Liquid crystal on silicon
Liquid crystal on silicon is a type of manufacturing process for making microdisplays and SLMs.
It can be pronounced "L-coss".
LCOS phase only SLMs operate on the principle of the birefringence of the liquid crystal material.
Construction[edit]
Layers[edit]
An LCOS module is layered.
The first layer is the top layer. It is the counter electrode (CE). It is made of a standard glass (such as Corning 1737F) covered by a layer of ITO.[1]
There is a top layer of ITO and a bottom layer of ITO. Between them is the liquid crystal. Underneath the bottom layer of ITO is a CMOS backplane.
Parameters[edit]
The counter electrode glass must have a thermal expansion coefficient that matches the backplane's as closely as possible.
The liquid crystal material used in LCOS gadgets is typically a nematic liquid crystal.
The distance from the backplane to the glass substrate may be around 2 microns.
Manufacturing[edit]
Manufacturing of LCOS gadgets can be separated from the process of etching the silicon. A manufacturing facility may be able to receive pre-etched and pixelated backplane CMOS wafers from a fab. Then the facility can simply fill the liquid crystal, do layer alignment, and packaging.
Inputs[edit]
The inputs to the manufacturing process are:
- CMOS silicon wafers with a TFT pattern etched into them
- cover glass wafers
- indium tin oxide
- liquid crystal
- polyamide or inorganic material for an alignment layer
The CMOS silicon wafers already have CMOS patterns in them.
The CMOS silicon wafer is known as a backplane.
Steps[edit]
- Liquid crystal fill and seal
- Electrode attachment
- Packaging
Display product companies[edit]
Silicon foundries[edit]
- Amkor[2]
- Fujitsu
- SMIC
- TSMC
- UMC