Dry Etching of Copper Using Plasma. Kejun Xia Semiconductor TCAD Lab. Auburn University, AL Oct 19, 2003. Outline. Background Introduction > Why Copper & low k for IC Interconnection > Some methods of getting fine copper lines Halogens Plasma Etching > Chlorine Plasma Etching
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Semiconductor TCAD Lab.
Auburn University, AL
Oct 19, 2003
> Why Copper & low k for IC Interconnection
> Some methods of getting fine copper lines
> Chlorine Plasma Etching
> Basic problems and solutions
> Chlorine-Argon Plasma Etching
> Using Iodine-containing substance
> line RC delay prevail over gates delay
> relatively high resistance (2.66um-Ohm)
Hillock formation Whisker bridging Accumulation
INTERCONNECT OF NEW MILLENNIUM: COPPER
BY SERDAR AKSU, FALL 1999
Dry etching using Chlorine Plasma
Main problem is low rate, improved with several methods
Unavailable when feature size down to 0.1um
High etching rate of CuO, 1um/min at 423K
Low rate of oxidation and the incompatibility with plasma
Chlorine Plasma’Copper Reaction in a New Copper Dry Etching Process
Journal of The Electrochemical Society, 148 ~9! G524-G529 ~2001
Difficult when feature size down to 0.1um
the main reaction product, has a low volatility.
Journal of The Electrochemical Society, 148 ~9! G524-G529 ~200112-20
1 min 2 min
at 25 0C, 20mTorr, 600W, Cl2 20sccm.
Grain size and porosity increases with time
because of ion bombardment
ppt:13-21Journal of The Electrochemical Society, 148 ~9! G524-G529 ~2001
CuClx remain increasing by enhancement of Cl
Ion bombardment play an important role
The thickness of CuClx decreases becoz of ion bombardment, but
Why should Cathode Self-Biased Voltage drop with increasing pressure?
The ratio of cathode area to anode area increases.
Higher etching rate
Why has a peak for CuClx ? Below 150oC, Cl transport rate and reaction rate increase; Above 150oC, Evaporation of CuClx dominates.
473-523K required in order to adequately remove this product. Thus it seems this will not be used for the sake of thermal budget in ICs fabrication.
Comparison of etching rate between with and without Argon
Russian Microelectronics, Vol. 31, No. 3, 2002, pp. 179–192. Translated from Mikroelektronika, Vol. 31, No. 3, 2002, pp. 211–226.
435.8nm CuCl band at different temperatures
Not all of the component desorbed
Etching rate is approximately five times higher than that without UV
Journal of The Electrochemical Society, 146 (8) 3119-3123 (1999)
200nm width copper lines with a granulated surface
Result in unsmooth profile
Etching rate 2 Larger than
Etching rate 1, consequently
Etching deviates from
the vertical direction.
Dark area is <110>plane which has a least atomic density.
In the case of multilayer interconnection, this is greatly harmful
Decrease etching selectivity
Dry Etching Considerations for Copper Metallizations V.V.Makarov, et dl, NPTest Inc., 150 Baytech Dr. San
Jose, CA D.P.Griffis, P.E.Russell, North Carolina State University, 1010 Main Campus Dr. Raleigh, NC
Without ion preliminary bombardment With ion preliminary bombardment
Hampden-Smitch, M.J. and Kodas, T.T., Copper Dry Etching:
New Chemical Approaches, Mater.Res.Bull,1996,no.6,p.39
Do favor to increase the concentration of atomic Chlorine; Accelerate removal of products With bombardment.
Why is the process gas preferable in some case to detect the starting and ending point other than CuCl?
CuCl has a low saturated pressure at room temperature, thus can not be detected accurately by OES.