April 22 - 26, 2024
Seattle, Washington
May 7 - 9, 2024 (Virtual)

Event Supporters

2024 MRS Spring Meeting
CH01.01.04

Epitaxial Si on Epitaxial-Gd2O3/Si(111) Virtual Substrate Using Low-Cost RF Sputtering for Silicon on Insulator (SOI) Application

When and Where

Apr 23, 2024
11:30am - 11:45am
Room 442, Level 4, Summit

Presenter(s)

Co-Author(s)

Shubham Patil1,Adityanarayan Pandey1,Swagata Bhunia1,Sandip Lashkare2,Apurba Laha1,Veeresh Deshpande1,Udayan Ganguly1

IIndian Institute of Technology Bombay1,Indian Institute of Technology Gandhinagar2

Abstract

Shubham Patil1,Adityanarayan Pandey1,Swagata Bhunia1,Sandip Lashkare2,Apurba Laha1,Veeresh Deshpande1,Udayan Ganguly1

IIndian Institute of Technology Bombay1,Indian Institute of Technology Gandhinagar2
There is an ever-growing need for 5G communication technology and the Internet of Things to achieve better-performing systems in speed and power consumption. Research has shown SOI technology to be very promising among different technologies (it offers low voltage and high-frequency operation capability) [1]. However, the costly smart-cut method for manufacturing SOI wafers is a challenge. Alternatively, the notion of using epitaxial rare earth (RE) oxides onto Si followed by epi-Si growth is a potential alternative to enable cheaper and high-volume manufacturing (HVM) of SOI wafers. Gd<sub>2</sub>O<sub>3</sub> oxide is the most promising among all rare oxides due to its large bandgap, sufficient band offsets, stable oxidation state, and low lattice mismatch with Si(111). In this context, our group patented a methodology to produce semiconductors on an insulator substrate using an HVM-friendly RF magnetron sputter system [2,3].<br/>In the work, we demonstrate epitaxial-Si on epitaxial-Gd<sub>2</sub>O<sub>3</sub>/Si(111) substrate by RF magnetron sputtering for SOI application. The fabricated heterostructure is characterized through XPS, HRXRD, cross-sectional HRTEM, and EDS analyses, providing compelling evidence for the formation of the epi-Si(111) layer on the epi-Gd<sub>2</sub>O<sub>3 </sub>surface.<br/>The cap-Gd<sub>2</sub>O<sub>3</sub>/Top-Si/BOX-Gd<sub>2</sub>O<sub>3</sub> (capping layer (cap)/channel (Top-Si)/Buried-oxide (BOX)) stack is deposited on Si(111) substrate using RF sputtering. The box layer is deposited at 750 <sup>o</sup>C with 20 W RF power (~0.12nm/min) for 100 min, followed by intrinsic-Si deposition (~0.3 nm/min) at 100 <sup>o</sup>C temperature. The Gd<sub>2</sub>O<sub>3</sub> capping layer is deposited at a higher temperature (750 <sup>o</sup>C) to crystallize the channel layer. The heterostructure is subsequently annealed at 850 <sup>o</sup>C to study the impact of rapid thermal annealing. The heterostructure thickness is 12 nm/15 nm/16 nm, confirmed using HRTEM. The capping layer is etched using an H<sub>2</sub>SO<sub>4</sub>: DI water wet etch, O<sub>2</sub> plasma ashing, followed by BHF etch. The conformal etching is verified by analyzing the XPS spectra. The absence of a Gadolinium (Gd3d and Gd4d) signature and a strong Si2p peak of bulk-Si confirms that the capping layer is properly etched. Next, HRXRD is employed to determine the structural nature of the BOX-Gd<sub>2</sub>O<sub>3</sub>.<br/>The full range <i>Φ</i> measurements at fixed <i>Χ </i>= 70.5<sup>o</sup> and <i>2θ </i>= 28.44<sup>o </sup>show two sets of peaks 120<sup>o</sup> apart correspond to the Si(-111) and c-Gd<sub>2</sub>O<sub>3</sub>(-222) planes. This observation indicates a 3-fold symmetrical nature of the peaks, establishing that the (222) planes of Gd<sub>2</sub>O<sub>3 </sub>are grown epitaxially onto the Si(111) substrate. The Si peaks are found to be rotated by 60<sup>o</sup> relative to Gd<sub>2</sub>O<sub>3</sub>, suggesting the presence of an A/B twinning relationship between Si and Gd<sub>2</sub>O<sub>3</sub>. The epitaxial quality of the BOX is further validated using a skew-symmetric ω-2θ scan.<br/>The HRTEM analysis demonstrates three key findings: (a) the formation of an atomically sharp interface at the BOX-Gd<sub>2</sub>O<sub>3</sub>/Si(111) interface, (b) the epitaxial nature of the BOX-Gd<sub>2</sub>O<sub>3</sub>and Top-Si layers, and (c) confirmation of the A/B/A stacking arrangement of Top-Si/BOX-Gd<sub>2</sub>O<sub>3</sub>/Si(111). The EDS analysis further confirms the formation of a flat and homogenous interface without significant Si(Gd) out-diffusion.<br/>In conclusion, we have developed a low-cost, high-volume, manufacturable state-of-the-art epitaxial Si-Gd<sub>2</sub>O<sub>3</sub> on Si (111) substrate (SOXI) by RF sputtering. The epitaxial nature of the heterostructure is confirmed through HRXRD and HRTEM analyses. In the near future, a SOXI MOSFET demonstration should be done.<br/><br/>References:<br/>[1] J. Hartmann <i>et al.,</i> IEEE CSICS, 2014. [2] Amita <i>et al.,</i> DRC, 2018. [3] Amita <i>et al.,</i> TSF, 2021

Keywords

Si | transmission electron microscopy (TEM) | x-ray diffraction (XRD)

Symposium Organizers

Liang Jin, Bioland Laboratory
Dongsheng Li, Pacific Northwest National Laboratory
Jan Ringnalda, FEI Company
Wenhui Wang, National University of Singapore

Symposium Support

Bronze
Gatan

Session Chairs

James De Yoreo
Dongsheng Li

In this Session