In
semiconductor manufacturing
Semiconductor device fabrication is the process used to manufacture semiconductor devices, typically integrated circuits (ICs) such as microprocessors, microcontrollers, and memories (such as Random-access memory, RAM and flash memory). It is a ...
, virtual metrology refers to methods to predict the properties of a
wafer based on machine parameters and sensor data in the production equipment, without performing the (costly) physical measurement of the wafer properties. Statistical methods such as classification and regression are used to perform such a task. Depending on the accuracy of this virtual data, it can be used in modelling for other purposes, such as predicting yield, preventative analysis, etc. This virtual data is helpful for modelling techniques that are adversely affected by missing data. Another option to handle missing data is to use imputation techniques on the dataset, but virtual metrology in many cases, can be a more accurate method.
Examples of virtual metrology include:
* the prediction of the silicon nitride (
) layer thickness in the
chemical vapor deposition process (CVD), using
multivariate regression
The general linear model or general multivariate regression model is a compact way of simultaneously writing several multiple linear regression models. In that sense it is not a separate statistical linear model. The various multiple linear regre ...
methods;
* the prediction of critical dimension in
photolithography
Photolithography (also known as optical lithography) is a process used in the manufacturing of integrated circuits. It involves using light to transfer a pattern onto a substrate, typically a silicon wafer.
The process begins with a photosensiti ...
, using multi-level and
regularization approaches;
* the prediction of layer width in
etching
Etching is traditionally the process of using strong acid or mordant to cut into the unprotected parts of a metal surface to create a design in intaglio (incised) in the metal. In modern manufacturing, other chemicals may be used on other type ...
.
References
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Semiconductor device fabrication
Industrial automation
Lithography (microfabrication)
Metrology