SOS Technology - UltraCMOS™ -

UltraCMOS™

UltraCMOS is a variation of SOI (Silicon On Insulator) technology which forms MOS transistors, resistors, capacitors, and other elements in the same way as regular silicon semiconductors, and uses SOS (Silicon On Sapphire) technology where a thin silicon film with low defect density is formed on a sapphire substrate. SOS technology itself has been developed by many manufacturers around the world in the past 30 years. However, conventional SOS technologies have had many defects so far, and despite its superior characteristics, it has been not possible to manufacture products in a low-cost range for general uses. Therefore, the use of SOS technology has been limited to special applications such as for military and space uses.
Peregrine Semiconductor Corporation, founded in 1990, was the first in the world to successfully develop silicon-on-sapphire substrates having crystal quality in the same level as conventional bulk silicon substrates. The technology is called UTSi® (Ultra Thin Silicon). This enabled manufacturing of LSIs with MOS transistors, resistors, capacitors, inductors, and other elements integrated on this SOS substrate at a low cost and in a high volume. By integrating CMOSs on an SOS substrate, LSIs with characteristics never achieved by conventional LSIs have been made available. This technology is called UltraCMOS.

In January 2003, OKI formed a comprehensive alliance with Peregrine for process development, LSI design, manufacturing, and sales of LSIs using the SOS-related technologies. Based on the contract with Peregrine, OKI has been developing wireless products such as RF switches for portable phones with Peregrine.

CMOS RF Switch

*Peregrine web site: http://www.psemi.com
*UltraCMOS and UTSi are trademarks or registered trademarks of Peregrine Semiconductor Corporation in USA and other countries.

Features of UltraCMOS

• Unlike conventional bulk CMOS LSIs, UltraCMOS can achieve ideal element characteristics in a simple structure and is particularly best suited for high-speed and high-frequency operation.
• Existing CMOS facilities and manufacturing equipments can be used.
• CMOS logic circuits can be integrated together.
• Transistors separated from each other by insulators can be stacked vertically for enabling high-voltage handling.
  
• Full depletion type SOI (FD-SOI) transistors without any substrate electrodes, which eliminates junction capacitance and brings superior voltage linearity.
• With respect to the on-chip inductors, superior characteristics can be obtained since no eddy-current is generated because of the use of an insulator for the substrate and the capacitance between the inductor and the substrate is zero.
• No additional mask and no additional processes are required for integrating non-volatile memory (EEPROM).

Sapphire

What is sapphire?

Sapphire is said to come from the Latin "sapphirus" (means blue). As its name implies, sapphire is a blue gemstone and is well-known as the birthstone associated with September. However, in its true form, it is a kind of colorless, transparent mineral known as corundum which consists of aluminum oxide (Al2O3). When mixed with small amounts of iron (Fe) and titanium (Ti), this corundum turns to beautiful blue sapphire. Mixtures with different substances bring a wide range of different colors. All of these mixtures are called sapphire except a mixture generating a distinctive color of red. The red corundum where chromium (Cr) is mixed is called rubby, which is well-known as a red gemstone.

Sapphire and rubby which have captured people's hearts with their beautiful colors fall into the same category as aluminum used for one-yen coins. Diamond which has been adored by many women consists only of carbon (C). So, Diamond is a member of carbon family. These facts may change your way of look at gemstones.

Different Facet from Gemstone

Besides being beautiful gemstone, sapphire also has another facet as a material with superior characteristics, and artificial sapphire has been used for a variety of applications. Artificial sapphire manufactured as a material has little impurities and therefore, is normally colorless and transparent. One of its superior characteristics is hardness. Its hardness is second only to diamond among minerals (Mohs Scale hardness: 9), and so it is often used as abrasives for lens and other substances. In our daily life, sapphire is used for the protective glass on wristwatches because of its excellent scratch resistance from its hardness and also of high transparency. Sapphire is employed in CD pickup lens and other components because of its high optical transparency and heat resistance. As an unexpected application, sapphire is mixed in traffic marking paints (such as for crosswalks) to prevent slipping because of its superior wear-resistance.

In this way, sapphire is widely used as an industrial and consumer material because of its mechanical characteristics, chemical characteristics, electrical characteristics, optical characteristics, and thermal characteristics in addition to its hardness,.

Usage in the Electronics Field

Improvements in the manufacturing technology of single crystal substrates have enabled high volume production of high-quality sapphire substrates. Sapphire substrates are also now widely used in the production of the white, blue, and other LED elements which have started to appear as new lighting on the market. This has drawn attention to the use of sapphire in the electronics field.

In the field of silicon semiconductors, SOS (Silicon On Sapphire) technology, forming silicon devices on sapphire substrates, has been a technical issue, and until recently, the use of SOS has been limited to certain special applications only. However, since this technical issue has been overcome with a new technology (UTSi) and the production of high-quality and large-diameter sapphire wafers has been achieved, high-volume production of consumer products has become possible. Using sapphire's excellent electrical insulation properties and low dielectric loss, superior products have become available especially in the RF field.

Although high-purity sapphire wafers do not have the blue sparkle as a gemstone, sapphire wafers continue to shine brightly in the RF field thanks to the superior characteristics as SOS technology.