Semiconductor fabrication plant

In the microelectronics industry, a semiconductor fabrication plant (commonly called a fab; sometimes foundry) is a factory for semiconductor device fabrication. Fabs require many expensive devices to function. Estimates put the cost of building a new fab over one billion U.S. dollars with values as high as

3–4 billion not being uncommon. TSMC invested

9.3 billion in its Fab15 300 mm wafer manufacturing facility in Taiwan. The same company estimations suggest that their future fab might cost $20 billion. A foundry model emerged in the 1990s: Foundries that produced their own designs were known as integrated device manufacturers (IDMs). Companies that farmed out manufacturing of their designs to foundries were termed fabless semiconductor companies. Those foundries, which did not create their own designs, were called pure-play semiconductor foundries. The central part of a fab is the clean room, an area where the environment is controlled to eliminate all dust, since even a single speck can ruin a microcircuit, which has nanoscale features much smaller than dust particles. The clean room must also be damped against vibration to enable nanometer-scale alignment of machines and must be kept within narrow bands of temperature and humidity. Vibration control may be achieved by using deep piles in the cleanroom's foundation that anchor the cleanroom to the bedrock, careful selection of the construction site, and/or using vibration dampers. Controlling temperature and humidity is critical for minimizing static electricity. Corona discharge sources can also be used to reduce static electricity. Often, a fab will be constructed in the following manner: (from top to bottom): the roof, which may contain air handling equipment that draws, purifies and cools outside air, an air plenum for distributing the air to several floor-mounted fan filter units, which are also part of the cleanroom's ceiling, the cleanroom itself, which may or may not have more than one story, a return air plenum, the clean subfab that may contain support equipment for the machines in the cleanroom such as chemical delivery, purification, recycling and destruction systems, and the ground floor, that may contain electrical equipment.

Fabrication of Single-Crystalline InSb-on-Insulator by Rapid Melt Growth

Anna Fontcuberta i Morral, Nicholas Paul Morgan, Heera Menon

InSb has the smallest bandgap and highest electron mobility among III-V semiconductors and is widely used for photodetectors and high-frequency electronic applications. Integration of InSb directly on Si would drastically reduce the fabrication cost and enable new applications, however, it is very challenging due to its 19% lattice mismatch with Si. Herein, the integration of single-crystalline InSb microstructures on insulator-covered Si through rapid melt growth (RMG) is reported and specifically provides details on the fabrication process. The importance of achieving high-quality conformal capping layers at low thermal budget to contain the InSb melt is assessed when the sample is annealed. The importance of ensuring a pristine Si seed area to achieve single-crystalline InSb is illustrated and demonstrated here for the first time.

2021

Contact resistance effects in organic n-channel thin-film transistors

Reinhold Rödel

Organic thin-film transistors (TFTs) have undergone tremendous progress in the past few years. Their great potential in terms of mechanical flexibility, light weight, low-cost and large-area fabrication makes them promising candidates for novel electronic products, such as sensor arrays, radio-frequency identification tags and flexible displays. For the realization of these applications and to improve their performance it is necessary to miniaturize organic TFTs to dimensions of a few micrometers or even less. However, with such aggressive scaling, the device physics becomes more and more important. Especially the contact resistance at and close to the interface between the organic semiconductor and the source/drain metal limits the performance of the organic TFTs at miniaturized dimensions. In this thesis, the contact properties of bottom-gate, top-contact n-channel organic transistors are investigated using the gated four-probe (GFP) technique. The TFTs employ the small-molecule semiconductor N,N'-bis-(1H,1H-heptafluorobutyl)-1,7-dicyano-perylene-3,4:9,10-tetracarboxylic diimide (PDI-FCN2) and are fabricated on flexible plastic substrates. The transistors are air-stable and can be operated at low voltages of about 3 V, owing to a thin hybrid gate dielectric composed of aluminum oxide and a self-assembled molecular monolayer. The GFP method enabled a detailed investigation of the influence of a multitude of factors, including the gate-source and drain-source voltages, the contact length, the temperature and the contact metal, on the contact resistance. The contact properties are found to be very sensitive to the thickness of the organic semiconductor layer. In transistors in which this layer is relatively thin, ohmic contact resistances as small as about 0.6 Ohm cm were measured. In transistors with a relatively thick organic semiconductor layer, device physics becomes more complex and the current-voltage characteristics of the contact become nonlinear. Space-charge limited currents are identified as the probable origin of this nonlinear behavior. The good performance of the PDI-FCN2 transistors allows the realization of simple integrated circuits. Flexible organic complementary ring oscillators are fabricated and signal propagation delays per stage as short as 6 µs are demonstrated at a supply voltage of 3.6 V.

EPFL2016

Contact resistance effects in organic n-channel thin-film transistors

Reinhold Rödel

EPFL2016