Fabrication of large-area patterned porous silicon distributed Bragg reflectors

Abstract

A process to fabricate porous silicon Bragg reflectors patterned on a micrometer lateral scale over wafer areas of several square centimeters is described. This process is based on a new type of projection system involving a megavolt accelerator and a quadrupole lens system to project a uniform distribution of MeV ions over a wafer surface, which is coated with a multilevel mask. In conjunction with electrochemical anodisation, this enables the rapid production of high-density arrays of a variety of optical and photonic components in silicon such as waveguides and optical microcavities for applications in high-definition reflective displays and optical communications.

Effects of focused MeV ion beam irradiation on the roughness of electrochemically micromachined silicon surfaces

“…2͑b͒ shows roughness measurements for the same wafer resistivity irradiated using a broad beam MeV ion irradiation facility, 17 where the fluence is very uniformly distributed across the wafer surface. Each measurement corresponds to one wafer irradiated with a certain fluence in a small area defined by a surface photoresist pattern, then anodized under similar conditions for 1 or 4 min.…”

“…17 There is, however, still an important role for focused beam irradiation, also called proton beam writing where it is easier to encompass a range of different fluences to produce more complex, multilevel structures. a͒ Electronic mail: g0601170@nus.edu.sg Moreover, no surface mask is required and better spatial resolution of irradiation may be achieved.…”

Modification of Porous Silicon Formation by Varying the End of Range of Ion Irradiation

“…Multilayer PSi is formed simply by alternatively carrying out the electrochemical anodization with two different current densities, hence achieving PSi layers with alternating porosity. 6 A multilayer here serves the purpose of tracking the progression of the PSi formation. With a low fluence of 2 Â 10 13 =cm 2 ( Fig.…”

“…A more recent development involves using standard ultraviolet photolithography to create patterned photoresist (PR) masks for shielding irradiation from a uniform broad ion beam. 3,6 This greatly improves irradiation in terms of irradiated area, time required and uniformity of fluence compared to using a focused ion beam. The experiments described here were performed using this method of irradiation.…”

Fabrication of 3D photonic components on bulk crystalline silicon

“…See [15,16] for an account of our work in 3D microfabrication using direct writing with a focused proton beam. However, this direct writing approach is not appropriate for upscaling to large volume production of 3D photonic components, so we have developed a facility [17] in which a high beam current of about 1 μA is used to uniformly irradiate large sample areas. This large area irradiation facility is used here to build up a pattern of three-dimensional micro-and nano-scale damage over large patterned areas of crystalline silicon, in order to fabricate multilevel components such as linear waveguide arrays and 3D splitters in conjunction with photolithography.…”