Semiconductor foundries or “fabs” are expensive to build and can take several weeks or months to produce finished chips for use in devices. Due to the costly materials, specialized equipment, and cleanroom environments required, most fabs operate with very small profit margins. This means a primary goal is maximizing yields with as little as possible.
Throughout a fab, temperature, humidity, particles, and contaminants must be strictly controlled. Some aspects of production require high humidity approaching the saturation point and others must be carried out at trace moisture levels, which are very dry. Incorrect relative humidity levels can significantly affect the materials and manufacturing process, leading to defective product and wasted materials.
Here, we’ll look at the importance of creating trace moisture environments for some semiconductor manufacturing processes, the problems that can occur if humidity is too high, and some of the processes that require trace moisture levels.
Why Humidity and Trace Moisture Control Matter in Semiconductor Manufacturing
Moisture can jeopardize almost any manufacturing process or facility. But in semiconductor manufacturing, precise environmental control is critical.
For certain processes, moisture greater than trace amounts can damage silicon wafer layers, contribute to corrosion, and create harmful condensation. The most significant effects of moisture and humidity are seen in these areas:
- Material Integrity: Moisture can damage or degrade laminated wafers, photoresist films, developer solvents, and other materials.
- Process Consistency: Poor moisture control can cause inconsistency in manufacturing processes, such as changes in bonding times or imperfections in the bonding results. This in turn creates waste and scrap, lowering overall yield rates for the facility.
- Device Performance: Semiconductors and finished chips are tested after manufacturing. However, if minor defects go undetected by quality control, chips may not function properly in the electronic devices they go into.
The Consequences of Uncontrolled Moisture in a Trace Moisture Environment
Semiconductors require tightly controlled cleanroom environments because all the components and processes involved in making them are highly sensitive to temperatures, moisture, and contaminants. Below are some examples of problems caused by exposure to moisture:
- Warping: Bonded wafers may warp or delaminate, which makes it impossible to correctly apply photoresist coatings and print patterns on the wafers.
- Chemical Degradation: Moisture can change the viscosity of photoresist film and developer solvents, leading to problems with UV lithography or causing surface moisture and swelling.
- Contamination: Excess moisture causes particles like dust to adhere to wafer surfaces and can encourage the growth of bacteria and molds.
- Corrosion: Moisture can cause metallic components to corrode or oxidize. For example, metal die components used to cut a wafer into chips and bond wires used in chip packages are at risk of corrosion if their environment is not properly maintained.
Semiconductor Processes Requiring Dry/Trace Moisture Control
It’s important to have humidity controls at every stage of semiconductor manufacturing. These are some of the processes that require trace moisture levels:
- Wafer-to-wafer bonding
- Photoresist coating
- Developer solvents
- Preparation for lithography and etching for chips, including microfluidic and standard patterns
Standard, semi-custom, and fully custom environmental control units (ECUs) can control areas from trace moisture to 85% relative humidity (RH) within ±0.5% tolerances in cleanroom environments for semiconductor manufacturing processes.
Contact Air Innovations to Achieve Precise Humidity and Trace Moisture Control
At Air Innovations, we provide custom humidity and temperature control systems for use in mission-critical environments, including semiconductor manufacturing facilities. We are dedicated to developing and testing innovative systems for cleanroom environmental control, and helping semiconductor manufacturers achieve high levels of quality and productivity.
Contact us today to discuss your requirements and learn how we can help.