Leland Stanford Junior University

Xerox Corporation

Shinya Akamine

Thomas R Albrecht

Calvin F Quate

Mark J Zdeblick

Thomas E Carver

Butrus Thomas Khuri-Yakub

Babur B Hadimioglu

Hirofumi Yamada

Acoustically thin capping structures and acoustic droplet ejectors having fluid wells and which use such capping structures to create fluid cells. The inventive capping structures permit the accurate positioning of the free surface of a fluid, permit acoustically induced fluid droplet ejection, and prevent fluid from spilling from the fluid wells. 'Acoustically thin' means that the thickness of the capping structure is small enough that the acoustic energy that is lost passing through the capping structure is less than 50% of the incident acoustic energy.

Capping structures for acoustic printing

Sharpened microminiature tips are produced by casting in a silicon/silicon dioxide mold. The silicon dioxide layer is formed by exposing cavities in a single crystal substrate to an oxidizing species at a low temperature. Anomalous oxidation of silicon results in a differential thickness in the silicon dioxide layer, providing a convex contour on the surface of the cavities, leading to a sharpened end. The tip can be made from any kind of material that can be cast in a silicon mold. The sharpened tip can be integrated with a member to form a cantilever. An improved scanning probe microscope can be built with the sharpened tip in the cantilever structure.

Casting sharpened microminiature tips

A combined atomic force and near field microscope assembly for atomic level inspection of a target object. The assembly includes a scanning probe with a sharp tip and a photosensitive region on its lower surface. A sample is disposed on a glass substrate and exposed to an evanescent wave generated on the glass substrate by total internal reflection. An optical probe comprising a microfabricated cantilever having an apex in close proximity to a photosensitive region is disposed in close proximity to a sample. The photosensitive region collects light generated by FTR at the apex of the optical probe due to local disruptions of the evanescent field caused by the probe tip. A cantilever displacement mechanism is included so as to allow for operation in a second mode as a conventional atomic force microscope.

Combined atomic force and near field scanning optical microscope with

A dielectric cantilever arm stylus with an integrally formed pyramidal tip is provided. The tip is molded in a pyramidal pit etched in a later-removed (100) silicon substrate. An integrally-formed cantilever arm is also formed as the tip is being formed. Various thin film materials form the cantilever arm and the tip. In one embodiment of the invention, the dielectric is silicon nitride. The cantilever arm is anodically bonded to a glass block.

Microfabricated cantilever stylus with integrated pyramidal tip

An acoustic microscope assembly for atomic level inspection of a target object includes a cantilever arm with a sharp tip on its lower surface and a zinc oxide piezoelectric thin film on its upper surface. High frequency excitation signals, having a frequency of at least 50 Megahertz, are applied to the piezoelectric thin film so as to generate high frequency acoustic signals that are transmitted through the sharp tip so as to impact on a target object. The assembly can either receive acoustic signals reflected by the target object, or it can receive acoustic signals that have propagated through the target object. One method of using this assembly is to apply a continuous wave signal to the piezoelectric thin film while scanning the target object, and measuring characteristics of the target object at various positions thereof by measuring the resonant frequency of the transmitted high frequency acoustic signals. Other methods include pulsed operation, and combining acoustic measurements with atomic force measurements and/or tunneling current measurements to characterize a target object. The acoustic microscope assembly can also be used for storing information on a substrate, by deforming the substrate at selected positions, and for reading such stored information by determining which positions on a substrate have been deformed.

Near field acoustic ultrasonic microscope system and method

Method of forming microfabricated cantilever stylus with integrated

Apparatus and method for forming a microfabricated cantilever with a single crystal, integral silicon tip on a nitride cantilever. A nitride-silicon-nitride sandwich structure is patterned and etched to form a cantilever structure, exposing sidewall portions of the silicon layer. The exposed sidewall portions of the silicon layer are oxidized to form oxide sidewalls. The top nitride layer is removed and the silicon layer is anisotropically etched and removed except fo a tetrahedral silicon tip formed on the rear nitride layer. The tetrahedral silicon tip has one exterior surface bounded by a (111) plane with two additional exterior surfaces bounded by the oxide sidewall. The oxide sidewall is removed to provide a tetrahedral silicon tip at the free end of the nitride cantilever. Alternative cantilever materials such as polysilicon and deposited oxide can be substituted for nitride. Doping the surface region of the cantilever form a P-N junction which provides a stop for electrochemical anisotropic etching of the silicon layer when an electrical potential is applied across the P-N position.

Microcantilever with integral self-aligned sharp tetrahedral tip

A cantilever stylus with an integrally formed conical tip is provided for atomic force microscopy AFM. The method for forming a stylus includes forming a circular masking pattern on the surface of a silicon substrate and anisotropically etching the silicon to form a post under the masking pattern. The post is then isotropically etched to produce a conical silicon tip mold. In one embodiment of the invention the silicon substrate and the conical silicon tip mold are thermally oxidized to form a cantilever stylus having including a cantilever arm with a conical tip fixed to its free end. In another embodiment of the invention the silicon substrate and the conical silicon tip mold are coated with a thin film of a dielectric material to form a cantilever stylus with a conical tip. In this embodiment the backside of the stylus is coated with a conductive material and a strong electric field is applied to the tip to cause electromigration of the conductive material to the point of the tip.

Microfabricated cantilever stylus with integrated conical tip

Integral sharp tips on thin film cantilevers are produced by forming a rectangular silicon post on a (100) silicon wafer. Etching the top of the post leaves sharp silicon tips at the corners of what remains of the silicon post. A silicon dioxide cantilever with an integral tip is thermally grown over the silicon wafer and the sharp silicon tips.

Growing community of inventors

Stanford, CA, United States of America

Shinya Akamine