Reality → Tech → Chips → Manufacturing
Modern chip manufacture (see video) is a dynamic, global, and highly competitive industry with multi-billion dollar factories [1] . Critical technical aspects of the manufacturing process include the use of wafers and photolithography:
Traditional vertical integration, most prominently exemplified by Intel with in-house design, manufacturing, and sale of high-end products, is still a prevailing business model. However, dedicated manufacturing by 'foundries' and design by ' fabless' companies is gaining ground worldwide, with TSMC of Taiwan now being the most prominent manufacturer and Qualcomm of USA the most prominent designer. GlobalFoundries, a medium-sized US manufacturer, mirrors the dynamism and globalism of the industry: created by spin-off from AMD and expanded by acquisitions, the company is now owned by the Emirate of Abu Dhabi. Fabrication plants face environmental issues, high capital cost and early obsolescence.
A silicon ingot is being pulled by the Czochralski process as a single crystal from molten silicon which, before doping, has been purified to less than 1 foreign atom per billion silicon atoms.
A 20 nm feature spans only 40 Si atoms bound in the crystal lattice. Ionized gases, oscillating electric fields, and ultra-vacuum are among the means applied to deposit and etch thin layers. Despite extreme cleanliness (less than 10 dust particles per m3), a significant share of a wafer's chips may still contain errors and has to be rejected.
Photomasks (a set of 30-60 masks is required to create the circuit pattern of a chip) are the most critical and expensive tools in photolithography. They are produced by writing computer-designed patterns with computer-controlled electron beams onto a chrome-coated quartz screen. Excimer laser light sent through the mask and a focussing lens system (commonly involving a 4:1 reduction) softens the exposed portions of a photosensitive (resist) coating on the wafer. Steppers or scanners extend the exposure over the whole wafer surface. The exposed areas are chemically removed, leaving a patterned resist structure that in stencil-like fashion guides various processing steps (in particular etching and depositing) on the wafer.
The ArF laser (193 nm wavelength) is todays common light source in photolithography. It allows the patterning of features well below its half wavelength (normally the resolution limit) by inserting a high-refraction immersion medium between lens and wafer and by employing multiple patterning. Also, contrast can be improved through the use of phase-shift masks.
Options for next-generation lithography include the use of extreme ultraviolet (EUV) or even X-ray electromagnetic radiation, as well as electron beams or ion beams. All of these options pose high technical and financial barriers.