JP7489898B2 - Substrate-less silicone adsorption sheet, laminate for wafer processing using said sheet, and wafer processing method using said laminate for processing - Google Patents

Description

In the fields of semiconductor-related material manufacturing, electrical/electronic component manufacturing, display device manufacturing, and the like, two members (examples of such members include glass substrates and silicon wafers) are bonded together with an adhesive, and one side of the resulting laminate consisting of member/adhesive/member is processed. The present invention relates to a substrate-less silicone adsorption sheet used in such fields, a wafer processing laminate using said sheet, and a wafer processing method using said processing laminate.

For example, in the semiconductor industry, semiconductor wafers are being made thinner and thinner to meet the demands of higher density chip stacking technology that is being achieved by making packages thinner and smaller. Thinning is achieved by backgrinding the surface of the wafer opposite to the surface (circuit surface) on which a pattern is formed. Conventionally, the wafer is held with a backgrind (hereinafter referred to as BG) protective tape attached, which has an adhesive layer that has a high peeling force with the wafer surface during the grinding process, but which reduces the peeling force with the wafer surface after the grinding process by light irradiation, heat treatment, etc., and after backgrinding, an adhesive protective tape called a dicing tape is attached to the back surface of the wafer and fixed to a ring frame, etc., and the peeling force between the adhesive layer and the wafer is reduced by light irradiation or heat treatment, the BG protective tape is peeled off, and individual chips are produced by dicing.

However, with the trend toward higher density, in flip chip mounting and the like, a semiconductor chip mounting technology is usually used in which bumps made of solder or the like are mounted on the circuit surface to bond the semiconductor chip to the substrate. Recently, the method in which bumps are pre-bonded to the circuit surface of the semiconductor wafer at high density is becoming mainstream. Therefore, the surface unevenness of the wafer surface can be several tens of μm, and in some cases, can exceed 100 μm. If the backside of such a bumped wafer is ground using a conventional BG protective tape, the adhesive layer does not follow the height difference of the bumps on the surface and is not embedded. During grinding, the pressure difference caused by the height difference between the parts with bumps and the parts without bumps directly affects the backside of the wafer, causing depressions called dimples and cracks on the backside of the wafer, which ultimately damages the semiconductor wafer.

One solution to this issue of conformability to uneven surfaces is to thicken the adhesive layer of the BG tape and increase the fluidity of the adhesive to bond the adhesive layer to the wafer, eliminating the pressure difference caused by the bump steps using the cushioning properties of the adhesive layer. However, making the adhesive layer thicker and increasing its fluidity makes it easier for the adhesive to get around the base of the bump. For this reason, the adhesive adhering to the base of the bump may undergo cohesive failure when the surface protection sheet is peeled off, leaving some of the adhesive on the circuit surface. If the adhesive remaining on the circuit surface is not removed by solvent cleaning or the like, it will remain as foreign matter inside the device and will impair the reliability of the completed device.

In addition, instead of thickening the adhesive layer, various proposals have been made to provide an intermediate layer between the base film of the surface protection tape and the adhesive layer, which has a so-called cushioning function to absorb and mitigate the height difference of the bumps. (For example, Patent Document 1) However, when the adhesive sheet proposed in Patent Document 1 is attached to the wafer surface and back grinding is performed, the intermediate layer softens due to the heat generated during grinding, which can reduce the grinding accuracy. Furthermore, when the adhesive sheet is wound into a roll, transported, stored, etc., it is exposed to high temperatures, especially in the summer, which can soften the intermediate layer and adhesive layer, causing resin components to seep out from the sides of the roll.

Furthermore, in response to the need for higher density through chip stacking technology that allows for thinner and smaller packages, hopes are being placed on three-dimensional semiconductor packaging, for example, to achieve even higher density, larger capacity, faster speeds, and lower power consumption. Three-dimensional semiconductor packaging technology is a semiconductor manufacturing technology in which a single semiconductor chip is thinned and then stacked in multiple layers while being connected using through-silicon vias (TSVs). To achieve this, it is necessary to thin the substrate on which the semiconductor circuits are formed by grinding the non-circuit formation surface (backside of the wafer), but there is now an increasingly high demand for the wafer thickness after grinding to be between 10 μm and 30 μm.

Even in the case of three-dimensional semiconductor mounting, as with flip-chip mounting, the surface of the wafer on which the circuits are formed usually has bumps and other features formed, making the surface uneven, and the surface protective layer must be able to conform to the uneven surface. Also, to prevent warping of the wafer with protective tape during grinding and to ensure thickness uniformity during grinding, a wafer support system using a temporary support is required.

Furthermore, in the case of three-dimensional semiconductor packaging, the grinding process is followed by a TSV formation process and a wiring layer formation process on the back side, which involves high-temperature processing at 200°C or higher. The adhesive layer used in conventional BG protective tapes, which reduces the peeling force through UV irradiation or heat treatment, has insufficient heat resistance and problems with peeling suitability arise. In addition, in the case of three-dimensional semiconductor packaging, which involves high positional precision in high-temperature processing, the thermal expansion coefficients of the temporary support, such as silicon wafers or glass, and the base film of the BG protective tape must be balanced. From this perspective, temporary adhesion without a base material is also desirable.

In general, it is difficult to separate fragile rigid members via an adhesive layer. For example, Patent Document 2 proposes a technology in which a heat-melting hydrocarbon compound is used as a substrate-less temporary adhesive, and bonding and peeling are performed in a heated and molten state. In this case, while it is simple because it is controlled only by heating, the thermal stability at high temperatures exceeding 200°C is insufficient, and furthermore, these temporary adhesives are not suitable for forming a uniform film thickness on a substrate with a high step difference, and for complete adhesion to the support.

On the other hand, Patent Documents 3 and 4 describe a wafer support system that is made using a UV-curable liquid adhesive material and a photothermal conversion adhesive paint, and is composed of a laminate including a semiconductor wafer (circuit surface)/a peelable UV-cured adhesive layer/a photothermal conversion layer/a light-transmitting temporary support. By using this system, the UV-cured adhesive layer on the circuit surface has excellent unevenness absorption properties, peeling between fragile rigid members is easy, ultra-thin grinding of the back surface of the wafer is possible, and it is also possible to handle three-dimensional mounting involving high-temperature processing.
However, in this case, in a wafer processing laminate consisting of a semiconductor wafer (circuit surface)/peelable UV-cured adhesive layer/photothermal conversion layer/light-transmitting temporary support, in order to peel the semiconductor wafer with the adhesive layer from a temporary support such as glass, it is necessary to irradiate the photothermal conversion layer containing a light-absorbing substance with high-intensity laser light and thermally decompose the adhesive layer, thereby peeling it off from the support, which requires expensive laser equipment and involves problems such as a long processing time per substrate.

As a means for solving the problems of Patent Document 3 and Patent Document 4, Patent Document 5 and Patent Document 6 describe a temporary adhesive for wafer processing, which is composed of a composite temporary adhesive layer having a three-layer structure of a first temporary adhesive layer composed of a non-silicone thermoplastic resin layer (A) that can be peelably adhered to the surface of a wafer, a second temporary adhesive layer composed of a thermosetting siloxane polymer layer (B) laminated on the first temporary adhesive layer, and a third temporary adhesive layer composed of a thermosetting siloxane modified polymer layer (C) that is laminated on the second temporary adhesive layer and can be peelably adhered to a temporary support, and a method for adhering a wafer to a temporary support.

However, the methods described in Patent Documents 5 and 6 are cumbersome because the person who creates the laminate for wafer processing must handle the thermosetting siloxane polymer or thermosetting siloxane modified polymer liquid and perform the thermal curing process. Furthermore, in semiconductor processing, handling of such liquids is generally avoided due to the adverse effects it may have on other processes. Also, it is not clearly stated which layers are peeled off when the wafer is peeled off from the temporary support.

Meanwhile, Patent Document 7 describes a substrateless silicone double-sided tape that is used when two members (examples of such members include a glass substrate and a silicon wafer) are bonded together with an adhesive, and one side of the resulting laminate consisting of members/adhesive/members is processed, the substrateless silicone double-sided tape having a laminate configuration in which a first release sheet, an adhesive layer formed from a silicone-based adhesive composition, and a second release sheet are arranged in that order, the difference in adhesive strength between the two main surfaces of the adhesive layer being 2 mN/25 mm or more and 20 mN/25 mm or less, and the adhesive strength of the main surface of the member with the higher adhesive strength in the adhesive layer being 700 mN/25 mm or less.

If a grinding member with a peelable UV-cured adhesive layer having excellent irregularity absorption properties for the circuit surface of a semiconductor wafer as described in Patent Documents 3, 4, 5, and 6, or a peelably adhesive non-silicone thermoplastic resin layer (hereinafter, these layers are referred to as a bonding layer), and a temporary support such as glass or silicon can be temporarily fixed with a substrateless silicone pressure-sensitive adhesive layer prepared using a substrateless double-sided silicone tape prepared in advance, and if the grinding member with the bonding layer can be peeled from the substrateless silicone pressure-sensitive adhesive layer even after the high-temperature processing is performed after the back surface of the wafer is ground, the work of preparing a laminate for wafer processing will be greatly facilitated, and a more suitable wafer support system can be expected due to the high heat resistance of the silicone pressure-sensitive adhesive layer.

On the other hand, as mentioned above, the peeling between rigid members which are easily broken through the adhesive layer is difficult compared with the peeling between rigid body and base film through the adhesive layer.The inventors, for example, have a glass temporary support with a surface roughness Ra of 0.08 μm and a thickness of 5.0 mm, and a silicone adsorption layer surface of a member with a crosslinked silicone adsorption layer of 20 μm described below is provided on the adhesive layer, and the silicone adsorption layer surface of the member is bonded to a glass grinding body with a surface roughness Ra of 0.08 μm and a thickness of 0.5 mm, and the peeling force of the silicone adsorption layer is changed.In the experiment, the inventors have found that if the peeling force between the silicone adsorption layer surface and the glass grinding body is 60 mN/25 mm or less and 5 mN/25 mm or more, the shear force is also maintained at 1 N/cm ² or more, and the glass grinding body can be ground in a fixed state in the grinding process of the glass grinding body, and the glass grinding body and the silicone adsorption layer can be smoothly peeled off after grinding.
However, when the peeling force between the rigid member and the silicone adsorption layer interface is in a low range, it is not easy to achieve this by using a substrate-less silicone adsorption sheet.For example, in the silicone adhesive layer of the substrate-less silicone double-sided tape described in Patent Document 7, the difference between the peeling force between the temporary support/the silicone adhesive layer and the peeling force between the grinding object/the silicone adhesive layer is too small, so there is a problem that it is difficult to reliably peel only the rigid body after grinding from the silicone adhesive layer interface.As a result, when the silicone adhesive layer remains on the bonding layer surface, the process of removing the silicone adhesive layer is also required in the process of removing the bonding layer afterwards.

JP 2001-203255 A JP 2006-328104 A JP 2004-064040 A JP 2005-159155 A JP 2015-179692 A JP 2016-119438 A JP 2014-198787 A

The present invention has been made in consideration of the above-mentioned circumstances, and a first object of the present invention is to provide a substrate-less silicone adsorption sheet that can be easily temporarily attached to a temporary support to the non-working surface of a member to be processed, such as grinding, and which enables reliable peeling between the processed member and the silicone adsorption layer.
The second object of the present invention is to provide a wafer processing laminate using the substrate-less silicone adsorption sheet, which has good conformability of the bonding layer to the unevenness of a high-step wafer substrate, is highly compatible with TSV formation and wafer back surface wiring processes, and has excellent resistance to wafer thermal processes such as CVD (chemical vapor deposition), is easy to peel, and can increase the productivity of thin wafers, and to provide a wafer processing method using the wafer processing laminate.

The following is a detailed explanation of the means by which the present invention achieves the above objectives.

The invention according to claim 1 provides a substrate-less silicone adsorption sheet having a structure of a first release film/a first silicone adsorption layer A formed from a silicone composition/a second silicone adsorption layer B formed from a silicone composition/a second release film,
The first and second silicone adsorption layers are silicone adsorption layers formed by crosslinking at least one silicone selected from a silicone made of a linear polyorganosiloxane having vinyl groups only at both ends and a silicone made of a linear polyorganosiloxane having vinyl groups at both ends and in a side chain,
the peel strength between the first release film and the first silicone adsorption layer A is greater than the peel strength between the second release film and the second silicone adsorption layer B, the difference between the peel strengths being 15 mN/25 mm or more, and the peel strength between the first release film and the first silicone adsorption layer A being 80 mN/25 mm or less;
This is a substrate-less silicone adsorption sheet, characterized in that the peel strength of the first silicone adsorption layer A after peeling off the first and second release films is 60 mN/25 mm or less and 5 mN/25 mm or more against a glass substrate having a surface roughness Ra of 0.08 μm for evaluation, and the peel strength of the second silicone adsorption layer B is 100 mN/25 mm or more against the glass substrate.

The invention of claim 2 is a substrate-less silicone adsorption sheet as described in claim 1, characterized in that the first silicone adsorption layer A contains an MQ resin consisting of M units (R ₃ SiO _1/2 : R is a monovalent organic group such as a methyl group or a phenyl group) and Q units (SiO _4/2 ) in an amount of 0 to 13 weight % of the solid content of the first silicone adsorption layer A, and the second silicone adsorption layer B contains the MQ resin in an amount of 20 to 30 weight % of the solid content of the second silicone adsorption layer B.

The invention according to claim 3 is a laminate for wafer processing, comprising a wafer in the form of a temporary support/the second silicone adsorption layer B/the first silicone adsorption layer A/a wafer surface on which a circuit is formed, with a silicone adsorption layer consisting of the first silicone adsorption layer A and the second silicone adsorption layer B of the substrate-less silicone adsorption sheet according to claims 1 and 2 interposed therebetween,
the wafer surface on which the circuits are formed is provided by a coating method with a radiation-sensitive resin composition containing a radiation-sensitive radical polymerization initiator, a bifunctional urethane (meth)acrylate oligomer having a number average molecular weight of 3,000 or more in a total amount of 40% by weight or more, and a bifunctional (meth)acrylic monomer in a total amount of 25% by weight or more, so that protruding portions of the wafer surface on which the circuits are formed are covered, and the radiation-sensitive resin composition is then cured by irradiation with radiation.

The invention according to claim 4 is a laminate for wafer processing, comprising a wafer in the form of a temporary support/the second silicone adsorption layer B/the first silicone adsorption layer A/a wafer surface on which a circuit is formed, with a silicone adsorption layer consisting of the first silicone adsorption layer A and the second silicone adsorption layer B of the substrate-less silicone adsorption sheet according to claims 1 and 2 interposed therebetween,
The wafer has a bonding layer formed on a surface of the wafer on which a circuit is formed, the bonding layer being formed by applying a radiation-sensitive resin composition containing (A) an alkali-soluble copolymer having a constituent unit derived from a radically polymerizable compound having at least a carboxyl group, (B) a compound having at least one ethylenically unsaturated double bond, and (C) a radiation-induced radical polymerization initiator by a coating method so that protruding portions of the wafer surface on which a circuit is formed are covered, and the bonding layer is then cured by irradiation with radiation, the cured bonding layer being removable with a stripping liquid consisting of an alkaline solution.

The invention according to claim 5 is a laminate for wafer processing according to claim 3 or claim 4, characterized in that after forming a bonding layer by applying the radiation-sensitive resin composition according to claim 3 or claim 4 to the surface of a wafer on which a circuit is formed so that the convex parts of the surface of the wafer on which the circuit is formed are covered, the bonding layer surface of the wafer is bonded to a transparent release substrate having a smooth surface, the bonding layer is cured by irradiating radiation from the transparent release substrate side, the transparent release substrate is peeled off, and the bonding layer surface of the wafer is bonded to the first silicone adsorption layer A surface of a member formed on a temporary support and consisting of a temporary support/the second silicone adsorption layer B/the first silicone adsorption layer A.

The invention according to claim 6 is a method for producing thin wafer singulation, which uses the laminate for wafer processing according to claim 3 to grind the non-circuit-forming surface of the wafer bonded to the temporary support, and then performs various processes on the thinned wafer as necessary. After that, a dicing tape is attached to the ground surface of the ground laminate, and the wafer is peeled together with the dicing tape between the first silicone adsorption layer A surface and the bonding layer surface, and the thinned wafer is diced into individual pieces, and then the bonding layer of the individualized chip is peeled off from the wafer surface on which the circuits are formed using an adhesive tape.

The invention of claim 7 is a method for producing thin wafer individual pieces, characterized in that the non-circuit forming surface of the wafer bonded to the temporary support is ground using the wafer processing laminate described in claim 4, the thinned wafer is subjected to various processes as necessary, a dicing tape is attached to the ground processed surface of the ground laminate, the wafer together with the dicing tape is peeled off between the first silicone adsorption layer A surface and the bonding layer surface, and the wafer is diced by the following process (1) or (2).
(1) removing the bonding layer from the surface of a wafer on which circuits are formed using a stripping solution made of an alkaline solution, and then dicing the thinned wafer into individual pieces; (2) dicing the thinned wafer having the bonding layer into individual pieces, and then removing the bonding layer from the surface of the individualized wafer on which circuits are formed using a stripping solution made of an alkaline solution.

The substrate-less silicone adsorption sheet of the present invention allows for easier grinding of thin wafers of 30 μm or less with less workability and without causing warping of the wafer during grinding. Furthermore, even after a process of performing a heat treatment at 200°C or higher or a treatment involving heat generation, the thinned semiconductor wafer can be smoothly peeled off from the temporary support, and the bonding layer can be easily peeled off or removed from the wafer without leaving any residue.

1 is a cross-sectional view showing an example of a layer structure of a laminate for wafer processing of the present invention.

The present invention relates to a substrate-less silicone adsorption sheet used in the fields of semiconductor-related material manufacturing, electrical and electronic component manufacturing, display device manufacturing, etc., a wafer processing laminate using said sheet, and a wafer processing method using said processing laminate. The present invention will be described in more detail below.

<Silicone Adsorption Layer>
The silicone adsorption layer of the present invention is made by crosslinking at least one silicone selected from the silicone of linear polyorganosiloxane having vinyl groups only at both ends and the silicone of linear polyorganosiloxane having vinyl groups at both ends and side chains, and as is well known in the art, the force (hereinafter referred to as shear force) that displaces the silicone adsorption layer surface and the adherend parallel to the adherend surface is usually a high value of 1.0 N/ ^cm2 or more, but the force (hereinafter referred to as peel force) when peeling the silicone adsorption layer from the adherend is small.Therefore, it has a high fixing power to the adherend like the acrylic pressure sensitive adhesive used in conventional BG tapes, and has physical properties different from the system that reduces the peel force by light irradiation, etc.

The high shear force exerted by the silicone adsorption layer on the adherend is due to the van der Waals force between closely spaced opposing solid molecules ("The Science of Friction," Shokabo Publishing, pp. 56-65 and "Basic Theory of Adhesion," Polymer Publishing, pp. 116-120). Therefore, the high shear force exerted by the silicone adsorption layer of the present invention on the adherend is effective when the silicone adsorption layer and the adherend surface are in close contact with each other.

<Substrate-less silicone adsorption sheet>
The substrate-less silicone adsorption sheet of the present invention is a substrate-less silicone adsorption sheet having a structure of a first release film/a first silicone adsorption layer A formed from a silicone composition/a second silicone adsorption layer B formed from a silicone composition/a second release film,
The first and second silicone adsorption layers are silicone adsorption layers formed by crosslinking at least one silicone selected from a silicone made of a linear polyorganosiloxane having vinyl groups only at both ends and a silicone made of a linear polyorganosiloxane having vinyl groups at both ends and in a side chain,
the peel strength between the first release film and the first silicone adsorption layer A is greater than the peel strength between the second release film and the second silicone adsorption layer B, the difference between the peel strengths being 15 mN/25 mm or more, and the peel strength between the first release film and the first silicone adsorption layer A being 80 mN/25 mm or less;
This is a substrate-less silicone adsorption sheet, characterized in that the peel strength of the first silicone adsorption layer A after peeling off the first and second release films is 60 mN/25 mm or less and 5 mN/25 mm or more against a glass substrate having a surface roughness Ra of 0.08 μm for evaluation, and the peel strength of the second silicone adsorption layer B is 100 mN/25 mm or more against the glass substrate.

The linear polyorganosiloxane having vinyl groups only at both ends, which is one form of silicone according to the present invention, is a compound represented by the following general formula (Chemical Formula 1).

（式中Ｒは下記有機基、ｍは整数を表す）
このビニル基以外のケイ素原子に結合した有機基（Ｒ）は異種でも同種でもよいが、具体例としてはメチル基、エチル基、プロピル基などのアルキル基、フェニル基、トリル基、などのアリール基、またはこれらの基の炭素原子に結合した水素原子の一部または全部をハロゲン原子、シアノ基などで置換した同種または異種の非置換または置換の脂肪族不飽和基を除く１価炭化水素基で好ましくはその少なくとも５０モル％がメチル基であるものなどが挙げられるが、このジオルガノポリシロキサンは単独でも２種以上の混合物であってもよい。

(In the formula, R represents an organic group and m represents an integer.)
The organic groups (R) bonded to the silicon atoms other than vinyl groups may be of the same or different types, and specific examples include alkyl groups such as methyl, ethyl, and propyl groups, aryl groups such as phenyl and tolyl groups, and the like, and the same or different monovalent hydrocarbon groups, excluding unsubstituted or substituted aliphatic unsaturated groups, in which some or all of the hydrogen atoms bonded to the carbon atoms of these groups have been substituted with halogen atoms, cyano groups, or the like, and preferably at least 50 mol % of these groups are methyl groups. This diorganopolysiloxane may be used alone or as a mixture of two or more types.

Another form of silicone according to the present invention, a silicone made of a linear polyorganosiloxane having vinyl groups at both ends and in the side chain, is a compound in which part of R in the above general formula (Chemical Formula 1) is a vinyl group.

The silicone of the present invention may also be in the form of a linear polyorganosiloxane having alkenyl groups with 4 or more carbon atoms at at least both ends, as disclosed in JP-A-10-120992 as a release agent.

The crosslinking agent used in the crosslinking reaction may be a known one. An example of a crosslinking agent is organohydrogenpolysiloxane. Organohydrogenpolysiloxane has at least three hydrogen atoms bonded to silicon atoms in one molecule, but in practice, it is preferable that those having two ≡SiH bonds in the molecule account for up to 50% by weight of the total amount, with the remainder containing at least three ≡SiH bonds in the molecule. A crosslinking accelerator may also be added. For example, 3-methyl-1-butene-3-ol is a preferred crosslinking accelerator.

Platinum catalysts used in the crosslinking reaction include chloroplatinic acids such as chloroplatinic acid and chloroplatinic acid, alcohol compounds of chloroplatinic acid, aldehyde compounds, and chain salts of chloroplatinic acid and various olefins. The polyorganosiloxane silicone resin obtained by the crosslinking reaction has flexibility like silicone gel, and this flexibility makes it easy to adhere to the rigid substrate that is the adherend.

A silicone adsorption layer is formed by crosslinking at least one silicone selected from a silicone consisting of a linear polyorganosiloxane having vinyl groups only at both ends and a silicone consisting of a linear polyorganosiloxane having vinyl groups at both ends and in the side chain, and a substrate-less silicone adsorption sheet having a first release film/silicone adsorption layer/second release film configuration is used to laminate a temporary support consisting of two fragile rigid substrates and a processing member with the silicone adsorption layer interposed therebetween.In order to enable smooth peeling between the processing member and the silicone adsorption layer after the back surface of the processing member is processed, the peel force between the processing member and the silicone adsorption layer must be sufficiently smaller than the peel force between the temporary support and the silicone adsorption layer.
Furthermore, as described below, in order to laminate the laminate, the peel force between the first release film and the silicone adsorption layer and the peel force between the second release film and the silicone adsorption layer must also be taken into consideration.

Typically, unlike the case of peeling between a rigid body such as glass and a flexible film via the silicone adsorption layer, it is difficult to smoothly peel between a rigid body such as a temporary support made of a fragile glass substrate and a rigid body such as a ground wafer with a bonding layer via the silicone adsorption layer. The inventors first conducted a preliminary experiment in which, for example, an adhesion layer was formed by a coating method on a temporary glass support having a surface roughness (Ra) of 0.08 μm and a thickness of 5.0 mm, and a crosslinked silicone adsorption layer (described below) of 20 μm was formed on the adhesion layer. The silicone adsorption layer surface of this member was then bonded to a glass body to be ground having a surface roughness (Ra) of 0.08 μm and a thickness of 0.5 mm, and the peel force of the silicone adsorption layer was varied. It was found that if the peel force between the silicone adsorption layer surface and the glass body to be ground was 60 mN/25 mm or less and 5 mN/25 mm or more, the shear force was also maintained at ¹ N/cm2 or more, and the glass body to be ground could be ground in a fixed state during the grinding process of the glass body to be ground, and smooth peeling between the glass body to be ground and the silicone adsorption layer was possible after grinding.

However, when the silicone adsorption layer is a single layer, the peel strength between the front and back of the crosslinked silicone adsorption layer itself does not change significantly. Even if the peel strength between the temporary support and the silicone adsorption layer can be made slightly greater than the peel strength between the processing member and the silicone adsorption layer by conventional techniques, there is a problem that peeling may occur at the interface between the temporary support and the silicone adsorption layer when attempting to peel the processing member and the silicone adsorption layer. One possible solution to this problem is to provide a peel strength improving layer for the silicone adsorption layer on the surface of the temporary support, but from the viewpoint of workability, the present invention aims to solve this problem without providing a peel strength improving layer.

In order to achieve reliable peeling between the bonding layer surface of the bonding layer-coated wafer and the silicone adsorption layer surface without peeling at the interface between the temporary support and the silicone adsorption layer, the inventors have conducted intensive research and found that if the silicone adsorption layer has a two-layer structure of a first silicone adsorption layer A and a second silicone adsorption layer B, and the peeling force of the first silicone adsorption layer is 60 mN/25 mm or less and 5 mN/25 mm or more against a glass substrate having a surface roughness Ra of 0.08 μm for evaluation, and the peeling force of the second silicone adsorption layer B is 100 mN/25 mm or more against the glass substrate, then smooth peeling is possible between the bonding layer surface of the bonding layer-coated wafer and the silicone adsorption layer A surface.
In other words, the difference between the peeling force between the second silicone adsorption layer B surface and the temporary support and the peeling force between the first silicone adsorption layer A surface and the bonding layer surface of the bonding layer-attached wafer must be 40 mN/25 mm or more. In addition, the peeling force between the first silicone adsorption layer A and the glass substrate is preferably 5 mN/25 mm or more so that the processed member does not fall off the silicone adsorption layer when handling the laminate. The upper limit of the second silicone adsorption layer with respect to the glass substrate is not particularly limited, but is preferably 500 mN/25 mm or less from the viewpoint of reusing the temporary support.

As a technical means for keeping the peeling strength of the first silicone adsorption layer A and the second silicone adsorption layer B within the above range, this can be achieved by adjusting the amount of MQ resin relative to the solid content of the first silicone adsorption layer A and the second silicone adsorption layer B, which are made by crosslinking at least one type of silicone selected from a silicone made of a linear polyorganosiloxane having vinyl groups only at both ends and a silicone made of a linear polyorganosiloxane having vinyl groups at both ends and in the side chain.

MQ resin is characterized as a silicone-based resin with a three-dimensional structure that is soluble in solvents such as toluene and is composed of general formula M units ( _{R3SiO1 /2} : R is a monovalent organic group such as a methyl group or a phenyl group) and general formula Q units (SiO4 _/2 ). By mixing it with addition reaction type silicone and curing it, it becomes possible to adjust the release force.
As the MQ resin for adjusting the release force, those having a molar ratio of R ₃ SiO _1/2 units/SiO _4/2 units of 0.6 to 1.8 and a number average molecular weight (Mn) of 5,000 to 300,000 are commercially available and are preferably used.

Regarding the amount of the MQ resin added, for the first silicone adsorption layer A, the MQ resin is contained in an amount of 0 to 13 weight % of the solid content of the first silicone adsorption layer A, and for the second silicone adsorption layer B, the MQ resin is contained in an amount of 20 to 30 weight % of the solid content of the second silicone adsorption layer B. This makes it possible to achieve the requirement that the peel strength of the first silicone adsorption layer A is 60 mN/25 mm or less and 5 mN/25 mm or more for a glass substrate having a surface roughness Ra of 0.08 μm, and the peel strength of the second silicone adsorption layer B is 100 mN/25 mm or more for the glass substrate, and the requirement of 500 mN/25 mm or less when considering reuse of the glass substrate in contact with the second silicone adsorption layer B.
If the amount of the MQ resin added to the second silicone adsorption layer B is less than the above range, the release force will be insufficient, while if it exceeds the above range, the silicone adsorption layer will be prone to plastic deformation and air bubbles will be prone to occur due to the inclusion of foreign matter. The linear polyorganosiloxane having vinyl groups, crosslinking agent, catalyst, and MQ resin constituting the first silicone adsorption layer A and the second silicone adsorption layer B may be the same or different.

The silicone composition according to the present invention is commercially available in the form of solventless, solvent, or emulsion, and any of these types can be used. Among these, the solventless type has great advantages in terms of safety, hygiene, and air pollution because it does not use a solvent, but even in the solventless type, aromatic hydrocarbon solvents such as toluene and xylene, aliphatic hydrocarbon solvents such as hexane, heptane, octane, and isoparaffin, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, ester solvents such as ethyl acetate and isobutyl acetate, ether solvents such as diisopropyl ether and 1,4-dioxane, or mixed solvents of these are used as necessary to adjust the viscosity to obtain the desired film thickness.

As described above, the shear force of the silicone adsorption layer formed by crosslinking at least one silicone selected from a silicone made of a linear polyorganosiloxane having vinyl groups only at both ends and a silicone made of a linear polyorganosiloxane having vinyl groups at both ends and in the side chain is high, usually 1.0 N/cm ² or more, but in order to satisfy this shear force, the total film thickness of the first silicone adsorption layer A and the second silicone adsorption layer B is preferably 10 to 100 μm. If it is less than 10 μm, the shear force against the adherend cannot be secured, and if it exceeds 100 μm, it is cost-effective.
The ratio of the film thicknesses of the first silicone adsorption layer A and the second silicone adsorption layer B within the range of the total film thickness of the first silicone adsorption layer A and the second silicone adsorption layer B can be adjusted within a range that satisfies the peel force relationship described in paragraph 0039.

As a method for applying the silicone composition according to the present invention, a multi-stage roll coater, such as a three-roll offset gravure coater or a five-roll coater, a direct gravure coater, a bar coater, an air knife coater, or the like, may be appropriately used.

<Relationship between the peeling force between the first release film and the first silicone adsorption layer A and the peeling force between the second release film and the second silicone adsorption layer B>
On the other hand, in order to prepare the processing laminate, it is necessary to satisfy the relationship between the glass substrate and the first silicone adsorption layer A, which has a low peel strength, and the relationship between the glass substrate and the second silicone adsorption layer B, which has a high peel strength, while also taking into consideration the relationship between the peel strength between the first release film and the first silicone adsorption layer A and the peel strength between the second release film and the second silicone adsorption layer B.
According to the inventors, in a substrate-less silicone adsorption sheet having a structure of first release film/first silicone adsorption layer A/second silicone adsorption layer B/second release film, in order to stably peel off only one of the release films from the adsorption sheet, the difference between the "peeling force between the first release film and first silicone adsorption layer A" and the "peeling force between the second release film and second silicone adsorption layer B" needs to be 15 mN/25 mm or more.

In view of this, the present inventors have conducted extensive research and have found that in a substrate-less silicone adsorption sheet having a configuration of first release film/first silicone adsorption layer A formed from a silicone composition/second silicone adsorption layer B formed from a silicone composition/second release film,
The first and second silicone adsorption layers are silicone adsorption layers formed by crosslinking at least one silicone selected from a silicone made of a linear polyorganosiloxane having vinyl groups only at both ends and a silicone made of a linear polyorganosiloxane having vinyl groups at both ends and in a side chain,
the peeling force of the first silicone adsorption layer A after peeling off the first and second release films is 60 mN/25 mm or less and 5 mN/25 mm or more with respect to a glass substrate having a surface roughness Ra of 0.08 μm for evaluation, and the peeling force of the second silicone adsorption layer B is 100 mN/25 mm or more with respect to the glass substrate;
and the substrate-less silicone adsorption sheet is characterized in that the peel strength between the first release film and the first silicone adsorption layer A having a low peel strength is greater than the peel strength between the second release film and the second silicone adsorption layer B having a high peel strength, the difference in the peel strengths being 15 mN/25 mm or more, and the peel strength between the first release film and the first silicone adsorption layer being 80 mN/25 mm or less.
It was found that only the second release film can be smoothly peeled off from the substrate-less silicone adsorption sheet, and then the second silicone adsorption layer B side of the adsorption sheet is bonded to a temporary support surface, after which only the first release film can be smoothly peeled off, and then the first silicone adsorption layer A side is bonded to the bonding layer surface of the bonding layer-coated wafer, and after the backside is ground, a dicing tape is applied to the ground wafer surface, and the ground wafer can be smoothly peeled off between the first silicone adsorption layer surface and the bonding layer surface.

Technical means for ensuring that the peel force between the first release film and the first silicone adsorption layer A, which has a low release force, is greater than the peel force between the second release film and the second silicone adsorption layer B, which has a high release force, with the difference in peel forces being 15 mN/25 mm or more, and for keeping the peel force between the first release film and the first silicone adsorption layer A within the range of 80 mN/25 mm or less, can be achieved by selecting the base film and release agent used in conventionally known release films, and by the lamination method of the first silicone adsorption layer and the second silicone adsorption layer.
One example is a method in which a fluorine-based release agent layer with excellent release properties is provided on one side of a polyester film, the second silicone adsorption layer B with high release strength is coated on the release agent layer surface, and the first silicone adsorption layer A with low release strength is further coated on the second silicone adsorption layer B, and then an untreated polyester film is laminated thereto, but this is not limited to this method.

Examples of the base film of the first and second release films include conventionally known polyethylene films, polypropylene films, polybutene films, polybutadiene films, polymethylpentene films, polyvinyl chloride films, vinyl chloride copolymer films, polyethylene terephthalate films, polyethylene naphthalate films, polybutylene terephthalate films, polyurethane films, ethylene vinyl acetate films, ionomer resin films, ethylene-(meth)acrylic acid copolymer films, ethylene-(meth)acrylic acid ester copolymer films, polystyrene films, polycarbonate films, polyimide films, polyetherimide films, polyaramid films, polyether ketone films, polyether ether ketone films, and fluororesin films, and may be laminated films of these.
The thickness of the base film is not particularly limited, but is preferably about 10 to 100 μm, and it is preferable that the thickness of the second release film, which is peeled off first, is thinner than the thickness of the first release film.

As the release agent when a release layer is provided on the release film of the present invention, a conventionally known release agent can be used, but a release layer formed from a fluorine-based release agent is particularly preferred, and the coating amount of the fluorine-based release agent is usually about 0.02 to 2.0 g/ ^m2 . The coating method is not particularly limited, and any known coating method may be used. Specific examples of the coating method include gravure coating, Mayer bar coating, and kiss coating.

The surface roughness Ra of the release film is preferably 0.2 μm or less. If the surface roughness is greater than 0.2 μm, the irregularities on the separator surface may be transferred to the silicone adsorption layer surface, and sufficient shear force may not be obtained with the adherend. In addition, air bubbles may easily become mixed in when the adsorption layer is attached to the adherend.

Next, we will explain a laminate for wafer processing that is composed of a temporary support/the second silicone adsorption layer B/the first silicone adsorption layer A/a wafer with a bonding layer that is applied by a coating method using the substrate-less silicone adsorption sheet of the present invention so that the convex portions of the wafer surface on which the circuit is formed are covered.

The first form of the bonding layer of the wafer with a bonding layer used in the present invention refers to a photocured resin layer which can be peeled off from the wafer surface on which the circuit is formed by using an adhesive tape or the like after grinding the back surface of the wafer of the wafer processing laminate and, if necessary, high-temperature processing, laminating a dicing tape or the like to the ground surface of the wafer with a bonding layer, and then peeling between the bonding layer surface of the wafer with a bonding layer and the first silicone adsorption layer A.
The bonding layer may be a non-silicone thermoplastic resin layer as described in Patent Documents 4 and 5, but from the viewpoint of heat resistance, it is possible to use a bonding layer that is peelable from the surface of a wafer on which a circuit is formed, which is made of a photocurable adhesive described in paragraphs 0040 to 0046 of Patent Document 4 and is photocured. For example, a UV-curable adhesive containing (1) an oligomer having a polymerizable vinyl group such as urethane acrylate, epoxy acrylate, or polyester acrylate, and/or (2) an acrylic or methacrylic monomer, a photopolymerization initiator, and, in some cases, an additive, is preferably used. Examples of additives include thickeners, plasticizers, dispersants, fillers, flame retardants, and heat aging inhibitors. In particular, an adhesive in which the total amount of bifunctional urethane (meth)acrylate oligomers having a number average molecular weight of 3,000 or more is 40% by weight or more, and the total amount of bifunctional (meth)acrylic monomers is 25% by weight or more is preferably used, but there is no particular limitation as long as the adhesive exhibits the required characteristics (adhesive strength, functional properties). As specific formulations of the photocurable adhesive, the examples described in Table 1 in paragraph 0052, Table 3 in paragraph 0059, and Table 4 in paragraph 0061, which are examples of Patent Document 4, can be used in the present invention.

The second form of the bonding layer of the bonding layer-attached wafer used in the present invention is a bonding layer that is photocured and can be removed by a stripping solution from the surface of the wafer on which a circuit is formed, after grinding the back surface of the wafer of the wafer processing laminate and processing it at high temperature as necessary, laminating a dicing tape or the like to the ground surface of the bonding layer-attached wafer, and then peeling between the bonding layer surface of the bonding layer-attached wafer and the first adsorption layer A, and the bonding layer is a photocured bonding layer made of a radiation-sensitive resin composition containing (A) an alkali-soluble copolymer having a constituent unit derived from a radical polymerizable compound having at least a carboxyl group, (B) a compound having at least one ethylenically unsaturated double bond, and (C) a radiation-induced radical polymerization initiator, and the cured bonding layer is a bonding layer that can be removed by a stripping solution made of an alkaline solution.

The radiation-sensitive resin composition for the bonding layer of the second embodiment used in the present invention may be a conventionally known radiation-sensitive resin composition that is used in dry film resists for plating or etching in the field of printed circuit board circuit formation and that can be stripped of cured resists with alkaline development/alkaline solutions, or a conventionally known radiation-sensitive resin composition that is used as a resist for bump formation in the field of semiconductor processing and that can be stripped of cured resists with alkaline development/alkaline solutions.

As for the coating liquid made of the radiation-sensitive resin composition used in the field of forming printed circuit boards, for example, the descriptions in JP-A-60-258539 and JP-A-2005-309097 can be cited.

As the radiation-sensitive resin composition for a bonding layer of the second embodiment used in the present invention, a more preferred radiation-sensitive resin composition for a bonding layer is a resist coating liquid comprising a radiation-sensitive resin composition for bump formation.
Usually, in the grinding and polishing process of silicon wafers, the laminate for wafer processing is rarely exposed to high temperatures of 200° C. or more for a long period of time. In addition, in the case of flip chip mounting, the laminate for wafer processing is rarely exposed to such high temperatures for a long period of time even in the dicing process.
However, as mentioned above, in the case of three-dimensional semiconductor packaging, a TSV formation process and a wiring layer formation process on the back surface are performed after the ultra-thinning grinding process, and high-temperature processing at 200° C. or higher may be required during this process. In this case, in the case of the resist for printed circuit boards, the photocured bonding layer may further undergo a thermal crosslinking reaction, making it difficult to remove the resist using a remover.
On the other hand, photopolymerization resists for bump formation are designed with consideration given to the need for heat resistance to the high temperature treatment that usually occurs during bump formation, and therefore the ease of removal of the photocured film by a remover after high temperature treatment. Also, for that purpose, the resist coating liquid is designed to enable the formation of a thick film in a single coating and to obtain adhesion to the surface on which the semiconductor circuit is formed. (See JSR TECHNICAL REVIEW No. 111/2004)
Therefore, it is more preferable to use a resist coating liquid made of a radiation-sensitive resin composition for bump formation, since it can be used not only for flip chip mounting but also for three-dimensional semiconductor mounting involving high temperature treatment. As a coating liquid, for example, the description in JP-A-2000-39709 can be cited, and as a commercially available coating liquid, the THB series (for example, THB-151N) manufactured by JSR Corporation can be used. As such a radiation-sensitive resin composition for bump formation, the description in JP-A-2000-039709 can be cited.

The bonding layer, whether it is the first type of bonding layer or the second type of bonding layer, is formed so as to cover the convex portions of the wafer circuit surface by a conventionally known coating method such as spray coating, spin coating, flow coating, screen printing, inkjet, or dispenser in order to satisfy the ability to conform to surface irregularities caused by bumps or the like formed on the wafer circuit surface.
This prevents the pressure difference caused by the difference in height between areas where bumps are present and areas where bumps are not present during grinding, when the bumps are not embedded in accordance with the difference in height on the surface, from directly affecting the back surface of the wafer and causing depressions called dimples or cracks on the back surface of the wafer, which ultimately damages the semiconductor wafer.

<Semiconductor wafer and circuit formation surface>
A wafer having a circuit-forming surface and a non-circuit-forming surface is a wafer having one surface on which a circuit is formed and the other surface on which a circuit is not formed. The wafer to which the present invention can be applied is usually a semiconductor wafer. Examples of the semiconductor wafer include not only silicon wafers but also Ge wafers and compound semiconductor (ZnSe, GaAs, GaN, InP, InGaAlP, InGaN, SiC, SiGe, etc.) wafers. The thickness of the wafer is not particularly limited, but is typically 600 to 800 μm, more typically 625 to 775 μm.
In flip chip mounting, etc., under bump metal (UBM) is usually formed on the wafer circuit formation surface after circuit formation, and solder, gold or copper bumps are formed. In this case, the surface unevenness of the wafer circuit formation surface may be several tens of μm, and in some cases may exceed 100 μm.

<Temporary Support>
There are no restrictions on the temporary support, and it can be a glass plate, a silicon wafer, a SUS plate, an acrylic plate, etc., as long as the surface to be bonded to the second silicone adsorption layer B surface is smooth. However, as mentioned above, in cases involving high-temperature processing such as three-dimensional semiconductor packaging, substrates such as silicon wafers, glass plates, and quartz are preferred from the viewpoint of the thermal expansion coefficient with silicon semiconductors.

<Lamination method of laminate for wafer processing>
The high shear force of the silicone adsorption layer used in the present invention on the adherend is most effective when the silicone adsorption layer and the adherend surface are in intimate contact with each other, as described above.
A method for laminating a laminate for wafer processing, in which the first silicone adsorption layer A surface of a laminate consisting of a temporary support/the second silicone adsorption layer B/the first silicone adsorption layer A is intimately bonded to a photocured bonding layer surface provided by a coating method so as to cover the convex portions of the wafer surface on which circuits are formed, using the substrate-less silicone adsorption sheet of the present invention, includes any one of the following steps (a) to (b), even in the case of the bonding layer of a wafer with a bonding layer of the first or second form.
The silicone adsorption layer of the present invention has good air release properties when it is attached to an adherend, but it is more preferable to attach it while drawing a vacuum in the following step.
In addition, either the following process (a) or process (b) is possible, but from the viewpoint of stable peelability between the first silicone adsorption layer A surface of the wafer processing laminate and the bonding layer surface of the uncured bonding layer-bearing wafer provided on the wafer surface on which the bonding layer is circuit-formed, the lamination method according to the following process (a) is preferred.
(a) a step of laminating an uncured bonding layer surface of the wafer with a transparent release substrate having a smooth surface, curing the bonding layer by irradiating radiation from the transparent release substrate side, peeling off the transparent release substrate, and laminating the cured bonding layer-attached wafer surface with the first silicone adsorption layer A surface of a laminate consisting of a temporary support/the second silicone adsorption layer B/the first silicone adsorption layer A using the substrate-less silicone adsorption sheet of the present invention; (b) a step in which, in the case where the temporary support is transparent, the substrate-less silicone adsorption sheet of the present invention is used to laminate the first silicone adsorption layer A surface of a laminate consisting of a temporary support/the second silicone adsorption layer B/the first silicone adsorption layer A with the bonding layer surface of an uncured bonding layer-attached wafer provided on the wafer surface on which the bonding layer is formed into a circuit, and then curing the bonding layer by irradiating radiation from the temporary support side.

The smooth transparent release substrate used in step (a) may be a silicone- or fluorine-treated glass plate, an acrylic plate, or a 188 μm polyester film, and the surface roughness Ra of the bonding surface of the transparent release substrate is preferably 0.2 μm or less.

<Step of grinding non-circuit-forming surface of wafer bonded to temporary support>
The method of grinding the wafer back side of the semiconductor processing laminate made of the semiconductor wafer having the photocured bonding layer surface formed by coating method so as to cover the temporary support and the convex part of the wafer surface where the circuit is formed, and to reduce the thickness of the wafer, is not particularly limited whether it is the first form or the second form, and any known grinding method is adopted. Grinding is preferably performed while spraying water on the wafer and grindstone (diamond, etc.) to cool them. After grinding, dry polishing or CMP polishing may be performed from the viewpoint of stress relief.

<Processing the non-circuit surface of the wafer after back grinding in the case of 3D packaging>
In the case of 3D packaging, a process is performed in which TSVs, electrodes, and the like are formed by a conventionally known method on the non-circuit-formed surface of a wafer processed body that has been thinned by back grinding.

<Step of peeling the ground wafer having the bonding layer from the temporary support and dividing the wafer into individual wafers>
This process involves subjecting the thinned wafer to various processes as necessary, and then peeling the ground wafer having the bonding layer from the temporary support of the wafer processing laminate and dividing it into individual wafers before dicing.

<In the case of the first type of bonding layer>
This is a method for producing thin wafer singulation, in which a non-circuit forming surface of the wafer bonded to the temporary support is ground using a wafer processing laminate having the bonding layer of the first form, and then the thinned wafer is subjected to various processes as necessary. After that, a dicing tape is attached to the ground processed surface of the ground laminate, and the wafer together with the dicing tape is peeled between the first silicone adsorption layer A surface and the bonding layer surface, the thinned wafer is diced into individual pieces, and then the bonding layer of the individualized chips is peeled off from the wafer surface on which the circuits are formed using an adhesive tape.

<In the case of the bonding layer of the second type>
This is a method for producing individual thin wafers, comprising the steps of: grinding the non-circuit forming surface of the wafer bonded to the temporary support using a wafer processing laminate having the bonding layer of the second form; subjecting the thinned wafer to various processes as necessary; attaching a dicing tape to the ground processed surface of the ground laminate; peeling the wafer together with the dicing tape between the first silicone adsorption layer A surface and the bonding layer surface; and dicing the wafer by the following steps (1) or (2).
(1) removing the bonding layer from the surface of a wafer on which circuits are formed using a stripping solution made of an alkaline solution, and then dicing the thinned wafer into individual pieces; (2) dicing the thinned wafer having the bonding layer into individual pieces, and then removing the bonding layer from the surface of the individualized wafer on which circuits are formed using a stripping solution made of an alkaline solution.

The alkaline component of the remover liquid, which is made of an alkaline solution and is used in the bonding layer process of the second embodiment, is preferably an amine such as diethanolamine or triethanolamine, or a tetra (substituted) alkyl ammonium hydroxide, etc., from the viewpoint of preventing contamination of the semiconductor. The solution is preferably water alone or a mixture of water and a polar solvent such as N-methylpyrrolidone, N,N-dimethylformamide, dimethyl sulfoxide, or 1,3-dimethyl-2-imidazolidinone, and Japanese Patent Application Laid-Open Nos. 2003-337433, 2004-93678, 2004-117889, and 10-239865 can be cited. In addition, the remover liquid THB-S series (for example, THB-S1) manufactured by JSR Corporation can be used as a remover liquid for the photocured layer of the bump formation resist.

The methods for measuring physical properties are as follows:

<Surface roughness>
The average surface roughness (Ra) was measured according to JIS-B0601-1994 using a surface roughness measuring instrument (Surfcorder SE3500 manufactured by Kosaka Laboratory Co., Ltd.) with a stylus radius of 2.0 μm, a load of 0.3 mN, a cut-off value of 2.5 mm, a measuring length of 12.5 mm, and a feed speed of 0.5 m/min.

<Method for measuring peel strength>
1. Peel force between the first release film and the first silicone adsorption layer A, and between the second release film and the second silicone adsorption layer B A substrate-less silicone adsorption sheet was cut to a width of 25 mm, and the release film was peeled off in the 180 degree direction at a speed of 1,200 mm/min, and the peel force was measured.
2. Peel force between the evaluation glass substrate and the first silicone adsorption layer A, and between the evaluation glass substrate and the second silicone adsorption layer B: A silicone adsorption layer described below was applied to a polyester film having an adhesive layer and dried to a thickness of 20 μm to prepare an adsorption sheet sample for evaluation, and this adsorption sheet sample for evaluation was cut to a width of 25 mm, and the silicone adsorption layer surface was attached to a glass substrate having a surface roughness Ra of 0.08 μm and a thickness of 0.5 mm. After leaving it at room temperature for 30 minutes, the peel force was measured when it was peeled off in a 180 degree direction at a speed of 1,200 mm/min.

<Method of measuring and evaluating shear force>
A substrate-less silicone adsorption sheet is cut into a square measuring 25 mm x 25 mm.
The first release film of the substrate-less silicone adsorption sheet is peeled off, and the first silicone adsorption layer B surface is placed in the center of a glass substrate 1 having a surface roughness Ra of 0.08 μm, a thickness of 5.0 mm, a width of 50 mm and a length of 50 mm. A 2 kgf roll as specified in JIS K 0237 is rolled back and forth once at a speed of 3 m/min from above the substrate-less silicone adsorption sheet to bond the glass substrate 1 and the first silicone adsorption layer B.
The second release film of the attached substrate-less silicone adsorption sheet is peeled off, and a glass substrate 2 having a surface roughness Ra of 0.08 μm, a thickness of 5.0 mm, a width of 50 mm and a length of 100 mm is placed on the second silicone adsorption layer A side, with the corners of the glass substrate 1 aligned. A 2 kgf roll as specified in JIS K 0237 is made to reciprocate once at a speed of 3 m/min from above the glass substrate 2 to attach the second silicone adsorption layer A side to the glass substrate 2, thereby producing a glass substrate laminate.
A double-sided adhesive tape for fixing is applied to the surface of the glass substrate 1 of the glass substrate laminate to which the silicone adsorption layer B is not applied, and the glass substrate laminate is placed on a measurement table that is fixed so as not to move, so that the double-sided adhesive tape surface is in contact with the surface. A 2 kgf roll as specified in JIS K 0237 is rolled back and forth once at a speed of 3 m/min from above the glass substrate 2 of the glass substrate laminate to fix the glass substrate laminate to the measurement table.
A rod tension gauge is fixed with adhesive tape to the end of glass substrate 2 of the glass substrate laminate not overlapping glass substrate 1, and the rod tension gauge is pulled horizontally at a speed of 300 mm/min and the maximum value is read.
The readings were converted to values per square centimeter and evaluated according to the following criteria.
◎: 5 N/cm2 or ^more ○: 1 N/ ^cm2 or more, less than 5 N/ ^cm2 ×: less than 1 N/ ^cm2

The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples. In each example, "parts" refers to "parts by weight" unless otherwise specified.

<Preparation of Silicone Adsorption Layer A and Silicone Adsorption Layer B Coating Solutions>
The formulations of coating solutions A-1 and A-2 for the silicone adsorption layer A and coating solution B-1 for the silicone adsorption layer B are shown in Table 1 below.

<Preparing the release film>
First release film 1: polyethylene terephthalate film (50 μm)
First release film 2: Polymethylpentene film (50 μm)
Second release film 1: A coating liquid containing fluorosilicone and a platinum catalyst was applied to one side of a polyethylene terephthalate film (25 μm) using a gravure coater in an environment of 23°C and 50% RH, and then crosslinked in an oven at 150°C for 100 seconds to form a release layer with a thickness of 0.2 μm, thereby producing a second release film 1.

<Preparation of substrate-less silicone adsorption sheet>
Example 1
The release layer surface of the second release film 1 was coated with the coating liquid B-1 of the silicone adsorption layer B by a die coater in an environment of 23°C, 50% RH, and then crosslinked in an oven at 150°C for 100 seconds to form a silicone adsorption layer B with a dry thickness of 20 μm. Next, the surface of the silicone adsorption layer B was coated with the coating liquid A-2 of the silicone adsorption layer A by a die coater in an environment of 23°C, 50% RH, and then crosslinked in an oven at 150°C for 100 seconds to form a silicone adsorption layer A with a dry thickness of 20 μm. Furthermore, the first release film 1 was attached to the surface of the silicone adsorption layer A and left to stand for 96 hours in an environment of 23°C, 50% RH to produce a substrate-less silicone adsorption sheet.

Example 2
The coating liquid A-1 of the silicone adsorption layer A was applied to one side of the first release film 2 by a die coater in an environment of 23°C, 50% RH, and then crosslinked in an oven at 150°C for 100 seconds to form a silicone adsorption layer A with a dry thickness of 20 μm. Next, the coating liquid B-1 of the silicone adsorption layer B was applied to the surface of the silicone adsorption layer A by a die coater in an environment of 23°C, 50% RH, and then crosslinked in an oven at 150°C for 100 seconds to form a silicone adsorption layer B with a dry thickness of 20 μm. Furthermore, the release layer surface of the second release film 1 was attached to the surface of the silicone adsorption layer B, and the surface was left to stand in an environment of 23°C, 50% RH for 96 hours to produce a substrate-less silicone adsorption sheet.

Example 3
A substrate-less silicone adsorption sheet was prepared in the same manner as in Example 1, except that the dry film thickness of the silicone adsorption layer B was changed to 10 μm.

Example 4
In Example 2, the coating liquid A-2 for the silicone adsorption layer A was used in place of the coating liquid A-1 for the silicone adsorption layer A, to prepare a substrate-less silicone adsorption sheet.

Example 5
In Example 1, the silicone adsorption layer A coating liquid A-1 was used in place of the silicone adsorption layer A coating liquid A-2, to prepare a substrate-less silicone adsorption sheet.

<Reference Example 1>
Coating liquid A-2 of the silicone adsorption layer A was applied to one side of the first release film 1 by a die coater in an environment of 23°C and 50% RH, and then crosslinked in an oven at 150°C for 100 seconds to form a silicone adsorption layer A with a dry thickness of 20 μm. Next, coating liquid B-1 of the silicone adsorption layer B was applied to the surface of the silicone adsorption layer A by a die coater in an environment of 23°C and 50% RH, and then crosslinked in an oven at 150°C for 100 seconds to form a silicone adsorption layer B with a dry thickness of 20 μm. Furthermore, the release layer surface of the second release film 1 was bonded to the surface of the silicone adsorption layer B to prepare a substrate-less silicone adsorption sheet.

<Evaluation 1 of substrate-less silicone adsorption sheet>
The physical properties of the substrate-less silicone adsorption sheets of Examples 1 to 5 and Reference Example 1 are shown in Table 2.
In addition, the substrate-less silicone adsorption sheet of Reference Example 1 has a peel strength of 600 for the first release film/adsorption layer A.
The adhesive strength was 25 mN/25 mm, and part of the silicone adsorption layer A remained on the first release film, so that the silicone adsorption layer A could not be used in the present invention.

<Evaluation of Substrate-less Silicone Adsorption Sheet 2>
Using the substrate-less silicone adsorption sheets of Examples 1 to 5, after peeling off the second release film, the silicone adsorption layer B side was bonded to a glass temporary support having a surface roughness Ra of 0.08 μm and a thickness of 5.0 mm. Next, the first release film was peeled off and the silicone adsorption layer A side was bonded to a glass body to be ground having a surface roughness Ra of 0.08 μm and a thickness of 0.5 mm while vacuuming. The back surface of the glass body to be ground was ground to 50 μm, after which a dicing tape was applied to the back surface and the ground glass together with the dicing tape was peeled off from the temporary support. During the grinding process of the glass body to be ground, it was possible to grind the glass body while it was fixed, and smooth peeling was possible between the glass body to be ground and the silicone adsorption layer A after grinding.

Next, the wafer processing laminate using the substrate-less silicone adsorption sheet of the present invention and the wafer processing method using the wafer processing laminate will be explained in more detail with reference to examples.

<Preparation of Coating Solution 1 for Bonding Layer of First Form>
As the bonding layer coating solution 1 of the first embodiment, the following coating solution was prepared.
Urethane acrylate (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., product name: UV7000B): 28.6 parts by weight Urethane acrylate (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., product name: UV6100B): 28.6 parts by weight 1,6-hexanediol diacrylate: 38.0 parts by weight Photopolymerization initiator (manufactured by IGM Resins B.V., product name: Omnirad 369): 4.8 parts by weight
Total 100.0 parts by weight

<Preparation of bonding layer coating solution 2 of second embodiment>
As a radiation-sensitive resin composition coating solution containing (A) an alkali-soluble copolymer having a constituent unit derived from a radically polymerizable compound having at least a carboxyl group, (B) a compound having at least one ethylenically unsaturated double bond, and (C) a radiation-induced radical polymerization initiator, a product name of THB-151N (solid content concentration: 51.9%, viscosity: 3,923 mPa) manufactured by JSR Corporation was prepared as bonding layer coating solution 2.

<Preparation of evaluation wafer>
An evaluation wafer having surface steps was prepared on a Si wafer having a diameter of 8 inches by providing protruding electrodes (Cu) with a size of φ80 μm, a height of 50 μm, and a pitch of 200 μm.

<Preparation of photocured bonding layer on evaluation wafer>
<Preparation of Wafer with Bonding Layer According to First Embodiment>
The bonding layer coating solution 1 was applied by a spray coater so that the protruding parts of the surface on which the protruding electrodes of the evaluation wafer were formed were covered to a dry thickness of 65 μm. Then, the wafer was laminated with a polyester film (surface roughness Ra: 0.05 μm, Ry: 0.12 μm) with a transparent release layer and a silicone release layer on one side of the polyester film with a thickness of 188 μm while vacuuming, and the bonding layer was cured from the polyester film with the transparent release layer with ultraviolet energy of 1,500 mj/ ^cm2 by a high-pressure mercury lamp, and then the polyester film with the transparent release layer was peeled off to produce a wafer with a cured bonding layer.

<Preparation of Wafer with Bonding Layer According to Second Embodiment>
The bonding layer coating solution 2 was applied by a spray coater so that the protruding parts of the surface on which the protruding electrodes of the evaluation wafer were formed were covered to a dry thickness of 65 μm. Then, a polyester film with a transparent release layer (surface roughness Ra: 0.05 μm, Ry: 0.12 μm) having a thickness of 188 μm and a silicone release layer on one side was bonded while drawing a vacuum, and the bonding layer was cured from the polyester film with the transparent release layer with ultraviolet energy of 1,000 mj/ ^cm2 by a high-pressure mercury lamp, and then the polyester film with the transparent release layer was peeled off to produce a wafer with a cured bonding layer.

Example 6
<Laminate for wafer processing having a configuration of temporary support with substrate-less silicone adsorption sheet interposed therebetween/silicone adsorption layer B/silicone adsorption layer A/wafer with bonding layer of second type, and wafer processing method using said laminate>
The second release film of the substrate-less silicone adsorption sheet of Example 5 was peeled off, and the second silicone adsorption layer B side was attached to a smooth glass plate (surface roughness Ra: 0.0032 μm, Ry: 0.014 μm) having a thickness of 5 mm as a temporary support. After the attachment, the first release film was peeled off, and the silicone adsorption layer A side consisting of the temporary support/silicone adsorption layer B/silicone adsorption layer A was attached to the bonding layer side of the second type of bonding layer-attached wafer while vacuuming, to produce a second type of bonding layer-attached wafer processing laminate.

The back surface of the wafer of the wafer processing laminate was ground with a polisher DGP8761HC (manufactured by DISCO) using #320 and #2,000 grindstones, followed by dry polishing for stress relief. After grinding and polishing the wafer to a thickness of 30 μm, a dicing tape was attached, and the wafer with the second type of bonding layer was able to be smoothly peeled off together with the dicing tape between the bonding layer surface and the first silicone adsorption layer A, and no warping or chipping of the wafer was observed during the process. Next, the bonding layer was removed without residue using a stripping solution THB-S1 manufactured by JSR Corporation. Then, individual chips were produced by dicing.

Example 7
<Laminate for wafer processing having a configuration of temporary support with substrate-less substrate-less silicone adsorption sheet interposed therebetween/silicone adsorption layer B/silicone adsorption layer A/wafer with bonding layer of first form, and wafer processing method using said laminate>
The method for producing the first embodiment of the laminate for processing the wafer with a bonding layer is the same as that of Example 5, except that the wafer with a bonding layer of the second embodiment of Example 5 is replaced with the wafer with a bonding layer of the first embodiment.
In addition, the back surface of the wafer of the first embodiment of the laminate for processing the wafer with the bonding layer was ground with a polisher DGP8761HC (manufactured by DISCO) using a grindstone of #320 and #2,000, and then dry polished for stress relief. After grinding and polishing the wafer to a thickness of 25 μm, a dicing tape was attached, and the wafer with the bonding layer of the first embodiment was able to be smoothly peeled off together with the dicing tape between the bonding layer surface and the first silicone adsorption layer A, and no warping or chipping of the wafer was observed during the operation. Then, individual chips were produced by dicing, and an adhesive tape (Scotch adhesive tape #3305, manufactured by 3M) was attached to the chip bonding layer surface, and the adhesive tape was peeled off in a 180° direction, thereby removing the bonding layer without damaging the chip.

1: Substrate-less silicone adsorption film 1-1: Silicone adsorption layer B
1-2: Silicone adsorption layer A
2: bonding layer 3: semiconductor wafer 4: circuit electrode 5: temporary support 6: laminate for wafer processing

Claims (7)

A substrate-less silicone adsorption sheet having a structure of a first release film/a first silicone adsorption layer A formed from a silicone composition/a second silicone adsorption layer B formed from a silicone composition/a second release film,
the first and second silicone adsorption layers are silicone adsorption layers formed by crosslinking at least one silicone selected from a silicone consisting of a linear polyorganosiloxane having vinyl groups only at both ends and a silicone consisting of a linear polyorganosiloxane having vinyl groups at both ends and in a side chain, wherein the peel force between the first release film and the first silicone adsorption layer A is greater than the peel force between the second release film and the second silicone adsorption layer B, the difference in the peel forces being 15 mN/25 mm or more, and the peel force between the first release film and the first silicone adsorption layer A being 80 mN/25 mm or less,
A substrate-less silicone adsorption sheet characterized in that the peel strength of the first silicone adsorption layer A after peeling off the first and second release films is 60 mN/25 mm or less and 5 mN/25 mm or more against a glass substrate having a surface roughness Ra of 0.08 μm for evaluation, and the peel strength of the second silicone adsorption layer B is 100 mN/25 mm or more against the glass substrate. The substrate-less silicone adsorption sheet according to claim 1,
A substrate-less silicone adsorption sheet characterized in that the first silicone adsorption layer A contains an MQ resin consisting of M units (R ₃ SiO _1/2 : R is a monovalent organic group such as a methyl group or a phenyl group) and Q units (SiO _4/2 ) in an amount of 0 to 13 weight % of the solid content of the first silicone adsorption layer A, and the second silicone adsorption layer B contains the MQ resin in an amount of 20 to 30 weight % of the solid content of the second silicone adsorption layer B. A laminate for wafer processing, comprising a wafer having a structure in which a temporary support/the second silicone adsorption layer B/the first silicone adsorption layer A/a wafer surface on which a circuit is formed are laminated together, with a silicone adsorption layer consisting of the first silicone adsorption layer A and the second silicone adsorption layer B of the substrate-less silicone adsorption sheet according to claims 1 or 2 being interposed therebetween,
a wafer having a peelable bonding layer formed by applying a radiation-sensitive resin composition containing a radiation-sensitive radical polymerization initiator, a bifunctional urethane (meth)acrylate oligomer having a number average molecular weight of 3,000 or more in a total amount of 40% by weight or more, and a bifunctional (meth)acrylic monomer in a total amount of 25% by weight or more to a wafer surface on which a circuit is formed, to cover convex portions of the wafer surface on which a circuit is formed, and then curing the applied radiation by irradiation with radiation. A laminate for wafer processing, comprising a wafer having a structure in which a temporary support/the second silicone adsorption layer B/the first silicone adsorption layer A/a wafer surface on which a circuit is formed are laminated together, with a silicone adsorption layer consisting of the first silicone adsorption layer A and the second silicone adsorption layer B of the substrate-less silicone adsorption sheet according to claims 1 or 2 being interposed therebetween,
a wafer having a bonding layer formed on a surface of the wafer on which a circuit is formed, the bonding layer being formed by applying a radiation-sensitive resin composition comprising (A) an alkali-soluble copolymer having a constituent unit derived from a radically polymerizable compound having at least a carboxyl group, (B) a compound having at least one ethylenically unsaturated double bond, and (C) a radiation-induced radical polymerization initiator by a coating method so that protruding portions of the surface of the wafer on which a circuit is formed are covered, and the bonding layer is then cured by irradiation with radiation, the cured bonding layer being removable with a stripping solution comprising an alkaline solution. The laminate for wafer processing according to claim 3 or claim 4, characterized in that the laminate is formed by forming a bonding layer by applying the radiation-sensitive resin composition according to claim 3 or claim 4 to the surface of a wafer on which a circuit is formed so as to cover the convex parts of the surface of the wafer on which the circuit is formed, bonding the bonding layer surface of the wafer to a transparent release substrate having a smooth surface, curing the bonding layer by irradiating radiation from the transparent release substrate side, peeling off the transparent release substrate, and bonding the bonding layer surface of the wafer to the first silicone adsorption layer A surface of a member provided on a temporary support and consisting of a temporary support, the second silicone adsorption layer B, and the first silicone adsorption layer A. A method for producing a thin wafer singulation, comprising: using the laminate for wafer processing according to claim 3, grinding the non-circuit-forming surface of the wafer bonded to the temporary support, subjecting the thinned wafer to various processes as necessary, attaching a dicing tape to the ground surface of the ground laminate, peeling the wafer together with the dicing tape between the first silicone adsorption layer A surface and the bonding layer surface, dicing the thinned wafer into individual pieces, and then peeling the bonding layer of the individualized chip from the wafer surface on which the circuits are formed using an adhesive tape. A method for producing individual thin wafers, comprising the steps of: grinding the non-circuit forming surface of the wafer bonded to the temporary support using the wafer processing laminate described in claim 4; subjecting the thinned wafer to various processes as necessary; attaching a dicing tape to the ground processed surface of the ground laminate; peeling the wafer together with the dicing tape between the first silicone adsorption layer A surface and the bonding layer surface; and dicing the wafer by the following process (1) or (2).
(1) removing the bonding layer from the surface of a wafer on which circuits are formed using a stripping solution made of an alkaline solution, and then dicing the thinned wafer into individual pieces; (2) dicing the thinned wafer having the bonding layer into individual pieces, and then removing the bonding layer from the surface of the individualized wafer on which circuits are formed using a stripping solution made of an alkaline solution.

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