The free-arm canopy comprises a mast, on which an extendable and retractable jib is arranged, with a transverse fitting at the end thereof on which a canopy is arranged on a canopy pole by means of a joint. By sticking the support wafer onto the semiconductor wafer with the two-sided adhesive sheet, sufficient strength and rigidity can be obtained even after a thinning process is carried out. A gap is kept between the internal sleeve oil seal and the outer annular member to contain an anti-friction ring and a second barrier. The second spacer is formed using a material with a lower melting point than the melting point of the material of the first spacer, this is inserted in the heat shielding space, and when the second spacer is melted by heat and flows out from the heat shielding space, the constitution is such that the heat shielding space shifts the heat insulation space.