| Metadata | Details |
|---|
| Publication Date | 2023-05-01 |
| Journal | IMAPSource Proceedings |
| Authors | Frank Muscolino |
| Analysis | Full AI Review Included |
- Core Value Proposition: Silicon Carbide (SiC) is a critical wide band gap material driving the electrical revolution, particularly in high-power applications (EVs, solar arrays, wind farms) where its properties significantly outperform Silicon (Si).
- Superior Material Properties: SiC exhibits a band gap approximately 3x and thermal conductivity nearly 5x that of Si, enabling high operating temperatures (>200 deg C), high voltages (>1000V), and low power/switching losses.
- Manufacturing Difficulty: The materialâs extreme hardness (Mohs 9.5) and brittleness necessitate specialized, slower processing steps for wafering (diamond sawing) and die singulation (laser scribing is gaining traction).
- Advanced Packaging Required: High operating conditions mandate specialized assembly techniques, including pressure or pressure-less silver sintering for die attach (melting point 960 deg C) and the use of thick copper wire/ribbon for high current handling.
- Assembly Challenges: Epoxy molding compounds must be specially formulated for high voltage breakdown and thermal stability, leading to higher costs and increased tool wear (due to aggressive compounds).
- Market Growth: The SiC semiconductor market is projected to grow significantly, reaching approximately $1.5B by 2026.
| Parameter | Value | Unit | Context |
|---|
| Band Gap Energy (4H-SiC) | 3.26 | eV | Wide band gap, compared to Si (1.1 eV) |
| Thermal Conduction (4H-SiC) | 3.7 | W/cm.K | High thermal dissipation, compared to Si (1.5 W/cm.K) |
| Electron Mobility (4H-SiC) | 900 | cm2/V.s | Compared to Si (1300 cm2/V.s) |
| Saturation Drift Velocity (4H-SiC) | 2 x 107 | cm/s | High speed performance |
| Mohs Hardness Rating | 9.5 | N/A | Extremely hard, requiring diamond tooling and slow processing. |
| Typical Operating Temperature | 200+ | deg C | Required thermal stability for devices and packaging. |
| Typical Operating Voltage | >1000 | V | Required voltage stability for devices and packaging. |
| Silver Sinter Die Attach Thermal Conductivity | 250 | W/mK | High performance die attach solution. |
| Silver Sinter Die Attach Electrical Conductivity | 41 | MS/m | Low electrical conductivity for die attach. |
| Silver Sinter Melting Point | 960 | deg C | High thermal stability of the die attach material. |
| SiC Wafer Size (Current) | 4 and 6 | inch | Enabling commercialization via standard CMOS fabrication processes. |
| SiC MOSFET FIT Rate (C2M) | 3.7 | N/A | Failures In Time (Fielded Hrs: 63 Billion). |
- Boule Growth (LPCVD): Single crystal SiC boules (pucks) are grown using a Low-Pressure Chemical Vapor Deposition (LPCVD) process. C and Si atoms are ionized by an arc and recombine on a substrate with a stoic geometry (approximately 1:1).
- Wafer Sawing: Due to SiCâs hardness and brittleness, boules are sliced into raw wafers using diamond-coated wires at very slow speeds (e.g., 2 hours to yield 15 wafers) to minimize damage.
- Wafer Polishing (CMP): Raw wafers are polished using standard Chemical Mechanical Polishing (CMP) techniques, but speeds must be lowered compared to Si to prevent edge chipping, resulting in lower throughput (UPH).
- Wafer Fabrication: Devices (diodes, transistors) are fabricated in facilities that must be retooled or newly built, as most existing Si fabs run 300 mm wafers, while SiC is currently 4-inch or 6-inch.
- Die Singulation: Traditional high-speed diamond sawing is used but is slow and causes rapid blade wear. A newer technique, laser scribing, is gaining traction, which forms internal âholesâ that create a cracking plane when the wafer is stretched, resulting in fewer defects.
- Die Attach (Silver Sintering): Individual die are attached to a copper leadframe using silver sintering paste. This process is often performed under pressure (e.g., 10 MPa at 240 deg C for 2 minutes) to achieve high thermal conductivity and reliability under extreme thermocycling. Pressure-less silver sintering pastes are also being developed.
- Wire Bonding: To handle the high current and heat dissipation requirements, standard wire bonding infrastructure is modified to accommodate thick copper wire, copper ribbon, or copper clip bonding, minimizing resistance and inductance.
- Epoxy Molding: Specialized epoxy molding compounds are required to protect the die. These compounds must offer enhanced temperature stability and higher breakdown voltages than standard Si epoxies, often leading to higher operating costs and increased tool wear.
- Electric Vehicles (EVs): Essential for the electrification drive, used in HV-LV DC-DC converters, On-Board Chargers (OBC), and off-board EV charging infrastructure.
- Renewable Energy: Critical components in high-power conversion systems for Central PV (Photovoltaic) arrays, String PV systems, and large-scale wind farms.
- High Power Electronics: SiC is ideally suited for high-power, moderate-frequency switching applications (10 kW to 1 MW range, 10 kHz to 1 MHz switching frequency).
- High Temperature/High Voltage Systems: Used in various applications where Si devices fail due to high operating temperatures (200+ deg C) and high voltages (>1000V).
- Industrial Volume Applications: Historically dominates in metallurgical, abrasive (Carborundum), and refractory industries, though semiconductor volume is rapidly increasing.
View Original Abstract
Silicon Carbide, SiC is one of the most widely used materials that plays a critical role in industries such as: aerospace, electronics, industrial furnaces and wear-resistant mechanical parts among others. Although SiC is widely used in electronics and other high technology applications, the metallurgical, abrasive, and refractory industries are dominate by volume. It is only in the last five or six years that SiC has gained a new and important role in the semiconductor industry. SiC has become a key material in the drive towards electrification. Itâs unique physical properties, wide band gap, especially, high temperature performance and âease of manufacturability makes it a key material going forward. The physical properties that make SiC so unique also represent some serious problems to large scale manufacturing of SiC diodes, transistors and modules. SiC is a very tough material, it has a Mohs hardness rating of 9.5 approaching that of diamond. Just as the semiconductor industry needed high quality defect free silicon wafers to move forward, so did the SiC industry. High quality defect free wafers have just come into the market. They are 4 and six wafers that will allow SiC. These boules can be âslicedâ in wafers and run on a standard CMOS fabrication process. Next comes the dicing of the wafers into devices. A diamond saw has to be run at a very slow rate to a material almost as hard as the diamond itself. Die attach brings an interesting problem the devices are generally rate at 200+ deg C and voltages >1000W. Standard epoxy and even Au/Si eutectic die attach has issues has issues at these extreme operating conditions. Lastly, the epoxy molding compound has to be capable of withstanding the harsh conditions and not breakdown. These are all challenges that are being met today. This is a continuing story of how the semiconductor industry adapts to ever changing requirements