可调谐FBAR用BST薄膜介电性能的研究

发布时间：2018-07-26 16:09

【摘要】：随着无线通信技术向多频段方向的迅速发展,对可调体声波谐振器(FBAR)的要求越来越高,不仅要求其具有高的调谐率,而且要求其具有较低的插入损耗。利用传统压电材料如AlN、Zn O等制作的FBAR,调谐范围小,功率承受能力差,不能满足实际的需要。与传统的压电材料相比,钛酸锶钡(BST)薄膜具有调谐率高、介电损耗小、功率承载能力强等优点,非常适合应用于可调FBAR。为了降低BST薄膜的介电损耗,提高薄膜的介电性能,本文对薄膜的组分梯度和掺杂展开了研究,主要内容如下:本文首先利用溶胶凝胶方法在Pt/Ti/SiO2/Si衬底上制备了厚度约为450nm的Ba0.3Sr0.7TiO3薄膜,并在不同的温度下烧结。实验表明750℃下烧结的薄膜具有最低的介电损耗、最高的介电常数和最高的优值因子,具有最佳的介电性能。薄膜组分梯度变化可以缓和材料中各向性能突变,有效改善BST薄膜的性能,本文在750℃下制备了单组分BaxSr1-xTiO3(x=0.3、0.5、0.7)薄膜和上组分梯度薄膜(远离基片方向,x从0.3到0.5再到0.7)以及下组分梯度薄膜(x从0.7到0.5再到0.3)。研究表明外加电场为110kV/cm时,Ba0.5Sr0.5TiO3薄膜取得最大的调谐率17.4%,室温下Ba0.5Sr0.5TiO3薄膜的工作温度更接近其居里温度点,工作在居里温度点附近的BST薄膜有较高的调谐率。下组分梯度薄膜取得最高的介电常数323,最低的介电损耗0.037和最高的优值因子4。相比于上组分薄膜,下组分薄膜的氧八面体中钛离子和氧离子间电偶极子极化较大,因此下组分薄膜的介电性能较好。Rb离子的半径与Ba离子和Sr离子非常接近,而且Rb作为受主杂质可以中和氧空位产生的电子,降低薄膜的介电损耗,此外国内外尚无有关Rb掺杂的BST薄膜的报道,为此本文还利用溶胶凝胶法制备了Rb的掺杂量为0mol%-8mol%的Ba0.3Sr0.7TiO3薄膜。研究表明Rb的掺杂量为4mol%时,Ba0.3Sr0.7TiO3薄膜具有最高的致密度、最高的介电常数292、最低的介电损耗0.028以及最高的优值因子8.1。
[Abstract]:With the rapid development of wireless communication technology to multi frequency direction, the demand for adjustable body acoustic resonator (FBAR) is getting higher and higher. It not only requires high tuning rate, but also requires low insertion loss. Using the traditional piezoelectric materials such as AlN, Zn O and so on, the tuning range is small and the power bearing capacity is poor, so it can not satisfy the reality. Compared with traditional piezoelectric materials, barium strontium titanate (BST) thin films have the advantages of high tuning rate, small dielectric loss and strong power bearing capacity. It is very suitable for the application of adjustable FBAR. to reduce dielectric loss of BST thin films and improve the dielectric properties of thin films. This paper has studied the composition gradient and doping of thin films, and the main contents of this paper are discussed in this paper. The results are as follows: in this paper, the Ba0.3Sr0.7TiO3 thin film with a thickness of about 450nm on the Pt/Ti/SiO2/Si substrate is prepared by the sol-gel method and sintered at different temperatures. The results show that the film sintered at 750 C has the lowest dielectric loss, the highest dielectric constant and the highest value factor, and has the best dielectric properties. The gradient change can mitigate the anisotropy of the material and effectively improve the properties of BST films. In this paper, a single component BaxSr1-xTiO3 (x=0.3,0.5,0.7) film and the upper component gradient film (away from the substrate, x from 0.3 to 0.5 to 0.7) and the lower component gradient film (x from 0.7 to 0.5 to 0.3) were prepared at 750 C. The applied electric field was 1. At 10kV/cm, the maximum tuning rate of Ba0.5Sr0.5TiO3 film is 17.4%. The working temperature of Ba0.5Sr0.5TiO3 film is closer to its Curie temperature point at room temperature. The BST film working near the Curie temperature point has a higher tuning rate. The highest dielectric constant is 323, the lowest dielectric loss 0.037 and the highest value factor are obtained in the lower component gradient film. 4. compared to the upper component film, the dipole polarization of the titanium and oxygen ions in the oxygen eight surface of the lower component film is larger, so the dielectric properties of the lower component films are better than that of the Ba ions and the Sr ions, and the dielectric loss of the.Rb ions can be neutralized by the acceptor impurity, and the dielectric loss of the film is reduced. There are no reports about Rb doped BST films in and out of foreign countries. Therefore, the Ba0.3Sr0.7TiO3 film of Rb doped with 0mol%-8mol% is also prepared by sol-gel method. The study shows that Ba0.3Sr0.7TiO3 film has the highest density, the highest dielectric constant 292, the lowest dielectric loss 0.028 and the highest when the doping amount of Rb is 4mol%. The optimal value factor 8.1.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.2

【相似文献】