Etching with electron beam generated plasmas

• Published in: Journal of vacuum science & technology. A, Vacuum, surfaces, and films Vol. 22; no. 6; pp. 2276 - 2283
• Main Authors: Leonhardt, D., Walton, S. G., Muratore, C., Fernsler, R. F., Meger, R. A.
• Format: Journal Article
• Language: English
• Published: United States 01-11-2004
• Subjects: ARGON; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ELECTRON BEAMS; ETCHING; EV RANGE 100-1000; ION BEAMS; ORGANIC SULFUR COMPOUNDS; OXYGEN; PASSIVATION; PLASMA; SILICON; SULFUR FLUORIDES; TEMPERATURE RANGE 0273-0400 K; resists
• ISSN: 0734-2101; 1520-8559
• DOI: 10.1116/1.1795827

A modulated electron beam generated plasma has been used to dry etch standard photoresist materials and silicon. Oxygen–argon mixtures were used to etch organic resist material and sulfur hexafluoride mixed with argon or oxygen was used for the silicon etching. Etch rates and anisotropy were determined with respect to gas compositions, incident ion energy (from an applied rf bias) and plasma duty factor. For 1818 negative resist and i-line resists the removal rate increased nearly linearly with ion energy (up to
220
nm
∕
min
at
100
eV
), with reasonable anisotropic pattern transfer above
50
eV
. Little change in etch rate was seen as gas composition went from pure oxygen to 70% argon, implying the resist removal mechanism in this system required the additional energy supplied by the ions. With silicon substrates at room temperature, mixtures of argon and sulfur hexafluoride etched approximately seven times faster (
1375
nm
∕
min
) than mixtures of oxygen and sulfur hexafluoride (
∼
200
nm
∕
min
) with
200
eV
ions, the difference is attributed to the passivation of the silicon by involatile silicon oxyfluoride
(
Si
O
x
F
y
)
compounds. At low incident ion energies, the
Ar
–
S
F
6
mixtures showed a strong chemical (lateral) etch component before an ion-assisted regime, which started at
∼
75
eV
. Etch rates were independent of the 0.5%–50% duty factors studied in this work.