ECR-CVD制备氟化非晶碳低k介质薄膜

Low-dielectric-constant fluorinated amorphous carbon films prepared by ECR-CVD

采用电子回旋共振等离子体化学气相沉积（ECR-CVD）方法，以C4F8和CH4为源气体在不同气体流量比R（R=[CH4]／{[CH4]＋[C4F8]}）条件下成功地沉积了氟化非晶碳（a-C：F）低介电常数（低后）材料。采用X光电子能谱和椭圆光谱方法分析了a-C：F薄膜的化学组分和光学性质。沉积的a-C：F薄膜介电常数约为2．1-2．4，热稳定性优于350℃。随着气体流量比的增大，沉积a-C：F薄膜中的碳含量增大，CF、CF2、CF3含量减少，C-C交链成分增加，从而使得π-π^＊吸收增强，并引起薄膜光学带隙下降。氮气气氛下350℃温度退火后应力释放引起a-C：F薄膜厚度变化，变化量小于4％。450℃温度退火后，由于热分解作用薄膜厚度变化量在30％左右。

Low - dielectric - constant （ low - k） fluorinated amorphous carbon （ a - C ： F） films were prepared by electron cyclotron resonance chemical vapor deposition （ ECR - CVD） method with varying the gas flow ratio R （ R = [ CH4 ] / { [ CH4 ] ＋ [ C4F8] } ）. Chemical compositions and optical properties were investigated by X-ray photoelectron spectroscopy （XPS） and spectral ellipsometry （SE）, respectively. a - C ： F films with dielectric constant of 2.1 - 2.4 and thermal stability higher than 350℃ were obtained. The CF, CF2 and CF3 bonds decrease and the C - C bonds increase with increasing gas flow ratio, which leads to enhancement of π - π^＊ absorption and reduction of optical gap. Film thickness change is less than 4% due to stress release between the a - C ： F films and the silicon substrates after 350℃ annealing. The film thickness change is around 30% mainly due to thermal decomposition of volatile fluorocarbon species after 450℃ heat treatment.