AVS 46th International Symposium
    Plasma Science and Technology Division Thursday Sessions
       Session PS1-ThA

Paper PS1-ThA10
Manufacturable Aluminum RIE Processes for 150 nm and Beyond

Thursday, October 28, 1999, 5:00 pm, Room 612

Session: High Fidelity Pattern Transfer
Presenter: G. Stojakovic, Siemens Microelectronics Inc. at IBM/Siemens/Toshiba DRAM Development Alliance
Authors: G. Stojakovic, Siemens Microelectronics Inc. at IBM/Siemens/Toshiba DRAM Development Alliance
X.J. Ning, Siemens Microelectronics Inc. at IBM/Siemens/Toshiba DRAM Development Alliance
E.W. Kiewra, IBM Microelectronics at IBM/Siemens/Toshiba DRAM Development Alliance
W. Kocon, IBM Microelectronics
Correspondent: Click to Email
Three different aluminum etch processes - all proven to be manufacturable - have been developed for 150nm line/150space structures. The three schemes are: Organic ARC with photoresist as an etch mask, inorganic silicon oxynitride dielectric ARC (DARC) with photoresist as an etch mask, and a tungsten cap layer as a hard mask. The total metal stack height used in this work was 435 nm, with top and bottom Ti/TiN diffusion barriers. The designed aspect ratio of the wire for a 175 nm technology is 2.5, with a worst case of approximately 3.2. For 150 nm lines, this aspect ratio is substantially higher. For the two processes that use photo resist as the etch mask, the main task of the RIE process is to minimize the consumption of the resist during etch (i.e. maximize the etch selectivity of metal to resist). The metal etch tool used in this work was a commercially available plasma reactive ion etch system. The etch sequence starts with an ARC, DARC, or W hard mask open, followed by a Cl2/BCl3 based Al stack etch. An overetch is performed after a triggered end-point. Subsequent processing includes a down-stream H2O/oxygen plasma ash, followed by a water rinse. The key process parameters, such as gas flow rate, flow ratio of gases, and temperature that affect the metal profile and yield are discussed. It is shown that the RIE process can clear a sub-100 nm space for metal stacks having a height of over 400 nm. This indicates that aluminum RIE can be extended for even smaller structures. In the schemes that use photoresist as etch mask, the thickness of total metal stack is limited by the thickness of the photoresist. In the scheme that uses a PVD W hard mask, the total metal thickness is not a limiting factor for metal etch. The electrostatic chuck temperature plays a major role influencing metal profile and shorts yield.