Optimized photoacoustic gas-microphone cell for semiconductor materials thermal conductivity monitoring

An approach for examination of semiconductor materials thermal conductivity based on the photoacoustical (PA) experimental results has been considered. Attention is drawn to the importance of PA cell design and normalization procedure that must be carried out in order to remove the parasitic signal caused by the PA cell effects as well as a contribution from the electronic components. The proposed technique makes it possible to quickly and reliably diagnose the thermal conductivity of various semiconductors materials for a better understanding of the heat transfer there for various technological applications. To test the methodology, thermal conductivity of monocrystalline silicon with different doping level was considered. The obtained dependence of thermal conductivity on the doping level is in a good agreement with well-known literature data. Thus, the results obtained in this work are important from a practical point of view.

Computational optimization of a 3D printed collimator

This contribution describes the computational methodology behind an optimization procedure for a scattered beam collimator. The workflow includes producing a file that can be manufactured via additive methods. A conical collimator, optimized for neutron diffraction experiments in a high pressure clamp cell, is presented as an example. In such a case the scattering from the sample is much smaller than that of the pressure cell. Monte Carlo Ray tracing in MCViNE was used to model scattering from a Si powder sample and the cell. A collimator was inserted into the simulation and the number and size of channels were optimized to maximize the rejection of the parasitic signal coming from the complex sample environment. Constraints, provided by the additive manufacturing process as well as a specific neutron diffractometer, were also included in the optimization. The source code and the tutorials are available in c3dp (Islam (2019)).

Piezoresistive Ring-Shaped AFM Sensors with Pico-Newton Force Resolution

A new concept of Atomic Force Microscope (AFM) oscillating probes using electrostatic excitation and piezoresistive detection is presented. The probe is characterized by electrical methods in a vacuum chamber and by mechanical methods in air. The frequency-mixing measurement technique is developed to reduce the parasitic signal level. These probes resonant in the 1MHz range and the quality factor is measured about 53000 in vacuum and 3000 in air. The ring probe is mounted onto a commercial AFM set-up and the surface topography of PMMA sample (2 µm square) is obtained. The force resolution deduced from the measurements is about 10 pN/Hz0.5.

Conception and Fabrication of Silicon Ring Resonator With Piezo-Resistive Detection for Force Sensing Applications

A new concept of Atomic Force Microscope (AFM) oscillating probes using electrostatic excitation and piezo-resistive detection is presented. The probe is characterized by electrical methods in vacuum chamber and by mechanical methods in air. The mixer measurement technique is developed to reduce the parasitic signal level. These probes resonance frequencies are in the 1MHz range and the quality factor is measured about 53,000 in vacuum and 3,000 in air. The force resolution deduced from the measurements is about 8 pN/Hz0.5.

Structural Transformation in PECVD Ultralow-k Material during Porogen Removal by UV Assisted Thermal Curing

ABSTRACTNext-generation microelectronic interconnects require the use of dielectrics with continuously lower permittivity (k) to overcome limitations induced by crosstalk parasitic signal delay. Using PECVD, Ultralow-k film (ULK, k ≤ 2.5) can be developed by creating pore inclusions within an organosilicate matrix through porogen approach. Both ULK deposition and subsequent curing process has to be adjusted in order to achieve optimized mechanical and electrical properties and maintain stability during integration. For this concern, the attention was recently focused on ultraviolet (UV) radiation to sustain the thermal curing. In the present work, a fundamental understanding of structural transformations occurring during porogen extraction from as-deposited ULK materials when exposed to thermal-assisted UV radiation is proposed. This thermal-assisted UV cure technique is very efficient in porogen removal since in a few minutes the desired porosity is reached. During the first stage of curing, the film shrinks strongly whereas the porosity is created. After porogen removal step, the porous film continues shrinking under UV radiation leading to an increase of SiOSi bonds concentration (film densification). The normalized FTIR SiOSi peak increase during UV curing (related in literature to an improvement of mechanical properties) is mainly due to the film densification, in addition to the SiOSi bridging bond creation. In this case, correlation is found between shrinkage and elastic modulus.