Influence of absorbed water components on SiOCH low-k reliability

We review the latest studies that address the fundamental understanding of low-k dielectric electrical properties and reliability. We focus on the results discussing the nature of process induced defects, leakage currents and breakdown behavior, as they are important factors to reveal material modification and damage. Issues related to the use of porogen based PECVD techniques during dielectric deposition are discussed, where we focus on the selection of matrix and porogen precursors and on the improvements related to post-deposition treatments. During damascene integration, low-k dielectrics are subjected to several processes that induce material damage, where we review recent learning about plasma exposure, barrier deposition and chemical mechanical polishing. In order to have a successful implementation of advanced ultralow-k films in back-end-of-line interconnects, we argue that more research efforts are needed with respect to its material development, integration and reliability and make some proposals for future work. The development and integration of reliable low-k materials is a key challenge for next generation interconnect technologies. Driven by the requirement of performance increase, highly porous low-k dielectrics are incorporated in deeply scaled back-end-of-line (BEOL) interconnects. In general, there are three important concerns during the study of low-k dielectric electrical properties and reliability: a) the k-value of the dielectric after integration should maintain relatively unchanged, b) the leakage current of the dielectric between metal lines should be low, and c) the time dependent dielectric breakdown (TDDB) failure time of the integrated BEOL structure at operating conditions should meet its specifications. 1Porous SiOCH low-k dielectrics deposited by plasma enhanced chemical vapor deposition (PECVD) techniques are the dominant choice for k>2.2 film depositions and are also potential candidates for ultralow-k (k<2.2) dielectric applications.2 In the past years, significant efforts have been spent to understand their material properties and integration challenges. The bond structures of low-k dielectrics is complex due to the non-equilibrium nature of the PECVD technique.

“…49 An annealing step is supposed to remove moisture and improve the film reliability. However, Li et al 50 suggested that the removal of physisorbed water by baking at 190…”

Section: Reliability After Integrationmentioning

confidence: 99%

Electrical Reliability Challenges of Advanced Low-k Dielectrics

Baklanov

et al. 2014

“…The need for the DB to block H 2 O/O 2 in-diffusion is due to the demonstrated ability of low-k a-SiOC:H ILD materials to readily uptake moisture [280][281][282][283][284] and the many deleterious resulting effects that have been reported. Specifically, moisture and O 2 permeation into a metal interconnect structure has been shown to result in a number of effects ranging from increased ILD viscoplasticity, 285 dielectric constants, [286][287][288] and leakage currents [289][290][291] to reduced ILD fracture strength, [292][293][294][295][296] ILD/DB adhesion, 297-299 DB/metal adhesion, 300 TDDB lifetimes, 301,302 and electromigration lifetimes. 303,304 Some of the above reliability issues, such as ILD/DB and DB/metal adhesion and electromigration, have been directly linked to H 2 O/O 2 diffusion through the DB and oxidation of the underlying metal and via/trench barrier.…”

Section: Ecs Journal Of Solid State Science and Technology 4 (1) N30mentioning

confidence: 99%

Dielectric Barrier, Etch Stop, and Metal Capping Materials for State of the Art and beyond Metal Interconnects

King

2014

131

115

Over the past decade, the primary focus for improving the performance of nano-electronic metal interconnect structures has been to reduce the impact of resistance-capacitance (RC) delays via utilizing insulating dielectrics with ever lower values of dielectric permittivity. The integration and implementation of such low dielectric constant (i.e. low-k) materials has been fraught with numerous challenges. For intermetal and interlayer (ILD) low-k dielectrics, these challenges have been largely associated to integration with metal interconnect fabrication processes and well documented and reviewed in the literature. Although equally important, less attention has been given to other low-k dielectrics utilized in metal interconnect structures that are commonly referred to as low-k dielectric barriers (DB), etch stops (ES), and/or Cu capping layers (CCL). These materials present numerous challenges as well for integration into metal interconnect fabrication processes. However, they also have more stringent integrated functionality requirements relative to low-k ILD materials that serve only a basic purpose of electrically isolating adjacent metal lines. In this article, we review the integration challenges and associated integrated functionality requirements for low-k DB/ES/CCL materials with a focus on the current status and future direction needed for these materials to facilitate both Moore's law (i.e. More Moore) and More than Moore scaling.

“…The adsorbed water molecules degrade dielectric constant and electrical reliability of low-k materials. 29 Absorption peaks from residual organic template and CH 2 groups from bridging organic groups are located between 3000 and 2750 cm −1 . No adsorbed water molecules (3700-3000 cm −1 ) are observed in the spectra of all pristine films (see the inset at the Figure 2).…”

Section: Resultsmentioning

confidence: 99%

Effect of Bridging and Terminal Alkyl Groups on Structural and Mechanical Properties of Porous Organosilicate Films

Nenashev

Wang

Liu

et al. 2017

Chemical composition, pore structure and mechanical properties of porous organosilicate low-k films with terminal and bridging organic groups are studied. It is shown that BTMSE based low-k films with alkyl bridge between the Si atoms have non-uniform pore structure with internal voids (ink-bottle like pores) while the films with terminal alkyl groups have pores with cylindrical shape. All studied spin-on deposited films have better mechanical properties than PECVD films with similar chemical composition and porosity. The best mechanical properties showed alkyl bridged low-k films. Moreover, the Young's modulus increases with BTMSE content because of higher concentration of bridging bonds. Porous organosilicate glasses (OSG) have many different applications such as catalysts, adsorbents, trapping agents, drug delivery agents, stationary phases in chromatography and chemical sensors. 1One of the most important applications of porous OSG films is related to interconnects in advanced ULSI (ultra large-scale integration) devices where they are used as insulators with low dielectric constant. Modern ICs can be made very compact, incorporating up to several billions transistors and other electronic components in an area of about 1 cm 2 . All transistors and other IC components have to be electrically interconnected to provide the proper functionality. The width of the conducting lines that connect different transistors in a circuit is becoming very small; in 2008, it dropped below 100 nm, and now is of the order of a few tens of nm. In parallel, the interconnect delay is becoming an increasing limitation factor of the overall signal propagation delay. The low dielectric constant materials are needed to reduce capacitance (C) between the metal (Cu) conductors. Together with low resistivity (R) of metal wires, low-k materials improve ULSI device performance by decreasing RC delay, cross talk noise and power consumption in interconnects.2 Different types of organosilicate films deposited by plasma enhanced chemical vapor deposition (PECVD) and spin-on glass (SOG) technology have been developed during the last 20 years. Using of appropriate precursors allows to control the chemical composition and porosity of these films. PECVD is currently the method of choice in microelectronic industry because this technique is easily integrated in the existing device manufacturing process.3 PECVD precursors (normally different types of organosilanes) are transferred to the reaction chamber where Si wafer is located on a heated pedestal. Quality of the deposited films depends on plasma characteristics and pedestal temperature. In the modern interconnect technology, the dielectric layer is deposited by PECVD and patterned first before the metal deposition using lithography and plasma etching. Lithography and plasma etching define the structure of interconnect wiring by forming certain patterns in the dielectric film. Then copper should fill the patterns in the dielectric film by superfilling electrodeposition and after chemicalmechanica...