The RCA clean
is a standard set of wafer cleaning steps which needs to be performed before high temp processing steps (oxidation, diffusion
Molecular diffusion, often called simply diffusion, is the thermal motion of all particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size of the particles...
Chemical vapor deposition is a chemical process used to produce high-purity, high-performance solid materials. The process is often used in the semiconductor industry to produce thin films. In a typical CVD process, the wafer is exposed to one or more volatile precursors, which react and/or...
) of silicon wafers in semiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...
manufacturing. RCA cleaning includes RCA-1 and RCA-2 cleaning procedures. RCA-1 involves removal of organic contaminants, while RCA-2 involves removal of oxides and RCA-3 metallic contaminants.
Werner Kern was a German chemist.- Life :Kern studied from 1924 to 1928 chemistry and physics in Freiburg and Heidelberg. The promotion took place in 1930 Hermann Staudinger, at which the habilitation on "The Poylacrylsäure, a model of the protein," followed...
developed the basic procedure in 1965 while working for RCA, the Radio Corporation of America It involves the following :
- Removal of the organic contaminants (Organic Clean)
- Removal of thin oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....
layer (Oxide Strip)
- Removal of ionic contamination (Ionic Clean)
The wafers are prepared by soaking them in DI water. The first step (called SC-1, where SC stands for Standard Clean) is performed with a 1:1:5 solution of NH4
OH (ammonium hydroxide) + H2
(hydrogen peroxide) + H2
O (water) at 75 or 80 °C typically for 10 minutes. This treatment results in the formation of a thin silicon dioxide
The chemical compound silicon dioxide, also known as silica , is an oxide of silicon with the chemical formula '. It has been known for its hardness since antiquity...
layer (about 10 Angstrom) on the silicon surface, along with a certain degree of metallic contamination (notably Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
) that shall be removed in subsequent steps. This is followed by transferring the wafers into a DI water bath.
The second step is a short immersion in a 1:50 solution of HF + H2
O at 25 °C, in order to remove the thin oxide layer and some fraction of ionic contaminants.
The third and last step (called SC-2) is performed with a 1:1:6 solution of HCl + H2
O at 75 or 80 °C. This treatment effectively removes the remaining traces of metallic (ionic) contaminants.
In his book, "Handbook of Semiconductor Wafer Cleaning Technology" , Werner Kern writes that the first step in the ex situ cleaning process is ultrasonically degrease in trichloroethylene
The chemical compound trichloroethylene is a chlorinated hydrocarbon commonly used as an industrial solvent. It is a clear non-flammable liquid with a sweet smell. It should not be confused with the similar 1,1,1-trichloroethane, which is commonly known as chlorothene.The IUPAC name is...
Acetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...
Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...
RCA cleaning (also known as SC1/SC2 etching) submits silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
wafers to oxidation by NH3
O mixtures, oxide removal in diluted HF, further oxidation by HCl:H2
O mixtures, and final etching in diluted HF.
- Wafer (electronics)
A wafer is a thin slice of semiconductor material, such as a silicon crystal, used in the fabrication of integrated circuits and other microdevices...
- Silicon on Insulator
Silicon on insulator technology refers to the use of a layered silicon-insulator-silicon substrate in place of conventional silicon substrates in semiconductor manufacturing, especially microelectronics, to reduce parasitic device capacitance and thereby improving performance...
- Chemical-Mechanical Polishing
Chemical Mechanical Polishing/Planarization is a process of smoothing surfaces with the combination of chemical and mechanical forces. It can be thought of as a hybrid of chemical etching and free abrasive polishing.-Description:...
- Piranha solution
Piranha solution, also known as piranha etch, is a mixture of sulfuric acid and hydrogen peroxide , used to clean organic residues off substrates...