Kai Arstila

Effects of Interfacial Strength and Dimension of Structures on Physical Cleaning Window

Four different types of FINs; amorphous Si (a-Si), annealed a-Si, polycrystalline Si (poly-Si) and crystalline Si (c-Si) were used to investigate the effect of interfacial strength and the length of structures on the physical cleaning window by measuring their collapse forces by atomic force microscope (AFM). A transmission electron microscope (TEM) and a nanoneedle with a nanomanipulator in a scanning electron microscope (SEM) were employed in order to explain the different collapse behavior and their forces. Different fracture shapes and collapse forces of FINs could explain the influence of the interfacial strength on the pattern strength. Furthermore, the different lengths of a-Si FINs were prepared and their collapse forces were measured and the shorter length reduced their pattern strength. Strong adhesion at the interface resulted in a wider process window while smaller dimensions made the process window narrower.

Compressively strained SiGe band-to-band tunneling model calibration based on p-i-n diodes and prospect of strained SiGe tunneling field-effect transistors

Band-to-band tunneling parameters of strained indirect bandgap materials are not well-known, hampering the reliability of performance predictions of tunneling devices based on these materials. The nonlocal band-to-band tunneling model for compressively strained SiGe is calibrated based on a comparison of strained SiGe p-i-n tunneling diode measurements and doping-profile-based diode simulations. Dopant and Ge profiles of the diodes are determined by secondary ion mass spectrometry and capacitance-voltage measurements. Theoretical parameters of the band-to-band tunneling model are calculated based on strain-dependent properties such as bandgap, phonon energy, deformation-potential-based electron-phonon coupling, and hole effective masses of strained SiGe. The latter is determined with a 6-band k·p model. The calibration indicates an underestimation of the theoretical electron-phonon coupling with nearly an order of magnitude. Prospects of compressively strained SiGe tunneling transistors are made by simulations with the calibrated model.

The growth of ErxGa2−xO3 films by atomic layer deposition from two different precursor systems

The atomic layer deposition (ALD) growth of ErxGa2−xO3 (0 ≤ n x n ≤ 2) thin films was demonstrated using two precursor systems: Er(thd)3, Ga(acac)3, and ozone and Er(C5H4Me)3, Ga2(NMe2)6, and water at substrate temperatures of 350 and 250 °C, respectively. Both processes provided uniform films and exhibited surface-limited ALD growth. The value of x in ErxGa2−xO3 was easily varied by selecting a pulse sequence with an appropriate erbium to gallium precursor ratio. The Er(thd)3, Ga(acac)3, and ozone precursor system provided stoichiometric ErxGa2−xO3 films with carbon, hydrogen, nitrogen, and fluorine levels of <0.2, <0.2, <0.3, and 0.6–2.2 atomic percent, respectively, as determined by Rutherford backscattering spectrometry (RBS) and time of flight-elastic recoil detection analysis (TOF-ERDA). The film growth rate was between 0.25 and 0.28 A cycle−1. The effective permittivity of representative samples was between 10.8 and 11.3. The Er(C5H4Me)3, Ga2(NMe2)6, and water precursor system provided stoichiometric ErxGa2−xO3 films with carbon, hydrogen, nitrogen, and fluorine levels of 2.0–6.1, 5.0–10.3, <0.3–0.7, and ≤0.1 atom percent, respectively, as determined by RBS and TOF-ERDA. The film growth rate was between 1.0 and 1.5 A cycle−1 and varied as a function of the Er(C5H4Me)3 to Ga2(NMe2)6 pulse ratio. The effective permittivity of representative samples was between 9.2 and 10.4. The as-deposited films of both precursor systems were amorphous, but crystallized either to Er3Ga5O12 or to a mixture of β-Ga2O3 and Er3Ga5O12 upon annealing between 900 and 1000 °C under a nitrogen atmosphere. Atomic force microscopy showed root mean square surface roughnesses of <1.0 nm for typical films regardless of precursor system or film composition.

Thin Film Characterisation Using MeV Ion Beams

This chapter focuses on the characterisation of very thin films having thicknesses from a few nanometres to tens of nanometres. The driving force for the ion beam analysis community has mostly been the rapid development of microelectronics — all the elements in new thin SiO2 replacing dielectrics, diffusion barriers, and silicide contacts need to be analysed with a depth resolution even better than a nanometre. This together with new film deposition techniques like atomic layer deposition (ALD) [1] have given a push to the ion beam analysis community to develop new and better techniques using energetic (>0.5 MeV) ion beams.

Towards the Understanding of Resistive Contrast Imaging in in-situ Dielectric Breakdown Studies Using a Nanoprober Setup

This work aims at attaining a more complete understanding of the principles governing resistive contrast imaging (RCI) of copper/low- k interconnects used for dielectric breakdown studies in a nanoprober scanning electron microscope (SEM) system. RCI is employed in such in situ dielectric breakdown studies to facilitate the localization of interconnect defect sites related to various stages in the degradation process of the low- k dielectric material. This work shows that RCI is suitable for detecting high-resistance sites, like opens, in copper/low- k interconnects. Moreover, RCI demonstrates potential in locating defects that lie deep in the test structure and are, thus, not detectable by SEM. A model is also proposed to explain the formation of RCI images of specific interconnect test structures with complex layout.

Metal/High-K Interface Interactions Upon High Temperature Annealing - Are They Cause of Workfunction Changes

The replacement of poly-silicon by metallic compounds in the gate stack leads to the search of metals with suitable work function. However, it is observed that thermal budget has a large influence on the effective work functions of several metals. In this paper, we investigated the possible modification of the chemical states by physical analysis techniques (XPS, ERD, SIMS) by studying the chemistry of the high-k oxide/metal interface. We show that in the case of the TiN/TaN/HfO2/SiO2/Si stack, several modifications occur upon 1000 °C N2 annealing: Increase of the nitrogen content of the TaN, interdiffusion of the Ti and TaN, and formation of Ta2O5 at the TaN/HfO2 interface.