Masking layer

With the help of a masking layer , it is possible to selectively carry out diffusion , ion implantation , etching or a physical vapor deposition onto a layer located under the masking. The masking layer is usually a so-called sacrificial layer , which means that it is removed again after the process in which it serves as a mask. The underlying layer is usually a silicon wafer , a blank for integrated semiconductor circuits, or a previously applied layer stack of different materials.

The mask itself is a template for the processes with which microfine, geometric structures are placed on or in the surface of the semiconductor substrate ( transistors , conductor tracks, etc.). Typical materials in addition to photoresist are silicon dioxide or nitride. The latter are also referred to as hard masks because, unlike photoresists, they are clearly resistant to various processes in semiconductor technology, for example plasma or wet chemical etching. For modern manufacturing steps but also other materials like coming amorphous carbon (Engl. Amorphous carbon and metallic layers, aC) tantalum nitride (TaN) or titanium nitride (TiN) as a hard mask is used.

A common method for producing a masking layer is photolithography, with which a masking layer is produced from photoresist, which can be used as an etching or implantation mask. In order to carry out diffusion processes, however, the resist mask is only used to structure the actual diffusion mask made of e.g. B. silicon dioxide , since a lacquer mask is not suitable for high process temperatures. Again, hard masks are used here.

Individual evidence

↑ Sami Franssila: Introduction to Microfabrication . John Wiley & Sons, 2010, ISBN 978-1-119-99189-2 , section 11.7.2. Etching with hard mask , p. 134-135 .
↑ Yayi Wei, Robert L. Brainard: Advanced Processes for 193-Nm Immersion Lithography . SPIE Press, 2009, ISBN 978-0-8194-7557-2 , pp. 171 ff .
↑ Mikhail Baklanov, Karen Maex, Martin Green: Dielectric Films for Advanced Microelectronics . John Wiley & Sons, 2007, ISBN 978-0-470-06541-9 , pp. 211 ( limited preview in Google Book search).

[1] Sami Franssila: Introduction to Microfabrication . John Wiley & Sons, 2010, ISBN 978-1-119-99189-2 , section 11.7.2. Etching with hard mask , p. 134-135 .

[2] Yayi Wei, Robert L. Brainard: Advanced Processes for 193-Nm Immersion Lithography . SPIE Press, 2009, ISBN 978-0-8194-7557-2 , pp. 171 ff .

[3] Mikhail Baklanov, Karen Maex, Martin Green: Dielectric Films for Advanced Microelectronics . John Wiley & Sons, 2007, ISBN 978-0-470-06541-9 , pp. 211 ( limited preview in Google Book search).