Direct-Patterning ZnO Deposition by Atomic-Layer Additive Manufacturing Using a Safe and Economical Precursor

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Engineering

Background:

• Area-selective atomic layer deposition (AS-ALD) is a nanofabrication technique with advantages over lithography but requires pre-patterned substrates and faces selectivity limitations.
• Existing AS-ALD methods are constrained by substrate choice and insufficient selectivity, hindering broader application.

Purpose of the Study:

• To introduce and evaluate atomic-layer additive manufacturing (ALAM) as a novel direct patterning method for nanofabrication.
• To explore the use of bis(dimethylaminopropyl)zinc, Zn(DMP)2, as a precursor in ALAM for zinc oxide (ZnO) deposition.
• To demonstrate the feasibility of ALAM for creating functional electronic devices.

Main Methods:

• Developed an ALAM process by adapting 3D-printing principles for atomic-layer manufacturing using a precursor supply nozzle.
• Replaced traditional diethylzinc with the less volatile Zn(DMP)2 precursor for reduced vapor consumption in ALAM.
• Investigated ZnO deposition characteristics, including growth rates and stoichiometry, across a temperature range of 200-250 °C using spectroscopic ellipsometry and X-ray spectroscopy.

Main Results:

• ALAM demonstrated effective direct patterning of ZnO with growth rates of 1.1 Å per pass, comparable to ALD's 0.9 Å per cycle.
• Stoichiometric and crystalline ZnO films were achieved within an intermediate temperature window of 200-250 °C.
• A functional thin-film transistor was successfully fabricated using an ALAM-deposited ZnO line, validating the process's utility.

Conclusions:

• ALAM circumvents AS-ALD's limitations by enabling direct patterning without pre-patterned substrates, offering enhanced selectivity and substrate flexibility.
• The novel ZnO ALAM process using Zn(DMP)2 yields high-quality, stoichiometric, crystalline material suitable for device fabrication.
• ALAM represents a promising advancement in additive manufacturing for nanoscale applications, particularly in creating functional thin-film devices.