Phase-change memory (PCM) materials such as GST
require CMP with tight control on the top surface structure. What manner of
metrology is needed to control the morphology?
I believe there will have to be two separate metrology strategies. A method like XPS is suitable for process development and setup, and perhaps even offline monitoring. Volume production will need something more robust and less expensive for in-line process control, and may depend on a secondary indicator. I'm not aware that such methods have been developed yet specifically for PCM CMP.
In addition to XPS for compositional control (at least in technology development) might we need AFM for dimensional control too? My understanding is that MOCVD/ALD will be used to fill small (~40nm diam.) vias with GST, and CMP will be essential to ensure that the top surface is highly planar to avoid current spikes during voltage programming of the cell. As Mike mentions (#2, above), we'll almost certainly need different metrology tools for volume manufacturing control.
We're now (January 20th, 2010) past the
official ending (the 18th) of this virtual roundtable discussion, after 4695 views of 129 replies to 18 questions. I'll
edit together Interesting discussions from most of the topics into a
summary document that will be posted to the Planarization Lounge.
We'll leave the topic posting open in case there are additional comments...but they would not be included in the summary.
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