STS Pegasus 4/Processes/LNF Unswitched Poly

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About this Process
STS Pegasus 4 Unswitched Poly 1 um.jpg
Process Details
Equipment STS Pegasus 4
Technology RIE
Material Silicon
Mask Materials PR, SiO2
Gases Used SF6, C4F8, O2

LNF Unswitched Poly is a single-step mixed-gas process intended for shallow silicon and thin film poly- and amorphous silicon etches.

The STS Pegasus is not designed for polysilicon etching. There are other tools at the LNF specifically designed for this, including the LAM 9400 and the P5000 RIE. Please make a helpdesk ticket if you need assistance determining the correct tool or recipe for your process.


Follow the standard operating procedure.


Parameter Units Setpoint
ICP Power W 500
Bias Power W 20
Bias Pulsing Hz 40 (80%)
Pressure mTorr 5
C4F8 Flow sccm 50
SF6 Flow sccm 100
Ar Flow sccm 50
Chuck Temperature °C 20


Etch rate

Etch rate will vary with feature size and loading.

Material Etch Rate Uniformity
Silicon 0.8 µm/min ?%
Etch rate is feature size dependent: narrow openings will etch slower than larger open areas.

Mask selectivity

Material Etch Rate Uniformity
SPR 220 250 Å/min 6%
Silicon dioxide 90 Å/min 7%
Silicon nitride 220 Å/min 4%
Low stress nitride 180 Å/min 4%

Etch profile

This process etches semi-isotropically. Vertical to lateral etch rate is approximately 2:1.


Etch length

This etch is designed for thin films and shallow etches (< 2 µm). It is not characterized for long processes.

Feature size

Remaining features that are narrower than the total depth will be etched away due to undercut during the etch.

Open area