Microelectronic Engineering 65 (2003) 307–318 www.elsevier.com / locate / mee Fabrication technology for improving pattern quality in focusing waveguide grating coupler manufacture a, b b b * Hae-Sung Kim , Tae-Youb Kim ,Yark-Yeon Kim , Gee-Pyeong Han , b a a Mun-Cheol Paek , Dong-Hoon Shin , Jin-Koo Rhee a Millimeter-wave INnovation Technology Research Center, Dongguk University,3 -26 Pildong, Joonggu, Seoul 100-715, South Korea b Data Storage Device Team, Electronics and Telecommunications Research Institute, 161 Gajeong-Dong, Yusong-Gu, Taejon 305-350, South Korea Received 2 May 2002; received in revised form 15 August 2002; accepted 1 October 2002 Abstract This paper presents several exposure strategies that greatly improve pattern quality in delineating curved gratings in the nanometer range. A focusing waveguide grating coupler (FWGC) was not fabricated by the ‘continuous path control’ writing strategy but by a single-step e-beam lithography system with conventional exposure mode. The exposure strategies proposed are to match the address grid, which is an exposure scan direction, to the grating period, and also to apply the grating period to an integer multiple of the address grid resolution (5 nm). The grating pitch period and aperture feature size of the FWGC designed and fabricated here 2 are 384.3–448.2 nm and 0.5 3 0.5-mm , respectively. The presented fabrication method will also reduce processing time and improve grating pattern quality through address grid resolution, grating direction, pitch size and shapes in the e-beam exposure. Here our investigations concentrate on the design and efficient fabrication of the FWGC for coupling from slab waveguide to a spot in free space.  2002 Elsevier Science B.V. All rights reserved. Keywords: Focusing waveguide grating coupler; Electron-beam lithography; Si N ; Dry etching 3 4 1. Introduction A focusing waveguide grating coupler (FWGC) has been developed for application to optical data storage; it has the potential to play an important role in a variety of integrated optics applications [1–5] such as guiding to LD or fiber couplers and integrated optic disk pickup devices because of its *Corresponding author. Tel.: 182-2-2260-8831; fax: 182-2-2260-3690. E-mail address: bigbang@phya.yonsei.ac.kr (H.-S. Kim). 0167-9317 / 02 / $ – see front matter  2002 Elsevier Science B.V. All rights reserved. PII: S0167-9317(02)00904-8