Aspect ratio of 52
The high aspect ratio of 52 etching is achived. The sidewall is smooth and the scallop size is less than 100 nm. Since the etching depth is limited by the mask thickness, the thicker the mask, the larger the aspect ratio can be processed, and if the mask thickness is sufficient for a 300 nm pattern, it is possible to process the aspect ratio of 100. Note that when competing for aspect ratio, the narrower the trench, the more advantageous it is.