The application and manufacturing process of alumina ceramics in the semiconductor field

Alumina ceramics for semiconductor applications use high-purity α-Al₂O₃ (99.5%–99.99%) as the base matrix. They are characterized by high electrical insulation, plasma corrosion resistance, high-temperature tolerance, low metal ion leaching, and high dimensional precision. These ceramics are widely used in wafer manufacturing equipment, chip packaging, and power electronics, serving as critical precision ceramic components in front-end semiconductor equipment.

 Main Applications in the Semiconductor Field

1. Components of etching and thin film deposition equipment (front-end process) Etching machines, CVD, ALD equipment: cavity linings, gas spray plates, insulating flanges, ceramic nozzles, inner lining protective parts. Performance requirements: Resistant to fluorine/chlorine-based plasma corrosion, with extremely low levels of Na, K, and Fe impurities to prevent wafer contamination caused by metal ion release. Low gas release at high temperatures, dense and free of pores, preventing particle spalling and wafer defects.

2. Wafer carrying and transmission components: electrostatic chucks (ESC), crystal boats, wafer carriers, ceramic mechanical fingertips, vacuum suction cups, positioning gaskets. Performance requirements: Ultra-precision surface processing, low roughness, wear-resistant, and no scratching of silicon wafers; It has stable dielectric properties and small dimensional deformation under thermal cycling.

3. Semiconductor Packaging & Power Electronics Substrates
HTCC (High-Temperature Co-fired Ceramic) substrates and alumina insulating substrates; used for IC packages, RF devices, and power semiconductor packaging.
DBC (Direct Bonded Copper) substrates, leveraging the high insulation and thermal conductivity of alumina, serving as heat dissipation and insulation carriers for IGBTs and power modules.
4. CMP (Chemical Mechanical Polishing/Planarization) Equipment
Ceramic platen and retaining rings; highly wear- and corrosion-resistant, ensuring wafer polishing flatness.
Key Specifications for Semiconductor-Grade Alumina Ceramics:
Purity: ≥99.8%
Densification: ≥99.5%
Impurity Control: Strict control over Na₂O and Fe₂O₃ content
Volume Resistivity: >10¹⁴ Ω·cm
Flexural Strength: 450–550 MPa
Surface Roughness (Ra): Down to the 0.1 μm level

 Complete preparation process flow: High-purity alumina raw powder → Slurry preparation → spray drying and granulation → Molding → de-gumming and degreasing → high-temperature sintering → Post-treatment and precision processing → Cleaning and inspection

1. For the preparation of powder and spray granulation of semiconductor components, high-purity α -AL ₂O₃ raw powder of 4N or above is preferred. The fluidity of ultrafine raw powder is poor, and it is necessary to prepare high-purity alumina granulation powder:

(1) High-purity medium ball milling, ultra-pure water slurry mixing, adding low-impurity dispersants, binders, and a small amount of sintering AIDS (such as MgO, etc., to inhibit abnormal grain growth); Strictly control the secondary pollution caused by grinding media and additives throughout the process.

(2) Spray drying granulation is carried out to obtain spherical granulated powder, ensuring good fluidity, appropriate particle breaking strength, and reducing defects such as hollow particles and satellite spheres.

(3) Screening and grading for standby. The quality of granulation powder directly determines the uniformity of the subsequent green body. Hollow particles and internal defects can cause sintering pores, which may peel off in a plasma environment and contaminate the wafer.

2. Forming Process

(1) Cold isostatic pressing (mainstream for large semiconductor parts/irregular parts) : Pressure 100-200 MPa, uniform green body density, few internal defects, suitable for large-sized components such as cavities and spray plates;

(2) Dry pressing forming: Suitable for simple sheet-like small parts, with high efficiency, but the uniformity of the green body density is limited.

(3) Roll forming: Specifically for preparing thin ceramic substrate sheets, used for HTCC and DBC substrates;

(4) Injection molding: Complex, small and irregular-shaped parts, with a large amount of organic additives and high difficulty in degreasing.

3. De-gumming and degreasing: Slowly increase the temperature at a low temperature to completely remove organic additives such as PVA and dispersants from the green body. Insufficient degreasing can cause sintering bubbles, carbon residues, and release contaminants under semiconductor operating conditions.

4. Sintering process: The sintering temperature for high-purity alumina is 1600-1800℃.

(1) Pressureless sintering: The mainstream for mass production, with a trace amount of MgO added to inhibit grain growth; Moderate cost;

(2) Hot isostatic pressing HIP: After sintering, HIP post-treatment is carried out to further eliminate internal closed pores, achieving a density close to the theoretical density and significantly enhancing the resistance to plasma corrosion. It is used for high-end etched components. High cost;

(3) Hot-pressing sintering: Suitable for small-sized samples, but difficult for large-scale mass production. Controlling the grain size is crucial: if the grains are too large, the plasma corrosion rate will accelerate. When the grains are too small, the mechanical strength of the ceramic decreases.

5. Precision machining and post-processing: After sintering is completed, ceramic-specific CNC, grinding, drilling, and ultrasonic processing are adopted to complete micro-hole, planar, and thread processing. The flatness of semiconductor components can reach the micrometer level, and the tolerance of micro-hole diameters is ± 0.01mm. Finally, perform a super-clean cleaning to remove processing dust and impurities, and complete the inspection and shipment.

Existing Technical Difficulties

1. Full-process impurity control: Ball milling media, binders, and equipment wear may all introduce impurities such as Na, Fe, and Si. Even trace amounts of impurities can cause wafer contamination.

2. Defect control of granulation powder: Hollow particles, internal cracks, sintering transformed into porosity defects;

3. Uniformity of sintering for large-sized components: Large-sized spray plates and cavity parts are prone to sintering deformation and cracking.

4. Resistance to plasma corrosion: The grain boundary phase is preferentially etched by plasma, causing particle shedding, which is the main reason for component failure.