Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 1 Chicane Deceleration – Qualifying a new technique to control energy contamination Nick White, John Chen, Chris Mulcahy, Sukanta Biswas, Russ Gwilliam

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 2 Introduction Implantation of high-current boron beams at 200eV for SDE with USJ Goal: Preserve the advantages of conventional implanters while meeting productivity requirements: Use of established source materials and technologies Accurate dosimetry Precise angle control Robust charging control Eliminate deep tails caused by energy contamination Quantify sources of variation

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 3 Figure shows 0.2, 0.5, 1.0 & 2.0 keV ion implants Energy Contamination during implantation can be observed in most of the implants 400 eV O 2 + was implemented for the lower energy implants whilst 700 eV was applied for the higher energy implants Lowest implant energies benefit from lower energy O 2 + 1E+15 1E+16 1E+17 1E+18 1E+19 1E+20 1E Depth / Angstroms Concentration / Atoms.cm -3 1E keV B 0.5 keV B 1.0 keV B 2.0 keV B ULE Boron and Energy Contamination Historical Data Earlier data compiled by Cascade.

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 4 Method

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 5 Chicane deceleration +5,800 V 6,000 eV 200 eV -Sending ions up a potential hill reduces their energy -Tortuous path removes particles with the wrong energy or charge 30:1 shown 4:1 to 30:1 available

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 6 Chicane

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 7 Beam currents used in these tests BF 2 current: 1.0 mA at 200eV 2.0 mA at 400eV 3.5 mA at 891eV Boron current: 2.5 mA at 200eV 4.5 mA at 1000eV Decel ratio from 10:1 to 30:1 (4:1 is available)

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 8 Direct measurement of angles in the beam Aperture plate Beam burns 150mm beyond plate

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 9 Beam Divergence and Angle Control Insignificant change in overall angles down to 200eV, but each beamlet spreads more at low energy.

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 10 Angular spread comes from thermal physics Lateral motion of beam ions in a beamlet is +/- 1680m/s max, or ~1160 m/s rms Ion source gas temperature is > 1500K Wall temperature measured at 1000K From the thermal motion of the ion source gas, the transverse rms velocity of the ions is > 700 m/s At 200 eV, ~2.3 degrees intrinsic angular spread is about the minimum possible. Use of plasma electron flood prevents blow-up m/s (for 200eV B) 2.3 degrees (measured) 1680 m/s (for 95%)

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 11 Effect of SIMS energy For this study we used 200eV O 2 + at 45 degrees, equivalent to ~70 eV O + at normal incidence.

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 12 Metrology We used 200eV O 2 + at 45 degrees, equivalent to 70 eV O + at normal incidence. The substrate must be fully amorphous beyond end- of-range. To probe for energy contamination, we compared bare wafers and 50% photoresist High doses of drift-mode 200eV boron unavailable Cannot compare with drift mode BF 2

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 13 Experimental Details Prime n-type wafers, 200mm Most wafers preamorphized 100keV Ge to 2e15 because we also investigated higher energies because if energy contamination was present, we did not want the tails to channel and be distorted Some coated 50% with photoresist Energy contamination from neutralization is proportional to pressure Outgassing from resist at high current must be evaluated Energy measured directly by voltmeter from ion source to endstation Only uncertainty is plasma potential in ion source.

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 14 Implant Matrix and Controls 891eV BF 2 has same velocity as 200eV B Surface oxide about 1.3 nm

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 15 Results

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 16 Boron 200eV 2.5 mA – raw data

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 17 Profile changes with dose

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 18 Saturation at 200eV? Retained dose by SIMS

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 19 Boron 200eV 2.5mA SIMS Profiles

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 20 Discussion of 200eV data First 0.5 nm: Surface is clean. Minimal oxide effects. Concentration as % of dose falls with dose nm Concentration is slightly higher with higher dose Ion beam mixing during implant >3 nm Effect of increased pressure is resolved Profile becomes ~0.23nm deeper >4 nm Channeling is distinct; level is approx 1.23% Range of channeled ions is ~4nm deeper for 0.1% of dose >10 nm No effect of pressure can be resolved Why does BF 2 have a lower background?

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 21 Discussion Possible Sources of profile shifts and deep tails: Channeling We used RBS to look for channeling Pilot experiments eliminated channeling as source of background variation Our amorphization was complete SIMS system background and SIMS knock-on BF 2 has a much lower background Does the fluorine inhibit SIMS knock-on? Higher energy beam components Neutralization close to exit of chicane

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 22 What contaminants get past the chicane? Zone of possible Energy contamination Ions can be neutralized within the chicane This process must occur within the exit zone if the contaminant is to reach the wafer The electric potentials limit the maximum energy contamination to a fraction of final energy Proportional to pressure

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 23 Highly resolved dopant shift due to PR outgassing -Obtained by subtracting SIMS from PR wafer from SIMS from bare wafer after re-normalizing -Dose on PR wafer was 5% lower due to beam neutralization and loss

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 24 USJ Implants using BF 2

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 25 USJ Implants using BF 2, smoothed

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 26 Conclusions: Chicane technique can deliver ~70 wph at 200eV B 5e14 with X j (unannealed) of < 7 nm Magnitude of energy contamination is ~22eV, or < 0.3 nm Channeling can modify the as-implanted profile by ~ 3nm Metrology must resolve 3nm! PAI required Chicane technique can deliver ~100 wph of 891eV BF 2 5e14 May have tighter profile and less diffusion PAI required Chicane technique can deliver ~33 wph for 200eV BF 2 5e14 with X j (unannealed) of < 5 nm Does not require PAI

Advanced Ion Beam Technology, Inc. A Hermes-Epitek Company Cascadescientific global analytical services 27 Acknowledgements: Implants and beam measurements: Ed Petersen Yap Han Chang SIMS analysis Neil Montgomery Paul Ebblewhite RBS analysis Chris Jeynes