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Diamond, sapphire wafers, anyone?

Posted: 16 Apr 2009 ?? ?Print Version ?Bookmark and Share

Keywords:sapphire wafer? wafer diamond? WiMAX?

Two vendors are separately utilizing new materials for emerging applications.

sp3 Diamond Technologies Inc. is taking orders for 2- and 4-inch silicon-on-diamond (SOD) wafers for use as gallium nitride (GaN) substrates.

The company is also accelerating development of 6-inch wafers for use as laterally diffused metal oxide semiconductor substrates. SOD wafers deliver higher thermal conductivity at a lower cost than existing silicon carbide (SiC) alternatives, according the sp3.

SOD wafers are used in devices, which are aimed for WiMAX base stations, radar communications equipment, weather and communications satellite equipment and hybrid power switching devices.

The SOD wafers are delivered as structured substrates with a top layer of device-quality, float-zone silicon. At fixed power, they can reduce junction temperature by more than 50 compared to GaN on silicon or SiC, the company said. GaN growth on SOD yields epi films equivalent to GaN on silicon, and sp3 can scale wafer size up to 300mm, it added.

"High-power, high-frequency devicessuch as high power radar and RF amplifiers, and DC/DC and AC/DC convertershave performance limitations due to the physical structure of standard silicon substrates," said Dwain Aidala, president and chief operating office of sp3 Diamond Technologies, in a statement.

"Military and industrial applications stand to benefit significantly from building devices on a diamond substrate with a device quality, thin silicon top layer," he said.

Sapphire boule
Meanwhile, Rubicon Technology Inc., a provider of sapphire substrates, claims that it has grown the world's largest sapphire crystal. The super boule weighs in at 200kg or 441 pounds.

It will enable Rubicon to offer next-generation wafer products with dimensions over 12 inches. Currently, Rubicon grows bulk sapphire crystals up to 85kg in production volumes and provides 8-inch wafers and optical windows up to 10 inch dimensions.

Sapphire is used for optical applications, due to its transmission in UV and IR wavelengths. Sapphire substrates are also used for LEDs and RFICs.

"The availability of cost effective large diameter sapphire wafers and also LED processing equipment capable of manufacturing large diameter wafers is enabling LED producers to improve their process yields and chip throughput which reduces their overall chip costs. These factors also reduce the overall capital investment necessary to keep up with this rapidly growing LED market," said Raja Parvez, CEO of Rubicon, in a separate statement.

Rubicon currently has high volume production capability at 2-, 3-, 4-, 6- and 8-inch sapphire substrates for use in the LED industry.

"We expect adoption of 4-inch wafers to continue to rapidly increase in 2009 and 2010. While Rubicon is currently already providing high-quality 6-inch wafers to our customers, we expect 6-inch wafers to move to volume production starting in 2010 with more widespread adoption in 2011. 8-inch and larger sapphire wafers are already available and will provide the roadmap for the future of LED production," he added.

- Mark LaPedus
EE Times

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