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Removing Microcontact Printed Alkanethiols

IP.com Disclosure Number: IPCOM000015229D
Original Publication Date: 2001-Oct-01
Included in the Prior Art Database: 2003-Jun-20
Document File: 3 page(s) / 32K

Publishing Venue

IBM

Abstract

Two methods for removing microcontact printed alkanethiols are presented. Microcontact printing (MCP) is a technique which utilizes an inked, micropatterned stamp to print chemicals or biomolecules onto a substrate [1]. The most important application of MCP is the printing of alkanethiols onto Au, Ag or Cu to form a self-assembled monolayer (SAM) in the regions of contact between the stamp and the substrate. In this case, the printed monolayer can protect its substrate from dissolution in an etch bath [2]. MCP can be used to print and etch selectively a layer on a substrate. MCP can be used for microfabrication purposes. Examples are microfabrication of Au, Ag, Cu, Pt, Pd microstructures and microelectrodes, patterning a catalyst for electroless deposition, patterning Cu interconnects, etc. Many microfabrication processes involve many steps and it is desirable to remove a SAM which has been used in one step before proceeding to the next steps of this process for several reasons. A Pd catalyst patterned on a surface using MCP should be cleaned to remove the thiols present on its surface to be an active catalyst, for example. The thiols used to structure a Cu layer should be removed before adding the next layer to minimize device-integration problems (bad contacts or adhesion between layers, degassing of thiols during a subsequent fabrication step). A patterned surface on which the SAM is left might have undesirable wetting properties.

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Removing Microcontact Printed Alkanethiols

  Two methods for removing microcontact printed alkanethiols are
presented.

Microcontact printing (MCP) is a technique which utilizes an
inked, micropatterned stamp to print chemicals or biomolecules
onto a substrate [1]. The most important application of MCP is
the printing of alkanethiols onto Au, Ag or Cu to form a
self-assembled monolayer (SAM) in the regions of contact between
the stamp and the substrate. In this case, the printed monolayer
can protect its substrate from dissolution in an etch bath [2].

MCP can be used to print and etch selectively a layer on a
substrate. MCP can be used for microfabrication purposes.
Examples are microfabrication of Au, Ag, Cu, Pt, Pd
microstructures and microelectrodes, patterning a catalyst for
electroless deposition, patterning Cu interconnects, etc.

Many microfabrication processes involve many steps and it is
desirable to remove a SAM which has been used in one step before
proceeding to the next steps of this process for several reasons.
A Pd catalyst patterned on a surface using MCP should be cleaned
to remove the thiols present on its surface to be an active
catalyst, for example. The thiols used to structure a Cu layer
should be removed before adding the next layer to minimize
device-integration problems (bad contacts or adhesion between
layers, degassing of thiols during a subsequent fabrication
step). A patterned surface on which the SAM is left might have
undesirable wetting properties.

It is conventional to remove organic residues using an oxygen
plasma cleaner in lithography. This method can be problematic
because samples are usually exposed to high local temperatures
during plasma cleaning. Plasmas tend to roughen some metals like
Au or to oxidize others such as Cu, Ag and Pd, moreover. Plasma
cleaning involves a vacuum step and might be costful for this
reason.

In the following two methods to remove SAMs from surfaces based
on (a) UV-ozone cleaning or (b) on chemical desorption are
described.

(a) UV-ozone removal of SAMs
A UV-ozone treatment can oxidize organic contaminants and layers
present on a surface. This method is simple, inexpensive and
slow. The typical rate of oxidation and removal of organic
material obtained with this method is fully compatible with SAMs
because SAMs are only a few nanometers thin. A UV-ozone treatment

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is advantageous compared to oxygen plasma treatment because it
can have a higher through and it does not produce highly reactive
and energ...