Shallow Fresnel lens fabrication using grey scale lithography made by high energy beam sensitive mask (HEBS) technology and reactive ion etching

Tali Nachmias*, Avi Ohayon, Shefer E. Melzer, Meni Kabla, Elie Louzon, Uriel Levy

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review

9 Scopus citations

Abstract

We describe the fabrication and the characterization of high efficiency Fresnel lenses by the use of gray scale lithography (GSL), followed by reactive ion etching (RIE) or deep reactive ion etching (DRIE) to transfer the pattern from the gray scale resist into the silicon substrate. Three versions of Fresnel lenses were fabricated, with height of 600nm, 1800nm and 5500nm. The desired lens height in silicon is determined from photoresist height and the selectivity of the etching process. A low selectivity DRIE process was developed in order to fabricated 1800nm and 5500nm Fresnel lenses. The 600nm Fresnel lens was fabricated using an RIE process because it requires a relatively slow etch rate and low selectivity, both could not be obtained by DRIE. According to the photoresist thickness developed in the gray scale lithography, an RIE process with a selectivity of 0.55 was required. We implement the DOE (design of experiment) method for finding the process parameters which gives the desirable selectivity and its tolerance which is crucial for determining the range of the Fresnel lens height. It was found that according to the selectivity tolerance, the Fresnel lens stands within ±10% tolerance oh its height. Finally, we demonstrated the imaging of an object using the 600 nm lens.

Original languageAmerican English
Article number72050B
JournalProceedings of SPIE - The International Society for Optical Engineering
Volume7205
DOIs
StatePublished - 2009
EventAdvanced Fabrication Technologies for Micro/Nano Optics and Photonics II - San Jose, CA, United States
Duration: 26 Jan 200928 Jan 2009

Keywords

  • Deep reactive ion etching (DRIE)
  • Design of experiment (DOE).
  • Fresnel lens
  • Gray scale lithography (GSL)
  • High energy beam sensitive (HEBS) glass
  • Reactive ion etching (RIE)

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