Roll-to-roll processing
Encyclopedia
In the field of electronic devices, Roll-to-roll processing, also known as web processing, reel-to-reel processing or R2R, is the process of creating electronic devices on a roll of flexible plastic or metal foil
. In other fields predating this use, it can refer to any process of applying coatings, printing, or performing other processes starting with a roll of a flexible material and re-reeling after the process to create an output roll.
s made with thin-film transistor
s and other devices can be easily pattern
ed onto these large substrates, which can be up to a few metres wide and 50 km long. Some of the devices can be patterned directly, much like an inkjet printer
deposits ink. For most semiconductor
s, however, the devices must be patterned using photolithography
techniques.
Roll-to-roll processing is a technology which is still in development. If semiconductor device
s can be fabricated in this way on large substrates, many devices could be fabricated at a fraction of the cost of traditional semiconductor manufacturing methods. Most notable would be solar cell
s, which are still prohibitively expensive for most markets due to the high cost per unit area of traditional bulk (mono-
or polycrystalline
) silicon manufacturing. Other applications could arise which take advantage of the flexible nature of the substrates, such as electronics embedded into clothing, large-area flexible displays, and roll-up portable displays.
rate of the microcrystalline
layer, and this can be tackled using four approaches:
Foil (chemistry)
A foil is a very thin sheet of metal, usually made by hammering or rolling a piece of metal. Foils are most easily made with malleable metals, such as aluminium, copper, tin, and gold. Foils usually bend under their own weight and can be torn easily. The more malleable a metal, the thinner foil can...
. In other fields predating this use, it can refer to any process of applying coatings, printing, or performing other processes starting with a roll of a flexible material and re-reeling after the process to create an output roll.
R2R in electronic devices
Large circuitIntegrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...
s made with thin-film transistor
Thin-film transistor
A thin-film transistor is a special kind of field-effect transistor made by depositing thin films of a semiconductor active layer as well as the dielectric layer and metallic contacts over a supporting substrate. A common substrate is glass, since the primary application of TFTs is in liquid...
s and other devices can be easily pattern
Pattern
A pattern, from the French patron, is a type of theme of recurring events or objects, sometimes referred to as elements of a set of objects.These elements repeat in a predictable manner...
ed onto these large substrates, which can be up to a few metres wide and 50 km long. Some of the devices can be patterned directly, much like an inkjet printer
Inkjet printer
An inkjet printer is a type of computer printer that creates a digital image by propelling droplets of ink onto paper. Inkjet printers are the most commonly used type of printer and range from small inexpensive consumer models to very large professional machines that can cost up to thousands of...
deposits ink. For most semiconductor
Semiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...
s, however, the devices must be patterned using photolithography
Photolithography
Photolithography is a process used in microfabrication to selectively remove parts of a thin film or the bulk of a substrate. It uses light to transfer a geometric pattern from a photomask to a light-sensitive chemical "photoresist", or simply "resist," on the substrate...
techniques.
Roll-to-roll processing is a technology which is still in development. If semiconductor device
Semiconductor device
Semiconductor devices are electronic components that exploit the electronic properties of semiconductor materials, principally silicon, germanium, and gallium arsenide, as well as organic semiconductors. Semiconductor devices have replaced thermionic devices in most applications...
s can be fabricated in this way on large substrates, many devices could be fabricated at a fraction of the cost of traditional semiconductor manufacturing methods. Most notable would be solar cell
Solar cell
A solar cell is a solid state electrical device that converts the energy of light directly into electricity by the photovoltaic effect....
s, which are still prohibitively expensive for most markets due to the high cost per unit area of traditional bulk (mono-
Monocrystalline silicon
Monocrystalline silicon or single-crystal Si, or mono-Si is the base material of the electronic industry. It consists of silicon in which the crystal lattice of the entire solid is continuous, unbroken to its edges. It can be prepared intrinsic, i.e...
or polycrystalline
Polycrystalline silicon
Polycrystalline silicon, also called polysilicon, is a material consisting of small silicon crystals. It differs from single-crystal silicon, used for electronics and solar cells, and from amorphous silicon, used for thin film devices and solar cells....
) silicon manufacturing. Other applications could arise which take advantage of the flexible nature of the substrates, such as electronics embedded into clothing, large-area flexible displays, and roll-up portable displays.
Thin-film cells
A crucial issue for a roll-to-roll thin-film cell production system is the depositionDeposition (physics)
Deposition is a process in which gas transforms into solid . The reverse of deposition is sublimation.One example of deposition is the process by which, in sub-freezing air, water vapor changes directly to ice without first becoming a liquid...
rate of the microcrystalline
Microcrystalline
A microcrystalline material is a crystallized substance or rock that contains small crystals visible only through microscopic examination.-See also:* Macrocrystalline* Microcrystalline silicon* Protocrystalline* Rock microstructure...
layer, and this can be tackled using four approaches:
- very high frequency plasma-enhanced chemical vapour deposition (VHF-PECVD)
- microwave (MWMicrowaveMicrowaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
)-PECVD - hot wire chemical vapour deposition (hot-wire CVDHot Wire-Track listing:*All Songs Written By Mel Galley, except where noted.# Back Street Love 5:01# Take It On Down The Road 4:45# Midnight Flyer 6:01# Wake Up, Shake Up 3:55# Turn It On 5:11# Steal A Mile 4:52# Goin' Home 5:14...
). - the use of ultrasonic nozzleUltrasonic NozzleThis type of spray nozzle uses high frequency vibration to produce very narrow drop size distribution and low velocity spray from a low viscosity liquid. The vibration of a piezoelectric crystal causes capillary waves on the nozzle surface liquid film...
s in an in-line process
See also
- Amorphous siliconAmorphous siliconAmorphous silicon is the non-crystalline allotropic form of silicon. It can be deposited in thin films at low temperatures onto a variety of substrates, offering some unique capabilities for a variety of electronics.-Description:...
- Low cost solar cell
- Printed electronicsPrinted electronicsPrinted electronics is a set of printing methods used to create electrical devices on various substrates. Printing typically uses common printing equipment or other low-cost equipment suitable for defining patterns on material, such as screen printing, flexography, gravure, offset lithography and...
- Roll-to-roll electronics inkjet printer
- Thin film solar cellThin film solar cellA thin-film solar cell , also called a thin-film photovoltaic cell , is a solar cell that is made by depositing one or more thin layers of photovoltaic material on a substrate...