Chemical Mechanical Planarization

Chemical mechanical planarization (CMP) is a critical process technology step in the semiconductor wafer fabrication process. In this process step, the top surface of the wafer is polished or planarized to create a flat surface.

The CMP tool is comprised a rotating platen, slurry, pad, holding ring, brush, and pad conditioner. The mechanical element of this system applies downward pressure to a wafer surface, while the chemical reaction increases the material removal rate. The value chain of the CMP market consists of different players, including semiconductor material suppliers, CMP integrated solution providers, semiconductor wafer suppliers, semiconductor device manufacturers, slurry & pad manufacturers, technology solution providers, and CMP equipment manufacturers.

While CMP is still used for its traditional polishing applications for interlayer dielectrics, it’s also finding employment in more advanced applications, such as bulk oxide polishing, shallow trench isolation, “stop on poly” isolation, and polishing of various dielectrics in advanced transistor designs.

According to a recent market research report published by MarketsandMarkets, the global CMP market is expected to reach $4.94 Billion by 2020, at an estimated CAGR of 6.83% from 2015 to 2020.

Though the CMP market is at the mature stage, it still continues to evolve depending on the end users. The industry is being forced to adopt much innovation in process technologies and applications; as a result, different CMP processes have been evolved with technology nodes and newer applications such as MEMS, advanced packaging, and advanced substrates.

Applied Materials, Inc. (U.S.) and Ebara Corporation (Japan) are the major CMP equipment suppliers. Phoenix-based Entrepix offers unique CMP foundry services.

CMP includes consumable products, polishing pads and slurries. This CMP consumables market is dominated by major market players such as Cabot Microelectronics Corporation (U.S.), Fujimi Incorporated (Japan), and Dow Electronic Materials (U.S.).

Success in CMP lies in optimizing the many process variables. In addition to wafer variables such as film type and pattern density, CMP variables include: time, pressure (force applied to the wafer and pad), velocity, temperature, slurry feed rate, polishing motion, slurry chemistry and pH potential, slurry particle size, pad elasticity, pad hardness and pad condition method. An optimized CMP process also depends on removal rates of the film being planarized, adhesion stability of the film, minimal defects such as scratchs or pits, minimal corrosion (in the case of Cu), and the adhesion of organic or inorganic surface residues formed during the CMP process.

With alternate channel materials on the horizon for future logic transistor, III-V materials such as gallium-arsenide (GaAs), gallium-indium-phosphide (GaInP), and indium-phosphide (InP) are now in R&D which leads to questions regarding direct process costs as well as indirect EHS costs. Much of the concern involves the possible reaction and release of toxic hydrides such as arsine, and phosphine. SEMATECH worked with imec to monitor hydrides produced during CMP processes for high-mobility compound semiconductors.

Suggested Additional Reading:

Chemical Mechanical Planarization: Historical Review and Future Direction

Northern California Chapter of American Vacuum Society: CMP Users Group

CMP Technology Evolving to Engineer Surfaces

Reduced defectivity and cost of ownership of copper CMP cleans

Safe CMP slurries for future IC materials

The rule of three

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