In situ real-time and ex situ spectroscopic analysis of Al2O3 films prepared by plasma enhanced atomic layer deposition

Abstract

In situ real-time ellipsometry (irtE) with a very high time resolution of 24 ms was applied to monitor the inductively coupled plasma enhanced atomic layer deposition (ALD) process of Al2O3 thin films to precisely resolve each step of the ALD process and its complete cycle. The influence of plasma power, plasma pulse duration, and deposition temperature on the film growth characteristics was investigated. Ex situ ellipsometry [UV-VIS-NIR-SE (ultraviolet-visible-nearinfrared-spectroscopic ellipsometry) and IR-SE (infrared spectroscopic ellipsometry)] and x-ray photoelectron spectroscopy revealed the bulk properties (thickness, refractive index, chemical composition, and carbon incorporation) of the films, which together with the in situ results are compared to those of the films prepared by thermal ALD (T-ALD). The ICPEALD (inductively coupled plasma enhanced ALD) films were deposited at substrate temperatures between 80 and 250 °C and the role of plasma power (50–300 W) and its pulse duration (1–20 s) was investigated at 250 °C. The reference T-ALD layers were prepared at 200 °C. The ICPEALD process of Al2O3 shows an increased growth rate, and the produced films exhibit higher carbon contaminations than the T-ALD Al2O3 films. Plasma pulse times of up to 15 s further increase the content of carbon and CH species; at the same time, the refractive index decreases. The optical properties of ICPEALD deposited Al2O3 films are comparable with those of the T-ALD films for low plasma power and short plasma pulse durations. For the ICPEALD films, UV absorption is found and it is dependent on the deposition parameters. irtE resolves process effects that correlate with the bulk properties of Al2O3, such as impurities and oxygen deficiencies.

Toward controlling the Al2O3/ZnO interface properties by in situ ALD preparation

“…77 The weak peak located at a BE of 1019.2 ± 0.1 eV and the strong peak at 1020.5 ± 0.1 eV are attributed to Zn-Al and Zn-Zn bonds, respectively. The distinct peak at an energy position of 1021.7 ± 0.1 eV corresponds to Zn-O; the weak signal appearing at a higher BE of 1023.8 ± 0.1 eV is assigned to defects or most likely O-H groups, 47 consistent with the represented O 1s decomposition (see Fig. 3).…”

“…The peak at a higher BE of 533.0 ± 0.5 eV corresponds to defects, vacancies, or, most likely, hydroxyl groups (O–H bonds). 47 In addition, for ZnO the weak signal centered at 529.5 ± 0.1 eV is tentatively attributed to excess oxygen and probably arises from incomplete purging after the H 2 O co-reaction within the TALD of ZnO. 52 The formation of O–H groups originates from the deposition process, in which the H 2 O oxidant in TALD and/or O 2 plasma with higher oxidation potential in the PEALD process introduce side products as previously observed.…”

“…Al 2 O 3 /ZnO films were deposited on a n-type (100)-oriented silicon substrate in a SI ALD reactor (SENTECH Instruments GmbH) 46 equipped with an ellipsometer for in situ ALD real-time monitoring (SENTECH, ALD Real Time Monitor). 47 The used multifunctional ALD system provides two different operation modes of either thermal ALD or PEALD. In this study, the TALD process was employed for the deposition of a 59 nm thick ZnO layer on top of the Si substrate using a diethylzinc (DEZ) precursor and H 2 O vapor.…”

“…Data from in situ ellipsometry 47 taken routinely during the growth of the films were used to determine the film thickness and homogeneity ( cf. ESI section 1†).…”

Plasma-Enhanced Atomic Layer Deposition of HfO2 with Substrate Biasing: Thin Films for High-Reflective Mirrors

“…They reported significantly higher GPC of HfO 2 thin films deposited at low deposition temperature with TDMAH than films deposited with TDMACpH precursors. A high GPC can also be due to high-density plasma generated due to the uniquely designed planar triple spiral antenna (PTSA) inductively coupled plasma (ICP) source of the SILAYO system. , On increasing bias voltage, the HfO 2 deposited in the SILAYO system shows a three-stage behavior. Initially, on increasing the substrate bias to −3 V, the GPC increases slightly.…”