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Tegal "film repair" tool set for LED production

A new type of cluster tool featuring cyclic CVD and plasma treatment stages will ship to a leading maker of high-brightness LEDs this summer.

Following two years of development work with a leading high-brightness LED manufacturer, a novel deposition tool from Tegal should soon move into volume wafer production.

The Petaluma, California, company's nanolayer deposition (NLD) tool does not just deposit films "“ it also features a plasma treatment stage that Tegal CTO Steve Selbrede says "repairs" the material deposited.

Having just signed a beta site agreement with its lead HB-LED customer, Tegal will deliver the 'Compact 360 NLD' system this summer, with volume commercial production slated for calendar 2009. Exactly what the new tool will be used to deposit isn't being revealed by Tegal or its customer, but it may have a number of applications in compound semiconductor fabrication.

Although it does not deposit epitaxial films, the tool can be used to produce high-quality layers for other parts of the wafer manufacturing process, usually for titanium-containing films but also material such as ZrO.

"Typically, we use MOCVD precursors to deposit the nanolayer film, then plasma treat that film to improve its properties," said the company.

One example where this might be advantageous is when the wafer materials are sensitive to high temperatures. Then, instead of directly depositing a high-quality film using MOCVD at 400°C, which could adversely affect the semiconductor wafer, the NLD approach could be used to deposit material at 290°C and then follow up with the plasma "repair" step.

"Lowering the deposition temperature often improves conformality [film thickness variation], by reducing the sticking coefficient," explained CTO Selbrede. "But at the expense of reduced film quality."

However, the plasma repair step rescues the film while maintaining the good conformality, even within the deep trench structures typical of high-aspect-ratio chip designs.

According to Tegal, NLD also has an advantage over the related approach of atomic-layer deposition (ALD). "We would normally have a much higher throughput with the NLD process, especially for thicker films."

Although primarily designed for mainstream semiconductor applications and 300 mm wafers, the NLD tool can be configured for the much smaller wafers used in LED fabrication. 100 mm wafers can be handled directly. Smaller diameters, on which the vast majority of LED manufacturing still takes place, are handled using wafer carriers.

Having worked with its beta site customer "“ undisclosed, but described by Tegal CEO Tom Mika as "the leading company in HB-LEDs" "“ for the past two years on NLD applications, Tegal now expects volume commercial production to get the go-ahead some time in 2009.

"We think this beta site agreement is the validation for the value of the NLD development work performed to date, as perceived by our LED customer," claimed the firm.

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