1. Pt-Ox Test Results Wafer Processing and SEM by Kenneth Leedle
Results compiled by Yunhan Chen
Spring 2016

2. Dense (0.6um line/ 1.4um space)/Iso ER
Pt-Ox Recipe 1
Recipe:
600W ICP/ 50W BP/ 45 CHF3/ 2 O2/ 5mT/ 4T He/ 10C Electrode/ 70C liner 90C Spool and 90C lid temp
Wafers:
Silicon wafer
Single crystal silicon wafer with 1.6mm 3612 photoresist and patterned with resolution mask.
Oxide wafer
1mm thermal SiO2 with 1.6mm 3612 photoresist and patterned with resolution mask.
Procedure:
Both patterned Silicon wafers and patterned Oxide wafers are etched using the above recipe.
For Silicon wafer, PR thickness is measured before and after etch using NanoSpec for getting PR etch rate. PR is then stripped and Si step height is measured for getting Si etch rate.
For Oxide wafer, Oxide thickness are measured pre and post etch in NanoSpec for getting Oxide etch rate.
Results:
PR Etch Rate
(nm/min)
Si Etch Rate
SiO2 Etch Rate (nm/min)
Ox:Si Selectivity
Ox:PR Selectivity
Dense (0.6um line/ 1.4um space)/Iso ER 86 27
176
6.5185
2.0585
0.733

3. 89o 0.90mm 0.66mm 0.98mm Cross section SEM image: Etching Time: 5min
Patterned Oxide wafer: SCS wafer with 1mm thermal oxide, patterned with 1.6mm 3612 photoresist and resolution mask pattern.
Comments:
Micro loading effect is observed. The etch rate matches the large area measurement while the dense area rate is lower. The etch rate for 0.6um line /1.4um space is ~27% lower than the open area measurement.
The side wall is smooth and vertical.
0.66mm
0.98mm
0.90mm
89o

4. Dense (0.6um line/ 1.4um space)/Iso ER
Pt-Ox Recipe 2
Recipe:
1400W ICP/ 100W BP/ 45 CHF3/ 2 O2/ 5mT/ 4T He/ 10C Electrode/ 70C liner 90C Spool and 90C lid temp
Wafers:
Silicon wafer
Single crystal silicon wafer with 1.6mm 3612 photoresist and patterned with resolution mask.
Oxide wafer
1mm thermal SiO2 with 1.6mm 3612 photoresist and patterned with resolution mask.
Procedure:
Both patterned Silicon wafers and patterned Oxide wafers are etched using the above recipe.
For Silicon wafer, PR thickness is measured before and after etch using NanoSpec for getting PR etch rate. PR is then stripped and Si step height is measured for getting Si etch rate.
For Oxide wafer, Oxide thickness are measured pre and post etch in NanoSpec for getting Oxide etch rate.
Results:
PR Etch Rate
(nm/min)
Si Etch Rate
SiO2 Etch Rate (nm/min)
Ox:Si Selectivity
Ox:PR Selectivity
Dense (0.6um line/ 1.4um space)/Iso ER
259
201
474
2.3641
1.8301
0.783

5. 87-88o 1.1mm 1.4mm 0.6mm 0.98mm 0.72mm 0.92mm Cross section SEM image:
Etching Time: 2min
Patterned Oxide wafer: SCS wafer with 1mm thermal oxide, patterned with 1.6mm 3612 photoresist and resolution mask pattern.
Comments:
Micro loading is observed. The etch rate matches the large area measurement while the dense area rate is ~22% lower.
Slight micro trenching at the bottom.
1.1mm
0.98mm
0.6mm
1.4mm
0.72mm
0.92mm
87-88o

6. Dense (0.6um line/ 1.4um space)/Iso ER
Pt-Ox Recipe 3
Recipe:
1400W ICP/ 150W BP/ 10 Ar/ 40 CHF3/ 10 C4F8/ 7mT/ 4T He/ 10C Electrode/ 70C liner 90C Spool and 90C lid temp
Wafers:
Silicon wafer
Single crystal silicon wafer with 1.6mm 3612 photoresist and patterned with resolution mask.
Oxide wafer
1mm thermal SiO2 with 1.6mm 3612 photoresist and patterned with resolution mask.
Procedure:
Both patterned Silicon wafers and patterned Oxide wafers are etched using the above recipe.
For Silicon wafer, PR thickness is measured before and after etch using NanoSpec for getting PR etch rate. PR is then stripped and Si step height is measured for getting Si etch rate.
For Oxide wafer, Oxide thickness are measured pre and post etch in NanoSpec for getting Oxide etch rate.
Results:
PR Etch Rate
(nm/min)
Si Etch Rate
SiO2 Etch Rate (nm/min)
Ox:Si Selectivity
Ox:PR Selectivity
Dense (0.6um line/ 1.4um space)/Iso ER
279
172
562
3.2674
2.0143
0.812

7. 0.95mm 0.91mm 0.98mm 1.4mm 0.6mm 86o 89o Cross section SEM image:
Etching Time: 2min
Patterned Oxide wafer: SCS wafer with 1mm thermal oxide, patterned with 1.6mm 3612 photoresist and resolution mask pattern.
Comments:
Micro loading effect is observed. The etch rate matches the large area measurement while the dense area rate is ~19% lower.
Slight micro trenching at the bottom.
0.95mm
0.91mm
0.98mm
1.4mm
0.6mm
86o
89o

8. Dense (0.6um line/ 1.4um space)/Iso ER
Summary
Comparison of the 3 recipes:
Recipe
Description
PR Etch Rate
(nm/min)
Si Etch Rate
SiO2 Etch Rate (nm/min)
Ox:Si Selectivity
Ox:PR Selectivity
Dense (0.6um line/ 1.4um space)/Iso ER #1
600W ICP/ 50W BP/ 45 CHF3/ 2 O2/ 5mT/ 4T He/ 10C Electrode/ 70C liner 90C Spool and 90C lid temp 86 27
176
6.5185
2.0585
0.733 #2
1400W ICP/ 100W BP/ 45 CHF3/ 2 O2/ 5mT/ 4T He/ 10C Electrode/ 70C liner 90C Spool and 90C lid temp
259
201
474
2.3641
1.8301
0.783 #3
 1400W ICP/ 150W BP/ 10 Ar/ 40 CHF3/ 10 C4F8/ 7mT/ 4T He/ 10C Electrode/ 70C liner 90C Spool and 90C lid
279
172
562
3.2674
2.0143
0.812
All the three recipes have microloading effect with dense areas etching ~20-25% slower than the isolated areas.
Recipe 3 (C4F8 based process as opposed to conventional CHF3 based one) offers lower microloading, higher etch rate with similar selectivity.
Profiles are acceptable but can be optimized further.
Recipe optimization is required to minimize microloading while improving selectivity and wall angle.