In situ stress measurements during electrodeposition of thin films studied.
To address these concerns, NIST researchers have established a Class II (1 mW) HeNe optical bench dedicated to the in situ measurement of residual stress during electrodeposition using the wafer curvature method. The substrate is a 60 mm X3 mm X0.1 mm wafer of borosilicate glass onto which 250 nm of gold is evaporated. The curvature of the substrate is monitored during electrodeposition by reflecting the laser off of the glass/metal interface, through a series of mirrors and onto a position-sensitive detector. The average in-plane stress of a metal film electrodeposited onto the Au can be calculated from the deflection of the beam as a function of time. The apparatus can resolve surface stresses on the order of 0.3 N/m while the beam is in solution, thus allowing researchers to observe the stresses associated with the entire deposition process.
As a demonstration, NIST researchers have followed stress development in the first 50 nm of Cu deposited onto Au. This system is known to follow classical Stranski-Krastanov growth, where three-dimensional islands grow on top of one or more Cu monolayers. Researchers have quantified the surface stresses associated with the formation of the first Cu monolayer, as well as the formation and coalescence of discrete Cu nuclei. It is expected that measurements such as these will allow the researchers to determine the root cause of stress in electrodeposited thin films and to propose mitigation strategies.
CONTACT: Gery Stafford, (301) 975-6412; email@example.com.
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|Title Annotation:||General Developments|
|Publication:||Journal of Research of the National Institute of Standards and Technology|
|Date:||Nov 1, 2003|
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