Laurent Favennec

The role of ultraviolet radiation during ultralow k films curing: Strengthening mechanisms and sacrificial porogen removal

This work proposes a fundamental understanding of structural transformation occurring during porogen extraction from as-deposited ultralow k (ULK) materials when exposed to ultraviolet (UV) radiation during thermal curing. Specific explanations are provided for as deposited films at high temperature (T>250 °C). This temperature range is sufficient to assess thin-film stability. Two distinguished regimes were identified in the curing process. During the first stage, the film shrinks strongly in similar proportion to SiCH3 break. Preferential impact of UV radiation on hydrocarbon porogen bonds leads also to a break of SiCH3 structures. In this work, 5 min of curing is enough to remove the porogen and create the max of porosity (33%). After the porogen removal step, the porous film shrinks under UV radiation leading to an increase of SiOSi bond concentration. A structural rearrangement of the bulk is initiated since the porogen is totally evacuated from the film. The increase of normalized infrared SiOSi pea...

Ultralow k using a plasma enhanced chemical vapor deposition porogen approach: Matrix structure and porogen loading influences

To improve integrated circuit performance, microelectronic chip interconnections need dielectric materials with ultralow k (ULK) values. Porous a-SiOCH, an ULK material, can be created using a two step strategy called a porogen approach. The first step consists of a hybrid film deposition, which is an a-SiOCH matrix containing an organic sacrificial phase. Afterwards, the organic phase is removed during a post-treatment to generate the porosity. In this work, hybrid deposition was performed by plasma enhanced chemical vapor deposition and the post-treatment was a thermal annealing. Firstly, hybrid films with different a-SiOCH matrix structures were created using two matrix precursors [decamethylcyclopentasiloxane (DMCPS) and diethoxymethylsilane (DEMS)] and an O2 addition in a plasma gas feed. For the same porogen loading, the shrinkage behavior during the porogen removal is correlated to the matrix structure. Fourier transform infrared spectroscopy and Si29 solid nuclear magnetic resonance are both used ...

Plasma-enhanced-chemical-vapor-deposited ultralow k for a postintegration porogen removal approach

Conventional Cu-ultra low K (ULK) integration schemes lead to a drastic increase of the effective dielectric constant due to porous material degradation during process steps. Although a postintegration porogen removal scheme allows overcoming these issues, only spin-on dielectrics were developed to validate this approach. In this letter, plasma-enhanced chemical-vapor deposition is used to deposit ULK dielectric (k<2.5). The precursor chemistry and the deposition conditions have been chosen to obtain a material with the required characteristics to use a postintegration porogen removal approach: porogen thermal stability up to 325°C, good mechanical properties of the hybrid film, no metallic barrier diffusion in the film, and a minimal shrinkage after the porogen removal treatment.

Crosslinking of porous SiOCH films involving Si–O–C bonds: Impact of deposition and curing

This paper focuses on the properties of nanoporous SiOCH thin films deposited using a porogen approach by plasma enhanced chemical vapor deposition. The impact of deposition temperature, porogen loading and porogen removal treatment is investigated using Fourier transform infrared spectroscopy, solid-state nuclear magnetic resonance analysis, and electrical and mechanical measurements. This work shows that a higher deposition temperature allows limiting the film shrinkage during the porogen removal treatment and leads to the best compromise in term of electrical and mechanical properties. Beside, the effect of Si–O–C bonds on the enhancement of mechanical properties is promoted since a typical crosslinking mechanism is highlighted in case of ultraviolet curing.

PECVD Versus Spin-on to Perform Porous ULK for Advanced Interconnects: Chemical Composition, Porosity and Mechanical Behavior

Porosity introduction in a-SiOCH matrix is a main research field in microelectronic. Two techniques are used to deposit these dielectric thin films: spin-on or Plasma Enhanced Chemical Vapor Deposition (PECVD). In this work, different porous a-SiOCH thin films (k close to 2.2 – 2.3) are studied. Several synthesis ways are used to deposit these a-SiOCH layers: by porogen approach, self assembling or nanoclustering techniques for spin-on, and using a porogen approach for PECVD. Impact of deposition process and curing on material crosslinking are investigated. The skeleton structure is correlated to the elastic properties whatever the deposition technique used. Finally, porosity and pore interconnectivity are studied and the results show that barrier diffusion is less pronounced in case of small pores size such as those obtained by PECVD.