The application of high-temperature Mini Pleat HEPA filters in high-temperature oxidation and diffusion furnaces in the semiconductor and electronics industry represents the highest level of cleanliness requirements for the production environment. This application is fundamental to ensuring chip yield and performance. Here is a detailed technical application description:
I. Application Stage and Core Functions
1. Application Equipment:
- Oxidation Furnace: Used for growing a high-quality silicon dioxide (SiO₂) film on the silicon wafer surface, serving as gate oxide, field oxide, or as a masking layer.
- Diffusion Furnace: Used for diffusing specific impurities (such as boron, phosphorus) into the silicon wafer at high temperatures to form PN junctions or doping.
- Other High-Temperature Process Equipment: Such as annealing furnaces, LPCVD (Low Pressure Chemical Vapor Deposition) furnaces, etc.
2. Application Location: Installed at the end of the process gas (usually high-purity oxygen or nitrogen) supply system of the above process equipment, as well as at the air inlet of the equipment chamber. Clean air or gas must be filtered before entering the quartz tube at temperatures above 1000°C.
3. Core Functions: To provide "ultra-clean" process gases and environmental gases for ultra-precision high-temperature processes.
- Prevent Crystal Defects: Any micrometer or sub-micrometer particle contaminants landing on the silicon wafer surface can become nucleation centers under high temperatures, leading to fatal defects such as dislocations and stacking faults in the silicon crystal.
- Ensure Gate Oxide Integrity: For oxidation processes, especially gate oxide growth, even a tiny particle can cause local thickness variations or pinholes in the oxide, leading to gate leakage or breakdown, rendering the entire chip inoperative.
- Control Doping Uniformity: In diffusion processes, particle contaminants can hinder the uniform diffusion of impurities, leading to poor PN junction characteristics and affecting the electrical parameters of the chip.
II. Why "High-Temperature" and "Ultra-High Efficiency" Filters Are Essential in This Stage?
1. Extreme High-Temperature Resistance (Typically 300°C - 500°C or Higher):
- Process Requirements: The temperatures for semiconductor oxidation and diffusion processes usually range from 900°C to 1200°C. The gases introduced are preheated before entering the reaction tube, so the filters must withstand the high temperatures generated by the front-end preheating system (usually designed above 300°C, with a margin).
- Material Stability: Special high-temperature glass fiber filter paper, stainless steel frames, and high-temperature resistant sealants must be used to ensure no cracking, no pulverization, and no release of any volatile substances under long-term high temperatures, otherwise, they themselves would become a source of contamination.
2. Ultra-High Filtration Efficiency (Typically H14 or U15 and Above):
- Capture Precision: The semiconductor industry deals with particles that can damage nano-scale circuit structures. There is usually a high capture efficiency requirement for particles ≥0.1μm or even ≥0.05μm. H14 level (efficiency ≥99.995% for 0.3μm particles) is a common starting point, and higher processes may use U15 (efficiency ≥99.9995% for 0.1μm particles) and other higher-grade filters.
- Advantages of Mini Pleat Design: No Risk of Metal Ion Release: Completely avoids the risk of metal ion release from aluminum partitions in partitioned filters. Sodium (Na), potassium (K), iron (Fe), and other metal ions are the "number one killer" in semiconductor processes, leading to severe device performance degradation.
- Compact Structure: Facilitates installation in the limited space of equipment gas lines.
- High Dust Holding Capacity: Suitable for long-term continuous production conditions.
III. Specific Technical Requirements and Industry Characteristics
1. Beyond Conventional Cleanliness Standards:
Semiconductor chip manufacturing is carried out in Class 1 (ISO 3 level) or higher cleanliness rooms. However, the cleanliness requirements inside the process equipment, especially the reaction chamber, are several orders of magnitude higher than the surrounding environment, known as "clean rooms within clean rooms". There are also strict requirements for airborne molecular contaminants (AMC), which require the filters themselves to have low chemical outgassing characteristics.
2. Ultimate Material Purity:
- All Materials of the Filter: All materials must meet ultra-pure application requirements. The stainless steel frame needs to be high-grade 316L or better to ensure extremely low metal ion leaching.
- Filter Media and Adhesives: Need to be specially treated to have low outgassing characteristics to prevent the release of organic or inorganic contaminants in high-temperature and high-vacuum environments.
3. Absolutely Reliable Sealing and Leak Detection:
- Installation: Must use knife-edge sealing or other absolutely airtight methods to ensure "zero leakage".
- Post-Installation: Must undergo strict on-site PAO/DOP scanning leak detection, with testing standards far more stringent than ordinary industries, and any minor leakage point is unacceptable.
IV. Summary of the Value and Importance of the Application
1. The Lifeline of Yield: In nanometer-scale chip manufacturing, a single dust particle larger than the circuit feature size can ruin a die (grain), or even an entire wafer (wafer). High-efficiency filters are a prerequisite for ensuring ultra-high yield (>95%).
2. Key Guarantee for Technological Nodes: As chip processes evolve from 28nm to 7nm, 5nm, and more advanced nodes, the control requirements for defects increase exponentially. High-temperature ultra-high efficiency filters are indispensable technologies for achieving advanced processes.
3. The Cornerstone of Product Reliability: Prevents potential defects, ensuring the electrical stability and reliability of chips during long-term use.
4. Compliance with Industry Standards: It is a basic requirement for semiconductor equipment by industry standards such as SEMI (International Semiconductor Industry Association).
Conclusion: In semiconductor high-temperature oxidation and diffusion furnaces, high-temperature Mini Pleat HEPA filters have transcended the general role of "filters"; they are a sophisticated "process gas purification component". Their performance directly determines whether the microcosm of integrated circuits can be perfectly "carved", and they are an indispensable "pearl" on the crown of the semiconductor industry, reflecting the ultimate performance requirements of cutting-edge manufacturing for basic industrial components.
This version has been carefully reviewed to ensure grammatical accuracy and professional expression.