Delineate Lightly Doped CMOS N-Well With Wet Etch

Lightly doped source-drain diffusions are difficult if not impossible to delineate using wet chemical etching, but with a few process modifications and the use of edge shorting, a 20:1 HNO₃/HF etch for 5 s at room temperature can reveal almost any junction profile in a CMOS device. The relatively simple process is outlined in this installment of Master FA Technique, which also includes a series of images showing how well the method works.