Intel unveils 45nm transistor breakthrough

Bent on carrying out Moore's Law, Intel Corp. announced in January that it has scored another achievement in transistor design with the use of high-k and metal gate for the insulating walls and switching gates of its 45nm transistors. The new material—with a property called high-k for the transistor gate dielectric and a combination of metal materials for the transistor gate electrode—is expected to improve transistor performance and reduce leakage power.

According to Intel, the combination of high-k gate dielectric with metal gate in its 45nm process technology provides more than 20 percent increase in drive current or higher transistor performance, a twofold increase in transistor density, 30 percent reduction in transistor switching power and 10x reduction in gate oxide leakage power. Moreover, the chipmaker claims that the use of high-k and metal gate will enable its 45nm technology to meet reliability requirements and improve the manufacturability of its 45nm processors.

"The use of high-k and metal materials marks the biggest change in transistor technology since the introduction of polysilicon gate MOS transistors in the late 1960s," said Gordon Moore, Intel co-founder.

For over 40 years, silicon dioxide (SiO₂) had been used to make transistor gate dielectric due to its manufacturability and capacity to deliver performance improvements even as it is made thinner. However, through the years, the thinning SiO₂ gate has become a major problem.

At 65nm, the continued shrinking of SiO₂ led to increased current leakage through the gate dialectric, resulting in wasted current and unnecessary heat. To address the issue, the company replaced SiO₂ with a thicker hafnium-based high-k material in the gate dielectric, reducing leakage by more than 10x compared to SiO₂.

Since the high-k gate dielectric is incompatible with today's silicon gate electrode, Intel developed new metal gate materials, combining different metals for the transistor gate electrodes. However, the company is not disclosing the specific metal gate and high-k dielectric materials it is using.

Early issues
Intel introduced the first working high-k and metal gate transistors in 2003, but was unsure then about the manufacturability of the devices.

"While our research group concluded that we can get significant performance and power management from the use of high-k and metal gate, we weren't sure whether it would be ready for high-volume manufacturing for 45nm. By the time we had our first working 45nm SRAM, we were becoming more confident," said Steve Smith, Intel's VP for DEG group operations.

Replacing silicon dioxide with high-k and metal gate materials provides performance and leakage improvements needed at 45nm.

The company's 45nm technology is following the same yield-improvement curve of 65nm, said Kaizad Mistry, Intel 45nm program manager, logic technology development. "45nm technology is manufacturable. We are able to improve the yield of this technology at the same rate that we did with our last technology, and we expect to be in a position where we have mature yield in 2H 2007 to begin our production ramp on our 45nm including the high-k plus metal gate."

Every two years, Intel introduces a new logic process that is scaled from the previous version. It began production at the 90nm node in 2003, 65nm in 2005 and 45nm this year. "We expect to deliver a new technology generation every two years. So Moore's law lives, at least at Intel," Mistry said.

For the 45nm generation, Intel uses 193nm dry lithography, the same lithography platform used for 90nm and 65nm production. According to Mistry, Intel is using the stable, well-known manufacturing lithography platform, unlike other companies that believe they need to shift to a new type of lithography for the 45nm process. The 193nm immersion lithography has the wavelength of 193nm, but the medium for the light conduction is changed from air to water.

"The new lithography platform has more risks. We do believe immersion lithography is a good technology that will be useful to us in the years to come. But for 45nm, we believe we can use the tried and proven 193nm dry lithography platform," Mistry said.

Penryn processors are ready for three different market segments—notebooks, desktops and servers.

Intel said that its 45nm product lineup includes second-generation quad-core processors. These 45nm processors include new microarchitecture features that aim for greater performance, low power consumption, higher core speed and larger cache.

Segment targetsTargeted at five computer segments, the first Penryn products will boot up Windows Vista, Mac OS, Windows XP and Linux OS. Smith said the Penryn processors are ready for three different market segments—notebooks, desktops and servers. He added that the first wave of 45nm processors tested in these segments includes just five of 15 products currently under development.

Intel's 300mm wafer fabs in Oregon, Arizona and Israel are all set to start 45nm volume manufacturing in 2H 2007.