In manufacturing semiconductor devices such as LSI and super-LSI or in manufacturing a liquid crystal display board or the like, a pattern is made by irradiating light to a semiconductor wafer or an original plate for liquid crystal, but if a dust gets to adhere to a photo mask or a reticle (hereinafter merely referred to as a “mask” for simplicity) during the irradiation operation, the dust absorbs light or refracts it, causing deformation of a transferred pattern, roughened edges or black stains on a base, and leads to a problem of damaged dimensions, poor quality, deformed appearance and the like.
Thus, these works are usually performed in a clean room, but it is still difficult to keep the mask clean all the time. Therefore, a pellicle is tentatively attached to a surface of the mask as a dust-fender before photo irradiation is carried out. Under such circumstances, foreign substances do not directly adhere to the surface of the mask but only onto the pellicle membrane, which is sufficiently removed from the mask surface, and thus by setting a photo focus on a lithography pattern on the mask, the foreign substances on the pellicle membrane fail to transfer their shadows on the mask and thus no longer become a problem to the image transfer performance.
In general, a pellicle is built up of a pellicle frame, which is an endless frame bar, and a transparent membrane or pellicle film, the latter being tensely pasted to one of two frame faces. The membrane material is selected from cellulose nitrate, cellulose acetate, fluorine-containing polymer and the like, which transmits light well, and the pellicle frame is made of aluminum, stainless, polyethylene or the like. A solvent capable of dissolving the pellicle film is applied to one of two frame faces of the pellicle frame and the pellicle film is laid onto it and the solvent is air-dried to complete the adhesion (Japanese Laid-open Patent Application S58-219023 or 1983-219023), or an adhesive such as acrylic resin, epoxy resin or the like is used to adhere the pellicle film onto the frame face (hereinafter this face is called “upper frame face”) (U.S. Pat. No. 4,861,402 and Japanese Pre-Patent Publication for Public Review S63-27707 or 1988-27707). The other frame face (hereinafter called “lower frame face”) of the pellicle frame is paved with a pressure-sensitive solid adhesive layer made of polybutene resin, polyvinyl acetate resin, acrylic resin, silicone resin or the like for attaching the pellicle frame to a mask, and over this pressure-sensitive solid adhesive layer is laid a separation layer (or releaser) for protecting the solid adhesive layer. (The applicants failed to find a document dealing with the pressure-sensitive solid adhesive layer from the view point of adhesiveness.)    [Publication-in-patent 1] Japanese Laid-open Patent Application S58-219023    [Publication-in-patent 2] U.S. Pat. No. 4,861,402    [Publication-in-patent 3] Japanese Pre-Patent Publication for Public Review S63-27707