Rainbow 4400B

The Rainbow 4400B is categorized as a plasma etch system and processes wafers of 8-inch diameter. The equipment was manufactured by Lam Research.^[1][3]

The Rainbow 4400B operates as a parallel-plate, radio-frequency (RF) driven plasma etcher. In such systems, a vacuum chamber contains two electrodes; the wafer is placed on the powered or grounded electrode, and a process gas is introduced. An RF electric field ionizes the gas into a plasma composed of ions, radicals, and electrons.

In a semiconductor fabrication line, the plasma etcher is used after photolithography to transfer the pattern defined in the photoresist into the underlying film. The Rainbow 4400B is typically employed in the etch step of a photomasking cycle, etching films such as silicon dioxide, polysilicon, or metals.

After etching, the remaining photoresist is removed in a separate strip (ashing) step, and the wafer proceeds to subsequent deposition, metrology, or cleaning operations. The Rainbow 4400B handles single wafers and is integrated into automated wafer transport systems.

The Rainbow 4400B is used for etching a variety of thin films in semiconductor device fabrication. Common applications include conductor etch (e.g., polysilicon gates, aluminum interconnects) and dielectric etch (e.g., oxide contacts and vias). The system can process both blanket and patterned wafers.