High Resolution RBS measurements GePb/Ge, HfO 2 /Ge

Transcription

1 High Resolution RBS measurements Pb/, HfO 2 / Saumitra K Vajandar Centre for Ion Beam Applications (CIBA) Department of Physics National University of Singapore Aug 11, 2016

2 Outline CIBA at a glance Beamlines, their uses rmanium-lead on PLA, capping layers RBS, HR-RBS results Hafnium oxide on HR-RBS damage Damage correction

3 CIBA Main Lab - Accelerator 3.5 MV Singletron accelerator Six beam lines: 4 microbeam lines + 2 RBS/HR-RBS beam lines HR-RBS High resolution RBS facility Nuclear microscope Beam lines Cell and tissue imaging beam line RBS/ERDA facility Proton beam writer prototype Next generation proton beam writing facility HR-RBS end station

4 Research at CIBA Primary research thrusts at CIBA, in six groups Andrew Bettiol: Micro and Nano photonics Metamaterials, proton beam modification of materials and bioimaging. Mark Breese: Proton modification of silicon: Silicon microstructure fabrication and silicon photonics: Frank Watt (Visiting): Proton microscopy in biomedicine: Trace elements in Alzheimers disease, Parkinsons disease, Atherosclerosis, and whole cell imaging. Thomas Osipowicz: Materials Characterization: Microbeam RBS/PIXE, High Res RBS/ERDA, Single Ion Applications (IBIC, STIM) Jeroen van Kan: Proton beam writing: Development, molds and stamps for Biochips. Chammika Udalagama: Fundamental studies: Ion beam/material interactions. Data acquisition systems.

5 Why rmanium? Scaling down of transistors large interest in alternative materials to replace Si Higher carrier mobilities than Si Easy integration with Si Direct band-gap compounds - Pb, Sn

6 Pb Laser Induced Epitaxy Motivation Need for crystalline Pb films Explore pulsed laser anneal (PLA) as a nonequilibrium process for dopant activation Study the effect of different capping layers on the behavior of Pb after PLA ECS Journal of Solid State Sci. and Tech., 2016

7 Pb thin film process flow Starting substrate n-type lightly doped Pre-deposition clean using HF:H 2 O Sputter deposition of Pb DC power on Pb target: 30 W RF power on substrate: 12 W Chamber pressure: 3 mtorr Capping layer α-pb Pulsed Laser Anneal Capping layer c-pb Capping layer deposition SiO 2, Si 3 N 4, or Al 2 O 3 Pulsed laser anneal Laser wavelength: 248 nm Fluence: 300, 350, 400, 450, or 500 mj/cm 2 5 pulses (pulse duration: 23 ns)

8 Counts Conventional RBS - Pb Before pulsed laser anneal - With capping layers α-pb SiO 2 α-pb Si 3 N 4 α-pb Al 2 O 3 α-pb Energy (MeV) Bulk signal Surface signal Pb signal Channel number

9 Counts Counts Conventional RBS - Pb Before pulsed laser anneal - With capping layers α-pb SiO 2 α-pb Energy (MeV) Si 3 N 4 α-pb Al 2 O 3 α-pb Energy (MeV) Reference SiO 2 -capped Si 3 N 4 -capped Al 2 O 3 -capped Pb Pb peak at lower energies Channel number Channel number

10 Counts Conventional RBS - Pb After pulsed laser anneal - Without capping layers α-pb SiO 2 α-pb Si 3 N 4 α-pb Al 2 O 3 α-pb Energy (MeV) Bulk signal Surface signal Pb signal Channel number

11 Counts Counts Conventional RBS - Pb After pulsed laser anneal - Without capping layers α-pb SiO 2 α-pb Si 3 N 4 α-pb Al 2 O 3 α-pb RBS in random direction After removing capping Fluence: 350 mj/cm 2 Energy (MeV) Reference SiO 2 -cap removed Si 3 N 4 -cap removed Energy (MeV) Al 2 O 3 -cap removed Pb Channel number Channel number

12 Counts Counts HR-RBS Pb SiO 2 cap removed Energy (kev) Energy (kev) Bulk signal Surface signal Pb Substitutionality: 70% SiO 2 -cap removed 350 mj/cm 2 Random Random Pb Pb signal Channeled Channeled Channel Channel

13 Counts Counts HR-RBS Pb Si 3 N 4 cap removed Energy (kev) Energy (kev) Bulk signal Random Surface signal Random Pb Substitutionality: 71% Si 3 N 4 -cap removed 350 mj/cm 2 Pb Channeled Pb signal Channeled Channel Channel

14 Counts Counts HR-RBS Pb Al 2 O 3 cap removed Energy (kev) Energy (kev) Bulk signal Random Surface signal Random Pb Substitutionality: 63% Al 2 O 3 -cap removed 350 mj/cm 2 Pb Channeled Pb signal Channeled Channel Channel

15 TEM SiO 2 -capped Before PLA After PLA Before PLA Al 2 O 3 -capped After PLA Epoxy SiO 2 (20 nm) α-pb (40 nm) 20 nm Epoxy c-pb Precipitate 20 nm Epoxy c-pb 5 nm Epoxy Al 2 O 3 (20 nm) α-pb (40 nm) Si 3 N 4 -capped Before PLA After PLA 20 nm 20 nm Epoxy c-pb Cavity Epoxy c-pb 5 nm Epoxy Si 3 N 4 (16 nm) α-pb (40 nm) Epoxy c-pb Epoxy c-pb 20 nm 20 nm 5 nm

16 HfO 2 on Motivation Transistor scale down Explore the HfO2/ interface using HR-RBS

17 HR-RBS To detector kev He + ALD hafnium oxide on Hf (1-x) O x ~ 2.5nm HfO ~ 7nm substrate

18 Depth profile Interface Depth resolution in at interface ~ 2.3 nm

19 Angular scans about <111> Order of measurement Accumulated charge (uc) Asymmetric curves damage

20 substrate damage Each spectrum measured up to a charge Surface and bulk damage propagation of 2 C and in the aligned orientation

21 Si substrate damage Each spectrum measured up to a charge of 2 C and in the aligned orientation

22 damage evolution with depth First level of correction factors Taken in aligned orientation Correct for an increase in counts with depth

23 Angular scans about <111> Before correction 6 7 Order of measurement Accumulated charge (uc) Order of measurement Symmetric angular scans

24 Angular scan about <111> After correction

25 Angular scan about <111> Before correction Bulk/Interface Data points at 0 deg within the bulk and at interface almost identical

26 Angular scan about <111> After correction - Bulk/Interface De-channeling effects Data points at 0 deg within the bulk higher than at interface Additional correction Preliminary interface strain ~ 0.02%? close to the detection limit

27 Future directions Hafnium oxide on Explore damage further Additional correction in place - quantify interface strain Cross-sectional TEM interface layer Interface strain with Pb, Sn as substrates

28 Acknowledgements Department of Electrical and Computer Engineering Yee-Chia Yeo Qian Zhou Edwin Bin Leong Ong Xiao Gong Wei Wang Department of Physics Eng Soon Tok Sin Leng Lim CIBA Taw Kuei Chan Thomas Osipowicz

29 Thank you!