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用新的制作方法,在具有非单向换能器的128°YX-LiNbO_3基片上,制成了图案尺寸为1平方毫米和亚微米指条周期双电极的两种千兆赫低损耗声表面波(SAW)滤波器,一种是周期为1微米、插入损耗为5分贝的0.9千兆赫滤波器,另一种是周期为0.5微米、插入损耗为7分贝的1.9千兆赫滤波器这种新的制作方法由晶片电子束直接记录、二级掩模转移和离子束刻蚀组成.从电子抗蚀剂PMMA到AZ-1350J光刻胶的掩模转移,保证了掩模的高精度和铝电极抗离子束刻蚀的高的能力.插入损耗的降低主要通过离子束刻蚀条件的最佳化,即由电极边缘几何形状、离子刻蚀表面损伤和电极膜吸收引起的声传播损耗的降低来实现.用作调谐元件的引线电感也有助于插入损耗的降低并能使封装小型化.制成的0.9千兆赫滤波器满足了日本地面移动式电话系统用的带通滤波器的所有性能,并能付诸系统实用.
Using a novel fabrication method, two gigahertz low-loss surface acoustic waves with a pattern size of 1 mm 2 and submicron finger-strip periodic electrodes were fabricated on a 128 ° YX-LiNbO_3 substrate with a non-unidirectional transducer (SAW) filter, a 0.9 gigahertz filter with a 1 micrometer period and an insertion loss of 5 dB, and a 1.9 gigahertz filter with a 0.5 microsecond period and a 7 dB insertion loss The fabrication method consists of the direct recording of the wafer electron beam, the transfer of the second stage mask and the ion beam etching.The mask transfer from the electronic resist PMMA to the AZ-1350J photoresist ensures the high precision of the mask and the high resistance of the aluminum electrode The high capability of ion beam etching is mainly due to the optimization of the ion beam etching conditions, namely the reduction of acoustic propagation loss caused by electrode edge geometry, ion etching surface damage and electrode film absorption The lead inductance used as a tuning element also contributes to the reduction of insertion loss and miniaturization of the package, and the manufactured 0.9 GHz filter satisfies all the performance of the bandpass filter for the terrestrial mobile telephone system in Japan and can Put into practical system.