Fabrication Cycle Time Research Articles

Low-Energy Ion Implantation and Deep-Mesa Si-Avalanche Photodiodes with Improved Fabrication Process.

Since the avalanche phenomenon was first found in bulk materials, avalanche photodiodes (APDs) have been exclusively investigated. Among the many devices that have been developed, silicon APDs stand out because of their low cost, performance stability, and compatibility with CMOS. However, the increasing industrial needs pose challenges for the fabrication cycle time and fabrication cost. In this work, we proposed an improved fabrication process for ultra-deep mesa-structured silicon APDs for photodetection in the visible and near-infrared wavelengths with improved performance and reduced costs. The improved process reduced the complexity through significantly reduced photolithography steps, e.g., half of the steps of the existing process. Additionally, single ion implantation was performed under low energy (lower than 30 keV) to further reduce the fabrication costs. Based on the improved ultra-concise process, a deep-mesa silicon APD with a 140 V breakdown voltage was obtained. The device exhibited a low capacitance of 500 fF, the measured rise time was 2.7 ns, and the reverse bias voltage was 55 V. Moreover, a high responsivity of 103 A/W@870 nm at 120 V was achieved, as well as a low dark current of 1 nA at punch-through voltage and a maximum gain exceeding 1000.

Rotation cycle time and delivery decision for a multi-item producer-retailer integrated system featuring overtime and random scrap

A multi-item producer-retailer integrated system featuring overtime and random scrap is studied. The objectives are to jointly decide the most economic rotation fabrication cycle time and distribution of products. In order to meet the increasing demands of diversified end items, production managers today need to plan a multiproduct fabrication schedule and to expedite both manufacturing and transportation times so that they can meet product demands as quickly as possible. Also, due to potential uncontrollable reasons, scrap items are generated randomly in a real fabrication process. To address the aforementioned issues, this study examines a multi-item producer-retailer integrated system featuring overtime and random scrap. We build a mathematical model to interpret the proposed multi-item producer-retailer integrated system which incorporates shipping and retailer’s holding cost. The Hessian matrix equations are used for solving the optimality of the system. Diverse important system information can now be exposed to backing managerial decision makings, which includes individual and combined influences of variations in particular system factor(s) (such as scrap rate and overtime related parameters) on the specific system performance.

Development and testing of an all-additively manufactured hybrid thruster for smallsats

Background: The design, development, and testing of a small-thruster system with additively-manufacturing key components is presented. The primary issue associated with conventionally-manufactured small thruster systems is the assembly complexity, where the motor case, injector, ignition electrodes, nozzle retainer, nozzle, fuel grain, insulting liner, and other components are fabricated individually and then assembled. For very small thruster systems, this detailed fabrication and assembly process is extremely labor intensive and time-consuming. Proposed "all- additive" designs reduce component fabrication and procurement cycle time, and may significantly reduce overall system complexity. Before committing to hardware, a student-lead design team reduced the trade-space to 2 design-options. Each option employs multiple additively-manufactured components including the oxidizer delivery system attachments, motor cap, motor casing, insulation, and the fuel grain. Components are additively manufactured using one of three different methods, fused-deposition modeling (FDM), stereo lithography (SL), and non-galvanic nickel plating (EN). Both designs feature an FDM-fabricated ABS fuel grain, with 1) a two material combustion chamber assembly fabricated from Veroclear® plastic using Polyjet 3-D SL printing technology, and 2) a chamber/fuel assembly additively fabricated from ABS, but plated with an external nickel coating. For simplicity the student prototype employs gaseous oxygen (GOX) and additively manufactured acrylonitrile-butadiene-styrene (ABS) as propellants. ABS has been previously demonstrated to be a highly efficient hybrid fuel material. The research campaign emphasized multiple objectives including hot and cold material testing burn lifetime survivability, system restart capability, and overall performance. Performance comparisons with hydrazine are presented.

Current-limiting amplifier for high speed measurement of resistive switching data.

Resistive switching devices, important for emerging memory and neuromorphic applications, face significant challenges related to the control of delicate filamentary states in the oxide material. As a device switches, its rapid conductivity change is involved in a positive feedback process that would lead to runaway destruction of the cell without current, voltage, or energy limitation. Typically, cells are directly patterned on MOS transistors to limit the current, but this approach is very restrictive as the necessary integration limits the materials available as well as the fabrication cycle time. In this article, we propose an external circuit to cycle resistive memory cells, capturing the full transfer curves while driving the cells in a way that suppresses runaway transitions. Using this circuit, we demonstrate the acquisition of 105 I, V loops per second without using on-wafer current limiting transistors. This setup brings voltage sweeping measurements to a relevant timescale for applications and enables many new experimental possibilities for device evaluation in a statistical context.

Cyclo olefin polymer-based solvent-free mass-productive microphysiological systems

A microphysiological system (MPS) holds great promise for drug screening and toxicological testing as an alternative to animal models. However, this platform faces several challenges in terms of the materials used (e.g. polydimethylsiloxane; PDMS). For instance, absorption of drug candidates and fluorescent dyes into PDMS, as well as the effect elicited by materials on cultured cells, can cause inaccurate or misleading results in cell assays. The use of PDMS also poses challenges for mass production and long-term storage of fabricated MPSs. Hence, to circumvent these issues, herein we describe the development of a cyclo olefin polymer (COP)-based MPS using photobonding processes and vacuum ultraviolet (VUV), designated as COP-VUV-MPS. COP is an amorphous polymer with chemical/physical stability, high purity and optical clarity. Due to the thermostability and high modulus of COP, the metal molding processes was applied for mass production of MPSs without deformation of microstructures and with quick fabrication cycle time (approx. 10 min/cycle). Moreover, VUV photobonding process with an excimer light at a 172nm wavelength allowed assembling COP materials without the use of additional solvents and tapes, which might cause cell damages. In comparison with the conventional MPS made of PDMS (PDMS-MPS), COP-VUV-MPS showed improved chemical resistance without causing molecule absorption. Moreover, COP-VUV-MPS maintained the stemness of environmentally sensitive human-induced pluripotent stem cells without causing undesired cellular phenotypes or gene expression. These results suggest that COP-VUV-MPS may be broadly applicable for the advancement of MPS and applications in drug development, as well as in vitro toxicological testing.

Fabrication Cycle Time and Shipment Decision for A Multiproduct Intra-Supply Chain System with External Source and Scrap

Managers of today’s transnational firms, facing competitive global business environments, always intend to optimize their intra-supply chain systems to meet customers’ multiproduct demands with perfect quality goods, timely delivery, and minimum fabrication-shipping expenses. In the production units of intra-supply chain systems, random scraps are inevitable due to various unforeseen factors. Also, since the in-house capacity is limited, implementing a partial outsourcing plan can help release machine workloads, smooth production schedule, and reduce fabrication uptime. Inspired by these facts, this study explores an intra-supply chain system with random scraps and an external source. We build a mathematical model to portray the characteristics of the studied problem. Model analyses and the renewal reward theorem help us to obtain the expected system cost function. Optimization techniques and Hessian matrix equations are used to jointly decide the optimal cycle time and shipment policy that minimize the expected system cost. Through numerical illustration, we expose the individual and joint impact of diverse system features on the optimal operating policies and other crucial parameters of the studied problem, thus, facilitate managerial decision makings.

Combining the delayed differentiation policy and common parts' partial outsourcing strategy into a multi-item FPR-based system

This study investigates a multi-item finite production rate(FPR-) based system incorporating a delayed product differentiation policy and common parts' outsourcing strategy. A two-stage fabrication scheme is proposed, wherein, in stage one, all common parts of the end products (assuming they have a known completion rate as compared with the finished products) are partially produced in-house and partially supplied by an outside contractor with an extra unit outsourcing; in stage two, all end products are finished in sequence, under a rotation fabrication cycle time discipline. An explicit model is developed to clearly represent the proposed problem. Through the optimization technique, the optimal rotation cycle decision is obtained. Thus, diverse characteristics of this particular multi-item, FPR-based system with postponement and outsourcing strategies can now be revealed. As demonstrated by numerical illustrations, these characteristics include the (i) convexity of the system cost function, (ii) impact of common parts' outsourcing strategy on the utilization, (iii) breakup of system cost components, (iv) combined impact of the outsourcing ratio and common parts' completion rate on the system cost function, and (v) effect of the outsourcing ratio on optimal rotation cycle decision. Our decision-support-type system can facilitate production managers in achieving their goals of reducing orders' response times and minimizing the overall system cost.

Meeting multiproduct demand with a hybrid inventory replenishment system featuring quality reassurance

Globalization has not only generated immense business opportunities, but also created a very competitive marketplace. To retain competitive advantage, a manufacturer must satisfy a client's multiproduct and quality requirements with limited in-house capacity. An outsourcing strategy can overcome capacity constraints and shorten the fabrication cycle time. This study explores a hybrid multiproduct single-machine inventory replenishment system incorporating an outsourcing plan. The in-house multiproduct fabrication process is under a common cycle time policy. That is, each product receives one replenishment in a common cycle length. All fabricated items are inspected for quality; items with random defects are sorted out as scrap and repairable, and the rework occurs immediately after the regular fabrication. All reworked products that fail the quality reassurance test are scrapped. The quality of outsourcing items is assumed to be guaranteed by the outside provider. Our objective is to determine the optimal common cycle time that minimizes the total relevant cost. An accurate model is constructed to represent the characteristics of the system studied; furthermore, we utilize mathematical analysis to derive the total system costs and apply differential calculus to find the optimal cycle length. A numerical example illustrates the applicability of our result and highlights the effect of variations in outsourcing- and quality-related attributes on the optimal solution, as well as the various performance indicators that facilitate planning and controlling decisions.

Optimized Bucky Paper-Based Bioelectrodes for Oxygen–Glucose Fed Enzymatic Biofuel Cells

This paper focuses on fabricating cost effective and time-efficient bioelectrodes for enzymatic bio fuel cells by immobilizing the enzymes, glucose oxidase, and laccase on the surface of buckeye composite Bucky paper (BP) without any redox cofactors. Electrochemical studies including linear sweep voltammetry, cyclic voltammetry open circuit potential, and electrochemical impedance spectroscopy were carried out to evaluate the performance of the prepared electrodes. Maximum current density of 9.79 mA/cm2 at 0.4 V and 2 mA/cm2 at 0.3 V was observed for anode and cathode, respectively, at a scan rate of 10 mV/s at 40-mM glucose concentration. Morphological studies using scanning electron microscope revealed uniform dispersion of the enzymes on the surface of the BP electrodes facilitating the presence of enzyme active sites for catalytic reactions. The absence of redox cofactors in this approach dramatically reduces the cost and fabrication cycle time and also preserves their biocompatible nature. The fabricated BP-based bioelectrodes have shown excellent performance and further encourage toward future studies at the microfluidics level.

A dynamic programming solution to automate fabrication sequencing of industrial construction components

Abstract Increasing complexity of petro-chemical projects, fast-tracked engineering, and tighter schedules pose a challenge for pipe spool fabrication shops. To maintain competitiveness, it is necessary to improve the shop performance, i.e. fabrication cycle time. Pipe spool fabrication sequence is found to have significant impact on cycle time and presents an area with potential for improvement. Traditionally, fabrication sequences are determined by shop foremen in a heuristic manner and optimality is not guaranteed. This paper presents a dynamic programming (DP) algorithm to automatically identify the optimal fabrication sequences for pipe spools. Simulation experiments are conducted to test the effectiveness of the algorithm by comparing the cycle times resulting from the algorithm-generated sequences and human-planner-designed sequences, respectively. The results show that the DP algorithm reduces unnecessary position-welding (9 out of 20 position-welds) and results in a reduction in the total fabrication cycle time by a range of 4.8% to 12%.

Z-Axis Interconnection: A Versatile Technology Solution for High Performance Electronics

This paper presents a novel Z-axis interconnect approach for extending performance beyond the limits imposed by traditional approaches. Specifically, metal-to-metal z-axis electrical interconnection among substrates (subcomposites) of the same or varying size, or among flexible and rigid elements (rigid-flex), to form a single structure is described. The structure employs an electrically conductive medium to interconnect thin coreless substrates. The substrates are built in parallel, aligned, and laminated to form a variety of multilayer high density structures including rigid, rigid-rigid, rigid-flex, stacked packages, or RF substrates. The z-interconnect based structures offer many advantages over more conventional build-up technologies. For example, it enables designs having increased wiring density, leading to greatly reduced layer counts. When an increase in metal layer counts is required, z-interconnect avoids the cumulative yield loss of sequential (build up) processing. The parallel processing of cores and/or subcomposites leads to reduced fabrication cycle time. Avoidance of through hole drilling allows for reduction or elimination of via stubs that cause signal attenuation at high frequencies. In addition, multilayer rigid-flex packages for a variety of applications are being developed. For these applications, z-interconnect allows for placement of flex elements into any layer of the substrate, the opportunity for multiple flex layers within a rigid-flex substrate, the ability to connect multiple multilayer substrates of varying size, and the ability to connect between any two arbitrary metal layers within the rigid region without the use of plated through holes (PTHs). The process allows fabrication of z-interconnect conductive joints having diameters in the range of 55–500 microns. Via or component pitches down to 150 microns have been demonstrated. A number of RF structures have been designed and built with z-interconnect technology, affording the flexibility to place wide signals, narrow signals and grounds and clearances only where needed. Electrically, S-parameter measurements revealed low loss at multi-gigahertz frequencies and the insertion loss for narrow, short lines and wide, long lines are similar. The electrically conductive adhesive used to form z-interconnects shows good signal transmission to 25GHz. Z-interconnect technology provides unique solutions for next generation complex packaging products.

An efficient job-releasing strategy for semiconductor turnkey factory

The semiconductor integrated circuit (IC) industry in Taiwan plays a significant role in the world, and accounts for a major market share of packaging and testing. Past studies have discussed job-releasing models for upstream IC manufacturing industries, but only few have discussed from an IC turnkey perspective for IC testing and assembly processes. This article proposes a job-releasing strategy for an IC turnkey factory that achieves the following objectives under limited resources: (1) increasing the overall equipment efficiency of IC test equipments, (2) reducing IC fabrication cycle time and (3) increasing on-time delivery rate. To balance capacity utilisation between IC assembly and testing operations, this study uses a genetic algorithm with workload regulation heuristics to find a good job-releasing plan. The proposed strategy is implemented in an IC turnkey factory and is found to outperform the conventional strategy.

English

This paper reports design, fabrication, and gait planning based on high walk diagonal trot gait pattern of an alligatorinspired robot having eight degrees of freedom. Each leg of the robot described in this paper has two revolute joints representing the hip and knee respectively which are actuated by servo motors. The body of the robot was fabricated on a CO2 laser cutting machine. The 3D leg design was dividedinto two 2D components to enable manufacturing on a laser cutting machine to reduce fabrication cycle time. Finally, a general-purpose kinematics based model has been reported that is used to designand implement a high-walk gait on the developed robot.

Modelling, analysis, and acceleration of a printed circuit board fabrication process

Product design and fabrication constitute an important business activity in any manufacturing firm. Designing an optimized product fabrication process is an important problem in itself and is of significant practical and research interest. In this paper, we look into a printed circuit board (PCB) fabrication process and investigate ways in which the fabrication cycle time can be minimized. Single class queueing networks constitute the modelling framework for our study. The model developed in this paper and the analysis experiments carried out are based on extensive data collected on a PCB fabrication company located in Bangalore, India. This is a representative PCB fabrication company involving multiple, concurrent fabrication works with contention for human/technical resources. Our model seeks to capture faithfully the flow of the fabrication process in this company and such other organisations, using queueing networks. Using the model developed, we explore how the cycle times can be reduced using input control, load balancing, and variability reduction. The model presented is sufficiently generic and conceptual; its scope extends beyond that of a PCB fabrication organization.

Rapid prototyping of active microfluidic components based on magnetically modified elastomeric materials

Replica molding of elastomeric materials has proven to be an extremely useful new technology for the formation of complex microfluidic systems. Recent demonstrations of convenient methods for production of such systems by simple, rapid methods that do not require expensive fabrication facilities have enabled the extensive use of microsystems in research and development into a host of new application fields. This report describes a simple new method for fabricating active elastomeric components in microfluidic systems that is based on deformation of elastic materials that have been impregnated or coated with magnetic materials. Computer controlled miniature electromagnets are used to activate switching valves within microfluidics systems. Similar fabrication techniques can be easily extended to construct complex, and potentially completely integrated, microfluidic systems containing active valves, pumps, injectors, mixers, and flow controllers. Preliminary results indicate fabrication of channels approximately 200 μm in width, with valves approximately 5 mm in size (including both valve chamber and valve actuator). The fabrication cycle time is on the order of one day using readily available benchtop equipment, and the valves seal hermetically against a 1.5 kPa back pressure.

Scheduling of mask shop E-beam writers

Reducing wafer fabrication cycle time and providing on-time wafer deliveries are among the top priorities of semiconductor companies. Mask manufacturing is essential to the overall wafer fabrication process since on-time delivery of masks significantly affects wafer fabrication cycle times. Moreover, delivering wafers on time means deliveries of masks must be on time as well. This research studies the scheduling problem of the bottleneck machine-the Electrical Beam (E-beam) Writer-of a mask shop. The criterion of minimum total tardiness is used as our performance measure to schedule this bottleneck operation. Using a predetermined Earliest-Due-Date (EDD) dispatch policy set by management, this study first addresses the problem of scheduling batches of a single mask size on a single machine. The approach is extended to the problem of scheduling batches of two mask sizes on a single machine; finally, a heuristic for a multiple-machine problem is developed. For the problem of a single machine under EDD dispatching policy, the problem can be formulated as a Dynamic Program (DP). Thus, it can be solved for an optimal solution in polynomial time. For the multiple machines problem, we heuristically allocate the masks to each machine. Each machine with allocated masks can then be solved by the DP formulation designed for the single machine problem. Based on the computational experiments in this study, the proposed DP approach reduces total tardiness by an average of 55% from the method currently in use at a major IC manufacturing foundry. Furthermore, in the case that due dates are set realistically, the DP approach reduces the tardiness about 95% from the shop's current method and about 88% from a simple full-batch method of scheduling.