Specific Process Knowledge/Etch/ICP Metal Etcher/silicon oxide/By BGHE

I (bghe@nanolab) tried with two different gas regimes: CF4 and C4F8. I only made a few tests with CF4 since I got a very bad selectivity to the resist mask and I dicided to go for the C4F8 instead.
Zhibo Li @ Danchip has also tried (December 2016) with similar setting, see his results in this file: File:Zhibo Li SiO2 ICP etch (dose205).docx

C4F8

I started out with a recipe developed by Peixiong called pxSiO2try9, look at his results here

Parameter	Mask material	Barc etch	Coil power	Platen power	Pressure	Flow rate C4F8	Flow rate H2	Flow rate Ar	T	Process time	Comment	Results	CD change (mask 55% trench) after s007467 is it <50% after barc etch trench opening as a fraction of pitch	Profile angles	Etch depth in SiO2	Etch rate	Etch depth in resist	Selectivity (resist:SiO2)	Etch rate in Si
s008684	880nm KRF	barc etch CF 50s	1000W	200W	2.5mTorr	13sccm	30sccm	0	0	1:30min	The layer in this case is 300nm Si3N4		35% (1µm pitch) 47% (6µm pitch)	83-88		>300nm/min (Si3N4)	240nm	~1:2 (Si3N4)	?
s007785	880nm KRF	pxbarcO2 25s	800W	200W	2.5mTorr	13sccm	26sccm	0	0	7 min	One of the good ones. the mask is well preserved		37% (1µm pitch) 48% (4µm pitch)	83-86	>1000 nm	>143nm/mi	250nm	>1:4	?
s007679	880nm KRF	barc etch CF 40s	800W	200W	2.5mTorr	13sccm	26sccm	0	0	8 min	One of the good ones. the mask is well preserved, CF barc etch		42% (1µm pitch) 48% (4µm pitch)	83-89	>1074 nm	>134nm/min	310nm	>1:3.5	?
s007592	880nm KRF	barc etch CF 40s	1000W	200W	2.5mTorr	10sccm	28sccm	0	0	5 min	One of the good ones. the mask is well preserved, CF barc etch		41% (1µm pitch) 47% (4µm pitch)	86-87	727 nm (1µm) 864 nm (4µm)	145 nm/min (1µm pitch) 172 nm/min (4µm pitch	170nm	1:4.3 (1µm P) 1:5.1 [4µm P)	?
s007593	880nm KRF	barc etch CF 40s	800W	100W	2.5mTorr	10sccm	28sccm	0	0	8 min	One of the good ones. the mask is well preserved, CF barc etch. The small pitch line are etched much slower that the higher pitch lines		32% (1µm pitch) 45% (4µm pitch)	85-86	501 nm (1µm) 881 nm (4µm)	63 nm/min (1µm pitch) 110 nm/min (4µm pitch	100nm	1:5.0 (1µm P) 1:8.8 [4µm P)	?
s007467 (as 18)	750nm KRF	none	1000W	150W	2.5mTorr	8sccm	30sccm	0	0	10min			? (2µm pitch) 52% (average) (3µm pitch) 51% (average) (6µm pitch)	77 (6µm p)	1015 nm (2µm pitch) 1032 nm (3µm pitch) 1060 nm (6µm pitch)	101.5 nm/min (2µm pitch) 103.2 nm/min (3µm pitch) 106.0 nm/min (6µm pitch)	210nm	1:4.8 (2µm pitch) 1:4.9 (3µm pitch) 1:5.0 (6µm pitch)
s007418	750nm KRF	none	1000W	150W	2.5mTorr	8sccm	30sccm	0	0	5min			46.5% (2µm pitch) 49.0% (4µm pitch)	87-88 (large structures)	400 nm (6µm pitch)	80 nm/min (6µm pitch)	200nm/76nm?	1:2 (6µm pitch) 1:5?
s007565 (as 16)	880nm KRF	barc etch CF 40s	800W	100W	2.5mTorr	13sccm	26sccm	0	0	8min	repeated s007416 and s007468 with a barc etch step. This improved the uniformity of the etch performance over different linewidth and improved the selectivity to the mask and the profile angle. After this I continued with barc etch. Nice		44.5% (2µm pitch) 46.8% (3µm pitch) 47.8% (4µm pitch)	87-88	779 nm (2µm pitch) 862 nm (3µm pitch) 854 nm (4µm pitch)	97.4 nm/min (2µm pitch) 107.8 nm/min (3µm pitch) 106.8 nm/min (4µm pitch)	130nm	1:6.0 (2µm pitch) 1:6.6 (3µm pitch) 1:6.6 (4µm pitch)
s007468 (as 16)	750nm KRF	none	800W	100W	2.5mTorr	13sccm	26sccm	0	0	10min	Repeated s007416 with double time.		17.3% (1µm pitch) 33.5% (2µm pitch) 38.3% (3µm pitch) 41.4% (4µm pitch)	76-78	850 nm (1µm pitch) 1034 nm (2µm pitch) 1048 nm (3µm pitch) 1055 nm (4µm pitch)	85 nm/min (1µm pitch) 103.4 nm/min (2µm pitch) 104.8 nm/min (3µm pitch) 105.5 nm/min (4µm pitch)	300nm	1:2.8 (1µm pitch) 1:3.4 (2µm pitch) 1:3.5 (3µm pitch) 1:3.5 (4µm pitch)
s007416	750nm KRF	none	800W	100W	2.5mTorr	13sccm	26sccm	0	0	5min	From S007411 the platen power was decreased to avoid trenching. The etch rate went down and some variation in profile angle is seen from small opening to large opening. Started plasma on the 4th try		38.6% (2µm pitch) 45.4% (5µm pitch)	77 (small structures) 90 (large structures)	346 nm (1.5µm pitch) 454 nm (5µm pitch)	69 nm/min (1.5µm pitch) 91 nm/min (5µm pitch)	50nm	1:7 (1.5µm pitch) 1:9 (5µm pitch)
s007411	750nm KRF	none	800W	150W	2.5mTorr	13sccm	26sccm	0	0	5min	From s007409 the Gas flow ratio between C4F8 and H2 has been changed to more C4F8 and less H2. This increased the etch rate (more fluorine). Trenching is seen and tappered sidewall is seen indicating a more physical etch.		47.0% (1µm pitch) 44.6% (2µm pitch)	83	708 nm	142 nm/min	294 nm	1:2.4
s007419	750nm KRF	none	800W	200W	2.5mTorr	8sccm	30sccm	0	0	5min	Increased the platen power. The selectivity and profile looks good but the resist profile has been rounded more on the edge and this will effect the profile for a deeper etch.		46.6% (1µm pitch) 47.8% (2µm pitch) 48.4% (4µm pitch)	86-90	270nm (1µm pitch) 400nm (2.5µm pitch)	54 nm/min (1µm pitch) 80 nm/min (2.5µm pitch)	100nm	1:4 (2.5µm pitch)
s007410	750nm KRF	none	800W	75W	2.5mTorr	8sccm	30sccm	0	0	7min	Reduced the platen power.Effect: ARDE - less CD increase but more possitive tappered profile.		42.3% (2µm pitch) 47.0% (average) (3µm pitch)	80-82	0 nm (1µm pitch) 270 nm (3µm pitch)	0 nm/min (1µm pitch) 39nm/min (?µm pitch)	100nm	1:0 (1µm pitch) 1:2.7 (2µm pitch)
s006656	750nm KRF	none	1000W	150W	2.5mTorr	15sccm	0sccm	30sccm	0	10min	Tried with C4F8/Ar instead of C4F8/H2 => much lower etch rate and bad selectivity to the resist.				358 nm	35.8 nm/min (2µm pitch)	526nm	1:0:68
s007409	750nm KRF	none	800W	150W	2.5mTorr	8sccm	30sccm	0	0	5min	Repeated Pexiongs recipe without barc etch and only 5 min's runs. It probably takes about 1 min to get through the barc. If you count that in then the etch rate and relectivity to resist is almost the same as for the first run. Effect: CD increase		47.4% (1µm pitch) 47.5% (2µm pitch) 50.0% (3µm pitch)	86-89	280 nm (1µm pitch) 370 nm (2µm pitch)	56 nm/min (1µm pitch) 74 nm/min (2µm pitch)	160nm	1:1.8 (1µm pitch) 1:2.3 (2µm pitch)
s006106	750nm KRF	Barc etch O2 75s	800W	150W	2.5mTorr	8sccm	30sccm	0	0	10min	From Peixiong		60%	79	1053 nm (center) 1043 nm (edge)	105 nm/min	280nm	1:3:75 (2µm pitch)

CF4

I stopped trying with CF4 because I got bad selectivty to the resist and decided to focus on the recipe with C4F8 instead.

Parameter/Wafer ID	s006687	s006701	s007258	s007350	s007352
Mask material	750nm KRF	750nm KRF	750nm KRF	750 nm KRF	750nm KRF
Barc etch	none	none	none	none	none
Coil power	800W	800W	800w	800w	800w
Platen power	100W	100W	100w	60W	30w
Pressure	4mTorr	4mTorr	4mTorr	4mTorr	4mTorr
Flow rate CF4	20sccm	25sccm	30sccm	30sccm	30sccm
Flow rate H2	20sccm	15sccm	10sccm	10sccm	10sccm
T	0	0	0	0	0
Process time	10min	10min	2min30	2min30	3min30
Comment			Little resist left, Trenching	A little trenching	very little trenching in large lines - anti trenching in small lines
Results	profile near edge Profile near middel	tilted profile	s007350 2µm pitch	s007350 2µm pitch s007350 1µm pitch	s007352 1µm pitch s007352 2µm pitch
Etch depth in SiO2	374nm	505nm	578nm	336nm	235nm
Etch rate	37.4nm/min	50.5nm/min	231nm/min	134.4nm/min	88nm/min
Etch depth in resist	345nm	633nm	700nm	405nm	308nm
Selectivity (resist:SiO2)	1:1.1	1:0.80	1:0.83	1:0.83	1:0.76