formation of ge quantum dots by selective oxidation of sige alloys for single-electron devices

Formation of Ge Quantum dots by Selective Oxidation of SiGe alloys for Single-Electron Devices P. W. Li, W. M. Liao, S. W. Lin, P. S. Chen 1 , S. C. Lu 1 , and M. J. Tsai 1 Department of Electrical Engineering, National Central University, ChungLi, Taiwan, R.O.C 320 1 Electronics Research and Service Organization, ITRI, Hsinchu, Taiwan, R.O.C Si will be preferentially oxidized during high-temperature oxidation of Si 1-x Ge x alloys while Ge is rejected from the oxide and pile s up along the SiO 2 /substrate interface. Germanium quantum dots would be formed during thermal oxidation of SiGe /Si-on-insulator Nano-scale Ge quantum dots (<10nm) Compatible to the prevailing CMOS technolog y Good controllability and reproducibility Ge pileup along the SiO2/Si interfa ce Unconsumed S i Buried Oxide Ge precipitio n Buried Oxide Ge dots versus thermal oxidation ti me Ge dots versus Ge composition in Si 1-x Ge x 15min 11min 20min 25min Plan-view TEM micrographs of Si 0.95 Ge 0.05 after 11min.~25min. oxidation at 900 ℃. Cross-sectional TEM micrographs of Si 0.95 Ge 0.05 after 11min. and 25min. oxidation at 900 ℃. Si 1-x Ge x layer was epitaxially grown on SOI wafer (S IMOX). Ge dots were formed by thermal oxidation of Si 1-x Ge x layer (Ge segregation and agglomeration). Si 0.9 Ge 0.1 Si 0.85 Ge 0. 15 Si 0.95 Ge 0. 05 Plan-view TEM micrographs of different Ge content, 11min. oxidation at 900 ℃. Ge dot size and density as a function of Ge composition in Si 1-x Ge x at 900 o C thermal oxida tion for 11min. Additional thermal oxidation or thermal anneal ing would provide more energy required for Ge a toms movement, but too much energy for Ge atoms migration and agglomeration will results in big ger Ge dots and lower dot density. The reduction of Ge dots’ size with increasing Ge com position in Si 1-x Ge x alloy comes from two factors: 1. Hi gher atomic mobility or moving speed of Ge atoms. 2. S horter oxidation time required for higher Ge-compositio nal Si 1-x Ge x to be completely oxidized . Si Buried Oxide Ge dots (a) Ge dots formation by selective oxidation of Si 1-x Ge x and Ge segregation. (b) SEM micrograph of a narrow wire. Structure Ge quantum dot Single-Electron devices Oxidati on Si Buried Oxide 375nm Si Buried Oxide Si~32n m Si 1-x Ge x ~8nm SiO 2 Ge dots Device Structure Sourc e Drain Drain Source I d -V g characteristic and transconduc tance of Ge SET at Room Temperatur e. Effect of oxidation time on the size and density o f Ge dots formed by thermally oxidized Si 0.95 Ge 0.05 at 900 o C.

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11min. 15min. 20min. 25min. Ge pileup along the SiO2/Si interface. Unconsumed Si. Buried Oxide. Formation of Ge Quantum dots by Selective Oxidation of SiGe alloys for Single-Electron Devices P. W. Li, W. M. Liao, S. W. Lin, P. S. Chen 1 , S. C. Lu 1 , and M. J. Tsai 1 - PowerPoint PPT Presentation

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Formation of Ge Quantum dots by Selective Oxidation of SiGe alloys for Single-Electron Devices

P. W. Li, W. M. Liao, S. W. Lin, P. S. Chen1, S. C. Lu1 , and M. J. Tsai1

Department of Electrical Engineering, National Central University, ChungLi, Taiwan, R.O.C 3201 Electronics Research and Service Organization, ITRI, Hsinchu, Taiwan, R.O.C

Si will be preferentially oxidized during high-temperature oxidation of Si1-xGex alloys while Ge is rejected from the oxide and pile

s up along the SiO2/substrate interface.

Germanium quantum dots would be formed during thermal oxidation of SiGe/Si-on-insulator

Nano-scale Ge quantum dots (<10nm)

Compatible to the prevailing CMOS technology

Good controllability and reproducibility

Ge pileup along the

SiO2/Si interface

Unconsumed Si Buried Oxide

Ge precipition

Buried Oxide

Ge dots versus thermal oxidation time

Ge dots versus Ge composition in Si1-xGex

15min11min 20min 25min

Plan-view TEM micrographs of Si0.95Ge0.05 after 11min.~25min. oxidation at 900 .℃

Cross-sectional TEM micrographs of Si0.95Ge0.05 after 11min. and 25min. oxidation at 900 .℃

Si1-xGex layer was epitaxially grown on SOI wafer (SIMOX).

Ge dots were formed by thermal oxidation of Si1-xGex layer (Ge segregation

and agglomeration).

Si0.9Ge0.1 Si0.85Ge0.15Si0.95Ge0.05

Plan-view TEM micrographs of different Ge content, 11min. oxidation at 900 .℃

Ge dot size and density as a function of Ge composition in Si1-xGex

at 900 oC thermal oxidation for 11min.

Additional thermal oxidation or thermal annealing would provide more energy required for Ge atoms movement, but too much energy for Ge atoms migration and agglomeration will results in bigger Ge dots and lower dot density.

The reduction of Ge dots’ size with increasing Ge composition in Si1-xGex alloy

comes from two factors: 1. Higher atomic mobility or moving speed of Ge atoms. 2. Shorter oxidation time required for higher Ge-compositional Si1-xGex to be com

pletely oxidized .

Buried OxideGe dots

(a) Ge dots formation by selective oxidation of Si1-xGex and Ge segregation.

(b) SEM micrograph of a narrow wire.

Structure

Ge quantum dot Single-Electron devices

Oxidation

Buried Oxide 375nm

Buried Oxide

Si~32nmSi1-xGex~8nm SiO2

Ge dots

Device Structure