CMP simultaneously attacks the wafer surface chemically with a reactive slurry and smooths it mechanically with a polishing pad. Raised features are removed faster than recessed areas, producing a globally planar surface. This is essential for multilevel interconnects, since each additional metal layer needs a flat base.
How does lithography work in chip manufacturing?
A light-sensitive photoresist is applied to the wafer and exposed to UV light through a mask. Depending on the resist type, either the exposed or unexposed areas dissolve away during development, transferring the mask pattern into the resist. This pattern then serves as a template for subsequent etch or doping steps.
How does ion implantation work?
Dopant ions are accelerated in an electric field and shot into the wafer at high energy. Penetration depth depends on energy and ion mass, while the dose sets the dopant concentration. A subsequent anneal repairs crystal damage and electrically activates the dopant atoms.
How does Chemical Vapor Deposition (CVD) work?
Gaseous precursors are fed into a reaction chamber, where they react at or near the heated wafer surface to form a solid film. Depending on pressure and temperature, this yields APCVD, LPCVD, PECVD, or ALD processes. The technique produces highly uniform films that conformally coat even complex 3D structures.
How does plasma etching work?
A process gas is converted by electrical energy into a plasma of ions, radicals, and electrons. Reactive radicals chemically attack the material being etched, while accelerated ions remove it physically as well. This combination enables anisotropic etching with steep, precise edge profiles.
How does epitaxy work?
In epitaxy, a crystalline layer grows atomic layer by layer on a single-crystal substrate and adopts its crystal orientation. This typically happens from the gas phase (e.g., silicon vapor-phase epitaxy) under precise temperature and gas-flow control. The result is ultra-pure layers with exactly defined doping.
How does a cleanroom work?
A cleanroom keeps airborne particle concentration extremely low through continuous filtration (HEPA/ULPA) and positive-pressure ventilation. Staff wear special clothing and follow strict procedures to avoid contamination. At nanometer-scale feature sizes, even a single dust particle can destroy an entire chip.
How does diffusion (doping) work?
In thermal diffusion, dopant atoms are applied to the wafer surface at high temperature and migrate into the crystal lattice, driven by the concentration gradient. The penetration depth roughly follows a Fickian diffusion profile and depends on temperature and process time. Unlike ion implantation, this causes no crystal damage, but the doping profile is harder to control precisely.
How does sputtering (PVD) work?
In sputtering, energetic argon ions from a plasma bombard a target made of the desired material and knock atoms loose from it. These atoms travel through the vacuum chamber and deposit as a thin film on the wafer. The technique is especially suited for metals and alloys that are difficult to deposit from the gas phase.
How does EUV lithography work?
EUV lithography uses extreme ultraviolet light with a 13.5 nm wavelength, generated in a plasma source by hitting tin droplets with a laser. Since this light is absorbed by ordinary lenses, the entire optical system uses special multilayer mirrors operating in vacuum. The short wavelength enables significantly finer structures than conventional 193 nm DUV lithography.