Silicon Nitride Deposition Mask Composition for Low-Warpage Flatness
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Solution Overview
Problem
The manufacture of deposition masks for high-resolution displays, such as those required for wearable devices like HMDs and AR glasses, is hindered by warpage due to differences in thermal expansion and residual stress between the substrate and membrane.
Innovation Solution
A deposition mask design with a membrane made of silicon nitride films, where the silicon content is higher than a silicon content, and the silicon content is higher, and nitrogen content is constant, and the silicon content is higher, with a controlled nitrogen content in the thickness direction, and a stepwise increase and decrease in nitrogen and silicon content, respectively, to manage interfacial residual stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a membrane is disposed on a substrate to form a deposition mask, then the mask structure is formed, but warpage occurs due to difference in coefficient of thermal expansion and residual stress
Solution Approach 1:
The patent applies parameter changes by controlling the nitrogen content in the silicon nitride membrane to be 30-40 atomic percent, which is higher than conventional stoichiometric silicon nitride. This compositional parameter change adjusts the thermal expansion coefficient and residual stress of the membrane, thereby reducing warpage. The method also involves controlling deposition parameters such as temperature (700-850°C) and pressure (200-300 mTorr) to achieve the desired nitrogen content and minimize warpage.
Solution Approach 2:
The patent employs composite materials by creating a silicon nitride membrane with non-stoichiometric composition (excess nitrogen) deposited on a silicon substrate. This composite structure with controlled composition gradients and specific layer configurations (including optional intermediate layers) helps match thermal expansion properties and reduce residual stress between the membrane and substrate, thereby minimizing warpage.
2Stability of the object's composition
If the nitrogen content in the membrane is increased to reduce warpage, then interfacial residual stress is reduced, but the membrane composition deviates from stoichiometric silicon nitride
Solution Approach 1:
The patent deliberately changes the compositional parameter by incorporating 30-40 atomic percent nitrogen in the silicon nitride membrane, which exceeds the stoichiometric ratio. This parameter change is achieved through controlled chemical vapor deposition processes with specific gas flow rates and deposition conditions, allowing precise control of nitrogen content while maintaining film quality and reducing residual stress.
Solution Approach 2:
The patent applies local quality by creating a nitrogen content gradient or specific nitrogen distribution within the membrane layers. Different regions or layers of the membrane have optimized nitrogen content to locally address stress requirements while maintaining overall compositional control. This may involve varying nitrogen content through the thickness or across different areas of the membrane.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively reduces warpage in the deposition mask, ensuring high-resolution manufacturing by maintaining interfacial residual stress within a manageable range, thereby preventing deformation.
Implementation Method 1
an interfacial residual stress between the mask frame and the membrane may be in a range about −30 megapascals (MPa) to about 30 MPa
Implementation Method 2
warpage may occur in the deposition mask due to a difference in coefficient of thermal expansion between the substrate and the membrane, residual stress of the membrane
Implementation Method 3
forming an inorganic film on a substrate, forming a plurality of pixel openings by patterning the inorganic film
Data Source
AI summary
A deposition mask includes a mask frame with a cell opening defined therein and a membrane disposed on the mask frame. The membrane includes a cell region disposed on the cell opening, a plurality of pixel openings is defined in the cell region to be connected to the cell opening, and an interfacial residual stress between the mask frame and the membrane is in a range of about −30 MPa to about 30 MPa.