STS APS DGRIE/Processes/uk submicron etch

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About this Process
Process Details
Technology RIE
Material SiO2
Mask Materials SPR 220, KMPR, Polysilicon
Gases Used C4F8, He
Date Created 5/21/2011
Authored By SPTS, Kevin Owen

The uk submicron etch is designed for thin-film (up to 8 μm) etching of silicon dioxide. Etch rate up to 2600 Å/min, depending on feature size. The etch exhibits extremely vertical sidewalls and can achieve down to 100 nm feature resolution.


Follow the SOP as shown on the STS APS DGRIE page and choose the uk_submicron etch.


Uk submicron 2um.jpg
Uk submicron 1um.jpg

Etch/Dep Rate

Etch rate is feature size dependent - smaller features will etch slower than larger ones. Bulk etch rate is approximately 2500 Å/min. The etch exhibits minimal loading effect.

  • Thermal oxide: 2450 Å/min
  • GSI Oxide 200C: 3500 Å/min
  • GSI Oxide 350C: 3000 Å/min
  • GSI Oxide 350 thin: 2900 Å/min
These values were last updated on Feb 25, 2019. For the most recent values for thermal oxide, please see the qualification section below.


Etch uniformity is < 1% across a 6" wafer.

Mask Selectivity

The etch rate of SPR 220 is approximately 1600 A/min (selectivity 1.5:1). Selectivity will be lower on smaller features, due to the decrease in oxide etch rate. This is the etch rate on a 6" wafer. Selectivity may be lower on samples/wafers mounted to a carrier due to increased sample heating.

  • SPR 200: 1600 Å/min (selectivity 1.5:1)
  • PMMA: approximately 1800 Å/min (selectivity ~1.3:1).
  • Stoichiometric LPCVD silicon nitride (Si3N4): 1750 Å/min (selectivity 1.4:1).
  • GSI nitride 200C: 2400 Å/min
  • Poly-Si: 450 Å/min


The etch may be run for a maximum of 30 minutes.


The bulk oxide etch rate is tested after each maintenance (every 1-2 weeks) by running a 2 min etch on an oxide coated 6" wafer and measured at 25 points around the wafer.