Specific Process Knowledge/Etch/DRIE-Pegasus/Pegasus-2/ORE with Al2O3 mask

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By Maria Farinha @nanolab, Jan 2023

Important! The pressure settings used below may no longer be permitted, always check with the Dry etch group.

As stated by Nguyen et al., the SF₆ and O₂ fluxes are only separated after 4 s during the C-step. Shorter time steps than that do not execute the function of the clearing. After testing recipes with only 2 s of clearing and with no clear step, it was understood it could be eliminated, showing more depth as well as less undercut when going for shorter cycles. From then on, not CORE but ORE recipes were applied D/E = O/RE.
Moreover, during the E-step, the MFC (mass flow controller) presented a delay to read the pressure when compared with the power, creating unwanted bias. To fight it, the E-step was divided into E₁ and E₂. The E₁ of only 2 s is enough to stabilize the pressure, and E₂ the profile is etch correctly, without the unwanted bias.

CORE process graphics and recipes: a) unwanted DC bias during the E-step; b) E-step separated into two steps, E₁ decreased the bias.

Pillars

1μm Pillar recipe from March 2022 - #244 = 122 min

	Time (s)	Pressure (valve control)	O2 flow (SCCM)	SF6 flow (SCCM)	Platen power (W)	Profile
O-step	10	3%	200	0	40
R-step	10	100%	0	5	40
E1-step	2	4%	0	350	40
E2-step	7	4%	0	350	300		Pillars with different etching times.

Holes

17.6 μm holes profile.

1μm holes recipe from March 2022 - #288 = 120 min

	Time (s)	Pressure	O2 flow (SCCM)	SF6 flow (SCCM)	Platen power (W)	Coil power (W)
O-step	10	220 mTorr	200	0	40	0
R-step	10	100%	0	40	40	0
E1-step	2	220 mTorr	0	1200	0	0
E2-step	1-5	220 mTorr	0	1200	1	2000

Nanoholes

200nm nanoholes recipe from March 2022

	Time (s)	Pressure (valve control)	O2 flow (SCCM)	SF6 flow (SCCM)	Platen power (W)
O-step
R-step
E1-step
E2-step