Thermal management for semiconductor process equipment

Thousands of cooling and temperature control systems are installed and operate continuously in fabrication facilities. The cooling capacity demands vary from a couple of hundred Watts (thermoelectric chiller and compressor based systems) to hundreds of kilowatts (liquid-to-liquid cooling systems) with required temperature control ranges from -80 to +150°C. The majority of applications only require one stable temperature set point. However, in the final chip test environment, temperatures are required to vary in order to stress the chip. Here different temperature set points need to be obtained by a single thermal management system. Due to the high-precision processes, tool manufacturers demand a very stable temperature environment. Typical of these requirements are ±0.1K stability (e.g. for etching) to ±0.001K (e.g. for lithography), while cooling capacities can be up to several kilowatts.

In semiconductor fabrication facilities, Laird's custom multistage compressor based chillers are used to support cooling for very low temperature requirements. Most standard chillers need some form of modification to meet semiconductor process facility requirements and may even require a water-cooled condenser. Laird’s liquid-to-liquid cooling systems operate close to ambient and are based on a fluid-to-fluid heat-exchange principle. Laird also offers cost-efficient thermoelectric-based (19" rack) cooling systems for etch applications.

Laird's custom cooling systems have a water-cooled evaporator instead of an air-cooled evaporator. A liquid-to-liquid solution is quieter than a liquid-to-air system because a fan is not required. More importantly, the heat can be rejected by available general facility cooling water and may not be rejected into the air temperature conditioned environment.

Laird cooling systems can be positioned near the production tool, hidden in a false floor or on the lower level in a sub-floor and are built to meet SEMI S2 or F47 standard, including seismic protection. Laird's cooling and temperature control systems can be configured to meet cleanroom requirements.

A semiconductor fabrication environment is one of the most challenging applications for designing and building liquid based cooling systems. Careful consideration is required not only for component selection, but also for the overall liquid cooling system unit and its integration with the semiconductor tools. System challenges that designers face include the type of heat transfer mechanism utilised on the control and heat dissipation sides, material compatibility, valve control, cleanliness, space optimisation, semi compliance and serviceability. These are all areas that need of attention to properly ensure optimised total cost of ownership.

Anders Kottenauer, Senior Vice President, Engineered Thermal Systems Business, Laird, commented: "Laird has expertise in engineering design services and a global presence that supports onsite concept generation, thermal modelling, mechanical and electrical design and rapid prototyping. We also offer validation test services to meet unique compliance standards for the semiconductor industry."

Laird's advanced temperature controllers also offer monitoring and alarm functionality, which is critical to maximising semiconductor equipment uptime.

In semiconductor fabrication applications, Laird's liquid cooling systems are designed to:

• Protect the tool process against chemical reaction by avoiding an unknown Wetted-Parts- Material-Mix;
• Achieve a stable temperature, independent from variations in facility water temperatures;
• Achieve a temperature below or above the facility water temperature; and
• Solve different temperature or fluid requirements at one tool with a multi-loop liquid cooling system.