● Etch factor & imaging errors factor
Generally speaking, etching is the process the copper and unprotected areas are removed, leaving the intended circuit. There’re about two methods for etching: chemical etch process and plasma etch. Actually, they’re different from several aspects though used for the same purpose. Namely, there exists the following difference between chemical etch process and plasma etch.
The biggest difference between chemical etch process and plasma etch is efficiency.
The chemical etch process for etching the unprotected area away is effective but inefficient, just like digging a ditch. While the new way of plasma etch creates new standards, improving efficiency greatly.
In addition, etch-back or undercutting always occurs during the chemical etch process, the trace widths must be increased. The thicker the copper, the longer the etch takes to remove the copper between the traces and under the etch resist. On the contrary, etch-back won’t happen in the new process of plasma etch. Thus, etch-back is another difference between chemical etch process and plasma etch.
Etch factor & imaging errors factor
Importantly, plasma etch eliminates imaging error using a direct imaging process of transferring the layer image to the material. This also helps to eliminate the etch factor. In contrast, the chemical etch process is a traditional method, the edge of a trace is malformed. There is an amount of slope for each raise of wire height.