US EPA

1729559 

Journal Article 

Full sulfate-free process: joint achievement of minimal residual ions and yield improvement - art. no. 67301F 

Ssinotti, F; Sartelli, L; Cassago, D; Miyashita, H 

2007 

Unk 

Proceedings of SPIE
ISSN: 0277-786X
EISSN: 1996-756X 

PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE) 

6730 

F7301-F7301 

WOS:000253477000045 

Reducing the amount of ionic residues coming from cleaning chemistry became necessary for photomask manufacturing process in order to eliminate the major cause of haze. The achievement of this target involves using sulphate-free steps from resist removal to final cleaning, maintaining good performances on particles or residues removal as well as minimization of pattern damages and preservation of the substrate properties. In this paper the cleaning strategies for high-end masks are discussed and a tight dependency on substrate and contamination type is highlighted as the major aspect that influences the good performances for ozone-based technique. The data collected from both tests and real production for sulfate-free cleaning show that the key point to achieve the full effectiveness is the careful definition of the sequence of treatments and rinses, allowing also the minimization of pattern damages.



The cleaning capability of the full sulphate-free process is tested on various types of contaminants and the achieving of excellent removal performance is demonstrated for contaminations of sizes down to 100nm. When the sulfate-free cleaning is not fully effective, a pre-treatment is applied before the cleaning in order to reduce the interaction between contamination and substrate, thus enlarging the removal capability of the ozone-based cleaning. The ion chromatography confirms that the sulphate residues can be reduced below the threshold value for haze formation. 

sulfate free; cleaning; surface treatment; residual ions; organic residues; ozone; UV