A Parametric Study Of Icp-Rie Etching On A Lithium Niobate Substrate

Z-cut LiNbO3 single crystal wafers were etched by the inductively coupled plasma reactive ion etching (ICP-RIE) technique by using the boron trichloride (BCl3)/ Argon (Ar) mixture gases. Effects of the ICP power and RF power ranged from 100 W to 700 W of the ICP-RIE system were studied on the etching rate, surface roughness, and corresponding DC bias under different working pressures ranged from 10 mTorr to 50 mTorr, respectively. Besides, photoresist, Cr(20%)/Ni(80%) alloy and Ni thin films were used as the etching mask, and the selective ratios of the three etching masks were also compared. The surface roughness of the etched LiNbO3 substrate was increased when the ICP power and RF power were increased. The etching rate of the LiNbO3 substrate was increased with increasing the ICP power and RF power. It is noted that the etching rate was greater than 100 nm/min when the working pressure was controlled at 30 mTorr. The selective ratios of the photoresist Cr/Ni and the nickel were calculated to be approximately 0.4, 7, 9, respectively. Under suitable processing parameters of ICP-RIE, the surface roughness less than 40 nm, structure depth greater than 3 mu m, and sidewall angle is estimated to be 120 degrees of the LiNbO3 substrate can be obtained within 28 min, which etching rate is greater than 117 nm/ min.