Fabrication of Photonic Wire and Crystal Circuits in Silicon-on-Insulator Using 193-nm Optical Lithography

High-index contrast silicon-on-insulator technology enables wavelength-scale compact photonic circuits. We report fabrication of photonic circuits in silicon-on-insulator using complementary metal-oxide-semiconductor processing technology. By switching from advanced optical lithography at 248 to 193 nm, combined with improved dry etching, a substantial improvement in process window, linearity, and proximity effect is achieved. With the developed fabrication process, propagation and bending loss of photonic wires were characterized. Measurements indicate a propagation loss of 2.7 dB/cm for 500-nm photonic wire and an excess bending loss of 0.013 dB/90deg bend of 5-mum radius. Through this paper, we demonstrate the suitability of high resolution optical lithography and dry etch processes for mass production of photonic integrated circuits.

I. Introduction

High refractive index contrast and transparency at telecom wavelengths (1300 nm/1500 nm) make silicon (Si) an ideal material for integrated photonic applications. Exploiting this high refractive index contrast, researchers have demonstrated low-loss waveguides and small radius bends [1]–[3]. Active functionalities such as modulators have recently been proposed and successfully demonstrated [4], [5]; aiming at compact components and circuits. However, as a consequence of the high index contrast and the waveguide dimensions being close to the diffraction limit, the device response is very sensitive to any dimensional variation. Therefore, we need an accurate dimensional control in the range of 1–5 nm. To achieve such requirement a high resolution fabrication process is needed.