Gate leakage, down and out?

R. Colin Johnson (12/04/2007 10:09 AM EST)

PORTLAND, Ore. — A high-k dielectric process for CMOS transistors promises to turn the International Semiconductor Roadmap into a freeway by eliminating the gate-leakage problem at advanced nodes down to 10 nanometers.
Overheating due to excessive gate leakage is the number one hurdle to reaching advanced semiconductor nodes below 45 nanometer. Now, a process with 1 million times less gate leakage could enable rapid migration to advanced nodes, according to Clemson University researchers.
The rapid-thermal process of atomic layer deposition achieved an effective gate oxide thickness (EOT) of 0.39 nanometers with only 10-12A/cm2.
"This is a process that is robust and manufacturing tools could be developed for it without any fundamental barriers. We are using standard CVD techniques and the same precursors as everybody else," said Rajendra Singh, director of the Center for Silicon Nanoelectronics at Clemson University. "The difference comes from our optimized process chemistry and our use of different kinds energy sources—that's what our patent covers."
As gate oxide thickness were slimmed for 45-nm nodes and below, the industry has moved to using high-k dielectrics. For instance, Clemson's hafnium gate oxide high-k dilectric measured 2.4 nanometers in thickness, but had an EOT of 0.39 nanometers when compared to conventional silicon dioxide.
The semiconductor roadmap calls for high-k dielectrics at the 65-nm node, but most manufacturers, including Intel Corp., have delayed going to high-K dielectrics until the 45-nm node. The reason is that manufacturers would have to solve the problem of higher gate leakages through dielectrics that insulate less well than silicon dioxide.
Clemson's results indicate that such high-k dielectrics were the right way to go, and should take the industry down to the 10-nm node.
"It has signiýcant impact on silicon IC manufacturing industry," said Singh. "Semiconductor manufacturers are currently debating whether its worth the cost to change to larger 450-millimeter wafers, but using our invention eliminates several processing steps resulting in an overall reduction in costs at advanced nodes."

100+ Lumens/watt LED bulbs

LLF claims efficiency record from high-CRI warm-white LED lamp LED Lighting Fixtures Inc (LLF) of Morrisville, NC, USA, which develops LED-based light fixtures for general illumination, says that its LRP-38 lamp has set a new standard for energy-efficient lighting by producing 659 lumens while consuming just 5.8W of wall-plug power (113.6 delivered lumens per watt), compared with 60W for an equally bright incandescent bulb, according to results of steady-state tests by the US National Institute of Standards and Technology (NIST) on LLF’s prototype PAR 38 self-ballasted lamp.
The lamp uses less than 9% and 30% of the energy consumed by incandescent and fluorescent sources, respectively. The lamp emitted a warm-white incandescent-like color of 2760K with a high color rendering index (CRI) of 91.2.
“The results of this prototype clearly demonstrate that LLF’s LED technology will surpass all existing forms of lighting in terms of performance,” says chief technology officer Gerry Negley. “The prototype lamp verifies that the LLF platform can be deployed in any form factor, which will allow full penetration of the global lighting market,” he adds. “We used Cree Inc XLamp and Osram Opto Semiconductors Golden Dragon products in the lamp, which we believe are the best LEDs available to maximize our proprietary system performance.”
The LRP-38 demonstration is the most energy-efficient, high-CRI white lighting solution ever developed, claims LLF’s Hong Kong managing director, Tony van de Ven. “While there is currently no timetable for a production release, this result shows that LLF’s technology with LED light sources has the ability to surpass 100 lumens per watt from a fixture, which is a revolutionary milestone.”
Currently, via 65 lighting sales agents across the USA and Canada (representing over 300 distributors), LLF sells its LR6 six-inch downlight product (designed for 50,000 hours of lifetime) in warm (2700K) and neutral (3500K) white colors.