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Etching and cleaning gases play an important role in the manufacturing of integrated circuits. As layer after layer of material is deposited on the wafer surface, each must be cleaned and etched to exacting tolerances. Etching gases are used in the process of integrated circuit fabrication to selectively remove excess materials such as silicon, silicon dioxide and silicon nitride in a defined pattern. In early IC manufacturing, wet chemistry etching (acid dip method) was used to etch waters. Today, due to the inability of wet etching to achieve acceptable fidelity of pattern transfer below two microns, plasma etching is the preferred method particularly in thin film etching for advanced applications.
With plasma etching, a number of organic and inorganic fluorides, chlorides and/or bromides (plasma etchants) react with the substrate layer to form volatile products that evaporate from the wafer surface and can be easily removed from the process. Plasma etch responses that must be considered to optimize the overall process include: |
- Etching rate
- Loss of critical dimension
- Edge profile
- Uniformity of etching
- Selectivity
Etching gases are used alone or in various combinations with other gases to achieve optimum process performance in terms of rate, selectivity, anisotropy and uniformity. Scott offers a wide range of products used in wafer etching and cleaning applications. Pure gases are available in a variety of purity grades. In most cases, Scott gas mixtures are provided in various purity grades of minor components and balance gases. These gases, along with available concentrations and balance gases, are summarized in the tables below.
For more detailed information on specific gases, see the individual product listings in the Pures and Mixtures sections.
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