Showing papers on "Surface micromachining published in 1987"

Introduction to microelectronic fabrication

Abstract: (NOTE: Each chapter concludes with Summary, References, and Problems) Preface 1 An Overview of Microelectronic Fabrication A Historical Perspective An Overview of Monolithic Fabrication Processes and Structures Metal-Oxide-Semiconductor (MOS) Processes Basic Bipolar Processing Safety 2 Lithography The Photolithographic Process Etching Techniques Photomask Fabrication Exposure Systems Exposure Sources Optical and Electron Microscopy Further Reading 3 Thermal Oxidation of Silicon The Oxidation Process Modeling Oxidation Factors Influencing Oxidation Rate Dopant Redistribution During Oxidation Masking Properties of Silicon Dioxide Technology of Oxidation Oxide Quality Selective Oxidation and Shallow Trench Formation Oxide Thickness Characterization Process Simulation 4 Diffusion The Diffusion Process Mathematical Model for Diffusion The Diffusion Coefficient Successive Diffusions Solid-Solubility Limits Junction Formation and Characterization Sheet Resistance Generation-Depth and Impurity Profile Measurement Diffusion Simulation Diffusion Systems Gettering 5 Ion Implantation Implantation Technology Mathematical Model for Ion Implantation Selective Implantation Junction Depth and Sheet Resistance Channeling, Lattice Damage, and Annealing Shallow Implantation Source Listing 6 Film Deposition Evaporation Sputtering Chemical Vapor Deposition Epitaxy Further Reading 7 Interconnections and Contacts Interconnections in Integrated Circuits Metal Interconnections and Contact Technology Diffused Interconnections Polysilicon Interconnections and Buried Contacts Silicides and Multilayer-Contact Technology The Liftoff Process Multilevel Metallization Copper Interconnects and Damascene Processes Further Reading 8 Packaging and Yield Testing Wafer Thinning and Die Separation Die Attachment Wire Bonding Packages Flip-Chip and Tape-Automated-Bonding Processes Yield Further Reading 9 MOS Process Integration Basic MOS Device Considerations MOS Transistor Layout and Design Rules Complementary MOS (CMOS) Technology Silicon on Insulator 10 Bipolar Process Integration The Junction-Isolated Structure Current Gain Transit Time Basewidth Breakdown Voltages Other Elements in SBC Technology Layout Considerations Advanced Bipolar Structures Other Bipolar Isolation Techniques BICMOS 11 Processes for Microelectromechanical Systems-MEMS Mechanical Properties of Silicon Bulk Micromachining Silicon Etchants Surface Micromachining High-Aspect-Ratio Micromachining: The LIGA Molding Process Silicon Wafer Bonding IC Process Compatibility Answers to Selected Problems Index

IC-Processed piezoelectric microphone

Abstract: A miniature diaphragm pressure transducer having sensitivity to acoustic signals at the level of conversational speech has been fabricated by combining micromachining procedures (to produce a thin silicon-nitride diaphragm) with ZnO thin-film processing. The sensor consists of a patterned ZnO layer (which acts as a piezoelectric transducer) deposited on a thin square micromachined diaphragm made of LPCVD silicon nitride. The diaphragm, 2 µm in thickness, is the thinnest yet reported for a piezoelectric readout structure of relatively large area (3 × 3 mm2). The transducer shows an unamplified response of roughly 50 µV/µbar when excited by sound waves at 1 kHz with the variation of the sensitivity from 20 Hz to 4 kHz being approximately 9 dB. These results are obtained using a 0.1-mm-wide annular pattern that measures 3.6 mm in circumference.

Micromachining of optical structures with focused ion beams

Abstract: For the first generation of lightwave devices, semiconductor lasers and detectors have been used as discrete elements. As the technology continues to evolve, integration of light sources with electronics or other optical elements will be necessary. However, an efficient and reliable method for generating laser facets and other optical elements internal to the integrated system must first be developed. Three dimensional features have been milled into optical materials by scanning a submicron focused gallium ion beam. Different shapes are obtained using computer controlled beam placement and dwell time during sputtering. We have used this technique to create micron‐sized facets and reflectors in the active areas of semiconductor lasers. Light output and quantum efficiency measurements indicate that these features are of sufficient quality to fabricate monolithic integrated optical devices. Some of the applications currently being investigated are laser–detector pairs, coupled cavity lasers, lasers with inte...

A Second Generation Focused Ion Beam Micromachining System

Abstract: We present a description of our second generation micromachining system. This machine has been developed at AT&T Bell Laboratories for applications including photomask repair, integrated circuit modification, and fabrication of integrated optical structures. The architecture incorporates many of the features and capabilities found separately in other systems, in a unique combination with emphasis on flexibility and ease of operation. The hardware features a 30 KeV Gallium beam with a one millimeter deflection field and 250 mm by 300 mm stage travel. Provisions have been made for secondary electron and ion imaging, charge neutralization, gas phase material deposition and secondary ion mass spectroscopy (SIMS).

300 mW operation of a surface-emitting phase-locked array of diode lasers

Abstract: The focused-ion-beam micromachining of an output coupler and a 45° turning mirror to form a surface-emitting, 10-element, phase-locked array of diode lasers is described. 330 mW optical power was emitted at the turning mirror in pulsed operation.

Focused ion-beam milling of a submicrometer aperture for a hydrodynamic Josephson-effect experiment

Abstract: We describe the technique used to manufacture a submicron aperture in a nickel microfoil used to look for the Josephson effect in superfluids. The size requirements for a superfluid weak link are briefly discussed. The micromachining is performed by means of a focused Ga ion beam. The ion probe is produced by a liquid‐metal‐ion source that is known to act as a near pointlike source. The source, optical lens, and deflection assembly are lumped as an attachment to a commercial scanning electron microscope. The obtained machining capabilities and scanning ion images are compatible with a probe size of 150–200 nm, a size that corresponds to our theoretical estimates.

Response Of Metallic Material To Micromachining

Abstract: The diamond turn process affects the metal-surface in a complex way. The knowledge of the relevant mechanisms (influence of polycrystallinity, crystal structure, grain size, mechanical behaviour) shows a new way to optimize optical metal surfaces by using micro-crystalline metals.

Sensors developed for in-process thermal sensing and imaging.

Abstract: This chapter deals with sensors development for in-process thermal sensing and imaging. Among various evaluation methods, noncontact, and nondestructive techniques including thermal and optical methods are of particular interest. Temperature profiles can be used to provide a diagnostic tool for in situ process control and to find optimal process conditions. Optical methods can provide material and process characterizing information, such as thin-film thickness and quality, carrier concentration, or content of contaminants. A variety of sensors are available in association with these noncontact methods, but infrared detectors are attractive because they can be used for both methods. Most of infrared detectors can be classified into two major categories: photon-type and thermal-type detectors. A thermopile, a type of thermal-type detector, can respond from ultraviolet to far infrared and its sensitivity is almost flat over this region. It can be operated over a relatively wide range of ambient temperatures and also at room temperature. A monolithic thermopile infrared detector array has been developed using conventional MOS technology and micromachining, and this type of array has a potential to be used for an inexpensive noncontact in situ process evaluation system.

Infrared Detector Based On An Integrated Silicon Thermopile

Abstract: A new thermal infrared detector fabricated using standard silicon IC technology and silicon micromachining is presented. The device consists of a 10-micron thick cantilever beam with one half covered by an absorbing layer and the other half containing a 44-strip p-Si/Al thermopile. The detectors have a responsivity (in vacuum) of 10 V/W and a relative detectivity D*, measured in air and for a 500 K blackbody source, of approximately 5 x 107 cmHzi/W.

Computer Controlled Ion Beam Machining For Precision Surface Finishing And Figuring

Abstract: Micromachining of mechanical structures by ion bombardment is reported. A 1.5 kV argon ion beam is used under computer control for workpiece stock removal. Generation of profiles with submicron precision is demonstrated and computer algorithms are used to predict machining conditions for producing specific surface characteristics and evaluating them geometrically.

Focused Ion Beam Sims for Micromachining Applications

Abstract: A secondary ion mass spectrometry (SIMS) system has been incorporated into the AT&T-BL second generation focused ion beam (FIB) micromachining system. The primary applications are end-point detection and topographical element mapping. End-point detection of Cr micromachining on photomasks was done with raster sizes ranging from 10 μm x 10 μm to 3 μm x 3 μm. SIMS end-points, total ions images, and transmitted light measurements show that the ion-milling can be controlled to stop prior to or after the Cr/glass interface. Mass selected secondary ion images have been obtained for high yield ions such as52Cr+ and27 A1+ on raster fields of 25 μm in time intervals ranging from 20 to 100 sec. Al+ SIMS images of 1 μm lines and spaces from a VLSI test pattern have been obtained.

On-chip integrated optic mirrors in Ti: LiNbO3 by ion-beam micromachining

Abstract: A complete process is described whereby on-chip mirrors may be fabricated in Ti : LiNbO3 stripe waveguide devices using micro-focal ion-beam machining. Experimental results are presented for a device operating at 1.523 μm wavelength, TM mode. An interferometric technique is used to distinguish the reflection from the on-chip mirror from other spurious reflections. Approximately 24% power reflectivity is observed. Results are compared with a simple theoretical model of the chip response under different conditions, and good agreement is obtained.

An apparatus for batch fabrication of micromechanical elements by ion beam machining

Abstract: An apparatus has been constructed for ion beam milling of micromechanical structures. A 3 cm Kaufman type source is used to provide argon ion current densities and energies of up to 25 mA/cm2 and 1.5 kV, respectively. Stencil masks prepared by chemical milling are used to produce an array of microbeams allowing batch fabrication of micromechanical elements by scanning the mask or workpiece. Algorithms have been developed for computer control of workpiece position, orientation, and rotation. Computer control of beam current and energy has also been implemented. A database of sputtering yields and redeposition rates allows optimum operating conditions to be selected for a given application. Investigations include micromachining of refractory metals, milling of slots, holes, and grooves, and surface texturing, polishing, and figuring micromechanical structures.

Technology Considerations For Integrated Multifunctional Silicon Sensors

Abstract: Multifunctional silicon integrated sensors have been fabricated for simultaneous measurement of several physical and chemical variables. These sensors are based on the compatible introduction of thin films of piezoelectric and pyroelectric zinc oxide combined with conventional MOS processing technology in the fabrication of 1) a 64-element infrared sensing array, 2) a mass air-flow sensor, 3) a tactile sensor array for precision robotics applications, 4) carbon monoxide sensor, 5) surface-acoustic wave chemical vapor sensor, 6) microbeam accelerometer, and 7) infrared charge-coupled device imager. This paper specifically addresses technology issues involved in incorporating sensors with high-performance silicon integrated circuits. Focus is directed toward 1) zinc oxide based sensors, 2) silicon micromachining pf sensor membranes, and 3) compatible processing issues necessary for a generic integrated sensor technology. Performance examples for a 64-element room-temperature pyroelectric imager are presented.

Realisation Of Polarisation Sensitive And Frequency Selective Surfaces On Microwave Reflectors By Laser Evaporation

Abstract: Gridded reflectors are used on communication satellites antennas to provide frequency reuse in dual linear polarisation mode of operation. The polarisation sensitive surface consists of metallic strips, forming a grid with width and spacings of the order of 0.1 mm. The use of frequency-selective surface (FSS) subreflectors allows the simultaneous generation of different microwave beams with the same main reflector. Such a reflector will require a structure of conductive arrays of either dipoles, rings, squares or square loops with typical dimensions of the order of 3-6 mm. Optimisation of the electrical design leads to critical dimensioning of these structures. By direct ablation of an aluminium surface coating by means of laser evaporation, high accuracies can be achieved. The major requirements were to minimize thermal damage of the substrate material and to produce dimensionally accurate grids. Experiments were carried out using a pulsed TEA-CO2 laser and a Q-switched Alexandrite laser. Details of the experimental set-up and conditions are described.

Air Bearings Machined On Ultra Precision, Hydrostatic CNC-Lathe

Abstract: Micromachining of precision elements requires an adequate machine concept to meet the high demand of surface finish, dimensional and shape accuracy. The Hembrug ultra precision lathes have been exclusively designed with hydrostatic principles for main spindle and guideways. This concept is to be explained with some major advantages of hydrostatics compared with aerostatics at universal micromachining applications. Hembrug has originally developed the conventional Mikroturn ultra precision facing lathes, for diamond turning of computer memory discs. This first generation of machines was followed by the advanced computer numerically controlled types for machining of complex precision workpieces. One of these parts, an aerostatic bearing component has been succesfully machined on the Super-Mikroturn CNC. A case study of airbearing machining confirms the statement that a good result of the micromachining does not depend on machine performance alone, but also on the technology applied.

Materials and Structures for High Density I/O Interconnection Systems

Abstract: In order to examine the use of a compliant cantilever structure as a contact scheme for a Multi-chip Interconnection System (MIS), multi-layer (metals and SiO 2 ) cantilever beams were fabricated utilizing standard silicon processing and micromachining technologies. The mechanical behavior and electrical characteristics of the beams were investigated in order to establish their optimum dimensions for use in the MIS. During the course of this study, a new mechanical testing method for thin films has also been developed, which makes use of the same cantilever beam structure and a “Nanoindenter.” The Young's modulus and yield strength of thermally grown SiO 2 and Au were measured using this technique.

Vertical Cantilever Beams For Optical Switching

Abstract: The feasibility of using micromechanical silicon cantilever beams for optical switching is under examination. These devices are easy to interface to optical fibres and could easily incorporate monitoring circuitry. They potentially offer several advantages over solid state electro-optical devices including small size, low fabrication cost and compatibility in size with optical fibres. In addition, control and monitoring coula readily be incorporated on the same chip, perhaps exploiting the anisotropic etching feature to further advantage. Their speed limitation is not a disadvantage in applications where the determining factor is the initial setting up time for the connection. This investigation has been concerned with the design and fabrication of vertical beams in (110) silicon wafers. The present work is aimed at evaluating silicon technology to assess the feasibility and define the parameters for an optical switch design. A numerical simulation of the deflection and damping characteristics of the beam has been carriea out and has identified a range of design parameters which could be useful for optical switching. A range of devices having a first resonant frequency of >5kHz and a beam deflection of ~20μm have been designed. The fabrication procedure employs conventional silicon planar technology to define the beam geometry on (110) wafers. The structures are etched using electrochemically controlled ethylene-diamine as an anisotropic etchant. The fabrication of these vertical beams involves a combination of micromaching and silicon planar technology to align the beams accurately along directions.