1. Epitaxial growth of SiC on Si covered by SiC nanocrystals G
Epitaxial growth of SiC on Si covered by SiC nanocrystals G. Battistig, Zs.E. Horváth, L. Dobos MTA MFA Research Institute for Technical Physics and Materials Science, P.O.Box 49, H-1525 Budapest, Hungary G. Attolini, M. Bosi, B.E. Watts Imem-CNR Institute, Parco Area delle Scienze 37 A, Fontanini, Parma, Italy

2. Outline
Motivation
SiC epitaxy on Si : poor crystalline quality, important stress inside the 3C-SiC layers, presence of voids at the 3C-SiC/Si interface
SiC nanocrystals at SiO2/Si interface The growth process
Investigation of the SiC nanocrystals
SiC epitaxy

3. Growth of the SiC nanocrystals
(100) Silicon with thermally grown SiO2
Quartz furnace
100% CO
Temperature above 900°C
30min - 8h

4. Growth mechanism
The carbon accumulation at the interface is independent from the thickness of the oxide layer  fast diffusion
Above 900°C from the 3 steps of the carbon transport (CO entering the oxide, diffusion through the SiO2, reaction in the Si) the reaction at the interface supposed to control the mechanism
2 CO + 2 SiO2  SiO2:Ci,Oi [Köhler, 2001] eV
2 (CO)g + 2 <SiO2>s  <SiC>s + 3 (O2)g eV
4 (CO)g + 6 <Si>s  4 <SiC>s + 2 (SiO2)s exoterm, eV

5. TEM measurements 3C-SiC crystallites grow
epitaxially with the Si matrix
(001) Si || (001) SiC and [100] Si || [100] SiC
no voids at the SiC/Si interface
faster lateral growth

6. Shape and size of SiC nanocrystals grown on (100) Si

7. SEM images of the (100) plane
100 nm SiO2 / Si
1150°C - 100% CO - 90 mins
plan view images after removing the protective 100 nm thick SiO2 layer with HF
100 nm SiO2 / Si
1150°C - 100% CO - 8 hours

8. SiO2 SiC Si The SiC/Si interface
Cross sectional TEM image of a (100) Si/SiO2 system annealed in 100% CO, 1 Bar at 1100oC for 2hrs

9. SiC
SiO2 Si
SiC Si
SiC
(100) Si

10. SiC epitaxy
Horizontal Vapour Phase Epitaxy - reactor at atmospheric pressure, using propane and silane diluted in hydrogen, induction heating with a growth temperature of 1200°C
The growth process: - thermal treatment (H2) - carbonisation (H2+C3H8) - SiC growth (H2+C3H8+SiH4)
- Etch (H2)

11. Microscopic structure of epi-SiC
#1: 90 mins nc-SiC – low density
polycrystalline 3C-SiC is formed (X-ray diffraction)
well oriented crystals (e-diffraction)
~ 70 nm SiC, rough surface and interface
Void – micropipe formation
SiC Si

12. SiC Si #2: 8 h nc-SiC – high density polycrystalline 3C-SiC layer
well oriented crystals (e-diffraction)
~ 70 nm SiC, smooth surface and interface
NO pit - void – micropipe formation
SiC Si

13. Conclusion 3C-SiC nanocrystals formed at SiO2/Si interface
Seeds for SiC epitaxy
High nc-SiC density – No pits, voids, micropipes
Improvement of the quality of SiC layer is needed
Possible lateral structuring

14. Thank you for your attention!