by Debra Vogler, senior technical editor, Solid State Technology
Nov. 19, 2008 - Aviza Technology recently introduced its 300mm-ready ion beam deposition (IBD) system, the StratIon fxP. The first system has been shipped to research center CEA-LETI-MINATEC for development of next-generation magnetic tunnel junction (MTJ)-based devices for applications including magnetic random access memory (MRAM), hard disk drive read heads, and RF components. The system will also be used for the deposition of metal gates for advanced CMOS processes.
The StratIon fxP system uses ion beam processing for the deposition of metal and dielectric thin films. Designed for high-volume manufacturing, the system can be configured with three standard chamber types (preclean, oxidation, and deposition), and additional Aviza deposition chambers such as atomic layer deposition (ALD) and magnetron physical vapor deposition (PVD) can be added.
According to David Butler, VP of marketing at Aviza, IBD delivers key advantages over traditional magnetron sputtering approaches. Citing the coming “age of MRAM and metal gates” that need very thin pure metal films, he told SST that purity, interface smoothness, and homogeneity cannot be done by conventional sputtering because the degree of control isn’t there. Film homogeneity in particularly is critical for pure, very thin metal films, he emphasized. “ALD can’t do pure metal films/magnetic films,” he said, but magnetron sputtering systems take ~70-80msec to reach a steady-state plasma condition. “Imagine you’re trying to put down a 10Å film — that’s a sizeable chunk of the total process time.” Conversely, the RF plasma in the new IBD system — switched by fast DC grids only — is always “on.” An oscilloscope trace (see figure) shows that it’s <4msec from 0 ion beam to steady-state (see image below). “So it’s almost 10× or more faster than a magnetron sputterer…that’s like getting the film you want almost immediately.” Butler also pointed out that the chemistries put into an ALD process will produce a film with a degree of impurities, and that’s not pure enough for the layers in an MTJ stack.
Oscilloscope trace shows <4msec from 0 to ion beam steady-state. (Source: Aviza Technology)
Smoothness is another critical parameter in MTJ stacks where the thinnest films are <10Å. The company reports that the new tool produces films with <2Å rms roughness and <0.5% thickness non-uniformity on 300mm wafers. Crucial to the performance achieved by the new tool is Aviza's patented Mori plasma source, which enables ultralow-pressure deposition producing films that Butler noted are twice as smooth as those produced by currently available MTJ sputter deposition tools.
With MTJs being the “heart of MRAMs,” it’s clear Aviza is counting on a surge of interest in the memories. “There’s a new age of extremely thin, stacked layers coming in for high-k/metal gates (HK+MG) — but more importantly for MRAMs,” an area now seeing a lot of investment, Butler told SST. “MRAM was a big topic a couple of years ago but it seemed to die off a bit — but this year it’s come back with a vengeance. How quickly it will start to penetrate into flash and DRAM is a different question, but I think it’s going to happen.”
In addition to the system shipment, Aviza and CEA-LETI have signed a three-year joint development program covering the development of MTJ deposition processes for future MRAM and spintronics devices. Though the new tool is capable for volume production now, MRAMs aren’t in volume production at this time. The company will not talk about other shipments or customers. — D.V.