After a circuit is formed on the surface of the semiconductor wafer, a grinding processing is performed to the backside of the wafer, the backside grinding step which controls the thickness of the wafer and the dicing step which separate the wafer into predetermined chip size are carried out. Also, followed by the backside grinding step, the processing treatment which involves a heat generation such as an etching treatment is further performed to the backside.
During the etching of the backside grinding, the adhesive sheet so called backgrind tape is stuck to the circuit surface of the wafer in order to protect the circuit. Also, during the dicing of the wafer, the adhesive sheet so called a dicing tape is stuck to the backside of the wafer in order to prevent the scattering of the chips which are formed by dicing (hereinafter, such adhesive sheet in total may be described as “a semiconductor wafer processing adhesive sheet” or “a wafer processing adhesive sheet”.
As for these wafer processing adhesive sheet, in particular as for the backgrind tape, it is required,
to prevent the damage to the circuit and the wafer body,
to have no residue of the adhesive agent (glue residue) of the adhesive agent on the circuit after the releasing,
to prevent the penetration of the grinding water to the circuit surface which washes out the grinding debris generated during the backside grinding and removes the heat generated during the grinding, and
to sufficiently maintain the precision of the wafer thickness after the grinding.
Further, when performing the processing treatment involving a generation of the heat or a heat application to the backside, it is required that the volatile component is not generated from the adhesive layer.
Also, as for the dicing tape, it is required,
to hold the wafer with a sufficient adhesive force during the dicing,
to release the chip easily from the dicing tape during the pickup of the chip,
to have no reside of the adhesive agent on the backside of the chip which is picked up, and
that the low molecular weight composition which is included in the adhesive layer does not flow out due to the dicing water during the dicing.
As for such wafer processing adhesive sheet, the adhesive sheet is widely used which is provided with the energy ray-curable adhesive layer, which cures by the energy ray such as ultraviolet ray, on the substrate consisting of the resin film. According to the adhesive sheet of the energy ray-curable type, during the backside grinding or dicing of the wafer, the wafer is held by strong adhesive force; therefore the grinding water is prevented from penetrating into the circuit surface and the chip is prevented from scattering. Also, after finishing the backside grinding or the dicing, the adhesive force is reduced since the adhesive layer cures by irradiating the energy ray thereto, hence the wafer (chip) is released from the adhesive sheet without the glue residue.
As for the energy ray-curable adhesive agent, the adhesive agent formed by blending the energy ray-curable resin having relatively low molecular weight and the photo polymerization initiator to the acrylic adhesive polymer, is well known. However, as for such adhesive agent, because it includes the low molecular weight substances each component is not necessarily mixed uniformly, and when the energy ray curing is carried out, an insufficient curing of the adhesive agent occurred in some cases, or the low molecular weight substances remained unreacted in some cases. Therefore, the adhesive agent remained on the wafer (chip) in some cases, or the wafer (chip) was contaminated by the low molecular weight substances in some cases.
In order to resolve such problems, the wafer processing adhesive sheet is proposed which comprises the energy ray-curable adhesive layer comprising the photo polymerization initiator and the energy ray-polymerizable adhesive polymer (hereinafter, it may be described as “polymerizable group adduct type adhesive agent”) introducing the energy ray-polymerizable group in the molecule of the adhesive polymer by reacting the acrylic adhesive polymer to the compound including the energy ray-polymerizable group (Patent document 1). According to such polymerizable adduct type adhesive agent, the polymerizable group is uniformly dispersed in the adhesive layer, and the contamination due to the insufficient curing or the low molecular weight substances is reduced since the low molecular weight substances low.
Similarly, the polymer is proposed which binds the group forming the free radical which initiates the polymerization reaction under the excitation by the energy ray to the adhesive polymer (Patent document 2), or the polymer binding the photo polymerization initiator to the adhesive polymer is proposed (Patent document 3) in order to prevent the insufficient curing of the adhesive agent after the energy ray irradiation (hereinafter, these may be described as “radical generating group adduct type adhesive agent”). These radical generating group adduct type adhesive agent does not have polymerizing property by itself, therefore it is used together with the energy ray-curable resin having relatively low molecular weight substances as described in the above.    Patent document 1: JP-A-H09-298173    Patent document 2: JP-A-H08-333555    Patent document 3: JP-A-H09-111200
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