Thin Silicon Shadow Masks for Organic Light Emitting Diodes (OLED) Deposition Processes
Date Issued
2005
Date
2005
Author(s)
Tseng, Ching-Chang
DOI
en-US
Abstract
In this thesis, we demonstrate thin silicon shadow masks used for vacuum thermal evaporation (VTE) for manufacturing compact-size OLED (organic light emitting diodes) displays.
Currently, the OLED displays attract many research attentions because novel organic materials for emitting the light at relative low cost. The fabrication processes of OLED make use of shadow masks for thermal deposition of organic materials due to etching difficulties. The metal shadow masks are widely used because of easy access. But in most cases, metal might be attacked by acids when it is cleaned to wash out residual organic or non-organic materials. Moreover, common metal masks have higher thermal expansion coefficient and lower young’s modulus these would cause pattern dispersion during the deposition of the high resolution sub-pixels. Besides, the openings of metal shadow masks are limited to vertical sidewall. It would cause shadow phenomenon and reduce deposition efficiency.
In order to modify the defect of metal mask, we propose to use TMAH anisotropic wet etching process to fabricate thin silicon shadow masks. Due to the crystal orientation of (100) silicon wafers, the etched aperture slope of the silicon shadow mask has approximately 54.7 degree sidewalls. This feature increases the accepting angle of the openings around the edge; reduces shadow phenomenon and increases deposition efficiency.
The simulation parts, we used 54.7 and 90 degree side wall mask to demonstrate the effects of changing mask thickness or separation of mask and substrate to the deposition patterns. We also compared with experimental results by changing the aperture size of 54.7 degree mask. The simulation results indicated that the separation of mask and substrate must be close to reduce resolution limit and the thickness of silicon shadow mask would not affect deposition profile.
The experimental deposition results showed the feasibility of shin silicon shadow mask used in the vacuum thermal evaporation process. The results indicated that we could have smoother pattern under precise evaporation rate control.
Subjects
真空熱蒸鍍
濕蝕刻
有機發光二極體
蒸鍍遮罩
micromachining
organic light emitting diodes displays
wet etching
shadow masks
thermal deposition
Type
thesis
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