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Nonlithographic ULSI Patterning of Silicon in Air with Atomic Force Microscopy

IP.com Disclosure Number: IPCOM000109571D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 2 page(s) / 118K

Publishing Venue

IBM

Related People

Kaufman, F: AUTHOR [+2]

Abstract

Deep submicron patterning for advanced Si devices has been demonstrated (1-6) using various on-wafer configurations with the scanning tunneling microscope (STM). The driving force for this work is the need to find novel alternatives to the traditional (resist/mask/lithographic expose/develop/RIE, etc.) patterning technologies currently in use. Viable alternatives would have many advantages such as lower cost, more rapid turn-around time (TAT), reduced contamination and less expensive tooling. This earlier STM work has involved deposition of organometallic precursors (1,2) exposure of resist (3), mechanical material removal of Si (4) and chemical modification of the Si surface (5).

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Nonlithographic ULSI Patterning of Silicon in Air with Atomic Force Microscopy

       Deep submicron patterning for advanced Si devices has
been demonstrated (1-6) using various on-wafer configurations with
the scanning tunneling microscope (STM).  The driving force for this
work is the need to find novel alternatives to the traditional
(resist/mask/lithographic expose/develop/RIE, etc.) patterning
technologies currently in use.  Viable alternatives would have many
advantages such as lower cost, more rapid turn-around time (TAT),
reduced contamination and less expensive tooling.  This earlier STM
work has involved deposition of organometallic precursors (1,2)
exposure of resist (3), mechanical material removal of Si (4) and
chemical modification of the Si surface (5).  In general, these
previous methods are unacceptable due to one or more of the following
concerns: complexity of process, uses toxic substances, requires
additional steps for imaging, nonpermanent images produced, etc.

      This invention comprises the use of an Atomic Force micocope
(AFM) operating in air in the repulsive mode, with the tip making
direct physical contact with a Si surface, and with the tip and Si
surface immersed in a chemically active water solution.  Movement of
the AFM tip across the Si surface results in the direct generation of
a recessed pattern in the Si, where the tip made the predetermined
surface contact.  The AFM is also used to read the previously written
pattern.

      Invention has been reduced to practice for (100)orientation Si
wafers.  The blanket Si wafers (SICMP-14) were polished for 1 minute
followed by a 1-minute 10:1 BHF clean and 1 minute DI rinse.  The
chemically active solution used in the AFM, was a pH 10 buffer at
20oC, freshly prepared.  The AFM used was a Nanoscope II made by
Digital Instruments with a liquid cell and with a Si3N4 tip of 100 o
approximate diameter at its end.  The writing step was performed at a
Force of 2 x 10-8 Newtons, by the tip on the Si surface, by having
the tip traverse a 250 nm square area writing 800 lines twice in 10
seconds.  The square recessed image area generated in this manner was
obtained by the AFM imagining at a Force of 10-9 Newtons.  We
estimate the depth of the writ...