AS-ALD has the potential to overcome many of the challenges the semiconductor industry is facing by enabling self-aligned fabrication, instead of lithography’s cost, resit, equipment. Main challenges in AS-ALD are the need for pre-patterned substrates, defects outside of the desired growing area resulting from insufficient selectivity, and limited selection of substrate materials that allow deposition. [1, 2]

To overcome these challenges, we chose for the first time the novelty of direct patterning with an AL-3D printer, also called atomic layer additive manufacturing (ALAM). 3D-printing is a flexible and efficient tool for reducing the cost and time spend for designing and manufacturing. AL-3D in principle functions similar to conventional g-ALD and the special design of nozzle led in producing direct patterning. All the commercially available precursors which have been used in g-ALD are compatible with our invented equipment and not only we can produce the same films conveniently but also this device allows us to use new precursors e.g. Zn(DMP)₂ opening a new chemistry window. We have already deposited different materials TiO₂, Pt, SiO₂, Al₂O₃ successfully using TTIP, (MeCp)PtMe₃, APTES, TMA as precursor. The ZnO process is very well behaved in ALD community as a diethylzinc (ZnEt₂) precursor’s very high vapor pressure and its very high reactivity to water. Our attempts at reducing the amount of vapor delivered were successful in part but the results were not sufficiently reproducible, therefore we turned to the use of a new zinc precursor instead.

In this work we focus on the new precursor Zn(DMP)₂ instead of ZnEt₂ for ZnO deposition. The Zn(DMP)₂ has a very low vapor pressure, the ethyl groups are complemented by dimethylamino substituents that stabilize central zinc ion and thereby render the molecule less reactive to water. Our characterization results shows the deposited ZnO films with our new precursor has same structure and composition as with ZnEt₂ with a constant growth rate of 1.0 Å per cycle. the crystals are oriented in a roughly isotropic manner.

After testing Zn(DMP)₂ in classical ALD we achieved to print homogeneous patterns with well-defined edges and uniform thicknesses among the whole pattern. The rough particulate deposits indicative of uncontrolled CVD-mode deposition obtained with the ZnEt₂ + water reaction are completely absent of lines obtained from the Zn(DMP)₂ + water reaction. Furthermore, we fabricate a metal oxide transistor MOSFET to demonstrate the practical applications of the device.

1. Clark; K. Tapily; K.-H. Yu; T. Hakamata; S. Consiglio; D. O´Meara; C. Wajda; J. Smith; G. Leusink; Perspective: New Process Technologies Required for Future Device and Scaling. APL Mater. 2018, 6, 05203
2. Fang; J. C. Ho, Area-Selective Atomic Layer Deposition: Conformal Coating, Subnanometer Thickness Control, and Smart Positioning. ACS Nano 2015, 9 (9), 8651-8654.