PhD - Leuven | More than two weeks ago
The next generation of nanoelectronics devices will all be based on three-dimensional (3D) architectures, such as TFETs, FinFets, Gate all around devices, vertical RAM, nanowires, etc.. which present severe challenges on metrology for probing the relevant parameters, such as dopant distributions, defect densities, junction locations, filament location in RRAM, etc. inside these devices. Moreover, with the strained-silicon channel being replaced by high-mobility materials, such as Ge, SiGe, GaSb, InGaAs, InP, InAs, and InSb as well as with the introduction of 2D-materials (graphene, MX2), the existing metrology concepts cannot be directly applied anymore to such heterostructures and monolayer materials anymore. Similarly in advanced memory such as RRAM, 3D-Nand, STT-MRAM there is a pressing need to provide metrology concepts apt to probe local filaments being formed and/or local conduction paths as this represents the key towards fundamentally understanding their formation and operation.
The goal of this PhD topic is therefore to study the fundamental principles for 3D-nanometer-scale electrical probing on heterostructures. Scanning probes, atomic force microscopy (AFM), scanning spreading resistance microscopy SSRM), etc., have established themselves as metrology concepts with near-atomic resolution on planar surfaces and devices. Extending their applicability from 2D towards 3D-metrology requires some innovative approaches apt to generate a sequence of 2D-maps as a function of depth. In the past years, imec has demonstrated several novel (and some still confidential) approaches to obtain 3-dimensional information on 3D-devices and memory cells. One of them is a slice-and-view approach, termed Scalpel AFM, whereby a scanning probe is alternatively removing material on the atomic scale and performing concurrent electrical measurements creating tomograms of FinFET and GAA transistors and nanoscopic metallic filaments of CBRAM structures. This new 3D metrology concept has attracted lots of attention from internal and external customers, as well as from tool manufacturers.
We are looking at the exploration of this capability towards novel devices and technologies in logic, memory and PV applications. Further progress requires a fundamental understanding of the physics of controlled nanoscopic material removal (including its molecular dynamics simulation) and its impact on the electrical properties to be measured. Besides the removal of material, one also needs to fundamentally understand the tip-sample interaction, the sample-tool contact, the mechanical sample properties, etc. in order to correctly interpret the results. Complementary to the theoretical work one needs to address its practical implementation as the probe tips used for materials removal and the actual electrical measurement may require different characteristics. Hence within this PhD research you will also develop and assess scanning and probe concepts for separating the removal and measurement action and optimizing the total slice-and-view concept. Imec's world leading expertise in diamond tips forms the backbone of this research aspect.
Demonstrating the industrial value of this approach will be pursued through collaborative studies with the logic and memory programs at Imec bringing them fundamental insight in their technology developments.
Required background: physics, engineering, material science
Type of work: 60% experimental, 40% theoretical
Supervisor: Margriet Van Bael
Co-supervisor: Claudia Fleischmann
Daily advisor: Thomas Hantschel
The reference code for this position is 2021-004. Mention this reference code on your application form.