Wafer processing sheet and wafer processing method

Abstract

The present invention relates to a wafer processing sheet having a base sheet in contact with a main surface of a wafer, wherein an exponential coefficient of an exponential approximation curve of a storage elastic modulus E' of the base sheet at 30°C to 80°C is -0.035 to -0.070. 30‑80 the exponential coefficient of the exponential approximation curve of the storage elastic modulus E' of the base sheet at 30°C to 80°C is -0.035 to -0.070.

Description

TECHNICAL FIELD

[0001] The present application relates to a sheet for wafer processing and a method for processing a wafer. BACKGROUND

[0002] In processing a wafer, a sheet is attached in order to protect the wafer from breakage due to the processing. For example, in a backgrinding process for thinning a wafer in which a bump or the like is formed on a surface, a step of attaching a sheet to a surface on which the bump or the like is formed is performed. In addition, in a dicing process in which a semiconductor chip is cut out from a wafer, dicing is performed while a sheet is attached to the wafer.

[0003] For such a sheet, followability (step difference followability) to the unevenness of the surface of the wafer is required. In the past, followability of a sheet has been improved by making the thickness of an adhesive thick or by providing a soft resin layer having a cushioning property between a base material film and an adhesive. However, in the case where the unevenness of the surface of the wafer is large, there are problems that followability is insufficient or that an adhesive layer enters a deep portion of a recess of the surface of the wafer, resulting in a decrease in yield due to adhesive residue and operation failure of a processed chip.

[0004] As a method for solving the above problems, Patent Literature 1 discloses a technology in which an adhesive portion is provided so as to surround a non-adhesive portion having a diameter smaller than the outer diameter of a semiconductor wafer to be attached, the adhesive portion has an adhesive strength of 500 mN or more at 23°C, and thus adhesive residue is prevented and a decrease in protective performance is prevented.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT LITERATURE

[0007] Patent Literature 1: Japanese Patent Application Publication No. 2013-211438 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] However, in the technology described in Patent Literature 1, only an adhesive portion that is bonded to the edge of a semiconductor wafer is provided, and a configuration in which a bump or the like is directly protected by a non-adhesive portion is not formed. Therefore, for example, in a backgrinding process, in the case where a protruding electrode is provided on a semiconductor wafer, backgrinding of the semiconductor wafer is performed in a state where only the tip end of the protruding electrode is in contact with a base material sheet, and thus, it is possible that an excessive load is applied to the protruding electrode during backgrinding and the protruding electrode is broken.

[0010] Furthermore, the technology described in Patent Document 1 only provides an adhesive portion bonded to the edge of a semiconductor wafer, and does not disclose that an adhesive portion contacting, for example, unevenness on the wafer surface can be peeled off satisfactorily without causing adhesive residue.

[0011] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a wafer processing sheet that exhibits appropriate followability to a wafer surface during heating and is also excellent in releasability, and a wafer processing method using the wafer processing sheet.

[0012] Means for solving problems

[0013] The inventors of the present application conducted intensive research to solve the above-mentioned problems and found that the above-mentioned problems can be solved by using a base sheet having predetermined storage elastic modulus characteristics as the sheet in contact with the main surface of the wafer, thereby completing the present invention.

[0014] That is, the present invention is as follows.

[0015] [1] A wafer processing sheet comprising a base sheet in contact with a main surface of a wafer,

[0016] Storage elastic modulus E' of the substrate sheet at 30°C to 80°C 30-80 The exponential coefficient of the exponential approximation curve is -0.035 to -0.070.

[0017] [2] The wafer processing sheet according to [1], wherein the storage elastic modulus E' of the substrate sheet at 30°C is 30 Storage elastic modulus E' at 80℃ 80 The difference (E' 30 -E' 80 ) is 4.00×10 7 ~4.00×10 8 Pa.

[0018] [3] The wafer processing sheet according to [1] or [2], wherein the storage elastic modulus E' of the substrate sheet at 80°C is 80 5.00×10 5 ~1.00×10 7 Pa.

[0019] [4] The wafer processing sheet according to any one of [1] to [3], wherein the storage elastic modulus E' of the base sheet in the temperature range of 80 to 110°C is 80-110 1.00×10 6 ~1.00×10 7 Pa.

[0020] [5] The wafer processing sheet according to any one of [1] to [4], wherein the loss elastic modulus E" of the substrate sheet at 80°C is 80 1.50×10 4 ~1.50×10 6 Pa.

[0021] [6] The wafer processing sheet according to any one of [1] to [5], wherein the loss modulus E" of the substrate sheet at 30°C is 30 1.00×10 6 ~1.50×10 8 Pa.

[0022] [7] The wafer processing sheet according to any one of [1] to [6], wherein the base sheet has a melting point of 70° C. or higher.

[0023] [8] A method for processing a wafer, comprising:

[0024] A laminating step of laminating the heated surface of the substrate sheet of the wafer processing sheet according to any one of [1] to [7] to the main surface of the wafer; and

[0025] A processing step of processing the wafer in a state where the base sheet and the wafer are bonded together.

[0026] [9] The wafer processing method according to [8], wherein in the processing step, the main surface of the wafer to which the base sheet is not bonded is polished to obtain a thinned wafer.

[0027]

[10] The wafer processing method as described in [8], wherein, in the above-mentioned processing step, the above-mentioned wafer is cut to obtain semiconductor chips.

[0028] Effects of the Invention

[0029] According to the present invention, it is possible to provide a wafer processing sheet that exhibits appropriate followability to a wafer surface during heating and is also excellent in releasability, and a wafer processing method using the wafer processing sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] [ Figure 1 ] is a cross-sectional view showing an example of back side grinding of a wafer using the wafer processing sheet according to the present embodiment.

[0031] [ Figure 2 ] is a cross-sectional view used to illustrate the followability of the sheet for chip processing.

[0032] [ Figure 3 ] is a coordinate diagram of the results of the dynamic viscoelasticity measurement of Example 1.

[0033] [ Figure 4 ] is a graph obtained by recording an exponential approximation curve in a graph showing the results of the dynamic viscoelasticity measurement of Example 1, showing a graph A showing the storage elastic modulus E' on a logarithmic scale and a graph B not showing it on a logarithmic scale.

[0034] [ Figure 5 ] is a coordinate graph showing the results of dynamic viscoelasticity measurement of Example 2.

[0035] [ Figure 6 ] is a coordinate graph showing the results of dynamic viscoelasticity measurement of Comparative Example 1.

[0036] [ Figure 7 ] is a coordinate graph showing the results of dynamic viscoelasticity measurement of Comparative Example 2.

[0037] [ Figure 8 ] is a coordinate graph showing the results of dynamic viscoelasticity measurement of Comparative Example 3.

[0038] [ Figure 9 ] is a coordinate graph showing the results of dynamic viscoelasticity measurement of Comparative Example 4.

[0039] [ Figure 10 ] is a coordinate graph showing the results of dynamic viscoelasticity measurement of Comparative Example 5.

[0040] [ Figure 11 ] is a coordinate graph showing the results of dynamic viscoelasticity measurement of Comparative Example 6.

[0041] [ Figure 12 ] is a photograph showing the cross section of the substrate sheet in Example 1, Comparative Example 2, and Comparative Example 3. DETAILED DESCRIPTION

[0042] The following describes an embodiment of the present invention (hereinafter referred to as the "present embodiment") in detail, but the present invention is not limited thereto and various modifications can be made without departing from the scope of the present invention. It should be noted that in the drawings, the same elements are marked with the same reference numerals, and repeated descriptions are omitted. In addition, unless otherwise specified, positional relationships such as up and down, left and right are based on the positional relationships shown in the drawings. In addition, the dimensional ratios in the drawings are not limited to the ratios shown in the drawings.

[0043] 〔Wafer processing sheets〕

[0044] The wafer processing sheet of this embodiment has a storage elastic modulus E' at 30°C to 80°C. 30-80 A base sheet having an exponential coefficient of the exponential approximation curve of -0.035 to -0.070 is used as the base sheet in contact with the main surface of the wafer.

[0045] By using a substrate sheet with such storage elastic modulus properties, it exhibits appropriate conformability to uneven wafer surfaces during heating. Furthermore, it exhibits excellent peelability after back grinding and dicing, which can prevent adhesive residue on the wafer surface. This allows for more appropriate protection and deprotection of the wafer surface during back grinding and dicing, contributing to improved semiconductor device yields.

[0046] First, the usage of the wafer processing sheet according to the present embodiment will be briefly described. Figure 1 A cross-sectional view showing an example of backside grinding of a wafer using the wafer processing sheet according to the present embodiment is shown. Figure 1 In the embodiment, the wafer processing sheet 10 includes a base sheet 11 and other layers 12 such as a buffer layer, and the semiconductor wafer 20 has a protrusion 20b on the wafer main surface 20a. The wafer processing sheet 10 of this embodiment is used by attaching the surface 11a of the base sheet 11 to the wafer main surface 20a during the processing of the semiconductor wafer 20, such as the back grinding process or the dicing process.

[0047] More specifically, before the processing, the substrate sheet 11 is heated with the wafer main surface 20a in contact with the surface 11a of the substrate sheet 11 (step A). ​​When heated, the elastic modulus of the substrate sheet 11 decreases, and the substrate sheet 11 adheres to the wafer main surface 20a so as to follow the protrusions 20b formed on the wafer main surface 20a (step B).

[0048] Then, the substrate sheet 11 is cooled and back grinding is performed on the back side 20a' of the semiconductor wafer 20 (process C). The specific method of back grinding is not particularly limited, and known methods can be used. For example, a method of thinning the semiconductor wafer 20 by grinding while supplying a slurry containing abrasive grains to the back side 20a' of the semiconductor wafer 20 can be cited. If the substrate sheet 11 is cooled before back grinding, the elastic modulus is restored while following the main surface 20a of the wafer, and the main surface 20a of the wafer is protected without offsetting the main surface 20a of the wafer and the surface 11a of the substrate sheet 11.

[0049] Finally, the substrate sheet 11 is peeled from the wafer's main surface 20a (step D). To prevent adhesive residue, the substrate sheet 11 preferably has moderate elasticity. This prevents excessive intrusion of sheet components into the recesses during the follow-up process in step B, further preventing adhesive residue from forming in those recesses. Furthermore, since the sheet components do not excessively intrude into the recesses, the protrusions are less likely to be loaded by the sheet components that have intruded into the recesses during peeling, resulting in excellent peelability.

[0050] In particular, for the wafer processing sheet of this embodiment, the followability in the above steps A to B is important. Figure 2 As shown in FIG. 3B , if the tracking performance is insufficient and the gap 32 becomes larger, it is difficult to fully protect the protrusion 20b formed on the main surface 20a of the wafer, which easily leads to a decrease in the yield rate in the processing process. In addition, if the tracking performance is insufficient, it is easy to cause the problem of ripples 33 on the back surface of the wafer processing sheet 10. On the other hand, if the tracking performance is insufficient, the back surface of the wafer processing sheet 10 may be easily damaged. Figure 2 As shown in C, when the base sheet enters the gap 34 of the convex portion 20b due to excessive followability, the following problems are likely to occur: it may get caught during peeling, damaging the convex portion 20b, or it may become impossible to peel.

[0051] Therefore, in the wafer processing sheet 10 of this embodiment, as Figure 2 As shown in A, it is important to have appropriate followability to achieve sufficient protection performance and to ensure releasability by not entering the gaps 31 between the protrusions 20b.

[0052] (Base sheet)

[0053] (Storage elastic modulus E')

[0054] In the processing of the semiconductor wafer 20 described above, in order to properly protect the wafer surface 20a, the substrate sheet 11 is required to follow the wafer main surface 20a. Therefore, in this embodiment, the decrease characteristics of the storage elastic modulus E' (elastic component) during heating are specified. More specifically, in this embodiment, as the above-mentioned decrease characteristics, the storage elastic modulus E' at 30°C to 80°C is represented by the following exponential approximation curve: 30-80 The exponential coefficient when (hereinafter also referred to as "exponential coefficient k") is specified.

[0055] Exponential approximation curve: y = αe kx

[0056] y: storage elastic modulus E'

[0057] x: temperature (°C)

[0058] α: coefficient

[0059] e: Napier constant

[0060] k: exponential coefficient

[0061] In this embodiment, the index coefficient k is -0.035 to -0.070, preferably -0.040 to -0.070, more preferably -0.045 to -0.070, and even more preferably -0.050 to -0.070. By setting the index coefficient k to -0.035 or less, the storage elastic modulus E' decreases significantly when the temperature is increased from 30°C to 80°C, further improving the conformability at high temperatures. On the other hand, by setting the index coefficient k to -0.070 or greater, it is possible to prevent the degradation of the peelability caused by excessive conformability at high temperatures.

[0062] The coefficient α in this embodiment is preferably 1.00×10 8 ~8.00×10 8 , more preferably 2.00×10 8 ~6.00×10 8 , more preferably 2.50×10 8 ~4.50×10 8 By setting the coefficient α within the above range, the followability and the peeling properties tend to be further improved.

[0063] The exponential approximation curve is used to represent the characteristics of the storage elastic modulus E' curve at 30°C to 80°C, and therefore, it is preferable that it has sufficient correlation with the storage elastic modulus E' curve. 2 It is preferably 0.90 to 1.00, more preferably 0.94 to 1.00, and even more preferably 0.98 to 1.00. 2 In the above range, the exponential approximation curve more accurately represents the curve of the storage modulus E' at 30° C. to 80° C. Therefore, the exponential coefficient k more appropriately represents the characteristics of the storage modulus E'.

[0064] Storage elastic modulus E' of the substrate sheet at 80°C 80 Preferably 5.00×10 5 ~1.00×10 7 Pa, more preferably 7.00×10 5 ~8.00×10 6 Pa, more preferably 1.00×10 6 ~7.00×10 6 Pa. By making the storage elastic modulus E' 80 5.00×10 5 Pa or more, so that the excessive followability at high temperature is suppressed and the peeling property is further improved. 80 1.00×10 7 Pa or less, the followability at high temperatures tends to be further improved.

[0065] In addition, the storage elastic modulus E' of the substrate sheet at 30°C 30 Preferably 5.00×10 6 ~1.50×10 8 Pa, more preferably 8.00×10 6 ~1.00×10 8 Pa, more preferably 3.00×10 7 ~8.00×10 7 Pa. By making the storage elastic modulus E' 30 5.00×10 6 Pa or more, there is a tendency that adhesive residue is suppressed and peelability is further improved. 30 1.50×10 8 When the thickness is Pa or less, even if the base sheet is caught in the gaps between the projections during peeling, the projections are less likely to be damaged, and the peelability tends to be further improved.

[0066] Storage elastic modulus E' of the substrate sheet in the temperature range of 80 to 110°C 80-110 Preferably 1.00×10 6 ~1.00×10 7 Pa, more preferably 1.00×10 6 ~7.50×10 6 Pa, more preferably 1.00×10 6 ~5.00×10 6 Pa. By making the storage elastic modulus E' 80-110 1.00×10 6 Pa or more, there is a tendency that the decrease of the storage elastic modulus E' in the high temperature region is blunted. Therefore, there is a tendency that the excessive improvement of the followability is suppressed in the lamination at high temperature, and the peelability is further improved. In addition, by making the storage elastic modulus E' 80-110 1.00×10 7 Pa or less, there is a tendency for the followability at high temperature to be further improved. 80-110 1.00×10 6 ~1.00×10 7 Pa" refers to the storage elastic modulus E' in the temperature range of 80-110℃, which is 1.00×10 6 ~1.00×10 7 Pa range.

[0067] Storage elastic modulus E' of the substrate sheet 30 and storage elastic modulus E' 80 The difference (E' 30-E' 80 ) is preferably 4.00×10 7 ~4.00×10 8 Pa, more preferably 4.00×10 7 ~1.00×10 8 Pa, more preferably 4.00×10 7 ~8.00×10 7 Pa. By making the difference (E' 30 -E' 80 ) is 4.00×10 7 Pa or more, there is a tendency that the elasticity is sufficiently reduced at high temperature and the followability is further improved. 30 -E' 80 ) is 4.00×10 8 Pa or less tends to suppress the gaps in which the base sheet follows the convex portions, and the peeling property tends to be further improved.

[0068] (Loss modulus of elasticity E')

[0069] The base sheet of this embodiment may further have a loss modulus E" (viscous component) specified from the viewpoint of followability and peelability. From this viewpoint, the loss modulus E" of the base sheet at 80°C may be specified. 80 Preferably 1.50×10 4 ~1.50×10 6 Pa, more preferably 7.50×10 4 ~1.00×10 6 Pa, more preferably 1.00×10 5 ~9.00×10 5 Pa. By making the loss elastic modulus E" 80 1.50×10 4 Pa or more, there is a tendency for the followability to be further improved at high temperatures. In addition, by setting the loss modulus E"80 to 1.50×10 6 Pa or less, there is a tendency to suppress excessive conformability at high temperatures and further improve the releasability.

[0070] In addition, the loss modulus E" of the substrate sheet at 30°C 30 Preferably 1.00×10 6 ~1.50×10 8 Pa, more preferably 1.00×10 6 ~7.50×10 7 Pa, more preferably 1.00×10 6 ~5.00×10 7 Pa. By making the loss elastic modulus E" 301.00×10 6 Pa or more, thereby having the following tendency: further suppressing the situation that the base sheet is hooked in the gap of the convex part during peeling and causing the convex part to be damaged, and the peeling property is further improved. In addition, by making the loss elastic modulus E" 30 1.50×10 8 Pa or less, adhesive residue is suppressed and the releasability tends to be further improved.

[0071] Loss modulus of elasticity E" of the substrate sheet 30 and loss modulus E' 80 The difference (E”) 30 -E" 80 ) is preferably 1.00×10 5 ~5.00×10 8 Pa, more preferably 5.00×10 5 ~1.00×10 8 Pa, more preferably 1.00×10 6 ~5.00×10 7 Pa. By making the difference (E" 30 -E" 80 ) is 1.00×10 5 Pa or more, there is a tendency for the followability to be further improved. In addition, by making the difference (E" 30 -E" 80 ) is 5.00×10 8 Pa or less, the peeling property tends to be further improved.

[0072] (Melting Point)

[0073] The melting point of the substrate sheet is preferably 70°C or higher, more preferably 80°C or higher, and even more preferably 85°C or higher. A melting point of 70°C or higher can suppress the tendency of the substrate sheet to melt during heating. This prevents the substrate sheet from entering the gaps between the protrusions, thereby further improving the peelability. The upper limit of the melting point of the substrate sheet is not particularly limited, but is preferably 200°C, more preferably 150°C or lower, and even more preferably 120°C or lower.

[0074] Storage elastic modulus E' and its exponential coefficient k and determination coefficient R of the approximate curve 2 , loss modulus E", and melting point can be controlled by adjusting the type of resin used in the base sheet and the composition of the base sheet.

[0075] In addition, the dynamic viscoelasticity measurement of the present embodiment can be carried out according to a conventional method. As a sample, for example, a sample maintained in a constant temperature and humidity chamber at a temperature of 23°C (±2°C) and a relative humidity of 50% (±5%) can be used. In addition, as an apparatus, for example, the apparatus name "Rheometric Series RSA III" (manufactured by TA Instruments) can be used. Regarding other conditions, there are no particular restrictions and the conditions described in the examples can be used for measurement.

[0076] The melting point of the base sheet can be measured in accordance with JIS K7121.

[0077] The base sheet is mainly composed of a resin and may contain additives as needed. The resin may be used alone or in combination of two or more.

[0078] (resin)

[0079] As the resin used in the substrate sheet, there is no particular limitation, for example, ionomer resin, ethylene-vinyl acetate copolymer, soft polypropylene resin, ethylene-(methyl) acrylic acid copolymer resin, ethylene-butadiene copolymer resin, hydride resin of ethylene-butadiene copolymer, ethylene-1-butene copolymer resin, soft acrylic resin etc. can be enumerated.Wherein, preferred ionomer resin and ethylene-vinyl acetate copolymer, more preferably ionomer resin.By using such resin, there is the tendency that followability and strippability further improve.It should be noted that resin can be used alone or in combination with two or more.

[0080] The ionomer resin is not particularly limited as long as it is a resin obtained by intermolecular bonding of a prescribed polymer with a metal ion. For example, polyolefin ionomers, acrylic ionomers, polystyrene ionomers, and polyester ionomers can be mentioned. One of the ionomer resins can be used alone, or two or more can be used in combination. Among them, polyolefin ionomers and acrylic ionomers are preferred, and polyolefin ionomers are more preferred. By using such a resin, there is a tendency for the followability and stripping properties to be further improved.

[0081] The polyolefin-based ionomer is not particularly limited, and examples thereof include ethylene-methacrylate copolymers, ethylene-acrylate copolymers, and ethylene-methacrylate-acrylate copolymers.

[0082] The acrylic ionomer is not particularly limited, and examples thereof include acrylate-acrylate copolymers, acrylate-methacrylate copolymers, methacrylate-acrylate copolymers, and methacrylate-methacrylate copolymers.

[0083] The polystyrene-based ionomer is not particularly limited, and examples thereof include styrene-styrene sulfonate copolymers, styrene-acrylate copolymers, styrene-methacrylate copolymers, styrene-styrene carboxylate copolymers, and styrene-N-methyl-4-vinylpyridinium copolymers.

[0084] The polyester ionomer is not particularly limited, and examples thereof include polyethylene terephthalate copolymerized with sulfoterephthalate, polyethylene terephthalate copolymerized with sulfoisophthalate, polybutylene terephthalate copolymerized with sulfoterephthalic acid, and polybutylene terephthalate copolymerized with sulfoisophthalic acid.

[0085] The metal ions constituting the salt of the ionomer resin are not particularly limited, and examples thereof include monovalent metal ions such as sodium ions and lithium ions; divalent metal ions such as zinc ions, calcium ions, and magnesium ions; and trivalent metal ions such as aluminum ions. The polymer and metal ions in the ionomer resin can be used in any combination based on the ionic functional groups in the polymer and the valence of the metal ions.

[0086] The ethylene-vinyl acetate copolymer is not particularly limited as long as it is a copolymer of ethylene and vinyl acetate. The vinyl acetate content in the ethylene-vinyl acetate copolymer is preferably 1 to 35 mol%, more preferably 3 to 25 mol%, and even more preferably 3 to 15 mol%, relative to the total molar number of structural units derived from ethylene and vinyl acetate. When the vinyl acetate content is within this range, conformability and releasability tend to be further improved.

[0087] The soft polypropylene resin is not particularly limited, and examples thereof include those obtained by blending a rubber component with a polypropylene resin. The rubber component used here is not particularly limited, and examples thereof include styrene-butadiene copolymer rubber, styrene-butadiene-styrene block copolymer rubber, styrene-isoprene-styrene block copolymer rubber, and ethylene-propylene copolymer rubber.

[0088] The weight average molecular weight (Mw) of the resin used in the substrate sheet is preferably 10,000 to 1,000,000, more preferably 50,000 to 500,000.

[0089] (thickness)

[0090] The thickness of the substrate sheet is preferably 50 to 500 μm, more preferably 70 to 400 μm, and even more preferably 100 to 300 μm. By setting the thickness of the substrate sheet within this range, the substrate sheet tends to adequately conform to the irregularities on the wafer surface while maintaining its sheet strength. Consequently, the sheet is less likely to break during peeling, further improving peelability.

[0091] (Other ingredients)

[0092] The base sheet may contain other additives such as known plasticizers, heat stabilizers, colorants, organic lubricants, inorganic lubricants, surfactants, and processing aids as needed.

[0093] (Other layers)

[0094] The wafer processing sheet 10 of this embodiment may have another layer 12 (see FIG. 1 ) on the surface of the base sheet 11 opposite to the surface 11a (which contacts the wafer main surface 20a). Figure 1 The other layers 12 are not particularly limited, and examples thereof include: an adhesive layer for fixing the substrate sheet 11 in a state of being bonded to the wafer 20 to the workbench; a buffer layer between the substrate sheet 11 and the workbench, and the like.

[0095] The wafer processing sheet 10 of this embodiment can be any sheet used for the purpose of protecting the wafer main surface 20a before the processing process. There is no particular limitation on the layer composition other than the base sheet 11, and the other layers 12 can be arbitrarily combined and used according to the type of processing. It should be noted that the other layers 12 can be a single layer or a stack of layers having the same or different functions.

[0096] In addition, the wafer processing sheet 10 of this embodiment has the surface 11a of the base sheet 11 in contact with the wafer main surface 20a. Therefore, it is preferable that the surface 11a in contact with the surface of the wafer main surface 20a where the protrusions 20b are formed does not have an adhesive layer or the like.

[0097] Wafer processing method

[0098] The wafer processing method of this embodiment includes: a bonding step of bonding the heated surface of the substrate sheet of the wafer processing sheet to the main surface of the wafer; and a processing step of processing the wafer while the substrate sheet and the wafer are bonded. Figure 1 Each process is described.

[0099] 〔Lamination process〕

[0100] In the laminating step, the heated surface 11a of the substrate sheet 11 of the wafer processing sheet 10 is laminated to the main surface 20a of the wafer. In the laminating step, the substrate sheet 11 may be laminated to the main surface 20a of the wafer in a preheated state, or the substrate sheet 11 may be heated after laminating to the main surface 20a of the wafer.

[0101] By laminating the surface 11a of the base sheet 11 to the main surface 20a of the wafer in a heated state, the surface 11a can be laminated to the main surface 20a of the wafer in a state where the surface 11a follows the main surface 20a of the wafer (see FIG. Figure 1 B). In this way, the protrusions 20b are sunken into the base sheet 11, thereby protecting the main surface 20a of the wafer having the protrusions 20b.

[0102] The heating temperature is preferably 60 to 150°C, more preferably 70 to 120°C, and even more preferably 80 to 120°C. Furthermore, the heating time for the substrate sheet 11 is preferably 3 to 120 seconds, more preferably 5 to 90 seconds. By setting the heating conditions within this range, the conformability of the substrate sheet 11 tends to be further improved.

[0103] 〔Processing procedures〕

[0104] The processing steps for processing the wafer 20 while the substrate sheet 11 and wafer 20 are bonded together are not particularly limited, and any suitable wafer processing technique may be appropriately applied. For example, the processing steps include backside grinding, in which the backside 20a' of the wafer not bonded to the substrate sheet 11 is ground to obtain a thinned wafer 21; and dicing, in which the wafer 20 is diced to obtain semiconductor chips. The wafer processing method of this embodiment is particularly suitable for backside grinding.

[0105] The specific method for back grinding is not particularly limited, and known methods can be used. For example, a method of grinding while supplying a slurry containing abrasive grains to the back surface 20a' of the wafer can be used. The thickness of the resulting thinned wafer 21 is not particularly limited, as long as it is suitable for the processing purpose. As an example, it is preferably 300 μm or less, more preferably 150 μm or less, and even more preferably 50 μm or less.

[0106] During back grinding, a load is applied in the thickness direction of the wafer, which may damage the protrusions 20b and the like, and thus easily lead to a decrease in the yield rate. In contrast, by using the wafer processing sheet of this embodiment, processing can be performed with at least a portion of the protrusions 20b embedded in the base sheet 11, thereby avoiding damage to the protrusions 20b and the like.

[0107] Furthermore, the wafer processing sheet of this embodiment, because it possesses predetermined viscoelastic properties, allows the base sheet 11 to follow the main surface 20a of the wafer 20, protecting it while also achieving appropriate adhesion. This eliminates problems such as adhesive residue on the main surface 20a of the wafer 20, which occurs when using conventional adhesive sheets in which the protrusions 20b come into contact with the adhesive. Furthermore, there is no need to adhere the adhesive layer to the outer periphery of the wafer 20 with high positional accuracy, as with conventional wafer processing sheets in which the adhesive layer is attached to the outer periphery of the wafer 20. This further simplifies the processing process.

[0108] [Peeling process]

[0109] The wafer processing method of this embodiment may include a peeling step of peeling the thinned wafer 21 from the base sheet 11. The peeling method of the base sheet 11 is not particularly limited, for example, Figure 1 As shown, this can be achieved by bending the base sheet 11 in the direction F so that one end of the base sheet 11 is away from the thinned wafer 21 .

[0110] The peeling step may be performed at room temperature or under heating. The temperature for performing the peeling step is preferably 10 to 70°C, more preferably 20 to 60°C.

[0111] When using a conventional wafer processing sheet having an adhesive layer, adhesive residue on the main surface 20a of the wafer 20 becomes a problem. However, the wafer processing sheet of this embodiment has predetermined viscoelastic properties, and thus can be peeled off without adhesive residue.

[0112] It should be noted that, as mentioned above, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made without departing from the scope of the present invention. In other words, the above-mentioned embodiments are merely illustrative in all respects and are not to be construed as limiting.

[0113] For example, the lamination in the lamination process can be performed under normal pressure or under reduced pressure. In addition, a curable resin can be used instead of other layers 12 or on its basis. When using a curable resin, for example, the curable resin is supplied to the film so that the curable resin is spread on the surface of the substrate sheet 11 opposite to the surface 11a (which contacts the wafer main surface 20a), so that the surface opposite to the surface 11a is placed opposite to the film and pressurized. Then, by hardening the curable resin, the wafer processing sheet 10 can be fixed to the film.

[0114] also, Figure 1Although the back grinding process is mainly exemplified, the wafer processing sheet of this embodiment can also be used in dicing and other wafer processing processes.

[0115] Example

[0116] Hereinafter, the present invention will be described in more detail using Examples and Comparative Examples. However, the present invention is not limited to the following Examples.

[0117] [Example 1]

[0118] An ethylene-methacrylic acid-acrylic acid ester zinc salt copolymer was formed into a 150 μm-thick base sheet (manufactured by GUNZE, product name “HMD-150”) by a T-die method.

[0119] [Example 2]

[0120] An ethylene-vinyl acetate copolymer was formed into a 150 μm-thick base sheet (manufactured by RIKENTECHNOS, product name “EU90B”, vinyl acetate content 6 mol%) by a T-die method.

[0121] [Comparative Example 1]

[0122] An ethylene methacrylic acid copolymer (a resin manufactured by DuPont Mitsui Chemicals, product name "Nucrel N0407") was formed into a base sheet having a thickness of 150 μm by the T-die method.

[0123] [Comparative Example 2]

[0124] Low-density polyethylene was formed into a base sheet having a thickness of 150 μm by an inflation method (product name: “N-280”, manufactured by Aicello Co., Ltd.).

[0125] [Comparative Example 3]

[0126] A linear low-density polyethylene was formed into a base sheet having a thickness of 150 μm by an inflation method (product name: “N-165”, manufactured by Aicello Co., Ltd.).

[0127] [Comparative Example 4]

[0128] A hydrogenated styrene-based thermoplastic elastomer (manufactured by Asahi Kasei Corporation, resin product name "H1041") was formed into a base sheet having a thickness of 150 μm by the T-die method.

[0129] [Comparative Example 5]

[0130] Unstretched polypropylene was formed into a base sheet having a thickness of 150 μm by a T-die method (manufactured by Futamura Co., Ltd., product name “FRTK-S”).

[0131] [Comparative Example 6]

[0132] Urethane resin was formed into a base sheet having a thickness of 150 μm by a T-die method (manufactured by Japan Matai Co., Ltd., product name: “Esmer URS”).

[0133] Dynamic viscoelasticity measurement

[0134] The dynamic viscoelasticity of each of the above-mentioned substrate sheets was measured under the following conditions. First, the substrate sheet was maintained in a constant temperature and humidity chamber at 23°C (±2°C) and 50% (±5%) relative humidity for 40 hours. The resulting substrate sheet was used as a sample and the dynamic viscoelasticity was measured under normal atmospheric conditions (dry state). A "Rheometric Series RSA III" (manufactured by TA Instruments) was used as the dynamic viscoelasticity measuring apparatus.

[0135] (Measurement conditions)

[0136] Measuring device: "Rheometric Series RSA III" (manufactured by TA Instruments)

[0137] Sample: 1cm long × 0.5cm wide × 0.2cm thick

[0138] Test length: 1cm

[0139] Sample pretreatment: Keep in an atmosphere with a temperature of 23°C and a relative humidity of 50% for 40 hours

[0140] Test mode: tensile

[0141] Frequency: 1.6 Hz (10 rad / s)

[0142] Temperature range: 0~150℃

[0143] Heating rate: 5℃ / min

[0144] Strain range: 0.10%

[0145] Initial load: 148g

[0146] Measurement interval: 1 point / °C

[0147] The storage elastic modulus E' and loss elastic modulus E" obtained by the above measurement are shown in Figure 3 、 5 ~11. In addition, based on Figure 3 、 5 ~11, calculate the storage elastic modulus E' at 30℃~80℃ 30-80The exponential approximation curve of the storage elastic modulus E' and the loss elastic modulus E", as well as the values ​​related to the exponential approximation curve are summarized in Table 1. It should be noted that Figure 4 As an example, the exponential approximation curve and the determination coefficient R are described in the graph showing the results of the dynamic viscoelasticity measurement of Example 1. 2 The resulting coordinate diagram. Figure 4 (a) is a coordinate diagram showing the storage elastic modulus E' on a logarithmic scale, and is Figure 3 The figure was extracted in the temperature range of 30℃~80℃. Figure 4 (b) is not expressed in logarithmic scale in order to show the shape of the exponential approximation curve. Figure 4 (a) Coordinate diagram of the storage elastic modulus E'.

[0148] Exponential approximation curve: y = αe kx

[0149] y: storage elastic modulus E'

[0150] x: temperature (°C)

[0151] α: coefficient

[0152] e: Napier constant

[0153] k: exponential coefficient

[0154] Follow-up test

[0155] The substrate sheet obtained in the above manner was used as a wafer processing sheet and was pressed at 100°C for 1 minute to adhere to the surface of the wafer on which the protrusions were formed. The wafer used was an 8-inch diameter, 725 μm thick wafer. Furthermore, the protrusions formed on the wafer had bumps (projecting electrodes) with a height of 230 μm formed in the area outside the 3.0 mm outer periphery.

[0156] Then, the temperature was temporarily lowered to room temperature (25°C), and the base sheet was peeled off from the wafer at room temperature. The cross section of the base sheet after peeling was observed and evaluated to see whether its cross section shape belonged to Figure 2 Which of A to C shown in the table. The results are shown in Table 1. Figure 12 Photographs showing cross sections of the substrate sheets in Example 1, Comparative Example 2, and Comparative Example 3 are shown.

[0157] 〔Peelability test〕

[0158] After the base sheet was peeled from the wafer as described above, the surface of the wafer was observed and the peelability was evaluated according to the following criteria.

[0159] (Evaluation criteria for adhesive residue)

[0160] A: No substrate sheet residue was observed on the wafer surface

[0161] B: Slight residue of the substrate sheet is observed on the wafer surface

[0162] C: Residue of the substrate sheet is observed on the wafer surface

[0163] (Evaluation criteria for convex part damage)

[0164] A: No damage is observed on the convex portion of the wafer, or the wafer can be easily peeled off.

[0165] B: Slight damage is observed on the convex portion of the wafer, or peeling requires a little effort, which may damage the convex portion.

[0166] C: Damage was observed on the convex portion of the wafer, or peeling required considerable effort, and the convex portion was likely damaged.

[0167] [Table 1]

[0168]

[0169] Although the followability of Comparative Examples 1 and 4 was relatively good, adhesive residue remained on the wafer surface, resulting in a decrease in the yield rate during the processing. Furthermore, in Comparative Examples 2 and 5, the followability was too high, resulting in the substrate sheet entering the gaps between the protrusions. This increased the likelihood of damage to the protrusions during peeling, and further, adhesive residue was likely to remain. Furthermore, in Comparative Examples 3 and 6, the followability was low, resulting in inadequate protection of the protrusions. Consequently, when back grinding of the semiconductor wafer was performed with only the front ends of the protrusions in contact with the substrate sheet, excessive load was applied to the protrusions during back grinding and other processing, causing damage to the protrusions, potentially leading to a decrease in the yield rate during the processing.

[0170] Industrial applicability

[0171] The wafer processing sheet of the present invention has industrial applicability as a protective sheet used in back grinding, dicing, and other wafer processing processes.

[0172] Description of Reference Numerals

[0173] 10 ...wafer processing sheet, 11 ...substrate sheet, 11a ...surface, 12 ...layer, 20 ...semiconductor wafer, 20a ...main surface, 20b ...protrusion, 20a' ...back surface, 21 ...thinned wafer, 31 ...gap, 32 ...space, 33 ...ripple, 34 ...gap

Claims

1. A wafer processing sheet comprising a base sheet in contact with a main surface of a wafer, The storage elastic modulus E' of the substrate sheet at 30°C to 80°C 30-80 The exponential coefficient of the exponential approximation curve is -0.035 to -0.070, and the resin used in the substrate sheet is one or more selected from ionomer resin, ethylene-vinyl acetate copolymer, soft polypropylene resin, ethylene-(meth)acrylic acid copolymer resin, ethylene-butadiene copolymer resin, hydrogenated resin of ethylene-butadiene copolymer, ethylene-1-butene copolymer resin, and soft acrylic resin.

2. The wafer processing sheet according to claim 1, wherein Storage elastic modulus E' of the substrate sheet at 30°C 30 Storage elastic modulus E' at 80℃ 80 The difference (E' 30 -E' 80 ) is 4.00×10 7 ~4.00×10 8 Pa.

3. The wafer processing sheet according to claim 1 or 2, wherein: Storage elastic modulus E' of the substrate sheet at 80°C 80 5.00×10 5 ~1.00×10 7 Pa.

4. The wafer processing sheet according to claim 1, wherein The storage elastic modulus E' of the substrate sheet in the temperature range of 80 to 110°C 80-110 1.00×10 6 ~1.00×10 7 Pa.

5. The wafer processing sheet according to claim 1, wherein Loss elastic modulus E" of the substrate sheet at 80°C 80 1.50×10 4 ~1.50×10 6 Pa.

6. The wafer processing sheet according to claim 1, wherein Loss elastic modulus E" of the substrate sheet at 30°C 30 1.00×10 6 ~1.50×10 8 Pa.

7. The wafer processing sheet according to claim 1, wherein The melting point of the substrate sheet is 70° C. or higher.

8. A method for processing a wafer, comprising: a laminating step of laminating the heated surface of the substrate sheet of the wafer processing sheet according to any one of claims 1 to 7 to the main surface of the wafer; and A processing step of processing the wafer in a state where the base sheet and the wafer are bonded together.

9. The wafer processing method according to claim 8, wherein: In the processing step, the main surface of the wafer to which the base sheet is not bonded is polished to obtain a thinned wafer.

10. The wafer processing method according to claim 8, wherein: In the processing step, the wafer is cut into pieces to obtain semiconductor chips.

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