HDP-CVD Silicon Nitride Film Stress Control for OLED Encapsulation
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Solution Overview
Problem
Conventional encapsulation layers in OLED devices fail to effectively prevent moisture and oxygen ingress, leading to degradation and reduced lifetimes due to compressive film stress in silicon nitride barrier layers deposited using conventional HDP-CVD processes.
Innovation Solution
A method involving high density plasma chemical vapor deposition (HDP-CVD) with controlled biasing of the substrate during silicon nitride deposition to achieve low film stress and compressive stress, resulting in superior barrier properties by depositing silicon nitride layers with tunable tensile or compressive stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional HDP-CVD process is used to deposit silicon nitride barrier layers, then the barrier layers provide encapsulation for OLED devices, but compressive film stress causes degradation and reduces device lifetime
Solution Approach 1:
The patent applies parameter changes by modifying the deposition conditions in HDP-CVD process, specifically changing the substrate bias voltage from conventional values to a specific range (-100V to -300V), and adjusting the ratio of silane to ammonia flow rates. These parameter modifications transform the film stress from compressive to tensile, resolving the contradiction between providing barrier function and avoiding stress-induced degradation.
2Object-affected harmful factors
If existing encapsulation layers are used, then they provide basic protection against moisture and oxygen ingress, but they fail to prevent failure of OLED devices over time
Solution Approach 1:
The patent modifies the deposition parameters to achieve tensile stress in the silicon nitride barrier layers, which fundamentally changes the mechanical properties of the encapsulation structure. This parameter change enables the barrier layers to better resist moisture and oxygen ingress over time, preventing the failure that occurs with conventional encapsulation layers.
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
The method enhances the barrier properties of silicon nitride layers, preventing moisture and oxygen ingress, thereby improving the longevity of OLED devices by maintaining stability and reducing cracks in the encapsulation structure.
Implementation Method 1
depositing a silicon nitride layer on the substrate... using high density plasma chemical vapor deposition (HDP-CVD)
Implementation Method 2
forming a high density plasma of the precursor gases
Data Source
AI summary
Embodiments of the present disclosure generally describe a method for depositing a barrier layer of SiN using a high density plasma chemical vapor deposition (HDP-CVD) process, and in particular, controlling a film stress of the deposited SiN layer by biasing the substrate during the deposition process.