JP2008038111A - Film-shaped adhesive and method for producing semiconductor package using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonconductive film-shaped adhesive enabling a semiconductor device to be mounted on a wiring board in a low-temperature region of ≤100°C at which the warp of the board is not caused, and having higher moisture-resistant reliability. <P>SOLUTION: The film-shaped adhesive consists essentially of (A) a dicyclopentadiene skeleton-containing epoxy resin, (B) a spherical silica having 3-20 μm average particle diameter and ≤3 ratio of (volume-average particle diameter)/(number-average particle diameter), (C) a phenoxy resin and (D) an epoxy resin curing agent, wherein the content of the spherical silica (B) is 30-80 wt.%. The method for producing the semiconductor package includes steps of sticking the film-shaped adhesive on the back surface of a wafer in which many semiconductor devices are formed, laminating a dicing tape on the film-shaped adhesive layer side, simultaneously dicing the film-shaped adhesive layer with the wafer to afford the semiconductor device with the film-shaped adhesive, peeling semiconductor device with the film-shaped adhesive from the dicing tape and subjecting the semiconductor device to die-attaching with an interposer board of an adherend. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a film adhesive, a method for manufacturing a semiconductor package using the same, and a semiconductor package obtained thereby. Specifically, the present invention relates to an insulating film adhesive suitable for bonding a semiconductor element in a semiconductor package and an interposer substrate.

  In recent years, with the progress of downsizing and higher functionality of electronic devices, the semiconductor package structure mounted inside is required to further improve the mounting efficiency within a limited mounting area. For example, chip size packages (hereinafter CSP) and ball grid arrays (BGA) with planar terminal arrangements are increasing instead of quad flat packages (hereinafter QFP) with peripheral terminal arrangements, and multiple packages within a single package. A typical example is the appearance of a stacked package aiming to add value to a memory mounted on a portable device or the like or increase a memory capacity by mounting a semiconductor element.

  In response to such a demand for high-density mounting, members used in the semiconductor package are made thinner. In stacked packages, in order to stack more semiconductor elements within the same package size, various members such as semiconductor elements, interposer substrates, sealing resins, die attach materials for bonding semiconductor elements and interposer substrates are thin. It has become.

  When the interposer substrate is thinned, substrate warpage due to heat tends to occur in a die attach process for mounting a semiconductor element on the interposer substrate. For example, in a bismaleimide triazine (BT) substrate, which is a typical interposer substrate material, when the substrate thickness is reduced, substrate warpage occurs at 100 ° C. or higher. This substrate warpage causes a bonding failure between the semiconductor element and the interposer substrate in the die attach process (see FIG. 3). Conventional film-like die attach materials (hereinafter referred to as die attach films) require high-temperature mounting conditions of 100 ° C. or higher that cause substrate warpage (see Patent Document 1).

  Further, since the surface of the interposer substrate is not necessarily a smooth surface state, air may be caught in the interface with the adherend in the die attach process. The entrained air not only lowers the adhesive strength after heat curing, but also causes package cracks. In order for the die attach film to follow the surface of the uneven interposer substrate well, it is necessary that the viscosity at the mounting temperature is low. Therefore, the die attach film material characteristics that can be mounted in the low temperature region without substrate warpage can reach the low viscosity region in the temperature range of 60 ° C to 90 ° C while maintaining high viscosity to maintain film properties at room temperature. Is required.

  In order to have such a low melt viscosity characteristic, it is easy to blend a large amount of a resin that is solid at room temperature and has a softening point in a low temperature region. However, many commonly used resin skeletons such as epoxy resins, polyimide resins, and acrylic resins contain heteroatoms (oxygen, nitrogen, etc.), and most of them easily absorb water molecules by hydrogen bonds. It is. For this reason, the water absorption rate increases with an increase in the resin compounding amount, and the absorbed water vaporizes and expands, so that semiconductor package cracks are easily generated.

  An epoxy resin is generally used for the thermosetting adhesive, but it is a known technique to use a dicyclopentadiene type epoxy resin in order to reduce the water absorption of the cured resin. For example, there is an example in which the water absorption of the composition is reduced by blending an acrylic adhesive component with a dicyclopentadiene type epoxy resin (see Patent Documents 2 and 3). However, in this case, since the water-absorbing rate of the acrylic adhesive component is high and inorganic fillers such as silica are not mixed, there is a limit to further imparting moisture resistance reliability.

Japanese Patent Laid-Open No. 2001-49220 JP 2003-55623 A JP 2003-55632 A

  An object of the present invention is to provide an insulating film adhesive having a higher moisture resistance reliability, which enables a semiconductor element to be mounted on a wiring board in a low temperature region of 100 ° C. or lower where substrate warpage does not occur. . Another object of the present invention is to provide a film adhesive excellent as a die attach film.

  That is, the present invention includes (A) a dicyclopentadiene skeleton-containing epoxy resin, (B) a spherical silica having an average particle diameter of 3 to 20 μm and a volume average particle diameter / number average particle diameter ratio of 3 or less, (C) A film-like adhesive comprising a phenoxy resin and (D) an epoxy resin curing agent as essential components, and (B) a spherical silica content in the composition of 30 to 80% by weight.

(式中、nは0〜10の整数である)で示されるエポキシ樹脂である上記のフィルム状接着剤である。更に、本発明は、厚さが10〜150μmのフィルム状である上記のフィルム状接着剤である。 In the present invention, the (A) dicyclopentadiene skeleton-containing epoxy resin has the formula (1)

(Wherein, n is an integer of 0 to 10). Furthermore, this invention is said film adhesive which is 10-150 micrometers in film form.

  The present invention also includes a step of providing the film-like adhesive layer on the wafer back surface on which a large number of semiconductor elements are formed, a step of bonding a dicing tape to the film-like adhesive layer side, a film-like adhesive layer and a wafer. A semiconductor package manufacturing method including a step of dicing simultaneously to form a semiconductor element with a film adhesive, a step of peeling the semiconductor element with a film adhesive from a dicing tape, and die attaching to an interposer substrate of an adherend, and this A semiconductor package manufactured by a manufacturing method.

  It is possible to mount a semiconductor element on an interposer substrate under a low temperature condition of 100 ° C. or less where no substrate warpage occurs, and film adhesive that prevents package cracking during reflow due to the low water absorption rate of the cured composition An agent is provided.

  The film-like adhesive of the present invention is a film-like composition comprising (A) a dicyclopentadiene skeleton-containing epoxy resin, (B) spherical silica, (C) a phenoxy resin, and (D) an epoxy resin curing agent. Formed.

  (A) A dicyclopentadiene skeleton-containing epoxy resin (hereinafter also referred to as a DCP type epoxy resin) is a resin having a dicyclopentadiene skeleton and a reactive epoxy group in the molecule, and is usually solid at room temperature. The softening point is preferably about 50 ° C to 100 ° C, more preferably about 60 ° C to 80 ° C. This is because it is necessary to reach a low viscosity region in a temperature range of 60 ° C. to 100 ° C. while maintaining a high viscosity for maintaining film properties at room temperature. The molecular weight is preferably 430 to 2000, more preferably 600 to 1200. Furthermore, the epoxy equivalent is preferably 200 to 300 g / eq, particularly preferably 240 to 280 g / eq.

  As such a DCP type epoxy resin, an epoxy resin represented by the above formula (1) is preferably used. In Formula (1), n is an integer of 0 to 0, preferably 0 to 5. As a DCP type epoxy resin, n is supplied as a mixture of 0 to 0. Specifically, XD-1000 (trade name: manufactured by Nippon Kayaku Co., Ltd.), HP-7200H (trade name: Dainippon Ink & Chemicals, Inc.) Etc.).

  Moreover, you may use together a DCP type epoxy resin and the other general purpose epoxy resin. In particular, when a DCP type epoxy resin having a high softening point is used, the viscosity of the composition increases and the film becomes brittle when used as a film. Therefore, it is necessary to blend a room temperature liquid epoxy resin having a molecular weight of 300 to 500. preferable. In this case, another epoxy resin is used in an amount of 5 to 70 parts by weight, more preferably 30 to 60 parts by weight with respect to 100 parts by weight of the DCP type epoxy resin.

  (B) Spherical silica (hereinafter referred to as spherical silica) contributes to reducing the water absorption of the composition and reducing the linear expansion coefficient. If the value of the coefficient of linear expansion is high, the difference in coefficient of linear expansion from the wiring board becomes large, so that the effect of suppressing stress with these adherends is low, which leads to generation of package cracks.

  Spherical silica is excellent in terms of high packing and fluidity. The average particle diameter of the spherical silica is 3 to 20 μm, and the volume average particle diameter / number average particle diameter ratio (hereinafter also referred to as the particle diameter ratio) is 3 or less. If the average particle size is less than 3 μm, the filler tends to aggregate, making it difficult to disperse in the resin binder, and since the specific surface area becomes large, the contact area with the resin is increased and the melt viscosity is increased. When the particle size is larger than 20 μm, when a thin film is produced with a coating machine such as a roll knife coater, the filler becomes a trigger, and it becomes easy to generate streaks on the film surface.

  The particle size ratio is used as an index representing the particle size distribution, and is generally volume average particle size / number average particle size ≧ 1, and the smaller this value, the sharper the particle size distribution. The larger the value, the broader the particle size distribution. When the ratio of the particle diameters exceeds 3, the composition has a structure in which fillers with small particle diameters exist in the gaps between the fillers with large particle diameters, and the filler is densely filled in the resin. The contact area becomes larger. Therefore, in the die attach process, the film-like adhesive is not easily melted by heat (see FIG. 1), and air is easily caught between the interposer substrate and the adhesive layer.

  The blending ratio of the spherical silica in the composition (in the adhesive) is 30 to 80% by weight. If the blending amount exceeds 80% by weight, the viscosity of the composition increases due to the lack of the resin component that acts as a binder and becomes brittle when made into a film, and if it is less than 30% by weight, the film surface tackiness occurs and handling properties are significantly deteriorated. To do.

  As the (C) phenoxy resin (hereinafter referred to as phenoxy resin), a known phenoxy resin can be used. The phenoxy resin is usually a thermoplastic resin having a molecular weight of 10,000 or more obtained from bisphenol such as bisphenol A and epichlorohydrin. Since this phenoxy resin has a similar structure to the epoxy resin, it has good compatibility, low resin melt viscosity, and good adhesion. A preferred phenoxy resin is YP-50S (trade name: manufactured by Toto Kasei Co., Ltd.) whose main skeleton is bisphenol A type, but FX-316 (trade name: product name: bisphenol F type which exhibits excellent melt viscosity properties). FX-280S (trade name: manufactured by Toto Kasei Co., Ltd.) having high heat resistance. The blending ratio of the phenoxy resin is 10 to 200 parts by weight, preferably 30 to 70 parts by weight with respect to 100 parts by weight of the DCP type epoxy resin. When the amount is less than 10 parts by weight, the film surface tackiness is caused and the handling property is remarkably deteriorated. When the amount exceeds 200 parts by weight, the film becomes hard and the film alone is easily broken.

  As the (D) epoxy resin curing agent (hereinafter also referred to as curing agent) used in the present invention, known curing agents such as amines, acid anhydrides and polyhydric phenols can be used, but preferably at room temperature. It is a latent curing agent that exhibits curability at the above predetermined temperature, for example, at or above the temperature at which the resin component exhibits the necessary tackiness, and also exhibits fast curability. As the latent curing agent, dicyandiamide, imidazoles, hydrazides, boron trifluoride-amine complexes, amine imides, polyamine salts and modified products thereof, and microcapsules can also be used. These can be used alone or in admixture of two or more. By using a latent curing agent, it is possible to provide a film adhesive with high storage stability that can be stored for a long period of time at room temperature. The usage-amount of an epoxy resin hardening | curing agent is the range of 0.5-50 wt% normally with respect to an epoxy resin.

  In the composition for forming an adhesive comprising the above (A) to (D) as essential components, other additives such as a coupling agent, an antioxidant, a flame retardant, a colorant, and a butadiene as a stress relaxation agent. It is also possible to contain a system rubber or a silicone rubber.

  The coupling agent is preferable for the purpose of reinforcing the interface with silica and exhibiting high breaking strength and improving the adhesive strength. As the coupling agent, those containing an amino group or an epoxy group are preferable.

  The film-like adhesive of the present invention is, for example, an aromatic hydrocarbon such as toluene or xylene, a ketone solvent such as MIBK or MEK, an ether solvent such as monoglyme or diglyme, or a mixture of the above (A) to (D ) Varnish in which a composition containing essential components is dissolved is applied to a base material (protective film) such as PP, PE, PET, etc., which has been subjected to mold release treatment, such as a roll knife coater, gravure coater, die coater, reverse coater It is obtained by coating according to a known method, applying a heat treatment not higher than the curing start temperature of the resin mixture, and drying. The thickness of the film adhesive of the present invention is preferably in the range of 10 to 150 μm.

  The viscosity of the film adhesive of the present invention or the composition thereof preferably has a high viscosity of 10000 Pas or more at room temperature and reaches 900 Pas or less in a temperature range of 60 ° C. to 90 ° C. at which no substrate warpage occurs. If the viscosity at room temperature is less than 10000 Pas, the film surface tackiness will be significantly deteriorated, and the handling properties will be significantly deteriorated. It becomes easy.

  The film adhesive is cured by heating or the like, and the water absorption rate (85 ° C., 85% RH, 100 hours) of the cured product is preferably 1.5% by weight or less. When the water absorption rate is high, when exposed to a high temperature during reflow, the volatilization of moisture increases, and package cracks are likely to occur. The DCP type epoxy resin is characterized by low water absorption, and is a resin suitable for imparting moisture resistance reliability.

  The case where the film adhesive of this invention is used as a die attach film is demonstrated with reference to drawings. FIG. 2 shows a process of thermocompression bonding the semiconductor element and the interposer substrate.

  First, a film-like adhesive (die attach film) 6 is attached to one surface of a silicon wafer 5, and then the silicon wafer and the film-like adhesive are cut using a dicing tape 7 as a base, thereby providing a semiconductor with a film-like adhesive. Element 1 is obtained. Next, the adhesive-attached semiconductor element 1 is peeled off from the dicing tape 7 and mounted on the interposer substrate under a heating condition of 100 ° C. or less that does not warp the interposer substrate 2, and the epoxy resin in the adhesive is cured by heating. The semiconductor element and the interposer substrate are subjected to thermocompression bonding. The heating temperature in this case is usually 80 ° C. to 180 ° C., and the heating time is 1 minute to 180 minutes. By such heating, the epoxy resin is cured and the semiconductor element and the interposer substrate can be firmly bonded. The semiconductor element bonded substrate 8 obtained by bonding is then connected to the semiconductor element and the interposer substrate with wires 9 and sealed with a sealing material 10 in a molding process.

  FIG. 3 schematically shows a conventional process for die-attaching the semiconductor element 1 to which the die-attach film is attached to the interposer substrate 2. When the interposer substrate heated by the heat stage 3 is a BT substrate, the BT substrate is warped by heating exceeding 100 ° C. Therefore, the non-contact surface 4 is formed on the die attach film surface of the semiconductor element to which the die attach film is attached and the adhesion surface of the BT substrate, and the adhesion force is reduced.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In the following Examples and Comparative Examples, “melt viscosity”, “water absorption”, and “surface tack” were evaluated as follows.

“Melting viscosity” About 10g of the film before thermosetting is cut out and processed into a 4cm high bar using a simple press. This sample was measured at each measurement temperature using a high-pressure flow tester (CFT-500A) manufactured by Shimadzu Corporation.

"Water absorption rate" Cut about 10g of the film before thermosetting, put it in a fixed dimension mold and melt it on a hot plate. After molding, the sample is cooled at room temperature and heat-treated at 180 ° C for 1 hour. The water absorption was determined from the weight increase of this sample after standing for 168 hours at 85 ° C. and 85% relative humidity.

"Surface tackiness" Tactile sensation of film before thermosetting and peelability from release-treated PET film were observed. ◎ (good), ○ (nearly good), △ (slightly bad), x (bad) It was evaluated with.

Example 1
XD-1000 (dicyclopentadiene type epoxy resin, softening point approx. 70 ° C, Nippon Kayaku Co., Ltd.) 60g, YP-50S (phenoxy resin, Tg approx. 100 ° C, Toto Kasei Co., Ltd.) 20g, Epicoat 828 (bisphenol A type) 44 g of epoxy resin (manufactured by Toto Kasei Co., Ltd.) was weighed and heated and stirred at 110 ° C. for 2 hours in a 500 ml separable flask using 70 g of MIBK as a solvent to obtain a resin varnish. 187 g of this solution was weighed in an 800 ml planetary mixer, and 72 g of FB-3SDX (spherical silica, average particle size 3 μm, particle size ratio = 2.4, manufactured by Denka) was added and mixed with three rolls. . Add 6g of AH-150 (Dicyandiamide, Ajinomoto Co., Inc.) and 2g of HX-3722 (Microcapsule type imidazole latent curing agent, Asahi Kasei Epoxy Co., Ltd.) to this mixture. To obtain a mixed varnish. The varnish was applied onto a 50 μm thick PET film which had been subjected to a release treatment, and then dried with hot air at 80 ° C./10 min and 150 ° C./1 min to obtain a 30 μm adhesive sheet, that is, a film adhesive.

Example 2
An adhesive sheet was produced in the same manner as in Example 1 except that 60 g of HP-7200H (dicyclopentadiene type epoxy resin, softening point of about 80 ° C., manufactured by Dainippon Ink and Chemicals) was used as the dicyclopentadiene type epoxy resin. And evaluated.

Example 3
An adhesive sheet was produced and evaluated in the same manner as in Example 1 except that 134 g of FB-3SDX was used as the spherical silica.

Example 4
An adhesive sheet was produced and evaluated in the same manner as in Example 1 except that 314 g of FB-3SDX was used as the spherical silica.

Comparative Example 1
Except that 58 g of FB-3SDX and 14 g of SO-25R (manufactured by Tatsumori Co., Ltd., fine spherical silica, average particle size 0.5 μm, particle size ratio = 4.3) were used as the spherical silica, the same as in Example 1. An adhesive sheet was manufactured and evaluated.

Comparative Example 2
An adhesive sheet was produced and evaluated in the same manner as in Example 1 except that 60 g of YDCN-702H (cresol novolac type epoxy resin, softening point: about 75 ° C., manufactured by Tohto Kasei Co., Ltd.) was used as the epoxy resin.

Comparative Example 3
An adhesive sheet was produced and evaluated in the same manner as in Example 1 except that 60 g of EPPN-501H (triphenylmethane type epoxy resin, softening point: about 55 ° C., manufactured by Nippon Kayaku Co., Ltd.) was used as the epoxy resin.

Comparative Example 4
An adhesive sheet was produced and evaluated in the same manner as in Example 1 except that spherical silica was not blended.
Table 1 summarizes the compositions and evaluation results of Examples 1 to 4 and Comparative Examples 1 to 4.

Example 5
XD-1000 (dicyclopentadiene type epoxy resin) 60g, YP-50S (phenoxy resin) 20g, Epicoat 828 (bisphenol A type epoxy resin) 44g, weighed 110g in a 500ml separable flask using 70g MIBK as solvent. The resin varnish was obtained by heating and stirring at 2 ° C. for 2 hours. 187 g of this solution was weighed in an 800 ml planetary mixer, and 72 g of FB-3SDX (spherical silica) was added and mixed to obtain a mixed varnish by vacuum degassing. The varnish was applied onto a 50 μm thick PET film which had been subjected to a release treatment, and then dried with hot air at 80 ° C./10 min and 150 ° C./1 min to obtain a 30 μm adhesive sheet, that is, a film adhesive. The melt viscosity before curing of this film was measured (see FIG. 1). In this example, an epoxy resin curing agent is not blended in order to measure the melt viscosity in an uncured state.

Comparative Example 5
An adhesive sheet was produced in the same manner as in Example 5 except that 36 g of FB-3SDX and 36 g of SO-25R were used as spherical silica, and the melt viscosity of this film was measured (see FIG. 1).

Comparative Example 6
An adhesive sheet was produced in the same manner as in Example 5 except that 72 g of SO-25R was used as the spherical silica, and the melt viscosity before curing of this film was measured (see FIG. 1).

The compositions and melt viscosity results of Example 5 and Comparative Examples 5 to 6 are shown in Table 2 and FIG. The particle size ratio values shown in Table 2 describe the value of the filler type in the case of a single filler compounding system, and in the mixed compounding system, the value of the particle size ratio of the mixed system was calculated by the following formula.
Ratio of particle diameter of mixed blending system = (blending ratio of filler A × [volume average particle diameter] of filler A / [number average particle diameter]) + (blending ratio of filler B × [volume average particle diameter] of filler B) / [Number average particle size])

Relationship between temperature and melt viscosity when the ratio of spherical silica particle size is changed Semiconductor package manufacturing process diagram using film adhesive Illustration of adhesion failure due to substrate warpage

Explanation of symbols

1: Semiconductor element with adhesive, 2: Interposer substrate, 3: Heat stage, 4: Non-contact surface, 5: Silicon wafer, 6: Film adhesive, 7: Dicing tape, 8: Semiconductor element adhesive substrate, 9 : Wire, 10: Sealing material

Claims (5)

  (A) a dicyclopentadiene skeleton-containing epoxy resin, (B) a spherical silica having an average particle diameter of 3 to 20 μm and a volume average particle diameter / number average particle diameter ratio of 3 or less, (C) a phenoxy resin, and ( D) A film adhesive having an epoxy resin curing agent as an essential component and (B) a spherical silica content of 30 to 80% by weight. (A) A dicyclopentadiene skeleton-containing epoxy resin has the formula (1)

2. The film adhesive according to claim 1, which is an epoxy resin represented by the formula (n is an integer of 0 to 0).   The film adhesive according to claim 1 or 2, wherein the film adhesive has a thickness of 10 to 150 µm.   The process of providing the film adhesive layer in any one of Claims 1-3 in the wafer back surface in which many semiconductor elements were formed, the process of bonding a dicing tape on the film adhesive layer side, a film adhesive layer A semiconductor device including a step of dicing a wafer and a wafer into a semiconductor element with a film adhesive, a step of peeling the semiconductor element with a film adhesive from a dicing tape, and die attaching to an interposer substrate of an adherend Method.   A semiconductor package manufactured by the method for manufacturing a semiconductor package according to claim 4.

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