Porous Dielectrics in Microelectronic Wiring Applications

Abstract

Porous insulators are utilized in the wiring structure of microelectronic devices as a means of reducing, through low dielectric permittivity, power consumption and signal delay in integrated circuits. They are typically based on low density modifications of amorphous SiO2 known as SiCOH or carbon-doped oxides, in which free volume is created through the removal of labile organic phases. Porous dielectrics pose a number of technological challenges related to chemical and mechanical stability, particularly in regard to semiconductor processing methods. This review discusses porous dielectric film preparation techniques, key issues encountered, and mitigation strategies.

Probing the microporosity of low-k organosilica films: MP and t-plot methods applied to ellipsometric porosimetry data

“…The obtained porous low-k samples consisted of a "bulk" SiOCH layer (k~2.55). One sample was further exposed for 30 s at 350 C to standard fluorinated plasma etching process used for line and via patterning [4] in order to modify its surface functionalization [18,19].…”

“…Therefore, to improve the signal propagation delay and limit the cross-talk phenomenon, insulating materials with lower dielectric constant (also referred to as low-k materials where k is the material capacitance) are required between conductive lines. For instance, fluorine and carbon atoms were incorporated in silica (k SiO2 ¼ 4.2) to obtain materials with lower k due to less polarizable chemical bonds (k SIOF ¼ 3.5 and k SiOC ¼ 2.9) [4]. Using plasma-enhanced chemical vapor deposition (PECVD), further decrease in k values was achieved by including interconnected porosity (10e30%) into the material (k pSiOCH < 2.7) through co-deposition of a matrix precursor with a sacrificial "porosity generator" molecule (porogen).…”

Dielectric behavior of organically modified siloxane melting gels

“…A major change in the previous decade was to lower the resistance and capacitance (RC) signal delay in back end of the line (BEOL) interconnects. A more recent change has been the replacement of the insulator, silica with dielectric constant (k) around 3.9 to 4.2, with a porous organically modified silica insulator of a lower k value [2]. This has enabled a higher transistor density, which lowers cost but incorporates more complicated materials.…”

Toward Successful Integration of Porous Low-k Materials: Strategies Addressing Plasma Damage

“…1,2 The initial strategy of increasing the carbon content and later by introducing porosity (air) to lower the dielectric constant of the insulating material were adopted early on. This was in large part due to the fact that it seemingly provided a long-term pathway for generational extendibility.…”