Bjurström Johan, Wingqvist Gunilla, Katardjiev Ilia
The Angström Laboratory, Uppsala University, Sweden.
IEEE Trans Ultrason Ferroelectr Freq Control. 2006 Nov;53(11):2095-100. doi: 10.1109/tuffc.2006.149.
A method for the deposition of thin piezoelectric aluminum nitride (AlN) films with a nonzero c-axis mean tilt has been developed. The deposition is done in a standard reactive magnetron sputter deposition system without any hardware modifications. In essence, the method consists of a two-stage deposition process. The resulting film has a distinct tilted texture with the mean tilt of the c-axis varying roughly in the interval 28 to 32 degrees over the radius of the wafer excluding a small exclusion zone at the center of the latter. The mean tilt angle distribution over the wafer has a circular symmetry. A membrane-type shear mode thickness-excited thin film bulk acoustic resonator together with a micro-fluidic transport system has been subsequently fabricated using the two stage AlN deposition as well as standard bulk micro machining of Si. The resonator consisted of a 2-microm-thick AlN film with 200nm-thick Al top and bottom electrodes. The resonator was characterized with a network analyzer when operating in both air and water. The shear mode resonance frequency was about 1.6 GHz, the extracted device Q around 350, and the electromechanical coupling kt2 2% when the resonator was operated in air, whereas the latter two dropped down to 150 and 1.8%, respectively, when the resonator was operated in pure water.
已开发出一种用于沉积具有非零 c 轴平均倾斜度的压电氮化铝（AlN）薄膜的方法。该沉积过程在标准反应磁控溅射沉积系统中进行，无需对硬件进行任何修改。从本质上讲，该方法包括一个两阶段沉积过程。所得薄膜具有明显的倾斜织构，c 轴的平均倾斜度在晶圆半径范围内大致在 28 至 32 度之间变化，但不包括晶圆中心的一个小禁区。晶圆上的平均倾斜角分布具有圆对称性。随后，利用两阶段 AlN 沉积以及 Si 的标准体微加工技术，制造了一种膜式剪切模式厚度激励薄膜体声波谐振器以及微流体传输系统。该谐振器由一层 2 微米厚的 AlN 薄膜以及顶部和底部各 200 纳米厚的 Al 电极组成。当在空气和水中运行时，使用网络分析仪对该谐振器进行了表征。当谐振器在空气中运行时，剪切模式共振频率约为 1.6 GHz，提取的器件品质因数约为 350，机电耦合系数 kt2 为 2%；而当谐振器在纯水中运行时，后两者分别降至 150 和 1.8%。
