Electron beam direct writing technology for printed wiring board

An electron-beam lithography system has been developed which can write electric circuit patterns directly on printed wiring boards from computer-aided design data without making the master and working film masks which are necessary for conventional photolithography. The electron beam is focused to 34 μm in diameter at an accelerating voltage of 60 kV. The sensitivity of an electrodeposited photoresist to electron-beam exposure is investigated. It is shown that the photoresist is very sensitive to the electron beam and has a threshold dosage of 0.2 μC/cm². The spatial contours of equienergy density deposited by the electron beam in a 20-μm-thick resist-copper substrate configuration have been calculated with a Monte Carlo computer method. The geometry of the resist patterns is determined according to the contour line corresponding to about 6×10¹⁸ eV/cm ³. It has been confirmed that fine patterns with linewidths less than 100 μm can be obtained and that this technology is efficient for meeting the constantly growing demand for greater density and shorter turnaround