Area-selective atomic layer deposition for self-aligned fabrication

Transcription

1 Area-selective atomic layer deposition for self-aligned fabrication Adrie Mackus Eindhoven University

2 Area-selective ALD for bottom-up processing Top-down Bottom-up Building technology Excavated from solid rock Bricks as building blocks Semiconductor fabrication Subtractive Additive processing 2 / 21 Adrie Mackus TU/e

3 What is area-selective ALD? HOPG Haider et al., RSC Adv. 6, (2016) Lee et al., Nano Lett. 13, 457 (2013) Weber et al., Nanotechnology 26, (2015) Kim et al., ACS Nano 10, 4451 (2016) Cao et al., Small (2017) Area-selective ALD = bottom-up fabrication by deposition of atoms at specific locations Lecture Richard Feynman There is plenty of room at the bottom What could we do with layered structures with just the right layers? What would the properties of materials be if we could really arrange the atoms the way we want them?.. when we have some control of the arrangement of things on small scale, we will get an enormously greater range of possible properties that substances can have 3 / 21 Richard Feynman, American Physical Society meeting, Adrie Mackus TU/e Caltech, Dec

4 The challenge of alignment at the nanoscale Patterned sample Alignment Resist film patterned by lithography After etching + resist strip Edge placement error Alignment becomes extremely challenging in future technology nodes 4 / 21 Adrie Mackus TU/e

5 Motivation: Enabling self-aligned fabrication Patterned sample Selective deposition Area-selective ALD: Fewer lithography and etch steps Eliminates alignment issues Self-aligned fabrication scheme 4 / 21 Adrie Mackus TU/e

6 Extension of area-selective ALD to plasma ALD 30 Al 2 O 3 Thickness (nm) SiO 2 Ta 2 O 5 ZnO 2 TiO 2 TiN TaN Thermal ALD processes are typically used as starting point for area-selective ALD Plasmas destructively interact with a self-assembled monolayer (SAM) Plasma-assisted ALD processes readily nucleate on most substrates ALD Cycles Development of area-selective ALD approaches based on plasma-assisted ALD processes will extend the set of materials that can be deposited selectively 5 / 21 Adrie Mackus TU/e Lee et al., J. Korean Phys. Soc. 56, 104 (2010)

7 Outline Area-selective ALD of SiO 2 using inhibitors in ABC-type cycles Proof-of-principle results In-situ Fourier transform infrared spectroscopy Area-selective ALD of Ru combination with selective etching Selective etching of Ru Demonstration on patterned samples Conclusions 6 / 21 Adrie Mackus TU/e

8 Regeneration of self-assembled monolayers SAM molecule Reference Re-dosing Results in area-selective ALD of 3 x thicker ZnO films 7 / 21 Adrie Mackus TU/e Minaye Hashemi and Bent, Adv. Mater. Interfaces 3, (2016)

9 Area-selective ALD using inhibitors in ABC-type cycles Growth area Non-growth area A. Inhibitor selectively adsorbs on the non-growth area B. Adsorbed inhibitor blocks the adsorption of the precursor C. Inhibitor molecules and precursor ligands are removed during co-reactant exposure Benefit: compatible with plasma-assisted or ozone-based ALD 8 / 21 Adrie Mackus TU/e Mameli et al., ACS Nano 11, 9303 (2013)

10 Area-selective growth of SiO 2 A= Acetylacetone (Hacac) B = BDEAS C = O 2 plasma Thickness (nm) Fast nucleation on SiO 2, SiN x, GeO 2, WO x Delay of cycles on HfO 2, TiO 2, Al 2 O 3 Unique selectivity: distinguishes between different metal oxide starting surfaces SiO 2 SiN x GeO 2 WO x HfO 2 TiO 2 Al 2 O 3 Number of cycles 9 / 21 Adrie Mackus TU/e Mameli et al., ACS Nano 11, 9303 (2013)

11 Sub-cycle ellipsometry data: case of Al 2 O 3 and SiO 2 A= Acetylacetone (Hacac) B = BDEAS Al 2 O 3 Apparent thickness (nm) AC cycles C = O 2 plasma SiO 2 Selective adsorption of Hacac on Al 2 O 3 and removal by O 2 plasma Apparent thickness (nm) Number of cycles 10 / 21 Adrie Mackus TU/e Mameli et al., ACS Nano 11, 9303 (2013)

12 Sub-cycle ellipsometry data: case of Al 2 O 3 and SiO 2 A= Acetylacetone (Hacac) B = BDEAS B = BDEAS Al 2 O 3 Apparent thickness (nm) ABC cycles C = O 2 plasma Adsorbed Hacac on Al 2 O 3 blocks adsorption of BDEAS SiO 2 Apparent thickness (nm) Number of cycles 0.09 nm/cycle 10 / 21 Adrie Mackus TU/e Mameli et al., ACS Nano 11, 9303 (2013)

13 Sub-cycle ellipsometry data: case of Al 2 O 3 and SiO 2 B = BDEAS B = BDEAS Al 2 O 3 Apparent thickness (nm) BC cycles C = O 2 plasma Growth rate equal to ABC cycles on SiO 2 SiO 2 Apparent thickness (nm) Number of cycles 0.09 nm/cycle 10 / 21 Adrie Mackus TU/e Mameli et al., ACS Nano 11, 9303 (2013)

14 In-situ Fourier transform infrared spectroscopy SiO 2 Al 2 O A: Hacac Hacac Absorbance A: Hacac B: BDEAS B: BDEAS C-H Si-H C-H Si-H Hacac Wavenumber (cm -1 ) Wavenumber (cm -1 ) Almost no adsorption of Hacac on SiO 2 Unrestricted adsorption of BDEAS Hacac adsorbs on Al 2 O 3 BDEAS adsorption is blocked by Hacac 11 / 21 Adrie Mackus TU/e Mameli et al., ACS Nano 11, 9303 (2013)

15 TOF-SIMS on Al 2 O 3 /GeO 2 patterned samples Ge + Al + Al 2 O 3 patterned on GeO 2 substrate. 15 ABC-type cycles of SiO 2 carried out Si + Intensity (a.u.) Ge + Al + Si + TOF-SIMS demonstrates: SiO 2 growth on GeO 2 regions. Almost no SiO 2 ALD observed on Al 2 O 3 regions Distance ( m) 12 / 21 Adrie Mackus TU/e Mameli et al., ACS Nano 11, 9303 (2013)

16 Outline Area-selective ALD of SiO 2 using inhibitors in ABC process Proof-of-principle In-situ Fourier transform infrared spectroscopy Area-selective ALD of Ru combination with selective etching Selective etching of Ru Demonstration on patterned samples Conclusions 13 / 21 Adrie Mackus TU/e

17 Thickness Main challenge: achieve high selectivity Metal Metal Oxide SiO 2 -coated TEM windows 500 cycles Ru ALD 275 o C 225 o C 150 o C Number of cycles It is extremely challenging to obtain area-selective ALD with a high selectivity due to growth initiation at defects and impurities Focus on metal-on-metal deposition, i.e. area-selective ALD of Ru Potential solution: combine area-selective ALD with selective etching 14 / 21 Adrie Mackus TU/e Vallat et al., J. Vac. Sci. Technol. A 35, 01B104 (2017)

18 Thickness Combination of ALD with selective etching Metal Oxide Number of cycles Starting point: deposition occurs at a faster rate on the metal surface An etch step is performed to remove any deposited atoms from metal oxide surface Supercycle is repeated until the desired thickness is reached Etch step should be self-limiting to preserve conformality and thickness control 15 / 21 Adrie Mackus TU/e

19 Etching of Ru ABC-type ALD cycles Etch cycle Ru Oxide O 3 or O 2 plasma O 3 or O 2 plasma RuO 2 Ru Oxide RuO 4 RuO 4 Supercycle ABC-type ALD cycle: A. (ethylbenzene)-(1,3-cyclohexadiene)ru(0) precursor B. O 2 gas C. H 2 gas Etch cycle: O 2 plasma + H 2 gas Ru can be etched using an O 3 or O 2 plasma: RuO 4 formed as volatile product O 3 does not etch RuO 2 Ru etching might be self-limiting Supercycle recipe developed 16 / 21 Adrie Mackus TU/e Nakahara et al. J. Vac. Sci. Technol. B, 19, 6 (2001) Hsu et al. J. Vac. Sci. Technol. B, 24, 1 (2006)

20 Ru ALD supercycle results In-situ spectroscopic ellipsometry Ru etch cycle after every 100 ALD cycles 0.02 nm etch 15 s O 2 plasma required to eliminate growth on SiO 2 O 2 plasma etch saturates (at 0.08 nm per step) 0.08 nm etch 0.08 nm etch 17 / 21 Adrie Mackus TU/e

21 Demonstration of selectivity Patterning of Pt seed layers using electron beam induced deposition (EBID) 500 cycles Ru ABC ALD 500 cycles + 3 min O 2 plasma etch 500 Ru cycles 15 s O 2 plasma etch every 100 cycles nm nm nm nm nm nm Negligible Ru deposition on SiO 2 observed when using supercycles 18 / 21 Adrie Mackus TU/e

22 ALD for semiconductor fabrication Key ALD-enabled innovations in semiconductor fabrication Area-selective ALD for self-aligned fabrication has the potential to become the next ALD-enabled innovation in semiconductor fabrication 19 / 21 Adrie Mackus TU/e

23 Conclusions Area-selective ALD will enable self-aligned fabrication in future technology nodes New approach developed for area-selective ALD based on selective adsorption of inhibitor molecules in ABC-type cycles Supercycles of Ru ALD and O 2 plasma etching allow for area-selective ALD of Ru with high selectivity Focus in area-selective ALD community is shifting: Deactivation of growth prior to deposition Adding steps during deposition to improve selectivity 20 / 21 Adrie Mackus TU/e

24 Acknowledgements Area-selective ALD team Marc Merkx Alfredo Mameli Sonali Chopra (UT Austin) Nick Thissen Fred Roozeboom Erwin Kessels Plasma & Materials Processing group 21 / 21 Adrie Mackus TU/e