ABSTRACT
I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
II. Outline of Current Wet Cleaning and Roles of Major Chemicals . . . . . . . . . . . . . . . . 36
III. Functions Essential for Cleaning Trace Contaminants . . . . . . . . . . . . . . . . . . . . . . . . 37
IV. Cleaning Mechanism of Metallic Contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
A. Desorption of Metallic Contaminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
B. Significance to Prevent Contaminants in the Cleaning Solutions from
Redepositing on the Substrate Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
C. Mechanism of Metallic Contaminant Adsorption . . . . . . . . . . . . . . . . . . . . . . . . 40
1. Electrochemical Adsorption of Noble Metals . . . . . . . . . . . . . . . . . . . . . . . 40
2. Metal Adsorption in Alkali Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
D. Technology to Prevent Metallic Contaminants from
Depositing on Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
1. Prevention of Electrochemical Adsorption of Noble Metals . . . . . . . . . . . . 45
2. Prevention of Metallic Contaminant Adsorption in Alkali Solution . . . . . . 48
E. Removal of Metallic Contaminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
V. Cleaning Mechanism of Particulate Contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
A. Mechanism of Particle Deposition in Solution . . . . . . . . . . . . . . . . . . . . . . . . . . 50
B. Technology to Prevent Particle Deposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
C. Removal of Particulate Contaminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
VI. Cleaning Mechanism of Organic Contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
VII. Improvement of Cleaning Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
VIII. Optimization of Cleaning Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
IX. Cleaning Issues to Note in Each Stage of ULSI
Manufacturing Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
A. Cleaning Steps in FEOL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
B. Cleaning Steps in BEOL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
X. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
The advanced manufacturing process of ultra large-scale integration (ULSI) and flat panel display
(FPD), in which circuits are fabricated in the nanometer order, is constantly engaged in battles
against contamination. Even in the most advanced manufacturing process armed with cleanroom,
process tools, and materials all of which feature uppermost cleanliness, the surface of substrates and
devices being processed is always exposed to contamination introduced through various sources.
Potential contaminants include particle and metallic impurity derived from chemical mechanical
polishing (CMP) process, photoresist residues, particles generated by sliding parts of process
tools, and organic impurity derived from outgassing components coming out of cleanroom
interiors. These contaminants need to be removed before being carried over to subsequent
process steps as they potentially deteriorate the yield and reliability of final devices. Wet cleaning
or dry cleaning is employed as a means to remove these contaminants. In ULSI-manufacturing line,
more than 100 cleaning steps are performed, which account for about 25% of the entire process. At
a temperature of about 1008C (the highest), wet-cleaning is capable of dissolving or dispersing most substances into the liquid solution and it causes no damages to the substrate surface. As it features
such outstanding characteristics, wet-cleaning grows in importance and value even in the current
device-manufacturing process which has significantly shifted toward the dry process.
