Introduction to RCA Cleaning Process

RCA cleaning technology is a standard and critical wet cleaning process in the semiconductor manufacturing industry, mainly used to remove contaminants such as organic residues, metal ions, and particulates on the surface of silicon wafers to ensure the high-quality progress of subsequent processes and the reliability of electronic components. Since the 70s of the 20th century, this technology has been proposed by the American Radio Company, and is still one of the mainstream cleaning methods in the industry due to its efficient cleaning effect and relatively mild treatment conditions.

The RCA cleaning method was first developed by Kern and Puotinen in 1965 while working for American Radio Corporation and was named after the company. This method can effectively remove various pollutants by combining multiple chemical solutions as cleaning solutions, and has become the basis for various subsequent front and rear cleaning processes. The cleaning process used by many semiconductor manufacturers today stems from the original RCA cleaning method, demonstrating its important position in this field.

0020-27113 CLAMP RING 6 SMF TI

Cleaning process and core steps

The core process of RCA cleaning mainly consists of two stages, Standard Cleaning 1 (SC-1) and Standard Cleaning 2 (SC-2), sometimes in combination with other cleaning solutions such as SPM and DHF. In the SC-1 stage, a proportional mixture of ammonia, hydrogen peroxide, and deionized water is usually used, with a typical ratio of NH₄OH:H₂O₂:H₂O = 1:1:5, and the temperature is controlled between 70°C and 80°C. This step effectively removes organic residues and particulate impurities while creating a thin oxide layer that helps remove particulates by slightly corroding the surface. It is then rinsed with deionized water to remove any residual SC-1 solution.

Next, the SC-2 stage is carried out, using a solution of hydrochloric acid, hydrogen peroxide and deionized water, with a typical ratio of HCl:H₂O₂:H₂O = 1:1:6, and the temperature is also controlled at 70°C to 80°C. The main function of this step is to remove metal ion contamination and make metal ions easily carried away by the solution by forming a stable metal chloride complex. The cleaning process concludes with a thorough rinse with deionized water and possibly immersion in heated ultrapure water to completely remove any residual chemicals.

Commonly used cleaning fluids and their effects

In addition to SC-1 and SC-2, several other cleaning fluids are commonly used in RCA cleaning. APM (i.e. SC-1) removes surface particles through oxidation and micro-etching, and can also remove light organic pollutants and some metal contaminants, but may cause surface roughness. HPM (i.e., SC-2) can dissolve alkali metal ions and hydroxides of aluminum, iron, and magnesium, and remove metal pollution by forming complexes with residual metal ions by chloride ions. SPM solution is composed of sulfuric acid and hydrogen peroxide, usually mixed with a mixing ratio of H₂SO₄:H₂O₂ = 2:1 to 4:1, at a temperature of 100°C to 130°C, mainly used to remove organic pollutants, and clean through dehydration, carbonization and oxidation reactions.

DHF is diluted hydrofluoric acid, mixed with HF:H₂O = 1:10, used at room temperature to remove the primary oxide layer and the chemical oxide layer formed after cleaning SC-1 and SC-2, and at the same time form silicon-hydrogen bonds on the surface of silicon, showing hydrophobicity. Ultrapure water is used for thorough rinsing after each chemical treatment to remove chemical residues through dilution and ensure a clean wafer surface.

0040-70319 FACEPLATE,WATER COOLED,SACVD 200mm PRODUCER

Process characteristics and importance

The thickness of the thin oxide layer produced during RCA cleaning is generally in the range of a few nanometers, which can effectively protect the silicon surface from subsequent contamination. The entire cleaning method relies on solvents, acids, surfactants, and water to remove contaminants through processes such as rinsing, purifying, oxidizing, etching, and dissolving without compromising wafer surface properties. This technology is critical for achieving cleanliness, consistency, and process control in semiconductor manufacturing, and its effectiveness is highly dependent on the reliability of the equipment used to ensure accurate and repeatable results for process engineers.

In summary, RCA cleaning ensures high cleanliness on the surface of silicon wafers through multi-step selective removal of different types of contaminants, which is an indispensable key process link in semiconductor manufacturing. Although this technology has some drawbacks, such as the possibility of dissolving metal wiring in the back-end process, it is still widely used by most companies due to its remarkable cleaning effect.