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450mm wafer standard gets industry nod

Posted: 24 Oct 2008 ?? ?Print Version ?Bookmark and Share

Keywords:450mm standard? wafer? silicon?

Hoping to accelerate the development of 450mm fabs, International Sematech and others have formulated a preliminary standard for 450mm silicon wafers.

But the 450mm era could get delayed amid the IC downturn and current economic crisis.

Meanwhile, after several competing proposals, Sematech, SEMI and the IC industry have settled on a wafer thickness standard of 925?m, plus or minus 25?m, for the so-called ''mechanical standard'' for 450mm silicon wafers. The ''mechanical standard'' is an early and preliminary standard. In comparison, a 300mm wafer has an overall thickness of 775?m.

A standard is key for 450mm wafers. This will enable the development of the initial wafer handling and other systems for 450mm fabs, said Michael Goldstein, materials principal engineer at Intel Corp., one of the driving forces behind the next-generation wafer size. Intel is one of the members of Sematech, which is driving the 450mm movement.

Voting commences
Then, in November, the industry will take the next step. It will vote upon a ''test wafer thickness'' standard for 450mm wafers, but 925?m appears to be the target. ''We do not expect a big change'' from the 925?m standard in the next proposal, he said.

Then, over time, the industry must decide upon the ''production wafer thickness'' for 450mm substrates. That could happen in 2010 or 2011.

To jumpstart the 450mm era, Sematech last year announced a plan to devise a "factory integration test bed" facility for the development of 450mm fab tools.

The proposed facility would help enable chip-equipment makers to develop the initial fab-automation gear, such as carriers, load ports, modules and other items.

The proposed pitch specification for 450mm tools is 10mm. Sematech will be demonstrating a pitch specification of 9.2mm and a wafer deflective sag value of 0.353. In comparison, Sematech last year demonstrated a pitch specification of 9.4mm and a wafer sag value of 0.613.

Vital stats
A 450mm wafer weights 330g, which can cause the substrate to bend or sag on a wafer handling system. The key is to make the substrates and handling systems robust enough to offset the sagging effect.

Still to be seen, however, is when 450mm fabs will appear. As reported, Intel, TSMC and Samsung are separately pushing for the advent of 450mm ''prototype'' fabs by 2012 or so. Some believe 450mm fabs will never happen, saying the R&D costs are too expensive.

If or when 450mm appears, the first production fabs could emerge at the 8nm or 5nm nodes, somewhere between the 2017 to 2019 timeframe, said Dean Freeman, an analyst with Gartner Inc. And in total, it could cost a staggering $20 billion to $40 billion to bring the next-generation wafer size to the market, Freeman said.

Leading the 450mm charge is chip-making consortium Sematech. Recently, Sematech unveiled two next-generation fab programs: 300mmPrime and the International Sematech Manufacturing Initiative's ISMI 450mm effort.

There is widespread support among the fab-tool community for 300mmPrime, which looks to boost the efficiency of existing 300mm fabs, thereby pushing out the need for 450mm plants.

The newer, more controversial ISMI 450mm program calls for some chipmakers to make a more direct transition from 300mm to the larger 450mm wafer size.

Many fab-tool vendors are reluctant to endorse the next-generation wafer size or devise 450mm tools, saying that it is simply too expensive. Many vendors claim that 300mm fabs are suitable for most applications and the real goal for the industry is to improve the productivity of current plants.

- Mark LaPedus
EE Times

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