Rca Cleaning
RCA Critical Cleaning Process
This paper was especially prepared by Werner Kern, the inventor of the RCA clean.
Introduction
The manufacturing of a silicon integrated circuit (IC) requires 500-600 process steps, depending on the specific type of device. Most steps are performed as unit processes with the complete wafers before dicing them into individual chips. Approximately 30% of the steps are cleaning operations, which indicate the importance of cleaning and surface conditioning. The device performance, reliability and product yield of silicon circuits are critically affected by the presence of chemical contaminants and particulate impurities on the wafer or device surface. Effective techniques for cleaning silicon wafers before thermal treatments such as oxidation, after patterning by etching, after ion implantation, and before and after film deposition are therefore critically important because of the extreme sensitivity of the semiconductor surface and the nanometer sizes of the device features. As a consequence, the preparation of ultraclean in silicon wafers has become one of the key technologies in the fabrication of advanced ICs [1]. One may ask about the nature, types and origins of the impurities that must be eliminated. Contaminants on the wafer surfaces exist as adsorbed ions and elements, thin films, discrete particles, particulates (clusters of particles) and adsorbed gases. Surface contaminant films and particles can be classified as molecular compounds, ionic materials, and atomic species. Molecular compounds are mostly particles or films of condensed organic vapors from lubricants, greases, photoresists, solvent residues, organic compounds from DI (deionized) water, fingerprints or plastic storage containers and inorganic compounds. Ionic materials comprise cations and anions mostly from inorganic chemicals that may be physically adsorbed or chemically bonded (chemisorbed), such as ions of sodium, fluorine, and chlorine. Atomic or elemental
This paper was especially prepared by Werner Kern, the inventor of the RCA clean.
Introduction
The manufacturing of a silicon integrated circuit (IC) requires 500-600 process steps, depending on the specific type of device. Most steps are performed as unit processes with the complete wafers before dicing them into individual chips. Approximately 30% of the steps are cleaning operations, which indicate the importance of cleaning and surface conditioning. The device performance, reliability and product yield of silicon circuits are critically affected by the presence of chemical contaminants and particulate impurities on the wafer or device surface. Effective techniques for cleaning silicon wafers before thermal treatments such as oxidation, after patterning by etching, after ion implantation, and before and after film deposition are therefore critically important because of the extreme sensitivity of the semiconductor surface and the nanometer sizes of the device features. As a consequence, the preparation of ultraclean in silicon wafers has become one of the key technologies in the fabrication of advanced ICs [1]. One may ask about the nature, types and origins of the impurities that must be eliminated. Contaminants on the wafer surfaces exist as adsorbed ions and elements, thin films, discrete particles, particulates (clusters of particles) and adsorbed gases. Surface contaminant films and particles can be classified as molecular compounds, ionic materials, and atomic species. Molecular compounds are mostly particles or films of condensed organic vapors from lubricants, greases, photoresists, solvent residues, organic compounds from DI (deionized) water, fingerprints or plastic storage containers and inorganic compounds. Ionic materials comprise cations and anions mostly from inorganic chemicals that may be physically adsorbed or chemically bonded (chemisorbed), such as ions of sodium, fluorine, and chlorine. Atomic or elemental