Inspiration to solve a difficult yield issue-interlayer delamination in polyimide dielectrics

Paul A. ZuccoWhile at IBM Microelectronics, East Fishkill , NY Facility

ArticlesInterdiffusion in Polyimide Thin Films1986 MRS Spring Meeting.Article author querykramer ej [Google Scholar]volksen w [Google Scholar]russell tp [Google Scholar]E. J. Kramera1, W. Volksena2 and T. P. Russella2

a1 Department of Materials Science and the Materials Science Center, Cornell University, Ithaca, NY 14850a2 IBM Almaden Research Center, San Jose, CA 95120AbstractThe interdiffusion in thin films of polyimide has been investigated using the forward recoil spectrometry (FRES) technique. Films 5–10 μm in thickness of polyamic acid spin coated onto a silicon substrate were imidized at a temperature TI. A second film, 300Å in thickness of perdeuterated polyamic acid was ∼spin-coated onto the first layer and heated to a temperature TD to allow interdiffusion of the two films and imidization of the second coating. Depth profiling of the deuterated polymer by FRES showed that no interdiffusion occurred if TI>TD and TI>200°C. Substantial interdiffusion occurred if TD>TI and TI<400° C. Time averaged tracer diffusion coefficients were found to vary with the TD and TI, as well as the length of time allowed for interdiffusion. Since conversion of the deuterated polyamic acid to polyimide occurs at the diffusion temperature, the results are consistent with a relatively large diffusion coefficient for the polyamic acid (D>2.5× 10−14 cm2/sec) which decreases to a negligible value as the molecule is fully converted to the corresponding polyimide

Inspiration from the Literature:

Challenge

1. Create a dual layer metalized Polyimide dielectric coating2. Double layer polyimide must survive a chemical polishing step

Issue-yield loss

Root Cause: Second layer of polyimide applied as polyamic acid was delaminating due to shear stress from the chemical mechanical polish

Proposed Solution

1. Reduce shear stress on film2. Improve inter-polymer diffusion3. Under cure first layer to allow diffusion without crazing

Steps1. Could not reduce stress in shear. Cu metal was being removed along with polyimide to create a plannarized surface

The main goal became improving the strength of the interface between the two coatings.

This is where the work performed by Prof. Kramer and the Almaden Research team directed us to:

a. Putdown the first polyamic acid film and only partially imidize the film. This allowed thesolvent from the second layer to pre-swell the surface. b. This allowed the polymer chains to inter-diffuse prior to full imidization of both films.

Results

By establishing the extent of imidization of the first layer using FTIR and by fully curing theTwo layers the yield loss became less than 1%.

Conference Paper Flip-chip interconnection technology for advanced thermal conduction modules S.K. Ray S.K. Ray Remove suggestion K. Beckham K. Beckham Remove suggestion R. Master R. Master Remove suggestion IBM Corp., East Fishkill, NY DOI: 10.1109/ECTC.1991.163967 Conference: Electronic Components and Technology Conference, 1991. Proceedings., 41st Source: IEEE Xplore ABSTRACT Area array solder bumps on silicon devices, known as C4 balls,have been successfully used in terminating logic and memory devices toceramic substrates in numerous IBM products over two decades. With theIBM System 390/ES9000 series of mainframe computers, this highlyreliable chip termination technology has achieved improvedinterconnection density and total number of chip I/O connections permodule. In addition, in the models 820 and 900 of ES9000 series, a novelmaterials set, namely glass-ceramic with Cu internal metallization alongwith thin-film redistribution wiring on top, has been introduced formultilayered ceramic substrates. Key elements of advanced glass-ceramicsubstrate technology relevant to flip-chip joining are reviewed. This isfollowed by a discussion of device join and replace processes used inadvanced thermal conduction modules which also have decouplingcapacitors which are attached by C4 solder reflow. Optimization of thetop surface metallurgy and device join parameters necessary to achievereliable joining of more than 70000 solder balls per module is discussed Flip-chip interconnection technology for advanced thermal conduction modules - ResearchGate. Available from: http://www.researchgate.net/publication/3523482_Flip-chip_interconnection_technology_for_advanced_thermal_conduction_modules [accessed Oct 14, 2015].