We present a Deep Level Transient Spectroscopy (DLTS) study on dedicated test samples to investigate the defect landscape of deep trench (DT) sidewalls. The DT is commonly used to prevent crosstalk between two neighboring optoelectronic devices or as a separator between different functional blocks on a monolithic semiconductor chip. However, in minority carrier-based optoelectronic devices, such as photodiodes, carriers might recombine at trap states located at the DT to silicon interface causing performance degradation. The extracted parameters of the DLTS study are further utilized to investigate this recombination in terms of TCAD simulations. The results suggest that carrier recombination at the DT sidewalls of DT-terminated photodiodes may lead to non-linear responsivities with respect to the optical radiant flux. Furthermore, on the example of silicon dangling bonds, we investigate the influence of structural relaxations at the defect sites which are incorporated in the nonradiative multiphonon (NMP) model. By a comparison between the NMP model to the conventional Shockley-Read-Hall (SRH) model we show, that a difference in the emission barrier of approx. 50 meV will arise, resulting in a strong shift of the corresponding DLTS transients.

The isolation of photodetectors by deep trenches filled with insulating material is widely used to minimize crosstalk between devices fabricated on the same chip. At the same time, however, the interface of the deep trench isolation (DTI) introduces trap states that can act as recombination centers and affect the performance of Si photodetectors. In this work, the impact of carrier interaction with trap states at the DTI sidewalls on the responsivity of Si photodetectors using a 180 nm complementary metal-oxide-semiconductor technology is investigated. It is observed that DTI-terminated island photodiodes show larger responsivities compared to n-well guard (NWG) terminated island photodiodes. This superiority in terms of responsivity is more pronounced at high radiant fluxes because of reduced Shockley–Read–Hall (SRH) surface recombination at the lateral DTI to Si interface. Therefore, the responsivity of the DTI-terminated devices becomes nonlinear with respect to the incoming radiant flux. We show that this can be explained by the nonlinear minority carrier surface recombination at the DTI sidewalls. Responsivity measurements on reference samples with an NWG termination do not show this flux dependency, which confirms our conclusions. Furthermore, we investigate the influence of DTI sidewall implants to passivate the lateral oxide to silicon interfaces with respect to the nonlinear response and overall spectral response (SR). Our experimental findings are supported by TCAD simulations which are also presented in this work.

Radiation-hard photodiode structures implemented in medical applications are designed in 180-nm CMOS technology. Designed photodiodes were tested against total ionizing doses (TIDs) of 100, 200, and 400 Gy(Si), respectively, and they show high stability in terms of dark current characteristics. After TID of 400 Gy(Si), the dark current increased by up to 15%, compared to the unirradiated characteristics values. TCAD electrical simulations were performed and calibrated with the dark current measurements in order to explain the impact of generated defects due to ionizing radiation. Parameters that are used to model TID radiation have been varied in physical boundaries in order to achieve the desired fitting with the measurements. It is shown that due to the filling of acceptor interface traps with electrons, the space charge region extends, but the extension is limited and partially compensated by the fixed positive charges in the silicon nitride layer. The presented photodiodes result in the improved radiation hardness over the design in 350-nm CMOS technology.

ams AG is a global leader in the design and manufacture of advanced sensor solutions, which are at the heart of the products and technologies that define our world today – from smartphones and mobile devices to smart homes and buildings, industrial automation, medical technology and connected vehicles. To build global leadership in optical sensing, ams is driving integration of sensor technologies into monolithically integrated solutions. This paper will provide an overview of ams’ integrated photosensor concepts including 3D integration, spectral sensing and radiation hard concepts.

In this paper, a variability Design of Experiment (DoE) is performed on a radiation-hard photodiode structure in order to understand how the physical parameters of the device impact its spectral responsivity and dark current. The varied physical parameters describe the carrier mobility, lifetime, energy bandgap and recombination models. The electrical and optical performance of the device are simulated using TCAD software, as a function of varied physical parameters. The simulations are calibrated to the device measurements. The analysis of the design showed that the carrier lifetime is the most influencing parameter that impacts both the spectral responsivity and the dark current. Mobility parameters and Auger recombination parameters impact the spectral responsivity, while the energy bandgap at 340 K impacts the dark current. Finally, the model parameters that fit the measured dark current are obtained by the thorough variation simulations.

This paper constitutes the analysis of the impact of low doped intrinsic p-type EPI thickness (20 µm and 30 µm) and bottom anti-reflective coating on the electrical and optical performance of various PIN photodiodes designs. The intrinsic p-type layer with a target resistivity of 400 Ω cm is an epitaxial layer (iEPI) grown on a low resistive substrate of 20 mΩ cm. Optimization of the photodiode’s spectral responsivity (for a specific wavelength) includes a Bottom Anti-Reflective Coating (BARC) layer deposited over the silicon surface. BARC thickness is optimized for λ = 425 nm, λ = 750 nm and λ = 900 nm wavelengths. With respective BARC in place, the photodiode’s quantum efficiency (QE) approaches 100% for λ = 750 nm with 20 µm and 30 µm iEPI thickness and for λ = 900 nm with 30 µm iEPI reaching also a maximum spectral response of 0.63 A/W at 800 nm. QE of 72% could be achieved at 425 nm. The leakage current varies from 3.5 pA for 20 µm iEPI thickness to 10 pA for 30 µm at 1 V reverse biasing for 365 µm circular PIN photodiode.

Many imaging applications, like medical or space applications, require radiation-hard sensors. Generally, during radiation, many different defects are created, depending on the type of the radiation. With TCAD software, cross-section of a radiation-hard photodiode was simulated, and afterwards the impact of different physical parameters was simulated. Physical parameters like epitaxial layer thickness or the trap density in the bulk, play a huge role towards the responsivity of the photodiode. This paper presents a variation experiment, where relevant physical parameters are varied and analysis of the spectral responsivity and dark current of the photodiode is discussed.

We describe an analysis of the main process parameters variability involved in electrical and optical output characteristics of an optical sensor integrating a standard silicon-based NWell in p-epitaxial substrate photodiode and an UV/IR blocking interference filter. This study is done with TCAD simulation following a standard 0.18 μm high voltage CMOS technology fabrication process. The TCAD simulations combined with specific Design of Experiments permit a better understanding of the main electrical and optical responses variabilities of the optical sensor. This results in an improvement of the inline process control parameters and a better modeling of the sensor for future circuit designs integrating this sensor.

A 3-D electron-beam-induced current (EBIC) model was implemented in technology computer aided design simulations. The model uses a carefully designed charge carrier generation profile that describes how an electron beam induces charge carriers in a semiconducting device and then drift-diffusion equations are solved to determine the resulting current. The simulation provides a map of the EBIC signal, which can be compared with experimental 2-D profiles. This comparison can be used to fit parameters such as the surface recombination rate which is otherwise difficult to fit in completed devices. Additional experimental data for these fits are obtained by performing the experiments at different electron beam energies and thereby generating carriers at different depths in the sample. The experiments were performed on cross sections of silicon photodiodes with varying surface preparations. A strong influence of the surface preparation method on the charge carrier diffusion was observed.

The effects of silicon etching and subsequent metallization during the fabrication of tungsten-lined open TSVs are examined using a combination of measurements and simulations. The total stress through a tungsten film deposited on a flat wafer is measured and finite element simulations are performed in order to identify the intrinsic and thermal stress components in the film. The data is then used to observe and model the stress through a TSV structure, which is etched using the DRIE process, resulting in scalloped inner sidewalls through the TSV opening. The scalloped structure is then compared to the ideal flat alternative with regard to the stress through the metal film and the TSV's electrical parameters, including resistance, capacitance, and inductance. It is found that the stress around the scallop varies significantly while the average stress through the tungsten in the flat TSV is only slightly higher than the stress observed through the scalloped structure. The resistance, capacitance, and inductance are all found to increase in the presence of scallops.

Analog behavioral models are widely used to reduce the complexity in hierarchical analog circuit design and verification. In the presence of process variations and atomic-level fluctuations, however, these models have to be extended to take variability into account. In this paper, we present a probabilistic solution that treats the behavioral model coefficients as multidimensional random variables and supports non-Gaussian as well as correlated parameters. A voltage divider and a bandgap voltage reference demonstrate the capabilities of our modeling approach in terms of accuracy and efficiency.

We describe a global methodology for the extraction and the quantification of the effects of the most relevant equipment parameters involved in TSV processing. With a specific focus on the DRIE step of the TSVs' fabrication, we propose a dedicated simulation flow describing the distribution of the species over the wafer inside the etching chamber, the physical plasma simulation of polymer deposition and etching loops, and the electrical performance simulation of the resulting structures. Statistical techniques such as Pareto Graphs and Design of Experiments are used for the extraction of the most relevant equipment parameters on the electrical and metal stress responses.

The electrical performance and reliability of a through-silicon via is investigated through two-dimensional and three-dimensional simulations. Due to the large differences in material thicknesses present in the structures, a 3D simulation is often not feasible. The thermo-mechanical stress, the electrical parameters including TSV resistance and capacitance, as well as the electromigration-induced stress are investigated. A comparison between the results obtained through 2D and 3D simulations is used to suggest which types of simulations require a 3D modelling approach. It is found that an appropriate analysis of the current density through the structure requires 3D simulation, meaning that electromigration phenomena must be studied with 3D simulation or at least a combination of 2D and 3D analysis. However, a 2D simulation with assumed rotational symmetry is sufficient to estimate the thermo-mechanical stress distribution through the structure as well as the parasitic capacitance and signal loss of the TSV.

This paper presents the electrical and optical behavior of Single Photon Avalanche Diode. Key parameters as reverse breakdown voltage, spectral responsivity, photon detection probability, dark count rate and time delay of the diode are extracted from dedicated TCAD simulations.

For high performance analog circuits, stringent requirements on leakage current and stray capacitance impose challenging constraints to protection circuits. An analysis of the contact region impact on the leakage performance of ESD-IO diodes is presented. The current limit of these elements given by the onset of leakage degradation is explained and its dependence on stress duration is analyzed.