Interactions between reductive ashing and subsequent wet cleans for low-k dielectric material
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The Second International Surface Cleaning Workshop at Northeastern University November 11-12, 2003 Boston, MA Interactions between reductive ashing and subsequent wet cleans for low-k dielectric material Eileen Sparks, Russell Stevens, Tom Kloffenstein ATMI, Danbury, CT, USA Qingyuan Han, Ivan Berry Axcelis Technologies, Inc., Rockville, MD, USA Abstract We have investigated the interactions between reductive ashing followed by wet cleaning, as they apply to copper/low-k materials proposed for the 65 nm node and beyond, in order to obtain a more comprehensive understanding of the interactions between ash and clean. The issues pertaining to low-k and ultra-low-k materials are generally related to mechanical properties such as brittleness, poor adhesion, and uptake of liquids, with damage to and degradation of the dielectric constant; these have been well described in the literature. Using a well-known MSQ material, we have performed reductive ash at Axcelis using He/H2 in a microwave plasma tool, followed immediately by one of a variety of wet chemical cleaning solutions. By careful selection of the methods and materials, good cleaning of residues is obtained, while preserving the structure and critical dimensions of the test material. Among the wet cleaning solutions, the best three systems of buffers and chelating agents at ATMI were tested. By judicial selection of buffers, surfactants, and chelating agents, and controlling pH carefully, less damage is inflicted upon the dielectric material during wet cleans. The use of a single wafer tool for wet cleaning substantially reduces the exposure of the dielectric material to chemicals, and promotes good rinsing. both critical to an optimal process. The results of the ashing/wet clean sequence were selected by characterization of physical damage using SEM. Initial wet cleans were done using beaker tests; subsequent tests were transferred to single wafer tools at ATMI, and an optimal process identified again using SEM imaging. Finally, the correlation between observed damage and expected yields in a semiconductor fab will be tested using electrical test wafers subjected to a matrix of ash/wet clean conditions. We identify those specific
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Transcript of Interactions between reductive ashing and subsequent wet cleans for low-k dielectric material
The Second International Surface Cleaning Workshop at Northeastern UniversityNovember 11-12, 2003
Boston, MA
Interactions between reductive ashing and subsequent wet cleans for low-k dielectric material
Eileen Sparks, Russell Stevens, Tom KloffensteinATMI, Danbury, CT, USA
Qingyuan Han, Ivan BerryAxcelis Technologies, Inc., Rockville, MD, USA
Abstract
We have investigated the interactions between reductive ashing followed by wet cleaning, as they apply to copper/low-k materials proposed for the 65 nm node and beyond, in order to obtain a more comprehensive understanding of the interactions between ash and clean. The issues pertaining to low-k and ultra-low-k materials are generally related to mechanical properties such as brittleness, poor adhesion, and uptake of liquids, with damage to and degradation of the dielectric constant; these have been well described in the literature. Using a well-known MSQ material, we have performed reductive ash at Axcelis using He/H2 in a microwave plasma tool, followed immediately by one of a variety of wet chemical cleaning solutions. By careful selection of the methods and materials, good cleaning of residues is obtained, while preserving the structure and critical dimensions of the test material. Among the wet cleaning solutions, the best three systems of buffers and chelating agents at ATMI were tested. By judicial selection of buffers, surfactants, and chelating agents, and controlling pH carefully, less damage is inflicted upon the dielectric material during wet cleans. The use of a single wafer tool for wet cleaning substantially reduces the exposure of the dielectric material to chemicals, and promotes good rinsing. both critical to an optimal process. The results of the ashing/wet clean sequence were selected by characterization of physical damage using SEM. Initial wet cleans were done using beaker tests; subsequent tests were transferred to single wafer tools at ATMI, and an optimal process identified again using SEM imaging. Finally, the correlation between observed damage and expected yields in a semiconductor fab will be tested using electrical test wafers subjected to a matrix of ash/wet clean conditions. We identify those specific ash/clean combinations that may have a positive impact on selected device parameters known to influence die yield.
Contact Information:
Eileen Sparks 301-865-8047 [email protected]
The Second International Surface Cleaning Workshop at Northeastern UniversityNovember 11-12, 2003
Boston, MATom Kloffenstein 408-933-6682 [email protected] Stevens 512-467-8054 [email protected] Han 301-284-5892 [email protected] Berry 301-284-5557 [email protected]
