Etching a substrate: processes – Masking of a substrate using material resistant to an etchant
Reexamination Certificate
2000-08-18
2003-06-17
Markoff, Alexander (Department: 1746)
Etching a substrate: processes
Masking of a substrate using material resistant to an etchant
C216S004000, C216S056000, C216S039000, C428S333000, C428S522000, C156S922000, C156S922000
Reexamination Certificate
active
06579463
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a method for manufacturing an array of nanostructures and a substrate with an ordered array of nanostructures, wherein the nanostructure size is controlled. More particularly, the method forms an ordered array of nanoscale holes by etching a surface through a patterned mask containing a regular array of nanoscale pores and/or deposits adatoms on the surface through the patterned mask. Also, more particularly, the substrate includes a regular array of nanoscale holes and/or a regular array of nanoclusters comprising adatoms.
2. Description of Related Art
The ability to control function by controlling size makes nanoclusters very attractive for technological applications in high-speed computing, high density data storage and display, and optical communications through devices such as the single-electron transistor and the quantum dot laser. Designs for such devices require not only sharp control of nanocluster size, but also fabrication of ordered arrays of nanoclusters and, in some cases, interconnections between clusters within the array.
As has been discussed elsewhere (for example, J.-M. Gerard, 1995), single layer quantum dot arrays have been demonstrated to have excellent optical properties such as high quantum efficiency, long radiative lifetimes, and very fast PL rise times. However, direct growth has been stymied by “the prerequisite of an ultrafine lithographic definition of the mask.”
Dramatic advances have been made recently in obtaining ordered arrays of nanoclusters from liquid phase syntheses by selective precipitation and Langmuir-Blodgett techniques (Murray et al. 1993; Ohara et al. 1995; Murray et al. 1995; Whetten et al. 1996; Luedtke et al. 1996; Heath et al. 1997). Ordered arrays have also been produced using films of close-packed polystyrene spheres as deposition masks (Hulteen et al. 1995). Ensembles of individual, size-controlled InP quantum dots grown by self-assembly in molecular beam lepitaxy on a GaAs surface have emitted light of very narrow bandwidth at a wavelength determined by the size of the dots (Grundmann et al. 1995); embedded between electron-injecting and hole-injecting layers, these dots have exhibited lasing (Kirstaedter 1996). However, because they grow at randomly distributed nucleation sites on the substrate, their location is difficult to control.
From the point of view of device fabrication, it is desirable to first define the desired nanoscale array pattern directly on the substrate and then grow or deposit the nanoclusters on the patterned substrate. The nanoclusters produced preferably have diameters less than about 25 nm to show true quantum confinement behavior.
In earlier work, Heath and co-workers (1996) studied the formation of clusters in confined geometries by defining 100 and 150 nm diameter holes in a thin oxide mask over a Si wafer and then growing Ge clusters on the Si surfaces exposed in the etched holes (Gillis et al. (1992)). They observed a few clusters in each 150 nm hole at locations distributed over the bottom of the hole. A few of the 100 nm holes contained a single cluster, but difficulties with that sample precluded complete analysis. Their results showed that the confining geometry of the 150 nm hole limited the number and size of clusters growing in the hole but did not precisely control their location.
Thus, there remains a need for a method of controlling the position as well as the size of arrayed nanoclusters.
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Douglas Kenneth
Winningham Thomas Andrew
Furst Marian J.
Marian J. Furst, Attorney at Law
Markoff Alexander
The Regents of the University of Colorado
Winter Gentle
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