Specific Process Knowledge/Etch/DRIE-Pegasus/Pegasus-4/SiO2 Etch/Cr mask

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

SiO2 trench etching with Cr mask

Start parameters, variations noted in the gallery headline	Recipe name: no 10 with lower platen power
Coil Power [W]	2500
Platen Power [W]	200
Platen temperature [oC]	20
H2 flow [sccm]	25.6
C4F8 flow [sccm]	25.6
He flow [sccm]	448.7
Pressure	Fully open APC valve (8-9 mTorr)
Electromagnetic coils (EM) 'outer coil' / 'inner coil'	'2 A' / '30 A' (PLEASE DO NOT RUN WITH THESE SETTINGS FOR MORE THAN 6 MIN)

• 100 nm Cr mask etched in ICP metal with 500nm DUV neg resist (NUV 2300-0.5) and 65 nm barc.

Cr mask before SiO2 etch 800 nm pitch 50% duty cycle. The The Cr linewidth is clearly less than designed

Results

Temporary conclusions on how the process parameters affect the results in this study:

What process parameters affect the results?

Going from full wafer to small piece on Si carrier: Seemed to give more sidewall passivation Platen power: lowering the platen power gives more sidewall passivation lower etch rate Less trenching Removing the H2 gave: less sidewall passivation Adding O2 gave: less sidewall passivation Process pressure/total gasflow rate Reducing total gasflow rate which reduced the pressur inside the chamber gave: less sidewall passivation Reduced the CD (Critical Dimensions) Coil power: Reducing coil power less CD loss more sidewall passivation Increasing process time: less sidewall passivation more sidewall bow CD loss due to larger mask faceting

Sidewall passivation↑ Sample size↓ Platen power↓ Coil power↓ H2 flow↑ O2 flow↓ Total gas flow rate/pressure↑

Profile SEM images

• SiO2 etch with Cr mask on full wafer 6 min etch
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• SiO2 etch with Cr mask on wafer piece on Si carrier 6 min etch
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• SiO2 etch with Cr mask on wafer piece on Si carrier 6 min etch, H2:0sccm
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• SiO2 etch with Cr mask on wafer piece on Si carrier 6 min etch, H2:0sccm, O2:5sccm
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• SiO2 etch with Cr mask on wafer piece on Si carrier 6 min etch, H2:0sccm, C4F8:13sccm He:225sccm, Pressure:3.35mTorr
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• SiO2 etch with Cr mask on wafer piece on Si carrier 6 min etch, H2:0sccm, C4F8:13sccm He:225sccm, Pressure:3.35mTorr; platen power 150W, coil power:1200W
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• SiO2 etch with Cr mask on wafer piece on Si carrier 6 min etch, H2:0sccm, C4F8:13sccm He:215sccm O2:10sccm, Pressure:3.6mTorr; platen power 150W, coil power:1200W
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• SiO2 etch with Cr mask on wafer piece on Si carrier 6 min etch, H2:0sccm, C4F8:13sccm He:205sccm O2:20sccm, Pressure:3.6mTorr; platen power 150W, coil power:1200W
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• SiO2 etch with Cr mask on wafer piece on Si carrier 6 min etch, H2:0sccm, C4F8:13sccm He:215sccm O2:10sccm, Pressure:3.6mTorr; platen power 150W, coil power:1800W
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• SiO2 etch with Cr mask on wafer piece on Si carrier 6 min etch, H2:0sccm, C4F8:13sccm He:205sccm O2:20sccm, Pressure:3.6mTorr; platen power 150W, coil power:1800W
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  pitch 800 nm
  Top 461 nm
  @edge 437 nm
  bottom 402 nm
  height 916 nm
  height from edge 827 nm
  Cr left 83.5 nm
  selectivity 55.5
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  156 nm/min
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• SiO2 etch with Cr mask on wafer piece on Si carrier 6 min etch, H2:0sccm, C4F8:13sccm He:205sccm O2:20sccm, Pressure:3.6mTorr; platen power 100W, coil power:1200W
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  pitch 800 nm
  Top 444 nm
  bottom 374 nm
  height 718 nm
  Cr left 85 nm
  selectivity 48
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• SiO2 etch with Cr mask on wafer piece on Si carrier 14 min etch (PLEASE DO NOT REPEAT THIS LONG TIME), H2:0sccm, C4F8:13sccm He:205sccm O2:20sccm, Pressure:3.6mTorr; platen power 100W, coil power:1200W
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  Etch on none patterned wafer, Uniformity: +- 6.4%

• SiO2 etch with Cr mask on wafer piece on Si carrier 10 min etch, H2:0sccm, C4F8:13sccm He:205sccm O2:20sccm, Pressure:3.6mTorr; platen power 150W, coil power:1800W
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• SiO2 etch with Cr mask on wafer piece on Si carrier 14 min etch, EM:0/0 H2:0sccm, C4F8:13sccm He:205sccm O2:20sccm, Pressure:3.9mTorr; platen power 100W, coil power:1200W
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  Etch on none patterned wafer, Uniformity: +-1.7%

Profile, top view at tilted SEM images on 800 nm pitch and 50% duty cycle ( look at the Cr mask in top of the page

• SiO2 etch with Cr mask on full wafer 6 min etch
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• SiO2 etch with Cr mask on wafer piece on Si carrier 6 min etch
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• SiO2 etch with Cr mask on wafer piece on Si carrier 6 min etch, H2:0sccm
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• SiO2 etch with Cr mask on wafer piece on Si carrier 6 min etch, H2:0sccm, O2:5sccm
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• SiO2 etch with Cr mask on wafer piece on Si carrier 6 min etch, H2:0sccm, C4F8:13sccm He:225sccm, Pressure:3.35mTorr
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• SiO2 etch with Cr mask on wafer piece on Si carrier 6 min etch, H2:0sccm, C4F8:13sccm He:225sccm, Pressure:3.35mTorr; platen power 150W, coil power:1200W
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• SiO2 etch with Cr mask on wafer piece on Si carrier 6 min etch, H2:0sccm, C4F8:13sccm He:215sccm O2:10sccm, Pressure:3.6mTorr; platen power 150W, coil power:1200W
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• SiO2 etch with Cr mask on wafer piece on Si carrier 6 min etch, H2:0sccm, C4F8:13sccm He:205sccm O2:20sccm, Pressure:3.6mTorr; platen power 150W, coil power:1200W
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• SiO2 etch with Cr mask on wafer piece on Si carrier 6 min etch, H2:0sccm, C4F8:13sccm He:215sccm O2:10sccm, Pressure:3.6mTorr; platen power 150W, coil power:1800W
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• SiO2 etch with Cr mask on wafer piece on Si carrier 6 min etch, H2:0sccm, C4F8:13sccm He:205sccm O2:20sccm, Pressure:3.6mTorr; platen power 150W, coil power:1800W
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  pitch 800 nm
  Top 461 nm
  @edge 437 nm
  bottom 402 nm
  height 916 nm
  height from edge 827 nm
  Cr left 83.5 nm
  selectivity 55.5

• SiO2 etch with Cr mask on wafer piece on Si carrier 6 min etch, H2:0sccm, C4F8:13sccm He:205sccm O2:20sccm, Pressure:3.6mTorr; platen power 100W, coil power:1200W
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  pitch 800 nm
  Top 444 nm
  bottom 374 nm
  height 718 nm
  Cr left 85 nm
  selectivity 48

• SiO2 etch with Cr mask on wafer piece on Si carrier 14 min etch (PLEASE DO NOT REPEAT THIS LONG TIME), H2:0sccm, C4F8:13sccm He:205sccm O2:20sccm, Pressure:3.6mTorr; platen power 100W, coil power:1200W
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• SiO2 etch with Cr mask on wafer piece on Si carrier 10 min etch, H2:0sccm, C4F8:13sccm He:205sccm O2:20sccm, Pressure:3.6mTorr; platen power 150W, coil power:1800W
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• SiO2 etch with Cr mask on wafer piece on Si carrier 14 min etch, EM:0/0 H2:0sccm, C4F8:13sccm He:205sccm O2:20sccm, Pressure:3.9mTorr; platen power 100W, coil power:1200W, the mask is removed by plasma ashing on top view and tilted view
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  tilt 30 degrees
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  tilt 30 degrees
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  tilt 20 degrees
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  tilt 20 degrees