1. Finishing of Silicon Film for Silicon-on-Glass
Alex Usenko
IEEE SOI 2010, San Diego, CA
October 13, 2010

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3. As-Transferred Silicon Film Has To Be Finished
Top part of as-transferred silicon film has:
Excessive roughness
Voids at the place of hydrogen bubbles and other structural defects
Usually roughness for H-only transfer it is ~ tens of nm, and thickness of damaged portion - around 100 nm; for H+He these thicknesses are several times smaller
Silicon
Barrier
Glass

4. Regular CMP Is Not for Silicon-on-Glass
Thickness of transferred silicon film is less than micron, while glass thickness variation is more than micron
Silicon film
Glass
300 mm

5. Existing Process for Silicon-on-Glass Finishing: Low Aperture CMP
Disadvantage: low throughput

6. New Process for Silicon-on-Glass Finishing
As-transferred → Plasma Oxidize → Strip Oxide
bottom interface of oxide would be smoother than top surface
if oxidized thickness equal to thickness of damaged part of silicon film, the damaged part would be removed

7. How Thick Oxide Can We Get by Plasma?
Plasma oxidation growth kinetics
published by
(1) Kraitchman
(2) Kimura
(3) Sugano
(4) Eljabaly
(5) Taylor

8. Oxidation Kinetics In Low Frequency – 30 kHz Oxygen Plasma at Room Temperature
Time, minutes

9. TEM on H-only Transfer Before Oxidation/Strip After
Thickness of Damaged Si – 144 nm
Thickness of Damaged Si – 124 nm
Much thicker oxide has to be formed to finish film in one cycle

10. TEM on H-He Transfer Before Oxidation/Strip After
Glass
Barrier
Silicon
Damaged Si
Glue
For H-He transfer, plasma oxidation allows finishing in a single cycle

11. AFM Roughness Peak-to-Valley, nm Before and After Oxidation/Strip Finishing Cycle
Sample 1
Sample 2
Before
After
After
Before

12. Conclusion
Plasma oxidation of damaged top part of transferred silicon film with subsequent stripping of the oxide was used for finishing silicon film in silicon-on-glass
Single cycle oxidation/strip process is sufficient to finish H-He transferred films
Damaged portion of as-transferred silicon film is completely removed by the process
Surface roughness of silicon film improves significantly upon the plasma/strip process
For finishing of H-only transferred films stronger plasma oxidation is required