La2O3 gate insulators prepared by atomic layer deposition: Optimal growth conditions and MgO/La2O3 stacks for improved metal-oxide-semiconductor characteristics

Abstract

The authors investigated the optimal growth conditions for atomic layer deposition of La2O3 using tris(iso-propylcyclopentadienyl) lanthanum, La(iPrCp)3, and H2O, and identified two necessary conditions for achieving self-limiting growth: A low growth temperature (Ts) of 150 °C–175 °C and an extremely long purging after the H2O feed. Low Ts was also preferable for improving the electrical properties of the metal-oxide-semiconductor devices such as the dielectric constant (k), leakage current, and effective mobility. As for the H2O feed time, a long feed resulted in increased interface-trap density, while a short feed resulted in increased leakage. An H2-plasma treatment inserted after the thin-La2O3 (0.5 nm) film growth reduced the leakage current by 3 orders of magnitude compared to the control sample. An MgO capping on the La2O3 remarkably increased the effective k value; however, it degraded the effective mobility. Transmission electron microscopy indicated that the k-value improvement by the MgO capping is due to suppression of La-silicate formation.

Effects of Annealing Ambient on the Characteristics of LaAlO3 Films Grown by Atomic Layer Deposition

“…Moreover, as shown in Fig. 4 , varying degrees of humps in the C-V curves could be observed, which may be caused by the existence of interfacial traps [ 26 , 27 ]. Compared with Fig.…”

Electrical Properties and Interfacial Issues of HfO2/Ge MIS Capacitors Characterized by the Thickness of La2O3 Interlayer

“…Besides, as the thickness of La 2 O 3 passivation layer increases, different degrees of frequency dispersion phenomenon at the weak inversion regions could be observed from the multi-frequency C-V curves in Figure 7, and the degrees of frequency dispersion phenomenon show a similar variation tendency with the anomalous humps in the C-V curves measured at 100 kHz. It has been reported that the existence of slow interface traps ( Q it ) should be responsible for the anomalous phenomenon at the weak inversion regions of C-V curves [26,27]. Considering this, the interface state density ( D it ) values of S1~S4 are discussed using the following relation of single-frequency approximation method through the forward swept C-V and G-V curves [28]:Dit=2qAGmaxω[(GmaxωCox)2+(1−CmaxCox)2] where q is the elementary charge (1.602 × 10 −19 C), A is the area of the top electrode, C ox is the gate oxide capacitance as defined in Equation (1), G max is the peak value of G-V curve, and C max is the capacitance corresponding to G max at the same gate applied voltage.…”

In situ infrared spectroscopy during La2O3 atomic layer deposition using La(iPrCp)3 and H2O

“…[7][8][9] Another is that deposition processes for La 2 O 3 have been problematic. Numerous studies of atomic layer deposition (ALD) of La 2 O 3 can be found in the literature, and to date, La cyclopentadienyls (Cp), [10][11][12][13][14][15][16][17][18][19] P-diketonates, 9 silylamides, 20 amidinates, 21,22 and formidinates 23 have all been examined along with H 2 O, 10,13,[15][16][17][18][19][20][21][22][23] O 3 , 9,14 and O 2 plasmas 12,17 for oxidation. Despite this work, there has been limited success in developing a chemistry that can provide high-purity La 2 O 3 by self-limiting reactions as desired for ALD.…”

“…18 Other work, in contrast, found that only low-temperature deposition (< 200 °C) resulted in self-limiting growth. 11,13 For Cp-type La compounds, the chemical insights obtainable from studying the effect of process variables on the growth of films appears to be limited.…”

“…We use in situ infrared (IR) spectroscopy to observe surface species present during the cyclical exposure of La( i PrCp) 3 and H 2 O under flow conditions. We utilize two temperatures: the lower temperature (160 °C) examines conditions suggested by Yasuda and co-workers 11,13 and the higher one (350 °C) is similar to those used by other researchers. 15,16 At low temperature, we find that carbonate formation occurs during each pulse but not during the purges, which indicates carbonates likely are not the result of intra-ligand, inter-ligand, or ligand-surface reactions.…”