Keeping Up with Keeping Up with Moore’s LawMoore’s Law

Who the heck is this Who the heck is this Moore guy anyway?Moore guy anyway?

Gordon E. Moore Gordon E. Moore was the cofounder was the cofounder of Intel of Intel CorporationCorporation

Earned a B.S. in Earned a B.S. in Chemistry from the Chemistry from the University of University of California at Berkeley California at Berkeley and a Ph.D. in and a Ph.D. in Chemistry and Chemistry and Physics Physics

And his law?And his law?

Moore’s Law states that every 18 Moore’s Law states that every 18 months, the number of devices on months, the number of devices on a microchip (and hence the a microchip (and hence the potential power of a computer) potential power of a computer) that can be squeezed on to a that can be squeezed on to a single chip is doubledsingle chip is doubled

This was proposed in 1965 and still This was proposed in 1965 and still holds true today!!!!holds true today!!!!

Integrated CircuitsIntegrated Circuits

Three basic components of Three basic components of integrated circuits are transistors integrated circuits are transistors and DRAM (dynamic random and DRAM (dynamic random access memory) and interconnectsaccess memory) and interconnects

The industry is trying to The industry is trying to simultaneously scale down these simultaneously scale down these components so more can be fit components so more can be fit onto a chip onto a chip

Transistors: Doping silicon Transistors: Doping silicon (it’s not what you think)(it’s not what you think)

Doping is adding Doping is adding atoms to a material atoms to a material to change its to change its electronic propertieselectronic properties

N-type silicon N-type silicon (phosphorous doped) (phosphorous doped) contains free contains free electronselectrons

P-type silicon (boron P-type silicon (boron doped) contains free doped) contains free “holes”“holes”

What’s a Transistor?What’s a Transistor? Transistors are Transistors are

composed of n-type composed of n-type and p-type silicon and p-type silicon

Made up of a source, Made up of a source, gate, and draingate, and drain

The distance between The distance between the source and the the source and the drain is called the drain is called the feature size.feature size.

Insulator (gate Insulator (gate dielectric) placed dielectric) placed between gate and p-between gate and p-type silicon.type silicon.

                                                                                                                                                                                               

Problems with reducing Problems with reducing transistor sizetransistor size

In scaling, the thickness of the In scaling, the thickness of the gate dielectric must decrease as gate dielectric must decrease as the gate length decreases (feature the gate length decreases (feature size). size).

Currently gates sizes are around Currently gates sizes are around 2nm and are projected to decrease 2nm and are projected to decrease to 0.5nm. (~2 atomic layers)to 0.5nm. (~2 atomic layers)

Tunneling induced leakage Tunneling induced leakage becomes a problem.becomes a problem.

Solutions?Solutions?

Thicker high dielectric insulators Thicker high dielectric insulators Reinvent the transistor:Reinvent the transistor:

Single-electron transistor (SET) (basis Single-electron transistor (SET) (basis for quantum computers)for quantum computers)

Use carbon nanotubes to conduct the Use carbon nanotubes to conduct the chargecharge

Organic compounds Organic compounds

What’s DRAM?What’s DRAM?

Essentially a capacitor that stores Essentially a capacitor that stores chargecharge

When charge is present, the binary When charge is present, the binary representation is 1 (the charge representation is 1 (the charge often leaks from the capacitor often leaks from the capacitor necessitating a periodic refresh)necessitating a periodic refresh)

When charge is not present, the When charge is not present, the binary representation is 0binary representation is 0

And how can we make it And how can we make it smaller than ~22smaller than ~22μmμm22??

By reducing the area of the capacitor, of By reducing the area of the capacitor, of course!course!

Since the charge remains constant, the Since the charge remains constant, the thickness of the silicon dioxide dielectric thickness of the silicon dioxide dielectric must be reduced (bc capaticence is must be reduced (bc capaticence is proportional to the dielectric area but proportional to the dielectric area but inversely proportional to the thickness)inversely proportional to the thickness)

The thickness has become so small that The thickness has become so small that quantum tunneling causes the charge to quantum tunneling causes the charge to leak faster than DRAM refresh ratesleak faster than DRAM refresh rates

Solutions?Solutions?

Find an insulator with a higher Find an insulator with a higher dielectric constantdielectric constant

Change the device geometry, Change the device geometry, structure, and processstructure, and process

InterconnectsInterconnects

Links components of the Links components of the integrated circuitintegrated circuit

Uses 70% of the chip’s areaUses 70% of the chip’s area Copper wiring is mainly used (but Copper wiring is mainly used (but

it can only be scaled down so far)it can only be scaled down so far) Will limit processing speed even if Will limit processing speed even if

reductions in transistor size occurreductions in transistor size occur

Developing technologies Developing technologies for faster interconnectsfor faster interconnects

Wireless interconnects (radio-Wireless interconnects (radio-frequency signals)frequency signals)

Optical interconnectsOptical interconnects Use high vertical cavity-surface-Use high vertical cavity-surface-

emitting lasers (VCSELs) to generate emitting lasers (VCSELs) to generate light and build waveguides on the chiplight and build waveguides on the chip

Use light from external sources and use Use light from external sources and use reflectors to direct themreflectors to direct them

Chip makingChip making

With the reduction of the size of IC With the reduction of the size of IC components, resolution in making them components, resolution in making them must increasemust increase

Limitations in lithography (method used to Limitations in lithography (method used to make chips) are economic (don’t know how make chips) are economic (don’t know how to print smaller components cost-to print smaller components cost-effectively)effectively)

Research is primarily concerned with high Research is primarily concerned with high volume production of these nano volume production of these nano componentscomponents

How the darn thing works How the darn thing works (pattern lithography)(pattern lithography)

The wafer is first covered The wafer is first covered by a photoresistby a photoresist

The light that passes The light that passes throught the photomask throught the photomask changes chemical changes chemical structure of the structure of the photoresist and that part photoresist and that part can be washed awaycan be washed away

The resulting pattern is The resulting pattern is then exposed to doping, then exposed to doping, deposition, or etching.deposition, or etching.

The rest of the photoresist The rest of the photoresist is then removed after a is then removed after a permanent change in the permanent change in the wafer is made.wafer is made.

Types of lithographyTypes of lithography

Optical Optical Electron beamElectron beam Proximity X-ray Proximity X-ray Extreme ultraviolet Extreme ultraviolet

So…who’s tired of me So…who’s tired of me talking?talking?

Well, it’s almost over.Well, it’s almost over.

To sum it all upTo sum it all up

Traditional scaling of integrated Traditional scaling of integrated circuits is coming to an end circuits is coming to an end (materials must change)(materials must change)

Quantum physics is becoming Quantum physics is becoming more significant in the quest for more significant in the quest for more computing powermore computing power

The International Technological The International Technological Roadmap for Semiconductors Roadmap for Semiconductors

(ITRS)(ITRS)

Developed by the Semiconductor Developed by the Semiconductor Industry Association in ‘99, it outlines Industry Association in ‘99, it outlines the advances of the industry til ’14the advances of the industry til ’14

To give you an idea by then feature To give you an idea by then feature lengths will be ~20nm, gate thicknesses lengths will be ~20nm, gate thicknesses will be ~0.5nm, and roughly 4 electrons will be ~0.5nm, and roughly 4 electrons would be required to switch on or off a would be required to switch on or off a transistor (as opposed to ~1000 transistor (as opposed to ~1000 electrons today)electrons today)

So, Moore’s Law is going So, Moore’s Law is going to always hold, right?to always hold, right?

WrongWrong Since computing is a physical system, it must abide by Since computing is a physical system, it must abide by

limits set by the laws of physicslimits set by the laws of physics Seth Lloyd of MIT actually computed the physical limits Seth Lloyd of MIT actually computed the physical limits

of computing using quantum mechanics (however, we of computing using quantum mechanics (however, we won’t be able to approach these limits because his won’t be able to approach these limits because his calculations are based on very simplistic “perfect” calculations are based on very simplistic “perfect” computers)computers)

But they are beyond my comprehension so I cannot But they are beyond my comprehension so I cannot explain them to youexplain them to you

And they are probably beyond your comprehension as And they are probably beyond your comprehension as wellwell

And you are probably thinking when will this And you are probably thinking when will this presentation endpresentation end

The EndThe End

ReferencesReferences

Peercy, Paul S. “The Drive to Peercy, Paul S. “The Drive to Miniaturization.” Miniaturization.” NatureNature. Aug 2000: . Aug 2000: 1023-1026.1023-1026.

Pescovitz, David. “Wired for Speed.” Pescovitz, David. “Wired for Speed.” Scientific AmericanScientific American. May 2000: 41-42.. May 2000: 41-42.

Mullins, Justin. “Integrated Circuits.” Mullins, Justin. “Integrated Circuits.” New ScientistNew Scientist. Dec 2000: insert 1-4.. Dec 2000: insert 1-4.

Ito, Takashi and Okazaki, Shinji. Ito, Takashi and Okazaki, Shinji. “Pushing the Limits of Lithography.” “Pushing the Limits of Lithography.” NatureNature. Aug 2000: 1027-1031.. Aug 2000: 1027-1031.