Abschlussarbeiten - Master
Atomic Level Processing for Self-aligned Patterning using CCP Plasma ALD and ALE
Art der Abschlussarbeit
Master
Autoren
- Thakur, Abhiskekkumar
Betreuer
- Prof. Dr. rer. nat. Johann Wolfgang Bartha
- Dr.-Ing. Martin Knaut
Weitere Betreuer
Dr. J. Sundqvist (Fh IKTS)
Abstract
Atomic layer deposition (ALD) based self-aligned multiple patterning (SAxP) has been the key process to continued chip scaling. SAxP demands plasma ALD for low temperature and conformal deposition of spacers on photoresist features for the subsequent etch based pitch splitting. Moreover, ALD is limited by low throughput that can be improved by raising the growth per cycle (GPC), using new ALD precursor, performing batch ALD or fast Spatial ALD, shrinking the ALD cycle length, or omitting purge steps to attain the shortest possible ALD cycle. Today’s latest and highly productive platforms facilitate very fast wafer transport in and out of the ALD chambers. Current 300mm ALD chambers for high volume manufacturing are mainly top-down or cross-flow single wafer chambers, vertical batch furnaces, or spatial ALD chambers.
At sub-10nm process nodes, the semiconductor industry is in dire need of atomic layer etching (ALE) as well to meet the tightening requirement for etch depth precision, post-etch roughness, and etch uniformity. Therefore, the next generation SAxP technology based on single chamber ALD and ALE processing necessitate ALE, too, to satisfy productivity and thermal budget prerequisites.
In our research during the thesis work on developing fast plasma ALD process, we used top down gas flow via showerhead to ignite capacitively coupled plasma (CCP) using 60MHz RF source in Applied Materials 300mm HART IV chamber. The chamber was modified to attain ultra-short (≤10ms) ALD precursor pulses along with very good uniformity using a ring injector with integrated de Laval nozzles enabling high speed, all-round precursor injection across the wafer. We shortlisted the TMA-O2 plasma ALD process to deposit Al2O3 for the hardware development and the productivity benchmarking.
Initially we used a single capillary injector for plasma ALD of Al2O3 at room temperature (30°C), wherein we shrunk the TMA pulse length from 2000ms down to 15ms maintaining the constant 1.7 Å GPC (Fig. 1), which confirmed the self-limiting nature of the TMA half-reaction. With the de Laval ring injector the saturation started at 10ms of TMA pulse length (Fig. 2), which is the tested switching limit of the electro-pneumatic ALD valve. The process linearity (Fig. 3) and the saturation curve indicated the ALD nature of the process. For 50ms of TMA pulse, a wide ALD temperature window (30-120°C) with constant 1.4 Å GPC was extracted (Fig. 4). We also achieved very good film growth uniformity across the entire 300mm Si substrate wafer with 50ms of TMA pulse (Fig. 5). XPS analysis of the deposited Al2O3 indicated that the film deposited at 120°C were more oxidized than the films at 30°C with the single injector. However, the elemental composition of films deposited with TMA pulse of 10ms vs. 50ms was indistinguishable. A surface carbon contamination was observed due to the wafer exposure to the outer atmosphere post processing. In addition, angular XPS depth profiling revealed considerable amounts of carbon in the “bulk of the film” as well.
At sub-10nm process nodes, the semiconductor industry is in dire need of atomic layer etching (ALE) as well to meet the tightening requirement for etch depth precision, post-etch roughness, and etch uniformity. Therefore, the next generation SAxP technology based on single chamber ALD and ALE processing necessitate ALE, too, to satisfy productivity and thermal budget prerequisites.
In our research during the thesis work on developing fast plasma ALD process, we used top down gas flow via showerhead to ignite capacitively coupled plasma (CCP) using 60MHz RF source in Applied Materials 300mm HART IV chamber. The chamber was modified to attain ultra-short (≤10ms) ALD precursor pulses along with very good uniformity using a ring injector with integrated de Laval nozzles enabling high speed, all-round precursor injection across the wafer. We shortlisted the TMA-O2 plasma ALD process to deposit Al2O3 for the hardware development and the productivity benchmarking.
Initially we used a single capillary injector for plasma ALD of Al2O3 at room temperature (30°C), wherein we shrunk the TMA pulse length from 2000ms down to 15ms maintaining the constant 1.7 Å GPC (Fig. 1), which confirmed the self-limiting nature of the TMA half-reaction. With the de Laval ring injector the saturation started at 10ms of TMA pulse length (Fig. 2), which is the tested switching limit of the electro-pneumatic ALD valve. The process linearity (Fig. 3) and the saturation curve indicated the ALD nature of the process. For 50ms of TMA pulse, a wide ALD temperature window (30-120°C) with constant 1.4 Å GPC was extracted (Fig. 4). We also achieved very good film growth uniformity across the entire 300mm Si substrate wafer with 50ms of TMA pulse (Fig. 5). XPS analysis of the deposited Al2O3 indicated that the film deposited at 120°C were more oxidized than the films at 30°C with the single injector. However, the elemental composition of films deposited with TMA pulse of 10ms vs. 50ms was indistinguishable. A surface carbon contamination was observed due to the wafer exposure to the outer atmosphere post processing. In addition, angular XPS depth profiling revealed considerable amounts of carbon in the “bulk of the film” as well.
Schlagwörter
-
Berichtsjahr
2019