原创 半导体的Post-CMOS时代: Graphene

  今年的ISSCC会议上, 关于Nana级别半导体工艺的研究,重新让人们把目光投向Graphene(石墨烯)上面. 这种移动度比硅大, 介电常数比硅小的材料. 是半导体工艺跨入10nm门槛后最值得期待的代替工艺之一. 硅工艺在100nm以后, 引入了Low-K, High-K Fin-FET, Trigate等基数, 工艺, 随着工艺复杂度急升, 开发成本连大公司都没法独自负担, 在这样的背景下, 人们一直在寻找开发代替硅的合适材料.

Graphene(石墨烯)跟钻石一样，都是纯碳，但它比钻石硬很多。石墨烯是由碳原子构成的二维晶体，碳原子排列与石墨的单原子层一样，成蜂窝状(honeycomb)。虽然它很结实，但是柔韧性跟塑料包装一样好，可以随意弯曲、折叠或者像卷轴一样卷起来。Graphene的晶体结构很稳定, 所以导电性很好, 电子运动速度很快.

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附上Eetime的原文

EETimes.com – ISSCC: Expert picks winner for post-CMOS era

”We will continue to scale vigorously for the next 15 years,” he said during a keynote at the International Solid State Circuit Conference (ISSCC) here. “Beyond silicon microchip technology, revolutionary developments in nanoelectronics, perhaps centering on graphene, may evolve.”

For processors, silicon could scale to the 7.9-nm node, which is slated for 2024. Before or after that, graphene could enable future terascale computing, he said.

So why graphene over the other post-CMOS technology candidates, such as spintronics, molecular electronics, and others? Some claim graphene chips are 100-to-1,000 times faster than silicon. Graphene is the crystalline form of carbon that self-assembles into two-dimension hexagonal arrays perfect for fabricating electronic devices.

Unfortunately, when conventional deposition techniques are used with carbon to grow sheets much larger than one inch, they tend to degenerate into irregular graphite structures. Graphene has higher carrier mobility than silicon, but has been hampered by the lack of a band gap, which has kept the on-off ratio of graphene transistors dismally low–usually less than 10 compared to hundreds for silicon.

Recently, several companies have made headlines in the area. A 100-GHz transistor has recently been demonstrated by IBM Research. Fabricated on new 2-inch graphene wafers and operating at room temperature, the RF graphene transistors are said to beat the speeds of all but the fastest GaAs transistors, paving the way to commercialization of high-speed, carbon-based electronics.

The next-generation of semiconductors could be based on carbon instead of silicon, according to Penn State researchers, who recently claimed to have perfected a method of fabricating pure sheets of carbon semiconductor–called graphene–on 100 millimeter (4-inch) wafers.

Here’s six reasons why Meindl thinks graphene will drive the industry in the post-CMOS era:

1. Graphene has ”a mechanical strength-to-weight ratio exceeding that of any known material.”

2. ”Carrier mobility exceeds 200,000-cm²/Vs.”

3. ”Carriers with zero effective mass that propagate as ‘Dirac fermions’ in a manner similar to photons with a velocity 300 times less than the speed of light without scattering for distances in the micrometer range.”

4. ”The capacity to conduct current densities as large as one thousand times greater than copper without electromigration.”

5. ”Record values of more than 5,000W/mK for room temperature thermal conductivity.”

6. ”The capability to serve as a source, channel drain regions of a field effect transistor (FET) and as an interconnect.”