AVS 59th Annual International Symposium and Exhibition
    Plasma Science and Technology Tuesday Sessions
       Session PS2-TuM

Paper PS2-TuM10
High-Efficiency Downstream Plasma Processes

Tuesday, October 30, 2012, 11:00 am, Room 25

Session: Advanced FEOL/Gate Etching 2
Presenter: L. Diao, Mattson Technology
Authors: L. Diao, Mattson Technology
R. Elliston, Mattson Technology
A. Kadavanich, Mattson Technology
C. Lee, Mattson Technology
V. Nagorny, Mattson Technology
H. PhanVu, Mattson Technology
O. Todor, Mattson Technology
V. Vaniapura, Mattson Technology
Correspondent: Click to Email
Photoresist (PR) strip processes continue to improve with major IC technology node advances and architecture changes. One of the new technologies currently being implemented for the 2x nanometer node, high-ĸ metal gate (HKMG) has emphasized the need for enhanced reducing chemistry processes, which are also widely used in other strip-over-metal applications. Three-dimensional vertical architectures present great challenges for high aspect ratio (HAR) processing, and stacked structures often require low-temperature process capability. Control specifications for critical processes are further tightened as more new materials are introduced at advanced geometries. Industry-wide strip process enhancements have diverged into two directions: increasing RF power or adding bias. In either case, wafer surface temperature increases significantly, which introduces pattern damage. Furthermore, there is increased risk of plasma-induced damage (PID). A new Mattson Technology dry strip source provides a solution to these challenges.

Based on the company’s proprietory Faraday-shielded inductively coupled plasma (ICP) source technology, the new source offers these distinctive features: (1) a specially designed plasma generation volume with improved electron confinement that provides high efficiency of electron heating and enhanced plasma stability, and (2) a gas injection system that directs all the gas flow through this volume to increase efficiency of gas utilization. This results in efficient use of process inputs (power, gases) while simultaneously widening the operational window in terms of pressure, power, temperature.

The new source demonstrated significant increase of the PR removal rate and reduction of non-uniformity across different chemistries. One major benefit was observed with pure reducing chemistry. The new source with high power nearly doubled the ash rate, at 20% H2 in N2 with non-uniformity of <5%. Its impact on critical dimension (CD) and sheet resistance (Rs) were minimum and enabled better strip over metal process. O2-rich reducing chemistry with high power was used in HAR PR removal in the middle-end-of-line (MEoL) contact container. It showed improved residue removal capability with challenging AR. One more time, Rs was well controlled over exposed metal liner with high power. CF4-containing chemistry for amorphous carbon hard mask removal demonstrated improved productivity and selectivity over oxide and nitride at extremely low temperatures. Avoiding high power usage, the enriched reactant species allow HDIS process with dry only residue free, less pattern damage, lower silicon (Si) loss and controlled oxidation with different chemistries.