Deep Etching of LiNbO₃ Using Inductively Coupled Plasma in SF₆-Based Gas Mixture

High-Quality Dry Etching of LiNbO3 Assisted by Proton Substitution through H2-Plasma Surface Treatment

“…Therefore, a surface treatment seems necessary to improve the quality of the Ti/Al/Cr metal mask on X-and Y-cuts. A similar treatment was carried out by [24] to engineer crystal properties of the LN using proton implantation. Alternatively, the PE process can also be employed with molten benzoic acid.…”

“…In our experiment, we used CHF 3 /Ar plasma treatment (CHF 3 : 30 sccm, Ar: 30 sccm, pressure: 5 mTorr, RF power: 100 W, ICP power: 150 W, DC bias: 40 V) to achieve high selectivity and higher etch rate with a Cr mask. The Argon gas increased the etching rate by enhancing the sputtering process during plasma etching [24]. To prevent heating effect on etching process (due to low thermal conductivity of LN), we implemented a periodic step process; 20 min etching followed by 4 min cooling (plasma is off).…”

“…Dry etching of LN substrates was studied by different research groups [18][19][20][21][22][23][24][25][26] and different plasma etch conditions have been investigated to optimize the quality of the resulting structures. Fluorine (F 2 ) based plasma sources have most commonly been used to etch LN [24]; however, the use of this source is accompanied by the redeposition of LiF and its byproducts, which reduce the etching rate and create unfavorable features due to local micro-masking effects. The byproducts from fluorine-based dry-etch evaporate at only 800 • C, thus remaining on the surfaces and the sidewalls of the structures.…”

Advances in lithium niobate photonics: development status and perspectives

“…These demonstrations can be divided into three categories. One involves using the plasma of pure halogen ions, 179,180,182,183,194,196 such as sulfur hexafluoride (SF 6 ), carbon tetrafluoride (CF 4 ), and boron trichloride (BCl 3 ). As halogen ions will chemically react with the lithium, the reactant produced in the process of dry etching will be a problem and later affect device performance.…”

Hybrid Dry and Wet Etching of LiNbO3 Domain-Wall Memory Devices with 90° Etching Angles and Excellent Electrical Properties

“…After the optimization, they achieved a fast etching rate of 306 nm/min on a smooth surface. However, the LiF byproducts lowered the sidewall etching angle down to 70° . To overcome this problem, other researchers proposed several solutions, such as adding different etching gases, increasing plasma concentration, applying a bias voltage, and utilizing a mask material in a higher etching selectivity. ,,, At the same time, Shen et al compared the etching effects of Cl-based gas, F-based gas, and pure Ar gas on the sidewall roughness and angles among which they found the lowest etching angle of 60° using a pure Ar gas in comparison to a higher angle of nearly 80° when using the Cl-based gas .…”