High‐Throughput Atomic Layer Deposition of P‐Type SnO Thin Film Transistors Using Tin(II)bis(tert‐amyloxide)

Abstract

interface engineering, in addition to effective doping strategies involving scalable and highly precise processing technology on large areas, have been deemed necessary to advance the development of p-type oxide materials. [5] Atomic layer deposition (ALD) is a layerby-layer thin film deposition method that allows for atomic-level control over thickness and material/interface properties, resulting in conformal and uniform deposition over large areas, and high aspect ratio substrates. [9,10] Such unique features stem from the fact that ALD relies on cyclic and self-limiting chemical reactions between the substrate surface and alternating exposure to a precursor and coreactant. [11] Recently, mobilities of 0.5, 1, and 6 cm 2 V -1 s -1 and on-current/off-current (I On /I Off ) ratios of 10 4 , 10 6 , and 10 2 have been reported for SnO deposited by temporal ALD, using bis(1-dimethylamino-2-methyl-2-butoxy)tin, Sn(dmamb) 2 , bis(1-dimethylamino-2-methyl-2-propoxy)tin Sn(dmamp) 2 , and N,N′-tert-butyl-1,1-dimethylethylenediamine stannylene(II), [12][13][14] respectively, as the Sn precursor with an H 2 O coreactant. Whilst these results are promising for the development of p-type transistors by ALD, the low deposition rate of temporal ALD, coupled with the low reactivity of current precursor technology may ultimately hinder large area industrial applications. The development of high deposition rate processes (i.e., high growth per cycle (GPC) and/or short cycle time) with atomic-level control, suitable for large-area applications, are therefore of paramount importance. High-throughput ALD can be obtained by improving two major aspects of the process; i) upgrades in deposition hardware (i.e., deposition equipment and methodology), which have the potential to reduce the overall cycle time and or ii) improvement of the underpinning chemistries involved (i.e., the development of novel and chemically optimized precursors) which can increase the GPC, and shorten overall cycle time, thus increasing deposition rate by harnessing higher reactivity with the substrate surface and coreactant.In conventional temporal ALD substrates are exposed to alternate precursor and coreactant doses which are separated in time by extensive purge steps to eliminate precursor mixing and afford self-limited deposition in a cyclic fashion. In contrast to temporal ALD, spatial ALD (sALD) relies on Spatial atomic layer deposition (sALD) of p-type SnO is demonstrated using a novel liquid ALD precursor, tin(II)-bis(tert-amyloxide), Sn(TAA) 2 , and H 2 O as the coreactant in a process which shows an increased deposition rate when compared to conventional temporal ALD. Compared to previously reported temporal ALD chemistries for the deposition of SnO, deposition rates of up to 19.5 times higher are obtained using Sn(TAA) 2 as a precursor in combination with atmospheric pressure sALD. Growths per cycle of 0.55 and 0.09 Å are measured at deposition temperatures of 100 and 210 °C, respectively. Common-gate thin film transistors (TFTs), fabricated using sAL...

Atmospheric-pressure plasma-enhanced spatial atomic layer deposition of silicon nitride at low temperature

“…In spatial mode, the ALD precursor and co-reactant are continuously dosed on a reciprocating or rotating substrate, and no extensive chamber-purge steps are needed to keep the precursor and co-reactant from reacting in the gas-phase (CVD-like reaction). Therefore much shorter ALD cycle times can be achieved [14]. Most of the literature on spatial ALD concerns metal oxides produced either by thermal or plasma-enhanced spatial ALD, [4,[15][16][17] and only a few examples have been published for spatial-ALD of metallic films (Ag and Cu) [18,19].…”

Room-Temperature Fabrication of p-Type SnO Semiconductors Using Ion-Beam-Assisted Deposition

“…To date, the feasibility of p-type conductivity in SnO has been experimentally demonstrated using several techniques, including reactive magnetron sputtering, ,, atomic layer deposition, , pulsed laser deposition, ,, e-beam evaporation, ,, and solution process. , However, the performance of the prepared SnO still varies greatly depending on the type of sample and the resulting crystal structure. For bulk SnO polycrystals, a hole mobility as high as 30.0 cm 2 V –1 s –1 has been reported .…”

“…Yet, this aspect needs to be addressed in order for the p-type oxides to be technologically commensurate with their n-type counterparts. 4 To date, the feasibility of p-type conductivity in SnO has been experimentally demonstrated using several techniques, including reactive magnetron sputtering, 14,15,20 atomic layer deposition, 5,21 pulsed laser deposition, 10,12,22 e-beam evaporation, 6,23,24 and solution process. 13,25 However, the performance of the prepared SnO still varies greatly depending on the type of sample and the resulting crystal structure.…”

SnO deposition via water based ALD employing tin(ii) formamidinate: precursor characterization and process development

“…25 Recently, Mameli et al reported a high-throughput spatial ALD process for SnO using tin(II) bis(tert-amyloxide) ([Sn(TAA) 2 ]) and water with GPC values of 0.09 Å to 0.55 Å. 26 It is thus apparent that the choice of the precursor is crucial for the successful process development and process characteristics of SnO films. Rational design of the precursor ligand sphere can significantly tune physicochemical parameters like reactivity, volatilization temperature (T vol ) and aggregation state and can be tailored towards the desired properties for the respective processes.…”

“…25 Recently, Mameli et al reported a high-throughput spatial ALD process for SnO using tin( ii ) bis( tert -amyloxide) ([Sn(TAA) 2 ]) and water with GPC values of 0.09 Å to 0.55 Å. 26…”