**1. Introduction**

58 Dielectric Material

Electron. Lett., vol. 32, pp. 609–610, 1996.

, vol.3, no.3, pp.217-228, May 2009

vol. 59, pp.4201-4208, 2011

[40] Z. D. Liu andP . S. Hall, "Dual-band antenna for handheld portable telephones,"

[41] J. Y. Jan andL. C. Tseng, "Planar monopole antennas for 2.4/5.2 GHz dual-band application," in Proc. IEEE-APS Int. Symp. Dig., Columbus, OH, 2003, pp. 158–161 [42] K. Hady, A. A. Kishk and D. Kajfez, "Dual-Band Compact DRA With Circular and Monopole-Like Linear Polarizations as a Concept for GPS and WLAN Applications",

[43] Rao, Q.; Denidni, T.A.; Sebak, A.R.; Johnston, R.H.; , "Compact Independent Dual-Band Hybrid Resonator Antenna With Multifunctional Beams," Antennas and Wireless

[44] Rotaru, M.; Sykulski, J.K.; , "Numerical investigation on compact multimode dielectric resonator antennas of very high permittivity," Science, Measurement & Technology, IET

[45] Qinjiang Rao; Denidni, T.A.; Sebak, A.R.; , "A hybrid resonator antenna suitable for wireless communication applications at 1.9 and 2.45 GHz," Antennas and Wireless

[46] R.A Kranenburg, S.A Long, "Microstrip transmission line excitation of dielectric resonator antennas," Electronics Letters , vol.24, no.18, pp.1156-1157, 1 Sep 1988 [47] L. Huitema, M. Koubeissi, M. Mouhamadou, E. Arnaud, C. Decroze And T. Monediere, "Compact and Multiband Dielectric Resonator Antenna with Pattern Diversity for Multi Standard Mobile Handheld Devices", IEEE Transaction on antennas and propagation,

IEEE Trans. on ant. and prpoag., Vol. 57, No. 9, 2591-2598, September 2009.

Propagation Letters, IEEE , vol.5, no.1, pp.239-242, Dec. 2006

Propagation Letters, IEEE , vol.4, no., pp. 341- 343, 2005

Over the past half century, low dielectric materials have been intensively researched by ceramic and polymer scientists. However, these materials possess a vast myriad of electrical, thermal, chemical, and mechanical properties that are just as crucial as the name that classifies them. Therefore, in many cases, the applications of low dielectric constant materials are dictated by these other properties, and the choice of low dielectric material may have a tremendous effect on a device's performance and lifetime.

In the field of microelectronics, many of the early low dielectric materials have been satisfactory in covering the required properties. But as the microelectronics industry continuously boomed through the 21st century, more and more advanced processes and materials have been in demand. Since the invention of microprocessor, the number of active devices on a chip has been exponentially increasing, approximately doubling every year, famously forecast by Gordon Moore in 1965. All of this is driven by the need for optimal electrical and functional performance.

Figure 1 shows the shrinking of the device dimensions over signal delay value. And while the total capacitance can be traded for resistance and vice versa by changing the geometry of the wire cross-section, the RC will always increase for future nodes. In other words, in order to enhance performance, decreasing the device size, as well as decreasing the interconnecting wire distance, gate and interconnect signals delay is the main challenge for ceramic and polymer scientists to overcome. In another approach to solve this RC delay problem, researchers have already changed the aluminum line to Cu line, which has lower resistance. But due to limitations in metal lines being applicable for use, research of low dielectric materials are continually being pursued today. The main challenge for researchers in the microelectronic industry is not to develop materials with the lowest dielectric constant, but to find materials that satisfy all of the electrical, thermal, chemical, and mechanical properties required for optimal device performance.

© 2012 Hwang et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Low Dielectric Materials for Microelectronics 61

**Figure 2.** Schematic illustration of a capacitor.

**3. Property requirements of low dielectric material** 

conductivity of polymers are inferior to those of SiO2.

Dielectirc constant Anisotropy Low dissipation Low leakage current Low charge trapping High electric-field

strength High reliability

Dielectric materials must meet stringent material property requirements for successful integration into the interconnect structures. These requirements are based on electrical properties, thermal stability, thermomechanical and thermal stress properties, and chemical stability. The desired electrical properties can be outlined as low dielectric constant, low dielectric loss and leakage current, and high breakdown voltage. As RC delay and crosstalk are primarily determined by the dielectric constant, in a typical CVD SiO2 film, the dielectric constant is around 4. And although many polymeric materials satisfy these electrical criteria, the dimensional stability, thermal and chemical stability, mechanical strength, and thermal

> Thickness uniformly Good adhesion Low stress High hardness Low shrinkage Crack resistance High tensile modulus

High thermal stability Low coefficient of thermal expansion Low thermal weight

loss

High thermal conductivity

Electrical Chemical Mechanical Thermal

Chemical resistance Etch selectivity Low moisture uptake Low solubility in H2O Low gas permeability

No metal corrosion Long storage life Enviromentally safe

High purity

**Table 1.** Property Requirements of Low-k Dielectrics


**Figure 1.** Calculated gate and interconnect dely as a function of technology node according to the National Technology Roadmap for Semiconductores(NTRS) in 1997 (top): █ ▲ gate delay; interconnect delay (Al and SiO2); ● sum of delays (Al and SiO2) and ITRS technology trend targets (bottom)
