Copper (Cu) has been the main choice of the metallization in advanced IC package technology. The epoxy molding compounds (EMC) and the solder flux used in the packaging devices can release ionic impurities. In the halide environment, the electrochemical migration (ECM) failure and corrosion related failure of copper redistribution layer (RDL) and the Cu bond pads respectively was studied. Electrolytic migration arises when the IC package undergoes testing as per JESD22-A110 standards (130oC, 85% RH for 96/256 hrs.). Copper migration is fundamentally an ionic process that requires an electrolyte, moisture, and bias. To accelerate the time for investigating these failures, it was important to benchmark the metrology for real time observation of ECM failure under high voltage. Metrology for electrochemical defect analysis (MEDA) was developed to provide insight on failure mechanism. The Cu RDL on wafer level chip scale package devices were tested by PEG drop test (PDT) using non-aqueous polyethylene glycol (PEG) matrix doped with ions (Cl-, ClO4-, SO4-) to simulate EMC environment. PDT was conducted to analyze the real time migration behavior of Cu electrodes using a potentiostat and microscope. A novel Cu-selective passivation coating was applied on Cu either by wet processes or chemical vapor deposition (CVD) that are IC manufacturing compatible. This Cu-selective passivation coating is thermally stable, strongly adheres to Cu, corrosion resistant, low cost and shows good potential to prevent ECM defects at the high voltage bHAST condition. FTIR and potentiodynamic polarization were utilized to characterize the Cu-selective passivation coating. Statistically union of selected analytical techniques help to acquire unique results about the chemical systems. Together, electrochemistry and spectroscopy help to gather chemical information about the composition near and on the electrode. Additionally, during the SnAgCu (SAC) solder ball bonding on the Cu wafer by mass reflow process, solder flux is used to reduce the native oxides on Cu and SAC solder ball. Post cleaning, residual amount of the solder flux corrodes the Cu wafer. Passivation coating is used as an organic solder preservative to avoid the solder flux while facilitating a good bond between the SAC solder ball and Cu wafer. We investigated the efficiency of the passivation coating in preventing the copper thermal oxidation. The intermetallic compound formation between the Cu wafer and SAC solder ball was studied on 2nm, 6nm, 30nm and 50nm passivated Cu wafer. Based on the SEM/EDS analysis 1.7 µm CuxSny IMC was formed on 2nm coated cu wafer with a Cu:Sn ratio of 1.8:1 & 0.13:1.
| Identifer | oai:union.ndltd.org:unt.edu/info:ark/67531/metadc2332524 |
| Date | 12 1900 |
| Creators | Salunke, Ashish Shivaji |
| Contributors | Chyan, Oliver Ming-Ren, Slaughter, LeGrande M., Acree, William E. (William Eugene), Berhe, Seare, Pillai, Karthikeyan |
| Publisher | University of North Texas |
| Source Sets | University of North Texas |
| Language | English |
| Detected Language | English |
| Type | Thesis or Dissertation |
| Format | Text |
| Rights | Public, Salunke, Ashish Shivaji, Copyright, Copyright is held by the author, unless otherwise noted. All rights Reserved. |
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