XR-1541.006 (FOx-12) Recipe

Application

tone	negative
special	Superior edge roughness
reference	J. Vac. Sci. Technol. B. 16 (1998) 69 - 76
spincoat	202 - 128 nm @ 1000 - 6000 rpm thinner layers can be obtained at Karl Suss spinner WITH lid closed: 61 - 44 nm @ 1000 - 2000 rpm or by diluting with MIBK (see spincurve below)
prebake	2 minutes on hotplate @ 150 °C 2 minutes on hotplate @ 220 °C or 30 minutes in vacuum at room termperature
exposure	about 500 µC/cm² @ 100 kV
development	1 min. in MF322 15 s in MF322 : demi-water = 1 : 9 15 s in demi-water

Results: Spincurves

Work done in FOx-12

15 nm single pass line in 44nm thick FOx-12, exposed with spot 21nm_740pa_400um_100kv and dose 5460 µC/cm² @ 100kV

20nm dense lines and spaces (single pass lines) in 50nm thick FOx-12, exposed with spot 21nm_740pa_400um_100kv and dose 6970 µC/cm² @ 100kV

Etchrates of FOx-12 resist in different plasmas in comparison with HPR504

GAS 1: SF6/He plasma on Leybold Z401:

SF₆	12.5 sccm
He	10 sscm
Pressure	10 µbar
P	40 W
Biaspotential	-60 V

GAS 2: CHF3/O2 plasma on Leybold Z401S

CHF₃	50 sccm
O₂	2.5 sccm
Pressure	7 µbar
P	50 W
Biaspotential	-350 V

GAS 3: O2 plasma on Leybold Z401S

O₂	20 sccm
Pressure	3 µbar
P	20 W
Biaspotential	-200 V

Etch rates (nm/min):

	Gas 1	Gas 2	Gas 3
HPR504	51	16	29
FOx-12	29	36	0.6

FOx-12/HPR bilayer resist combination

HSQ can also be used in a bilayer combination with hard baked HPR for high aspect ratio nanoscale e-beam lithography.

For this reason a few steps should be added to the processing flowchart:

After spincoating and baking HMDS and before following the FOx-12 flowchart HPR504 should be spincoated (5000rpm 937nm) and baked on a hotplate at successive 100, 200 and 250 ⁰C, each temperature for 2 minutes.
After development of the FOx-12 resist the HPR is etched in above mentioned O₂ plasma (gas 3).

A few examples of work done in a bilayer resist of FOx-12 and HPR

80nm multi pass lines (10 passes) written in 44nm thick FOx-12 on top of 937nm thick HPR, exposed with spot 21nm_740pa_400um_100kv and dose 290 µC/cm² @ 100kV

80nm multi pass lines (10 passes) written in 44nm thick FOx-12 on top of 635nm thick HPR, exposed with spot 21nm_740pa_400um_100kv and dose 990 µC/cm² @ 100kV

26nm semi-dense lines written in 30nm thick FOx-12 on top of 155nm thick HPR, exposed with spot 21nm_740pa_400um_100kv and dose 815 µC/cm² @ 100kV

40nm dense lines and spaces (1:1) written in 30nm thick FOx-12 on top of 129nm thick HPR, exposed with spot 21nm_740pa_400um_100kv and dose 1646 µC/cm² @ 100kV