在离子束抛光工艺过程中, 材料确定性去除特性对预测光学元件的各工位材料去除量和驻留时间具有极其重要的作用。采用射频离子源对熔石英光学元件的离子束刻蚀特性进行了研究, 利用ZYGO激光干涉仪获得准确的去除函数, 系统分析了气体流量、屏栅电压、离子束入射角和工作距离等因素对熔石英去除函数的影响, 并分析了各单一工艺因素微小扰动时, 材料峰值去除率、半高宽和体积去除率的相对变化率。实验结果表明, 相同工作真空条件下, 工作气体质量流量的微小变化对去除函数影响极小, 在典型的工艺条件下, 屏栅电压在±5 V、离子束入射角±1°、工作距离在±0.5 mm范围内变化时, 熔石英峰值去除率、体积去除率和峰值半高宽的相对变化均小于5%, 去除函数具有较好的确定性和稳定性。

The characterization of the deterministic material removal plays an important role in the ion-beam figuring (IBF) polishing process, which is used to predict the material removal and help to determine the dwell time needed at different positions of the workpiece. The ion beam etching characteristics of fused quartz optical components were studied by radio frequency(RF) ion source, the precise removal function was calculated and obtained by using ZYGO interferometer, and the influences of the plasma source operational parameters such as work gas mass flow rate, screen voltage, incidence angle of ion beam and work distance on the material removal function of fused quarts were investigated. Furthermore, the relative change rates of the material peak removal rate, the full-width-at-half-maximum (FWHM) of peak and the material volume removal rate were measured and calculated when individual work parameter was perturbed. The experiment results show that the variation of removal functions varies slightly with the gas mass flow rate under the same work vacuum pressure. It is found that the relative errors of the removal function′s peak removal efficiency, the FWHM and the volume removal efficiency can all controlled in 5% when the screen voltage fluctuation is ±5 V, the incidence angle deviation of ion beam is ±1° and the work distance deviation is ±0.5 mm, respectively. Hence the removal function of IBF for fused quartz by using RF focusing ion source has better certainty and stability.