Home » The engineering and optimization of the hafnium based metal oxide semiconductor structure. by Monica Sawkar Mathur
The engineering and optimization of the hafnium based metal oxide semiconductor structure. Monica Sawkar Mathur

The engineering and optimization of the hafnium based metal oxide semiconductor structure.

Monica Sawkar Mathur

Published
ISBN : 9780549977902
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223 pages
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This thesis focuses on the engineering and optimization of the hafnium based metal-oxide-semiconductor structure to realize its scalability in metal oxide semiconductor field effect transistor (MOSFET) devices. First, the effect of dopants wasMoreThis thesis focuses on the engineering and optimization of the hafnium based metal-oxide-semiconductor structure to realize its scalability in metal oxide semiconductor field effect transistor (MOSFET) devices. First, the effect of dopants was investigated through the incorporation of nitrogen in the HfO2 gate dielectric layer, where the dielectric constant was increased and the leakage current density was decreased. Second, the use of an alternative gate electrode was investigated through the sputtered deposition of HfxRuy and HfxRuyNz metals on HfO2 gate dielectrics, where effective work functions (EWFs) of 5.0 and 5.2 eV were achieved for Hf0.26Ru0.74 and Hf0.05Ru0.77N0.18, respectively, viable for integration in pMOSFET devices and circumventing the gate depletion effects observed with polysilicon gate electrodes. The fortuitous introduction of oxygen in the metal layer proved to be beneficial in suppressing Fermi level pinning, providing a means of achieving the near band edge work functions required for pMOSFET devices. Third, the use of a crystalline oxide, SrHfO 3, was investigated through an in-depth structural study using synchrotron techniques, where good crystalline quality and nearly epitaxial growth with minimal defects were observed for 4 nm SrHfO3 films grown by molecular beam epitaxy on Si(100). The analysis performed validates the use of SrHfO 3 as a lattice matched crystalline oxide on Si, effectively eliminating the interfacial issues found at the amorphous oxide/crystalline Si interface. Fourth, the use of an alternative substrate with an intrinsically higher carrier mobility was investigated through the atomic layer deposition (ALD) of Hf xAlyOz films on Ge, where the use of a GeO xNy interfacial layer and the incorporation of aluminum were found to drastically improve the interfacial characteristics of hafnium-based oxides on Ge. The much improved interfacial properties makes Ge a viable replacement channel material when Si-based MOSFETs reach their scaling limit. The strategy of optimizing the gate stack enables the necessary scalability of MOSFET devices to permit further improvements in their electrical performance. The implementation of a MOS structure based on what has been investigated in this work could provide the necessary improvements in MOSFET performance to provide a solution in the coming generations.