Haze Defects Research Articles

Luminance-based methodology for assessment of low level haze in glazing

AbstractVisual defects, in particular haze, in glass and façade technologies can significantly impact the aesthetic quality and human experience of daylight and views in buildings. The glass and façade industry increasingly requires methods that can objectively predict and measure the subjective user experience of haze. This is required to appropriately inform the manufacturing process, ensuring optimal functionality and performance, and avoiding material waste and economic losses due to the replacement of defective glazing. Existing methods for measuring haze are not appropriate for assessing large samples, either at manufacturing sites or in-situ. However, haze defects are often only exhibited and visible when glazing is produced in large samples or installed under real luminous conditions. This paper introduces a novel luminance-based method that measures haze by evaluating the halo around a light source that is observed through the glazing. This method is initially tested in a controlled laboratory setting on small glazing samples with varying level of haze. The halo serves as a proxy for haze severity and it is quantified by using luminance-based measurements. In this work, the newly-proposed method is verified by comparing the ranking in haze severity of different samples as performed by means of a standard haze meter and the newly proposed method. Additionally, the paper examines the dependence of this ranking on factors such as camera setup distance and light intensity. It was found that the proposed method was able to effectively ranks samples differing in haze intensity by more than 0.1 orders of magnitude. Positioning the camera closer to the glazing and using higher light intensity yielded more accurate results. However, for haze levels below 1% and differences smaller than 0.1 orders of magnitude, the accuracy is insufficient. To define the expected level of accuracy of methods for haze characterisation in-situ, the sensitivity of the human eye to haze under varying luminous environments and view content needs to be quantified.

Haze in sapphire crystals grown by SAPMAC method

AbstractHaze defect in SAPMAC method grown sapphire crystal was studied in detail. It is shown that haze is composed by a large number of CO2 bubbles, and haze always appears in the axis region of the crystal since the bubbles formed in front of the crystallization surface are most always draged to the convection rolls in front of the central part of the crystallizaiton surface by melt and then engulfed by the rolls. Moreover, the effects of pulling rate on the formation of haze were analyzed and means for restraining haze was suggested. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effect of process related and haze defects on 193nm immersion lithography

In this article, the effect of a defective mask on 193nm immersion lithography with a 6% attenuated phase-shifting mask is investigated. Two types of defect are studied: process related defect and haze defect. Several factors including defect location, size, transmission, phase, and illumination settings are considered. Exposure using a standard 45nm SRAM cell shows that the printability of a defect on a mask depends on the pattern density and defect size and it is also shown that the impact of a defect on a polysilicon gate layer is worse than that on an active layer. A defect that is adjacent to a main feature causes more critical dimension (CD) variation than that between two main features. Simulation using a through pitch line and space pattern is used to investigate the impact of a haze defect. A change in transmission results in an increase in the CD variation in the main feature but not the critical defect size. However, a larger phase difference between the defect and background would increase the CD variation and reduces the critical defect size. Illumination with a low partial coherence setting increases the CD variation caused by defects.

Haze Defects due to Pellicle Adhesive

The minimum feature size of a semiconductor device will be smaller and smaller because of the increasing demand for high integration of the devices. According to the recently proposed international technology roadmap of semiconductor, ArF immersion lithography will be used for 65 to 45 nm technology nodes. In the 193 nm exposure process, outgassing from the adhesive of the pellicle is a serious problem in the semiconductor industry because it causes haze to form. Various materials contribute to photomask haze including chemical residuals from mask cleaning, outgassing from pellicle adhesive/materials, and contaminants from the scanner ambient. The pellicle lifetime is important in exposure processes, is directly related to the throughput in mass production, and is affected by exposure dose and the environment surrounding the mask. The dependence of the pellicle lifetime on the dose and location of exposure is the subject of this study. The distance between the adhesive of the pellicle and the exposed area was varied to determine the direct relationship between the adhesive and the haze. A 193 nm (ArF) excimer laser was used to expose the mask with and without a pellicle. The surrounding environment of the mask with and without nitrogen purging was also varied. We compared haze formation as a function of accumulated dose. As expected, the crystal growth or haze formation increased as the accumulated dose increased. The adhesive and pellicle material contribute to haze formation; nitrogen purging can reduce haze formation.

Control of Time-Dependent Contamination during Bonding of Semiconductor and Optical Substrates

Microcontamination control is a key parameter for enhancing yield in terms of density of voids within the interface of a bonded wafer. One important cause of void density is time-dependent haze (TDH) or surface-particulate defect density. TDH on silicon surfaces is generated by the interaction of organic volatiles with moisture on the silicon surfaces. Sub-micrometer particle defect density, or haze level, is mainly affected by contamination arising from five factors: people, process, equipment, environment, and processing chemicals and gases. Direct wafer bonding (DWB) is a three-step sequence consisting of ultra-clean surface preparation, contacting, and thermal annealing. Contacting is an operation of ultrafine alignment and face-to-face joining of two substrates. Prior to joining, each contacting substrate is chemically cleaned in order to minimize surface haze and particulate contamination. Both sub-micrometer particle density and surface haze can be greatly reduced by point-of-use (POU) microfiltration and purification of deionized (DI) water as well as application of ultra-dilute concentration of ultra-pure chemicals containing extremely low levels of liquid particle counts. Ultra-pure DI water is filtered with a high-efficiency membrane filter that removes particles down to 0.02 micrometer (μm), thus reducing metal ions to sub-parts-per-billion (ppb) levels. As a result, surface haze and sub-micrometer light-point defects density on a contacting surface are minimized to reduce the density of voided or disbonded regions. A 1-μm particle, for instance, can cause a void as large as 1 centimeter (cm) in diameter during the bonding operation. Data is presented in terms of fractional areas of the voided regions for direct silicon wafer-bonded substrates. In addition to semiconductor wafer substrates, surface contamination is discussed for optical substrates such as fused silica. Minimizing microcontamination and TDH on the surface of optical substrates is important in maximizing ultraviolet (UV) transmission rates at wavelengths between 190 and 250 nanometers (nm). Methods and techniques are recommended for minimizing trace levels of surface contamination to improve UV transmission rates. No data for bonding of optical components is included in this study.

Biofilm Formation and Contamination of Cheese by Nonstarter Lactic Acid Bacteria in The Dairy Environment

Defects in cheese, such as undesirable flavors, gas formation, or white surface haze from calcium lactate crystals, can result from growth of nonstarter lactic acid bacteria (NSLAB). The potential for biofilm formation by NSLAB during cheese manufacturing, the effect of cleaning and sanitizing on the biofilm, and bacterial growth and formation of defects during ripening of the contaminated cheese were studied. Stirred-curd Cheddar cheese was made in the presence of stainless steel chips containing biofilms of either of two strains of erythromycin-resistant NSLAB (Lactobacillus curvatus strain JBL2126 or Lactobacillus fermentum strain AWL4001). During ripening, the cheese was assayed for total lactic acid bacteria, numbers of NSLAB, and percentage of lactic acid isomers. Biofilms of L. curvatus formed during cheese making survived the cleaning process and persisted in a subsequent batch of cheese. The starter culture also survived the cleaning process. Additionally, L. curvatus biofilms present in the vat dislodged, grew to high numbers, and caused a calcium lactate white haze defect in cheese during ripening. On the other hand, biofilms of L. fermentum sloughed off during cheese making but could not compete with other NSLAB present in cheese during ripening.Pulsed-field gel electrophoresis results verified the presence of the two biofilm strains during cheese making and in the ripening cheese. Probable contamination sites in the plant for other NSLAB isolated in the cheese were identified, thus supporting the hypothesis that resident NSLAB biofilms are a viable source of contamination in the dairy environment.