掺镁铌酸锂晶体的ICP刻蚀性能

掺镁铌酸锂晶体(Mg:LiNbO3)是一种相对难刻蚀的晶体,Mg:LiNbO3的干法刻蚀速率和刻蚀形貌控制是铌酸锂光电子器件加工中的关键技术之一。采用牛津仪器公司的Plasmalab System 100以SF6/Ar为刻蚀气体,具体研究Mg:LiNbO3的刻蚀速率随着感应耦合等离子体(ICP)功率、反应离子刻蚀(RIE)功率、气室压强和气体流量配比等刻蚀参数的变化,同时研究发现SF6/(Ar+SF6)气体流量配比还会影响刻蚀表面的粗糙度。实验结果表明:在ICP功率为1000W,RIE功率为150W,标准状态(0℃,1个标准大气压)下气体总流量为52mL/min,压强为0.532Pa,SF6/(Ar+SF6)气体体积分数为0.077的条件下,刻蚀速率可达到152nm/min,刻蚀表面粗糙度为1.37nm,可获得刻蚀深度为2.5μm,侧壁角度为74.8°的表面平整脊形Mg:LiNbO3结构。

Etching Characteristics of MgO Doped Lithium Niobate in Inductively Coupled Plasma

MgO doped lithium niobate (MgLiNbO3) is a relatively hard crystal and is difficult for dry etching. Dry etching rate and morphology control of MgLiNbO3 are key technologies in fabricating optoelectronic devices based on lithium niobate. Etching characteristics of MgLiNbO3 crystal are studied by using Plasmalab System 100 (Oxford Instruments) with mixture gases of SF6/Ar. The etching rates of different working parameters including inductively coupled plasma (ICP) power, reactive ion etching (RIE) power, working pressure and SF6/Ar flow ratio are evaluated. The surface profile is also affected by various ratios of SF6/Ar gas mixture. The optimal etching conditions for MgLiNbO3 ridge-shaped waveguide are found to be ICP power of 1000 W, RIE power of 150 W, total gas flux of 52 mL/min (standard condition of 0 ℃, 1 atm), chamber pressure of 0.532 Pa and the gas volume ratio of SF6/(Ar+SF6) of 0.077. Optical ridge-shaped waveguide with approximately 2.5 μm depth, 74.8° etching sidewalls and smooth top surface is successfully fabricated using the optimized etching conditions.