Tokyo Electron Limited  Annual Report 08

F e at u r e

Semiconductor Manufacturing Technology:

Bringing Together Science’s Best
Fabrication of LSI circuits requires precision equivalent to targeting a 5mm line-width
LSI circuits of approximately 1cm are formed from disc-shaped silicon
within a 30km-diameter circle
2wafers 30cm in diameter. The most advanced manufacturing technolo-

30km diametergies enable fabrication of transistors in an LSI circuit on a scale as small
as less than 50 nanometers (nm),*1 allowing several hundred million transis-Central Tokyotors to be incorporated into one LSI.
In terms of precision, 50nm LSI circuit fabrication on a silicon wafer
30cm in diameter is equivalent to 5mm fabrication on a circle 30km indiameter—an area that would hold the 23 wards of Central Tokyo.
*1 1 nanometer=1 billionth of a meter

The level of precision requiredin semiconductor fabrication× 100,000

is equivalent to targeting

30nm

a 5mm line-width within a30km-diameter circle

Microfabrication

Silicon wafer

30cm diameterTokyo Electron develops and supplies semiconductor production
LSI fabrication involves the formation of transistors or interconnects on aing the pattern to light, and then developing the exposed pattern. A coater/

silicon wafer through repeated circuit pattern formation processes

developer is used in the lithography process to evenly apply the photoresist

including lithography, etching, cleaning, deposition, doping, planariza-

while spinning the wafer at a high speed and then to develop the pattern.

tion and other processes.

Following the lithography sequence, the wafer is etched to create

The lithography process involves a series of pattern transcription steps

circuit elements. Sections of the films not covered by the resist areincluding coating a photoresist (light-sensitive agent) onto a silicon wafer,removed using etching gas in a plasma state in the reaction chamber ofprojecting a mask pattern onto the wafer using a stepper/scanner, expos-an etching system.

Semiconductor Manufacturing Process Flow
Oxide film formation, Nitride film formation

Patterning*
Photoresist coatingExposure
Glass mask

SiN film
Oxide thin film

Development

Etching

In a developer module, thewafers are uniformly covered
with developing agent. With apositive photoresist, only theportions exposed to UV lightdissolve in the developersolution, forming a mask pattern.

A plasma dry etch system isused to strip the films in accordance with the mask pattern.
The portion protected by thephotoresist remains intact, thus
preserving the original pattern
structure under the resist.

UV light

Photoresist

Silicon wafer

Wafers are placed in a hightemperature furnace. O2 gas isstreamed over the wafers toform an SiO2 film on the surface.
Next, an SiN film is formed on
top by the CVD method using
SiH4 and NH3 gases.

The wafers are then uniformly
coated with photoresist via ahigh-speed spin in a coater.
The resist characteristics
change when the coating isexposed to ultraviolet (UV) light.

Glass masks with IC patterns
are aligned over the wafers. UVlight is then applied using astepper to transfer the patterns
to the photoresist.

* Patterning: The process of forming circuit patterns by means of a photolithography method. Patterning takes place at a number of stages during front-end processing.

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Annual Report 08 Tokyo Electron Limited

Semiconductors, LCD Panels and Photovoltaic Cells—
Different Products, Similar Fabrication Technologies
The front-end processing (wafer processing) that takes place in semi-In semiconductors, technological themes are miniaturization, higherconductor manufacturing is highly similar to that performed when manu-speed, and lower energy consumption. Themes for LCD panels arefacturing LCD panels (TFT*1 array processing). Lithography, etching, andlarger sizes and higher resolution, while high conversion efficiency is thethin-film formation and other techniques used in semiconductor produc-key objective with PV cells. Making these attributes possible in a highlytion are also used in the manufacturing of LCD panels.

reliable manner is the role of production equipment manufacturers, andThe difference is that while semiconductors are formed on a sub-these themes will also be the driving force for growth in each respective

strate consisting of a 300mm round silicon wafer, LCD panels areequipment market.

formed on quite large sheets of rectangular glass that can be up to two

Going forward, in addition to semiconductor and FPD production

meters on each side. Moreover, semiconductors, which require highequipment, Tokyo Electron will look to PV cell production equipment asintegration, are fabricated on an ultra-precise nanometer*2 scale, while

another new pillar for growth.

LCD panels are fabricated on a micrometer*3 level.

*1 TFT: Thin Film Transistor*2 1 nanometer=1 billionth of a meter*3 1 micrometer=1 millionth of a meter

The manufacturing method for these LCD panels is also similar toCommon production technologies

that for producing thin-film silicon photovoltaic (PV) cells, which aredrawing significant attention as a clean energy technology. Processing

Semiconductor
manufacturing technology

these PV cells does not require fine patterning, but it is based on a technique in which a thin film of silicon is formed on a glass substrate via aplasma CVD method, which uses almost the same materials.

Thin-film PV cellmanufacturing technology
LCD manufacturing
technology

equipment capable of nanoscale microfabrication
Oxidation/diffusion systems or LPCVD (low-pressure chemical vapor

tungsten (W), for example. CVD is a method of forming layers of thindeposition) systems, thermal processing systems, are used to form

films on a wafer using heat or plasma energy to cause a chemical reac-oxide or nitride dielectric films on the wafer.

tion with the gas materials used.

A cleaning system is used to remove residual materials or particles
following the processes of photoresist strip, CVD and others.

Focusing on the wafer fabrication processes, Tokyo Electron supplies a wide range of products that play key roles in manufacturing

Single wafer CVD systems create metal films that form the contacts

advanced semiconductors.

between the transistors and interconnects using titanium (Ti or TiN) or

Gate formation, Source/Drain formation

Contact formation

Interconnect formation

Ashing / Cleaning

Wafer test
Probe testingGate

Contact plug

Impurities
Isolation
SourceAfter the etch process, thephotoresist is removed byplasma oxidation. The wafers
are then dipped in chemicalsolvents to remove particles
and impurities.

Drain

A gate dielectric is formed
through oxidation, followed byplasma nitridation. A gateelectrode is then deposited andpatterned to create source/
drain regions. The impurities
are implanted into theseregions, and then uniformly
diffused through annealment.

A pre-metal dielectric isdeposited by CVD and thenplanarized. Contact holes areformed using a patterning
process and filled with metal
film using CVD. Excess metal isremoved by polishing.

A low-dielectric-constant film isdeposited. Trenches are formedin the film through a patterning
process. The trenches are filledwith metal film, and the excess
metal is polished away. These
processes are repeated tocreate a multi-level interconnect.

Each fabricated wafer contains
several hundred identical LSI
chips. Prober pins makecontact with chips and transmit
an electrical signal to test theirelectrical characteristics.

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