特别报道:摩尔定律问世40周年 常见问题解答

作者: CNET科技资讯网 翻译:李海
CNETNews.com.cn
2005-04-04 09:26 AM



CNET科技资讯网4月4日国际报道 40年前,电子学杂志请求英特尔的创始人Gordon Moore写一篇关于电子工业状况的文章。

这篇文章描述了后来闻名于世的摩尔定律:芯片上的控制电子信号开/关的晶体管数量在一定时期内可以翻番。金科玉律似的摩尔定律让高科技一面成为一个不断高速发展,一面风险又不断增加的行业。

以下是摩尔定律产生的影响、冲击的常见问题解答。

什么是摩尔定律?

摩 尔在1965年文章中指出,芯片中的晶体管和电阻器的数量每年会翻番,原因是工程师可以不断缩小晶体管的体积。这就意味着,半导体的性能与容量将以指数级 增长,并且这种增长趋势将继续延续下去。1975年,摩尔又修正了摩尔定律,他认为,每隔24个月,晶体管的数量将翻番。

这篇文章发表的时候,芯片上的元件大约只有60种,而现在,英特尔最新的Itanium芯片上有17亿个硅晶体管。

尽管这一定律后来成为里程碑似的东西,但这篇文章当时并没有放在首要位置,文章所在的页码是114页。

摩尔最近说:“当时,你不会想把这种东西放入你的档案中的,我当时没有想到它会如此的精确。”

为什么是硅?

这是一个材料科学上奇迹。硅是是一种很好的半导体(它能够导电,但同时也可以控制的方式进行的),尽管收缩,硅的晶体结构仍然能保持完整。

摩尔定律现在失效了吗?

没有,尽管很多分析师与企业的官员已经放言摩尔定律将过时,但它可能仍然发挥作用。

一些人,比如惠普实验室的 Stan Williams与Phil Kuekes认为,到2010年,晶体管的收缩将成为一个问题。因此,厂商需要找到新的替代材料,比如惠普的“交叉开关”(crossbar switches)。

另外一些人,比如英特尔的科技战略部主任 Paolo Gargini则宣称,到2015年,制造商们才开始转向混合芯片(hybrid chips),比如结合了传统晶体管元素与新出现材料,比如纳米线的芯片。到 2020年,新型芯片才会完全投入使用。

从 理论的角度讲,硅晶体管还能够继续缩小,直到4纳米级别生产工艺出现为止,时间可能在2023年左右。到那个时候,由于控制电流的晶体管门 (transistor gate) 以及氧化栅极(gate oxide)距离将非常贴近,因此,将发生电子漂移现象(electrons drift)。如果发生这种情况,晶体管会失去可靠性,原因是晶体管会由此无法控制电子的进出,从而无法制造出1和0出来。

(注:纳米是衡量芯片的体积单位。一纳米是一米的十亿分之一。目前的芯片一般使用90纳米工艺制造。)

如果失效会怎样?

很难讲。如果替代晶体管的材料永远找不到,摩尔定律便会失效。如果替代材料出现了,那么类似摩尔定律的规律讲仍然出现。

最好的替代材料是什么?

天知道?碳纳米管,硅纳米线晶体管,分子开关(molecular crossbars),相态变化材料( phase change materials),自旋电子(spintronics)目前都处于试验阶段。

尽管硅有局限性,但制造商与设计师们仍然喜欢这种材料。硅将继续出现在某些设备当中。

摩尔表示:“我认为,硅技术仍然是制造复杂微结构及材料的基本方法。”

谁提出了摩尔定律?

加 州理工学院的教授Carver Mead也参与了摩尔定律的提出。摩尔表示,20年来,他对人们称他为摩尔定律创始人的做法受之有愧。英特尔的前官员David House曾经推断说,晶体管的数量每18个月翻番。实际上,芯片的性能每隔18个月翻番一次。摩尔强调说,他从;从来没有说过18个月。

摩尔定律不适合于硬盘驱动器的容量或者其它设备之上。摩尔开玩笑的说:“摩尔定律已经被应用于任何呈现指数级增长的东西上面,我很高兴因此而获得好评。”

翻番有何用途?

晶体管数量翻倍带来的好处可以总结为:更快,更小,更便宜。根据摩尔定律,芯片设计师的主要任务便是缩小晶体管的大小,然后让芯片能够容纳越多的晶体管。晶体管的增加可以让设计师为芯片添加更多的功能,比如3D显卡,从而节约成本。

晶体管的增加也能够让设计师将精力放在依靠芯片的总体性能上。由于新旧芯片的体积一一样,因此新款芯片的成本与旧款芯片一样。

另外,小的晶体管意味着电子不需要传得过远,从而提升了芯片的性能。

摩尔定律如何影响实际产品?

摩尔定律让生产找到了提升其产品性能的途径。18年前,“华尔街”这部电影里面的麦克尔道格拉斯拿的手机象一块砖,而现在,晶体管数量的增加让多功能手机得以出现,电视,7百万象素照相机,MP3 音乐播放器都能够融于小小的一只手机当中。

功能更加强大,价格更加便宜的芯片让软件开发商们得以开发出既时通讯,3D游戏以及网页浏览器这样的东西。

技术难点在哪里?

将电流弄进晶体管相当困难,晶体管会发热,这是一个问题。一些晶体管结构,譬如氧化栅极,仅有几个原子那么薄,因此很容易漏电。

硅的出路在何方?

趋势是将硅应用到新地方。未来几年,各种才起步的公司希望在墙壁上,家具中甚至野生动物身上嵌入传感器。微流体芯片(Microfluidics Chip)可以让医生用笔记本电脑获知许多病人的身体状况。

经济方面的影响有哪些?

仅有几个行业会受此影响。汽车制造商们已经表示将会改造汽车内部的茶托(cup holders )以及汽车的外形,因为汽车的引擎不会朝令夕改。

摩尔定律对于经济健康吗?

是也不是。专门衡量摩尔定律的一个规则叫做Rock定律。Rock定律说,芯片工厂的组装成本每四年会翻番。现在,新的组装工厂会耗资数十亿美元。出于成本原因,绝大多数的芯片公司现在并不拥有组装工厂。

华尔街的分析师,未来学家,甚至芯片企业的官员一直在表示,高昂的成本将终结或者减弱摩尔定律的使用。

摩尔还做了哪些别的预测?

摩尔还是预测过家用电脑以及电子表。 上个世纪70年代初,在电子学杂志的,摩尔还预测了“奥弗辛斯基效应应用电子标准内存”(Ovonics Unified Memory)。

并不是摩尔说的每样东西都变为了现实。他曾经预测说,现在的晶圆(wafers)直径会达到56英寸,现在的晶圆直径已经突破了12英寸。 (编辑:孙莹)

FAQ: Forty years of Moore's Law

Published: April 1, 2005, 4:00 AM PST
By Michael Kanellos
Staff Writer, CNET News.com

Forty years ago, Electronics Magazine asked Intel co-founder Gordon Moore to write an article summarizing the state of the electronics industry.

The article outlined what became known as Moore's Law, the observation that the number of transistors--tiny on/off switches that churn out electrical signals that get represented as 1s and 0s--on a chip can be doubled in a short period of time. Adopted as a yardstick by the tech industry, the concept is one of the reasons the industry evolved into a high-growth, but high-risk, affair.

This FAQ explains the impact and consequences of the principles set down in the April 19, 1965, article.

What is Moore's Law?
When writing the article, Moore noted that the number of devices (which then included transistors and resistors) inside chips was doubling every year, largely because engineers could shrink the size of transistors. That meant that the performance and capabilities of semiconductors was growing exponentially and would continue to. In 1975, Moore amended the law to state that the number of transistors doubled about every 24 months.

When the paper first came out, chips sported about 60 distinct devices. By contrast, Intel's latest Itanium chip comes with 1.7 billion silicon transistors.

As monumental as the article has become, it wasn't a big deal then. It started on page 114 of the magazine.

"It wasn't something you expected to join the archives," Moore said in a recent gathering with reporters. "I didn't think it would be especially accurate."

Why is it possible?
It's the miracle of industrial chemistry. Silicon is a good semiconductor (which means it can conduct electricity, but in a manner that can be controlled), and the crystalline structure remains intact despite shrinkage.

Is the law now dead?
No, though various analysts and executives have incorrectly predicted its demise. It will, however, likely begin to slow down to a three-year cycle in the next decade and require companies to adopt alternative technologies.

Some people, such as Stan Williams and Phil Kuekes of HP Labs, say the ability to shrink transistors will start to become problematic by around 2010. That should prompt manufacturers to adopt alternatives, such as HP's crossbar switches, to control electrical signals.

Others, such as Intel's director of technology strategy, Paolo Gargini, paint a more gradual picture. Around 2015, they say, manufacturers will start to move toward hybrid chips, which combine elements of traditional transistors with newfangled technology such as nanowires. A full conversion to new types of chips may not occur until the 2020s.

From a theoretical point of view, silicon transistors could continue to be shrunk until about the 4-nanometer manufacturing generation, which could appear about 2023. At that point, the source and the drain, which are separated by the transistor gate and gate oxide, will be so close

that electrons will drift over on their own. When that happens, transistors will lose their reliability, because it will be impossible to control the flow of electrons and hence the creation of 1s and 0s.

(The nanometer measurement refers to the average feature size on a chip. A nanometer is a billionth of a meter. Current chips are made on a 90-nanometer process, while experimental devices about 6 nanometers long have been produced.)

What happens then?
Hard to say. If alternatives to silicon transistors never materialize, Moore's Law stops. If alternatives emerge, progress could accelerate under similar principles.

What's the best alternative?
Who knows? Carbon nanotube transistors, silicon nanowire transistors, molecular crossbars, phase change materials and spintronics are mostly now lab experiments.

Silicon, though, won't go easy. Manufacturers and designers love it. Chances are, silicon will continue to be incorporated into these new devices in some fashion.

"I view (silicon) technology as a fundamental way for bringing out complex microstructures and materials," Moore said.

Who said what?
California Institute of Technology Professor Carver Mead was the one who dubbed it Moore's Law, a lofty title Moore said he was too embarrassed to utter himself for about 20 years. David House, a former Intel executive, extrapolated that the doubling of transistors doubles performance every 18 months. Actually, performance doubles more like every 20 months. Moore emphatically says he never said 18 months for anything.

The rule also doesn't apply to hard-drive densities or to the growth of other devices. "Moore's Law has come to be applied to anything that changes exponentially, and I am happy to take credit for it," Moore joked.

What does doubling do?
The impact can be summed up as follows: faster, smaller, cheaper. Under Moore's Law, chip designers essentially shrink the size of transistors--which are now measured in nanometers--and then fill up the resulting empty space on the chip with more transistors. More transistors let designers add features, such as 3D graphics, that used to exist on separate chips--thereby cutting costs.

The designers can also choose to dedicate more transistors to speeding up how the chip performs its usual functions. Despite the extra transistors, these enhanced chips cost about the same as the old ones, because they take up the same surface area of silicon.

As an added bonus, smaller transistors mean electrons don't have to travel as far, boosting performance. Though chip designs vary widely, manufacturers try to get some or all of these advantages.

How does that affect products?
Put into practice, Moore's Law spells out a way for companies to enhance their products at a rapid clip. Eighteen years ago, Michael Douglas, in the movie "Wall Street," spoke on a cell phone that was about the size and shape of a brick. Shrinkage and integration has lead to phones with television tuners, 7-megapixel cameras and MP3 players. Declining costs have also put them in the hands of billions of people.

More-powerful, cheaper chips have in turn allowed software makers to develop applications such as instant messaging, 3D games and Web

browsers that would have been cumbersome only a few years before they were invented. Consumers and analysts regularly complain that progress outstrips their needs, but rarely does anyone revert.

What are the technical problems?
Getting electricity to transistors is difficult, and dissipating the heat generated by these transistors is just as challenging. Some transistor structures, such as the gate oxide, are only a few atoms thick, so they leak electricity.

Where does it go next?
The trend now is to put silicon where it isn't. In the coming years, various start-ups hope to embed sensors in walls, household appliances and even wild animals. Microfluidics chips will let doctors quickly harvest large amounts of patient data with less lab equipment.

What's the economic impact?
Very few industries are this lucky. Car manufacturers have to entice customers with new cup holders or different body types, because engine performance doesn't change that rapidly. Moore noted that if car manufacturers had something like this, cars would get 100,000 miles to the gallon and it would be cheaper to buy a Rolls Royce than park it. (Cars would also be only a half an inch long.)

The fear now is that the treadmill will slow.

"Replacement has always been predicated on our industry's ability to come up with neat new things to buy. That in turn has been predicated on greater integration, allowing richer features due to the progress of Moore's Law," wrote Dan Hutcheson of VLSI Research in his newsletter "The Chip Insider." "Slow it down, and end users are likely to slow their replacement rate. Slow this, and the market slows with it."

Are the economics healthy?
Yes and no. One of the unsavory consequences of tracking Moore's Law is called Rock's Law, named after venture capitalist Arthur Rock. It states that the cost of fabrication facilities doubles every four years. Now fabs cost billions of dollars and the cafeterias in them generally cost more than the old fabs, noted Craig Barrett, Intel's CEO. Most chip companies now do not own their own factories because of the costs.

Wall Street analysts, conference futurists and even some chip executives have regularly declared that the outrageous expenses will lead to the end or a slowing of Moore's Law. Most companies, though, never take the advice: Falling off the pace would just ensure extermination by faster-moving competitors anyway. The chip industry remains a multibillion-dollar industry.

What else did Moore predict?
Re-reading the paper after 40 years, Moore noticed that he also predicted the home computer and electronic wristwatches.

In the early '70s, in another article for Electronics Magazine, Moore also forecast the growth of Ovonics Unified Memory, a type of memory made from a similar material as CD disks. In February, Intel said it may come out with Ovonics memory in a few years.

Not everything he's said, however, has come true. He once predicted that wafers, the round disks out of which chips are harvested, would measure 56 inches in diameter about now. They measure 300 millimeters, or 12 inches.

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