Spatial ALD Ismo Heikkinen 10.3.2016

From Temporal to Spatial ALD ALD has unique advantages: precise film thickness control, highly conformal coatings, low T processing… …but batch ALD is slow Solution: separate the precursors in space rather than in time Poodt, P et al. Spatial atomic layer deposition: A route towards further industrialization of atomic layer deposition. J. Vac. Sci. Tech. A, 2012, 30, 010802. Muños-Rojas D.; et al. Spatial atmospheric atomic layer deposition: a new laboratory and industrial tool for low-cost photovoltaics. Mater. Horiz. 2014, 1, 314.

How does Spatial ALD work? In SALD the sample is moved under precursor and purge zones to reproduce the ALD cycle Cycle time notably reduced, film quality maintained 5-10 times faster than temporal ALD Poodt, P et al. Spatial atomic layer deposition: A route towards further industrialization of atomic layer deposition. J. Vac. Sci. Tech. A, 2012, 30, 010802. Muños-Rojas D.; et al. Spatial atmospheric atomic layer deposition: a new laboratory and industrial tool for low-cost photovoltaics. Mater. Horiz. 2014, 1, 314.

Spatial ALD systems Poodt, P et al. Spatial atomic layer deposition: A route towards further industrialization of atomic layer deposition. J. Vac. Sci. Tech. A, 2012, 30, 010802 Maydannik P.S. et al. Roll-to-roll atomic layer deposition process for flexible electronics encapsulation applications. J. Vac. Sci. Tech. A, 2014, 32, 051603

SALD in practice Photovoltaics: Encapsulation and moisture barriers: Passivation of c-Si solar cells with Al2O3 Buffer layers for CIGS solar cells Antireflection coatings Encapsulation and moisture barriers: Flexible electronics OLEDs Packaging …and emerging applications Illiberi A. et al. Spatial Atmospheric Atomic Layer Deposition of AlxZn1-xO. ACS Appl. Mater. Interfaces 2013, 5, 13124-13128. Choi H. et al. Fast spatial atomic layer deposition of Al2O3 at low temperature (<100 °C) as a gas permeation barrier for flexible organic light-emitting diode displays. J. Vac. Sci. Tech. A, 2016, 34, 01A121. Illiberi A. et al. Spatial Atmospheric ALD of functional layers for CIGS Solar Cells. ECS Transactions, 2015, 69 (7), 31-37.

Why go Spatial? Conclusions Advantages High throughput in nm/s for high-quality films Efficient precursor utilization (growth only on the substrate) Disadvantages Limited to 2-dimensional substrates (glass, Si wafers, plastic and metal sheets…) Not so many processes available as with temporal ALD

Questions are welcome!

Information slides - Basics of Spatial ALD Temporal ALD is financially viable in large batches, but: Sensitive samples (such as OLEDs) might be damaged by long preheat times A big amount of expensive samples in one big batch is a huge risk Spatial ALD reduces these risks and increases the throughput in nm/min Materials deposited with Spatial ALD: Al2O3, TiO2, ZnO, ZnS, Al:ZnO, ZnOxSy… Poodt, P et al. Spatial atomic layer deposition: A route towards further industrialization of atomic layer deposition. J. Vac. Sci. Tech. A, 2012, 30, 010802. Muños-Rojas D.; et al. Spatial atmospheric atomic layer deposition: a new laboratory and industrial tool for low-cost photovoltaics. Mater. Horiz. 2014, 1, 314.

Basics of Spatial ALD Spatial ALD devices are based on: Spatially separated precursor zones Moving substrate and/or a moving gas distribution head Inert gas barrier between half-reaction zones to prevent the mixing of precursors No need for purging a reactor chamber -> much faster ALD cycles than in temporal ALD From tens of seconds to less than one second SALD 5-10 times faster than temporal ALD Limitation to 2D materials is a big downside Muños-Rojas D.; et al. Spatial atmospheric atomic layer deposition: a new laboratory and industrial tool for low-cost photovoltaics. Mater. Horiz. 2014, 1, 314. Choi H. et al. Fast spatial atomic layer deposition of Al2O3 at low temperature (<100 °C) as a gas permeation barrier for flexible organic light-emitting diode displays. J. Vac. Sci. Tech. A, 2016, 34, 01A121.

How does Spatial ALD work? Poodt, P et al. Spatial atomic layer deposition: A route towards further industrialization of atomic layer deposition. J. Vac. Sci. Tech. A, 2012, 30, 010802.

Different approaches to SALD Rotary SALD Sample is e.g. a Si wafer which rotates and is sequentially exposed to precursors Produces a ring-shaped thin film coating View from top of the reactor -> Poodt, P et al. Spatial atomic layer deposition: A route towards further industrialization of atomic layer deposition. J. Vac. Sci. Tech. A, 2012, 30, 010802.

Different approaches to SALD Roll-to-roll SALD Flexible substrate is transported through the coating area Can have a rotating gas injection system which makes the ALD cycle faster Applications in encapsulating flexible electronics and functionalizing textiles Maydannik P.S. et al. Roll-to-roll atomic layer deposition process for flexible electronics encapsulation applications. J. Vac. Sci. Tech. A, 2014, 32, 051603.

Different approaches to SALD Close proximity SALD Distance between the gas injector and the substrate in the order of 100 μm Possibility to accurately coat small areas and detailed structures Muños-Rojas D.; et al. Spatial atmospheric atomic layer deposition: a new laboratory and industrial tool for low-cost photovoltaics. Mater. Horiz. 2014, 1, 314. Muñoz-Rojas D. et al. High-speed atmospheric atomic layer deposition of ultrathin amorphous TiO2 blocking layers at100 ° C for inverted bulk heterojunction solar cells. Prog. Photovolt. Res. Appl. 2013, 21, 393-400

Different approaches to SALD SALD for wafers, sheets and glass substrates From one to few mm between the sample and the gas injector Large substrate size is possible, e.g. 400 x 500 mm2 Choi H. et al. Fast spatial atomic layer deposition of Al2O3 at low temperature (<100 °C) as a gas permeation barrier for flexible organic light-emitting diode displays. J. Vac. Sci. Tech. A, 2016, 34, 01A121. Beneq Oy, Espoo, Finland. Size matters (and speed too), HIGH-THROUGHPUT THIN FILM COATING WITH LARGE-AREA SPATIAL ALD EQUIPMENT. Blog post, 04.02.2016. Available: http://www.beneq.com/blog/201602/size-matters-and-speed-too.html. Cited 9.3.2016

References Muños-Rojas D.; et al. Spatial atmospheric atomic layer deposition: a new laboratory and industrial tool for low-cost photovoltaics. Mater. Horiz. 2014, 1, 314. Poodt, P et al. Spatial atomic layer deposition: A route towards further industrialization of atomic layer deposition. J. Vac. Sci. Tech. A, 2012, 30, 010802. Illiberi A. et al. Spatial Atmospheric Atomic Layer Deposition of AlxZn1-xO. ACS Appl. Mater. Interfaces 2013, 5, 13124-13128. Choi H. et al. Fast spatial atomic layer deposition of Al2O3 at low temperature (<100 °C) as a gas permeation barrier for flexible organic light-emitting diode displays. J. Vac. Sci. Tech. A, 2016, 34, 01A121. Maydannik P.S. et al. Roll-to-roll atomic layer deposition process for flexible electronics encapsulation applications. J. Vac. Sci. Tech. A, 2014, 32, 051603. Illiberi A. et al. Spatial Atmospheric ALD of functional layers for CIGS Solar Cells. ECS Transactions, 2015, 69 (7), 31-37.

References Muñoz-Rojas D. et al. High-speed atmospheric atomic layer deposition of ultrathin amorphous TiO2 blocking layers at 100 ° C for inverted bulk heterojunction solar cells. Prog. Photovolt. Res. Appl. 2013, 21, 393-400 Beneq Oy, Espoo, Finland. Size matters (and speed too), HIGH-THROUGHPUT THIN FILM COATING WITH LARGE-AREA SPATIAL ALD EQUIPMENT. Blog post, 04.02.2016. Available: http://www.beneq.com/blog/201602/size-matters-and-speed-too.html. Cited 9.3.2016