Only individual piece-like flexible wiring boards produced separately and judged to be non-defective products in an inspection step in advance are mounted at regular intervals on a carrying support film to thereby obtain a TAB tape carrier. Saturable absorbers are arranged in paths of the Mach-Zehnder interferometer, respectively. SIP is promoted by a small magnetron having poles of unequal magnetic strength and a high power applied to the target during sputtering.