Integrating High-k Ceramic Thin Film Capacitors into Organic Substrates Via Low-Cost Solution Processing

• Published in: IEEE transactions on components and packaging technologies Vol. 30; no. 4; pp. 585 - 594
• Main Authors: Raj, P.M., Balaraman, D., Abothu, I.R., Chong Yoon, Nam-Kee Kang, Rao Tummala
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.12.2007; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Capacitance; Capacitors; Ceramics; Copper; Decoupling; Density; Dielectric thin films; embedded; High K dielectric materials; High-K gate dielectrics; hydrothermal; organic; Packages; Packaging; Radio frequency; Sol gel process; sol-gel; Substrates; Thin films; Transistors; hydrothermal; Capacitors; decoupling; embedded; organic; sol-gel
• ISSN: 1521-3331; 1557-9972
• DOI: 10.1109/TCAPT.2007.901737

Current organic package-compatible embedded decoupling capacitors are based on thick film (8-16 m) polymer-ceramic composites with dielectric constant (k) of 20-30 and do not have sufficient capacitance density to meet the impedance requirements for emerging high-speed circuits and high power density microprocessors. High-k/high capacitance density ceramics films that can meet the performance targets are generally deposited by high-temperature processing or costly vacuum technology (radio frequency sputtering, PECVD) which are expensive and also incompatible with organic packages. The objective of this project is to develop ultra thin films (100-300nm) with high dielectric constant using organic compatible processes to meet future decoupling applications. In the current study, direct deposition of crystalline ceramic films on organic boards at temperatures less than 100C was demonstrated with the hydrothermal method. Post-hydrothermal treatments were shown to minimize the defects in the as-synthesized hydrothermal barium titanate films and improve the breakdown voltage (BDV) and leakage characteristics. Thin films with high capacitance densities and breakdown voltages of 10V were demonstrated. As an alternate technique, sol-gel technology was also demonstrated to integrate ceramic thin films in organic packages. A major barrier to synthesis of sol-gel films on copper foils is the process incompatibility of the sol-gel barium titanate with the copper electrodes. To enable process compatibility, process variables like sol pyrolysis temperature and time, and sintering conditions/atmosphere were optimized. Capacitance densities above 1.1F/cm was demonstrated on commercial copper foils with a BDV above 10 V. The two technologies reported in this study can potentially meet midfrequency decoupling requirements of digital systems.