An investigation of supercritical-CO₂copper electroplating parameters for application in TSV chips

Abstract

This study uses supercritical electroplating for the filling of through silicon vias (TSVs) in chips. The present study utilizes the inductively coupled plasma reactive ion etching (ICP RIE) process technique to etch the TSVs and discusses different supercritical-CO2 electroplating parameters, such as the supercritical pressure, the electroplating current density’s effect on the TSV Cu pillar filling time, the I–V curve, the electrical resistance and the hermeticity. In addition, the results for all the tests mentioned above have been compared to results from traditional electroplating techniques. For the testing, we will first discuss the hermeticity of the TSV Cu pillars, using a helium leaking test apparatus to assess the vacuum sealing of the fabricated TSV Cu pillars. In addition, this study also conducts tests for the electrical properties, which include the measurement of the electrical resistance of the TSV at both ends in the horizontal direction, followed by the passing of a high current (10 A, due to probe limitations) to check if the TSV can withstand it without burnout. Finally, the TSV is cut in half in cross-section to observe the filling of Cu pillars by the supercritical electroplating and check for voids. The important characteristic of this study is the use of the supercritical electroplating process without the addition of any surfactants to aid the filling of the TSVs, but by taking advantage of the high permeability and low surface tension of supercritical fluids to achieve our goal. The results of this investigation point to a supercritical pressure of 2000 psi and a current density of 3 A dm−2 giving off the best electroplating filling and hermeticity, while also being able to withstand a high current of 10 A, with a relatively short electroplating time of 3 h (when compared to our own traditional dc electroplating).

The Effect of Surfactant Content over Cu-Ni Coatings Electroplated by the sc-CO2 Technique

“…However, for this specific study, current density and Ni ion concentration remained fixed throughout the experiment, reducing the number of affecting factors. The sc-CO 2 parameters chosen were the optimal parameters found from previous studies [ 17 , 18 , 19 , 22 ], thus, their deposition mechanism was understood. Differences in surfactant content are seen to affect the crystalline structure of coatings, shifting the intensity of the measured peaks.…”

“…The sample was placed inside the high-pressure electroplating chamber, where liquefied CO 2 was pumped in; temperature and pressure were adjusted to achieve optimal sc-CO 2 electroplating parameters (pressure: 15 MPa, temperature: 50 °C) [ 18 , 19 ]. Magnetic agitation was started at 500 rpm for 30 minutes to allow homogenous mixing between the sc-CO 2 and electrolyte, then kept constant throughout the remainder of the experiment.…”

Cu Wiring Fabrication by Supercritical Fluid Deposition for MEMS Devices

“…This percolation chain is instantly severed, realizing pulse-like electroplating and leading to improved crystallinity and growth rate. The application of supercritical CO 2 fluids to Cu through-Si vias (TSVs) was also reported [19], demonstrating the versatility of this method.…”

Optimization of Additive and Current Conditions for Void-Free Filled Through-Silicon Via

“…TSV samples with blind vias AR 1:2-1:3 (about 60 µm in diameter, about 120 µm/150 µm/180 µm in depth) on Si substrate were prepared using the Bosch process of inductively coupled plasma reactive ion etching (ICP-RIE) for the TSV filling experiment [10,11]. Si wafer of 1 × 1 cm 2 size was used for small scale deposition.…”