Researching On The Characteristics Of Siliconoptical Elements Etched By Free Radical Plasma

Radical plasma source?RPS?synthesizes a plasma outside the reaction zone,and then introduces the plasma into the reaction zone under the action of an electric field,magnetic field,and air current.This design is different from the existing plasma etching.Technology,radical plasma technology can obtain a large area of??plasma uniform area,has the advantages of low temperature non-ion sputtering,high processing efficiency.It is mainly used in the semiconductor photovoltaic industry,flat panel processing,etc.And has been successful in engineering applications,but so far has not been applied in the field of optical processing.In this paper,a commercially-available radical plasma source is used to establish a medium and large-diameter optical element processing platform.The processing capabilities of the equipment and the basic etching process are studied.The etching characteristics of single crystal silicon optical elements and fused silica are developed the study.The results show:?1?Exploring the change law of the process parameters of the radical plasma technology on the etching effect,and obtained the main factors affecting the etching effect:microwave power,etching gas flow ratio?CF₄/O₂?,negative bias power.?2?Using orthogonal experiments to study the etching process of single crystal silicon materials,the order of influence of the factors is:gas flow ratio?CF₄/O₂?>microwave power>DC bias;free radical plasma etching polishing is obtained The best etching process parameters for the system to etch silicon:etch time is 5min,microwave power is 2500W,working pressure is 120Pa,etching gas flow ratio?CF₄/O₂?is 150:150,and DC bias voltage is 100V.With the best parameters,the etching rate of silicon is stable at?918.46±16.24?nm/min,and the average surface roughness Rq value is optimized from 0.80 nm before etching to 0.44 nm.?3?Research on the homogeneity and stability of free-radical plasma etching of single crystal silicon.The test shows that the uniformity of etching in the range of 300mm can reach2.95%,less than 3%;The etch stability in the time range is 4.45%,which is less than 5%.?4?Orthogonal experiments were used to study the etching process of fused quartz materials.The order of influence of the factors was:microwave power>gas flow ratio>radio frequency bias power;the free radical plasma etching polishing system was used to etch fused quartz The best process parameters are:etching time 30min,microwave power 2400W,working pressure 300Pa,etching gas flow ratio?CF₄/O₂?is 500:500,RF bias 50W.With the best parameters,the etch rate of fused quartz is stable at?12.56±1.04?nm/min,and the average surface roughness Rq value is reduced from 3.511 nm to 1.846 nm.Moreover,the subsurface damage characteristics of fused quartz removed by free radical plasma were studied.The experimental results show that the free radical plasma etching method can quickly and effectively remove the subsurface damaged layer of fused quartz.