JP5256641B2 - Adhesive composition - Google Patents

Description

  The present invention relates to an adhesive composition for temporarily fixing a substrate to a support when processing the substrate such as a semiconductor wafer.

  In a semiconductor device manufacturing process, a large number of circuits such as ICs and LSIs are formed in a lattice shape on the surface of a substantially disc-shaped semiconductor wafer, and each region where the circuits are formed is diced along a predetermined cutting line. Thus, individual semiconductor elements are manufactured. When manufacturing semiconductor elements in this way, the semiconductor elements are made as thin as possible in order to improve the heat dissipation of the semiconductor elements and to reduce the size and cost of mobile devices such as mobile phones. It is hoped to do. Therefore, before the semiconductor wafer is divided into individual elements, a grinding process is performed in which the back surface is ground to a predetermined thickness. In this grinding step, the semiconductor element needs to be firmly fixed to a support such as a surface plate of a grinding machine with a temporary adhesive, but after the grinding is finished, it must be peeled off from the support.

  Conventionally, wax has been widely used as a temporary fixing adhesive in the field of compound semiconductors, and various waxes have been proposed. For example, Patent Document 1 discloses a wax containing polyglycerins having an HLB value of 7 to 13 as an active ingredient, and Patent Document 2 discloses a rosin resin having an acid value of 100 or more, a rosin resin derivative, a rosin resin A wax containing one or more of a modified product and a styrene-acrylic copolymer is disclosed.

However, such conventional waxes are
(1) Since the wax flows at high temperature and the adhesive strength cannot be maintained, it cannot be adapted to processing at 200 ° C.
(2) The in-plane variation accuracy of the substrate bonding thickness is not sufficient, and (3) when the thinly ground substrate is peeled from the support, the peelability is poor and the substrate is easily damaged.
There were problems such as.
JP 7-224270 A JP-A-9-157628

  An adhesive composition that can temporarily fix a substrate such as a semiconductor wafer to a support with an arbitrary bonding thickness, and exhibits good heat resistance and adhesiveness during processing of the substrate. It is an object of the present invention to provide an adhesive composition that can easily peel the substrate from the support and can cleanly remove the adhesive attached to the substrate.

  The present inventors have solved the above-mentioned problems, and can temporarily fix a substrate such as a semiconductor wafer to a support, exhibiting good heat resistance and adhesiveness during substrate processing, and after processing Has intensively studied an adhesive composition capable of easily peeling the substrate from the support, and completed the present invention.

That is, the present invention includes the following matters.
The adhesive composition of the present invention has a molecular weight of 200 to 1000, and contains 80 to 100% by weight of a compound containing 3 to 10 aromatic ring structures in the molecule (provided that the adhesive is used) The total solid component in the composition is 100% by weight).

  The compound has a compound containing a structural unit represented by the following formulas (A), (B), (C), (D) and (E), an aromatic compound (F) having an oxazoline ring, and a condensed ring. It is preferably at least one selected from an aromatic compound (G) and a tetraphenylethane derivative (H).

［式中、Ｒ₁〜Ｒ₅₆は、水素原子、水酸基、炭素数１〜１２の鎖状もしくは環状のアルキ
ル基または置換アルキル基、および炭素数１〜１２の置換もしくは非置換のフェニル基から選ばれる置換基であって、それぞれ同じでも異なってもよい。Ａｒは、芳香族複素環または炭素環である。］
前記化合物の融点は、８０〜３００℃であることが好ましい。

[Wherein, R _{1 to} R ₅₆ are selected from a hydrogen atom, a hydroxyl group, a linear or cyclic alkyl group having 1 to 12 carbon atoms or a substituted alkyl group, and a substituted or unsubstituted phenyl group having 1 to 12 carbon atoms. Each of which may be the same or different. Ar is an aromatic heterocycle or carbocycle. ]
The melting point of the compound is preferably 80 to 300 ° C.

The compound is preferably a hindered phenol compound.
The compound preferably has no functional group other than a hydroxyl group in the molecule.

  According to the adhesive composition of the present invention, the substrate and the support are heated and melted, overlapped, and solidified at a predetermined temperature, whereby the support and the substrate are easily and uniformly bonded to each other with an arbitrary thickness. be able to. Furthermore, by heating and melting the adhesive layer again, the substrate can be easily peeled from the support, and the adhesive residue remaining on the substrate can be cleaned and removed cleanly. Therefore, the adhesive composition of the present invention is suitable as an adhesive for temporarily fixing a substrate in, for example, ultra-thin grinding processing of a semiconductor substrate and micro-processing processing of various material surfaces.

  In the present invention, by containing a specific low molecular weight compound at a high content, when it is heated to a specific temperature (melting temperature) specific to the compound, the state changes instantaneously from a solid to a liquid to become a low viscosity liquid, When the temperature is controlled to a specific temperature (solidification temperature or crystallization temperature) specific to the compound, a phenomenon of changing to a solid state again is expressed as adhesiveness. Since the viscosity is low in the liquid state, the unevenness of the substrate is filled with the adhesive component, and the film thickness can be made uniform by self-leveling properties while suppressing residual bubbles in the adhesive layer. Further, when peeling by heating and melting, the substrate can be peeled without applying a large stress because of low viscosity. On the other hand, since the adhesiveness is maintained until the solid state reaches a specific temperature or higher, the substrate can be processed up to the melting start temperature. That is, it is possible to process a substrate or the like in a wider temperature range as the melting temperature is higher.

  The adhesive composition of the present invention is characterized in that it exhibits an adhesion-non-adhesion function only by changing the state of the adhesive composition without causing a chemical change in the process from adhesion to peeling. An adhesive-non-adhesive state can be expressed with good reproducibility without being affected by gas generation and reaction rate variation associated with a chemical reaction. In the present invention, the liquid-solid state change is controlled to an appropriate temperature range by using the above specific compound, and it is possible to bond and peel off a substrate such as a semiconductor wafer and to clean and remove the adhesive layer. .

Hereinafter, the adhesive composition of the present invention will be described in detail.
[Each component of adhesive composition]
The adhesive composition of the present invention contains a compound that expresses an adhesive function (hereinafter also referred to as “functional component”), a volatile component (such as a solvent), and other additives. The content of the functional component when the total solid content of the adhesive composition is 100% by weight is 80 to 100% by weight, preferably 90 to 100% by weight, and more preferably 97 to 100% by weight. If the content of the functional component is less than 80% by weight, it will become a low-viscosity liquid state when heated and dissolved, and the state change that crystallizes when controlled to a specific temperature will slow down. As a result, the upper limit of the processing process temperature is lowered.

  In addition, the adhesive composition of the present invention has 10 particles / mL or less of particles having a particle size of 1 μm or more, and the total content of alkali metal ions and heavy metal ions is 100 ppm or less. Since it can reduce, it is preferable.

[Functional ingredients]
The functional component used in the present invention is a compound having a molecular weight of 200 to 1000, preferably 230 to 900, containing 3 to 10 aromatic ring structures in the molecule. When the molecular weight is less than 200, the volatility is large at the melting temperature, and the volatile matter remains in the form of bubbles when the substrates are bonded together, so that a sufficient bonding area cannot be secured and the bonding strength is weakened. On the other hand, when the molecular weight exceeds 1000, the viscosity at the time of melting increases, and the stress applied to the substrate at the time of peeling increases, which may damage the substrate.

  The functional component used in the present invention contains 3 to 10, preferably 3 to 7 aromatic ring structures in the molecule. If the number of aromatic rings is less than 3, the molecular weight is small, and the volatility is increased as described above, so that the adhesive strength is weakened. On the other hand, when the number of aromatic rings is 10 or more, the molecular weight is large and not only the viscosity becomes high as described above, but also the molecular structure is complicated, it is difficult to take a stable crystal state, and the reproducibility of the adhesive state is reduced. Adhesive strength is weakened.

The melting temperature of the functional component used in the present invention is 80 to 300 ° C, preferably 80 to 280 ° C, more preferably 80 to 260 ° C. Here, the “melting temperature” refers to the temperature of the main peak in the melting peak curve measured by a differential scanning calorimeter (DSC). The allowable temperature for processing can be predicted from the melting temperature of the functional component. The higher the melting temperature, the higher the allowable processing temperature, and it can be applied to various processing. In addition, the volatility of the functional component used in the present invention is that when 10 mg of the functional component is held at a melting temperature + 15 ° C. for 1 hour using a differential thermothermal gravimetric simultaneous measurement device (TG / DTA300 manufactured by SII Nanotechnology). When the weight loss is measured, it is 0 to 10%, preferably 0 to 2%, based on the initial weight. When the volatility is within the above range, it is preferable because bubbles hardly remain on the bonding surface.

  The solidification temperature of the functional component used in the present invention is determined by the peak temperature of the exothermic peak curve when measured under nitrogen at 5 ° C./min using a differential scanning calorimeter (“RDC220” (manufactured by Seiko)). The solidification temperature is generally about 5 to 50 ° C. lower than the melting temperature, but the temperature range is not particularly limited.

  In the step of adhering after melting the adhesive composition, it is preferable that the temperature is lower by about 5 to 20 ° C. than the melting temperature because the burden of process temperature control is small. Conversely, when the adhesive composition is not melted, the lower the solidification temperature, the more preferable it is because the amount of heat for bonding can be reduced.

  It is acceptable as a functional group that the functional component has from the viewpoints that it does not damage the wiring and insulation film formed on the substrate, does not cause contamination, and does not cause chemical change or deterioration of the adhesive layer when melted. It is only the hydroxyl group. It is not preferable to contain ether and ester structures as well as highly active functional groups such as carboxyl groups other than hydroxyl groups, amino groups, imino groups, nitro groups, nitroso groups, epoxy groups, thiol groups and halogens. Further, metals that diffuse into the medium and adversely affect the insulation properties (for example, Na, K, Ca, Fe, Cu, Ni, Cr, Al, etc.) such as alkali metals are subjected to a metal-free treatment. The content is preferably 100 ppm or less, preferably 10 ppm or less. In addition, the metal oxide etc. which exist in a stable form are not this limitation.

  Examples of the compound satisfying the above-described requirements include compounds represented by the following chemical formulas (A) to (E), an aromatic compound (F) having an oxazoline ring, and an aromatic compound (G) having a condensed ring. And tetraphenylethane derivative (H).

[式中、Ｒ₁〜Ｒ₅₆は水素原子、水酸基、炭素数１〜１２の鎖状もしくは環状のアルキル基または置換アルキル基、および炭素数１〜１２の置換もしくは非置換のフェニル基から選ばれる置換基であって、それぞれ同じでも異なってもよい。Ａｒは、芳香族複素環または脂肪族複素環である。]
化学式（Ａ）で表される構造ユニットを含む化合物としては、たとえば、１，１，１−トリス（４−ヒドロキシフェニル）エタンや、以下の化学式で示される化合物などが挙げられる。

[Wherein, R _{1 to} R ₅₆ are selected from a hydrogen atom, a hydroxyl group, a linear or cyclic alkyl group having 1 to 12 carbon atoms or a substituted alkyl group, and a substituted or unsubstituted phenyl group having 1 to 12 carbon atoms. Substituents, which may be the same or different. Ar is an aromatic heterocyclic ring or an aliphatic heterocyclic ring. ]
Examples of the compound including the structural unit represented by the chemical formula (A) include 1,1,1-tris (4-hydroxyphenyl) ethane and compounds represented by the following chemical formula.

化学式（Ｂ）で表される構造ユニットを含む化合物としては、以下の化学式に例示されるようなノボラック樹脂（重合度３〜１０）が挙げられる。

Examples of the compound containing the structural unit represented by the chemical formula (B) include novolak resins (degree of polymerization: 3 to 10) as exemplified by the following chemical formula.

化学式（Ｃ）で表される構造ユニットを含む化合物としては、たとえば、ｍ−ターフェニル、ｏ−ターフェニル、およびｐ−ターフェニルなどが挙げられる。

Examples of the compound containing the structural unit represented by the chemical formula (C) include m-terphenyl, o-terphenyl, and p-terphenyl.

  Examples of the compound containing the structural unit represented by the chemical formula (D) include 1,3,5-tris (3 ′, 5′-di-tert-butyl-4′-hydroxybenzyl) isocyanuric acid. .

  Examples of the compound containing the structural unit represented by the chemical formula (E) include 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene. 2,2-bis (4-hydroxy-3,5-bis (2-hydroxy-5-methylbenzyl) phenyl) propane and the like, and a compound containing a structural unit represented by the following chemical formula.

縮合環を有する芳香族化合物（Ｆ）としては、たとえば、α−ナフトールベンゼン、チモールフタレイン、α−ナフトールフタレイン、トリプチセンおよびコランニュレンなど；
オキサゾリン環を有する芳香族化合物（Ｇ）としては、たとえば、１，４−ビス［２−（４−メチル−５−フェニルオキサゾリル）］ベンゼンおよび１，４−ビス［２−（５−フェニルオキサゾリル）］ベンゼンなどのポリオキサゾリンオリゴマー、ならびに、その誘導体が挙げられる。ただし、前記誘導体のうち、エステル誘導体は融点が低く、熱分解したときに酸性となり接着面を浸食する可能性があるなどの理由から好ましくない。

Examples of the aromatic compound (F) having a condensed ring include α-naphtholbenzene, thymolphthalein, α-naphtholphthalein, triptycene, and corannulene;
Examples of the aromatic compound (G) having an oxazoline ring include 1,4-bis [2- (4-methyl-5-phenyloxazolyl)] benzene and 1,4-bis [2- (5-phenyl). Oxazolyl)] polyoxazoline oligomers such as benzene, and derivatives thereof. However, among the above derivatives, ester derivatives are not preferable because they have a low melting point and become acidic when thermally decomposed and may erode the adhesive surface.

  Among the above compounds, a so-called hindered phenol compound having a large steric hindrance due to the presence of a substituent at the ortho position shown in the following chemical formula 4 or the like is preferably used.

化学式（Ｄ）で表される化合物、化学式（Ｅ）で表される化合物およびオキサゾリン環を有する芳香族化合物（Ｇ）、テトラフェニルエタン誘導体（Ｈ）が、溶融時の揮発分が少なく、熱安定性も良好であり好ましく、化学式（Ｄ）または化学式（Ｅ）に属するヒンダードフェノール化合物である、１，３，５−トリス（３’，５’−ジ−ｔｅｒｔ−ブチル−４’−ヒドロキシベンジル）イソシアヌル酸、１，３，５−トリメチル−２，４，６−トリス（３，５−ジ−ｔｅｒｔ−ブチル−４−ヒドロキシベンジル）ベンゼン、２，２−ビス（４−ヒドロキシ−３，５−ビス（２−ヒドロキシ−５−メチルベンジル）フェニル）プロパンおよびオキサゾリン環を有する芳香族化合物（Ｇ）、以下の化学式で示されるテトラフェニルエタン誘導体（Ｈ）がさらに好ましい。

The compound represented by the chemical formula (D), the compound represented by the chemical formula (E), the aromatic compound (G) having an oxazoline ring, and the tetraphenylethane derivative (H) have a low volatile content at the time of melting and are stable. 1,3,5-tris (3 ′, 5′-di-tert-butyl-4′-hydroxybenzyl) which is a hindered phenol compound belonging to chemical formula (D) or chemical formula (E) ) Isocyanuric acid, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 2,2-bis (4-hydroxy-3,5) -Aromatic compound (G) having bis (2-hydroxy-5-methylbenzyl) phenyl) propane and oxazoline ring, tetraphenylethane derivative (H) represented by the following chemical formula But more preferable.

前記機能成分は、後述する溶融特性および接着性を損なわない限り、これらの化合物を単独で用いても、２種以上を混合して用いてもよい。

These functional components may be used alone or in admixture of two or more, as long as the melting properties and adhesiveness described below are not impaired.

  Among the functional components, the melting temperature range from solid to liquid is 0.5 to 30 ° C., preferably 1 to 20 ° C., and the melt viscosity at the melting temperature is 0.0001 to 0.1 Pa · s, preferably Is 0.001 to 0.05 Pa · s, particularly preferably 0.001 to 0.01 Pa · s. Here, the “melting temperature range” refers to the difference between the starting point temperature and the ending point temperature of the main peak in the melting peak curve measured by a differential scanning calorimeter (DSC). When the melting temperature range and the melt viscosity are in the above ranges, the ease of peeling is improved, so that the external force applied when peeling the wafer from the support can be reduced.

It is also preferable to purify the functional component in order to narrow the melting temperature range of the functional component, reduce the melt viscosity, and further reduce the amount of free metal ions. As a purification method of the functional component, for example,
(A) A method in which a functional component is dissolved in a solvent, and the solvent is gradually distilled off to recrystallize; and (b) a functional component is dissolved in a solvent, and the solution is brought into contact with an ion exchange resin to remove free metal. The method of removing is mentioned.

〔solvent〕
The functional component used in the present invention can be used in a varnish state dissolved in an organic solvent, or in a dispersion or paste state dispersed in an organic solvent and / or water. In some cases, the handleability of the adhesive composition is better.

  In order to form the functional component in a desired film thickness in the varnish state, it is preferable that the functional component can be dissolved under a temperature condition of 5% to 80%, preferably 10% to 60%, and 40 ° C. When the solubility is lower than the above range, the film thickness of the functional component that can be formed becomes thin, and it becomes difficult to increase the adhesion thickness between the support and the substrate. On the other hand, if the solubility exceeds the above range, the viscosity of the varnish becomes too high and the applicability to the substrate may be deteriorated. The type of solvent is not particularly limited as long as it satisfies the above-mentioned solubility, but hydrocarbon solvents such as toluene, mesitylene, limonene and tert-butylbenzene; alcohols such as propylene glycol monomethyl ether and terpineol; 2-heptanone and Ketones such as cyclohexanone, acetone, and methyl isobutyl ketone; and propylene glycol monomethyl ether acetate. Among these, mesitylene, acetone, methyl isobutyl ketone, cyclohexanone, and propylene glycol monomethyl ether acetate are preferable from the viewpoints of coating properties and coating film thickness uniformity.

  In the case of a dispersion or paste, it is preferable to use a solvent having a low functional component solubility and a solvent having a low vapor pressure. For example, water, ethylene glycol, diethylene glycol monoethyl ether, glycol solvents such as diethylene glycol monoethyl ether acetate and 2- (2-ethoxyethoxy) ethanol; propylene carbonate; cyclic ethers such as dioxane, and the like. The said compound may be used independently or may be used in mixture of 2 or more types.

Moreover, when making it into a paste state, in order to optimize the viscosity characteristic as a paste, you may contain the resin and filler which are mentioned later in an adhesive composition.
[Other additives]
Various additives can be contained in the functional component. For example, to improve the wettability to the substrate, to add a surfactant, to add a resin to improve the film formability of the applied functional component, to control the fluidity of the coating liquid It is possible to add a filler. In order not to impair the original performance of the functional component, the addition amount is 0.001 to 10 parts by weight, preferably 0.01 to 5 parts by weight, when the total solid content is 100 parts by weight.

Examples of the surfactant include C ₉ F ₁₉ CONHC ₁₂ H ₂₅ , C ₈ F ₁₇ SO ₂ NH— (C ₂
H ₄ O) ₆ H, “F-top EF301, EF303 and EF352” (manufactured by Shin-Akita Kasei Co., Ltd.), “Megafac F171 and F173” (manufactured by Dainippon Ink and Co., Ltd.), “Asahi Guard AG710” "Asahi Glass Co., Ltd.", "Florard FC-170C, FC430 and FC431" (Sumitomo 3M Ltd.), "Surflon S-382, SC101, SC102, SC103, SC104, SC104, SC105" And SC106 "(Asahi Glass Co., Ltd.)," BM-1000 and 1100 "(manufactured by B.M-Chemie)," Schsego-Fluor "(manufactured by Schwegmann) and" FS1265 "(Toray Dow Corning Silicone ( Fluorosurfactants such as manufactured by Co., Ltd .; Polyetheralkyl surfactants such as ter, polyoxyethylene allyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester and oxyethyleneoxypropylene block polymer It is done.

Specific examples of the polyether alkyl-based surfactant include “Emulgen 105, 430, 810 and 920”, “Rhedol SP-40S and Rhedol TW-L120”, “Emanol 3199 and 4110”, “Exel P-40S”. "," Bridge 3
"0, 52, 72 and 92", "Alassell 20", "Emazole 320", "Tween 20 and 60", "Merge 45" (manufactured by Kao Corporation), "Noniball 55" (manufactured by Sanyo Chemical Co., Ltd.) , “SH-28PA, -190 and -193” and “SZ-6032 and SF-8428” (manufactured by Toray Dow Corning Silicone Co., Ltd.).

  Nonionic surfactants include, for example, polyoxyethylene fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and polyalkylene oxide block copolymers. Specifically, “Chemistat 2500” (Sanyo Chemical Industries ( Co., Ltd.), “SN-EX9228” (manufactured by San Nopco Co., Ltd.), “Nonal 530” (manufactured by Toho Chemical Industry Co., Ltd.), and the like.

As the resin, various thickeners can be suitably used. As the thickener, those which improve the film formability with a small addition amount and are soluble in the same solvent as the functional component are preferable. For example, polyvinylpyrrolidone, hydroxypropylcellulose, polyacrylamide, methylcellulose, polyacrylamide, agarose , Starch and dextrin.
Furthermore, a thickener having higher heat resistance than that of the functional component and having a low metal impurity content is more preferably used.

Examples of the filler include metal oxides such as aluminum oxide, zirconium oxide, titanium oxide and silicon oxide, and polystyrene cross-linked particles (for example, “Micropearl SPN and SPS series” (manufactured by Sekisui Chemical Co., Ltd.)), phenol resin Cross-linked fibers (for example, “Kynol fiber, Kynol carbon fiber, Kynol activated carbon fiber series” (manufactured by Nippon Kainol Co., Ltd.)) phenol resin particles (for example, “Marilyn series” (manufactured by Gunei Chemical Industry Co., Ltd.)) are mentioned. These fillers may not only control the viscosity of the dispersion or paste to optimize the applicability but also serve as spacers for controlling the gaps that occur during bonding. In addition, a filler having a large surface area with a BET specific surface area value exceeding 100 m 2 / g can be used to adjust the fluidity of the melt when the functional component is melted. For example, conductive carbon (ECP, ECP) -600JD (Lion Corporation),
Fumed silica (aerosil series (made by degussa)) can be mentioned.

[Usage method of adhesive composition]
[Base material]
The adhesive composition of the present invention is used to temporarily bond substrates together. The substrate used in the present invention is a substrate used in the semiconductor field, and requires heat removal under processing temperature conditions, and removal of residues after peeling is difficult, and thus requires easy peeling. The board | substrate used by this invention is a flat plate comprised from the base material for 1 or more processing chosen from glass, a semiconductor, a metal, and a ceramic. Specific examples include base materials such as semiconductor wafers, compound semiconductor wafers, alkali-free glass, alumina, zirconia, titania, and various metal plates on which semiconductor elements are formed. Moreover, the base material with which metal films or wiring structures, such as copper, gold | metal | money, SUS, and nickel, were formed on the surface is also mentioned.

[how to use]
The use method of the adhesive composition of the present invention will be described in detail below, taking the use as a temporary adhesive for semiconductor wafers as an example, but the present invention is not limited to this use method.

The processing method of a semiconductor wafer is usually
(1) applying and drying the adhesive composition of the present invention on a semiconductor wafer or support;
(2) heating and melting the uniformly applied functional component, and fixing the semiconductor wafer to the support;
(3) a step of processing the semiconductor wafer fixed to the support;
(4) peeling the processed semiconductor wafer from the support;
(5) cleaning the peeled semiconductor wafer. Each step will be described below.

<Step (1)>
The adhesive composition of the present invention can be used for application to the semiconductor wafer in any form such as varnish, dispersion, and paste. Examples of the coating method include spin coating, spray coating, cast coating, scan coating, dip coating, and printing. The coating film of functional components is thinly and evenly coated on a substrate surface such as a support and dried. To form. It is also possible to partially form a plurality of types of functional components on the substrate surface.

The thickness of the adhesive layer can be controlled by the coating amount of the adhesive composition and the pressure at the time of adhesion, and is 0.01 μm to 2 mm, preferably 0.05 μm to 1 mm, more preferably 0.1.
The range is from μm to 0.5 mm. If the thickness of the adhesive layer is thinner than the above range, the adhesive layer may not be sufficiently bonded. On the other hand, when the thickness of the adhesive layer exceeds the above range, the adhesive strength is lowered, the adhesive is peeled off from the adhesive surface, and material destruction may occur.

  When the adhesive composition of the present invention is applied to a semiconductor wafer or a support, the surface of the semiconductor wafer or the support may be hydrophobized in advance in order to make the spread of the functional components in-plane uniform. preferable. Alternatively, it is also preferable to apply a solvent to the semiconductor wafer in advance and wet it.

  After applying the adhesive composition of the present invention to a semiconductor wafer, it is necessary to dry it. However, as described above, a surface treatment agent may be applied in advance to the surface of the semiconductor wafer or the support and hydrophobicized. preferable.

Examples of the surface treatment agent include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-aminopropyltrimethoxysilane, 2-aminopropyltriethoxysilane, N- (2-aminoethyl)- 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N-ethoxycarbonyl-3-aminopropyl Trimethoxysilane, N-ethoxycarbonyl-3-aminopropyltriethoxysilane, N-triethoxysilylpropyltriethylenetriamine, N-trimethoxysilylpropyltriethylenetriamine, 10-trimethoxysilyl-1,4,7- Riazadecane, 10-triethoxysilyl-1,4,7-triazadecane, 9-trimethoxysilyl-3,6-diazanonyl acetate, 9-triethoxysilyl-3,6-diazanonyl acetate, N-benzyl- 3-aminopropyltrimethoxysilane, N-benzyl-3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltriethoxysilane, N-bis (oxyethylene ) -3-Aminopropyltrimethoxysilane, N-bis (oxyethylene) -3-aminopropyltriethoxysilane, and hexamethyldisilazane.

<Step (2)>
The step of fixing the semiconductor wafer to the support is performed under a reduced pressure of 200 Torr or less in order to remove bubbles in the functional components and bubbles in the irregularities on the wafer and the surface of the support and to keep the thickness of the adhesive layer constant. It is preferable.

  The temperature at which the functional component of the present invention is heated and melted is “melting temperature + 2 ° C.” to “melting temperature + 50 ° C.”, preferably “melting temperature + 2 ° C.” to “melting temperature + 30 ° C.”, particularly preferably “melting temperature + 5 ° C.” "To" melting temperature + 20 ° C ". When the temperature to be melted by heating is lower than the above range, the functional component may not be sufficiently spread in the adherend surface, and uneven adhesion may occur. On the other hand, when the heating and melting temperature exceeds the above range, volatilization or decomposition of the functional component partially proceeds, and desired adhesiveness may not be obtained.

  In the bonding operation, it is preferable to use a hot press apparatus having a function of mechanically controlling the distance between the semiconductor wafer and the support in consideration of the case where the semiconductor wafer or the support has uneven film thickness. By controlling the pressure or the distance between the upper and lower press plates using such a hot press device, the thickness of the adhesive layer or the flatness of the bonded product can be suppressed within a predetermined range.

After bonding the semiconductor wafer and the support, when the temperature is lowered to the solidification temperature of the functional component, the semiconductor wafer and the support are firmly bonded.
Note that, depending on the functional component, due to the thermal characteristics of the functional component, it is possible to perform adhesion and crystallization using only a heating press without melting.
As shown in FIG. 1, the adhesive strength was prepared by preparing a sample in which a silicon wafer and a glass substrate were bonded together using only functional components as an adhesive, and using a Tensilon type tensile tester, the tensile strength was 1.67 × 10. pulling up and down ^-4 m / sec, when the adhesive strength was measured in the shear direction when the 0.4 kgf / cm ² or more, preferably 1.0 kgf / cm ² or more. An adhesive strength within the above range is preferable because it can withstand the impact of back surface grinding and conveyance.

<Step (3)>
The processing of the semiconductor wafer fixed to the support is preferably performed at a temperature lower than the melting temperature of the functional component. Processing methods include mechanical grinding, polishing or wet etching of semiconductor wafers, as well as sputter film formation, resist pattern formation, insulating film formation, wiring formation, drilling, reactive ion etching, and electrical discharge machining. Examples of the method include hole formation, groove formation, dicing, and attachment to an adhesive sheet.

<Process (4)>
After processing the semiconductor wafer, the semiconductor wafer is peeled from the support. In this peeling step, at least one of the semiconductor wafer and the support is heated to a functional component at a melting temperature or higher so that the adhesive layer becomes liquid and the semiconductor wafer is peeled from the support. It can also be peeled off without heating until the adhesive layer becomes liquid. For example, the adhesive layer can be cut and peeled, or either the semiconductor wafer or the support can be convex at the center. It may be peeled off after the outer peripheral portion is lifted by bending until it becomes.

<Step (5)>
If the adhesive remains on the surface of the semiconductor wafer after peeling, it can be removed by washing with the above solvent. Examples of the cleaning method include a method of immersing a wafer in a cleaning solution and a method of spraying a cleaning solution on the wafer. Although the temperature of a washing | cleaning liquid is not specifically limited, Preferably it is 20-80 degreeC, More preferably, it is 30-50 degreeC.

[Example]
EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

In addition, the functional component used in the examples is a tetrahydrofuran solution in advance, 20 parts by weight of ion exchange resin is added, and the mixture is stirred and mixed for 10 hours to perform deionization treatment,
It was used after confirming that each metal content of Na, K, Ca, Fe, Cu, Ni, Cr and Al was 1 ppm or less. The characteristic values of the functional components were determined by the following measurement and evaluation methods.

<Melting temperature, melting temperature range and solidification temperature>
Using a differential scanning calorimeter (“RDC220” (manufactured by Seiko)), the value of only the functional component was measured at 5 ° C./min under nitrogen. The main peak temperature of the melting peak curve was defined as the melting temperature, and the temperature difference between the start point and the end point of the melting peak curve was defined as the melting temperature width. The peak temperature of the exothermic peak curve was defined as the solidification temperature.

<Melt viscosity>
Using a B-type viscometer (manufactured by Toki Sangyo Co., Ltd.), the viscosity (mPa · s) of only the functional component was measured at the melting temperature of the functional component.

<Volatile>
Differential thermothermogravimetric simultaneous measurement device (made by SII Nanotechnology Co., Ltd.)
TG / DTA300) was used to determine what percentage of the initial weight the weight loss when held at melting temperature + 15 ° C. for 1 hour. The case of less than 2% is good, the case of 2% to 10% is acceptable, and the case of 10% or more is judged as poor because volatile matter remains as bubbles in the adhesive layer at the time of bonding.

<Processing allowable temperature>
As shown in FIG. 1, when a silicon wafer and a glass substrate are bonded using only functional components as an adhesive, and the sample is heated with a heating heater while the substrate is pulled under a load of 50 g, and the substrate is peeled off. Was set as the processing allowable temperature (° C.). This allowable processing temperature was used as a guideline for the upper limit temperature when performing various processing as described above.

<Adhesive strength>
As shown in FIG. 1, a sample in which a silicon wafer and a glass substrate are bonded together using only functional components as an adhesive is prepared, and this is pulled using a Tensilon type tensile tester with a tensile speed of 1.67 × 10 ⁻⁴ m. The adhesive strength in the shear direction was measured by pulling up and down at / second. The measurement was performed at room temperature, in the case of 0.4 kgf / cm ² or less failure, and 0.4~2kgf / cm ² is determined Yes, in the case of 2 kgf / cm ² or more favorable.

<Peeling and cleaning removal>
A silicon wafer piece (12 mm x 50 mm) in which copper is sputtered on a silicon wafer and 100 cylindrical solder patterns of 50 μmφ and 30 μm height are formed on the copper with a pattern interval of 0.1 mm and a glass substrate function. A sample as shown in FIG. 1 in which only the components were bonded as an adhesive was prepared, heated to the melting temperature, and peeled off in the shear direction. The shape change of 100 cylindrical solder patterns of the peeled silicon wafer piece was observed with a microscope, and the number of patterns without shape change was measured, and used as an index of ease of peeling. In other words, the larger the number of patterns whose shape does not change, the easier the peeling. When a cellophane tape was applied on the silicon wafer on which the solder pattern was formed and peeled off in a direction perpendicular to the silicon wafer piece, 60 of the 100 solder patterns were dropped. Further, the peeled silicon wafer piece was immersed in isopropyl alcohol at 40 ° C. for 10 minutes, and whether or not the adhesive remained on the solder pattern forming surface was converted into an organic substance in the region of 2800 to 3200 cm ⁻¹ by FT-IR analysis. Judgment was made based on whether or not the resulting CH stretching vibration peak was observed.

<Uniformity of coating film>
The adhesive composition is applied to the entire surface of an 8-inch silicon wafer by an appropriate application method so that the film thickness is in the range of 2 to 20 μm, a coating film is formed, and the thickness at any 10 points in the surface is a stylus type It measured using the film thickness meter, and the thickness difference of the maximum film thickness and the minimum film thickness was computed. The film thickness uniformity was evaluated by calculating the percentage of the thickness difference with respect to the average film thickness. When the percentage of the thickness difference with respect to the average film thickness was 5% or less, it was judged that the film was uniform. The coating film uniformity also affects the adhesion uniformity after bonding.

[Example 1]
<Preparation of adhesive composition and characteristic evaluation>
1,3,5-trimethyl-2,4,6-tris (3,5-ditert-butyl-4-hydroxybenzyl) benzene (molecular weight 775.2; melting temperature 247 ° C .; melting temperature range 15 ° C.) Solidifying temperature: 167 ° C .; melt viscosity of 2 mPa · s) was dissolved in 20 g of cyclohexanone to prepare an adhesive solution (1) having a solid content concentration of 20% and a solution viscosity of 6 mPa · s. When this solution was purified by filtration with a membrane filter (pore size 0.5 μm) three times, the number of particles having a particle size of 1 μm or more was reduced to 1 / mL. When the test shown in FIG. 1 was performed using this adhesive solution (1), the adhesive strength was good and the allowable processing temperature was 230 ° C., so that it was resistant to a process at 200 ° C. I understood that. FIG. 2 shows a DSC thermogram of this functional component. Table 1 shows the properties of this adhesive composition. Table 2
Shows the measurement and evaluation results when the adhesive composition is used.

<Demonstration evaluation of processed substrate>
A 6-inch silicon wafer (thickness: 650 μm) in which a 5% isopropyl alcohol solution of hexamethyldisilazane (HMDS) was spin-coated in advance and then subjected to a hydrophobic treatment on the surface was used as a support plate.

The adhesive solution (1) was formed on the support plate using a scan coating method and dried on a 90 ° C. hot plate for 10 minutes to form a thin adhesive layer having a thickness of 3 μm.
On the obtained support plate, another 6 inch silicon wafer (thickness: 650 μm) was allowed to stand, put into a vacuum hot press apparatus to reduce the pressure to 100 Torr, and held for 5 minutes. Next, the upper and lower heaters of the vacuum hot press apparatus are heated to 260 ° C. When the temperature reaches 260 ° C., the upper and lower press plates are immediately pressed to the thickness of the set value (1302 μm), returned to normal pressure, and simultaneously cooled to room temperature. did. Thereafter, the press was released and the mixture was heated at 220 ° C. for 5 minutes, and then cooled to room temperature.

  When the thickness of the obtained bonded product was measured with a micrometer, it was 1302.5 ± 1 μm, and the thickness of the adhesive layer was controlled within the range of 2.5 ± 1 μm including the variation of the silicon wafer. .

  Next, the back surface of the bonded silicon wafer was polished using a commercially available polishing apparatus (“MA-400D” (manufactured by Musashino Electronics Co., Ltd.)) until the wafer thickness became 30 μm. At this time, the temperature of the wafer reached 60 ° C., but the wafer was not peeled off. When the thickness of the bonded product was measured again, the in-plane thickness variation was in the range of ± 1 μm, and it was found that the in-plane uniform polishing was possible.

  Sputter-deposited titanium to a thickness of 0.1 μm on the entire polished surface of the silicon wafer thinned to 30 μm and copper to a thickness of 0.3 μm, and this is used as a seed layer to form copper to a thickness of 5 μm. To grow. Further, a photosensitive insulating film (“WPR1201” (manufactured by JSR Corporation)) was formed on the copper so as to have a film thickness of 15 μm and cured at 200 ° C. for 1 hour. The thinned wafer was not peeled off from the support even by plating, insulating film application and curing treatment.

  The obtained sample was placed on a hot plate with a vacuum chuck function heated to 260 ° C. with the insulating film layer facing down, and the support plate could be easily peeled by moving the support plate on the side. . Next, the peeled thinned wafer was cooled to room temperature while being chucked, and sprayed with isopropyl alcohol at 40 ° C. to remove the remaining functional components. Even when the support was peeled off, the thinned wafer did not warp. Further, when the peeled surface of the wafer was surface-analyzed by a reflection type FT-IR, no absorption due to the organic compound was observed, and it was found that the adhesive used for bonding was removed by washing. Table 3 shows the results.

[Examples 2 to 4]
The adhesive composition was prepared and properties were evaluated in the same manner as in Example 1 except that the functional components were changed to the compounds shown in Table 1. Tables 1 and 2 show the results.

[Example 5]
<Preparation of adhesive composition and characteristic evaluation>
5 g of the functional component of Example 1 and 0.15 g of Megafac F171 were dissolved in a mixed solvent of 4.5 g of cyclohexanone and 10.5 g of acetone, and an adhesive solution (2% solid content concentration and a solution viscosity of 1.5 mPa · s) ) Was prepared. When this solution was purified by filtration with a membrane filter (pore size 0.5 μm) three times, the number of particles having a particle size of 1 μm or more was reduced to 1 / mL. When this adhesive solution (2) was used for the test as shown in FIG. 1, the adhesive strength was good and the allowable processing temperature was 230 ° C., so that it was resistant to a process at 200 ° C. I found out. Tables 1 to 3 show the results.

<Demonstration evaluation of processed substrate>
On a copper-sputtered 6-inch silicon wafer (thickness: 650 μm), cylindrical protrusions with a diameter of 30 μm and a height of 15 μm were formed by copper plating at intervals of 1 mm, and this was used as a substrate.

A film of the adhesive solution (2) was formed on the substrate by a spin coating method, and dried for 10 minutes on a 50 ° C. hot plate to form a thin adhesive layer having a thickness of 17 μm.
A 6-inch silicon wafer (thickness: 650 μm) in which an adhesive solution (2) was formed into a film with a thickness of 3 μm by spin coating and dried at 180 ° C. for 3 minutes on the obtained substrate was allowed to stand, and this was vacuum-treated. It put into the hot press apparatus, and reduced pressure to 100 Torr, and held for 5 minutes. Next, the upper and lower heaters of the vacuum hot press apparatus are heated to 130 ° C., the upper and lower press plates are pressed to a thickness of a set value (1320 μm) under a load of 300 kgf, and after reaching 130 ° C., held for 1 minute, At the same time as returning, it was rapidly cooled to room temperature. The press was released after cooling to room temperature.

  When the thickness of the obtained bonded product was measured with a micrometer, it was 1319 ± 1 μm, and the thickness of the adhesive layer was controlled in the range of 19 ± 1 μm including the variation of the silicon wafer.

  Next, using a commercially available polishing apparatus (“MA-400D” (manufactured by Musashino Electronics Co., Ltd.)), the back surface of the silicon wafer provided with protrusions was polished until the wafer thickness became 30 μm (not including protrusions). At this time, the temperature of the wafer reached 50 ° C., but the wafer was not peeled off. When the thickness of the bonded product was measured again, it was found that the surface thickness variation was in the range of ± 1 μm, and the surface was uniformly polished.

  A dicing tape (“T-120HW” (manufactured by Toyo Adtec Co., Ltd.)) was bonded to the polished surface of the thinned silicon wafer, and the dicing tape was adsorbed and fixed to a vacuum chuck. The outer periphery of the adhesive layer was cut with a cutter knife, and the support (6 inch silicon wafer) adsorbed with a vacuum chuck was peeled off starting from the cut. The thinned wafer with protrusions was fixed to the dicing tape without being damaged.

  Functional components remaining on the copper protrusions were removed by spraying 40 ° C. isopropyl alcohol. The surface of the copper surface was analyzed by reflective FT-IR, but no absorption due to the organic compound was observed, and it was found that the adhesive used for bonding was removed by washing. The results are shown in Table 3.

[Comparative Example 1]
As a functional component, when the physical property value was measured using 4,4′-butylidenebis (6-tert-butyl-4-methylphenol) having two aromatic rings in the molecule, as shown in FIG. A clear peak due to solidification did not appear, and the allowable processing temperature was 110 ° C., which is 100 ° C. lower than the melting temperature. Further, the adhesive strength is low, and the processing is greatly limited. Tables 1 and 2 show the results.

[Comparative Example 2]
When the physical property value was measured using anthracene (molecular weight 178) as a functional component, the compound sublimated without melting. This compound was found to be unsuitable as an adhesive because of its extremely high volatility. Tables 1 and 2 show the results.

[Comparative Example 3]
When the physical property value was measured using cholesterol having 0 aromatic ring in the molecule as a functional component, the processing allowable temperature was 130 ° C., but the adhesive strength, peeling and washing removal were possible. Since the allowable processing temperature is 130 ° C., it is not suitable for processing at a high temperature (200 ° C.), but it was determined that it can be used as an adhesive if the application range is limited. Tables 1 and 2 show the results.

[Comparative Example 4]
As a functional component, the physical properties were measured using a mixture of 70 parts of the compound of Example 1 and 30 parts of the compound of Comparative Example 3. As a result, the melting temperature range was as wide as 40 ° C., and a clear peak due to solidification was I found that it didn't appear. The adhesive strength was weak and the allowable processing temperature was the same as in Comparative Example 3. Tables 1 and 2 show the results.

[Comparative Example 5]
When a novolak resin containing a large number of aromatic rings was used as a functional component, the viscosity at the time of melting was as high as 980 mPa · s, and the ease of peeling and cleaning removal were poor. Tables 1 and 2 show the results.

[Comparative Example 6]
Characteristic evaluation was performed using a commercially available electron wax ("Wax H" (Furuuchi Chemical Co., Ltd.)) as a functional component. Wax H is a stick-like solid, has an average molecular weight of 2000, and has no aromatic ring. The stick was pressed against a heated substrate and used in an appropriate amount, or it was scraped with a knife and powdered for evaluation. Although it melted at 70 ° C., it was a viscous liquid with a viscosity of 40 mPa · s, and the allowable processing temperature was as low as 40 ° C. Tables 1 and 2 show the results.

表１中の記号は以下の通りである。
Ｆ−１：１，３，５−トリメチル−２，４，６−トリス（３，５−ジｔｅｒｔ−ブチル−４−ヒドロキシベンジル）ベンゼン
Ｆ−２：１，４−ビス［２−（５−フェニルオキサゾリル）］ベンゼン
Ｆ−３：１，１，１−トリス（４−ヒドロキシフェニル）エタン
Ｆ−４：ｍ−ターフェニル
Ｆ−５：４，４’−ブチリデンビス（６−ｔｅｒｔ−ブチル−３−メチルフェノール）
Ｆ−６：アントラセン
Ｆ−７：コレステロール
Ｆ−８：ノボラック樹脂（「レジトップ ＰＳＭ−４３２６」（群栄化学工業社製））
Ｆ−９：エレクトロンワックス（「ワックスH」（フルウチ化学社製））
ＤＧＭＥＡ：酢酸ジエチレングリコールモノエチルエーテル

The symbols in Table 1 are as follows.
F-1: 1,3,5-trimethyl-2,4,6-tris (3,5-ditert-butyl-4-hydroxybenzyl) benzene F-2: 1,4-bis [2- (5- Phenyloxazolyl)] benzene F-3: 1,1,1-tris (4-hydroxyphenyl) ethane F-4: m-terphenyl F-5: 4,4'-butylidenebis (6-tert-butyl- 3-methylphenol)
F-6: Anthracene F-7: Cholesterol F-8: Novolac resin ("Resist Top PSM-4326" (manufactured by Gunei Chemical Industry Co., Ltd.))
F-9: Electron wax ("Wax H" (Furuuchi Chemical Co., Ltd.))
DGMEA: Acetic acid diethylene glycol monoethyl ether

It is a figure which shows the measuring method of process allowable temperature. 2 is a DSC thermogram of 1,3,5-trimethyl-2,4,6-tris (3,5-ditert-butyl-4-hydroxy) benzene.

Claims (2)

1,3,5-trimethyl-2,4,6-tris (3,5-ditert-butyl-4-hydroxybenzyl) benzene, 1,4-bis [2- (5-phenyloxazolyl)] benzene , 1,1,1-tris (4-hydroxyphenyl) ethane or m-terphenyl 80 to 100% by weight adhesive composition for temporary fixing (however, 100% by weight of all solid components in the adhesive composition) %.) The adhesive composition according to claim 1, wherein the adhesive composition is used for temporarily fixing the substrate to a support in a fine processing of a semiconductor substrate.

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