United States Patent (19)
`Umehara et al.
`
`54
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`(75)
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`WAFER DICING/BONDING SHEET AND
`PROCESS FOR PRODUCING
`SEMCONDUCTOR DEVICE
`
`Inventors: Norito Umehara; Masazumi Amagai,
`both of Hayami-gun; Mamoru
`Kobayashi, Yoshikawa; Kazuyoshi
`Ebe, Minamisaitama-gun, all of Japan
`
`Assignees: Texas Instruments Japan, Ltd.; Lintec
`Corporation, both of Japan
`
`Appl. No.: 09/099,229
`Filed:
`Jun. 17, 1998
`Related U.S. Application Data
`
`62
`
`Division of application No. 08/786,659, Jan. 21, 1997, Pat.
`No. 5,882.956.
`Foreign Application Priority Data
`30
`Jan. 22, 1996
`JP
`Japan ........................................ 8-8049
`Int. Cl." ............................................... B32B 27/06
`51
`52)
`U.S. Cl. ..................
`... 428/473.5; 428/480
`58
`Field of Search ................................. 428/473.5, 480,
`428/213
`
`56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`4,687,693 8/1987 Sheyon et al. .......................... 428/148
`4.793,883 12/1988 Sheyon et al. .......................... 156/235
`
`USOO6007920A
`Patent Number:
`11
`(45) Date of Patent:
`
`6,007,920
`Dec. 28, 1999
`
`5,110,388 5/1992 Komyama et al. ..................... 156/229
`5,118,567 6/1992 Komiyama et al. .................... 428/345
`5,316,853 5/1994 Shibata et al. .......................... 428/416
`5,411,921
`5/1995 Negoro .................................... 438/118
`5,527,998 6/1996 Anderson et al. ...................... 174/255
`5,692,297 12/1997 Noda ......................................... 29/845
`5,705,016
`1/1998 Senoo et al. ............................ 156/289
`
`FOREIGN PATENT DOCUMENTS
`0478250 4/1992 European Pat. Off..
`622833 11/1994 European Pat. Off..
`5-191918 4/1993 Japan.
`5-191919 7/1993 Japan.
`5-335354A 12/1993 Japan.
`WO9512895 5/1995 WIPO.
`
`Primary Examiner D. S. Nakarani
`Attorney, Agent, or Firm Webb Ziesenheim Logsdon
`Orkin & Hanson, P.C.
`57
`ABSTRACT
`The wafer dicing/bonding sheet of the present invention
`comprises a Soft film, a preSSure Sensitive adhesive layer
`formed on the Soft film, a processing film for polyimide type
`resin composed of a heat resistant resin which has been
`formed on the pressure Sensitive adhesive layer and a
`polyimide adhesive layer formed on the processing film. It
`is preferred that the processing film be a polyethylene
`naphthalate film whose Surface has been Subjected to an
`alkyd release treatment. The present invention facilitates
`expansion to be conducted after the wafer dicing.
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`5 Claims, 2 Drawing Sheets
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`U.S. Patent
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`Dec. 28, 1999
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`MICRON 1034
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`U.S. Patent
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`Dec. 28, 1999
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`1
`WAFER DICING/BONDING SHEET AND
`PROCESS FOR PRODUCING
`SEMCONDUCTOR DEVICE
`
`CROSS REFERENCE TO RELATED
`APPLICATION
`This application is a divisional of U.S. patent application
`Ser. No. 08/786,659 entitled “Wafer Dicing/Bonding Sheet
`and Process for Producing Semiconductor Device' filed on
`Jan. 21, 1997, now U.S. Pat. No. 5,882,956, which corre
`sponds to Japanese Application No. 008049/1996 filed on
`Jan. 22, 1996.
`
`FIELD OF THE INVENTION
`The present invention relates to a wafer bonding sheet for
`use in the process in which a plurality of Semiconducting
`integrated circuits formed on a Semiconductor wafer, for
`example, a Silicon wafer are diced into individual Separate
`Semiconducting integrated circuits, i.e., IC chips (also
`referred to as “chips” or “dies”) and the IC chips are
`mounted on, for example, a lead frame for package and
`relates to a process for producing a Semiconductor device
`which includes the above process.
`
`BACKGROUND OF THE INVENTION
`A Semiconductor wafer of, for example Silicon or gallium
`arsenide is produced in the form of a large diameter. This
`wafer is cut and separated (diced) into IC chips and is
`Subjected to the Subsequent die bonding step (also referred
`to as "mounting Step') in which the IC chips are mounted on
`a lead frame for package. In this process, the Semiconductor
`Wafer undergoes dicing, cleaning, drying, expansion and
`pickup Steps in the State of being attached to an adhesive
`sheet, and transferred to the Subsequent die bonding Step.
`Adhesive sheets which are intended for use in the pro
`cessing Steps of wafers, from the dicing Step up to the pickup
`Step, are desired to have an adhesive force Sufficient to retain
`wafers and/or chips thereon in the course from the dicing
`Step up to the expanding Step, but in the pickup step, they are
`desired to only retain an adhesion force of Such an extent
`that no adhesive remains on the picked-up wafer and/or
`chips.
`In the die bonding Step, the picked up IC chips are fixed
`on IC chip mount Zones (simply, mount Zones) of a lead
`frame by means of an IC chip bonding adhesive Such as an
`epoxy adhesive, a polyimide adhesive or a Silver paste which
`is fed in the form of a Viscous liquid to form an adhesive coat
`on the mount Zones, followed by being Subjected to the wire
`bonding Step and resin mold Step, thereby obtaining a
`semiconductor device. However, when the size of each of
`the IC chips is very small, it is difficult to uniformly apply
`an appropriate amount of adhesive with the use of the above
`liquid adhesive, so that the adhesive outflows the IC chips.
`On the other hand, when the size of each of the IC chips is
`very large, the use of the above liquid adhesive has encoun
`tered the problems such that the amount of the adhesive is
`Short to thereby disenable bonding which ensures a Satis
`factory bonding Strength. In recent years, the degree of
`integration of each Semiconductor chip tends to increase, So
`that the chip tends to have an enlarged Surface area and the
`wiring tends to become fine and a multilayer. On the other
`hand, the package in which the chips are accommodated
`tends to become miniaturized and thinner So that the mount
`on a printed wiring board can be conducted in high density.
`The obtained thin package with an enlarged Surface area has
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`encountered the problems. Such that the thermal shock and
`hot moisture resistances are poor and the package is likely
`to crack in the Surface mount Step, as compared with that of
`the prior art.
`A film adhesive of a polyimide type resin having excellent
`heat resistance has been proposed for use in the bonding of
`IC chips to the lead frame. Further, it has been proposed to
`employ a dicing sheet comprising a Substrate film and,
`detachably laminated thereto, Such an adhesive for bonding
`of IC chips, which dicing sheet can Simultaneously be used
`in dicing and die bonding.
`However, the use of the polyimide adhesive in the above
`dicing sheet has encountered the limitation in employable
`Substrate film because the Solvent component of the poly
`imide adhesive has high boiling point and high polarity.
`Further, the above substrate film is generally so hard that the
`expansion thereof is not easy. Thus, it is difficult to enlarge
`the IC chip spacing with the result that erroneous operation
`is occasionally caused in the pickup of IC chips.
`
`OBJECT OF THE INVENTION
`The present invention has been made in the above situ
`ation of the prior art. It is an object of the present invention
`to facilitate the expansion of the wafer dicing/bonding sheet
`in which a polyimide adhesive is used. Another object of the
`present invention is to provide a process for producing a
`Semiconductor device in which package cracking hardly
`CWC OCCU.S.
`
`SUMMARY OF THE INVENTION
`The wafer dicing/bonding sheet of the present invention is
`composed of
`a sheet for expanding process comprising a Soft film and,
`formed thereon, a pressure Sensitive adhesive layer, and
`a polyimide bonding sheet comprising a processing film
`for polyimide type resin and, formed thereon, a poly
`imide adhesive layer.
`The first process for producing a Semiconductor device
`according to the present invention comprises the Steps of:
`conducting a thermocompression bonding of a Semicon
`ductor wafer to a polyimide adhesive layer of the wafer
`dicing/bonding sheet which is composed of
`a sheet for expanding process comprising a Soft film and,
`formed thereon, a pressure Sensitive adhesive layer, and
`a polyimide bonding Sheet comprising a processing
`film for polyimide type resin and, formed thereon, the
`polyimide adhesive layer,
`dicing the Semiconductor wafer into IC chips,
`expanding the wafer dicing/bonding sheet So as to enlarge
`IC chip spacings,
`peeling from the processing film for polyimide type resin
`the IC chips having the polyimide adhesive layer
`Sticking thereto on their backs, and
`placing the IC chips on a lead frame in a manner Such that
`the polyimide adhesive layer is interposed between the
`IC chips and the lead frame to thereby bond the IC
`chips to the lead frame.
`The Second proceSS for producing a Semiconductor device
`according to the present invention comprises the Steps of:
`conducting a thermocompression bonding of a Semicon
`ductor wafer to a polyimide adhesive layer of a poly
`imide bonding sheet which comprises
`a processing film for polyimide type resin and, formed
`thereon, the polyimide adhesive layer;
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`attaching a sheet for expanding proceSS comprising a Soft
`film and, formed thereon, a pressure Sensitive adhesive
`layer to the polyimide bonding sheet in a manner Such
`that the pressure Sensitive adhesive layer contacts an
`exposed Surface of the processing film for polyimide
`type resin of the polyimide bonding Sheet,
`dicing the Semiconductor wafer into IC chips,
`expanding the sheet for expanding proceSSSO as to enlarge
`IC chip spacings,
`peeling from the processing film for polyimide type resin
`the IC chips having the polyimide adhesive layer
`Sticking thereto on their backs, and
`placing the IC chips on a lead frame in a manner Such that
`the polyimide adhesive layer is interposed between the
`IC chips and the lead frame to thereby bond the IC
`chips to the lead frame.
`In the present invention as described above, it is preferred
`that the processing film for polyimide type resin as a
`constituent member of the polyimide bonding sheet be made
`from a resin having a melting point of 230 C. or higher,
`preferably, 250 to 300° C. The processing film for polyimide
`type resin is preferred to have a Surface tension of less than
`40 dyn/cm. In particular, in the present invention, it is
`preferred that the processing film for polyimide type resin be
`composed of a polyethylene naphthalate resin.
`Further, in the present invention, it is preferred that the
`preSSure Sensitive adhesive layer have a Surface area which
`can be Supported by a wafer dicing ring frame and the
`polyimide adhesive layer have an outside diameter which is
`Smaller than an inside diameter of the wafer dicing ring
`frame.
`
`BRIEF DESCRIPTION OF THE DRAWING
`FIG. 1 is a sectional view of the wafer dicing/bonding
`sheet of the present invention;
`FIG. 2 shows the state of fixing the wafer dicing/bonding
`sheet by means of a ring frame;
`FIG. 3 shows the state of being about to fix the polyimide
`bonding sheet having a Silicon wafer attached thereto by
`thermocompression bonding on the sheet for expanding
`proceSS,
`FIG. 4 shows the state of dicing the silicon wafer; and
`FIG. 5 shows the state of picking up the IC chips after
`expanding the wafer dicing/bonding Sheet.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`The wafer dicing/bonding sheet, process for producing a
`Semiconductor device, polyimide bonding sheet and pro
`cessing film for polyimide type resin according to the
`present invention will be described in detail below.
`Referring to FIG. 1, the wafer dicing/bonding sheet 10 of
`the present invention is composed of
`a sheet for expanding proceSS 8 comprising a Soft film 1
`and, formed thereon, a pressure Sensitive adhesive layer
`2, and
`the polyimide bonding sheet 7 comprising a processing
`film for polyimide type resin 3 being formed on the
`preSSure Sensitive adhesive layer 2 and, formed
`thereon, a polyimide adhesive layer 4. Before the use of
`the wafer dicing/bonding sheet 10 of the present
`invention, a release film may be laminated to the upper
`Surface thereof in order to protect the pressure Sensitive
`adhesive layer 2 and the polyimide adhesive layer 4.
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`4
`The configuration of the wafer dicing/bonding sheet of the
`present invention is not particularly limited, and, for
`example, the wafer dicing/bonding sheet may have the form
`of a tape or a label.
`The Soft film 1 as a constituent member of the sheet for
`expanding process 8 is composed of a resin film which is
`extensible in not only the direction of the length but also the
`direction of the width. Although various resin films are
`available, it is preferred that the Young's modulus thereof be
`not greater than 10x10 kg/cm, especially, in the range of
`5.0x10 to 5.0x10 kg/cm.
`Examples of such soft film 1 include a film of
`polyethylene, poly Vinyl chloride, poly but ene,
`polybutadiene, polyurethane, polyester, polyamide,
`ethylene/vinyl acetate copolymer, ethylene/(meth) acrylic
`acid copolymer, ethylene/methyl (meth)acrylate copolymer,
`ethylene/ethyl (meth)acrylate copolymer or the like. The
`soft film 1 may also be a laminate of at least two films
`selected from among the above. The thickness of the soft
`film 1 generally ranges from about 10 to 300 um, preferably,
`from about 50 to 200 um.
`The preSSure Sensitive adhesive layer 2 as a constituent
`member of the sheet for expanding process 8 holds the
`processing film for polyimide type resin 3 to adhere to the
`Soft film 1 during the dicing and pickup steps. By adjusting
`the Surface areas of processing film for polyimide type resin
`3 and polyimide adhesive layer 4 being smaller than the
`inside diameter of the ring frame, it is possible to detachably
`Support the ring frame on the pressure Sensitive adhesive
`layer 2.
`The pressure Sensitive adhesive layer 2 can be composed
`of various conventional pressure Sensitive adhesives Such as
`acrylic, rubber, polyurethane, Silicone and polyester adhe
`Sives. Among them, acrylic adhesive is preferred from the
`Viewpoint, for example, that the control of adhesion char
`acteristics is easy.
`The acrylic pressure Sensitive adhesive comprises an
`acrylic copolymer as a principal component.
`The acrylic copolymer is generally obtained by copoly
`merizing a (meth)acrylic ester monomer having an alkyl
`group of 1 to 18 carbon atoms as a main monomer with a
`monomer having a functional group Such as hydroxyl,
`carboxyl or amino or other copolymerizable monomer.
`Although the molecular weight of the acrylic copolymer
`is not particularly limited, the weight average molecular
`weight thereof generally ranges from 1.0x10 to 1.0x10,
`preferably, from 4.0x10 to 8.0x10.
`The adhesive and cohesive forces of the acrylic pressure
`Sensitive adhesive having a functional group can be con
`trolled by adding an appropriate crosslinking agent. This
`crosslinking agent may be, for example, a polyvalent iso
`cyanate compound, a polyvalent epoxy compound, a poly
`Valent aziridine compound, a metal chelate compound or the
`like.
`The above component of the pressure Sensitive adhesive
`can be used singly or the combination of two or more
`components. Further, additives Such as a tackifier and a filler
`may be added to the pressure Sensitive adhesive.
`The thickness of the pressure Sensitive adhesive layer 2 is
`preferred to range from 1 to 50 lum, especially, from 5 to 30
`plm.
`The processing film for polyimide type resin 3 as a
`constituent member of the polyimide bonding sheet 7 is
`preferably made from a heat resistant resin. The melting
`point of the above resin is preferably at least 230 C., still
`preferably, 250 to 300° C. and, yet still preferably, 260 to
`280 C. The surface tension of the processing film for
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`polyimide type resin 3 is preferred to be less than 40 dyn/cm,
`especially, 30 to 40 dyn/cm. It is desired that the below
`described polyimide adhesive layer 4 be formed on the
`Surface having the above Surface tension. The employment
`of the surface tension of 30 to 40 dyn/cm ensures excellent
`transferability of the polyimide adhesive layer 4 from the
`processing film for polyimide type resin 3 and excellent chip
`retention at the use in dicing.
`Examples of Such processing film for polyimide type resin
`3 include a film of polyethylene naphthalate, polyethylene
`terephthalate, polybutylene terephthalate, polyimide,
`polyether-imide, polyaramid, polyether-ketone, polyether
`ether-ketone, polyphenylene Sulfide or the like. The proceSS
`ing film for polyimide type resin 3 may also be a laminate
`of at least two films Selected from among the above or a
`laminate of a film Selected from among the above and
`another film. Of them, the use of a polyethylene naphthalate
`film is especially preferred.
`The thickness of the processing film for polyimide type
`resin 3 generally ranges from about 10 to 300 um,
`preferably, from about 16 to 100 um, although depending on
`the type of the material thereof. For realizing the above
`Surface tension value, it is preferred to Subject one side of the
`processing film for polyimide type resin 3 with a release
`treatment and dispose the polyimide adhesive layer 4 on the
`Surface having been Subjected to the release treatment.
`The above release agent used in the release treatment is,
`for example, an alkyd, a Silicone, a fluorinated, an unsatur
`ated polyester, a polyolefin or a wax release agent. Of these,
`alkyd, Silicone and fluorinated release agents are preferred
`because of their Superior heat resistances. The alkyd release
`agent is especially preferred because its adherence to the
`processing film for polyimide type resin as a Substrate is
`high and the regulation of the Surface tension is easy.
`In the release treatment of the Surface of the processing
`film for polyimide type resin 3 with the use of the above
`release agent, the release agent as it is without the use of any
`solvent or after being diluted with a solvent or emulsified is
`applied by means of a gravure coater, a Mayor bar coater, an
`air knife coater, a roll coater or the like and cured at ordinary
`temperature or raised temperature or with electron beam
`radiation. Alternatively, a laminate may be formed by the use
`of a wet lamination, a dry lamination, a hot melt lamination,
`a melt extrusion lamination or a coextrusion technique.
`The use of the above processing film for polyimide type
`resin 3 avoids the direct contact of the below described
`polyimide adhesive layer 4 with the pressure Sensitive
`adhesive layer 2, So that component migration can be
`prevented therebetween to thereby reduce package cracking
`in the Semiconductor device as a final product.
`The polyimide type resin used in the polyimide adhesive
`layer 4 as a constituent member of the polyimide bonding
`sheet 7 includes a polyimide resin itself and a precursor of
`polyimide resin. The polyimide resin has an imide bond in
`its side chain or main chain. The precursor of polyimide
`resin is those giving the above polyimide resin at the final
`bonding Stage. Examples of Such polyimide type resin
`include a polyimide resin, a polyisoimide resin, a maleimide
`resin, a bismaleimide resin, a polyamide-imide resin, a
`polyether-imide re S in and a polyimide -
`isolindoloquinazolinedionimide resin. These resins may be
`used either individually or in combination. Of them, a
`polyimide type resin is especially preferred.
`The molecular weight of the polyimide type resin is
`preferred to range from 10,000 to 1,000,000, especially,
`from about 50,000 to 100,000.
`A thermoplastic polyimide type resin having no reactive
`functional group and a thermosetting polyimide type resin
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`which undergoes an imidation reaction upon heating are
`available and both may be used in the present invention. In
`the use of the thermosetting polyimide type resin, a tempo
`rary bonding is first effected with the use of the resin in a
`Semicured Stage (generally known as "B Stage') and then a
`thermal curing is performed to thereby convert the adhesive
`layer into a polyimide. Thus, the bonding Step is completed.
`The polyimide adhesive may comprise another polymer
`or oligomer or a low molecular weight compound in addi
`tion to the polyimide type resin. Examples of Such additives
`include various polymers and oligomerS Such as epoxy,
`amide, urethane, amic acid, acrylic and Silicone resins and
`nitrogen-containing organic compounds Such as triethano
`lamine and C, co-bis(3-amino-propyl) polyethylene glycol
`ether.
`A solvent which can uniformly dissolve or disperse the
`above components can be used in the preparation of a
`composition of the polyimide adhesive. This Solvent is not
`particularly limited as long as it can uniformly dissolve or
`disperse the above materials, and examples of Such Solvents
`include dimethylformamide, dimethylacetamide,
`N-methylpyrrolidone, dimethylsulfoxide, diethylene glycol
`dimethyl ether, toluene, benzene, Xylene, methyl ethyl
`ketone, tetrahydrofuran, ethyl celloSolve, dioxane, cyclo
`pentanone and cyclohexanone. These may be used either
`individually or in combination.
`The thickness of the polyimide adhesive layer 4 is pre
`ferred to range from about 1 to 50 lum, especially, from about
`5 to 20 lum.
`The wafer dicing/bonding sheet 10 of the present inven
`tion comprises the sheet for expanding process 8 and, fixed
`thereto, the polyimide bonding sheet 7. Concretely, the
`wafer dicing/bonding sheet 10 is obtained by piling the soft
`film 1, pressure Sensitive adhesive layer 2, processing film
`for polyimide type resin 3 and polyimide adhesive layer 4
`one upon another in this order. Also, the wafer dicing/
`bonding sheet 10 can be produced by Separately preparing a
`laminate (sheet for expanding process 8) of the soft film 1
`and the pressure Sensitive adhesive layer 2 and a laminate
`(polyimide bonding sheet 7) of the processing film for
`polyimide type resin 3 and the polyimide adhesive layer 4
`and then piling the laminates one upon the other.
`In the wafer dicing/bonding sheet 10 of the present
`invention, it is preferred that the Surface area of the preSSure
`Sensitive adhesive layer 2 be made larger than that of the
`processing film for polyimide type resin 3 to thereby expose
`part of the pressure Sensitive adhesive layer 2, as shown in
`FIG. 1. The exposed part of the pressure sensitive adhesive
`layer 2 is used to bond the ring frame 5 for fixing the sheet
`10 at the time of dicing, as shown in FIG. 2.
`That is, in the wafer dicing/bonding sheet 10 of the
`present invention, it is preferred that the pressure Sensitive
`adhesive layer 2 have a Surface area which can be Supported
`by a wafer dicing ring frame 5 and the polyimide adhesive
`layer 4 have an outside diameter which is Smaller than an
`inside diameter of the wafer dicing ring frame 5. In this
`wafer dicing/bonding sheet 10, the outside diameter of the
`processing film for polyimide type resin 3 is identical with
`or larger than the outside diameter of the polyimide adhesive
`layer 4 and is Smaller than the inside diameter of the ring
`frame.
`A wafer can be bonded at an adhesive Strength of,
`preferably, at least 100 g/25 mm and, still preferably, at least
`400 g/25 mm onto the wafer dicing/bonding sheet of the
`present invention by a thermocompression bonding which is
`conducted at about 100 to 300° C., preferably, about 120 to
`150° C. under a pressure of about 1 to 10 kg/cm’, preferably,
`about 1 to 4 kg/cm.
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`The proceSS for producing a Semiconductor device
`according to the present invention will be described below.
`In the first proceSS for producing a Semiconductor device
`according to the present invention, initially, the bonding
`sheet 10 is fixed on a dicing apparatus by means of the ring
`frame 5, and a thermocompression bonding of one side of a
`Silicon wafer 6 is conducted to the polyimide adhesive layer
`4 of the bonding sheet 10. The thermocompression bonding
`is conducted under the above conditions. Subsequently, the
`above silicon wafer 6 is cut into IC chips by the use of
`cutting means Such as a dicing Saw (refer to FIG. 4). The
`cutting depth is determined taking into account the thickneSS
`of the silicon wafer 6, the polyimide adhesive layer 4, the
`processing film for polyimide type resin 3 and the dicing Saw
`wear. Thereafter, the bonding sheet 10 is expanded so that
`the IC chip Spacings are enlarged to thereby facilitate the
`pickup of IC chips, as shown in FIG. 5. The pickup of IC
`chips enables peeling from the processing film for polyimide
`type resin 3 the IC chips in the state of having the cut
`polyimide adhesive layer Sticking thereto on their backS.
`That is, the adhesive strength between the IC chips and the
`polyimide adhesive layer is greater than that between the
`polyimide adhesive layer and the processing film for poly
`imide type resin, So that the IC chips can be peeled in the
`State of having the polyimide adhesive layer Sticking thereto
`on their one sides from the processing film for polyimide
`type resin.
`In the Second proceSS for producing a Semiconductor
`device according to the present invention, a polyimide
`bonding sheet 7 comprising a heat resistant processing film
`for polyimide type resin 3 and, formed thereon, a polyimide
`adhesive layer 4 and a sheet for expanding process 8
`comprising a Soft film 1 and, formed thereon, a preSSure
`Sensitive adhesive layer 2 are separately provided.
`Subsequently, referring to FIG. 3, a thermocompression
`bonding of a Silicon wafer 6 is conducted to the polyimide
`adhesive layer 4 of the polyimide bonding sheet 7. The
`thermocompression bonding is conducted under the above
`conditions. Thereafter, the processing film for polyimide
`type resin 3 of the polyimide bonding sheet 7 attached by
`thermocompression bonding to the Silicon wafer 6 is fixed
`on the sheet for expanding proceSS 8, and these are fixed by
`means of the ring frame 5. The resultant assembly is
`Subjected to the same dicing, expansion and pickup Steps as
`in the above first process.
`The resultant IC chips having the polyimide adhesive
`layer Sticking thereto are placed on a lead frame in a manner
`Such that the polyimide adhesive layer is interposed between
`the IC chips and the lead frame. Prior to or immediately after
`the placing of the IC chips, the lead frame is heated at,
`generally, 100 to 300° C. and, preferably, 150 to 250° C. for
`a period of, generally, 1 Sec to 60 min and, preferably, 1 Sec
`to 1 min. This heating fuses or cures the polyimide type resin
`with the result that the IC chips can firmly be bonded to the
`lead frame.
`The bonding sheet of the present invention can be utilized
`in not only the above use but also the bonding of a
`Semiconductor compound, a glass, a ceramic, a metal, etc.
`EFFECT OF THE INVENTION
`In the present invention, the wafer dicing/bonding sheet
`including the polyimide adhesive layer can easily be
`expanded. The present invention provides the wafer dicing/
`bonding sheet which can be used as a dicing tape at the time
`of dicing, can be mounted as an adhesive on the back of a
`wafer, ensures high adhesive Strength in the bonding of, for
`example, the lead frame and is provided with the polyimide
`
`8
`adhesive layer exhibiting excellent heat resistance and aging
`resistance after the die bonding thereof. Further, the present
`invention enables reducing material loSS at the use of the
`polyimide adhesive and enables forming an adhesive layer
`with uniform thickness. Moreover, the thermal and mechani
`cal damageS which the wafer is likely to Suffer from can be
`avoided at the transfer of the polyimide adhesive layer to the
`wafer. Still further, the present invention provides the poly
`imide bonding sheet and processing film for polyimide type
`resin which can suitably be used in the above wafer bonding
`sheet and process for producing a Semiconductor device.
`Still further, the present invention provides the process for
`producing a Semiconductor device by which package crack
`ing is hardly occurred.
`
`15
`
`25
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`EXAMPLE
`The present invention will further be illustrated below
`with reference to the following Examples which in no way
`limit the Scope of the invention.
`In the following Examples and Comparative Examples,
`the “expansion ratio”, “ratio of package crack”, “quantity of
`Scattered chips' and “chip peeling Strength' were evaluated
`in the following manners.
`Expansion ratio:
`A 4-inch silicon wafer was fixed to the polyimide adhe
`Sive Surface of a wafer dicing/bonding sheet by a thermo
`compression bonding (140° C., 2.0 kg/cm), and a ring
`frame was fixed on the pressure Sensitive adhesive layer of
`the wafer dicing/bonding sheet. Then, a full cut dicing was
`performed to a depth of the processing film for polyimide
`type resin of the wafer dicing/bonding sheet according to the
`common procedure to thereby effect splitting into 10
`mmx10 mm IC chips, and the outside diameter of the split
`wafer (transverse direction=X, longitudinal direction=Y)
`was measured.
`Thereafter, an expansion was conducted by drawing as
`much as an expansion length of 17 mm, So that the wafer (IC
`chip spacing) was expanded. The outside diameter of the
`expanded wafer was measured, and the ratio of expansion of
`the outside diameter of the wafer by the expansion was
`calculated by the following formula:
`
`outside diameter of wafer
`after expansion
`x 100
`expansion ratio (%) =
`outside diameter of wafer
`before expansion
`
`Ratio of Package Crack:
`Chips were picked up from the wafer dicing/bonding
`sheet after dicing and mounted on a lead frame. Bonding
`was conducted and a high pressure Sealing was effected with
`the use of a preselected mold resin (biphenyl type epoxy
`resin). This resin was cured by heating at 175 C. for 6 hr,
`So that packages were completed. The packages were
`allowed to stand still in an 85 C.x85% RH atmosphere for
`168 hr. Thereafter, a vapor phase soldering (VPS, duration:
`1 min) was conducted at 215 C. thrice, and whether or not
`the Sealing resin cracked was inspected by a Scanning
`acoustic tomography (SAT). The ratio of the number of
`cracked Specimens to the Sum of input test Specimens was
`determined and expressed as "ratio of package crack'.
`Quantity of Scattered Chips:
`The number of Scattered chips (including irregular pieces
`at peripheral portions) was counted after the dicing into each
`chip size.
`
`MICRON 1034
`
`

`

`9
`
`6,007,920
`
`Chip Peeling Strength:
`After dicing the wafer adhered on the dicing/bonding
`sheet into each chip size, the sheet for expanding process of
`the dicing/bonding sheet was fixed on 10 mm-thick glass
`plate by means of a pressure Sensitive adhesive double
`coated sheet. A vertical hanging jig was fixed to a diced chip
`Surface with the use of an instantaneous adhesive. A nylon
`loop was fixed to a cross head part of Instron model no. 4204
`universal tester (manufactured by Instron Corporation) and
`interlocked with a hooked part of the above jig. Then, the
`tester was operated at a croSS head Speed of 500 mm/min to
`thereby effect vertical peeling. The maximum of applied
`force was determined and expressed as “chip peeling
`Strength”.
`
`Example 1
`A soft polyvinyl chloride film (100 um thick) being
`extensible in both the direction of the length and the direc
`tion of the width as a soft film was coated with an acrylic
`pressure Sensitive adhesive (Solid contents coating thick
`ness: 10 um) to provide a pressure Sensitive adhesive layer,
`thereby obtaining a sheet for expanding process. Separately,
`the treated Surface of a polyethylene naphthalate film treated
`with an alkyd release agent (thickness: 25 um, melting point:
`272 C., surface tension: 34 dyn/cm. was coated with a
`Solution of thermoplastic polyimide adhesive in cyclohex
`anone (coating thickness: 10 um) and dried (140°C., 3 min),
`thereby obtaining a polyimide bonding sheet. The polyimide
`bonding Sheet was laminated to the Sheet for expanding
`proceSS in a manner Such that the untreated Surface of the
`polyethylene naphthalate film contacted the preSSure Sensi
`tive adhesive layer. Punching was performed So that the
`sheet for expanding process and the polyimide bonding
`sheet were formed into concentric circles of 207 mm and
`