Title
Local stress analysis in devices by FIB
Author
Kregting, R.
Gielen, A.W.J.
van Driel, W.
Alkemade, P.
Miro, H.
Kamminga, J.-D.
TNO Industrie en Techniek
Publication year
2010
Abstract
Intrinsic stresses in bondpads may lead to early failure of IC's. In order to determine the intrinsic stresses in semiconductor structures, a new procedure is set up. This procedure is a combined experimental/numerical approach which consists of the following steps: First, a conductive gold layer (20 nm thickness) is deposited on the power line surface; subsequently markers (small holes) for Digital Image Correlation (DIC) purposes are added using a focused ion beam (FIB). Next, a scanning electron microscope (SEM) is used to image the original ('before') surface. The FIB is then used to mill a slot into the surface to release the intrinsic stresses, which results in contraction of the surface. Finally, a SEM image is made of the contracted ('after') surface. DIC is used to determine in-plane displacements due to FIB milling. DIC performance was verified by the traditional strain gauge approach. An inverse Finite Element (FE) modelling approach is used to determine the before mentioned stresses. The slot displacements found with DIC are inserted into an FE model of the product. Stresses which now emerge from closing the (virtual) FIB slot correspond to the intrinsic stresses which were originally present in the product. Favorable positions for FIB milling are near the edge of the structure and displacements are determined to be in the nanometer range. This indicates a presence of substantial (50-250 MPa) compressive stresses. Displacements near the center of the structure appear to be smaller than DIC resolution. ©2010 IEEE.
Subject
Mechatronics, Mechanics & Materials
MIP - Materials for Integrated Products
TS - Technical Sciences
High Tech Systems & Materials
Materials
Industrial Innovation
Bond pad
Digital image correlations
Early failure
FE model
FIB milling
Finite elements
Gold layer
In-plane displacement
Intrinsic stress
Local stress analysis
Nano meter range
Power lines
Scanning electron microscopes
SEM image
Semiconductor structure
Small Hole
Strain gauge
Gages
Gold coatings
Microsystems
Milling (machining)
Plant shutdowns
Scanning electron microscopy
Stress analysis
Microelectronics
To reference this document use:
http://resolver.tudelft.nl/uuid:cc2e3fd6-bd42-4f6e-a1ea-490652ec9233
TNO identifier
364413
ISBN
9781424470266
Source
11th International Conference on Thermal, Mechanical and Multi-Physics Simulation, and Experiments in Microelectronics and Microsystems, EuroSimE, 26-28 April 2010, Bordeaux, France
Article number
No.: 5464520
Document type
conference paper