The Forming Process Researched in Sandblasting Separation of Masked Silicon Wafers

Abstract

The object of study is a semiconductor silicon disc-crystal currently used in the design of semiconductor diodes. The disc-crystal is manufactured by the sandblasting separation of a premasked silicon wafer into individual elements. The crystal has frustum-of-a-cone shape with its top diameter determined by a protective masking disc diameter and the bottom one defined by the features of the forming process. The apex angle of the cone 2α or a half-angle α between the lateral surface of the cone and the normal drawn to its base is used as a reference value.The work has studied the influence a thickness of the separated wafer and a width of the gap between the masked discs on the crystal shape. The masking cover is a set of square protective elements (3x3 mm), spaced at 0.6; 0.7; 0.8 and 0.9 mm. The mask material is a self-adhesive PVC-film with thickness of 200 microns. Pilot-plant semi-automatic sandblasting equipment was used to for separation.After processing of results (the angle 2α at the top of the cone) the following conclusions have been made:- with increasing thickness of the silicon wafers the gap between the protective discs of mask must be increased;- in case a range of the minimum gaps between the protective discs is within 0.35 - 1.20 mm the half-angle α, which defines the shape of the cut surface, can be considered to be constant and equal to 12º ... 14º.

Keywords

• microwave diode
• silicon plate
• disc-crystal
• sandblasting cutting
• abrasive material
• masking material