Silicon has become the poster child of the semiconductor material world. Currently, this base material serves as the substrate of choice for a large majority of semiconductor wafers. However, silicon carbide's (SiC) distinguishing performance has earned it a stronghold in various industries as well. Let's explore the basic differences between the world-famous silicon and the rising-star silicon carbide.
What are Silicon and Silicon Carbide Made Of?
When synthesized in its purest form, silicon forms a crystalline structure where a single silicon atom forms a bond with four other adjacent silicon atoms. This silicon base substrate can then be doped with various other elements to form semiconductor junctions on a wafer of the silicon substrate.
Silicon carbide, on the other hand, is a blend of silicon and carbon atoms that forms a variety of crystalline structures. The most widely adopted structures for semiconductor use are 3C, 4C, and 6H silicon carbide, all of which have different electrical properties and advantages when doped with various elements. Silicon wafers grow up to 8-12 inches and form from a molten phase of pure silicon. Silicon carbide, however, generally synthesizes from the vapor phase and can grow up to six inches.
The most significant difference between these two substrate structures is the difference in material structure. As is true for all structures, the atom's valence band and conduction band have fixed energy levels―the difference in energy between these two bands is called the "bandgap." Silicon's bandgap ranges from 1 to 1.5 eV, while silicon carbide's bandgap can range from 2.3 to 3.3 eV. While this does make it more difficult for electrons in silicon carbide to move to the conduction band, it also allows for silicon carbide to withstand nearly ten times the amount of electric fields silicon can tolerate.
Silicon & Silicon Carbide Properties: Power and Speed
Given its ability to withstand higher electric fields, silicon carbide substrate materials can withstand higher voltages before breaking down. Silicon has a breakdown voltage of around 600V, while silicon carbide can withstand voltages 5-10 times higher. What this means in practice is that high-power applications will be able to utilize semiconductor technology, or that a device of the same voltage difference can get nearly ten times smaller.
Smaller devices that maintain the same voltage difference result in two intriguing characteristics that give silicon carbide its two inarguable advantages
- Switching speed increases
- Resistance decreases
Silicon carbide can switch at nearly ten times the rate of silicon, which results in smaller control circuitry. Additionally, the decrease in resistance results in less energy loss during operation, making silicon carbide nearly ten times more efficient at higher voltages than silicon.
In practice, silicon carbide is drastically more advantageous for high-voltage applications due to its capability, compactness, and efficiency. Currently, the only downside to silicon carbide is its higher capital cost between similar components. Current manufacturing methods of commercially usable silicon carbide are limited to wafer sizes of about six inches, which is significantly smaller than silicon wafers. Reduction in wafer size results in a higher chip production cost and, therefore, higher capital expense for silicon carbide designs.
Silicon & Silicon Carbide Applications in the Real World
One great industry example of implementing silicon carbide over silicon is in the electric vehicle industry. When driving an EV, the electronics system is designed to support the full load of the vehicle's power capability, which is achievable in both silicon and silicon carbide-based designs. Silicon IGBTs are commonly utilized in EV inverters, where they drive battery-powered motors. However, given a car's normal drive cycle of a car (i.e., not utilizing a full load), silicon's high resistivity makes it rather inefficient. Since silicon carbide can handle the same load design requirements at a much smaller size, silicon carbide becomes significantly more efficient and can subsequently increase the entire inverter system's efficiency by nearly 80%.
Silicon carbide's greatest strength is its drastic efficiency increase. Aside from its nearly immediate adoption into energy-oriented industries such as EVs and solar energy, silicon carbide shows significant promise at drastically increasing electronic efficiencies across industries, with the goal of reducing carbon footprints worldwide. Be sure to stay up to date on silicon carbide, semiconductor products, and more on arrow.com.