RESEARCH


Why is everything wrapped in aluminum foil??


Chamber 1 -Selective Atomic Layer Deposition and Low Temperature-STM
Operated by: Yunil and James

The home-built atomic layer deposition (ALD) chamber with a base pressure of 10-7 Torr is optimized for selective atomic layer deposition processes. It is equipped with a plasma generator for in-situ sample cleaning, a sample holder which can carry up to three samples on a 26"-long bellows+transfer arm, and an in-situ cartridge heater. The samples can be transferred in-situ to an ultra-high vacuum chamber which has a base pressure of 10-9 Torr and is equipped with a sputter gun, X-ray photoelectron spectroscopy (XPS) and low-temperature scanning tunneling microscopy (LT-STM). The system is intended for the study of selective ALD of metal oxides on Si, SiO2, SiCOH and Cu. XPS and STM are mainly used for studying the surface chemistry. Currently, the materials studied in this chamber include Si (001), SiO2, SiCOH, Cu, metal oxides, metal halides and organometallic precursors. The ultimate goal of this research is to gain an atomistic and electronic understanding of the surface chemistry of different substrates with different ALD precursors. This can help elucidate the physical and chemical principles guiding the development of MOSFET devices, for both academic and industrial application points of view.


Chamber 2 - Variable Temperature-STM/AFM with KPFM
Operated by: Mike and Victor

Currently, this machine has the capability to perform in situ ALD, XPS, STM/STS, LEED, and mass spectrometry. Additionally, a thermal gas cracker is installed for performing atomic hydrogen dosing on samples. Recently, the work on this chamber has included thermal ALD of nitrides, including silicon nitride, boron nitride, titanium nitride and tantalum nitride utilizing more reactive hydrazine chemistry. Thermal ALD has the capability to deposit conformal films with good thickness control for back end of line processing on high aspect ratio features. XPS has been used to determine the chemical composition of deposited ALD films on Si, SiO2 and SiGe surfaces. The ALD reactor is a home-built chamber that utilizes automated dosing to deliver essentially any precursor that is desired. Precursors that have been studied include Si2Cl6, BCl3, TiCl4, TDMAT, TBTDET, N2H4, NH3. The previous heater in the ALD chamber used a pyrolytic boron nitride heater that was in vacuum and could be shorted out when conductive films were deposited; thus improvements for the heater have been made which includes utilizing an "air side" cartridge heater that cannot be shorted out. In addition to the characterization techniques available in situ in this chamber, there is also ex situ AFM and 4 point probe measurements that can be performed. Most currently, developing an in situ 4 point probe measurement is underway to be able to accurately measure film resistivity before air exposing samples. Future work include looking at selective ALD of metal films (Co, Rh, Ru), as well as testing out lower valence Ti and Ta precursors for deposition of more conductive films.


Chamber 3 - Variable Temperature-STM/AFM with KPFM and XPS
Operated by: Aaron and Ping-Che

This home-built system is composed of four vacuum chambers and manipulator systems for sample transfer without vacuum break: a load lock, an atomic layer deposition system with plasma source, a sputtering chamber with DC, RF, and HiPIMS power supplies, and an analytical chamber with Auger, XPS, mass spectrometry and low-temperature scanning tunneling microscopy capabilities. Currently, the ALD chamber is being used to develop atomic layer annealing (ALA) techniques for the deposition of crystalline group III-nitride materials at low temperature (<400 ˚C). We combine this process with precursors suited for low-temperature deposition: tris(dimethylamido) aluminum and gallium complexes paired with anhydrous hydrazine. This deposition system is unique in having the ability to apply a DC or RF substrate bias, such that the kinetic energy of the bombarding ions in ALA can be controlled independently of ion flux. This allows for optimization of the surface adatom mobility, which enables the deposition of crystalline materials. Further, the periodic ion bombardment employed in ALA removes residual ligands from the growth surface, leading to deposition of nearly contaminant-free films: typical oxygen and carbon content is <2.0 at.% by XPS. The sputtering chamber is currently being used for bipolar high power impulse magnetron sputtering (HiPIMS) of aluminum nitride for the deposition of films with high thermal conductivity. These two deposition techniques can be combined to first deposit a highly crystalline template layer by ALA on a non-lattice matched or insulating substrate, which then enhances the crystallinity of material sputtered onto the template layer. Such stacked structures have demonstrated greater thermal conductivities relative to purely sputtered films of equivalent thickness. All of these films can be characterized by Auger electron spectroscopy and/or x-ray photoelectron spectroscopy to quantify film composition and trace impurities.


Chamber 4 - Cluster tool with nitride/phosphide/oxide chamber and AES
Operated by: Jimmy/SeongUk/Harshil

For nitride chamber, Jimmy is studying the synthesis of the Titanium nitride using thermal ALD in the patterned sample. Harshil is fabricating the the high-k material HZO using oxide chamber. SeongUk is working on low temperature deposition of crystalline AIP and GaP on semiconductors using several ALD techniques; thermal ALD, electron enhanced ALD, atomic layer annealing, and plasma enhanced ALD.


Research Poster


Last updated: 03/25/2020