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High-Speed and Less Power Consumption: Strained SiGe
(silicon germanium) technology, pioneered by IBM
Microelectronics (NYSE:IBM), was first introduced into high-volume
bipolar
chip production in 1989 and is now standard in
the manufacturing of chips used in high-data-rate wireless
local area network (WLAN) products. In this technology,
a nano-layer of SiGe is deposited on a silicon substrate
wafer at high temperatures. Compressive
stresses induced by Ge atoms reduce the energy bandgap, which in turn increases
electron
mobility across the transistor channel.
Because
manufacturing of defect-free SiGe wafers requires precise
control of the SiGe deposition process, development and
production costs of SiGe wafers is high.
Last year, United Microelectronics Corporation
(NYSE-ADR:UMC), Taiwan’s second largest semiconductor foundry, introduced its strained silicon technology in its high performance CMOS chip process using wafers supplied by
privately-owned AmberWave Systems, a small silicon supplier based in Salem, NH. UMC claimed that its strained silicon process exhibited
significant CMOS performance enhancement, with over 20% current driving capability successfully demonstrated on a 70-nm strained silicon transistor
and speed enhancement of over 10% on a test circuit.
The large-volume commercial silicon wafer
supplier MEMC Electronic Materials, is now investing in new developments by signing an agreement with the Inter-university MicroElectronics Center
(IMEC) in Leuven, Belgium to license advanced IMEC strained silicon technology. The licensing agreement will allow MEMC to produce blanket strained silicon
substrate wafers using IMEC's thin strain relaxed buffer
(SRB) technology. By participating in the program, MEMC researchers work within IMEC, in cooperation with researchers from several semiconductor device manufacturers,
for the goal of improved device performance by implementing strained silicon in the transistor channel regions.
Silicon-On-Insulator (SOI): In sub-100nm technology,
CPU manufacturers, including Advanced Microdevices (NYSE:AMD),
are using SOI wafers as starting materials because it
is possible to design a SOI circuit with up to 30
percent faster transistor operation than the current MOS
circuit built on silicon. Typical commercial SOI wafers
consist of a thin silicon top layer, > 50nm, and a
bottom silicon substrate wafer having a thickness of
several hundred microns. The top silicon layer and
substrate wafer are separated (insulated) by a thin
oxide layer of ~ 150nm thick.
SOI wafers are manufactured using either a Separation by Implantation of Oxygen
(SIMOX) or Smart Cut™
processes. Both processes, which are fundamentally
different from each other, involve intense research and
development work as well as high set-up and production
costs. Because of its premium price, the SOI wafer market
is still relatively small compared to that of silicon and
epitaxial wafers, ~ $5 billion last year. The demand
for SOI wafers is expected to increase as the wafer
price becomes economically feasible for the mass production of
low-cost chips.
Danvers, MA-based Ibis Technology
(NASDAQ:IBIS), which
specializes in SIMOX wafers, sells their SOI wafers to customers
including IBM (92% of sales) and China-based Shanghai Simgui.
Last year, the company had a revenue of $18.4 million
from sales of wafers and equipment used for the SOI wafer
manufacturing. Ibis
recently formed a marketing alliance with MEMC Electronic Materials, which is also its primary supplier of silicon wafer substrates.
Bernin,
France-based Soitec is the world's leading manufacturer of SOI wafers
based on the Smart Cut™ approach. The company's first strategic licensing partner was Shin-Etsu Handotai, which
already began production of Smart Cut™
SOI wafers for shipment to third-party customers. Last year,
the company set up its pilot line facility to produced full Smart Cut™ strained
SiGe on insulator wafers (SGOI). The SGOI process was first
developed by IBM in 2002 for use in making high-performance chips at the 65-nm
node. Soitec, which is traded on the French "Nouveau Marche" at the Paris Stock
Exchange, had a revenue of $109 million in 2003. ($1.28 = 1 Euro).
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