Ruthenium Oxide

Jim McVittie mcvittie at cis.Stanford.EDU
Tue Mar 2 14:47:31 PST 2004


A new user ( Jim Kruger) wants to dep Ru (mp 2300C) in the Metallica,
cover it with SiO2 in the STS PECVD tool, wet etch the SiO2 and then
sputter etch the Ru in the MRC. Ru by itself is not toxic and not a
problem. The problem is that one of its oxides (RuO4) is very toxic and
and a has high vapor pressure (mp 25C and BP 130C). The cas number for
RuO4 is 20427-56-9.  However, it does not form RuO4 very easily.  
Ruthenium is largely immune to atmospheric attack. On heating with oxygen
(800C in air), ruthenium metal gives ruthenium (IV)  oxide, RuO2. THe MDSD
says to avoid strong oxidizers so I assume it probably form RuO4 in HNO3
or H2SO4. Kruger's note below inducates that RuO4 is formed in a O2

What do you think? Sputtering etch Ru in the MRC is problably a problem
since a lot of O2 plasma work gets done is there. Metalica is probably not 
a problem since the Ru will be quickly buried and we are not currently 
doing any O2 reactive sputtering in it. STS dep may also be a problem 
since you use a N2/SiH4/O2 mix to deposition PECVD oxide.


On Fri, 27 Feb 2004, jim kruger wrote:

> Hello Jim,
> I am still working on the formal "New Materials
> Request" for Ru.
> The interest in Ru is that it is used as a capping
> layer to protect EUV mirrors from oxidation.
> I find out that Ru resists tarnishing in air , but can
> form a highly volatile, highly toxic oxide, RuO4 in
> for example, plasmas.  Is this going to be a
> show-stopper?
> Briefly, I propose to:
>  deposit ~ 1000 A Ru in Metallica,
>  cap with PECVD SiO2, pattern to form a hard mask by
> wet etching with BOE or HF
> expose to Ar or He plasmas to check erosion
> strip the hard mask in HF
> measure erosion step with AFM
> I hope to see you Monday at the group meeting.
> Jim Kruger
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Jim McVittie, Ph.D.    			Senior Research Scientist 
Allen Center for Integrated Systems     Electrical Engineering
Stanford University             	jmcvittie at
Rm. 336, 330 Serra Mall			Fax: (650) 723-4659
Stanford, CA 94305-4075			Tel: (650) 725-3640

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