Film Uniformity in Atomic Layer Deposition

Abstract

The sources of non-uniformity in thin films produced using atomic layer deposition (ALD) have been investigated by reviewing the mechanical hardware of ALD reactors, precursors, and the by-products of surface reactions. The most common causes of non-uniformity are overlapping pulses, thermal self-decomposition of precursors, and non-uniform gas distribution. Less studied, however, are the consequences of downstream surface reactions of gaseous by-products. In particular, titanium nitride films have been found to be significantly less uniform than those of transition metal oxides deposited from metal halides. The influence of reaction by-products on the TiN film growth has been studied by comparing the deposition in the cross-flow and showerhead style reactors. Finally, the sources of non-uniformity in plasma enhanced (PE) ALD are illustrated by studying the TiN deposition process.

Antireflection Coatings for Strongly Curved Glass Lenses by Atomic Layer Deposition

“…The processes in the Sunale R200 ALD reactor result in a thickness non-uniformity of about ±2.1% for Al 2 O 3 and ±4.0% for Ta 2 O 5 , see Table 2. Elers et al [39] discussed the sources of non-uniformities in ALD processes including overlapping precursor pulses due to short purge times, death pockets, etc., but also non-uniform gas and temperature distributions in the reactor chamber. Figure 2a shows the surface mapping of a 200 mm wafer after thermal Al 2 O 3 ALD process using 1156 cycles (TMA + H 2 O).…”

Remote plasma enhanced atomic layer deposition of ZnO for thin film electronic applications

“…This increase is due to the insufficient Ar purge, which leads to the simultaneous presence of both precursors in the gas phase near the substrate resulting in chemical vapor deposition (CVD) type growth. CVD growth reactions can lead to particle formation such as carbon impurity which degrades device performance [20]. Very low plasma pressure during deposition (<50 mTorr) also results in very high carbon concentration.…”

“…This is called thermal ALD and has been extensively studied and can be considered as a model system for ALD [6][7][8][9][10]. Recently, plasma assisted ALD method has been explored [11][12][13][14][15][16][17][18][19][20] and it is found that the use of plasma species as reactants allows more freedom in processing conditions and wider range of material properties compared with the conventional thermal ALD. The use of plasma also significantly reduced the OH impurity which affect the conductivity of the semiconductor film and induce defects in dielectric materials [16].…”

“…The use of plasma also significantly reduced the OH impurity which affect the conductivity of the semiconductor film and induce defects in dielectric materials [16]. In the advent of this, remote PEALD has been widely reported to form high quality dielectric films, particularly for high-k dielectric materials [18][19][20]. Very few have reported using remote PEALD for semiconductor layer especially ZnO film [11,12].…”

Plasma-Enhanced Atomic Layer Deposition (PEALD) of TiN using the Organic Precursor Tetrakis(ethylmethylamido)Titanium (TEMAT)

“…The most commonly used precursor for ALD TiN is titanium tetrachloride (TiCl 4 ), together with ammonia (NH 3 ) [4][5][6]. However, growth rates are low and the hydrochloric acid (HCl) byproduct may cause selfetching [7], copper pitting [4][5] and/or reactive site poisoning [5,7]. The drawbacks of using TiCl 4 precursor has lead to research into metalorganic precursors like tetrakis(dimethylamido)titanium (TDMAT) [8][9], tetrakis(ethylmethylamido)titanium (TEMAT) [8], and tetrakis(diethylamido)titanium (TDEAT) [8,10].…”