We wish to form a square pyramid on a (100) silicon wafer using wet etching. On a silicon dioxide mask, a 20 - μ m - wide square window is formed whose sides are aligned with the < 110 > directions. If the undercut is negligible, find the length of the side (corresponding to the mask window) of the pyramid after wet etching. If the sides of the mask window make an angle of 45 ° with the < 110 > directions, determine the length of the side of the pyramid after finishing the etching.