Fabrication of 3-dimensionally shaped Si diaphragm dynamic focusing mirror

Abstract

To obtain a dynamic focusing mirror with optically ideal or parabolic deformation, a thin Si diaphragm with a 3-D specific thickness profile has been fabricated by a unique processing method. The specific thickness profile which allows optically ideal deformation is determined by the finite-element method (FEM). The mirror is approximately 10 mm in diameter and 9- mu m in thickness. Its specific profile of the mirror is created by a dry-etching method. Photoresist on a Si substrate is first exposed to a specific energy profile through a mask made by the dither method. The photoresist is then developed to form a specific curved profile which complies with the optical energy profile. The curved profile is transcribed to the Si substrate by dry etching in CF/sub 4//O/sub 2/ plasma. The processed 3-D profile matches the design with less than 2% deviation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>