Paper PS-WeM12
Towards the Elimination of Ultra-Low k Ash Damage Using an In Situ Plasma Polymerized Film during Etch
Wednesday, November 1, 2017, 11:40 am, Room 23
Ultra-low-k SiCOH films (ULK) are commonly used as an interlayer dielectric layer in the back-end-of-line. Unfortunately, as the industry moves towards new lower-k materials, particularly for the 7 nm node and beyond, not only does the extent of the damage caused by ash to the ULK increase, but so does the effect of damaged material on device performance. Such damage can adversely alter the feature profile and CD, RC response, and device lifetime and because of the nature of the plasma etch can be difficult to prevent. The reduction or elimination of such ash damage would facilitate the continuation of in-situ ash during the dielectric open process while opening the door to more novel integration schemes that are currently limited by the creation of a damaged layer. In order to reduce the damage, we have developed a process to deposit a plasma polymerized organic film in-situ during the etch process. The process utilizes a novel fluorine-free chemistry using a CxHyNz precursor to produce a conformal film in an etch chamber. The deposition process was optimized using patterned substrates such that the effects of the plasma ash on the sidewalls and feature bottom could be monitored and compared. Because the deposition step occurs in the etch chamber, the deposition and etch steps can be cycled such that even the feature sidewalls are constantly protected. By tuning the deposition and subsequent ash plasma parameters, the resulting damage to the ULK was significantly reduced through the use of the protecting polymer film.