NIST-SS25-21

PLEASE NOTE THIS A SOURCES SOUGHT NOTICE ONLY

Title:  Micro specimens of thin film electroplated copper and micro-sized lead-free solder for mechanical testing to fracture.

BACKGROUND

The Applied Chemicals and Materials Division, in the Material Measurement Laboratory at NIST, is developing new metrology to measure the micromechanical properties, to fracture, of thin-film electroplated copper (Cu) and micro-sized lead-free solder. These materials are critical as interconnects for heterogeneous integration for advanced packaging. Cu is used for Cu-to-Cu hybrid bonding, the most advanced interconnect technology today and in the near future, while Sn-Ag-Cu (SAC) solder is used for all levels of packaging. The packaging industry relies on physics-based models and finite element models to predict the thermomechanical performance of these interconnects as well as to guide their design and process development and understand reliability-related issues. Such models require accurate material property data as inputs. Mechanical property data, to fracture, are lacking or sparse for these materials with size scales, chemical composition and microstructure similar to that of the interconnects. The characteristic length for Cu hybrid bonds is 1 micron, and that of solder can range from 1 micron to over 100 microns. Common practice is to use material property data measured from samples of Cu and/or solder that are dissimilar in size scales and/or with dissimilar microstructures from those used in Cu hybrid bonding and solder bumping, but such data is not accurate due to the effects of size, processing and microstructure on the properties. A state-of-the-art technique is to use nanoindentation to measure mechanical properties, however, nanoindentation tests are typically not to fracture, especially for ductile materials such as metals. NIST is therefore developing new measurement tools and techniques to measure various mechanical properties (such as tensile, shear, bending, fatigue) of freestanding micro-sized metal specimens with NIST-designed geometries, and to conduct these tests to fracture. However, NIST lacks a way to make appropriate specimens of Cu and solder.

NIST has a need for a Research and Development (R&D) partner to fabricate appropriate micro-sized specimens for NIST to measure. These specimens need to be free-standing 1-10 micron-thick electroplated Cu, and 10 – 25 micron-thick SAC solder, with geometries designed by NIST, and with chemical composition and microstructure tailored to be similar to those of Cu hybrid bonded and solder bonded interconnects used in the heterogeneous integration industry. NIST needs the R&D partner to fabricate the specimens from different sources of materials: using in-house processing as well as by “cutting out” the required geometries from samples provided by NIST. NIST also needs the R&D partner to eventually transfer their fabrication methods and knowledge to NIST employees and allow the NIST employees to use their facilities to perform the fabrication work.

These are the minimum requirements for the specimens and for the contractor are as follows:

1. The contractor shall fabricate micro “dog-bone” specimens from both electroplated Cu films and Sn-Ag-Cu (SAC) solder, using designs provided by NIST. These specimens may include but are not limited to tensile specimens, notched tensile specimens, shear specimens, fatigue specimens. The specimens shall have variations in their geometries and dimensions, as designed by NIST.

a. The Cu specimens shall have thickness of 1 – 10 microns.

b. The solder specimens shall have thickness of 10 – 25 microns.

c. The widths of the specimens will be between 10 – 100 microns, subject to NIST’s needs which are to be determined based on the results of the R&D.

d. The contractor shall characterize the specimens’ chemical composition and microstructure, and tailor the composition and microstructure to be similar to Cu hybrid bonds and solder microbumps used in industry for heterogeneous integration.

e. The specimens shall be free-standing.

f. The specimens shall include additional structural components suitable for interfacing with NIST’s measurement instruments.

g. The specimens shall be fabricated entirely at the vendor’s location and shipped to NIST without being damaged.

h. The first set of specimens shall be delivered to NIST within 12 months from receipt of funds. Additional specimens shall be delivered to NIST as and when NIST requests.

i. The specimens shall be made by the vendor “from scratch”, as well as by excising from materials provided by NIST.

j. Specimens made “from scratch” shall have chemical composition and microstructure