Content: Semiconductors are materials with electrical conductivity between that of a conductor (like metals) and an insulator (like ceramics). They have unique electronic properties that allow control over their conductivity. Semiconductor technology is utilized in simple devices like solar cells and LEDs, and more commonly in the manufacturing of chips, which are then processed into various electronic components. These include IC (Integrated Circuits), microprocessors in servers, memory chips, communication modules (like Bluetooth, Wi-Fi, mobile communication), and ABS (Anti-lock Braking Systems). Semiconductor technology is extensively applied across various fields, significantly contributing to advancements in modern technology.
A semiconductor, typically silicon, begins as a thin slice cut from a large single crystal ingot. The Czochralski process is often used to grow silicon ingots up to 450mm in diameter, which are then sliced into thin wafers. The size of wafers has increased over time, with 300mm diameter wafers now common in high-volume manufacturing. These wafers are highly polished for subsequent photolithography processes, where tiny components are etched at nearly atomic scale across the surface. Larger wafers allow for more dies per wafer, significantly reducing costs.
In the global context, semiconductor capacity is projected to reach new heights, with significant growth driven by advances in technology like generative AI and high-performance computing. The demand for semiconductors is rising across various sectors, including automotive, computation, data storage, and wireless technologies. This surge in demand and the strategic importance of semiconductor manufacturing are driving investments and innovations in the industry
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What's the difference between a wafer and a chip? A wafer serves as the initial material for manufacturing chips. It is a thin, circular silicon substrate typically made of single-crystal silicon. The wafer manufacturing process involves two main stages: the first stage, which includes wafer cleaning, crystal growth, ingot pulling, wafer slicing, and polishing; and the second stage, known as wafer fabrication, which includes processes such as vapor deposition, photoresist coating, exposure, developing, etching, photoresist stripping and final cleaning.
Wafer Cleaning
The wafer raw materials' surfaces are cleaned through high-temperature melting and solvents like HF hydrofluoric acid or KOH potassium hydroxide to remove contaminants and organic residues, ensuring excellent substrate quality.
Crystal Growth
High-purity silicon raw material, silicon dioxide, is placed into a furnace for refining, reducing it to metallurgical-grade silicon. After distillation purification, it undergoes a slow decomposition process to produce "polycrystalline silicon.
Ingot Pulling
Polycrystalline silicon is melted with boric acid and phosphorus in a quartz crucible, and then, at high temperatures, a single crystal silicon rod (seed crystal) is immersed and pulled up while rotating. The silicon adheres to the seed crystal and solidifies evenly on the rod, forming a columnar single crystal silicon ingot.
Wafer Slicing
The freshly produced crystal column has an uneven surface. It needs industrial-grade diamond tools for processing, removal of tapered ends, diameter adjustment, and cutting into wafer slices using high-hardness saw blades or wire saws.
Polishing & Lapping
After wafer dicing, the surface becomes rough and requires polishing and grinding. Polishing aims to make the crystal surface smoother and shinier, while grinding rounds the wafer's edges into a smooth curve.
CVD (Chemical Vapor Deposition)
CVD is a process where gaseous precursors are introduced into a reaction chamber. When these gases come into contact with a heated substrate, they generate deposited materials, forming a thin film on the substrate's surface, used for creating insulating or conducting layers.
Photoresist Coating
When exposed, photoresist undergoes a chemical change. Initially, a uniform photoresist layer is coated onto the wafer's surface, allowing it to be removed or retained in subsequent exposure and development steps, forming the desired pattern.
Exposure
Using patterns on the photomask, expose the photoresist layer to ultraviolet light. Align the photomask onto the wafer coated with photoresist, causing a chemical reaction in the photoresist layer in the illuminated areas, initiating a photochemical reaction.
Photolithography
Exposing wafers to a developing solution (possibly containing alkalis like sodium hydroxide, potassium hydroxide, and additives) selectively removes unexposed areas of the photoresist layer, leaving behind a template in the exposed regions.
Etching
Using acidic or alkaline etching solutions, remove underlying materials based on the pattern on the photoresist layer, leaving the protected areas on the wafer surface (exposed photoresist areas) unaffected, shaping the microstructures of the chip.
Photoresist Stripping
After development, residual photoresist is removed through chemical, thermal, or mechanical methods, like stripping solution, to prevent adverse effects on device performance.
Final Cleaning
Finally, the chips undergo a secondary cleaning process, which may involve organic or inorganic solvents, surfactants, or ultrasonic cleaning techniques, to remove residual chemicals and particles from the manufacturing process, ensuring the produced chips are clean and meet specifications.