Metal mask free dry-etching process for integrated optical devices applying highly photostabilized resist.

Photostabilization is a widely used post lithographic resist treatment process, which allows to harden the resist profile in order to maintain critical dimensions and to increase selectivity in subsequent process steps such as reactive ion etching. In this paper we present the optimization of deep UV-curing of 0,3-3.3 μm thick positive resist profiles followed by heat treatment up to 280 °C. The effectiveness of this resist treatment allows for metal mask free reactive ion etching with selectivity up to 6 for silicon structures, thermal silicon oxide and silicon oxynitride. This procedure is demonstrated by the results obtained in etching of various integrated optical structures

Structuring of sapphire by laser-assisted methods, ion-beam implantation, and chemical wet etching

Sapphire is an attractive material for micro- and opto-electronic systems applications because of its excellent mechanical and chemical properties. However, because of its hardness, sapphire is difficult to machine. Titanium-doped sapphire is a well-known broadly tunable and short-pulse laser material and a promising broadband light source for applications in low-coherence interferometry. We investigated several methods to fabricate rib structures in sapphire that can induce channel waveguiding in Ti:sapphire planar waveguides. These methods include direct laser ablation, laser-micromachined polyimide stripes, selective reactive ion etching, and ion-beam implantation followed by chemical wet etching. Depending on the method, we fabricated channels with depths of up to 1.5 µm. We will discuss and compare these methods. Reactive ion etching through laser-structured polyimide contact-masks has so far provided the best results in terms of etching speed and roughness of the etched structures

Fabricating Ultra-Thin Silicon Carbide Diaphragms

A process for fabricating relatively thin SiC diaphragms may include fast Reactive Ion Etching (RIE) followed by Dopant Selective Reactive Ion Etching (DSRIE). The process may produce silicon carbide (SiC) diaphragms thinner than 10 microns. These thinner, more sensitive diaphragms may then be used to effectively resolve sub-psi pressures in jet engines, for example

Impact of sidewalls on electrical characterization

In this article the impact of sidewalls, formed during reactive ion etching, on the electrical behavior of thin film structures is presented. The presence of sidewalls was experimentally characterized by sheet resistance measurements on Van der Pauw structures. The effect of these sidewalls on the extraction of specific contact resistance from Cross Bridge Kelvin Resistance (CBKR) structures is discussed

Ga^+ beam lithography for nanoscale silicon reactive ion etching

By using a dry etch chemistry which relies on the highly preferential etching of silicon, over that of gallium (Ga), we show resist-free fabrication of precision, high aspect ratio nanostructures and microstructures in silicon using a focused ion beam (FIB) and an inductively coupled plasma reactive ion etcher (ICP-RIE). Silicon etch masks are patterned via Ga^+ ion implantation in a FIB and then anisotropically etched in an ICP-RIE using fluorinated etch chemistries. We determine the critical areal density of the implanted Ga layer in silicon required to achieve a desired etch depth for both a Pseudo Bosch (SF_6/C_4F_8) and cryogenic fluorine (SF_6/O_2) silicon etching. High fidelity nanoscale structures down to 30 nm and high aspect ratio structures of 17:1 are demonstrated. Since etch masks may be patterned on uneven surfaces, we utilize this lithography to create multilayer structures in silicon. The linear selectivity versus implanted Ga density enables grayscale lithography. Limits on the ultimate resolution and selectivity of Ga lithography are also discussed

Monolithic integration of erbium-doped amplifiers with silicon-on-insulator waveguides

Monolithic integration of Al2O3:Er3+ amplifier technology with passive silicon-on-insulator waveguides is demonstrated. A signal enhancement of >7 dB at 1533 nm wavelength is obtained. The straightforward wafer-scale fabrication process, which includes reactive co-sputtering and subsequent reactive ion etching, allows for parallel integration of multiple amplifier and laser sections with silicon or other photonic circuits on a chip

Nd-doped aluminum oxide integrated amplifiers at 880 nm, 1060 nm, and 1330 nm

Neodymium-doped Al2O3 layers were deposited on thermally oxidized Si substrates and channel waveguides were patterned using reactive-ion etching. Internal net gain on the Nd3+ transitions at 880, 1064, and 1330 nm was investigated,\ud yielding a maximum gain of 6.3 dB/cm at 1064 nm. Values for the energy-transfer upconversion parameter for different Nd3+\ud concentrations were deduced

A novel high-speed polymeric EO modulator based on a combination of a microring resonator and an MZI

A Mach-Zehnder interferometer with an electrooptic polymer mircroring resonator adjacent to one of its branches is realized in a polymer layer stack. The microresonator is defined by reactive ion etching in the nonlinear PMMA-DR1 polymer and waveguide definition is done without etching, by using a negative photoresist (SU8) as waveguide layer. Electrooptic coefficients of 10 pm/V and modulation frequencies of 1 GHz were measured

Fabrication of bismuth nanowires with a silver nanocrystal shadowmask

We fabricated bismuth (Bi) nanowires with low energy electron beam lithography using silver (Ag) nanocrystal shadowmasks and a subsequent chlorine reactive ion etching. Submicron-size metal contacts on the single Bi nanowire were successfully prepared by in situ focused ion beam metal deposition for transport measurements. The temperature dependent resistance measurements on the 50 nm wide Bi nanowires showed that the resistance increased with decreasing temperature, which is characteristic of semiconductors and insulators