What is a semiconductor?
A semiconductor is a material with properties intermediately between conductors like metals, which conduct electricity well, and insulators like rubber or glass, which conduct electricity poorly. Most semiconductors are made from silicon (Si). Additionally, integrated circuits (ICs) and transistors that use these semiconductors are sometimes also called semiconductors. Semiconductors possess the property that the flow of electricity can be controlled by conditions such as temperature, voltage, light, and the addition of impurities (doping). Used in all modern electronic devices, such as smartphones, computers, home appliances, and automobiles, semiconductors have become indispensable to our lives.
What is the semiconductor manufacturing process?
The semiconductor manufacturing process is the series of steps involved in forming microscopic electronic circuits on a silicon wafer and completing them as IC chips. This manufacturing process is broadly categorized into the design process, wafer manufacturing process, front-end process, and back-end process.
What is the design process?
In the semiconductor design process, circuits and patterns are first designed to meet the required product specifications. After repeated simulations to determine the most efficient layout, the patterns are drawn onto a transparent glass plate to create a master called a photomask. This is necessary for transferring the fine circuits onto the wafer in the subsequent front-end process.
What is the wafer manufacturing process?
High-purity silicon (Si) is used to create cylindrical single-crystal ingots, which are then sliced thinly using wire saws to produce circular wafers. The surface of a freshly sliced wafer is uneven, so it undergoes grinding processes like lapping and polishing to achieve a flat, smooth, mirror-like finish. This wafer serves as the substrate for semiconductors, and many chips are manufactured from a single wafer.
What is the front-end process?
The front-end process in semiconductor manufacturing refers to the series of processes that form precise integrated circuits (ICs) onto the numerous microchip areas arranged on a silicon wafer. While the specific steps vary depending on product specifications and design requirements, it generally consists of the following processes:
Wafer Surface Oxidation
Expose the wafer to high-temperature oxygen to form an oxide film on its surface.
Film deposition
Form the required thin film layer on the wafer.
Photoresist coating
Apply a thin, uniform layer of photoresist (photosensitive material) onto the surface of a rapidly rotating wafer. Depending on the situation, the entire sequence of processes up to exposure and development is referred to as lithography.
Exposure and development
Light is projected onto the wafer surface through a photomask and lens, transferring the circuit pattern previously drawn on the photomask. Subsequently, a developer solution is used to dissolve the unwanted photoresist film from either the exposed or unexposed areas.
Etching
Remove the unwanted oxide film and thin film. The thin film beneath the remaining photoresist (resist mask) is left intact.
Resist removal
Remove any remaining photoresist.
Impurity injection
Ions are injected into the wafer to adjust the electrical properties of the semiconductor.
Chemical Mechanical Polishing (CMP)
Polish the wafer surface to flatten pattern irregularities.
Inspection
Each chip formed on the wafer is electrically inspected for defects.
Note
The sequence of processes, the number and scope of process repetitions, and the frequency of inspections and cleaning vary depending on the semiconductor's required specifications.
What is the back-end process?
The “back-end process” in semiconductor manufacturing refers to the steps that transform the silicon wafer—on which integrated circuits have been formed in the chip area during the “front-end process”—into the final product. The typical steps are as follows:
Dicing
The wafer, with its circuitry fabricated in the previous process, is cut using a diamond blade to divide it into numerous IC chips (dies).
Lasers may also be used for cutting.
Wire bonding
Connect the electrodes on the metal base, called the lead frame, to the chip placed in the predetermined position using extremely thin metal bonding wires.
Molding
The chip, which has undergone wire bonding, is encapsulated in resin to protect it from external influences such as scratches, impact, and dust.
Inspection
Perform chip functionality verification, electrical characteristic testing, visual inspection, and long-term endurance testing to eliminate defective products.
Note
The details of process steps, sequence, and inspection vary depending on the semiconductor requirements.
What is semiconductor equipment?
Semiconductor equipment refers to various high-precision devices used to form microscopic circuits on silicon wafers and produce semiconductor chips. Key equipment includes lithography systems that transfer circuit patterns, deposition systems that form thin films, etching systems that remove unwanted thin films, ion implantation systems that introduce impurities, and others. All require extremely high processing precision within a cleanroom environment.
Semiconductor equipment and gears
In semiconductor equipment, the fundamental role of gears remains unchanged. KHK Gears supplies worm gears, rack and pinion systems, spur gears, and other gears to enable movements such as translation, rotation, and opening/closing for deposition equipment, etching equipment, cleaning equipment, and more. However, semiconductor manufacturing demands extremely high precision and a clean environment within cleanrooms. Therefore, overcoming challenges such as managing gear backlash, devising lubrication methods, and preventing dust generation from wear is essential. Particularly in processes directly handling wafers or chips, high precision at the nanometer level is typically required. Since gear backlash is usually measured in millimeters or micrometers, using gears in conventional ways is difficult.