A new process design for manufacturing sapphire wafers

Uhlmann, Eckart; List, Michael G.; Patraschkov, Marcel; Trachta, Gerd

doi:10.1016/j.precisioneng.2018.03.011

Cited by 29 publications

(9 citation statements)

References 2 publications

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“…It is used in several fields such as the military, aerospace industry, biomedical industry and lighting-display field (Zhankui et al , 2021; Yu et al , 2021). The surface of sapphire wafers for light emitting diode ( LED) substrates should be ultra-smooth and damage-free (Uhlmann et al , 2018; Shi et al , 2018).…”

Section: Introductionmentioning

confidence: 99%

Surface quality prediction and lapping process optimisation on the fixed-abrasive lapping plate of sapphire wafers

Yan

Wang²,

Liu³

2022

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Purpose Lapping is a vital flattening process to improve the quality of processed semiconductor wafers such as single-crystal sapphire wafers. This study aims to optimise the lapping process of the fixed-abrasive lapping plate of sapphire wafers with good overall performance [i.e. high material removal rate (MRR), small surface roughness (Ra) of the wafers after lapping and small lapping plate wear ratio (η)]. Design/methodology/approach The influence of process parameters such as lapping time, abrasive size, abrasive concentration, lapping pressure and lapping speed on MRR, Ra and η of lapping-processed sapphire wafers was studied, and the results were combined with experimental data to establish a regression model. The multi-evaluation index optimisation problem was transformed into a single-index optimisation problem via an entropy method and the grey relational analysis (GRA) to comprehensively evaluate the performance of each parameter. Findings The results revealed that lapping time, abrasive size, abrasive concentration, lapping pressure and lapping speed had different influence degrees on MRR, Ra and η. Among these parameters, lapping time, lapping speed and abrasive size had the most significant effects on MRR, Ra and η, and the established regression equations predicted the response values of MRR, Ra and η to be 99.56%, 99.51% and 93.88% and the relative errors between the predicted and actual measured values were <12%, respectively. With increased lapping time, MRR, Ra and η gradually decreased. With increased abrasive size, MRR increased nearly linearly, whereas Ra and η initially decreased but subsequently increased. With an increase in abrasive concentration, MRR, Ra and η initially increased but subsequently decreased. With increased lapping pressure, MRR and η increased nearly linearly and continuously, whereas Ra decreased nearly linearly and continuously. With increased lapping speed, Ra initially decreased sharply but subsequently increased gradually, whereas η initially increased sharply but subsequently decreased gradually; however, the change in MRR was not significant. Comparing the optimised results obtained via the analysis of influence law, the parameters optimised via the entropy method and GRA were used to obtain sapphire wafers lapping with an MRR of 4.26 µm/min, Ra of 0.141 µm and η of 25.08, and the lapping effect was significantly improved. Originality/value Therefore, GRA can provide new ideas for ultra-precision processing and process optimisation of semiconductor materials such as sapphire wafers.

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Section: Introductionmentioning

confidence: 99%

Surface quality prediction and lapping process optimisation on the fixed-abrasive lapping plate of sapphire wafers

Yan

Wang²,

Liu³

2022

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“…These movements result from the overlapping of the driven grinding wheels, the rotation of the inner pin ring and the eventuating workpiece holder rotation. Due to the planar contact of the grinding wheels, the surfaces of a workpiece are evenly loaded [1][2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Analysis of influencing factors for the dressing process in double side face grinding

Uhlmann

Lichtschlag

2021

Int J Adv Manuf Technol

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In grinding, the design of the dressing process is an essential part of work preparation and restoration of the grinding wheel’s profile and cutting ability. In contrast to most grinding processes, the choice of dressing parameters in double face grinding with planetary kinematics has so far only been experience-based. As a consequence, the dressing process causes a higher degree of tool wear than the machining of the workpieces. A focused design of the dressing process based on a scientific data could help to improve the ecological and the economic efficiency by reducing tool wear and the amount of dressing tools used. In this paper, methods for determining the wear condition and the result of the dressing process, including macro- and microscopic characteristic are presented. This includes a correlation analysis between parameters of wear characteristics and workpiece surface quality. Furthermore, technological investigations are carried out in order to systematically limit the main influencing factors on the dressing process. As a result, the parameters dresser grain size dgd, rotational speed ratio nld and the machined dresser height ∆hd are identified as significant for dressing. The knowledge about their principal influence on the dressing result could provide the basis for further research.

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“…In general, the lower the surface roughness, the smaller the thickness of the subsurface damaged layer. The flatness of the substrate is represented by the total thickness variation (TTV), which is the difference between the maximum and minimum thicknesses in the measurement area [12][13][14]. These lapping characteristics are complexly influenced by various factors, such as the rotational speed of the platen, the pressing force, the slurry Micromachines 2020, 11, 775 2 of 13 properties, the lapping platen shape, the platen grooves density, etc.…”

Section: Introductionmentioning

confidence: 99%

Effect of the Lapping Platen Groove Density on the Characteristics of Microabrasive-Based Lapping

et al. 2020

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Microabrasive-based lapping is widely used in the manufacturing of single-crystal substrates such as sapphire, SiC, and GaN. Although many studies have been conducted to improve the lapping process characteristics, most of them focused on process conditions or consumables. In this study, the effect of the lapping platen groove density on the lapping characteristics was studied using a sapphire substrate. Groove density was defined as the ratio of groove width to groove pitch, and the displacement of the lapping head was measured to calculate the oil film thickness. It was confirmed that, for groove densities below 0.30, hydroplaning occurs when the oil film thickness increases. When the oil film thickness is larger than the abrasive particle size, the material removal rate is low because the abrasive does not participate in the lapping process. When the oil film was developed, the experimental results showed a high surface roughness and poor flatness of the substrate, as only large abrasive particles participated in the lapping process. Therefore, to improve the lapping characteristics, it is important to reduce the groove density by reducing the groove pitch, which prevents the development of the oil film.

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A new process design for manufacturing sapphire wafers

Cited by 29 publications

References 2 publications

Surface quality prediction and lapping process optimisation on the fixed-abrasive lapping plate of sapphire wafers

Surface quality prediction and lapping process optimisation on the fixed-abrasive lapping plate of sapphire wafers

Analysis of influencing factors for the dressing process in double side face grinding

Effect of the Lapping Platen Groove Density on the Characteristics of Microabrasive-Based Lapping

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