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

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This page is written by Berit Herstrøm @ DTU Nanolab (BGHE) if nothing else is stated
I (bghe@nanolab 2016) 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

Unless otherwise stated, all content in this section was done by Berit Herstrøm, DTU Nanolab
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
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