Reactive Ion Etching Processes

SiO2 Etch Recipes

SiO2:Cr 377:6.9 nm/min

RF Power [W] 70
ICP Power [W] 1500
Pressure [mTorr] 6
C4F8 [sccm] 45
O2 [sccm] 5
DC Bias [V] 132
Temperature [°C] 20

SiO2:HSQ 126:204 nm/min

RF Power [W] 70
ICP Power [W] 500
Pressure [mTorr] 6
C4F8 [sccm] 45
O2 [sccm] 5
DC Bias [V] 218
Temperature [°C] 20
Helium [°Torr] 10

The selectivity of this process is approximately 0.6:1 for SiO2:HSQ for a range of ICP power from 350 to 1500 W. Curiously, we observe that at an ICP power of 200 W, the selectivity is 1.1. Read the SiO2:HSQ process development page for more details.

SiO2:PMMA 29:29 nm/min

RF Power [W] 200
ICP Power [W] 0
Pressure [mTorr] 50
CHF3 [sccm] 50
O2 [sccm] 2
DC Bias [V] 400
Temperature [°C] 20
Helium [Torr] 10

According to the work of Ephrath1982, it is possible to achieve a selectivity of SiO2:PMMA of 5:1.

Cornell NananoScale Facility has recipes with reported selectivity of SiO2:Resist of 2:1.

SiO2:mrI7000R 25:12 nm/min

RF Power [W] 200
ICP Power [W] 0
Pressure [mTorr] 50
CHF3 [sccm] 50
O2 [sccm] 2
Temperature [°C] 20
Helium [Torr] 10

SiO2:AZ1512 45:13 nm/min

RF Power [W] 300
ICP Power [W] 200
Pressure [mTorr] 30
CHF3 [sccm] 40
O2 [sccm] 2
Temperature [°C] 20

The etch rate of AZ appears to vary from 7-60 nm/min.

Si Etch Recipes

Si:AZ1512 2858:325 nm/min (Bosch)

Common process parameters:

RF Power [W] 25
ICP Power [W] 700
Pressure [mTorr] 30
Temperature [°C] 15

Deposition step parameters:

C4F8 [sccm] 100
SF6 [sccm] 1
DC Bias [V] 150
Duration [s] 5

Etch step parameters:

C4F8 [sccm] 1
SF6 [sccm] 100
DC Bias [V] 150
Duration [s] 8

The Bosch process repeats a deposition step followed by an etch step many times to produce high aspect ratio etch with near vertical sidewalls. For this particular recipe, each cycle of deposition and etch removes approximately 572 nm of Si and 22 nm of AZ1512. The selectivity for this process is 26:1 for Si:AZ1512. This process has not been optimized and it may be possible to achieve a selectivity of up to 75:1.

Si:PMMA 330:156 nm/min

RF Power [W] 30
ICP Power [W] 450
Pressure [mTorr] 10
SF6 [sccm] 30
C4F8 [sccm] 45
O2 [sccm] 3
Temperature [°C] 20

Polymer Etch Recipes

PMMA 70 nm/min

RF Power [W] 70
ICP Power [W] 0
Pressure [mTorr] 10
O2 [sccm] 50
DC Bias [V] 250
Temperature [°C] 20
Helium [Torr] 10

mrI7000R 64 nm/min

RF Power [W] 70
ICP Power [W] 0
Pressure [mTorr] 10
O2 [sccm] 50
DC Bias [V] 240
Temperature [°C] 20
Helium [Torr] 10

NXR1025 55 nm/min

RF Power [W] 70
ICP Power [W] 0
Pressure [mTorr] 10
O2 [sccm] 50
DC Bias [V] 250
Temperature [°C] 20
Helium [Torr] 10

Miscellaneous Recipes

Anti-stick Coating

RF Power [W] 50
ICP Power [W] 0
Pressure [mTorr] 80
C4F8 [sccm] 100
DC Bias [V] 45
Temperature [°C] 20
Helium [Torr] 10
Time [s] 30

This anti-sticking layer (ASL) recipe is used to coat a mold before imprinting to prevent resist from sticking to the mold. The surface produced by this coating has a contact angle of 110°. This coating is sufficient for patterns 200 nm and larger. An alternative, more popular, method is demonstrated by Beck.

Photoresist Adhesion Promotion

RF Power [W] 70
ICP Power [W] 0
Pressure [mTorr] 10
O2 [sccm] 50
DC Bias [V] 233
Temperature [°C] 20
Helium [Torr] 10
Time [s] 60

This recipe is used to improve the adhesion of photoresist to a Silicon wafer.