Room-temperature Chemical Vapor Deposition of Aluminum and Aluminum Oxides on Alkanethiolate Self-Assembled Monolayers

Abstract

We have investigated the reaction of trimethylaluminum (TMA) with -CH 3 , -OH, and -COOH terminated self-assembled monolayers (SAMs) adsorbed on Au, using time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy. TMA is a well-known atomic layer deposition precursor that is employed commercially to deposit compound semiconductors, alumina, and nitrides. We demonstrate that TMA can be employed to deposit both alumina and aluminum on SAMs at room temperature. TMA reacts with -OH and -COOH terminated SAMs to form a surface-bound dimethyl aluminum complex but does not react with -CH 3 terminal groups. If deposition is performed in a nitrogen-purged glovebox, an alumina film is grown on -CH 3 , -OH and -COOH terminated SAMs. The alumina film can be removed from -CH 3 terminated SAMs by rinsing with organic solvents. However if the base pressure of the deposition chamber is below 10 -8 Torr, a metallic Al overlayer is selectively deposited on -OH and -COOH terminated SAMs, and no reaction is observed on -CH 3 terminated SAMs. Using these reactions, we demonstrate that alumina and aluminum can be selectively deposited on patterned SAMs. The possible reaction pathways involved in the film growth on these different surfaces are discussed.

Building Robust and Reliable Molecular Constructs: Patterning, Metallic Contacts, and Layer-by-Layer Assembly

“…We have demonstrated that aluminum (and alumina) can be selectively deposited on SAMs at room temperature using the ALD precursor, trimethyl aluminum (TMA). 29 TMA reacts with -OH-and -COOH-terminated SAMs to form a surface-bound dimethyl aluminum complex, but it does not react with terminal groups that do not contain oxygen, for example, -CH 3 -terminated SAMs. If the deposition is carried out under very high vacuum (<10 -8 torr), a metallic overlayer is deposited on -OH-and -COOH-terminated SAMs with no reaction on -CH 3 -terminated SAMs.…”

Issues and Challenges in Vapor-Deposited Top Metal Contacts for Molecule-Based Electronic Devices

“…No reaction was observed with -CH 3 but reactions were observed with -OH and -COOH. In the latter cases room temperature deposition created Al oxide and Al layers under conditions of N 2 purging and UHV, respectively [79,88,89].…”

Towards Molecular Electronics: Solution-Based Methods for Selective Deposition of Metals and Semiconductors

“…Technologies besides PVD to deposit metals and other materials in Si-based microelectronics include CVD [18], atomic layer deposition (ALD) [19] and electrodeposition [20]. CVD [13] and ALD [21] have been demonstrated to produce stable contacts, but these methods are generally very slow and so are not practical.…”

“…Second, a SAM of different composition is adsorbed in the areas where the first to construct complex 2-D and 3-D structures. PVD and room temperature CVD is employed to selectively deposit Mg [12] and Al [13], respectively, on patterned -COOH/-CH 3 terminated SAMs. Compound semiconductors, e.g.…”

“…Finally, physical vapor deposition (PVD) [12], chemical vapor deposition (CVD) [13] or electroless deposition (ELD) [15] is employed to deposit metal atoms on the patterned SAM surface. Semiconductors can be deposited by chemical bath deposition (CBD) [14] and CVD [13], while biomolecules are attached to the surface using standard coupling chemistries [16]. By using SAMs with different terminal groups, we can control where and how metals, semiconductors and biomolecules deposit on the construct.…”