Low-Energy High-Current Ion Source for Ion-Milling Equipment

Abstract

Summary Ion-milling technique using ion-shower equipments has become practical in several applications, including surface cleaning, fine machining, etc. However, the removal rate is generally not very high comparing with other dry etching processes. On the other hand, in many cases lower ion energy than usual 500eV is desirable, because it is expected that a lower energy bombardment gives less damage on the machined surface. Consequently, a low-energy high-current ion beam is in a great demand. However, the two requirements contradict each other. In a Kaufman type equipment those beam characteristics chiefly depend upon the ion extractor or the grid system. Authors made tests for developing a grid system with high ion extracting efficiency in low range of extracting voltage. Several types of grid systems including conventional two grid system were tested on their applicability, and following conclusions were obtained. Theorectical possibility of conventional two-grid systems was confirmed. However, following two types were found to be more hopeful ones because of their high performance and simpler structure. 1) single grid with insulating layer. 2) Insulator-substrate grid. Especially the insulator-substrate grid was found to be promising for its possibility of wide application.