Patrick Verdonck

Effect of pore structure of nanometer scale porous films on the measured elastic modulus.

The impact of pore structure of nanoporous films on the measured elastic modulus is demonstrated for silica-based nanoporous low-k films that are fabricated using an alternative manufacturing sequence which allows a separate control of porosity and matrix properties. For this purpose, different experimental techniques for measuring the elastic properties were compared, including nanoindentation, laser-induced surface acoustic wave spectroscopy (LAwave), and ellipsometric porosimetry (EP). The link between the elastic response of these nanoporous materials and their internal pore structure was investigated using positronium annihilation lifetime spectroscopy (PALS), EP, and diffusion experiments. It is shown that the absolute value of the Berkovich indentation modulus is very sensitive to the local pore structure and stiffness of the substrate and can be influenced by densification and/or anisotropic elasticity upon indentation, while on the other hand spherical indentation results are less sensitive to the local pore structure. The comparison of Berkovich and spherical indentation results combined with finite element simulations can potentially reveal changes in the internal structure of the film. For nanoporous films with porosity above the percolation threshold, the elastic modulus results obtained with LAwave and EP agree very well with spherical indentation results. On the other hand, below the percolation threshold, the elastic modulus values determined by these techniques deviate from the spherical indentation results. This was explained in terms of specific technique related effects that appear to be sensitive to the specific arrangement and morphology of the pores.

The Effect of Ar/H2 Plasma Pretreatments on Porous K=2.0 Dielectrics for Pore Sealing by Self-Assembled Monolayers Deposition

Self-assembled monolayers (SAMs) deposition is being recently explored to help sealing the pores of a k=2.0 material. In order to enable a covalent chemical low-k surface functionalization by SAMs, a hydroxyl groups density as high as 1 to 2.5 OH groups/nm2 is required. This surface modification must be carefully controlled to confine the k below 10%. In this paper, the effects of plasma temperature, time and power on the SAMs deposition and plasma-induced damage are investigated. The main findings are that there is always a trade-off between surface hydroxyl groups density and bulk damage. A thick modified layer allows the SAM molecules to penetrate inside the pores which results in a decreased porosity and an increased k value with respect to correspondent plasma-treated pristine substrates.

Development of multi-stack dielectric wafer bonding

We investigate multi-stack dielectric wafer bonding through two integration schemes, which provide different paths to realize vertical integration of multiple device layers. Key process steps are evaluated and optimized to enable void-less bonds at different bonding layers. Meanwhile, issues related to the wafer edge are discovered during the backside processing and the impact is analyzed. Finally, N=4 stacks are successfully demonstrated with high quality interfaces formed by dielectric bonding.

Electrical comparison of iN7 EUV hybrid and EUV single patterning BEOL metal layers

The semiconductor scaling roadmap shows the continuous node to node scaling to push Moore’s law down to the next generations. In that context, the foundry N5 node requires 32nm metal pitch interconnects for the advanced logic Back- End of Line (BEoL). 193immersion usage now requires self-aligned and/or multiple patterning technique combinations to enable such critical dimension. On the other hand, EUV insertion investigation shows that 32nm metal pitch is still a challenge but, related to process flow complexity, presents some clear motivations. Imec has already evaluated on test chip vehicles with different patterning approaches: 193i SAQP (Self-Aligned Quadruple Patterning), LE3 (triple patterning Litho Etch), tone inversion, EUV SE (Single Exposure) with SMO (Source-mask optimization). Following the run path in the technology development for EUV insertion, imec N7 platform (iN7, corresponding node to the foundry N5) is developed for those BEoL layers. In this paper, following technical motivation and development learning, a comparison between the iArF SAQP/EUV block hybrid integration scheme and a single patterning EUV flow is proposed. These two integration patterning options will be finally compared from current morphological and electrical criteria.

Low f-number microlens array fabricated in thick resist

In certain applications of MOEMS devices, it is often necessary to produce microlens array structures that concentrate optical power in semiconductor photodetectors. In this work, the design and fabrication of a low f-number cylindrical microlens array is presented. The lenses were fabricated in thick photo resist - 12 μm thick - using a contact printer exposure through a mask with a repetitive 6 μm line - 4 μm space pattern. The width of the resulting microlens array was determined to be 10 μm, with f-number of 0.5. Numerical calculations based on scalar diffraction theory were employed to model the light propagation inside the resist, determining the aerial image as a function of its thickness. Than the resist response characteristics, expressed by its contrast curve, and absorption rate were used to obtain a cross section profile. A good match between numerical and experimental results were found.

Opto‐acousto‐optic evaluation of the physical properties of nanoporous materials

The porous materials with the characteristic dimensions of the pores from few nanometers up to a few hundred of nanometers find applications in microelectronic industry (as low‐k materials), in photovoltaics and for developing of effective chemical sensors. When the pores are ordered in a spatially periodic structure, these systems present photonic and/or phononic properties which are of a prime interest in applied optics and telecommunication (light and/or phonons spectrum control). Here we report how the methods of picosecond laser ultrasonics based on the generation and detection by lasers of the acoustic waves with frequencies in the band of 10 GHz ‐ 1 THz (with the lengths of hundreds of nanometers down to few nanometers) are applied for the evaluation of the mechanical and optical properties of these materials.

Full complex amplitude modulation proximity printing mask fabricated on DLC and SiO2 substrates--SUBSCRIPT

Proximity printing is a well known lithographic technique. The final density of the resulting patterns is limited by diffraction effects and by the alignment accuracy of the different masks used e.g. for integrated circuit fabrication. To overcome these limitations, a full complex-amplitude modulation proximity printing mask is proposed. A patterned fused silica substrate is used to modulate the phase and a diamond like carbon layer, deposited and patterned on top of the substrate, to modulate the amplitude of the UV light. The proposed diffractive structure modulates both phase and amplitude of the UV exposure beam, forming the required image at a predetermined distance of 50 micron behind the mask.

Fabrication of a continuous parabolic surface relief array using a silicon-based wet-etch micromachining

A process for fabrication of sub-masters of continuous parabolic surface relief arrays is presented. The device was fabricated employing a silicon-based wet-etch micromachining. Devices with good optical forms are obtained.