What Are Semiconductor Raw Materials?

Semiconductor raw materials are the unprocessed substances used in the manufacturing of semiconductor devices, such as transistors and microchips.

Common raw materials

Silicon (Si)

Refined from silica (SiO₂), silicon is the most widely used semiconductor material processed into high-purity silicon wafers for chip manufacturing.

Other substrates

• Gallium Arsenide (GaAs) – Used in high-frequency and optoelectronic devices, including solar cells, LEDs, and integrated circuits (ICs).

• Silicon Carbide (SiC) – Suitable for high-power and high-temperature applications like power transistors and inverters.

• Gallium Nitride (GaN) – Used in LEDs and power electronics like chargers.

• Germanium (Ge) – Found in high-speed transistors and fiber optic systems.

Dopants

• Boron (B) – P-type dopant for silicon, germanium, and SiC. Its low activation energy allows devices to work well at cooler temperatures.

• Phosphorus (P), Arsenic (As), and Antimony (Sb) – N-type dopants for silicon and germanium. They improve conductivity and stability in high-speed and high-power devices.

• Indium (In) – P-type dopant for silicon and germanium. Its high solubility and low activation energy help improve device efficiency and performance at lower temperatures.

Metals and interconnect materials

• Copper (Cu) – The primary material for interconnects in modern ICs due to its low electrical resistance.

• Aluminium (Al) – Previously used for interconnects but is now usually replaced by Copper. It is still found in some older or lower-cost semiconductor devices due to its good conductivity and ease of use.

• Tungsten (W), Titanium (Ti), Tantalum (Ta) – Used for barrier layers and contact points, crucial for maintaining integrity and performance.

Precious metals

• Gold (Au) – Used for its excellent conductivity and resistance to corrosion, ensuring reliable electrical connections.

• Platinum (Pt) – Its stability and high-temperature resistance make it ideal for precision components that need to perform under extreme conditions.

• Silver (Ag), Palladium (Pd), and Ruthenium (Ru) – Used in specific semiconductor processes for their conductivity and durability.

Dielectric and insulating layers

• Silica (SiO₂) – A key insulating material in semiconductor manufacturing.

• Silicon Nitride (Si₃N₄) – Used as a protective and insulating layer.

• Hafnium Oxide (HfO₂) – Has a high dielectric constant, which allows it to store more charge in smaller spaces, improving the performance of ICs.

• Boron Phosphosilicate Glass (BPSG) – Provides excellent dielectric properties while helping to smooth surfaces during semiconductor fabrication.

Role of raw materials in semiconductor production

Each category of raw materials plays a critical role in ensuring the functionality, performance, and reliability of semiconductor devices. Here is an overview:

• Substrates provide the surface upon which all other layers, such as doped regions, metal interconnects, and dielectric materials, are built. In most cases, Si is the primary substrate, but other materials like GaN and SiC are also used in specific applications due to their unique properties.

• Dopants are added to semiconductors to modify their electrical properties and control the flow of current by creating regions with an excess (N-type) or shortage (P-type) of electrons.

• Interconnect materials are used to create conductive paths between different components in semiconductor devices. Copper has mostly replaced Aluminium due to its excellent conductivity, but the latter may still be used in certain applications due to its lower cost and ease of processing.

• Precious metals minimize electrical flow disruption and improve the performance and lifespan of ICs. These are often used in small amounts for their excellent conductivity, durability, and resistance to corrosion. 

• Dielectric and insulating layers are used to insulate different parts of semiconductor devices to prevent unintended electrical interactions.

Quality and purity requirements

Specific standards for the quality and purity of raw materials in microchip manufacturing help ensure the production of high-performance, reliable devices. Silicon and other substrates must have a purity level of 99.9999% (6N) to 99.9999999% (9N) to avoid defects and ensure efficient operation. Dopants also need to be extremely pure to precisely control electrical properties. Metals, precious metals, and dielectrics require purity levels of 4N to 5N to minimize resistance in interconnects and ensure reliable connections and performance.

Physical properties like thickness and strength are tested for each raw material to ensure compatibility with processes like photolithography and durability under manufacturing conditions. Defect levels should be low, as wafers require smooth, contamination-free surfaces. 

Sourcing raw materials

Here are a few factors to consider while sourcing raw materials for manufacturing ICs:

• Geographical concentration: Critical raw materials like silicon, germanium, and gallium are concentrated in specific regions, particularly China. This dependency on one area can create supply risks due to political instability, trade restrictions, or natural disasters.

• Supply chain complexity: As materials pass through multiple stages and geographical regions, from mining to refining, they require effective coordination and vendor management.

• Risk management: Companies manage risks by diversifying suppliers, establishing long-term contracts, investing in stockpiles, and monitoring geopolitical and economic factors to avoid supply chain disruptions.

• Compliance: Adhering to local and international laws, such as the EU Conflict Minerals Regulation, REACH (Registration, Evaluation, Authorization, and Restriction of Chemicals), and export control regulations, is necessary to ensure that materials are sourced legally and responsibly.

• Environmental and ethical concerns: The industry is focused on reducing the environmental impact of mining energy, water use, and waste management. It also prioritizes ethical practices, such as upholding fair labor standards and responsibly sourcing conflict minerals.