PECVD System for LED and Micro-LED Manufacturers Using PSS Technology
🌟 Introduction: Engineering the Foundation of Optoelectronics
In the high-performance world of LEDs, Micro-LED displays, GaN power electronics, and photonic devices, materials innovation starts with the substrate. For over two decades, single-crystal sapphire (Al₂O₃) has dominated as the substrate of choice for GaN-based devices. But the frontier has moved forward: industry leaders now rely on Patterned Sapphire Substrates (PSS) to boost performance.
To meet the increasing complexity of optical design and fabrication processes, manufacturers demand dielectric coatings with precise control of thickness, refractive index, and surface conformity, especially on non-flat substrates like PSS. Among several deposition methods, Plasma-Enhanced Chemical Vapor Deposition (PECVD) has become the preferred solution for low-temperature, high-uniformity thin films.
SIMVACO proudly presents its advanced PSS-compatible PECVD system—a platform designed for high-throughput, low-n SiO₂ film deposition with industry-leading uniformity, contamination control, and process scalability.
🔬 Part I: Technical Foundation
🔷 What is Sapphire and Why Use It?
Sapphire (Al₂O₃) is a wide bandgap dielectric crystal with a unique combination of thermal, mechanical, and optical properties:
| Property | Value |
|---|---|
| Thermal Stability | > 2000 °C |
| Hardness | Mohs 9 |
| Transparency | UV to mid-IR (200 nm – 5 µm) |
| Refractive Index | ~1.76–1.78 |
| Electrical Conductivity | Insulating |
Applications:
- GaN LED epitaxy
- Power transistors (GaN-on-sapphire)
- UV-C emitters
- Watch covers, optical windows, RF devices
🔷 What is PSS (Patterned Sapphire Substrate)?
Patterned Sapphire Substrates (PSS) are sapphire wafers with micron or submicron surface patterns, typically cones, domes, or arrays fabricated using photolithography and dry etching (ICP-RIE). These patterns:
- Improve light extraction efficiency (LEE) by scattering trapped photons.
- Reduce threading dislocation density (TDD) in GaN layers through lateral overgrowth.
- Enable more efficient epitaxial nucleation for uniform crystal growth.
📈 According to Yole Développement and TrendForce, >85% of all high-brightness LED chips use some form of PSS. In Micro-LED and UV-C applications, PSS with additional dielectric structuring is essential for achieving optical performance and pixel uniformity.
🔬 Part II: The Role of PECVD in PSS Applications
🔹 What is PECVD?
Plasma-Enhanced Chemical Vapor Deposition (PECVD) is a thin-film technique that activates chemical reactions using low-temperature plasma (typically <450 °C), enabling the formation of high-quality dielectric films on sensitive or structured substrates.
Typical PECVD dielectrics:
- SiO₂ (Silicon Dioxide)
- Si₃N₄ (Silicon Nitride)
- AlN (Aluminum Nitride)
- SiOCH (Organosilicates for low-k)
🔹 How PECVD Works:
- Precursor gases (e.g., SiH₄ and N₂O) are introduced into a vacuum chamber.
- RF plasma activates gas-phase reactions.
- The precursors dissociate and form solid films on the wafer surface.
- Volatile byproducts are pumped out via vacuum exhaust.
🔹 Advantages of PECVD for PSS Coating:
| Feature | Benefit |
|---|---|
| Low processing temperature | Prevents thermal damage to substrates and pre-patterned layers |
| Good step coverage | Essential for microstructured surfaces like PSS |
| Refractive index control | Tailored optical behavior (e.g., antireflection, photonic filtering) |
| High deposition rate | Scalable for mass production |
| Dense, pinhole-free films | Optical and etch masking reliability |
🔬 Part III: SIMVACO's PECVD System for PSS Applications
🧩 Purpose-Built for PSS + SiO₂
SIMVACO's PECVD system has been specifically engineered for 2 µm thick SiO₂ films with low refractive index (1.45–1.50) on patterned sapphire surfaces.
Key Features:
| Spec | Value |
|---|---|
| Substrate compatibility | 2"–6" sapphire (PSS or flat) |
| Target film | PECVD SiO₂ |
| Refractive index | 1.45–1.50 (633 nm) |
| Deposition thickness | Up to 2.0 μm |
| Uniformity (1σ STD) | <1.5% |
| Throughput | ≥1 wafer/min |
| Process gases | SiH₄ + N₂O + N₂ |
| Chamber temp | 300–400 °C |
| AOI yield | >99% at 10 µm detection |
🔬 Part IV: Technical Innovations
🧪 Multi-Zone Plasma Control
- RF excitation at 13.56 MHz with segmented electrodes
- Adaptive tuning for plasma distribution over micro-patterned surfaces
- Uniform plasma density for repeatable growth rates
🌬️ Precision Gas Flow & Index Control
- Real-time MFC feedback for SiH₄:N₂O ratio optimization
- Linear tuning of refractive index between 1.45 and 1.50
- Precursor pre-mixing reduces local hotspots and powder formation
🔁 Rotating Chuck for 360° Uniformity
- Quartz or anodized aluminum electrode
- Edge-to-center uniformity improved via rotation
- Optional electrostatic chuck for ultra-flat wafers
🧼 Ultra-Clean Chamber Design
- Low-particle gas nozzles and showerhead
- In-situ plasma cleaning and N₂ purging
- Loadlock for wafer isolation
📊 Automation & Inline Metrology
- AOI-ready interface for film inspection
- SEMI-standard robotic loading
- Real-time ellipsometry and film thickness feedback (optional)
💡 Use Cases & Application Scenarios
| Application | Role of SiO₂ PECVD Layer |
|---|---|
| LED on PSS | Buffer or optical layer between sapphire and GaN |
| Micro-LED | Planarization or etch masking on patterned substrate |
| UV-C LED | Light extraction management |
| Photonic IC | Base oxide layer on microstructured wafers |
| Wafer-level packaging | Spacer or interlayer dielectric |
🌍 Global Relevance & Market Trends
- According to SEMI and LEDinside, the demand for PSS-enabled substrates is expected to grow at >8% CAGR through 2028.
- Micro-LED display backplanes increasingly rely on PECVD oxide layers for pixel separation, passivation, and photonic filtering.
- SIMVACO’s solution is already in use across fabs in China, India, Southeast Asia, and Europe, enabling flexible mass production of sapphire-based optoelectronic devices.
📞 Learn More or Request a Demo
SIMVACO’s PECVD platform offers:
- Tailored recipes for SiO₂ coating on PSS
- High-throughput, particle-controlled production
- Integration with AOI, RIE, and MOCVD process lines
📧 Email: simon@simvaco.com
🌐 Website: https://simvaco.com
📲 WhatsApp: +86-15958205967