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The RCA clean is a standard set of wafer cleaning steps which need to be performed before high-temperature processing steps (oxidation, diffusion, CVD) of silicon wafers in semiconductor manufacturing. Werner Kern developed the basic procedure in 1965 while working for RCA, the Radio Corporation of America.
Piranha solution, also known as piranha etch, is a mixture of sulfuric acid (H 2 SO 4) and hydrogen peroxide (H 2 O 2). The resulting mixture is used to clean organic residues off substrates , for example silicon wafers . [ 1 ]
Etching tanks used to perform Piranha, hydrofluoric acid or RCA clean on 4-inch wafer batches at LAAS technological facility in Toulouse, France. Etching is used in microfabrication to chemically remove layers from the surface of a wafer during manufacturing.
Wafer size has grown over time, from 25 mm (1 inch) in 1960, to 50 mm (2 inches) in 1969, 100 mm (4 inches) in 1976, 125 mm (5 inches) in 1981, 150 mm (6 inches) in 1983 and 200 mm in 1992. [41] [42] In the era of 2-inch wafers, these were handled manually using tweezers and held manually for the time required for a given process.
RCA-1 clean in ammonia-peroxide solution removes organic contamination and particles; RCA-2 cleaning in hydrogen chloride-peroxide mixture removes metallic impurities. Sulfuric acid-peroxide mixture (a.k.a. Piranha) removes organics. Hydrogen fluoride removes native oxide from silicon surface. These are all wet cleaning steps in solutions.
The silicon wafers start out blank and pure. The circuits are built in layers in clean rooms. First, photoresist patterns are photo-masked in micrometer detail onto the wafers' surface. The wafers are then exposed to short-wave ultraviolet light and the unexposed areas are thus etched away and cleaned.
Piranha solution in particular constitutes quite a harsh treatment that can potentially damage the integrity of the silicon surface. Finlayson-Pitts et al. investigated the effect of certain treatments on silicon and concluded that both the roughness (3-5 Å) and the presence of scattered large particles were preserved after 1 cycle of plasma ...
[2] The procedural steps of the direct bonding process of wafers any surface is divided into wafer preprocessing, pre-bonding at room temperature and; annealing at elevated temperatures. Even though direct bonding as a wafer bonding technique is able to process nearly all materials, silicon is the most established material up to now. Therefore ...