| AVS 57th International Symposium & Exhibition | |
| Plasma Science and Technology | Wednesday Sessions |
| Session PS-WeM |
| Session: | Plasma Surface Interactions (Fundamentals & Applications) I |
| Presenter: | Y. Wu, Oxford Instruments, Lawrence Berkeley National Laboratory |
| Authors: | Y. Wu, Oxford Instruments, Lawrence Berkeley National Laboratory D. Olynick, Lawrence Berkeley National Laboratory A. Goodyear, Oxford Instruments C. Peroz, Abeam Technologies S. Dhuey, Lawrence Berkeley National Laboratory X. Liang, Lawrence Berkeley National Laboratory S. Cabrini, Lawrence Berkeley National Laboratory |
| Correspondent: | Click to Email |
We present work on the development of a cryogenic silicon etch process suitable for etching shallow and high aspect ratio nanoscale features below 50 nm for use in nanophotonics applications. With shrinking feature sizes, profile and critical dimension control tolerance is reduced and appropriate processes must be developed. Cryogenic silicon etching using SF6-O2 offers several advantages over fluorocarbon or heavier halogen based processes. For example, low bias voltages can be used, reducing mask erosion and ion damage. In addition, the etching process is not purely ion dependent which reduces some of the problems at small feature sizes associated with the ion angular distribution and ion interaction with the sidewall which can cause less than ideal profiles. Furthermore, sidewall contamination is minimal eliminating critical dimension (CD) variations due to etch residue cleaning. Two challenges to creating a suitable cryogenic SF6-O2 process for 50-100 nm features and below, is optimizing the passivant to eliminate undercut and reducing the etch rate enough to control the process. Furthermore, an etch process which changes in time accordingly to the etch depth and aspect ratio may be necessary for features below 20 nm.
The cryogenic SF6-O2 based silicon etching process was investigated in an Oxford Instruments ICP 380 using a L18 Taguchi design of experiments (DOE) matrix. For the DOE, trench type features sized 300-500 nm are investigated. Parameters varied include pressure, temperature, RF power, ICP power, He backing pressure, and oxygen content. The effects on the etch rate, selectivity, profile angle, and surface roughness were examined. The process was then finely tuned for etching of densely packed silicon trenches ranging from 100 to 10 nm. These features are patterned both with electron beam lithography and nano-imprint lithography techniques. Resist selectivity is high in both cases: from 10:1 to 20:1. Vertical and smooth sidewalls were obtained . Etched patterns were used to create nanophotonic devices such as nanospectrometers and laser waveguides and imprint masks for high resolution applications.