Filtration, Washing, and Drying for Third-Generation Semiconductor Materials Equipment Applications from SiC Powder Purification to GaN Precursor Processing

A silicon carbide (SiC) substrate, from raw material to the final wafer used in power devices, must go through a long sequence of processes: powder synthesis → crushing and classification → washing and purification → crystal growth → slicing → grinding and polishing. Along this process chain, there is one step that appears fundamental yet directly determines the success or failure of subsequent crystal growth — the washing and purification of SiC powder.

According to industry forecasts, the SiC device market is expected to reach $8.9 billion in 2026, with the substrate market reaching $1.7 billion — together exceeding $10 billion. Chinese companies have already achieved an annual production capacity of over 2 million pieces (equivalent to 6-inch) in the 8-inch SiC substrate sector, and SICC has globally pioneered the 12-inch N-type substrate. However, behind this capacity expansion, the stable supply of high-purity powder has become one of the core bottlenecks constraining industry development.

I. How SiC Powder Purity Affects Substrate Quality

The mainstream method for SiC single crystal growth is the Physical Vapor Transport (PVT) method — SiC powder is sublimated at high temperatures and recrystallized on a seed crystal. In this process, the purity of the powder directly determines the quality of the crystal: impurities introduce crystal defects, micropipes, and dislocations, ultimately leading to reduced device yield.

The preparation of high-purity SiC powder mainly employs processes such as carbothermal reduction, high-temperature synthesis, and chemical vapor deposition. However, regardless of the method used, the synthesized powder inevitably requires post-treatment processes including acid washing, water washing, and drying to remove residual free carbon, free silicon, metal ions, and surface oxides.

II. Main Issues in Conventional Post-Treatment

Challenge 1: Powder Oxidation

Ultra-fine SiC powder has a large specific surface area and can oxidize at elevated temperatures in open filtration and drying equipment. The resulting SiO₂ layer lowers powder purity and may disturb thermal-field uniformity during crystal growth.

Challenge 2: Residual Ionic Impurities

After acid washing, ionic impurities such as Cl⁻, SO₄²⁻, and Fe³⁺ may remain on the powder surface and in pores. The conventional combination of centrifuge + oven cannot achieve deep washing and uniform drying, and residual ionic impurities directly affect the crystal's electrical properties.

Challenge 3: Particle Size Distribution Damage

Agglomeration during drying, especially hard agglomeration, damages the particle size distribution of the powder. For PVT growth, the uniformity of powder particle size directly affects the sublimation rate and crystal growth stability.

III. Applying the 3-in-1 Filter-Dryer to SiC Powder Purification

Wuxi Zhanghua's 3-in-1 Filter-Dryer performs filtration, washing, and drying of acid- or water-washed powder in one sealed vessel, reducing oxidation, contamination, and transfer losses.

1. Fully Enclosed Operation to Reduce Oxidation and Contamination

The equipment is fully enclosed from feeding to discharge, with N₂ or Ar protection available. The powder never comes into contact with the atmosphere during the entire process, effectively preventing high-temperature oxidation while eliminating dust leakage — for nano-scale SiC powder, this also protects operators.

2. Deep Washing — Reducing Ionic Impurities

The equipment features a fully automatic spray system, combined with the S-type agitator's lifting and bi-directional rotation, enabling multi-stage counter-current washing. The washing liquid uniformly penetrates deep into the filter cake, effectively reducing critical ion residues such as Cl⁻, SO₄²⁻, and Fe³⁺, ensuring powder purity meets semiconductor-grade requirements.

3. Vacuum Low-Temperature Drying — Preventing Hard Agglomeration

Drying under vacuum effectively reduces drying temperature, avoiding high-temperature-induced surface oxidation. Meanwhile, the gentle agitation ensures uniform heat distribution, effectively suppressing hard agglomeration caused by capillary forces and protecting the powder's particle size distribution.

4. Process Data Records to Support Customer Audits

The PLC+HMI system records and archives process parameters, providing data for quality documentation, customer audits, and batch traceability.

IV. Process Applicability: Beyond SiC

Gallium Nitride (GaN)

Gallium nitride has no liquid phase and cannot be pulled into single crystals using the traditional Czochralski method; it relies purely on gas-phase reaction synthesis. Currently, GaN substrate applications are still primarily based on epitaxial growth on sapphire, silicon wafers, or SiC wafers. However, whether for GaN powder synthesis or precursor processing, the fully enclosed operation and precision filtration capabilities of the 3-in-1 Filter-Dryer have clear applications.

Gallium Oxide (Ga₂O₃)

The preparation of high-purity gallium oxide powder involves precipitation, filtration, washing, and drying — a process that aligns closely with the 3-in-1 Filter-Dryer's capabilities. As gallium oxide substrate technology gradually matures, the value of the 3-in-1 Filter-Dryer will be further amplified.

V. Wuxi Zhanghua's Manufacturing and Certification Capabilities

Wuxi Zhanghua Pharm & Chem Equipment Co., Ltd. was founded in 1976 and has focused on the R&D and manufacturing of reaction, crystallization, filtration, and drying equipment for nearly 50 years.

Core Capability | Value to Substrate Material Customers

Special Materials Manufacturing: Hastelloy C-276, titanium, and PTFE/PFA linings for corrosive media such as acid washing.

Helium Leak Testing: First in China to pass CSEI certification; leakage rate below 1 x 10^-9 Pa.m3/s, meeting the sealing requirements of high-purity processes.

Geneva Gold Medal Indentation Tester: Non-destructive testing of material properties, providing mechanical-performance data for substrate customers and end users.

International Certifications: ASME, PED, CE, and ATEX, supporting the compliance requirements of semiconductor customers' global procurement.

Industry Standards: One of the drafting organizations for T/CSTM 00824.

As SiC substrates evolve toward 8-inch and 12-inch, the requirements for powder purity and consistency in crystal growth will only become more stringent. The 3-in-1 Filter-Dryer's characteristics of "fully enclosed + high purity + traceable" make it an important post-treatment step in the substrate material preparation process chain.

From SiC powder purification to GaN precursor processing, the 3-in-1 Filter-Dryer can support post-treatment steps that require containment, washing, low-temperature drying, and data recording.

Wuxi Zhanghua Pharm & Chem Equipment Co., Ltd.

Founded in 1976 · Nearly 50 years as a core manufacturer of reaction, crystallization, filtration, and drying equipment

3-in-1 Filter-Dryer (ANFD) — Applicable for SiC powder purification, GaN precursor processing, Ga₂O₃ powder post-treatment, and other third-generation semiconductor substrate material preparation fields

Contact us for technical proposals and case references.

Contact: Manager Zhang

Tel: 13961802200 (same number on WeChat)

Email: zqz008@126.com

Website: www.jszhanghua.com