High aspect ratio deep RIE for novel 3D radiation sensors in high energy physics applications

3D detectors with electrodes penetrating through the entire silicon substrate have many advantages over conventional planar silicon technology, for example, high radiation tolerance. High aspect ratio through-wafer holes are essential in such fabrication, and deep reactive ion etching (DRIE) is used. A series of DRIE processes were tested and optimised to achieve the required aspect ratio, and in 5-¿m wide trenches, aspect ratios of 58:1 were achieved.