Material Modeling in Semiconductor Process Applications

Integration of reactive process modeling into semiconductor technology development

The growth of wireless applications in the low GHz range has been a catalyst in numerous research activities to develop wireless applications in standard digital CMOS processes. The relatively lower costs in developing single chip solutions for wireless applications in CMOS technology is considered its main advantage over other semiconductor processes. Thus, with the integration of RF systems in CMOS, planar inductors will have a dominant role in defining the achievable performance of the system as a whole. In this paper, the characterization of square spiral inductors is presented. The performance of inductors is analyzed using an inductor model based on the model proposed by Yue. Two inductors with values, 1.8 nH and 10 nH, are implemented on a 0.25 /spl mu/m digital CMOS process. Q-enhancement techniques are also implemented together with the inductors to investigate their effectiveness in improving the quality factor of inductors.

Over the last decade, Additive Manufacturing (AM) has gained wide importance on several industrial fields, with however severe limitations in the dimensions on the outcomes, constrained to the limits imposed by the printer environment. As such, the applications of these innovative manufacturing technologies in construction have been limited to few explorations on small pieces, to be used as connection parts.
\nWith the advent of a new weld-based AM process, referred to as Wire-and-Arc Additive Manufacturing (WAAM), the scale of the printed outcomes increased up to several meters span, thus becoming suitable for real-scale applications in construction. Nonetheless, the outcomes from the printing process require specific considerations for structural design purposes in terms of geometrical irregularities and marked anisotropy
\nAs such, the study is focused on the characterization of WAAM-produced 308LSi stainless steel for structural applications and divided in three parts: Part A, Part B and Part C. 
\nPart A and B are devoted to study the so-called “continuous printing” strategy, to realize planar elements, and “dot-by-dot printing” strategy, to realize lattice and rod-like elements, respectively. Both parts are articulated as follows: (i) definition of a suitable design approach from the specifics of the printing process; (ii) experimental characterization of the WAAM-produced elements from the microstructural, geometrical and mechanical points of view; (iii) calibration of an orthotropic material model and definition of first design guidelines (according to Eurocode provisions); (iv) exploration of topologically-optimized shapes for new structural members realized with WAAM.
\nPart C is devoted to present new technologies and future developments on WAAM applications in construction. It is articulated as follows: (i) presentation of a new mobile 3D printing system; (ii) exploration of new perspectives for real-time monitoring systems.

In semiconductor manufacturing, as some of the variables in processes cannot be easily measured during or after the production, virtual metrology (VM) is employed to predict metrology outputs using ancillary process variables. However, because of changeable processes and high-dimensional inputs, VM can be expensive or difficult to implement. In this work, just-in-time (JIT) modeling is used to cope with changes in process characteristics and to automatically update the statistical model. In addition, owing to the non-uniform data distribution, Gaussian process regression (GPR) as a probabilistic approach is a typical method to enhance the robustness of the system in the probability density space. With high-dimensional input variables in deposition processes, a variable shrinkage and selection method for GPR is proposed. It is superior to the conventional methods. The features of the proposed method are shown by way of illustrative examples and the proposed method is compared to conventional work based on real semiconductor process data.

In recent years, the broad applicability, non-contact nature, high precision, and low energy consumption of laser processing have made its application increasingly widespread in fields such as aerospace, medical, and electronic consumer products. Femtosecond and nanosecond lasers are representatives of high quality and high efficiency, respectively. This article takes semiconductor silicon as the research object, and carries out experiments to enhance processing efficiency under different delays and different energy ratios through the combined technical path of femtosecond and nanosecond lasers. Combined with the measurement results of the material’s three-dimensional morphology, the ablation area and roughness are used as criteria to study the impact of delay and energy ratio on the enhancement effect. The experimental results show that for semiconductor silicon, the enhancement phenomenon occurs at positive delays, and effective enhancement will only occur when the femtosecond energy density exceeds the damage threshold. As the femtosecond laser intensity increases from 0.5F_th-to 25F_th-, the enhancement effect becomes more significant.

Ultra-low temperature chillers have seen increasing demand with the advancement of semiconductor technology. Mixed refrigerant (MR) cascade refrigeration systems (CRSs) are widely utilized for their stability and high cooling performance at low temperatures. Extensive research has been conducted on optimizing MR, which has a significant impact on CRS performance. However, most previous studies have either fixed the system pressure or used the refrigeration effect as the sole performance indicator. This did not account for the potential of achieving higher performance with an optimal MR composition at the same target temperature. In this study, a detailed parametric analysis was performed to investigate how the mass fractions of high-, mid-, and low boiling point refrigerants affect the coefficient of performance (COP) and exergy in ultra-low temperature CRSs without fixing the suction pressure. The analysis revealed that at the point of maximum COP, the refrigeration effect was relatively low, highlighting the limitations of using the refrigeration effect alone as a performance indicator. Additionally, COP was found to inversely correlate with total exergy destruction. As cascade temperature increases, COP tends to decrease, emphasizing the need for appropriate cascade temperature selection for MR CRS performance. This study introduces a novel approach to optimizing MR composition under various operating conditions, contributing to the advancement of ultra-low temperature CRSs.