METHOD FOR SOLDERING PROCESS WHICH IMPROVES SURFACE PROPERTY THROUGH THIN FILM STICKING

PROBLEM TO BE SOLVED: To eliminate the possibility of any reactive material such as solder flowing out to, depositing to, or reacting with, the side wall of a mesa structure, by letting non-reactive material deposit to the side wall of the mesa structure, and cleaning the exposed horizontal surface of the mesa structure. SOLUTION: Non-reactive material is selectively deposited to the vertical side wall of a mesa structure by sputtering. The conditions of the sputtering are as follows: The exposed horizontal surface of the mesa structure should be cleaned so that a horizontal surface more reactive than the side wall of the mesa structure can be obtained; and the speed at which the non-reactive material is stuck to the side wall should be equal to the difference between the speed of sticking by sputtering and the speed of removal. As a result, a non-reactive thin film cannot grow on the more horizontal surface. Only a few non-reactive material is preset on the exposed horizontal surface in the equilibrium state of sputtering.