Feature Sidewalls Research Articles

Dry etching of GaN and related materials: comparison of techniques

The etch rates and feature anisotropy for GaN, AlN, and InN etched in Cl/sub 2/-Ar plasmas with four different techniques were examined. Conventional reactive ion etching produces the slowest etch rates, even when high dc self-biases (>-900 V) are employed, and this leads to mask erosion and sloped feature sidewalls during ridge waveguide fabrication. Two high-ion-density techniques, inductively coupled plasma and electron cyclotron resonance, provide the highest etch rates and most anisotropic features through their combination of high-ion flux and moderate-ion energy. Etch selectivities of GaN to AlN and InN are typically /spl les/4 in these tools. Reactive ion beam etching utilizing a high density (ICP) source is also an attractive option for pattern transfer in the nitrides, although its etch rates are slower than for ICP or ECR due to its lower operating pressure.

The Role of the Substrate on Pattern‐Dependent Charging

Monte Carlo simulations of charging and profile evolution during plasma etching reveal that the substrate can mediate current imbalance across the wafer. This function couples patterned areas, where the electron shading effect dominates, to substrate areas directly exposed to the plasma. When a net positive current flows through the pattern features to the substrate, increasing the exposed area decreases the substrate potential, thereby causing notching at the connected feature sidewalls to worsen, in agreement with experimental observations.

Design and testing of a rapid fire, lightweight, ultra stiff railgun for a cannon caliber electromagnetic launcher system

The goal of the Cannon Caliber Program is to drive 185 g integrated launch packages to 1850 m/s. Three, five-round salvos with a firing rate of 5 Hz are intended to defeat specified targets at a range of up to 3 km. After an extensive alternative study, the design team consisting of United Defence FMC/BMY, the Center for Electromechanics at The University of Texas at Austin (CEM-UT) and Kaman Electromagnetics Corporation (KEC) has chosen to use an air-core, compensated pulsed alternator (compulsator) to power a rapid fire railgun to accomplish this task. A railgun launcher has been designed to fulfil the rapid fire requirements of the system just described. The design incorporates a directional preloading feature and ceramic sidewalls which combined make the railgun structurally stiff and lightweight. This publication focuses on the design, development and initial testing of the railgun launcher. >

The Impact of Gas Phase and Surface Chemical Reactions on Step Coverage in Lpcvd

AbstractThe characteristic step coverage behavior which a given LPCVD process exhibits depends on the nature of the controlling gas phase and/or surface chemical reactions. Physically-based ballistic transport and reaction film profile evolution simulation has provided a structure wherein the origins of step coverage limitations can be understood in the context of the interaction of transport and the controlling chemistry. Based on comparisons of the simulations to literature and in-house experimental data, we have categorized LPCVD mechanisms into one of three types. In heterogeneous deposition, conformal step coverage can usually be found under at least some process conditions. Step coverage typically degrades with increasing deposition temperature. In homogeneous precursor-mediateddeposition, a reactive intermediate is formed in the gas-phase above the wafer surface, resulting in poor to moderate step coverage. Step coverage may or may not degrade with increasing temperature. In byproduct-inhibited deposition, a gas-phase byproduct generated via a surface reaction readsorbs on the growing film surface and slows the deposition rate, yielding a poor to moderate, relatively temperature-insensitive step coverage. Poor step coverage is manifested in a marked film thickness discontinuity at the feature mouth, with a relatively uniform film down the feature sidewalls.

Chemically assisted sputter etching of permalloy using CO or CL2

Redeposition-free patterns have been etched in 3000 Å thick permalloy films using the technique of chemically assisted sputter etching. This technique involves the simultaneous adsorption of a reactant gas from a molecular beam source and normally incident argon ion bombardment. Experimental conditions with Cl2 adsorption can be maintained to etch the permalloy at 80 Å/min and to etch positive photoresist at 110 Å/min. These etch rates are not significantly different from rates obtained with argon ion milling, even though the permalloy surface is known to incorporate Cl2. Redeposited material observed with Cl2 chemically assisted sputtering has been shown to be water soluble, and can be completely removed from feature sidewalls prior to stripping the resist. Linewidth measurements show that no feature broadening occurs on 2 μ line and space patterns, within the precision of the measurement (±0.2 μ). Chemically assisted sputter etching with the adsorption of CO resulted in reduced etch rates and increased redeposition. Both of these effects are attributed to the formation of carbides on the alloy surface during the process.

Cl2 Chemically Assisted Sputter-Etching of Permalloy

AbstractRedeposition-free patterns have been etched in 3000Å thick permalloy films using the technique of chemically assisted sputter-etching. This technique involves the simultaneous adsorption of a reactant gas from a molecular beam source and normally incident argon ion bombardment. Experimental conditions with Cl2 adsorption can be maintained to etch the permalloy at 80Å/min and to etch positive photoresist at 110Å/min. These etch rates are not significantly different from rates obtained with argon ion milling, even though the permalloy surface is known to incorporate Cl2. Re-deposited material observed with Cl2 chemically assisted sputtering has been shown to be water soluble, and can be completely removed from feature side-walls prior to stripping the resist. Linewidth measurements show that no feature broadening occurs on 2 micron line and space patterns, within the precision of the measurement (±0.2 micron).