Ronnie R. Fesperman

High-pressure phase transformation of silicon nitride

We provide evidence for a high-pressure phase transformation (HPPT) in the ceramic material silicon nitride. This HPPT is inferred by a high-pressure diamond anvil cell, Raman spectroscopy, scanning/transmission electron microscopy, and optical and acoustic microscope inspection. In the case of silicon nitride, the HPPT involves a ductile or metallike behavior that is observed in severe deformation processes, such as nanoindentation and micromachining. This pressure-induced plasticity is believed to be similar to that found in silicon and germanium with its origin in the high-pressure metallic β-Sn phase formation.

Experimental and Numerical Investigation of Ductile Regime Machining of Silicon Nitride

Recent research has shown that many semiconductor and ceramic materials can be machined in ductile fashion under very high pressures and at low depths of cut. In a previous study, the authors reported results from numerical simulations of orthogonal machining of Silicon Nitride using a pressure‐independent material model with von Mises yield criterion. Experimental evidence strongly suggests that the brittle‐to‐ductile transition of Silicon Nitride is pressure‐dependent. Specifically, experiments indicate that the ductile regime machining is possible when the hydrostatic pressure within the workpiece is of the same order of magnitude as the hardness. In the present work, the ductile behavior of Silicon Nitride is studied by carrying out single point diamond turning operation on Silicon Nitride samples at depths of cut ranging from 250nm to 10μm. Force and surface roughness data collected from machining tests are presented. Chip morphology is also investigated to determine the depth of cut at which brittle...

Mechatronics and Control of a Precision Motion Stage for Nano-Manufacturing

High precision motion is critical in the semiconductor industry and as feature size continues to decrease, the need for higher precision increases. This paper presents the control system design and integration of a novel multi-degree of freedom precision stage for nano-manufacturing. It is composed of a 6 DOF wafer holder and a 3 DOF module holder. The modules can be chosen for a desired task, such as a nano-imprint lithography module. Capacitance gauges, interferometers, and photo detectors provide position feedback of the stage. Piezo-electric actuators and linear motors, that produce two orthogonal forces each, produce the desired output. Modeling of the coordinate transformation among the spaces of sensors, stage position, and actuators along with dynamic modeling of the stage is presented. Controller design, hardware, and software is described and results comparing simulation and implementation show a closed-loop positioning of less than 1 nm error in x and y and 0.01 arc seconds in θ z with a sensor noise level of less than 0.2 nm.Copyright

Engineering Nanotechnology: The Top Down Approach

Nanotechnology can be defined as “the study, development and processing of materials, devices, and systems in which structure on a dimension of less than 100 nm is essential to obtain the required functional performance.” There are currently two very different approaches to nanotechnology, the first and more classical approach is commonly called engineering nanotechnology. This approach involves using classical deterministic mechanical and electrical engineering principles to build structures with tolerances at levels approaching a nanometer. The other approach, sometimes called molecular nanotechnology, is concerned with self-assembled machines and the like and is far more speculative. At UNC Charlotte’s Center for Precision Metrology we have been working in engineering nanotechnology for more than a decade. We started with molecular manipulation with scanning probe microscopes in the late 1980s [1] and have continued to develop new measurement systems [2], nano-machining systems [3,4], and nano-positioning devices. One of the largest challenges is precision motion control of macroscopic stages. Currently we have three stages under development or modification. The first is the Sub Atomic Measuring Machine (SAMM) [5] which is being modified to provide picometer resolution; the second is the Multi-Scale Alignment and Positioning System (MAPS) initially to be used for nanoimprinting; the third is an Ultra-Precision Vacuum Stage [6], which is the subject of another paper in this conference. This paper will discuss the first two systems.