![]() In summary, a quick gas switching every 0.1 sec is used to avoid the mixing of C 4F 8 and SF 6 gases.Ĥ Different sidewall profiles with Bosch process. In addition, the fluorine radicals disappear as they are consumed by the termination reaction and thus, etching cannot occur. In the presence of SF 6, the fluorine radicals from the dissociation of SF 6 react with the chain -(CF 2) 4– groups and terminate the polymerization reaction. The polymer forms the passivating film on the surfaces of the etched trenches. The polymerization reaction occurs when -(CF 2) 4– groups react with each other to form longer chains. The ring structure of C 4F 8 is broken and the chain-shaped C 4F 8 is generated in plasma. NF 3 nitridates the surface of silicon and prevents etching of silicon leading the etch rate to be about one-third of that of SF 6.ģ Why is it important to separate film deposition and etching steps? However, the decomposition reaction is reversible, and it is not possible to produce a large amount of atomic fluorine from CF 4. Therefore, a large amount of atomic fluorine can be produced and participates in the etching reaction.ĬF 4 decomposes to form atomic fluorine in plasma. SF 4 is so stable that fluorine atoms cannot recombine with it. Both SF 4 and the etching reaction product, SiF 4, exist as gases that are evacuated from the chamber. SF 6 dissociates in plasma to form SF 4 or SF 2 and atomic fluorine that reacts with silicon. SF 6 is usually used as an etching gas for film etching and silicon etching. This mem- brane functions as a passivation film during the silicon etching step preventing etching of the sidewalls. The active parts of the chain combine with other molecules and the chain grows in length, attaching to the silicon and forming a membrane. Both ends of the C 4F 8 chain are active. C 4F 8 is a cyclic molecule (ring shaped), and in plasma, its ring is broken and it becomes a short chain molecule. The deposition step typically uses C 4F 8 gas as the deposition gas. 1).Ģ What is the chemical reaction of the Bosch process? In the silicon etching step, only the silicon at the trench bottom, where the passivation film has been removed, is etched (Fig. ![]() ![]() In the bottom film etching step, the passivation film on the trench bottom is selectively etched. ![]() In the deposition process, a passivation film is deposited on the sidewalls and bottom surface of the trench. This process consists of a three-step cycle: Film deposition, bottom film etching, and silicon etching. The Bosch process is capable of producing deep features with exceptional anisotropy, etch-rate, and etch mask selectivity. However, conventional plasma etching processes are designed for etch depths of only a few microns and are lacking in etch-rate and etch mask selectivity. Copper & Silver Plasma Cleaning without Surface Oxidation for Electronics Packagingĭeep reactive ion etching (DRIE) of silicon to create high aspect ratio microstructures is one of the key processes in the advanced MEMS field and through silicon via (TSV) applications.Polymer Plasma Treatment & Bonding for Microfluidics.SiC Trench Etch for SiC MOSFET Power Device Fabrication.GaN/AlGaN Etch for GaN Power Device Fabrication.Plasma Dicing of Si & III-V (GaAs/InP/GaN).Cathode PECVD for High-rate SiO 2 and SiN x deposition.Low-temperature PECVD for SiO 2 & SiN x Deposition.Remote Source Plasma Cleaners (Downstream Plasma).
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