer 1 whose back surface 12 is ground according to the present invention. (b) shows the wafer 1 with the protective adhesive tape 3 applied to the surface 11 of the wafer 1 by the step (1) using the protective adhesive tape 3 as a protective layer. (c) shows the wafer 1 in which the base layer 31 of the protective adhesive tape 3 has been flattened by the step (2). (d) shows the wafer 1 in which the adhesive layer 4 is formed on the flattened base layer 33 of the protective adhesive tape 3 obtained in step (2). (e) shows the wafer 1 to which the support 5 and the flattened base material layer 33 of the protective adhesive tape 3 are adhered via the adhesive layer 4 in step (3).

The present invention
A method for grinding the back surface of a wafer having an uneven surface, comprising, prior to grinding the back surface of the wafer,
step (1) of forming a protective layer on the surface of the wafer;
Step (2) of flattening the surface of the protective layer that is not in contact with the wafer, and Step (3) of bonding the surface of the protective layer that is not in contact with the wafer and a support via an adhesive layer,
A wafer backside grinding method comprising:

Wafer having Concavo-convex Surface The wafer to be back-ground by the method of the present invention has concavo-convex surface. The irregularities on the wafer surface include, for example, electrodes, circuit patterns, thick polyimide (5 to 20 μm) protective films, defect marks (5 to 100 μm) for identifying defective chips, and gold for bump bonding instead of wire bonding. Those derived from bumps (10 to 100 μm), solder bumps (50 to 300 μm), etc. can be mentioned, and the height of the irregularities can be 5 to 300 μm.

The material of the wafer is usually used in the manufacture of electronic devices, is a material that can be used to form electronic circuits, etc., and is expected to be thin as a base material to be ground. For example, silicon wafers, compound semiconductor wafers such as SiC, AlSb, AlAs, AlN, AlP, BN, BP, BAs, GaSb, GaAs, GaN, GaP, InSb, InAs, InN, or InP, crystal wafers, sapphire, glass, etc. include, but are not limited to. Silicon wafers and compound semiconductor wafers may be doped.

Wafers with uneven surfaces in particular include power device wafers used in electronic devices such as power converters 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 The protective layer is intended to prevent electronic circuits and the like on the front surface of the wafer from being damaged and contaminated with grinding dust and grinding water during back grinding of the wafer. In order to grind the back surface of the wafer, the wafer is sucked and held on a vacuum chuck type chuck table, and the chuck table is rotated to rotate the wafer while pressing a grinding tool such as a whetstone against the back surface of the wafer. Feed grinding is generally employed. When grinding the back surface of the wafer in this way, the surface of the wafer is covered with a protective layer, and the surface of the wafer is in direct contact with the holding surface of the chuck table. Care is taken not to damage the electronic circuits on the surface of the wafer.
In one aspect, the protective layer includes, for example, a protective adhesive tape, a protective resin layer, and the like, and the protective layer is preferably a protective adhesive tape.

The protective layer in the present invention has a thickness suitable for protecting the surface of the wafer, and at the same time, it has a thickness that can withstand flattening in step (2) described later, that is, has a thickness that is sufficient for the required cutting thickness.

It is preferable to use a protective adhesive tape as the protective layer. When the protective layer is a protective adhesive tape, step (1) is a step of applying the protective adhesive tape to the surface of the wafer. The application of the protective adhesive tape to the surface of the wafer may be performed by a conventionally known method, but is preferably performed using an automatic application device. It is preferable to appropriately adjust the pressure, temperature, time, and the like.

Protective adhesive tape The protective adhesive tape as a preferable protective layer used in the method of the present invention has adhesiveness to withstand flattening in step (2) described later, machinability, and adhesiveness to withstand back-grinding described later. There is no particular limitation as long as it can be removed from the wafer with chemical resistance and heat resistance that can withstand the back surface treatment process, and finally, the contamination of the surface of the wafer is reduced. It is preferably selected from those used as and can also be used.

Materials for the base layer of the protective adhesive tape include, for example, 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 (homoPP), polybutene (PB), polymethylpentene (PMP), ethylene-vinyl acetate copolymer (EVA), ethylene acrylic acid copolymers, ethylene methacrylic acid copolymers and their metal crosslinked products (ionomers) and other polyolefins, and polyethylene terephthalate (PET) and polyethylene naphthalate (PEN). ), polybutylene terephthalate (PBT), and polyesters such as liquid crystal polymer (LCP), polyurethane (PU), polycarbonate (PC), polyimide (PI), polyether ether ketone (PEEK), Polyetherimide (PEI), polyamide (PA), wholly aromatic polyamide, polyphenyl sulfide (PPS), fluororesin, polyvinyl chloride, polyvinylidene chloride, cellulose resin and the like are also included. Also, the above resin may be used alone as a single-layer base material, or a combination of a plurality of the above resins may be blended, or a multi-layer structure of different resins may be used. From the viewpoint of heat resistance, substrates having a melting point or glass transition temperature of 100° C. or higher are preferred, and those having a melting point or glass transition temperature of 150° C. or higher are particularly preferred.
In one embodiment, it is particularly preferred that the base layer of the protective adhesive tape contains PET, PEN, PBT, LCP, PI, PA, PEEK, PPS considering the following conditions.

Since the base layer of the protective adhesive tape must be able to withstand flattening, it preferably has a thickness of 10 to 1000 μm, particularly preferably 25 to 500 μm, before flattening. If the thickness of the base layer of the protective pressure-sensitive adhesive tape is reduced, the thickness of the protective layer is reduced and the amount that can be ground during flattening is limited, so the effect of flattening the protective layer tends to be reduced. Therefore, when the unevenness on the wafer surface is large, the thickness accuracy of the wafer after grinding may be degraded due to its influence. On the other hand, when the thickness of the protective layer before flattening is increased, the rigidity of the protective layer is high, and workability in the form of tape tends to deteriorate, and cuttability when cutting the tape into a wafer form tends to deteriorate. In addition, due to its rigidity, the protective adhesive tape is less likely to be deformed, so there is a tendency for the releasability of the protective adhesive tape to deteriorate in the step of removing the protective layer after backside grinding of the wafer.

The base layer of the protective tape preferably has a tensile modulus of elasticity of 1×10 ⁷ Pa or more at 23° C. according to JIS K7113, more preferably 5×10 ⁷ Pa or more. . A low tensile modulus tends to affect flattening of the base layer of the masking tape. Specifically, even after flattening, there is a tendency for the thickness accuracy of the wafer after back grinding to decrease due to the unevenness of the surface of the wafer. On the other hand, the tensile modulus of elasticity is preferably 1×10 ¹⁰ Pa or less, more preferably 6×10 ⁹ Pa or less, from the viewpoints of workability, cuttability, bendability, etc. of the base material layer.

For the adhesive layer of the protective adhesive tape, commonly used pressure-sensitive adhesives and curable adhesives can be used. In general, the adhesive layer may be a single layer or multiple layers, and from the viewpoint of conforming to the unevenness of the wafer surface, a multiple layer in which a flexible intermediate layer and a low-contamination adhesive layer are laminated. It may be a layered structure.

Examples of the pressure-sensitive adhesive include acrylic adhesives, rubber-based adhesives, and silicone-based adhesives. Acrylic adhesive with acrylic polymer as the base polymer in terms of adhesiveness to semiconductor wafers and substrate layers, and cleanability with organic solvents such as ultrapure water and alcohol after peeling off the protective adhesive tape. agents are preferred.

Examples of the curable adhesive include a photocurable adhesive that is crosslinked and cured by light irradiation and a thermosetting adhesive that is crosslinked and cured by heating. Examples of the photocurable adhesive include a photocurable adhesive containing a photopolymerization initiator as a main component of a polymerizable polymer. Examples of the thermosetting adhesive include a thermosetting adhesive containing a polymerizable polymer as a main component and a thermal polymerization initiator.

If the adhesive layer of the protective adhesive tape has a low peeling adhesive strength, the adhesive strength to the wafer will be insufficient against the shearing force applied when flattening the base layer of the protective adhesive tape, and the protective adhesive tape will peel off from the wafer. There is a problem that it will be lost. On the other hand, if the peel adhesive strength is high, it may become difficult to peel the protective adhesive tape from the wafer. Therefore, the thickness is preferably 5 to 500 μm, particularly preferably 10 to 100 μm, from the viewpoint of the final separation from the wafer. Except for using a silicon mirror wafer as the adherend, the 180° peeling adhesive strength (peeling speed 300 mm/min) according to JIS Z0237 (2009) is preferably 0.3 to 10 N/25 mm, and 0.5 to 7 N /25 mm is particularly preferred. Within this range, it is adjusted as appropriate according to the process.

A protective resin layer can also be used as the protective layer. When the protective layer is a protective resin layer, the protective resin layer is formed by applying a raw material resin dissolved in a solvent or a liquid raw material resin itself (hereinafter referred to as a precursor resin liquid) by a known method such as spin coating, followed by light irradiation, It functions as a solid protective layer by being hardened by heating, drying, or the like. It may be formed in multiple layers.

Protective resin layer The protective resin layer that can be used as a protective layer has adhesiveness and machinability that can withstand flattening in the step (2) described later, and adhesiveness that can withstand backside grinding described later. There is no particular limitation as long as it can be removed from the wafer with durable chemical resistance, heat resistance, and finally, contamination of the surface of the wafer is reduced, and is preferably selected from known materials for temporarily fixing the device wafer to the support, can also be used. Examples of the precursor resin liquid include rubber-based resin liquid in which rubber, elastomer, etc. are dissolved in a solvent, one-component thermosetting resin liquid based on epoxy, urethane, etc., and two-component thermosetting resin liquid based on epoxy, urethane, acrylic, etc. Liquid mixing reaction type resin liquids, hot melt adhesives, ultraviolet (UV) or electron beam curing type resin liquids based on acrylic, epoxy, etc., and water dispersion type resin liquids can be used. A UV curable resin liquid obtained by adding a photopolymerization initiator to an oligomer having a polymerizable vinyl group such as urethane acrylate, epoxy acrylate or polyester acrylate and/or an acrylic or methacrylic monomer and, in some cases, additives is preferably used. be. Additives include thickeners, plasticizers, dispersants, fillers, flame retardants, heat antioxidants, and the like. A plurality of protective resin layers may be formed.

Step (2)
Step (2) is a step of 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. In step (1), when a protective adhesive tape is attached to the surface of the wafer, the unevenness of the wafer surface is transferred to the base layer of the protective adhesive tape. Therefore, the unevenness of the base layer of the protective adhesive tape is reflected, and the unevenness is transferred to the back surface of the wafer. Even when the protective layer is formed from a protective resin layer, sufficient flattening may not be achieved by simple spin coating, and unevenness may occur on the surface of the protective layer, which may be transferred to the back surface of the wafer.
By flattening the base layer of the protective adhesive tape onto which the unevenness has been transferred in this way prior to back grinding, the force of the back grinder is applied uniformly, thereby preventing the unevenness from being transferred to the back surface of the wafer. can be prevented.

The planarization is not particularly limited as long as it can prevent unevenness from being transferred to the back surface of the wafer, but for example, it preferably satisfies the following conditions.
The difference between the concave portions and the convex portions on 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 1 μm or less over the entire cut surface. preferable.
In one embodiment, the planarization is performed by cutting, grinding or polishing.

In one embodiment, the cutting is performed with a cutting tool. By cutting with a cutting tool, problems such as clogging of the whetstone during polishing can be solved, and flattening can be easily performed, as compared with the case where flattening is performed by polishing with a polishing machine. Bite cutting may be performed by a surface planer.

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

Adhesive Layer The adhesive layer is used to adhere the surface of the protective layer not in contact with the wafer to the support. The tacky-adhesive layer is formed by temporarily fixing the wafer to the support, and after processing is completed, for example, IR laser method, UV irradiation method, laser lift-off method, solvent peeling method, heat/UV foaming method, mechanical peeling method, etc. A known temporary fixing material that can be easily separated may be applied, and a liquid adhesive (such as an adhesive dissolved in a solvent) may be applied by spin coating or the like and molded, or an adhesive tape may be used. The adhesive layer may be formed on the support, on the protective layer, or on both. Variation in the 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 or a laminate of multiple layers, and may be a double-sided tape containing a base film in the layer. may

Support The support preferably has sufficient strength and rigidity, and is excellent in heat resistance, chemical resistance, and thickness accuracy. By using such a support, even if the wafer is thinned after grinding, it becomes possible to handle the wafer stably, and the wafer can be processed into multiple and/or multi-layered wafers without bending or the like. It becomes possible to provide for the process of

A known support can be used as the support, and preferred materials include silicon, sapphire, crystal, metals (e.g., aluminum, copper, steel, stainless steel), various glasses and ceramics, and resins (e.g., , polyimide, polyamide, epoxy, phenol, polyphenylene ether, polyetheretherketone, polyetherimide, wholly aromatic polyamide, polyphenylsulfide resin). The support may be composed of a single material, but it may also be composed of multiple materials and may include other materials deposited on the substrate. For example, it may have a deposited layer of silicon nitride or the like on a silicon wafer. Particularly preferably, the support is made of glass, silicon, ceramic, metal, resin, or a composite material thereof.

In one embodiment, the adhesive layer may be formed on the base layer of the protective adhesive tape flattened in step (2), or may be formed on the surface of the support, It may be formed on both sides. As a method for forming the adhesive layer, for example, when the adhesive layer is a liquid adhesive (adhesive dissolved in a solvent, etc.), spin coating is performed, and when the adhesive layer is a tape, the tape is applied. Examples include, but are not limited to, methods involving lamination.

Backside Grinding Process The backside grinding process is typically wafer grinding and polishing, but is not limited to this, and may include singulation and the like.
When grinding or polishing a wafer having electrodes formed on its surface, the electrode-free surface (back surface) is ground or polished. The thickness of the wafer after such back surface grinding or polishing varies depending on the electronic equipment in which the obtained semiconductor device is used, but is preferably set to 200 μm or less, more preferably set to 50 μm or less. As a result, the thickness of the semiconductor device obtained is reduced, and the size reduction of electronic equipment using such a semiconductor device is realized.

When the wafer is ground or polished, in step (3), it is laminated with a rigid support with an adhesive layer interposed therebetween to form a laminate with high thickness accuracy, whereby the wafer can be processed with superior processing accuracy. After grinding, etc., the wafer can be subjected to a back surface treatment step, which will be described later, and can be easily separated from the support and the adhesive layer without damaging the wafer.

In one embodiment, the wafer backside grinding method of the present invention includes at least one of a wafer backside processing step, a support removing step, an adhesive layer removing step, or a protective adhesive tape removing step after the wafer backside grinding. Further steps can be included.

Back surface treatment step The wafer back surface grinding method of the present invention may further include processing and/or chemical treatment of the wafer as a back surface treatment step after back surface grinding of the wafer.

The above processing includes, for example, annealing, back electrode formation (sputtering), vapor deposition, etching, chemical vapor deposition (CVD), physical vapor deposition (PVD), resist coating/patterning, reflow, and dopant ionization. Injection and the like include, but are not limited to.

The chemical treatment is typically a treatment using an acid, an alkali, or an organic solvent. Examples include, but are not limited to, wet etching, resist stripping processes using N-methyl-2-pyrrolidone, monoethanolamine, DMSO, etc., and cleaning processes using concentrated sulfuric acid, ammonia water, hydrogen peroxide water, etc. .

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

Support Removal Step The support removal step is a step of removing the support from the laminate. Examples of methods for removing the support include, but are not limited to, IR laser method, UV irradiation method, laser lift-off method, solvent peeling method, heat/UV foaming method, and mechanical peeling method.

Protective Layer and Adhesive Layer Removal Step The protective layer and adhesive layer removal step is a step of removing the protective layer and the like from the thinned wafer. The protective layer and the adhesive layer may be removed simultaneously or sequentially. can be intentionally removed. Examples of the removal method include peeling, washing, and the like.

In one aspect, there is provided a method for manufacturing an electronic device that includes the wafer backside grinding method of the present invention in the manufacturing process. That is, the wafer ground by the wafer backside grinding method of the present invention can be further subjected to the subsequent steps to produce the final product. When circuits, etc. are formed on the wafer, dicing, bonding, packaging, sealing, and other processes normally used in the manufacture of semiconductor devices or electronic devices are performed, and semiconductor devices and electronic devices as products are processed. Devices can be manufactured.

In one embodiment, the electronic device is a power device. As described above, power devices are used in power converters such as inverters and converters, and the wafer surface has irregularities due to its characteristics, structure, manufacturing process, and the like. According to the present invention, it is possible to suppress the influence of the unevenness on the device characteristics.
In addition, not only in grinding the backside of the wafer, but also in a wide variety of processing processes, the influence of unevenness can be suppressed and the handling property can be improved. It can also be applied to bump wafer grinding applications.

The method for grinding the back surface of a wafer according to one embodiment of the present invention will be further described below with reference to the drawings, but the present invention is not limited to these embodiments.

(Embodiment 1)
Reference numeral 1 in FIG. 1(a) denotes a semiconductor wafer (hereinafter referred to as a wafer) which is thinned by back grinding. This wafer 1 is a silicon wafer or the like, and has a uniform thickness of, for example, 700 μm to 800 μm before processing. A plurality of rectangular devices are partitioned on the surface 11 of the wafer 1 by grid-like dividing lines. Electrodes and the like are formed in the device, and the surface 11 of the wafer 1 is uneven.

In the wafer backside grinding method of the present embodiment, as shown in FIGS. 31 is flattened by grinding with a bite, then the flattened base layer 33 of the protective adhesive tape 3 and the support 5 are adhered via the adhesive layer 4, and then the back surface 12 of the wafer 1 is ground. is thinned to a target thickness (for example, 200 μm or less). The process will be described in detail below.

As described above, in this embodiment, the protective adhesive tape 3 is attached to the surface 11 of the wafer 1 first. The sticking is performed by reducing the pressure to 100 Pa or less using an automatic sticking device and heating at 100° C. or less. As shown in FIG. 1B, the irregularities on the surface 11 of the wafer 1 are transferred to the base layer 31 of the protective adhesive tape 3 attached.

After the wafer 1 with the protective adhesive tape 3 attached to the surface 11, the base layer 31 of the protective adhesive tape 3 is cut flat. A surface planer is used for the cutting. According to this surface planer, the back surface 12 of the wafer 1 is held by being attracted to the suction surface of a vacuum chuck type chuck table, and the substrate layer 31 of the protective adhesive tape 3 is flattened by the rotating cutting tool of the cutting unit. is cut to

Next, the adhesive layer 4 is formed on the flattened base layer 33 of the protective adhesive tape. In order to form this adhesive layer 4, the substrate layer 33 of the flattened protective adhesive tape is exposed on a table that is driven to rotate, and the center of the wafer 1 is aligned with the rotation axis of the table. The wafer 1 is placed and held so as to match, the table is rotated, the liquid adhesive is dropped onto the center of the rotating wafer 1, and the adhesive is applied to the base of the protective adhesive tape flattened by centrifugal force. A spin coating method, in which the material is spread over the entire surface of the material layer 33 and applied, is preferably employed. An adhesive layer 4 is formed on the base layer 33 of the protective adhesive tape that has been flattened as shown in FIG. 1(d).

Then, by bonding the support 5 to the adhesive layer 4, the laminate shown in FIG. 1(e) can be obtained. In the laminated body thus obtained, since the base layer 33 of the protective adhesive tape 3 has no unevenness, the unevenness of the front surface 11 of the wafer 1 is not transferred by grinding the back surface 12 of the wafer 1. Even if the substrate 1 is thinned, it still has the support 5, so that it does not lose handling properties such as transportability in the subsequent treatment processes.

Next, the back surface 12 of the wafer 1 is ground to thin the wafer 1 to a desired thickness. A grinding apparatus that performs infeed grinding is preferably used for grinding the back surface of the wafer 1 . According to this grinding apparatus, the back surface 12 of the wafer 1 is ground by two grinding units (one for rough grinding and one for finish grinding). Rough grinding and finish grinding are performed in order.

In this case, to remove the thinned wafer 1, the protective adhesive tape 3 is removed after the support 5 is removed. The support 5 is removed by a mechanical peeling method in which a remover is inserted into the interface between the support 5 and the adhesive layer 4 and the support 5 is pulled up. Removal of the protective adhesive tape 3 is performed by peeling off the protective adhesive tape 3 from the wafer 1 . The use of the protective adhesive tape 3 eliminates or minimizes the need for cleaning the wafer after peeling, resulting in excellent workability and lower manufacturing costs for semiconductor devices and electronic devices.

(Embodiment 2)
A protective resin layer can be used instead of the protective adhesive tape 3 of the first embodiment to protect the surface 11 of the wafer 1 . In this case, the wafer 1 is placed and held on a rotationally driven table such that the surface 11 of the wafer 1 is exposed and the center of the wafer 1 coincides with the rotation axis of the table, and the table is rotated. A spin coating method is preferably employed in which the precursor resin liquid is dropped onto the center of the rotating wafer 1 and spread over the entire surface 11 of the wafer 1 by centrifugal force. The coating film after spin coating is placed on a hot plate and dried to completely remove the solvent in the film to form a protective layer. Other steps are the same as in the first embodiment.

In this case, instead of removing the protective adhesive tape 3 in Embodiment 1, the protective layer is removed by a washing process. In the cleaning process, the wafer 1 is fixed on a rotating table with the protective layer facing up, the cleaning solvent is sprayed, the cleaning solvent is placed on the wafer, the cleaning solvent is left to stand, the cleaning solvent is discarded, and the wafer is placed again in the same manner. After repeating the same operation of placing the cleaning solvent on the wafer 1 and allowing it to stand still twice, the wafer 1 is rinsed by spraying isopropyl alcohol (IPA) while rotating it.

The wafer backside grinding method of the present invention can suppress the influence of unevenness on the surface of the wafer and can improve the handleability in a wide variety of processing processes after thinning the wafer, so that it can be used for semiconductor devices, electronic devices, and the like. It greatly contributes to the improvement of productivity and has high applicability in various industrial fields such as the semiconductor process industry and other electronic component industries, the electrical and electronic industry that uses electronic components, the transport machinery industry, the information and communication industry, and the precision equipment industry. have

1 Semiconductor Wafer 11 Wafer Front Surface 12 Wafer Back Surface 3 Protective Adhesive Tape 31 Protective Adhesive Tape Base Layer 32 Protective Adhesive Tape Adhesive Layer 33 Flattened Protective Adhesive Tape Base Layer 4 Adhesive Layer 5 Support

Claims

A method for grinding the back surface of a wafer having an uneven surface, comprising, prior to grinding the back surface of the wafer,
step (1) of forming a protective layer on the surface of the wafer;
Step (2) of flattening the surface of the protective layer that is not in contact with the wafer, and Step (3) of bonding the surface of the protective layer that is not in contact with the wafer and a support via an adhesive layer,
A wafer backside grinding method comprising:
The wafer backside grinding method according to claim 1, wherein the protective layer is a protective adhesive tape.
The back surface of the wafer according to claim 2, wherein the base layer of the protective adhesive tape contains at least one resin selected from the group consisting of PET, PEN, PBT, LCP, PI, PA, PEEK and PPS. grinding method.
4. The wafer having unevenness on its surface is a wafer having unevenness due to at least one of electrodes, circuit patterns, polyimide, defective marks, or bumps formed on the surface. wafer backgrinding method.
The wafer backside grinding method according to any one of claims 1 to 4, wherein the planarizing step is a step of planarizing by cutting, grinding, or polishing.
The wafer backside grinding method according to claim 5, wherein the cutting is performed by cutting with a cutting tool.
The wafer backside grinding method according to any one of claims 1 to 6, wherein the adhesive layer is a liquid adhesive or an adhesive tape.
The wafer backside grinding method according to any one of claims 1 to 7, wherein the support is made of glass, silicon, ceramic, metal, resin, or a composite material thereof.
After the step (2) and before the step (3), the adhesive layer is applied to the flattened surface of the protective layer that is not in contact with the wafer, the surface of the support, or both. The wafer backside grinding method according to any one of claims 1 to 8, comprising the step of forming a
The wafer backside grinding method according to any one of claims 1 to 9, further comprising a wafer backside processing step after the wafer backside grinding.
The wafer backside grinding method according to claim 10, wherein the wafer backside processing step includes at least one of etching, electrode formation, ion implantation, and annealing.
The wafer backside grinding method according to claims 1 to 11, wherein the thickness of the wafer after backside grinding is 200 µm or less.
A method for manufacturing an electronic device including the method for grinding the wafer back surface according to any one of claims 1 to 12 in the manufacturing process.
The method for manufacturing an electronic device according to claim 13, wherein the electronic device is a device having an electrode on the back side as well.
15. The method of manufacturing an electronic device according to claim 14, wherein said electronic device is a power device.