Silicon carbide (SiC) is an important wide bandgap semiconductor material widely used in high-power and high-frequency electronic devices. The following are some key parameters of silicon carbide wafers and their detailed explanations:
Lattice Parameters:
Ensure that the lattice constant of the substrate matches the epitaxial layer to be grown to reduce defects and stress.
For example, 4H-SiC and 6H-SiC have different lattice constants, which affects their epitaxial layer quality and device performance.
Stacking Sequence:
SiC is composed of silicon atoms and carbon atoms in a 1:1 ratio on a macro scale, but the arrangement order of the atomic layers is different, which will form different crystal structures.
Common crystal forms include 3C-SiC (cubic structure), 4H-SiC (hexagonal structure), and 6H-SiC (hexagonal structure), and the corresponding stacking sequences are: ABC, ABCB, ABCACB, etc. Each crystal form has different electronic characteristics and physical properties, so choosing the right crystal form is crucial for specific applications.
Mohs Hardness: Determines the hardness of the substrate, which affects the ease of processing and wear resistance.
Silicon carbide has a very high Mohs hardness, usually between 9-9.5, making it a very hard material suitable for applications that require high wear resistance.
Density: Affects the mechanical strength and thermal properties of the substrate.
High density generally means better mechanical strength and thermal conductivity.
Thermal Expansion Coefficient: Refers to the increase in the length or volume of the substrate relative to the original length or volume when the temperature rises by one degree Celsius.
The fit between the substrate and the epitaxial layer under temperature changes affects the thermal stability of the device.
Refractive Index: For optical applications, the refractive index is a key parameter in the design of optoelectronic devices.
Differences in refractive index affect the speed and path of light waves in the material.
Dielectric Constant: Affects the capacitance characteristics of the device.
A lower dielectric constant helps reduce parasitic capacitance and improve device performance.
Thermal Conductivity:
Critical for high-power and high-temperature applications, affecting the cooling efficiency of the device.
The high thermal conductivity of silicon carbide makes it well suited for high-power electronic devices because it can effectively conduct heat away from the device.
Band-gap:
Refers to the energy difference between the top of the valence band and the bottom of the conduction band in a semiconductor material.
Wide-gap materials require higher energy to stimulate electron transitions, which makes silicon carbide perform well in high-temperature and high-radiation environments.
Break-Down Electrical Field:
The limit voltage that a semiconductor material can withstand.
Silicon carbide has a very high breakdown electric field, which allows it to withstand extremely high voltages without breaking down.
Saturation Drift Velocity:
The maximum average speed that carriers can reach after a certain electric field is applied in a semiconductor material.
When the electric field strength increases to a certain level, the carrier velocity will no longer increase with further enhancement of the electric field. The velocity at this time is called the saturation drift velocity. SiC has a high saturation drift velocity, which is beneficial for the realization of high-speed electronic devices.
These parameters together determine the performance and applicability of SiC wafers in various applications, especially those in high-power, high-frequency and high-temperature environments.
Post time: Jul-30-2024