ALD takes one step forward, one step back

ALD takes one step forward, one step back
SAN JOSE, Calif. — Atomic layer deposition (ALD) continues to make major inroads — and has stalled — in living up to its promises of becoming an enabling technology for mainstream chip production.

Call it a story of the good, bad and ugly. For some time, DRAM makers have successfully used ALD technology as a means to scale the capacitor in a memory device.

But on the copper/barrier seed front, ALD has been pushed out to the 32-nm node. And due to a possible delay for high-k dielectrics in logic designs, ALD has stalled as the deposition technology of choice.

ALD, which has been around for decades, deposits ultra-thin films one atomic layer at a time. Unlike conventional deposition technologies, ALD offers control of the thickness and uniformity of monolayer films of less than 100 angstroms.

In total, the ALD equipment market is projected to grow 23.1 percent, from $172.4 million in 2005 to $487.3 million by 2010, according to a report from Robert Maire, an analyst with Needham and Co. LLC. Among the equipment players in ALD include Applied Materials, ASMI, Aviza, Genus, IPS, Novellus, TEL, Veeco and others.

ALD has been a smash hit in DRAMs. At one time, DRAM makers were using conventional techniques to deposit silicon dioxide or oxide-nitride-oxide (ONO) dielectric materials for capacitor applications.

Then, starting at the 130-nm node, South Korea's Samsung Electronics Co. Ltd. was said to be the first DRAM maker to deploy high-k dielectric films via ALD for stack capacitor applications.

Other DRAM suppliers followed suit. In this application, capacitor area decreases with each technology node, forcing DRAM makers to deploy high-k films via ALD, said Subrata Chatterji, vice president and general manager at ALD Business Unit at Aviza (Scotts Valley, Calif.).

Now, DRAM makers have a new requirement, which, in some cases, is the Achilles' heel for suppliers of ALD gear: higher throughput. Many DRAM makers are using single-wafer ALD tools, which deposit highly conformal films — sometimes at the expense of throughput.

"People are now moving from single wafer to batch," said Chatterji. "Throughput continues to be a challenge with single wafer tools. But the challenge with batch is whether or not all of the new materials can be handled in a batch environment."

Aviza sells a batch-enabled ALD tool. In May, Aviza introduced its next-generation, single-wafer ALD machine and said that the company has shipped one these products, apparently to Chinese silicon foundry provider Semiconductor Manufacturing International. Corp. (SMIC).

Aviza said the system, dubbed Celsior, is aimed at the 90-nm node and beyond. It is built on a platform that was acquired through a joint-development partnership with Trikon Technologies prior to Aviza's acquisition of that company last December.

Celsior features a new chamber, which, according to Aviza, lowers the tool's cost of ownership by offering increased throughput, lower chemical consumption and an extended process window. The tool utilizes a patented showerhead designed to meet stringent ALD process needs, including less than 1 percent thickness uniformity requirements across a 300-mm wafer, Aviza said.