Semiconductor device fabrication |
Semiconductor device fabrication is a multiple-step sequence of
predominantly chemical processing steps to create chips used in everyday electrical and electronic devices. Silicon is the most common semiconductor used today, although also gallium arsenide, germanium and some other materials are
used in special applications.
To create the standard silicon-based chips that are used in most computers, raw
silicon dioxide, which is the most common part of sand or glass, is heated in the presence of hydrogen to produce pure silicon
and water which is extracted. The silicon is then melted and formed into ingots, that are sliced into wafers.
Once the wafers are prepared, a large number of process steps are still necessary to produce the desired semiconductor
integrated circuits. In general the steps can be grouped into
four areas: Front End Processing, Back End Processing, Test and Packaging.
Front End Processing refers to the initial steps in the fabrication. In this stage the actual semiconductor devices or
transistors are created. A typical front end process includes: preparation of
the wafer surface, patterning and subsequent implantation of dopants to obtain the desired electrical properties, growth or
deposition of a gate dielectric, and growth or deposition of insulating materials to isolate neighboring devices.
Once the various semiconductor devices have been created they must be interconnected to form the desired electrical circuits.
This "Back End Processing" involves depositing various layers of metal and insulating material in the desired pattern. Typically
the metal layers consist of aluminum or more recently copper. The insulating material was traditionally a form of SiO2
or a silicate glass, but recently new low-K materials are being used. The various metal layers are interconnected by etching
holes, called "vias" in the insulating material and depositing Tungsten in them.
Once the Back End Processing has been completed, the semiconductor devices are subjected to a variety of electrical tests to
determine if they function properly.
Finally, the wafer is cut into individual die, which are then packaged in ceramic or plastic packages with pins or other
connectors to the outside world.
- Wafer fabrication
- Wet cleans
- Photolithography
- Ion implantation (in which dopants are embedded in the wafer creating regions of increased ( or decreased ) conductivity)
- Dry Etching
- Wet Etching
- Plasma ashing
- Thermal
treatments
- Rapid thermal
anneal
- Furnace anneals
- Oxidation
- Chemical vapor deposition (CVD)
- Physical vapor deposition(PVD)
- Molecular beam epitaxy (MBE)
- Electroplating
- Chemical mechanical polish (CMP)
- Wafer testing (where the
electrical performance is verified)
- Wafer
backgrinding (to reduce the thickness of the wafer so the resulting chip can be put into a thin device like a smartcard or PCMCIA card.)
- Die preparation
- Wafer mounting
- Die cutting
- IC packaging
- Die attaching
- IC Bonding
- Wire bonding
- Flip chip
- Tab bonding
- IC encapsulation
- IC testing
External link
Semiconductor Manufacturing
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