纳米多孔氧化硅薄膜的表征及其基于UAFM弹性性能的检测

Characterization and Measurement of Elastic Modulus Based on Ultrasonic Atomic Force Microscopy for Nano-porous Silicon Oxide Film

纳米级多孔氧化硅薄膜介电常数低,和铝复合后可以大大降低电阻损耗,是最有希望的新一代低介电材料。在纳电子器中低介电薄膜孔隙率及孔尺寸可以控制其机械性能。薄膜的弹性模量是器件设计的必需参数,然而传统方法很难在纳米尺度表征弹性模量。采用等离子体增强化学气相沉积法,以六甲基二硅氧烷为单体,氧气作为反应气体,再加入少量的有机物质在玻璃基材上沉积纳米厚度的氧化硅薄膜,再进行热处理使氧化硅薄膜中的有机成分挥发形成孔隙(以下称纳米多孔氧化硅薄膜),从而降低薄膜介电常数。结果表明氧化硅薄膜的折射率热处理后得到减小,当放电功率为100 W时,氧气与单体的比例为1∶4时,放电时间10 min沉积的薄膜热处理后的纳米多孔氧化硅薄膜的折射率最小,介电常数1.885。首次采用超声原子力显微镜技术对纳米多孔氧化硅薄膜的弹性性能进行无损检测,分别检测纳米氧化硅薄膜和纳米多孔氧化硅薄膜的前两阶接触谐振频率。以纳米氧化硅薄膜为参考试样,利用参考法计算得到纳米多孔氧化硅薄膜的压痕模量为35.24 GPa。相比纳米氧化硅薄膜的压痕模量78.18 GPa,纳米多孔氧化硅薄膜的压痕模量降低了42.94 GPa。

Nano-porous silicon oxide film with low dielectric constant, compositing with aluminum can greatly reduce the resistance loss, it is the most promising of the new generation of low dielectric material. In nano-electronics, the mechanical properties of the low dielectric film can be controlled by its porosity and pore size. The elastic modulus is a required parameter in device designs. However, the traditional methods can not characterize the elastic modulus at the nano-scale. Herein, using plasma enhanced chemical vapor deposition(PECVD) method, hexamethyldisiloxane(HMDSO) is as monomer and oxygen as a reaction gas, meanwhile a small amount of organic material is added, the silicon oxide film is deposited on the glass substrate surface with glow discharge plasma, then the film is heat-treated at a high temperature, so organic components such hydrogen bonds are removed and the pores are formed(hereafter refer to nano-porous silicon oxide film) to reduce the dielectric constant. The results show that the refractive index of the silicon oxide film is reduced with heat treatment, wherein when the discharge power is 100 W, ratio of oxygen to monomer is 1∶4, the discharge time is 10 min, the refractive index of the film is minimized after the heat treatment, the dielectric constant is 1.885. At the same time, using ultrasonic atomic force microscopy system(UAFM) the elastic modulus of the nano-porous silicon oxide film is tested with non-destructive. Silicon oxide nano-film as a reference sample, elastic properties silicon oxide films with heat-treated is detected experimentally. Indentation modulus of silicon oxide nano-film after heat treatment is 35.24 GPa. Comparing to the silicon oxide nano-film with 78.8 GPa indentation modulus, it reduces 42.94 GPa for nano-porous silicon oxide film.