Oregon State University



Event Details

MS Final Examination – Tyler Klarr

Friday, May 20, 2016 9:00 AM - 11:00 AM

Assessment of Barrier Heights between ZrCuAlNi Amorphous Metal and SiO2, Al2O3, HfO2, and ZrO2 using Internal Photoemission Spectroscopy
As scaling of Si based devices approaches fundamental limits, thin film metal-insulator-metal (MIM) tunnel diodes are attracting interest due to their potential for high speed operation. Because operation of these devices is based on tunneling, electrode / interfacial roughness is critical. Recently, it was shown that combining ultra-smooth bottom electrodes with insulators deposited via atomic layer deposition (ALD) enabled reproducible fabrication of MIM diodes with stable I-V behavior.1 Key performance parameters of MIM diodes include high I-V asymmetry and low turn-on voltage. The standard way to achieve asymmetry relies on the use of non-equivalent workfunction metal electrodes to induce a built-in field that creates polarity dependent electron tunneling barrier.  Thus the electrical performance of MIM diodes are directly impacted by the nature of the energy barriers at the interfaces.

In this work, we report the first use of internal photoemission spectroscopy (IPE) to measure barrier heights between an amorphous ZrCuAlNi (ZCAN) metal bottom electrode and several high-k dielectrics. MIM stacks were fabricated on Si substrates capped with 100 nm of thermally grown SiO2 and a 150 nm thick ZCAN amorphous metal bottom electrode deposited via DC magnetron sputtering. Al2O3, HfO2, and ZrO2 were deposited via thermal ALD while SiO2 was deposited using plasma-enhanced ALD (PEALD). For IPE measurements, semitransparent top electrodes were formed by electron beam evaporation of Al (0.04mm2) and patterned by a multistep photolithography process. In IPE, the conduction band offset between two materials is characterized by measuring the additional current created by photo-excitation of carriers under an applied bias (Vapp). Devices were tested in a custom built IPE system in which incident photon energy (Eph) from a broadband 150W xenon lamp source was swept from 1.5 to 5eV while the increase in current (photoemission yield) was monitored. The Vapp polarity was such that photoemission occurs at the ZCAN/insulator interface. The photoemission yield1/2 was plotted vs. Eph to determine the spectral threshold at each Vapp.  Finally, a Schottky plot of spectral threshold vs. Vapp1/2 was used to estimate the zero field barrier heights from the y-axis intercept.

Major Advisor: John Conley
Committee: Larry Cheng
Committee: Matthew Johnston
GCR: Leonard Coop

Strand Agriculture Hall (campus map)
Nicole Thompson
1 541 737 3617
Nicole.Thompson at oregonstate.edu
Sch Elect Engr/Comp Sci
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