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Process control and quality assurance in remote laser beam welding by optical coherence tomography
摘要： Remote laser beam welding significantly outperforms conventional joining techniques in terms of flexibility and productivity. This process benefits in particular from a highly focused laser radiation and thus from a well-defined heat input. The small spot sizes of high brilliance laser beam sources, however, require a highly dynamic and precise positioning of the beam. Also, the laser intensities typically applied in this context result in high process dynamics and in demand for a method to ensure a sufficient weld quality. A novel sensor concept for remote laser processing based on optical coherence tomography (OCT) was used for both quality assurance and edge tracking. The OCT sensor was integrated into a 3D scanner head equipped with an additional internal scanner to deflect the measuring beam independently of the processing beam. With this system, the surface topography of the process zone as well as the surrounding area can be recorded. Fundamental investigations on aluminum, copper, and galvanized steel were carried out. Initially, the influence of the material, the angle of incidence, the welding position within the scanning field, and the temperature on the OCT measuring signal were evaluated. Based on this, measuring strategies for edge tracking were developed and validated. It was shown that orthogonal measuring lines in the advance of the process zone can reliably track the edge of a fillet weld. By recording the topography in the trailing area of the process zone, it was possible to assess the weld seam quality. Comparing the results to microscopic measurements, it was shown that the system is capable of clearly identifying characteristic features of the weld seam. Also, it was possible to observe an influence of the welding process on the surface properties in the heat-affected zone, based on the quality of the measuring signal.
关键词： inline quality assurance,optical coherence tomography,remote laser beam welding,process control
更新于2025-11-28 14:24:20
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In-situ monitoring method of PECVD process equipment condition
摘要： A key to successfully have a consistent plasma processing is the maintaining a consistent process chamber condition over a certain production period. To alleviate the concern, in-situ process monitoring sensors are optical emission spectroscopy (OES), optical plasma monitoring sensor (OPMS), VI-probe, and self-plasma optical emission spectroscopy (SP-OES). During the deposition, we perform the monitoring of plasma condition associated with the applied RF power via OES, OPMS and VI-probe. In the chamber cleaning step using remote plasma system does not allow plasma monitoring through sidewall because the plasma is not formed in the process chamber, thus we employed SP-OES to monitor by-product gas chemistry during the chamber cleaning process step. Successful monitoring results with some useful applications, such as arc detection, part failure detection, and cleaning process chemistry analysis, are presented in this paper. The use of in-situ sensors with proper combination can help understanding plasma process better to achieve more precise control of the plasma processing.
关键词： in-situ monitoring,advanced process control,advanced equipment control
更新于2025-09-23 15:23:52
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Spatial Correlated Data Monitoring in Semiconductor Manufacturing Using Gaussian Process Model
摘要： In semiconductor manufacturing, various wafer tests are conducted in each stage. The analysis and monitoring of collected wafer testing data plays an important role in identifying potential problems and improving process yield. There exists three variation sources: lot-to-lot variation, wafer-to-wafer variation and site-to-site variation, which means the measurements cannot be considered independently. However, most existing control charts for monitoring wafer quality are based on the assumption that data are independently and identically distributed. To deal with the variations, we propose a mixed-effects model incorporating a Gaussian process to account for the variations. Based on the model, two control charts are implemented to detect anomalies of the measurements which can monitor the changes of the variations and the quality of products respectively. Simulation studies and results from real applications show that this model and control scheme is effective in estimating and monitoring the variation sources in the manufacturing process.
关键词： semiconductor manufacturing,mixed-effects model,statistical process control (SPC),Gaussian process
更新于2025-09-23 15:21:01
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Design of a laser control system with continuously variable power and its application in additive manufacturing
摘要： system adjusts the laser position. This paper will also discuss the development and advanced laser control techniques enable a higher level of control over the processing process relies heavily on understanding and controlling the thermodynamics of the polymer melt temperatures and lead to more uniform components. Currently, there are no commercial options for a laser power controller that allows continuously variable power to be used as a galvanometer process. One of the biggest challenges SLS faces is lack of adequate process control, which leads to comparatively high component variations. It has been shown that implementing more manufacturing processes with applications in aerospace, biomedical, tooling, prototyping, and beyond. SLS is capable of creating unique, functional parts with little waste and no tooling by using a high-powered laser to selectively melt powdered polymer into desired shapes. This Selective laser sintering (SLS) is one of the most popular industrial polymer additive implementation of a galvanometer controller solution that works in conjunction with an off-the-shelf unit to enable this crucial functionality and will present results showing that, when applied laser sintering (SLS) additive manufacturing. The work contained in this paper is a continuation of previous work that developed a method of controlling laser power is SLS in order to improve the consistency of components built [1]. This previous effort was capable of improving temperature uniformity of SLS components by up to 57% and strength uniformity by up to 45%. Powder Bed Fusion
关键词： Laser Control,Additive Manufacturing,Surrogate Modeling,Powder Bed Fusion,Process Control
更新于2025-09-23 15:19:57
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In-Situ Testing of the Thermal Diffusivity of Polysilicon Thin Films
摘要： This paper presents an intuitive yet effective in-situ thermal diffusivity testing structure and testing method. The structure consists of two doubly clamped beams with the same width and thickness but different lengths. When the electric current is applied through two terminals of one beam, the beam serves as thermal resistor and the resistance R(t) varies as temperature rises. A delicate thermodynamic model considering thermal convection, thermal radiation, and film-to-substrate heat conduction was established for the testing structure. The presented in-situ thermal diffusivity testing structure can be fabricated by various commonly used micro electro mechanical systems (MEMS) fabrication methods, i.e., it requires no extra customized processes yet provides electrical input and output interfaces for in-situ testing. Meanwhile, the testing environment and equipment had no stringent restriction, measurements were carried out at normal temperatures and pressures, and the results are relatively accurate.
关键词： in-situ testing,thermal diffusivity,process control monitoring (PCM),thin film
更新于2025-09-19 17:15:36
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Color Quantification for Process Monitoring and Appearance Control of Thin Film PV
摘要： Product color and appearance uniformity are a critical manufacturing consideration in any industry, including solar module manufacturing. These considerations become even more important as modules are increasingly installed in locations where aesthetics is a prime consideration, such as BIPV, automotive, and consumer products. Additionally, the interaction of PV materials with visible light enables objective color characterization to be a useful tool for control of film deposition processes. In this paper we describe our efforts, learning and results controlling product color and using color as a process monitoring and control tool.
关键词： optical reflection,color,photovoltaic cells,thin film devices,process control
更新于2025-09-19 17:13:59
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Copper-Plating Metallization With Alternative Seed Layers for c-Si Solar Cells Embedding Carrier-Selective Passivating Contacts
摘要： In this article, we develop in parallel two fabrication methods for copper (Cu) electroplated contacts suitable for either silicon nitride or transparent conductive oxide antire?ective coatings. We employ alternative seed layers, such as evaporated Ag or Ti, and optimize the Ti–Cu or Ag–Cu contacts with respect to uniformity of plating and aspect ratio of the ?nal plated grid. Moreover, we test plating/deplating sequence instead of a direct current plating or the SiO2 layer approach to solve undesired plating outside the designed contact openings. The main objective of this paper is to explore the physical limit of this contact formation technology keeping the process compatible with industrial needs. In addition, we employ the optimized Cu-plating contacts in three different front/back-contacted crystalline silicon solar cells archi- tectures: 1) silicon heterojunction solar cell with hydrogenated nanocrystalline silicon oxide as doped layers, 2) thin SiO2/doped poly-Si-poly-Si solar cell, and 3) hybrid solar cell endowed with rear thin SiO2/poly-Si contact and front heterojunction contact. To investigate the metallization quality, we compare fabricated devices to reference ones obtained with standard front metallization (Ag screen printing and Al evaporation). We observe a relatively small drop in VOC by 5 to 10 mV by using Cu-plating front grid, whereas ?ll factor was improved for solar cells with Cu-plated front contact if compared with evaporated Al.
关键词： Photovoltaic (PV),Si PV device fabrication,photovoltaic cells,PV process control
更新于2025-09-16 10:30:52
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Influence of temperature and clamping force on the strength of the joint over different composite-metal combinations joined by laser
摘要： Vehicle weight in automobile industry is a strict limitation which can be overcome with novel material combinations. Laser conduction joining is an arising alternative but it still poses challenges for joining dissimilar metal-composite materials. Up to now, main research lines have been developed using constant process parameters (laser power and clamping force), so, the behavior of these composite-metal joints under different process parameters, and the control of the process itself, are unknown areas of investigation so far. This paper is focused on the implementation of closed-loop control systems for temperature and clamping force. Tests at different set-points have been carried out for different composite-metal combinations, and the strength of the joints has been assessed by single lap shear tests. The optimal joining process parameters have been found for each material combination.
关键词： Quality assurance,Laser joining,Metal-composite joining,Laser bonding,Process control
更新于2025-09-12 10:27:22
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A Distributed-Parameter Approach for the Surface Temperature Estimation of an LED Heated Silicon Wafer
摘要： A variety of processes in the semiconductor industry require heating of the silicon wafer to the desired temperature. This process is widely referred to as rapid thermal processing. However, the contactless measurement of the surface temperature of the wafer is still a major challenge, especially in the case of rotating wafers. Measurements using infrared cameras are not suitable due to the fact that silicon is transparent in this wavelength range. Special sensors based on the principle of pyrometry are available, but such sensors can only measure the surface temperature at one single point. This paper presents an observer approach that estimates the wafer’s surface temperature by using the temperature measurement of only one pyrometer. The approach is based on a mathematical model capturing the dynamical behavior of the wafer’s temperature. It relies mainly on the quasi-linear heat equation. Real world experiments demonstrate the achieved accuracy of the proposed approach.
关键词： Rapid thermal processing,semiconductor device manufacture,distributed parameter systems,process control
更新于2025-09-11 14:15:04
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Statistical Process Control for Monitoring the Particles with Excess Zero Counts in Semiconductor Manufacturing
摘要： In modern semiconductor manufacturing, one type of measured particle count data contains excess zeros, and the ratio of zeros in the measurements is usually larger than 50%. This type of particle count sample data cannot be well modeled by popular defect models such as Poisson, zero-inflated Poisson (ZIP), generalized (GZIP), Neyman and Gamma-Poisson models. In this paper, a threshold-Poisson model was proposed to describe the particles with excess zero counts, and the method for parameter estimation was developed. Via comparison with those popular models by using 15 measured samples, it showed that the measurements are better modeled by the threshold-Poisson model. A control chart called threshold-c control chart was proposed and the control limits were derived. A reasonable minimum sample size for constructing control chart was also discussed based on simulations.
关键词： process control,particle count,control charts,quality control,statistical process control,particle,excess zeros
更新于2025-09-10 09:29:36