采用等离子体化学气相沉积法在硅基底上沉积氧化硅薄膜, 研究在不同工艺条件下薄膜的应力变化情况和折射率分布规律.利用应力测试仪测定晶圆在镀膜前后的形变量进而获得应力值, 并用棱镜耦合仪测试薄膜折射率.在其他条件相同的情况下, SiH4与N2O的流量比分别设为24、27.6和30时, 在1 539 nm波长下薄膜平均折射率分别为1.466 7、1.459 2和1.455 7, 对应的晶圆应力向着压应力增加, 分别为-50 MPa、-200 MPa和-430 MPa.掺入8.3×10-7 m3/s GeH4后, SiH4与N2O的流量比分别设为22.6、24和27.6时, 薄膜平均折射率分别为1.475 8、1.471 4和1.463 3, 对应的晶圆应力分别为25 MPa、-210 MPa和-270 MPa, 是从拉应力向压应力变化的过程.结果表明, SiH4与N2O的流量比相同时, 掺入GeH4后折射率和对应的压应力明显增加.因此, 通过对工艺条件的合理选择, 可制备出折射率稳定的氧化硅波导薄膜, 从而提高器件在整个晶片上的成品率.

Silica films were deposited on a silicon substrate by a plasma enhanced chemical vapor deposition method to study the stress variation and the refractive index distribution at different process conditions. The stress tester was used to measure the deformation of the wafer before and after coating, allowing the calculation of the film stress, and the prism coupler was used to measure the refractive index distribution. Under the same condition, when the flow ratio of SiH4 to N2O is set to 24, 27.6 and 30, the average refractive index of the film are 1.466 7, 1.459 2 and 1.455 7, respectively, at the wavelength of 1 539 nm, and the correspoonding compressive stress of the film are -50 MPa, -200 MPa, and -430 MPa, respectively. When the flow ratio of SiH4 to N2O is set to 22.6, 24, and 27.6 after minxing 8.3×10-7 m3/s GeH4, the average refractive indices are 1.4758, 1.4714 and 1.4633, respectively, and the corresponding wafer stresses are 25 MPa, -210 MPa and -270 MPa, respectively, which is a changing process from the tensile stress to the compressive stress. The result show that at the same flow ratio of SiH4 to N2O, GeH4 diffusion increases the refractive index and the compressive stress of the film. It turns out that with the reasonable selection of the process conditions, a refractive index stabilized silicon oxide waveguide film can be prepared, thereby improving the yield of the device over the entire wafer.