Do-Haing Lee

Precise Depth Control of Silicon Etching Using Chlorine Atomic Layer Etching

In this study, the atomic layer etching (ALE) of Si was carried out using Cl2 adsorption followed by Ar+ ion beam irradiation with a low energy Ar+ ion beam generated by an inductively coupled plasma ion gun. A saturated silicon etch rate due to chlorine ALE could be obtained when the Ar+ ion acceleration voltage of the ion gun was in the range of 70 to 90 V, as a result of the preferential etching of silicon chloride formed during the chlorine adsorption period by the Ar+ ions while the silicon sputter etch rate remains insignificant. This was attributed to the differences in the silicon-to-silicon and silicon-to-silicon chloride binding energies. The saturated silicon etch rate by ALE was dependent on the chlorine flow rate, i.e. the surface coverage of chlorine and the Ar+ ion irradiation time. In this experiment, a silicon etch rate of 1.36 A/cycle, which is a (100) silicon monolayer per cycle, could be obtained by flowing more than 10 sccm chlorine gas followed by bombarding the surface by Ar+ ions with an acceleration voltage of 70 V for more than 40 seconds. Under this condition, when a 30 nm scale silicon etch profile was examined after 200 cycles, a silicon etch profile with no undercut could be obtained.

Etching characteristics of SrBi2Ta2O9 film with Ar/CHF3 plasma

Among the ferroelectric thin films that have been widely investigated for ferroelectric random access memory (FRAM) applications, the SrBi2Ta2O9 (SBT) thin film is appropriate as a memory capacitor material due to its excellent fatigue endurance. However, very few studies on the etch properties of SBT thin films have been reported, even though dry etching is an area that demands a great deal of attention in the very-large-scale integration of ferroelectric thin-film capacitors for FRAM applications. In this study, SrBi2Ta2O9 thin films were etched using a magnetically enhanced inductively coupled Ar/CHF3 plasma. Etch properties, such as etch rate, selectivity, and profile, were measured for different gas mixing ratios of CHF3/(Ar+CHF3), while the other process conditions were fixed at rf power of 600 W, dc-bias voltage of −150 V, and chamber pressure of 5 mTorr. The maximum etch rate of SBT thin films was 1650 A/min under CHF3/(Ar+CHF3) of 0.1. Selectivities of SBT to Pt and photoresist masks were 1.35 an...

Damage during SiO2 Etching by Low-Angle Forward Reflected Neutral Beam.

In this study, energetic reactive radical beams were formed with SF6 using a low-angle forward reflected neutral beam technique and the etch properties of SiO2 and possible damage induced by the radical beam were investigated. The results showed that when SiO2 was etched with the energetic reactive radical beams generated with SF6, SiO2 etch rates higher than 22 nm/min could be obtained. Also, when the etch damage was studied in terms of the capacitance–voltage (C–V) and current–voltage (I–V) characteristics of metal-nitride-oxide-silicon (MNOS) and metal-oxide-silicon (MOS) devices exposed to the radical beams, nearly no etch damage could be found.

Effects of Axial Magnetic Field on Neutral Beam Etching by Low-Angle Forward-Reflected Neutral Beam Method

A low axial magnetic field was applied to an inductively coupled plasma (ICP) ion source used to generate a neutral beam for a low-angle forward-reflected neutral (LAFRN) beam system, and its effects on the ICP ion source and the features of Si and SiO2 etching using the LAFRN beam system for SF6 gas were investigated. As a result of applying a low axial magnetic field of approximately 20 G, a significant increase in SF3+ ion flux extracted from the source was observed among the various reactive ions generated using SF6 gas, and the etch rates of Si and SiO2 using a neutral beam formed by the magnetically enhanced SF6 ICP source were also increased. The application of the low axial magnetic field also improved the etch uniformity of the neutral beam etching system.