Editing Semiconductor device fabrication (section)

==Wafer metrology==
The highly serialized nature of wafer processing has increased the demand for [[metrology]] in between the various processing steps.  For example, thin film metrology based on [[ellipsometry]] or [[reflectometry]] is used to tightly control the thickness of gate oxide, as well as the thickness, [[Refractive index#Complex refractive index|refractive index, and extinction coefficient]] of photoresist and other coatings.<ref name = "Löper2015">{{cite journal | last1 = Löper | first1 = Philipp | last2 = Stuckelberger | first2 = Michael | last3 = Niesen | first3 = Bjoern | last4 = Werner | first4 = Jérémie | last5 = Filipič | first5 = Miha | last6 = Moon | first6 = Soo-Jin | last7 = Yum | first7 = Jun-Ho | last8 = Topič | first8 = Marko | last9 = De Wolf | first9 = Stefaan | last10 = Ballif | first10 = Christophe | title = Complex Refractive Index Spectra of CH3NH3PbI3 Perovskite Thin Films Determined by Spectroscopic Ellipsometry and Spectrophotometry | journal = The Journal of Physical Chemistry Letters | volume = 6 | issue = 1 | pages = 66–71 | year = 2015 | url = https://doi.org/10.1021/jz502471h | doi = 10.1021/jz502471h | pmid = 26263093 | access-date = 2021-11-16}}</ref> Wafer metrology equipment/tools, or wafer inspection tools are used to verify that the wafers haven't been damaged by previous processing steps up until testing; if too many [[Die (integrated circuit)|dies]] on one wafer have failed, the entire wafer is scrapped to avoid the costs of further processing. [[Virtual metrology]] has been used to predict wafer properties based on statistical methods without performing the physical measurement itself.<ref name="berlin-regression-methods">{{cite journal |author1=Hendrik Purwins |author2=Bernd Barak |author3=Ahmed Nagi |author4=Reiner Engel |author5=Uwe Höckele |author6=Andreas Kyek |author7=Srikanth Cherla |author8=Benjamin Lenz |author9=Günter Pfeifer |author10=Kurt Weinzierl |url=https://ieeexplore.ieee.org/document/6570490 |title=Regression Methods for Virtual Metrology of Layer Thickness in Chemical Vapor Deposition |journal=IEEE/ASME Transactions on Mechatronics |date=2014 |volume=19 |issue=1 |pages=1–8 |doi=10.1109/TMECH.2013.2273435 |s2cid=12369827 |access-date=November 9, 2015}}</ref>