- •Brian Carl Morgan, Doctor of Philosophy, 2006
- •1. Introduction
- •Introduction
- •Passive Techniques
- •Active Techniques
- •Thesis Objectives and Structure
- •Chapter 2: gray-scale technology
- •Introduction
- •Gray-scale Background
- •Theoretical Background
- •Optical Mask Constraints
- •Standard Lithography Process
- •Design and Lithography Advancements
- •Minimum Feature Limitations
- •2.3.3. Double Exposures
- •Pattern Transfer
- •Deep Reactive Ion Etching (drie)
- •Selectivity Characterizations
- •Technology Collaborations
- •Phase Fresnel Lens (nasa)
- •2.5.2.1. Compensated Aspect Ratio Dependent Etching (carde)
- •Conclusion
- •Chapter 3: elect rostatic comb-drives using goay-scale technology
- •Introduction
- •Electrostatic Actuation Fundamentals
- •Tailored Comb-finger Design and Simulation
- •Analytical Displacement Simulations (2-d)
- •Finite Element Analysis (3-d)
- •Instability Considerations
- •Reduced Height Suspensions
- •Fabrication
- •Comb-drive Testing
- •Reduced Height Comb-fingers
- •Conclusion
- •Introduction
- •Tunable mems Resonator Operation
- •1. Introduction 1
- •1.1. Introduction 1
- •2.1. Introduction 11
- •3.1. Introduction 36
- •4.1. Introduction 51
- •Gray-scale Electrostatic Springs
- •Testing and Characterization
- •Conclusion
- •Introduction
- •Device Concept
- •Figure 5.5: Calculated coupling as two co-axial single-mode fibers are separated longitudinally.
- •Figure 5.6: Alignment schematic for a bent fiber cantilever coupling to a fixed output fiber.
- •Alignment Wedges
- •Fabrication
- •Assembly
- •Actuation Concept Demonstration
- •Introduction
- •Experimental Setup
- •Static Testing
- •Table 6.3: Measured fiber locations for discrete actuation voltages. These 4 points form the corners of a diamond shaped alignment area.
- •Channel a (va2)
- •1. Introduction 1
- •1.1. Introduction 1
- •2.1. Introduction 11
- •3.1. Introduction 36
- •4.1. Introduction 51
- •Horizontal displacement
- •Voltage Squared (v2)
- •Auto-alignment Algorithms
- •Figure 6.16: Simplified hill-climbing algorithm block diagram.
- •Automated Fiber Alignment Results
- •Settling Time, Coarse Threshold Power (%Peak)
- •Testing Summary and Discussion
- •Conclusion
- •Summary of Accomplishments
- •Future Work
Thesis Objectives and Structure
The purpose of this research is two-fold: First, to develop gray-scale technology as an integrative MEMS-based 3-D fabrication tool, and second, to demonstrate the first MEMS actuators of any kind to utilize gray-scale fabricated features for improved performance and capabilities. The advances in gray-scale technology pioneered in this work firmly establish gray-scale as an attractive platform technology for MEMS device development. As part of this research on the core technology, multiple novel static devices were demonstrated, including: static micro-compressors, 3-D packaging substrates for MOSFET relays, and soft X-ray phase Fresnel lenses. The variable-height comb-drive actuators and resonators developed in this work are the first demonstration of achieving tailored electrostatic actuator behavior while maintaining a compact device layout. This dissertation also reports the first 2-axis on-chip optical fiber alignment system that uses the coupled in-plane motion of gray-scale shaped actuators to create actuation both in- and out- of the plane of the wafer. Alignment of an optical fiber cantilever in 2-axes over a large range (40nm x 40nm), with high resolution (<1nm), and fast alignment times (routinely <20 seconds), establish this device as a realistic on-chip platform for the packaging and integration of optoelectronic devices.
This PhD dissertation is organized as follows: Chapter 1 has reviewed the motivation behind this research, summarized the main contributions contained in this dissertation, and briefly reviewed the relevant literature.
Chapter 2 will discuss the gray-scale technology process in detail. Specific attention will be paid to profile control and pattern transfer. Three demonstrations of static 3-D applications developed with gray-scale technology will be presented as technology collaborations with different partners: the U.S. Army Research Laboratory, the Toshiba Corporation, and the NASA-Goddard Space Flight Center.
The development of the first electrostatic MEMS actuators integrating variable height structures fabricated with gray-scale technology will be presented in Chapter 3. Issues related to the design and integration of gray-scale structures into a comb-drive actuator will be reviewed, while test results will confirm their improved performance. Chapter 4 will build upon this work and discuss a more specific application of gray-scale tailored actuators: tunable MEMS resonators. The theoretical framework for such actuators will be presented, along with test results from multiple embodiments.
Chapters 5 and 6 will discuss the development of a new on-chip 2-axis optical fiber alignment system developed using gray-scale technology. The concept, design, and fabrication of the basic system will be discussed in detail in Chapter 5, while Chapter 6 will review all optical testing and alignment results.
Chapter 7 has been reserved for discussions on potential extensions of the work presented in this dissertation, as well as concluding remarks. Topics to be covered include: low frequency tunable resonator applications, prospects for miniaturizing fiber alignment systems towards dense array packaging, and methods for clamping optical fibers after alignment has been achieved.