Industrial Technology Research Institute

Tsung-Kuei Kang

Tsung-Ju Yang

Chien-Mei Wang

The present invention is a method for making intermetal dielectrics (IMD) on integrated circuits using a low dielectric constant (low k) spin-on polymers without via hole poisoning. A patterned conductive layer is used to form metal interconnection for the integrated circuits. A IMD layer is then formed by depositing sequentially three IMD layers, IMD1, IMD2 and IMD3 respectively. The IMD1 is deposited first and is a low k polymer. IMD2 composed of silicon nitride (Si.sub.3 N.sub.4) and a thick IMD3 composed of silicon oxide (SiO.sub.2) is deposited next. The IMD3 is planarized, and a photoresist mask is used to pattern openings in IMD3 to form a hard mask for etching the remaining via holes in IMD2 and IMD3. The IMD2 layer protects the low k polymer (IMD1) from damage while plasma ashing in oxygen is used to removal the photoresist mask. This method circumvents the problems with more conventional processing in which the low k polymer exposed in the via hole during oxygen plasma removal of the photoresist results in a porous and highly hygroscopic polymer leading to via hole poisoning. In a second approach a thick low k polymer layer (IMD1) is planarized and the PECVD silicon oxide (IMD2) a nd a PECVD silicon nitride (IMD3) is deposited and then the via holes are etched as in the first approach using IMD3 as a hard mask.

Growing community of inventors

Hsin-chu, Taiwan

Tsung-Kuei Kang