James E. Morris

TITLE:

Discontinuous Metal Thin Film Applications in Electronics Packaging

ABSTRACT:

When a metal is deposited on insulating substrate, e.g., Au on glass in vacuo it initially grows as discrete nanoscale metal islands separated by nm gaps. Such films conduct charge by interisland tunnelling with an electrostatic activation energy [13]. The presentation will briefly cover the widely accepted conduction model [2 ] and a revised contact injection version [3], which explains most of the former’s problems, as an introduction, along with the need for chip/package sensors for reliability [4-6]. An obvious application given discontinuous metal thin films’ (DMTFs) sensitivity to temperature is as a temperature sensor [7], but there is a larger body of literature on DMTF applications as strain gauges [8-10] and hydrogen sensors [11141 which both have potential applications as reliability sensors in electronics packaging, but the presentation will also include less developed technologies suggested by modelling and a recent analysis of AC data [3, 15, 16]. The DMTF strain gauge takes advantage of the exponential dependence of tunnelling resistance which provides a linear dependence of the gauge factor on interisland separation [8] with the strain variation of the activation energy as a second order effect [9, 10]. DMTFs are sensitive to ambient gaseous environments which increase the metal work function by surface adhesion [17] but the Pd/H2 system is unique in that Pd absorption of H2 by the lattice decreases the tunneling resistance [11-14]. Detection of H2 is routinely used to identify galvanic corrosion. Other more specific systems can be designed, e.g., [18]. Early interest in these DMTFs was frustrated by a lack of reproducibility in their fabrication and subsequent drift in properties and the presentation will briefly survey some suggestions to solve both the reproducibility and reliability problems. It will conclude with the description of a fabrication technique [3] which holds the promise of manufacturability and commercial applications.
References:
[1] C.A. Neugebauer & M.B. Webb “Electrical Conduction Mechanism in Ultrathin, Evaporated Metal Films” J Appl Phys (1962) 33 74-82 [2] J.E. Morris & T. J. Coutts “Electrical conduction in discontinuous metal films; a discussion” Thin Solid Films 47 3-65 (1977) [3] J.E. Morris “Electron Transport in Discontinuous Metal Thin Films” Nano Express, vol. 3, 014002 (open access) 2022 doi:10.1088/2632-959X/ac550c [4] D.W. Palmer “Test Structures as a Way to Evaluate Packaging Reliability” MRS Bulletin, December 1993, 55-58 [5] J.C. Suhling & R.C. Jaeger “Silicon Piezoresistive Stress Sensors and Their Application in Electronic Packaging” IEEE Sensors Journal 1 (2001) 14-30 [6] J.E. Morris “Reliability testing of nano-particle system packaging” Microsystem Technologies 15(1) Jan 2009, 139-143 [7] P.G. Borziak et al “A composite system of metal particles in a dielectric matrix for use as a thermoresistor” Int. J. Electronics 77, (1994) No. 3, 347-349 [8] B.T. Boiko et al Sov. Phys.-Doklady 17 (1972) 395 [9] A.G. Bishay et al “Effect of strain on the frequency-independent parameters of the equivalent circuit of island gold films” J. Mater. Sci: Mater. Electron. (2006) 17: 489-496 DOI 10.1007/s/10854-006-8223-3. [10] J.E. Morris “The effect of strain on the electrical properties of discontinuous thin metal films” Thin Solid Films 11 (1972) 259-272 [11] A. Barr “The effect of hydrogen absorption on the electrical conduction in discontinuous palladium films” Thin Solid Films 41 (1977) 217-227 [12] J.E. Morris & F. Wu “The Effects of Hydrogen Absorption on the Resistance of Discontinuous Palladium Films” Thin Solid Films 246 (1994) 17-23. [13] J.E. Morris et al “The effect of hydrogen absorption on the electrical conduction of discontinuous palladium thin films” Int. J. Electronics 81(4) (1996) 441-447 [14] J.E. Morris “Recent progress in discontinuous thin metal film devices” Vacuum 50(1-2) May/June (1998) 107-113 [15] J.E. Morris “AC Effects in Asymmetric Discontinuous Metal Films” Thin Solid Films 193/194 (1990) 110-116 [16] S.A. Nepijko et al “Sensor and microelectronic elements based on nanoscale granular systems,” J. Nanopart. Res. (2011) 13:6263-6281, DOI 10.1007/s11051-011-0560-3 [17] J.E. Morris “Resistance changes of discontinuous thin gold films in air” Thin Solid Films 5 (1970) 339-353 [18] D. Filenko et al “Chemical gas sensors based on calixarene-coated discontinuous gold films” Sensors & Actuators B 111-112 (2005) 264-270

BIO:

Jim is an ECE Professor Emeritus at Portland State University (PSU), Oregon, and an IEEE Life Fellow. He served as EE/ECE Department Chair at both SUNY-Binghamton and PSU. He has B.Sc. (1965) and M.Sc.(hons) degrees (1967) in Physics from the University of Auckland, a Ph.D. in EE (1971) from the University of Saskatchewan, and the Doctor Honoris Causa degree (2015) from Bucharest Polytechnic University. Jim has served the IEEE Electronics Packaging Society (EPS) and Nanotechnology Council (NTC) in multiple roles since 1991 and 2008 respectively, including as NTC President (2020-2021) and General Chair of 6 international conferences. His research interests have ranged from isotropic conductive adhesives, nanopackaging, nanoelectronics simulation, and discontinuous thin metal films to automotive engine control. Jim has taught continuously for over 60 years and published 10 books, 63 journal papers, 107 refereed conference papers, 33 book chapters, and one patent, plus >80 other conference presentations.