原子层沉积超薄氮化铝薄膜的椭圆偏振光谱法表征

采用原子层沉积(ALD)工艺在硅衬底上生长了35 nm以下不同厚度的超薄氮化铝(AlN)晶态薄膜。利用椭圆偏振光谱法在波长275~900 nm内测量并拟合薄膜的厚度及折射率和消光系数等光学参数。利用原子力显微镜(AFM)表征AlN晶粒尺寸随生长循环次数的变化,计算得到薄膜表面粗糙度并用于辅助椭偏模型拟合。针对ALD工艺特点建立合适的椭偏模型,可获得AlN超薄膜的生长速率为0.0535 nm/cycle,AlN超薄膜的折射率随着生长循环次数的增加而增大,并逐渐趋于稳定,薄膜厚度为6.88 nm时,其折射率为1.6535,薄膜厚度为33.01 nm时,其折射率为1.8731。该模型为超薄介质薄膜提供了稳定、可靠的椭圆偏振光谱法表征。

Ellipsometry Characterization of Ultrathin AlN Film Grown by Atomic Layer Deposition

Ultrathin aluminum nitride(AlN)crystalline films with different thicknesses below 35 nm were grown on silicon substrates by atomic layer deposition(ALD)process.The thickness,refractive index,extinction coefficient and other optical parameters of the films were mea-sured and fitted in the wavelength range of 275-900 nm by ellipsometry.The variation of AlN grain size with the growth cycle numbers was characterized by atomic force microscope(AFM),and the surface roughness of the film was calculated to assist fitting of the ellipsometry model.According to the characteristics of the ALD process,an appropriate ellipsometry model was established.It can be obtained that the growth rate of the AlN ultrathin film is 0.0535 nm/cycle.With the increase of the growth cycle numbers,the refractive index of the AlN ultrathin film increases and tends to be stable.The refractive index is 1.6535 for a film thickness of 6.88 nm,and 1.8731 for a film thickness of 33.01 nm.The model provides a stable and reliable ellipsometry characterization for ultrathin dielectric films.