High accuracy electron‐beam grating lithography for optical and optoelectronic devices

Much of the development of recent optoelectronic and optical devices has been undertaken using the lithographic tools designed for conventional microelectronic circuits. For the latter, the need for spatial linearity and accuracy is mainly concerned with overlay accuracy and device yield. But the characteristics of optical structures, such as gratings, can be affected by the spatial errors of the tools used to make them. The linearity of a Leica Cambridge EBMF‐10.5 electron beam lithography system has been investigated with particular regard to the writing of gratings for distributed feedback lasers and optical waveguide devices. Since the gratings can be narrow, it is possible to take advantage of the lower distortions associated with scanning in a single axis. The distortion correction system has been shown to provide significant improvements in linearity even at small field sizes of around 1 mm, and an overall beam placement accuracy of 20 nm within the writing field has been demonstrated. The applicat...