What are the materials for producing MOSFETs?

The production material system of MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is complex and highly specialized, and its selection directly determines the performance limit, reliability, and applicable scenarios of the device. From basic semiconductor materials to auxiliary packaging materials, the selection of materials for each layer must meet strict physical, chemical, and process requirements. The following analysis will be conducted from three dimensions: material classification, functional characteristics, and technological evolution:
1、 Core semiconductor materials: the basis for determining device performance
Silicon (Si) material
Status: Occupying over 95% of global MOSFET production, it is the preferred choice for low-voltage (<600V) devices.
Advantages: Rich resources, low density of crystal defects (<1/cm ²), high quality of oxide layer (SiO ₂ interface state density<10 ¹⁰cm ⁻² eV ⁻¹).
Application: Conventional scenarios such as consumer electronics power supplies and automotive electronic control systems.
Wide bandgap semiconductor (WBG)
Silicon carbide (SiC): The critical breakdown electric field reaches 3MV/cm, which is 10 times that of Si, and is suitable for high voltage (>600V) scenarios such as electric vehicle OBC and photovoltaic inverters.
Gallium Nitride (GaN): With an electron mobility of 2000cm ²/V · s, three times that of Si, it has excellent high-frequency characteristics (>1MHz) and is used for 5G base station power supply and fast charging heads.
Ultra wide bandgap material (UWBG)
Diamond: With a thermal conductivity of 22W/cm · K, which is 5 times that of Si, it is suitable for extreme high temperature environments (>500 ℃).
Aluminum nitride (AlN): With a bandgap width of 6.2 eV, it has strong radiation resistance and is used in aerospace electronics.
2、 Metal and dielectric materials: constructing conductive and insulating systems
Metallic materials
Gate:
Polycrystalline silicon (Poly Si): has a low density of states at the interface with SiO ₂, but a high resistivity (>10 ΩΩ· cm), and needs to be used in conjunction with metal silicides (such as CoSi ₂).
Aluminum metal (Al): has a low resistivity (2.65 μ Ω· cm), but is prone to electromigration and is now commonly used in low-end devices.
Copper (Cu): with a resistivity of 1.68 μ Ω· cm, it has strong resistance to electromigration and requires the use of double Damascus technology.
Source/Drain:
Aluminum silicon copper alloy (AlSiCu): Balancing conductivity and thermal expansion coefficient.
Nickel silicide (NiSi): with a contact resistance as low as 10 ΩΩ· cm ², used in advanced processes.
dielectric material
Gate oxide layer (SiO ₂): The thickness has approached the physical limit (<1nm), and the equivalent oxide layer thickness (EOT) is further reduced by High-k materials (such as HfO ₂).
Interlayer dielectric (ILD): Fluorinated glass (FSG) reduces parasitic capacitance, while carbon doped silicon oxide (CDO) enhances mechanical strength.
3、 Packaging Material: Ensuring Device Reliability
Substrate material
Direct bonding copper (DBC): Aluminum oxide ceramic bonded to copper layer, with a thermal conductivity of 24W/m · K, used for medium power devices.
Active Metal Brazing (AMB): Brazing silicon nitride ceramics with copper layers increases thermal cycle life by 5 times and is suitable for electric vehicle motor controllers.
Encapsulation shell
Plastic packaging: Epoxy resin molding compound (EMC) has low cost but temperature resistance<175 ℃, and is used for consumer electronics.
Ceramic packaging: Aluminum oxide (Al ₂ O ∝) or aluminum nitride (AlN) ceramics, temperature resistance>300 ℃, used in aerospace.
Heat dissipation material
Thermal Interface Material (TIM): Thermal conductive silicone grease (TC<5W/m · K) or phase change material (TC>10W/m · K), filling the gap between the chip and the substrate.
Heat sink: Aluminum extruded heat sink (low cost) or copper heat pipe (thermal conductivity 400W/m · K), used for high-power devices.
4、 Special Process Materials: Breaking through Physical Limits
Stress Memory Technology (SMT)
Silicon nitride (Si ∝ N ₄) stress film: improves electron mobility (>10%) through tensile stress, used for high-end mobile phone processors.
3D integrated materials
TSV filling material: copper (Cu) or tungsten (W), achieving vertical interconnection of chips and reducing parasitic inductance by 80%.
Lithography materials
EUV Resist: sensitive to a wavelength of 13.5nm, used for gate patterning in processes below 7nm.
5、 Technology Trend: Material Innovation Drives Performance Leap
SiC epitaxial layer: Low defect density epitaxial wafers (<1cm ²) are grown by chemical vapor deposition (CVD) to improve the yield of high-voltage devices.
GaN on Si: Heterogeneous integration of GaN on 8-inch silicon wafers reduces costs by 50%, promoting the popularization of 5G communication modules.
Two dimensional materials: atomic thickness materials such as graphene and molybdenum disulfide (MoS ₂), exploring future ultra micro MOSFETs.
conclusion
The material system of MOSFET is an interdisciplinary field of semiconductor technology, metallization technology, and packaging science. From silicon-based to wide bandgap materials, from single functional layers to composite heterostructures, material selection always revolves around three core requirements: reducing losses, improving voltage resistance, and enhancing heat dissipation. In the future, with the cost reduction of SiC/GaN devices and breakthroughs in two-dimensional material technology, the material boundaries of MOSFETs will continue to expand, promoting the evolution of power electronic systems towards higher efficiency and compactness.