STS APS DGRIE/Processes/uk submicron etch

About this Process
Process Details
Equipment	STS APS DGRIE
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.

Procedure

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

Characterization

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.

Uniformity

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

Breakthrough Step

The process has a standard 30sec Ar breakthrough which can be helpful to get through photoresist scum. If you are using very thin e-beam resist you many want to remove the breakthrough step.

The etch depths below are on 6" blanket films with the 30 sec breakthrough step.

• SPR 220 ː 59nm
• SiO₂ ː 37nm

Limitations

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

Qualification

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.