Spacer (semiconductor technology)

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Spacer formation on any existing structure by conformal deposition and subsequent anisotropic etching of a layer.
Cross-section through an IC on a Silicon-on-Sapphire substrate . A simple spacer is shown on the side of the gate layer stack

As a spacer (engl. For, spacers, placeholder shim '), and side wall spacer may be mentioned, in the semiconductor technology , thin layers referred to a side wall or step. In general, the term is related to layers of metal-insulator-semiconductor field-effect transistors located on the side of the gate layer stack . They usually consist of silicon dioxide or silicon nitride , two standard materials in semiconductor technology. Such spacers are used during the production of microelectronic circuits, among other things, as a protective layer for the gate layer stack against etching attacks by wet chemical etching or are used as a sacrificial layer in certain production processes.

Manufacturing

The production of spacers takes place in two essential steps. First, a layer of silicon dioxide or silicon nitride is deposited using a coating process, which is primarily characterized by good edge coverage (usually a chemical vapor deposition process ). In the second step, this layer is removed from above using a strongly anistotropic etching step ( dry etching ). Due to the strong anisotropy, the layer on the top of the gate electrode, the source and drain regions and the insulation regions is removed, but remains on the side walls of the gate electrode.

application

Spacers are used, among other things, to protect edges and steps on the wafer against external attacks or to isolate them electrically, for example the side surfaces of a gate electrode. They are also used to move an existing edge or step. As a rule, this is an offset that is significantly less than the resolution of the lithographic structuring used. This approach also offers the advantage that there is no overlay offset compared to the previous masking. Techniques that use spacers in this way are often referred to as “self-aligning”, for example the production of self-aligning source / drain contacts or self-aligning implantation areas. For this purpose, spacers are also used in a multiple structuring technique to produce smaller periodic structures than photolithographic structuring allows, the self-aligned (spacer) double pattering (SaDP) .

literature

  • Michael Reisch: Semiconductor components . 2nd Edition. Springer, Berlin / Heidelberg 2007, ISBN 3-540-73199-7 , pp. 271-272 .
  • Dietrich Widmann, Hermann Mader, Hans Friedrich: Technology of highly integrated circuits . 2nd Edition. Springer, Berlin / Heidelberg 1996, ISBN 3-540-59357-8 , pp. 64–66 ( limited preview in Google Book Search).

Individual evidence

  1. ↑ Dietrich Widmann, Hermann Mader, Hans Friedrich: Technology of highly integrated circuits . 2nd Edition. Springer, Berlin / Heidelberg 1996, ISBN 3-540-59357-8 , pp. 64–66 ( limited preview in Google Book Search).
  2. ↑ Kurt Hoffmann: System integration: From the transistor to the large-scale integrated circuit . Oldenbourg Verlag, 2006, ISBN 978-3-486-57894-2 , p. 150 .