Specific Process Knowledge/Etch/ICP Metal Etcher/silicon oxide/By BGHE
I 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) |
83-88 |
>300nm/min (Si3N4) |
240nm |
~1:2 (Si3N4) |
? | ||
s007785 | 880nm KRF | pxbarcO2 25s | 800W | 200W | 2.5mTorr | 13sccm | 26sccm | 0 | 0 | 7 min |
37% (1µm pitch) |
83-86 |
>1000 nm |
>143nm/mi |
250nm |
>1:4 |
? | ||
s007467 (as 18) | 750nm KRF | none | 1000W | 150W | 2.5mTorr | 8sccm | 30sccm | 0 | 0 | 10min |
? (2µm pitch) |
77 (6µm p) |
1015 nm (2µm pitch) |
101.5 nm/min (2µm pitch) |
210nm |
1:4.8 (2µm pitch) |
|||
s007418 | 750nm KRF | none | 1000W | 150W | 2.5mTorr | 8sccm | 30sccm | 0 | 0 | 5min |
46.5% (2µm pitch) |
87-88 (large structures) |
400 nm (6µm pitch) |
80 nm/min (6µm pitch) |
200nm/76nm? |
1:2 (6µm pitch) |
| ||
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) |
87-88 |
779 nm (2µm pitch) |
97.4 nm/min (2µm pitch) |
130nm |
1:6.0 (2µm 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) |
76-78 |
850 nm (1µm pitch) |
85 nm/min (1µm pitch) |
300nm |
1:2.8 (1µm 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) |
77 (small structures) 90 (large structures) |
346 nm (1.5µm pitch) |
69 nm/min (1.5µm pitch) |
50nm |
1:7 (1.5µm 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) |
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) |
86-90 |
270nm (1µm pitch) |
54 nm/min (1µm 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) |
80-82 |
0 nm (1µm pitch) |
0 nm/min (1µm pitch) |
100nm |
1:0 (1µm 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) |
86-89 |
280 nm (1µm pitch) |
56 nm/min (1µm pitch) |
160nm |
1:1.8 (1µm pitch) |
||
s006106 | 750nm KRF | Barc etch O2 75s | 800W | 150W | 2.5mTorr | 8sccm | 30sccm | 0 | 0 | 10min | From Peixiong |
60% |
79 |
1053 nm (center) |
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 | |||||
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 |