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Monitoring of Undercut after Isotropic Etching in Thin Films

IP.com Disclosure Number: IPCOM000117820D
Original Publication Date: 1996-Jun-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 81K

Publishing Venue

IBM

Related People

Buelow, D: AUTHOR [+3]

Abstract

Disclosed is a process for easily and non-destructively monitoring the undercut immediately after the etching process.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 59% of the total text.

Monitoring of Undercut after Isotropic Etching in Thin Films

      Disclosed is a process for easily and non-destructively
monitoring the undercut immediately after the etching process.

      For the manufacture of flexible printed circuit boards,
hybrides thin electrical layers are used.

      Through-holes have to be etched into these thin layers in order
to be able to electrically contact several planes of the printed
circuit board.  These holes become smaller and smaller so that the
drilling of holes is replaced by more effective processes, e.g.,
isotropic etching.

      If isotropic etching is used, underetching will take place and
an undercut will form.  This undercut determines the dimensions of
the etched structure, controls subsequent process steps, limits the
pitch and is of decisive importance for the quality of the product to
be manufactured.  Therefore, a permanent control of the undercut is
necessary.  This was up to now done by preparing a polished specimen
or by etching the etch mask.

      By means of the process to be described, the disadvantages of
the prior art can be overcome and the undercut can be determined in a
non-destructive and simple way.

      For that purpose, special test structures are produced
simultaneously with the active structures and the undercut is
directly determined after the process using these test structures.

      From Fig. 1, it can be seen that the etch front isotropically
penetrates benea...