Abstract: According to one embodiment, a wafer carrier cleaning method is provided. The wafer carrier cleaning method includes cleaning a wafer carrier with a chemical solution containing a weak acid that can dissolve metals, and cleaning the wafer carrier cleaned with the chemical solution, with pure water. The weak acid contained in the chemical solution is preferably citric acid that can dissolve heavy metals and does not damage the wafer carrier.

Abstract: The present invention is a waterproof sheet for a tunnel containing a base sheet containing a synthetic resin having on a surface thereof a silica-containing surface layer containing silica having a silicon dioxide content of 90% by mass or more in a ratio of from 30 to 200 mg/cm3, formed over a depth of from 5 to 30 ?m from the surface of the waterproof sheet, and having a tensile breaking strength of 10 MPa or more and a mortar adhesion strength of 15 N/cm or more, and thus provides a waterproof sheet for a tunnel that forms no gap between the sheet and the concrete structure even when a prolonged period of time is elapsed from the installation, or the installed surface suffers large deterioration in evenness or levelness, ground subsidence or earthquake, and also does not cause problems including breakage and the like upon installation and after installation in the tunnel, thereby preventing smoothly water seeping from the earth or the ground from leaking into the tunnel.