Surface-micromachined Bragg Reflectors Based on Multiple Airgap/SiO2 Layers for CMOS-compatible Fabry-perot Filters in the UV-visible Spectral Range

Ghaderi, M.; Ayerden, N. Pelin; Graaf, G. de; Wolffenbuttel, R.F.

doi:10.1016/j.proeng.2014.11.591

Cited by 6 publications

(3 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…There have been multiple approaches to the deposition or growth of a SiO 2 film for optical and PIC devices while controlling for the stress of the deposited films. One approach is to use a thermal oxide to achieve a low-stress suspended SiO 2 structure [ 12 ]. Considering that a thermal oxide is grown at a high temperature and requires a silicon layer for growth, this approach is not compatible with devices requiring low temperature fabrication or no silicon layers.…”

Section: Introductionmentioning

confidence: 99%

Stress and Refractive Index Control of SiO2 Thin Films for Suspended Waveguides

Wostbrock

Busani

2020

Nanomaterials

View full text Add to dashboard Cite

Film stress and refractive index play an important role in the fabrication of suspended waveguides. SiO2 waveguides were successfully fabricated on multiple substrates including Si, Ge, and Al2O3 wafers; the waveguides were deposited using inductively coupled plasma chemical vapor deposition at 100 °C. The precursor gases were SiH4 and N2O at 1:3 and 1:9 ratios with variable flow rates. The occurrence of intrinsic stress was validated through the fabrication of suspended SiO2 bridges, where the curvature of the bridge corresponded to measured intrinsic stress, which measured less than 1 µm thick and up to 50 µm in length. The flow rates allow film stress tunability between 50 and −65 MPa, where a negative number indicates a compressive state of the SiO2. We also found that the gas ratios have a slight influence on the refractive index in the UV and visible range but do not affect the stress in the SiO2 bridges. To test if this method can be used to produce multi-layer devices, three layers of SiO2 bridges with air cladding between each bridge were fabricated on a silicon substrate. We concluded that a combination of low temperature deposition (100 °C) and photoresist as the sacrificial layer allows for versatile SiO2 bridge fabrication that is substrate and refractive index independent, providing a framework for future tunable waveguide fabrication.

show abstract

Section: Introductionmentioning

confidence: 99%

Stress and Refractive Index Control of SiO2 Thin Films for Suspended Waveguides

Wostbrock

Busani

2020

Nanomaterials

View full text Add to dashboard Cite

show abstract

“…In an optical MEMS, the performance of the optical components defines the functionality of the entire system and is highly sensitive to the details of the shape and surface quality [3]. While electrical contacting is essential in traditional MEMS and limits the number of movable layers to be stacked, the optical characteristics of the layers are much more important in optical MEMS [4,5].…”

Section: Introductionmentioning

confidence: 99%

“…Thin-film membranes have been commonly implemented in various optical devices for applications such as; flexible reflectors [6], Fabry-Perot-based filters [7,8] and airgap filters. The use of air as a low-index optical layer in large-area UV-visible optical filters has been previously introduced [4]. The refractive index contrast between the low and high-index materials in an optical interference filter determines the optical quality of the filter.…”

Section: Introductionmentioning

confidence: 99%

Thermal annealing of thin PECVD silicon-oxide films for airgap-based optical filters

Ghaderi

Graaf

Wolffenbuttel

2016

J. Micromech. Microeng.

View full text Add to dashboard Cite

This paper investigates the mechanical and optical properties of thin PECVD silicon-oxide layers for optical applications. The different deposition parameters in PECVD provide a promising tool to manipulate and control the film structure. Membranes for use in optical filters typically are of ~λ/4n thickness and should be slightly tensile for remaining flat, thus avoiding scattering. The effect of the thermal budget of the process on the mechanical characteristics of the deposited films was studied. Films with compressive stress ranging from −100 to 0 MPa were deposited. Multiple thermal annealing cycles were applied to wafers and the in situ residual stress and ex situ optical properties were measured. The residual stress in the films was found to be highly temperature dependent. Annealing during the subsequent process steps results in tensile stress from 100 to 300 MPa in sub-micron thick PECVD silicon-oxide films. However, sub-100 nm thick PECVD silicon-oxide layers exhibit a lower dependence on the thermal annealing cycles, resulting in lower stress variations in films after the annealing. It is also shown that the coefficient of thermal expansion, hence the residual stress in layers, varies with the thickness. Finally, several free-standing membranes were fabricated and the results are compared.

show abstract