Role of Desiccants in Semiconductor Manufacturing
Semiconductor manufacturing is a multifaceted process involving several stages with each stage requiring strict environmental control. The process starts with fabricating silicon wafers, which are cut from a single silicon crystal.
These wafers undergo chemical and physical treatments, including doping, etching, and material deposition. After wafer processing, the wafers are sliced into individual chips, tested for functionality, and packaged. The packaging phase protects the semiconductor from damage and environmental factors such as moisture and contaminants.
Role of Desiccants in Semiconductor
Semiconductor components are highly sensitive to moisture due to the delicate and intricate design. By upholding a dry and clean environment at all stages, defects are prevented and product quality, reliability and performance can be ensured.
Moisture can cause oxidation and corrosion of the metal layers and connections, leading to short circuits and increased resistance. Moisture can also disrupt the lithography process, transferring patterns onto silicon wafers. Additionally, moisture can compromise the integrity of packaging materials that protect the semiconductor chips.
Desiccants absorb excess moisture and maintain dry conditions within cleanrooms and storage environments. Desiccants are proven to help prevent moisture-related issues. The following sections will explore the types of desiccants used in the semiconductor industry, their applications, as well as the benefits offered.
Common Types of Desiccants Used With Semiconductors
Each type of desiccant offers unique properties that make it suitable for specific applications within the industry. The selection of a specific desiccant depends on the application, the level of moisture control needed, and the environmental conditions.
| Desiccant Type | Composition | Applications | Advantages |
|---|---|---|---|
| Silica Gel | Silicon dioxide | Storage and transportation | Non-toxic, stable, reusable after regeneration, absorbs up to 40% of its weight in moisture |
| Molecular Sieves | Crystalline aluminosilicates | Lithography, etching processes | High adsorption capacity, rapid moisture uptake, stability under extreme conditions |
| Activated Alumina | Porous aluminium oxide | Air and gas drying systems | High adsorption capacity, resistant to thermal shock, reusable after regeneration |
| Montmorillonite Clay | Natural clay | Packaging and storage | Good adsorption capacity, cost-effective |
| Desiccant Bags | Blend of various desiccants | Tailored moisture control for semiconductor components | Customisable to specific requirements, versatile in application |
Applications of Desiccants for Different Stages
Wafer Fabrication: During wafer fabrication, maintaining low humidity ensures the accuracy of the lithography process and the integrity of the chemical treatments. Desiccants such as molecular sieves are used in cleanrooms to control moisture levels.
Packaging: During the packaging stage, semiconductor chips are enclosed in protective materials to shield them from physical damage and environmental factors. Desiccants like silica gel and desiccant packs are included in moisture barrier bags to maintain a dry environment.
Storage and Transport: During storage and transport, semiconductor components are at risk of exposure to varying environmental conditions. Container desiccants are used in shipping containers to control moisture levels and protect the components.
Integration of Desiccants in Cleanroom Environments
Effective integration involves the strategic placement of desiccants to ensure uniform moisture control throughout the cleanroom.
- Placement: Desiccants should be placed near moisture-sensitive processes and equipment to provide localised moisture control.
- Desiccant Chambers: Use desiccant chambers or cabinets for storing moisture-sensitive materials and components within the cleanroom.
- Continuous Monitoring: Implement humidity sensors and data monitoring recorders to track moisture levels in real-time and to maintain the chip’s effectiveness.
- Regular Replacement: Schedule regular replacement of desiccants based on their absorption capacity and the cleanroom’s humidity levels.
Best Practices for Desiccant Usage
To maximize the effectiveness of desiccants, it is important to follow these best practices for proper usage and maintenance.
- Proper Handling: Handle desiccants with care to avoid contamination. Use gloves and clean tools when placing or replacing desiccants.
- Regeneration: Desiccants can be regenerated by heating them to remove absorbed moisture.
- Storage: Store unused desiccants in airtight containers to prevent them from absorbing moisture.
- Monitoring: Continuously monitor humidity levels in areas where desiccants are used. Replace desiccants when they reach their absorption capacity.
- Documentation: Keep detailed records of desiccant usage, including placement locations, replacement schedules, and regeneration cycles.
Case Studies of Successful Applications
Case Study 1: Enhancing Wafer Fabrication
A leading semiconductor manufacturer faced challenges with moisture control during the wafer fabrication process. High humidity levels were causing defects in the lithography stage, leading to reduced yields and increased production costs. The company implemented molecular sieves.
Outcome: The precise moisture control provided by the molecular sieves resulted in a significant reduction in defects. The yield improved by 15%, and the overall production efficiency increased, leading to cost savings and higher-quality products.
Case Study 2: Improving Packaging and Storage
A major semiconductor packaging company was experiencing issues with oxidation and corrosion of metal connections during the storage and transportation of semiconductor devices. To address this, the company integrated silica gel desiccants into their packaging solutions.
Outcome: The inclusion of silica gel effectively absorbed residual moisture within the packaging, preventing oxidation and corrosion. The reliability of the semiconductor devices improved, leading to a decrease in return rates and customer complaints. The company also reported enhanced customer satisfaction and confidence in their products.
Case Study 3: Optimising Cleanroom Air Quality
A semiconductor manufacturer needed to maintain ultra-low humidity levels in their cleanroom to prevent contamination during sensitive processes. They implemented a desiccant air drying system using activated alumina in their HVAC system.
Outcome: The activated alumina provided consistent and reliable moisture control, maintaining the cleanroom’s humidity levels within the required range. This led to improved process stability and product quality. The company also noted a reduction in equipment downtime and maintenance costs due to fewer humidity-related issues.
Conclusion
The use of desiccants plays a vital role in maintaining optimal environmental conditions, preventing defects, and ensuring the reliability and longevity of semiconductor devices. As the semiconductor industry continues to advance, the need for stringent moisture control remains essential.
Humi Pak is a manufacturer of desiccant packs in Malaysia and a packaging supplier to the semiconductor industry. Our products ensure optimal moisture control to protect sensitive components. Connect with us to learn more about our desiccant solutions.